blob: 2cc17dc7ab8470e59629149e2cc9d3636141dd7d [file] [log] [blame]
Al Stoneb10d79f2015-03-24 14:02:41 +00001 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -08002 Advanced Configuration and Power Interface
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +02003 Format: { force | on | off | strict | noirq | rsdt |
Rami Rosene58d1542015-09-26 19:27:57 +03004 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 force -- enable ACPI if default was off
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +02006 on -- enable ACPI but allow fallback to DT [arm64]
Linus Torvalds1da177e2005-04-16 15:20:36 -07007 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07009 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +080011 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +080012 copy_dsdt -- copy DSDT to memory
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +020013 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
14 are available
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Paul Bolle395cf962011-08-15 02:02:26 +020016 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
Len Browna1fdcc02007-03-11 03:26:14 -040018 acpi_apic_instance= [ACPI, IOAPIC]
19 Format: <int>
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -040022 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -040023
Thomas Renningerc3d6de62008-08-01 17:37:55 +020024 acpi_backlight= [HW,ACPI]
25 acpi_backlight=vendor
26 acpi_backlight=video
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
30
Colin Ian Kingb2ca5da2016-01-21 17:05:47 +000031 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
36
Dominik Brodowskief694492015-05-14 15:31:28 +020037 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
44
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070045 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070048 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -060055 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Bjorn Helgaase76f4272008-11-13 17:30:13 -060059 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070063 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070066 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +020068
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070069 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +080072
Dominik Brodowskief694492015-05-14 15:31:28 +020073 acpi_enforce_resources= [ACPI]
74 { strict | lax | no }
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
88
Lv Zheng4fc0a7e2014-05-31 08:15:02 +080089 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
92 size limitation.
93
Randy Dunlap0cb55ad2009-04-05 15:55:22 -070094 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
96 default in APIC mode
97
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
100 default in PIC mode
101
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
104
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
106 use by PCI
107 Format: <irq>,<irq>...
108
Lv Zheng9c4aa1e2016-12-16 12:07:57 +0800109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
113 the GPE dispatcher.
114 This facility can be used to prevent such uncontrolled
115 GPE floodings.
116 Format: <int>
Lv Zheng9c4aa1e2016-12-16 12:07:57 +0800117
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800118 acpi_no_auto_serialize [HW,ACPI]
119 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800120 AML control methods that contain the opcodes to create
121 named objects will be marked as "Serialized" by the
122 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800123 This feature is enabled by default.
124 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800125
Dominik Brodowskief694492015-05-14 15:31:28 +0200126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
127 kernels.
128
Lv Zhenga94e88c2014-04-04 12:39:11 +0800129 acpi_no_static_ssdt [HW,ACPI]
130 Disable installation of static SSDTs at early boot time
131 By default, SSDTs contained in the RSDT/XSDT will be
132 installed automatically and they will appear under
133 /sys/firmware/acpi/tables.
134 This option turns off this feature.
135 Note that specifying this option does not affect
136 dynamic table installation which will install SSDT
137 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700138
Dominik Brodowskief694492015-05-14 15:31:28 +0200139 acpi_rsdp= [ACPI,EFI,KEXEC]
140 Pass the RSDP address to the kernel, mostly used
141 on machines running EFI runtime service to boot the
142 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800143
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700144 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
145 Format: To spoof as Windows 98: ="Microsoft Windows"
146
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200147 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
148 of 2 which is mandated by ACPI 6) as the supported ACPI
149 specification revision (when using this switch, it may
150 be necessary to carry out a cold reboot _twice_ in a
151 row to make it take effect on the platform firmware).
152
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700153 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800154 acpi_osi="string1" # add string1
155 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800156 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800157 acpi_osi=! # disable all built-in OS vendor
158 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800159 acpi_osi=!! # enable all built-in OS vendor
160 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700161 acpi_osi= # disable all strings
162
Lv Zheng5dc17982013-07-22 16:08:25 +0800163 'acpi_osi=!' can be used in combination with single or
164 multiple 'acpi_osi="string1"' to support specific OS
165 vendor string(s). Note that such command can only
166 affect the default state of the OS vendor strings, thus
167 it cannot affect the default state of the feature group
168 strings and the current state of the OS vendor strings,
169 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800170 is meaningless. This command is useful when one do not
171 care about the state of the feature group strings which
172 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800173 Examples:
174 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
175 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
176 can make '_OSI("Windows 2000")' TRUE.
177
178 'acpi_osi=' cannot be used in combination with other
179 'acpi_osi=' command lines, the _OSI method will not
180 exist in the ACPI namespace. NOTE that such command can
181 only affect the _OSI support state, thus specifying it
182 multiple times through kernel command line is also
183 meaningless.
184 Examples:
185 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
186 FALSE.
187
Lv Zheng741d8122013-07-22 16:08:36 +0800188 'acpi_osi=!*' can be used in combination with single or
189 multiple 'acpi_osi="string1"' to support specific
190 string(s). Note that such command can affect the
191 current state of both the OS vendor strings and the
192 feature group strings, thus specifying it multiple times
193 through kernel command line is meaningful. But it may
194 still not able to affect the final state of a string if
195 there are quirks related to this string. This command
196 is useful when one want to control the state of the
197 feature group strings to debug BIOS issues related to
198 the OSPM features.
199 Examples:
200 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
201 '_OSI("Module Device")' FALSE.
202 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
203 '_OSI("Module Device")' TRUE.
204 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
205 equivalent to
206 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
207 and
208 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
209 they all will make '_OSI("Windows 2000")' TRUE.
210
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530211 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700212 Override the pmtimer bug detection: force the kernel
213 to assume that this machine's pmtimer latches its value
214 and always returns good values.
215
Randy Dunlap4af94f32009-04-17 18:30:28 -0700216 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
217 Format: { level | edge | high | low }
218
Randy Dunlap4af94f32009-04-17 18:30:28 -0700219 acpi_skip_timer_override [HW,ACPI]
220 Recognize and ignore IRQ0/pin2 Interrupt Override.
221 For broken nForce2 BIOS resulting in XT-PIC timer.
222
223 acpi_sleep= [HW,ACPI] Sleep options
224 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Rafael J. Wysocki57044032017-11-15 02:16:55 +0100225 old_ordering, nonvs, sci_force_enable, nobl }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700226 See Documentation/power/video.txt for information on
227 s3_bios and s3_mode.
228 s3_beep is for debugging; it makes the PC's speaker beep
229 as soon as the kernel's real-mode entry point is called.
230 s4_nohwsig prevents ACPI hardware signature from being
231 used during resume from hibernation.
232 old_ordering causes the ACPI 1.0 ordering of the _PTS
233 control method, with respect to putting devices into
234 low power states, to be enforced (the ACPI 2.0 ordering
235 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200236 nonvs prevents the kernel from saving/restoring the
237 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800238 sci_force_enable causes the kernel to set SCI_EN directly
239 on resume from S1/S3 (which is against the ACPI spec,
240 but some broken systems don't work without it).
Rafael J. Wysocki57044032017-11-15 02:16:55 +0100241 nobl causes the internal blacklist of systems known to
242 behave incorrectly in some ways with respect to system
243 suspend and resume to be ignored (use wisely).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700244
245 acpi_use_timer_override [HW,ACPI]
246 Use timer override. For some broken Nvidia NF5 boards
247 that require a timer override, but don't have HPET
248
Randy Dunlap4af94f32009-04-17 18:30:28 -0700249 add_efi_memmap [EFI; X86] Include EFI memory map in
250 kernel's map of available physical RAM.
251
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700252 agp= [AGP]
253 { off | try_unsupported }
254 off: disable AGP support
255 try_unsupported: try to drive unsupported chipsets
256 (may crash computer or cause data corruption)
257
Randy Dunlapbcfde332010-06-07 17:10:38 -0700258 ALSA [HW,ALSA]
259 See Documentation/sound/alsa/alsa-parameters.txt
260
Russell Kingd944d542010-02-20 16:13:29 +0000261 alignment= [KNL,ARM]
262 Allow the default userspace alignment fault handler
263 behaviour to be specified. Bit 0 enables warnings,
264 bit 1 enables fixups, and bit 2 sends a segfault.
265
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200266 align_va_addr= [X86-64]
267 Align virtual addresses by clearing slice [14:12] when
268 allocating a VMA at process creation time. This option
269 gives you up to 3% performance improvement on AMD F15h
270 machines (where it is enabled by default) for a
271 CPU-intensive style benchmark, and it can vary highly in
272 a microbenchmark depending on workload and compiler.
273
Borislav Petkov8360ee22011-11-21 12:10:19 +0100274 32: only for 32-bit processes
275 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200276 on: enable for both 32- and 64-bit processes
277 off: disable for both 32- and 64-bit processes
278
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500279 alloc_snapshot [FTRACE]
280 Allocate the ftrace snapshot buffer on boot up when the
281 main buffer is allocated. This is handy if debugging
282 and you need to use tracing_snapshot() on boot up, and
283 do not want to use tracing_snapshot_alloc() as it needs
284 to be done where GFP_KERNEL allocations are allowed.
285
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100286 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200287 Pass parameters to the AMD IOMMU driver in the system.
288 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900289 fullflush - enable flushing of IO/TLB entries when
290 they are unmapped. Otherwise they are
291 flushed before they will be reused, which
292 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200293 off - do not initialize any AMD IOMMU found in
294 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100295 force_isolation - Force device isolation for all
296 devices. The IOMMU driver is not
297 allowed anymore to lift isolation
298 requirements as needed. This option
299 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900300
Shuah Khanc099cf12012-05-24 15:58:25 -0600301 amd_iommu_dump= [HW,X86-64]
302 Enable AMD IOMMU driver option to dump the ACPI table
303 for AMD IOMMU. With this option enabled, AMD IOMMU
304 driver will print ACPI tables for AMD IOMMU during
305 IOMMU initialization.
306
Suravee Suthikulpanit3928aa32016-08-23 13:52:32 -0500307 amd_iommu_intr= [HW,X86-64]
308 Specifies one of the following AMD IOMMU interrupt
309 remapping modes:
310 legacy - Use legacy interrupt remapping mode.
311 vapic - Use virtual APIC mode, which allows IOMMU
312 to inject interrupts directly into guest.
313 This mode requires kvm-amd.avic=1.
314 (Default when IOMMU HW support is present.)
315
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 amijoy.map= [HW,JOY] Amiga joystick support
317 Map of devices attached to JOY0DAT and JOY1DAT
318 Format: <a>,<b>
Tom Saeger17521182017-10-10 12:36:23 -0500319 See also Documentation/input/joydev/joystick.rst
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320
321 analog.map= [HW,JOY] Analog joystick and gamepad support
322 Specifies type or capabilities of an analog joystick
323 connected to one of 16 gameports
324 Format: <type1>,<type2>,..<type16>
325
Randy Dunlapa9913042005-10-23 12:57:11 -0700326 apc= [HW,SPARC]
327 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 Format: noidle
329 Disable APC CPU standby support. SPARCstation-Fox does
330 not play well with APC CPU idle - disable it if you have
331 APC and your system crashes randomly.
332
Dou Liyang64e05d12017-12-04 12:03:13 +0800333 apic= [APIC,X86] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700334 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700335 Format: { quiet (default) | verbose | debug }
336 Change the amount of debugging information output
337 when initialising the APIC and IO-APIC components.
Dou Liyang64e05d12017-12-04 12:03:13 +0800338 For X86-32, this can also be used to specify an APIC
339 driver name.
340 Format: apic=driver_name
341 Examples: apic=bigsmp
Randy Dunlapa9913042005-10-23 12:57:11 -0700342
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100343 apic_extnmi= [APIC,X86] External NMI delivery setting
344 Format: { bsp (default) | all | none }
345 bsp: External NMI is delivered only to CPU 0
346 all: External NMIs are broadcast to all CPUs as a
347 backup of CPU 0
348 none: External NMI is masked for all CPUs. This is
349 useful so that a dump capture kernel won't be
350 shot down by NMI
351
Brian Haleyb0f83b22010-02-04 13:36:50 -0800352 autoconf= [IPV6]
353 See Documentation/networking/ipv6.txt.
354
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
363
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700365 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
369
370 ataflop= [HW,M68k]
371
372 atarimouse= [HW,MOUSE] Atari Mouse
373
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
375 EzKey and similar keyboards
376
377 atkbd.reset= [HW] Reset keyboard during initialization
378
Randy Dunlapa9913042005-10-23 12:57:11 -0700379 atkbd.set= [HW] Select keyboard code set
380 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381
382 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
383 keyboards
384
385 atkbd.softraw= [HW] Choose between synthetic and real raw mode
386 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700387
388 atkbd.softrepeat= [HW]
389 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400391 audit= [KNL] Enable the audit sub-system
392 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500393 0 - kernel audit is disabled and can not be enabled
394 until the next reboot
395 unset - kernel audit is initialized but disabled and
396 will be fully enabled by the userspace auditd.
397 1 - kernel audit is initialized and partially enabled,
398 storing at most audit_backlog_limit messages in
399 RAM until it is fully enabled by the userspace
400 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400401 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400402
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400403 audit_backlog_limit= [KNL] Set the audit queue size limit.
404 Format: <int> (must be >=0)
405 Default: 64
406
Alex Thorlton1c532e02016-03-31 14:18:29 -0500407 bau= [X86_UV] Enable the BAU on SGI UV. The default
408 behavior is to disable the BAU (i.e. bau=0).
409 Format: { "0" | "1" }
410 0 - Disable the BAU.
411 1 - Enable the BAU.
412 unset - Disable the BAU.
413
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414 baycom_epp= [HW,AX25]
415 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700416
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
418 Format: <io>,<mode>
419 See header of drivers/net/hamradio/baycom_par.c.
420
Randy Dunlapa9913042005-10-23 12:57:11 -0700421 baycom_ser_fdx= [HW,AX25]
422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423 Format: <io>,<irq>,<mode>[,<baud>]
424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
425
Randy Dunlapa9913042005-10-23 12:57:11 -0700426 baycom_ser_hdx= [HW,AX25]
427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428 Format: <io>,<irq>,<mode>
429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
430
Paul Gortmaker080506a2013-09-30 13:45:19 -0700431 blkdevparts= Manual partition parsing of block device(s) for
432 embedded devices based on command line input.
433 See Documentation/block/cmdline-partition.txt
434
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700435 boot_delay= Milliseconds to delay each printk during boot.
436 Values larger than 10 seconds (10000) are changed to
437 no delay (0).
438 Format: integer
439
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700440 bootmem_debug [KNL] Enable bootmem allocator debug messages.
441
Huang Yinga3e2acc2016-06-29 13:04:29 -0700442 bert_disable [ACPI]
443 Disable BERT OS support on buggy BIOSes.
444
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700446 bttv.radio= Most important insmod options are available as
447 kernel args too.
Tom Saegera405ed82017-10-10 12:36:37 -0500448 bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
Paul Bolle395cf962011-08-15 02:02:26 +0200449 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000451 bulk_remove=off [PPC] This parameter disables the use of the pSeries
452 firmware feature for flushing multiple hpte entries
453 at a time.
454
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455 c101= [NET] Moxa C101 synchronous serial card
456
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700457 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 Sometimes CPU hardware bugs make them report the cache
459 size incorrectly. The kernel will attempt work arounds
460 to fix known problems, but for some CPUs it is not
461 possible to determine what the correct size should be.
462 This option provides an override for these situations.
463
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300464 ca_keys= [KEYS] This parameter identifies a specific key(s) on
465 the system trusted keyring to be used for certificate
466 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300467 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300468
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700469 cca= [MIPS] Override the kernel pages' cache coherency
470 algorithm. Accepted values range from 0 to 7
471 inclusive. See arch/mips/include/asm/pgtable-bits.h
472 for platform specific values (SB1, Loongson3 and
473 others).
474
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100475 ccw_timeout_log [S390]
476 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477
Paul Menage8bab8dd2008-04-04 14:29:57 -0700478 cgroup_disable= [KNL] Disable a particular controller
479 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800480 The effects of cgroup_disable=foo are:
481 - foo isn't auto-mounted if you mount all cgroups in
482 a single hierarchy
483 - foo isn't visible as an individually mountable
484 subsystem
485 {Currently only "memory" controller deal with this and
486 cut the overhead, others just disable the usage. So
487 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700488
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500489 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
490 Format: { controller[,controller...] | "all" }
491 Like cgroup_disable, but only applies to cgroup v1;
492 the blacklisted controllers remain available in cgroup2.
493
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800494 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
495 Format: <string>
496 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800497 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800498
Linus Torvalds1da177e2005-04-16 15:20:36 -0700499 checkreqprot [SELINUX] Set initial checkreqprot flag value.
500 Format: { "0" | "1" }
501 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700502 0 -- check protection applied by kernel (includes
503 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 1 -- check protection requested by application.
505 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700506 Value can be changed at runtime via
507 /selinux/checkreqprot.
508
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100509 cio_ignore= [S390]
510 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700511 clk_ignore_unused
512 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700513 Prevents the clock framework from automatically gating
514 clocks that have not been explicitly enabled by a Linux
515 device driver but are enabled in hardware at reset or
516 by the bootloader/firmware. Note that this does not
517 force such clocks to be always-on nor does it reserve
518 those clocks in any way. This parameter is useful for
519 debug and development, but should not be needed on a
520 platform with proper driver support. For more
521 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100522
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700523 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700524 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200525 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700526 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200527 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 Format: { pit | tsc | cyclone | pmtmr }
529
John Stultz592913e2010-07-13 17:56:20 -0700530 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700531 Format: <string>
532 Override the default clocksource and use the clocksource
533 with the name specified.
534 Some clocksource names to choose from, depending on
535 the platform:
536 [all] jiffies (this is the base, fallback clocksource)
537 [ACPI] acpi_pm
538 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
539 pxa_timer,timer3,32k_counter,timer0_1
Alok Kataria9863c902010-08-23 14:49:11 -0700540 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700541 scx200_hrt on Geode; cyclone on IBM x440
542 [MIPS] MIPS
543 [PARISC] cr16
544 [S390] tod
545 [SH] SuperH
546 [SPARC64] tick
547 [X86-64] hpet,tsc
548
Will Deacon46fd5c62016-06-27 17:30:13 +0100549 clocksource.arm_arch_timer.evtstrm=
550 [ARM,ARM64]
551 Format: <bool>
552 Enable/disable the eventstream feature of the ARM
553 architected timer so that code using WFE-based polling
554 loops can be debugged more effectively on production
555 systems.
556
Andi Kleenac72e782008-01-30 13:33:21 +0100557 clearcpuid=BITNUM [X86]
558 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100559 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800560 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100561 stable over kernel options, but the vendor specific
562 ones should be.
563 Also note that user programs calling CPUID directly
564 or using the feature without checking anything
565 will still see it. This just prevents it from
566 being used by the kernel or shown in /proc/cpuinfo.
567 Also note the kernel might malfunction if you disable
568 some critical bits.
569
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700570 cma=nn[MG]@[start[MG][-end[MG]]]
571 [ARM,X86,KNL]
572 Sets the size of kernel global memory area for
573 contiguous memory allocations and optionally the
574 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700575 memory allocations. A value of 0 disables CMA
576 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100577 include/linux/dma-contiguous.h
578
Robert Jennings14f966e2009-04-15 05:55:32 +0000579 cmo_free_hint= [PPC] Format: { yes | no }
580 Specify whether pages are marked as being inactive
581 when they are freed. This is used in CMO environments
582 to determine OS memory pressure for page stealing by
583 a hypervisor.
584 Default: yes
585
Marek Szyprowskic7909502011-12-29 13:09:51 +0100586 coherent_pool=nn[KMG] [ARM,KNL]
587 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200588 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100589
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530590 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100591 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100592 Range: 0 - 8192
593 Default: 64
594
Linus Torvalds1da177e2005-04-16 15:20:36 -0700595 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700596 Format:
597 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598
599 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
600 Format: <io>[,<irq>]
601
Randy Dunlapa9913042005-10-23 12:57:11 -0700602 com90xx= [HW,NET]
603 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 Format: <io>[,<irq>[,<memstart>]]
605
606 condev= [HW,S390] console device
607 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700608
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 console= [KNL] Output console device and options.
610
611 tty<n> Use the virtual console device <n>.
612
613 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800614 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800616 the form "bbbbpnf", where "bbbb" is the baud rate,
617 "p" is parity ("n", "o", or "e"), "n" is number of
618 bits, and "f" is flow control ("r" for RTS or
619 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620
Jani Nikulae52347b2016-11-03 12:10:10 +0200621 See Documentation/admin-guide/serial-console.rst for more
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800622 information. See
623 Documentation/networking/netconsole.txt for an
624 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700626 uart[8250],io,<addr>[,options]
627 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900628 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400629 uart[8250],mmio32,<addr>[,options]
630 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 Start an early, polled-mode console on the 8250/16550
632 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400633 switching to the matching ttyS device later.
634 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900635 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
636 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
637 to be equivalent to 'mmio'. 'options' are specified in
638 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400639 the h/w is not re-initialized.
640
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500641 hvc<n> Use the hypervisor console device <n>. This is for
642 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700644 If the device connected to the port is not a TTY but a braille
645 device, prepend "brl," before the device type, for instance
646 console=brl,ttyS0
647 For now, only VisioBraille is supported.
648
Sergey Senozhatskycca10d52017-12-21 14:41:49 +0900649 console_msg_format=
650 [KNL] Change console messages format
651 default
652 By default we print messages on consoles in
653 "[time stamp] text\n" format (time stamp may not be
654 printed, depending on CONFIG_PRINTK_TIME or
655 `printk_time' param).
656 syslog
657 Switch to syslog format: "<%u>[time stamp] text\n"
658 IOW, each message will have a facility and loglevel
659 prefix. The format is similar to one used by syslog()
660 syscall, or to executing "dmesg -S --raw" or to reading
661 from /proc/kmsg.
662
Daniel Mackf324edc2009-06-16 15:33:52 -0700663 consoleblank= [KNL] The console blank (screen saver) timeout in
Daniel Xuac0a3142017-09-18 22:21:25 -0700664 seconds. A value of 0 disables the blank timer.
665 Defaults to 0.
Daniel Mackf324edc2009-06-16 15:33:52 -0700666
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800667 coredump_filter=
668 [KNL] Change the default value for
669 /proc/<pid>/coredump_filter.
670 See also Documentation/filesystems/proc.txt.
671
Leo Yan62a31ce2017-06-05 14:15:12 -0600672 coresight_cpu_debug.enable
673 [ARM,ARM64]
674 Format: <bool>
675 Enable/disable the CPU sampling based debugging.
676 0: default value, disable debugging
677 1: enable debugging at boot time
678
Len Brown62027ae2011-04-01 18:13:10 -0400679 cpuidle.off=1 [CPU_IDLE]
680 disable the cpuidle sub-system
681
Len Brownd82f2692017-02-28 16:44:16 -0500682 cpufreq.off=1 [CPU_FREQ]
683 disable the cpufreq sub-system
684
Len Brownd68921f2015-05-11 17:27:09 -0400685 cpu_init_udelay=N
686 [X86] Delay for N microsec between assert and de-assert
687 of APIC INIT to start processors. This delay occurs
688 on every CPU online, such as boot, and resume from suspend.
689 Default: 10000
690
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700692 Format:
693 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800695 crashkernel=size[KMG][@offset[KMG]]
696 [KNL] Using kexec, Linux can switch to a 'crash kernel'
697 upon panic. This parameter reserves the physical
698 memory region [offset, offset + size] for that kernel
699 image. If '@offset' is omitted, then a suitable offset
700 is selected automatically. Check
701 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700702
Bernhard Wallefb391592007-10-18 23:41:02 -0700703 crashkernel=range1:size1[,range2:size2,...][@offset]
704 [KNL] Same as above, but depends on the memory
705 in the running system. The syntax of range is
706 start-[end] where start and end are both
707 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800708 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700709
Yinghai Luadbc7422013-04-15 22:23:48 -0700710 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700711 [KNL, x86_64] range could be above 4G. Allow kernel
712 to allocate physical memory region from top, so could
713 be above 4G if system have more than 4G ram installed.
714 Otherwise memory region will be allocated below 4G, if
715 available.
716 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700717 crashkernel=size[KMG],low
718 [KNL, x86_64] range under 4G. When crashkernel=X,high
719 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700720 above 4G, that cause second kernel crash on system
721 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800722 requires at least 64M+32K low memory, also enough extra
723 low memory is needed to make sure DMA buffers for 32-bit
724 devices won't run out. Kernel would try to allocate at
725 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700726 This one let user to specify own low range under 4G
727 for second kernel instead.
728 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700729 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700730 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700731
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100732 cryptomgr.notests
733 [KNL] Disable crypto self-tests
734
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735 cs89x0_dma= [HW,NET]
736 Format: <dma>
737
738 cs89x0_media= [HW,NET]
739 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700740
Randy Dunlapa9913042005-10-23 12:57:11 -0700741 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742 See header of drivers/s390/block/dasd_devmap.c.
743
744 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
745 (one device per port)
746 Format: <port#>,<type>
Tom Saeger17521182017-10-10 12:36:23 -0500747 See also Documentation/input/devices/joystick-parport.rst
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748
Thomas Renningera648ec02010-08-06 16:11:02 +0200749 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
Steffen Maier787e3072017-06-14 12:24:12 +0200750 time. See
751 Documentation/admin-guide/dynamic-debug-howto.rst for
Jim Cromie29e36c92012-04-27 14:30:41 -0600752 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200753
Linus Torvalds1da177e2005-04-16 15:20:36 -0700754 debug [KNL] Enable kernel debugging (events log level).
755
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700756 debug_locks_verbose=
757 [KNL] verbose self-tests
758 Format=<0|1>
759 Print debugging info while doing the locking API
760 self-tests.
761 We default to 0 (no extra messages), setting it to
762 1 will print _a lot_ more information - normally
763 only useful to kernel developers.
764
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700765 debug_objects [KNL] Enable object debugging
766
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500767 no_debug_objects
768 [KNL] Disable object debugging
769
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800770 debug_guardpage_minorder=
771 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
772 parameter allows control of the order of pages that will
773 be intentionally kept free (and hence protected) by the
774 buddy allocator. Bigger value increase the probability
775 of catching random memory corruption, but reduce the
776 amount of memory for normal system use. The maximum
777 possible value is MAX_ORDER/2. Setting this parameter
778 to 1 or 2 should be enough to identify most random
779 memory corruption problems caused by bugs in kernel or
780 driver code when a CPU writes to (or reads from) a
781 random memory location. Note that there exists a class
782 of memory corruptions problems caused by buggy H/W or
783 F/W or by drivers badly programing DMA (basically when
784 memory is written at bus level and the CPU MMU is
785 bypassed) which are not detectable by
786 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
787 tracking down these problems.
788
Joonsoo Kim031bc572014-12-12 16:55:52 -0800789 debug_pagealloc=
790 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
791 parameter enables the feature at boot time. In
792 default, it is disabled. We can avoid allocating huge
793 chunk of memory for debug pagealloc if we don't enable
794 it at boot time and the system will work mostly same
795 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
796 on: enable the feature
797
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200798 debugpat [X86] Enable PAT debugging
799
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200800 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801 Format: <area>[,<node>]
802 See also Documentation/networking/decnet.txt.
803
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700804 default_hugepagesz=
805 [same as hugepagesz=] The size of the default
806 HugeTLB page size. This is the size represented by
807 the legacy /proc/ hugepages APIs, used for SHM, and
808 default size when mounting hugetlbfs filesystems.
809 Defaults to the default architecture's huge page size
810 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700811
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 dhash_entries= [KNL]
813 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700814
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000815 disable_1tb_segments [PPC]
816 Disables the use of 1TB hash page table segments. This
817 causes the kernel to fall back to 256MB segments which
818 can be useful when debugging issues that require an SLB
819 miss to occur.
820
Brian Haleyb0f83b22010-02-04 13:36:50 -0800821 disable= [IPV6]
822 See Documentation/networking/ipv6.txt.
823
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530824 disable_radix [PPC]
825 Disable RADIX MMU mode on POWER9
826
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900827 disable_cpu_apicid= [X86,APIC,SMP]
828 Format: <int>
829 The number of initial APIC ID for the
830 corresponding CPU to be disabled at boot,
831 mostly used for the kdump 2nd kernel to
832 disable BSP to wake up multiple CPUs without
833 causing system reset or hang due to sending
834 INIT from AP to BSP.
835
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000836 disable_ddw [PPC/PSERIES]
837 Disable Dynamic DMA Window support. Use this if
838 to workaround buggy firmware.
839
Brian Haleyb0f83b22010-02-04 13:36:50 -0800840 disable_ipv6= [IPV6]
841 See Documentation/networking/ipv6.txt.
842
Yinghai Lu95ffa242008-04-29 03:52:33 -0700843 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700844 The kernel tries to adjust MTRR layout from continuous
845 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700846 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700847
Yinghai Lu093af8d2008-01-30 13:33:32 +0100848 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100849 By default the kernel will trim any uncacheable
850 memory out of your available memory pool based on
851 MTRR settings. This parameter disables that behavior,
852 possibly causing your machine to run very slowly.
853
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530854 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700855 Disable PIN 1 of APIC timer
856 Can be useful to work around chipset bugs.
857
Prarit Bhargavace14c582015-08-25 13:34:53 -0400858 dis_ucode_ldr [X86] Disable the microcode loader.
859
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700860 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
861 this option disables the debugging code at boot.
862
863 dma_debug_entries=<number>
864 This option allows to tune the number of preallocated
865 entries for DMA-API debugging code. One entry is
866 required per DMA-API allocation. Use this if the
867 DMA-API debugging code disables itself because the
868 architectural default is too low.
869
Joerg Roedel1745de52009-05-22 21:49:51 +0200870 dma_debug_driver=<driver_name>
871 With this option the DMA-API debugging driver
872 filter feature can be enabled at boot time. Just
873 pass the driver to filter for as the parameter.
874 The filter can be disabled or changed to another
875 driver later using sysfs.
876
Jani Nikula53fd40a2017-09-12 11:19:26 +0300877 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
Bob Paauwe96206e22015-08-27 10:04:13 -0700878 Broken monitors, graphic adapters, KVMs and EDIDless
879 panels may send no or incorrect EDID data sets.
880 This parameter allows to specify an EDID data sets
881 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100882 Generic built-in EDID data sets are used, if one of
883 edid/1024x768.bin, edid/1280x1024.bin,
884 edid/1680x1050.bin, or edid/1920x1080.bin is given
885 and no file with the same name exists. Details and
886 instructions how to build your own EDID data are
887 available in Documentation/EDID/HOWTO.txt. An EDID
888 data set will only be used for a particular connector,
889 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700890 name. Each connector may use a unique EDID data
891 set by separating the files with a comma. An EDID
892 data set with no connector name will be used for
893 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100894
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895 dscc4.setup= [NET]
896
Nicholas Piggina2b05b72017-05-11 21:24:41 +1000897 dt_cpu_ftrs= [PPC]
898 Format: {"off" | "known"}
899 Control how the dt_cpu_ftrs device-tree binding is
900 used for CPU feature discovery and setup (if it
901 exists).
902 off: Do not use it, fall back to legacy cpu table.
903 known: Do not pass through unknown features to guests
904 or userspace, only those that the kernel is aware of.
905
Lukas Wunner58c54752016-11-12 21:32:36 +0000906 dump_apple_properties [X86]
907 Dump name and content of EFI device properties on
908 x86 Macs. Useful for driver authors to determine
909 what data is available or for reverse-engineering.
910
Jim Cromie29e36c92012-04-27 14:30:41 -0600911 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
912 module.dyndbg[="val"]
913 Enable debug messages at boot time. See
Steffen Maier787e3072017-06-14 12:24:12 +0200914 Documentation/admin-guide/dynamic-debug-howto.rst
915 for details.
Jim Cromie29e36c92012-04-27 14:30:41 -0600916
Dave Hansen8c3641e2015-06-07 11:37:02 -0700917 nompx [X86] Disables Intel Memory Protection Extensions.
918 See Documentation/x86/intel_mpx.txt for more
919 information about the feature.
920
Dave Hansen06976942016-02-12 13:02:29 -0800921 nopku [X86] Disable Memory Protection Keys CPU feature found
922 in some Intel CPUs.
923
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700924 module.async_probe [KNL]
925 Enable asynchronous probe on this module.
926
Mark Salter56aeeba2014-04-07 15:39:53 -0700927 early_ioremap_debug [KNL]
928 Enable debug messages in early_ioremap support. This
929 is useful for tracking down temporary early mappings
930 which are not unmapped.
931
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700932 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500933
Prarit Bhargava0231d002018-01-18 10:09:51 -0500934 [ARM64] The early console is determined by the
935 stdout-path property in device tree's chosen node,
936 or determined by the ACPI SPCR table.
937
938 [X86] When used with no options the early console is
939 determined by the ACPI SPCR table.
Scott Wood5664f762015-09-14 19:54:07 -0500940
Scott Telfordc41251b2016-09-22 16:58:16 +0100941 cdns,<addr>[,options]
942 Start an early, polled-mode console on a Cadence
943 (xuartps) serial port at the specified address. Only
944 supported option is baud rate. If baud rate is not
945 specified, the serial port must already be setup and
946 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +0200947
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700948 uart[8250],io,<addr>[,options]
949 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700950 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300951 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400952 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700953 Start an early, polled-mode console on the 8250/16550
954 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700955 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300956 (mmio) or 32-bit (mmio32 or mmio32be).
957 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
958 to be equivalent to 'mmio'. 'options' are specified
959 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400960 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700961
Rob Herring0d3c6732014-04-18 17:19:57 -0500962 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -0600963 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -0500964 Start an early, polled-mode console on a pl011 serial
965 port at the specified address. The pl011 serial port
966 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -0600967 yet supported. If 'mmio32' is specified, then only
968 the driver will use only 32-bit accessors to read/write
969 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -0500970
Andreas Färber736d5532016-03-06 12:21:24 +0100971 meson,<addr>
972 Start an early, polled-mode console on a meson serial
973 port at the specified address. The serial port must
974 already be setup and configured. Options are not yet
975 supported.
976
Stephen Boyd0efe7292014-09-15 17:22:51 -0700977 msm_serial,<addr>
978 Start an early, polled-mode console on an msm serial
979 port at the specified address. The serial port
980 must already be setup and configured. Options are not
981 yet supported.
982
983 msm_serial_dm,<addr>
984 Start an early, polled-mode console on an msm serial
985 dm port at the specified address. The serial port
986 must already be setup and configured. Options are not
987 yet supported.
988
Andreas Färbere36361d2017-06-19 03:46:40 +0200989 owl,<addr>
990 Start an early, polled-mode console on a serial port
991 of an Actions Semi SoC, such as S500 or S900, at the
992 specified address. The serial port must already be
993 setup and configured. Options are not yet supported.
994
Rob Herringd50d7262014-04-18 17:19:58 -0500995 smh Use ARM semihosting calls for early console.
996
Tomasz Figab94ba032015-01-23 14:47:41 +0100997 s3c2410,<addr>
998 s3c2412,<addr>
999 s3c2440,<addr>
1000 s3c6400,<addr>
1001 s5pv210,<addr>
1002 exynos4210,<addr>
1003 Use early console provided by serial driver available
1004 on Samsung SoCs, requires selecting proper type and
1005 a correct base address of the selected UART port. The
1006 serial port must already be setup and configured.
1007 Options are not yet supported.
1008
Martin Blumenstinglec84aa02016-12-11 21:42:23 +01001009 lantiq,<addr>
1010 Start an early, polled-mode console on a lantiq serial
1011 (lqasc) port at the specified address. The serial port
1012 must already be setup and configured. Options are not
1013 yet supported.
1014
Stefan Agner1d59b382015-10-17 00:45:55 -07001015 lpuart,<addr>
1016 lpuart32,<addr>
1017 Use early console provided by Freescale LP UART driver
1018 found on Freescale Vybrid and QorIQ LS1021A processors.
1019 A valid base address must be provided, and the serial
1020 port must already be setup and configured.
1021
Andre Przywaraf7c864e2017-05-04 00:49:36 +01001022 ar3700_uart,<addr>
Wilson Ding30530792016-02-16 19:14:53 +01001023 Start an early, polled-mode console on the
1024 Armada 3700 serial port at the specified
1025 address. The serial port must already be setup
1026 and configured. Options are not yet supported.
1027
Heiko Carstens89175cf2017-01-11 09:14:52 +01001028 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001030 earlyprintk=efi
Heiko Carstens89175cf2017-01-11 09:14:52 +01001031 earlyprintk=sclp
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001032 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001034 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001035 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001036 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001037 earlyprintk=pciserial,bus:device.function[,baudrate]
Lu Baolu1b5aeeb2017-03-21 16:01:31 +08001038 earlyprintk=xdbc[xhciController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001039
Dave Hansen147ea092013-04-10 14:03:38 -07001040 earlyprintk is useful when the kernel crashes before
1041 the normal console is initialized. It is not enabled by
1042 default because it has some cosmetic problems.
1043
Randy Dunlapa9913042005-10-23 12:57:11 -07001044 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045 takes over.
1046
Matt Fleming72548e82013-10-04 09:36:56 +01001047 Only one of vga, efi, serial, or usb debug port can
1048 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049
Dave Hansen147ea092013-04-10 14:03:38 -07001050 Currently only ttyS0 and ttyS1 may be specified by
1051 name. Other I/O ports may be explicitly specified
1052 on some architectures (x86 and arm at least) by
1053 replacing ttySn with an I/O port address, like this:
1054 earlyprintk=serial,0x1008,115200
1055 You can find the port for a given device in
1056 /proc/tty/driver/serial:
1057 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058
1059 Interaction with the standard serial driver is not
1060 very good.
1061
Matt Fleming72548e82013-10-04 09:36:56 +01001062 The VGA and EFI output is eventually overwritten by
1063 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001065 The xen output can only be used by Xen PV guests.
1066
Heiko Carstens89175cf2017-01-11 09:14:52 +01001067 The sclp output can only be used on s390.
1068
Chen, Gongc700f012013-12-06 01:17:08 -05001069 edac_report= [HW,EDAC] Control how to report EDAC event
1070 Format: {"on" | "off" | "force"}
1071 on: enable EDAC to report H/W event. May be overridden
1072 by other higher priority error reporting module.
1073 off: disable H/W event reporting through EDAC.
1074 force: enforce the use of EDAC to report H/W event.
1075 default: on.
1076
Jason Wessel97311912010-05-20 21:04:30 -05001077 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1078 ekgdboc=kbd
1079
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001080 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001081 the boot argument: earlyprintk=vga
1082
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001084 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001085
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001086 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001087 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001088 old_map [X86-64]: switch to the old ioremap-based EFI
1089 runtime services mapping. 32-bit still uses this one by
1090 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001091 nochunk: disable reading files in "chunks" in the EFI
1092 boot stub, as chunking can cause problems with some
1093 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001094 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001095 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001096
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001097 efi_no_storage_paranoia [EFI; X86]
1098 Using this parameter you can use more than 50% of
1099 your efi variable storage. Use this parameter only if
1100 you are really sure that your UEFI does sane gc and
1101 fulfills the spec otherwise your board may brick.
1102
Taku Izumi0f96a992015-09-30 23:01:56 +09001103 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1104 Add arbitrary attribute to specific memory range by
1105 updating original EFI memory map.
1106 Region of memory which aa attribute is added to is
1107 from ss to ss+nn.
1108 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1109 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1110 attribute is added to range 0x100000000-0x180000000 and
1111 0x10a0000000-0x1120000000.
1112
1113 Using this parameter you can do debugging of EFI memmap
1114 related feature. For example, you can do debugging of
1115 Address Range Mirroring feature even if your box
1116 doesn't support it.
1117
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001118 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1119 that is to be dynamically loaded by Linux. If there are
1120 multiple variables with the same name but with different
1121 vendor GUIDs, all of them will be loaded. See
1122 Documentation/acpi/ssdt-overlays.txt for details.
1123
1124
Linus Torvalds1da177e2005-04-16 15:20:36 -07001125 eisa_irq_edge= [PARISC,HW]
1126 See header of drivers/parisc/eisa.c.
1127
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001128 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001130 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131
1132 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001133 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001134 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001135 Documentation/block/deadline-iosched.txt for details.
1136
Michael Holzheud3bf37952011-10-30 15:16:37 +01001137 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001138 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001139 image elf header and optionally the size. Generally
1140 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001141 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001143 enable_mtrr_cleanup [X86]
1144 The kernel tries to adjust MTRR layout from continuous
1145 to discrete, to make X server driver able to add WB
1146 entry later. This parameter enables that.
1147
Randy Dunlapca1eda22009-05-06 16:02:58 -07001148 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001149 Enable PIN 1 of APIC timer
1150 Can be useful to work around chipset bugs
1151 (in particular on some ATI chipsets).
1152 The kernel tries to set a reasonable default.
1153
Linus Torvalds1da177e2005-04-16 15:20:36 -07001154 enforcing [SELINUX] Set initial enforcing status.
1155 Format: {"0" | "1"}
1156 See security/selinux/Kconfig help text.
1157 0 -- permissive (log only, no denials).
1158 1 -- enforcing (deny and log).
1159 Default value is 0.
1160 Value can be changed at runtime via /selinux/enforce.
1161
Huang Yinga08f82d2010-05-18 14:35:21 +08001162 erst_disable [ACPI]
1163 Disable Error Record Serialization Table (ERST)
1164 support.
1165
Linus Torvalds1da177e2005-04-16 15:20:36 -07001166 ether= [HW,NET] Ethernet cards parameters
1167 This option is obsoleted by the "netdev=" option, which
1168 has equivalent usage. See its documentation for details.
1169
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001170 evm= [EVM]
1171 Format: { "fix" }
1172 Permit 'security.evm' to be updated regardless of
1173 current integrity status.
1174
Akinobu Mitade1ba092006-12-08 02:39:42 -08001175 failslab=
1176 fail_page_alloc=
1177 fail_make_request=[KNL]
1178 General fault injection mechanism.
1179 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001180 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001181
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001183 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184
Alex Chiangf13ae302008-05-08 14:03:23 -06001185 force_pal_cache_flush
1186 [IA-64] Avoid check_sal_cache_flush which may hang on
1187 buggy SAL_CACHE_FLUSH implementations. Using this
1188 parameter will force ia64_sal_cache_flush to call
1189 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1190
Chris Bainbridge69f23662014-03-07 18:40:42 +07001191 forcepae [X86-32]
1192 Forcefully enable Physical Address Extension (PAE).
1193 Many Pentium M systems disable PAE but may have a
1194 functionally usable PAE implementation.
1195 Warning: use of this parameter will taint the kernel
1196 and may cause unknown problems.
1197
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001198 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001199 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001200 as early as possible in order to facilitate early
1201 boot debugging.
1202
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001203 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001204 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001205 If no parameter is passed, ftrace will dump
1206 buffers of all CPUs, but if you pass orig_cpu, it will
1207 dump only the buffer of the CPU that triggered the
1208 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001209
1210 ftrace_filter=[function-list]
1211 [FTRACE] Limit the functions traced by the function
1212 tracer at boot up. function-list is a comma separated
1213 list of functions. This list can be changed at run
1214 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001215 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001216
1217 ftrace_notrace=[function-list]
1218 [FTRACE] Do not trace the functions specified in
1219 function-list. This list can be changed at run time
1220 by the set_ftrace_notrace file in the debugfs
1221 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001222
Stefan Assmann369bc182009-10-12 22:17:21 +02001223 ftrace_graph_filter=[function-list]
1224 [FTRACE] Limit the top level callers functions traced
1225 by the function graph tracer at boot up.
1226 function-list is a comma separated list of functions
1227 that can be changed at run time by the
1228 set_graph_function file in the debugfs tracing directory.
1229
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001230 ftrace_graph_notrace=[function-list]
1231 [FTRACE] Do not trace from the functions specified in
1232 function-list. This list is a comma separated list of
1233 functions that can be changed at run time by the
1234 set_graph_notrace file in the debugfs tracing directory.
1235
Todd Brandt65a50c62017-03-02 16:12:15 -08001236 ftrace_graph_max_depth=<uint>
1237 [FTRACE] Used with the function graph tracer. This is
1238 the max depth it will trace into a function. This value
1239 can be changed at run time by the max_graph_depth file
1240 in the tracefs tracing directory. default: 0 (no limit)
1241
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242 gamecon.map[2|3]=
1243 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1244 support via parallel port (up to 5 devices per port)
1245 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
Tom Saeger17521182017-10-10 12:36:23 -05001246 See also Documentation/input/devices/joystick-parport.rst
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247
1248 gamma= [HW,DRM]
1249
Yinghai Luaaf23042008-01-30 13:33:09 +01001250 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1251 Format: off | on
1252 default: on
1253
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001254 gcov_persist= [GCOV] When non-zero (default), profiling data for
1255 kernel modules is saved and remains accessible via
1256 debugfs, even when the module is unloaded/reloaded.
1257 When zero, profiling data is discarded and associated
1258 debugfs files are removed at module unload time.
1259
Thomas Gleixner47512cf2017-02-15 11:11:50 +01001260 goldfish [X86] Enable the goldfish android emulator platform.
1261 Don't use this when you are not running on the
1262 android emulator
1263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001265 invalid Protective MBR to be treated as GPT. If the
1266 primary GPT is corrupted, it enables the backup/alternate
1267 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001268
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001269 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1270 the "Enable 0" bit of the configuration register.
1271 Format: 0 | 1
1272 Default: 0
1273 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1274 the "Enable 0" bit of the configuration register.
1275 Format: 0 | 1
1276 Default: 0
1277 grcan.select= [HW] Select which physical interface to use.
1278 Format: 0 | 1
1279 Default: 0
1280 grcan.txsize= [HW] Sets the size of the tx buffer.
1281 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1282 Default: 1024
1283 grcan.rxsize= [HW] Sets the size of the rx buffer.
1284 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1285 Default: 1024
1286
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001287 gpio-mockup.gpio_mockup_ranges
1288 [HW] Sets the ranges of gpiochip of for this device.
1289 Format: <start1>,<end1>,<start2>,<end2>...
1290
Jiri Kosina55537872015-11-05 18:44:41 -08001291 hardlockup_all_cpu_backtrace=
1292 [KNL] Should the hard-lockup detector generate
1293 backtraces on all cpus.
1294 Format: <integer>
1295
Linus Torvalds1da177e2005-04-16 15:20:36 -07001296 hashdist= [KNL,NUMA] Large hashes allocated during boot
1297 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001298 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001299 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300
1301 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1302
1303 hd= [EIDE] (E)IDE hard drive subsystem geometry
1304 Format: <cyl>,<head>,<sect>
1305
Huang Yingea8c0712010-05-18 14:35:15 +08001306 hest_disable [ACPI]
1307 Disable Hardware Error Source Table (HEST) support;
1308 corresponding firmware-first mode error processing
1309 logic will be disabled.
1310
Linus Torvalds1da177e2005-04-16 15:20:36 -07001311 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1312 size of <nn>. This works even on boxes that have no
1313 highmem otherwise. This also works to reduce highmem
1314 size on bigger boxes.
1315
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001316 highres= [KNL] Enable/disable high resolution timer mode.
1317 Valid parameters: "on", "off"
1318 Default: "on"
1319
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320 hisax= [HW,ISDN]
1321 See Documentation/isdn/README.HiSax.
1322
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001323 hlt [BUGS=ARM,SH]
1324
1325 hpet= [X86-32,HPET] option to control HPET usage
1326 Format: { enable (default) | disable | force |
1327 verbose }
1328 disable: disable HPET and use PIT instead
1329 force: allow force enabled of undocumented chips (ICH4,
1330 VIA, nVidia)
1331 verbose: show contents of HPET registers during setup
1332
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001333 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1334 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1335
Andi Kleenb4718e62008-07-23 21:27:51 -07001336 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1337 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001338 On x86-64 and powerpc, this option can be specified
1339 multiple times interleaved with hugepages= to reserve
1340 huge pages of different sizes. Valid pages sizes on
1341 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001342 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001343
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001344 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1345 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001346 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1347 If specified, z/VM IUCV HVC accepts connections
1348 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001349
James Hoganfdabf522012-10-09 11:00:27 +01001350 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1351 hardware thread id mappings.
1352 Format: <cpu>:<hwthread>
1353
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001354 keep_bootcon [KNL]
1355 Do not unregister boot console at start. This is only
1356 useful for debugging when something happens in the window
1357 between unregistering the boot console and initializing
1358 the real console.
1359
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001360 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001361 or register an additional I2C bus that is not
1362 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001363 Format:
1364 <bus_id>,<clkrate>
1365
Jiri Kosina36d95732008-10-06 02:51:09 -04001366 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001367 i8042.unmask_kbd_data
1368 [HW] Enable printing of interrupt data from the KBD port
1369 (disabled by default, and as a pre-condition
1370 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001372 i8042.dumbkbd [HW] Pretend that controller can only read data from
1373 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374 (Don't attempt to blink the leds)
1375 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001376 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001377 i8042.noloop [HW] Disable the AUX Loopback command while probing
1378 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001380 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1382 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001383 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e19242016-10-01 12:07:35 -07001384 i8042.reset [HW] Reset the controller during init, cleanup and
1385 suspend-to-ram transitions, only during s2r
1386 transitions, or never reset
1387 Format: { 1 | Y | y | 0 | N | n }
1388 1, Y, y: always reset controller
1389 0, N, n: don't ever reset controller
1390 Default: only on s2r transitions on x86; most other
1391 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001393 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394
1395 i810= [HW,DRM]
1396
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001397 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1398 indicates that the driver is running on unsupported
1399 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001400 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1401 does not match list of supported models.
1402 i8k.power_status
1403 [HW] Report power status in /proc/i8k
1404 (disabled by default)
1405 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1406 capability is set.
1407
Carsten Emde4dca20e2012-03-15 15:56:26 +01001408 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001409 [DRM] Invert the sense of the variable that is used to
1410 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001411 brightness value of 0 indicates backlight switched off,
1412 and the maximum of the brightness value sets the backlight
1413 to maximum brightness. If this parameter is set to 0
1414 (default) and the machine requires it, or this parameter
1415 is set to 1, a brightness value of 0 sets the backlight
1416 to maximum brightness, and the maximum of the brightness
1417 value switches the backlight off.
1418 -1 -- never invert brightness
1419 0 -- machine default
1420 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001421
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422 icn= [HW,ISDN]
1423 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1424
David Fries0af80c02009-02-25 20:28:21 +01001425 ide-core.nodma= [HW] (E)IDE subsystem
1426 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001427 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1428 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001429 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001430
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001431 ide-generic.probe-mask= [HW] (E)IDE subsystem
1432 Format: <int>
1433 Probe mask for legacy ISA IDE ports. Depending on
1434 platform up to 6 ports are supported, enabled by
1435 setting corresponding bits in the mask to 1. The
1436 default value is 0x0, which has a special meaning.
1437 On systems that have PCI, it triggers scanning the
1438 PCI bus for the first and the second port, which
1439 are then probed. On systems without PCI the value
1440 of 0x0 enables probing the two first ports as if it
1441 was 0x3.
1442
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001443 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1444 Claim all unknown PCI IDE storage controllers.
1445
Andi Kleenf039b752007-05-02 19:27:12 +02001446 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001447 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001448 Poll forces a polling idle loop that can slightly
1449 improve the performance of waking up a idle CPU, but
1450 will use a lot of power and make the system run hot.
1451 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001452 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001453 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001454 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001455
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001456 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1457 Format: { strict | legacy | 2008 | relaxed }
1458 Default: strict
1459
1460 Choose which programs will be accepted for execution
1461 based on the IEEE 754 NaN encoding(s) supported by
1462 the FPU and the NaN encoding requested with the value
1463 of an ELF file header flag individually set by each
1464 binary. Hardware implementations are permitted to
1465 support either or both of the legacy and the 2008 NaN
1466 encoding mode.
1467
1468 Available settings are as follows:
1469 strict accept binaries that request a NaN encoding
1470 supported by the FPU
1471 legacy only accept legacy-NaN binaries, if supported
1472 by the FPU
1473 2008 only accept 2008-NaN binaries, if supported
1474 by the FPU
1475 relaxed accept any binaries regardless of whether
1476 supported by the FPU
1477
1478 The FPU emulator is always able to support both NaN
1479 encodings, so if no FPU hardware is present or it has
1480 been disabled with 'nofpu', then the settings of
1481 'legacy' and '2008' strap the emulator accordingly,
1482 'relaxed' straps the emulator for both legacy-NaN and
1483 2008-NaN, whereas 'strict' enables legacy-NaN only on
1484 legacy processors and both NaN encodings on MIPS32 or
1485 MIPS64 CPUs.
1486
1487 The setting for ABS.fmt/NEG.fmt instruction execution
1488 mode generally follows that for the NaN encoding,
1489 except where unsupported by hardware.
1490
Ingo Molnar792908222006-12-06 20:40:51 -08001491 ignore_loglevel [KNL]
1492 Ignore loglevel setting - this will print /all/
1493 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001494 We also add it as printk module parameter, so users
1495 could change it dynamically, usually by
1496 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001497
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001498 ignore_rlimit_data
1499 Ignore RLIMIT_DATA setting for data mappings,
1500 print warning at first misuse. Can be changed via
1501 /sys/module/kernel/parameters/ignore_rlimit_data.
1502
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 ihash_entries= [KNL]
1504 Set number of hash buckets for inode cache.
1505
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001506 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001507 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001508 default: "enforce"
1509
Mimi Zohar07f6a792011-03-09 22:25:48 -05001510 ima_appraise_tcb [IMA]
1511 The builtin appraise policy appraises all files
1512 owned by uid=0.
1513
Mimi Zohard68a6fe2016-12-19 16:22:57 -08001514 ima_canonical_fmt [IMA]
1515 Use the canonical format for the binary runtime
1516 measurements, instead of host native format.
1517
Mimi Zohar3323eec2009-02-04 09:06:58 -05001518 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001519 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1520 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001521 default: "sha1"
1522
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001523 The list of supported hash algorithms is defined
1524 in crypto/hash_info.h.
1525
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001526 ima_policy= [IMA]
Mimi Zohar33ce9542017-04-24 12:04:09 -04001527 The builtin policies to load during IMA setup.
Mimi Zohar9e670282018-02-21 11:36:32 -05001528 Format: "tcb | appraise_tcb | secure_boot |
1529 fail_securely"
Mimi Zohar33ce9542017-04-24 12:04:09 -04001530
1531 The "tcb" policy measures all programs exec'd, files
1532 mmap'd for exec, and all files opened with the read
1533 mode bit set by either the effective uid (euid=0) or
1534 uid=0.
1535
1536 The "appraise_tcb" policy appraises the integrity of
1537 all files owned by root. (This is the equivalent
1538 of ima_appraise_tcb.)
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001539
Mimi Zohar503ceae2017-04-21 18:58:27 -04001540 The "secure_boot" policy appraises the integrity
1541 of files (eg. kexec kernel image, kernel modules,
1542 firmware, policy, etc) based on file signatures.
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001543
Mimi Zohar9e670282018-02-21 11:36:32 -05001544 The "fail_securely" policy forces file signature
1545 verification failure also on privileged mounted
1546 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1547 flag.
1548
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001549 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001550 Load a policy which meets the needs of the Trusted
1551 Computing Base. This means IMA will measure all
1552 programs exec'd, files mmap'd for exec, and all files
1553 opened for read by uid=0.
1554
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001555 ima_template= [IMA]
1556 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001557 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001558 Default: "ima-ng"
1559
Roberto Sassuc2426d22014-10-13 14:08:42 +02001560 ima_template_fmt=
1561 [IMA] Define a custom template format.
1562 Format: { "field1|...|fieldN" }
1563
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001564 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1565 Format: <min_file_size>
1566 Set the minimal file size for using asynchronous hash.
1567 If left unspecified, ahash usage is disabled.
1568
1569 ahash performance varies for different data sizes on
1570 different crypto accelerators. This option can be used
1571 to achieve the best performance for a particular HW.
1572
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001573 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1574 Format: <bufsize>
1575 Set hashing buffer size. Default: 4k.
1576
1577 ahash performance varies for different chunk sizes on
1578 different crypto accelerators. This option can be used
1579 to achieve best performance for particular HW.
1580
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581 init= [KNL]
1582 Format: <full_path>
1583 Run specified binary instead of /sbin/init as init
1584 process.
1585
1586 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1587 for working out where the kernel is dying during
1588 startup.
1589
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001590 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1591 initcall functions. Useful for debugging built-in
1592 modules and initcalls.
1593
Linus Torvalds1da177e2005-04-16 15:20:36 -07001594 initrd= [BOOT] Specify the location of the initial ramdisk
1595
Dave Hansenacd547b2016-07-29 09:30:21 -07001596 init_pkru= [x86] Specify the default memory protection keys rights
1597 register contents for all processes. 0x55555554 by
1598 default (disallow access to all but pkey 0). Can
1599 override in debugfs after boot.
1600
Linus Torvalds1da177e2005-04-16 15:20:36 -07001601 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1602 Format: <irq>
1603
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001604 int_pln_enable [x86] Enable power limit notification interrupt
1605
Mimi Zohard726d8d2013-03-18 14:48:02 -04001606 integrity_audit=[IMA]
1607 Format: { "0" | "1" }
1608 0 -- basic integrity auditing messages. (Default)
1609 1 -- additional integrity auditing messages.
1610
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001611 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001612 on
1613 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001614 off
1615 Disable intel iommu driver.
1616 igfx_off [Default Off]
1617 By default, gfx is mapped as normal device. If a gfx
1618 device has a dedicated DMAR unit, the DMAR unit is
1619 bypassed by not enabling DMAR with this option. In
1620 this case, gfx device will use physical address for
1621 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001622 forcedac [x86_64]
1623 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001624 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001625 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001626 than 32-bit addressing. The default is to look
1627 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001628 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001629 strict [Default Off]
1630 With this option on every unmap_single operation will
1631 result in a hardware IOTLB flush operation as opposed
1632 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001633 sp_off [Default Off]
1634 By default, super page will be supported if Intel IOMMU
1635 has the capability. With this option, super page will
1636 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001637 ecs_off [Default Off]
1638 By default, extended context tables will be supported if
1639 the hardware advertises that it has support both for the
1640 extended tables themselves, and also PASID support. With
1641 this option set, extended tables will not be used even
1642 on hardware which claims to support them.
Shaohua Libfd20f12017-04-26 09:18:35 -07001643 tboot_noforce [Default Off]
1644 Do not force the Intel IOMMU enabled under tboot.
1645 By default, tboot will force Intel IOMMU on, which
1646 could harm performance of some high-throughput
1647 devices like 40GBit network cards, even if identity
1648 mapping is enabled.
1649 Note that using this option lowers the security
1650 provided by tboot because it makes the system
1651 vulnerable to DMA attacks.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001652
1653 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1654 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001655 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001656
Dirk Brandewie6be26492013-02-15 22:55:10 +01001657 intel_pstate= [X86]
1658 disable
1659 Do not enable intel_pstate as the default
1660 scaling driver for the supported processors
Rafael J. Wysocki001c76f2016-11-17 23:34:17 +01001661 passive
1662 Use intel_pstate as a scaling driver, but configure it
1663 to work with generic cpufreq governors (instead of
1664 enabling its internal governor). This mode cannot be
1665 used along with the hardware-managed P-states (HWP)
1666 feature.
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001667 force
1668 Enable intel_pstate on systems that prohibit it by default
1669 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1670 instead of acpi-cpufreq may disable platform features, such
1671 as thermal controls and power capping, that rely on ACPI
1672 P-States information being indicated to OSPM and therefore
1673 should be used with caution. This option does not work with
1674 processors that aren't supported by the intel_pstate driver
1675 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001676 no_hwp
1677 Do not enable hardware P state control (HWP)
1678 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001679 hwp_only
1680 Only load intel_pstate on systems which support
1681 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001682 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001683 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1684 Description Table, specifies preferred power management
1685 profile as "Enterprise Server" or "Performance Server",
1686 then this feature is turned on by default.
Srinivas Pandruvada22449c02016-10-25 13:20:43 -07001687 per_cpu_perf_limits
1688 Allow per-logical-CPU P-State performance control limits using
1689 cpufreq sysfs interface
Dirk Brandewie6be26492013-02-15 22:55:10 +01001690
Chris Wrightd1423d52010-07-20 11:06:49 -07001691 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001692 on enable Interrupt Remapping (default)
1693 off disable Interrupt Remapping
1694 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001695 no_x2apic_optout
1696 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001697 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001698
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001699 iomem= Disable strict checking of access to MMIO memory
1700 strict regions from userspace.
1701 relaxed
1702
1703 iommu= [x86]
1704 off
1705 force
1706 noforce
1707 biomerge
1708 panic
1709 nopanic
1710 merge
1711 nomerge
1712 forcesac
1713 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001714 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001715 nobypass [PPC/POWERNV]
1716 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001717
Will Deaconfccb4e32017-01-05 18:38:26 +00001718 iommu.passthrough=
1719 [ARM64] Configure DMA to bypass the IOMMU by default.
1720 Format: { "0" | "1" }
1721 0 - Use IOMMU translation for DMA.
1722 1 - Bypass the IOMMU for DMA.
1723 unset - Use IOMMU translation for DMA.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001724
1725 io7= [HW] IO7 for Marvel based alpha systems
1726 See comment before marvel_specify_io7 in
1727 arch/alpha/kernel/core_marvel.c.
1728
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301729 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001730 0x80
1731 Standard port 0x80 based delay
1732 0xed
1733 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001734 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001735 Simple two microseconds delay
1736 none
1737 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001738
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001740 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001742 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001743 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001744
Marc Zyngier09622892017-10-27 10:34:22 +02001745 irqchip.gicv2_force_probe=
1746 [ARM, ARM64]
1747 Format: <bool>
1748 Force the kernel to look for the second 4kB page
1749 of a GICv2 controller even if the memory range
1750 exposed by the device tree is too small.
1751
Alan Cox200803d2005-06-28 20:45:18 -07001752 irqfixup [HW]
1753 When an interrupt is not handled search all handlers
1754 for it. Intended to get systems with badly broken
1755 firmware running.
1756
1757 irqpoll [HW]
1758 When an interrupt is not handled search all handlers
1759 for it. Also check all handlers each timer
1760 interrupt. Intended to get systems with badly broken
1761 firmware running.
1762
Linus Torvalds1da177e2005-04-16 15:20:36 -07001763 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001764 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765
Frederic Weisbeckerd94d1052017-12-14 19:18:27 +01001766 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
Frederic Weisbeckerb0d40d22017-10-31 04:18:34 +01001767 [Deprecated - use cpusets instead]
1768 Format: [flag-list,]<cpu-list>
Li Zefanb225d442008-11-06 12:53:39 -08001769
Frederic Weisbeckerb0d40d22017-10-31 04:18:34 +01001770 Specify one or more CPUs to isolate from disturbances
1771 specified in the flag list (default: domain):
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772
Frederic Weisbeckerb0d40d22017-10-31 04:18:34 +01001773 nohz
1774 Disable the tick when a single task runs.
1775 domain
1776 Isolate from the general SMP balancing and scheduling
1777 algorithms. Note that performing domain isolation this way
1778 is irreversible: it's not possible to bring back a CPU to
1779 the domains once isolated through isolcpus. It's strongly
1780 advised to use cpusets instead to disable scheduler load
1781 balancing through the "cpuset.sched_load_balance" file.
1782 It offers a much more flexible interface where CPUs can
1783 move in and out of an isolated set anytime.
1784
1785 You can move a process onto or off an "isolated" CPU via
1786 the CPU affinity syscalls or cpuset.
1787 <cpu number> begins at 0 and the maximum value is
1788 "number of CPUs in system - 1".
1789
1790 The format of <cpu-list> is described above.
1791
1792
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793
Randy Dunlapa9913042005-10-23 12:57:11 -07001794 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001795
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001796 ivrs_ioapic [HW,X86_64]
1797 Provide an override to the IOAPIC-ID<->DEVICE-ID
1798 mapping provided in the IVRS ACPI table. For
1799 example, to map IOAPIC-ID decimal 10 to
1800 PCI device 00:14.0 write the parameter as:
1801 ivrs_ioapic[10]=00:14.0
1802
1803 ivrs_hpet [HW,X86_64]
1804 Provide an override to the HPET-ID<->DEVICE-ID
1805 mapping provided in the IVRS ACPI table. For
1806 example, to map HPET-ID decimal 0 to
1807 PCI device 00:14.0 write the parameter as:
1808 ivrs_hpet[0]=00:14.0
1809
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001810 ivrs_acpihid [HW,X86_64]
1811 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1812 mapping provided in the IVRS ACPI table. For
1813 example, to map UART-HID:UID AMD0020:0 to
1814 PCI device 00:14.5 write the parameter as:
1815 ivrs_acpihid[00:14.5]=AMD0020:0
1816
Linus Torvalds1da177e2005-04-16 15:20:36 -07001817 js= [HW,JOY] Analog joystick
Tom Saeger17521182017-10-10 12:36:23 -05001818 See Documentation/input/joydev/joystick.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819
Kees Cook65fe9352016-06-13 15:10:02 -07001820 nokaslr [KNL]
1821 When CONFIG_RANDOMIZE_BASE is set, this disables
1822 kernel and module base offset ASLR (Address Space
1823 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001824
Mark Rutlandb0845ce2017-03-31 15:12:04 -07001825 kasan_multi_shot
1826 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1827 report on every invalid memory access. Without this
1828 parameter KASAN will print report only for the first
1829 invalid access.
1830
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001831 keepinitrd [HW,ARM]
1832
Taku Izumi342332e2016-03-15 14:55:22 -07001833 kernelcore= [KNL,X86,IA-64,PPC]
1834 Format: nn[KMGTPE] | "mirror"
1835 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001836 specifies the amount of memory usable by the kernel
1837 for non-movable allocations. The requested amount is
1838 spread evenly throughout all nodes in the system. The
1839 remaining memory in each node is used for Movable
1840 pages. In the event, a node is too small to have both
1841 kernelcore and Movable pages, kernelcore pages will
1842 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001843 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001844 allocation of pages that may be reclaimed or moved
1845 by the page migration subsystem. This means that
1846 HugeTLB pages may not be allocated from this zone.
1847 Note that allocations like PTEs-from-HighMem still
1848 use the HighMem zone if it exists, and the Normal
1849 zone if it does not.
1850
Taku Izumi342332e2016-03-15 14:55:22 -07001851 Instead of specifying the amount of memory (nn[KMGTPE]),
1852 you can specify "mirror" option. In case "mirror"
1853 option is specified, mirrored (reliable) memory is used
1854 for non-movable allocations and remaining memory is used
1855 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1856 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1857 time.
1858
Jason Wessel4fe1da42010-05-20 21:04:31 -05001859 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1860 Format: <Controller#>[,poll interval]
1861 The controller # is the number of the ehci usb debug
1862 port as it is probed via PCI. The poll interval is
1863 optional and is the number seconds in between
1864 each poll cycle to the debug port in case you need
1865 the functionality for interrupting the kernel with
1866 gdb or control-c on the dbgp connection. When
1867 not using this parameter you use sysrq-g to break into
1868 the kernel debugger.
1869
Jason Wessel84c08fd2010-05-20 21:04:24 -05001870 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001871 Requires a tty driver that supports console polling,
1872 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001873 Serial only format: <serial_device>[,baud]
1874 keyboard only format: kbd
1875 keyboard and serial format: kbd,<serial_device>[,baud]
1876 Optional Kernel mode setting:
1877 kms, kbd format: kms,kbd
1878 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001879
Jason Wessel84c08fd2010-05-20 21:04:24 -05001880 kgdbwait [KGDB] Stop kernel execution and enter the
1881 kernel debugger at the earliest opportunity.
1882
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001883 kmac= [MIPS] korina ethernet MAC address.
1884 Configure the RouterBoard 532 series on-chip
1885 Ethernet adapter MAC address.
1886
Catalin Marinas04f70332009-06-11 13:22:39 +01001887 kmemleak= [KNL] Boot-time kmemleak enable/disable
1888 Valid arguments: on, off
1889 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001890 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1891 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001892
Andre Przywarafef07aa2009-07-10 14:20:35 +02001893 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1894 Default is 0 (don't ignore, but inject #GP)
1895
Xiao Guangronga182d872010-09-20 22:17:48 +08001896 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1897 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001898 Default is 0 (off)
1899
Andre Przywarafef07aa2009-07-10 14:20:35 +02001900 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001901 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001902
1903 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1904 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001905 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001906
Marc Zyngiere23f62f2017-06-09 12:49:46 +01001907 kvm-arm.vgic_v3_group0_trap=
1908 [KVM,ARM] Trap guest accesses to GICv3 group-0
1909 system registers
1910
Marc Zyngier182936e2017-06-09 12:49:41 +01001911 kvm-arm.vgic_v3_group1_trap=
1912 [KVM,ARM] Trap guest accesses to GICv3 group-1
1913 system registers
1914
Marc Zyngierff895112017-06-09 12:49:53 +01001915 kvm-arm.vgic_v3_common_trap=
1916 [KVM,ARM] Trap guest accesses to GICv3 common
1917 system registers
1918
Marc Zyngiera7546052017-10-27 15:28:54 +01001919 kvm-arm.vgic_v4_enable=
1920 [KVM,ARM] Allow use of GICv4 for direct injection of
1921 LPIs.
1922
Andre Przywarafef07aa2009-07-10 14:20:35 +02001923 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1924 (virtualized MMU) support on capable Intel chips.
1925 Default is 1 (enabled)
1926
1927 kvm-intel.emulate_invalid_guest_state=
1928 [KVM,Intel] Enable emulation of invalid guest states
1929 Default is 0 (disabled)
1930
1931 kvm-intel.flexpriority=
1932 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1933 Default is 1 (enabled)
1934
Sasha Levine1a72ae2011-08-09 14:28:35 +03001935 kvm-intel.nested=
1936 [KVM,Intel] Enable VMX nesting (nVMX).
1937 Default is 0 (disabled)
1938
Andre Przywarafef07aa2009-07-10 14:20:35 +02001939 kvm-intel.unrestricted_guest=
1940 [KVM,Intel] Disable unrestricted guest feature
1941 (virtualized real and unpaged mode) on capable
1942 Intel chips. Default is 1 (enabled)
1943
1944 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1945 feature (tagged TLBs) on capable Intel chips.
1946 Default is 1 (enabled)
1947
Linus Torvalds1da177e2005-04-16 15:20:36 -07001948 l2cr= [PPC]
1949
Robert Brosea78bfbf2008-03-29 07:20:23 +11001950 l3cr= [PPC]
1951
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001952 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001953 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001954
Suresh Siddha279f1462012-10-22 14:37:58 -07001955 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1956 value for LAPIC timer one-shot implementation. Default
1957 back to the programmable timer unit in the LAPIC.
1958
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301959 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001960 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001961
FD Camifcb71f62008-01-06 19:08:56 +01001962 libata.dma= [LIBATA] DMA control
1963 libata.dma=0 Disable all PATA and SATA DMA
1964 libata.dma=1 PATA and SATA Disk DMA only
1965 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001966 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001967 Combinations also work, so libata.dma=3 enables DMA
1968 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001969
Michael Prokop20308872009-08-06 00:14:10 +02001970 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1971 libata.ignore_hpa=0 keep BIOS limits (default)
1972 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001973
Dave Jones78e70c22007-09-27 11:50:13 -04001974 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1975 when set.
1976 Format: <int>
1977
Tejun Heo33267322008-02-13 09:15:09 +09001978 libata.force= [LIBATA] Force configurations. The format is comma
1979 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001980 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001981 matching port, link or device. Basically, it matches
1982 the ATA ID string printed on console by libata. If
1983 the whole ID part is omitted, the last PORT and DEVICE
1984 values are used. If ID hasn't been specified yet, the
1985 configuration applies to all ports, links and devices.
1986
1987 If only DEVICE is omitted, the parameter applies to
1988 the port and all links and devices behind it. DEVICE
1989 number of 0 either selects the first device or the
1990 first fan-out link behind PMP device. It does not
1991 select the host link. DEVICE number of 15 selects the
1992 host link and device attached to it.
1993
1994 The VAL specifies the configuration to force. As long
1995 as there's no ambiguity shortcut notation is allowed.
1996 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1997 The following configurations can be forced.
1998
1999 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2000 Any ID with matching PORT is used.
2001
2002 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2003
2004 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2005 udma[/][16,25,33,44,66,100,133] notation is also
2006 allowed.
2007
2008 * [no]ncq: Turn on or off NCQ.
2009
Martin K. Petersend7b16e42015-05-04 21:54:18 -04002010 * [no]ncqtrim: Turn off queued DSM TRIM.
2011
Tejun Heo05944bd2008-08-13 20:19:09 +09002012 * nohrst, nosrst, norst: suppress hard, soft
2013 and both resets.
2014
Dan Williamsca6d43b2012-06-21 23:41:41 -07002015 * rstonce: only attempt one reset during
2016 hot-unplug link recovery
2017
Tejun Heo43c9c592010-05-23 12:59:11 +02002018 * dump_id: dump IDENTIFY data.
2019
Vincent Pelletier966fbe12013-05-21 22:30:58 +02002020 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2021
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08002022 * disable: Disable this device.
2023
Tejun Heo33267322008-02-13 09:15:09 +09002024 If there are multiple matching configurations changing
2025 the same attribute, the last one is used.
2026
Yinghai Lu95f72d12010-07-12 14:36:09 +10002027 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08002028
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002030 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002031
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002032 lockd.nlm_grace_period=P [NFS] Assign grace period.
2033 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002034
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002035 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2036 Format: <integer>
2037
2038 lockd.nlm_timeout=T [NFS] Assign timeout value.
2039 Format: <integer>
2040
2041 lockd.nlm_udpport=M [NFS] Assign UDP port.
2042 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002043
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07002044 locktorture.nreaders_stress= [KNL]
2045 Set the number of locking read-acquisition kthreads.
2046 Defaults to being automatically set based on the
2047 number of online CPUs.
2048
2049 locktorture.nwriters_stress= [KNL]
2050 Set the number of locking write-acquisition kthreads.
2051
2052 locktorture.onoff_holdoff= [KNL]
2053 Set time (s) after boot for CPU-hotplug testing.
2054
2055 locktorture.onoff_interval= [KNL]
2056 Set time (s) between CPU-hotplug operations, or
2057 zero to disable CPU-hotplug testing.
2058
2059 locktorture.shuffle_interval= [KNL]
2060 Set task-shuffle interval (jiffies). Shuffling
2061 tasks allows some CPUs to go into dyntick-idle
2062 mode during the locktorture test.
2063
2064 locktorture.shutdown_secs= [KNL]
2065 Set time (s) after boot system shutdown. This
2066 is useful for hands-off automated testing.
2067
2068 locktorture.stat_interval= [KNL]
2069 Time (s) between statistics printk()s.
2070
2071 locktorture.stutter= [KNL]
2072 Time (s) to stutter testing, for example,
2073 specifying five seconds causes the test to run for
2074 five seconds, wait for five seconds, and so on.
2075 This tests the locking primitive's ability to
2076 transition abruptly to and from idle.
2077
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07002078 locktorture.torture_type= [KNL]
2079 Specify the locking implementation to test.
2080
2081 locktorture.verbose= [KNL]
2082 Enable additional printk() statements.
2083
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2085 Format: <irq>
2086
2087 loglevel= All Kernel Messages with a loglevel smaller than the
2088 console loglevel will be printed to the console. It can
2089 also be changed with klogd or other programs. The
2090 loglevels are defined as follows:
2091
2092 0 (KERN_EMERG) system is unusable
2093 1 (KERN_ALERT) action must be taken immediately
2094 2 (KERN_CRIT) critical conditions
2095 3 (KERN_ERR) error conditions
2096 4 (KERN_WARNING) warning conditions
2097 5 (KERN_NOTICE) normal but significant condition
2098 6 (KERN_INFO) informational
2099 7 (KERN_DEBUG) debug-level messages
2100
Randy Dunlapc756d082011-02-20 20:08:35 -08002101 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07002102 in bytes. n must be a power of two and greater
2103 than the minimal size. The minimal size is defined
2104 by LOG_BUF_SHIFT kernel config parameter. There is
2105 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2106 that allows to increase the default size depending on
2107 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108
Randy Dunlapaccaa242007-10-16 01:29:37 -07002109 logo.nologo [FB] Disables display of the built-in Linux logo.
2110 This may be used to provide more screen space for
2111 kernel log messages and is useful when debugging
2112 kernel boot problems.
2113
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114 lp=0 [LP] Specify parallel ports to use, e.g,
2115 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2116 lp=reset first parallel port). 'lp=0' disables the
2117 lp=auto printer driver. 'lp=reset' (which can be
2118 specified in addition to the ports) causes
2119 attached printers to be reset. Using
2120 lp=port1,port2,... specifies the parallel ports
2121 to associate lp devices with, starting with
2122 lp0. A port specification may be 'none' to skip
2123 that lp device, or a parport name such as
2124 'parport0'. Specifying 'lp=auto' instead of a
2125 port specification list means that device IDs
2126 from each port should be examined, to see if
2127 an IEEE 1284-compliant printer is attached; if
2128 so, the driver will manage that printer.
2129 See also header of drivers/char/lp.c.
2130
2131 lpj=n [KNL]
2132 Sets loops_per_jiffy to given constant, thus avoiding
2133 time-consuming boot-time autodetection (up to 250 ms per
2134 CPU). 0 enables autodetection (default). To determine
2135 the correct value for your kernel, boot with normal
2136 autodetection and see what value is printed. Note that
2137 on SMP systems the preset will be applied to all CPUs,
2138 which is likely to cause problems if your CPUs need
2139 significantly divergent settings. An incorrect value
2140 will cause delays in the kernel to be wrong, leading to
2141 unpredictable I/O errors and other breakage. Although
2142 unlikely, in the extreme case this might damage your
2143 hardware.
2144
2145 ltpc= [NET]
2146 Format: <io>,<irq>,<dma>
2147
Randy Dunlap16290242011-08-13 12:34:52 -07002148 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002149 (machvec) in a generic kernel.
2150 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151
Wu Zhangjin3209e702009-07-02 23:27:12 +08002152 machtype= [Loongson] Share the same kernel image file between different
2153 yeeloong laptop.
2154 Example: machtype=lemote-yeeloong-2f-7inch
2155
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002156 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2157 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158
2159 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002160 will bring up during bootup. maxcpus=n : n >= 0 limits
2161 the kernel to bring up 'n' processors. Surely after
2162 bootup you can bring up the other plugged cpu by executing
2163 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2164 only takes effect during system bootup.
2165 While n=0 is a special case, it is equivalent to "nosmp",
2166 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002167
Kay Sieversd134b002011-07-31 22:08:04 +02002168 max_loop= [LOOP] The number of loop block devices that get
2169 (loop.max_loop) unconditionally pre-created at init time. The default
2170 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2171 of statically allocating a predefined number, loop
2172 devices can be requested on-demand with the
2173 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002174
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002175 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002176
Uwe Hermann71cced62008-10-20 09:32:21 -07002177 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002178
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 md= [HW] RAID subsystems devices and level
Jani Nikulae52347b2016-11-03 12:10:10 +02002180 See Documentation/admin-guide/md.rst.
Randy Dunlapa9913042005-10-23 12:57:11 -07002181
Linus Torvalds1da177e2005-04-16 15:20:36 -07002182 mdacon= [MDA]
2183 Format: <first>,<last>
2184 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002185
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2187 Amount of memory to be used when the kernel is not able
2188 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002189 [X86] Work as limiting max address. Use together
2190 with memmap= to avoid physical address space collisions.
2191 Without memmap= PCI devices could be placed at addresses
2192 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002193
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002194 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002195 memory.
2196
Paul Mundt6902aa82008-09-21 17:14:42 +09002197 memchunk=nn[KMG]
2198 [KNL,SH] Allow user to override the default size for
2199 per-device physically contiguous DMA buffers.
2200
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002201 memhp_default_state=online/offline
2202 [KNL] Set the initial state for the memory hotplug
2203 onlining policy. If not specified, the default value is
2204 set according to the
2205 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2206 option.
2207 See Documentation/memory-hotplug.txt.
2208
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302209 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002210 E820 memory map, as specified by the user.
2211 Such memmap=exactmap lines can be constructed based on
2212 BIOS output or other requirements. See the memmap=nn@ss
2213 option description.
2214
2215 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002216 [KNL] Force usage of a specific region of memory.
2217 Region of memory to be used is from ss to ss+nn.
Baoquan He8fcc9bc2017-05-13 13:46:30 +08002218 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2219 which limits max address to nn[KMG].
2220 Multiple different regions can be specified,
2221 comma delimited.
2222 Example:
2223 memmap=100M@2G,100M#3G,1G!1024G
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224
2225 memmap=nn[KMG]#ss[KMG]
2226 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002227 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002228
2229 memmap=nn[KMG]$ss[KMG]
2230 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002231 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002232 Example: Exclude memory from 0x18690000-0x1869ffff
2233 memmap=64K$0x18690000
2234 or
2235 memmap=0x10000$0x18690000
Baoquan He8fcc9bc2017-05-13 13:46:30 +08002236 Some bootloaders may need an escape character before '$',
2237 like Grub2, otherwise '$' and the following number
2238 will be eaten.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002239
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002240 memmap=nn[KMG]!ss[KMG]
2241 [KNL,X86] Mark specific memory as protected.
2242 Region of memory to be used, from ss to ss+nn.
2243 The memory region may be marked as e820 type 12 (0xc)
2244 and is NVDIMM or ADR memory.
2245
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002246 memory_corruption_check=0/1 [X86]
2247 Some BIOSes seem to corrupt the first 64k of
2248 memory when doing things like suspend/resume.
2249 Setting this option will scan the memory
2250 looking for corruption. Enabling this will
2251 both detect corruption and prevent the kernel
2252 from using the memory being corrupted.
2253 However, its intended as a diagnostic tool; if
2254 repeatable BIOS-originated corruption always
2255 affects the same memory, you can use memmap=
2256 to prevent the kernel from using that memory.
2257
2258 memory_corruption_check_size=size [X86]
2259 By default it checks for corruption in the low
2260 64k, making this memory unavailable for normal
2261 use. Use this parameter to scan for
2262 corruption in more or less memory.
2263
2264 memory_corruption_check_period=seconds [X86]
2265 By default it checks for corruption every 60
2266 seconds. Use this parameter to check at some
2267 other rate. 0 disables periodic checking.
2268
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002269 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002270 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002271 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002272 Specifies the number of memtest passes to be
2273 performed. Each pass selects another test
2274 pattern from a given set of patterns. Memtest
2275 fills the memory with this pattern, validates
2276 memory contents and reserves bad memory
2277 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002278
Tom Lendackyc262f3b2017-07-17 16:09:58 -05002279 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2280 Valid arguments: on, off
2281 Default (depends on kernel configuration option):
2282 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2283 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2284 mem_encrypt=on: Activate SME
2285 mem_encrypt=off: Do not activate SME
2286
2287 Refer to Documentation/x86/amd-memory-encryption.txt
2288 for details on when memory encryption can be activated.
2289
Rafael J. Wysocki406e7932016-11-21 22:45:40 +01002290 mem_sleep_default= [SUSPEND] Default system suspend mode:
2291 s2idle - Suspend-To-Idle
2292 shallow - Power-On Suspend or equivalent (if supported)
2293 deep - Suspend-To-RAM or equivalent (if supported)
Rafael J. Wysocki58e7cb92017-10-06 00:38:49 +02002294 See Documentation/admin-guide/pm/sleep-states.rst.
Rafael J. Wysocki406e7932016-11-21 22:45:40 +01002295
Linus Torvalds1da177e2005-04-16 15:20:36 -07002296 meye.*= [HW] Set MotionEye Camera parameters
Tom Saegera405ed82017-10-10 12:36:37 -05002297 See Documentation/media/v4l-drivers/meye.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002298
Andres Salomon8f368812007-10-12 23:04:06 +02002299 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2300 Multi-Function General Purpose Timers on AMD Geode
2301 platforms.
2302
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002303 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2304 the BIOS has incorrectly applied a workaround. TinyBIOS
2305 version 0.98 is known to be affected, 0.99 fixes the
2306 problem by letting the user disable the workaround.
2307
Linus Torvalds1da177e2005-04-16 15:20:36 -07002308 mga= [HW,DRM]
2309
Randy Dunlap1c207f952008-11-19 15:36:16 -08002310 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2311 physical address is ignored.
2312
Michel Pollet39f45d72009-05-20 11:10:31 +01002313 mini2440= [ARM,HW,KNL]
2314 Format:[0..2][b][c][t]
2315 Default: "0tb"
2316 MINI2440 configuration specification:
2317 0 - The attached screen is the 3.5" TFT
2318 1 - The attached screen is the 7" TFT
2319 2 - The VGA Shield is attached (1024x768)
2320 Leaving out the screen size parameter will not load
2321 the TFT driver, and the framebuffer will be left
2322 unconfigured.
2323 b - Enable backlight. The TFT backlight pin will be
2324 linked to the kernel VESA blanking code and a GPIO
2325 LED. This parameter is not necessary when using the
2326 VGA shield.
2327 c - Enable the s3c camera interface.
2328 t - Reserved for enabling touchscreen support. The
2329 touchscreen support is not enabled in the mainstream
2330 kernel as of 2.6.30, a preliminary port can be found
2331 in the "bleeding edge" mini2440 support kernel at
2332 http://repo.or.cz/w/linux-2.6/mini2440.git
2333
Mel Gorman6b74ab92008-07-23 21:26:49 -07002334 mminit_loglevel=
2335 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2336 parameter allows control of the logging verbosity for
2337 the additional memory initialisation checks. A value
2338 of 0 disables mminit logging and a level of 4 will
2339 log everything. Information is printed at KERN_DEBUG
2340 so loglevel=8 may also need to be specified.
2341
Rusty Russell106a4ee2012-09-26 10:09:40 +01002342 module.sig_enforce
2343 [KNL] When CONFIG_MODULE_SIG is set, this means that
2344 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002345 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002346 is always true, so this option does nothing.
2347
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302348 module_blacklist= [KNL] Do not load a comma-separated list of
2349 modules. Useful for debugging problem modules.
2350
Linus Torvalds1da177e2005-04-16 15:20:36 -07002351 mousedev.tap_time=
2352 [MOUSE] Maximum time between finger touching and
2353 leaving touchpad surface for touch to be considered
2354 a tap and be reported as a left button click (for
2355 touchpads working in absolute mode only).
2356 Format: <msecs>
2357 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2358 reporting absolute coordinates, such as tablets
2359 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2360 reporting absolute coordinates, such as tablets
2361
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302362 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002363 is similar to kernelcore except it specifies the
2364 amount of memory used for migratable allocations.
2365 If both kernelcore and movablecore is specified,
2366 then kernelcore will be at *least* the specified
2367 value but may be more. If movablecore on its own
2368 is specified, the administrator must be careful
2369 that the amount of memory usable for all allocations
2370 is not too small.
2371
Michal Hockof70029b2017-07-06 15:41:02 -07002372 movable_node [KNL] Boot-time switch to make hotplugable memory
2373 NUMA nodes to be movable. This means that the memory
2374 of such nodes will be usable only for movable
2375 allocations which rules out almost all kernel
2376 allocations. Use with caution!
Tang Chenc5320922013-11-12 15:08:10 -08002377
Linus Torvalds1da177e2005-04-16 15:20:36 -07002378 MTD_Partition= [MTD]
2379 Format: <name>,<region-number>,<size>,<offset>
2380
Randy Dunlapa9913042005-10-23 12:57:11 -07002381 MTD_Region= [MTD] Format:
2382 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002383
2384 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002385 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002386
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002387 multitce=off [PPC] This parameter disables the use of the pSeries
2388 firmware feature for updating multiple TCE entries
2389 at a time.
2390
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002391 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2392
2393 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2394
2395 boundary - index of last SLC block on Flex-OneNAND.
2396 The remaining blocks are configured as MLC blocks.
2397 lock - Configure if Flex-OneNAND boundary should be locked.
2398 Once locked, the boundary cannot be changed.
2399 1 indicates lock status, 0 indicates unlock status.
2400
Ben Dooks9db829f2008-07-03 11:24:29 +01002401 mtdset= [ARM]
2402 ARM/S3C2412 JIVE boot control
2403
2404 See arch/arm/mach-s3c2412/mach-jive.c
2405
Linus Torvalds1da177e2005-04-16 15:20:36 -07002406 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002407 [HW] Make the MicroTouch USB driver use raw coordinates
2408 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002409
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002410 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002411 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002412 that could hold holes aka. UC entries.
2413
2414 mtrr_gran_size=nn[KMG] [X86]
2415 Used for mtrr cleanup. It is granularity of mtrr block.
2416 Default is 1.
2417 Large value could prevent small alignment from
2418 using up MTRRs.
2419
2420 mtrr_spare_reg_nr=n [X86]
2421 Format: <integer>
2422 Range: 0,7 : spare reg number
2423 Default : 1
2424 Used for mtrr cleanup. It is spare mtrr entries number.
2425 Set to 2 or more if your graphical card needs more.
2426
Linus Torvalds1da177e2005-04-16 15:20:36 -07002427 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2428
Linus Torvalds1da177e2005-04-16 15:20:36 -07002429 netdev= [NET] Network devices parameters
2430 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2431 Note that mem_start is often overloaded to mean
2432 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002433 This usage is only documented in each driver source
2434 file if at all.
2435
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002436 nf_conntrack.acct=
2437 [NETFILTER] Enable connection tracking flow accounting
2438 0 to disable accounting
2439 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002440 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002441
Chuck Lever306a0752010-09-17 10:54:37 -04002442 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002443 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002444
2445 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002446 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002447
Chuck Lever306a0752010-09-17 10:54:37 -04002448 nfsrootdebug [NFS] enable nfsroot debugging messages.
2449 See Documentation/filesystems/nfs/nfsroot.txt.
2450
Trond Myklebust5405fc42016-08-29 20:03:52 -04002451 nfs.callback_nr_threads=
2452 [NFSv4] set the total number of threads that the
2453 NFS client will assign to service NFSv4 callback
2454 requests.
2455
Trond Myklebusta72b4422006-01-03 09:55:41 +01002456 nfs.callback_tcpport=
2457 [NFS] set the TCP port on which the NFSv4 callback
2458 channel should listen.
2459
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002460 nfs.cache_getent=
2461 [NFS] sets the pathname to the program which is used
2462 to update the NFS client cache entries.
2463
2464 nfs.cache_getent_timeout=
2465 [NFS] sets the timeout after which an attempt to
2466 update a cache entry is deemed to have failed.
2467
Trond Myklebust58df0952006-01-03 09:55:57 +01002468 nfs.idmap_cache_timeout=
2469 [NFS] set the maximum lifetime for idmapper cache
2470 entries.
2471
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002472 nfs.enable_ino64=
2473 [NFS] enable 64-bit inode numbers.
2474 If zero, the NFS client will fake up a 32-bit inode
2475 number for the readdir() and stat() syscalls instead
2476 of returning the full 64-bit number.
2477 The default is to return 64-bit inode numbers.
2478
Trond Myklebust5405fc42016-08-29 20:03:52 -04002479 nfs.max_session_cb_slots=
2480 [NFSv4.1] Sets the maximum number of session
2481 slots the client will assign to the callback
2482 channel. This determines the maximum number of
2483 callbacks the client will process in parallel for
2484 a particular server.
2485
Trond Myklebustef159e92012-02-06 19:50:40 -05002486 nfs.max_session_slots=
2487 [NFSv4.1] Sets the maximum number of session slots
2488 the client will attempt to negotiate with the server.
2489 This limits the number of simultaneous RPC requests
2490 that the client can send to the NFSv4.1 server.
2491 Note that there is little point in setting this
2492 value higher than the max_tcp_slot_table_limit.
2493
Trond Myklebustb064eca22011-02-22 15:44:32 -08002494 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002495 [NFSv4] When set to the default of '1', this option
2496 ensures that both the RPC level authentication
2497 scheme and the NFS level operations agree to use
2498 numeric uids/gids if the mount is using the
2499 'sec=sys' security flavour. In effect it is
2500 disabling idmapping, which can make migration from
2501 legacy NFSv2/v3 systems to NFSv4 easier.
2502 Servers that do not support this mode of operation
2503 will be autodetected by the client, and it will fall
2504 back to using the idmapper.
2505 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002506 nfs.nfs4_unique_id=
2507 [NFS4] Specify an additional fixed unique ident-
2508 ification string that NFSv4 clients can insert into
2509 their nfs_client_id4 string. This is typically a
2510 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002511
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002512 nfs.send_implementation_id =
2513 [NFSv4.1] Send client implementation identification
2514 information in exchange_id requests.
2515 If zero, no implementation identification information
2516 will be sent.
2517 The default is to send the implementation identification
2518 information.
Jani Nikulae52347b2016-11-03 12:10:10 +02002519
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002520 nfs.recover_lost_locks =
2521 [NFSv4] Attempt to recover locks that were lost due
2522 to a lease timeout on the server. Please note that
2523 doing this risks data corruption, since there are
2524 no guarantees that the file will remain unchanged
2525 after the locks are lost.
2526 If you want to enable the kernel legacy behaviour of
2527 attempting to recover these locks, then set this
2528 parameter to '1'.
2529 The default parameter value of '0' causes the kernel
2530 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002531
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002532 nfs4.layoutstats_timer =
2533 [NFSv4.2] Change the rate at which the kernel sends
2534 layoutstats to the pNFS metadata server.
2535
2536 Setting this to value to 0 causes the kernel to use
2537 whatever value is the default set by the layout
2538 driver. A non-zero value sets the minimum interval
2539 in seconds between layoutstats transmissions.
2540
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002541 nfsd.nfs4_disable_idmapping=
2542 [NFSv4] When set to the default of '1', the NFSv4
2543 server will return only numeric uids and gids to
2544 clients using auth_sys, and will accept numeric uids
2545 and gids from such clients. This is intended to ease
2546 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002547
Hans-Christian Noren Egtvedtc0c74ac2017-02-26 13:17:39 +01002548 nmi_debug= [KNL,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002549 when a NMI is triggered.
2550 Format: [state][,regs][,debounce][,die]
2551
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302552 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002553 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002554 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002555 0 - turn hardlockup detector in nmi_watchdog off
2556 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002557 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002558 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002559 default). To disable both hard and soft lockup detectors,
2560 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002561 This is useful when you use a panic=... timeout and
2562 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002563
Scott Woodd22881d2017-12-10 01:48:46 -06002564 These settings can be accessed at runtime via
2565 the nmi_watchdog and hardlockup_panic sysctls.
2566
Anton Vorontsovbff38772009-07-08 11:10:56 -07002567 netpoll.carrier_timeout=
2568 [NET] Specifies amount of time (in seconds) that
2569 netpoll should wait for a carrier. By default netpoll
2570 waits 4 seconds.
2571
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002572 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002573 emulation library even if a 387 maths coprocessor
2574 is present.
2575
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002576 no_console_suspend
2577 [HW] Never suspend the console
2578 Disable suspending of consoles during suspend and
2579 hibernate operations. Once disabled, debugging
2580 messages can reach various consoles while the rest
2581 of the system is being put to sleep (ie, while
2582 debugging driver suspend/resume hooks). This may
2583 not work reliably with all consoles, but is known
2584 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002585 To facilitate more flexible debugging, we also add
2586 console_suspend, a printk module parameter to control
2587 it. Users could use console_suspend (usually
2588 /sys/module/printk/parameters/console_suspend) to
2589 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002590
Christoph Lameterc1aee212007-05-31 00:40:47 -07002591 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2592 caches in the slab allocator. Saves per-node memory,
2593 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002594
Randy Dunlapa9913042005-10-23 12:57:11 -07002595 noalign [KNL,ARM]
2596
Vasily Gorbik686140a2017-10-12 13:01:47 +02002597 noaltinstr [S390] Disables alternative instructions patching
2598 (CPU alternatives feature).
2599
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 noapic [SMP,APIC] Tells the kernel to not make use of any
2601 IOAPICs that may be present in the system.
2602
Mike Galbraith5091faa2010-11-30 14:18:03 +01002603 noautogroup Disable scheduler automatic task group creation.
2604
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605 nobats [PPC] Do not use BATs for mapping kernel lowmem
2606 on "Classic" PPC cores.
2607
2608 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002609
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002610 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2611
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002612 nodelayacct [KNL] Disable per-task delay accounting
2613
Paul Mundt6902aa82008-09-21 17:14:42 +09002614 nodsp [SH] Disable hardware DSP at boot time.
2615
Dave Youngb2e0a542014-08-14 17:15:26 +08002616 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002617
Linus Torvalds1da177e2005-04-16 15:20:36 -07002618 noexec [IA-64]
2619
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302620 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002621 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002623 noexec=off: disable non-executable mappings
2624
H. Peter Anvin52b61792012-09-21 12:43:13 -07002625 nosmap [X86]
2626 Disable SMAP (Supervisor Mode Access Prevention)
2627 even if it is supported by processor.
2628
Fenghua Yude5397a2011-05-11 16:51:05 -07002629 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002630 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002631 even if it is supported by processor.
2632
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002633 noexec32 [X86-64]
2634 This affects only 32-bit executables.
2635 noexec32=on: enable non-executable mappings (default)
2636 read doesn't imply executable mappings
2637 noexec32=off: disable non-executable mappings
2638 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002639
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002640 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002641
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002642 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002643 register save and restore. The kernel will only save
2644 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002645
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002646 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2647
Sascha Silbe52c48c52016-04-05 12:53:38 +02002648 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2649 Equivalent to smt=1.
2650
David Woodhouseda285122018-01-11 21:46:26 +00002651 nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2
2652 (indirect branch prediction) vulnerability. System may
2653 allow data leaks with this option, which is equivalent
2654 to spectre_v2=off.
2655
Suresh Siddha0c752a92009-05-22 12:17:45 -07002656 noxsave [BUGS=X86] Disables x86 extended register state save
2657 and restore using xsave. The kernel will fallback to
2658 enabling legacy floating-point and sse state.
2659
Fenghua Yub6f42a42014-05-29 11:12:31 -07002660 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2661 register states. The kernel will fall back to use
2662 xsave to save the states. By using this parameter,
2663 performance of saving the states is degraded because
2664 xsave doesn't support modified optimization while
2665 xsaveopt supports it on xsaveopt enabled systems.
2666
2667 noxsaves [X86] Disables xsaves and xrstors used in saving and
2668 restoring x86 extended register state in compacted
2669 form of xsave area. The kernel will fall back to use
2670 xsaveopt and xrstor to save and restore the states
2671 in standard form of xsave area. By using this
2672 parameter, xsave area per process might occupy more
2673 memory on xsaves enabled systems.
2674
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002675 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2676 wfi(ARM) instruction doesn't work correctly and not to
2677 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002678
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002679 no_file_caps Tells the kernel not to honor file capabilities. The
2680 only way then for a file to be executed with privilege
2681 is to be setuid root or executed by root.
2682
Linus Torvalds1da177e2005-04-16 15:20:36 -07002683 nohalt [IA-64] Tells the kernel not to use the power saving
2684 function PAL_HALT_LIGHT when idle. This increases
2685 power-consumption. On the positive side, it reduces
2686 interrupt wake-up latency, which may improve performance
2687 in certain environments such as networked servers or
2688 real-time systems.
2689
Kees Cooka6e15a32014-06-13 13:30:35 -07002690 nohibernate [HIBERNATION] Disable hibernation and resume.
2691
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002692 nohz= [KNL] Boottime enable/disable dynamic ticks
2693 Valid arguments: on, off
2694 Default: on
2695
Frederic Weisbeckerd94d1052017-12-14 19:18:27 +01002696 nohz_full= [KNL,BOOT,SMP,ISOL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002697 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002698 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002699 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002700 whenever possible. The boot CPU will be forced outside
Paul E. McKenneyf99bcb22017-06-02 11:26:43 -07002701 the range to maintain the timekeeping. Any CPUs
2702 in this list will have their RCU callbacks offloaded,
2703 just as if they had also been called out in the
2704 rcu_nocbs= boot parameter.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002705
Paul Mundteeee7852009-04-02 12:31:16 +09002706 noiotrap [SH] Disables trapped I/O port accesses.
2707
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002708 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002709 disable unhandled interrupt sources.
2710
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302711 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002712 broken timer IRQ sources.
2713
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714 noisapnp [ISAPNP] Disables ISA PnP code.
2715
2716 noinitrd [RAM] Tells the kernel not to load any configured
2717 initial RAM disk.
2718
Weidong Han03ea8152009-04-17 16:42:15 +08002719 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2720 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002721 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002722
Linus Torvalds1da177e2005-04-16 15:20:36 -07002723 nointroute [IA-64]
2724
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002725 noinvpcid [X86] Disable the INVPCID cpu feature.
2726
Randy Dunlap16290242011-08-13 12:34:52 -07002727 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002728
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002729 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2730
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002731 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2732 fault handling.
2733
Alexey Makhalov80e9a4f2016-10-28 00:54:32 -07002734 no-vmw-sched-clock
2735 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2736 clock and use the default one.
2737
Glauber Costad910f5c2011-07-11 15:28:19 -04002738 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2739 steal time is computed, but won't influence scheduler
2740 behaviour
2741
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002742 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002743
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002744 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002745
Linus Torvalds1da177e2005-04-16 15:20:36 -07002746 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002747 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002748
Horms312f1f02006-02-22 09:57:55 +09002749 nomca [IA-64] Disable machine check abort handling
2750
Masanari Iida13696e02015-05-16 02:16:43 +09002751 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002752
Andres Salomon83d73842007-10-12 23:04:06 +02002753 nomfgpt [X86-32] Disable Multi-Function General Purpose
2754 Timer usage (for AMD Geode machines).
2755
Don Zickusbda62632011-10-13 15:14:27 -04002756 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2757 shutdown the other cpus. Instead use the REBOOT_VECTOR
2758 irq.
2759
Dave Young02608be2012-02-01 10:33:14 +08002760 nomodule Disable module load
2761
Jiri Kosina016ddd92010-01-18 17:05:40 +01002762 nopat [X86] Disable PAT (page attribute table extension of
2763 pagetables) support.
2764
Andy Lutomirski0790c9a2017-06-29 08:53:20 -07002765 nopcid [X86-64] Disable the PCID cpu feature.
2766
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002767 norandmaps Don't use address space randomization. Equivalent to
2768 echo 0 > /proc/sys/kernel/randomize_va_space
2769
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002770 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002771 with UP alternatives
2772
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002773 nordrand [X86] Disable kernel use of the RDRAND and
2774 RDSEED instructions even if they are supported
2775 by the processor. RDRAND and RDSEED are still
2776 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002777
Randy Dunlapa9913042005-10-23 12:57:11 -07002778 noresume [SWSUSP] Disables resume and restores original swap
2779 space.
2780
Linus Torvalds1da177e2005-04-16 15:20:36 -07002781 no-scroll [VGA] Disables scrollback.
2782 This is required for the Braillex ib80-piezo Braille
2783 reader made by F.H. Papenmeier (Germany).
2784
2785 nosbagart [IA-64]
2786
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002787 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002788
Len Brown61ec7562007-08-16 03:34:22 -04002789 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2790 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002791
Dave Jones97842212007-07-15 23:41:05 -07002792 nosoftlockup [KNL] Disable the soft-lockup detector.
2793
Linus Torvalds1da177e2005-04-16 15:20:36 -07002794 nosync [HW,M68K] Disables sync negotiation for all devices.
2795
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002796 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002797
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002798 nowatchdog [KNL] Disable both lockup detectors, i.e.
2799 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002800
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002802
Weidong Han2b2fd872009-04-17 16:42:12 +08002803 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2804
Fenghua Yuf78cff42012-11-13 11:32:38 -08002805 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2806 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2807 Some features depend on CPU0. Known dependencies are:
2808 1. Resume from suspend/hibernate depends on CPU0.
2809 Suspend/hibernate will fail if CPU0 is offline and you
2810 need to online CPU0 before suspend/hibernate.
2811 2. PIC interrupts also depend on CPU0. CPU0 can't be
2812 removed if a PIC interrupt is detected.
2813 It's said poweroff/reboot may depend on CPU0 on some
2814 machines although I haven't seen such issues so far
2815 after CPU0 is offline on a few tested machines.
2816 If the dependencies are under your control, you can
2817 turn on cpu0_hotplug.
2818
Noam Camus35b55ef2017-06-15 11:43:57 +03002819 nps_mtm_hs_ctr= [KNL,ARC]
2820 This parameter sets the maximum duration, in
2821 cycles, each HW thread of the CTOP can run
2822 without interruptions, before HW switches it.
2823 The actual maximum duration is 16 times this
2824 parameter's value.
2825 Format: integer between 1 and 255
2826 Default: 255
2827
Randy Dunlap16290242011-08-13 12:34:52 -07002828 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002829 purges which is reported from either PAL_VM_SUMMARY or
2830 SAL PALO.
2831
Yinghai Lu2b633e32010-02-10 01:20:37 -08002832 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2833 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002834 support 'n' processors. It could be larger than the
2835 number of already plugged CPU during bootup, later in
2836 runtime you can physically add extra cpu until it reaches
2837 n. So during boot up some boot time memory for per-cpu
2838 variables need be pre-allocated for later physical cpu
2839 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002840
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002841 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2842
Mel Gorman1a687c22012-11-22 11:16:36 +00002843 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2844 Allowed values are enable and disable
2845
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002846 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
Michal Hockoc9bff3e2017-09-06 16:20:13 -07002847 'node', 'default' can be specified
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002848 This can be set from sysctl after boot.
2849 See Documentation/sysctl/vm.txt for details.
2850
Randy Dunlap7c4be252009-01-06 14:42:44 -08002851 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2852 See Documentation/debugging-via-ohci1394.txt for more
2853 info.
2854
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002855 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2856 Rather than timing out after 20 ms if an EC
2857 command is not properly ACKed, override the length
2858 of the timeout. We have interrupts disabled while
2859 waiting for the ACK, so if this is set too high
2860 interrupts *may* be lost!
2861
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002862 omap_mux= [OMAP] Override bootloader pin multiplexing.
2863 Format: <mux_mode0.mode_name=value>...
2864 For example, to override I2C bus2:
2865 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2866
Linus Torvalds1da177e2005-04-16 15:20:36 -07002867 oprofile.timer= [HW]
2868 Use timer interrupt instead of performance counters
2869
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002870 oprofile.cpu_type= Force an oprofile cpu type
2871 This might be useful if you have an older oprofile
2872 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002873 Format: { arch_perfmon }
2874 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002875 perfmon on Intel CPUs instead of the
2876 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002877 timer: [X86] Force use of architectural NMI
2878 timer mode (see also oprofile.timer
2879 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002880
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002881 oops=panic Always panic on oopses. Default is to just kill the
2882 process, but there is a small probability of
2883 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002884 This will also cause panics on machine check exceptions.
2885 Useful together with panic=30 to trigger a reboot.
2886
Randy Dunlapbcfde332010-06-07 17:10:38 -07002887 OSS [HW,OSS]
2888 See Documentation/sound/oss/oss-parameters.txt
2889
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002890 page_owner= [KNL] Boot-time page_owner enabling option.
2891 Storage of the information about who allocated
2892 each page is disabled in default. With this switch,
2893 we can turn it on.
2894 on: enable the feature
2895
Laura Abbott8823b1d2016-03-15 14:56:27 -07002896 page_poison= [KNL] Boot-time parameter changing the state of
2897 poisoning on the buddy allocator.
2898 off: turn off poisoning
2899 on: turn on poisoning
2900
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002901 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002902 timeout > 0: seconds before rebooting
2903 timeout = 0: wait forever
2904 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002905 Format: <timeout>
2906
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002907 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2908 on a WARN().
2909
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002910 crash_kexec_post_notifiers
2911 Run kdump after running panic-notifiers and dumping
2912 kmsg. This only for the users who doubt kdump always
2913 succeeds in any situation.
2914 Note that this also increases risks of kdump failure,
2915 because some panic notifiers can make the crashed
2916 kernel more unstable.
2917
Linus Torvalds1da177e2005-04-16 15:20:36 -07002918 parkbd.port= [HW] Parallel port number the keyboard adapter is
2919 connected to, default is 0.
2920 Format: <parport#>
2921 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2922 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002923 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002924
Randy Dunlapa9913042005-10-23 12:57:11 -07002925 parport= [HW,PPT] Specify parallel ports. 0 disables.
2926 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2927 Use 'auto' to force the driver to use any
2928 IRQ/DMA settings detected (the default is to
2929 ignore detected IRQ/DMA settings because of
2930 possible conflicts). You can specify the base
2931 address, IRQ, and DMA settings; IRQ and DMA
2932 should be numbers, or 'auto' (for using detected
2933 settings on that particular port), or 'nofifo'
2934 (to avoid using a FIFO even if it is detected).
2935 Parallel ports are assigned in the order they
2936 are specified on the command line, starting
2937 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002938
Randy Dunlapa9913042005-10-23 12:57:11 -07002939 parport_init_mode= [HW,PPT]
2940 Configure VIA parallel port to operate in
2941 a specific mode. This is necessary on Pegasos
2942 computer where firmware has no options for setting
2943 up parallel port mode and sets it to spp.
2944 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002945 Format: [spp|ps2|epp|ecp|ecpepp]
2946
Andrew Mortondd287792006-03-23 03:00:57 -08002947 pause_on_oops=
2948 Halt all CPUs after the first oops has been printed for
2949 the specified number of seconds. This is to be used if
2950 your oopses keep scrolling off the screen.
2951
Linus Torvalds1da177e2005-04-16 15:20:36 -07002952 pcbit= [HW,ISDN]
2953
2954 pcd. [PARIDE]
2955 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002956 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002957
Randy Dunlapa9913042005-10-23 12:57:11 -07002958 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002959 earlydump [X86] dump PCI config space before the kernel
2960 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002961 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002962 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002963 the hardware directly. Use this if your machine
2964 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002965 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002966 hardware access methods are allowed. Use this
2967 if you experience crashes upon bootup and you
2968 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002969 conf1 [X86] Force use of PCI Configuration Access
2970 Mechanism 1 (config address in IO port 0xCF8,
2971 data in IO port 0xCFC, both 32-bit).
2972 conf2 [X86] Force use of PCI Configuration Access
2973 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2974 the function, IO port 0xCFA, also 8-bit, sets
2975 bus number. The config space is then accessed
2976 through ports 0xC000-0xCFFF).
2977 See http://wiki.osdev.org/PCI for more info
2978 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002979 noaer [PCIE] If the PCIEAER kernel config parameter is
2980 enabled, this kernel boot option can be used to
2981 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002982 nodomains [PCI] Disable support for multiple PCI
2983 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302984 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002985 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002986 check_enable_amd_mmconf [X86] check for and enable
2987 properly configured MMIO access to PCI
2988 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002989 nomsi [MSI] If the PCI_MSI kernel config parameter is
2990 enabled, this kernel boot option can be used to
2991 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002992 noioapicquirk [APIC] Disable all boot interrupt quirks.
2993 Safety option to keep boot IRQs enabled. This
2994 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002995 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2996 primary IO-APIC for bridges that cannot disable
2997 boot IRQs. This fixes a source of spurious IRQs
2998 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002999 noioapicreroute [APIC] Disable workaround that uses the
3000 boot IRQ equivalent of an IRQ that connects to
3001 a chipset where boot IRQs cannot be disabled.
3002 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003003 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07003004 routing table. These calls are known to be buggy
3005 on several machines and they hang the machine
3006 when used, but on other computers it's the only
3007 way to get the interrupt routing table. Try
3008 this option if the kernel is unable to allocate
3009 IRQs or discover secondary PCI buses on your
3010 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02003011 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07003012 Use with caution as certain devices share
3013 address decoders between ROMs and other
3014 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02003015 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07003016 expansion ROMs that do not already have
3017 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07003018 nobar [X86] Do not assign address space to the
3019 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02003020 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07003021 assigned automatically to PCI devices. You can
3022 make the kernel exclude IRQs of your ISA cards
3023 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02003024 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07003025 of the PIRQ table (normally generated
3026 by the BIOS) if it is outside the
3027 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02003028 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07003029 useful if the kernel is unable to find your
3030 secondary buses and you want to tell it
3031 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02003032 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07003033 numbers ourselves, overriding
3034 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02003035 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07003036 in the BIOS $PIR table. This is needed on
3037 some systems with broken BIOSes, notably
3038 some HP Pavilion N5400 and Omnibook XE3
3039 notebooks. This will have no effect if ACPI
3040 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02003041 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07003042 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07003043 use_crs [X86] Use PCI host bridge window information
3044 from ACPI. On BIOSes from 2008 or later, this
3045 is enabled by default. If you need to use this,
3046 please report a bug.
3047 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3048 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07003049 routeirq Do IRQ routing for all PCI devices.
3050 This is normally done in pci_enable_device(),
3051 so this option is a temporary workaround
3052 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07003053 skip_isa_align [X86] do not align io start addr, so can
3054 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02003055 noearly [X86] Don't do any early type 1 scanning.
3056 This might help on some broken boards which
3057 machine check when some devices' config space
3058 is read. But various workarounds are disabled
3059 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003060 bfsort Sort PCI devices into breadth-first order.
3061 This sorting is done to get a device
3062 order compatible with older (<= 2.4) kernels.
3063 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08003064 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3065 tuning and use the BIOS-configured MPS defaults.
3066 pcie_bus_safe Set every device's MPS to the largest value
3067 supported by all devices below the root complex.
3068 pcie_bus_perf Set device MPS to the largest allowable MPS
3069 based on its parent bus. Also set MRRS (Max
3070 Read Request Size) to the largest supported
3071 value (no larger than the MPS that the device
3072 or bus can support) for best performance.
3073 pcie_bus_peer2peer Set every device's MPS to 128B, which
3074 every device is guaranteed to support. This
3075 configuration allows peer-to-peer DMA between
3076 any pair of devices, possibly at the cost of
3077 reduced performance. This also guarantees
3078 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08003079 cbiosize=nn[KMG] The fixed amount of bus space which is
3080 reserved for the CardBus bridge's IO window.
3081 The default value is 256 bytes.
3082 cbmemsize=nn[KMG] The fixed amount of bus space which is
3083 reserved for the CardBus bridge's memory
3084 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003085 resource_alignment=
3086 Format:
3087 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00003088 [<order of align>@]pci:<vendor>:<device>\
3089 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003090 Specifies alignment and device to reassign
3091 aligned memory resources.
3092 If <order of align> is not specified,
3093 PAGE_SIZE is used as alignment.
3094 PCI-PCI bridge can be specified, if resource
3095 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02003096 To specify the alignment for several
3097 instances of a device, the PCI vendor,
3098 device, subvendor, and subdevice may be
3099 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06003100 ecrc= Enable/disable PCIe ECRC (transaction layer
3101 end-to-end CRC checking).
3102 bios: Use BIOS/firmware settings. This is the
3103 the default.
3104 off: Turn ECRC off
3105 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08003106 hpiosize=nn[KMG] The fixed amount of bus space which is
3107 reserved for hotplug bridge's IO window.
3108 Default size is 256 bytes.
3109 hpmemsize=nn[KMG] The fixed amount of bus space which is
3110 reserved for hotplug bridge's memory window.
3111 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06003112 hpbussize=nn The minimum amount of additional bus numbers
3113 reserved for buses below a hotplug bridge.
3114 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08003115 realloc= Enable/disable reallocating PCI bridge resources
3116 if allocations done by BIOS are too small to
3117 accommodate resources required by all child
3118 devices.
3119 off: Turn realloc off
3120 on: Turn realloc on
3121 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01003122 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06003123 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3124 only look for one device below a PCIe downstream
3125 port.
=?UTF-8?q?Christian=20K=C3=B6nig?=f32ab752018-01-11 14:23:29 +01003126 big_root_window Try to add a big 64bit memory window to the PCIe
3127 root complex on AMD CPUs. Some GFX hardware
3128 can resize a BAR to allow access to all VRAM.
3129 Adding the window is slightly risky (it may
3130 conflict with unreported devices), so this
3131 taints the kernel.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003132
Chuck Ebberte5665a42008-09-24 20:40:34 -04003133 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3134 Management.
3135 off Disable ASPM.
3136 force Enable ASPM even on devices that claim not to support it.
3137 WARNING: Forcing ASPM on may cause system lockups.
3138
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05003139 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3140 nomsi Do not use MSI for PCI Express Native Hotplug (this
3141 makes all PCIe ports use INTx for hotplug services).
3142
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003143 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003144 auto Ask the BIOS whether or not to use native PCIe services
3145 associated with PCIe ports (PME, hot-plug, AER). Use
3146 them only if that is allowed by the BIOS.
3147 native Use native PCIe services associated with PCIe ports
3148 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003149 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3150 ports driver.
3151
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03003152 pcie_port_pm= [PCIE] PCIe port power management handling:
3153 off Disable power management of all PCIe ports
3154 force Forcibly enable power management of all PCIe ports
3155
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003156 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003157 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003158 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003159
Linus Torvalds1da177e2005-04-16 15:20:36 -07003160 pcmv= [HW,PCMCIA] BadgePAD 4
3161
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303162 pd_ignore_unused
3163 [PM]
3164 Keep all power-domains already enabled by bootloader on,
3165 even if no driver has claimed them. This is useful
3166 for debug and development, but should not be
3167 needed on a platform with proper driver support.
3168
Linus Torvalds1da177e2005-04-16 15:20:36 -07003169 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003170 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003171
3172 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3173 boot time.
3174 Format: { 0 | 1 }
3175 See arch/parisc/kernel/pdc_chassis.c
3176
Tejun Heof58dc012009-08-14 15:00:50 +09003177 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003178 Currently supported values are "embed" and "page".
3179 Archs may support subset or none of the selections.
3180 See comments in mm/percpu.c for details on each
3181 allocator. This parameter is primarily for debugging
3182 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003183
Linus Torvalds1da177e2005-04-16 15:20:36 -07003184 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003185 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003186
3187 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003188 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003189
3190 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003191 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003192
3193 plip= [PPT,NET] Parallel port network link
3194 Format: { parport<nr> | timid | 0 }
Tom Saeger3ba9b1b2017-10-10 12:36:16 -05003195 See also Documentation/admin-guide/parport.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196
Randy Dunlap16290242011-08-13 12:34:52 -07003197 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003198 Override pmtimer IOPort with a hex value.
3199 e.g. pmtmr=0x508
3200
Bjorn Helgaas96242112011-08-11 12:14:05 -06003201 pnp.debug=1 [PNP]
3202 Enable PNP debug messages (depends on the
3203 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3204 via /sys/module/pnp/parameters/debug. We always show
3205 current resource usage; turning this on also shows
3206 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003207
Linus Torvalds1da177e2005-04-16 15:20:36 -07003208 pnpacpi= [ACPI]
3209 { off }
3210
3211 pnpbios= [ISAPNP]
3212 { on | off | curr | res | no-curr | no-res }
3213
3214 pnp_reserve_irq=
3215 [ISAPNP] Exclude IRQs for the autoconfiguration
3216
3217 pnp_reserve_dma=
3218 [ISAPNP] Exclude DMAs for the autoconfiguration
3219
3220 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003221 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003222
3223 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003224 [ISAPNP] Exclude memory regions for the
3225 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003226 Ranges are in pairs (memory base and size).
3227
Randy Dunlap4af94f32009-04-17 18:30:28 -07003228 ports= [IP_VS_FTP] IPVS ftp helper module
3229 Default is 21.
3230 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3231 may be specified.
3232 Format: <port>,<port>....
3233
Balbir Singhc3cbd072016-12-02 00:08:26 +11003234 powersave=off [PPC] This option disables power saving features.
3235 It specifically disables cpuidle and sets the
3236 platform machine description specific power_save
3237 function to NULL. On Idle the CPU just reduces
3238 execution priority.
3239
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003240 ppc_strict_facility_enable
3241 [PPC] This option catches any kernel floating point,
3242 Altivec, VSX and SPE outside of regions specifically
3243 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3244 There is some performance impact when enabling this.
3245
Cyril Bur07fd1762017-10-12 21:17:16 +11003246 ppc_tm= [PPC]
3247 Format: {"off"}
3248 Disable Hardware Transactional Memory
3249
Ingo Molnar45807a12007-07-15 23:40:10 -07003250 print-fatal-signals=
3251 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003252
3253 If enabled, warn about various signal handling
3254 related application anomalies: too many signals,
3255 too many POSIX.1 timers, fatal signals causing a
3256 coredump - etc.
3257
3258 If you hit the warning due to signal overflow,
3259 you might want to try "ulimit -i unlimited".
3260
Ingo Molnar45807a12007-07-15 23:40:10 -07003261 default: off.
3262
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003263 printk.always_kmsg_dump=
3264 Trigger kmsg_dump for cases other than kernel oops or
3265 panics
3266 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3267 default: disabled
3268
Borislav Petkov750afe72016-08-02 14:04:07 -07003269 printk.devkmsg={on,off,ratelimit}
3270 Control writing to /dev/kmsg.
3271 on - unlimited logging to /dev/kmsg from userspace
3272 off - logging to /dev/kmsg disabled
3273 ratelimit - ratelimit the logging
3274 Default: ratelimit
3275
Randy Dunlape84845c2007-07-15 23:40:25 -07003276 printk.time= Show timing data prefixed to each printk message line
3277 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3278
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003279 processor.max_cstate= [HW,ACPI]
3280 Limit processor to maximum C-state
3281 max_cstate=9 overrides any DMI blacklist limit.
3282
3283 processor.nocst [HW,ACPI]
3284 Ignore the _CST method to determine C-states,
3285 instead using the legacy FADT method
3286
Linus Torvalds1da177e2005-04-16 15:20:36 -07003287 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlape7e61fc2017-11-19 21:08:11 -08003288 Format: [<profiletype>,]<number>
3289 Param: <profiletype>: "schedule", "sleep", or "kvm"
3290 [defaults to kernel profiling]
Randy Dunlapa9913042005-10-23 12:57:11 -07003291 Param: "schedule" - profile schedule points.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003292 Param: "sleep" - profile D-state sleeping (millisecs).
3293 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003294 Param: "kvm" - profile VM exits.
Randy Dunlape7e61fc2017-11-19 21:08:11 -08003295 Param: <number> - step/bucket size as a power of 2 for
3296 statistical time based profiling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003297
Linus Torvalds1da177e2005-04-16 15:20:36 -07003298 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3299 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003300 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003301
Randy Dunlapa9913042005-10-23 12:57:11 -07003302 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3303 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003304 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3305 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003306 psmouse.resetafter= [HW,MOUSE]
3307 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003308 (0 = never).
3309 psmouse.resolution=
3310 [HW,MOUSE] Set desired mouse resolution, in dpi.
3311 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003312 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003313 0 = disabled, 1 = enabled (default).
3314
Matthew Garrettdee28e72011-07-21 16:57:55 -04003315 pstore.backend= Specify the name of the pstore backend to use
3316
Linus Torvalds1da177e2005-04-16 15:20:36 -07003317 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003318 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003319
Dave Hansen01c9b172018-01-05 09:44:36 -08003320 pti= [X86_64] Control Page Table Isolation of user and
3321 kernel address spaces. Disabling this feature
3322 removes hardening, but improves performance of
3323 system calls and interrupts.
3324
3325 on - unconditionally enable
3326 off - unconditionally disable
3327 auto - kernel detects whether your CPU model is
3328 vulnerable to issues that PTI mitigates
3329
3330 Not specifying this option is equivalent to pti=auto.
3331
3332 nopti [X86_64]
3333 Equivalent to pti=off
Borislav Petkov41f4c202017-12-12 14:39:52 +01003334
Kay Sieversdc8c8582007-08-15 12:25:38 +02003335 pty.legacy_count=
3336 [KNL] Number of legacy pty's. Overwrites compiled-in
3337 default number.
3338
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003339 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003340
Linus Torvalds1da177e2005-04-16 15:20:36 -07003341 r128= [HW,DRM]
3342
3343 raid= [HW,RAID]
Jani Nikulae52347b2016-11-03 12:10:10 +02003344 See Documentation/admin-guide/md.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003345
Linus Torvalds1da177e2005-04-16 15:20:36 -07003346 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003347 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003348
Borislav Petkov011d8262017-03-27 11:33:02 +02003349 ras=option[,option,...] [KNL] RAS-specific options
3350
3351 cec_disable [X86]
3352 Disable the Correctable Errors Collector,
3353 see CONFIG_RAS_CEC help text.
3354
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003355 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003356 The argument is a cpu list, as described above.
3357
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003358 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3359 the specified list of CPUs to be no-callback CPUs.
3360 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003361 be offloaded to "rcuox/N" kthreads created for
3362 that purpose, where "x" is "b" for RCU-bh, "p"
3363 for RCU-preempt, and "s" for RCU-sched, and "N"
3364 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003365 offloaded CPUs, which can be useful for HPC and
3366 real-time workloads. It can also improve energy
3367 efficiency for asymmetric multiprocessors.
3368
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003369 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003370 Rather than requiring that offloaded CPUs
3371 (specified by rcu_nocbs= above) explicitly
3372 awaken the corresponding "rcuoN" kthreads,
3373 make these kthreads poll for callbacks.
3374 This improves the real-time response for the
3375 offloaded CPUs by relieving them of the need to
3376 wake up the corresponding kthread, but degrades
3377 energy efficiency by requiring that the kthreads
3378 periodically wake up to do the polling.
3379
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003380 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003381 Set maximum number of finished RCU callbacks to
3382 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003383
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003384 rcutree.dump_tree= [KNL]
3385 Dump the structure of the rcu_node combining tree
3386 out at early boot. This is used for diagnostic
3387 purposes, to verify correct tree setup.
3388
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003389 rcutree.gp_cleanup_delay= [KNL]
3390 Set the number of jiffies to delay each step of
Paul E. McKenney90040c92017-05-10 14:36:55 -07003391 RCU grace-period cleanup.
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003392
Paul E. McKenney37745d22015-01-22 18:24:08 -08003393 rcutree.gp_init_delay= [KNL]
3394 Set the number of jiffies to delay each step of
Paul E. McKenney90040c92017-05-10 14:36:55 -07003395 RCU grace-period initialization.
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003396
3397 rcutree.gp_preinit_delay= [KNL]
3398 Set the number of jiffies to delay each step of
3399 RCU grace-period pre-initialization, that is,
3400 the propagation of recent CPU-hotplug changes up
Paul E. McKenney90040c92017-05-10 14:36:55 -07003401 the rcu_node combining tree.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003402
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003403 rcutree.rcu_fanout_exact= [KNL]
3404 Disable autobalancing of the rcu_node combining
3405 tree. This is used by rcutorture, and might
3406 possibly be useful for architectures having high
3407 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003408
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003409 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003410 Change the number of CPUs assigned to each
3411 leaf rcu_node structure. Useful for very
3412 large systems, which will choose the value 64,
3413 and for NUMA systems with large remote-access
3414 latencies, which will choose a value aligned
3415 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003416
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003417 rcutree.jiffies_till_sched_qs= [KNL]
3418 Set required age in jiffies for a
3419 given grace period before RCU starts
3420 soliciting quiescent-state help from
3421 rcu_note_context_switch().
3422
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003423 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003424 Set delay from grace-period initialization to
3425 first attempt to force quiescent states.
3426 Units are jiffies, minimum value is zero,
3427 and maximum value is HZ.
3428
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003429 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003430 Set delay between subsequent attempts to force
3431 quiescent states. Units are jiffies, minimum
3432 value is one, and maximum value is HZ.
3433
Clark Williams21871d72014-09-12 21:21:09 -05003434 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003435 Set the SCHED_FIFO priority of the RCU per-CPU
3436 kthreads (rcuc/N). This value is also used for
3437 the priority of the RCU boost threads (rcub/N)
3438 and for the RCU grace-period kthreads (rcu_bh,
3439 rcu_preempt, and rcu_sched). If RCU_BOOST is
3440 set, valid values are 1-99 and the default is 1
3441 (the least-favored priority). Otherwise, when
3442 RCU_BOOST is not set, valid values are 0-99 and
3443 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003444
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003445 rcutree.rcu_nocb_leader_stride= [KNL]
3446 Set the number of NOCB kthread groups, which
3447 defaults to the square root of the number of
3448 CPUs. Larger numbers reduces the wakeup overhead
3449 on the per-CPU grace-period kthreads, but increases
3450 that same overhead on each group's leader.
3451
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003452 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003453 Set threshold of queued RCU callbacks beyond which
3454 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003455
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003456 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003457 Set threshold of queued RCU callbacks below which
3458 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003459
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003460 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003461 Set wakeup interval for idle CPUs that have
3462 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003463
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003464 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003465 Set wakeup interval for idle CPUs that have
3466 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3467 Lazy RCU callbacks are those which RCU can
3468 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003469
Paul E. McKenneye3c50df2017-01-06 15:14:11 -08003470 rcutree.rcu_kick_kthreads= [KNL]
3471 Cause the grace-period kthread to get an extra
3472 wake_up() if it sleeps three times longer than
3473 it should at force-quiescent-state time.
3474 This wake_up() will be accompanied by a
3475 WARN_ONCE() splat and an ftrace_dump().
3476
Paul E. McKenney881ed592017-04-17 12:47:10 -07003477 rcuperf.gp_async= [KNL]
3478 Measure performance of asynchronous
3479 grace-period primitives such as call_rcu().
3480
3481 rcuperf.gp_async_max= [KNL]
3482 Specify the maximum number of outstanding
3483 callbacks per writer thread. When a writer
3484 thread exceeds this limit, it invokes the
3485 corresponding flavor of rcu_barrier() to allow
3486 previously posted callbacks to drain.
3487
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003488 rcuperf.gp_exp= [KNL]
3489 Measure performance of expedited synchronous
3490 grace-period primitives.
3491
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003492 rcuperf.holdoff= [KNL]
3493 Set test-start holdoff period. The purpose of
3494 this parameter is to delay the start of the
3495 test until boot completes in order to avoid
3496 interference.
3497
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003498 rcuperf.nreaders= [KNL]
3499 Set number of RCU readers. The value -1 selects
3500 N, where N is the number of CPUs. A value
3501 "n" less than -1 selects N-n+1, where N is again
3502 the number of CPUs. For example, -2 selects N
3503 (the number of CPUs), -3 selects N+1, and so on.
3504 A value of "n" less than or equal to -N selects
3505 a single reader.
3506
3507 rcuperf.nwriters= [KNL]
3508 Set number of RCU writers. The values operate
3509 the same as for rcuperf.nreaders.
3510 N, where N is the number of CPUs
3511
Paul E. McKenney820687a2017-04-25 15:12:56 -07003512 rcuperf.perf_type= [KNL]
3513 Specify the RCU implementation to test.
3514
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003515 rcuperf.shutdown= [KNL]
3516 Shut the system down after performance tests
3517 complete. This is useful for hands-off automated
3518 testing.
3519
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003520 rcuperf.verbose= [KNL]
3521 Enable additional printk() statements.
3522
Paul E. McKenney820687a2017-04-25 15:12:56 -07003523 rcuperf.writer_holdoff= [KNL]
3524 Write-side holdoff between grace periods,
3525 in microseconds. The default of zero says
3526 no holdoff.
3527
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003528 rcutorture.cbflood_inter_holdoff= [KNL]
3529 Set holdoff time (jiffies) between successive
3530 callback-flood tests.
3531
3532 rcutorture.cbflood_intra_holdoff= [KNL]
3533 Set holdoff time (jiffies) between successive
3534 bursts of callbacks within a given callback-flood
3535 test.
3536
3537 rcutorture.cbflood_n_burst= [KNL]
3538 Set the number of bursts making up a given
3539 callback-flood test. Set this to zero to
3540 disable callback-flood testing.
3541
3542 rcutorture.cbflood_n_per_burst= [KNL]
3543 Set the number of callbacks to be registered
3544 in a given burst of a callback-flood test.
3545
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003546 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003547 Set duration of force_quiescent_state bursts
3548 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003549
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003550 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003551 Set holdoff time within force_quiescent_state bursts
3552 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003553
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003554 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003555 Set wait time between force_quiescent_state bursts
3556 in seconds.
3557
3558 rcutorture.gp_cond= [KNL]
3559 Use conditional/asynchronous update-side
3560 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003561
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003562 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003563 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003564
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003565 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003566 Use normal (non-expedited) asynchronous
3567 update-side primitives, if available.
3568
3569 rcutorture.gp_sync= [KNL]
3570 Use normal (non-expedited) synchronous
3571 update-side primitives, if available. If all
3572 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3573 rcutorture.gp_normal=, and rcutorture.gp_sync=
3574 are zero, rcutorture acts as if is interpreted
3575 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003576
3577 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003578 Set callbacks/threads for rcu_barrier() testing.
3579
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003580 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003581 Set number of concurrent RCU writers. These just
3582 stress RCU, they don't participate in the actual
3583 test, hence the "fake".
3584
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003585 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003586 Set number of RCU readers. The value -1 selects
3587 N-1, where N is the number of CPUs. A value
3588 "n" less than -1 selects N-n-2, where N is again
3589 the number of CPUs. For example, -2 selects N
3590 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003591
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003592 rcutorture.object_debug= [KNL]
3593 Enable debug-object double-call_rcu() testing.
3594
3595 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003596 Set time (s) after boot for CPU-hotplug testing.
3597
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003598 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003599 Set time (s) between CPU-hotplug operations, or
3600 zero to disable CPU-hotplug testing.
3601
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003602 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003603 Set task-shuffle interval (s). Shuffling tasks
3604 allows some CPUs to go into dyntick-idle mode
3605 during the rcutorture test.
3606
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003607 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003608 Set time (s) after boot system shutdown. This
3609 is useful for hands-off automated testing.
3610
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003611 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003612 Duration of CPU stall (s) to test RCU CPU stall
3613 warnings, zero to disable.
3614
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003615 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003616 Time to wait (s) after boot before inducing stall.
3617
Paul E. McKenney2b1516e2017-08-18 16:11:37 -07003618 rcutorture.stall_cpu_irqsoff= [KNL]
3619 Disable interrupts while stalling if set.
3620
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003621 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003622 Time (s) between statistics printk()s.
3623
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003624 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003625 Time (s) to stutter testing, for example, specifying
3626 five seconds causes the test to run for five seconds,
3627 wait for five seconds, and so on. This tests RCU's
3628 ability to transition abruptly to and from idle.
3629
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003630 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003631 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3632 "Maybe" means test if the RCU implementation
3633 under test support RCU priority boosting.
3634
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003635 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003636 Duration (s) of each individual boost test.
3637
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003638 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003639 Interval (s) between each boost test.
3640
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003641 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003642 Test RCU's dyntick-idle handling. See also the
3643 rcutorture.shuffle_interval parameter.
3644
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003645 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003646 Specify the RCU implementation to test.
3647
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003648 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003649 Enable additional printk() statements.
3650
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003651 rcupdate.rcu_cpu_stall_suppress= [KNL]
3652 Suppress RCU CPU stall warning messages.
3653
3654 rcupdate.rcu_cpu_stall_timeout= [KNL]
3655 Set timeout for RCU CPU stall warning messages.
3656
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003657 rcupdate.rcu_expedited= [KNL]
3658 Use expedited grace-period primitives, for
3659 example, synchronize_rcu_expedited() instead
3660 of synchronize_rcu(). This reduces latency,
3661 but can increase CPU utilization, degrade
3662 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003663 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003664
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003665 rcupdate.rcu_normal= [KNL]
3666 Use only normal grace-period primitives,
3667 for example, synchronize_rcu() instead of
3668 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003669 real-time latency, CPU utilization, and
3670 energy efficiency, but can expose users to
3671 increased grace-period latency. This parameter
3672 overrides rcupdate.rcu_expedited. No effect on
3673 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003674
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003675 rcupdate.rcu_normal_after_boot= [KNL]
3676 Once boot has completed (that is, after
3677 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003678 only normal grace-period primitives. No effect
3679 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003680
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003681 rcupdate.rcu_task_stall_timeout= [KNL]
3682 Set timeout in jiffies for RCU task stall warning
3683 messages. Disable with a value less than or equal
3684 to zero.
3685
Pranith Kumar74860fe2014-09-19 11:34:09 -04003686 rcupdate.rcu_self_test= [KNL]
3687 Run the RCU early boot self tests
3688
3689 rcupdate.rcu_self_test_bh= [KNL]
3690 Run the RCU bh early boot self tests
3691
3692 rcupdate.rcu_self_test_sched= [KNL]
3693 Run the RCU sched early boot self tests
3694
Olof Johanssonffdfc402005-09-06 15:17:19 -07003695 rdinit= [KNL]
3696 Format: <full_path>
3697 Run specified binary instead of /init from the ramdisk,
3698 used for early userspace startup. See initrd.
3699
Tony Luck1d9807f2017-08-24 09:26:51 -07003700 rdt= [HW,X86,RDT]
3701 Turn on/off individual RDT features. List is:
Fenghua Yu31516de2017-12-20 14:57:24 -08003702 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
3703 mba.
Tony Luck1d9807f2017-08-24 09:26:51 -07003704 E.g. to turn on cmt and turn off mba use:
3705 rdt=cmt,!mba
3706
Robin Holt1b3a5d02013-07-08 16:01:42 -07003707 reboot= [KNL]
3708 Format (x86 or x86_64):
3709 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3710 [[,]s[mp]#### \
3711 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3712 [[,]f[orce]
3713 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3714 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3715 reboot_force is either force or not specified,
3716 reboot_cpu is s[mp]#### with #### being the processor
3717 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003718
Paul Jackson46b6d942008-07-04 10:00:09 -07003719 relax_domain_level=
3720 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003721 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003722
Bjorn Helgaasffd2e8d2017-12-01 11:50:33 -06003723 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
3724 Format: <base1>,<size1>[,<base2>,<size2>,...]
3725 Reserve I/O ports or memory so the kernel won't use
3726 them. If <base> is less than 0x10000, the region
3727 is assumed to be I/O ports; otherwise it is memory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003728
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003729 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003730 Format: nn[KMG]
3731 Reserves a hole at the top of the kernel virtual
3732 address space.
3733
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003734 reservelow= [X86]
3735 Format: nn[K]
3736 Set the amount of memory to reserve for BIOS at
3737 the bottom of the address space.
3738
Vivek Goyal7e962872006-09-27 01:50:44 -07003739 reset_devices [KNL] Force drivers to reset the underlying device
3740 during initialization.
3741
Randy Dunlapa9913042005-10-23 12:57:11 -07003742 resume= [SWSUSP]
3743 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003744 Format:
3745 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003746
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003747 resume_offset= [SWSUSP]
3748 Specify the offset from the beginning of the partition
3749 given by "resume=" at which the swap header is located,
3750 in <PAGE_SIZE> units (needed only for swap files).
3751 See Documentation/power/swsusp-and-swap-files.txt
3752
Barry Songf126f732011-10-10 23:38:41 +02003753 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3754 read the resume files
3755
Barry Song6f8d7022011-10-06 20:34:46 +02003756 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3757 Useful for devices that are detected asynchronously
3758 (e.g. USB and MMC devices).
3759
Bojan Smojverf996fc92010-09-09 23:06:23 +02003760 hibernate= [HIBERNATION]
3761 noresume Don't check if there's a hibernation image
3762 present during boot.
3763 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003764 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003765 protect_image Turn on image protection during restoration
3766 (that will set all pages holding image data
3767 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003768
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003769 retain_initrd [RAM] Keep initrd memory after extraction
3770
Andrew Clausen0efbb782015-01-09 20:24:55 +00003771 rfkill.default_state=
3772 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3773 etc. communication is blocked by default.
3774 1 Unblocked.
3775
3776 rfkill.master_switch_mode=
3777 0 The "airplane mode" button does nothing.
3778 1 The "airplane mode" button toggles between everything
3779 blocked and the previous configuration.
3780 2 The "airplane mode" button toggles between everything
3781 blocked and everything unblocked.
3782
Linus Torvalds1da177e2005-04-16 15:20:36 -07003783 rhash_entries= [KNL,NET]
3784 Set number of hash buckets for route cache
3785
Grzegorz Andrejczuke16fd002017-01-20 14:22:36 +01003786 ring3mwait=disable
3787 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3788 CPUs.
3789
Linus Torvalds1da177e2005-04-16 15:20:36 -07003790 ro [KNL] Mount root device read-only on boot
3791
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003792 rodata= [KNL]
3793 on Mark read-only kernel memory as read-only (default).
3794 off Leave read-only kernel memory writable for debugging.
3795
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003796 rockchip.usb_uart
3797 Enable the uart passthrough on the designated usb port
3798 on Rockchip SoCs. When active, the signals of the
3799 debug-uart get routed to the D+ and D- pins of the usb
3800 port and the regular usb controller gets disabled.
3801
Linus Torvalds1da177e2005-04-16 15:20:36 -07003802 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003803 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003804
3805 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3806 mount the root filesystem
3807
3808 rootflags= [KNL] Set root filesystem mount option string
3809
3810 rootfstype= [KNL] Set root filesystem type
3811
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003812 rootwait [KNL] Wait (indefinitely) for root device to show up.
3813 Useful for devices that are detected asynchronously
3814 (e.g. USB and MMC devices).
3815
Robert Tivy5c71d612013-03-28 18:41:46 -07003816 rproc_mem=nn[KMG][@address]
3817 [KNL,ARM,CMA] Remoteproc physical memory block.
3818 Memory area to be used by remote processor image,
3819 managed by CMA.
3820
Linus Torvalds1da177e2005-04-16 15:20:36 -07003821 rw [KNL] Mount root device read-write on boot
3822
3823 S [KNL] Run init in single mode
3824
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003825 s390_iommu= [HW,S390]
3826 Set s390 IOTLB flushing mode
3827 strict
3828 With strict flushing every unmap operation will result in
3829 an IOTLB flush. Default is lazy flushing before reuse,
3830 which is faster.
3831
Linus Torvalds1da177e2005-04-16 15:20:36 -07003832 sa1100ir [NET]
3833 See drivers/net/irda/sa1100_ir.c.
3834
Linus Torvalds1da177e2005-04-16 15:20:36 -07003835 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003836
Mike Travisf6630112009-11-17 18:22:15 -06003837 sched_debug [KNL] Enables verbose scheduler debug messages.
3838
Mel Gormancb251762016-02-05 09:08:36 +00003839 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3840 Allowed values are enable and disable. This feature
3841 incurs a small amount of overhead in the scheduler
3842 but is useful for debugging and performance tuning.
3843
Mike Galbraith5307c952012-05-08 12:20:58 +02003844 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3845 xtime_lock contention on larger systems, and/or RCU lock
3846 contention on all systems with CONFIG_MAXSMP set.
3847 Format: { "0" | "1" }
3848 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3849 1 -- enable.
3850 Note: increases power consumption, thus should only be
3851 enabled if running jitter sensitive (HPC/RT) workloads.
3852
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003853 security= [SECURITY] Choose a security module to enable at boot.
3854 If this boot parameter is not specified, only the first
3855 security module asking for security registration will be
3856 loaded. An invalid security module name will be treated
3857 as if no module has been chosen.
3858
3859 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003860 Format: { "0" | "1" }
3861 See security/selinux/Kconfig help text.
3862 0 -- disable.
3863 1 -- enable.
3864 Default value is set via kernel config option.
3865 If enabled at boot time, /selinux/disable can be used
3866 later to disable prior to initial policy load.
3867
John Johansenc1c124e2010-07-29 14:48:09 -07003868 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3869 Format: { "0" | "1" }
3870 See security/apparmor/Kconfig help text
3871 0 -- disable.
3872 1 -- enable.
3873 Default value is set via kernel config option.
3874
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003875 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003876
Linus Torvalds1da177e2005-04-16 15:20:36 -07003877 shapers= [NET]
3878 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003879
Linus Torvalds1da177e2005-04-16 15:20:36 -07003880 simeth= [IA-64]
3881 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003882
Linus Torvalds1da177e2005-04-16 15:20:36 -07003883 slram= [HW,MTD]
3884
Joonsoo Kim423c9292014-10-09 15:26:22 -07003885 slab_nomerge [MM]
3886 Disable merging of slabs with similar size. May be
3887 necessary if there is some reason to distinguish
Kees Cook7660a6f2017-07-06 15:36:40 -07003888 allocs to different slabs, especially in hardened
3889 environments where the risk of heap overflows and
3890 layout control by attackers can usually be
3891 frustrated by disabling merging. This will reduce
3892 most of the exposure of a heap attack to a single
3893 cache (risks via metadata attacks are mostly
3894 unchanged). Debug options disable merging on their
3895 own.
Joonsoo Kim423c9292014-10-09 15:26:22 -07003896 For more information see Documentation/vm/slub.txt.
3897
David Rientjes3df1ccc2011-10-18 22:09:28 -07003898 slab_max_order= [MM, SLAB]
3899 Determines the maximum allowed order for slabs.
3900 A high setting may cause OOMs due to memory
3901 fragmentation. Defaults to 1 for systems with
3902 more than 32MB of RAM, 0 otherwise.
3903
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003904 slub_debug[=options[,slabs]] [MM, SLUB]
3905 Enabling slub_debug allows one to determine the
3906 culprit if slab objects become corrupted. Enabling
3907 slub_debug can create guard zones around objects and
3908 may poison objects when not in use. Also tracks the
3909 last alloc / free. For more information see
3910 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003911
Tejun Heo1663f262017-02-22 15:41:39 -08003912 slub_memcg_sysfs= [MM, SLUB]
3913 Determines whether to enable sysfs directories for
3914 memory cgroup sub-caches. 1 to enable, 0 to disable.
3915 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3916 Enabling this can lead to a very high number of debug
3917 directories and files being created under
3918 /sys/kernel/slub.
3919
Christoph Lameterc1aee212007-05-31 00:40:47 -07003920 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003921 Determines the maximum allowed order for slabs.
3922 A high setting may cause OOMs due to memory
3923 fragmentation. For more information see
3924 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003925
3926 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003927 The minimum number of objects per slab. SLUB will
3928 increase the slab order up to slub_max_order to
3929 generate a sufficiently large slab able to contain
3930 the number of objects indicated. The higher the number
3931 of objects the smaller the overhead of tracking slabs
3932 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003933 For more information see Documentation/vm/slub.txt.
3934
3935 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003936 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003937 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003938 For more information see Documentation/vm/slub.txt.
3939
3940 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003941 Same with slab_nomerge. This is supported for legacy.
3942 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003943
Linus Torvalds1da177e2005-04-16 15:20:36 -07003944 smart2= [HW]
3945 Format: <io1>[,<io2>[,...,<io8>]]
3946
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003947 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3948 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3949 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3950 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3951 smsc-ircc2.ircc_irq= [HW] IRQ line
3952 smsc-ircc2.ircc_dma= [HW] DMA channel
3953 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3954 0: Toshiba Satellite 1800 (GP data pin select)
3955 1: Fast pin select (default)
3956 2: ATC IRMode
3957
Sascha Silbe52c48c52016-04-05 12:53:38 +02003958 smt [KNL,S390] Set the maximum number of threads (logical
3959 CPUs) to use per physical CPU on systems capable of
3960 symmetric multithreading (SMT). Will be capped to the
3961 actual hardware limit.
3962 Format: <integer>
3963 Default: -1 (no limit)
3964
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003965 softlockup_panic=
3966 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003967 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003968
Borislav Petkov3ce62382017-10-03 17:54:07 +02003969 A nonzero value instructs the soft-lockup detector
3970 to panic the machine when a soft-lockup occurs. This
3971 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
3972 which is the respective build-time switch to that
3973 functionality.
3974
Aaron Tomlined235872014-06-23 13:22:05 -07003975 softlockup_all_cpu_backtrace=
3976 [KNL] Should the soft-lockup detector generate
3977 backtraces on all cpus.
3978 Format: <integer>
3979
Linus Torvalds1da177e2005-04-16 15:20:36 -07003980 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003981 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003982
David Woodhouseda285122018-01-11 21:46:26 +00003983 spectre_v2= [X86] Control mitigation of Spectre variant 2
3984 (indirect branch speculation) vulnerability.
3985
3986 on - unconditionally enable
3987 off - unconditionally disable
3988 auto - kernel detects whether your CPU model is
3989 vulnerable
3990
3991 Selecting 'on' will, and 'auto' may, choose a
3992 mitigation method at run time according to the
3993 CPU, the available microcode, the setting of the
3994 CONFIG_RETPOLINE configuration option, and the
3995 compiler with which the kernel was built.
3996
3997 Specific mitigations can also be selected manually:
3998
3999 retpoline - replace indirect branches
4000 retpoline,generic - google's original retpoline
4001 retpoline,amd - AMD-specific minimal thunk
4002
4003 Not specifying this option is equivalent to
4004 spectre_v2=auto.
4005
Linus Torvalds1da177e2005-04-16 15:20:36 -07004006 spia_io_base= [HW,MTD]
4007 spia_fio_base=
4008 spia_pedr=
4009 spia_peddr=
4010
Paul E. McKenneyc350c002017-05-03 15:35:32 -07004011 srcutree.counter_wrap_check [KNL]
4012 Specifies how frequently to check for
4013 grace-period sequence counter wrap for the
4014 srcu_data structure's ->srcu_gp_seq_needed field.
4015 The greater the number of bits set in this kernel
4016 parameter, the less frequently counter wrap will
4017 be checked for. Note that the bottom two bits
4018 are ignored.
4019
Paul E. McKenney22607d62017-04-25 14:03:11 -07004020 srcutree.exp_holdoff [KNL]
4021 Specifies how many nanoseconds must elapse
4022 since the end of the last SRCU grace period for
4023 a given srcu_struct until the next normal SRCU
4024 grace period will be considered for automatic
4025 expediting. Set to zero to disable automatic
4026 expediting.
4027
Hugh Dickins1be71072017-06-19 04:03:24 -07004028 stack_guard_gap= [MM]
4029 override the default stack gap protection. The value
4030 is in page units and it defines how many pages prior
4031 to (for stacks growing down) resp. after (for stacks
4032 growing up) the main stack are reserved for no other
4033 mapping. Default value is 256 pages.
4034
Steven Rostedtf38f1d22008-12-16 23:06:40 -05004035 stacktrace [FTRACE]
4036 Enabled the stack tracer on boot up.
4037
Steven Rostedt762e1202011-12-19 22:01:00 -05004038 stacktrace_filter=[function-list]
4039 [FTRACE] Limit the functions that the stack tracer
4040 will trace at boot up. function-list is a comma separated
4041 list of functions. This list can be changed at run
4042 time by the stack_trace_filter file in the debugfs
4043 tracing directory. Note, this enables stack tracing
4044 and the stacktrace above is not needed.
4045
Linus Torvalds1da177e2005-04-16 15:20:36 -07004046 sti= [PARISC,HW]
4047 Format: <num>
4048 Set the STI (builtin display/keyboard on the HP-PARISC
4049 machines) console (graphic card) which should be used
4050 as the initial boot-console.
4051 See also comment in drivers/video/console/sticore.c.
4052
4053 sti_font= [HW]
4054 See comment in drivers/video/console/sticore.c.
4055
4056 stifb= [HW]
4057 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
4058
Trond Myklebustcbf11072009-08-09 15:06:19 -04004059 sunrpc.min_resvport=
4060 sunrpc.max_resvport=
4061 [NFS,SUNRPC]
4062 SunRPC servers often require that client requests
4063 originate from a privileged port (i.e. a port in the
4064 range 0 < portnr < 1024).
4065 An administrator who wishes to reserve some of these
4066 ports for other uses may adjust the range that the
4067 kernel's sunrpc client considers to be privileged
4068 using these two parameters to set the minimum and
4069 maximum port values.
4070
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04004071 sunrpc.svc_rpc_per_connection_limit=
4072 [NFS,SUNRPC]
4073 Limit the number of requests that the server will
4074 process in parallel from a single connection.
4075 The default value is 0 (no limit).
4076
Greg Banks42a7fc42007-03-06 01:42:23 -08004077 sunrpc.pool_mode=
4078 [NFS]
4079 Control how the NFS server code allocates CPUs to
4080 service thread pools. Depending on how many NICs
4081 you have and where their interrupts are bound, this
4082 option will affect which CPUs will do NFS serving.
4083 Note: this parameter cannot be changed while the
4084 NFS server is running.
4085
4086 auto the server chooses an appropriate mode
4087 automatically using heuristics
4088 global a single global pool contains all CPUs
4089 percpu one pool for each CPU
4090 pernode one pool for each NUMA node (equivalent
4091 to global on non-NUMA machines)
4092
Trond Myklebustcbf11072009-08-09 15:06:19 -04004093 sunrpc.tcp_slot_table_entries=
4094 sunrpc.udp_slot_table_entries=
4095 [NFS,SUNRPC]
4096 Sets the upper limit on the number of simultaneous
4097 RPC calls that can be sent from the client to a
4098 server. Increasing these values may allow you to
4099 improve throughput, but will also increase the
4100 amount of memory reserved for use by the client.
4101
Brian Norris1d4a9c12015-02-22 21:16:49 -08004102 suspend.pm_test_delay=
4103 [SUSPEND]
4104 Sets the number of seconds to remain in a suspend test
4105 mode before resuming the system (see
4106 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4107 is set. Default value is 5.
4108
Michal Hocko07555ac2013-08-22 16:35:46 -07004109 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08004110 [KNL] Enable accounting of swap in memory resource
4111 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09004112 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08004113
Jiri Kosina91fec0f2013-11-27 13:48:09 +01004114 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01004115 Format: { <int> | force | noforce }
Jiri Kosina91fec0f2013-11-27 13:48:09 +01004116 <int> -- Number of I/O TLB slabs
4117 force -- force using of bounce buffers even if they
4118 wouldn't be automatically used by the kernel
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01004119 noforce -- Never use bounce buffers (for debugging)
Randy Dunlapa9913042005-10-23 12:57:11 -07004120
Linus Torvalds1da177e2005-04-16 15:20:36 -07004121 switches= [HW,M68k]
4122
Andi Kleene52eec12010-09-08 16:54:17 +02004123 sysfs.deprecated=0|1 [KNL]
4124 Enable/disable old style sysfs layout for old udev
4125 on older distributions. When this option is enabled
4126 very new udev will not work anymore. When this option
4127 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4128 in older udev will not work anymore.
4129 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4130 the kernel configuration.
4131
Ingo Molnar5d6f6472006-12-13 00:34:36 -08004132 sysrq_always_enabled
4133 [KNL]
4134 Ignore sysrq setting - this boot parameter will
4135 neutralize any effect of /proc/sys/kernel/sysrq.
4136 Useful for debugging.
4137
Fabian Frederick747029a2014-11-06 19:46:50 +01004138 tcpmhash_entries= [KNL,NET]
4139 Set the number of tcp_metrics_hash slots.
4140 Default value is 8192 or 16384 depending on total
4141 ram pages. This is used to specify the TCP metrics
4142 cache size. See Documentation/networking/ip-sysctl.txt
4143 "tcp_no_metrics_save" section for more details.
4144
Linus Torvalds1da177e2005-04-16 15:20:36 -07004145 tdfx= [HW,DRM]
4146
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07004147 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07004148 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07004149 standby suspend) or "freeze" (for suspend type freeze)
4150 as the system sleep state during system startup with
4151 the optional capability to repeat N number of times.
4152 The system is woken from this state using a
4153 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07004154
Linus Torvalds1da177e2005-04-16 15:20:36 -07004155 thash_entries= [KNL,NET]
4156 Set number of hash buckets for TCP connection
4157
Len Brownf8707ec2007-08-12 00:12:54 -04004158 thermal.act= [HW,ACPI]
4159 -1: disable all active trip points in all thermal zones
4160 <degrees C>: override all lowest active trip points
4161
Len Brownc52a7412007-08-14 15:49:32 -04004162 thermal.crt= [HW,ACPI]
4163 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04004164 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04004165
Len Brownf5487142007-08-12 00:12:44 -04004166 thermal.nocrt= [HW,ACPI]
4167 Set to disable actions on ACPI thermal zone
4168 critical and hot trip points.
4169
Len Brown72b33ef2007-08-12 00:12:17 -04004170 thermal.off= [HW,ACPI]
4171 1: disable ACPI thermal control
4172
Len Browna70cdc52007-08-12 00:12:35 -04004173 thermal.psv= [HW,ACPI]
4174 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08004175 <degrees C>: override all passive trip points to this
4176 value
Len Browna70cdc52007-08-12 00:12:35 -04004177
Len Brown730ff342007-08-12 00:12:26 -04004178 thermal.tzp= [HW,ACPI]
4179 Specify global default ACPI thermal zone polling rate
4180 <deci-seconds>: poll all this frequency
4181 0: no polling (default)
4182
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004183 threadirqs [KNL]
4184 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09004185 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004186
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004187 tmem [KNL,XEN]
4188 Enable the Transcendent memory driver if built-in.
4189
4190 tmem.cleancache=0|1 [KNL, XEN]
4191 Default is on (1). Disable the usage of the cleancache
4192 API to send anonymous pages to the hypervisor.
4193
4194 tmem.frontswap=0|1 [KNL, XEN]
4195 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04004196 API to send swap pages to the hypervisor. If disabled
4197 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004198
4199 tmem.selfballooning=0|1 [KNL, XEN]
4200 Default is on (1). Disable the driving of swap pages
4201 to the hypervisor.
4202
4203 tmem.selfshrinking=0|1 [KNL, XEN]
4204 Default is on (1). Partial swapoff that immediately
4205 transfers pages from Xen hypervisor back to the
4206 kernel based on different criteria.
4207
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004208 topology= [S390]
4209 Format: {off | on}
4210 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07004211 topology information if the hardware supports this.
4212 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004213 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02004214 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004215
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07004216 topology_updates= [KNL, PPC, NUMA]
4217 Format: {off}
4218 Specify if the kernel should ignore (off)
4219 topology updates sent by the hypervisor to this
4220 LPAR.
4221
Linus Torvalds1da177e2005-04-16 15:20:36 -07004222 tp720= [HW,PS2]
4223
Rajiv Andrade225a9be2010-03-25 00:55:32 -03004224 tpm_suspend_pcr=[HW,TPM]
4225 Format: integer pcr id
4226 Specify that at suspend time, the tpm driver
4227 should extend the specified pcr with zeros,
4228 as a workaround for some chips which fail to
4229 flush the last written pcr on TPM_SaveState.
4230 This will guarantee that all the other pcrs
4231 are saved.
4232
Li Zefan9d612be2009-06-24 17:33:15 +08004233 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09004234 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09004235
Li Zefan020e5f82009-07-01 10:47:05 +08004236 trace_event=[event-list]
4237 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07004238 to facilitate early boot debugging. The event-list is a
4239 comma separated list of trace events to enable. See
4240 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08004241
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04004242 trace_options=[option-list]
4243 [FTRACE] Enable or disable tracer options at boot.
4244 The option-list is a comma delimited list of options
4245 that can be enabled or disabled just as if you were
4246 to echo the option name into
4247
4248 /sys/kernel/debug/tracing/trace_options
4249
4250 For example, to enable stacktrace option (to dump the
4251 stack trace of each event), add to the command line:
4252
4253 trace_options=stacktrace
4254
4255 See also Documentation/trace/ftrace.txt "trace options"
4256 section.
4257
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05004258 tp_printk[FTRACE]
4259 Have the tracepoints sent to printk as well as the
4260 tracing ring buffer. This is useful for early boot up
4261 where the system hangs or reboots and does not give the
4262 option for reading the tracing buffer or performing a
4263 ftrace_dump_on_oops.
4264
4265 To turn off having tracepoints sent to printk,
4266 echo 0 > /proc/sys/kernel/tracepoint_printk
4267 Note, echoing 1 into this file without the
4268 tracepoint_printk kernel cmdline option has no effect.
4269
4270 ** CAUTION **
4271
4272 Having tracepoints sent to printk() and activating high
4273 frequency tracepoints such as irq or sched, can cause
4274 the system to live lock.
4275
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004276 traceoff_on_warning
4277 [FTRACE] enable this option to disable tracing when a
4278 warning is hit. This turns off "tracing_on". Tracing can
4279 be enabled again by echoing '1' into the "tracing_on"
4280 file located in /sys/kernel/debug/tracing/
4281
4282 This option is useful, as it disables the trace before
4283 the WARNING dump is called, which prevents the trace to
4284 be filled with content caused by the warning output.
4285
4286 This option can also be set at run time via the sysctl
4287 option: kernel/traceoff_on_warning
4288
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004289 transparent_hugepage=
4290 [KNL]
4291 Format: [always|madvise|never]
4292 Can be used to control the default behavior of the system
4293 with respect to transparent hugepages.
4294 See Documentation/vm/transhuge.txt for more details.
4295
john stultzd3b8f882009-08-17 16:40:47 -07004296 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004297 Format: <string>
4298 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004299 disables clocksource verification at runtime, as well
4300 as the stability checks done at bootup. Used to enable
4301 high-resolution timer mode on older hardware, and in
4302 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004303 [x86] noirqtime: Do not use TSC to do irq accounting.
4304 Used to run time disable IRQ_TIME_ACCOUNTING on any
4305 platforms where RDTSC is slow and this accounting
4306 can add overhead.
Dou Liyang6be53522017-10-09 17:03:33 +08004307 [x86] unstable: mark the TSC clocksource as unstable, this
4308 marks the TSC unconditionally unstable at bootup and
4309 avoids any further wobbles once the TSC watchdog notices.
Alok Kataria395628e2008-10-24 17:22:01 -07004310
Randy Dunlapa9913042005-10-23 12:57:11 -07004311 turbografx.map[2|3]= [HW,JOY]
4312 TurboGraFX parallel port interface
4313 Format:
4314 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Tom Saeger17521182017-10-10 12:36:23 -05004315 See also Documentation/input/devices/joystick-parport.rst
Linus Torvalds1da177e2005-04-16 15:20:36 -07004316
Christian Kujaub6935f82011-05-31 15:22:05 +00004317 udbg-immortal [PPC] When debugging early kernel crashes that
Jani Nikulae52347b2016-11-03 12:10:10 +02004318 happen after console_init() and before a proper
Christian Kujaub6935f82011-05-31 15:22:05 +00004319 console driver takes over, this boot options might
4320 help "seeing" what's going on.
4321
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004322 uhash_entries= [KNL,NET]
4323 Set number of hash buckets for UDP/UDP-Lite connections
4324
Alan Stern5f8364b2006-12-05 16:29:55 -05004325 uhci-hcd.ignore_oc=
4326 [USB] Ignore overcurrent events (default N).
4327 Some badly-designed motherboards generate lots of
4328 bogus events, for ports that aren't wired to
4329 anything. Set this parameter to avoid log spamming.
4330 Note that genuine overcurrent events won't be
4331 reported either.
4332
Simon Arlotte3a61b02008-07-19 23:32:54 +01004333 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004334 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004335
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004336 usbcore.authorized_default=
4337 [USB] Default USB device authorization:
4338 (default -1 = authorized except for wireless USB,
4339 0 = not authorized, 1 = authorized)
4340
Alan Sternb5e795f2007-02-20 15:00:53 -05004341 usbcore.autosuspend=
4342 [USB] The autosuspend time delay (in seconds) used
4343 for newly-detected USB devices (default 2). This
4344 is the time required before an idle device will be
4345 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004346 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004347
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004348 usbcore.usbfs_snoop=
4349 [USB] Set to log all usbfs traffic (default 0 = off).
4350
Alan Stern0290cc92015-11-20 13:53:22 -05004351 usbcore.usbfs_snoop_max=
4352 [USB] Maximum number of bytes to snoop in each URB
4353 (default = 65536).
4354
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004355 usbcore.blinkenlights=
4356 [USB] Set to cycle leds on hubs (default 0 = off).
4357
4358 usbcore.old_scheme_first=
4359 [USB] Start with the old device initialization
4360 scheme (default 0 = off).
4361
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004362 usbcore.usbfs_memory_mb=
4363 [USB] Memory limit (in MB) for buffers allocated by
4364 usbfs (default = 16, 0 = max = 2047).
4365
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004366 usbcore.use_both_schemes=
4367 [USB] Try the other device initialization scheme
4368 if the first one fails (default 1 = enabled).
4369
4370 usbcore.initial_descriptor_timeout=
4371 [USB] Specifies timeout for the initial 64-byte
4372 USB_REQ_GET_DESCRIPTOR request in milliseconds
4373 (default 5000 = 5.0 seconds).
4374
Oliver Neukum40d58142015-12-03 15:03:32 +01004375 usbcore.nousb [USB] Disable the USB subsystem
4376
Linus Torvalds1da177e2005-04-16 15:20:36 -07004377 usbhid.mousepoll=
4378 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004379
Tobias Jakobi933bfe42017-02-25 20:27:27 +01004380 usbhid.jspoll=
4381 [USBHID] The interval which joysticks are to be polled at.
4382
Alan Sternd4f373e2008-11-10 14:07:45 -05004383 usb-storage.delay_use=
4384 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004385 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004386
4387 usb-storage.quirks=
4388 [UMS] A list of quirks entries to supplement or
4389 override the built-in unusual_devs list. List
4390 entries are separated by commas. Each entry has
4391 the form VID:PID:Flags where VID and PID are Vendor
4392 and Product ID values (4-digit hex numbers) and
4393 Flags is a set of characters, each corresponding
4394 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004395 a = SANE_SENSE (collect more than 18 bytes
4396 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004397 b = BAD_SENSE (don't collect more than 18
4398 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004399 c = FIX_CAPACITY (decrease the reported
4400 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004401 d = NO_READ_DISC_INFO (don't use
4402 READ_DISC_INFO command);
4403 e = NO_READ_CAPACITY_16 (don't use
4404 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004405 f = NO_REPORT_OPCODES (don't use report opcodes
4406 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004407 g = MAX_SECTORS_240 (don't transfer more than
4408 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004409 h = CAPACITY_HEURISTICS (decrease the
4410 reported device capacity by one
4411 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004412 i = IGNORE_DEVICE (don't bind to this
4413 device);
Hans de Goede13630742016-04-12 12:27:09 +02004414 j = NO_REPORT_LUNS (don't use report luns
4415 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004416 l = NOT_LOCKABLE (don't try to lock and
4417 unlock ejectable media);
4418 m = MAX_SECTORS_64 (don't transfer more
4419 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004420 n = INITIAL_READ10 (force a retry of the
4421 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004422 o = CAPACITY_OK (accept the capacity
4423 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004424 p = WRITE_CACHE (the device cache is ON
4425 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004426 r = IGNORE_RESIDUE (the device reports
4427 bogus residue values);
4428 s = SINGLE_LUN (the device has only one
4429 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004430 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4431 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004432 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004433 w = NO_WP_DETECT (don't test whether the
4434 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004435 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4436 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004437 Example: quirks=0419:aaf5:rl,0421:0433:rc
4438
Stephen Boydac1667d2011-08-13 12:34:50 -07004439 user_debug= [KNL,ARM]
4440 Format: <int>
4441 See arch/arm/Kconfig.debug help text.
4442 1 - undefined instruction events
4443 2 - system calls
4444 4 - invalid data aborts
4445 8 - SIGSEGV faults
4446 16 - SIGBUS faults
4447 Example: user_debug=31
4448
Ian Campbell14315592010-02-17 10:38:10 +00004449 userpte=
4450 [X86] Flags controlling user PTE allocations.
4451
4452 nohigh = do not allocate PTE pages in
4453 HIGHMEM regardless of setting
4454 of CONFIG_HIGHPTE.
4455
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304456 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004457 On X86_32, this is an alias for vdso32=. Otherwise:
4458
4459 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004460 vdso=0: disable VDSO mapping
4461
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004462 vdso32= [X86] Control the 32-bit vDSO
4463 vdso32=1: enable 32-bit VDSO
4464 vdso32=0 or vdso32=2: disable 32-bit VDSO
4465
4466 See the help text for CONFIG_COMPAT_VDSO for more
4467 details. If CONFIG_COMPAT_VDSO is set, the default is
4468 vdso32=0; otherwise, the default is vdso32=1.
4469
4470 For compatibility with older kernels, vdso32=2 is an
4471 alias for vdso32=0.
4472
4473 Try vdso32=0 if you encounter an error that says:
4474 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004475
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004476 vector= [IA-64,SMP]
4477 vector=percpu: enable percpu vector domain
4478
Linus Torvalds1da177e2005-04-16 15:20:36 -07004479 video= [FB] Frame buffer configuration
4480 See Documentation/fb/modedb.txt.
4481
Aaron Lu3afe6da2013-06-20 15:08:55 +08004482 video.brightness_switch_enabled= [0,1]
4483 If set to 1, on receiving an ACPI notify event
4484 generated by hotkey, video driver will adjust brightness
4485 level and then send out the event to user space through
4486 the allocated input device; If set to 0, video driver
4487 will only send out the event without touching backlight
4488 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004489 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004490
Pawel Moll81a054c2012-05-09 18:30:16 +01004491 virtio_mmio.device=
4492 [VMMIO] Memory mapped virtio (platform) device.
4493
4494 <size>@<baseaddr>:<irq>[:<id>]
4495 where:
4496 <size> := size (can use standard suffixes
4497 like K, M and G)
4498 <baseaddr> := physical base address
4499 <irq> := interrupt number (as passed to
4500 request_irq())
4501 <id> := (optional) platform device id
4502 example:
4503 virtio_mmio.device=1K@0x100b0000:48:7
4504
4505 Can be used multiple times for multiple devices.
4506
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004507 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004508 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004509 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004510 Use vga=ask for menu.
4511 This is actually a boot loader parameter; the value is
4512 passed to the kernel using a special protocol.
4513
Randy Dunlapa9913042005-10-23 12:57:11 -07004514 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004515 size of <nn>. This can be used to increase the
4516 minimum size (128MB on x86). It can also be used to
4517 decrease the size and leave more room for directly
4518 mapped kernel RAM.
4519
Heiko Carstens3f429842017-08-07 15:16:15 +02004520 vmcp_cma=nn[MG] [KNL,S390]
4521 Sets the memory size reserved for contiguous memory
4522 allocations for the vmcp device driver.
4523
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004524 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4525 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004526
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004527 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4528 Format: <command>
4529
4530 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4531 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004532
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004533 vsyscall= [X86-64]
4534 Controls the behavior of vsyscalls (i.e. calls to
4535 fixed addresses of 0xffffffffff600x00 from legacy
4536 code). Most statically-linked binaries and older
4537 versions of glibc use these calls. Because these
4538 functions are at fixed addresses, they make nice
4539 targets for exploits that can control RIP.
4540
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004541 emulate [default] Vsyscalls turn into traps and are
4542 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004543
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004544 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004545 This is a little bit faster than trapping
4546 and makes a few dynamic recompilers work
4547 better than they would in emulation mode.
4548 It also makes exploits much easier to write.
4549
4550 none Vsyscalls don't work at all. This makes
4551 them quite hard to use for exploits but
4552 might break your system.
4553
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004554 vt.color= [VT] Default text color.
4555 Format: 0xYX, X = foreground, Y = background.
4556 Default: 0x07 = light gray on black.
4557
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004558 vt.cur_default= [VT] Default cursor shape.
4559 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4560 the parameters of the <Esc>[?A;B;Cc escape sequence;
4561 see VGA-softcursor.txt. Default: 2 = underline.
4562
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004563 vt.default_blu= [VT]
4564 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4565 Change the default blue palette of the console.
4566 This is a 16-member array composed of values
4567 ranging from 0-255.
4568
4569 vt.default_grn= [VT]
4570 Format: <green0>,<green1>,<green2>,...,<green15>
4571 Change the default green palette of the console.
4572 This is a 16-member array composed of values
4573 ranging from 0-255.
4574
4575 vt.default_red= [VT]
4576 Format: <red0>,<red1>,<red2>,...,<red15>
4577 Change the default red palette of the console.
4578 This is a 16-member array composed of values
4579 ranging from 0-255.
4580
4581 vt.default_utf8=
4582 [VT]
4583 Format=<0|1>
4584 Set system-wide default UTF-8 mode for all tty's.
4585 Default is 1, i.e. UTF-8 mode is enabled for all
4586 newly opened terminals.
4587
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004588 vt.global_cursor_default=
4589 [VT]
4590 Format=<-1|0|1>
4591 Set system-wide default for whether a cursor
4592 is shown on new VTs. Default is -1,
4593 i.e. cursors will be created by default unless
4594 overridden by individual drivers. 0 will hide
4595 cursors, 1 will display them.
4596
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004597 vt.italic= [VT] Default color for italic text; 0-15.
4598 Default: 2 = green.
4599
4600 vt.underline= [VT] Default color for underlined text; 0-15.
4601 Default: 3 = cyan.
4602
Randy Dunlap4724ba572010-05-03 11:42:52 -07004603 watchdog timers [HW,WDT] For information on watchdog timers,
4604 see Documentation/watchdog/watchdog-parameters.txt
4605 or other driver-specific files in the
4606 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004607
Tejun Heo82607adc2015-12-08 11:28:04 -05004608 workqueue.watchdog_thresh=
4609 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4610 warn stall conditions and dump internal state to
4611 help debugging. 0 disables workqueue stall
4612 detection; otherwise, it's the stall threshold
4613 duration in seconds. The default value is 30 and
4614 it can be updated at runtime by writing to the
4615 corresponding sysfs file.
4616
Tejun Heod55262c2013-04-01 11:23:38 -07004617 workqueue.disable_numa
4618 By default, all work items queued to unbound
4619 workqueues are affine to the NUMA nodes they're
4620 issued on, which results in better behavior in
4621 general. If NUMA affinity needs to be disabled for
4622 whatever reason, this option can be used. Note
4623 that this also can be controlled per-workqueue for
4624 workqueues visible under /sys/bus/workqueue/.
4625
Viresh Kumarcee22a12013-04-08 16:45:40 +05304626 workqueue.power_efficient
4627 Per-cpu workqueues are generally preferred because
4628 they show better performance thanks to cache
4629 locality; unfortunately, per-cpu workqueues tend to
4630 be more power hungry than unbound workqueues.
4631
4632 Enabling this makes the per-cpu workqueues which
4633 were observed to contribute significantly to power
4634 consumption unbound, leading to measurably lower
4635 power usage at the cost of small performance
4636 overhead.
4637
4638 The default value of this parameter is determined by
4639 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4640
Tejun Heof303fccb2016-02-09 17:59:38 -05004641 workqueue.debug_force_rr_cpu
4642 Workqueue used to implicitly guarantee that work
4643 items queued without explicit CPU specified are put
4644 on the local CPU. This guarantee is no longer true
4645 and while local CPU is still preferred work items
4646 may be put on foreign CPUs. This debug option
4647 forces round-robin CPU selection to flush out
4648 usages which depend on the now broken guarantee.
4649 When enabled, memory and cache locality will be
4650 impacted.
4651
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004652 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4653 default x2apic cluster mode on platforms
4654 supporting x2apic.
4655
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004656 x86_intel_mid_timer= [X86-32,APBT]
4657 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004658 Two valid options are apbt timer only and lapic timer
4659 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004660 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004661
Juergen Grossc70727a2015-07-17 06:51:36 +02004662 xen_512gb_limit [KNL,X86-64,XEN]
4663 Restricts the kernel running paravirtualized under Xen
4664 to use only up to 512 GB of RAM. The reason to do so is
4665 crash analysis tools and Xen tools for doing domain
4666 save/restore/migration must be enabled to handle larger
4667 domains.
4668
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004669 xen_emul_unplug= [HW,X86,XEN]
4670 Unplug Xen emulated devices
4671 Format: [unplug0,][unplug1]
4672 ide-disks -- unplug primary master IDE devices
4673 aux-ide-disks -- unplug non-primary-master IDE devices
4674 nics -- unplug network devices
4675 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004676 unnecessary -- unplugging emulated devices is
4677 unnecessary even if the host did not respond to
4678 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004679 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004680
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004681 xen_nopvspin [X86,XEN]
4682 Disables the ticketlock slowpath using Xen PV
4683 optimizations.
4684
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004685 xen_nopv [X86]
4686 Disables the PV optimizations forcing the HVM guest to
4687 run as generic HVM guest with no PV drivers.
4688
Linus Torvalds1da177e2005-04-16 15:20:36 -07004689 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004690 Format:
4691 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]