blob: 2ba45caabada3e88339e88ebdfaaedbb322085c8 [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>
117 Support masking of GPEs numbered from 0x00 to 0x7f.
118
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800119 acpi_no_auto_serialize [HW,ACPI]
120 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800121 AML control methods that contain the opcodes to create
122 named objects will be marked as "Serialized" by the
123 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800124 This feature is enabled by default.
125 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800126
Dominik Brodowskief694492015-05-14 15:31:28 +0200127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
128 kernels.
129
Lv Zhenga94e88c2014-04-04 12:39:11 +0800130 acpi_no_static_ssdt [HW,ACPI]
131 Disable installation of static SSDTs at early boot time
132 By default, SSDTs contained in the RSDT/XSDT will be
133 installed automatically and they will appear under
134 /sys/firmware/acpi/tables.
135 This option turns off this feature.
136 Note that specifying this option does not affect
137 dynamic table installation which will install SSDT
138 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700139
Dominik Brodowskief694492015-05-14 15:31:28 +0200140 acpi_rsdp= [ACPI,EFI,KEXEC]
141 Pass the RSDP address to the kernel, mostly used
142 on machines running EFI runtime service to boot the
143 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800144
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
146 Format: To spoof as Windows 98: ="Microsoft Windows"
147
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
149 of 2 which is mandated by ACPI 6) as the supported ACPI
150 specification revision (when using this switch, it may
151 be necessary to carry out a cold reboot _twice_ in a
152 row to make it take effect on the platform firmware).
153
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800155 acpi_osi="string1" # add string1
156 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800157 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800158 acpi_osi=! # disable all built-in OS vendor
159 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800160 acpi_osi=!! # enable all built-in OS vendor
161 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700162 acpi_osi= # disable all strings
163
Lv Zheng5dc17982013-07-22 16:08:25 +0800164 'acpi_osi=!' can be used in combination with single or
165 multiple 'acpi_osi="string1"' to support specific OS
166 vendor string(s). Note that such command can only
167 affect the default state of the OS vendor strings, thus
168 it cannot affect the default state of the feature group
169 strings and the current state of the OS vendor strings,
170 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800171 is meaningless. This command is useful when one do not
172 care about the state of the feature group strings which
173 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800174 Examples:
175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
177 can make '_OSI("Windows 2000")' TRUE.
178
179 'acpi_osi=' cannot be used in combination with other
180 'acpi_osi=' command lines, the _OSI method will not
181 exist in the ACPI namespace. NOTE that such command can
182 only affect the _OSI support state, thus specifying it
183 multiple times through kernel command line is also
184 meaningless.
185 Examples:
186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
187 FALSE.
188
Lv Zheng741d8122013-07-22 16:08:36 +0800189 'acpi_osi=!*' can be used in combination with single or
190 multiple 'acpi_osi="string1"' to support specific
191 string(s). Note that such command can affect the
192 current state of both the OS vendor strings and the
193 feature group strings, thus specifying it multiple times
194 through kernel command line is meaningful. But it may
195 still not able to affect the final state of a string if
196 there are quirks related to this string. This command
197 is useful when one want to control the state of the
198 feature group strings to debug BIOS issues related to
199 the OSPM features.
200 Examples:
201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
202 '_OSI("Module Device")' FALSE.
203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
204 '_OSI("Module Device")' TRUE.
205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 equivalent to
207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 and
209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
210 they all will make '_OSI("Windows 2000")' TRUE.
211
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530212 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700213 Override the pmtimer bug detection: force the kernel
214 to assume that this machine's pmtimer latches its value
215 and always returns good values.
216
Randy Dunlap4af94f32009-04-17 18:30:28 -0700217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
218 Format: { level | edge | high | low }
219
Randy Dunlap4af94f32009-04-17 18:30:28 -0700220 acpi_skip_timer_override [HW,ACPI]
221 Recognize and ignore IRQ0/pin2 Interrupt Override.
222 For broken nForce2 BIOS resulting in XT-PIC timer.
223
224 acpi_sleep= [HW,ACPI] Sleep options
225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200226 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700227 See Documentation/power/video.txt for information on
228 s3_bios and s3_mode.
229 s3_beep is for debugging; it makes the PC's speaker beep
230 as soon as the kernel's real-mode entry point is called.
231 s4_nohwsig prevents ACPI hardware signature from being
232 used during resume from hibernation.
233 old_ordering causes the ACPI 1.0 ordering of the _PTS
234 control method, with respect to putting devices into
235 low power states, to be enforced (the ACPI 2.0 ordering
236 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200237 nonvs prevents the kernel from saving/restoring the
238 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800239 sci_force_enable causes the kernel to set SCI_EN directly
240 on resume from S1/S3 (which is against the ACPI spec,
241 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700242
243 acpi_use_timer_override [HW,ACPI]
244 Use timer override. For some broken Nvidia NF5 boards
245 that require a timer override, but don't have HPET
246
Randy Dunlap4af94f32009-04-17 18:30:28 -0700247 add_efi_memmap [EFI; X86] Include EFI memory map in
248 kernel's map of available physical RAM.
249
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700250 agp= [AGP]
251 { off | try_unsupported }
252 off: disable AGP support
253 try_unsupported: try to drive unsupported chipsets
254 (may crash computer or cause data corruption)
255
Randy Dunlapbcfde332010-06-07 17:10:38 -0700256 ALSA [HW,ALSA]
257 See Documentation/sound/alsa/alsa-parameters.txt
258
Russell Kingd944d542010-02-20 16:13:29 +0000259 alignment= [KNL,ARM]
260 Allow the default userspace alignment fault handler
261 behaviour to be specified. Bit 0 enables warnings,
262 bit 1 enables fixups, and bit 2 sends a segfault.
263
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200264 align_va_addr= [X86-64]
265 Align virtual addresses by clearing slice [14:12] when
266 allocating a VMA at process creation time. This option
267 gives you up to 3% performance improvement on AMD F15h
268 machines (where it is enabled by default) for a
269 CPU-intensive style benchmark, and it can vary highly in
270 a microbenchmark depending on workload and compiler.
271
Borislav Petkov8360ee22011-11-21 12:10:19 +0100272 32: only for 32-bit processes
273 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200274 on: enable for both 32- and 64-bit processes
275 off: disable for both 32- and 64-bit processes
276
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500277 alloc_snapshot [FTRACE]
278 Allocate the ftrace snapshot buffer on boot up when the
279 main buffer is allocated. This is handy if debugging
280 and you need to use tracing_snapshot() on boot up, and
281 do not want to use tracing_snapshot_alloc() as it needs
282 to be done where GFP_KERNEL allocations are allowed.
283
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100284 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200285 Pass parameters to the AMD IOMMU driver in the system.
286 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900287 fullflush - enable flushing of IO/TLB entries when
288 they are unmapped. Otherwise they are
289 flushed before they will be reused, which
290 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200291 off - do not initialize any AMD IOMMU found in
292 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100293 force_isolation - Force device isolation for all
294 devices. The IOMMU driver is not
295 allowed anymore to lift isolation
296 requirements as needed. This option
297 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900298
Shuah Khanc099cf12012-05-24 15:58:25 -0600299 amd_iommu_dump= [HW,X86-64]
300 Enable AMD IOMMU driver option to dump the ACPI table
301 for AMD IOMMU. With this option enabled, AMD IOMMU
302 driver will print ACPI tables for AMD IOMMU during
303 IOMMU initialization.
304
Suravee Suthikulpanit3928aa32016-08-23 13:52:32 -0500305 amd_iommu_intr= [HW,X86-64]
306 Specifies one of the following AMD IOMMU interrupt
307 remapping modes:
308 legacy - Use legacy interrupt remapping mode.
309 vapic - Use virtual APIC mode, which allows IOMMU
310 to inject interrupts directly into guest.
311 This mode requires kvm-amd.avic=1.
312 (Default when IOMMU HW support is present.)
313
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
316 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200317 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
323
Randy Dunlapa9913042005-10-23 12:57:11 -0700324 apc= [HW,SPARC]
325 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 Format: noidle
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
330
Randy Dunlapca1eda22009-05-06 16:02:58 -0700331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700332 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700336
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100337 apic_extnmi= [APIC,X86] External NMI delivery setting
338 Format: { bsp (default) | all | none }
339 bsp: External NMI is delivered only to CPU 0
340 all: External NMIs are broadcast to all CPUs as a
341 backup of CPU 0
342 none: External NMI is masked for all CPUs. This is
343 useful so that a dump capture kernel won't be
344 shot down by NMI
345
Brian Haleyb0f83b22010-02-04 13:36:50 -0800346 autoconf= [IPV6]
347 See Documentation/networking/ipv6.txt.
348
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
350 Limit apic dumping. The parameter defines the maximal
351 number of local apics being dumped. Also it is possible
352 to set it to "all" by meaning -- no limit here.
353 Format: { 1 (default) | 2 | ... | all }.
354 The parameter valid if only apic=debug or
355 apic=verbose is specified.
356 Example: apic=debug show_lapic=all
357
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700359 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
362 Format: <io>,<irq>,<nodeID>
363
364 ataflop= [HW,M68k]
365
366 atarimouse= [HW,MOUSE] Atari Mouse
367
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
370
371 atkbd.reset= [HW] Reset keyboard during initialization
372
Randy Dunlapa9913042005-10-23 12:57:11 -0700373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 keyboards
378
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700381
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400385 audit= [KNL] Enable the audit sub-system
386 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500387 0 - kernel audit is disabled and can not be enabled
388 until the next reboot
389 unset - kernel audit is initialized but disabled and
390 will be fully enabled by the userspace auditd.
391 1 - kernel audit is initialized and partially enabled,
392 storing at most audit_backlog_limit messages in
393 RAM until it is fully enabled by the userspace
394 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400395 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400396
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400397 audit_backlog_limit= [KNL] Set the audit queue size limit.
398 Format: <int> (must be >=0)
399 Default: 64
400
Alex Thorlton1c532e02016-03-31 14:18:29 -0500401 bau= [X86_UV] Enable the BAU on SGI UV. The default
402 behavior is to disable the BAU (i.e. bau=0).
403 Format: { "0" | "1" }
404 0 - Disable the BAU.
405 1 - Enable the BAU.
406 unset - Disable the BAU.
407
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 baycom_epp= [HW,AX25]
409 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700410
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
412 Format: <io>,<mode>
413 See header of drivers/net/hamradio/baycom_par.c.
414
Randy Dunlapa9913042005-10-23 12:57:11 -0700415 baycom_ser_fdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 Format: <io>,<irq>,<mode>[,<baud>]
418 See header of drivers/net/hamradio/baycom_ser_fdx.c.
419
Randy Dunlapa9913042005-10-23 12:57:11 -0700420 baycom_ser_hdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 Format: <io>,<irq>,<mode>
423 See header of drivers/net/hamradio/baycom_ser_hdx.c.
424
Paul Gortmaker080506a2013-09-30 13:45:19 -0700425 blkdevparts= Manual partition parsing of block device(s) for
426 embedded devices based on command line input.
427 See Documentation/block/cmdline-partition.txt
428
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700429 boot_delay= Milliseconds to delay each printk during boot.
430 Values larger than 10 seconds (10000) are changed to
431 no delay (0).
432 Format: integer
433
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700434 bootmem_debug [KNL] Enable bootmem allocator debug messages.
435
Huang Yinga3e2acc2016-06-29 13:04:29 -0700436 bert_disable [ACPI]
437 Disable BERT OS support on buggy BIOSes.
438
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700440 bttv.radio= Most important insmod options are available as
441 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200443 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
447 at a time.
448
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 c101= [NET] Moxa C101 synchronous serial card
450
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
457
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300458 ca_keys= [KEYS] This parameter identifies a specific key(s) on
459 the system trusted keyring to be used for certificate
460 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300461 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300462
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700463 cca= [MIPS] Override the kernel pages' cache coherency
464 algorithm. Accepted values range from 0 to 7
465 inclusive. See arch/mips/include/asm/pgtable-bits.h
466 for platform specific values (SB1, Loongson3 and
467 others).
468
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100469 ccw_timeout_log [S390]
470 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471
Paul Menage8bab8dd2008-04-04 14:29:57 -0700472 cgroup_disable= [KNL] Disable a particular controller
473 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800474 The effects of cgroup_disable=foo are:
475 - foo isn't auto-mounted if you mount all cgroups in
476 a single hierarchy
477 - foo isn't visible as an individually mountable
478 subsystem
479 {Currently only "memory" controller deal with this and
480 cut the overhead, others just disable the usage. So
481 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700482
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
484 Format: { controller[,controller...] | "all" }
485 Like cgroup_disable, but only applies to cgroup v1;
486 the blacklisted controllers remain available in cgroup2.
487
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800488 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
489 Format: <string>
490 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800491 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800492
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 checkreqprot [SELINUX] Set initial checkreqprot flag value.
494 Format: { "0" | "1" }
495 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700496 0 -- check protection applied by kernel (includes
497 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 1 -- check protection requested by application.
499 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700500 Value can be changed at runtime via
501 /selinux/checkreqprot.
502
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100503 cio_ignore= [S390]
504 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700505 clk_ignore_unused
506 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700507 Prevents the clock framework from automatically gating
508 clocks that have not been explicitly enabled by a Linux
509 device driver but are enabled in hardware at reset or
510 by the bootloader/firmware. Note that this does not
511 force such clocks to be always-on nor does it reserve
512 those clocks in any way. This parameter is useful for
513 debug and development, but should not be needed on a
514 platform with proper driver support. For more
515 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100516
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700518 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200519 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700520 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200521 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 Format: { pit | tsc | cyclone | pmtmr }
523
John Stultz592913e2010-07-13 17:56:20 -0700524 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700525 Format: <string>
526 Override the default clocksource and use the clocksource
527 with the name specified.
528 Some clocksource names to choose from, depending on
529 the platform:
530 [all] jiffies (this is the base, fallback clocksource)
531 [ACPI] acpi_pm
532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
533 pxa_timer,timer3,32k_counter,timer0_1
534 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700535 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700536 scx200_hrt on Geode; cyclone on IBM x440
537 [MIPS] MIPS
538 [PARISC] cr16
539 [S390] tod
540 [SH] SuperH
541 [SPARC64] tick
542 [X86-64] hpet,tsc
543
Will Deacon46fd5c62016-06-27 17:30:13 +0100544 clocksource.arm_arch_timer.evtstrm=
545 [ARM,ARM64]
546 Format: <bool>
547 Enable/disable the eventstream feature of the ARM
548 architected timer so that code using WFE-based polling
549 loops can be debugged more effectively on production
550 systems.
551
Andi Kleenac72e782008-01-30 13:33:21 +0100552 clearcpuid=BITNUM [X86]
553 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100554 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800555 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100556 stable over kernel options, but the vendor specific
557 ones should be.
558 Also note that user programs calling CPUID directly
559 or using the feature without checking anything
560 will still see it. This just prevents it from
561 being used by the kernel or shown in /proc/cpuinfo.
562 Also note the kernel might malfunction if you disable
563 some critical bits.
564
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700565 cma=nn[MG]@[start[MG][-end[MG]]]
566 [ARM,X86,KNL]
567 Sets the size of kernel global memory area for
568 contiguous memory allocations and optionally the
569 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700570 memory allocations. A value of 0 disables CMA
571 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100572 include/linux/dma-contiguous.h
573
Robert Jennings14f966e2009-04-15 05:55:32 +0000574 cmo_free_hint= [PPC] Format: { yes | no }
575 Specify whether pages are marked as being inactive
576 when they are freed. This is used in CMO environments
577 to determine OS memory pressure for page stealing by
578 a hypervisor.
579 Default: yes
580
Marek Szyprowskic7909502011-12-29 13:09:51 +0100581 coherent_pool=nn[KMG] [ARM,KNL]
582 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200583 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100584
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530585 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100586 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100587 Range: 0 - 8192
588 Default: 64
589
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700591 Format:
592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
595 Format: <io>[,<irq>]
596
Randy Dunlapa9913042005-10-23 12:57:11 -0700597 com90xx= [HW,NET]
598 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 Format: <io>[,<irq>[,<memstart>]]
600
601 condev= [HW,S390] console device
602 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700603
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 console= [KNL] Output console device and options.
605
606 tty<n> Use the virtual console device <n>.
607
608 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800609 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800611 the form "bbbbpnf", where "bbbb" is the baud rate,
612 "p" is parity ("n", "o", or "e"), "n" is number of
613 bits, and "f" is flow control ("r" for RTS or
614 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615
Jani Nikulae52347b2016-11-03 12:10:10 +0200616 See Documentation/admin-guide/serial-console.rst for more
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800617 information. See
618 Documentation/networking/netconsole.txt for an
619 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700621 uart[8250],io,<addr>[,options]
622 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900623 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400624 uart[8250],mmio32,<addr>[,options]
625 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 Start an early, polled-mode console on the 8250/16550
627 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400628 switching to the matching ttyS device later.
629 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900630 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
632 to be equivalent to 'mmio'. 'options' are specified in
633 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400634 the h/w is not re-initialized.
635
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500636 hvc<n> Use the hypervisor console device <n>. This is for
637 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700639 If the device connected to the port is not a TTY but a braille
640 device, prepend "brl," before the device type, for instance
641 console=brl,ttyS0
642 For now, only VisioBraille is supported.
643
Daniel Mackf324edc2009-06-16 15:33:52 -0700644 consoleblank= [KNL] The console blank (screen saver) timeout in
645 seconds. Defaults to 10*60 = 10mins. A value of 0
646 disables the blank timer.
647
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800648 coredump_filter=
649 [KNL] Change the default value for
650 /proc/<pid>/coredump_filter.
651 See also Documentation/filesystems/proc.txt.
652
Len Brown62027ae2011-04-01 18:13:10 -0400653 cpuidle.off=1 [CPU_IDLE]
654 disable the cpuidle sub-system
655
Len Brownd82f2692017-02-28 16:44:16 -0500656 cpufreq.off=1 [CPU_FREQ]
657 disable the cpufreq sub-system
658
Len Brownd68921f2015-05-11 17:27:09 -0400659 cpu_init_udelay=N
660 [X86] Delay for N microsec between assert and de-assert
661 of APIC INIT to start processors. This delay occurs
662 on every CPU online, such as boot, and resume from suspend.
663 Default: 10000
664
Linus Torvalds1da177e2005-04-16 15:20:36 -0700665 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700666 Format:
667 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800669 crashkernel=size[KMG][@offset[KMG]]
670 [KNL] Using kexec, Linux can switch to a 'crash kernel'
671 upon panic. This parameter reserves the physical
672 memory region [offset, offset + size] for that kernel
673 image. If '@offset' is omitted, then a suitable offset
674 is selected automatically. Check
675 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700676
Bernhard Wallefb391592007-10-18 23:41:02 -0700677 crashkernel=range1:size1[,range2:size2,...][@offset]
678 [KNL] Same as above, but depends on the memory
679 in the running system. The syntax of range is
680 start-[end] where start and end are both
681 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800682 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700683
Yinghai Luadbc7422013-04-15 22:23:48 -0700684 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700685 [KNL, x86_64] range could be above 4G. Allow kernel
686 to allocate physical memory region from top, so could
687 be above 4G if system have more than 4G ram installed.
688 Otherwise memory region will be allocated below 4G, if
689 available.
690 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700691 crashkernel=size[KMG],low
692 [KNL, x86_64] range under 4G. When crashkernel=X,high
693 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700694 above 4G, that cause second kernel crash on system
695 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800696 requires at least 64M+32K low memory, also enough extra
697 low memory is needed to make sure DMA buffers for 32-bit
698 devices won't run out. Kernel would try to allocate at
699 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700700 This one let user to specify own low range under 4G
701 for second kernel instead.
702 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700703 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700704 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700705
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100706 cryptomgr.notests
707 [KNL] Disable crypto self-tests
708
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709 cs89x0_dma= [HW,NET]
710 Format: <dma>
711
712 cs89x0_media= [HW,NET]
713 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700714
Randy Dunlapa9913042005-10-23 12:57:11 -0700715 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 See header of drivers/s390/block/dasd_devmap.c.
717
718 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
719 (one device per port)
720 Format: <port#>,<type>
721 See also Documentation/input/joystick-parport.txt
722
Thomas Renningera648ec02010-08-06 16:11:02 +0200723 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
724 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600725 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200726
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 debug [KNL] Enable kernel debugging (events log level).
728
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700729 debug_locks_verbose=
730 [KNL] verbose self-tests
731 Format=<0|1>
732 Print debugging info while doing the locking API
733 self-tests.
734 We default to 0 (no extra messages), setting it to
735 1 will print _a lot_ more information - normally
736 only useful to kernel developers.
737
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700738 debug_objects [KNL] Enable object debugging
739
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500740 no_debug_objects
741 [KNL] Disable object debugging
742
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800743 debug_guardpage_minorder=
744 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
745 parameter allows control of the order of pages that will
746 be intentionally kept free (and hence protected) by the
747 buddy allocator. Bigger value increase the probability
748 of catching random memory corruption, but reduce the
749 amount of memory for normal system use. The maximum
750 possible value is MAX_ORDER/2. Setting this parameter
751 to 1 or 2 should be enough to identify most random
752 memory corruption problems caused by bugs in kernel or
753 driver code when a CPU writes to (or reads from) a
754 random memory location. Note that there exists a class
755 of memory corruptions problems caused by buggy H/W or
756 F/W or by drivers badly programing DMA (basically when
757 memory is written at bus level and the CPU MMU is
758 bypassed) which are not detectable by
759 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
760 tracking down these problems.
761
Joonsoo Kim031bc572014-12-12 16:55:52 -0800762 debug_pagealloc=
763 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
764 parameter enables the feature at boot time. In
765 default, it is disabled. We can avoid allocating huge
766 chunk of memory for debug pagealloc if we don't enable
767 it at boot time and the system will work mostly same
768 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
769 on: enable the feature
770
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200771 debugpat [X86] Enable PAT debugging
772
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200773 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774 Format: <area>[,<node>]
775 See also Documentation/networking/decnet.txt.
776
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700777 default_hugepagesz=
778 [same as hugepagesz=] The size of the default
779 HugeTLB page size. This is the size represented by
780 the legacy /proc/ hugepages APIs, used for SHM, and
781 default size when mounting hugetlbfs filesystems.
782 Defaults to the default architecture's huge page size
783 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700784
Linus Torvalds1da177e2005-04-16 15:20:36 -0700785 dhash_entries= [KNL]
786 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700787
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000788 disable_1tb_segments [PPC]
789 Disables the use of 1TB hash page table segments. This
790 causes the kernel to fall back to 256MB segments which
791 can be useful when debugging issues that require an SLB
792 miss to occur.
793
Brian Haleyb0f83b22010-02-04 13:36:50 -0800794 disable= [IPV6]
795 See Documentation/networking/ipv6.txt.
796
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530797 disable_radix [PPC]
798 Disable RADIX MMU mode on POWER9
799
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900800 disable_cpu_apicid= [X86,APIC,SMP]
801 Format: <int>
802 The number of initial APIC ID for the
803 corresponding CPU to be disabled at boot,
804 mostly used for the kdump 2nd kernel to
805 disable BSP to wake up multiple CPUs without
806 causing system reset or hang due to sending
807 INIT from AP to BSP.
808
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000809 disable_ddw [PPC/PSERIES]
810 Disable Dynamic DMA Window support. Use this if
811 to workaround buggy firmware.
812
Brian Haleyb0f83b22010-02-04 13:36:50 -0800813 disable_ipv6= [IPV6]
814 See Documentation/networking/ipv6.txt.
815
Yinghai Lu95ffa242008-04-29 03:52:33 -0700816 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700817 The kernel tries to adjust MTRR layout from continuous
818 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700819 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700820
Yinghai Lu093af8d2008-01-30 13:33:32 +0100821 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100822 By default the kernel will trim any uncacheable
823 memory out of your available memory pool based on
824 MTRR settings. This parameter disables that behavior,
825 possibly causing your machine to run very slowly.
826
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530827 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700828 Disable PIN 1 of APIC timer
829 Can be useful to work around chipset bugs.
830
Prarit Bhargavace14c582015-08-25 13:34:53 -0400831 dis_ucode_ldr [X86] Disable the microcode loader.
832
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700833 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
834 this option disables the debugging code at boot.
835
836 dma_debug_entries=<number>
837 This option allows to tune the number of preallocated
838 entries for DMA-API debugging code. One entry is
839 required per DMA-API allocation. Use this if the
840 DMA-API debugging code disables itself because the
841 architectural default is too low.
842
Joerg Roedel1745de52009-05-22 21:49:51 +0200843 dma_debug_driver=<driver_name>
844 With this option the DMA-API debugging driver
845 filter feature can be enabled at boot time. Just
846 pass the driver to filter for as the parameter.
847 The filter can be disabled or changed to another
848 driver later using sysfs.
849
Bob Paauwe96206e22015-08-27 10:04:13 -0700850 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
851 Broken monitors, graphic adapters, KVMs and EDIDless
852 panels may send no or incorrect EDID data sets.
853 This parameter allows to specify an EDID data sets
854 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100855 Generic built-in EDID data sets are used, if one of
856 edid/1024x768.bin, edid/1280x1024.bin,
857 edid/1680x1050.bin, or edid/1920x1080.bin is given
858 and no file with the same name exists. Details and
859 instructions how to build your own EDID data are
860 available in Documentation/EDID/HOWTO.txt. An EDID
861 data set will only be used for a particular connector,
862 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700863 name. Each connector may use a unique EDID data
864 set by separating the files with a comma. An EDID
865 data set with no connector name will be used for
866 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100867
Linus Torvalds1da177e2005-04-16 15:20:36 -0700868 dscc4.setup= [NET]
869
Lukas Wunner58c54752016-11-12 21:32:36 +0000870 dump_apple_properties [X86]
871 Dump name and content of EFI device properties on
872 x86 Macs. Useful for driver authors to determine
873 what data is available or for reverse-engineering.
874
Jim Cromie29e36c92012-04-27 14:30:41 -0600875 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
876 module.dyndbg[="val"]
877 Enable debug messages at boot time. See
878 Documentation/dynamic-debug-howto.txt for details.
879
Dave Hansen8c3641e2015-06-07 11:37:02 -0700880 nompx [X86] Disables Intel Memory Protection Extensions.
881 See Documentation/x86/intel_mpx.txt for more
882 information about the feature.
883
Dave Hansen06976942016-02-12 13:02:29 -0800884 nopku [X86] Disable Memory Protection Keys CPU feature found
885 in some Intel CPUs.
886
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700887 module.async_probe [KNL]
888 Enable asynchronous probe on this module.
889
Mark Salter56aeeba2014-04-07 15:39:53 -0700890 early_ioremap_debug [KNL]
891 Enable debug messages in early_ioremap support. This
892 is useful for tracking down temporary early mappings
893 which are not unmapped.
894
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700895 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500896
Scott Wood5664f762015-09-14 19:54:07 -0500897 When used with no options, the early console is
898 determined by the stdout-path property in device
899 tree's chosen node.
900
Scott Telfordc41251b2016-09-22 16:58:16 +0100901 cdns,<addr>[,options]
902 Start an early, polled-mode console on a Cadence
903 (xuartps) serial port at the specified address. Only
904 supported option is baud rate. If baud rate is not
905 specified, the serial port must already be setup and
906 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +0200907
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700908 uart[8250],io,<addr>[,options]
909 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700910 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300911 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400912 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700913 Start an early, polled-mode console on the 8250/16550
914 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700915 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300916 (mmio) or 32-bit (mmio32 or mmio32be).
917 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
918 to be equivalent to 'mmio'. 'options' are specified
919 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400920 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700921
Rob Herring0d3c6732014-04-18 17:19:57 -0500922 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -0600923 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -0500924 Start an early, polled-mode console on a pl011 serial
925 port at the specified address. The pl011 serial port
926 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -0600927 yet supported. If 'mmio32' is specified, then only
928 the driver will use only 32-bit accessors to read/write
929 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -0500930
Andreas Färber736d5532016-03-06 12:21:24 +0100931 meson,<addr>
932 Start an early, polled-mode console on a meson serial
933 port at the specified address. The serial port must
934 already be setup and configured. Options are not yet
935 supported.
936
Stephen Boyd0efe7292014-09-15 17:22:51 -0700937 msm_serial,<addr>
938 Start an early, polled-mode console on an msm serial
939 port at the specified address. The serial port
940 must already be setup and configured. Options are not
941 yet supported.
942
943 msm_serial_dm,<addr>
944 Start an early, polled-mode console on an msm serial
945 dm port at the specified address. The serial port
946 must already be setup and configured. Options are not
947 yet supported.
948
Rob Herringd50d7262014-04-18 17:19:58 -0500949 smh Use ARM semihosting calls for early console.
950
Tomasz Figab94ba032015-01-23 14:47:41 +0100951 s3c2410,<addr>
952 s3c2412,<addr>
953 s3c2440,<addr>
954 s3c6400,<addr>
955 s5pv210,<addr>
956 exynos4210,<addr>
957 Use early console provided by serial driver available
958 on Samsung SoCs, requires selecting proper type and
959 a correct base address of the selected UART port. The
960 serial port must already be setup and configured.
961 Options are not yet supported.
962
Martin Blumenstinglec84aa02016-12-11 21:42:23 +0100963 lantiq,<addr>
964 Start an early, polled-mode console on a lantiq serial
965 (lqasc) port at the specified address. The serial port
966 must already be setup and configured. Options are not
967 yet supported.
968
Stefan Agner1d59b382015-10-17 00:45:55 -0700969 lpuart,<addr>
970 lpuart32,<addr>
971 Use early console provided by Freescale LP UART driver
972 found on Freescale Vybrid and QorIQ LS1021A processors.
973 A valid base address must be provided, and the serial
974 port must already be setup and configured.
975
Wilson Ding30530792016-02-16 19:14:53 +0100976 armada3700_uart,<addr>
977 Start an early, polled-mode console on the
978 Armada 3700 serial port at the specified
979 address. The serial port must already be setup
980 and configured. Options are not yet supported.
981
Heiko Carstens89175cf2017-01-11 09:14:52 +0100982 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100984 earlyprintk=efi
Heiko Carstens89175cf2017-01-11 09:14:52 +0100985 earlyprintk=sclp
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500986 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700988 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500989 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500990 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +0600991 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700992
Dave Hansen147ea092013-04-10 14:03:38 -0700993 earlyprintk is useful when the kernel crashes before
994 the normal console is initialized. It is not enabled by
995 default because it has some cosmetic problems.
996
Randy Dunlapa9913042005-10-23 12:57:11 -0700997 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998 takes over.
999
Matt Fleming72548e82013-10-04 09:36:56 +01001000 Only one of vga, efi, serial, or usb debug port can
1001 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002
Dave Hansen147ea092013-04-10 14:03:38 -07001003 Currently only ttyS0 and ttyS1 may be specified by
1004 name. Other I/O ports may be explicitly specified
1005 on some architectures (x86 and arm at least) by
1006 replacing ttySn with an I/O port address, like this:
1007 earlyprintk=serial,0x1008,115200
1008 You can find the port for a given device in
1009 /proc/tty/driver/serial:
1010 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011
1012 Interaction with the standard serial driver is not
1013 very good.
1014
Matt Fleming72548e82013-10-04 09:36:56 +01001015 The VGA and EFI output is eventually overwritten by
1016 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001018 The xen output can only be used by Xen PV guests.
1019
Heiko Carstens89175cf2017-01-11 09:14:52 +01001020 The sclp output can only be used on s390.
1021
Chen, Gongc700f012013-12-06 01:17:08 -05001022 edac_report= [HW,EDAC] Control how to report EDAC event
1023 Format: {"on" | "off" | "force"}
1024 on: enable EDAC to report H/W event. May be overridden
1025 by other higher priority error reporting module.
1026 off: disable H/W event reporting through EDAC.
1027 force: enforce the use of EDAC to report H/W event.
1028 default: on.
1029
Jason Wessel97311912010-05-20 21:04:30 -05001030 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1031 ekgdboc=kbd
1032
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001033 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001034 the boot argument: earlyprintk=vga
1035
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001037 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001039 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001040 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001041 old_map [X86-64]: switch to the old ioremap-based EFI
1042 runtime services mapping. 32-bit still uses this one by
1043 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001044 nochunk: disable reading files in "chunks" in the EFI
1045 boot stub, as chunking can cause problems with some
1046 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001047 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001048 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001049
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001050 efi_no_storage_paranoia [EFI; X86]
1051 Using this parameter you can use more than 50% of
1052 your efi variable storage. Use this parameter only if
1053 you are really sure that your UEFI does sane gc and
1054 fulfills the spec otherwise your board may brick.
1055
Taku Izumi0f96a992015-09-30 23:01:56 +09001056 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1057 Add arbitrary attribute to specific memory range by
1058 updating original EFI memory map.
1059 Region of memory which aa attribute is added to is
1060 from ss to ss+nn.
1061 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1062 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1063 attribute is added to range 0x100000000-0x180000000 and
1064 0x10a0000000-0x1120000000.
1065
1066 Using this parameter you can do debugging of EFI memmap
1067 related feature. For example, you can do debugging of
1068 Address Range Mirroring feature even if your box
1069 doesn't support it.
1070
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001071 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1072 that is to be dynamically loaded by Linux. If there are
1073 multiple variables with the same name but with different
1074 vendor GUIDs, all of them will be loaded. See
1075 Documentation/acpi/ssdt-overlays.txt for details.
1076
1077
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 eisa_irq_edge= [PARISC,HW]
1079 See header of drivers/parisc/eisa.c.
1080
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001081 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001083 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084
1085 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001086 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001087 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001088 Documentation/block/deadline-iosched.txt for details.
1089
Michael Holzheud3bf37952011-10-30 15:16:37 +01001090 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001091 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001092 image elf header and optionally the size. Generally
1093 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001094 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001096 enable_mtrr_cleanup [X86]
1097 The kernel tries to adjust MTRR layout from continuous
1098 to discrete, to make X server driver able to add WB
1099 entry later. This parameter enables that.
1100
Randy Dunlapca1eda22009-05-06 16:02:58 -07001101 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001102 Enable PIN 1 of APIC timer
1103 Can be useful to work around chipset bugs
1104 (in particular on some ATI chipsets).
1105 The kernel tries to set a reasonable default.
1106
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 enforcing [SELINUX] Set initial enforcing status.
1108 Format: {"0" | "1"}
1109 See security/selinux/Kconfig help text.
1110 0 -- permissive (log only, no denials).
1111 1 -- enforcing (deny and log).
1112 Default value is 0.
1113 Value can be changed at runtime via /selinux/enforce.
1114
Huang Yinga08f82d2010-05-18 14:35:21 +08001115 erst_disable [ACPI]
1116 Disable Error Record Serialization Table (ERST)
1117 support.
1118
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 ether= [HW,NET] Ethernet cards parameters
1120 This option is obsoleted by the "netdev=" option, which
1121 has equivalent usage. See its documentation for details.
1122
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001123 evm= [EVM]
1124 Format: { "fix" }
1125 Permit 'security.evm' to be updated regardless of
1126 current integrity status.
1127
Akinobu Mitade1ba092006-12-08 02:39:42 -08001128 failslab=
1129 fail_page_alloc=
1130 fail_make_request=[KNL]
1131 General fault injection mechanism.
1132 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001133 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001134
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001136 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137
Alex Chiangf13ae302008-05-08 14:03:23 -06001138 force_pal_cache_flush
1139 [IA-64] Avoid check_sal_cache_flush which may hang on
1140 buggy SAL_CACHE_FLUSH implementations. Using this
1141 parameter will force ia64_sal_cache_flush to call
1142 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1143
Chris Bainbridge69f23662014-03-07 18:40:42 +07001144 forcepae [X86-32]
1145 Forcefully enable Physical Address Extension (PAE).
1146 Many Pentium M systems disable PAE but may have a
1147 functionally usable PAE implementation.
1148 Warning: use of this parameter will taint the kernel
1149 and may cause unknown problems.
1150
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001151 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001152 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001153 as early as possible in order to facilitate early
1154 boot debugging.
1155
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001156 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001157 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001158 If no parameter is passed, ftrace will dump
1159 buffers of all CPUs, but if you pass orig_cpu, it will
1160 dump only the buffer of the CPU that triggered the
1161 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001162
1163 ftrace_filter=[function-list]
1164 [FTRACE] Limit the functions traced by the function
1165 tracer at boot up. function-list is a comma separated
1166 list of functions. This list can be changed at run
1167 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001168 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001169
1170 ftrace_notrace=[function-list]
1171 [FTRACE] Do not trace the functions specified in
1172 function-list. This list can be changed at run time
1173 by the set_ftrace_notrace file in the debugfs
1174 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001175
Stefan Assmann369bc182009-10-12 22:17:21 +02001176 ftrace_graph_filter=[function-list]
1177 [FTRACE] Limit the top level callers functions traced
1178 by the function graph tracer at boot up.
1179 function-list is a comma separated list of functions
1180 that can be changed at run time by the
1181 set_graph_function file in the debugfs tracing directory.
1182
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001183 ftrace_graph_notrace=[function-list]
1184 [FTRACE] Do not trace from the functions specified in
1185 function-list. This list is a comma separated list of
1186 functions that can be changed at run time by the
1187 set_graph_notrace file in the debugfs tracing directory.
1188
Todd Brandt65a50c62017-03-02 16:12:15 -08001189 ftrace_graph_max_depth=<uint>
1190 [FTRACE] Used with the function graph tracer. This is
1191 the max depth it will trace into a function. This value
1192 can be changed at run time by the max_graph_depth file
1193 in the tracefs tracing directory. default: 0 (no limit)
1194
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195 gamecon.map[2|3]=
1196 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1197 support via parallel port (up to 5 devices per port)
1198 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1199 See also Documentation/input/joystick-parport.txt
1200
1201 gamma= [HW,DRM]
1202
Yinghai Luaaf23042008-01-30 13:33:09 +01001203 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1204 Format: off | on
1205 default: on
1206
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001207 gcov_persist= [GCOV] When non-zero (default), profiling data for
1208 kernel modules is saved and remains accessible via
1209 debugfs, even when the module is unloaded/reloaded.
1210 When zero, profiling data is discarded and associated
1211 debugfs files are removed at module unload time.
1212
Thomas Gleixner47512cf2017-02-15 11:11:50 +01001213 goldfish [X86] Enable the goldfish android emulator platform.
1214 Don't use this when you are not running on the
1215 android emulator
1216
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001218 invalid Protective MBR to be treated as GPT. If the
1219 primary GPT is corrupted, it enables the backup/alternate
1220 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001222 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1223 the "Enable 0" bit of the configuration register.
1224 Format: 0 | 1
1225 Default: 0
1226 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1227 the "Enable 0" bit of the configuration register.
1228 Format: 0 | 1
1229 Default: 0
1230 grcan.select= [HW] Select which physical interface to use.
1231 Format: 0 | 1
1232 Default: 0
1233 grcan.txsize= [HW] Sets the size of the tx buffer.
1234 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1235 Default: 1024
1236 grcan.rxsize= [HW] Sets the size of the rx buffer.
1237 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1238 Default: 1024
1239
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001240 gpio-mockup.gpio_mockup_ranges
1241 [HW] Sets the ranges of gpiochip of for this device.
1242 Format: <start1>,<end1>,<start2>,<end2>...
1243
Jiri Kosina55537872015-11-05 18:44:41 -08001244 hardlockup_all_cpu_backtrace=
1245 [KNL] Should the hard-lockup detector generate
1246 backtraces on all cpus.
1247 Format: <integer>
1248
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249 hashdist= [KNL,NUMA] Large hashes allocated during boot
1250 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001251 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001252 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253
1254 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1255
1256 hd= [EIDE] (E)IDE hard drive subsystem geometry
1257 Format: <cyl>,<head>,<sect>
1258
Huang Yingea8c0712010-05-18 14:35:15 +08001259 hest_disable [ACPI]
1260 Disable Hardware Error Source Table (HEST) support;
1261 corresponding firmware-first mode error processing
1262 logic will be disabled.
1263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1265 size of <nn>. This works even on boxes that have no
1266 highmem otherwise. This also works to reduce highmem
1267 size on bigger boxes.
1268
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001269 highres= [KNL] Enable/disable high resolution timer mode.
1270 Valid parameters: "on", "off"
1271 Default: "on"
1272
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273 hisax= [HW,ISDN]
1274 See Documentation/isdn/README.HiSax.
1275
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001276 hlt [BUGS=ARM,SH]
1277
1278 hpet= [X86-32,HPET] option to control HPET usage
1279 Format: { enable (default) | disable | force |
1280 verbose }
1281 disable: disable HPET and use PIT instead
1282 force: allow force enabled of undocumented chips (ICH4,
1283 VIA, nVidia)
1284 verbose: show contents of HPET registers during setup
1285
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001286 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1287 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1288
Andi Kleenb4718e62008-07-23 21:27:51 -07001289 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1290 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001291 On x86-64 and powerpc, this option can be specified
1292 multiple times interleaved with hugepages= to reserve
1293 huge pages of different sizes. Valid pages sizes on
1294 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001295 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001296
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001297 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1298 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001299 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1300 If specified, z/VM IUCV HVC accepts connections
1301 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001302
James Hoganfdabf522012-10-09 11:00:27 +01001303 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1304 hardware thread id mappings.
1305 Format: <cpu>:<hwthread>
1306
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001307 keep_bootcon [KNL]
1308 Do not unregister boot console at start. This is only
1309 useful for debugging when something happens in the window
1310 between unregistering the boot console and initializing
1311 the real console.
1312
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001313 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001314 or register an additional I2C bus that is not
1315 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001316 Format:
1317 <bus_id>,<clkrate>
1318
Jiri Kosina36d95732008-10-06 02:51:09 -04001319 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001320 i8042.unmask_kbd_data
1321 [HW] Enable printing of interrupt data from the KBD port
1322 (disabled by default, and as a pre-condition
1323 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001325 i8042.dumbkbd [HW] Pretend that controller can only read data from
1326 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001327 (Don't attempt to blink the leds)
1328 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001329 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001330 i8042.noloop [HW] Disable the AUX Loopback command while probing
1331 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001333 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1335 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001336 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e19242016-10-01 12:07:35 -07001337 i8042.reset [HW] Reset the controller during init, cleanup and
1338 suspend-to-ram transitions, only during s2r
1339 transitions, or never reset
1340 Format: { 1 | Y | y | 0 | N | n }
1341 1, Y, y: always reset controller
1342 0, N, n: don't ever reset controller
1343 Default: only on s2r transitions on x86; most other
1344 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001346 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347
1348 i810= [HW,DRM]
1349
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001350 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1351 indicates that the driver is running on unsupported
1352 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1354 does not match list of supported models.
1355 i8k.power_status
1356 [HW] Report power status in /proc/i8k
1357 (disabled by default)
1358 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1359 capability is set.
1360
Carsten Emde4dca20e2012-03-15 15:56:26 +01001361 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001362 [DRM] Invert the sense of the variable that is used to
1363 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001364 brightness value of 0 indicates backlight switched off,
1365 and the maximum of the brightness value sets the backlight
1366 to maximum brightness. If this parameter is set to 0
1367 (default) and the machine requires it, or this parameter
1368 is set to 1, a brightness value of 0 sets the backlight
1369 to maximum brightness, and the maximum of the brightness
1370 value switches the backlight off.
1371 -1 -- never invert brightness
1372 0 -- machine default
1373 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001374
Linus Torvalds1da177e2005-04-16 15:20:36 -07001375 icn= [HW,ISDN]
1376 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1377
David Fries0af80c02009-02-25 20:28:21 +01001378 ide-core.nodma= [HW] (E)IDE subsystem
1379 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001380 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1381 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001382 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001384 ide-generic.probe-mask= [HW] (E)IDE subsystem
1385 Format: <int>
1386 Probe mask for legacy ISA IDE ports. Depending on
1387 platform up to 6 ports are supported, enabled by
1388 setting corresponding bits in the mask to 1. The
1389 default value is 0x0, which has a special meaning.
1390 On systems that have PCI, it triggers scanning the
1391 PCI bus for the first and the second port, which
1392 are then probed. On systems without PCI the value
1393 of 0x0 enables probing the two first ports as if it
1394 was 0x3.
1395
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001396 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1397 Claim all unknown PCI IDE storage controllers.
1398
Andi Kleenf039b752007-05-02 19:27:12 +02001399 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001400 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001401 Poll forces a polling idle loop that can slightly
1402 improve the performance of waking up a idle CPU, but
1403 will use a lot of power and make the system run hot.
1404 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001405 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001406 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001407 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001408
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001409 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1410 Format: { strict | legacy | 2008 | relaxed }
1411 Default: strict
1412
1413 Choose which programs will be accepted for execution
1414 based on the IEEE 754 NaN encoding(s) supported by
1415 the FPU and the NaN encoding requested with the value
1416 of an ELF file header flag individually set by each
1417 binary. Hardware implementations are permitted to
1418 support either or both of the legacy and the 2008 NaN
1419 encoding mode.
1420
1421 Available settings are as follows:
1422 strict accept binaries that request a NaN encoding
1423 supported by the FPU
1424 legacy only accept legacy-NaN binaries, if supported
1425 by the FPU
1426 2008 only accept 2008-NaN binaries, if supported
1427 by the FPU
1428 relaxed accept any binaries regardless of whether
1429 supported by the FPU
1430
1431 The FPU emulator is always able to support both NaN
1432 encodings, so if no FPU hardware is present or it has
1433 been disabled with 'nofpu', then the settings of
1434 'legacy' and '2008' strap the emulator accordingly,
1435 'relaxed' straps the emulator for both legacy-NaN and
1436 2008-NaN, whereas 'strict' enables legacy-NaN only on
1437 legacy processors and both NaN encodings on MIPS32 or
1438 MIPS64 CPUs.
1439
1440 The setting for ABS.fmt/NEG.fmt instruction execution
1441 mode generally follows that for the NaN encoding,
1442 except where unsupported by hardware.
1443
Ingo Molnar792908222006-12-06 20:40:51 -08001444 ignore_loglevel [KNL]
1445 Ignore loglevel setting - this will print /all/
1446 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001447 We also add it as printk module parameter, so users
1448 could change it dynamically, usually by
1449 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001450
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001451 ignore_rlimit_data
1452 Ignore RLIMIT_DATA setting for data mappings,
1453 print warning at first misuse. Can be changed via
1454 /sys/module/kernel/parameters/ignore_rlimit_data.
1455
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456 ihash_entries= [KNL]
1457 Set number of hash buckets for inode cache.
1458
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001459 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001460 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001461 default: "enforce"
1462
Mimi Zohar07f6a792011-03-09 22:25:48 -05001463 ima_appraise_tcb [IMA]
1464 The builtin appraise policy appraises all files
1465 owned by uid=0.
1466
Mimi Zohard68a6fe2016-12-19 16:22:57 -08001467 ima_canonical_fmt [IMA]
1468 Use the canonical format for the binary runtime
1469 measurements, instead of host native format.
1470
Mimi Zohar3323eec2009-02-04 09:06:58 -05001471 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001472 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1473 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001474 default: "sha1"
1475
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001476 The list of supported hash algorithms is defined
1477 in crypto/hash_info.h.
1478
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001479 ima_policy= [IMA]
1480 The builtin measurement policy to load during IMA
1481 setup. Specyfing "tcb" as the value, measures all
1482 programs exec'd, files mmap'd for exec, and all files
1483 opened with the read mode bit set by either the
1484 effective uid (euid=0) or uid=0.
1485 Format: "tcb"
1486
1487 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001488 Load a policy which meets the needs of the Trusted
1489 Computing Base. This means IMA will measure all
1490 programs exec'd, files mmap'd for exec, and all files
1491 opened for read by uid=0.
1492
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001493 ima_template= [IMA]
1494 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001495 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001496 Default: "ima-ng"
1497
Roberto Sassuc2426d22014-10-13 14:08:42 +02001498 ima_template_fmt=
1499 [IMA] Define a custom template format.
1500 Format: { "field1|...|fieldN" }
1501
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001502 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1503 Format: <min_file_size>
1504 Set the minimal file size for using asynchronous hash.
1505 If left unspecified, ahash usage is disabled.
1506
1507 ahash performance varies for different data sizes on
1508 different crypto accelerators. This option can be used
1509 to achieve the best performance for a particular HW.
1510
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001511 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1512 Format: <bufsize>
1513 Set hashing buffer size. Default: 4k.
1514
1515 ahash performance varies for different chunk sizes on
1516 different crypto accelerators. This option can be used
1517 to achieve best performance for particular HW.
1518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 init= [KNL]
1520 Format: <full_path>
1521 Run specified binary instead of /sbin/init as init
1522 process.
1523
1524 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1525 for working out where the kernel is dying during
1526 startup.
1527
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001528 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1529 initcall functions. Useful for debugging built-in
1530 modules and initcalls.
1531
Linus Torvalds1da177e2005-04-16 15:20:36 -07001532 initrd= [BOOT] Specify the location of the initial ramdisk
1533
Dave Hansenacd547b2016-07-29 09:30:21 -07001534 init_pkru= [x86] Specify the default memory protection keys rights
1535 register contents for all processes. 0x55555554 by
1536 default (disallow access to all but pkey 0). Can
1537 override in debugfs after boot.
1538
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1540 Format: <irq>
1541
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001542 int_pln_enable [x86] Enable power limit notification interrupt
1543
Mimi Zohard726d8d2013-03-18 14:48:02 -04001544 integrity_audit=[IMA]
1545 Format: { "0" | "1" }
1546 0 -- basic integrity auditing messages. (Default)
1547 1 -- additional integrity auditing messages.
1548
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001549 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001550 on
1551 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001552 off
1553 Disable intel iommu driver.
1554 igfx_off [Default Off]
1555 By default, gfx is mapped as normal device. If a gfx
1556 device has a dedicated DMAR unit, the DMAR unit is
1557 bypassed by not enabling DMAR with this option. In
1558 this case, gfx device will use physical address for
1559 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001560 forcedac [x86_64]
1561 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001562 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001563 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001564 than 32-bit addressing. The default is to look
1565 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001566 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001567 strict [Default Off]
1568 With this option on every unmap_single operation will
1569 result in a hardware IOTLB flush operation as opposed
1570 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001571 sp_off [Default Off]
1572 By default, super page will be supported if Intel IOMMU
1573 has the capability. With this option, super page will
1574 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001575 ecs_off [Default Off]
1576 By default, extended context tables will be supported if
1577 the hardware advertises that it has support both for the
1578 extended tables themselves, and also PASID support. With
1579 this option set, extended tables will not be used even
1580 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001581
1582 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1583 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001584 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001585
Dirk Brandewie6be26492013-02-15 22:55:10 +01001586 intel_pstate= [X86]
1587 disable
1588 Do not enable intel_pstate as the default
1589 scaling driver for the supported processors
Rafael J. Wysocki001c76f2016-11-17 23:34:17 +01001590 passive
1591 Use intel_pstate as a scaling driver, but configure it
1592 to work with generic cpufreq governors (instead of
1593 enabling its internal governor). This mode cannot be
1594 used along with the hardware-managed P-states (HWP)
1595 feature.
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001596 force
1597 Enable intel_pstate on systems that prohibit it by default
1598 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1599 instead of acpi-cpufreq may disable platform features, such
1600 as thermal controls and power capping, that rely on ACPI
1601 P-States information being indicated to OSPM and therefore
1602 should be used with caution. This option does not work with
1603 processors that aren't supported by the intel_pstate driver
1604 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001605 no_hwp
1606 Do not enable hardware P state control (HWP)
1607 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001608 hwp_only
1609 Only load intel_pstate on systems which support
1610 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001611 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001612 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1613 Description Table, specifies preferred power management
1614 profile as "Enterprise Server" or "Performance Server",
1615 then this feature is turned on by default.
Srinivas Pandruvada22449c02016-10-25 13:20:43 -07001616 per_cpu_perf_limits
1617 Allow per-logical-CPU P-State performance control limits using
1618 cpufreq sysfs interface
Dirk Brandewie6be26492013-02-15 22:55:10 +01001619
Chris Wrightd1423d52010-07-20 11:06:49 -07001620 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001621 on enable Interrupt Remapping (default)
1622 off disable Interrupt Remapping
1623 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001624 no_x2apic_optout
1625 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001626 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001627
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001628 iomem= Disable strict checking of access to MMIO memory
1629 strict regions from userspace.
1630 relaxed
1631
1632 iommu= [x86]
1633 off
1634 force
1635 noforce
1636 biomerge
1637 panic
1638 nopanic
1639 merge
1640 nomerge
1641 forcesac
1642 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001643 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001644 nobypass [PPC/POWERNV]
1645 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001646
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001647
1648 io7= [HW] IO7 for Marvel based alpha systems
1649 See comment before marvel_specify_io7 in
1650 arch/alpha/kernel/core_marvel.c.
1651
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301652 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001653 0x80
1654 Standard port 0x80 based delay
1655 0xed
1656 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001657 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001658 Simple two microseconds delay
1659 none
1660 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001661
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001663 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001665 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001666 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001667
Alan Cox200803d2005-06-28 20:45:18 -07001668 irqfixup [HW]
1669 When an interrupt is not handled search all handlers
1670 for it. Intended to get systems with badly broken
1671 firmware running.
1672
1673 irqpoll [HW]
1674 When an interrupt is not handled search all handlers
1675 for it. Also check all handlers each timer
1676 interrupt. Intended to get systems with badly broken
1677 firmware running.
1678
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001680 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681
1682 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Noam Camus2d13e6c2016-10-11 13:51:35 -07001683 The argument is a cpu list, as described above.
Li Zefanb225d442008-11-06 12:53:39 -08001684
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685 This option can be used to specify one or more CPUs
1686 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001687 algorithms. You can move a process onto or off an
1688 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689 <cpu number> begins at 0 and the maximum value is
1690 "number of CPUs in system - 1".
1691
1692 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001693 alternative -- manually setting the CPU mask of all
1694 tasks in the system -- can cause problems and
1695 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696
Randy Dunlapa9913042005-10-23 12:57:11 -07001697 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001698
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001699 ivrs_ioapic [HW,X86_64]
1700 Provide an override to the IOAPIC-ID<->DEVICE-ID
1701 mapping provided in the IVRS ACPI table. For
1702 example, to map IOAPIC-ID decimal 10 to
1703 PCI device 00:14.0 write the parameter as:
1704 ivrs_ioapic[10]=00:14.0
1705
1706 ivrs_hpet [HW,X86_64]
1707 Provide an override to the HPET-ID<->DEVICE-ID
1708 mapping provided in the IVRS ACPI table. For
1709 example, to map HPET-ID decimal 0 to
1710 PCI device 00:14.0 write the parameter as:
1711 ivrs_hpet[0]=00:14.0
1712
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001713 ivrs_acpihid [HW,X86_64]
1714 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1715 mapping provided in the IVRS ACPI table. For
1716 example, to map UART-HID:UID AMD0020:0 to
1717 PCI device 00:14.5 write the parameter as:
1718 ivrs_acpihid[00:14.5]=AMD0020:0
1719
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720 js= [HW,JOY] Analog joystick
1721 See Documentation/input/joystick.txt.
1722
Kees Cook65fe9352016-06-13 15:10:02 -07001723 nokaslr [KNL]
1724 When CONFIG_RANDOMIZE_BASE is set, this disables
1725 kernel and module base offset ASLR (Address Space
1726 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001727
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001728 keepinitrd [HW,ARM]
1729
Taku Izumi342332e2016-03-15 14:55:22 -07001730 kernelcore= [KNL,X86,IA-64,PPC]
1731 Format: nn[KMGTPE] | "mirror"
1732 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001733 specifies the amount of memory usable by the kernel
1734 for non-movable allocations. The requested amount is
1735 spread evenly throughout all nodes in the system. The
1736 remaining memory in each node is used for Movable
1737 pages. In the event, a node is too small to have both
1738 kernelcore and Movable pages, kernelcore pages will
1739 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001740 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001741 allocation of pages that may be reclaimed or moved
1742 by the page migration subsystem. This means that
1743 HugeTLB pages may not be allocated from this zone.
1744 Note that allocations like PTEs-from-HighMem still
1745 use the HighMem zone if it exists, and the Normal
1746 zone if it does not.
1747
Taku Izumi342332e2016-03-15 14:55:22 -07001748 Instead of specifying the amount of memory (nn[KMGTPE]),
1749 you can specify "mirror" option. In case "mirror"
1750 option is specified, mirrored (reliable) memory is used
1751 for non-movable allocations and remaining memory is used
1752 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1753 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1754 time.
1755
Jason Wessel4fe1da42010-05-20 21:04:31 -05001756 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1757 Format: <Controller#>[,poll interval]
1758 The controller # is the number of the ehci usb debug
1759 port as it is probed via PCI. The poll interval is
1760 optional and is the number seconds in between
1761 each poll cycle to the debug port in case you need
1762 the functionality for interrupting the kernel with
1763 gdb or control-c on the dbgp connection. When
1764 not using this parameter you use sysrq-g to break into
1765 the kernel debugger.
1766
Jason Wessel84c08fd2010-05-20 21:04:24 -05001767 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001768 Requires a tty driver that supports console polling,
1769 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001770 Serial only format: <serial_device>[,baud]
1771 keyboard only format: kbd
1772 keyboard and serial format: kbd,<serial_device>[,baud]
1773 Optional Kernel mode setting:
1774 kms, kbd format: kms,kbd
1775 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001776
Jason Wessel84c08fd2010-05-20 21:04:24 -05001777 kgdbwait [KGDB] Stop kernel execution and enter the
1778 kernel debugger at the earliest opportunity.
1779
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001780 kmac= [MIPS] korina ethernet MAC address.
1781 Configure the RouterBoard 532 series on-chip
1782 Ethernet adapter MAC address.
1783
Catalin Marinas04f70332009-06-11 13:22:39 +01001784 kmemleak= [KNL] Boot-time kmemleak enable/disable
1785 Valid arguments: on, off
1786 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001787 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1788 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001789
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001790 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1791 Valid arguments: 0, 1, 2
1792 kmemcheck=0 (disabled)
1793 kmemcheck=1 (enabled)
1794 kmemcheck=2 (one-shot mode)
1795 Default: 2 (one-shot mode)
1796
Andre Przywarafef07aa2009-07-10 14:20:35 +02001797 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1798 Default is 0 (don't ignore, but inject #GP)
1799
Xiao Guangronga182d872010-09-20 22:17:48 +08001800 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1801 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001802 Default is 0 (off)
1803
Andre Przywarafef07aa2009-07-10 14:20:35 +02001804 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001805 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001806
1807 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1808 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001809 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001810
Andre Przywarafef07aa2009-07-10 14:20:35 +02001811 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1812 (virtualized MMU) support on capable Intel chips.
1813 Default is 1 (enabled)
1814
1815 kvm-intel.emulate_invalid_guest_state=
1816 [KVM,Intel] Enable emulation of invalid guest states
1817 Default is 0 (disabled)
1818
1819 kvm-intel.flexpriority=
1820 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1821 Default is 1 (enabled)
1822
Sasha Levine1a72ae2011-08-09 14:28:35 +03001823 kvm-intel.nested=
1824 [KVM,Intel] Enable VMX nesting (nVMX).
1825 Default is 0 (disabled)
1826
Andre Przywarafef07aa2009-07-10 14:20:35 +02001827 kvm-intel.unrestricted_guest=
1828 [KVM,Intel] Disable unrestricted guest feature
1829 (virtualized real and unpaged mode) on capable
1830 Intel chips. Default is 1 (enabled)
1831
1832 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1833 feature (tagged TLBs) on capable Intel chips.
1834 Default is 1 (enabled)
1835
Linus Torvalds1da177e2005-04-16 15:20:36 -07001836 l2cr= [PPC]
1837
Robert Brosea78bfbf2008-03-29 07:20:23 +11001838 l3cr= [PPC]
1839
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001840 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001841 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001842
Suresh Siddha279f1462012-10-22 14:37:58 -07001843 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1844 value for LAPIC timer one-shot implementation. Default
1845 back to the programmable timer unit in the LAPIC.
1846
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301847 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001848 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001849
FD Camifcb71f62008-01-06 19:08:56 +01001850 libata.dma= [LIBATA] DMA control
1851 libata.dma=0 Disable all PATA and SATA DMA
1852 libata.dma=1 PATA and SATA Disk DMA only
1853 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001854 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001855 Combinations also work, so libata.dma=3 enables DMA
1856 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001857
Michael Prokop20308872009-08-06 00:14:10 +02001858 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1859 libata.ignore_hpa=0 keep BIOS limits (default)
1860 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001861
Dave Jones78e70c22007-09-27 11:50:13 -04001862 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1863 when set.
1864 Format: <int>
1865
Tejun Heo33267322008-02-13 09:15:09 +09001866 libata.force= [LIBATA] Force configurations. The format is comma
1867 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001868 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001869 matching port, link or device. Basically, it matches
1870 the ATA ID string printed on console by libata. If
1871 the whole ID part is omitted, the last PORT and DEVICE
1872 values are used. If ID hasn't been specified yet, the
1873 configuration applies to all ports, links and devices.
1874
1875 If only DEVICE is omitted, the parameter applies to
1876 the port and all links and devices behind it. DEVICE
1877 number of 0 either selects the first device or the
1878 first fan-out link behind PMP device. It does not
1879 select the host link. DEVICE number of 15 selects the
1880 host link and device attached to it.
1881
1882 The VAL specifies the configuration to force. As long
1883 as there's no ambiguity shortcut notation is allowed.
1884 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1885 The following configurations can be forced.
1886
1887 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1888 Any ID with matching PORT is used.
1889
1890 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1891
1892 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1893 udma[/][16,25,33,44,66,100,133] notation is also
1894 allowed.
1895
1896 * [no]ncq: Turn on or off NCQ.
1897
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001898 * [no]ncqtrim: Turn off queued DSM TRIM.
1899
Tejun Heo05944bd2008-08-13 20:19:09 +09001900 * nohrst, nosrst, norst: suppress hard, soft
1901 and both resets.
1902
Dan Williamsca6d43b2012-06-21 23:41:41 -07001903 * rstonce: only attempt one reset during
1904 hot-unplug link recovery
1905
Tejun Heo43c9c592010-05-23 12:59:11 +02001906 * dump_id: dump IDENTIFY data.
1907
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001908 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1909
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001910 * disable: Disable this device.
1911
Tejun Heo33267322008-02-13 09:15:09 +09001912 If there are multiple matching configurations changing
1913 the same attribute, the last one is used.
1914
Yinghai Lu95f72d12010-07-12 14:36:09 +10001915 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001916
Linus Torvalds1da177e2005-04-16 15:20:36 -07001917 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001918 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001919
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001920 lockd.nlm_grace_period=P [NFS] Assign grace period.
1921 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001922
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001923 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1924 Format: <integer>
1925
1926 lockd.nlm_timeout=T [NFS] Assign timeout value.
1927 Format: <integer>
1928
1929 lockd.nlm_udpport=M [NFS] Assign UDP port.
1930 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001931
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001932 locktorture.nreaders_stress= [KNL]
1933 Set the number of locking read-acquisition kthreads.
1934 Defaults to being automatically set based on the
1935 number of online CPUs.
1936
1937 locktorture.nwriters_stress= [KNL]
1938 Set the number of locking write-acquisition kthreads.
1939
1940 locktorture.onoff_holdoff= [KNL]
1941 Set time (s) after boot for CPU-hotplug testing.
1942
1943 locktorture.onoff_interval= [KNL]
1944 Set time (s) between CPU-hotplug operations, or
1945 zero to disable CPU-hotplug testing.
1946
1947 locktorture.shuffle_interval= [KNL]
1948 Set task-shuffle interval (jiffies). Shuffling
1949 tasks allows some CPUs to go into dyntick-idle
1950 mode during the locktorture test.
1951
1952 locktorture.shutdown_secs= [KNL]
1953 Set time (s) after boot system shutdown. This
1954 is useful for hands-off automated testing.
1955
1956 locktorture.stat_interval= [KNL]
1957 Time (s) between statistics printk()s.
1958
1959 locktorture.stutter= [KNL]
1960 Time (s) to stutter testing, for example,
1961 specifying five seconds causes the test to run for
1962 five seconds, wait for five seconds, and so on.
1963 This tests the locking primitive's ability to
1964 transition abruptly to and from idle.
1965
1966 locktorture.torture_runnable= [BOOT]
1967 Start locktorture running at boot time.
1968
1969 locktorture.torture_type= [KNL]
1970 Specify the locking implementation to test.
1971
1972 locktorture.verbose= [KNL]
1973 Enable additional printk() statements.
1974
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1976 Format: <irq>
1977
1978 loglevel= All Kernel Messages with a loglevel smaller than the
1979 console loglevel will be printed to the console. It can
1980 also be changed with klogd or other programs. The
1981 loglevels are defined as follows:
1982
1983 0 (KERN_EMERG) system is unusable
1984 1 (KERN_ALERT) action must be taken immediately
1985 2 (KERN_CRIT) critical conditions
1986 3 (KERN_ERR) error conditions
1987 4 (KERN_WARNING) warning conditions
1988 5 (KERN_NOTICE) normal but significant condition
1989 6 (KERN_INFO) informational
1990 7 (KERN_DEBUG) debug-level messages
1991
Randy Dunlapc756d082011-02-20 20:08:35 -08001992 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001993 in bytes. n must be a power of two and greater
1994 than the minimal size. The minimal size is defined
1995 by LOG_BUF_SHIFT kernel config parameter. There is
1996 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1997 that allows to increase the default size depending on
1998 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001999
Randy Dunlapaccaa242007-10-16 01:29:37 -07002000 logo.nologo [FB] Disables display of the built-in Linux logo.
2001 This may be used to provide more screen space for
2002 kernel log messages and is useful when debugging
2003 kernel boot problems.
2004
Linus Torvalds1da177e2005-04-16 15:20:36 -07002005 lp=0 [LP] Specify parallel ports to use, e.g,
2006 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2007 lp=reset first parallel port). 'lp=0' disables the
2008 lp=auto printer driver. 'lp=reset' (which can be
2009 specified in addition to the ports) causes
2010 attached printers to be reset. Using
2011 lp=port1,port2,... specifies the parallel ports
2012 to associate lp devices with, starting with
2013 lp0. A port specification may be 'none' to skip
2014 that lp device, or a parport name such as
2015 'parport0'. Specifying 'lp=auto' instead of a
2016 port specification list means that device IDs
2017 from each port should be examined, to see if
2018 an IEEE 1284-compliant printer is attached; if
2019 so, the driver will manage that printer.
2020 See also header of drivers/char/lp.c.
2021
2022 lpj=n [KNL]
2023 Sets loops_per_jiffy to given constant, thus avoiding
2024 time-consuming boot-time autodetection (up to 250 ms per
2025 CPU). 0 enables autodetection (default). To determine
2026 the correct value for your kernel, boot with normal
2027 autodetection and see what value is printed. Note that
2028 on SMP systems the preset will be applied to all CPUs,
2029 which is likely to cause problems if your CPUs need
2030 significantly divergent settings. An incorrect value
2031 will cause delays in the kernel to be wrong, leading to
2032 unpredictable I/O errors and other breakage. Although
2033 unlikely, in the extreme case this might damage your
2034 hardware.
2035
2036 ltpc= [NET]
2037 Format: <io>,<irq>,<dma>
2038
Randy Dunlap16290242011-08-13 12:34:52 -07002039 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002040 (machvec) in a generic kernel.
2041 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042
Wu Zhangjin3209e702009-07-02 23:27:12 +08002043 machtype= [Loongson] Share the same kernel image file between different
2044 yeeloong laptop.
2045 Example: machtype=lemote-yeeloong-2f-7inch
2046
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002047 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2048 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002049
2050 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002051 will bring up during bootup. maxcpus=n : n >= 0 limits
2052 the kernel to bring up 'n' processors. Surely after
2053 bootup you can bring up the other plugged cpu by executing
2054 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2055 only takes effect during system bootup.
2056 While n=0 is a special case, it is equivalent to "nosmp",
2057 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002058
Kay Sieversd134b002011-07-31 22:08:04 +02002059 max_loop= [LOOP] The number of loop block devices that get
2060 (loop.max_loop) unconditionally pre-created at init time. The default
2061 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2062 of statically allocating a predefined number, loop
2063 devices can be requested on-demand with the
2064 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002065
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002066 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002067
Uwe Hermann71cced62008-10-20 09:32:21 -07002068 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002069
Linus Torvalds1da177e2005-04-16 15:20:36 -07002070 md= [HW] RAID subsystems devices and level
Jani Nikulae52347b2016-11-03 12:10:10 +02002071 See Documentation/admin-guide/md.rst.
Randy Dunlapa9913042005-10-23 12:57:11 -07002072
Linus Torvalds1da177e2005-04-16 15:20:36 -07002073 mdacon= [MDA]
2074 Format: <first>,<last>
2075 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002076
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2078 Amount of memory to be used when the kernel is not able
2079 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002080 [X86] Work as limiting max address. Use together
2081 with memmap= to avoid physical address space collisions.
2082 Without memmap= PCI devices could be placed at addresses
2083 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002085 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086 memory.
2087
Paul Mundt6902aa82008-09-21 17:14:42 +09002088 memchunk=nn[KMG]
2089 [KNL,SH] Allow user to override the default size for
2090 per-device physically contiguous DMA buffers.
2091
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002092 memhp_default_state=online/offline
2093 [KNL] Set the initial state for the memory hotplug
2094 onlining policy. If not specified, the default value is
2095 set according to the
2096 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2097 option.
2098 See Documentation/memory-hotplug.txt.
2099
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302100 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101 E820 memory map, as specified by the user.
2102 Such memmap=exactmap lines can be constructed based on
2103 BIOS output or other requirements. See the memmap=nn@ss
2104 option description.
2105
2106 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002107 [KNL] Force usage of a specific region of memory.
2108 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109
2110 memmap=nn[KMG]#ss[KMG]
2111 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002112 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002113
2114 memmap=nn[KMG]$ss[KMG]
2115 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002116 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002117 Example: Exclude memory from 0x18690000-0x1869ffff
2118 memmap=64K$0x18690000
2119 or
2120 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002122 memmap=nn[KMG]!ss[KMG]
2123 [KNL,X86] Mark specific memory as protected.
2124 Region of memory to be used, from ss to ss+nn.
2125 The memory region may be marked as e820 type 12 (0xc)
2126 and is NVDIMM or ADR memory.
2127
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002128 memory_corruption_check=0/1 [X86]
2129 Some BIOSes seem to corrupt the first 64k of
2130 memory when doing things like suspend/resume.
2131 Setting this option will scan the memory
2132 looking for corruption. Enabling this will
2133 both detect corruption and prevent the kernel
2134 from using the memory being corrupted.
2135 However, its intended as a diagnostic tool; if
2136 repeatable BIOS-originated corruption always
2137 affects the same memory, you can use memmap=
2138 to prevent the kernel from using that memory.
2139
2140 memory_corruption_check_size=size [X86]
2141 By default it checks for corruption in the low
2142 64k, making this memory unavailable for normal
2143 use. Use this parameter to scan for
2144 corruption in more or less memory.
2145
2146 memory_corruption_check_period=seconds [X86]
2147 By default it checks for corruption every 60
2148 seconds. Use this parameter to check at some
2149 other rate. 0 disables periodic checking.
2150
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002151 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002152 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002153 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002154 Specifies the number of memtest passes to be
2155 performed. Each pass selects another test
2156 pattern from a given set of patterns. Memtest
2157 fills the memory with this pattern, validates
2158 memory contents and reserves bad memory
2159 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002160
Rafael J. Wysocki406e7932016-11-21 22:45:40 +01002161 mem_sleep_default= [SUSPEND] Default system suspend mode:
2162 s2idle - Suspend-To-Idle
2163 shallow - Power-On Suspend or equivalent (if supported)
2164 deep - Suspend-To-RAM or equivalent (if supported)
2165 See Documentation/power/states.txt.
2166
Linus Torvalds1da177e2005-04-16 15:20:36 -07002167 meye.*= [HW] Set MotionEye Camera parameters
2168 See Documentation/video4linux/meye.txt.
2169
Andres Salomon8f368812007-10-12 23:04:06 +02002170 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2171 Multi-Function General Purpose Timers on AMD Geode
2172 platforms.
2173
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002174 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2175 the BIOS has incorrectly applied a workaround. TinyBIOS
2176 version 0.98 is known to be affected, 0.99 fixes the
2177 problem by letting the user disable the workaround.
2178
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 mga= [HW,DRM]
2180
Randy Dunlap1c207f952008-11-19 15:36:16 -08002181 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2182 physical address is ignored.
2183
Michel Pollet39f45d72009-05-20 11:10:31 +01002184 mini2440= [ARM,HW,KNL]
2185 Format:[0..2][b][c][t]
2186 Default: "0tb"
2187 MINI2440 configuration specification:
2188 0 - The attached screen is the 3.5" TFT
2189 1 - The attached screen is the 7" TFT
2190 2 - The VGA Shield is attached (1024x768)
2191 Leaving out the screen size parameter will not load
2192 the TFT driver, and the framebuffer will be left
2193 unconfigured.
2194 b - Enable backlight. The TFT backlight pin will be
2195 linked to the kernel VESA blanking code and a GPIO
2196 LED. This parameter is not necessary when using the
2197 VGA shield.
2198 c - Enable the s3c camera interface.
2199 t - Reserved for enabling touchscreen support. The
2200 touchscreen support is not enabled in the mainstream
2201 kernel as of 2.6.30, a preliminary port can be found
2202 in the "bleeding edge" mini2440 support kernel at
2203 http://repo.or.cz/w/linux-2.6/mini2440.git
2204
Mel Gorman6b74ab92008-07-23 21:26:49 -07002205 mminit_loglevel=
2206 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2207 parameter allows control of the logging verbosity for
2208 the additional memory initialisation checks. A value
2209 of 0 disables mminit logging and a level of 4 will
2210 log everything. Information is printed at KERN_DEBUG
2211 so loglevel=8 may also need to be specified.
2212
Rusty Russell106a4ee2012-09-26 10:09:40 +01002213 module.sig_enforce
2214 [KNL] When CONFIG_MODULE_SIG is set, this means that
2215 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002216 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002217 is always true, so this option does nothing.
2218
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302219 module_blacklist= [KNL] Do not load a comma-separated list of
2220 modules. Useful for debugging problem modules.
2221
Linus Torvalds1da177e2005-04-16 15:20:36 -07002222 mousedev.tap_time=
2223 [MOUSE] Maximum time between finger touching and
2224 leaving touchpad surface for touch to be considered
2225 a tap and be reported as a left button click (for
2226 touchpads working in absolute mode only).
2227 Format: <msecs>
2228 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2229 reporting absolute coordinates, such as tablets
2230 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2231 reporting absolute coordinates, such as tablets
2232
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302233 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002234 is similar to kernelcore except it specifies the
2235 amount of memory used for migratable allocations.
2236 If both kernelcore and movablecore is specified,
2237 then kernelcore will be at *least* the specified
2238 value but may be more. If movablecore on its own
2239 is specified, the administrator must be careful
2240 that the amount of memory usable for all allocations
2241 is not too small.
2242
Reza Arbab39fa104d2016-12-12 16:42:55 -08002243 movable_node [KNL] Boot-time switch to enable the effects
Tang Chenc5320922013-11-12 15:08:10 -08002244 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2245
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 MTD_Partition= [MTD]
2247 Format: <name>,<region-number>,<size>,<offset>
2248
Randy Dunlapa9913042005-10-23 12:57:11 -07002249 MTD_Region= [MTD] Format:
2250 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251
2252 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002253 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002255 multitce=off [PPC] This parameter disables the use of the pSeries
2256 firmware feature for updating multiple TCE entries
2257 at a time.
2258
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002259 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2260
2261 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2262
2263 boundary - index of last SLC block on Flex-OneNAND.
2264 The remaining blocks are configured as MLC blocks.
2265 lock - Configure if Flex-OneNAND boundary should be locked.
2266 Once locked, the boundary cannot be changed.
2267 1 indicates lock status, 0 indicates unlock status.
2268
Ben Dooks9db829f2008-07-03 11:24:29 +01002269 mtdset= [ARM]
2270 ARM/S3C2412 JIVE boot control
2271
2272 See arch/arm/mach-s3c2412/mach-jive.c
2273
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002275 [HW] Make the MicroTouch USB driver use raw coordinates
2276 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002277
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002278 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002279 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002280 that could hold holes aka. UC entries.
2281
2282 mtrr_gran_size=nn[KMG] [X86]
2283 Used for mtrr cleanup. It is granularity of mtrr block.
2284 Default is 1.
2285 Large value could prevent small alignment from
2286 using up MTRRs.
2287
2288 mtrr_spare_reg_nr=n [X86]
2289 Format: <integer>
2290 Range: 0,7 : spare reg number
2291 Default : 1
2292 Used for mtrr cleanup. It is spare mtrr entries number.
2293 Set to 2 or more if your graphical card needs more.
2294
Linus Torvalds1da177e2005-04-16 15:20:36 -07002295 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2296
Linus Torvalds1da177e2005-04-16 15:20:36 -07002297 netdev= [NET] Network devices parameters
2298 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2299 Note that mem_start is often overloaded to mean
2300 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002301 This usage is only documented in each driver source
2302 file if at all.
2303
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002304 nf_conntrack.acct=
2305 [NETFILTER] Enable connection tracking flow accounting
2306 0 to disable accounting
2307 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002308 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002309
Chuck Lever306a0752010-09-17 10:54:37 -04002310 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002311 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002312
2313 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002314 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315
Chuck Lever306a0752010-09-17 10:54:37 -04002316 nfsrootdebug [NFS] enable nfsroot debugging messages.
2317 See Documentation/filesystems/nfs/nfsroot.txt.
2318
Trond Myklebust5405fc42016-08-29 20:03:52 -04002319 nfs.callback_nr_threads=
2320 [NFSv4] set the total number of threads that the
2321 NFS client will assign to service NFSv4 callback
2322 requests.
2323
Trond Myklebusta72b4422006-01-03 09:55:41 +01002324 nfs.callback_tcpport=
2325 [NFS] set the TCP port on which the NFSv4 callback
2326 channel should listen.
2327
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002328 nfs.cache_getent=
2329 [NFS] sets the pathname to the program which is used
2330 to update the NFS client cache entries.
2331
2332 nfs.cache_getent_timeout=
2333 [NFS] sets the timeout after which an attempt to
2334 update a cache entry is deemed to have failed.
2335
Trond Myklebust58df0952006-01-03 09:55:57 +01002336 nfs.idmap_cache_timeout=
2337 [NFS] set the maximum lifetime for idmapper cache
2338 entries.
2339
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002340 nfs.enable_ino64=
2341 [NFS] enable 64-bit inode numbers.
2342 If zero, the NFS client will fake up a 32-bit inode
2343 number for the readdir() and stat() syscalls instead
2344 of returning the full 64-bit number.
2345 The default is to return 64-bit inode numbers.
2346
Trond Myklebust5405fc42016-08-29 20:03:52 -04002347 nfs.max_session_cb_slots=
2348 [NFSv4.1] Sets the maximum number of session
2349 slots the client will assign to the callback
2350 channel. This determines the maximum number of
2351 callbacks the client will process in parallel for
2352 a particular server.
2353
Trond Myklebustef159e92012-02-06 19:50:40 -05002354 nfs.max_session_slots=
2355 [NFSv4.1] Sets the maximum number of session slots
2356 the client will attempt to negotiate with the server.
2357 This limits the number of simultaneous RPC requests
2358 that the client can send to the NFSv4.1 server.
2359 Note that there is little point in setting this
2360 value higher than the max_tcp_slot_table_limit.
2361
Trond Myklebustb064eca22011-02-22 15:44:32 -08002362 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002363 [NFSv4] When set to the default of '1', this option
2364 ensures that both the RPC level authentication
2365 scheme and the NFS level operations agree to use
2366 numeric uids/gids if the mount is using the
2367 'sec=sys' security flavour. In effect it is
2368 disabling idmapping, which can make migration from
2369 legacy NFSv2/v3 systems to NFSv4 easier.
2370 Servers that do not support this mode of operation
2371 will be autodetected by the client, and it will fall
2372 back to using the idmapper.
2373 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002374 nfs.nfs4_unique_id=
2375 [NFS4] Specify an additional fixed unique ident-
2376 ification string that NFSv4 clients can insert into
2377 their nfs_client_id4 string. This is typically a
2378 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002379
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002380 nfs.send_implementation_id =
2381 [NFSv4.1] Send client implementation identification
2382 information in exchange_id requests.
2383 If zero, no implementation identification information
2384 will be sent.
2385 The default is to send the implementation identification
2386 information.
Jani Nikulae52347b2016-11-03 12:10:10 +02002387
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002388 nfs.recover_lost_locks =
2389 [NFSv4] Attempt to recover locks that were lost due
2390 to a lease timeout on the server. Please note that
2391 doing this risks data corruption, since there are
2392 no guarantees that the file will remain unchanged
2393 after the locks are lost.
2394 If you want to enable the kernel legacy behaviour of
2395 attempting to recover these locks, then set this
2396 parameter to '1'.
2397 The default parameter value of '0' causes the kernel
2398 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002399
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002400 nfs4.layoutstats_timer =
2401 [NFSv4.2] Change the rate at which the kernel sends
2402 layoutstats to the pNFS metadata server.
2403
2404 Setting this to value to 0 causes the kernel to use
2405 whatever value is the default set by the layout
2406 driver. A non-zero value sets the minimum interval
2407 in seconds between layoutstats transmissions.
2408
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002409 nfsd.nfs4_disable_idmapping=
2410 [NFSv4] When set to the default of '1', the NFSv4
2411 server will return only numeric uids and gids to
2412 clients using auth_sys, and will accept numeric uids
2413 and gids from such clients. This is intended to ease
2414 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002415
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002416 objlayoutdriver.osd_login_prog=
2417 [NFS] [OBJLAYOUT] sets the pathname to the program which
2418 is used to automatically discover and login into new
2419 osd-targets. Please see:
2420 Documentation/filesystems/pnfs.txt for more explanations
2421
Paul Mundt1e1030d2009-09-01 17:38:32 +09002422 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002423 when a NMI is triggered.
2424 Format: [state][,regs][,debounce][,die]
2425
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302426 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002427 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002428 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002429 0 - turn hardlockup detector in nmi_watchdog off
2430 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002431 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002432 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002433 default). To disable both hard and soft lockup detectors,
2434 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002435 This is useful when you use a panic=... timeout and
2436 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002437
Anton Vorontsovbff38772009-07-08 11:10:56 -07002438 netpoll.carrier_timeout=
2439 [NET] Specifies amount of time (in seconds) that
2440 netpoll should wait for a carrier. By default netpoll
2441 waits 4 seconds.
2442
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002443 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002444 emulation library even if a 387 maths coprocessor
2445 is present.
2446
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002447 no_console_suspend
2448 [HW] Never suspend the console
2449 Disable suspending of consoles during suspend and
2450 hibernate operations. Once disabled, debugging
2451 messages can reach various consoles while the rest
2452 of the system is being put to sleep (ie, while
2453 debugging driver suspend/resume hooks). This may
2454 not work reliably with all consoles, but is known
2455 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002456 To facilitate more flexible debugging, we also add
2457 console_suspend, a printk module parameter to control
2458 it. Users could use console_suspend (usually
2459 /sys/module/printk/parameters/console_suspend) to
2460 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002461
Christoph Lameterc1aee212007-05-31 00:40:47 -07002462 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2463 caches in the slab allocator. Saves per-node memory,
2464 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002465
Randy Dunlapa9913042005-10-23 12:57:11 -07002466 noalign [KNL,ARM]
2467
Linus Torvalds1da177e2005-04-16 15:20:36 -07002468 noapic [SMP,APIC] Tells the kernel to not make use of any
2469 IOAPICs that may be present in the system.
2470
Mike Galbraith5091faa2010-11-30 14:18:03 +01002471 noautogroup Disable scheduler automatic task group creation.
2472
Linus Torvalds1da177e2005-04-16 15:20:36 -07002473 nobats [PPC] Do not use BATs for mapping kernel lowmem
2474 on "Classic" PPC cores.
2475
2476 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002477
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002478 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2479
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002480 nodelayacct [KNL] Disable per-task delay accounting
2481
Paul Mundt6902aa82008-09-21 17:14:42 +09002482 nodsp [SH] Disable hardware DSP at boot time.
2483
Dave Youngb2e0a542014-08-14 17:15:26 +08002484 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002485
Linus Torvalds1da177e2005-04-16 15:20:36 -07002486 noexec [IA-64]
2487
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302488 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002489 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002491 noexec=off: disable non-executable mappings
2492
H. Peter Anvin52b61792012-09-21 12:43:13 -07002493 nosmap [X86]
2494 Disable SMAP (Supervisor Mode Access Prevention)
2495 even if it is supported by processor.
2496
Fenghua Yude5397a2011-05-11 16:51:05 -07002497 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002498 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002499 even if it is supported by processor.
2500
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002501 noexec32 [X86-64]
2502 This affects only 32-bit executables.
2503 noexec32=on: enable non-executable mappings (default)
2504 read doesn't imply executable mappings
2505 noexec32=off: disable non-executable mappings
2506 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002507
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002508 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002509
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002510 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002511 register save and restore. The kernel will only save
2512 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002514 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2515
Sascha Silbe52c48c52016-04-05 12:53:38 +02002516 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2517 Equivalent to smt=1.
2518
Suresh Siddha0c752a92009-05-22 12:17:45 -07002519 noxsave [BUGS=X86] Disables x86 extended register state save
2520 and restore using xsave. The kernel will fallback to
2521 enabling legacy floating-point and sse state.
2522
Fenghua Yub6f42a42014-05-29 11:12:31 -07002523 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2524 register states. The kernel will fall back to use
2525 xsave to save the states. By using this parameter,
2526 performance of saving the states is degraded because
2527 xsave doesn't support modified optimization while
2528 xsaveopt supports it on xsaveopt enabled systems.
2529
2530 noxsaves [X86] Disables xsaves and xrstors used in saving and
2531 restoring x86 extended register state in compacted
2532 form of xsave area. The kernel will fall back to use
2533 xsaveopt and xrstor to save and restore the states
2534 in standard form of xsave area. By using this
2535 parameter, xsave area per process might occupy more
2536 memory on xsaves enabled systems.
2537
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002538 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2539 wfi(ARM) instruction doesn't work correctly and not to
2540 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002541
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002542 no_file_caps Tells the kernel not to honor file capabilities. The
2543 only way then for a file to be executed with privilege
2544 is to be setuid root or executed by root.
2545
Linus Torvalds1da177e2005-04-16 15:20:36 -07002546 nohalt [IA-64] Tells the kernel not to use the power saving
2547 function PAL_HALT_LIGHT when idle. This increases
2548 power-consumption. On the positive side, it reduces
2549 interrupt wake-up latency, which may improve performance
2550 in certain environments such as networked servers or
2551 real-time systems.
2552
Kees Cooka6e15a32014-06-13 13:30:35 -07002553 nohibernate [HIBERNATION] Disable hibernation and resume.
2554
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002555 nohz= [KNL] Boottime enable/disable dynamic ticks
2556 Valid arguments: on, off
2557 Default: on
2558
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002559 nohz_full= [KNL,BOOT]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002560 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002561 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002562 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002563 whenever possible. The boot CPU will be forced outside
2564 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002565 The CPUs in this range must also be included in the
2566 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002567
Paul Mundteeee7852009-04-02 12:31:16 +09002568 noiotrap [SH] Disables trapped I/O port accesses.
2569
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002570 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002571 disable unhandled interrupt sources.
2572
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302573 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002574 broken timer IRQ sources.
2575
Linus Torvalds1da177e2005-04-16 15:20:36 -07002576 noisapnp [ISAPNP] Disables ISA PnP code.
2577
2578 noinitrd [RAM] Tells the kernel not to load any configured
2579 initial RAM disk.
2580
Weidong Han03ea8152009-04-17 16:42:15 +08002581 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2582 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002583 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002584
Linus Torvalds1da177e2005-04-16 15:20:36 -07002585 nointroute [IA-64]
2586
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002587 noinvpcid [X86] Disable the INVPCID cpu feature.
2588
Randy Dunlap16290242011-08-13 12:34:52 -07002589 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002590
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002591 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2592
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002593 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2594 fault handling.
2595
Alexey Makhalov80e9a4f2016-10-28 00:54:32 -07002596 no-vmw-sched-clock
2597 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2598 clock and use the default one.
2599
Glauber Costad910f5c2011-07-11 15:28:19 -04002600 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2601 steal time is computed, but won't influence scheduler
2602 behaviour
2603
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002604 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002606 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002607
Linus Torvalds1da177e2005-04-16 15:20:36 -07002608 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002609 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002610
Horms312f1f02006-02-22 09:57:55 +09002611 nomca [IA-64] Disable machine check abort handling
2612
Masanari Iida13696e02015-05-16 02:16:43 +09002613 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002614
Andres Salomon83d73842007-10-12 23:04:06 +02002615 nomfgpt [X86-32] Disable Multi-Function General Purpose
2616 Timer usage (for AMD Geode machines).
2617
Don Zickusbda62632011-10-13 15:14:27 -04002618 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2619 shutdown the other cpus. Instead use the REBOOT_VECTOR
2620 irq.
2621
Dave Young02608be2012-02-01 10:33:14 +08002622 nomodule Disable module load
2623
Jiri Kosina016ddd92010-01-18 17:05:40 +01002624 nopat [X86] Disable PAT (page attribute table extension of
2625 pagetables) support.
2626
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002627 norandmaps Don't use address space randomization. Equivalent to
2628 echo 0 > /proc/sys/kernel/randomize_va_space
2629
Jiri Kosinabbff2162010-08-11 18:34:09 +02002630 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002631
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002632 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002633 with UP alternatives
2634
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002635 nordrand [X86] Disable kernel use of the RDRAND and
2636 RDSEED instructions even if they are supported
2637 by the processor. RDRAND and RDSEED are still
2638 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002639
Randy Dunlapa9913042005-10-23 12:57:11 -07002640 noresume [SWSUSP] Disables resume and restores original swap
2641 space.
2642
Linus Torvalds1da177e2005-04-16 15:20:36 -07002643 no-scroll [VGA] Disables scrollback.
2644 This is required for the Braillex ib80-piezo Braille
2645 reader made by F.H. Papenmeier (Germany).
2646
2647 nosbagart [IA-64]
2648
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002649 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002650
Len Brown61ec7562007-08-16 03:34:22 -04002651 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2652 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653
Dave Jones97842212007-07-15 23:41:05 -07002654 nosoftlockup [KNL] Disable the soft-lockup detector.
2655
Linus Torvalds1da177e2005-04-16 15:20:36 -07002656 nosync [HW,M68K] Disables sync negotiation for all devices.
2657
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002658 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002659
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002660 nowatchdog [KNL] Disable both lockup detectors, i.e.
2661 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002662
Linus Torvalds1da177e2005-04-16 15:20:36 -07002663 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002664
Weidong Han2b2fd872009-04-17 16:42:12 +08002665 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2666
Fenghua Yuf78cff42012-11-13 11:32:38 -08002667 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2668 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2669 Some features depend on CPU0. Known dependencies are:
2670 1. Resume from suspend/hibernate depends on CPU0.
2671 Suspend/hibernate will fail if CPU0 is offline and you
2672 need to online CPU0 before suspend/hibernate.
2673 2. PIC interrupts also depend on CPU0. CPU0 can't be
2674 removed if a PIC interrupt is detected.
2675 It's said poweroff/reboot may depend on CPU0 on some
2676 machines although I haven't seen such issues so far
2677 after CPU0 is offline on a few tested machines.
2678 If the dependencies are under your control, you can
2679 turn on cpu0_hotplug.
2680
Randy Dunlap16290242011-08-13 12:34:52 -07002681 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002682 purges which is reported from either PAL_VM_SUMMARY or
2683 SAL PALO.
2684
Yinghai Lu2b633e32010-02-10 01:20:37 -08002685 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2686 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002687 support 'n' processors. It could be larger than the
2688 number of already plugged CPU during bootup, later in
2689 runtime you can physically add extra cpu until it reaches
2690 n. So during boot up some boot time memory for per-cpu
2691 variables need be pre-allocated for later physical cpu
2692 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002693
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002694 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2695
Mel Gorman1a687c22012-11-22 11:16:36 +00002696 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2697 Allowed values are enable and disable
2698
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002699 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2700 one of ['zone', 'node', 'default'] can be specified
2701 This can be set from sysctl after boot.
2702 See Documentation/sysctl/vm.txt for details.
2703
Randy Dunlap7c4be252009-01-06 14:42:44 -08002704 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2705 See Documentation/debugging-via-ohci1394.txt for more
2706 info.
2707
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002708 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2709 Rather than timing out after 20 ms if an EC
2710 command is not properly ACKed, override the length
2711 of the timeout. We have interrupts disabled while
2712 waiting for the ACK, so if this is set too high
2713 interrupts *may* be lost!
2714
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002715 omap_mux= [OMAP] Override bootloader pin multiplexing.
2716 Format: <mux_mode0.mode_name=value>...
2717 For example, to override I2C bus2:
2718 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2719
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720 oprofile.timer= [HW]
2721 Use timer interrupt instead of performance counters
2722
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002723 oprofile.cpu_type= Force an oprofile cpu type
2724 This might be useful if you have an older oprofile
2725 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002726 Format: { arch_perfmon }
2727 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002728 perfmon on Intel CPUs instead of the
2729 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002730 timer: [X86] Force use of architectural NMI
2731 timer mode (see also oprofile.timer
2732 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002733
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002734 oops=panic Always panic on oopses. Default is to just kill the
2735 process, but there is a small probability of
2736 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002737 This will also cause panics on machine check exceptions.
2738 Useful together with panic=30 to trigger a reboot.
2739
Randy Dunlapbcfde332010-06-07 17:10:38 -07002740 OSS [HW,OSS]
2741 See Documentation/sound/oss/oss-parameters.txt
2742
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002743 page_owner= [KNL] Boot-time page_owner enabling option.
2744 Storage of the information about who allocated
2745 each page is disabled in default. With this switch,
2746 we can turn it on.
2747 on: enable the feature
2748
Laura Abbott8823b1d2016-03-15 14:56:27 -07002749 page_poison= [KNL] Boot-time parameter changing the state of
2750 poisoning on the buddy allocator.
2751 off: turn off poisoning
2752 on: turn on poisoning
2753
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002754 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002755 timeout > 0: seconds before rebooting
2756 timeout = 0: wait forever
2757 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002758 Format: <timeout>
2759
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002760 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2761 on a WARN().
2762
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002763 crash_kexec_post_notifiers
2764 Run kdump after running panic-notifiers and dumping
2765 kmsg. This only for the users who doubt kdump always
2766 succeeds in any situation.
2767 Note that this also increases risks of kdump failure,
2768 because some panic notifiers can make the crashed
2769 kernel more unstable.
2770
Linus Torvalds1da177e2005-04-16 15:20:36 -07002771 parkbd.port= [HW] Parallel port number the keyboard adapter is
2772 connected to, default is 0.
2773 Format: <parport#>
2774 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2775 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002776 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002777
Randy Dunlapa9913042005-10-23 12:57:11 -07002778 parport= [HW,PPT] Specify parallel ports. 0 disables.
2779 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2780 Use 'auto' to force the driver to use any
2781 IRQ/DMA settings detected (the default is to
2782 ignore detected IRQ/DMA settings because of
2783 possible conflicts). You can specify the base
2784 address, IRQ, and DMA settings; IRQ and DMA
2785 should be numbers, or 'auto' (for using detected
2786 settings on that particular port), or 'nofifo'
2787 (to avoid using a FIFO even if it is detected).
2788 Parallel ports are assigned in the order they
2789 are specified on the command line, starting
2790 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002791
Randy Dunlapa9913042005-10-23 12:57:11 -07002792 parport_init_mode= [HW,PPT]
2793 Configure VIA parallel port to operate in
2794 a specific mode. This is necessary on Pegasos
2795 computer where firmware has no options for setting
2796 up parallel port mode and sets it to spp.
2797 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002798 Format: [spp|ps2|epp|ecp|ecpepp]
2799
Andrew Mortondd287792006-03-23 03:00:57 -08002800 pause_on_oops=
2801 Halt all CPUs after the first oops has been printed for
2802 the specified number of seconds. This is to be used if
2803 your oopses keep scrolling off the screen.
2804
Linus Torvalds1da177e2005-04-16 15:20:36 -07002805 pcbit= [HW,ISDN]
2806
2807 pcd. [PARIDE]
2808 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002809 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002810
Randy Dunlapa9913042005-10-23 12:57:11 -07002811 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002812 earlydump [X86] dump PCI config space before the kernel
2813 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002814 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002815 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002816 the hardware directly. Use this if your machine
2817 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002818 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002819 hardware access methods are allowed. Use this
2820 if you experience crashes upon bootup and you
2821 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002822 conf1 [X86] Force use of PCI Configuration Access
2823 Mechanism 1 (config address in IO port 0xCF8,
2824 data in IO port 0xCFC, both 32-bit).
2825 conf2 [X86] Force use of PCI Configuration Access
2826 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2827 the function, IO port 0xCFA, also 8-bit, sets
2828 bus number. The config space is then accessed
2829 through ports 0xC000-0xCFFF).
2830 See http://wiki.osdev.org/PCI for more info
2831 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002832 noaer [PCIE] If the PCIEAER kernel config parameter is
2833 enabled, this kernel boot option can be used to
2834 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002835 nodomains [PCI] Disable support for multiple PCI
2836 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302837 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002838 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002839 check_enable_amd_mmconf [X86] check for and enable
2840 properly configured MMIO access to PCI
2841 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002842 nomsi [MSI] If the PCI_MSI kernel config parameter is
2843 enabled, this kernel boot option can be used to
2844 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002845 noioapicquirk [APIC] Disable all boot interrupt quirks.
2846 Safety option to keep boot IRQs enabled. This
2847 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002848 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2849 primary IO-APIC for bridges that cannot disable
2850 boot IRQs. This fixes a source of spurious IRQs
2851 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002852 noioapicreroute [APIC] Disable workaround that uses the
2853 boot IRQ equivalent of an IRQ that connects to
2854 a chipset where boot IRQs cannot be disabled.
2855 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002856 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002857 routing table. These calls are known to be buggy
2858 on several machines and they hang the machine
2859 when used, but on other computers it's the only
2860 way to get the interrupt routing table. Try
2861 this option if the kernel is unable to allocate
2862 IRQs or discover secondary PCI buses on your
2863 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002864 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002865 Use with caution as certain devices share
2866 address decoders between ROMs and other
2867 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002868 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002869 expansion ROMs that do not already have
2870 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002871 nobar [X86] Do not assign address space to the
2872 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002873 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002874 assigned automatically to PCI devices. You can
2875 make the kernel exclude IRQs of your ISA cards
2876 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002877 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002878 of the PIRQ table (normally generated
2879 by the BIOS) if it is outside the
2880 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002881 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002882 useful if the kernel is unable to find your
2883 secondary buses and you want to tell it
2884 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002885 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002886 numbers ourselves, overriding
2887 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002888 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002889 in the BIOS $PIR table. This is needed on
2890 some systems with broken BIOSes, notably
2891 some HP Pavilion N5400 and Omnibook XE3
2892 notebooks. This will have no effect if ACPI
2893 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002894 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002895 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002896 use_crs [X86] Use PCI host bridge window information
2897 from ACPI. On BIOSes from 2008 or later, this
2898 is enabled by default. If you need to use this,
2899 please report a bug.
2900 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2901 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002902 routeirq Do IRQ routing for all PCI devices.
2903 This is normally done in pci_enable_device(),
2904 so this option is a temporary workaround
2905 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002906 skip_isa_align [X86] do not align io start addr, so can
2907 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02002908 noearly [X86] Don't do any early type 1 scanning.
2909 This might help on some broken boards which
2910 machine check when some devices' config space
2911 is read. But various workarounds are disabled
2912 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002913 bfsort Sort PCI devices into breadth-first order.
2914 This sorting is done to get a device
2915 order compatible with older (<= 2.4) kernels.
2916 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002917 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2918 tuning and use the BIOS-configured MPS defaults.
2919 pcie_bus_safe Set every device's MPS to the largest value
2920 supported by all devices below the root complex.
2921 pcie_bus_perf Set device MPS to the largest allowable MPS
2922 based on its parent bus. Also set MRRS (Max
2923 Read Request Size) to the largest supported
2924 value (no larger than the MPS that the device
2925 or bus can support) for best performance.
2926 pcie_bus_peer2peer Set every device's MPS to 128B, which
2927 every device is guaranteed to support. This
2928 configuration allows peer-to-peer DMA between
2929 any pair of devices, possibly at the cost of
2930 reduced performance. This also guarantees
2931 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002932 cbiosize=nn[KMG] The fixed amount of bus space which is
2933 reserved for the CardBus bridge's IO window.
2934 The default value is 256 bytes.
2935 cbmemsize=nn[KMG] The fixed amount of bus space which is
2936 reserved for the CardBus bridge's memory
2937 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002938 resource_alignment=
2939 Format:
2940 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00002941 [<order of align>@]pci:<vendor>:<device>\
2942 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002943 Specifies alignment and device to reassign
2944 aligned memory resources.
2945 If <order of align> is not specified,
2946 PAGE_SIZE is used as alignment.
2947 PCI-PCI bridge can be specified, if resource
2948 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02002949 To specify the alignment for several
2950 instances of a device, the PCI vendor,
2951 device, subvendor, and subdevice may be
2952 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06002953 ecrc= Enable/disable PCIe ECRC (transaction layer
2954 end-to-end CRC checking).
2955 bios: Use BIOS/firmware settings. This is the
2956 the default.
2957 off: Turn ECRC off
2958 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002959 hpiosize=nn[KMG] The fixed amount of bus space which is
2960 reserved for hotplug bridge's IO window.
2961 Default size is 256 bytes.
2962 hpmemsize=nn[KMG] The fixed amount of bus space which is
2963 reserved for hotplug bridge's memory window.
2964 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06002965 hpbussize=nn The minimum amount of additional bus numbers
2966 reserved for buses below a hotplug bridge.
2967 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08002968 realloc= Enable/disable reallocating PCI bridge resources
2969 if allocations done by BIOS are too small to
2970 accommodate resources required by all child
2971 devices.
2972 off: Turn realloc off
2973 on: Turn realloc on
2974 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002975 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002976 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2977 only look for one device below a PCIe downstream
2978 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002979
Chuck Ebberte5665a42008-09-24 20:40:34 -04002980 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2981 Management.
2982 off Disable ASPM.
2983 force Enable ASPM even on devices that claim not to support it.
2984 WARNING: Forcing ASPM on may cause system lockups.
2985
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002986 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2987 nomsi Do not use MSI for PCI Express Native Hotplug (this
2988 makes all PCIe ports use INTx for hotplug services).
2989
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002990 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002991 auto Ask the BIOS whether or not to use native PCIe services
2992 associated with PCIe ports (PME, hot-plug, AER). Use
2993 them only if that is allowed by the BIOS.
2994 native Use native PCIe services associated with PCIe ports
2995 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002996 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2997 ports driver.
2998
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03002999 pcie_port_pm= [PCIE] PCIe port power management handling:
3000 off Disable power management of all PCIe ports
3001 force Forcibly enable power management of all PCIe ports
3002
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003003 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003004 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003005 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003006
Linus Torvalds1da177e2005-04-16 15:20:36 -07003007 pcmv= [HW,PCMCIA] BadgePAD 4
3008
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303009 pd_ignore_unused
3010 [PM]
3011 Keep all power-domains already enabled by bootloader on,
3012 even if no driver has claimed them. This is useful
3013 for debug and development, but should not be
3014 needed on a platform with proper driver support.
3015
Linus Torvalds1da177e2005-04-16 15:20:36 -07003016 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003017 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003018
3019 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3020 boot time.
3021 Format: { 0 | 1 }
3022 See arch/parisc/kernel/pdc_chassis.c
3023
Tejun Heof58dc012009-08-14 15:00:50 +09003024 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003025 Currently supported values are "embed" and "page".
3026 Archs may support subset or none of the selections.
3027 See comments in mm/percpu.c for details on each
3028 allocator. This parameter is primarily for debugging
3029 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003030
Linus Torvalds1da177e2005-04-16 15:20:36 -07003031 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003032 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003033
3034 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003035 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003036
3037 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003038 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003039
3040 plip= [PPT,NET] Parallel port network link
3041 Format: { parport<nr> | timid | 0 }
3042 See also Documentation/parport.txt.
3043
Randy Dunlap16290242011-08-13 12:34:52 -07003044 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003045 Override pmtimer IOPort with a hex value.
3046 e.g. pmtmr=0x508
3047
Bjorn Helgaas96242112011-08-11 12:14:05 -06003048 pnp.debug=1 [PNP]
3049 Enable PNP debug messages (depends on the
3050 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3051 via /sys/module/pnp/parameters/debug. We always show
3052 current resource usage; turning this on also shows
3053 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003054
Linus Torvalds1da177e2005-04-16 15:20:36 -07003055 pnpacpi= [ACPI]
3056 { off }
3057
3058 pnpbios= [ISAPNP]
3059 { on | off | curr | res | no-curr | no-res }
3060
3061 pnp_reserve_irq=
3062 [ISAPNP] Exclude IRQs for the autoconfiguration
3063
3064 pnp_reserve_dma=
3065 [ISAPNP] Exclude DMAs for the autoconfiguration
3066
3067 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003068 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003069
3070 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003071 [ISAPNP] Exclude memory regions for the
3072 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003073 Ranges are in pairs (memory base and size).
3074
Randy Dunlap4af94f32009-04-17 18:30:28 -07003075 ports= [IP_VS_FTP] IPVS ftp helper module
3076 Default is 21.
3077 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3078 may be specified.
3079 Format: <port>,<port>....
3080
Balbir Singhc3cbd072016-12-02 00:08:26 +11003081 powersave=off [PPC] This option disables power saving features.
3082 It specifically disables cpuidle and sets the
3083 platform machine description specific power_save
3084 function to NULL. On Idle the CPU just reduces
3085 execution priority.
3086
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003087 ppc_strict_facility_enable
3088 [PPC] This option catches any kernel floating point,
3089 Altivec, VSX and SPE outside of regions specifically
3090 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3091 There is some performance impact when enabling this.
3092
Ingo Molnar45807a12007-07-15 23:40:10 -07003093 print-fatal-signals=
3094 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003095
3096 If enabled, warn about various signal handling
3097 related application anomalies: too many signals,
3098 too many POSIX.1 timers, fatal signals causing a
3099 coredump - etc.
3100
3101 If you hit the warning due to signal overflow,
3102 you might want to try "ulimit -i unlimited".
3103
Ingo Molnar45807a12007-07-15 23:40:10 -07003104 default: off.
3105
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003106 printk.always_kmsg_dump=
3107 Trigger kmsg_dump for cases other than kernel oops or
3108 panics
3109 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3110 default: disabled
3111
Borislav Petkov750afe72016-08-02 14:04:07 -07003112 printk.devkmsg={on,off,ratelimit}
3113 Control writing to /dev/kmsg.
3114 on - unlimited logging to /dev/kmsg from userspace
3115 off - logging to /dev/kmsg disabled
3116 ratelimit - ratelimit the logging
3117 Default: ratelimit
3118
Randy Dunlape84845c2007-07-15 23:40:25 -07003119 printk.time= Show timing data prefixed to each printk message line
3120 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3121
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003122 processor.max_cstate= [HW,ACPI]
3123 Limit processor to maximum C-state
3124 max_cstate=9 overrides any DMI blacklist limit.
3125
3126 processor.nocst [HW,ACPI]
3127 Ignore the _CST method to determine C-states,
3128 instead using the legacy FADT method
3129
Linus Torvalds1da177e2005-04-16 15:20:36 -07003130 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003131 Format: [schedule,]<number>
3132 Param: "schedule" - profile schedule points.
3133 Param: <number> - step/bucket size as a power of 2 for
3134 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003135 Param: "sleep" - profile D-state sleeping (millisecs).
3136 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003137 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003138
Linus Torvalds1da177e2005-04-16 15:20:36 -07003139 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3140 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003141 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003142
Randy Dunlapa9913042005-10-23 12:57:11 -07003143 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3144 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003145 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3146 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003147 psmouse.resetafter= [HW,MOUSE]
3148 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003149 (0 = never).
3150 psmouse.resolution=
3151 [HW,MOUSE] Set desired mouse resolution, in dpi.
3152 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003153 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003154 0 = disabled, 1 = enabled (default).
3155
Matthew Garrettdee28e72011-07-21 16:57:55 -04003156 pstore.backend= Specify the name of the pstore backend to use
3157
Linus Torvalds1da177e2005-04-16 15:20:36 -07003158 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003159 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003160
Kay Sieversdc8c8582007-08-15 12:25:38 +02003161 pty.legacy_count=
3162 [KNL] Number of legacy pty's. Overwrites compiled-in
3163 default number.
3164
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003165 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003166
Linus Torvalds1da177e2005-04-16 15:20:36 -07003167 r128= [HW,DRM]
3168
3169 raid= [HW,RAID]
Jani Nikulae52347b2016-11-03 12:10:10 +02003170 See Documentation/admin-guide/md.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003171
Linus Torvalds1da177e2005-04-16 15:20:36 -07003172 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003173 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003174
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003175 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003176 The argument is a cpu list, as described above.
3177
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003178 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3179 the specified list of CPUs to be no-callback CPUs.
3180 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003181 be offloaded to "rcuox/N" kthreads created for
3182 that purpose, where "x" is "b" for RCU-bh, "p"
3183 for RCU-preempt, and "s" for RCU-sched, and "N"
3184 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003185 offloaded CPUs, which can be useful for HPC and
3186 real-time workloads. It can also improve energy
3187 efficiency for asymmetric multiprocessors.
3188
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003189 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003190 Rather than requiring that offloaded CPUs
3191 (specified by rcu_nocbs= above) explicitly
3192 awaken the corresponding "rcuoN" kthreads,
3193 make these kthreads poll for callbacks.
3194 This improves the real-time response for the
3195 offloaded CPUs by relieving them of the need to
3196 wake up the corresponding kthread, but degrades
3197 energy efficiency by requiring that the kthreads
3198 periodically wake up to do the polling.
3199
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003200 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003201 Set maximum number of finished RCU callbacks to
3202 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003203
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003204 rcutree.dump_tree= [KNL]
3205 Dump the structure of the rcu_node combining tree
3206 out at early boot. This is used for diagnostic
3207 purposes, to verify correct tree setup.
3208
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003209 rcutree.gp_cleanup_delay= [KNL]
3210 Set the number of jiffies to delay each step of
3211 RCU grace-period cleanup. This only has effect
3212 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3213
Paul E. McKenney37745d22015-01-22 18:24:08 -08003214 rcutree.gp_init_delay= [KNL]
3215 Set the number of jiffies to delay each step of
3216 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003217 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3218 is set.
3219
3220 rcutree.gp_preinit_delay= [KNL]
3221 Set the number of jiffies to delay each step of
3222 RCU grace-period pre-initialization, that is,
3223 the propagation of recent CPU-hotplug changes up
3224 the rcu_node combining tree. This only has effect
3225 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003226
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003227 rcutree.rcu_fanout_exact= [KNL]
3228 Disable autobalancing of the rcu_node combining
3229 tree. This is used by rcutorture, and might
3230 possibly be useful for architectures having high
3231 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003232
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003233 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003234 Change the number of CPUs assigned to each
3235 leaf rcu_node structure. Useful for very
3236 large systems, which will choose the value 64,
3237 and for NUMA systems with large remote-access
3238 latencies, which will choose a value aligned
3239 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003240
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003241 rcutree.jiffies_till_sched_qs= [KNL]
3242 Set required age in jiffies for a
3243 given grace period before RCU starts
3244 soliciting quiescent-state help from
3245 rcu_note_context_switch().
3246
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003247 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003248 Set delay from grace-period initialization to
3249 first attempt to force quiescent states.
3250 Units are jiffies, minimum value is zero,
3251 and maximum value is HZ.
3252
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003253 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003254 Set delay between subsequent attempts to force
3255 quiescent states. Units are jiffies, minimum
3256 value is one, and maximum value is HZ.
3257
Clark Williams21871d72014-09-12 21:21:09 -05003258 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003259 Set the SCHED_FIFO priority of the RCU per-CPU
3260 kthreads (rcuc/N). This value is also used for
3261 the priority of the RCU boost threads (rcub/N)
3262 and for the RCU grace-period kthreads (rcu_bh,
3263 rcu_preempt, and rcu_sched). If RCU_BOOST is
3264 set, valid values are 1-99 and the default is 1
3265 (the least-favored priority). Otherwise, when
3266 RCU_BOOST is not set, valid values are 0-99 and
3267 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003268
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003269 rcutree.rcu_nocb_leader_stride= [KNL]
3270 Set the number of NOCB kthread groups, which
3271 defaults to the square root of the number of
3272 CPUs. Larger numbers reduces the wakeup overhead
3273 on the per-CPU grace-period kthreads, but increases
3274 that same overhead on each group's leader.
3275
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003276 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003277 Set threshold of queued RCU callbacks beyond which
3278 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003279
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003280 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003281 Set threshold of queued RCU callbacks below which
3282 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003283
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003284 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003285 Set wakeup interval for idle CPUs that have
3286 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003287
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003288 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003289 Set wakeup interval for idle CPUs that have
3290 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3291 Lazy RCU callbacks are those which RCU can
3292 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003293
Paul E. McKenneye3c50df2017-01-06 15:14:11 -08003294 rcutree.rcu_kick_kthreads= [KNL]
3295 Cause the grace-period kthread to get an extra
3296 wake_up() if it sleeps three times longer than
3297 it should at force-quiescent-state time.
3298 This wake_up() will be accompanied by a
3299 WARN_ONCE() splat and an ftrace_dump().
3300
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003301 rcuperf.gp_exp= [KNL]
3302 Measure performance of expedited synchronous
3303 grace-period primitives.
3304
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003305 rcuperf.holdoff= [KNL]
3306 Set test-start holdoff period. The purpose of
3307 this parameter is to delay the start of the
3308 test until boot completes in order to avoid
3309 interference.
3310
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003311 rcuperf.nreaders= [KNL]
3312 Set number of RCU readers. The value -1 selects
3313 N, where N is the number of CPUs. A value
3314 "n" less than -1 selects N-n+1, where N is again
3315 the number of CPUs. For example, -2 selects N
3316 (the number of CPUs), -3 selects N+1, and so on.
3317 A value of "n" less than or equal to -N selects
3318 a single reader.
3319
3320 rcuperf.nwriters= [KNL]
3321 Set number of RCU writers. The values operate
3322 the same as for rcuperf.nreaders.
3323 N, where N is the number of CPUs
3324
3325 rcuperf.perf_runnable= [BOOT]
3326 Start rcuperf running at boot time.
3327
3328 rcuperf.shutdown= [KNL]
3329 Shut the system down after performance tests
3330 complete. This is useful for hands-off automated
3331 testing.
3332
3333 rcuperf.perf_type= [KNL]
3334 Specify the RCU implementation to test.
3335
3336 rcuperf.verbose= [KNL]
3337 Enable additional printk() statements.
3338
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003339 rcutorture.cbflood_inter_holdoff= [KNL]
3340 Set holdoff time (jiffies) between successive
3341 callback-flood tests.
3342
3343 rcutorture.cbflood_intra_holdoff= [KNL]
3344 Set holdoff time (jiffies) between successive
3345 bursts of callbacks within a given callback-flood
3346 test.
3347
3348 rcutorture.cbflood_n_burst= [KNL]
3349 Set the number of bursts making up a given
3350 callback-flood test. Set this to zero to
3351 disable callback-flood testing.
3352
3353 rcutorture.cbflood_n_per_burst= [KNL]
3354 Set the number of callbacks to be registered
3355 in a given burst of a callback-flood test.
3356
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003357 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003358 Set duration of force_quiescent_state bursts
3359 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003360
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003361 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003362 Set holdoff time within force_quiescent_state bursts
3363 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003364
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003365 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003366 Set wait time between force_quiescent_state bursts
3367 in seconds.
3368
3369 rcutorture.gp_cond= [KNL]
3370 Use conditional/asynchronous update-side
3371 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003372
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003373 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003374 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003375
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003376 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003377 Use normal (non-expedited) asynchronous
3378 update-side primitives, if available.
3379
3380 rcutorture.gp_sync= [KNL]
3381 Use normal (non-expedited) synchronous
3382 update-side primitives, if available. If all
3383 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3384 rcutorture.gp_normal=, and rcutorture.gp_sync=
3385 are zero, rcutorture acts as if is interpreted
3386 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003387
3388 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003389 Set callbacks/threads for rcu_barrier() testing.
3390
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003391 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003392 Set number of concurrent RCU writers. These just
3393 stress RCU, they don't participate in the actual
3394 test, hence the "fake".
3395
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003396 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003397 Set number of RCU readers. The value -1 selects
3398 N-1, where N is the number of CPUs. A value
3399 "n" less than -1 selects N-n-2, where N is again
3400 the number of CPUs. For example, -2 selects N
3401 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003402
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003403 rcutorture.object_debug= [KNL]
3404 Enable debug-object double-call_rcu() testing.
3405
3406 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003407 Set time (s) after boot for CPU-hotplug testing.
3408
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003409 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003410 Set time (s) between CPU-hotplug operations, or
3411 zero to disable CPU-hotplug testing.
3412
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003413 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003414 Set task-shuffle interval (s). Shuffling tasks
3415 allows some CPUs to go into dyntick-idle mode
3416 during the rcutorture test.
3417
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003418 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003419 Set time (s) after boot system shutdown. This
3420 is useful for hands-off automated testing.
3421
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003422 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003423 Duration of CPU stall (s) to test RCU CPU stall
3424 warnings, zero to disable.
3425
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003426 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003427 Time to wait (s) after boot before inducing stall.
3428
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003429 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003430 Time (s) between statistics printk()s.
3431
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003432 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003433 Time (s) to stutter testing, for example, specifying
3434 five seconds causes the test to run for five seconds,
3435 wait for five seconds, and so on. This tests RCU's
3436 ability to transition abruptly to and from idle.
3437
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003438 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003439 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3440 "Maybe" means test if the RCU implementation
3441 under test support RCU priority boosting.
3442
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003443 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003444 Duration (s) of each individual boost test.
3445
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003446 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003447 Interval (s) between each boost test.
3448
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003449 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003450 Test RCU's dyntick-idle handling. See also the
3451 rcutorture.shuffle_interval parameter.
3452
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003453 rcutorture.torture_runnable= [BOOT]
3454 Start rcutorture running at boot time.
3455
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003456 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003457 Specify the RCU implementation to test.
3458
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003459 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003460 Enable additional printk() statements.
3461
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003462 rcupdate.rcu_cpu_stall_suppress= [KNL]
3463 Suppress RCU CPU stall warning messages.
3464
3465 rcupdate.rcu_cpu_stall_timeout= [KNL]
3466 Set timeout for RCU CPU stall warning messages.
3467
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003468 rcupdate.rcu_expedited= [KNL]
3469 Use expedited grace-period primitives, for
3470 example, synchronize_rcu_expedited() instead
3471 of synchronize_rcu(). This reduces latency,
3472 but can increase CPU utilization, degrade
3473 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003474 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003475
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003476 rcupdate.rcu_normal= [KNL]
3477 Use only normal grace-period primitives,
3478 for example, synchronize_rcu() instead of
3479 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003480 real-time latency, CPU utilization, and
3481 energy efficiency, but can expose users to
3482 increased grace-period latency. This parameter
3483 overrides rcupdate.rcu_expedited. No effect on
3484 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003485
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003486 rcupdate.rcu_normal_after_boot= [KNL]
3487 Once boot has completed (that is, after
3488 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003489 only normal grace-period primitives. No effect
3490 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003491
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003492 rcupdate.rcu_task_stall_timeout= [KNL]
3493 Set timeout in jiffies for RCU task stall warning
3494 messages. Disable with a value less than or equal
3495 to zero.
3496
Pranith Kumar74860fe2014-09-19 11:34:09 -04003497 rcupdate.rcu_self_test= [KNL]
3498 Run the RCU early boot self tests
3499
3500 rcupdate.rcu_self_test_bh= [KNL]
3501 Run the RCU bh early boot self tests
3502
3503 rcupdate.rcu_self_test_sched= [KNL]
3504 Run the RCU sched early boot self tests
3505
Olof Johanssonffdfc402005-09-06 15:17:19 -07003506 rdinit= [KNL]
3507 Format: <full_path>
3508 Run specified binary instead of /init from the ramdisk,
3509 used for early userspace startup. See initrd.
3510
Robin Holt1b3a5d02013-07-08 16:01:42 -07003511 reboot= [KNL]
3512 Format (x86 or x86_64):
3513 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3514 [[,]s[mp]#### \
3515 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3516 [[,]f[orce]
3517 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3518 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3519 reboot_force is either force or not specified,
3520 reboot_cpu is s[mp]#### with #### being the processor
3521 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003522
Paul Jackson46b6d942008-07-04 10:00:09 -07003523 relax_domain_level=
3524 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003525 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003526
Linus Torvalds1da177e2005-04-16 15:20:36 -07003527 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3528
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003529 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003530 Format: nn[KMG]
3531 Reserves a hole at the top of the kernel virtual
3532 address space.
3533
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003534 reservelow= [X86]
3535 Format: nn[K]
3536 Set the amount of memory to reserve for BIOS at
3537 the bottom of the address space.
3538
Vivek Goyal7e962872006-09-27 01:50:44 -07003539 reset_devices [KNL] Force drivers to reset the underlying device
3540 during initialization.
3541
Randy Dunlapa9913042005-10-23 12:57:11 -07003542 resume= [SWSUSP]
3543 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003544 Format:
3545 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003546
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003547 resume_offset= [SWSUSP]
3548 Specify the offset from the beginning of the partition
3549 given by "resume=" at which the swap header is located,
3550 in <PAGE_SIZE> units (needed only for swap files).
3551 See Documentation/power/swsusp-and-swap-files.txt
3552
Barry Songf126f732011-10-10 23:38:41 +02003553 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3554 read the resume files
3555
Barry Song6f8d7022011-10-06 20:34:46 +02003556 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3557 Useful for devices that are detected asynchronously
3558 (e.g. USB and MMC devices).
3559
Bojan Smojverf996fc92010-09-09 23:06:23 +02003560 hibernate= [HIBERNATION]
3561 noresume Don't check if there's a hibernation image
3562 present during boot.
3563 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003564 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003565 protect_image Turn on image protection during restoration
3566 (that will set all pages holding image data
3567 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003568
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003569 retain_initrd [RAM] Keep initrd memory after extraction
3570
Andrew Clausen0efbb782015-01-09 20:24:55 +00003571 rfkill.default_state=
3572 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3573 etc. communication is blocked by default.
3574 1 Unblocked.
3575
3576 rfkill.master_switch_mode=
3577 0 The "airplane mode" button does nothing.
3578 1 The "airplane mode" button toggles between everything
3579 blocked and the previous configuration.
3580 2 The "airplane mode" button toggles between everything
3581 blocked and everything unblocked.
3582
Linus Torvalds1da177e2005-04-16 15:20:36 -07003583 rhash_entries= [KNL,NET]
3584 Set number of hash buckets for route cache
3585
Grzegorz Andrejczuke16fd002017-01-20 14:22:36 +01003586 ring3mwait=disable
3587 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3588 CPUs.
3589
Linus Torvalds1da177e2005-04-16 15:20:36 -07003590 ro [KNL] Mount root device read-only on boot
3591
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003592 rodata= [KNL]
3593 on Mark read-only kernel memory as read-only (default).
3594 off Leave read-only kernel memory writable for debugging.
3595
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003596 rockchip.usb_uart
3597 Enable the uart passthrough on the designated usb port
3598 on Rockchip SoCs. When active, the signals of the
3599 debug-uart get routed to the D+ and D- pins of the usb
3600 port and the regular usb controller gets disabled.
3601
Linus Torvalds1da177e2005-04-16 15:20:36 -07003602 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003603 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003604
3605 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3606 mount the root filesystem
3607
3608 rootflags= [KNL] Set root filesystem mount option string
3609
3610 rootfstype= [KNL] Set root filesystem type
3611
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003612 rootwait [KNL] Wait (indefinitely) for root device to show up.
3613 Useful for devices that are detected asynchronously
3614 (e.g. USB and MMC devices).
3615
Robert Tivy5c71d612013-03-28 18:41:46 -07003616 rproc_mem=nn[KMG][@address]
3617 [KNL,ARM,CMA] Remoteproc physical memory block.
3618 Memory area to be used by remote processor image,
3619 managed by CMA.
3620
Linus Torvalds1da177e2005-04-16 15:20:36 -07003621 rw [KNL] Mount root device read-write on boot
3622
3623 S [KNL] Run init in single mode
3624
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003625 s390_iommu= [HW,S390]
3626 Set s390 IOTLB flushing mode
3627 strict
3628 With strict flushing every unmap operation will result in
3629 an IOTLB flush. Default is lazy flushing before reuse,
3630 which is faster.
3631
Linus Torvalds1da177e2005-04-16 15:20:36 -07003632 sa1100ir [NET]
3633 See drivers/net/irda/sa1100_ir.c.
3634
Linus Torvalds1da177e2005-04-16 15:20:36 -07003635 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003636
Mike Travisf6630112009-11-17 18:22:15 -06003637 sched_debug [KNL] Enables verbose scheduler debug messages.
3638
Mel Gormancb251762016-02-05 09:08:36 +00003639 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3640 Allowed values are enable and disable. This feature
3641 incurs a small amount of overhead in the scheduler
3642 but is useful for debugging and performance tuning.
3643
Mike Galbraith5307c952012-05-08 12:20:58 +02003644 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3645 xtime_lock contention on larger systems, and/or RCU lock
3646 contention on all systems with CONFIG_MAXSMP set.
3647 Format: { "0" | "1" }
3648 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3649 1 -- enable.
3650 Note: increases power consumption, thus should only be
3651 enabled if running jitter sensitive (HPC/RT) workloads.
3652
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003653 security= [SECURITY] Choose a security module to enable at boot.
3654 If this boot parameter is not specified, only the first
3655 security module asking for security registration will be
3656 loaded. An invalid security module name will be treated
3657 as if no module has been chosen.
3658
3659 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003660 Format: { "0" | "1" }
3661 See security/selinux/Kconfig help text.
3662 0 -- disable.
3663 1 -- enable.
3664 Default value is set via kernel config option.
3665 If enabled at boot time, /selinux/disable can be used
3666 later to disable prior to initial policy load.
3667
John Johansenc1c124e2010-07-29 14:48:09 -07003668 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3669 Format: { "0" | "1" }
3670 See security/apparmor/Kconfig help text
3671 0 -- disable.
3672 1 -- enable.
3673 Default value is set via kernel config option.
3674
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003675 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003676
Linus Torvalds1da177e2005-04-16 15:20:36 -07003677 shapers= [NET]
3678 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003679
Linus Torvalds1da177e2005-04-16 15:20:36 -07003680 simeth= [IA-64]
3681 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003682
Linus Torvalds1da177e2005-04-16 15:20:36 -07003683 slram= [HW,MTD]
3684
Joonsoo Kim423c9292014-10-09 15:26:22 -07003685 slab_nomerge [MM]
3686 Disable merging of slabs with similar size. May be
3687 necessary if there is some reason to distinguish
3688 allocs to different slabs. Debug options disable
3689 merging on their own.
3690 For more information see Documentation/vm/slub.txt.
3691
David Rientjes3df1ccc2011-10-18 22:09:28 -07003692 slab_max_order= [MM, SLAB]
3693 Determines the maximum allowed order for slabs.
3694 A high setting may cause OOMs due to memory
3695 fragmentation. Defaults to 1 for systems with
3696 more than 32MB of RAM, 0 otherwise.
3697
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003698 slub_debug[=options[,slabs]] [MM, SLUB]
3699 Enabling slub_debug allows one to determine the
3700 culprit if slab objects become corrupted. Enabling
3701 slub_debug can create guard zones around objects and
3702 may poison objects when not in use. Also tracks the
3703 last alloc / free. For more information see
3704 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003705
Tejun Heo1663f262017-02-22 15:41:39 -08003706 slub_memcg_sysfs= [MM, SLUB]
3707 Determines whether to enable sysfs directories for
3708 memory cgroup sub-caches. 1 to enable, 0 to disable.
3709 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3710 Enabling this can lead to a very high number of debug
3711 directories and files being created under
3712 /sys/kernel/slub.
3713
Christoph Lameterc1aee212007-05-31 00:40:47 -07003714 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003715 Determines the maximum allowed order for slabs.
3716 A high setting may cause OOMs due to memory
3717 fragmentation. For more information see
3718 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003719
3720 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003721 The minimum number of objects per slab. SLUB will
3722 increase the slab order up to slub_max_order to
3723 generate a sufficiently large slab able to contain
3724 the number of objects indicated. The higher the number
3725 of objects the smaller the overhead of tracking slabs
3726 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003727 For more information see Documentation/vm/slub.txt.
3728
3729 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003730 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003731 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003732 For more information see Documentation/vm/slub.txt.
3733
3734 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003735 Same with slab_nomerge. This is supported for legacy.
3736 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003737
Linus Torvalds1da177e2005-04-16 15:20:36 -07003738 smart2= [HW]
3739 Format: <io1>[,<io2>[,...,<io8>]]
3740
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003741 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3742 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3743 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3744 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3745 smsc-ircc2.ircc_irq= [HW] IRQ line
3746 smsc-ircc2.ircc_dma= [HW] DMA channel
3747 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3748 0: Toshiba Satellite 1800 (GP data pin select)
3749 1: Fast pin select (default)
3750 2: ATC IRMode
3751
Sascha Silbe52c48c52016-04-05 12:53:38 +02003752 smt [KNL,S390] Set the maximum number of threads (logical
3753 CPUs) to use per physical CPU on systems capable of
3754 symmetric multithreading (SMT). Will be capped to the
3755 actual hardware limit.
3756 Format: <integer>
3757 Default: -1 (no limit)
3758
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003759 softlockup_panic=
3760 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003761 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003762
Aaron Tomlined235872014-06-23 13:22:05 -07003763 softlockup_all_cpu_backtrace=
3764 [KNL] Should the soft-lockup detector generate
3765 backtraces on all cpus.
3766 Format: <integer>
3767
Linus Torvalds1da177e2005-04-16 15:20:36 -07003768 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003769 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003770
Linus Torvalds1da177e2005-04-16 15:20:36 -07003771 spia_io_base= [HW,MTD]
3772 spia_fio_base=
3773 spia_pedr=
3774 spia_peddr=
3775
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003776 stacktrace [FTRACE]
3777 Enabled the stack tracer on boot up.
3778
Steven Rostedt762e1202011-12-19 22:01:00 -05003779 stacktrace_filter=[function-list]
3780 [FTRACE] Limit the functions that the stack tracer
3781 will trace at boot up. function-list is a comma separated
3782 list of functions. This list can be changed at run
3783 time by the stack_trace_filter file in the debugfs
3784 tracing directory. Note, this enables stack tracing
3785 and the stacktrace above is not needed.
3786
Linus Torvalds1da177e2005-04-16 15:20:36 -07003787 sti= [PARISC,HW]
3788 Format: <num>
3789 Set the STI (builtin display/keyboard on the HP-PARISC
3790 machines) console (graphic card) which should be used
3791 as the initial boot-console.
3792 See also comment in drivers/video/console/sticore.c.
3793
3794 sti_font= [HW]
3795 See comment in drivers/video/console/sticore.c.
3796
3797 stifb= [HW]
3798 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3799
Trond Myklebustcbf11072009-08-09 15:06:19 -04003800 sunrpc.min_resvport=
3801 sunrpc.max_resvport=
3802 [NFS,SUNRPC]
3803 SunRPC servers often require that client requests
3804 originate from a privileged port (i.e. a port in the
3805 range 0 < portnr < 1024).
3806 An administrator who wishes to reserve some of these
3807 ports for other uses may adjust the range that the
3808 kernel's sunrpc client considers to be privileged
3809 using these two parameters to set the minimum and
3810 maximum port values.
3811
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003812 sunrpc.svc_rpc_per_connection_limit=
3813 [NFS,SUNRPC]
3814 Limit the number of requests that the server will
3815 process in parallel from a single connection.
3816 The default value is 0 (no limit).
3817
Greg Banks42a7fc42007-03-06 01:42:23 -08003818 sunrpc.pool_mode=
3819 [NFS]
3820 Control how the NFS server code allocates CPUs to
3821 service thread pools. Depending on how many NICs
3822 you have and where their interrupts are bound, this
3823 option will affect which CPUs will do NFS serving.
3824 Note: this parameter cannot be changed while the
3825 NFS server is running.
3826
3827 auto the server chooses an appropriate mode
3828 automatically using heuristics
3829 global a single global pool contains all CPUs
3830 percpu one pool for each CPU
3831 pernode one pool for each NUMA node (equivalent
3832 to global on non-NUMA machines)
3833
Trond Myklebustcbf11072009-08-09 15:06:19 -04003834 sunrpc.tcp_slot_table_entries=
3835 sunrpc.udp_slot_table_entries=
3836 [NFS,SUNRPC]
3837 Sets the upper limit on the number of simultaneous
3838 RPC calls that can be sent from the client to a
3839 server. Increasing these values may allow you to
3840 improve throughput, but will also increase the
3841 amount of memory reserved for use by the client.
3842
Brian Norris1d4a9c12015-02-22 21:16:49 -08003843 suspend.pm_test_delay=
3844 [SUSPEND]
3845 Sets the number of seconds to remain in a suspend test
3846 mode before resuming the system (see
3847 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3848 is set. Default value is 5.
3849
Michal Hocko07555ac2013-08-22 16:35:46 -07003850 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003851 [KNL] Enable accounting of swap in memory resource
3852 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003853 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08003854
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003855 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003856 Format: { <int> | force | noforce }
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003857 <int> -- Number of I/O TLB slabs
3858 force -- force using of bounce buffers even if they
3859 wouldn't be automatically used by the kernel
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003860 noforce -- Never use bounce buffers (for debugging)
Randy Dunlapa9913042005-10-23 12:57:11 -07003861
Linus Torvalds1da177e2005-04-16 15:20:36 -07003862 switches= [HW,M68k]
3863
Andi Kleene52eec12010-09-08 16:54:17 +02003864 sysfs.deprecated=0|1 [KNL]
3865 Enable/disable old style sysfs layout for old udev
3866 on older distributions. When this option is enabled
3867 very new udev will not work anymore. When this option
3868 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3869 in older udev will not work anymore.
3870 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3871 the kernel configuration.
3872
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003873 sysrq_always_enabled
3874 [KNL]
3875 Ignore sysrq setting - this boot parameter will
3876 neutralize any effect of /proc/sys/kernel/sysrq.
3877 Useful for debugging.
3878
Fabian Frederick747029a2014-11-06 19:46:50 +01003879 tcpmhash_entries= [KNL,NET]
3880 Set the number of tcp_metrics_hash slots.
3881 Default value is 8192 or 16384 depending on total
3882 ram pages. This is used to specify the TCP metrics
3883 cache size. See Documentation/networking/ip-sysctl.txt
3884 "tcp_no_metrics_save" section for more details.
3885
Linus Torvalds1da177e2005-04-16 15:20:36 -07003886 tdfx= [HW,DRM]
3887
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003888 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003889 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003890 standby suspend) or "freeze" (for suspend type freeze)
3891 as the system sleep state during system startup with
3892 the optional capability to repeat N number of times.
3893 The system is woken from this state using a
3894 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003895
Linus Torvalds1da177e2005-04-16 15:20:36 -07003896 thash_entries= [KNL,NET]
3897 Set number of hash buckets for TCP connection
3898
Len Brownf8707ec2007-08-12 00:12:54 -04003899 thermal.act= [HW,ACPI]
3900 -1: disable all active trip points in all thermal zones
3901 <degrees C>: override all lowest active trip points
3902
Len Brownc52a7412007-08-14 15:49:32 -04003903 thermal.crt= [HW,ACPI]
3904 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003905 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003906
Len Brownf5487142007-08-12 00:12:44 -04003907 thermal.nocrt= [HW,ACPI]
3908 Set to disable actions on ACPI thermal zone
3909 critical and hot trip points.
3910
Len Brown72b33ef2007-08-12 00:12:17 -04003911 thermal.off= [HW,ACPI]
3912 1: disable ACPI thermal control
3913
Len Browna70cdc52007-08-12 00:12:35 -04003914 thermal.psv= [HW,ACPI]
3915 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003916 <degrees C>: override all passive trip points to this
3917 value
Len Browna70cdc52007-08-12 00:12:35 -04003918
Len Brown730ff342007-08-12 00:12:26 -04003919 thermal.tzp= [HW,ACPI]
3920 Specify global default ACPI thermal zone polling rate
3921 <deci-seconds>: poll all this frequency
3922 0: no polling (default)
3923
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003924 threadirqs [KNL]
3925 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003926 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003927
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003928 tmem [KNL,XEN]
3929 Enable the Transcendent memory driver if built-in.
3930
3931 tmem.cleancache=0|1 [KNL, XEN]
3932 Default is on (1). Disable the usage of the cleancache
3933 API to send anonymous pages to the hypervisor.
3934
3935 tmem.frontswap=0|1 [KNL, XEN]
3936 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003937 API to send swap pages to the hypervisor. If disabled
3938 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003939
3940 tmem.selfballooning=0|1 [KNL, XEN]
3941 Default is on (1). Disable the driving of swap pages
3942 to the hypervisor.
3943
3944 tmem.selfshrinking=0|1 [KNL, XEN]
3945 Default is on (1). Partial swapoff that immediately
3946 transfers pages from Xen hypervisor back to the
3947 kernel based on different criteria.
3948
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003949 topology= [S390]
3950 Format: {off | on}
3951 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003952 topology information if the hardware supports this.
3953 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003954 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003955 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003956
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003957 topology_updates= [KNL, PPC, NUMA]
3958 Format: {off}
3959 Specify if the kernel should ignore (off)
3960 topology updates sent by the hypervisor to this
3961 LPAR.
3962
Linus Torvalds1da177e2005-04-16 15:20:36 -07003963 tp720= [HW,PS2]
3964
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003965 tpm_suspend_pcr=[HW,TPM]
3966 Format: integer pcr id
3967 Specify that at suspend time, the tpm driver
3968 should extend the specified pcr with zeros,
3969 as a workaround for some chips which fail to
3970 flush the last written pcr on TPM_SaveState.
3971 This will guarantee that all the other pcrs
3972 are saved.
3973
Li Zefan9d612be2009-06-24 17:33:15 +08003974 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003975 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003976
Li Zefan020e5f82009-07-01 10:47:05 +08003977 trace_event=[event-list]
3978 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07003979 to facilitate early boot debugging. The event-list is a
3980 comma separated list of trace events to enable. See
3981 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08003982
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003983 trace_options=[option-list]
3984 [FTRACE] Enable or disable tracer options at boot.
3985 The option-list is a comma delimited list of options
3986 that can be enabled or disabled just as if you were
3987 to echo the option name into
3988
3989 /sys/kernel/debug/tracing/trace_options
3990
3991 For example, to enable stacktrace option (to dump the
3992 stack trace of each event), add to the command line:
3993
3994 trace_options=stacktrace
3995
3996 See also Documentation/trace/ftrace.txt "trace options"
3997 section.
3998
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003999 tp_printk[FTRACE]
4000 Have the tracepoints sent to printk as well as the
4001 tracing ring buffer. This is useful for early boot up
4002 where the system hangs or reboots and does not give the
4003 option for reading the tracing buffer or performing a
4004 ftrace_dump_on_oops.
4005
4006 To turn off having tracepoints sent to printk,
4007 echo 0 > /proc/sys/kernel/tracepoint_printk
4008 Note, echoing 1 into this file without the
4009 tracepoint_printk kernel cmdline option has no effect.
4010
4011 ** CAUTION **
4012
4013 Having tracepoints sent to printk() and activating high
4014 frequency tracepoints such as irq or sched, can cause
4015 the system to live lock.
4016
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004017 traceoff_on_warning
4018 [FTRACE] enable this option to disable tracing when a
4019 warning is hit. This turns off "tracing_on". Tracing can
4020 be enabled again by echoing '1' into the "tracing_on"
4021 file located in /sys/kernel/debug/tracing/
4022
4023 This option is useful, as it disables the trace before
4024 the WARNING dump is called, which prevents the trace to
4025 be filled with content caused by the warning output.
4026
4027 This option can also be set at run time via the sysctl
4028 option: kernel/traceoff_on_warning
4029
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004030 transparent_hugepage=
4031 [KNL]
4032 Format: [always|madvise|never]
4033 Can be used to control the default behavior of the system
4034 with respect to transparent hugepages.
4035 See Documentation/vm/transhuge.txt for more details.
4036
john stultzd3b8f882009-08-17 16:40:47 -07004037 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004038 Format: <string>
4039 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004040 disables clocksource verification at runtime, as well
4041 as the stability checks done at bootup. Used to enable
4042 high-resolution timer mode on older hardware, and in
4043 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004044 [x86] noirqtime: Do not use TSC to do irq accounting.
4045 Used to run time disable IRQ_TIME_ACCOUNTING on any
4046 platforms where RDTSC is slow and this accounting
4047 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004048
Randy Dunlapa9913042005-10-23 12:57:11 -07004049 turbografx.map[2|3]= [HW,JOY]
4050 TurboGraFX parallel port interface
4051 Format:
4052 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004053 See also Documentation/input/joystick-parport.txt
4054
Christian Kujaub6935f82011-05-31 15:22:05 +00004055 udbg-immortal [PPC] When debugging early kernel crashes that
Jani Nikulae52347b2016-11-03 12:10:10 +02004056 happen after console_init() and before a proper
Christian Kujaub6935f82011-05-31 15:22:05 +00004057 console driver takes over, this boot options might
4058 help "seeing" what's going on.
4059
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004060 uhash_entries= [KNL,NET]
4061 Set number of hash buckets for UDP/UDP-Lite connections
4062
Alan Stern5f8364b2006-12-05 16:29:55 -05004063 uhci-hcd.ignore_oc=
4064 [USB] Ignore overcurrent events (default N).
4065 Some badly-designed motherboards generate lots of
4066 bogus events, for ports that aren't wired to
4067 anything. Set this parameter to avoid log spamming.
4068 Note that genuine overcurrent events won't be
4069 reported either.
4070
Simon Arlotte3a61b02008-07-19 23:32:54 +01004071 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004072 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004073
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004074 usbcore.authorized_default=
4075 [USB] Default USB device authorization:
4076 (default -1 = authorized except for wireless USB,
4077 0 = not authorized, 1 = authorized)
4078
Alan Sternb5e795f2007-02-20 15:00:53 -05004079 usbcore.autosuspend=
4080 [USB] The autosuspend time delay (in seconds) used
4081 for newly-detected USB devices (default 2). This
4082 is the time required before an idle device will be
4083 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004084 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004085
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004086 usbcore.usbfs_snoop=
4087 [USB] Set to log all usbfs traffic (default 0 = off).
4088
Alan Stern0290cc92015-11-20 13:53:22 -05004089 usbcore.usbfs_snoop_max=
4090 [USB] Maximum number of bytes to snoop in each URB
4091 (default = 65536).
4092
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004093 usbcore.blinkenlights=
4094 [USB] Set to cycle leds on hubs (default 0 = off).
4095
4096 usbcore.old_scheme_first=
4097 [USB] Start with the old device initialization
4098 scheme (default 0 = off).
4099
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004100 usbcore.usbfs_memory_mb=
4101 [USB] Memory limit (in MB) for buffers allocated by
4102 usbfs (default = 16, 0 = max = 2047).
4103
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004104 usbcore.use_both_schemes=
4105 [USB] Try the other device initialization scheme
4106 if the first one fails (default 1 = enabled).
4107
4108 usbcore.initial_descriptor_timeout=
4109 [USB] Specifies timeout for the initial 64-byte
4110 USB_REQ_GET_DESCRIPTOR request in milliseconds
4111 (default 5000 = 5.0 seconds).
4112
Oliver Neukum40d58142015-12-03 15:03:32 +01004113 usbcore.nousb [USB] Disable the USB subsystem
4114
Linus Torvalds1da177e2005-04-16 15:20:36 -07004115 usbhid.mousepoll=
4116 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004117
Alan Sternd4f373e2008-11-10 14:07:45 -05004118 usb-storage.delay_use=
4119 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004120 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004121
4122 usb-storage.quirks=
4123 [UMS] A list of quirks entries to supplement or
4124 override the built-in unusual_devs list. List
4125 entries are separated by commas. Each entry has
4126 the form VID:PID:Flags where VID and PID are Vendor
4127 and Product ID values (4-digit hex numbers) and
4128 Flags is a set of characters, each corresponding
4129 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004130 a = SANE_SENSE (collect more than 18 bytes
4131 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004132 b = BAD_SENSE (don't collect more than 18
4133 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004134 c = FIX_CAPACITY (decrease the reported
4135 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004136 d = NO_READ_DISC_INFO (don't use
4137 READ_DISC_INFO command);
4138 e = NO_READ_CAPACITY_16 (don't use
4139 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004140 f = NO_REPORT_OPCODES (don't use report opcodes
4141 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004142 g = MAX_SECTORS_240 (don't transfer more than
4143 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004144 h = CAPACITY_HEURISTICS (decrease the
4145 reported device capacity by one
4146 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004147 i = IGNORE_DEVICE (don't bind to this
4148 device);
Hans de Goede13630742016-04-12 12:27:09 +02004149 j = NO_REPORT_LUNS (don't use report luns
4150 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004151 l = NOT_LOCKABLE (don't try to lock and
4152 unlock ejectable media);
4153 m = MAX_SECTORS_64 (don't transfer more
4154 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004155 n = INITIAL_READ10 (force a retry of the
4156 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004157 o = CAPACITY_OK (accept the capacity
4158 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004159 p = WRITE_CACHE (the device cache is ON
4160 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004161 r = IGNORE_RESIDUE (the device reports
4162 bogus residue values);
4163 s = SINGLE_LUN (the device has only one
4164 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004165 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4166 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004167 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004168 w = NO_WP_DETECT (don't test whether the
4169 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004170 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4171 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004172 Example: quirks=0419:aaf5:rl,0421:0433:rc
4173
Stephen Boydac1667d2011-08-13 12:34:50 -07004174 user_debug= [KNL,ARM]
4175 Format: <int>
4176 See arch/arm/Kconfig.debug help text.
4177 1 - undefined instruction events
4178 2 - system calls
4179 4 - invalid data aborts
4180 8 - SIGSEGV faults
4181 16 - SIGBUS faults
4182 Example: user_debug=31
4183
Ian Campbell14315592010-02-17 10:38:10 +00004184 userpte=
4185 [X86] Flags controlling user PTE allocations.
4186
4187 nohigh = do not allocate PTE pages in
4188 HIGHMEM regardless of setting
4189 of CONFIG_HIGHPTE.
4190
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304191 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004192 On X86_32, this is an alias for vdso32=. Otherwise:
4193
4194 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004195 vdso=0: disable VDSO mapping
4196
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004197 vdso32= [X86] Control the 32-bit vDSO
4198 vdso32=1: enable 32-bit VDSO
4199 vdso32=0 or vdso32=2: disable 32-bit VDSO
4200
4201 See the help text for CONFIG_COMPAT_VDSO for more
4202 details. If CONFIG_COMPAT_VDSO is set, the default is
4203 vdso32=0; otherwise, the default is vdso32=1.
4204
4205 For compatibility with older kernels, vdso32=2 is an
4206 alias for vdso32=0.
4207
4208 Try vdso32=0 if you encounter an error that says:
4209 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004210
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004211 vector= [IA-64,SMP]
4212 vector=percpu: enable percpu vector domain
4213
Linus Torvalds1da177e2005-04-16 15:20:36 -07004214 video= [FB] Frame buffer configuration
4215 See Documentation/fb/modedb.txt.
4216
Aaron Lu3afe6da2013-06-20 15:08:55 +08004217 video.brightness_switch_enabled= [0,1]
4218 If set to 1, on receiving an ACPI notify event
4219 generated by hotkey, video driver will adjust brightness
4220 level and then send out the event to user space through
4221 the allocated input device; If set to 0, video driver
4222 will only send out the event without touching backlight
4223 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004224 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004225
Pawel Moll81a054c2012-05-09 18:30:16 +01004226 virtio_mmio.device=
4227 [VMMIO] Memory mapped virtio (platform) device.
4228
4229 <size>@<baseaddr>:<irq>[:<id>]
4230 where:
4231 <size> := size (can use standard suffixes
4232 like K, M and G)
4233 <baseaddr> := physical base address
4234 <irq> := interrupt number (as passed to
4235 request_irq())
4236 <id> := (optional) platform device id
4237 example:
4238 virtio_mmio.device=1K@0x100b0000:48:7
4239
4240 Can be used multiple times for multiple devices.
4241
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004242 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004243 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004244 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004245 Use vga=ask for menu.
4246 This is actually a boot loader parameter; the value is
4247 passed to the kernel using a special protocol.
4248
Randy Dunlapa9913042005-10-23 12:57:11 -07004249 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004250 size of <nn>. This can be used to increase the
4251 minimum size (128MB on x86). It can also be used to
4252 decrease the size and leave more room for directly
4253 mapped kernel RAM.
4254
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004255 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4256 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004257
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004258 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4259 Format: <command>
4260
4261 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4262 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004263
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004264 vsyscall= [X86-64]
4265 Controls the behavior of vsyscalls (i.e. calls to
4266 fixed addresses of 0xffffffffff600x00 from legacy
4267 code). Most statically-linked binaries and older
4268 versions of glibc use these calls. Because these
4269 functions are at fixed addresses, they make nice
4270 targets for exploits that can control RIP.
4271
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004272 emulate [default] Vsyscalls turn into traps and are
4273 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004274
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004275 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004276 This is a little bit faster than trapping
4277 and makes a few dynamic recompilers work
4278 better than they would in emulation mode.
4279 It also makes exploits much easier to write.
4280
4281 none Vsyscalls don't work at all. This makes
4282 them quite hard to use for exploits but
4283 might break your system.
4284
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004285 vt.color= [VT] Default text color.
4286 Format: 0xYX, X = foreground, Y = background.
4287 Default: 0x07 = light gray on black.
4288
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004289 vt.cur_default= [VT] Default cursor shape.
4290 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4291 the parameters of the <Esc>[?A;B;Cc escape sequence;
4292 see VGA-softcursor.txt. Default: 2 = underline.
4293
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004294 vt.default_blu= [VT]
4295 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4296 Change the default blue palette of the console.
4297 This is a 16-member array composed of values
4298 ranging from 0-255.
4299
4300 vt.default_grn= [VT]
4301 Format: <green0>,<green1>,<green2>,...,<green15>
4302 Change the default green palette of the console.
4303 This is a 16-member array composed of values
4304 ranging from 0-255.
4305
4306 vt.default_red= [VT]
4307 Format: <red0>,<red1>,<red2>,...,<red15>
4308 Change the default red palette of the console.
4309 This is a 16-member array composed of values
4310 ranging from 0-255.
4311
4312 vt.default_utf8=
4313 [VT]
4314 Format=<0|1>
4315 Set system-wide default UTF-8 mode for all tty's.
4316 Default is 1, i.e. UTF-8 mode is enabled for all
4317 newly opened terminals.
4318
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004319 vt.global_cursor_default=
4320 [VT]
4321 Format=<-1|0|1>
4322 Set system-wide default for whether a cursor
4323 is shown on new VTs. Default is -1,
4324 i.e. cursors will be created by default unless
4325 overridden by individual drivers. 0 will hide
4326 cursors, 1 will display them.
4327
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004328 vt.italic= [VT] Default color for italic text; 0-15.
4329 Default: 2 = green.
4330
4331 vt.underline= [VT] Default color for underlined text; 0-15.
4332 Default: 3 = cyan.
4333
Randy Dunlap4724ba572010-05-03 11:42:52 -07004334 watchdog timers [HW,WDT] For information on watchdog timers,
4335 see Documentation/watchdog/watchdog-parameters.txt
4336 or other driver-specific files in the
4337 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004338
Tejun Heo82607adc2015-12-08 11:28:04 -05004339 workqueue.watchdog_thresh=
4340 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4341 warn stall conditions and dump internal state to
4342 help debugging. 0 disables workqueue stall
4343 detection; otherwise, it's the stall threshold
4344 duration in seconds. The default value is 30 and
4345 it can be updated at runtime by writing to the
4346 corresponding sysfs file.
4347
Tejun Heod55262c2013-04-01 11:23:38 -07004348 workqueue.disable_numa
4349 By default, all work items queued to unbound
4350 workqueues are affine to the NUMA nodes they're
4351 issued on, which results in better behavior in
4352 general. If NUMA affinity needs to be disabled for
4353 whatever reason, this option can be used. Note
4354 that this also can be controlled per-workqueue for
4355 workqueues visible under /sys/bus/workqueue/.
4356
Viresh Kumarcee22a12013-04-08 16:45:40 +05304357 workqueue.power_efficient
4358 Per-cpu workqueues are generally preferred because
4359 they show better performance thanks to cache
4360 locality; unfortunately, per-cpu workqueues tend to
4361 be more power hungry than unbound workqueues.
4362
4363 Enabling this makes the per-cpu workqueues which
4364 were observed to contribute significantly to power
4365 consumption unbound, leading to measurably lower
4366 power usage at the cost of small performance
4367 overhead.
4368
4369 The default value of this parameter is determined by
4370 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4371
Tejun Heof303fccb2016-02-09 17:59:38 -05004372 workqueue.debug_force_rr_cpu
4373 Workqueue used to implicitly guarantee that work
4374 items queued without explicit CPU specified are put
4375 on the local CPU. This guarantee is no longer true
4376 and while local CPU is still preferred work items
4377 may be put on foreign CPUs. This debug option
4378 forces round-robin CPU selection to flush out
4379 usages which depend on the now broken guarantee.
4380 When enabled, memory and cache locality will be
4381 impacted.
4382
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004383 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4384 default x2apic cluster mode on platforms
4385 supporting x2apic.
4386
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004387 x86_intel_mid_timer= [X86-32,APBT]
4388 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004389 Two valid options are apbt timer only and lapic timer
4390 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004391 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004392
Juergen Grossc70727a2015-07-17 06:51:36 +02004393 xen_512gb_limit [KNL,X86-64,XEN]
4394 Restricts the kernel running paravirtualized under Xen
4395 to use only up to 512 GB of RAM. The reason to do so is
4396 crash analysis tools and Xen tools for doing domain
4397 save/restore/migration must be enabled to handle larger
4398 domains.
4399
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004400 xen_emul_unplug= [HW,X86,XEN]
4401 Unplug Xen emulated devices
4402 Format: [unplug0,][unplug1]
4403 ide-disks -- unplug primary master IDE devices
4404 aux-ide-disks -- unplug non-primary-master IDE devices
4405 nics -- unplug network devices
4406 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004407 unnecessary -- unplugging emulated devices is
4408 unnecessary even if the host did not respond to
4409 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004410 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004411
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004412 xen_nopvspin [X86,XEN]
4413 Disables the ticketlock slowpath using Xen PV
4414 optimizations.
4415
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004416 xen_nopv [X86]
4417 Disables the PV optimizations forcing the HVM guest to
4418 run as generic HVM guest with no PV drivers.
4419
Linus Torvalds1da177e2005-04-16 15:20:36 -07004420 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004421 Format:
4422 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]