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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
Rusty Russell5888bcc2014-05-14 10:33:45 +09304The following is a consolidated list of the kernel parameters as
5implemented by the __setup(), core_param() and module_param() macros
6and sorted into English Dictionary order (defined as ignoring all
7punctuation and sorting digits before letters in a case insensitive
8manner), and with descriptions where known.
Linus Torvalds1da177e2005-04-16 15:20:36 -07009
Rusty Russell5888bcc2014-05-14 10:33:45 +093010The kernel parses parameters from the kernel command line up to "--";
11if it doesn't recognize a parameter and it doesn't contain a '.', the
12parameter gets passed to init: parameters with '=' go into init's
13environment, others are passed as command line arguments to init.
14Everything after "--" is passed as an argument to init.
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Rusty Russell5888bcc2014-05-14 10:33:45 +093016Module parameters can be specified in two ways: via the kernel command
17line with a module name prefix, or via modprobe, e.g.:
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Rusty Russell5888bcc2014-05-14 10:33:45 +093019 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
Rusty Russell5888bcc2014-05-14 10:33:45 +093022Parameters for modules which are built into the kernel need to be
23specified on the kernel command line. modprobe looks through the
24kernel command line (/proc/cmdline) and collects module parameters
25when it loads a module, so the kernel command line can be used for
26loadable modules too.
Linus Torvalds1da177e2005-04-16 15:20:36 -070027
Randy Dunlapca1eda22009-05-06 16:02:58 -070028Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30can also be entered as
31 log-buf-len=1M print_fatal_signals=1
32
Rusty Russell5888bcc2014-05-14 10:33:45 +093033Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
Randy Dunlapca1eda22009-05-06 16:02:58 -070035
Stefan Richtera901ebb2006-04-01 01:43:18 +020036This document may not be entirely up to date and comprehensive. The command
37"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38module. Loadable modules, after being loaded into the running kernel, also
39reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40parameters may be changed at runtime by the command
41"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
42
Stefan Richter6585fa82006-04-01 01:44:30 +020043The parameters listed below are only valid if certain kernel build options were
44enabled and if respective hardware is present. The text in square brackets at
45the beginning of each description states the restrictions within which a
46parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100049 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070053 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020054 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080056 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070057 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070058 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000059 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040064 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070066 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070067 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050070 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070072 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080073 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050077 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020078 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070079 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070086 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070088 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070089 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070094 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070098 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -0700107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -0700109 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700111 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900113 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300118 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500120 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100124 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700129 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700132 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100134 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135
136In addition, the following text indicates that the option:
137
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
141
142Parameters denoted with BOOT are actually interpreted by the boot
143loader, and have no meaning to the kernel directly.
144Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500145need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146
Karsten Weiss55588702007-02-13 13:26:21 +0100147There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700148See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100149
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151a trailing = on the name of any parameter states that that parameter will
152be entered as an environment variable, whereas its absence indicates that
153it will appear as a kernel argument readable via /proc/cmdline by programs
154running once the system is up.
155
jens m. noedler9c4751f2006-09-29 02:00:27 -0700156The number of kernel parameters is not limited, but the length of the
157complete command line (parameters including spaces etc.) is limited to
158a fixed number of characters. This limit depends on the architecture
159and is between 256 and 4096 characters. It is defined in the file
160./include/asm/setup.h as COMMAND_LINE_SIZE.
161
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800162Finally, the [KMG] suffix is commonly described after a number of kernel
163parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165bytes respectively. Such letter suffixes can also be entirely omitted.
166
jens m. noedler9c4751f2006-09-29 02:00:27 -0700167
Al Stoneb10d79f2015-03-24 14:02:41 +0000168 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800169 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500170 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700174 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800176 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800177 copy_dsdt -- copy DSDT to memory
Al Stoneb10d79f2015-03-24 14:02:41 +0000178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179
Paul Bolle395cf962011-08-15 02:02:26 +0200180 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181
Len Browna1fdcc02007-03-11 03:26:14 -0400182 acpi_apic_instance= [ACPI, IOAPIC]
183 Format: <int>
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400186 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400187
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
190 acpi_backlight=video
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
194
Dominik Brodowskief694492015-05-14 15:31:28 +0200195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
202
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200226
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800230
Dominik Brodowskief694492015-05-14 15:31:28 +0200231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
246
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
250 size limitation.
251
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
254 default in APIC mode
255
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
258 default in PIC mode
259
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
262
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
264 use by PCI
265 Format: <irq>,<irq>...
266
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800272 This feature is enabled by default.
273 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800274
Dominik Brodowskief694492015-05-14 15:31:28 +0200275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
276 kernels.
277
Lv Zhenga94e88c2014-04-04 12:39:11 +0800278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700287
Dominik Brodowskief694492015-05-14 15:31:28 +0200288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800292
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
295
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200296 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297 of 2 which is mandated by ACPI 6) as the supported ACPI
298 specification revision (when using this switch, it may
299 be necessary to carry out a cold reboot _twice_ in a
300 row to make it take effect on the platform firmware).
301
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700302 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800303 acpi_osi="string1" # add string1
304 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800305 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800306 acpi_osi=! # disable all built-in OS vendor
307 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700308 acpi_osi= # disable all strings
309
Lv Zheng5dc17982013-07-22 16:08:25 +0800310 'acpi_osi=!' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific OS
312 vendor string(s). Note that such command can only
313 affect the default state of the OS vendor strings, thus
314 it cannot affect the default state of the feature group
315 strings and the current state of the OS vendor strings,
316 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800317 is meaningless. This command is useful when one do not
318 care about the state of the feature group strings which
319 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800320 Examples:
321 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323 can make '_OSI("Windows 2000")' TRUE.
324
325 'acpi_osi=' cannot be used in combination with other
326 'acpi_osi=' command lines, the _OSI method will not
327 exist in the ACPI namespace. NOTE that such command can
328 only affect the _OSI support state, thus specifying it
329 multiple times through kernel command line is also
330 meaningless.
331 Examples:
332 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
333 FALSE.
334
Lv Zheng741d8122013-07-22 16:08:36 +0800335 'acpi_osi=!*' can be used in combination with single or
336 multiple 'acpi_osi="string1"' to support specific
337 string(s). Note that such command can affect the
338 current state of both the OS vendor strings and the
339 feature group strings, thus specifying it multiple times
340 through kernel command line is meaningful. But it may
341 still not able to affect the final state of a string if
342 there are quirks related to this string. This command
343 is useful when one want to control the state of the
344 feature group strings to debug BIOS issues related to
345 the OSPM features.
346 Examples:
347 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348 '_OSI("Module Device")' FALSE.
349 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350 '_OSI("Module Device")' TRUE.
351 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
352 equivalent to
353 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
354 and
355 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356 they all will make '_OSI("Windows 2000")' TRUE.
357
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530358 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700359 Override the pmtimer bug detection: force the kernel
360 to assume that this machine's pmtimer latches its value
361 and always returns good values.
362
Randy Dunlap4af94f32009-04-17 18:30:28 -0700363 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
364 Format: { level | edge | high | low }
365
Randy Dunlap4af94f32009-04-17 18:30:28 -0700366 acpi_skip_timer_override [HW,ACPI]
367 Recognize and ignore IRQ0/pin2 Interrupt Override.
368 For broken nForce2 BIOS resulting in XT-PIC timer.
369
370 acpi_sleep= [HW,ACPI] Sleep options
371 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200372 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700373 See Documentation/power/video.txt for information on
374 s3_bios and s3_mode.
375 s3_beep is for debugging; it makes the PC's speaker beep
376 as soon as the kernel's real-mode entry point is called.
377 s4_nohwsig prevents ACPI hardware signature from being
378 used during resume from hibernation.
379 old_ordering causes the ACPI 1.0 ordering of the _PTS
380 control method, with respect to putting devices into
381 low power states, to be enforced (the ACPI 2.0 ordering
382 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200383 nonvs prevents the kernel from saving/restoring the
384 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800385 sci_force_enable causes the kernel to set SCI_EN directly
386 on resume from S1/S3 (which is against the ACPI spec,
387 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700388
389 acpi_use_timer_override [HW,ACPI]
390 Use timer override. For some broken Nvidia NF5 boards
391 that require a timer override, but don't have HPET
392
Randy Dunlap4af94f32009-04-17 18:30:28 -0700393 add_efi_memmap [EFI; X86] Include EFI memory map in
394 kernel's map of available physical RAM.
395
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700396 agp= [AGP]
397 { off | try_unsupported }
398 off: disable AGP support
399 try_unsupported: try to drive unsupported chipsets
400 (may crash computer or cause data corruption)
401
Randy Dunlapbcfde332010-06-07 17:10:38 -0700402 ALSA [HW,ALSA]
403 See Documentation/sound/alsa/alsa-parameters.txt
404
Russell Kingd944d542010-02-20 16:13:29 +0000405 alignment= [KNL,ARM]
406 Allow the default userspace alignment fault handler
407 behaviour to be specified. Bit 0 enables warnings,
408 bit 1 enables fixups, and bit 2 sends a segfault.
409
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200410 align_va_addr= [X86-64]
411 Align virtual addresses by clearing slice [14:12] when
412 allocating a VMA at process creation time. This option
413 gives you up to 3% performance improvement on AMD F15h
414 machines (where it is enabled by default) for a
415 CPU-intensive style benchmark, and it can vary highly in
416 a microbenchmark depending on workload and compiler.
417
Borislav Petkov8360ee22011-11-21 12:10:19 +0100418 32: only for 32-bit processes
419 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200420 on: enable for both 32- and 64-bit processes
421 off: disable for both 32- and 64-bit processes
422
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500423 alloc_snapshot [FTRACE]
424 Allocate the ftrace snapshot buffer on boot up when the
425 main buffer is allocated. This is handy if debugging
426 and you need to use tracing_snapshot() on boot up, and
427 do not want to use tracing_snapshot_alloc() as it needs
428 to be done where GFP_KERNEL allocations are allowed.
429
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100430 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200431 Pass parameters to the AMD IOMMU driver in the system.
432 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900433 fullflush - enable flushing of IO/TLB entries when
434 they are unmapped. Otherwise they are
435 flushed before they will be reused, which
436 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200437 off - do not initialize any AMD IOMMU found in
438 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100439 force_isolation - Force device isolation for all
440 devices. The IOMMU driver is not
441 allowed anymore to lift isolation
442 requirements as needed. This option
443 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900444
Shuah Khanc099cf12012-05-24 15:58:25 -0600445 amd_iommu_dump= [HW,X86-64]
446 Enable AMD IOMMU driver option to dump the ACPI table
447 for AMD IOMMU. With this option enabled, AMD IOMMU
448 driver will print ACPI tables for AMD IOMMU during
449 IOMMU initialization.
450
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 amijoy.map= [HW,JOY] Amiga joystick support
452 Map of devices attached to JOY0DAT and JOY1DAT
453 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200454 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455
456 analog.map= [HW,JOY] Analog joystick and gamepad support
457 Specifies type or capabilities of an analog joystick
458 connected to one of 16 gameports
459 Format: <type1>,<type2>,..<type16>
460
Randy Dunlapa9913042005-10-23 12:57:11 -0700461 apc= [HW,SPARC]
462 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 Format: noidle
464 Disable APC CPU standby support. SPARCstation-Fox does
465 not play well with APC CPU idle - disable it if you have
466 APC and your system crashes randomly.
467
Randy Dunlapca1eda22009-05-06 16:02:58 -0700468 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700469 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470 Format: { quiet (default) | verbose | debug }
471 Change the amount of debugging information output
472 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700473
Brian Haleyb0f83b22010-02-04 13:36:50 -0800474 autoconf= [IPV6]
475 See Documentation/networking/ipv6.txt.
476
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400477 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
478 Limit apic dumping. The parameter defines the maximal
479 number of local apics being dumped. Also it is possible
480 to set it to "all" by meaning -- no limit here.
481 Format: { 1 (default) | 2 | ... | all }.
482 The parameter valid if only apic=debug or
483 apic=verbose is specified.
484 Example: apic=debug show_lapic=all
485
Linus Torvalds1da177e2005-04-16 15:20:36 -0700486 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700487 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490 Format: <io>,<irq>,<nodeID>
491
492 ataflop= [HW,M68k]
493
494 atarimouse= [HW,MOUSE] Atari Mouse
495
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
497 EzKey and similar keyboards
498
499 atkbd.reset= [HW] Reset keyboard during initialization
500
Randy Dunlapa9913042005-10-23 12:57:11 -0700501 atkbd.set= [HW] Select keyboard code set
502 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503
504 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
505 keyboards
506
507 atkbd.softraw= [HW] Choose between synthetic and real raw mode
508 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700509
510 atkbd.softrepeat= [HW]
511 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400513 audit= [KNL] Enable the audit sub-system
514 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500515 0 - kernel audit is disabled and can not be enabled
516 until the next reboot
517 unset - kernel audit is initialized but disabled and
518 will be fully enabled by the userspace auditd.
519 1 - kernel audit is initialized and partially enabled,
520 storing at most audit_backlog_limit messages in
521 RAM until it is fully enabled by the userspace
522 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400523 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400524
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400525 audit_backlog_limit= [KNL] Set the audit queue size limit.
526 Format: <int> (must be >=0)
527 Default: 64
528
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529 baycom_epp= [HW,AX25]
530 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700531
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
533 Format: <io>,<mode>
534 See header of drivers/net/hamradio/baycom_par.c.
535
Randy Dunlapa9913042005-10-23 12:57:11 -0700536 baycom_ser_fdx= [HW,AX25]
537 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538 Format: <io>,<irq>,<mode>[,<baud>]
539 See header of drivers/net/hamradio/baycom_ser_fdx.c.
540
Randy Dunlapa9913042005-10-23 12:57:11 -0700541 baycom_ser_hdx= [HW,AX25]
542 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 Format: <io>,<irq>,<mode>
544 See header of drivers/net/hamradio/baycom_ser_hdx.c.
545
Paul Gortmaker080506a2013-09-30 13:45:19 -0700546 blkdevparts= Manual partition parsing of block device(s) for
547 embedded devices based on command line input.
548 See Documentation/block/cmdline-partition.txt
549
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700550 boot_delay= Milliseconds to delay each printk during boot.
551 Values larger than 10 seconds (10000) are changed to
552 no delay (0).
553 Format: integer
554
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700555 bootmem_debug [KNL] Enable bootmem allocator debug messages.
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700558 bttv.radio= Most important insmod options are available as
559 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200561 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700562
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000563 bulk_remove=off [PPC] This parameter disables the use of the pSeries
564 firmware feature for flushing multiple hpte entries
565 at a time.
566
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 c101= [NET] Moxa C101 synchronous serial card
568
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700569 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 Sometimes CPU hardware bugs make them report the cache
571 size incorrectly. The kernel will attempt work arounds
572 to fix known problems, but for some CPUs it is not
573 possible to determine what the correct size should be.
574 This option provides an override for these situations.
575
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300576 ca_keys= [KEYS] This parameter identifies a specific key(s) on
577 the system trusted keyring to be used for certificate
578 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300579 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300580
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700581 cca= [MIPS] Override the kernel pages' cache coherency
582 algorithm. Accepted values range from 0 to 7
583 inclusive. See arch/mips/include/asm/pgtable-bits.h
584 for platform specific values (SB1, Loongson3 and
585 others).
586
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100587 ccw_timeout_log [S390]
588 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589
Paul Menage8bab8dd2008-04-04 14:29:57 -0700590 cgroup_disable= [KNL] Disable a particular controller
591 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800592 The effects of cgroup_disable=foo are:
593 - foo isn't auto-mounted if you mount all cgroups in
594 a single hierarchy
595 - foo isn't visible as an individually mountable
596 subsystem
597 {Currently only "memory" controller deal with this and
598 cut the overhead, others just disable the usage. So
599 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700600
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 checkreqprot [SELINUX] Set initial checkreqprot flag value.
602 Format: { "0" | "1" }
603 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700604 0 -- check protection applied by kernel (includes
605 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 1 -- check protection requested by application.
607 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700608 Value can be changed at runtime via
609 /selinux/checkreqprot.
610
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100611 cio_ignore= [S390]
612 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700613 clk_ignore_unused
614 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700615 Prevents the clock framework from automatically gating
616 clocks that have not been explicitly enabled by a Linux
617 device driver but are enabled in hardware at reset or
618 by the bootloader/firmware. Note that this does not
619 force such clocks to be always-on nor does it reserve
620 those clocks in any way. This parameter is useful for
621 debug and development, but should not be needed on a
622 platform with proper driver support. For more
623 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100624
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700625 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700626 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200627 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700628 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200629 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 Format: { pit | tsc | cyclone | pmtmr }
631
John Stultz592913e2010-07-13 17:56:20 -0700632 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700633 Format: <string>
634 Override the default clocksource and use the clocksource
635 with the name specified.
636 Some clocksource names to choose from, depending on
637 the platform:
638 [all] jiffies (this is the base, fallback clocksource)
639 [ACPI] acpi_pm
640 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641 pxa_timer,timer3,32k_counter,timer0_1
642 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700643 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700644 scx200_hrt on Geode; cyclone on IBM x440
645 [MIPS] MIPS
646 [PARISC] cr16
647 [S390] tod
648 [SH] SuperH
649 [SPARC64] tick
650 [X86-64] hpet,tsc
651
Andi Kleenac72e782008-01-30 13:33:21 +0100652 clearcpuid=BITNUM [X86]
653 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800654 arch/x86/include/asm/cpufeature.h for the valid bit
655 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100656 stable over kernel options, but the vendor specific
657 ones should be.
658 Also note that user programs calling CPUID directly
659 or using the feature without checking anything
660 will still see it. This just prevents it from
661 being used by the kernel or shown in /proc/cpuinfo.
662 Also note the kernel might malfunction if you disable
663 some critical bits.
664
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700665 cma=nn[MG]@[start[MG][-end[MG]]]
666 [ARM,X86,KNL]
667 Sets the size of kernel global memory area for
668 contiguous memory allocations and optionally the
669 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700670 memory allocations. A value of 0 disables CMA
671 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100672 include/linux/dma-contiguous.h
673
Robert Jennings14f966e2009-04-15 05:55:32 +0000674 cmo_free_hint= [PPC] Format: { yes | no }
675 Specify whether pages are marked as being inactive
676 when they are freed. This is used in CMO environments
677 to determine OS memory pressure for page stealing by
678 a hypervisor.
679 Default: yes
680
Marek Szyprowskic7909502011-12-29 13:09:51 +0100681 coherent_pool=nn[KMG] [ARM,KNL]
682 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200683 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100684
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530685 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100686 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100687 Range: 0 - 8192
688 Default: 64
689
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700691 Format:
692 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693
694 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
695 Format: <io>[,<irq>]
696
Randy Dunlapa9913042005-10-23 12:57:11 -0700697 com90xx= [HW,NET]
698 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699 Format: <io>[,<irq>[,<memstart>]]
700
701 condev= [HW,S390] console device
702 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700703
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 console= [KNL] Output console device and options.
705
706 tty<n> Use the virtual console device <n>.
707
708 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800709 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800711 the form "bbbbpnf", where "bbbb" is the baud rate,
712 "p" is parity ("n", "o", or "e"), "n" is number of
713 bits, and "f" is flow control ("r" for RTS or
714 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800716 See Documentation/serial-console.txt for more
717 information. See
718 Documentation/networking/netconsole.txt for an
719 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400723 uart[8250],mmio32,<addr>[,options]
724 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725 Start an early, polled-mode console on the 8250/16550
726 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400727 switching to the matching ttyS device later.
728 MMIO inter-register address stride is either 8-bit
729 (mmio) or 32-bit (mmio32).
730 If none of [io|mmio|mmio32], <addr> is assumed to be
731 equivalent to 'mmio'. 'options' are specified in the
732 same format described for ttyS above; if unspecified,
733 the h/w is not re-initialized.
734
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500735 hvc<n> Use the hypervisor console device <n>. This is for
736 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700738 If the device connected to the port is not a TTY but a braille
739 device, prepend "brl," before the device type, for instance
740 console=brl,ttyS0
741 For now, only VisioBraille is supported.
742
Daniel Mackf324edc2009-06-16 15:33:52 -0700743 consoleblank= [KNL] The console blank (screen saver) timeout in
744 seconds. Defaults to 10*60 = 10mins. A value of 0
745 disables the blank timer.
746
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800747 coredump_filter=
748 [KNL] Change the default value for
749 /proc/<pid>/coredump_filter.
750 See also Documentation/filesystems/proc.txt.
751
Len Brown62027ae2011-04-01 18:13:10 -0400752 cpuidle.off=1 [CPU_IDLE]
753 disable the cpuidle sub-system
754
Len Brownd68921f2015-05-11 17:27:09 -0400755 cpu_init_udelay=N
756 [X86] Delay for N microsec between assert and de-assert
757 of APIC INIT to start processors. This delay occurs
758 on every CPU online, such as boot, and resume from suspend.
759 Default: 10000
760
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700762 Format:
763 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800765 crashkernel=size[KMG][@offset[KMG]]
766 [KNL] Using kexec, Linux can switch to a 'crash kernel'
767 upon panic. This parameter reserves the physical
768 memory region [offset, offset + size] for that kernel
769 image. If '@offset' is omitted, then a suitable offset
770 is selected automatically. Check
771 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700772
Bernhard Wallefb391592007-10-18 23:41:02 -0700773 crashkernel=range1:size1[,range2:size2,...][@offset]
774 [KNL] Same as above, but depends on the memory
775 in the running system. The syntax of range is
776 start-[end] where start and end are both
777 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800778 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700779
Yinghai Luadbc7422013-04-15 22:23:48 -0700780 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700781 [KNL, x86_64] range could be above 4G. Allow kernel
782 to allocate physical memory region from top, so could
783 be above 4G if system have more than 4G ram installed.
784 Otherwise memory region will be allocated below 4G, if
785 available.
786 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700787 crashkernel=size[KMG],low
788 [KNL, x86_64] range under 4G. When crashkernel=X,high
789 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700790 above 4G, that cause second kernel crash on system
791 that require some amount of low memory, e.g. swiotlb
792 requires at least 64M+32K low memory. Kernel would
793 try to allocate 72M below 4G automatically.
794 This one let user to specify own low range under 4G
795 for second kernel instead.
796 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700797 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700798 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700799
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800 cs89x0_dma= [HW,NET]
801 Format: <dma>
802
803 cs89x0_media= [HW,NET]
804 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700805
Randy Dunlapa9913042005-10-23 12:57:11 -0700806 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807 See header of drivers/s390/block/dasd_devmap.c.
808
809 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
810 (one device per port)
811 Format: <port#>,<type>
812 See also Documentation/input/joystick-parport.txt
813
Thomas Renningera648ec02010-08-06 16:11:02 +0200814 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600816 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200817
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 debug [KNL] Enable kernel debugging (events log level).
819
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700820 debug_locks_verbose=
821 [KNL] verbose self-tests
822 Format=<0|1>
823 Print debugging info while doing the locking API
824 self-tests.
825 We default to 0 (no extra messages), setting it to
826 1 will print _a lot_ more information - normally
827 only useful to kernel developers.
828
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700829 debug_objects [KNL] Enable object debugging
830
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500831 no_debug_objects
832 [KNL] Disable object debugging
833
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800834 debug_guardpage_minorder=
835 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836 parameter allows control of the order of pages that will
837 be intentionally kept free (and hence protected) by the
838 buddy allocator. Bigger value increase the probability
839 of catching random memory corruption, but reduce the
840 amount of memory for normal system use. The maximum
841 possible value is MAX_ORDER/2. Setting this parameter
842 to 1 or 2 should be enough to identify most random
843 memory corruption problems caused by bugs in kernel or
844 driver code when a CPU writes to (or reads from) a
845 random memory location. Note that there exists a class
846 of memory corruptions problems caused by buggy H/W or
847 F/W or by drivers badly programing DMA (basically when
848 memory is written at bus level and the CPU MMU is
849 bypassed) which are not detectable by
850 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851 tracking down these problems.
852
Joonsoo Kim031bc572014-12-12 16:55:52 -0800853 debug_pagealloc=
854 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855 parameter enables the feature at boot time. In
856 default, it is disabled. We can avoid allocating huge
857 chunk of memory for debug pagealloc if we don't enable
858 it at boot time and the system will work mostly same
859 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860 on: enable the feature
861
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200862 debugpat [X86] Enable PAT debugging
863
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200864 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865 Format: <area>[,<node>]
866 See also Documentation/networking/decnet.txt.
867
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700868 default_hugepagesz=
869 [same as hugepagesz=] The size of the default
870 HugeTLB page size. This is the size represented by
871 the legacy /proc/ hugepages APIs, used for SHM, and
872 default size when mounting hugetlbfs filesystems.
873 Defaults to the default architecture's huge page size
874 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700875
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 dhash_entries= [KNL]
877 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700878
Brian Haleyb0f83b22010-02-04 13:36:50 -0800879 disable= [IPV6]
880 See Documentation/networking/ipv6.txt.
881
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900882 disable_cpu_apicid= [X86,APIC,SMP]
883 Format: <int>
884 The number of initial APIC ID for the
885 corresponding CPU to be disabled at boot,
886 mostly used for the kdump 2nd kernel to
887 disable BSP to wake up multiple CPUs without
888 causing system reset or hang due to sending
889 INIT from AP to BSP.
890
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000891 disable_ddw [PPC/PSERIES]
892 Disable Dynamic DMA Window support. Use this if
893 to workaround buggy firmware.
894
Brian Haleyb0f83b22010-02-04 13:36:50 -0800895 disable_ipv6= [IPV6]
896 See Documentation/networking/ipv6.txt.
897
Yinghai Lu95ffa242008-04-29 03:52:33 -0700898 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700899 The kernel tries to adjust MTRR layout from continuous
900 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700901 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700902
Yinghai Lu093af8d2008-01-30 13:33:32 +0100903 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100904 By default the kernel will trim any uncacheable
905 memory out of your available memory pool based on
906 MTRR settings. This parameter disables that behavior,
907 possibly causing your machine to run very slowly.
908
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530909 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700910 Disable PIN 1 of APIC timer
911 Can be useful to work around chipset bugs.
912
Prarit Bhargavace14c582015-08-25 13:34:53 -0400913 dis_ucode_ldr [X86] Disable the microcode loader.
914
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700915 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
916 this option disables the debugging code at boot.
917
918 dma_debug_entries=<number>
919 This option allows to tune the number of preallocated
920 entries for DMA-API debugging code. One entry is
921 required per DMA-API allocation. Use this if the
922 DMA-API debugging code disables itself because the
923 architectural default is too low.
924
Joerg Roedel1745de52009-05-22 21:49:51 +0200925 dma_debug_driver=<driver_name>
926 With this option the DMA-API debugging driver
927 filter feature can be enabled at boot time. Just
928 pass the driver to filter for as the parameter.
929 The filter can be disabled or changed to another
930 driver later using sysfs.
931
Carsten Emdeda0df922012-03-18 22:37:33 +0100932 drm_kms_helper.edid_firmware=[<connector>:]<file>
933 Broken monitors, graphic adapters and KVMs may
934 send no or incorrect EDID data sets. This parameter
935 allows to specify an EDID data set in the
936 /lib/firmware directory that is used instead.
937 Generic built-in EDID data sets are used, if one of
938 edid/1024x768.bin, edid/1280x1024.bin,
939 edid/1680x1050.bin, or edid/1920x1080.bin is given
940 and no file with the same name exists. Details and
941 instructions how to build your own EDID data are
942 available in Documentation/EDID/HOWTO.txt. An EDID
943 data set will only be used for a particular connector,
944 if its name and a colon are prepended to the EDID
945 name.
946
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 dscc4.setup= [NET]
948
Jim Cromie29e36c92012-04-27 14:30:41 -0600949 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
950 module.dyndbg[="val"]
951 Enable debug messages at boot time. See
952 Documentation/dynamic-debug-howto.txt for details.
953
Dave Hansen8c3641e2015-06-07 11:37:02 -0700954 nompx [X86] Disables Intel Memory Protection Extensions.
955 See Documentation/x86/intel_mpx.txt for more
956 information about the feature.
957
Borislav Petkovf29ba612015-03-27 16:15:18 +0100958 eagerfpu= [X86]
959 on enable eager fpu restore
960 off disable eager fpu restore
961 auto selects the default scheme, which automatically
962 enables eagerfpu restore for xsaveopt.
963
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700964 module.async_probe [KNL]
965 Enable asynchronous probe on this module.
966
Mark Salter56aeeba2014-04-07 15:39:53 -0700967 early_ioremap_debug [KNL]
968 Enable debug messages in early_ioremap support. This
969 is useful for tracking down temporary early mappings
970 which are not unmapped.
971
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700972 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500973
Michal Simek6fa62fc2014-09-10 12:43:02 +0200974 cdns,<addr>
975 Start an early, polled-mode console on a cadence serial
976 port at the specified address. The cadence serial port
977 must already be setup and configured. Options are not
978 yet supported.
979
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700980 uart[8250],io,<addr>[,options]
981 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700982 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300983 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400984 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700985 Start an early, polled-mode console on the 8250/16550
986 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700987 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300988 (mmio) or 32-bit (mmio32 or mmio32be).
989 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
990 to be equivalent to 'mmio'. 'options' are specified
991 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400992 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700993
Rob Herring0d3c6732014-04-18 17:19:57 -0500994 pl011,<addr>
995 Start an early, polled-mode console on a pl011 serial
996 port at the specified address. The pl011 serial port
997 must already be setup and configured. Options are not
998 yet supported.
999
Stephen Boyd0efe7292014-09-15 17:22:51 -07001000 msm_serial,<addr>
1001 Start an early, polled-mode console on an msm serial
1002 port at the specified address. The serial port
1003 must already be setup and configured. Options are not
1004 yet supported.
1005
1006 msm_serial_dm,<addr>
1007 Start an early, polled-mode console on an msm serial
1008 dm port at the specified address. The serial port
1009 must already be setup and configured. Options are not
1010 yet supported.
1011
Rob Herringd50d7262014-04-18 17:19:58 -05001012 smh Use ARM semihosting calls for early console.
1013
Tomasz Figab94ba032015-01-23 14:47:41 +01001014 s3c2410,<addr>
1015 s3c2412,<addr>
1016 s3c2440,<addr>
1017 s3c6400,<addr>
1018 s5pv210,<addr>
1019 exynos4210,<addr>
1020 Use early console provided by serial driver available
1021 on Samsung SoCs, requires selecting proper type and
1022 a correct base address of the selected UART port. The
1023 serial port must already be setup and configured.
1024 Options are not yet supported.
1025
Finn Thain7913ad12014-04-12 23:48:56 +10001026 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001027 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001028 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001029 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001031 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001032 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001033 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001034 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035
Dave Hansen147ea092013-04-10 14:03:38 -07001036 earlyprintk is useful when the kernel crashes before
1037 the normal console is initialized. It is not enabled by
1038 default because it has some cosmetic problems.
1039
Randy Dunlapa9913042005-10-23 12:57:11 -07001040 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 takes over.
1042
Matt Fleming72548e82013-10-04 09:36:56 +01001043 Only one of vga, efi, serial, or usb debug port can
1044 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045
Dave Hansen147ea092013-04-10 14:03:38 -07001046 Currently only ttyS0 and ttyS1 may be specified by
1047 name. Other I/O ports may be explicitly specified
1048 on some architectures (x86 and arm at least) by
1049 replacing ttySn with an I/O port address, like this:
1050 earlyprintk=serial,0x1008,115200
1051 You can find the port for a given device in
1052 /proc/tty/driver/serial:
1053 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054
1055 Interaction with the standard serial driver is not
1056 very good.
1057
Matt Fleming72548e82013-10-04 09:36:56 +01001058 The VGA and EFI output is eventually overwritten by
1059 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001061 The xen output can only be used by Xen PV guests.
1062
Chen, Gongc700f012013-12-06 01:17:08 -05001063 edac_report= [HW,EDAC] Control how to report EDAC event
1064 Format: {"on" | "off" | "force"}
1065 on: enable EDAC to report H/W event. May be overridden
1066 by other higher priority error reporting module.
1067 off: disable H/W event reporting through EDAC.
1068 force: enforce the use of EDAC to report H/W event.
1069 default: on.
1070
Jason Wessel97311912010-05-20 21:04:30 -05001071 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1072 ekgdboc=kbd
1073
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001074 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001075 the boot argument: earlyprintk=vga
1076
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001078 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001080 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001081 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001082 old_map [X86-64]: switch to the old ioremap-based EFI
1083 runtime services mapping. 32-bit still uses this one by
1084 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001085 nochunk: disable reading files in "chunks" in the EFI
1086 boot stub, as chunking can cause problems with some
1087 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001088 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001089 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001090
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001091 efi_no_storage_paranoia [EFI; X86]
1092 Using this parameter you can use more than 50% of
1093 your efi variable storage. Use this parameter only if
1094 you are really sure that your UEFI does sane gc and
1095 fulfills the spec otherwise your board may brick.
1096
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097 eisa_irq_edge= [PARISC,HW]
1098 See header of drivers/parisc/eisa.c.
1099
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001100 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001102 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103
1104 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001105 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001106 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001107 Documentation/block/deadline-iosched.txt for details.
1108
Michael Holzheud3bf37952011-10-30 15:16:37 +01001109 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001110 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001111 image elf header and optionally the size. Generally
1112 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001113 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001115 enable_mtrr_cleanup [X86]
1116 The kernel tries to adjust MTRR layout from continuous
1117 to discrete, to make X server driver able to add WB
1118 entry later. This parameter enables that.
1119
Randy Dunlapca1eda22009-05-06 16:02:58 -07001120 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001121 Enable PIN 1 of APIC timer
1122 Can be useful to work around chipset bugs
1123 (in particular on some ATI chipsets).
1124 The kernel tries to set a reasonable default.
1125
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 enforcing [SELINUX] Set initial enforcing status.
1127 Format: {"0" | "1"}
1128 See security/selinux/Kconfig help text.
1129 0 -- permissive (log only, no denials).
1130 1 -- enforcing (deny and log).
1131 Default value is 0.
1132 Value can be changed at runtime via /selinux/enforce.
1133
Huang Yinga08f82d2010-05-18 14:35:21 +08001134 erst_disable [ACPI]
1135 Disable Error Record Serialization Table (ERST)
1136 support.
1137
Linus Torvalds1da177e2005-04-16 15:20:36 -07001138 ether= [HW,NET] Ethernet cards parameters
1139 This option is obsoleted by the "netdev=" option, which
1140 has equivalent usage. See its documentation for details.
1141
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001142 evm= [EVM]
1143 Format: { "fix" }
1144 Permit 'security.evm' to be updated regardless of
1145 current integrity status.
1146
Akinobu Mitade1ba092006-12-08 02:39:42 -08001147 failslab=
1148 fail_page_alloc=
1149 fail_make_request=[KNL]
1150 General fault injection mechanism.
1151 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001152 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001153
Linus Torvalds1da177e2005-04-16 15:20:36 -07001154 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001155 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156
Alex Chiangf13ae302008-05-08 14:03:23 -06001157 force_pal_cache_flush
1158 [IA-64] Avoid check_sal_cache_flush which may hang on
1159 buggy SAL_CACHE_FLUSH implementations. Using this
1160 parameter will force ia64_sal_cache_flush to call
1161 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1162
Chris Bainbridge69f23662014-03-07 18:40:42 +07001163 forcepae [X86-32]
1164 Forcefully enable Physical Address Extension (PAE).
1165 Many Pentium M systems disable PAE but may have a
1166 functionally usable PAE implementation.
1167 Warning: use of this parameter will taint the kernel
1168 and may cause unknown problems.
1169
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001170 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001171 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001172 as early as possible in order to facilitate early
1173 boot debugging.
1174
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001175 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001176 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001177 If no parameter is passed, ftrace will dump
1178 buffers of all CPUs, but if you pass orig_cpu, it will
1179 dump only the buffer of the CPU that triggered the
1180 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001181
1182 ftrace_filter=[function-list]
1183 [FTRACE] Limit the functions traced by the function
1184 tracer at boot up. function-list is a comma separated
1185 list of functions. This list can be changed at run
1186 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001187 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001188
1189 ftrace_notrace=[function-list]
1190 [FTRACE] Do not trace the functions specified in
1191 function-list. This list can be changed at run time
1192 by the set_ftrace_notrace file in the debugfs
1193 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001194
Stefan Assmann369bc182009-10-12 22:17:21 +02001195 ftrace_graph_filter=[function-list]
1196 [FTRACE] Limit the top level callers functions traced
1197 by the function graph tracer at boot up.
1198 function-list is a comma separated list of functions
1199 that can be changed at run time by the
1200 set_graph_function file in the debugfs tracing directory.
1201
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001202 ftrace_graph_notrace=[function-list]
1203 [FTRACE] Do not trace from the functions specified in
1204 function-list. This list is a comma separated list of
1205 functions that can be changed at run time by the
1206 set_graph_notrace file in the debugfs tracing directory.
1207
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208 gamecon.map[2|3]=
1209 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1210 support via parallel port (up to 5 devices per port)
1211 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1212 See also Documentation/input/joystick-parport.txt
1213
1214 gamma= [HW,DRM]
1215
Yinghai Luaaf23042008-01-30 13:33:09 +01001216 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1217 Format: off | on
1218 default: on
1219
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001220 gcov_persist= [GCOV] When non-zero (default), profiling data for
1221 kernel modules is saved and remains accessible via
1222 debugfs, even when the module is unloaded/reloaded.
1223 When zero, profiling data is discarded and associated
1224 debugfs files are removed at module unload time.
1225
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001227 invalid Protective MBR to be treated as GPT. If the
1228 primary GPT is corrupted, it enables the backup/alternate
1229 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001231 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1232 the "Enable 0" bit of the configuration register.
1233 Format: 0 | 1
1234 Default: 0
1235 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1236 the "Enable 0" bit of the configuration register.
1237 Format: 0 | 1
1238 Default: 0
1239 grcan.select= [HW] Select which physical interface to use.
1240 Format: 0 | 1
1241 Default: 0
1242 grcan.txsize= [HW] Sets the size of the tx buffer.
1243 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1244 Default: 1024
1245 grcan.rxsize= [HW] Sets the size of the rx buffer.
1246 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1247 Default: 1024
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
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337 i8042.reset [HW] Reset the controller during init and cleanup
1338 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001339 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340
1341 i810= [HW,DRM]
1342
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001343 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1344 indicates that the driver is running on unsupported
1345 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1347 does not match list of supported models.
1348 i8k.power_status
1349 [HW] Report power status in /proc/i8k
1350 (disabled by default)
1351 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1352 capability is set.
1353
Carsten Emde4dca20e2012-03-15 15:56:26 +01001354 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001355 [DRM] Invert the sense of the variable that is used to
1356 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001357 brightness value of 0 indicates backlight switched off,
1358 and the maximum of the brightness value sets the backlight
1359 to maximum brightness. If this parameter is set to 0
1360 (default) and the machine requires it, or this parameter
1361 is set to 1, a brightness value of 0 sets the backlight
1362 to maximum brightness, and the maximum of the brightness
1363 value switches the backlight off.
1364 -1 -- never invert brightness
1365 0 -- machine default
1366 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001367
Linus Torvalds1da177e2005-04-16 15:20:36 -07001368 icn= [HW,ISDN]
1369 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1370
David Fries0af80c02009-02-25 20:28:21 +01001371 ide-core.nodma= [HW] (E)IDE subsystem
1372 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001373 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1374 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001375 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001377 ide-generic.probe-mask= [HW] (E)IDE subsystem
1378 Format: <int>
1379 Probe mask for legacy ISA IDE ports. Depending on
1380 platform up to 6 ports are supported, enabled by
1381 setting corresponding bits in the mask to 1. The
1382 default value is 0x0, which has a special meaning.
1383 On systems that have PCI, it triggers scanning the
1384 PCI bus for the first and the second port, which
1385 are then probed. On systems without PCI the value
1386 of 0x0 enables probing the two first ports as if it
1387 was 0x3.
1388
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001389 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1390 Claim all unknown PCI IDE storage controllers.
1391
Andi Kleenf039b752007-05-02 19:27:12 +02001392 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001393 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001394 Poll forces a polling idle loop that can slightly
1395 improve the performance of waking up a idle CPU, but
1396 will use a lot of power and make the system run hot.
1397 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001398 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001399 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001400 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001401
Ingo Molnar792908222006-12-06 20:40:51 -08001402 ignore_loglevel [KNL]
1403 Ignore loglevel setting - this will print /all/
1404 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001405 We also add it as printk module parameter, so users
1406 could change it dynamically, usually by
1407 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001408
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409 ihash_entries= [KNL]
1410 Set number of hash buckets for inode cache.
1411
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001412 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001413 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001414 default: "enforce"
1415
Mimi Zohar07f6a792011-03-09 22:25:48 -05001416 ima_appraise_tcb [IMA]
1417 The builtin appraise policy appraises all files
1418 owned by uid=0.
1419
Mimi Zohar3323eec92009-02-04 09:06:58 -05001420 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001421 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1422 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001423 default: "sha1"
1424
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001425 The list of supported hash algorithms is defined
1426 in crypto/hash_info.h.
1427
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001428 ima_policy= [IMA]
1429 The builtin measurement policy to load during IMA
1430 setup. Specyfing "tcb" as the value, measures all
1431 programs exec'd, files mmap'd for exec, and all files
1432 opened with the read mode bit set by either the
1433 effective uid (euid=0) or uid=0.
1434 Format: "tcb"
1435
1436 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001437 Load a policy which meets the needs of the Trusted
1438 Computing Base. This means IMA will measure all
1439 programs exec'd, files mmap'd for exec, and all files
1440 opened for read by uid=0.
1441
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001442 ima_template= [IMA]
1443 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001444 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001445 Default: "ima-ng"
1446
Roberto Sassuc2426d22014-10-13 14:08:42 +02001447 ima_template_fmt=
1448 [IMA] Define a custom template format.
1449 Format: { "field1|...|fieldN" }
1450
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001451 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1452 Format: <min_file_size>
1453 Set the minimal file size for using asynchronous hash.
1454 If left unspecified, ahash usage is disabled.
1455
1456 ahash performance varies for different data sizes on
1457 different crypto accelerators. This option can be used
1458 to achieve the best performance for a particular HW.
1459
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001460 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1461 Format: <bufsize>
1462 Set hashing buffer size. Default: 4k.
1463
1464 ahash performance varies for different chunk sizes on
1465 different crypto accelerators. This option can be used
1466 to achieve best performance for particular HW.
1467
Linus Torvalds1da177e2005-04-16 15:20:36 -07001468 init= [KNL]
1469 Format: <full_path>
1470 Run specified binary instead of /sbin/init as init
1471 process.
1472
1473 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1474 for working out where the kernel is dying during
1475 startup.
1476
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001477 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1478 initcall functions. Useful for debugging built-in
1479 modules and initcalls.
1480
Linus Torvalds1da177e2005-04-16 15:20:36 -07001481 initrd= [BOOT] Specify the location of the initial ramdisk
1482
1483 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1484 Format: <irq>
1485
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001486 int_pln_enable [x86] Enable power limit notification interrupt
1487
Mimi Zohard726d8d2013-03-18 14:48:02 -04001488 integrity_audit=[IMA]
1489 Format: { "0" | "1" }
1490 0 -- basic integrity auditing messages. (Default)
1491 1 -- additional integrity auditing messages.
1492
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001493 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001494 on
1495 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001496 off
1497 Disable intel iommu driver.
1498 igfx_off [Default Off]
1499 By default, gfx is mapped as normal device. If a gfx
1500 device has a dedicated DMAR unit, the DMAR unit is
1501 bypassed by not enabling DMAR with this option. In
1502 this case, gfx device will use physical address for
1503 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001504 forcedac [x86_64]
1505 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001506 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001507 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001508 than 32-bit addressing. The default is to look
1509 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001510 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001511 strict [Default Off]
1512 With this option on every unmap_single operation will
1513 result in a hardware IOTLB flush operation as opposed
1514 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001515 sp_off [Default Off]
1516 By default, super page will be supported if Intel IOMMU
1517 has the capability. With this option, super page will
1518 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001519 ecs_off [Default Off]
1520 By default, extended context tables will be supported if
1521 the hardware advertises that it has support both for the
1522 extended tables themselves, and also PASID support. With
1523 this option set, extended tables will not be used even
1524 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001525
1526 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1527 0 disables intel_idle and fall back on acpi_idle.
1528 1 to 6 specify maximum depth of C-state.
1529
Dirk Brandewie6be26492013-02-15 22:55:10 +01001530 intel_pstate= [X86]
1531 disable
1532 Do not enable intel_pstate as the default
1533 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001534 force
1535 Enable intel_pstate on systems that prohibit it by default
1536 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1537 instead of acpi-cpufreq may disable platform features, such
1538 as thermal controls and power capping, that rely on ACPI
1539 P-States information being indicated to OSPM and therefore
1540 should be used with caution. This option does not work with
1541 processors that aren't supported by the intel_pstate driver
1542 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001543 no_hwp
1544 Do not enable hardware P state control (HWP)
1545 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001546 hwp_only
1547 Only load intel_pstate on systems which support
1548 hardware P state control (HWP) if available.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001549
Chris Wrightd1423d52010-07-20 11:06:49 -07001550 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001551 on enable Interrupt Remapping (default)
1552 off disable Interrupt Remapping
1553 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001554 no_x2apic_optout
1555 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001556
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001557 iomem= Disable strict checking of access to MMIO memory
1558 strict regions from userspace.
1559 relaxed
1560
1561 iommu= [x86]
1562 off
1563 force
1564 noforce
1565 biomerge
1566 panic
1567 nopanic
1568 merge
1569 nomerge
1570 forcesac
1571 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001572 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001573 nobypass [PPC/POWERNV]
1574 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001575
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001576
1577 io7= [HW] IO7 for Marvel based alpha systems
1578 See comment before marvel_specify_io7 in
1579 arch/alpha/kernel/core_marvel.c.
1580
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301581 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001582 0x80
1583 Standard port 0x80 based delay
1584 0xed
1585 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001586 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001587 Simple two microseconds delay
1588 none
1589 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001590
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001592 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001593
Alan Cox200803d2005-06-28 20:45:18 -07001594 irqfixup [HW]
1595 When an interrupt is not handled search all handlers
1596 for it. Intended to get systems with badly broken
1597 firmware running.
1598
1599 irqpoll [HW]
1600 When an interrupt is not handled search all handlers
1601 for it. Also check all handlers each timer
1602 interrupt. Intended to get systems with badly broken
1603 firmware running.
1604
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001606 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607
1608 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001609 Format:
1610 <cpu number>,...,<cpu number>
1611 or
Li Zefanb225d442008-11-06 12:53:39 -08001612 <cpu number>-<cpu number>
1613 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001614 or a mixture
1615 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001616
Linus Torvalds1da177e2005-04-16 15:20:36 -07001617 This option can be used to specify one or more CPUs
1618 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001619 algorithms. You can move a process onto or off an
1620 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621 <cpu number> begins at 0 and the maximum value is
1622 "number of CPUs in system - 1".
1623
1624 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001625 alternative -- manually setting the CPU mask of all
1626 tasks in the system -- can cause problems and
1627 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628
Randy Dunlapa9913042005-10-23 12:57:11 -07001629 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001631 ivrs_ioapic [HW,X86_64]
1632 Provide an override to the IOAPIC-ID<->DEVICE-ID
1633 mapping provided in the IVRS ACPI table. For
1634 example, to map IOAPIC-ID decimal 10 to
1635 PCI device 00:14.0 write the parameter as:
1636 ivrs_ioapic[10]=00:14.0
1637
1638 ivrs_hpet [HW,X86_64]
1639 Provide an override to the HPET-ID<->DEVICE-ID
1640 mapping provided in the IVRS ACPI table. For
1641 example, to map HPET-ID decimal 0 to
1642 PCI device 00:14.0 write the parameter as:
1643 ivrs_hpet[0]=00:14.0
1644
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 js= [HW,JOY] Analog joystick
1646 See Documentation/input/joystick.txt.
1647
Kees Cook24f2e022014-06-13 13:30:36 -07001648 kaslr/nokaslr [X86]
1649 Enable/disable kernel and module base offset ASLR
1650 (Address Space Layout Randomization) if built into
1651 the kernel. When CONFIG_HIBERNATION is selected,
1652 kASLR is disabled by default. When kASLR is enabled,
1653 hibernation will be disabled.
1654
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001655 keepinitrd [HW,ARM]
1656
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301657 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001658 specifies the amount of memory usable by the kernel
1659 for non-movable allocations. The requested amount is
1660 spread evenly throughout all nodes in the system. The
1661 remaining memory in each node is used for Movable
1662 pages. In the event, a node is too small to have both
1663 kernelcore and Movable pages, kernelcore pages will
1664 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001665 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001666 allocation of pages that may be reclaimed or moved
1667 by the page migration subsystem. This means that
1668 HugeTLB pages may not be allocated from this zone.
1669 Note that allocations like PTEs-from-HighMem still
1670 use the HighMem zone if it exists, and the Normal
1671 zone if it does not.
1672
Jason Wessel4fe1da42010-05-20 21:04:31 -05001673 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1674 Format: <Controller#>[,poll interval]
1675 The controller # is the number of the ehci usb debug
1676 port as it is probed via PCI. The poll interval is
1677 optional and is the number seconds in between
1678 each poll cycle to the debug port in case you need
1679 the functionality for interrupting the kernel with
1680 gdb or control-c on the dbgp connection. When
1681 not using this parameter you use sysrq-g to break into
1682 the kernel debugger.
1683
Jason Wessel84c08fd2010-05-20 21:04:24 -05001684 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001685 Requires a tty driver that supports console polling,
1686 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001687 Serial only format: <serial_device>[,baud]
1688 keyboard only format: kbd
1689 keyboard and serial format: kbd,<serial_device>[,baud]
1690 Optional Kernel mode setting:
1691 kms, kbd format: kms,kbd
1692 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001693
Jason Wessel84c08fd2010-05-20 21:04:24 -05001694 kgdbwait [KGDB] Stop kernel execution and enter the
1695 kernel debugger at the earliest opportunity.
1696
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001697 kmac= [MIPS] korina ethernet MAC address.
1698 Configure the RouterBoard 532 series on-chip
1699 Ethernet adapter MAC address.
1700
Catalin Marinas04f70332009-06-11 13:22:39 +01001701 kmemleak= [KNL] Boot-time kmemleak enable/disable
1702 Valid arguments: on, off
1703 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001704 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1705 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001706
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001707 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1708 Valid arguments: 0, 1, 2
1709 kmemcheck=0 (disabled)
1710 kmemcheck=1 (enabled)
1711 kmemcheck=2 (one-shot mode)
1712 Default: 2 (one-shot mode)
1713
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301714 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001715 in oops dumps.
1716
Andre Przywarafef07aa2009-07-10 14:20:35 +02001717 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1718 Default is 0 (don't ignore, but inject #GP)
1719
Xiao Guangronga182d872010-09-20 22:17:48 +08001720 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1721 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001722 Default is 0 (off)
1723
Andre Przywarafef07aa2009-07-10 14:20:35 +02001724 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001725 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001726
1727 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1728 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001729 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001730
Andre Przywarafef07aa2009-07-10 14:20:35 +02001731 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1732 (virtualized MMU) support on capable Intel chips.
1733 Default is 1 (enabled)
1734
1735 kvm-intel.emulate_invalid_guest_state=
1736 [KVM,Intel] Enable emulation of invalid guest states
1737 Default is 0 (disabled)
1738
1739 kvm-intel.flexpriority=
1740 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1741 Default is 1 (enabled)
1742
Sasha Levine1a72ae2011-08-09 14:28:35 +03001743 kvm-intel.nested=
1744 [KVM,Intel] Enable VMX nesting (nVMX).
1745 Default is 0 (disabled)
1746
Andre Przywarafef07aa2009-07-10 14:20:35 +02001747 kvm-intel.unrestricted_guest=
1748 [KVM,Intel] Disable unrestricted guest feature
1749 (virtualized real and unpaged mode) on capable
1750 Intel chips. Default is 1 (enabled)
1751
1752 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1753 feature (tagged TLBs) on capable Intel chips.
1754 Default is 1 (enabled)
1755
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 l2cr= [PPC]
1757
Robert Brosea78bfbf2008-03-29 07:20:23 +11001758 l3cr= [PPC]
1759
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001760 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001761 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762
Suresh Siddha279f1462012-10-22 14:37:58 -07001763 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1764 value for LAPIC timer one-shot implementation. Default
1765 back to the programmable timer unit in the LAPIC.
1766
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301767 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001768 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001769
FD Camifcb71f62008-01-06 19:08:56 +01001770 libata.dma= [LIBATA] DMA control
1771 libata.dma=0 Disable all PATA and SATA DMA
1772 libata.dma=1 PATA and SATA Disk DMA only
1773 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001774 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001775 Combinations also work, so libata.dma=3 enables DMA
1776 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001777
Michael Prokop20308872009-08-06 00:14:10 +02001778 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1779 libata.ignore_hpa=0 keep BIOS limits (default)
1780 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001781
Dave Jones78e70c22007-09-27 11:50:13 -04001782 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1783 when set.
1784 Format: <int>
1785
Tejun Heo33267322008-02-13 09:15:09 +09001786 libata.force= [LIBATA] Force configurations. The format is comma
1787 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001788 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001789 matching port, link or device. Basically, it matches
1790 the ATA ID string printed on console by libata. If
1791 the whole ID part is omitted, the last PORT and DEVICE
1792 values are used. If ID hasn't been specified yet, the
1793 configuration applies to all ports, links and devices.
1794
1795 If only DEVICE is omitted, the parameter applies to
1796 the port and all links and devices behind it. DEVICE
1797 number of 0 either selects the first device or the
1798 first fan-out link behind PMP device. It does not
1799 select the host link. DEVICE number of 15 selects the
1800 host link and device attached to it.
1801
1802 The VAL specifies the configuration to force. As long
1803 as there's no ambiguity shortcut notation is allowed.
1804 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1805 The following configurations can be forced.
1806
1807 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1808 Any ID with matching PORT is used.
1809
1810 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1811
1812 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1813 udma[/][16,25,33,44,66,100,133] notation is also
1814 allowed.
1815
1816 * [no]ncq: Turn on or off NCQ.
1817
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001818 * [no]ncqtrim: Turn off queued DSM TRIM.
1819
Tejun Heo05944bd2008-08-13 20:19:09 +09001820 * nohrst, nosrst, norst: suppress hard, soft
1821 and both resets.
1822
Dan Williamsca6d43b2012-06-21 23:41:41 -07001823 * rstonce: only attempt one reset during
1824 hot-unplug link recovery
1825
Tejun Heo43c9c592010-05-23 12:59:11 +02001826 * dump_id: dump IDENTIFY data.
1827
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001828 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1829
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001830 * disable: Disable this device.
1831
Tejun Heo33267322008-02-13 09:15:09 +09001832 If there are multiple matching configurations changing
1833 the same attribute, the last one is used.
1834
Yinghai Lu95f72d12010-07-12 14:36:09 +10001835 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001836
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001838 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001840 lockd.nlm_grace_period=P [NFS] Assign grace period.
1841 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001842
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001843 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1844 Format: <integer>
1845
1846 lockd.nlm_timeout=T [NFS] Assign timeout value.
1847 Format: <integer>
1848
1849 lockd.nlm_udpport=M [NFS] Assign UDP port.
1850 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001851
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001852 locktorture.nreaders_stress= [KNL]
1853 Set the number of locking read-acquisition kthreads.
1854 Defaults to being automatically set based on the
1855 number of online CPUs.
1856
1857 locktorture.nwriters_stress= [KNL]
1858 Set the number of locking write-acquisition kthreads.
1859
1860 locktorture.onoff_holdoff= [KNL]
1861 Set time (s) after boot for CPU-hotplug testing.
1862
1863 locktorture.onoff_interval= [KNL]
1864 Set time (s) between CPU-hotplug operations, or
1865 zero to disable CPU-hotplug testing.
1866
1867 locktorture.shuffle_interval= [KNL]
1868 Set task-shuffle interval (jiffies). Shuffling
1869 tasks allows some CPUs to go into dyntick-idle
1870 mode during the locktorture test.
1871
1872 locktorture.shutdown_secs= [KNL]
1873 Set time (s) after boot system shutdown. This
1874 is useful for hands-off automated testing.
1875
1876 locktorture.stat_interval= [KNL]
1877 Time (s) between statistics printk()s.
1878
1879 locktorture.stutter= [KNL]
1880 Time (s) to stutter testing, for example,
1881 specifying five seconds causes the test to run for
1882 five seconds, wait for five seconds, and so on.
1883 This tests the locking primitive's ability to
1884 transition abruptly to and from idle.
1885
1886 locktorture.torture_runnable= [BOOT]
1887 Start locktorture running at boot time.
1888
1889 locktorture.torture_type= [KNL]
1890 Specify the locking implementation to test.
1891
1892 locktorture.verbose= [KNL]
1893 Enable additional printk() statements.
1894
Linus Torvalds1da177e2005-04-16 15:20:36 -07001895 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1896 Format: <irq>
1897
1898 loglevel= All Kernel Messages with a loglevel smaller than the
1899 console loglevel will be printed to the console. It can
1900 also be changed with klogd or other programs. The
1901 loglevels are defined as follows:
1902
1903 0 (KERN_EMERG) system is unusable
1904 1 (KERN_ALERT) action must be taken immediately
1905 2 (KERN_CRIT) critical conditions
1906 3 (KERN_ERR) error conditions
1907 4 (KERN_WARNING) warning conditions
1908 5 (KERN_NOTICE) normal but significant condition
1909 6 (KERN_INFO) informational
1910 7 (KERN_DEBUG) debug-level messages
1911
Randy Dunlapc756d082011-02-20 20:08:35 -08001912 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001913 in bytes. n must be a power of two and greater
1914 than the minimal size. The minimal size is defined
1915 by LOG_BUF_SHIFT kernel config parameter. There is
1916 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1917 that allows to increase the default size depending on
1918 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001919
Randy Dunlapaccaa242007-10-16 01:29:37 -07001920 logo.nologo [FB] Disables display of the built-in Linux logo.
1921 This may be used to provide more screen space for
1922 kernel log messages and is useful when debugging
1923 kernel boot problems.
1924
Linus Torvalds1da177e2005-04-16 15:20:36 -07001925 lp=0 [LP] Specify parallel ports to use, e.g,
1926 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1927 lp=reset first parallel port). 'lp=0' disables the
1928 lp=auto printer driver. 'lp=reset' (which can be
1929 specified in addition to the ports) causes
1930 attached printers to be reset. Using
1931 lp=port1,port2,... specifies the parallel ports
1932 to associate lp devices with, starting with
1933 lp0. A port specification may be 'none' to skip
1934 that lp device, or a parport name such as
1935 'parport0'. Specifying 'lp=auto' instead of a
1936 port specification list means that device IDs
1937 from each port should be examined, to see if
1938 an IEEE 1284-compliant printer is attached; if
1939 so, the driver will manage that printer.
1940 See also header of drivers/char/lp.c.
1941
1942 lpj=n [KNL]
1943 Sets loops_per_jiffy to given constant, thus avoiding
1944 time-consuming boot-time autodetection (up to 250 ms per
1945 CPU). 0 enables autodetection (default). To determine
1946 the correct value for your kernel, boot with normal
1947 autodetection and see what value is printed. Note that
1948 on SMP systems the preset will be applied to all CPUs,
1949 which is likely to cause problems if your CPUs need
1950 significantly divergent settings. An incorrect value
1951 will cause delays in the kernel to be wrong, leading to
1952 unpredictable I/O errors and other breakage. Although
1953 unlikely, in the extreme case this might damage your
1954 hardware.
1955
1956 ltpc= [NET]
1957 Format: <io>,<irq>,<dma>
1958
Randy Dunlap16290242011-08-13 12:34:52 -07001959 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001960 (machvec) in a generic kernel.
1961 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001962
Wu Zhangjin3209e702009-07-02 23:27:12 +08001963 machtype= [Loongson] Share the same kernel image file between different
1964 yeeloong laptop.
1965 Example: machtype=lemote-yeeloong-2f-7inch
1966
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001967 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1968 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001969
1970 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001971 should make use of. maxcpus=n : n >= 0 limits the
1972 kernel to using 'n' processors. n=0 is a special case,
1973 it is equivalent to "nosmp", which also disables
1974 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975
Kay Sieversd134b002011-07-31 22:08:04 +02001976 max_loop= [LOOP] The number of loop block devices that get
1977 (loop.max_loop) unconditionally pre-created at init time. The default
1978 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1979 of statically allocating a predefined number, loop
1980 devices can be requested on-demand with the
1981 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001982
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001983 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001984
Uwe Hermann71cced62008-10-20 09:32:21 -07001985 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001986
Linus Torvalds1da177e2005-04-16 15:20:36 -07001987 md= [HW] RAID subsystems devices and level
1988 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001989
Linus Torvalds1da177e2005-04-16 15:20:36 -07001990 mdacon= [MDA]
1991 Format: <first>,<last>
1992 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001993
Linus Torvalds1da177e2005-04-16 15:20:36 -07001994 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1995 Amount of memory to be used when the kernel is not able
1996 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001997 [X86] Work as limiting max address. Use together
1998 with memmap= to avoid physical address space collisions.
1999 Without memmap= PCI devices could be placed at addresses
2000 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002001
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002002 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003 memory.
2004
Paul Mundt6902aa82008-09-21 17:14:42 +09002005 memchunk=nn[KMG]
2006 [KNL,SH] Allow user to override the default size for
2007 per-device physically contiguous DMA buffers.
2008
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302009 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002010 E820 memory map, as specified by the user.
2011 Such memmap=exactmap lines can be constructed based on
2012 BIOS output or other requirements. See the memmap=nn@ss
2013 option description.
2014
2015 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002016 [KNL] Force usage of a specific region of memory.
2017 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018
2019 memmap=nn[KMG]#ss[KMG]
2020 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002021 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022
2023 memmap=nn[KMG]$ss[KMG]
2024 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002025 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002026 Example: Exclude memory from 0x18690000-0x1869ffff
2027 memmap=64K$0x18690000
2028 or
2029 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002030
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002031 memmap=nn[KMG]!ss[KMG]
2032 [KNL,X86] Mark specific memory as protected.
2033 Region of memory to be used, from ss to ss+nn.
2034 The memory region may be marked as e820 type 12 (0xc)
2035 and is NVDIMM or ADR memory.
2036
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002037 memory_corruption_check=0/1 [X86]
2038 Some BIOSes seem to corrupt the first 64k of
2039 memory when doing things like suspend/resume.
2040 Setting this option will scan the memory
2041 looking for corruption. Enabling this will
2042 both detect corruption and prevent the kernel
2043 from using the memory being corrupted.
2044 However, its intended as a diagnostic tool; if
2045 repeatable BIOS-originated corruption always
2046 affects the same memory, you can use memmap=
2047 to prevent the kernel from using that memory.
2048
2049 memory_corruption_check_size=size [X86]
2050 By default it checks for corruption in the low
2051 64k, making this memory unavailable for normal
2052 use. Use this parameter to scan for
2053 corruption in more or less memory.
2054
2055 memory_corruption_check_period=seconds [X86]
2056 By default it checks for corruption every 60
2057 seconds. Use this parameter to check at some
2058 other rate. 0 disables periodic checking.
2059
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002060 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002061 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002062 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002063 Specifies the number of memtest passes to be
2064 performed. Each pass selects another test
2065 pattern from a given set of patterns. Memtest
2066 fills the memory with this pattern, validates
2067 memory contents and reserves bad memory
2068 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002069
Linus Torvalds1da177e2005-04-16 15:20:36 -07002070 meye.*= [HW] Set MotionEye Camera parameters
2071 See Documentation/video4linux/meye.txt.
2072
Andres Salomon8f368812007-10-12 23:04:06 +02002073 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2074 Multi-Function General Purpose Timers on AMD Geode
2075 platforms.
2076
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002077 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2078 the BIOS has incorrectly applied a workaround. TinyBIOS
2079 version 0.98 is known to be affected, 0.99 fixes the
2080 problem by letting the user disable the workaround.
2081
Linus Torvalds1da177e2005-04-16 15:20:36 -07002082 mga= [HW,DRM]
2083
Randy Dunlap1c207f92008-11-19 15:36:16 -08002084 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2085 physical address is ignored.
2086
Michel Pollet39f45d72009-05-20 11:10:31 +01002087 mini2440= [ARM,HW,KNL]
2088 Format:[0..2][b][c][t]
2089 Default: "0tb"
2090 MINI2440 configuration specification:
2091 0 - The attached screen is the 3.5" TFT
2092 1 - The attached screen is the 7" TFT
2093 2 - The VGA Shield is attached (1024x768)
2094 Leaving out the screen size parameter will not load
2095 the TFT driver, and the framebuffer will be left
2096 unconfigured.
2097 b - Enable backlight. The TFT backlight pin will be
2098 linked to the kernel VESA blanking code and a GPIO
2099 LED. This parameter is not necessary when using the
2100 VGA shield.
2101 c - Enable the s3c camera interface.
2102 t - Reserved for enabling touchscreen support. The
2103 touchscreen support is not enabled in the mainstream
2104 kernel as of 2.6.30, a preliminary port can be found
2105 in the "bleeding edge" mini2440 support kernel at
2106 http://repo.or.cz/w/linux-2.6/mini2440.git
2107
Mel Gorman6b74ab92008-07-23 21:26:49 -07002108 mminit_loglevel=
2109 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2110 parameter allows control of the logging verbosity for
2111 the additional memory initialisation checks. A value
2112 of 0 disables mminit logging and a level of 4 will
2113 log everything. Information is printed at KERN_DEBUG
2114 so loglevel=8 may also need to be specified.
2115
Rusty Russell106a4ee2012-09-26 10:09:40 +01002116 module.sig_enforce
2117 [KNL] When CONFIG_MODULE_SIG is set, this means that
2118 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002119 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002120 is always true, so this option does nothing.
2121
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122 mousedev.tap_time=
2123 [MOUSE] Maximum time between finger touching and
2124 leaving touchpad surface for touch to be considered
2125 a tap and be reported as a left button click (for
2126 touchpads working in absolute mode only).
2127 Format: <msecs>
2128 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2129 reporting absolute coordinates, such as tablets
2130 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2131 reporting absolute coordinates, such as tablets
2132
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302133 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002134 is similar to kernelcore except it specifies the
2135 amount of memory used for migratable allocations.
2136 If both kernelcore and movablecore is specified,
2137 then kernelcore will be at *least* the specified
2138 value but may be more. If movablecore on its own
2139 is specified, the administrator must be careful
2140 that the amount of memory usable for all allocations
2141 is not too small.
2142
Tang Chenc5320922013-11-12 15:08:10 -08002143 movable_node [KNL,X86] Boot-time switch to enable the effects
2144 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2145
Linus Torvalds1da177e2005-04-16 15:20:36 -07002146 MTD_Partition= [MTD]
2147 Format: <name>,<region-number>,<size>,<offset>
2148
Randy Dunlapa9913042005-10-23 12:57:11 -07002149 MTD_Region= [MTD] Format:
2150 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151
2152 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002153 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002155 multitce=off [PPC] This parameter disables the use of the pSeries
2156 firmware feature for updating multiple TCE entries
2157 at a time.
2158
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002159 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2160
2161 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2162
2163 boundary - index of last SLC block on Flex-OneNAND.
2164 The remaining blocks are configured as MLC blocks.
2165 lock - Configure if Flex-OneNAND boundary should be locked.
2166 Once locked, the boundary cannot be changed.
2167 1 indicates lock status, 0 indicates unlock status.
2168
Ben Dooks9db829f2008-07-03 11:24:29 +01002169 mtdset= [ARM]
2170 ARM/S3C2412 JIVE boot control
2171
2172 See arch/arm/mach-s3c2412/mach-jive.c
2173
Linus Torvalds1da177e2005-04-16 15:20:36 -07002174 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002175 [HW] Make the MicroTouch USB driver use raw coordinates
2176 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002177
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002178 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002179 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002180 that could hold holes aka. UC entries.
2181
2182 mtrr_gran_size=nn[KMG] [X86]
2183 Used for mtrr cleanup. It is granularity of mtrr block.
2184 Default is 1.
2185 Large value could prevent small alignment from
2186 using up MTRRs.
2187
2188 mtrr_spare_reg_nr=n [X86]
2189 Format: <integer>
2190 Range: 0,7 : spare reg number
2191 Default : 1
2192 Used for mtrr cleanup. It is spare mtrr entries number.
2193 Set to 2 or more if your graphical card needs more.
2194
Linus Torvalds1da177e2005-04-16 15:20:36 -07002195 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2196
Linus Torvalds1da177e2005-04-16 15:20:36 -07002197 netdev= [NET] Network devices parameters
2198 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2199 Note that mem_start is often overloaded to mean
2200 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002201 This usage is only documented in each driver source
2202 file if at all.
2203
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002204 nf_conntrack.acct=
2205 [NETFILTER] Enable connection tracking flow accounting
2206 0 to disable accounting
2207 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002208 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002209
Chuck Lever306a0752010-09-17 10:54:37 -04002210 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002211 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212
2213 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002214 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002215
Chuck Lever306a0752010-09-17 10:54:37 -04002216 nfsrootdebug [NFS] enable nfsroot debugging messages.
2217 See Documentation/filesystems/nfs/nfsroot.txt.
2218
Trond Myklebusta72b4422006-01-03 09:55:41 +01002219 nfs.callback_tcpport=
2220 [NFS] set the TCP port on which the NFSv4 callback
2221 channel should listen.
2222
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002223 nfs.cache_getent=
2224 [NFS] sets the pathname to the program which is used
2225 to update the NFS client cache entries.
2226
2227 nfs.cache_getent_timeout=
2228 [NFS] sets the timeout after which an attempt to
2229 update a cache entry is deemed to have failed.
2230
Trond Myklebust58df0952006-01-03 09:55:57 +01002231 nfs.idmap_cache_timeout=
2232 [NFS] set the maximum lifetime for idmapper cache
2233 entries.
2234
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002235 nfs.enable_ino64=
2236 [NFS] enable 64-bit inode numbers.
2237 If zero, the NFS client will fake up a 32-bit inode
2238 number for the readdir() and stat() syscalls instead
2239 of returning the full 64-bit number.
2240 The default is to return 64-bit inode numbers.
2241
Trond Myklebustef159e92012-02-06 19:50:40 -05002242 nfs.max_session_slots=
2243 [NFSv4.1] Sets the maximum number of session slots
2244 the client will attempt to negotiate with the server.
2245 This limits the number of simultaneous RPC requests
2246 that the client can send to the NFSv4.1 server.
2247 Note that there is little point in setting this
2248 value higher than the max_tcp_slot_table_limit.
2249
Trond Myklebustb064eca22011-02-22 15:44:32 -08002250 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002251 [NFSv4] When set to the default of '1', this option
2252 ensures that both the RPC level authentication
2253 scheme and the NFS level operations agree to use
2254 numeric uids/gids if the mount is using the
2255 'sec=sys' security flavour. In effect it is
2256 disabling idmapping, which can make migration from
2257 legacy NFSv2/v3 systems to NFSv4 easier.
2258 Servers that do not support this mode of operation
2259 will be autodetected by the client, and it will fall
2260 back to using the idmapper.
2261 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002262 nfs.nfs4_unique_id=
2263 [NFS4] Specify an additional fixed unique ident-
2264 ification string that NFSv4 clients can insert into
2265 their nfs_client_id4 string. This is typically a
2266 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002267
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002268 nfs.send_implementation_id =
2269 [NFSv4.1] Send client implementation identification
2270 information in exchange_id requests.
2271 If zero, no implementation identification information
2272 will be sent.
2273 The default is to send the implementation identification
2274 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002275
2276 nfs.recover_lost_locks =
2277 [NFSv4] Attempt to recover locks that were lost due
2278 to a lease timeout on the server. Please note that
2279 doing this risks data corruption, since there are
2280 no guarantees that the file will remain unchanged
2281 after the locks are lost.
2282 If you want to enable the kernel legacy behaviour of
2283 attempting to recover these locks, then set this
2284 parameter to '1'.
2285 The default parameter value of '0' causes the kernel
2286 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002287
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002288 nfs4.layoutstats_timer =
2289 [NFSv4.2] Change the rate at which the kernel sends
2290 layoutstats to the pNFS metadata server.
2291
2292 Setting this to value to 0 causes the kernel to use
2293 whatever value is the default set by the layout
2294 driver. A non-zero value sets the minimum interval
2295 in seconds between layoutstats transmissions.
2296
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002297 nfsd.nfs4_disable_idmapping=
2298 [NFSv4] When set to the default of '1', the NFSv4
2299 server will return only numeric uids and gids to
2300 clients using auth_sys, and will accept numeric uids
2301 and gids from such clients. This is intended to ease
2302 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002303
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002304 objlayoutdriver.osd_login_prog=
2305 [NFS] [OBJLAYOUT] sets the pathname to the program which
2306 is used to automatically discover and login into new
2307 osd-targets. Please see:
2308 Documentation/filesystems/pnfs.txt for more explanations
2309
Paul Mundt1e1030d2009-09-01 17:38:32 +09002310 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002311 when a NMI is triggered.
2312 Format: [state][,regs][,debounce][,die]
2313
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302314 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002315 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002316 Valid num: 0 or 1
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002317 0 - turn nmi_watchdog off
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002318 1 - turn nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002319 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002320 timeout occurs (or 'nopanic' to override the opposite
2321 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002322 This is useful when you use a panic=... timeout and
2323 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002324
Anton Vorontsovbff38772009-07-08 11:10:56 -07002325 netpoll.carrier_timeout=
2326 [NET] Specifies amount of time (in seconds) that
2327 netpoll should wait for a carrier. By default netpoll
2328 waits 4 seconds.
2329
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002330 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002331 emulation library even if a 387 maths coprocessor
2332 is present.
2333
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002334 no_console_suspend
2335 [HW] Never suspend the console
2336 Disable suspending of consoles during suspend and
2337 hibernate operations. Once disabled, debugging
2338 messages can reach various consoles while the rest
2339 of the system is being put to sleep (ie, while
2340 debugging driver suspend/resume hooks). This may
2341 not work reliably with all consoles, but is known
2342 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002343 To facilitate more flexible debugging, we also add
2344 console_suspend, a printk module parameter to control
2345 it. Users could use console_suspend (usually
2346 /sys/module/printk/parameters/console_suspend) to
2347 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002348
Christoph Lameterc1aee212007-05-31 00:40:47 -07002349 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2350 caches in the slab allocator. Saves per-node memory,
2351 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002352
Randy Dunlapa9913042005-10-23 12:57:11 -07002353 noalign [KNL,ARM]
2354
Linus Torvalds1da177e2005-04-16 15:20:36 -07002355 noapic [SMP,APIC] Tells the kernel to not make use of any
2356 IOAPICs that may be present in the system.
2357
Mike Galbraith5091faa2010-11-30 14:18:03 +01002358 noautogroup Disable scheduler automatic task group creation.
2359
Linus Torvalds1da177e2005-04-16 15:20:36 -07002360 nobats [PPC] Do not use BATs for mapping kernel lowmem
2361 on "Classic" PPC cores.
2362
2363 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002364
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002365 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2366
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002367 nodelayacct [KNL] Disable per-task delay accounting
2368
Linus Torvalds1da177e2005-04-16 15:20:36 -07002369 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2370
Paul Mundt6902aa82008-09-21 17:14:42 +09002371 nodsp [SH] Disable hardware DSP at boot time.
2372
Dave Youngb2e0a542014-08-14 17:15:26 +08002373 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002374
Linus Torvalds1da177e2005-04-16 15:20:36 -07002375 noexec [IA-64]
2376
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302377 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002378 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002379 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002380 noexec=off: disable non-executable mappings
2381
H. Peter Anvin52b61792012-09-21 12:43:13 -07002382 nosmap [X86]
2383 Disable SMAP (Supervisor Mode Access Prevention)
2384 even if it is supported by processor.
2385
Fenghua Yude5397a2011-05-11 16:51:05 -07002386 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002387 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002388 even if it is supported by processor.
2389
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002390 noexec32 [X86-64]
2391 This affects only 32-bit executables.
2392 noexec32=on: enable non-executable mappings (default)
2393 read doesn't imply executable mappings
2394 noexec32=off: disable non-executable mappings
2395 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002396
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002397 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002398
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002399 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002400 register save and restore. The kernel will only save
2401 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002402
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002403 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2404
Suresh Siddha0c752a92009-05-22 12:17:45 -07002405 noxsave [BUGS=X86] Disables x86 extended register state save
2406 and restore using xsave. The kernel will fallback to
2407 enabling legacy floating-point and sse state.
2408
Fenghua Yub6f42a42014-05-29 11:12:31 -07002409 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2410 register states. The kernel will fall back to use
2411 xsave to save the states. By using this parameter,
2412 performance of saving the states is degraded because
2413 xsave doesn't support modified optimization while
2414 xsaveopt supports it on xsaveopt enabled systems.
2415
2416 noxsaves [X86] Disables xsaves and xrstors used in saving and
2417 restoring x86 extended register state in compacted
2418 form of xsave area. The kernel will fall back to use
2419 xsaveopt and xrstor to save and restore the states
2420 in standard form of xsave area. By using this
2421 parameter, xsave area per process might occupy more
2422 memory on xsaves enabled systems.
2423
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002424 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2425 wfi(ARM) instruction doesn't work correctly and not to
2426 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002427
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002428 no_file_caps Tells the kernel not to honor file capabilities. The
2429 only way then for a file to be executed with privilege
2430 is to be setuid root or executed by root.
2431
Linus Torvalds1da177e2005-04-16 15:20:36 -07002432 nohalt [IA-64] Tells the kernel not to use the power saving
2433 function PAL_HALT_LIGHT when idle. This increases
2434 power-consumption. On the positive side, it reduces
2435 interrupt wake-up latency, which may improve performance
2436 in certain environments such as networked servers or
2437 real-time systems.
2438
Kees Cooka6e15a32014-06-13 13:30:35 -07002439 nohibernate [HIBERNATION] Disable hibernation and resume.
2440
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002441 nohz= [KNL] Boottime enable/disable dynamic ticks
2442 Valid arguments: on, off
2443 Default: on
2444
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002445 nohz_full= [KNL,BOOT]
2446 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002447 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002448 whenever possible. The boot CPU will be forced outside
2449 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002450 The CPUs in this range must also be included in the
2451 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002452
Paul Mundteeee7852009-04-02 12:31:16 +09002453 noiotrap [SH] Disables trapped I/O port accesses.
2454
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002455 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456 disable unhandled interrupt sources.
2457
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302458 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002459 broken timer IRQ sources.
2460
Linus Torvalds1da177e2005-04-16 15:20:36 -07002461 noisapnp [ISAPNP] Disables ISA PnP code.
2462
2463 noinitrd [RAM] Tells the kernel not to load any configured
2464 initial RAM disk.
2465
Weidong Han03ea8152009-04-17 16:42:15 +08002466 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2467 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002468 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002469
Linus Torvalds1da177e2005-04-16 15:20:36 -07002470 nointroute [IA-64]
2471
Randy Dunlap16290242011-08-13 12:34:52 -07002472 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002473
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002474 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2475
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002476 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2477 fault handling.
2478
Glauber Costad910f5c2011-07-11 15:28:19 -04002479 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2480 steal time is computed, but won't influence scheduler
2481 behaviour
2482
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002483 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002484
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002485 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002486
Linus Torvalds1da177e2005-04-16 15:20:36 -07002487 noltlbs [PPC] Do not use large page/tlb entries for kernel
2488 lowmem mapping on PPC40x.
2489
Horms312f1f02006-02-22 09:57:55 +09002490 nomca [IA-64] Disable machine check abort handling
2491
Masanari Iida13696e02015-05-16 02:16:43 +09002492 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002493
Andres Salomon83d73842007-10-12 23:04:06 +02002494 nomfgpt [X86-32] Disable Multi-Function General Purpose
2495 Timer usage (for AMD Geode machines).
2496
Don Zickusbda62632011-10-13 15:14:27 -04002497 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2498 shutdown the other cpus. Instead use the REBOOT_VECTOR
2499 irq.
2500
Dave Young02608be2012-02-01 10:33:14 +08002501 nomodule Disable module load
2502
Jiri Kosina016ddd92010-01-18 17:05:40 +01002503 nopat [X86] Disable PAT (page attribute table extension of
2504 pagetables) support.
2505
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002506 norandmaps Don't use address space randomization. Equivalent to
2507 echo 0 > /proc/sys/kernel/randomize_va_space
2508
Jiri Kosinabbff2162010-08-11 18:34:09 +02002509 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002510
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002511 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002512 with UP alternatives
2513
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002514 nordrand [X86] Disable kernel use of the RDRAND and
2515 RDSEED instructions even if they are supported
2516 by the processor. RDRAND and RDSEED are still
2517 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002518
Randy Dunlapa9913042005-10-23 12:57:11 -07002519 noresume [SWSUSP] Disables resume and restores original swap
2520 space.
2521
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522 no-scroll [VGA] Disables scrollback.
2523 This is required for the Braillex ib80-piezo Braille
2524 reader made by F.H. Papenmeier (Germany).
2525
2526 nosbagart [IA-64]
2527
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002528 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002529
Len Brown61ec7562007-08-16 03:34:22 -04002530 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2531 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002532
Dave Jones97842212007-07-15 23:41:05 -07002533 nosoftlockup [KNL] Disable the soft-lockup detector.
2534
Linus Torvalds1da177e2005-04-16 15:20:36 -07002535 nosync [HW,M68K] Disables sync negotiation for all devices.
2536
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002537 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002538
2539 nousb [USB] Disable the USB subsystem
2540
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002541 nowatchdog [KNL] Disable both lockup detectors, i.e.
2542 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002543
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002545
Weidong Han2b2fd872009-04-17 16:42:12 +08002546 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2547
Fenghua Yuf78cff42012-11-13 11:32:38 -08002548 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2549 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2550 Some features depend on CPU0. Known dependencies are:
2551 1. Resume from suspend/hibernate depends on CPU0.
2552 Suspend/hibernate will fail if CPU0 is offline and you
2553 need to online CPU0 before suspend/hibernate.
2554 2. PIC interrupts also depend on CPU0. CPU0 can't be
2555 removed if a PIC interrupt is detected.
2556 It's said poweroff/reboot may depend on CPU0 on some
2557 machines although I haven't seen such issues so far
2558 after CPU0 is offline on a few tested machines.
2559 If the dependencies are under your control, you can
2560 turn on cpu0_hotplug.
2561
Randy Dunlap16290242011-08-13 12:34:52 -07002562 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002563 purges which is reported from either PAL_VM_SUMMARY or
2564 SAL PALO.
2565
Yinghai Lu2b633e32010-02-10 01:20:37 -08002566 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2567 could support. nr_cpus=n : n >= 1 limits the kernel to
2568 supporting 'n' processors. Later in runtime you can not
2569 use hotplug cpu feature to put more cpu back to online.
2570 just like you compile the kernel NR_CPUS=n
2571
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002572 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2573
Mel Gorman1a687c22012-11-22 11:16:36 +00002574 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2575 Allowed values are enable and disable
2576
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002577 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2578 one of ['zone', 'node', 'default'] can be specified
2579 This can be set from sysctl after boot.
2580 See Documentation/sysctl/vm.txt for details.
2581
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002582 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2583 See Documentation/debugging-via-ohci1394.txt for more
2584 info.
2585
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002586 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2587 Rather than timing out after 20 ms if an EC
2588 command is not properly ACKed, override the length
2589 of the timeout. We have interrupts disabled while
2590 waiting for the ACK, so if this is set too high
2591 interrupts *may* be lost!
2592
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002593 omap_mux= [OMAP] Override bootloader pin multiplexing.
2594 Format: <mux_mode0.mode_name=value>...
2595 For example, to override I2C bus2:
2596 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2597
Linus Torvalds1da177e2005-04-16 15:20:36 -07002598 oprofile.timer= [HW]
2599 Use timer interrupt instead of performance counters
2600
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002601 oprofile.cpu_type= Force an oprofile cpu type
2602 This might be useful if you have an older oprofile
2603 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002604 Format: { arch_perfmon }
2605 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002606 perfmon on Intel CPUs instead of the
2607 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002608 timer: [X86] Force use of architectural NMI
2609 timer mode (see also oprofile.timer
2610 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002611 [s390] Force legacy basic mode sampling
2612 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002613
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002614 oops=panic Always panic on oopses. Default is to just kill the
2615 process, but there is a small probability of
2616 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002617 This will also cause panics on machine check exceptions.
2618 Useful together with panic=30 to trigger a reboot.
2619
Randy Dunlapbcfde332010-06-07 17:10:38 -07002620 OSS [HW,OSS]
2621 See Documentation/sound/oss/oss-parameters.txt
2622
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002623 page_owner= [KNL] Boot-time page_owner enabling option.
2624 Storage of the information about who allocated
2625 each page is disabled in default. With this switch,
2626 we can turn it on.
2627 on: enable the feature
2628
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002629 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002630 timeout > 0: seconds before rebooting
2631 timeout = 0: wait forever
2632 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002633 Format: <timeout>
2634
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002635 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2636 on a WARN().
2637
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002638 crash_kexec_post_notifiers
2639 Run kdump after running panic-notifiers and dumping
2640 kmsg. This only for the users who doubt kdump always
2641 succeeds in any situation.
2642 Note that this also increases risks of kdump failure,
2643 because some panic notifiers can make the crashed
2644 kernel more unstable.
2645
Linus Torvalds1da177e2005-04-16 15:20:36 -07002646 parkbd.port= [HW] Parallel port number the keyboard adapter is
2647 connected to, default is 0.
2648 Format: <parport#>
2649 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2650 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002651 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002652
Randy Dunlapa9913042005-10-23 12:57:11 -07002653 parport= [HW,PPT] Specify parallel ports. 0 disables.
2654 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2655 Use 'auto' to force the driver to use any
2656 IRQ/DMA settings detected (the default is to
2657 ignore detected IRQ/DMA settings because of
2658 possible conflicts). You can specify the base
2659 address, IRQ, and DMA settings; IRQ and DMA
2660 should be numbers, or 'auto' (for using detected
2661 settings on that particular port), or 'nofifo'
2662 (to avoid using a FIFO even if it is detected).
2663 Parallel ports are assigned in the order they
2664 are specified on the command line, starting
2665 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002666
Randy Dunlapa9913042005-10-23 12:57:11 -07002667 parport_init_mode= [HW,PPT]
2668 Configure VIA parallel port to operate in
2669 a specific mode. This is necessary on Pegasos
2670 computer where firmware has no options for setting
2671 up parallel port mode and sets it to spp.
2672 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002673 Format: [spp|ps2|epp|ecp|ecpepp]
2674
Andrew Mortondd287792006-03-23 03:00:57 -08002675 pause_on_oops=
2676 Halt all CPUs after the first oops has been printed for
2677 the specified number of seconds. This is to be used if
2678 your oopses keep scrolling off the screen.
2679
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680 pcbit= [HW,ISDN]
2681
2682 pcd. [PARIDE]
2683 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002684 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002685
Randy Dunlapa9913042005-10-23 12:57:11 -07002686 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002687 earlydump [X86] dump PCI config space before the kernel
2688 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002689 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002690 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002691 the hardware directly. Use this if your machine
2692 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002693 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002694 hardware access methods are allowed. Use this
2695 if you experience crashes upon bootup and you
2696 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002697 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002698 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002699 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002700 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002701 noaer [PCIE] If the PCIEAER kernel config parameter is
2702 enabled, this kernel boot option can be used to
2703 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002704 nodomains [PCI] Disable support for multiple PCI
2705 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302706 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002707 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002708 check_enable_amd_mmconf [X86] check for and enable
2709 properly configured MMIO access to PCI
2710 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002711 nomsi [MSI] If the PCI_MSI kernel config parameter is
2712 enabled, this kernel boot option can be used to
2713 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002714 noioapicquirk [APIC] Disable all boot interrupt quirks.
2715 Safety option to keep boot IRQs enabled. This
2716 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002717 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2718 primary IO-APIC for bridges that cannot disable
2719 boot IRQs. This fixes a source of spurious IRQs
2720 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002721 noioapicreroute [APIC] Disable workaround that uses the
2722 boot IRQ equivalent of an IRQ that connects to
2723 a chipset where boot IRQs cannot be disabled.
2724 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002725 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002726 routing table. These calls are known to be buggy
2727 on several machines and they hang the machine
2728 when used, but on other computers it's the only
2729 way to get the interrupt routing table. Try
2730 this option if the kernel is unable to allocate
2731 IRQs or discover secondary PCI buses on your
2732 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002733 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002734 Use with caution as certain devices share
2735 address decoders between ROMs and other
2736 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002737 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002738 expansion ROMs that do not already have
2739 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002740 nobar [X86] Do not assign address space to the
2741 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002742 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002743 assigned automatically to PCI devices. You can
2744 make the kernel exclude IRQs of your ISA cards
2745 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002746 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002747 of the PIRQ table (normally generated
2748 by the BIOS) if it is outside the
2749 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002750 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002751 useful if the kernel is unable to find your
2752 secondary buses and you want to tell it
2753 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002754 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002755 numbers ourselves, overriding
2756 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002757 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002758 in the BIOS $PIR table. This is needed on
2759 some systems with broken BIOSes, notably
2760 some HP Pavilion N5400 and Omnibook XE3
2761 notebooks. This will have no effect if ACPI
2762 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002763 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002764 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002765 use_crs [X86] Use PCI host bridge window information
2766 from ACPI. On BIOSes from 2008 or later, this
2767 is enabled by default. If you need to use this,
2768 please report a bug.
2769 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2770 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002771 routeirq Do IRQ routing for all PCI devices.
2772 This is normally done in pci_enable_device(),
2773 so this option is a temporary workaround
2774 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002775 skip_isa_align [X86] do not align io start addr, so can
2776 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002777 firmware [ARM] Do not re-enumerate the bus but instead
2778 just use the configuration from the
2779 bootloader. This is currently used on
2780 IXP2000 systems where the bus has to be
2781 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002782 noearly [X86] Don't do any early type 1 scanning.
2783 This might help on some broken boards which
2784 machine check when some devices' config space
2785 is read. But various workarounds are disabled
2786 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002787 bfsort Sort PCI devices into breadth-first order.
2788 This sorting is done to get a device
2789 order compatible with older (<= 2.4) kernels.
2790 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002791 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2792 tuning and use the BIOS-configured MPS defaults.
2793 pcie_bus_safe Set every device's MPS to the largest value
2794 supported by all devices below the root complex.
2795 pcie_bus_perf Set device MPS to the largest allowable MPS
2796 based on its parent bus. Also set MRRS (Max
2797 Read Request Size) to the largest supported
2798 value (no larger than the MPS that the device
2799 or bus can support) for best performance.
2800 pcie_bus_peer2peer Set every device's MPS to 128B, which
2801 every device is guaranteed to support. This
2802 configuration allows peer-to-peer DMA between
2803 any pair of devices, possibly at the cost of
2804 reduced performance. This also guarantees
2805 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002806 cbiosize=nn[KMG] The fixed amount of bus space which is
2807 reserved for the CardBus bridge's IO window.
2808 The default value is 256 bytes.
2809 cbmemsize=nn[KMG] The fixed amount of bus space which is
2810 reserved for the CardBus bridge's memory
2811 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002812 resource_alignment=
2813 Format:
2814 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2815 Specifies alignment and device to reassign
2816 aligned memory resources.
2817 If <order of align> is not specified,
2818 PAGE_SIZE is used as alignment.
2819 PCI-PCI bridge can be specified, if resource
2820 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002821 ecrc= Enable/disable PCIe ECRC (transaction layer
2822 end-to-end CRC checking).
2823 bios: Use BIOS/firmware settings. This is the
2824 the default.
2825 off: Turn ECRC off
2826 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002827 hpiosize=nn[KMG] The fixed amount of bus space which is
2828 reserved for hotplug bridge's IO window.
2829 Default size is 256 bytes.
2830 hpmemsize=nn[KMG] The fixed amount of bus space which is
2831 reserved for hotplug bridge's memory window.
2832 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002833 realloc= Enable/disable reallocating PCI bridge resources
2834 if allocations done by BIOS are too small to
2835 accommodate resources required by all child
2836 devices.
2837 off: Turn realloc off
2838 on: Turn realloc on
2839 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002840 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002841 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2842 only look for one device below a PCIe downstream
2843 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002844
Chuck Ebberte5665a42008-09-24 20:40:34 -04002845 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2846 Management.
2847 off Disable ASPM.
2848 force Enable ASPM even on devices that claim not to support it.
2849 WARNING: Forcing ASPM on may cause system lockups.
2850
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002851 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2852 nomsi Do not use MSI for PCI Express Native Hotplug (this
2853 makes all PCIe ports use INTx for hotplug services).
2854
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002855 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002856 auto Ask the BIOS whether or not to use native PCIe services
2857 associated with PCIe ports (PME, hot-plug, AER). Use
2858 them only if that is allowed by the BIOS.
2859 native Use native PCIe services associated with PCIe ports
2860 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002861 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2862 ports driver.
2863
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002864 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002865 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002866 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002867
Linus Torvalds1da177e2005-04-16 15:20:36 -07002868 pcmv= [HW,PCMCIA] BadgePAD 4
2869
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302870 pd_ignore_unused
2871 [PM]
2872 Keep all power-domains already enabled by bootloader on,
2873 even if no driver has claimed them. This is useful
2874 for debug and development, but should not be
2875 needed on a platform with proper driver support.
2876
Linus Torvalds1da177e2005-04-16 15:20:36 -07002877 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002878 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002879
2880 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2881 boot time.
2882 Format: { 0 | 1 }
2883 See arch/parisc/kernel/pdc_chassis.c
2884
Tejun Heof58dc012009-08-14 15:00:50 +09002885 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002886 Currently supported values are "embed" and "page".
2887 Archs may support subset or none of the selections.
2888 See comments in mm/percpu.c for details on each
2889 allocator. This parameter is primarily for debugging
2890 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002891
Linus Torvalds1da177e2005-04-16 15:20:36 -07002892 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002893 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002894
2895 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002896 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002897
2898 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002899 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002900
2901 plip= [PPT,NET] Parallel port network link
2902 Format: { parport<nr> | timid | 0 }
2903 See also Documentation/parport.txt.
2904
Randy Dunlap16290242011-08-13 12:34:52 -07002905 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002906 Override pmtimer IOPort with a hex value.
2907 e.g. pmtmr=0x508
2908
Bjorn Helgaas96242112011-08-11 12:14:05 -06002909 pnp.debug=1 [PNP]
2910 Enable PNP debug messages (depends on the
2911 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2912 via /sys/module/pnp/parameters/debug. We always show
2913 current resource usage; turning this on also shows
2914 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002915
Linus Torvalds1da177e2005-04-16 15:20:36 -07002916 pnpacpi= [ACPI]
2917 { off }
2918
2919 pnpbios= [ISAPNP]
2920 { on | off | curr | res | no-curr | no-res }
2921
2922 pnp_reserve_irq=
2923 [ISAPNP] Exclude IRQs for the autoconfiguration
2924
2925 pnp_reserve_dma=
2926 [ISAPNP] Exclude DMAs for the autoconfiguration
2927
2928 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002929 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002930
2931 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002932 [ISAPNP] Exclude memory regions for the
2933 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002934 Ranges are in pairs (memory base and size).
2935
Randy Dunlap4af94f32009-04-17 18:30:28 -07002936 ports= [IP_VS_FTP] IPVS ftp helper module
2937 Default is 21.
2938 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2939 may be specified.
2940 Format: <port>,<port>....
2941
Ingo Molnar45807a12007-07-15 23:40:10 -07002942 print-fatal-signals=
2943 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002944
2945 If enabled, warn about various signal handling
2946 related application anomalies: too many signals,
2947 too many POSIX.1 timers, fatal signals causing a
2948 coredump - etc.
2949
2950 If you hit the warning due to signal overflow,
2951 you might want to try "ulimit -i unlimited".
2952
Ingo Molnar45807a12007-07-15 23:40:10 -07002953 default: off.
2954
Matthew Garrettc22ab332012-03-05 14:59:10 -08002955 printk.always_kmsg_dump=
2956 Trigger kmsg_dump for cases other than kernel oops or
2957 panics
2958 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2959 default: disabled
2960
Randy Dunlape84845c2007-07-15 23:40:25 -07002961 printk.time= Show timing data prefixed to each printk message line
2962 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2963
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002964 processor.max_cstate= [HW,ACPI]
2965 Limit processor to maximum C-state
2966 max_cstate=9 overrides any DMI blacklist limit.
2967
2968 processor.nocst [HW,ACPI]
2969 Ignore the _CST method to determine C-states,
2970 instead using the legacy FADT method
2971
Linus Torvalds1da177e2005-04-16 15:20:36 -07002972 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002973 Format: [schedule,]<number>
2974 Param: "schedule" - profile schedule points.
2975 Param: <number> - step/bucket size as a power of 2 for
2976 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002977 Param: "sleep" - profile D-state sleeping (millisecs).
2978 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002979 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002980
Linus Torvalds1da177e2005-04-16 15:20:36 -07002981 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2982 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002983 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002984
Randy Dunlapa9913042005-10-23 12:57:11 -07002985 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2986 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002987 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2988 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002989 psmouse.resetafter= [HW,MOUSE]
2990 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002991 (0 = never).
2992 psmouse.resolution=
2993 [HW,MOUSE] Set desired mouse resolution, in dpi.
2994 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002995 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002996 0 = disabled, 1 = enabled (default).
2997
Matthew Garrettdee28e72011-07-21 16:57:55 -04002998 pstore.backend= Specify the name of the pstore backend to use
2999
Linus Torvalds1da177e2005-04-16 15:20:36 -07003000 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003001 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003002
Kay Sieversdc8c8582007-08-15 12:25:38 +02003003 pty.legacy_count=
3004 [KNL] Number of legacy pty's. Overwrites compiled-in
3005 default number.
3006
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003007 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003008
Linus Torvalds1da177e2005-04-16 15:20:36 -07003009 r128= [HW,DRM]
3010
3011 raid= [HW,RAID]
3012 See Documentation/md.txt.
3013
Randy Dunlapa9913042005-10-23 12:57:11 -07003014 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003015 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07003016
Linus Torvalds1da177e2005-04-16 15:20:36 -07003017 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003018 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003019
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003020 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003021 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3022 the specified list of CPUs to be no-callback CPUs.
3023 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003024 be offloaded to "rcuox/N" kthreads created for
3025 that purpose, where "x" is "b" for RCU-bh, "p"
3026 for RCU-preempt, and "s" for RCU-sched, and "N"
3027 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003028 offloaded CPUs, which can be useful for HPC and
3029 real-time workloads. It can also improve energy
3030 efficiency for asymmetric multiprocessors.
3031
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003032 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003033 Rather than requiring that offloaded CPUs
3034 (specified by rcu_nocbs= above) explicitly
3035 awaken the corresponding "rcuoN" kthreads,
3036 make these kthreads poll for callbacks.
3037 This improves the real-time response for the
3038 offloaded CPUs by relieving them of the need to
3039 wake up the corresponding kthread, but degrades
3040 energy efficiency by requiring that the kthreads
3041 periodically wake up to do the polling.
3042
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003043 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003044 Set maximum number of finished RCU callbacks to
3045 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003046
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003047 rcutree.dump_tree= [KNL]
3048 Dump the structure of the rcu_node combining tree
3049 out at early boot. This is used for diagnostic
3050 purposes, to verify correct tree setup.
3051
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003052 rcutree.gp_cleanup_delay= [KNL]
3053 Set the number of jiffies to delay each step of
3054 RCU grace-period cleanup. This only has effect
3055 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3056
Paul E. McKenney37745d22015-01-22 18:24:08 -08003057 rcutree.gp_init_delay= [KNL]
3058 Set the number of jiffies to delay each step of
3059 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003060 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3061 is set.
3062
3063 rcutree.gp_preinit_delay= [KNL]
3064 Set the number of jiffies to delay each step of
3065 RCU grace-period pre-initialization, that is,
3066 the propagation of recent CPU-hotplug changes up
3067 the rcu_node combining tree. This only has effect
3068 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003069
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003070 rcutree.rcu_fanout_exact= [KNL]
3071 Disable autobalancing of the rcu_node combining
3072 tree. This is used by rcutorture, and might
3073 possibly be useful for architectures having high
3074 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003075
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003076 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003077 Increase the number of CPUs assigned to each
3078 leaf rcu_node structure. Useful for very large
3079 systems.
3080
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003081 rcutree.jiffies_till_sched_qs= [KNL]
3082 Set required age in jiffies for a
3083 given grace period before RCU starts
3084 soliciting quiescent-state help from
3085 rcu_note_context_switch().
3086
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003087 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003088 Set delay from grace-period initialization to
3089 first attempt to force quiescent states.
3090 Units are jiffies, minimum value is zero,
3091 and maximum value is HZ.
3092
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003093 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003094 Set delay between subsequent attempts to force
3095 quiescent states. Units are jiffies, minimum
3096 value is one, and maximum value is HZ.
3097
Clark Williams21871d72014-09-12 21:21:09 -05003098 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003099 Set the SCHED_FIFO priority of the RCU per-CPU
3100 kthreads (rcuc/N). This value is also used for
3101 the priority of the RCU boost threads (rcub/N)
3102 and for the RCU grace-period kthreads (rcu_bh,
3103 rcu_preempt, and rcu_sched). If RCU_BOOST is
3104 set, valid values are 1-99 and the default is 1
3105 (the least-favored priority). Otherwise, when
3106 RCU_BOOST is not set, valid values are 0-99 and
3107 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003108
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003109 rcutree.rcu_nocb_leader_stride= [KNL]
3110 Set the number of NOCB kthread groups, which
3111 defaults to the square root of the number of
3112 CPUs. Larger numbers reduces the wakeup overhead
3113 on the per-CPU grace-period kthreads, but increases
3114 that same overhead on each group's leader.
3115
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003116 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003117 Set threshold of queued RCU callbacks beyond which
3118 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003119
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003120 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003121 Set threshold of queued RCU callbacks below which
3122 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003123
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003124 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003125 Set wakeup interval for idle CPUs that have
3126 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003127
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003128 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003129 Set wakeup interval for idle CPUs that have
3130 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3131 Lazy RCU callbacks are those which RCU can
3132 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003133
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003134 rcutorture.cbflood_inter_holdoff= [KNL]
3135 Set holdoff time (jiffies) between successive
3136 callback-flood tests.
3137
3138 rcutorture.cbflood_intra_holdoff= [KNL]
3139 Set holdoff time (jiffies) between successive
3140 bursts of callbacks within a given callback-flood
3141 test.
3142
3143 rcutorture.cbflood_n_burst= [KNL]
3144 Set the number of bursts making up a given
3145 callback-flood test. Set this to zero to
3146 disable callback-flood testing.
3147
3148 rcutorture.cbflood_n_per_burst= [KNL]
3149 Set the number of callbacks to be registered
3150 in a given burst of a callback-flood test.
3151
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003152 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003153 Set duration of force_quiescent_state bursts
3154 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003155
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003156 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003157 Set holdoff time within force_quiescent_state bursts
3158 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003159
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003160 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003161 Set wait time between force_quiescent_state bursts
3162 in seconds.
3163
3164 rcutorture.gp_cond= [KNL]
3165 Use conditional/asynchronous update-side
3166 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003167
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003168 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003169 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003170
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003171 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003172 Use normal (non-expedited) asynchronous
3173 update-side primitives, if available.
3174
3175 rcutorture.gp_sync= [KNL]
3176 Use normal (non-expedited) synchronous
3177 update-side primitives, if available. If all
3178 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3179 rcutorture.gp_normal=, and rcutorture.gp_sync=
3180 are zero, rcutorture acts as if is interpreted
3181 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003182
3183 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003184 Set callbacks/threads for rcu_barrier() testing.
3185
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003186 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003187 Set number of concurrent RCU writers. These just
3188 stress RCU, they don't participate in the actual
3189 test, hence the "fake".
3190
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003191 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003192 Set number of RCU readers. The value -1 selects
3193 N-1, where N is the number of CPUs. A value
3194 "n" less than -1 selects N-n-2, where N is again
3195 the number of CPUs. For example, -2 selects N
3196 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003197
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003198 rcutorture.object_debug= [KNL]
3199 Enable debug-object double-call_rcu() testing.
3200
3201 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003202 Set time (s) after boot for CPU-hotplug testing.
3203
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003204 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003205 Set time (s) between CPU-hotplug operations, or
3206 zero to disable CPU-hotplug testing.
3207
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003208 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003209 Set task-shuffle interval (s). Shuffling tasks
3210 allows some CPUs to go into dyntick-idle mode
3211 during the rcutorture test.
3212
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003213 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003214 Set time (s) after boot system shutdown. This
3215 is useful for hands-off automated testing.
3216
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003217 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003218 Duration of CPU stall (s) to test RCU CPU stall
3219 warnings, zero to disable.
3220
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003221 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003222 Time to wait (s) after boot before inducing stall.
3223
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003224 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003225 Time (s) between statistics printk()s.
3226
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003227 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003228 Time (s) to stutter testing, for example, specifying
3229 five seconds causes the test to run for five seconds,
3230 wait for five seconds, and so on. This tests RCU's
3231 ability to transition abruptly to and from idle.
3232
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003233 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003234 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3235 "Maybe" means test if the RCU implementation
3236 under test support RCU priority boosting.
3237
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003238 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003239 Duration (s) of each individual boost test.
3240
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003241 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003242 Interval (s) between each boost test.
3243
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003244 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003245 Test RCU's dyntick-idle handling. See also the
3246 rcutorture.shuffle_interval parameter.
3247
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003248 rcutorture.torture_runnable= [BOOT]
3249 Start rcutorture running at boot time.
3250
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003251 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003252 Specify the RCU implementation to test.
3253
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003254 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003255 Enable additional printk() statements.
3256
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003257 rcupdate.rcu_expedited= [KNL]
3258 Use expedited grace-period primitives, for
3259 example, synchronize_rcu_expedited() instead
3260 of synchronize_rcu(). This reduces latency,
3261 but can increase CPU utilization, degrade
3262 real-time latency, and degrade energy efficiency.
3263
3264 rcupdate.rcu_cpu_stall_suppress= [KNL]
3265 Suppress RCU CPU stall warning messages.
3266
3267 rcupdate.rcu_cpu_stall_timeout= [KNL]
3268 Set timeout for RCU CPU stall warning messages.
3269
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003270 rcupdate.rcu_task_stall_timeout= [KNL]
3271 Set timeout in jiffies for RCU task stall warning
3272 messages. Disable with a value less than or equal
3273 to zero.
3274
Pranith Kumar74860fe2014-09-19 11:34:09 -04003275 rcupdate.rcu_self_test= [KNL]
3276 Run the RCU early boot self tests
3277
3278 rcupdate.rcu_self_test_bh= [KNL]
3279 Run the RCU bh early boot self tests
3280
3281 rcupdate.rcu_self_test_sched= [KNL]
3282 Run the RCU sched early boot self tests
3283
Olof Johanssonffdfc402005-09-06 15:17:19 -07003284 rdinit= [KNL]
3285 Format: <full_path>
3286 Run specified binary instead of /init from the ramdisk,
3287 used for early userspace startup. See initrd.
3288
Robin Holt1b3a5d02013-07-08 16:01:42 -07003289 reboot= [KNL]
3290 Format (x86 or x86_64):
3291 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3292 [[,]s[mp]#### \
3293 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3294 [[,]f[orce]
3295 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3296 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3297 reboot_force is either force or not specified,
3298 reboot_cpu is s[mp]#### with #### being the processor
3299 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003300
Paul Jackson46b6d942008-07-04 10:00:09 -07003301 relax_domain_level=
3302 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003303 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003304
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003305 relative_sleep_states=
3306 [SUSPEND] Use sleep state labeling where the deepest
3307 state available other than hibernation is always "mem".
3308 Format: { "0" | "1" }
3309 0 -- Traditional sleep state labels.
3310 1 -- Relative sleep state labels.
3311
Linus Torvalds1da177e2005-04-16 15:20:36 -07003312 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3313
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003314 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003315 Format: nn[KMG]
3316 Reserves a hole at the top of the kernel virtual
3317 address space.
3318
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003319 reservelow= [X86]
3320 Format: nn[K]
3321 Set the amount of memory to reserve for BIOS at
3322 the bottom of the address space.
3323
Vivek Goyal7e962872006-09-27 01:50:44 -07003324 reset_devices [KNL] Force drivers to reset the underlying device
3325 during initialization.
3326
Randy Dunlapa9913042005-10-23 12:57:11 -07003327 resume= [SWSUSP]
3328 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003329 Format:
3330 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003331
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003332 resume_offset= [SWSUSP]
3333 Specify the offset from the beginning of the partition
3334 given by "resume=" at which the swap header is located,
3335 in <PAGE_SIZE> units (needed only for swap files).
3336 See Documentation/power/swsusp-and-swap-files.txt
3337
Barry Songf126f732011-10-10 23:38:41 +02003338 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3339 read the resume files
3340
Barry Song6f8d7022011-10-06 20:34:46 +02003341 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3342 Useful for devices that are detected asynchronously
3343 (e.g. USB and MMC devices).
3344
Bojan Smojverf996fc92010-09-09 23:06:23 +02003345 hibernate= [HIBERNATION]
3346 noresume Don't check if there's a hibernation image
3347 present during boot.
3348 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003349 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003350
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003351 retain_initrd [RAM] Keep initrd memory after extraction
3352
Andrew Clausen0efbb782015-01-09 20:24:55 +00003353 rfkill.default_state=
3354 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3355 etc. communication is blocked by default.
3356 1 Unblocked.
3357
3358 rfkill.master_switch_mode=
3359 0 The "airplane mode" button does nothing.
3360 1 The "airplane mode" button toggles between everything
3361 blocked and the previous configuration.
3362 2 The "airplane mode" button toggles between everything
3363 blocked and everything unblocked.
3364
Linus Torvalds1da177e2005-04-16 15:20:36 -07003365 rhash_entries= [KNL,NET]
3366 Set number of hash buckets for route cache
3367
Linus Torvalds1da177e2005-04-16 15:20:36 -07003368 ro [KNL] Mount root device read-only on boot
3369
3370 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003371 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003372
3373 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3374 mount the root filesystem
3375
3376 rootflags= [KNL] Set root filesystem mount option string
3377
3378 rootfstype= [KNL] Set root filesystem type
3379
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003380 rootwait [KNL] Wait (indefinitely) for root device to show up.
3381 Useful for devices that are detected asynchronously
3382 (e.g. USB and MMC devices).
3383
Robert Tivy5c71d612013-03-28 18:41:46 -07003384 rproc_mem=nn[KMG][@address]
3385 [KNL,ARM,CMA] Remoteproc physical memory block.
3386 Memory area to be used by remote processor image,
3387 managed by CMA.
3388
Linus Torvalds1da177e2005-04-16 15:20:36 -07003389 rw [KNL] Mount root device read-write on boot
3390
3391 S [KNL] Run init in single mode
3392
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003393 s390_iommu= [HW,S390]
3394 Set s390 IOTLB flushing mode
3395 strict
3396 With strict flushing every unmap operation will result in
3397 an IOTLB flush. Default is lazy flushing before reuse,
3398 which is faster.
3399
Linus Torvalds1da177e2005-04-16 15:20:36 -07003400 sa1100ir [NET]
3401 See drivers/net/irda/sa1100_ir.c.
3402
Linus Torvalds1da177e2005-04-16 15:20:36 -07003403 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003404
Mike Travisf6630112009-11-17 18:22:15 -06003405 sched_debug [KNL] Enables verbose scheduler debug messages.
3406
Mike Galbraith5307c952012-05-08 12:20:58 +02003407 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3408 xtime_lock contention on larger systems, and/or RCU lock
3409 contention on all systems with CONFIG_MAXSMP set.
3410 Format: { "0" | "1" }
3411 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3412 1 -- enable.
3413 Note: increases power consumption, thus should only be
3414 enabled if running jitter sensitive (HPC/RT) workloads.
3415
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003416 security= [SECURITY] Choose a security module to enable at boot.
3417 If this boot parameter is not specified, only the first
3418 security module asking for security registration will be
3419 loaded. An invalid security module name will be treated
3420 as if no module has been chosen.
3421
3422 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003423 Format: { "0" | "1" }
3424 See security/selinux/Kconfig help text.
3425 0 -- disable.
3426 1 -- enable.
3427 Default value is set via kernel config option.
3428 If enabled at boot time, /selinux/disable can be used
3429 later to disable prior to initial policy load.
3430
John Johansenc1c124e2010-07-29 14:48:09 -07003431 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3432 Format: { "0" | "1" }
3433 See security/apparmor/Kconfig help text
3434 0 -- disable.
3435 1 -- enable.
3436 Default value is set via kernel config option.
3437
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003438 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003439
Linus Torvalds1da177e2005-04-16 15:20:36 -07003440 shapers= [NET]
3441 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003442
Yinghai Lub05f78f2008-08-22 01:32:50 -07003443 show_msr= [x86] show boot-time MSR settings
3444 Format: { <integer> }
3445 Show boot-time (BIOS-initialized) MSR settings.
3446 The parameter means the number of CPUs to show,
3447 for example 1 means boot CPU only.
3448
Linus Torvalds1da177e2005-04-16 15:20:36 -07003449 simeth= [IA-64]
3450 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003451
Linus Torvalds1da177e2005-04-16 15:20:36 -07003452 slram= [HW,MTD]
3453
Joonsoo Kim423c9292014-10-09 15:26:22 -07003454 slab_nomerge [MM]
3455 Disable merging of slabs with similar size. May be
3456 necessary if there is some reason to distinguish
3457 allocs to different slabs. Debug options disable
3458 merging on their own.
3459 For more information see Documentation/vm/slub.txt.
3460
David Rientjes3df1ccc2011-10-18 22:09:28 -07003461 slab_max_order= [MM, SLAB]
3462 Determines the maximum allowed order for slabs.
3463 A high setting may cause OOMs due to memory
3464 fragmentation. Defaults to 1 for systems with
3465 more than 32MB of RAM, 0 otherwise.
3466
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003467 slub_debug[=options[,slabs]] [MM, SLUB]
3468 Enabling slub_debug allows one to determine the
3469 culprit if slab objects become corrupted. Enabling
3470 slub_debug can create guard zones around objects and
3471 may poison objects when not in use. Also tracks the
3472 last alloc / free. For more information see
3473 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003474
3475 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003476 Determines the maximum allowed order for slabs.
3477 A high setting may cause OOMs due to memory
3478 fragmentation. For more information see
3479 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003480
3481 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003482 The minimum number of objects per slab. SLUB will
3483 increase the slab order up to slub_max_order to
3484 generate a sufficiently large slab able to contain
3485 the number of objects indicated. The higher the number
3486 of objects the smaller the overhead of tracking slabs
3487 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003488 For more information see Documentation/vm/slub.txt.
3489
3490 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003491 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003492 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003493 For more information see Documentation/vm/slub.txt.
3494
3495 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003496 Same with slab_nomerge. This is supported for legacy.
3497 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003498
Linus Torvalds1da177e2005-04-16 15:20:36 -07003499 smart2= [HW]
3500 Format: <io1>[,<io2>[,...,<io8>]]
3501
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003502 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3503 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3504 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3505 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3506 smsc-ircc2.ircc_irq= [HW] IRQ line
3507 smsc-ircc2.ircc_dma= [HW] DMA channel
3508 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3509 0: Toshiba Satellite 1800 (GP data pin select)
3510 1: Fast pin select (default)
3511 2: ATC IRMode
3512
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003513 softlockup_panic=
3514 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003515 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003516
Aaron Tomlined235872014-06-23 13:22:05 -07003517 softlockup_all_cpu_backtrace=
3518 [KNL] Should the soft-lockup detector generate
3519 backtraces on all cpus.
3520 Format: <integer>
3521
Linus Torvalds1da177e2005-04-16 15:20:36 -07003522 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003523 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003524
Linus Torvalds1da177e2005-04-16 15:20:36 -07003525 spia_io_base= [HW,MTD]
3526 spia_fio_base=
3527 spia_pedr=
3528 spia_peddr=
3529
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003530 stacktrace [FTRACE]
3531 Enabled the stack tracer on boot up.
3532
Steven Rostedt762e1202011-12-19 22:01:00 -05003533 stacktrace_filter=[function-list]
3534 [FTRACE] Limit the functions that the stack tracer
3535 will trace at boot up. function-list is a comma separated
3536 list of functions. This list can be changed at run
3537 time by the stack_trace_filter file in the debugfs
3538 tracing directory. Note, this enables stack tracing
3539 and the stacktrace above is not needed.
3540
Linus Torvalds1da177e2005-04-16 15:20:36 -07003541 sti= [PARISC,HW]
3542 Format: <num>
3543 Set the STI (builtin display/keyboard on the HP-PARISC
3544 machines) console (graphic card) which should be used
3545 as the initial boot-console.
3546 See also comment in drivers/video/console/sticore.c.
3547
3548 sti_font= [HW]
3549 See comment in drivers/video/console/sticore.c.
3550
3551 stifb= [HW]
3552 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3553
Trond Myklebustcbf11072009-08-09 15:06:19 -04003554 sunrpc.min_resvport=
3555 sunrpc.max_resvport=
3556 [NFS,SUNRPC]
3557 SunRPC servers often require that client requests
3558 originate from a privileged port (i.e. a port in the
3559 range 0 < portnr < 1024).
3560 An administrator who wishes to reserve some of these
3561 ports for other uses may adjust the range that the
3562 kernel's sunrpc client considers to be privileged
3563 using these two parameters to set the minimum and
3564 maximum port values.
3565
Greg Banks42a7fc42007-03-06 01:42:23 -08003566 sunrpc.pool_mode=
3567 [NFS]
3568 Control how the NFS server code allocates CPUs to
3569 service thread pools. Depending on how many NICs
3570 you have and where their interrupts are bound, this
3571 option will affect which CPUs will do NFS serving.
3572 Note: this parameter cannot be changed while the
3573 NFS server is running.
3574
3575 auto the server chooses an appropriate mode
3576 automatically using heuristics
3577 global a single global pool contains all CPUs
3578 percpu one pool for each CPU
3579 pernode one pool for each NUMA node (equivalent
3580 to global on non-NUMA machines)
3581
Trond Myklebustcbf11072009-08-09 15:06:19 -04003582 sunrpc.tcp_slot_table_entries=
3583 sunrpc.udp_slot_table_entries=
3584 [NFS,SUNRPC]
3585 Sets the upper limit on the number of simultaneous
3586 RPC calls that can be sent from the client to a
3587 server. Increasing these values may allow you to
3588 improve throughput, but will also increase the
3589 amount of memory reserved for use by the client.
3590
Brian Norris1d4a9c12015-02-22 21:16:49 -08003591 suspend.pm_test_delay=
3592 [SUSPEND]
3593 Sets the number of seconds to remain in a suspend test
3594 mode before resuming the system (see
3595 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3596 is set. Default value is 5.
3597
Michal Hocko07555ac2013-08-22 16:35:46 -07003598 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003599 [KNL] Enable accounting of swap in memory resource
3600 controller if no parameter or 1 is given or disable
3601 it if 0 is given (See Documentation/cgroups/memory.txt)
3602
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003603 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3604 Format: { <int> | force }
3605 <int> -- Number of I/O TLB slabs
3606 force -- force using of bounce buffers even if they
3607 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003608
Linus Torvalds1da177e2005-04-16 15:20:36 -07003609 switches= [HW,M68k]
3610
Andi Kleene52eec12010-09-08 16:54:17 +02003611 sysfs.deprecated=0|1 [KNL]
3612 Enable/disable old style sysfs layout for old udev
3613 on older distributions. When this option is enabled
3614 very new udev will not work anymore. When this option
3615 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3616 in older udev will not work anymore.
3617 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3618 the kernel configuration.
3619
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003620 sysrq_always_enabled
3621 [KNL]
3622 Ignore sysrq setting - this boot parameter will
3623 neutralize any effect of /proc/sys/kernel/sysrq.
3624 Useful for debugging.
3625
Fabian Frederick747029a2014-11-06 19:46:50 +01003626 tcpmhash_entries= [KNL,NET]
3627 Set the number of tcp_metrics_hash slots.
3628 Default value is 8192 or 16384 depending on total
3629 ram pages. This is used to specify the TCP metrics
3630 cache size. See Documentation/networking/ip-sysctl.txt
3631 "tcp_no_metrics_save" section for more details.
3632
Linus Torvalds1da177e2005-04-16 15:20:36 -07003633 tdfx= [HW,DRM]
3634
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003635 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003636 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003637 standby suspend) or "freeze" (for suspend type freeze)
3638 as the system sleep state during system startup with
3639 the optional capability to repeat N number of times.
3640 The system is woken from this state using a
3641 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003642
Linus Torvalds1da177e2005-04-16 15:20:36 -07003643 thash_entries= [KNL,NET]
3644 Set number of hash buckets for TCP connection
3645
Len Brownf8707ec2007-08-12 00:12:54 -04003646 thermal.act= [HW,ACPI]
3647 -1: disable all active trip points in all thermal zones
3648 <degrees C>: override all lowest active trip points
3649
Len Brownc52a7412007-08-14 15:49:32 -04003650 thermal.crt= [HW,ACPI]
3651 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003652 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003653
Len Brownf5487142007-08-12 00:12:44 -04003654 thermal.nocrt= [HW,ACPI]
3655 Set to disable actions on ACPI thermal zone
3656 critical and hot trip points.
3657
Len Brown72b33ef2007-08-12 00:12:17 -04003658 thermal.off= [HW,ACPI]
3659 1: disable ACPI thermal control
3660
Len Browna70cdc52007-08-12 00:12:35 -04003661 thermal.psv= [HW,ACPI]
3662 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003663 <degrees C>: override all passive trip points to this
3664 value
Len Browna70cdc52007-08-12 00:12:35 -04003665
Len Brown730ff342007-08-12 00:12:26 -04003666 thermal.tzp= [HW,ACPI]
3667 Specify global default ACPI thermal zone polling rate
3668 <deci-seconds>: poll all this frequency
3669 0: no polling (default)
3670
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003671 threadirqs [KNL]
3672 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003673 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003674
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003675 tmem [KNL,XEN]
3676 Enable the Transcendent memory driver if built-in.
3677
3678 tmem.cleancache=0|1 [KNL, XEN]
3679 Default is on (1). Disable the usage of the cleancache
3680 API to send anonymous pages to the hypervisor.
3681
3682 tmem.frontswap=0|1 [KNL, XEN]
3683 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003684 API to send swap pages to the hypervisor. If disabled
3685 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003686
3687 tmem.selfballooning=0|1 [KNL, XEN]
3688 Default is on (1). Disable the driving of swap pages
3689 to the hypervisor.
3690
3691 tmem.selfshrinking=0|1 [KNL, XEN]
3692 Default is on (1). Partial swapoff that immediately
3693 transfers pages from Xen hypervisor back to the
3694 kernel based on different criteria.
3695
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003696 topology= [S390]
3697 Format: {off | on}
3698 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003699 topology information if the hardware supports this.
3700 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003701 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003702 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003703
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003704 topology_updates= [KNL, PPC, NUMA]
3705 Format: {off}
3706 Specify if the kernel should ignore (off)
3707 topology updates sent by the hypervisor to this
3708 LPAR.
3709
Linus Torvalds1da177e2005-04-16 15:20:36 -07003710 tp720= [HW,PS2]
3711
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003712 tpm_suspend_pcr=[HW,TPM]
3713 Format: integer pcr id
3714 Specify that at suspend time, the tpm driver
3715 should extend the specified pcr with zeros,
3716 as a workaround for some chips which fail to
3717 flush the last written pcr on TPM_SaveState.
3718 This will guarantee that all the other pcrs
3719 are saved.
3720
Li Zefan9d612be2009-06-24 17:33:15 +08003721 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003722 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003723
Li Zefan020e5f82009-07-01 10:47:05 +08003724 trace_event=[event-list]
3725 [FTRACE] Set and start specified trace events in order
3726 to facilitate early boot debugging.
3727 See also Documentation/trace/events.txt
3728
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003729 trace_options=[option-list]
3730 [FTRACE] Enable or disable tracer options at boot.
3731 The option-list is a comma delimited list of options
3732 that can be enabled or disabled just as if you were
3733 to echo the option name into
3734
3735 /sys/kernel/debug/tracing/trace_options
3736
3737 For example, to enable stacktrace option (to dump the
3738 stack trace of each event), add to the command line:
3739
3740 trace_options=stacktrace
3741
3742 See also Documentation/trace/ftrace.txt "trace options"
3743 section.
3744
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003745 tp_printk[FTRACE]
3746 Have the tracepoints sent to printk as well as the
3747 tracing ring buffer. This is useful for early boot up
3748 where the system hangs or reboots and does not give the
3749 option for reading the tracing buffer or performing a
3750 ftrace_dump_on_oops.
3751
3752 To turn off having tracepoints sent to printk,
3753 echo 0 > /proc/sys/kernel/tracepoint_printk
3754 Note, echoing 1 into this file without the
3755 tracepoint_printk kernel cmdline option has no effect.
3756
3757 ** CAUTION **
3758
3759 Having tracepoints sent to printk() and activating high
3760 frequency tracepoints such as irq or sched, can cause
3761 the system to live lock.
3762
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003763 traceoff_on_warning
3764 [FTRACE] enable this option to disable tracing when a
3765 warning is hit. This turns off "tracing_on". Tracing can
3766 be enabled again by echoing '1' into the "tracing_on"
3767 file located in /sys/kernel/debug/tracing/
3768
3769 This option is useful, as it disables the trace before
3770 the WARNING dump is called, which prevents the trace to
3771 be filled with content caused by the warning output.
3772
3773 This option can also be set at run time via the sysctl
3774 option: kernel/traceoff_on_warning
3775
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003776 transparent_hugepage=
3777 [KNL]
3778 Format: [always|madvise|never]
3779 Can be used to control the default behavior of the system
3780 with respect to transparent hugepages.
3781 See Documentation/vm/transhuge.txt for more details.
3782
john stultzd3b8f882009-08-17 16:40:47 -07003783 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003784 Format: <string>
3785 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003786 disables clocksource verification at runtime, as well
3787 as the stability checks done at bootup. Used to enable
3788 high-resolution timer mode on older hardware, and in
3789 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003790 [x86] noirqtime: Do not use TSC to do irq accounting.
3791 Used to run time disable IRQ_TIME_ACCOUNTING on any
3792 platforms where RDTSC is slow and this accounting
3793 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003794
Randy Dunlapa9913042005-10-23 12:57:11 -07003795 turbografx.map[2|3]= [HW,JOY]
3796 TurboGraFX parallel port interface
3797 Format:
3798 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003799 See also Documentation/input/joystick-parport.txt
3800
Christian Kujaub6935f82011-05-31 15:22:05 +00003801 udbg-immortal [PPC] When debugging early kernel crashes that
3802 happen after console_init() and before a proper
3803 console driver takes over, this boot options might
3804 help "seeing" what's going on.
3805
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003806 uhash_entries= [KNL,NET]
3807 Set number of hash buckets for UDP/UDP-Lite connections
3808
Alan Stern5f8364b2006-12-05 16:29:55 -05003809 uhci-hcd.ignore_oc=
3810 [USB] Ignore overcurrent events (default N).
3811 Some badly-designed motherboards generate lots of
3812 bogus events, for ports that aren't wired to
3813 anything. Set this parameter to avoid log spamming.
3814 Note that genuine overcurrent events won't be
3815 reported either.
3816
Simon Arlotte3a61b02008-07-19 23:32:54 +01003817 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003818 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003819
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003820 usbcore.authorized_default=
3821 [USB] Default USB device authorization:
3822 (default -1 = authorized except for wireless USB,
3823 0 = not authorized, 1 = authorized)
3824
Alan Sternb5e795f2007-02-20 15:00:53 -05003825 usbcore.autosuspend=
3826 [USB] The autosuspend time delay (in seconds) used
3827 for newly-detected USB devices (default 2). This
3828 is the time required before an idle device will be
3829 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003830 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003831
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003832 usbcore.usbfs_snoop=
3833 [USB] Set to log all usbfs traffic (default 0 = off).
3834
3835 usbcore.blinkenlights=
3836 [USB] Set to cycle leds on hubs (default 0 = off).
3837
3838 usbcore.old_scheme_first=
3839 [USB] Start with the old device initialization
3840 scheme (default 0 = off).
3841
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003842 usbcore.usbfs_memory_mb=
3843 [USB] Memory limit (in MB) for buffers allocated by
3844 usbfs (default = 16, 0 = max = 2047).
3845
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003846 usbcore.use_both_schemes=
3847 [USB] Try the other device initialization scheme
3848 if the first one fails (default 1 = enabled).
3849
3850 usbcore.initial_descriptor_timeout=
3851 [USB] Specifies timeout for the initial 64-byte
3852 USB_REQ_GET_DESCRIPTOR request in milliseconds
3853 (default 5000 = 5.0 seconds).
3854
Linus Torvalds1da177e2005-04-16 15:20:36 -07003855 usbhid.mousepoll=
3856 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003857
Alan Sternd4f373e2008-11-10 14:07:45 -05003858 usb-storage.delay_use=
3859 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00003860 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05003861
3862 usb-storage.quirks=
3863 [UMS] A list of quirks entries to supplement or
3864 override the built-in unusual_devs list. List
3865 entries are separated by commas. Each entry has
3866 the form VID:PID:Flags where VID and PID are Vendor
3867 and Product ID values (4-digit hex numbers) and
3868 Flags is a set of characters, each corresponding
3869 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003870 a = SANE_SENSE (collect more than 18 bytes
3871 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003872 b = BAD_SENSE (don't collect more than 18
3873 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003874 c = FIX_CAPACITY (decrease the reported
3875 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003876 d = NO_READ_DISC_INFO (don't use
3877 READ_DISC_INFO command);
3878 e = NO_READ_CAPACITY_16 (don't use
3879 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003880 f = NO_REPORT_OPCODES (don't use report opcodes
3881 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02003882 g = MAX_SECTORS_240 (don't transfer more than
3883 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003884 h = CAPACITY_HEURISTICS (decrease the
3885 reported device capacity by one
3886 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003887 i = IGNORE_DEVICE (don't bind to this
3888 device);
3889 l = NOT_LOCKABLE (don't try to lock and
3890 unlock ejectable media);
3891 m = MAX_SECTORS_64 (don't transfer more
3892 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003893 n = INITIAL_READ10 (force a retry of the
3894 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003895 o = CAPACITY_OK (accept the capacity
3896 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003897 p = WRITE_CACHE (the device cache is ON
3898 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003899 r = IGNORE_RESIDUE (the device reports
3900 bogus residue values);
3901 s = SINGLE_LUN (the device has only one
3902 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003903 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3904 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003905 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003906 w = NO_WP_DETECT (don't test whether the
3907 medium is write-protected).
3908 Example: quirks=0419:aaf5:rl,0421:0433:rc
3909
Stephen Boydac1667d2011-08-13 12:34:50 -07003910 user_debug= [KNL,ARM]
3911 Format: <int>
3912 See arch/arm/Kconfig.debug help text.
3913 1 - undefined instruction events
3914 2 - system calls
3915 4 - invalid data aborts
3916 8 - SIGSEGV faults
3917 16 - SIGBUS faults
3918 Example: user_debug=31
3919
Ian Campbell14315592010-02-17 10:38:10 +00003920 userpte=
3921 [X86] Flags controlling user PTE allocations.
3922
3923 nohigh = do not allocate PTE pages in
3924 HIGHMEM regardless of setting
3925 of CONFIG_HIGHPTE.
3926
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303927 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003928 On X86_32, this is an alias for vdso32=. Otherwise:
3929
3930 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003931 vdso=0: disable VDSO mapping
3932
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003933 vdso32= [X86] Control the 32-bit vDSO
3934 vdso32=1: enable 32-bit VDSO
3935 vdso32=0 or vdso32=2: disable 32-bit VDSO
3936
3937 See the help text for CONFIG_COMPAT_VDSO for more
3938 details. If CONFIG_COMPAT_VDSO is set, the default is
3939 vdso32=0; otherwise, the default is vdso32=1.
3940
3941 For compatibility with older kernels, vdso32=2 is an
3942 alias for vdso32=0.
3943
3944 Try vdso32=0 if you encounter an error that says:
3945 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003946
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003947 vector= [IA-64,SMP]
3948 vector=percpu: enable percpu vector domain
3949
Linus Torvalds1da177e2005-04-16 15:20:36 -07003950 video= [FB] Frame buffer configuration
3951 See Documentation/fb/modedb.txt.
3952
Aaron Lu3afe6da2013-06-20 15:08:55 +08003953 video.brightness_switch_enabled= [0,1]
3954 If set to 1, on receiving an ACPI notify event
3955 generated by hotkey, video driver will adjust brightness
3956 level and then send out the event to user space through
3957 the allocated input device; If set to 0, video driver
3958 will only send out the event without touching backlight
3959 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02003960 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08003961
Pawel Moll81a054c2012-05-09 18:30:16 +01003962 virtio_mmio.device=
3963 [VMMIO] Memory mapped virtio (platform) device.
3964
3965 <size>@<baseaddr>:<irq>[:<id>]
3966 where:
3967 <size> := size (can use standard suffixes
3968 like K, M and G)
3969 <baseaddr> := physical base address
3970 <irq> := interrupt number (as passed to
3971 request_irq())
3972 <id> := (optional) platform device id
3973 example:
3974 virtio_mmio.device=1K@0x100b0000:48:7
3975
3976 Can be used multiple times for multiple devices.
3977
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003978 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003979 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003980 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003981 Use vga=ask for menu.
3982 This is actually a boot loader parameter; the value is
3983 passed to the kernel using a special protocol.
3984
Randy Dunlapa9913042005-10-23 12:57:11 -07003985 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003986 size of <nn>. This can be used to increase the
3987 minimum size (128MB on x86). It can also be used to
3988 decrease the size and leave more room for directly
3989 mapped kernel RAM.
3990
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003991 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3992 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003993
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003994 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3995 Format: <command>
3996
3997 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3998 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003999
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004000 vsyscall= [X86-64]
4001 Controls the behavior of vsyscalls (i.e. calls to
4002 fixed addresses of 0xffffffffff600x00 from legacy
4003 code). Most statically-linked binaries and older
4004 versions of glibc use these calls. Because these
4005 functions are at fixed addresses, they make nice
4006 targets for exploits that can control RIP.
4007
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004008 emulate [default] Vsyscalls turn into traps and are
4009 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004010
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004011 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004012 This is a little bit faster than trapping
4013 and makes a few dynamic recompilers work
4014 better than they would in emulation mode.
4015 It also makes exploits much easier to write.
4016
4017 none Vsyscalls don't work at all. This makes
4018 them quite hard to use for exploits but
4019 might break your system.
4020
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004021 vt.color= [VT] Default text color.
4022 Format: 0xYX, X = foreground, Y = background.
4023 Default: 0x07 = light gray on black.
4024
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004025 vt.cur_default= [VT] Default cursor shape.
4026 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4027 the parameters of the <Esc>[?A;B;Cc escape sequence;
4028 see VGA-softcursor.txt. Default: 2 = underline.
4029
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004030 vt.default_blu= [VT]
4031 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4032 Change the default blue palette of the console.
4033 This is a 16-member array composed of values
4034 ranging from 0-255.
4035
4036 vt.default_grn= [VT]
4037 Format: <green0>,<green1>,<green2>,...,<green15>
4038 Change the default green palette of the console.
4039 This is a 16-member array composed of values
4040 ranging from 0-255.
4041
4042 vt.default_red= [VT]
4043 Format: <red0>,<red1>,<red2>,...,<red15>
4044 Change the default red palette of the console.
4045 This is a 16-member array composed of values
4046 ranging from 0-255.
4047
4048 vt.default_utf8=
4049 [VT]
4050 Format=<0|1>
4051 Set system-wide default UTF-8 mode for all tty's.
4052 Default is 1, i.e. UTF-8 mode is enabled for all
4053 newly opened terminals.
4054
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004055 vt.global_cursor_default=
4056 [VT]
4057 Format=<-1|0|1>
4058 Set system-wide default for whether a cursor
4059 is shown on new VTs. Default is -1,
4060 i.e. cursors will be created by default unless
4061 overridden by individual drivers. 0 will hide
4062 cursors, 1 will display them.
4063
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004064 vt.italic= [VT] Default color for italic text; 0-15.
4065 Default: 2 = green.
4066
4067 vt.underline= [VT] Default color for underlined text; 0-15.
4068 Default: 3 = cyan.
4069
Randy Dunlap4724ba572010-05-03 11:42:52 -07004070 watchdog timers [HW,WDT] For information on watchdog timers,
4071 see Documentation/watchdog/watchdog-parameters.txt
4072 or other driver-specific files in the
4073 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004074
Tejun Heod55262c2013-04-01 11:23:38 -07004075 workqueue.disable_numa
4076 By default, all work items queued to unbound
4077 workqueues are affine to the NUMA nodes they're
4078 issued on, which results in better behavior in
4079 general. If NUMA affinity needs to be disabled for
4080 whatever reason, this option can be used. Note
4081 that this also can be controlled per-workqueue for
4082 workqueues visible under /sys/bus/workqueue/.
4083
Viresh Kumarcee22a12013-04-08 16:45:40 +05304084 workqueue.power_efficient
4085 Per-cpu workqueues are generally preferred because
4086 they show better performance thanks to cache
4087 locality; unfortunately, per-cpu workqueues tend to
4088 be more power hungry than unbound workqueues.
4089
4090 Enabling this makes the per-cpu workqueues which
4091 were observed to contribute significantly to power
4092 consumption unbound, leading to measurably lower
4093 power usage at the cost of small performance
4094 overhead.
4095
4096 The default value of this parameter is determined by
4097 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4098
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004099 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4100 default x2apic cluster mode on platforms
4101 supporting x2apic.
4102
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004103 x86_intel_mid_timer= [X86-32,APBT]
4104 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004105 Two valid options are apbt timer only and lapic timer
4106 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004107 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004108
Juergen Grossc70727a2015-07-17 06:51:36 +02004109 xen_512gb_limit [KNL,X86-64,XEN]
4110 Restricts the kernel running paravirtualized under Xen
4111 to use only up to 512 GB of RAM. The reason to do so is
4112 crash analysis tools and Xen tools for doing domain
4113 save/restore/migration must be enabled to handle larger
4114 domains.
4115
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004116 xen_emul_unplug= [HW,X86,XEN]
4117 Unplug Xen emulated devices
4118 Format: [unplug0,][unplug1]
4119 ide-disks -- unplug primary master IDE devices
4120 aux-ide-disks -- unplug non-primary-master IDE devices
4121 nics -- unplug network devices
4122 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004123 unnecessary -- unplugging emulated devices is
4124 unnecessary even if the host did not respond to
4125 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004126 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004127
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004128 xen_nopvspin [X86,XEN]
4129 Disables the ticketlock slowpath using Xen PV
4130 optimizations.
4131
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004132 xen_nopv [X86]
4133 Disables the PV optimizations forcing the HVM guest to
4134 run as generic HVM guest with no PV drivers.
4135
Linus Torvalds1da177e2005-04-16 15:20:36 -07004136 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004137 Format:
4138 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004139
Randy Dunlapa9913042005-10-23 12:57:11 -07004140______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004141
4142TODO:
4143
Linus Torvalds1da177e2005-04-16 15:20:36 -07004144 Add more DRM drivers.