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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
Rami Rosene58d1542015-09-26 19:27:57 +0300170 Format: { force | off | strict | noirq | rsdt |
171 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700175 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800177 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800178 copy_dsdt -- copy DSDT to memory
Al Stoneb10d79f2015-03-24 14:02:41 +0000179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
Paul Bolle395cf962011-08-15 02:02:26 +0200181 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182
Len Browna1fdcc02007-03-11 03:26:14 -0400183 acpi_apic_instance= [ACPI, IOAPIC]
184 Format: <int>
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400187 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400188
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
191 acpi_backlight=video
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
195
Dominik Brodowskief694492015-05-14 15:31:28 +0200196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
203
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200227
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800231
Dominik Brodowskief694492015-05-14 15:31:28 +0200232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
247
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
251 size limitation.
252
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
255 default in APIC mode
256
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
259 default in PIC mode
260
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
263
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 use by PCI
266 Format: <irq>,<irq>...
267
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800273 This feature is enabled by default.
274 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800275
Dominik Brodowskief694492015-05-14 15:31:28 +0200276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
277 kernels.
278
Lv Zhenga94e88c2014-04-04 12:39:11 +0800279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700288
Dominik Brodowskief694492015-05-14 15:31:28 +0200289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800293
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
296
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
302
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800306 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800307 acpi_osi=! # disable all built-in OS vendor
308 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700309 acpi_osi= # disable all strings
310
Lv Zheng5dc17982013-07-22 16:08:25 +0800311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800321 Examples:
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
325
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
331 meaningless.
332 Examples:
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
334 FALSE.
335
Lv Zheng741d8122013-07-22 16:08:36 +0800336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
346 the OSPM features.
347 Examples:
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
353 equivalent to
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
355 and
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
358
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530359 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
363
Randy Dunlap4af94f32009-04-17 18:30:28 -0700364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
366
Randy Dunlap4af94f32009-04-17 18:30:28 -0700367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
370
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200373 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700374 See Documentation/power/video.txt for information on
375 s3_bios and s3_mode.
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700389
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
393
Randy Dunlap4af94f32009-04-17 18:30:28 -0700394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
396
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700397 agp= [AGP]
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
402
Randy Dunlapbcfde332010-06-07 17:10:38 -0700403 ALSA [HW,ALSA]
404 See Documentation/sound/alsa/alsa-parameters.txt
405
Russell Kingd944d542010-02-20 16:13:29 +0000406 alignment= [KNL,ARM]
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
410
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
418
Borislav Petkov8360ee22011-11-21 12:10:19 +0100419 32: only for 32-bit processes
420 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
423
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
430
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100431 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200432 Pass parameters to the AMD IOMMU driver in the system.
433 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
437 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200438 off - do not initialize any AMD IOMMU found in
439 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900445
Shuah Khanc099cf12012-05-24 15:58:25 -0600446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
451
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
454 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200455 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
461
Randy Dunlapa9913042005-10-23 12:57:11 -0700462 apc= [HW,SPARC]
463 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 Format: noidle
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
468
Randy Dunlapca1eda22009-05-06 16:02:58 -0700469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700470 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700474
Brian Haleyb0f83b22010-02-04 13:36:50 -0800475 autoconf= [IPV6]
476 See Documentation/networking/ipv6.txt.
477
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400478 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
479 Limit apic dumping. The parameter defines the maximal
480 number of local apics being dumped. Also it is possible
481 to set it to "all" by meaning -- no limit here.
482 Format: { 1 (default) | 2 | ... | all }.
483 The parameter valid if only apic=debug or
484 apic=verbose is specified.
485 Example: apic=debug show_lapic=all
486
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700488 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
491 Format: <io>,<irq>,<nodeID>
492
493 ataflop= [HW,M68k]
494
495 atarimouse= [HW,MOUSE] Atari Mouse
496
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
498 EzKey and similar keyboards
499
500 atkbd.reset= [HW] Reset keyboard during initialization
501
Randy Dunlapa9913042005-10-23 12:57:11 -0700502 atkbd.set= [HW] Select keyboard code set
503 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504
505 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
506 keyboards
507
508 atkbd.softraw= [HW] Choose between synthetic and real raw mode
509 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700510
511 atkbd.softrepeat= [HW]
512 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400514 audit= [KNL] Enable the audit sub-system
515 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500516 0 - kernel audit is disabled and can not be enabled
517 until the next reboot
518 unset - kernel audit is initialized but disabled and
519 will be fully enabled by the userspace auditd.
520 1 - kernel audit is initialized and partially enabled,
521 storing at most audit_backlog_limit messages in
522 RAM until it is fully enabled by the userspace
523 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400524 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400525
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400526 audit_backlog_limit= [KNL] Set the audit queue size limit.
527 Format: <int> (must be >=0)
528 Default: 64
529
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 baycom_epp= [HW,AX25]
531 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700532
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
534 Format: <io>,<mode>
535 See header of drivers/net/hamradio/baycom_par.c.
536
Randy Dunlapa9913042005-10-23 12:57:11 -0700537 baycom_ser_fdx= [HW,AX25]
538 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539 Format: <io>,<irq>,<mode>[,<baud>]
540 See header of drivers/net/hamradio/baycom_ser_fdx.c.
541
Randy Dunlapa9913042005-10-23 12:57:11 -0700542 baycom_ser_hdx= [HW,AX25]
543 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544 Format: <io>,<irq>,<mode>
545 See header of drivers/net/hamradio/baycom_ser_hdx.c.
546
Paul Gortmaker080506a2013-09-30 13:45:19 -0700547 blkdevparts= Manual partition parsing of block device(s) for
548 embedded devices based on command line input.
549 See Documentation/block/cmdline-partition.txt
550
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700551 boot_delay= Milliseconds to delay each printk during boot.
552 Values larger than 10 seconds (10000) are changed to
553 no delay (0).
554 Format: integer
555
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700556 bootmem_debug [KNL] Enable bootmem allocator debug messages.
557
Linus Torvalds1da177e2005-04-16 15:20:36 -0700558 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700559 bttv.radio= Most important insmod options are available as
560 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200562 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000564 bulk_remove=off [PPC] This parameter disables the use of the pSeries
565 firmware feature for flushing multiple hpte entries
566 at a time.
567
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 c101= [NET] Moxa C101 synchronous serial card
569
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700570 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 Sometimes CPU hardware bugs make them report the cache
572 size incorrectly. The kernel will attempt work arounds
573 to fix known problems, but for some CPUs it is not
574 possible to determine what the correct size should be.
575 This option provides an override for these situations.
576
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300577 ca_keys= [KEYS] This parameter identifies a specific key(s) on
578 the system trusted keyring to be used for certificate
579 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300580 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300581
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700582 cca= [MIPS] Override the kernel pages' cache coherency
583 algorithm. Accepted values range from 0 to 7
584 inclusive. See arch/mips/include/asm/pgtable-bits.h
585 for platform specific values (SB1, Loongson3 and
586 others).
587
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100588 ccw_timeout_log [S390]
589 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590
Paul Menage8bab8dd2008-04-04 14:29:57 -0700591 cgroup_disable= [KNL] Disable a particular controller
592 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800593 The effects of cgroup_disable=foo are:
594 - foo isn't auto-mounted if you mount all cgroups in
595 a single hierarchy
596 - foo isn't visible as an individually mountable
597 subsystem
598 {Currently only "memory" controller deal with this and
599 cut the overhead, others just disable the usage. So
600 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700601
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602 checkreqprot [SELINUX] Set initial checkreqprot flag value.
603 Format: { "0" | "1" }
604 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700605 0 -- check protection applied by kernel (includes
606 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 1 -- check protection requested by application.
608 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700609 Value can be changed at runtime via
610 /selinux/checkreqprot.
611
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100612 cio_ignore= [S390]
613 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700614 clk_ignore_unused
615 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700616 Prevents the clock framework from automatically gating
617 clocks that have not been explicitly enabled by a Linux
618 device driver but are enabled in hardware at reset or
619 by the bootloader/firmware. Note that this does not
620 force such clocks to be always-on nor does it reserve
621 those clocks in any way. This parameter is useful for
622 debug and development, but should not be needed on a
623 platform with proper driver support. For more
624 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100625
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700626 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700627 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200628 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700629 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200630 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 Format: { pit | tsc | cyclone | pmtmr }
632
John Stultz592913e2010-07-13 17:56:20 -0700633 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700634 Format: <string>
635 Override the default clocksource and use the clocksource
636 with the name specified.
637 Some clocksource names to choose from, depending on
638 the platform:
639 [all] jiffies (this is the base, fallback clocksource)
640 [ACPI] acpi_pm
641 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
642 pxa_timer,timer3,32k_counter,timer0_1
643 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700644 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700645 scx200_hrt on Geode; cyclone on IBM x440
646 [MIPS] MIPS
647 [PARISC] cr16
648 [S390] tod
649 [SH] SuperH
650 [SPARC64] tick
651 [X86-64] hpet,tsc
652
Andi Kleenac72e782008-01-30 13:33:21 +0100653 clearcpuid=BITNUM [X86]
654 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800655 arch/x86/include/asm/cpufeature.h for the valid bit
656 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100657 stable over kernel options, but the vendor specific
658 ones should be.
659 Also note that user programs calling CPUID directly
660 or using the feature without checking anything
661 will still see it. This just prevents it from
662 being used by the kernel or shown in /proc/cpuinfo.
663 Also note the kernel might malfunction if you disable
664 some critical bits.
665
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700666 cma=nn[MG]@[start[MG][-end[MG]]]
667 [ARM,X86,KNL]
668 Sets the size of kernel global memory area for
669 contiguous memory allocations and optionally the
670 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700671 memory allocations. A value of 0 disables CMA
672 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100673 include/linux/dma-contiguous.h
674
Robert Jennings14f966e2009-04-15 05:55:32 +0000675 cmo_free_hint= [PPC] Format: { yes | no }
676 Specify whether pages are marked as being inactive
677 when they are freed. This is used in CMO environments
678 to determine OS memory pressure for page stealing by
679 a hypervisor.
680 Default: yes
681
Marek Szyprowskic7909502011-12-29 13:09:51 +0100682 coherent_pool=nn[KMG] [ARM,KNL]
683 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200684 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100685
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530686 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100687 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100688 Range: 0 - 8192
689 Default: 64
690
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700692 Format:
693 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694
695 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
696 Format: <io>[,<irq>]
697
Randy Dunlapa9913042005-10-23 12:57:11 -0700698 com90xx= [HW,NET]
699 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 Format: <io>[,<irq>[,<memstart>]]
701
702 condev= [HW,S390] console device
703 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700704
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705 console= [KNL] Output console device and options.
706
707 tty<n> Use the virtual console device <n>.
708
709 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800710 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800712 the form "bbbbpnf", where "bbbb" is the baud rate,
713 "p" is parity ("n", "o", or "e"), "n" is number of
714 bits, and "f" is flow control ("r" for RTS or
715 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800717 See Documentation/serial-console.txt for more
718 information. See
719 Documentation/networking/netconsole.txt for an
720 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700722 uart[8250],io,<addr>[,options]
723 uart[8250],mmio,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400724 uart[8250],mmio32,<addr>[,options]
725 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726 Start an early, polled-mode console on the 8250/16550
727 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400728 switching to the matching ttyS device later.
729 MMIO inter-register address stride is either 8-bit
730 (mmio) or 32-bit (mmio32).
731 If none of [io|mmio|mmio32], <addr> is assumed to be
732 equivalent to 'mmio'. 'options' are specified in the
733 same format described for ttyS above; if unspecified,
734 the h/w is not re-initialized.
735
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500736 hvc<n> Use the hypervisor console device <n>. This is for
737 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700739 If the device connected to the port is not a TTY but a braille
740 device, prepend "brl," before the device type, for instance
741 console=brl,ttyS0
742 For now, only VisioBraille is supported.
743
Daniel Mackf324edc2009-06-16 15:33:52 -0700744 consoleblank= [KNL] The console blank (screen saver) timeout in
745 seconds. Defaults to 10*60 = 10mins. A value of 0
746 disables the blank timer.
747
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800748 coredump_filter=
749 [KNL] Change the default value for
750 /proc/<pid>/coredump_filter.
751 See also Documentation/filesystems/proc.txt.
752
Len Brown62027ae2011-04-01 18:13:10 -0400753 cpuidle.off=1 [CPU_IDLE]
754 disable the cpuidle sub-system
755
Len Brownd68921f2015-05-11 17:27:09 -0400756 cpu_init_udelay=N
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
759 on every CPU online, such as boot, and resume from suspend.
760 Default: 10000
761
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700763 Format:
764 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700765
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800766 crashkernel=size[KMG][@offset[KMG]]
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
768 upon panic. This parameter reserves the physical
769 memory region [offset, offset + size] for that kernel
770 image. If '@offset' is omitted, then a suitable offset
771 is selected automatically. Check
772 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700773
Bernhard Wallefb391592007-10-18 23:41:02 -0700774 crashkernel=range1:size1[,range2:size2,...][@offset]
775 [KNL] Same as above, but depends on the memory
776 in the running system. The syntax of range is
777 start-[end] where start and end are both
778 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800779 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700780
Yinghai Luadbc7422013-04-15 22:23:48 -0700781 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700782 [KNL, x86_64] range could be above 4G. Allow kernel
783 to allocate physical memory region from top, so could
784 be above 4G if system have more than 4G ram installed.
785 Otherwise memory region will be allocated below 4G, if
786 available.
787 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700788 crashkernel=size[KMG],low
789 [KNL, x86_64] range under 4G. When crashkernel=X,high
790 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700791 above 4G, that cause second kernel crash on system
792 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800793 requires at least 64M+32K low memory, also enough extra
794 low memory is needed to make sure DMA buffers for 32-bit
795 devices won't run out. Kernel would try to allocate at
796 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700797 This one let user to specify own low range under 4G
798 for second kernel instead.
799 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700800 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700801 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700802
Linus Torvalds1da177e2005-04-16 15:20:36 -0700803 cs89x0_dma= [HW,NET]
804 Format: <dma>
805
806 cs89x0_media= [HW,NET]
807 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700808
Randy Dunlapa9913042005-10-23 12:57:11 -0700809 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700810 See header of drivers/s390/block/dasd_devmap.c.
811
812 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
813 (one device per port)
814 Format: <port#>,<type>
815 See also Documentation/input/joystick-parport.txt
816
Thomas Renningera648ec02010-08-06 16:11:02 +0200817 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
818 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600819 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200820
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821 debug [KNL] Enable kernel debugging (events log level).
822
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700823 debug_locks_verbose=
824 [KNL] verbose self-tests
825 Format=<0|1>
826 Print debugging info while doing the locking API
827 self-tests.
828 We default to 0 (no extra messages), setting it to
829 1 will print _a lot_ more information - normally
830 only useful to kernel developers.
831
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700832 debug_objects [KNL] Enable object debugging
833
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500834 no_debug_objects
835 [KNL] Disable object debugging
836
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800837 debug_guardpage_minorder=
838 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
839 parameter allows control of the order of pages that will
840 be intentionally kept free (and hence protected) by the
841 buddy allocator. Bigger value increase the probability
842 of catching random memory corruption, but reduce the
843 amount of memory for normal system use. The maximum
844 possible value is MAX_ORDER/2. Setting this parameter
845 to 1 or 2 should be enough to identify most random
846 memory corruption problems caused by bugs in kernel or
847 driver code when a CPU writes to (or reads from) a
848 random memory location. Note that there exists a class
849 of memory corruptions problems caused by buggy H/W or
850 F/W or by drivers badly programing DMA (basically when
851 memory is written at bus level and the CPU MMU is
852 bypassed) which are not detectable by
853 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
854 tracking down these problems.
855
Joonsoo Kim031bc572014-12-12 16:55:52 -0800856 debug_pagealloc=
857 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
858 parameter enables the feature at boot time. In
859 default, it is disabled. We can avoid allocating huge
860 chunk of memory for debug pagealloc if we don't enable
861 it at boot time and the system will work mostly same
862 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
863 on: enable the feature
864
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200865 debugpat [X86] Enable PAT debugging
866
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200867 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700868 Format: <area>[,<node>]
869 See also Documentation/networking/decnet.txt.
870
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700871 default_hugepagesz=
872 [same as hugepagesz=] The size of the default
873 HugeTLB page size. This is the size represented by
874 the legacy /proc/ hugepages APIs, used for SHM, and
875 default size when mounting hugetlbfs filesystems.
876 Defaults to the default architecture's huge page size
877 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700878
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 dhash_entries= [KNL]
880 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700881
Brian Haleyb0f83b22010-02-04 13:36:50 -0800882 disable= [IPV6]
883 See Documentation/networking/ipv6.txt.
884
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900885 disable_cpu_apicid= [X86,APIC,SMP]
886 Format: <int>
887 The number of initial APIC ID for the
888 corresponding CPU to be disabled at boot,
889 mostly used for the kdump 2nd kernel to
890 disable BSP to wake up multiple CPUs without
891 causing system reset or hang due to sending
892 INIT from AP to BSP.
893
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000894 disable_ddw [PPC/PSERIES]
895 Disable Dynamic DMA Window support. Use this if
896 to workaround buggy firmware.
897
Brian Haleyb0f83b22010-02-04 13:36:50 -0800898 disable_ipv6= [IPV6]
899 See Documentation/networking/ipv6.txt.
900
Yinghai Lu95ffa242008-04-29 03:52:33 -0700901 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700902 The kernel tries to adjust MTRR layout from continuous
903 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700904 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700905
Yinghai Lu093af8d2008-01-30 13:33:32 +0100906 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100907 By default the kernel will trim any uncacheable
908 memory out of your available memory pool based on
909 MTRR settings. This parameter disables that behavior,
910 possibly causing your machine to run very slowly.
911
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530912 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700913 Disable PIN 1 of APIC timer
914 Can be useful to work around chipset bugs.
915
Prarit Bhargavace14c582015-08-25 13:34:53 -0400916 dis_ucode_ldr [X86] Disable the microcode loader.
917
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700918 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
919 this option disables the debugging code at boot.
920
921 dma_debug_entries=<number>
922 This option allows to tune the number of preallocated
923 entries for DMA-API debugging code. One entry is
924 required per DMA-API allocation. Use this if the
925 DMA-API debugging code disables itself because the
926 architectural default is too low.
927
Joerg Roedel1745de52009-05-22 21:49:51 +0200928 dma_debug_driver=<driver_name>
929 With this option the DMA-API debugging driver
930 filter feature can be enabled at boot time. Just
931 pass the driver to filter for as the parameter.
932 The filter can be disabled or changed to another
933 driver later using sysfs.
934
Bob Paauwe96206e22015-08-27 10:04:13 -0700935 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
936 Broken monitors, graphic adapters, KVMs and EDIDless
937 panels may send no or incorrect EDID data sets.
938 This parameter allows to specify an EDID data sets
939 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100940 Generic built-in EDID data sets are used, if one of
941 edid/1024x768.bin, edid/1280x1024.bin,
942 edid/1680x1050.bin, or edid/1920x1080.bin is given
943 and no file with the same name exists. Details and
944 instructions how to build your own EDID data are
945 available in Documentation/EDID/HOWTO.txt. An EDID
946 data set will only be used for a particular connector,
947 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700948 name. Each connector may use a unique EDID data
949 set by separating the files with a comma. An EDID
950 data set with no connector name will be used for
951 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100952
Linus Torvalds1da177e2005-04-16 15:20:36 -0700953 dscc4.setup= [NET]
954
Jim Cromie29e36c92012-04-27 14:30:41 -0600955 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
956 module.dyndbg[="val"]
957 Enable debug messages at boot time. See
958 Documentation/dynamic-debug-howto.txt for details.
959
Dave Hansen8c3641e2015-06-07 11:37:02 -0700960 nompx [X86] Disables Intel Memory Protection Extensions.
961 See Documentation/x86/intel_mpx.txt for more
962 information about the feature.
963
Borislav Petkovf29ba612015-03-27 16:15:18 +0100964 eagerfpu= [X86]
965 on enable eager fpu restore
966 off disable eager fpu restore
967 auto selects the default scheme, which automatically
968 enables eagerfpu restore for xsaveopt.
969
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700970 module.async_probe [KNL]
971 Enable asynchronous probe on this module.
972
Mark Salter56aeeba2014-04-07 15:39:53 -0700973 early_ioremap_debug [KNL]
974 Enable debug messages in early_ioremap support. This
975 is useful for tracking down temporary early mappings
976 which are not unmapped.
977
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700978 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500979
Scott Wood5664f762015-09-14 19:54:07 -0500980 When used with no options, the early console is
981 determined by the stdout-path property in device
982 tree's chosen node.
983
Michal Simek6fa62fc2014-09-10 12:43:02 +0200984 cdns,<addr>
985 Start an early, polled-mode console on a cadence serial
986 port at the specified address. The cadence serial port
987 must already be setup and configured. Options are not
988 yet supported.
989
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700990 uart[8250],io,<addr>[,options]
991 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700992 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300993 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400994 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700995 Start an early, polled-mode console on the 8250/16550
996 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700997 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300998 (mmio) or 32-bit (mmio32 or mmio32be).
999 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1000 to be equivalent to 'mmio'. 'options' are specified
1001 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001002 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001003
Rob Herring0d3c6732014-04-18 17:19:57 -05001004 pl011,<addr>
1005 Start an early, polled-mode console on a pl011 serial
1006 port at the specified address. The pl011 serial port
1007 must already be setup and configured. Options are not
1008 yet supported.
1009
Stephen Boyd0efe7292014-09-15 17:22:51 -07001010 msm_serial,<addr>
1011 Start an early, polled-mode console on an msm serial
1012 port at the specified address. The serial port
1013 must already be setup and configured. Options are not
1014 yet supported.
1015
1016 msm_serial_dm,<addr>
1017 Start an early, polled-mode console on an msm serial
1018 dm port at the specified address. The serial port
1019 must already be setup and configured. Options are not
1020 yet supported.
1021
Rob Herringd50d7262014-04-18 17:19:58 -05001022 smh Use ARM semihosting calls for early console.
1023
Tomasz Figab94ba032015-01-23 14:47:41 +01001024 s3c2410,<addr>
1025 s3c2412,<addr>
1026 s3c2440,<addr>
1027 s3c6400,<addr>
1028 s5pv210,<addr>
1029 exynos4210,<addr>
1030 Use early console provided by serial driver available
1031 on Samsung SoCs, requires selecting proper type and
1032 a correct base address of the selected UART port. The
1033 serial port must already be setup and configured.
1034 Options are not yet supported.
1035
Stefan Agner1d59b382015-10-17 00:45:55 -07001036 lpuart,<addr>
1037 lpuart32,<addr>
1038 Use early console provided by Freescale LP UART driver
1039 found on Freescale Vybrid and QorIQ LS1021A processors.
1040 A valid base address must be provided, and the serial
1041 port must already be setup and configured.
1042
Finn Thain7913ad12014-04-12 23:48:56 +10001043 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001045 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001046 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001048 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001049 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001050 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001051 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052
Dave Hansen147ea092013-04-10 14:03:38 -07001053 earlyprintk is useful when the kernel crashes before
1054 the normal console is initialized. It is not enabled by
1055 default because it has some cosmetic problems.
1056
Randy Dunlapa9913042005-10-23 12:57:11 -07001057 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 takes over.
1059
Matt Fleming72548e82013-10-04 09:36:56 +01001060 Only one of vga, efi, serial, or usb debug port can
1061 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062
Dave Hansen147ea092013-04-10 14:03:38 -07001063 Currently only ttyS0 and ttyS1 may be specified by
1064 name. Other I/O ports may be explicitly specified
1065 on some architectures (x86 and arm at least) by
1066 replacing ttySn with an I/O port address, like this:
1067 earlyprintk=serial,0x1008,115200
1068 You can find the port for a given device in
1069 /proc/tty/driver/serial:
1070 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071
1072 Interaction with the standard serial driver is not
1073 very good.
1074
Matt Fleming72548e82013-10-04 09:36:56 +01001075 The VGA and EFI output is eventually overwritten by
1076 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001078 The xen output can only be used by Xen PV guests.
1079
Chen, Gongc700f012013-12-06 01:17:08 -05001080 edac_report= [HW,EDAC] Control how to report EDAC event
1081 Format: {"on" | "off" | "force"}
1082 on: enable EDAC to report H/W event. May be overridden
1083 by other higher priority error reporting module.
1084 off: disable H/W event reporting through EDAC.
1085 force: enforce the use of EDAC to report H/W event.
1086 default: on.
1087
Jason Wessel97311912010-05-20 21:04:30 -05001088 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1089 ekgdboc=kbd
1090
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001091 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001092 the boot argument: earlyprintk=vga
1093
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001095 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001097 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001098 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001099 old_map [X86-64]: switch to the old ioremap-based EFI
1100 runtime services mapping. 32-bit still uses this one by
1101 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001102 nochunk: disable reading files in "chunks" in the EFI
1103 boot stub, as chunking can cause problems with some
1104 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001105 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001106 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001107
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001108 efi_no_storage_paranoia [EFI; X86]
1109 Using this parameter you can use more than 50% of
1110 your efi variable storage. Use this parameter only if
1111 you are really sure that your UEFI does sane gc and
1112 fulfills the spec otherwise your board may brick.
1113
Taku Izumi0f96a992015-09-30 23:01:56 +09001114 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1115 Add arbitrary attribute to specific memory range by
1116 updating original EFI memory map.
1117 Region of memory which aa attribute is added to is
1118 from ss to ss+nn.
1119 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1120 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1121 attribute is added to range 0x100000000-0x180000000 and
1122 0x10a0000000-0x1120000000.
1123
1124 Using this parameter you can do debugging of EFI memmap
1125 related feature. For example, you can do debugging of
1126 Address Range Mirroring feature even if your box
1127 doesn't support it.
1128
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129 eisa_irq_edge= [PARISC,HW]
1130 See header of drivers/parisc/eisa.c.
1131
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001132 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001134 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135
1136 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001137 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001138 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001139 Documentation/block/deadline-iosched.txt for details.
1140
Michael Holzheud3bf37952011-10-30 15:16:37 +01001141 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001142 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001143 image elf header and optionally the size. Generally
1144 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001145 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001147 enable_mtrr_cleanup [X86]
1148 The kernel tries to adjust MTRR layout from continuous
1149 to discrete, to make X server driver able to add WB
1150 entry later. This parameter enables that.
1151
Randy Dunlapca1eda22009-05-06 16:02:58 -07001152 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001153 Enable PIN 1 of APIC timer
1154 Can be useful to work around chipset bugs
1155 (in particular on some ATI chipsets).
1156 The kernel tries to set a reasonable default.
1157
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 enforcing [SELINUX] Set initial enforcing status.
1159 Format: {"0" | "1"}
1160 See security/selinux/Kconfig help text.
1161 0 -- permissive (log only, no denials).
1162 1 -- enforcing (deny and log).
1163 Default value is 0.
1164 Value can be changed at runtime via /selinux/enforce.
1165
Huang Yinga08f82d2010-05-18 14:35:21 +08001166 erst_disable [ACPI]
1167 Disable Error Record Serialization Table (ERST)
1168 support.
1169
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 ether= [HW,NET] Ethernet cards parameters
1171 This option is obsoleted by the "netdev=" option, which
1172 has equivalent usage. See its documentation for details.
1173
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001174 evm= [EVM]
1175 Format: { "fix" }
1176 Permit 'security.evm' to be updated regardless of
1177 current integrity status.
1178
Akinobu Mitade1ba092006-12-08 02:39:42 -08001179 failslab=
1180 fail_page_alloc=
1181 fail_make_request=[KNL]
1182 General fault injection mechanism.
1183 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001184 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001185
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001187 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188
Alex Chiangf13ae302008-05-08 14:03:23 -06001189 force_pal_cache_flush
1190 [IA-64] Avoid check_sal_cache_flush which may hang on
1191 buggy SAL_CACHE_FLUSH implementations. Using this
1192 parameter will force ia64_sal_cache_flush to call
1193 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1194
Chris Bainbridge69f23662014-03-07 18:40:42 +07001195 forcepae [X86-32]
1196 Forcefully enable Physical Address Extension (PAE).
1197 Many Pentium M systems disable PAE but may have a
1198 functionally usable PAE implementation.
1199 Warning: use of this parameter will taint the kernel
1200 and may cause unknown problems.
1201
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001202 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001203 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001204 as early as possible in order to facilitate early
1205 boot debugging.
1206
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001207 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001208 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001209 If no parameter is passed, ftrace will dump
1210 buffers of all CPUs, but if you pass orig_cpu, it will
1211 dump only the buffer of the CPU that triggered the
1212 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001213
1214 ftrace_filter=[function-list]
1215 [FTRACE] Limit the functions traced by the function
1216 tracer at boot up. function-list is a comma separated
1217 list of functions. This list can be changed at run
1218 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001219 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001220
1221 ftrace_notrace=[function-list]
1222 [FTRACE] Do not trace the functions specified in
1223 function-list. This list can be changed at run time
1224 by the set_ftrace_notrace file in the debugfs
1225 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001226
Stefan Assmann369bc182009-10-12 22:17:21 +02001227 ftrace_graph_filter=[function-list]
1228 [FTRACE] Limit the top level callers functions traced
1229 by the function graph tracer at boot up.
1230 function-list is a comma separated list of functions
1231 that can be changed at run time by the
1232 set_graph_function file in the debugfs tracing directory.
1233
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001234 ftrace_graph_notrace=[function-list]
1235 [FTRACE] Do not trace from the functions specified in
1236 function-list. This list is a comma separated list of
1237 functions that can be changed at run time by the
1238 set_graph_notrace file in the debugfs tracing directory.
1239
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240 gamecon.map[2|3]=
1241 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1242 support via parallel port (up to 5 devices per port)
1243 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1244 See also Documentation/input/joystick-parport.txt
1245
1246 gamma= [HW,DRM]
1247
Yinghai Luaaf23042008-01-30 13:33:09 +01001248 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1249 Format: off | on
1250 default: on
1251
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001252 gcov_persist= [GCOV] When non-zero (default), profiling data for
1253 kernel modules is saved and remains accessible via
1254 debugfs, even when the module is unloaded/reloaded.
1255 When zero, profiling data is discarded and associated
1256 debugfs files are removed at module unload time.
1257
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001259 invalid Protective MBR to be treated as GPT. If the
1260 primary GPT is corrupted, it enables the backup/alternate
1261 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001263 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1264 the "Enable 0" bit of the configuration register.
1265 Format: 0 | 1
1266 Default: 0
1267 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1268 the "Enable 0" bit of the configuration register.
1269 Format: 0 | 1
1270 Default: 0
1271 grcan.select= [HW] Select which physical interface to use.
1272 Format: 0 | 1
1273 Default: 0
1274 grcan.txsize= [HW] Sets the size of the tx buffer.
1275 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1276 Default: 1024
1277 grcan.rxsize= [HW] Sets the size of the rx buffer.
1278 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1279 Default: 1024
1280
Jiri Kosina55537872015-11-05 18:44:41 -08001281 hardlockup_all_cpu_backtrace=
1282 [KNL] Should the hard-lockup detector generate
1283 backtraces on all cpus.
1284 Format: <integer>
1285
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 hashdist= [KNL,NUMA] Large hashes allocated during boot
1287 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001288 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001289 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001290
1291 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1292
1293 hd= [EIDE] (E)IDE hard drive subsystem geometry
1294 Format: <cyl>,<head>,<sect>
1295
Huang Yingea8c0712010-05-18 14:35:15 +08001296 hest_disable [ACPI]
1297 Disable Hardware Error Source Table (HEST) support;
1298 corresponding firmware-first mode error processing
1299 logic will be disabled.
1300
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1302 size of <nn>. This works even on boxes that have no
1303 highmem otherwise. This also works to reduce highmem
1304 size on bigger boxes.
1305
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001306 highres= [KNL] Enable/disable high resolution timer mode.
1307 Valid parameters: "on", "off"
1308 Default: "on"
1309
Linus Torvalds1da177e2005-04-16 15:20:36 -07001310 hisax= [HW,ISDN]
1311 See Documentation/isdn/README.HiSax.
1312
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001313 hlt [BUGS=ARM,SH]
1314
1315 hpet= [X86-32,HPET] option to control HPET usage
1316 Format: { enable (default) | disable | force |
1317 verbose }
1318 disable: disable HPET and use PIT instead
1319 force: allow force enabled of undocumented chips (ICH4,
1320 VIA, nVidia)
1321 verbose: show contents of HPET registers during setup
1322
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001323 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1324 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1325
Andi Kleenb4718e62008-07-23 21:27:51 -07001326 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1327 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001328 On x86-64 and powerpc, this option can be specified
1329 multiple times interleaved with hugepages= to reserve
1330 huge pages of different sizes. Valid pages sizes on
1331 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001332 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001333
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001334 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1335 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001336 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1337 If specified, z/VM IUCV HVC accepts connections
1338 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001339
James Hoganfdabf522012-10-09 11:00:27 +01001340 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1341 hardware thread id mappings.
1342 Format: <cpu>:<hwthread>
1343
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001344 keep_bootcon [KNL]
1345 Do not unregister boot console at start. This is only
1346 useful for debugging when something happens in the window
1347 between unregistering the boot console and initializing
1348 the real console.
1349
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001350 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001351 or register an additional I2C bus that is not
1352 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001353 Format:
1354 <bus_id>,<clkrate>
1355
Jiri Kosina36d95732008-10-06 02:51:09 -04001356 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001357 i8042.unmask_kbd_data
1358 [HW] Enable printing of interrupt data from the KBD port
1359 (disabled by default, and as a pre-condition
1360 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001362 i8042.dumbkbd [HW] Pretend that controller can only read data from
1363 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 (Don't attempt to blink the leds)
1365 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001366 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001367 i8042.noloop [HW] Disable the AUX Loopback command while probing
1368 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001369 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001370 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1372 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001373 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374 i8042.reset [HW] Reset the controller during init and cleanup
1375 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001376 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001377
1378 i810= [HW,DRM]
1379
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001380 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1381 indicates that the driver is running on unsupported
1382 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1384 does not match list of supported models.
1385 i8k.power_status
1386 [HW] Report power status in /proc/i8k
1387 (disabled by default)
1388 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1389 capability is set.
1390
Carsten Emde4dca20e2012-03-15 15:56:26 +01001391 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001392 [DRM] Invert the sense of the variable that is used to
1393 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001394 brightness value of 0 indicates backlight switched off,
1395 and the maximum of the brightness value sets the backlight
1396 to maximum brightness. If this parameter is set to 0
1397 (default) and the machine requires it, or this parameter
1398 is set to 1, a brightness value of 0 sets the backlight
1399 to maximum brightness, and the maximum of the brightness
1400 value switches the backlight off.
1401 -1 -- never invert brightness
1402 0 -- machine default
1403 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001404
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405 icn= [HW,ISDN]
1406 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1407
David Fries0af80c02009-02-25 20:28:21 +01001408 ide-core.nodma= [HW] (E)IDE subsystem
1409 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001410 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1411 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001412 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001414 ide-generic.probe-mask= [HW] (E)IDE subsystem
1415 Format: <int>
1416 Probe mask for legacy ISA IDE ports. Depending on
1417 platform up to 6 ports are supported, enabled by
1418 setting corresponding bits in the mask to 1. The
1419 default value is 0x0, which has a special meaning.
1420 On systems that have PCI, it triggers scanning the
1421 PCI bus for the first and the second port, which
1422 are then probed. On systems without PCI the value
1423 of 0x0 enables probing the two first ports as if it
1424 was 0x3.
1425
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001426 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1427 Claim all unknown PCI IDE storage controllers.
1428
Andi Kleenf039b752007-05-02 19:27:12 +02001429 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001430 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001431 Poll forces a polling idle loop that can slightly
1432 improve the performance of waking up a idle CPU, but
1433 will use a lot of power and make the system run hot.
1434 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001435 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001436 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001437 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001438
Ingo Molnar792908222006-12-06 20:40:51 -08001439 ignore_loglevel [KNL]
1440 Ignore loglevel setting - this will print /all/
1441 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001442 We also add it as printk module parameter, so users
1443 could change it dynamically, usually by
1444 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001445
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446 ihash_entries= [KNL]
1447 Set number of hash buckets for inode cache.
1448
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001449 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001450 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001451 default: "enforce"
1452
Mimi Zohar07f6a792011-03-09 22:25:48 -05001453 ima_appraise_tcb [IMA]
1454 The builtin appraise policy appraises all files
1455 owned by uid=0.
1456
Mimi Zohar3323eec92009-02-04 09:06:58 -05001457 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001458 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1459 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001460 default: "sha1"
1461
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001462 The list of supported hash algorithms is defined
1463 in crypto/hash_info.h.
1464
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001465 ima_policy= [IMA]
1466 The builtin measurement policy to load during IMA
1467 setup. Specyfing "tcb" as the value, measures all
1468 programs exec'd, files mmap'd for exec, and all files
1469 opened with the read mode bit set by either the
1470 effective uid (euid=0) or uid=0.
1471 Format: "tcb"
1472
1473 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001474 Load a policy which meets the needs of the Trusted
1475 Computing Base. This means IMA will measure all
1476 programs exec'd, files mmap'd for exec, and all files
1477 opened for read by uid=0.
1478
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001479 ima_template= [IMA]
1480 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001481 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001482 Default: "ima-ng"
1483
Roberto Sassuc2426d22014-10-13 14:08:42 +02001484 ima_template_fmt=
1485 [IMA] Define a custom template format.
1486 Format: { "field1|...|fieldN" }
1487
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001488 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1489 Format: <min_file_size>
1490 Set the minimal file size for using asynchronous hash.
1491 If left unspecified, ahash usage is disabled.
1492
1493 ahash performance varies for different data sizes on
1494 different crypto accelerators. This option can be used
1495 to achieve the best performance for a particular HW.
1496
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001497 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1498 Format: <bufsize>
1499 Set hashing buffer size. Default: 4k.
1500
1501 ahash performance varies for different chunk sizes on
1502 different crypto accelerators. This option can be used
1503 to achieve best performance for particular HW.
1504
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505 init= [KNL]
1506 Format: <full_path>
1507 Run specified binary instead of /sbin/init as init
1508 process.
1509
1510 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1511 for working out where the kernel is dying during
1512 startup.
1513
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001514 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1515 initcall functions. Useful for debugging built-in
1516 modules and initcalls.
1517
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518 initrd= [BOOT] Specify the location of the initial ramdisk
1519
1520 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1521 Format: <irq>
1522
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001523 int_pln_enable [x86] Enable power limit notification interrupt
1524
Mimi Zohard726d8d2013-03-18 14:48:02 -04001525 integrity_audit=[IMA]
1526 Format: { "0" | "1" }
1527 0 -- basic integrity auditing messages. (Default)
1528 1 -- additional integrity auditing messages.
1529
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001530 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001531 on
1532 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001533 off
1534 Disable intel iommu driver.
1535 igfx_off [Default Off]
1536 By default, gfx is mapped as normal device. If a gfx
1537 device has a dedicated DMAR unit, the DMAR unit is
1538 bypassed by not enabling DMAR with this option. In
1539 this case, gfx device will use physical address for
1540 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001541 forcedac [x86_64]
1542 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001543 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001544 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001545 than 32-bit addressing. The default is to look
1546 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001547 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001548 strict [Default Off]
1549 With this option on every unmap_single operation will
1550 result in a hardware IOTLB flush operation as opposed
1551 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001552 sp_off [Default Off]
1553 By default, super page will be supported if Intel IOMMU
1554 has the capability. With this option, super page will
1555 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001556 ecs_off [Default Off]
1557 By default, extended context tables will be supported if
1558 the hardware advertises that it has support both for the
1559 extended tables themselves, and also PASID support. With
1560 this option set, extended tables will not be used even
1561 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001562
1563 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1564 0 disables intel_idle and fall back on acpi_idle.
1565 1 to 6 specify maximum depth of C-state.
1566
Dirk Brandewie6be26492013-02-15 22:55:10 +01001567 intel_pstate= [X86]
1568 disable
1569 Do not enable intel_pstate as the default
1570 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001571 force
1572 Enable intel_pstate on systems that prohibit it by default
1573 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1574 instead of acpi-cpufreq may disable platform features, such
1575 as thermal controls and power capping, that rely on ACPI
1576 P-States information being indicated to OSPM and therefore
1577 should be used with caution. This option does not work with
1578 processors that aren't supported by the intel_pstate driver
1579 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001580 no_hwp
1581 Do not enable hardware P state control (HWP)
1582 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001583 hwp_only
1584 Only load intel_pstate on systems which support
1585 hardware P state control (HWP) if available.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001586
Chris Wrightd1423d52010-07-20 11:06:49 -07001587 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001588 on enable Interrupt Remapping (default)
1589 off disable Interrupt Remapping
1590 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001591 no_x2apic_optout
1592 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001593 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001594
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001595 iomem= Disable strict checking of access to MMIO memory
1596 strict regions from userspace.
1597 relaxed
1598
1599 iommu= [x86]
1600 off
1601 force
1602 noforce
1603 biomerge
1604 panic
1605 nopanic
1606 merge
1607 nomerge
1608 forcesac
1609 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001610 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001611 nobypass [PPC/POWERNV]
1612 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001613
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001614
1615 io7= [HW] IO7 for Marvel based alpha systems
1616 See comment before marvel_specify_io7 in
1617 arch/alpha/kernel/core_marvel.c.
1618
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301619 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001620 0x80
1621 Standard port 0x80 based delay
1622 0xed
1623 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001624 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001625 Simple two microseconds delay
1626 none
1627 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001628
Linus Torvalds1da177e2005-04-16 15:20:36 -07001629 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001630 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631
Alan Cox200803d2005-06-28 20:45:18 -07001632 irqfixup [HW]
1633 When an interrupt is not handled search all handlers
1634 for it. Intended to get systems with badly broken
1635 firmware running.
1636
1637 irqpoll [HW]
1638 When an interrupt is not handled search all handlers
1639 for it. Also check all handlers each timer
1640 interrupt. Intended to get systems with badly broken
1641 firmware running.
1642
Linus Torvalds1da177e2005-04-16 15:20:36 -07001643 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001644 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645
1646 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001647 Format:
1648 <cpu number>,...,<cpu number>
1649 or
Li Zefanb225d442008-11-06 12:53:39 -08001650 <cpu number>-<cpu number>
1651 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001652 or a mixture
1653 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001654
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 This option can be used to specify one or more CPUs
1656 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001657 algorithms. You can move a process onto or off an
1658 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659 <cpu number> begins at 0 and the maximum value is
1660 "number of CPUs in system - 1".
1661
1662 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001663 alternative -- manually setting the CPU mask of all
1664 tasks in the system -- can cause problems and
1665 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666
Randy Dunlapa9913042005-10-23 12:57:11 -07001667 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001669 ivrs_ioapic [HW,X86_64]
1670 Provide an override to the IOAPIC-ID<->DEVICE-ID
1671 mapping provided in the IVRS ACPI table. For
1672 example, to map IOAPIC-ID decimal 10 to
1673 PCI device 00:14.0 write the parameter as:
1674 ivrs_ioapic[10]=00:14.0
1675
1676 ivrs_hpet [HW,X86_64]
1677 Provide an override to the HPET-ID<->DEVICE-ID
1678 mapping provided in the IVRS ACPI table. For
1679 example, to map HPET-ID decimal 0 to
1680 PCI device 00:14.0 write the parameter as:
1681 ivrs_hpet[0]=00:14.0
1682
Linus Torvalds1da177e2005-04-16 15:20:36 -07001683 js= [HW,JOY] Analog joystick
1684 See Documentation/input/joystick.txt.
1685
Kees Cook24f2e022014-06-13 13:30:36 -07001686 kaslr/nokaslr [X86]
1687 Enable/disable kernel and module base offset ASLR
1688 (Address Space Layout Randomization) if built into
1689 the kernel. When CONFIG_HIBERNATION is selected,
1690 kASLR is disabled by default. When kASLR is enabled,
1691 hibernation will be disabled.
1692
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001693 keepinitrd [HW,ARM]
1694
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301695 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001696 specifies the amount of memory usable by the kernel
1697 for non-movable allocations. The requested amount is
1698 spread evenly throughout all nodes in the system. The
1699 remaining memory in each node is used for Movable
1700 pages. In the event, a node is too small to have both
1701 kernelcore and Movable pages, kernelcore pages will
1702 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001703 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001704 allocation of pages that may be reclaimed or moved
1705 by the page migration subsystem. This means that
1706 HugeTLB pages may not be allocated from this zone.
1707 Note that allocations like PTEs-from-HighMem still
1708 use the HighMem zone if it exists, and the Normal
1709 zone if it does not.
1710
Jason Wessel4fe1da42010-05-20 21:04:31 -05001711 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1712 Format: <Controller#>[,poll interval]
1713 The controller # is the number of the ehci usb debug
1714 port as it is probed via PCI. The poll interval is
1715 optional and is the number seconds in between
1716 each poll cycle to the debug port in case you need
1717 the functionality for interrupting the kernel with
1718 gdb or control-c on the dbgp connection. When
1719 not using this parameter you use sysrq-g to break into
1720 the kernel debugger.
1721
Jason Wessel84c08fd2010-05-20 21:04:24 -05001722 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001723 Requires a tty driver that supports console polling,
1724 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001725 Serial only format: <serial_device>[,baud]
1726 keyboard only format: kbd
1727 keyboard and serial format: kbd,<serial_device>[,baud]
1728 Optional Kernel mode setting:
1729 kms, kbd format: kms,kbd
1730 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001731
Jason Wessel84c08fd2010-05-20 21:04:24 -05001732 kgdbwait [KGDB] Stop kernel execution and enter the
1733 kernel debugger at the earliest opportunity.
1734
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001735 kmac= [MIPS] korina ethernet MAC address.
1736 Configure the RouterBoard 532 series on-chip
1737 Ethernet adapter MAC address.
1738
Catalin Marinas04f70332009-06-11 13:22:39 +01001739 kmemleak= [KNL] Boot-time kmemleak enable/disable
1740 Valid arguments: on, off
1741 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001742 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1743 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001744
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001745 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1746 Valid arguments: 0, 1, 2
1747 kmemcheck=0 (disabled)
1748 kmemcheck=1 (enabled)
1749 kmemcheck=2 (one-shot mode)
1750 Default: 2 (one-shot mode)
1751
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301752 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001753 in oops dumps.
1754
Andre Przywarafef07aa2009-07-10 14:20:35 +02001755 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1756 Default is 0 (don't ignore, but inject #GP)
1757
Xiao Guangronga182d872010-09-20 22:17:48 +08001758 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1759 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001760 Default is 0 (off)
1761
Andre Przywarafef07aa2009-07-10 14:20:35 +02001762 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001763 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001764
1765 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1766 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001767 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001768
Andre Przywarafef07aa2009-07-10 14:20:35 +02001769 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1770 (virtualized MMU) support on capable Intel chips.
1771 Default is 1 (enabled)
1772
1773 kvm-intel.emulate_invalid_guest_state=
1774 [KVM,Intel] Enable emulation of invalid guest states
1775 Default is 0 (disabled)
1776
1777 kvm-intel.flexpriority=
1778 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1779 Default is 1 (enabled)
1780
Sasha Levine1a72ae2011-08-09 14:28:35 +03001781 kvm-intel.nested=
1782 [KVM,Intel] Enable VMX nesting (nVMX).
1783 Default is 0 (disabled)
1784
Andre Przywarafef07aa2009-07-10 14:20:35 +02001785 kvm-intel.unrestricted_guest=
1786 [KVM,Intel] Disable unrestricted guest feature
1787 (virtualized real and unpaged mode) on capable
1788 Intel chips. Default is 1 (enabled)
1789
1790 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1791 feature (tagged TLBs) on capable Intel chips.
1792 Default is 1 (enabled)
1793
Linus Torvalds1da177e2005-04-16 15:20:36 -07001794 l2cr= [PPC]
1795
Robert Brosea78bfbf2008-03-29 07:20:23 +11001796 l3cr= [PPC]
1797
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001798 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001799 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800
Suresh Siddha279f1462012-10-22 14:37:58 -07001801 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1802 value for LAPIC timer one-shot implementation. Default
1803 back to the programmable timer unit in the LAPIC.
1804
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301805 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001806 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001807
FD Camifcb71f62008-01-06 19:08:56 +01001808 libata.dma= [LIBATA] DMA control
1809 libata.dma=0 Disable all PATA and SATA DMA
1810 libata.dma=1 PATA and SATA Disk DMA only
1811 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001812 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001813 Combinations also work, so libata.dma=3 enables DMA
1814 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001815
Michael Prokop20308872009-08-06 00:14:10 +02001816 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1817 libata.ignore_hpa=0 keep BIOS limits (default)
1818 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001819
Dave Jones78e70c22007-09-27 11:50:13 -04001820 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1821 when set.
1822 Format: <int>
1823
Tejun Heo33267322008-02-13 09:15:09 +09001824 libata.force= [LIBATA] Force configurations. The format is comma
1825 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001826 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001827 matching port, link or device. Basically, it matches
1828 the ATA ID string printed on console by libata. If
1829 the whole ID part is omitted, the last PORT and DEVICE
1830 values are used. If ID hasn't been specified yet, the
1831 configuration applies to all ports, links and devices.
1832
1833 If only DEVICE is omitted, the parameter applies to
1834 the port and all links and devices behind it. DEVICE
1835 number of 0 either selects the first device or the
1836 first fan-out link behind PMP device. It does not
1837 select the host link. DEVICE number of 15 selects the
1838 host link and device attached to it.
1839
1840 The VAL specifies the configuration to force. As long
1841 as there's no ambiguity shortcut notation is allowed.
1842 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1843 The following configurations can be forced.
1844
1845 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1846 Any ID with matching PORT is used.
1847
1848 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1849
1850 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1851 udma[/][16,25,33,44,66,100,133] notation is also
1852 allowed.
1853
1854 * [no]ncq: Turn on or off NCQ.
1855
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001856 * [no]ncqtrim: Turn off queued DSM TRIM.
1857
Tejun Heo05944bd2008-08-13 20:19:09 +09001858 * nohrst, nosrst, norst: suppress hard, soft
1859 and both resets.
1860
Dan Williamsca6d43b2012-06-21 23:41:41 -07001861 * rstonce: only attempt one reset during
1862 hot-unplug link recovery
1863
Tejun Heo43c9c592010-05-23 12:59:11 +02001864 * dump_id: dump IDENTIFY data.
1865
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001866 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1867
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001868 * disable: Disable this device.
1869
Tejun Heo33267322008-02-13 09:15:09 +09001870 If there are multiple matching configurations changing
1871 the same attribute, the last one is used.
1872
Yinghai Lu95f72d12010-07-12 14:36:09 +10001873 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001874
Linus Torvalds1da177e2005-04-16 15:20:36 -07001875 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001876 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001877
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001878 lockd.nlm_grace_period=P [NFS] Assign grace period.
1879 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001880
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001881 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1882 Format: <integer>
1883
1884 lockd.nlm_timeout=T [NFS] Assign timeout value.
1885 Format: <integer>
1886
1887 lockd.nlm_udpport=M [NFS] Assign UDP port.
1888 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001889
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001890 locktorture.nreaders_stress= [KNL]
1891 Set the number of locking read-acquisition kthreads.
1892 Defaults to being automatically set based on the
1893 number of online CPUs.
1894
1895 locktorture.nwriters_stress= [KNL]
1896 Set the number of locking write-acquisition kthreads.
1897
1898 locktorture.onoff_holdoff= [KNL]
1899 Set time (s) after boot for CPU-hotplug testing.
1900
1901 locktorture.onoff_interval= [KNL]
1902 Set time (s) between CPU-hotplug operations, or
1903 zero to disable CPU-hotplug testing.
1904
1905 locktorture.shuffle_interval= [KNL]
1906 Set task-shuffle interval (jiffies). Shuffling
1907 tasks allows some CPUs to go into dyntick-idle
1908 mode during the locktorture test.
1909
1910 locktorture.shutdown_secs= [KNL]
1911 Set time (s) after boot system shutdown. This
1912 is useful for hands-off automated testing.
1913
1914 locktorture.stat_interval= [KNL]
1915 Time (s) between statistics printk()s.
1916
1917 locktorture.stutter= [KNL]
1918 Time (s) to stutter testing, for example,
1919 specifying five seconds causes the test to run for
1920 five seconds, wait for five seconds, and so on.
1921 This tests the locking primitive's ability to
1922 transition abruptly to and from idle.
1923
1924 locktorture.torture_runnable= [BOOT]
1925 Start locktorture running at boot time.
1926
1927 locktorture.torture_type= [KNL]
1928 Specify the locking implementation to test.
1929
1930 locktorture.verbose= [KNL]
1931 Enable additional printk() statements.
1932
Linus Torvalds1da177e2005-04-16 15:20:36 -07001933 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1934 Format: <irq>
1935
1936 loglevel= All Kernel Messages with a loglevel smaller than the
1937 console loglevel will be printed to the console. It can
1938 also be changed with klogd or other programs. The
1939 loglevels are defined as follows:
1940
1941 0 (KERN_EMERG) system is unusable
1942 1 (KERN_ALERT) action must be taken immediately
1943 2 (KERN_CRIT) critical conditions
1944 3 (KERN_ERR) error conditions
1945 4 (KERN_WARNING) warning conditions
1946 5 (KERN_NOTICE) normal but significant condition
1947 6 (KERN_INFO) informational
1948 7 (KERN_DEBUG) debug-level messages
1949
Randy Dunlapc756d082011-02-20 20:08:35 -08001950 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001951 in bytes. n must be a power of two and greater
1952 than the minimal size. The minimal size is defined
1953 by LOG_BUF_SHIFT kernel config parameter. There is
1954 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1955 that allows to increase the default size depending on
1956 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001957
Randy Dunlapaccaa242007-10-16 01:29:37 -07001958 logo.nologo [FB] Disables display of the built-in Linux logo.
1959 This may be used to provide more screen space for
1960 kernel log messages and is useful when debugging
1961 kernel boot problems.
1962
Linus Torvalds1da177e2005-04-16 15:20:36 -07001963 lp=0 [LP] Specify parallel ports to use, e.g,
1964 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1965 lp=reset first parallel port). 'lp=0' disables the
1966 lp=auto printer driver. 'lp=reset' (which can be
1967 specified in addition to the ports) causes
1968 attached printers to be reset. Using
1969 lp=port1,port2,... specifies the parallel ports
1970 to associate lp devices with, starting with
1971 lp0. A port specification may be 'none' to skip
1972 that lp device, or a parport name such as
1973 'parport0'. Specifying 'lp=auto' instead of a
1974 port specification list means that device IDs
1975 from each port should be examined, to see if
1976 an IEEE 1284-compliant printer is attached; if
1977 so, the driver will manage that printer.
1978 See also header of drivers/char/lp.c.
1979
1980 lpj=n [KNL]
1981 Sets loops_per_jiffy to given constant, thus avoiding
1982 time-consuming boot-time autodetection (up to 250 ms per
1983 CPU). 0 enables autodetection (default). To determine
1984 the correct value for your kernel, boot with normal
1985 autodetection and see what value is printed. Note that
1986 on SMP systems the preset will be applied to all CPUs,
1987 which is likely to cause problems if your CPUs need
1988 significantly divergent settings. An incorrect value
1989 will cause delays in the kernel to be wrong, leading to
1990 unpredictable I/O errors and other breakage. Although
1991 unlikely, in the extreme case this might damage your
1992 hardware.
1993
1994 ltpc= [NET]
1995 Format: <io>,<irq>,<dma>
1996
Randy Dunlap16290242011-08-13 12:34:52 -07001997 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001998 (machvec) in a generic kernel.
1999 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000
Wu Zhangjin3209e702009-07-02 23:27:12 +08002001 machtype= [Loongson] Share the same kernel image file between different
2002 yeeloong laptop.
2003 Example: machtype=lemote-yeeloong-2f-7inch
2004
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002005 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2006 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002007
2008 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04002009 should make use of. maxcpus=n : n >= 0 limits the
2010 kernel to using 'n' processors. n=0 is a special case,
2011 it is equivalent to "nosmp", which also disables
2012 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002013
Kay Sieversd134b002011-07-31 22:08:04 +02002014 max_loop= [LOOP] The number of loop block devices that get
2015 (loop.max_loop) unconditionally pre-created at init time. The default
2016 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2017 of statically allocating a predefined number, loop
2018 devices can be requested on-demand with the
2019 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002020
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002021 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022
Uwe Hermann71cced62008-10-20 09:32:21 -07002023 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002024
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025 md= [HW] RAID subsystems devices and level
2026 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002027
Linus Torvalds1da177e2005-04-16 15:20:36 -07002028 mdacon= [MDA]
2029 Format: <first>,<last>
2030 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002031
Linus Torvalds1da177e2005-04-16 15:20:36 -07002032 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2033 Amount of memory to be used when the kernel is not able
2034 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002035 [X86] Work as limiting max address. Use together
2036 with memmap= to avoid physical address space collisions.
2037 Without memmap= PCI devices could be placed at addresses
2038 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002040 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 memory.
2042
Paul Mundt6902aa82008-09-21 17:14:42 +09002043 memchunk=nn[KMG]
2044 [KNL,SH] Allow user to override the default size for
2045 per-device physically contiguous DMA buffers.
2046
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302047 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048 E820 memory map, as specified by the user.
2049 Such memmap=exactmap lines can be constructed based on
2050 BIOS output or other requirements. See the memmap=nn@ss
2051 option description.
2052
2053 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002054 [KNL] Force usage of a specific region of memory.
2055 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002056
2057 memmap=nn[KMG]#ss[KMG]
2058 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002059 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060
2061 memmap=nn[KMG]$ss[KMG]
2062 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002063 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002064 Example: Exclude memory from 0x18690000-0x1869ffff
2065 memmap=64K$0x18690000
2066 or
2067 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002068
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002069 memmap=nn[KMG]!ss[KMG]
2070 [KNL,X86] Mark specific memory as protected.
2071 Region of memory to be used, from ss to ss+nn.
2072 The memory region may be marked as e820 type 12 (0xc)
2073 and is NVDIMM or ADR memory.
2074
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002075 memory_corruption_check=0/1 [X86]
2076 Some BIOSes seem to corrupt the first 64k of
2077 memory when doing things like suspend/resume.
2078 Setting this option will scan the memory
2079 looking for corruption. Enabling this will
2080 both detect corruption and prevent the kernel
2081 from using the memory being corrupted.
2082 However, its intended as a diagnostic tool; if
2083 repeatable BIOS-originated corruption always
2084 affects the same memory, you can use memmap=
2085 to prevent the kernel from using that memory.
2086
2087 memory_corruption_check_size=size [X86]
2088 By default it checks for corruption in the low
2089 64k, making this memory unavailable for normal
2090 use. Use this parameter to scan for
2091 corruption in more or less memory.
2092
2093 memory_corruption_check_period=seconds [X86]
2094 By default it checks for corruption every 60
2095 seconds. Use this parameter to check at some
2096 other rate. 0 disables periodic checking.
2097
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002098 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002099 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002100 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002101 Specifies the number of memtest passes to be
2102 performed. Each pass selects another test
2103 pattern from a given set of patterns. Memtest
2104 fills the memory with this pattern, validates
2105 memory contents and reserves bad memory
2106 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002107
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108 meye.*= [HW] Set MotionEye Camera parameters
2109 See Documentation/video4linux/meye.txt.
2110
Andres Salomon8f368812007-10-12 23:04:06 +02002111 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2112 Multi-Function General Purpose Timers on AMD Geode
2113 platforms.
2114
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002115 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2116 the BIOS has incorrectly applied a workaround. TinyBIOS
2117 version 0.98 is known to be affected, 0.99 fixes the
2118 problem by letting the user disable the workaround.
2119
Linus Torvalds1da177e2005-04-16 15:20:36 -07002120 mga= [HW,DRM]
2121
Randy Dunlap1c207f92008-11-19 15:36:16 -08002122 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2123 physical address is ignored.
2124
Michel Pollet39f45d72009-05-20 11:10:31 +01002125 mini2440= [ARM,HW,KNL]
2126 Format:[0..2][b][c][t]
2127 Default: "0tb"
2128 MINI2440 configuration specification:
2129 0 - The attached screen is the 3.5" TFT
2130 1 - The attached screen is the 7" TFT
2131 2 - The VGA Shield is attached (1024x768)
2132 Leaving out the screen size parameter will not load
2133 the TFT driver, and the framebuffer will be left
2134 unconfigured.
2135 b - Enable backlight. The TFT backlight pin will be
2136 linked to the kernel VESA blanking code and a GPIO
2137 LED. This parameter is not necessary when using the
2138 VGA shield.
2139 c - Enable the s3c camera interface.
2140 t - Reserved for enabling touchscreen support. The
2141 touchscreen support is not enabled in the mainstream
2142 kernel as of 2.6.30, a preliminary port can be found
2143 in the "bleeding edge" mini2440 support kernel at
2144 http://repo.or.cz/w/linux-2.6/mini2440.git
2145
Mel Gorman6b74ab92008-07-23 21:26:49 -07002146 mminit_loglevel=
2147 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2148 parameter allows control of the logging verbosity for
2149 the additional memory initialisation checks. A value
2150 of 0 disables mminit logging and a level of 4 will
2151 log everything. Information is printed at KERN_DEBUG
2152 so loglevel=8 may also need to be specified.
2153
Rusty Russell106a4ee2012-09-26 10:09:40 +01002154 module.sig_enforce
2155 [KNL] When CONFIG_MODULE_SIG is set, this means that
2156 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002157 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002158 is always true, so this option does nothing.
2159
Linus Torvalds1da177e2005-04-16 15:20:36 -07002160 mousedev.tap_time=
2161 [MOUSE] Maximum time between finger touching and
2162 leaving touchpad surface for touch to be considered
2163 a tap and be reported as a left button click (for
2164 touchpads working in absolute mode only).
2165 Format: <msecs>
2166 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2167 reporting absolute coordinates, such as tablets
2168 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2169 reporting absolute coordinates, such as tablets
2170
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302171 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002172 is similar to kernelcore except it specifies the
2173 amount of memory used for migratable allocations.
2174 If both kernelcore and movablecore is specified,
2175 then kernelcore will be at *least* the specified
2176 value but may be more. If movablecore on its own
2177 is specified, the administrator must be careful
2178 that the amount of memory usable for all allocations
2179 is not too small.
2180
Tang Chenc5320922013-11-12 15:08:10 -08002181 movable_node [KNL,X86] Boot-time switch to enable the effects
2182 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2183
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 MTD_Partition= [MTD]
2185 Format: <name>,<region-number>,<size>,<offset>
2186
Randy Dunlapa9913042005-10-23 12:57:11 -07002187 MTD_Region= [MTD] Format:
2188 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002189
2190 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002191 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002192
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002193 multitce=off [PPC] This parameter disables the use of the pSeries
2194 firmware feature for updating multiple TCE entries
2195 at a time.
2196
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002197 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2198
2199 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2200
2201 boundary - index of last SLC block on Flex-OneNAND.
2202 The remaining blocks are configured as MLC blocks.
2203 lock - Configure if Flex-OneNAND boundary should be locked.
2204 Once locked, the boundary cannot be changed.
2205 1 indicates lock status, 0 indicates unlock status.
2206
Ben Dooks9db829f2008-07-03 11:24:29 +01002207 mtdset= [ARM]
2208 ARM/S3C2412 JIVE boot control
2209
2210 See arch/arm/mach-s3c2412/mach-jive.c
2211
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002213 [HW] Make the MicroTouch USB driver use raw coordinates
2214 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002215
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002216 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002217 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002218 that could hold holes aka. UC entries.
2219
2220 mtrr_gran_size=nn[KMG] [X86]
2221 Used for mtrr cleanup. It is granularity of mtrr block.
2222 Default is 1.
2223 Large value could prevent small alignment from
2224 using up MTRRs.
2225
2226 mtrr_spare_reg_nr=n [X86]
2227 Format: <integer>
2228 Range: 0,7 : spare reg number
2229 Default : 1
2230 Used for mtrr cleanup. It is spare mtrr entries number.
2231 Set to 2 or more if your graphical card needs more.
2232
Linus Torvalds1da177e2005-04-16 15:20:36 -07002233 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2234
Linus Torvalds1da177e2005-04-16 15:20:36 -07002235 netdev= [NET] Network devices parameters
2236 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2237 Note that mem_start is often overloaded to mean
2238 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002239 This usage is only documented in each driver source
2240 file if at all.
2241
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002242 nf_conntrack.acct=
2243 [NETFILTER] Enable connection tracking flow accounting
2244 0 to disable accounting
2245 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002246 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002247
Chuck Lever306a0752010-09-17 10:54:37 -04002248 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002249 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250
2251 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002252 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253
Chuck Lever306a0752010-09-17 10:54:37 -04002254 nfsrootdebug [NFS] enable nfsroot debugging messages.
2255 See Documentation/filesystems/nfs/nfsroot.txt.
2256
Trond Myklebusta72b4422006-01-03 09:55:41 +01002257 nfs.callback_tcpport=
2258 [NFS] set the TCP port on which the NFSv4 callback
2259 channel should listen.
2260
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002261 nfs.cache_getent=
2262 [NFS] sets the pathname to the program which is used
2263 to update the NFS client cache entries.
2264
2265 nfs.cache_getent_timeout=
2266 [NFS] sets the timeout after which an attempt to
2267 update a cache entry is deemed to have failed.
2268
Trond Myklebust58df0952006-01-03 09:55:57 +01002269 nfs.idmap_cache_timeout=
2270 [NFS] set the maximum lifetime for idmapper cache
2271 entries.
2272
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002273 nfs.enable_ino64=
2274 [NFS] enable 64-bit inode numbers.
2275 If zero, the NFS client will fake up a 32-bit inode
2276 number for the readdir() and stat() syscalls instead
2277 of returning the full 64-bit number.
2278 The default is to return 64-bit inode numbers.
2279
Trond Myklebustef159e92012-02-06 19:50:40 -05002280 nfs.max_session_slots=
2281 [NFSv4.1] Sets the maximum number of session slots
2282 the client will attempt to negotiate with the server.
2283 This limits the number of simultaneous RPC requests
2284 that the client can send to the NFSv4.1 server.
2285 Note that there is little point in setting this
2286 value higher than the max_tcp_slot_table_limit.
2287
Trond Myklebustb064eca22011-02-22 15:44:32 -08002288 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002289 [NFSv4] When set to the default of '1', this option
2290 ensures that both the RPC level authentication
2291 scheme and the NFS level operations agree to use
2292 numeric uids/gids if the mount is using the
2293 'sec=sys' security flavour. In effect it is
2294 disabling idmapping, which can make migration from
2295 legacy NFSv2/v3 systems to NFSv4 easier.
2296 Servers that do not support this mode of operation
2297 will be autodetected by the client, and it will fall
2298 back to using the idmapper.
2299 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002300 nfs.nfs4_unique_id=
2301 [NFS4] Specify an additional fixed unique ident-
2302 ification string that NFSv4 clients can insert into
2303 their nfs_client_id4 string. This is typically a
2304 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002305
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002306 nfs.send_implementation_id =
2307 [NFSv4.1] Send client implementation identification
2308 information in exchange_id requests.
2309 If zero, no implementation identification information
2310 will be sent.
2311 The default is to send the implementation identification
2312 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002313
2314 nfs.recover_lost_locks =
2315 [NFSv4] Attempt to recover locks that were lost due
2316 to a lease timeout on the server. Please note that
2317 doing this risks data corruption, since there are
2318 no guarantees that the file will remain unchanged
2319 after the locks are lost.
2320 If you want to enable the kernel legacy behaviour of
2321 attempting to recover these locks, then set this
2322 parameter to '1'.
2323 The default parameter value of '0' causes the kernel
2324 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002325
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002326 nfs4.layoutstats_timer =
2327 [NFSv4.2] Change the rate at which the kernel sends
2328 layoutstats to the pNFS metadata server.
2329
2330 Setting this to value to 0 causes the kernel to use
2331 whatever value is the default set by the layout
2332 driver. A non-zero value sets the minimum interval
2333 in seconds between layoutstats transmissions.
2334
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002335 nfsd.nfs4_disable_idmapping=
2336 [NFSv4] When set to the default of '1', the NFSv4
2337 server will return only numeric uids and gids to
2338 clients using auth_sys, and will accept numeric uids
2339 and gids from such clients. This is intended to ease
2340 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002341
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002342 objlayoutdriver.osd_login_prog=
2343 [NFS] [OBJLAYOUT] sets the pathname to the program which
2344 is used to automatically discover and login into new
2345 osd-targets. Please see:
2346 Documentation/filesystems/pnfs.txt for more explanations
2347
Paul Mundt1e1030d2009-09-01 17:38:32 +09002348 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002349 when a NMI is triggered.
2350 Format: [state][,regs][,debounce][,die]
2351
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302352 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002353 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002354 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002355 0 - turn hardlockup detector in nmi_watchdog off
2356 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002357 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002358 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002359 default). To disable both hard and soft lockup detectors,
2360 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002361 This is useful when you use a panic=... timeout and
2362 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002363
Anton Vorontsovbff38772009-07-08 11:10:56 -07002364 netpoll.carrier_timeout=
2365 [NET] Specifies amount of time (in seconds) that
2366 netpoll should wait for a carrier. By default netpoll
2367 waits 4 seconds.
2368
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002369 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002370 emulation library even if a 387 maths coprocessor
2371 is present.
2372
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002373 no_console_suspend
2374 [HW] Never suspend the console
2375 Disable suspending of consoles during suspend and
2376 hibernate operations. Once disabled, debugging
2377 messages can reach various consoles while the rest
2378 of the system is being put to sleep (ie, while
2379 debugging driver suspend/resume hooks). This may
2380 not work reliably with all consoles, but is known
2381 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002382 To facilitate more flexible debugging, we also add
2383 console_suspend, a printk module parameter to control
2384 it. Users could use console_suspend (usually
2385 /sys/module/printk/parameters/console_suspend) to
2386 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002387
Christoph Lameterc1aee212007-05-31 00:40:47 -07002388 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2389 caches in the slab allocator. Saves per-node memory,
2390 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002391
Randy Dunlapa9913042005-10-23 12:57:11 -07002392 noalign [KNL,ARM]
2393
Linus Torvalds1da177e2005-04-16 15:20:36 -07002394 noapic [SMP,APIC] Tells the kernel to not make use of any
2395 IOAPICs that may be present in the system.
2396
Mike Galbraith5091faa2010-11-30 14:18:03 +01002397 noautogroup Disable scheduler automatic task group creation.
2398
Linus Torvalds1da177e2005-04-16 15:20:36 -07002399 nobats [PPC] Do not use BATs for mapping kernel lowmem
2400 on "Classic" PPC cores.
2401
2402 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002403
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002404 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2405
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002406 nodelayacct [KNL] Disable per-task delay accounting
2407
Linus Torvalds1da177e2005-04-16 15:20:36 -07002408 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2409
Paul Mundt6902aa82008-09-21 17:14:42 +09002410 nodsp [SH] Disable hardware DSP at boot time.
2411
Dave Youngb2e0a542014-08-14 17:15:26 +08002412 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002413
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 noexec [IA-64]
2415
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302416 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002417 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002418 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002419 noexec=off: disable non-executable mappings
2420
H. Peter Anvin52b61792012-09-21 12:43:13 -07002421 nosmap [X86]
2422 Disable SMAP (Supervisor Mode Access Prevention)
2423 even if it is supported by processor.
2424
Fenghua Yude5397a2011-05-11 16:51:05 -07002425 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002426 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002427 even if it is supported by processor.
2428
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002429 noexec32 [X86-64]
2430 This affects only 32-bit executables.
2431 noexec32=on: enable non-executable mappings (default)
2432 read doesn't imply executable mappings
2433 noexec32=off: disable non-executable mappings
2434 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002436 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002437
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002438 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002439 register save and restore. The kernel will only save
2440 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002441
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002442 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2443
Suresh Siddha0c752a92009-05-22 12:17:45 -07002444 noxsave [BUGS=X86] Disables x86 extended register state save
2445 and restore using xsave. The kernel will fallback to
2446 enabling legacy floating-point and sse state.
2447
Fenghua Yub6f42a42014-05-29 11:12:31 -07002448 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2449 register states. The kernel will fall back to use
2450 xsave to save the states. By using this parameter,
2451 performance of saving the states is degraded because
2452 xsave doesn't support modified optimization while
2453 xsaveopt supports it on xsaveopt enabled systems.
2454
2455 noxsaves [X86] Disables xsaves and xrstors used in saving and
2456 restoring x86 extended register state in compacted
2457 form of xsave area. The kernel will fall back to use
2458 xsaveopt and xrstor to save and restore the states
2459 in standard form of xsave area. By using this
2460 parameter, xsave area per process might occupy more
2461 memory on xsaves enabled systems.
2462
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002463 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2464 wfi(ARM) instruction doesn't work correctly and not to
2465 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002466
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002467 no_file_caps Tells the kernel not to honor file capabilities. The
2468 only way then for a file to be executed with privilege
2469 is to be setuid root or executed by root.
2470
Linus Torvalds1da177e2005-04-16 15:20:36 -07002471 nohalt [IA-64] Tells the kernel not to use the power saving
2472 function PAL_HALT_LIGHT when idle. This increases
2473 power-consumption. On the positive side, it reduces
2474 interrupt wake-up latency, which may improve performance
2475 in certain environments such as networked servers or
2476 real-time systems.
2477
Kees Cooka6e15a32014-06-13 13:30:35 -07002478 nohibernate [HIBERNATION] Disable hibernation and resume.
2479
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002480 nohz= [KNL] Boottime enable/disable dynamic ticks
2481 Valid arguments: on, off
2482 Default: on
2483
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002484 nohz_full= [KNL,BOOT]
2485 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002486 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002487 whenever possible. The boot CPU will be forced outside
2488 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002489 The CPUs in this range must also be included in the
2490 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002491
Paul Mundteeee7852009-04-02 12:31:16 +09002492 noiotrap [SH] Disables trapped I/O port accesses.
2493
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002494 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002495 disable unhandled interrupt sources.
2496
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302497 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002498 broken timer IRQ sources.
2499
Linus Torvalds1da177e2005-04-16 15:20:36 -07002500 noisapnp [ISAPNP] Disables ISA PnP code.
2501
2502 noinitrd [RAM] Tells the kernel not to load any configured
2503 initial RAM disk.
2504
Weidong Han03ea8152009-04-17 16:42:15 +08002505 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2506 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002507 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002508
Linus Torvalds1da177e2005-04-16 15:20:36 -07002509 nointroute [IA-64]
2510
Randy Dunlap16290242011-08-13 12:34:52 -07002511 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002512
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002513 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2514
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002515 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2516 fault handling.
2517
Glauber Costad910f5c2011-07-11 15:28:19 -04002518 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2519 steal time is computed, but won't influence scheduler
2520 behaviour
2521
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002522 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002523
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002524 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002525
Linus Torvalds1da177e2005-04-16 15:20:36 -07002526 noltlbs [PPC] Do not use large page/tlb entries for kernel
2527 lowmem mapping on PPC40x.
2528
Horms312f1f02006-02-22 09:57:55 +09002529 nomca [IA-64] Disable machine check abort handling
2530
Masanari Iida13696e02015-05-16 02:16:43 +09002531 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002532
Andres Salomon83d73842007-10-12 23:04:06 +02002533 nomfgpt [X86-32] Disable Multi-Function General Purpose
2534 Timer usage (for AMD Geode machines).
2535
Don Zickusbda62632011-10-13 15:14:27 -04002536 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2537 shutdown the other cpus. Instead use the REBOOT_VECTOR
2538 irq.
2539
Dave Young02608be2012-02-01 10:33:14 +08002540 nomodule Disable module load
2541
Jiri Kosina016ddd92010-01-18 17:05:40 +01002542 nopat [X86] Disable PAT (page attribute table extension of
2543 pagetables) support.
2544
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002545 norandmaps Don't use address space randomization. Equivalent to
2546 echo 0 > /proc/sys/kernel/randomize_va_space
2547
Jiri Kosinabbff2162010-08-11 18:34:09 +02002548 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002549
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002550 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002551 with UP alternatives
2552
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002553 nordrand [X86] Disable kernel use of the RDRAND and
2554 RDSEED instructions even if they are supported
2555 by the processor. RDRAND and RDSEED are still
2556 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002557
Randy Dunlapa9913042005-10-23 12:57:11 -07002558 noresume [SWSUSP] Disables resume and restores original swap
2559 space.
2560
Linus Torvalds1da177e2005-04-16 15:20:36 -07002561 no-scroll [VGA] Disables scrollback.
2562 This is required for the Braillex ib80-piezo Braille
2563 reader made by F.H. Papenmeier (Germany).
2564
2565 nosbagart [IA-64]
2566
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002567 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002568
Len Brown61ec7562007-08-16 03:34:22 -04002569 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2570 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002571
Dave Jones97842212007-07-15 23:41:05 -07002572 nosoftlockup [KNL] Disable the soft-lockup detector.
2573
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 nosync [HW,M68K] Disables sync negotiation for all devices.
2575
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002576 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002577
2578 nousb [USB] Disable the USB subsystem
2579
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002580 nowatchdog [KNL] Disable both lockup detectors, i.e.
2581 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002584
Weidong Han2b2fd872009-04-17 16:42:12 +08002585 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2586
Fenghua Yuf78cff42012-11-13 11:32:38 -08002587 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2588 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2589 Some features depend on CPU0. Known dependencies are:
2590 1. Resume from suspend/hibernate depends on CPU0.
2591 Suspend/hibernate will fail if CPU0 is offline and you
2592 need to online CPU0 before suspend/hibernate.
2593 2. PIC interrupts also depend on CPU0. CPU0 can't be
2594 removed if a PIC interrupt is detected.
2595 It's said poweroff/reboot may depend on CPU0 on some
2596 machines although I haven't seen such issues so far
2597 after CPU0 is offline on a few tested machines.
2598 If the dependencies are under your control, you can
2599 turn on cpu0_hotplug.
2600
Randy Dunlap16290242011-08-13 12:34:52 -07002601 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002602 purges which is reported from either PAL_VM_SUMMARY or
2603 SAL PALO.
2604
Yinghai Lu2b633e32010-02-10 01:20:37 -08002605 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2606 could support. nr_cpus=n : n >= 1 limits the kernel to
2607 supporting 'n' processors. Later in runtime you can not
2608 use hotplug cpu feature to put more cpu back to online.
2609 just like you compile the kernel NR_CPUS=n
2610
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002611 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2612
Mel Gorman1a687c22012-11-22 11:16:36 +00002613 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2614 Allowed values are enable and disable
2615
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002616 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2617 one of ['zone', 'node', 'default'] can be specified
2618 This can be set from sysctl after boot.
2619 See Documentation/sysctl/vm.txt for details.
2620
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002621 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2622 See Documentation/debugging-via-ohci1394.txt for more
2623 info.
2624
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002625 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2626 Rather than timing out after 20 ms if an EC
2627 command is not properly ACKed, override the length
2628 of the timeout. We have interrupts disabled while
2629 waiting for the ACK, so if this is set too high
2630 interrupts *may* be lost!
2631
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002632 omap_mux= [OMAP] Override bootloader pin multiplexing.
2633 Format: <mux_mode0.mode_name=value>...
2634 For example, to override I2C bus2:
2635 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2636
Linus Torvalds1da177e2005-04-16 15:20:36 -07002637 oprofile.timer= [HW]
2638 Use timer interrupt instead of performance counters
2639
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002640 oprofile.cpu_type= Force an oprofile cpu type
2641 This might be useful if you have an older oprofile
2642 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002643 Format: { arch_perfmon }
2644 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002645 perfmon on Intel CPUs instead of the
2646 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002647 timer: [X86] Force use of architectural NMI
2648 timer mode (see also oprofile.timer
2649 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002650 [s390] Force legacy basic mode sampling
2651 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002652
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002653 oops=panic Always panic on oopses. Default is to just kill the
2654 process, but there is a small probability of
2655 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002656 This will also cause panics on machine check exceptions.
2657 Useful together with panic=30 to trigger a reboot.
2658
Randy Dunlapbcfde332010-06-07 17:10:38 -07002659 OSS [HW,OSS]
2660 See Documentation/sound/oss/oss-parameters.txt
2661
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002662 page_owner= [KNL] Boot-time page_owner enabling option.
2663 Storage of the information about who allocated
2664 each page is disabled in default. With this switch,
2665 we can turn it on.
2666 on: enable the feature
2667
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002668 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002669 timeout > 0: seconds before rebooting
2670 timeout = 0: wait forever
2671 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002672 Format: <timeout>
2673
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002674 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2675 on a WARN().
2676
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002677 crash_kexec_post_notifiers
2678 Run kdump after running panic-notifiers and dumping
2679 kmsg. This only for the users who doubt kdump always
2680 succeeds in any situation.
2681 Note that this also increases risks of kdump failure,
2682 because some panic notifiers can make the crashed
2683 kernel more unstable.
2684
Linus Torvalds1da177e2005-04-16 15:20:36 -07002685 parkbd.port= [HW] Parallel port number the keyboard adapter is
2686 connected to, default is 0.
2687 Format: <parport#>
2688 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2689 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002690 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002691
Randy Dunlapa9913042005-10-23 12:57:11 -07002692 parport= [HW,PPT] Specify parallel ports. 0 disables.
2693 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2694 Use 'auto' to force the driver to use any
2695 IRQ/DMA settings detected (the default is to
2696 ignore detected IRQ/DMA settings because of
2697 possible conflicts). You can specify the base
2698 address, IRQ, and DMA settings; IRQ and DMA
2699 should be numbers, or 'auto' (for using detected
2700 settings on that particular port), or 'nofifo'
2701 (to avoid using a FIFO even if it is detected).
2702 Parallel ports are assigned in the order they
2703 are specified on the command line, starting
2704 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002705
Randy Dunlapa9913042005-10-23 12:57:11 -07002706 parport_init_mode= [HW,PPT]
2707 Configure VIA parallel port to operate in
2708 a specific mode. This is necessary on Pegasos
2709 computer where firmware has no options for setting
2710 up parallel port mode and sets it to spp.
2711 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002712 Format: [spp|ps2|epp|ecp|ecpepp]
2713
Andrew Mortondd287792006-03-23 03:00:57 -08002714 pause_on_oops=
2715 Halt all CPUs after the first oops has been printed for
2716 the specified number of seconds. This is to be used if
2717 your oopses keep scrolling off the screen.
2718
Linus Torvalds1da177e2005-04-16 15:20:36 -07002719 pcbit= [HW,ISDN]
2720
2721 pcd. [PARIDE]
2722 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002723 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724
Randy Dunlapa9913042005-10-23 12:57:11 -07002725 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002726 earlydump [X86] dump PCI config space before the kernel
2727 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002728 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002729 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002730 the hardware directly. Use this if your machine
2731 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002732 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002733 hardware access methods are allowed. Use this
2734 if you experience crashes upon bootup and you
2735 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002736 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002737 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002738 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002739 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002740 noaer [PCIE] If the PCIEAER kernel config parameter is
2741 enabled, this kernel boot option can be used to
2742 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002743 nodomains [PCI] Disable support for multiple PCI
2744 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302745 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002746 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002747 check_enable_amd_mmconf [X86] check for and enable
2748 properly configured MMIO access to PCI
2749 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002750 nomsi [MSI] If the PCI_MSI kernel config parameter is
2751 enabled, this kernel boot option can be used to
2752 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002753 noioapicquirk [APIC] Disable all boot interrupt quirks.
2754 Safety option to keep boot IRQs enabled. This
2755 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002756 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2757 primary IO-APIC for bridges that cannot disable
2758 boot IRQs. This fixes a source of spurious IRQs
2759 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002760 noioapicreroute [APIC] Disable workaround that uses the
2761 boot IRQ equivalent of an IRQ that connects to
2762 a chipset where boot IRQs cannot be disabled.
2763 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002764 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002765 routing table. These calls are known to be buggy
2766 on several machines and they hang the machine
2767 when used, but on other computers it's the only
2768 way to get the interrupt routing table. Try
2769 this option if the kernel is unable to allocate
2770 IRQs or discover secondary PCI buses on your
2771 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002772 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002773 Use with caution as certain devices share
2774 address decoders between ROMs and other
2775 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002776 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002777 expansion ROMs that do not already have
2778 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002779 nobar [X86] Do not assign address space to the
2780 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002781 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002782 assigned automatically to PCI devices. You can
2783 make the kernel exclude IRQs of your ISA cards
2784 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002785 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002786 of the PIRQ table (normally generated
2787 by the BIOS) if it is outside the
2788 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002789 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002790 useful if the kernel is unable to find your
2791 secondary buses and you want to tell it
2792 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002793 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002794 numbers ourselves, overriding
2795 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002796 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002797 in the BIOS $PIR table. This is needed on
2798 some systems with broken BIOSes, notably
2799 some HP Pavilion N5400 and Omnibook XE3
2800 notebooks. This will have no effect if ACPI
2801 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002802 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002803 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002804 use_crs [X86] Use PCI host bridge window information
2805 from ACPI. On BIOSes from 2008 or later, this
2806 is enabled by default. If you need to use this,
2807 please report a bug.
2808 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2809 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002810 routeirq Do IRQ routing for all PCI devices.
2811 This is normally done in pci_enable_device(),
2812 so this option is a temporary workaround
2813 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002814 skip_isa_align [X86] do not align io start addr, so can
2815 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002816 firmware [ARM] Do not re-enumerate the bus but instead
2817 just use the configuration from the
2818 bootloader. This is currently used on
2819 IXP2000 systems where the bus has to be
2820 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002821 noearly [X86] Don't do any early type 1 scanning.
2822 This might help on some broken boards which
2823 machine check when some devices' config space
2824 is read. But various workarounds are disabled
2825 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002826 bfsort Sort PCI devices into breadth-first order.
2827 This sorting is done to get a device
2828 order compatible with older (<= 2.4) kernels.
2829 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002830 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2831 tuning and use the BIOS-configured MPS defaults.
2832 pcie_bus_safe Set every device's MPS to the largest value
2833 supported by all devices below the root complex.
2834 pcie_bus_perf Set device MPS to the largest allowable MPS
2835 based on its parent bus. Also set MRRS (Max
2836 Read Request Size) to the largest supported
2837 value (no larger than the MPS that the device
2838 or bus can support) for best performance.
2839 pcie_bus_peer2peer Set every device's MPS to 128B, which
2840 every device is guaranteed to support. This
2841 configuration allows peer-to-peer DMA between
2842 any pair of devices, possibly at the cost of
2843 reduced performance. This also guarantees
2844 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002845 cbiosize=nn[KMG] The fixed amount of bus space which is
2846 reserved for the CardBus bridge's IO window.
2847 The default value is 256 bytes.
2848 cbmemsize=nn[KMG] The fixed amount of bus space which is
2849 reserved for the CardBus bridge's memory
2850 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002851 resource_alignment=
2852 Format:
2853 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2854 Specifies alignment and device to reassign
2855 aligned memory resources.
2856 If <order of align> is not specified,
2857 PAGE_SIZE is used as alignment.
2858 PCI-PCI bridge can be specified, if resource
2859 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002860 ecrc= Enable/disable PCIe ECRC (transaction layer
2861 end-to-end CRC checking).
2862 bios: Use BIOS/firmware settings. This is the
2863 the default.
2864 off: Turn ECRC off
2865 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002866 hpiosize=nn[KMG] The fixed amount of bus space which is
2867 reserved for hotplug bridge's IO window.
2868 Default size is 256 bytes.
2869 hpmemsize=nn[KMG] The fixed amount of bus space which is
2870 reserved for hotplug bridge's memory window.
2871 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002872 realloc= Enable/disable reallocating PCI bridge resources
2873 if allocations done by BIOS are too small to
2874 accommodate resources required by all child
2875 devices.
2876 off: Turn realloc off
2877 on: Turn realloc on
2878 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002879 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002880 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2881 only look for one device below a PCIe downstream
2882 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002883
Chuck Ebberte5665a42008-09-24 20:40:34 -04002884 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2885 Management.
2886 off Disable ASPM.
2887 force Enable ASPM even on devices that claim not to support it.
2888 WARNING: Forcing ASPM on may cause system lockups.
2889
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002890 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2891 nomsi Do not use MSI for PCI Express Native Hotplug (this
2892 makes all PCIe ports use INTx for hotplug services).
2893
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002894 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002895 auto Ask the BIOS whether or not to use native PCIe services
2896 associated with PCIe ports (PME, hot-plug, AER). Use
2897 them only if that is allowed by the BIOS.
2898 native Use native PCIe services associated with PCIe ports
2899 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002900 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2901 ports driver.
2902
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002903 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002904 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002905 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002906
Linus Torvalds1da177e2005-04-16 15:20:36 -07002907 pcmv= [HW,PCMCIA] BadgePAD 4
2908
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302909 pd_ignore_unused
2910 [PM]
2911 Keep all power-domains already enabled by bootloader on,
2912 even if no driver has claimed them. This is useful
2913 for debug and development, but should not be
2914 needed on a platform with proper driver support.
2915
Linus Torvalds1da177e2005-04-16 15:20:36 -07002916 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002917 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002918
2919 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2920 boot time.
2921 Format: { 0 | 1 }
2922 See arch/parisc/kernel/pdc_chassis.c
2923
Tejun Heof58dc012009-08-14 15:00:50 +09002924 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002925 Currently supported values are "embed" and "page".
2926 Archs may support subset or none of the selections.
2927 See comments in mm/percpu.c for details on each
2928 allocator. This parameter is primarily for debugging
2929 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002930
Linus Torvalds1da177e2005-04-16 15:20:36 -07002931 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002932 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002933
2934 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002935 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002936
2937 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002938 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002939
2940 plip= [PPT,NET] Parallel port network link
2941 Format: { parport<nr> | timid | 0 }
2942 See also Documentation/parport.txt.
2943
Randy Dunlap16290242011-08-13 12:34:52 -07002944 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002945 Override pmtimer IOPort with a hex value.
2946 e.g. pmtmr=0x508
2947
Bjorn Helgaas96242112011-08-11 12:14:05 -06002948 pnp.debug=1 [PNP]
2949 Enable PNP debug messages (depends on the
2950 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2951 via /sys/module/pnp/parameters/debug. We always show
2952 current resource usage; turning this on also shows
2953 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002954
Linus Torvalds1da177e2005-04-16 15:20:36 -07002955 pnpacpi= [ACPI]
2956 { off }
2957
2958 pnpbios= [ISAPNP]
2959 { on | off | curr | res | no-curr | no-res }
2960
2961 pnp_reserve_irq=
2962 [ISAPNP] Exclude IRQs for the autoconfiguration
2963
2964 pnp_reserve_dma=
2965 [ISAPNP] Exclude DMAs for the autoconfiguration
2966
2967 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002968 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002969
2970 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002971 [ISAPNP] Exclude memory regions for the
2972 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002973 Ranges are in pairs (memory base and size).
2974
Randy Dunlap4af94f32009-04-17 18:30:28 -07002975 ports= [IP_VS_FTP] IPVS ftp helper module
2976 Default is 21.
2977 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2978 may be specified.
2979 Format: <port>,<port>....
2980
Ingo Molnar45807a12007-07-15 23:40:10 -07002981 print-fatal-signals=
2982 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002983
2984 If enabled, warn about various signal handling
2985 related application anomalies: too many signals,
2986 too many POSIX.1 timers, fatal signals causing a
2987 coredump - etc.
2988
2989 If you hit the warning due to signal overflow,
2990 you might want to try "ulimit -i unlimited".
2991
Ingo Molnar45807a12007-07-15 23:40:10 -07002992 default: off.
2993
Matthew Garrettc22ab332012-03-05 14:59:10 -08002994 printk.always_kmsg_dump=
2995 Trigger kmsg_dump for cases other than kernel oops or
2996 panics
2997 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2998 default: disabled
2999
Randy Dunlape84845c2007-07-15 23:40:25 -07003000 printk.time= Show timing data prefixed to each printk message line
3001 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3002
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003003 processor.max_cstate= [HW,ACPI]
3004 Limit processor to maximum C-state
3005 max_cstate=9 overrides any DMI blacklist limit.
3006
3007 processor.nocst [HW,ACPI]
3008 Ignore the _CST method to determine C-states,
3009 instead using the legacy FADT method
3010
Linus Torvalds1da177e2005-04-16 15:20:36 -07003011 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003012 Format: [schedule,]<number>
3013 Param: "schedule" - profile schedule points.
3014 Param: <number> - step/bucket size as a power of 2 for
3015 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003016 Param: "sleep" - profile D-state sleeping (millisecs).
3017 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003018 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003019
Linus Torvalds1da177e2005-04-16 15:20:36 -07003020 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3021 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003022 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003023
Randy Dunlapa9913042005-10-23 12:57:11 -07003024 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3025 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003026 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3027 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003028 psmouse.resetafter= [HW,MOUSE]
3029 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003030 (0 = never).
3031 psmouse.resolution=
3032 [HW,MOUSE] Set desired mouse resolution, in dpi.
3033 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003034 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003035 0 = disabled, 1 = enabled (default).
3036
Matthew Garrettdee28e72011-07-21 16:57:55 -04003037 pstore.backend= Specify the name of the pstore backend to use
3038
Linus Torvalds1da177e2005-04-16 15:20:36 -07003039 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003040 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003041
Kay Sieversdc8c8582007-08-15 12:25:38 +02003042 pty.legacy_count=
3043 [KNL] Number of legacy pty's. Overwrites compiled-in
3044 default number.
3045
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003046 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003047
Linus Torvalds1da177e2005-04-16 15:20:36 -07003048 r128= [HW,DRM]
3049
3050 raid= [HW,RAID]
3051 See Documentation/md.txt.
3052
Randy Dunlapa9913042005-10-23 12:57:11 -07003053 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003054 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07003055
Linus Torvalds1da177e2005-04-16 15:20:36 -07003056 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003057 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003058
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003059 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003060 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3061 the specified list of CPUs to be no-callback CPUs.
3062 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003063 be offloaded to "rcuox/N" kthreads created for
3064 that purpose, where "x" is "b" for RCU-bh, "p"
3065 for RCU-preempt, and "s" for RCU-sched, and "N"
3066 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003067 offloaded CPUs, which can be useful for HPC and
3068 real-time workloads. It can also improve energy
3069 efficiency for asymmetric multiprocessors.
3070
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003071 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003072 Rather than requiring that offloaded CPUs
3073 (specified by rcu_nocbs= above) explicitly
3074 awaken the corresponding "rcuoN" kthreads,
3075 make these kthreads poll for callbacks.
3076 This improves the real-time response for the
3077 offloaded CPUs by relieving them of the need to
3078 wake up the corresponding kthread, but degrades
3079 energy efficiency by requiring that the kthreads
3080 periodically wake up to do the polling.
3081
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003082 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003083 Set maximum number of finished RCU callbacks to
3084 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003085
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003086 rcutree.dump_tree= [KNL]
3087 Dump the structure of the rcu_node combining tree
3088 out at early boot. This is used for diagnostic
3089 purposes, to verify correct tree setup.
3090
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003091 rcutree.gp_cleanup_delay= [KNL]
3092 Set the number of jiffies to delay each step of
3093 RCU grace-period cleanup. This only has effect
3094 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3095
Paul E. McKenney37745d22015-01-22 18:24:08 -08003096 rcutree.gp_init_delay= [KNL]
3097 Set the number of jiffies to delay each step of
3098 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003099 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3100 is set.
3101
3102 rcutree.gp_preinit_delay= [KNL]
3103 Set the number of jiffies to delay each step of
3104 RCU grace-period pre-initialization, that is,
3105 the propagation of recent CPU-hotplug changes up
3106 the rcu_node combining tree. This only has effect
3107 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003108
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003109 rcutree.rcu_fanout_exact= [KNL]
3110 Disable autobalancing of the rcu_node combining
3111 tree. This is used by rcutorture, and might
3112 possibly be useful for architectures having high
3113 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003114
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003115 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003116 Change the number of CPUs assigned to each
3117 leaf rcu_node structure. Useful for very
3118 large systems, which will choose the value 64,
3119 and for NUMA systems with large remote-access
3120 latencies, which will choose a value aligned
3121 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003122
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003123 rcutree.jiffies_till_sched_qs= [KNL]
3124 Set required age in jiffies for a
3125 given grace period before RCU starts
3126 soliciting quiescent-state help from
3127 rcu_note_context_switch().
3128
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003129 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003130 Set delay from grace-period initialization to
3131 first attempt to force quiescent states.
3132 Units are jiffies, minimum value is zero,
3133 and maximum value is HZ.
3134
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003135 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003136 Set delay between subsequent attempts to force
3137 quiescent states. Units are jiffies, minimum
3138 value is one, and maximum value is HZ.
3139
Clark Williams21871d72014-09-12 21:21:09 -05003140 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003141 Set the SCHED_FIFO priority of the RCU per-CPU
3142 kthreads (rcuc/N). This value is also used for
3143 the priority of the RCU boost threads (rcub/N)
3144 and for the RCU grace-period kthreads (rcu_bh,
3145 rcu_preempt, and rcu_sched). If RCU_BOOST is
3146 set, valid values are 1-99 and the default is 1
3147 (the least-favored priority). Otherwise, when
3148 RCU_BOOST is not set, valid values are 0-99 and
3149 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003150
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003151 rcutree.rcu_nocb_leader_stride= [KNL]
3152 Set the number of NOCB kthread groups, which
3153 defaults to the square root of the number of
3154 CPUs. Larger numbers reduces the wakeup overhead
3155 on the per-CPU grace-period kthreads, but increases
3156 that same overhead on each group's leader.
3157
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003158 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003159 Set threshold of queued RCU callbacks beyond which
3160 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003161
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003162 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003163 Set threshold of queued RCU callbacks below which
3164 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003165
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003166 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003167 Set wakeup interval for idle CPUs that have
3168 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003169
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003170 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003171 Set wakeup interval for idle CPUs that have
3172 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3173 Lazy RCU callbacks are those which RCU can
3174 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003175
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003176 rcutorture.cbflood_inter_holdoff= [KNL]
3177 Set holdoff time (jiffies) between successive
3178 callback-flood tests.
3179
3180 rcutorture.cbflood_intra_holdoff= [KNL]
3181 Set holdoff time (jiffies) between successive
3182 bursts of callbacks within a given callback-flood
3183 test.
3184
3185 rcutorture.cbflood_n_burst= [KNL]
3186 Set the number of bursts making up a given
3187 callback-flood test. Set this to zero to
3188 disable callback-flood testing.
3189
3190 rcutorture.cbflood_n_per_burst= [KNL]
3191 Set the number of callbacks to be registered
3192 in a given burst of a callback-flood test.
3193
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003194 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003195 Set duration of force_quiescent_state bursts
3196 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003197
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003198 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003199 Set holdoff time within force_quiescent_state bursts
3200 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003201
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003202 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003203 Set wait time between force_quiescent_state bursts
3204 in seconds.
3205
3206 rcutorture.gp_cond= [KNL]
3207 Use conditional/asynchronous update-side
3208 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003209
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003210 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003211 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003212
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003213 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003214 Use normal (non-expedited) asynchronous
3215 update-side primitives, if available.
3216
3217 rcutorture.gp_sync= [KNL]
3218 Use normal (non-expedited) synchronous
3219 update-side primitives, if available. If all
3220 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3221 rcutorture.gp_normal=, and rcutorture.gp_sync=
3222 are zero, rcutorture acts as if is interpreted
3223 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003224
3225 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003226 Set callbacks/threads for rcu_barrier() testing.
3227
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003228 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003229 Set number of concurrent RCU writers. These just
3230 stress RCU, they don't participate in the actual
3231 test, hence the "fake".
3232
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003233 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003234 Set number of RCU readers. The value -1 selects
3235 N-1, where N is the number of CPUs. A value
3236 "n" less than -1 selects N-n-2, where N is again
3237 the number of CPUs. For example, -2 selects N
3238 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003239
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003240 rcutorture.object_debug= [KNL]
3241 Enable debug-object double-call_rcu() testing.
3242
3243 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003244 Set time (s) after boot for CPU-hotplug testing.
3245
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003246 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003247 Set time (s) between CPU-hotplug operations, or
3248 zero to disable CPU-hotplug testing.
3249
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003250 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003251 Set task-shuffle interval (s). Shuffling tasks
3252 allows some CPUs to go into dyntick-idle mode
3253 during the rcutorture test.
3254
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003255 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003256 Set time (s) after boot system shutdown. This
3257 is useful for hands-off automated testing.
3258
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003259 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003260 Duration of CPU stall (s) to test RCU CPU stall
3261 warnings, zero to disable.
3262
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003263 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003264 Time to wait (s) after boot before inducing stall.
3265
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003266 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003267 Time (s) between statistics printk()s.
3268
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003269 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003270 Time (s) to stutter testing, for example, specifying
3271 five seconds causes the test to run for five seconds,
3272 wait for five seconds, and so on. This tests RCU's
3273 ability to transition abruptly to and from idle.
3274
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003275 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003276 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3277 "Maybe" means test if the RCU implementation
3278 under test support RCU priority boosting.
3279
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003280 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003281 Duration (s) of each individual boost test.
3282
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003283 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003284 Interval (s) between each boost test.
3285
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003286 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003287 Test RCU's dyntick-idle handling. See also the
3288 rcutorture.shuffle_interval parameter.
3289
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003290 rcutorture.torture_runnable= [BOOT]
3291 Start rcutorture running at boot time.
3292
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003293 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003294 Specify the RCU implementation to test.
3295
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003296 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003297 Enable additional printk() statements.
3298
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003299 rcupdate.rcu_expedited= [KNL]
3300 Use expedited grace-period primitives, for
3301 example, synchronize_rcu_expedited() instead
3302 of synchronize_rcu(). This reduces latency,
3303 but can increase CPU utilization, degrade
3304 real-time latency, and degrade energy efficiency.
3305
3306 rcupdate.rcu_cpu_stall_suppress= [KNL]
3307 Suppress RCU CPU stall warning messages.
3308
3309 rcupdate.rcu_cpu_stall_timeout= [KNL]
3310 Set timeout for RCU CPU stall warning messages.
3311
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003312 rcupdate.rcu_task_stall_timeout= [KNL]
3313 Set timeout in jiffies for RCU task stall warning
3314 messages. Disable with a value less than or equal
3315 to zero.
3316
Pranith Kumar74860fe2014-09-19 11:34:09 -04003317 rcupdate.rcu_self_test= [KNL]
3318 Run the RCU early boot self tests
3319
3320 rcupdate.rcu_self_test_bh= [KNL]
3321 Run the RCU bh early boot self tests
3322
3323 rcupdate.rcu_self_test_sched= [KNL]
3324 Run the RCU sched early boot self tests
3325
Olof Johanssonffdfc402005-09-06 15:17:19 -07003326 rdinit= [KNL]
3327 Format: <full_path>
3328 Run specified binary instead of /init from the ramdisk,
3329 used for early userspace startup. See initrd.
3330
Robin Holt1b3a5d02013-07-08 16:01:42 -07003331 reboot= [KNL]
3332 Format (x86 or x86_64):
3333 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3334 [[,]s[mp]#### \
3335 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3336 [[,]f[orce]
3337 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3338 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3339 reboot_force is either force or not specified,
3340 reboot_cpu is s[mp]#### with #### being the processor
3341 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003342
Paul Jackson46b6d942008-07-04 10:00:09 -07003343 relax_domain_level=
3344 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003345 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003346
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003347 relative_sleep_states=
3348 [SUSPEND] Use sleep state labeling where the deepest
3349 state available other than hibernation is always "mem".
3350 Format: { "0" | "1" }
3351 0 -- Traditional sleep state labels.
3352 1 -- Relative sleep state labels.
3353
Linus Torvalds1da177e2005-04-16 15:20:36 -07003354 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3355
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003356 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003357 Format: nn[KMG]
3358 Reserves a hole at the top of the kernel virtual
3359 address space.
3360
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003361 reservelow= [X86]
3362 Format: nn[K]
3363 Set the amount of memory to reserve for BIOS at
3364 the bottom of the address space.
3365
Vivek Goyal7e962872006-09-27 01:50:44 -07003366 reset_devices [KNL] Force drivers to reset the underlying device
3367 during initialization.
3368
Randy Dunlapa9913042005-10-23 12:57:11 -07003369 resume= [SWSUSP]
3370 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003371 Format:
3372 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003373
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003374 resume_offset= [SWSUSP]
3375 Specify the offset from the beginning of the partition
3376 given by "resume=" at which the swap header is located,
3377 in <PAGE_SIZE> units (needed only for swap files).
3378 See Documentation/power/swsusp-and-swap-files.txt
3379
Barry Songf126f732011-10-10 23:38:41 +02003380 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3381 read the resume files
3382
Barry Song6f8d7022011-10-06 20:34:46 +02003383 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3384 Useful for devices that are detected asynchronously
3385 (e.g. USB and MMC devices).
3386
Bojan Smojverf996fc92010-09-09 23:06:23 +02003387 hibernate= [HIBERNATION]
3388 noresume Don't check if there's a hibernation image
3389 present during boot.
3390 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003391 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003392
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003393 retain_initrd [RAM] Keep initrd memory after extraction
3394
Andrew Clausen0efbb782015-01-09 20:24:55 +00003395 rfkill.default_state=
3396 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3397 etc. communication is blocked by default.
3398 1 Unblocked.
3399
3400 rfkill.master_switch_mode=
3401 0 The "airplane mode" button does nothing.
3402 1 The "airplane mode" button toggles between everything
3403 blocked and the previous configuration.
3404 2 The "airplane mode" button toggles between everything
3405 blocked and everything unblocked.
3406
Linus Torvalds1da177e2005-04-16 15:20:36 -07003407 rhash_entries= [KNL,NET]
3408 Set number of hash buckets for route cache
3409
Linus Torvalds1da177e2005-04-16 15:20:36 -07003410 ro [KNL] Mount root device read-only on boot
3411
3412 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003413 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003414
3415 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3416 mount the root filesystem
3417
3418 rootflags= [KNL] Set root filesystem mount option string
3419
3420 rootfstype= [KNL] Set root filesystem type
3421
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003422 rootwait [KNL] Wait (indefinitely) for root device to show up.
3423 Useful for devices that are detected asynchronously
3424 (e.g. USB and MMC devices).
3425
Robert Tivy5c71d612013-03-28 18:41:46 -07003426 rproc_mem=nn[KMG][@address]
3427 [KNL,ARM,CMA] Remoteproc physical memory block.
3428 Memory area to be used by remote processor image,
3429 managed by CMA.
3430
Linus Torvalds1da177e2005-04-16 15:20:36 -07003431 rw [KNL] Mount root device read-write on boot
3432
3433 S [KNL] Run init in single mode
3434
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003435 s390_iommu= [HW,S390]
3436 Set s390 IOTLB flushing mode
3437 strict
3438 With strict flushing every unmap operation will result in
3439 an IOTLB flush. Default is lazy flushing before reuse,
3440 which is faster.
3441
Linus Torvalds1da177e2005-04-16 15:20:36 -07003442 sa1100ir [NET]
3443 See drivers/net/irda/sa1100_ir.c.
3444
Linus Torvalds1da177e2005-04-16 15:20:36 -07003445 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003446
Mike Travisf6630112009-11-17 18:22:15 -06003447 sched_debug [KNL] Enables verbose scheduler debug messages.
3448
Mike Galbraith5307c952012-05-08 12:20:58 +02003449 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3450 xtime_lock contention on larger systems, and/or RCU lock
3451 contention on all systems with CONFIG_MAXSMP set.
3452 Format: { "0" | "1" }
3453 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3454 1 -- enable.
3455 Note: increases power consumption, thus should only be
3456 enabled if running jitter sensitive (HPC/RT) workloads.
3457
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003458 security= [SECURITY] Choose a security module to enable at boot.
3459 If this boot parameter is not specified, only the first
3460 security module asking for security registration will be
3461 loaded. An invalid security module name will be treated
3462 as if no module has been chosen.
3463
3464 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003465 Format: { "0" | "1" }
3466 See security/selinux/Kconfig help text.
3467 0 -- disable.
3468 1 -- enable.
3469 Default value is set via kernel config option.
3470 If enabled at boot time, /selinux/disable can be used
3471 later to disable prior to initial policy load.
3472
John Johansenc1c124e2010-07-29 14:48:09 -07003473 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3474 Format: { "0" | "1" }
3475 See security/apparmor/Kconfig help text
3476 0 -- disable.
3477 1 -- enable.
3478 Default value is set via kernel config option.
3479
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003480 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003481
Linus Torvalds1da177e2005-04-16 15:20:36 -07003482 shapers= [NET]
3483 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003484
Yinghai Lub05f78f2008-08-22 01:32:50 -07003485 show_msr= [x86] show boot-time MSR settings
3486 Format: { <integer> }
3487 Show boot-time (BIOS-initialized) MSR settings.
3488 The parameter means the number of CPUs to show,
3489 for example 1 means boot CPU only.
3490
Linus Torvalds1da177e2005-04-16 15:20:36 -07003491 simeth= [IA-64]
3492 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003493
Linus Torvalds1da177e2005-04-16 15:20:36 -07003494 slram= [HW,MTD]
3495
Joonsoo Kim423c9292014-10-09 15:26:22 -07003496 slab_nomerge [MM]
3497 Disable merging of slabs with similar size. May be
3498 necessary if there is some reason to distinguish
3499 allocs to different slabs. Debug options disable
3500 merging on their own.
3501 For more information see Documentation/vm/slub.txt.
3502
David Rientjes3df1ccc2011-10-18 22:09:28 -07003503 slab_max_order= [MM, SLAB]
3504 Determines the maximum allowed order for slabs.
3505 A high setting may cause OOMs due to memory
3506 fragmentation. Defaults to 1 for systems with
3507 more than 32MB of RAM, 0 otherwise.
3508
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003509 slub_debug[=options[,slabs]] [MM, SLUB]
3510 Enabling slub_debug allows one to determine the
3511 culprit if slab objects become corrupted. Enabling
3512 slub_debug can create guard zones around objects and
3513 may poison objects when not in use. Also tracks the
3514 last alloc / free. For more information see
3515 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003516
3517 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003518 Determines the maximum allowed order for slabs.
3519 A high setting may cause OOMs due to memory
3520 fragmentation. For more information see
3521 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003522
3523 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003524 The minimum number of objects per slab. SLUB will
3525 increase the slab order up to slub_max_order to
3526 generate a sufficiently large slab able to contain
3527 the number of objects indicated. The higher the number
3528 of objects the smaller the overhead of tracking slabs
3529 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003530 For more information see Documentation/vm/slub.txt.
3531
3532 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003533 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003534 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003535 For more information see Documentation/vm/slub.txt.
3536
3537 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003538 Same with slab_nomerge. This is supported for legacy.
3539 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003540
Linus Torvalds1da177e2005-04-16 15:20:36 -07003541 smart2= [HW]
3542 Format: <io1>[,<io2>[,...,<io8>]]
3543
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003544 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3545 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3546 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3547 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3548 smsc-ircc2.ircc_irq= [HW] IRQ line
3549 smsc-ircc2.ircc_dma= [HW] DMA channel
3550 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3551 0: Toshiba Satellite 1800 (GP data pin select)
3552 1: Fast pin select (default)
3553 2: ATC IRMode
3554
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003555 softlockup_panic=
3556 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003557 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003558
Aaron Tomlined235872014-06-23 13:22:05 -07003559 softlockup_all_cpu_backtrace=
3560 [KNL] Should the soft-lockup detector generate
3561 backtraces on all cpus.
3562 Format: <integer>
3563
Linus Torvalds1da177e2005-04-16 15:20:36 -07003564 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003565 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003566
Linus Torvalds1da177e2005-04-16 15:20:36 -07003567 spia_io_base= [HW,MTD]
3568 spia_fio_base=
3569 spia_pedr=
3570 spia_peddr=
3571
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003572 stacktrace [FTRACE]
3573 Enabled the stack tracer on boot up.
3574
Steven Rostedt762e1202011-12-19 22:01:00 -05003575 stacktrace_filter=[function-list]
3576 [FTRACE] Limit the functions that the stack tracer
3577 will trace at boot up. function-list is a comma separated
3578 list of functions. This list can be changed at run
3579 time by the stack_trace_filter file in the debugfs
3580 tracing directory. Note, this enables stack tracing
3581 and the stacktrace above is not needed.
3582
Linus Torvalds1da177e2005-04-16 15:20:36 -07003583 sti= [PARISC,HW]
3584 Format: <num>
3585 Set the STI (builtin display/keyboard on the HP-PARISC
3586 machines) console (graphic card) which should be used
3587 as the initial boot-console.
3588 See also comment in drivers/video/console/sticore.c.
3589
3590 sti_font= [HW]
3591 See comment in drivers/video/console/sticore.c.
3592
3593 stifb= [HW]
3594 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3595
Trond Myklebustcbf11072009-08-09 15:06:19 -04003596 sunrpc.min_resvport=
3597 sunrpc.max_resvport=
3598 [NFS,SUNRPC]
3599 SunRPC servers often require that client requests
3600 originate from a privileged port (i.e. a port in the
3601 range 0 < portnr < 1024).
3602 An administrator who wishes to reserve some of these
3603 ports for other uses may adjust the range that the
3604 kernel's sunrpc client considers to be privileged
3605 using these two parameters to set the minimum and
3606 maximum port values.
3607
Greg Banks42a7fc42007-03-06 01:42:23 -08003608 sunrpc.pool_mode=
3609 [NFS]
3610 Control how the NFS server code allocates CPUs to
3611 service thread pools. Depending on how many NICs
3612 you have and where their interrupts are bound, this
3613 option will affect which CPUs will do NFS serving.
3614 Note: this parameter cannot be changed while the
3615 NFS server is running.
3616
3617 auto the server chooses an appropriate mode
3618 automatically using heuristics
3619 global a single global pool contains all CPUs
3620 percpu one pool for each CPU
3621 pernode one pool for each NUMA node (equivalent
3622 to global on non-NUMA machines)
3623
Trond Myklebustcbf11072009-08-09 15:06:19 -04003624 sunrpc.tcp_slot_table_entries=
3625 sunrpc.udp_slot_table_entries=
3626 [NFS,SUNRPC]
3627 Sets the upper limit on the number of simultaneous
3628 RPC calls that can be sent from the client to a
3629 server. Increasing these values may allow you to
3630 improve throughput, but will also increase the
3631 amount of memory reserved for use by the client.
3632
Brian Norris1d4a9c12015-02-22 21:16:49 -08003633 suspend.pm_test_delay=
3634 [SUSPEND]
3635 Sets the number of seconds to remain in a suspend test
3636 mode before resuming the system (see
3637 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3638 is set. Default value is 5.
3639
Michal Hocko07555ac2013-08-22 16:35:46 -07003640 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003641 [KNL] Enable accounting of swap in memory resource
3642 controller if no parameter or 1 is given or disable
3643 it if 0 is given (See Documentation/cgroups/memory.txt)
3644
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003645 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3646 Format: { <int> | force }
3647 <int> -- Number of I/O TLB slabs
3648 force -- force using of bounce buffers even if they
3649 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003650
Linus Torvalds1da177e2005-04-16 15:20:36 -07003651 switches= [HW,M68k]
3652
Andi Kleene52eec12010-09-08 16:54:17 +02003653 sysfs.deprecated=0|1 [KNL]
3654 Enable/disable old style sysfs layout for old udev
3655 on older distributions. When this option is enabled
3656 very new udev will not work anymore. When this option
3657 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3658 in older udev will not work anymore.
3659 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3660 the kernel configuration.
3661
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003662 sysrq_always_enabled
3663 [KNL]
3664 Ignore sysrq setting - this boot parameter will
3665 neutralize any effect of /proc/sys/kernel/sysrq.
3666 Useful for debugging.
3667
Fabian Frederick747029a2014-11-06 19:46:50 +01003668 tcpmhash_entries= [KNL,NET]
3669 Set the number of tcp_metrics_hash slots.
3670 Default value is 8192 or 16384 depending on total
3671 ram pages. This is used to specify the TCP metrics
3672 cache size. See Documentation/networking/ip-sysctl.txt
3673 "tcp_no_metrics_save" section for more details.
3674
Linus Torvalds1da177e2005-04-16 15:20:36 -07003675 tdfx= [HW,DRM]
3676
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003677 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003678 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003679 standby suspend) or "freeze" (for suspend type freeze)
3680 as the system sleep state during system startup with
3681 the optional capability to repeat N number of times.
3682 The system is woken from this state using a
3683 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003684
Linus Torvalds1da177e2005-04-16 15:20:36 -07003685 thash_entries= [KNL,NET]
3686 Set number of hash buckets for TCP connection
3687
Len Brownf8707ec2007-08-12 00:12:54 -04003688 thermal.act= [HW,ACPI]
3689 -1: disable all active trip points in all thermal zones
3690 <degrees C>: override all lowest active trip points
3691
Len Brownc52a7412007-08-14 15:49:32 -04003692 thermal.crt= [HW,ACPI]
3693 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003694 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003695
Len Brownf5487142007-08-12 00:12:44 -04003696 thermal.nocrt= [HW,ACPI]
3697 Set to disable actions on ACPI thermal zone
3698 critical and hot trip points.
3699
Len Brown72b33ef2007-08-12 00:12:17 -04003700 thermal.off= [HW,ACPI]
3701 1: disable ACPI thermal control
3702
Len Browna70cdc52007-08-12 00:12:35 -04003703 thermal.psv= [HW,ACPI]
3704 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003705 <degrees C>: override all passive trip points to this
3706 value
Len Browna70cdc52007-08-12 00:12:35 -04003707
Len Brown730ff342007-08-12 00:12:26 -04003708 thermal.tzp= [HW,ACPI]
3709 Specify global default ACPI thermal zone polling rate
3710 <deci-seconds>: poll all this frequency
3711 0: no polling (default)
3712
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003713 threadirqs [KNL]
3714 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003715 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003716
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003717 tmem [KNL,XEN]
3718 Enable the Transcendent memory driver if built-in.
3719
3720 tmem.cleancache=0|1 [KNL, XEN]
3721 Default is on (1). Disable the usage of the cleancache
3722 API to send anonymous pages to the hypervisor.
3723
3724 tmem.frontswap=0|1 [KNL, XEN]
3725 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003726 API to send swap pages to the hypervisor. If disabled
3727 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003728
3729 tmem.selfballooning=0|1 [KNL, XEN]
3730 Default is on (1). Disable the driving of swap pages
3731 to the hypervisor.
3732
3733 tmem.selfshrinking=0|1 [KNL, XEN]
3734 Default is on (1). Partial swapoff that immediately
3735 transfers pages from Xen hypervisor back to the
3736 kernel based on different criteria.
3737
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003738 topology= [S390]
3739 Format: {off | on}
3740 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003741 topology information if the hardware supports this.
3742 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003743 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003744 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003745
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003746 topology_updates= [KNL, PPC, NUMA]
3747 Format: {off}
3748 Specify if the kernel should ignore (off)
3749 topology updates sent by the hypervisor to this
3750 LPAR.
3751
Linus Torvalds1da177e2005-04-16 15:20:36 -07003752 tp720= [HW,PS2]
3753
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003754 tpm_suspend_pcr=[HW,TPM]
3755 Format: integer pcr id
3756 Specify that at suspend time, the tpm driver
3757 should extend the specified pcr with zeros,
3758 as a workaround for some chips which fail to
3759 flush the last written pcr on TPM_SaveState.
3760 This will guarantee that all the other pcrs
3761 are saved.
3762
Li Zefan9d612be2009-06-24 17:33:15 +08003763 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003764 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003765
Li Zefan020e5f82009-07-01 10:47:05 +08003766 trace_event=[event-list]
3767 [FTRACE] Set and start specified trace events in order
3768 to facilitate early boot debugging.
3769 See also Documentation/trace/events.txt
3770
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003771 trace_options=[option-list]
3772 [FTRACE] Enable or disable tracer options at boot.
3773 The option-list is a comma delimited list of options
3774 that can be enabled or disabled just as if you were
3775 to echo the option name into
3776
3777 /sys/kernel/debug/tracing/trace_options
3778
3779 For example, to enable stacktrace option (to dump the
3780 stack trace of each event), add to the command line:
3781
3782 trace_options=stacktrace
3783
3784 See also Documentation/trace/ftrace.txt "trace options"
3785 section.
3786
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003787 tp_printk[FTRACE]
3788 Have the tracepoints sent to printk as well as the
3789 tracing ring buffer. This is useful for early boot up
3790 where the system hangs or reboots and does not give the
3791 option for reading the tracing buffer or performing a
3792 ftrace_dump_on_oops.
3793
3794 To turn off having tracepoints sent to printk,
3795 echo 0 > /proc/sys/kernel/tracepoint_printk
3796 Note, echoing 1 into this file without the
3797 tracepoint_printk kernel cmdline option has no effect.
3798
3799 ** CAUTION **
3800
3801 Having tracepoints sent to printk() and activating high
3802 frequency tracepoints such as irq or sched, can cause
3803 the system to live lock.
3804
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003805 traceoff_on_warning
3806 [FTRACE] enable this option to disable tracing when a
3807 warning is hit. This turns off "tracing_on". Tracing can
3808 be enabled again by echoing '1' into the "tracing_on"
3809 file located in /sys/kernel/debug/tracing/
3810
3811 This option is useful, as it disables the trace before
3812 the WARNING dump is called, which prevents the trace to
3813 be filled with content caused by the warning output.
3814
3815 This option can also be set at run time via the sysctl
3816 option: kernel/traceoff_on_warning
3817
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003818 transparent_hugepage=
3819 [KNL]
3820 Format: [always|madvise|never]
3821 Can be used to control the default behavior of the system
3822 with respect to transparent hugepages.
3823 See Documentation/vm/transhuge.txt for more details.
3824
john stultzd3b8f882009-08-17 16:40:47 -07003825 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003826 Format: <string>
3827 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003828 disables clocksource verification at runtime, as well
3829 as the stability checks done at bootup. Used to enable
3830 high-resolution timer mode on older hardware, and in
3831 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003832 [x86] noirqtime: Do not use TSC to do irq accounting.
3833 Used to run time disable IRQ_TIME_ACCOUNTING on any
3834 platforms where RDTSC is slow and this accounting
3835 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003836
Randy Dunlapa9913042005-10-23 12:57:11 -07003837 turbografx.map[2|3]= [HW,JOY]
3838 TurboGraFX parallel port interface
3839 Format:
3840 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003841 See also Documentation/input/joystick-parport.txt
3842
Christian Kujaub6935f82011-05-31 15:22:05 +00003843 udbg-immortal [PPC] When debugging early kernel crashes that
3844 happen after console_init() and before a proper
3845 console driver takes over, this boot options might
3846 help "seeing" what's going on.
3847
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003848 uhash_entries= [KNL,NET]
3849 Set number of hash buckets for UDP/UDP-Lite connections
3850
Alan Stern5f8364b2006-12-05 16:29:55 -05003851 uhci-hcd.ignore_oc=
3852 [USB] Ignore overcurrent events (default N).
3853 Some badly-designed motherboards generate lots of
3854 bogus events, for ports that aren't wired to
3855 anything. Set this parameter to avoid log spamming.
3856 Note that genuine overcurrent events won't be
3857 reported either.
3858
Simon Arlotte3a61b02008-07-19 23:32:54 +01003859 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003860 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003861
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003862 usbcore.authorized_default=
3863 [USB] Default USB device authorization:
3864 (default -1 = authorized except for wireless USB,
3865 0 = not authorized, 1 = authorized)
3866
Alan Sternb5e795f2007-02-20 15:00:53 -05003867 usbcore.autosuspend=
3868 [USB] The autosuspend time delay (in seconds) used
3869 for newly-detected USB devices (default 2). This
3870 is the time required before an idle device will be
3871 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003872 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003873
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003874 usbcore.usbfs_snoop=
3875 [USB] Set to log all usbfs traffic (default 0 = off).
3876
3877 usbcore.blinkenlights=
3878 [USB] Set to cycle leds on hubs (default 0 = off).
3879
3880 usbcore.old_scheme_first=
3881 [USB] Start with the old device initialization
3882 scheme (default 0 = off).
3883
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003884 usbcore.usbfs_memory_mb=
3885 [USB] Memory limit (in MB) for buffers allocated by
3886 usbfs (default = 16, 0 = max = 2047).
3887
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003888 usbcore.use_both_schemes=
3889 [USB] Try the other device initialization scheme
3890 if the first one fails (default 1 = enabled).
3891
3892 usbcore.initial_descriptor_timeout=
3893 [USB] Specifies timeout for the initial 64-byte
3894 USB_REQ_GET_DESCRIPTOR request in milliseconds
3895 (default 5000 = 5.0 seconds).
3896
Linus Torvalds1da177e2005-04-16 15:20:36 -07003897 usbhid.mousepoll=
3898 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003899
Alan Sternd4f373e2008-11-10 14:07:45 -05003900 usb-storage.delay_use=
3901 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00003902 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05003903
3904 usb-storage.quirks=
3905 [UMS] A list of quirks entries to supplement or
3906 override the built-in unusual_devs list. List
3907 entries are separated by commas. Each entry has
3908 the form VID:PID:Flags where VID and PID are Vendor
3909 and Product ID values (4-digit hex numbers) and
3910 Flags is a set of characters, each corresponding
3911 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003912 a = SANE_SENSE (collect more than 18 bytes
3913 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003914 b = BAD_SENSE (don't collect more than 18
3915 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003916 c = FIX_CAPACITY (decrease the reported
3917 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003918 d = NO_READ_DISC_INFO (don't use
3919 READ_DISC_INFO command);
3920 e = NO_READ_CAPACITY_16 (don't use
3921 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003922 f = NO_REPORT_OPCODES (don't use report opcodes
3923 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02003924 g = MAX_SECTORS_240 (don't transfer more than
3925 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003926 h = CAPACITY_HEURISTICS (decrease the
3927 reported device capacity by one
3928 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003929 i = IGNORE_DEVICE (don't bind to this
3930 device);
3931 l = NOT_LOCKABLE (don't try to lock and
3932 unlock ejectable media);
3933 m = MAX_SECTORS_64 (don't transfer more
3934 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003935 n = INITIAL_READ10 (force a retry of the
3936 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003937 o = CAPACITY_OK (accept the capacity
3938 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003939 p = WRITE_CACHE (the device cache is ON
3940 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003941 r = IGNORE_RESIDUE (the device reports
3942 bogus residue values);
3943 s = SINGLE_LUN (the device has only one
3944 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003945 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3946 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003947 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003948 w = NO_WP_DETECT (don't test whether the
3949 medium is write-protected).
3950 Example: quirks=0419:aaf5:rl,0421:0433:rc
3951
Stephen Boydac1667d2011-08-13 12:34:50 -07003952 user_debug= [KNL,ARM]
3953 Format: <int>
3954 See arch/arm/Kconfig.debug help text.
3955 1 - undefined instruction events
3956 2 - system calls
3957 4 - invalid data aborts
3958 8 - SIGSEGV faults
3959 16 - SIGBUS faults
3960 Example: user_debug=31
3961
Ian Campbell14315592010-02-17 10:38:10 +00003962 userpte=
3963 [X86] Flags controlling user PTE allocations.
3964
3965 nohigh = do not allocate PTE pages in
3966 HIGHMEM regardless of setting
3967 of CONFIG_HIGHPTE.
3968
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303969 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003970 On X86_32, this is an alias for vdso32=. Otherwise:
3971
3972 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003973 vdso=0: disable VDSO mapping
3974
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003975 vdso32= [X86] Control the 32-bit vDSO
3976 vdso32=1: enable 32-bit VDSO
3977 vdso32=0 or vdso32=2: disable 32-bit VDSO
3978
3979 See the help text for CONFIG_COMPAT_VDSO for more
3980 details. If CONFIG_COMPAT_VDSO is set, the default is
3981 vdso32=0; otherwise, the default is vdso32=1.
3982
3983 For compatibility with older kernels, vdso32=2 is an
3984 alias for vdso32=0.
3985
3986 Try vdso32=0 if you encounter an error that says:
3987 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003988
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003989 vector= [IA-64,SMP]
3990 vector=percpu: enable percpu vector domain
3991
Linus Torvalds1da177e2005-04-16 15:20:36 -07003992 video= [FB] Frame buffer configuration
3993 See Documentation/fb/modedb.txt.
3994
Aaron Lu3afe6da2013-06-20 15:08:55 +08003995 video.brightness_switch_enabled= [0,1]
3996 If set to 1, on receiving an ACPI notify event
3997 generated by hotkey, video driver will adjust brightness
3998 level and then send out the event to user space through
3999 the allocated input device; If set to 0, video driver
4000 will only send out the event without touching backlight
4001 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004002 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004003
Pawel Moll81a054c2012-05-09 18:30:16 +01004004 virtio_mmio.device=
4005 [VMMIO] Memory mapped virtio (platform) device.
4006
4007 <size>@<baseaddr>:<irq>[:<id>]
4008 where:
4009 <size> := size (can use standard suffixes
4010 like K, M and G)
4011 <baseaddr> := physical base address
4012 <irq> := interrupt number (as passed to
4013 request_irq())
4014 <id> := (optional) platform device id
4015 example:
4016 virtio_mmio.device=1K@0x100b0000:48:7
4017
4018 Can be used multiple times for multiple devices.
4019
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004020 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004021 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004022 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004023 Use vga=ask for menu.
4024 This is actually a boot loader parameter; the value is
4025 passed to the kernel using a special protocol.
4026
Randy Dunlapa9913042005-10-23 12:57:11 -07004027 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004028 size of <nn>. This can be used to increase the
4029 minimum size (128MB on x86). It can also be used to
4030 decrease the size and leave more room for directly
4031 mapped kernel RAM.
4032
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004033 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4034 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004035
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004036 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4037 Format: <command>
4038
4039 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4040 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004041
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004042 vsyscall= [X86-64]
4043 Controls the behavior of vsyscalls (i.e. calls to
4044 fixed addresses of 0xffffffffff600x00 from legacy
4045 code). Most statically-linked binaries and older
4046 versions of glibc use these calls. Because these
4047 functions are at fixed addresses, they make nice
4048 targets for exploits that can control RIP.
4049
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004050 emulate [default] Vsyscalls turn into traps and are
4051 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004052
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004053 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004054 This is a little bit faster than trapping
4055 and makes a few dynamic recompilers work
4056 better than they would in emulation mode.
4057 It also makes exploits much easier to write.
4058
4059 none Vsyscalls don't work at all. This makes
4060 them quite hard to use for exploits but
4061 might break your system.
4062
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004063 vt.color= [VT] Default text color.
4064 Format: 0xYX, X = foreground, Y = background.
4065 Default: 0x07 = light gray on black.
4066
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004067 vt.cur_default= [VT] Default cursor shape.
4068 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4069 the parameters of the <Esc>[?A;B;Cc escape sequence;
4070 see VGA-softcursor.txt. Default: 2 = underline.
4071
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004072 vt.default_blu= [VT]
4073 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4074 Change the default blue palette of the console.
4075 This is a 16-member array composed of values
4076 ranging from 0-255.
4077
4078 vt.default_grn= [VT]
4079 Format: <green0>,<green1>,<green2>,...,<green15>
4080 Change the default green palette of the console.
4081 This is a 16-member array composed of values
4082 ranging from 0-255.
4083
4084 vt.default_red= [VT]
4085 Format: <red0>,<red1>,<red2>,...,<red15>
4086 Change the default red palette of the console.
4087 This is a 16-member array composed of values
4088 ranging from 0-255.
4089
4090 vt.default_utf8=
4091 [VT]
4092 Format=<0|1>
4093 Set system-wide default UTF-8 mode for all tty's.
4094 Default is 1, i.e. UTF-8 mode is enabled for all
4095 newly opened terminals.
4096
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004097 vt.global_cursor_default=
4098 [VT]
4099 Format=<-1|0|1>
4100 Set system-wide default for whether a cursor
4101 is shown on new VTs. Default is -1,
4102 i.e. cursors will be created by default unless
4103 overridden by individual drivers. 0 will hide
4104 cursors, 1 will display them.
4105
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004106 vt.italic= [VT] Default color for italic text; 0-15.
4107 Default: 2 = green.
4108
4109 vt.underline= [VT] Default color for underlined text; 0-15.
4110 Default: 3 = cyan.
4111
Randy Dunlap4724ba572010-05-03 11:42:52 -07004112 watchdog timers [HW,WDT] For information on watchdog timers,
4113 see Documentation/watchdog/watchdog-parameters.txt
4114 or other driver-specific files in the
4115 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004116
Tejun Heod55262c2013-04-01 11:23:38 -07004117 workqueue.disable_numa
4118 By default, all work items queued to unbound
4119 workqueues are affine to the NUMA nodes they're
4120 issued on, which results in better behavior in
4121 general. If NUMA affinity needs to be disabled for
4122 whatever reason, this option can be used. Note
4123 that this also can be controlled per-workqueue for
4124 workqueues visible under /sys/bus/workqueue/.
4125
Viresh Kumarcee22a12013-04-08 16:45:40 +05304126 workqueue.power_efficient
4127 Per-cpu workqueues are generally preferred because
4128 they show better performance thanks to cache
4129 locality; unfortunately, per-cpu workqueues tend to
4130 be more power hungry than unbound workqueues.
4131
4132 Enabling this makes the per-cpu workqueues which
4133 were observed to contribute significantly to power
4134 consumption unbound, leading to measurably lower
4135 power usage at the cost of small performance
4136 overhead.
4137
4138 The default value of this parameter is determined by
4139 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4140
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004141 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4142 default x2apic cluster mode on platforms
4143 supporting x2apic.
4144
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004145 x86_intel_mid_timer= [X86-32,APBT]
4146 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004147 Two valid options are apbt timer only and lapic timer
4148 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004149 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004150
Juergen Grossc70727a2015-07-17 06:51:36 +02004151 xen_512gb_limit [KNL,X86-64,XEN]
4152 Restricts the kernel running paravirtualized under Xen
4153 to use only up to 512 GB of RAM. The reason to do so is
4154 crash analysis tools and Xen tools for doing domain
4155 save/restore/migration must be enabled to handle larger
4156 domains.
4157
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004158 xen_emul_unplug= [HW,X86,XEN]
4159 Unplug Xen emulated devices
4160 Format: [unplug0,][unplug1]
4161 ide-disks -- unplug primary master IDE devices
4162 aux-ide-disks -- unplug non-primary-master IDE devices
4163 nics -- unplug network devices
4164 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004165 unnecessary -- unplugging emulated devices is
4166 unnecessary even if the host did not respond to
4167 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004168 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004169
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004170 xen_nopvspin [X86,XEN]
4171 Disables the ticketlock slowpath using Xen PV
4172 optimizations.
4173
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004174 xen_nopv [X86]
4175 Disables the PV optimizations forcing the HVM guest to
4176 run as generic HVM guest with no PV drivers.
4177
Linus Torvalds1da177e2005-04-16 15:20:36 -07004178 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004179 Format:
4180 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004181
Randy Dunlapa9913042005-10-23 12:57:11 -07004182______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004183
4184TODO:
4185
Linus Torvalds1da177e2005-04-16 15:20:36 -07004186 Add more DRM drivers.