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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 Dilek89e0b9a32011-12-05 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
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100475 apic_extnmi= [APIC,X86] External NMI delivery setting
476 Format: { bsp (default) | all | none }
477 bsp: External NMI is delivered only to CPU 0
478 all: External NMIs are broadcast to all CPUs as a
479 backup of CPU 0
480 none: External NMI is masked for all CPUs. This is
481 useful so that a dump capture kernel won't be
482 shot down by NMI
483
Brian Haleyb0f83b22010-02-04 13:36:50 -0800484 autoconf= [IPV6]
485 See Documentation/networking/ipv6.txt.
486
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400487 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
488 Limit apic dumping. The parameter defines the maximal
489 number of local apics being dumped. Also it is possible
490 to set it to "all" by meaning -- no limit here.
491 Format: { 1 (default) | 2 | ... | all }.
492 The parameter valid if only apic=debug or
493 apic=verbose is specified.
494 Example: apic=debug show_lapic=all
495
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700497 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498
Linus Torvalds1da177e2005-04-16 15:20:36 -0700499 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
500 Format: <io>,<irq>,<nodeID>
501
502 ataflop= [HW,M68k]
503
504 atarimouse= [HW,MOUSE] Atari Mouse
505
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
507 EzKey and similar keyboards
508
509 atkbd.reset= [HW] Reset keyboard during initialization
510
Randy Dunlapa9913042005-10-23 12:57:11 -0700511 atkbd.set= [HW] Select keyboard code set
512 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513
514 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
515 keyboards
516
517 atkbd.softraw= [HW] Choose between synthetic and real raw mode
518 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700519
520 atkbd.softrepeat= [HW]
521 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400523 audit= [KNL] Enable the audit sub-system
524 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500525 0 - kernel audit is disabled and can not be enabled
526 until the next reboot
527 unset - kernel audit is initialized but disabled and
528 will be fully enabled by the userspace auditd.
529 1 - kernel audit is initialized and partially enabled,
530 storing at most audit_backlog_limit messages in
531 RAM until it is fully enabled by the userspace
532 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400533 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400534
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400535 audit_backlog_limit= [KNL] Set the audit queue size limit.
536 Format: <int> (must be >=0)
537 Default: 64
538
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539 baycom_epp= [HW,AX25]
540 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700541
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
543 Format: <io>,<mode>
544 See header of drivers/net/hamradio/baycom_par.c.
545
Randy Dunlapa9913042005-10-23 12:57:11 -0700546 baycom_ser_fdx= [HW,AX25]
547 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548 Format: <io>,<irq>,<mode>[,<baud>]
549 See header of drivers/net/hamradio/baycom_ser_fdx.c.
550
Randy Dunlapa9913042005-10-23 12:57:11 -0700551 baycom_ser_hdx= [HW,AX25]
552 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 Format: <io>,<irq>,<mode>
554 See header of drivers/net/hamradio/baycom_ser_hdx.c.
555
Paul Gortmaker080506a2013-09-30 13:45:19 -0700556 blkdevparts= Manual partition parsing of block device(s) for
557 embedded devices based on command line input.
558 See Documentation/block/cmdline-partition.txt
559
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700560 boot_delay= Milliseconds to delay each printk during boot.
561 Values larger than 10 seconds (10000) are changed to
562 no delay (0).
563 Format: integer
564
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700565 bootmem_debug [KNL] Enable bootmem allocator debug messages.
566
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700568 bttv.radio= Most important insmod options are available as
569 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200571 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000573 bulk_remove=off [PPC] This parameter disables the use of the pSeries
574 firmware feature for flushing multiple hpte entries
575 at a time.
576
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577 c101= [NET] Moxa C101 synchronous serial card
578
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700579 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 Sometimes CPU hardware bugs make them report the cache
581 size incorrectly. The kernel will attempt work arounds
582 to fix known problems, but for some CPUs it is not
583 possible to determine what the correct size should be.
584 This option provides an override for these situations.
585
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300586 ca_keys= [KEYS] This parameter identifies a specific key(s) on
587 the system trusted keyring to be used for certificate
588 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300589 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300590
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700591 cca= [MIPS] Override the kernel pages' cache coherency
592 algorithm. Accepted values range from 0 to 7
593 inclusive. See arch/mips/include/asm/pgtable-bits.h
594 for platform specific values (SB1, Loongson3 and
595 others).
596
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100597 ccw_timeout_log [S390]
598 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599
Paul Menage8bab8dd2008-04-04 14:29:57 -0700600 cgroup_disable= [KNL] Disable a particular controller
601 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800602 The effects of cgroup_disable=foo are:
603 - foo isn't auto-mounted if you mount all cgroups in
604 a single hierarchy
605 - foo isn't visible as an individually mountable
606 subsystem
607 {Currently only "memory" controller deal with this and
608 cut the overhead, others just disable the usage. So
609 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700610
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800611 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string>
613 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800614 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800615
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 checkreqprot [SELINUX] Set initial checkreqprot flag value.
617 Format: { "0" | "1" }
618 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700619 0 -- check protection applied by kernel (includes
620 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700621 1 -- check protection requested by application.
622 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700623 Value can be changed at runtime via
624 /selinux/checkreqprot.
625
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100626 cio_ignore= [S390]
627 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700628 clk_ignore_unused
629 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700630 Prevents the clock framework from automatically gating
631 clocks that have not been explicitly enabled by a Linux
632 device driver but are enabled in hardware at reset or
633 by the bootloader/firmware. Note that this does not
634 force such clocks to be always-on nor does it reserve
635 those clocks in any way. This parameter is useful for
636 debug and development, but should not be needed on a
637 platform with proper driver support. For more
638 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100639
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700640 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700641 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200642 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700643 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200644 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645 Format: { pit | tsc | cyclone | pmtmr }
646
John Stultz592913e2010-07-13 17:56:20 -0700647 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700648 Format: <string>
649 Override the default clocksource and use the clocksource
650 with the name specified.
651 Some clocksource names to choose from, depending on
652 the platform:
653 [all] jiffies (this is the base, fallback clocksource)
654 [ACPI] acpi_pm
655 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
656 pxa_timer,timer3,32k_counter,timer0_1
657 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700658 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700659 scx200_hrt on Geode; cyclone on IBM x440
660 [MIPS] MIPS
661 [PARISC] cr16
662 [S390] tod
663 [SH] SuperH
664 [SPARC64] tick
665 [X86-64] hpet,tsc
666
Andi Kleenac72e782008-01-30 13:33:21 +0100667 clearcpuid=BITNUM [X86]
668 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800669 arch/x86/include/asm/cpufeature.h for the valid bit
670 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100671 stable over kernel options, but the vendor specific
672 ones should be.
673 Also note that user programs calling CPUID directly
674 or using the feature without checking anything
675 will still see it. This just prevents it from
676 being used by the kernel or shown in /proc/cpuinfo.
677 Also note the kernel might malfunction if you disable
678 some critical bits.
679
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700680 cma=nn[MG]@[start[MG][-end[MG]]]
681 [ARM,X86,KNL]
682 Sets the size of kernel global memory area for
683 contiguous memory allocations and optionally the
684 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700685 memory allocations. A value of 0 disables CMA
686 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100687 include/linux/dma-contiguous.h
688
Robert Jennings14f966e2009-04-15 05:55:32 +0000689 cmo_free_hint= [PPC] Format: { yes | no }
690 Specify whether pages are marked as being inactive
691 when they are freed. This is used in CMO environments
692 to determine OS memory pressure for page stealing by
693 a hypervisor.
694 Default: yes
695
Marek Szyprowskic7909502011-12-29 13:09:51 +0100696 coherent_pool=nn[KMG] [ARM,KNL]
697 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200698 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100699
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530700 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100701 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100702 Range: 0 - 8192
703 Default: 64
704
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700706 Format:
707 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708
709 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
710 Format: <io>[,<irq>]
711
Randy Dunlapa9913042005-10-23 12:57:11 -0700712 com90xx= [HW,NET]
713 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714 Format: <io>[,<irq>[,<memstart>]]
715
716 condev= [HW,S390] console device
717 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700718
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719 console= [KNL] Output console device and options.
720
721 tty<n> Use the virtual console device <n>.
722
723 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800724 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800726 the form "bbbbpnf", where "bbbb" is the baud rate,
727 "p" is parity ("n", "o", or "e"), "n" is number of
728 bits, and "f" is flow control ("r" for RTS or
729 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700730
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800731 See Documentation/serial-console.txt for more
732 information. See
733 Documentation/networking/netconsole.txt for an
734 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700736 uart[8250],io,<addr>[,options]
737 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900738 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400739 uart[8250],mmio32,<addr>[,options]
740 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700741 Start an early, polled-mode console on the 8250/16550
742 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400743 switching to the matching ttyS device later.
744 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900745 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
746 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
747 to be equivalent to 'mmio'. 'options' are specified in
748 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400749 the h/w is not re-initialized.
750
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500751 hvc<n> Use the hypervisor console device <n>. This is for
752 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700754 If the device connected to the port is not a TTY but a braille
755 device, prepend "brl," before the device type, for instance
756 console=brl,ttyS0
757 For now, only VisioBraille is supported.
758
Daniel Mackf324edc2009-06-16 15:33:52 -0700759 consoleblank= [KNL] The console blank (screen saver) timeout in
760 seconds. Defaults to 10*60 = 10mins. A value of 0
761 disables the blank timer.
762
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800763 coredump_filter=
764 [KNL] Change the default value for
765 /proc/<pid>/coredump_filter.
766 See also Documentation/filesystems/proc.txt.
767
Len Brown62027ae2011-04-01 18:13:10 -0400768 cpuidle.off=1 [CPU_IDLE]
769 disable the cpuidle sub-system
770
Len Brownd68921f2015-05-11 17:27:09 -0400771 cpu_init_udelay=N
772 [X86] Delay for N microsec between assert and de-assert
773 of APIC INIT to start processors. This delay occurs
774 on every CPU online, such as boot, and resume from suspend.
775 Default: 10000
776
Linus Torvalds1da177e2005-04-16 15:20:36 -0700777 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700778 Format:
779 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700780
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800781 crashkernel=size[KMG][@offset[KMG]]
782 [KNL] Using kexec, Linux can switch to a 'crash kernel'
783 upon panic. This parameter reserves the physical
784 memory region [offset, offset + size] for that kernel
785 image. If '@offset' is omitted, then a suitable offset
786 is selected automatically. Check
787 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700788
Bernhard Wallefb391592007-10-18 23:41:02 -0700789 crashkernel=range1:size1[,range2:size2,...][@offset]
790 [KNL] Same as above, but depends on the memory
791 in the running system. The syntax of range is
792 start-[end] where start and end are both
793 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800794 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700795
Yinghai Luadbc7422013-04-15 22:23:48 -0700796 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700797 [KNL, x86_64] range could be above 4G. Allow kernel
798 to allocate physical memory region from top, so could
799 be above 4G if system have more than 4G ram installed.
800 Otherwise memory region will be allocated below 4G, if
801 available.
802 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700803 crashkernel=size[KMG],low
804 [KNL, x86_64] range under 4G. When crashkernel=X,high
805 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700806 above 4G, that cause second kernel crash on system
807 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800808 requires at least 64M+32K low memory, also enough extra
809 low memory is needed to make sure DMA buffers for 32-bit
810 devices won't run out. Kernel would try to allocate at
811 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700812 This one let user to specify own low range under 4G
813 for second kernel instead.
814 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700815 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700816 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700817
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 cs89x0_dma= [HW,NET]
819 Format: <dma>
820
821 cs89x0_media= [HW,NET]
822 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700823
Randy Dunlapa9913042005-10-23 12:57:11 -0700824 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825 See header of drivers/s390/block/dasd_devmap.c.
826
827 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
828 (one device per port)
829 Format: <port#>,<type>
830 See also Documentation/input/joystick-parport.txt
831
Thomas Renningera648ec02010-08-06 16:11:02 +0200832 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
833 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600834 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200835
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836 debug [KNL] Enable kernel debugging (events log level).
837
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700838 debug_locks_verbose=
839 [KNL] verbose self-tests
840 Format=<0|1>
841 Print debugging info while doing the locking API
842 self-tests.
843 We default to 0 (no extra messages), setting it to
844 1 will print _a lot_ more information - normally
845 only useful to kernel developers.
846
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700847 debug_objects [KNL] Enable object debugging
848
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500849 no_debug_objects
850 [KNL] Disable object debugging
851
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800852 debug_guardpage_minorder=
853 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
854 parameter allows control of the order of pages that will
855 be intentionally kept free (and hence protected) by the
856 buddy allocator. Bigger value increase the probability
857 of catching random memory corruption, but reduce the
858 amount of memory for normal system use. The maximum
859 possible value is MAX_ORDER/2. Setting this parameter
860 to 1 or 2 should be enough to identify most random
861 memory corruption problems caused by bugs in kernel or
862 driver code when a CPU writes to (or reads from) a
863 random memory location. Note that there exists a class
864 of memory corruptions problems caused by buggy H/W or
865 F/W or by drivers badly programing DMA (basically when
866 memory is written at bus level and the CPU MMU is
867 bypassed) which are not detectable by
868 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
869 tracking down these problems.
870
Joonsoo Kim031bc572014-12-12 16:55:52 -0800871 debug_pagealloc=
872 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
873 parameter enables the feature at boot time. In
874 default, it is disabled. We can avoid allocating huge
875 chunk of memory for debug pagealloc if we don't enable
876 it at boot time and the system will work mostly same
877 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
878 on: enable the feature
879
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200880 debugpat [X86] Enable PAT debugging
881
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200882 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 Format: <area>[,<node>]
884 See also Documentation/networking/decnet.txt.
885
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700886 default_hugepagesz=
887 [same as hugepagesz=] The size of the default
888 HugeTLB page size. This is the size represented by
889 the legacy /proc/ hugepages APIs, used for SHM, and
890 default size when mounting hugetlbfs filesystems.
891 Defaults to the default architecture's huge page size
892 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700893
Linus Torvalds1da177e2005-04-16 15:20:36 -0700894 dhash_entries= [KNL]
895 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700896
Brian Haleyb0f83b22010-02-04 13:36:50 -0800897 disable= [IPV6]
898 See Documentation/networking/ipv6.txt.
899
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900900 disable_cpu_apicid= [X86,APIC,SMP]
901 Format: <int>
902 The number of initial APIC ID for the
903 corresponding CPU to be disabled at boot,
904 mostly used for the kdump 2nd kernel to
905 disable BSP to wake up multiple CPUs without
906 causing system reset or hang due to sending
907 INIT from AP to BSP.
908
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000909 disable_ddw [PPC/PSERIES]
910 Disable Dynamic DMA Window support. Use this if
911 to workaround buggy firmware.
912
Brian Haleyb0f83b22010-02-04 13:36:50 -0800913 disable_ipv6= [IPV6]
914 See Documentation/networking/ipv6.txt.
915
Yinghai Lu95ffa242008-04-29 03:52:33 -0700916 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700917 The kernel tries to adjust MTRR layout from continuous
918 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700919 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700920
Yinghai Lu093af8d2008-01-30 13:33:32 +0100921 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100922 By default the kernel will trim any uncacheable
923 memory out of your available memory pool based on
924 MTRR settings. This parameter disables that behavior,
925 possibly causing your machine to run very slowly.
926
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530927 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700928 Disable PIN 1 of APIC timer
929 Can be useful to work around chipset bugs.
930
Prarit Bhargavace14c582015-08-25 13:34:53 -0400931 dis_ucode_ldr [X86] Disable the microcode loader.
932
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700933 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
934 this option disables the debugging code at boot.
935
936 dma_debug_entries=<number>
937 This option allows to tune the number of preallocated
938 entries for DMA-API debugging code. One entry is
939 required per DMA-API allocation. Use this if the
940 DMA-API debugging code disables itself because the
941 architectural default is too low.
942
Joerg Roedel1745de52009-05-22 21:49:51 +0200943 dma_debug_driver=<driver_name>
944 With this option the DMA-API debugging driver
945 filter feature can be enabled at boot time. Just
946 pass the driver to filter for as the parameter.
947 The filter can be disabled or changed to another
948 driver later using sysfs.
949
Bob Paauwe96206e22015-08-27 10:04:13 -0700950 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
951 Broken monitors, graphic adapters, KVMs and EDIDless
952 panels may send no or incorrect EDID data sets.
953 This parameter allows to specify an EDID data sets
954 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100955 Generic built-in EDID data sets are used, if one of
956 edid/1024x768.bin, edid/1280x1024.bin,
957 edid/1680x1050.bin, or edid/1920x1080.bin is given
958 and no file with the same name exists. Details and
959 instructions how to build your own EDID data are
960 available in Documentation/EDID/HOWTO.txt. An EDID
961 data set will only be used for a particular connector,
962 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700963 name. Each connector may use a unique EDID data
964 set by separating the files with a comma. An EDID
965 data set with no connector name will be used for
966 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100967
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 dscc4.setup= [NET]
969
Jim Cromie29e36c92012-04-27 14:30:41 -0600970 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
971 module.dyndbg[="val"]
972 Enable debug messages at boot time. See
973 Documentation/dynamic-debug-howto.txt for details.
974
Dave Hansen8c3641e2015-06-07 11:37:02 -0700975 nompx [X86] Disables Intel Memory Protection Extensions.
976 See Documentation/x86/intel_mpx.txt for more
977 information about the feature.
978
Borislav Petkovf29ba612015-03-27 16:15:18 +0100979 eagerfpu= [X86]
980 on enable eager fpu restore
981 off disable eager fpu restore
982 auto selects the default scheme, which automatically
983 enables eagerfpu restore for xsaveopt.
984
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700985 module.async_probe [KNL]
986 Enable asynchronous probe on this module.
987
Mark Salter56aeeba2014-04-07 15:39:53 -0700988 early_ioremap_debug [KNL]
989 Enable debug messages in early_ioremap support. This
990 is useful for tracking down temporary early mappings
991 which are not unmapped.
992
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700993 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500994
Scott Wood5664f762015-09-14 19:54:07 -0500995 When used with no options, the early console is
996 determined by the stdout-path property in device
997 tree's chosen node.
998
Michal Simek6fa62fc2014-09-10 12:43:02 +0200999 cdns,<addr>
1000 Start an early, polled-mode console on a cadence serial
1001 port at the specified address. The cadence serial port
1002 must already be setup and configured. Options are not
1003 yet supported.
1004
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001005 uart[8250],io,<addr>[,options]
1006 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -07001007 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +03001008 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -04001009 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001010 Start an early, polled-mode console on the 8250/16550
1011 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -07001012 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +03001013 (mmio) or 32-bit (mmio32 or mmio32be).
1014 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1015 to be equivalent to 'mmio'. 'options' are specified
1016 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001017 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001018
Rob Herring0d3c6732014-04-18 17:19:57 -05001019 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -06001020 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -05001021 Start an early, polled-mode console on a pl011 serial
1022 port at the specified address. The pl011 serial port
1023 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -06001024 yet supported. If 'mmio32' is specified, then only
1025 the driver will use only 32-bit accessors to read/write
1026 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -05001027
Stephen Boyd0efe7292014-09-15 17:22:51 -07001028 msm_serial,<addr>
1029 Start an early, polled-mode console on an msm serial
1030 port at the specified address. The serial port
1031 must already be setup and configured. Options are not
1032 yet supported.
1033
1034 msm_serial_dm,<addr>
1035 Start an early, polled-mode console on an msm serial
1036 dm port at the specified address. The serial port
1037 must already be setup and configured. Options are not
1038 yet supported.
1039
Rob Herringd50d7262014-04-18 17:19:58 -05001040 smh Use ARM semihosting calls for early console.
1041
Tomasz Figab94ba032015-01-23 14:47:41 +01001042 s3c2410,<addr>
1043 s3c2412,<addr>
1044 s3c2440,<addr>
1045 s3c6400,<addr>
1046 s5pv210,<addr>
1047 exynos4210,<addr>
1048 Use early console provided by serial driver available
1049 on Samsung SoCs, requires selecting proper type and
1050 a correct base address of the selected UART port. The
1051 serial port must already be setup and configured.
1052 Options are not yet supported.
1053
Stefan Agner1d59b382015-10-17 00:45:55 -07001054 lpuart,<addr>
1055 lpuart32,<addr>
1056 Use early console provided by Freescale LP UART driver
1057 found on Freescale Vybrid and QorIQ LS1021A processors.
1058 A valid base address must be provided, and the serial
1059 port must already be setup and configured.
1060
Finn Thain7913ad12014-04-12 23:48:56 +10001061 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001063 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001064 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001066 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001067 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001068 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001069 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070
Dave Hansen147ea092013-04-10 14:03:38 -07001071 earlyprintk is useful when the kernel crashes before
1072 the normal console is initialized. It is not enabled by
1073 default because it has some cosmetic problems.
1074
Randy Dunlapa9913042005-10-23 12:57:11 -07001075 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001076 takes over.
1077
Matt Fleming72548e82013-10-04 09:36:56 +01001078 Only one of vga, efi, serial, or usb debug port can
1079 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080
Dave Hansen147ea092013-04-10 14:03:38 -07001081 Currently only ttyS0 and ttyS1 may be specified by
1082 name. Other I/O ports may be explicitly specified
1083 on some architectures (x86 and arm at least) by
1084 replacing ttySn with an I/O port address, like this:
1085 earlyprintk=serial,0x1008,115200
1086 You can find the port for a given device in
1087 /proc/tty/driver/serial:
1088 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001089
1090 Interaction with the standard serial driver is not
1091 very good.
1092
Matt Fleming72548e82013-10-04 09:36:56 +01001093 The VGA and EFI output is eventually overwritten by
1094 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001096 The xen output can only be used by Xen PV guests.
1097
Chen, Gongc700f012013-12-06 01:17:08 -05001098 edac_report= [HW,EDAC] Control how to report EDAC event
1099 Format: {"on" | "off" | "force"}
1100 on: enable EDAC to report H/W event. May be overridden
1101 by other higher priority error reporting module.
1102 off: disable H/W event reporting through EDAC.
1103 force: enforce the use of EDAC to report H/W event.
1104 default: on.
1105
Jason Wessel97311912010-05-20 21:04:30 -05001106 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1107 ekgdboc=kbd
1108
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001109 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001110 the boot argument: earlyprintk=vga
1111
Linus Torvalds1da177e2005-04-16 15:20:36 -07001112 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001113 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001115 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001116 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001117 old_map [X86-64]: switch to the old ioremap-based EFI
1118 runtime services mapping. 32-bit still uses this one by
1119 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001120 nochunk: disable reading files in "chunks" in the EFI
1121 boot stub, as chunking can cause problems with some
1122 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001123 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001124 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001125
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001126 efi_no_storage_paranoia [EFI; X86]
1127 Using this parameter you can use more than 50% of
1128 your efi variable storage. Use this parameter only if
1129 you are really sure that your UEFI does sane gc and
1130 fulfills the spec otherwise your board may brick.
1131
Taku Izumi0f96a992015-09-30 23:01:56 +09001132 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1133 Add arbitrary attribute to specific memory range by
1134 updating original EFI memory map.
1135 Region of memory which aa attribute is added to is
1136 from ss to ss+nn.
1137 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1138 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1139 attribute is added to range 0x100000000-0x180000000 and
1140 0x10a0000000-0x1120000000.
1141
1142 Using this parameter you can do debugging of EFI memmap
1143 related feature. For example, you can do debugging of
1144 Address Range Mirroring feature even if your box
1145 doesn't support it.
1146
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147 eisa_irq_edge= [PARISC,HW]
1148 See header of drivers/parisc/eisa.c.
1149
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001150 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001151 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001152 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153
1154 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001155 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001156 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001157 Documentation/block/deadline-iosched.txt for details.
1158
Michael Holzheud3bf37952011-10-30 15:16:37 +01001159 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001160 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001161 image elf header and optionally the size. Generally
1162 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001163 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001165 enable_mtrr_cleanup [X86]
1166 The kernel tries to adjust MTRR layout from continuous
1167 to discrete, to make X server driver able to add WB
1168 entry later. This parameter enables that.
1169
Randy Dunlapca1eda22009-05-06 16:02:58 -07001170 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001171 Enable PIN 1 of APIC timer
1172 Can be useful to work around chipset bugs
1173 (in particular on some ATI chipsets).
1174 The kernel tries to set a reasonable default.
1175
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176 enforcing [SELINUX] Set initial enforcing status.
1177 Format: {"0" | "1"}
1178 See security/selinux/Kconfig help text.
1179 0 -- permissive (log only, no denials).
1180 1 -- enforcing (deny and log).
1181 Default value is 0.
1182 Value can be changed at runtime via /selinux/enforce.
1183
Huang Yinga08f82d2010-05-18 14:35:21 +08001184 erst_disable [ACPI]
1185 Disable Error Record Serialization Table (ERST)
1186 support.
1187
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188 ether= [HW,NET] Ethernet cards parameters
1189 This option is obsoleted by the "netdev=" option, which
1190 has equivalent usage. See its documentation for details.
1191
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001192 evm= [EVM]
1193 Format: { "fix" }
1194 Permit 'security.evm' to be updated regardless of
1195 current integrity status.
1196
Akinobu Mitade1ba092006-12-08 02:39:42 -08001197 failslab=
1198 fail_page_alloc=
1199 fail_make_request=[KNL]
1200 General fault injection mechanism.
1201 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001202 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001203
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001205 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001206
Alex Chiangf13ae302008-05-08 14:03:23 -06001207 force_pal_cache_flush
1208 [IA-64] Avoid check_sal_cache_flush which may hang on
1209 buggy SAL_CACHE_FLUSH implementations. Using this
1210 parameter will force ia64_sal_cache_flush to call
1211 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1212
Chris Bainbridge69f23662014-03-07 18:40:42 +07001213 forcepae [X86-32]
1214 Forcefully enable Physical Address Extension (PAE).
1215 Many Pentium M systems disable PAE but may have a
1216 functionally usable PAE implementation.
1217 Warning: use of this parameter will taint the kernel
1218 and may cause unknown problems.
1219
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001220 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001221 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001222 as early as possible in order to facilitate early
1223 boot debugging.
1224
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001225 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001226 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001227 If no parameter is passed, ftrace will dump
1228 buffers of all CPUs, but if you pass orig_cpu, it will
1229 dump only the buffer of the CPU that triggered the
1230 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001231
1232 ftrace_filter=[function-list]
1233 [FTRACE] Limit the functions traced by the function
1234 tracer at boot up. function-list is a comma separated
1235 list of functions. This list can be changed at run
1236 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001237 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001238
1239 ftrace_notrace=[function-list]
1240 [FTRACE] Do not trace the functions specified in
1241 function-list. This list can be changed at run time
1242 by the set_ftrace_notrace file in the debugfs
1243 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001244
Stefan Assmann369bc182009-10-12 22:17:21 +02001245 ftrace_graph_filter=[function-list]
1246 [FTRACE] Limit the top level callers functions traced
1247 by the function graph tracer at boot up.
1248 function-list is a comma separated list of functions
1249 that can be changed at run time by the
1250 set_graph_function file in the debugfs tracing directory.
1251
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001252 ftrace_graph_notrace=[function-list]
1253 [FTRACE] Do not trace from the functions specified in
1254 function-list. This list is a comma separated list of
1255 functions that can be changed at run time by the
1256 set_graph_notrace file in the debugfs tracing directory.
1257
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258 gamecon.map[2|3]=
1259 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1260 support via parallel port (up to 5 devices per port)
1261 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1262 See also Documentation/input/joystick-parport.txt
1263
1264 gamma= [HW,DRM]
1265
Yinghai Luaaf23042008-01-30 13:33:09 +01001266 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1267 Format: off | on
1268 default: on
1269
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001270 gcov_persist= [GCOV] When non-zero (default), profiling data for
1271 kernel modules is saved and remains accessible via
1272 debugfs, even when the module is unloaded/reloaded.
1273 When zero, profiling data is discarded and associated
1274 debugfs files are removed at module unload time.
1275
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001277 invalid Protective MBR to be treated as GPT. If the
1278 primary GPT is corrupted, it enables the backup/alternate
1279 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001281 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1282 the "Enable 0" bit of the configuration register.
1283 Format: 0 | 1
1284 Default: 0
1285 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1286 the "Enable 0" bit of the configuration register.
1287 Format: 0 | 1
1288 Default: 0
1289 grcan.select= [HW] Select which physical interface to use.
1290 Format: 0 | 1
1291 Default: 0
1292 grcan.txsize= [HW] Sets the size of the tx buffer.
1293 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1294 Default: 1024
1295 grcan.rxsize= [HW] Sets the size of the rx buffer.
1296 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1297 Default: 1024
1298
Jiri Kosina55537872015-11-05 18:44:41 -08001299 hardlockup_all_cpu_backtrace=
1300 [KNL] Should the hard-lockup detector generate
1301 backtraces on all cpus.
1302 Format: <integer>
1303
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304 hashdist= [KNL,NUMA] Large hashes allocated during boot
1305 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001306 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001307 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001308
1309 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1310
1311 hd= [EIDE] (E)IDE hard drive subsystem geometry
1312 Format: <cyl>,<head>,<sect>
1313
Huang Yingea8c0712010-05-18 14:35:15 +08001314 hest_disable [ACPI]
1315 Disable Hardware Error Source Table (HEST) support;
1316 corresponding firmware-first mode error processing
1317 logic will be disabled.
1318
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1320 size of <nn>. This works even on boxes that have no
1321 highmem otherwise. This also works to reduce highmem
1322 size on bigger boxes.
1323
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001324 highres= [KNL] Enable/disable high resolution timer mode.
1325 Valid parameters: "on", "off"
1326 Default: "on"
1327
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328 hisax= [HW,ISDN]
1329 See Documentation/isdn/README.HiSax.
1330
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001331 hlt [BUGS=ARM,SH]
1332
1333 hpet= [X86-32,HPET] option to control HPET usage
1334 Format: { enable (default) | disable | force |
1335 verbose }
1336 disable: disable HPET and use PIT instead
1337 force: allow force enabled of undocumented chips (ICH4,
1338 VIA, nVidia)
1339 verbose: show contents of HPET registers during setup
1340
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001341 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1342 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1343
Andi Kleenb4718e62008-07-23 21:27:51 -07001344 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1345 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001346 On x86-64 and powerpc, this option can be specified
1347 multiple times interleaved with hugepages= to reserve
1348 huge pages of different sizes. Valid pages sizes on
1349 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001350 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001351
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001352 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1353 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001354 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1355 If specified, z/VM IUCV HVC accepts connections
1356 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001357
James Hoganfdabf522012-10-09 11:00:27 +01001358 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1359 hardware thread id mappings.
1360 Format: <cpu>:<hwthread>
1361
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001362 keep_bootcon [KNL]
1363 Do not unregister boot console at start. This is only
1364 useful for debugging when something happens in the window
1365 between unregistering the boot console and initializing
1366 the real console.
1367
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001368 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001369 or register an additional I2C bus that is not
1370 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001371 Format:
1372 <bus_id>,<clkrate>
1373
Jiri Kosina36d95732008-10-06 02:51:09 -04001374 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001375 i8042.unmask_kbd_data
1376 [HW] Enable printing of interrupt data from the KBD port
1377 (disabled by default, and as a pre-condition
1378 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001380 i8042.dumbkbd [HW] Pretend that controller can only read data from
1381 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382 (Don't attempt to blink the leds)
1383 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001384 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001385 i8042.noloop [HW] Disable the AUX Loopback command while probing
1386 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001387 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001388 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1390 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001391 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392 i8042.reset [HW] Reset the controller during init and cleanup
1393 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001394 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001395
1396 i810= [HW,DRM]
1397
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001398 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1399 indicates that the driver is running on unsupported
1400 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1402 does not match list of supported models.
1403 i8k.power_status
1404 [HW] Report power status in /proc/i8k
1405 (disabled by default)
1406 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1407 capability is set.
1408
Carsten Emde4dca20e2012-03-15 15:56:26 +01001409 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001410 [DRM] Invert the sense of the variable that is used to
1411 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001412 brightness value of 0 indicates backlight switched off,
1413 and the maximum of the brightness value sets the backlight
1414 to maximum brightness. If this parameter is set to 0
1415 (default) and the machine requires it, or this parameter
1416 is set to 1, a brightness value of 0 sets the backlight
1417 to maximum brightness, and the maximum of the brightness
1418 value switches the backlight off.
1419 -1 -- never invert brightness
1420 0 -- machine default
1421 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001422
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423 icn= [HW,ISDN]
1424 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1425
David Fries0af80c02009-02-25 20:28:21 +01001426 ide-core.nodma= [HW] (E)IDE subsystem
1427 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001428 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1429 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001430 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001432 ide-generic.probe-mask= [HW] (E)IDE subsystem
1433 Format: <int>
1434 Probe mask for legacy ISA IDE ports. Depending on
1435 platform up to 6 ports are supported, enabled by
1436 setting corresponding bits in the mask to 1. The
1437 default value is 0x0, which has a special meaning.
1438 On systems that have PCI, it triggers scanning the
1439 PCI bus for the first and the second port, which
1440 are then probed. On systems without PCI the value
1441 of 0x0 enables probing the two first ports as if it
1442 was 0x3.
1443
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001444 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1445 Claim all unknown PCI IDE storage controllers.
1446
Andi Kleenf039b752007-05-02 19:27:12 +02001447 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001448 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001449 Poll forces a polling idle loop that can slightly
1450 improve the performance of waking up a idle CPU, but
1451 will use a lot of power and make the system run hot.
1452 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001453 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001454 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001455 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001456
Ingo Molnar792908222006-12-06 20:40:51 -08001457 ignore_loglevel [KNL]
1458 Ignore loglevel setting - this will print /all/
1459 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001460 We also add it as printk module parameter, so users
1461 could change it dynamically, usually by
1462 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001463
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 ihash_entries= [KNL]
1465 Set number of hash buckets for inode cache.
1466
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001467 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001468 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001469 default: "enforce"
1470
Mimi Zohar07f6a792011-03-09 22:25:48 -05001471 ima_appraise_tcb [IMA]
1472 The builtin appraise policy appraises all files
1473 owned by uid=0.
1474
Mimi Zohar3323eec2009-02-04 09:06:58 -05001475 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001476 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1477 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001478 default: "sha1"
1479
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001480 The list of supported hash algorithms is defined
1481 in crypto/hash_info.h.
1482
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001483 ima_policy= [IMA]
1484 The builtin measurement policy to load during IMA
1485 setup. Specyfing "tcb" as the value, measures all
1486 programs exec'd, files mmap'd for exec, and all files
1487 opened with the read mode bit set by either the
1488 effective uid (euid=0) or uid=0.
1489 Format: "tcb"
1490
1491 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001492 Load a policy which meets the needs of the Trusted
1493 Computing Base. This means IMA will measure all
1494 programs exec'd, files mmap'd for exec, and all files
1495 opened for read by uid=0.
1496
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001497 ima_template= [IMA]
1498 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001499 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001500 Default: "ima-ng"
1501
Roberto Sassuc2426d22014-10-13 14:08:42 +02001502 ima_template_fmt=
1503 [IMA] Define a custom template format.
1504 Format: { "field1|...|fieldN" }
1505
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001506 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1507 Format: <min_file_size>
1508 Set the minimal file size for using asynchronous hash.
1509 If left unspecified, ahash usage is disabled.
1510
1511 ahash performance varies for different data sizes on
1512 different crypto accelerators. This option can be used
1513 to achieve the best performance for a particular HW.
1514
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001515 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1516 Format: <bufsize>
1517 Set hashing buffer size. Default: 4k.
1518
1519 ahash performance varies for different chunk sizes on
1520 different crypto accelerators. This option can be used
1521 to achieve best performance for particular HW.
1522
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 init= [KNL]
1524 Format: <full_path>
1525 Run specified binary instead of /sbin/init as init
1526 process.
1527
1528 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1529 for working out where the kernel is dying during
1530 startup.
1531
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001532 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1533 initcall functions. Useful for debugging built-in
1534 modules and initcalls.
1535
Linus Torvalds1da177e2005-04-16 15:20:36 -07001536 initrd= [BOOT] Specify the location of the initial ramdisk
1537
1538 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1539 Format: <irq>
1540
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001541 int_pln_enable [x86] Enable power limit notification interrupt
1542
Mimi Zohard726d8d2013-03-18 14:48:02 -04001543 integrity_audit=[IMA]
1544 Format: { "0" | "1" }
1545 0 -- basic integrity auditing messages. (Default)
1546 1 -- additional integrity auditing messages.
1547
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001548 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001549 on
1550 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001551 off
1552 Disable intel iommu driver.
1553 igfx_off [Default Off]
1554 By default, gfx is mapped as normal device. If a gfx
1555 device has a dedicated DMAR unit, the DMAR unit is
1556 bypassed by not enabling DMAR with this option. In
1557 this case, gfx device will use physical address for
1558 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001559 forcedac [x86_64]
1560 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001561 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001562 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001563 than 32-bit addressing. The default is to look
1564 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001565 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001566 strict [Default Off]
1567 With this option on every unmap_single operation will
1568 result in a hardware IOTLB flush operation as opposed
1569 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001570 sp_off [Default Off]
1571 By default, super page will be supported if Intel IOMMU
1572 has the capability. With this option, super page will
1573 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001574 ecs_off [Default Off]
1575 By default, extended context tables will be supported if
1576 the hardware advertises that it has support both for the
1577 extended tables themselves, and also PASID support. With
1578 this option set, extended tables will not be used even
1579 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001580
1581 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1582 0 disables intel_idle and fall back on acpi_idle.
1583 1 to 6 specify maximum depth of C-state.
1584
Dirk Brandewie6be26492013-02-15 22:55:10 +01001585 intel_pstate= [X86]
1586 disable
1587 Do not enable intel_pstate as the default
1588 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001589 force
1590 Enable intel_pstate on systems that prohibit it by default
1591 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1592 instead of acpi-cpufreq may disable platform features, such
1593 as thermal controls and power capping, that rely on ACPI
1594 P-States information being indicated to OSPM and therefore
1595 should be used with caution. This option does not work with
1596 processors that aren't supported by the intel_pstate driver
1597 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001598 no_hwp
1599 Do not enable hardware P state control (HWP)
1600 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001601 hwp_only
1602 Only load intel_pstate on systems which support
1603 hardware P state control (HWP) if available.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001604
Chris Wrightd1423d52010-07-20 11:06:49 -07001605 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001606 on enable Interrupt Remapping (default)
1607 off disable Interrupt Remapping
1608 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001609 no_x2apic_optout
1610 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001611 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001612
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001613 iomem= Disable strict checking of access to MMIO memory
1614 strict regions from userspace.
1615 relaxed
1616
1617 iommu= [x86]
1618 off
1619 force
1620 noforce
1621 biomerge
1622 panic
1623 nopanic
1624 merge
1625 nomerge
1626 forcesac
1627 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001628 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001629 nobypass [PPC/POWERNV]
1630 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001631
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001632
1633 io7= [HW] IO7 for Marvel based alpha systems
1634 See comment before marvel_specify_io7 in
1635 arch/alpha/kernel/core_marvel.c.
1636
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301637 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001638 0x80
1639 Standard port 0x80 based delay
1640 0xed
1641 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001642 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001643 Simple two microseconds delay
1644 none
1645 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001646
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001648 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649
Alan Cox200803d2005-06-28 20:45:18 -07001650 irqfixup [HW]
1651 When an interrupt is not handled search all handlers
1652 for it. Intended to get systems with badly broken
1653 firmware running.
1654
1655 irqpoll [HW]
1656 When an interrupt is not handled search all handlers
1657 for it. Also check all handlers each timer
1658 interrupt. Intended to get systems with badly broken
1659 firmware running.
1660
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001662 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663
1664 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001665 Format:
1666 <cpu number>,...,<cpu number>
1667 or
Li Zefanb225d442008-11-06 12:53:39 -08001668 <cpu number>-<cpu number>
1669 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001670 or a mixture
1671 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001672
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673 This option can be used to specify one or more CPUs
1674 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001675 algorithms. You can move a process onto or off an
1676 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001677 <cpu number> begins at 0 and the maximum value is
1678 "number of CPUs in system - 1".
1679
1680 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001681 alternative -- manually setting the CPU mask of all
1682 tasks in the system -- can cause problems and
1683 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684
Randy Dunlapa9913042005-10-23 12:57:11 -07001685 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001686
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001687 ivrs_ioapic [HW,X86_64]
1688 Provide an override to the IOAPIC-ID<->DEVICE-ID
1689 mapping provided in the IVRS ACPI table. For
1690 example, to map IOAPIC-ID decimal 10 to
1691 PCI device 00:14.0 write the parameter as:
1692 ivrs_ioapic[10]=00:14.0
1693
1694 ivrs_hpet [HW,X86_64]
1695 Provide an override to the HPET-ID<->DEVICE-ID
1696 mapping provided in the IVRS ACPI table. For
1697 example, to map HPET-ID decimal 0 to
1698 PCI device 00:14.0 write the parameter as:
1699 ivrs_hpet[0]=00:14.0
1700
Linus Torvalds1da177e2005-04-16 15:20:36 -07001701 js= [HW,JOY] Analog joystick
1702 See Documentation/input/joystick.txt.
1703
Kees Cook24f2e022014-06-13 13:30:36 -07001704 kaslr/nokaslr [X86]
1705 Enable/disable kernel and module base offset ASLR
1706 (Address Space Layout Randomization) if built into
1707 the kernel. When CONFIG_HIBERNATION is selected,
1708 kASLR is disabled by default. When kASLR is enabled,
1709 hibernation will be disabled.
1710
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001711 keepinitrd [HW,ARM]
1712
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301713 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001714 specifies the amount of memory usable by the kernel
1715 for non-movable allocations. The requested amount is
1716 spread evenly throughout all nodes in the system. The
1717 remaining memory in each node is used for Movable
1718 pages. In the event, a node is too small to have both
1719 kernelcore and Movable pages, kernelcore pages will
1720 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001721 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001722 allocation of pages that may be reclaimed or moved
1723 by the page migration subsystem. This means that
1724 HugeTLB pages may not be allocated from this zone.
1725 Note that allocations like PTEs-from-HighMem still
1726 use the HighMem zone if it exists, and the Normal
1727 zone if it does not.
1728
Jason Wessel4fe1da42010-05-20 21:04:31 -05001729 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1730 Format: <Controller#>[,poll interval]
1731 The controller # is the number of the ehci usb debug
1732 port as it is probed via PCI. The poll interval is
1733 optional and is the number seconds in between
1734 each poll cycle to the debug port in case you need
1735 the functionality for interrupting the kernel with
1736 gdb or control-c on the dbgp connection. When
1737 not using this parameter you use sysrq-g to break into
1738 the kernel debugger.
1739
Jason Wessel84c08fd2010-05-20 21:04:24 -05001740 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001741 Requires a tty driver that supports console polling,
1742 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001743 Serial only format: <serial_device>[,baud]
1744 keyboard only format: kbd
1745 keyboard and serial format: kbd,<serial_device>[,baud]
1746 Optional Kernel mode setting:
1747 kms, kbd format: kms,kbd
1748 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001749
Jason Wessel84c08fd2010-05-20 21:04:24 -05001750 kgdbwait [KGDB] Stop kernel execution and enter the
1751 kernel debugger at the earliest opportunity.
1752
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001753 kmac= [MIPS] korina ethernet MAC address.
1754 Configure the RouterBoard 532 series on-chip
1755 Ethernet adapter MAC address.
1756
Catalin Marinas04f70332009-06-11 13:22:39 +01001757 kmemleak= [KNL] Boot-time kmemleak enable/disable
1758 Valid arguments: on, off
1759 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001760 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1761 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001762
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001763 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1764 Valid arguments: 0, 1, 2
1765 kmemcheck=0 (disabled)
1766 kmemcheck=1 (enabled)
1767 kmemcheck=2 (one-shot mode)
1768 Default: 2 (one-shot mode)
1769
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301770 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001771 in oops dumps.
1772
Andre Przywarafef07aa2009-07-10 14:20:35 +02001773 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1774 Default is 0 (don't ignore, but inject #GP)
1775
Xiao Guangronga182d872010-09-20 22:17:48 +08001776 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1777 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001778 Default is 0 (off)
1779
Andre Przywarafef07aa2009-07-10 14:20:35 +02001780 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001781 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001782
1783 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1784 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001785 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001786
Andre Przywarafef07aa2009-07-10 14:20:35 +02001787 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1788 (virtualized MMU) support on capable Intel chips.
1789 Default is 1 (enabled)
1790
1791 kvm-intel.emulate_invalid_guest_state=
1792 [KVM,Intel] Enable emulation of invalid guest states
1793 Default is 0 (disabled)
1794
1795 kvm-intel.flexpriority=
1796 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1797 Default is 1 (enabled)
1798
Sasha Levine1a72ae2011-08-09 14:28:35 +03001799 kvm-intel.nested=
1800 [KVM,Intel] Enable VMX nesting (nVMX).
1801 Default is 0 (disabled)
1802
Andre Przywarafef07aa2009-07-10 14:20:35 +02001803 kvm-intel.unrestricted_guest=
1804 [KVM,Intel] Disable unrestricted guest feature
1805 (virtualized real and unpaged mode) on capable
1806 Intel chips. Default is 1 (enabled)
1807
1808 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1809 feature (tagged TLBs) on capable Intel chips.
1810 Default is 1 (enabled)
1811
Linus Torvalds1da177e2005-04-16 15:20:36 -07001812 l2cr= [PPC]
1813
Robert Brosea78bfbf2008-03-29 07:20:23 +11001814 l3cr= [PPC]
1815
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001816 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001817 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001818
Suresh Siddha279f1462012-10-22 14:37:58 -07001819 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1820 value for LAPIC timer one-shot implementation. Default
1821 back to the programmable timer unit in the LAPIC.
1822
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301823 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001824 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001825
FD Camifcb71f62008-01-06 19:08:56 +01001826 libata.dma= [LIBATA] DMA control
1827 libata.dma=0 Disable all PATA and SATA DMA
1828 libata.dma=1 PATA and SATA Disk DMA only
1829 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001830 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001831 Combinations also work, so libata.dma=3 enables DMA
1832 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001833
Michael Prokop20308872009-08-06 00:14:10 +02001834 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1835 libata.ignore_hpa=0 keep BIOS limits (default)
1836 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001837
Dave Jones78e70c22007-09-27 11:50:13 -04001838 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1839 when set.
1840 Format: <int>
1841
Tejun Heo33267322008-02-13 09:15:09 +09001842 libata.force= [LIBATA] Force configurations. The format is comma
1843 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001844 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001845 matching port, link or device. Basically, it matches
1846 the ATA ID string printed on console by libata. If
1847 the whole ID part is omitted, the last PORT and DEVICE
1848 values are used. If ID hasn't been specified yet, the
1849 configuration applies to all ports, links and devices.
1850
1851 If only DEVICE is omitted, the parameter applies to
1852 the port and all links and devices behind it. DEVICE
1853 number of 0 either selects the first device or the
1854 first fan-out link behind PMP device. It does not
1855 select the host link. DEVICE number of 15 selects the
1856 host link and device attached to it.
1857
1858 The VAL specifies the configuration to force. As long
1859 as there's no ambiguity shortcut notation is allowed.
1860 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1861 The following configurations can be forced.
1862
1863 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1864 Any ID with matching PORT is used.
1865
1866 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1867
1868 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1869 udma[/][16,25,33,44,66,100,133] notation is also
1870 allowed.
1871
1872 * [no]ncq: Turn on or off NCQ.
1873
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001874 * [no]ncqtrim: Turn off queued DSM TRIM.
1875
Tejun Heo05944bd2008-08-13 20:19:09 +09001876 * nohrst, nosrst, norst: suppress hard, soft
1877 and both resets.
1878
Dan Williamsca6d43b2012-06-21 23:41:41 -07001879 * rstonce: only attempt one reset during
1880 hot-unplug link recovery
1881
Tejun Heo43c9c592010-05-23 12:59:11 +02001882 * dump_id: dump IDENTIFY data.
1883
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001884 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1885
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001886 * disable: Disable this device.
1887
Tejun Heo33267322008-02-13 09:15:09 +09001888 If there are multiple matching configurations changing
1889 the same attribute, the last one is used.
1890
Yinghai Lu95f72d12010-07-12 14:36:09 +10001891 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001892
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001894 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001895
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001896 lockd.nlm_grace_period=P [NFS] Assign grace period.
1897 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001898
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001899 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1900 Format: <integer>
1901
1902 lockd.nlm_timeout=T [NFS] Assign timeout value.
1903 Format: <integer>
1904
1905 lockd.nlm_udpport=M [NFS] Assign UDP port.
1906 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001907
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001908 locktorture.nreaders_stress= [KNL]
1909 Set the number of locking read-acquisition kthreads.
1910 Defaults to being automatically set based on the
1911 number of online CPUs.
1912
1913 locktorture.nwriters_stress= [KNL]
1914 Set the number of locking write-acquisition kthreads.
1915
1916 locktorture.onoff_holdoff= [KNL]
1917 Set time (s) after boot for CPU-hotplug testing.
1918
1919 locktorture.onoff_interval= [KNL]
1920 Set time (s) between CPU-hotplug operations, or
1921 zero to disable CPU-hotplug testing.
1922
1923 locktorture.shuffle_interval= [KNL]
1924 Set task-shuffle interval (jiffies). Shuffling
1925 tasks allows some CPUs to go into dyntick-idle
1926 mode during the locktorture test.
1927
1928 locktorture.shutdown_secs= [KNL]
1929 Set time (s) after boot system shutdown. This
1930 is useful for hands-off automated testing.
1931
1932 locktorture.stat_interval= [KNL]
1933 Time (s) between statistics printk()s.
1934
1935 locktorture.stutter= [KNL]
1936 Time (s) to stutter testing, for example,
1937 specifying five seconds causes the test to run for
1938 five seconds, wait for five seconds, and so on.
1939 This tests the locking primitive's ability to
1940 transition abruptly to and from idle.
1941
1942 locktorture.torture_runnable= [BOOT]
1943 Start locktorture running at boot time.
1944
1945 locktorture.torture_type= [KNL]
1946 Specify the locking implementation to test.
1947
1948 locktorture.verbose= [KNL]
1949 Enable additional printk() statements.
1950
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1952 Format: <irq>
1953
1954 loglevel= All Kernel Messages with a loglevel smaller than the
1955 console loglevel will be printed to the console. It can
1956 also be changed with klogd or other programs. The
1957 loglevels are defined as follows:
1958
1959 0 (KERN_EMERG) system is unusable
1960 1 (KERN_ALERT) action must be taken immediately
1961 2 (KERN_CRIT) critical conditions
1962 3 (KERN_ERR) error conditions
1963 4 (KERN_WARNING) warning conditions
1964 5 (KERN_NOTICE) normal but significant condition
1965 6 (KERN_INFO) informational
1966 7 (KERN_DEBUG) debug-level messages
1967
Randy Dunlapc756d082011-02-20 20:08:35 -08001968 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001969 in bytes. n must be a power of two and greater
1970 than the minimal size. The minimal size is defined
1971 by LOG_BUF_SHIFT kernel config parameter. There is
1972 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1973 that allows to increase the default size depending on
1974 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975
Randy Dunlapaccaa242007-10-16 01:29:37 -07001976 logo.nologo [FB] Disables display of the built-in Linux logo.
1977 This may be used to provide more screen space for
1978 kernel log messages and is useful when debugging
1979 kernel boot problems.
1980
Linus Torvalds1da177e2005-04-16 15:20:36 -07001981 lp=0 [LP] Specify parallel ports to use, e.g,
1982 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1983 lp=reset first parallel port). 'lp=0' disables the
1984 lp=auto printer driver. 'lp=reset' (which can be
1985 specified in addition to the ports) causes
1986 attached printers to be reset. Using
1987 lp=port1,port2,... specifies the parallel ports
1988 to associate lp devices with, starting with
1989 lp0. A port specification may be 'none' to skip
1990 that lp device, or a parport name such as
1991 'parport0'. Specifying 'lp=auto' instead of a
1992 port specification list means that device IDs
1993 from each port should be examined, to see if
1994 an IEEE 1284-compliant printer is attached; if
1995 so, the driver will manage that printer.
1996 See also header of drivers/char/lp.c.
1997
1998 lpj=n [KNL]
1999 Sets loops_per_jiffy to given constant, thus avoiding
2000 time-consuming boot-time autodetection (up to 250 ms per
2001 CPU). 0 enables autodetection (default). To determine
2002 the correct value for your kernel, boot with normal
2003 autodetection and see what value is printed. Note that
2004 on SMP systems the preset will be applied to all CPUs,
2005 which is likely to cause problems if your CPUs need
2006 significantly divergent settings. An incorrect value
2007 will cause delays in the kernel to be wrong, leading to
2008 unpredictable I/O errors and other breakage. Although
2009 unlikely, in the extreme case this might damage your
2010 hardware.
2011
2012 ltpc= [NET]
2013 Format: <io>,<irq>,<dma>
2014
Randy Dunlap16290242011-08-13 12:34:52 -07002015 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002016 (machvec) in a generic kernel.
2017 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018
Wu Zhangjin3209e702009-07-02 23:27:12 +08002019 machtype= [Loongson] Share the same kernel image file between different
2020 yeeloong laptop.
2021 Example: machtype=lemote-yeeloong-2f-7inch
2022
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002023 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2024 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025
2026 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04002027 should make use of. maxcpus=n : n >= 0 limits the
2028 kernel to using 'n' processors. n=0 is a special case,
2029 it is equivalent to "nosmp", which also disables
2030 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002031
Kay Sieversd134b002011-07-31 22:08:04 +02002032 max_loop= [LOOP] The number of loop block devices that get
2033 (loop.max_loop) unconditionally pre-created at init time. The default
2034 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2035 of statically allocating a predefined number, loop
2036 devices can be requested on-demand with the
2037 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002038
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002039 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002040
Uwe Hermann71cced62008-10-20 09:32:21 -07002041 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002042
Linus Torvalds1da177e2005-04-16 15:20:36 -07002043 md= [HW] RAID subsystems devices and level
2044 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002045
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 mdacon= [MDA]
2047 Format: <first>,<last>
2048 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002049
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2051 Amount of memory to be used when the kernel is not able
2052 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002053 [X86] Work as limiting max address. Use together
2054 with memmap= to avoid physical address space collisions.
2055 Without memmap= PCI devices could be placed at addresses
2056 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002057
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002058 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002059 memory.
2060
Paul Mundt6902aa82008-09-21 17:14:42 +09002061 memchunk=nn[KMG]
2062 [KNL,SH] Allow user to override the default size for
2063 per-device physically contiguous DMA buffers.
2064
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302065 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002066 E820 memory map, as specified by the user.
2067 Such memmap=exactmap lines can be constructed based on
2068 BIOS output or other requirements. See the memmap=nn@ss
2069 option description.
2070
2071 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002072 [KNL] Force usage of a specific region of memory.
2073 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002074
2075 memmap=nn[KMG]#ss[KMG]
2076 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002077 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078
2079 memmap=nn[KMG]$ss[KMG]
2080 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002081 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002082 Example: Exclude memory from 0x18690000-0x1869ffff
2083 memmap=64K$0x18690000
2084 or
2085 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002087 memmap=nn[KMG]!ss[KMG]
2088 [KNL,X86] Mark specific memory as protected.
2089 Region of memory to be used, from ss to ss+nn.
2090 The memory region may be marked as e820 type 12 (0xc)
2091 and is NVDIMM or ADR memory.
2092
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002093 memory_corruption_check=0/1 [X86]
2094 Some BIOSes seem to corrupt the first 64k of
2095 memory when doing things like suspend/resume.
2096 Setting this option will scan the memory
2097 looking for corruption. Enabling this will
2098 both detect corruption and prevent the kernel
2099 from using the memory being corrupted.
2100 However, its intended as a diagnostic tool; if
2101 repeatable BIOS-originated corruption always
2102 affects the same memory, you can use memmap=
2103 to prevent the kernel from using that memory.
2104
2105 memory_corruption_check_size=size [X86]
2106 By default it checks for corruption in the low
2107 64k, making this memory unavailable for normal
2108 use. Use this parameter to scan for
2109 corruption in more or less memory.
2110
2111 memory_corruption_check_period=seconds [X86]
2112 By default it checks for corruption every 60
2113 seconds. Use this parameter to check at some
2114 other rate. 0 disables periodic checking.
2115
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002116 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002117 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002118 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002119 Specifies the number of memtest passes to be
2120 performed. Each pass selects another test
2121 pattern from a given set of patterns. Memtest
2122 fills the memory with this pattern, validates
2123 memory contents and reserves bad memory
2124 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002125
Linus Torvalds1da177e2005-04-16 15:20:36 -07002126 meye.*= [HW] Set MotionEye Camera parameters
2127 See Documentation/video4linux/meye.txt.
2128
Andres Salomon8f368812007-10-12 23:04:06 +02002129 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2130 Multi-Function General Purpose Timers on AMD Geode
2131 platforms.
2132
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002133 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2134 the BIOS has incorrectly applied a workaround. TinyBIOS
2135 version 0.98 is known to be affected, 0.99 fixes the
2136 problem by letting the user disable the workaround.
2137
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138 mga= [HW,DRM]
2139
Randy Dunlap1c207f952008-11-19 15:36:16 -08002140 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2141 physical address is ignored.
2142
Michel Pollet39f45d72009-05-20 11:10:31 +01002143 mini2440= [ARM,HW,KNL]
2144 Format:[0..2][b][c][t]
2145 Default: "0tb"
2146 MINI2440 configuration specification:
2147 0 - The attached screen is the 3.5" TFT
2148 1 - The attached screen is the 7" TFT
2149 2 - The VGA Shield is attached (1024x768)
2150 Leaving out the screen size parameter will not load
2151 the TFT driver, and the framebuffer will be left
2152 unconfigured.
2153 b - Enable backlight. The TFT backlight pin will be
2154 linked to the kernel VESA blanking code and a GPIO
2155 LED. This parameter is not necessary when using the
2156 VGA shield.
2157 c - Enable the s3c camera interface.
2158 t - Reserved for enabling touchscreen support. The
2159 touchscreen support is not enabled in the mainstream
2160 kernel as of 2.6.30, a preliminary port can be found
2161 in the "bleeding edge" mini2440 support kernel at
2162 http://repo.or.cz/w/linux-2.6/mini2440.git
2163
Mel Gorman6b74ab92008-07-23 21:26:49 -07002164 mminit_loglevel=
2165 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2166 parameter allows control of the logging verbosity for
2167 the additional memory initialisation checks. A value
2168 of 0 disables mminit logging and a level of 4 will
2169 log everything. Information is printed at KERN_DEBUG
2170 so loglevel=8 may also need to be specified.
2171
Rusty Russell106a4ee2012-09-26 10:09:40 +01002172 module.sig_enforce
2173 [KNL] When CONFIG_MODULE_SIG is set, this means that
2174 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002175 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002176 is always true, so this option does nothing.
2177
Linus Torvalds1da177e2005-04-16 15:20:36 -07002178 mousedev.tap_time=
2179 [MOUSE] Maximum time between finger touching and
2180 leaving touchpad surface for touch to be considered
2181 a tap and be reported as a left button click (for
2182 touchpads working in absolute mode only).
2183 Format: <msecs>
2184 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2185 reporting absolute coordinates, such as tablets
2186 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2187 reporting absolute coordinates, such as tablets
2188
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302189 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002190 is similar to kernelcore except it specifies the
2191 amount of memory used for migratable allocations.
2192 If both kernelcore and movablecore is specified,
2193 then kernelcore will be at *least* the specified
2194 value but may be more. If movablecore on its own
2195 is specified, the administrator must be careful
2196 that the amount of memory usable for all allocations
2197 is not too small.
2198
Tang Chenc5320922013-11-12 15:08:10 -08002199 movable_node [KNL,X86] Boot-time switch to enable the effects
2200 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2201
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202 MTD_Partition= [MTD]
2203 Format: <name>,<region-number>,<size>,<offset>
2204
Randy Dunlapa9913042005-10-23 12:57:11 -07002205 MTD_Region= [MTD] Format:
2206 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207
2208 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002209 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002210
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002211 multitce=off [PPC] This parameter disables the use of the pSeries
2212 firmware feature for updating multiple TCE entries
2213 at a time.
2214
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002215 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2216
2217 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2218
2219 boundary - index of last SLC block on Flex-OneNAND.
2220 The remaining blocks are configured as MLC blocks.
2221 lock - Configure if Flex-OneNAND boundary should be locked.
2222 Once locked, the boundary cannot be changed.
2223 1 indicates lock status, 0 indicates unlock status.
2224
Ben Dooks9db829f2008-07-03 11:24:29 +01002225 mtdset= [ARM]
2226 ARM/S3C2412 JIVE boot control
2227
2228 See arch/arm/mach-s3c2412/mach-jive.c
2229
Linus Torvalds1da177e2005-04-16 15:20:36 -07002230 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002231 [HW] Make the MicroTouch USB driver use raw coordinates
2232 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002233
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002234 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002235 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002236 that could hold holes aka. UC entries.
2237
2238 mtrr_gran_size=nn[KMG] [X86]
2239 Used for mtrr cleanup. It is granularity of mtrr block.
2240 Default is 1.
2241 Large value could prevent small alignment from
2242 using up MTRRs.
2243
2244 mtrr_spare_reg_nr=n [X86]
2245 Format: <integer>
2246 Range: 0,7 : spare reg number
2247 Default : 1
2248 Used for mtrr cleanup. It is spare mtrr entries number.
2249 Set to 2 or more if your graphical card needs more.
2250
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2252
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253 netdev= [NET] Network devices parameters
2254 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2255 Note that mem_start is often overloaded to mean
2256 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002257 This usage is only documented in each driver source
2258 file if at all.
2259
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002260 nf_conntrack.acct=
2261 [NETFILTER] Enable connection tracking flow accounting
2262 0 to disable accounting
2263 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002264 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002265
Chuck Lever306a0752010-09-17 10:54:37 -04002266 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002267 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268
2269 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002270 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002271
Chuck Lever306a0752010-09-17 10:54:37 -04002272 nfsrootdebug [NFS] enable nfsroot debugging messages.
2273 See Documentation/filesystems/nfs/nfsroot.txt.
2274
Trond Myklebusta72b4422006-01-03 09:55:41 +01002275 nfs.callback_tcpport=
2276 [NFS] set the TCP port on which the NFSv4 callback
2277 channel should listen.
2278
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002279 nfs.cache_getent=
2280 [NFS] sets the pathname to the program which is used
2281 to update the NFS client cache entries.
2282
2283 nfs.cache_getent_timeout=
2284 [NFS] sets the timeout after which an attempt to
2285 update a cache entry is deemed to have failed.
2286
Trond Myklebust58df0952006-01-03 09:55:57 +01002287 nfs.idmap_cache_timeout=
2288 [NFS] set the maximum lifetime for idmapper cache
2289 entries.
2290
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002291 nfs.enable_ino64=
2292 [NFS] enable 64-bit inode numbers.
2293 If zero, the NFS client will fake up a 32-bit inode
2294 number for the readdir() and stat() syscalls instead
2295 of returning the full 64-bit number.
2296 The default is to return 64-bit inode numbers.
2297
Trond Myklebustef159e92012-02-06 19:50:40 -05002298 nfs.max_session_slots=
2299 [NFSv4.1] Sets the maximum number of session slots
2300 the client will attempt to negotiate with the server.
2301 This limits the number of simultaneous RPC requests
2302 that the client can send to the NFSv4.1 server.
2303 Note that there is little point in setting this
2304 value higher than the max_tcp_slot_table_limit.
2305
Trond Myklebustb064eca22011-02-22 15:44:32 -08002306 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002307 [NFSv4] When set to the default of '1', this option
2308 ensures that both the RPC level authentication
2309 scheme and the NFS level operations agree to use
2310 numeric uids/gids if the mount is using the
2311 'sec=sys' security flavour. In effect it is
2312 disabling idmapping, which can make migration from
2313 legacy NFSv2/v3 systems to NFSv4 easier.
2314 Servers that do not support this mode of operation
2315 will be autodetected by the client, and it will fall
2316 back to using the idmapper.
2317 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002318 nfs.nfs4_unique_id=
2319 [NFS4] Specify an additional fixed unique ident-
2320 ification string that NFSv4 clients can insert into
2321 their nfs_client_id4 string. This is typically a
2322 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002323
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002324 nfs.send_implementation_id =
2325 [NFSv4.1] Send client implementation identification
2326 information in exchange_id requests.
2327 If zero, no implementation identification information
2328 will be sent.
2329 The default is to send the implementation identification
2330 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002331
2332 nfs.recover_lost_locks =
2333 [NFSv4] Attempt to recover locks that were lost due
2334 to a lease timeout on the server. Please note that
2335 doing this risks data corruption, since there are
2336 no guarantees that the file will remain unchanged
2337 after the locks are lost.
2338 If you want to enable the kernel legacy behaviour of
2339 attempting to recover these locks, then set this
2340 parameter to '1'.
2341 The default parameter value of '0' causes the kernel
2342 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002343
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002344 nfs4.layoutstats_timer =
2345 [NFSv4.2] Change the rate at which the kernel sends
2346 layoutstats to the pNFS metadata server.
2347
2348 Setting this to value to 0 causes the kernel to use
2349 whatever value is the default set by the layout
2350 driver. A non-zero value sets the minimum interval
2351 in seconds between layoutstats transmissions.
2352
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002353 nfsd.nfs4_disable_idmapping=
2354 [NFSv4] When set to the default of '1', the NFSv4
2355 server will return only numeric uids and gids to
2356 clients using auth_sys, and will accept numeric uids
2357 and gids from such clients. This is intended to ease
2358 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002359
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002360 objlayoutdriver.osd_login_prog=
2361 [NFS] [OBJLAYOUT] sets the pathname to the program which
2362 is used to automatically discover and login into new
2363 osd-targets. Please see:
2364 Documentation/filesystems/pnfs.txt for more explanations
2365
Paul Mundt1e1030d2009-09-01 17:38:32 +09002366 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002367 when a NMI is triggered.
2368 Format: [state][,regs][,debounce][,die]
2369
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302370 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002371 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002372 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002373 0 - turn hardlockup detector in nmi_watchdog off
2374 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002375 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002376 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002377 default). To disable both hard and soft lockup detectors,
2378 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002379 This is useful when you use a panic=... timeout and
2380 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381
Anton Vorontsovbff38772009-07-08 11:10:56 -07002382 netpoll.carrier_timeout=
2383 [NET] Specifies amount of time (in seconds) that
2384 netpoll should wait for a carrier. By default netpoll
2385 waits 4 seconds.
2386
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002387 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388 emulation library even if a 387 maths coprocessor
2389 is present.
2390
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002391 no_console_suspend
2392 [HW] Never suspend the console
2393 Disable suspending of consoles during suspend and
2394 hibernate operations. Once disabled, debugging
2395 messages can reach various consoles while the rest
2396 of the system is being put to sleep (ie, while
2397 debugging driver suspend/resume hooks). This may
2398 not work reliably with all consoles, but is known
2399 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002400 To facilitate more flexible debugging, we also add
2401 console_suspend, a printk module parameter to control
2402 it. Users could use console_suspend (usually
2403 /sys/module/printk/parameters/console_suspend) to
2404 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002405
Christoph Lameterc1aee212007-05-31 00:40:47 -07002406 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2407 caches in the slab allocator. Saves per-node memory,
2408 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002409
Randy Dunlapa9913042005-10-23 12:57:11 -07002410 noalign [KNL,ARM]
2411
Linus Torvalds1da177e2005-04-16 15:20:36 -07002412 noapic [SMP,APIC] Tells the kernel to not make use of any
2413 IOAPICs that may be present in the system.
2414
Mike Galbraith5091faa2010-11-30 14:18:03 +01002415 noautogroup Disable scheduler automatic task group creation.
2416
Linus Torvalds1da177e2005-04-16 15:20:36 -07002417 nobats [PPC] Do not use BATs for mapping kernel lowmem
2418 on "Classic" PPC cores.
2419
2420 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002421
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002422 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2423
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002424 nodelayacct [KNL] Disable per-task delay accounting
2425
Linus Torvalds1da177e2005-04-16 15:20:36 -07002426 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2427
Paul Mundt6902aa82008-09-21 17:14:42 +09002428 nodsp [SH] Disable hardware DSP at boot time.
2429
Dave Youngb2e0a542014-08-14 17:15:26 +08002430 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002431
Linus Torvalds1da177e2005-04-16 15:20:36 -07002432 noexec [IA-64]
2433
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302434 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002435 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002436 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002437 noexec=off: disable non-executable mappings
2438
H. Peter Anvin52b61792012-09-21 12:43:13 -07002439 nosmap [X86]
2440 Disable SMAP (Supervisor Mode Access Prevention)
2441 even if it is supported by processor.
2442
Fenghua Yude5397a2011-05-11 16:51:05 -07002443 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002444 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002445 even if it is supported by processor.
2446
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002447 noexec32 [X86-64]
2448 This affects only 32-bit executables.
2449 noexec32=on: enable non-executable mappings (default)
2450 read doesn't imply executable mappings
2451 noexec32=off: disable non-executable mappings
2452 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002453
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002454 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002455
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002456 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002457 register save and restore. The kernel will only save
2458 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002459
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002460 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2461
Suresh Siddha0c752a92009-05-22 12:17:45 -07002462 noxsave [BUGS=X86] Disables x86 extended register state save
2463 and restore using xsave. The kernel will fallback to
2464 enabling legacy floating-point and sse state.
2465
Fenghua Yub6f42a42014-05-29 11:12:31 -07002466 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2467 register states. The kernel will fall back to use
2468 xsave to save the states. By using this parameter,
2469 performance of saving the states is degraded because
2470 xsave doesn't support modified optimization while
2471 xsaveopt supports it on xsaveopt enabled systems.
2472
2473 noxsaves [X86] Disables xsaves and xrstors used in saving and
2474 restoring x86 extended register state in compacted
2475 form of xsave area. The kernel will fall back to use
2476 xsaveopt and xrstor to save and restore the states
2477 in standard form of xsave area. By using this
2478 parameter, xsave area per process might occupy more
2479 memory on xsaves enabled systems.
2480
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002481 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2482 wfi(ARM) instruction doesn't work correctly and not to
2483 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002484
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002485 no_file_caps Tells the kernel not to honor file capabilities. The
2486 only way then for a file to be executed with privilege
2487 is to be setuid root or executed by root.
2488
Linus Torvalds1da177e2005-04-16 15:20:36 -07002489 nohalt [IA-64] Tells the kernel not to use the power saving
2490 function PAL_HALT_LIGHT when idle. This increases
2491 power-consumption. On the positive side, it reduces
2492 interrupt wake-up latency, which may improve performance
2493 in certain environments such as networked servers or
2494 real-time systems.
2495
Kees Cooka6e15a32014-06-13 13:30:35 -07002496 nohibernate [HIBERNATION] Disable hibernation and resume.
2497
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002498 nohz= [KNL] Boottime enable/disable dynamic ticks
2499 Valid arguments: on, off
2500 Default: on
2501
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002502 nohz_full= [KNL,BOOT]
2503 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002504 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002505 whenever possible. The boot CPU will be forced outside
2506 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002507 The CPUs in this range must also be included in the
2508 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002509
Paul Mundteeee7852009-04-02 12:31:16 +09002510 noiotrap [SH] Disables trapped I/O port accesses.
2511
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002512 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513 disable unhandled interrupt sources.
2514
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302515 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002516 broken timer IRQ sources.
2517
Linus Torvalds1da177e2005-04-16 15:20:36 -07002518 noisapnp [ISAPNP] Disables ISA PnP code.
2519
2520 noinitrd [RAM] Tells the kernel not to load any configured
2521 initial RAM disk.
2522
Weidong Han03ea8152009-04-17 16:42:15 +08002523 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2524 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002525 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002526
Linus Torvalds1da177e2005-04-16 15:20:36 -07002527 nointroute [IA-64]
2528
Randy Dunlap16290242011-08-13 12:34:52 -07002529 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002530
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002531 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2532
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002533 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2534 fault handling.
2535
Glauber Costad910f5c2011-07-11 15:28:19 -04002536 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2537 steal time is computed, but won't influence scheduler
2538 behaviour
2539
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002540 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002542 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002543
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 noltlbs [PPC] Do not use large page/tlb entries for kernel
2545 lowmem mapping on PPC40x.
2546
Horms312f1f02006-02-22 09:57:55 +09002547 nomca [IA-64] Disable machine check abort handling
2548
Masanari Iida13696e02015-05-16 02:16:43 +09002549 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002550
Andres Salomon83d73842007-10-12 23:04:06 +02002551 nomfgpt [X86-32] Disable Multi-Function General Purpose
2552 Timer usage (for AMD Geode machines).
2553
Don Zickusbda62632011-10-13 15:14:27 -04002554 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2555 shutdown the other cpus. Instead use the REBOOT_VECTOR
2556 irq.
2557
Dave Young02608be2012-02-01 10:33:14 +08002558 nomodule Disable module load
2559
Jiri Kosina016ddd92010-01-18 17:05:40 +01002560 nopat [X86] Disable PAT (page attribute table extension of
2561 pagetables) support.
2562
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002563 norandmaps Don't use address space randomization. Equivalent to
2564 echo 0 > /proc/sys/kernel/randomize_va_space
2565
Jiri Kosinabbff2162010-08-11 18:34:09 +02002566 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002567
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002568 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002569 with UP alternatives
2570
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002571 nordrand [X86] Disable kernel use of the RDRAND and
2572 RDSEED instructions even if they are supported
2573 by the processor. RDRAND and RDSEED are still
2574 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002575
Randy Dunlapa9913042005-10-23 12:57:11 -07002576 noresume [SWSUSP] Disables resume and restores original swap
2577 space.
2578
Linus Torvalds1da177e2005-04-16 15:20:36 -07002579 no-scroll [VGA] Disables scrollback.
2580 This is required for the Braillex ib80-piezo Braille
2581 reader made by F.H. Papenmeier (Germany).
2582
2583 nosbagart [IA-64]
2584
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002585 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002586
Len Brown61ec7562007-08-16 03:34:22 -04002587 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2588 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002589
Dave Jones97842212007-07-15 23:41:05 -07002590 nosoftlockup [KNL] Disable the soft-lockup detector.
2591
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592 nosync [HW,M68K] Disables sync negotiation for all devices.
2593
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002594 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002596 nowatchdog [KNL] Disable both lockup detectors, i.e.
2597 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002598
Linus Torvalds1da177e2005-04-16 15:20:36 -07002599 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002600
Weidong Han2b2fd872009-04-17 16:42:12 +08002601 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2602
Fenghua Yuf78cff42012-11-13 11:32:38 -08002603 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2604 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2605 Some features depend on CPU0. Known dependencies are:
2606 1. Resume from suspend/hibernate depends on CPU0.
2607 Suspend/hibernate will fail if CPU0 is offline and you
2608 need to online CPU0 before suspend/hibernate.
2609 2. PIC interrupts also depend on CPU0. CPU0 can't be
2610 removed if a PIC interrupt is detected.
2611 It's said poweroff/reboot may depend on CPU0 on some
2612 machines although I haven't seen such issues so far
2613 after CPU0 is offline on a few tested machines.
2614 If the dependencies are under your control, you can
2615 turn on cpu0_hotplug.
2616
Randy Dunlap16290242011-08-13 12:34:52 -07002617 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002618 purges which is reported from either PAL_VM_SUMMARY or
2619 SAL PALO.
2620
Yinghai Lu2b633e32010-02-10 01:20:37 -08002621 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2622 could support. nr_cpus=n : n >= 1 limits the kernel to
2623 supporting 'n' processors. Later in runtime you can not
2624 use hotplug cpu feature to put more cpu back to online.
2625 just like you compile the kernel NR_CPUS=n
2626
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002627 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2628
Mel Gorman1a687c22012-11-22 11:16:36 +00002629 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2630 Allowed values are enable and disable
2631
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002632 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2633 one of ['zone', 'node', 'default'] can be specified
2634 This can be set from sysctl after boot.
2635 See Documentation/sysctl/vm.txt for details.
2636
Randy Dunlap7c4be252009-01-06 14:42:44 -08002637 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2638 See Documentation/debugging-via-ohci1394.txt for more
2639 info.
2640
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002641 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2642 Rather than timing out after 20 ms if an EC
2643 command is not properly ACKed, override the length
2644 of the timeout. We have interrupts disabled while
2645 waiting for the ACK, so if this is set too high
2646 interrupts *may* be lost!
2647
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002648 omap_mux= [OMAP] Override bootloader pin multiplexing.
2649 Format: <mux_mode0.mode_name=value>...
2650 For example, to override I2C bus2:
2651 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2652
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653 oprofile.timer= [HW]
2654 Use timer interrupt instead of performance counters
2655
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002656 oprofile.cpu_type= Force an oprofile cpu type
2657 This might be useful if you have an older oprofile
2658 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002659 Format: { arch_perfmon }
2660 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002661 perfmon on Intel CPUs instead of the
2662 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002663 timer: [X86] Force use of architectural NMI
2664 timer mode (see also oprofile.timer
2665 for generic hr timer mode)
Andreas Krebbeldd3c46702011-11-25 20:03:05 +01002666 [s390] Force legacy basic mode sampling
2667 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002668
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002669 oops=panic Always panic on oopses. Default is to just kill the
2670 process, but there is a small probability of
2671 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002672 This will also cause panics on machine check exceptions.
2673 Useful together with panic=30 to trigger a reboot.
2674
Randy Dunlapbcfde332010-06-07 17:10:38 -07002675 OSS [HW,OSS]
2676 See Documentation/sound/oss/oss-parameters.txt
2677
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002678 page_owner= [KNL] Boot-time page_owner enabling option.
2679 Storage of the information about who allocated
2680 each page is disabled in default. With this switch,
2681 we can turn it on.
2682 on: enable the feature
2683
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002684 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002685 timeout > 0: seconds before rebooting
2686 timeout = 0: wait forever
2687 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002688 Format: <timeout>
2689
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002690 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2691 on a WARN().
2692
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002693 crash_kexec_post_notifiers
2694 Run kdump after running panic-notifiers and dumping
2695 kmsg. This only for the users who doubt kdump always
2696 succeeds in any situation.
2697 Note that this also increases risks of kdump failure,
2698 because some panic notifiers can make the crashed
2699 kernel more unstable.
2700
Linus Torvalds1da177e2005-04-16 15:20:36 -07002701 parkbd.port= [HW] Parallel port number the keyboard adapter is
2702 connected to, default is 0.
2703 Format: <parport#>
2704 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2705 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002706 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002707
Randy Dunlapa9913042005-10-23 12:57:11 -07002708 parport= [HW,PPT] Specify parallel ports. 0 disables.
2709 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2710 Use 'auto' to force the driver to use any
2711 IRQ/DMA settings detected (the default is to
2712 ignore detected IRQ/DMA settings because of
2713 possible conflicts). You can specify the base
2714 address, IRQ, and DMA settings; IRQ and DMA
2715 should be numbers, or 'auto' (for using detected
2716 settings on that particular port), or 'nofifo'
2717 (to avoid using a FIFO even if it is detected).
2718 Parallel ports are assigned in the order they
2719 are specified on the command line, starting
2720 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002721
Randy Dunlapa9913042005-10-23 12:57:11 -07002722 parport_init_mode= [HW,PPT]
2723 Configure VIA parallel port to operate in
2724 a specific mode. This is necessary on Pegasos
2725 computer where firmware has no options for setting
2726 up parallel port mode and sets it to spp.
2727 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002728 Format: [spp|ps2|epp|ecp|ecpepp]
2729
Andrew Mortondd287792006-03-23 03:00:57 -08002730 pause_on_oops=
2731 Halt all CPUs after the first oops has been printed for
2732 the specified number of seconds. This is to be used if
2733 your oopses keep scrolling off the screen.
2734
Linus Torvalds1da177e2005-04-16 15:20:36 -07002735 pcbit= [HW,ISDN]
2736
2737 pcd. [PARIDE]
2738 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002739 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002740
Randy Dunlapa9913042005-10-23 12:57:11 -07002741 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002742 earlydump [X86] dump PCI config space before the kernel
2743 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002744 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002745 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002746 the hardware directly. Use this if your machine
2747 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002748 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002749 hardware access methods are allowed. Use this
2750 if you experience crashes upon bootup and you
2751 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002752 conf1 [X86] Force use of PCI Configuration Access
2753 Mechanism 1 (config address in IO port 0xCF8,
2754 data in IO port 0xCFC, both 32-bit).
2755 conf2 [X86] Force use of PCI Configuration Access
2756 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2757 the function, IO port 0xCFA, also 8-bit, sets
2758 bus number. The config space is then accessed
2759 through ports 0xC000-0xCFFF).
2760 See http://wiki.osdev.org/PCI for more info
2761 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002762 noaer [PCIE] If the PCIEAER kernel config parameter is
2763 enabled, this kernel boot option can be used to
2764 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002765 nodomains [PCI] Disable support for multiple PCI
2766 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302767 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002768 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002769 check_enable_amd_mmconf [X86] check for and enable
2770 properly configured MMIO access to PCI
2771 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002772 nomsi [MSI] If the PCI_MSI kernel config parameter is
2773 enabled, this kernel boot option can be used to
2774 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002775 noioapicquirk [APIC] Disable all boot interrupt quirks.
2776 Safety option to keep boot IRQs enabled. This
2777 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002778 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2779 primary IO-APIC for bridges that cannot disable
2780 boot IRQs. This fixes a source of spurious IRQs
2781 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002782 noioapicreroute [APIC] Disable workaround that uses the
2783 boot IRQ equivalent of an IRQ that connects to
2784 a chipset where boot IRQs cannot be disabled.
2785 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002786 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002787 routing table. These calls are known to be buggy
2788 on several machines and they hang the machine
2789 when used, but on other computers it's the only
2790 way to get the interrupt routing table. Try
2791 this option if the kernel is unable to allocate
2792 IRQs or discover secondary PCI buses on your
2793 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002794 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002795 Use with caution as certain devices share
2796 address decoders between ROMs and other
2797 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002798 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002799 expansion ROMs that do not already have
2800 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002801 nobar [X86] Do not assign address space to the
2802 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002803 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002804 assigned automatically to PCI devices. You can
2805 make the kernel exclude IRQs of your ISA cards
2806 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002807 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002808 of the PIRQ table (normally generated
2809 by the BIOS) if it is outside the
2810 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002811 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002812 useful if the kernel is unable to find your
2813 secondary buses and you want to tell it
2814 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002815 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002816 numbers ourselves, overriding
2817 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002818 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002819 in the BIOS $PIR table. This is needed on
2820 some systems with broken BIOSes, notably
2821 some HP Pavilion N5400 and Omnibook XE3
2822 notebooks. This will have no effect if ACPI
2823 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002824 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002825 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002826 use_crs [X86] Use PCI host bridge window information
2827 from ACPI. On BIOSes from 2008 or later, this
2828 is enabled by default. If you need to use this,
2829 please report a bug.
2830 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2831 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002832 routeirq Do IRQ routing for all PCI devices.
2833 This is normally done in pci_enable_device(),
2834 so this option is a temporary workaround
2835 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002836 skip_isa_align [X86] do not align io start addr, so can
2837 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002838 firmware [ARM] Do not re-enumerate the bus but instead
2839 just use the configuration from the
2840 bootloader. This is currently used on
2841 IXP2000 systems where the bus has to be
2842 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002843 noearly [X86] Don't do any early type 1 scanning.
2844 This might help on some broken boards which
2845 machine check when some devices' config space
2846 is read. But various workarounds are disabled
2847 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002848 bfsort Sort PCI devices into breadth-first order.
2849 This sorting is done to get a device
2850 order compatible with older (<= 2.4) kernels.
2851 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002852 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2853 tuning and use the BIOS-configured MPS defaults.
2854 pcie_bus_safe Set every device's MPS to the largest value
2855 supported by all devices below the root complex.
2856 pcie_bus_perf Set device MPS to the largest allowable MPS
2857 based on its parent bus. Also set MRRS (Max
2858 Read Request Size) to the largest supported
2859 value (no larger than the MPS that the device
2860 or bus can support) for best performance.
2861 pcie_bus_peer2peer Set every device's MPS to 128B, which
2862 every device is guaranteed to support. This
2863 configuration allows peer-to-peer DMA between
2864 any pair of devices, possibly at the cost of
2865 reduced performance. This also guarantees
2866 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002867 cbiosize=nn[KMG] The fixed amount of bus space which is
2868 reserved for the CardBus bridge's IO window.
2869 The default value is 256 bytes.
2870 cbmemsize=nn[KMG] The fixed amount of bus space which is
2871 reserved for the CardBus bridge's memory
2872 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002873 resource_alignment=
2874 Format:
2875 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2876 Specifies alignment and device to reassign
2877 aligned memory resources.
2878 If <order of align> is not specified,
2879 PAGE_SIZE is used as alignment.
2880 PCI-PCI bridge can be specified, if resource
2881 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002882 ecrc= Enable/disable PCIe ECRC (transaction layer
2883 end-to-end CRC checking).
2884 bios: Use BIOS/firmware settings. This is the
2885 the default.
2886 off: Turn ECRC off
2887 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002888 hpiosize=nn[KMG] The fixed amount of bus space which is
2889 reserved for hotplug bridge's IO window.
2890 Default size is 256 bytes.
2891 hpmemsize=nn[KMG] The fixed amount of bus space which is
2892 reserved for hotplug bridge's memory window.
2893 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002894 realloc= Enable/disable reallocating PCI bridge resources
2895 if allocations done by BIOS are too small to
2896 accommodate resources required by all child
2897 devices.
2898 off: Turn realloc off
2899 on: Turn realloc on
2900 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002901 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002902 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2903 only look for one device below a PCIe downstream
2904 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002905
Chuck Ebberte5665a42008-09-24 20:40:34 -04002906 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2907 Management.
2908 off Disable ASPM.
2909 force Enable ASPM even on devices that claim not to support it.
2910 WARNING: Forcing ASPM on may cause system lockups.
2911
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002912 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2913 nomsi Do not use MSI for PCI Express Native Hotplug (this
2914 makes all PCIe ports use INTx for hotplug services).
2915
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002916 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002917 auto Ask the BIOS whether or not to use native PCIe services
2918 associated with PCIe ports (PME, hot-plug, AER). Use
2919 them only if that is allowed by the BIOS.
2920 native Use native PCIe services associated with PCIe ports
2921 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002922 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2923 ports driver.
2924
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002925 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002926 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002927 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002928
Linus Torvalds1da177e2005-04-16 15:20:36 -07002929 pcmv= [HW,PCMCIA] BadgePAD 4
2930
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302931 pd_ignore_unused
2932 [PM]
2933 Keep all power-domains already enabled by bootloader on,
2934 even if no driver has claimed them. This is useful
2935 for debug and development, but should not be
2936 needed on a platform with proper driver support.
2937
Linus Torvalds1da177e2005-04-16 15:20:36 -07002938 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002939 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002940
2941 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2942 boot time.
2943 Format: { 0 | 1 }
2944 See arch/parisc/kernel/pdc_chassis.c
2945
Tejun Heof58dc012009-08-14 15:00:50 +09002946 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002947 Currently supported values are "embed" and "page".
2948 Archs may support subset or none of the selections.
2949 See comments in mm/percpu.c for details on each
2950 allocator. This parameter is primarily for debugging
2951 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002952
Linus Torvalds1da177e2005-04-16 15:20:36 -07002953 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002954 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002955
2956 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002957 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002958
2959 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002960 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002961
2962 plip= [PPT,NET] Parallel port network link
2963 Format: { parport<nr> | timid | 0 }
2964 See also Documentation/parport.txt.
2965
Randy Dunlap16290242011-08-13 12:34:52 -07002966 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002967 Override pmtimer IOPort with a hex value.
2968 e.g. pmtmr=0x508
2969
Bjorn Helgaas96242112011-08-11 12:14:05 -06002970 pnp.debug=1 [PNP]
2971 Enable PNP debug messages (depends on the
2972 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2973 via /sys/module/pnp/parameters/debug. We always show
2974 current resource usage; turning this on also shows
2975 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002976
Linus Torvalds1da177e2005-04-16 15:20:36 -07002977 pnpacpi= [ACPI]
2978 { off }
2979
2980 pnpbios= [ISAPNP]
2981 { on | off | curr | res | no-curr | no-res }
2982
2983 pnp_reserve_irq=
2984 [ISAPNP] Exclude IRQs for the autoconfiguration
2985
2986 pnp_reserve_dma=
2987 [ISAPNP] Exclude DMAs for the autoconfiguration
2988
2989 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002990 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002991
2992 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002993 [ISAPNP] Exclude memory regions for the
2994 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002995 Ranges are in pairs (memory base and size).
2996
Randy Dunlap4af94f32009-04-17 18:30:28 -07002997 ports= [IP_VS_FTP] IPVS ftp helper module
2998 Default is 21.
2999 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3000 may be specified.
3001 Format: <port>,<port>....
3002
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003003 ppc_strict_facility_enable
3004 [PPC] This option catches any kernel floating point,
3005 Altivec, VSX and SPE outside of regions specifically
3006 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3007 There is some performance impact when enabling this.
3008
Ingo Molnar45807a12007-07-15 23:40:10 -07003009 print-fatal-signals=
3010 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003011
3012 If enabled, warn about various signal handling
3013 related application anomalies: too many signals,
3014 too many POSIX.1 timers, fatal signals causing a
3015 coredump - etc.
3016
3017 If you hit the warning due to signal overflow,
3018 you might want to try "ulimit -i unlimited".
3019
Ingo Molnar45807a12007-07-15 23:40:10 -07003020 default: off.
3021
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003022 printk.always_kmsg_dump=
3023 Trigger kmsg_dump for cases other than kernel oops or
3024 panics
3025 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3026 default: disabled
3027
Randy Dunlape84845c2007-07-15 23:40:25 -07003028 printk.time= Show timing data prefixed to each printk message line
3029 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3030
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003031 processor.max_cstate= [HW,ACPI]
3032 Limit processor to maximum C-state
3033 max_cstate=9 overrides any DMI blacklist limit.
3034
3035 processor.nocst [HW,ACPI]
3036 Ignore the _CST method to determine C-states,
3037 instead using the legacy FADT method
3038
Linus Torvalds1da177e2005-04-16 15:20:36 -07003039 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003040 Format: [schedule,]<number>
3041 Param: "schedule" - profile schedule points.
3042 Param: <number> - step/bucket size as a power of 2 for
3043 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003044 Param: "sleep" - profile D-state sleeping (millisecs).
3045 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003046 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003047
Linus Torvalds1da177e2005-04-16 15:20:36 -07003048 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3049 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003050 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003051
Randy Dunlapa9913042005-10-23 12:57:11 -07003052 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3053 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003054 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3055 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003056 psmouse.resetafter= [HW,MOUSE]
3057 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003058 (0 = never).
3059 psmouse.resolution=
3060 [HW,MOUSE] Set desired mouse resolution, in dpi.
3061 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003062 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003063 0 = disabled, 1 = enabled (default).
3064
Matthew Garrettdee28e72011-07-21 16:57:55 -04003065 pstore.backend= Specify the name of the pstore backend to use
3066
Linus Torvalds1da177e2005-04-16 15:20:36 -07003067 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003068 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003069
Kay Sieversdc8c8582007-08-15 12:25:38 +02003070 pty.legacy_count=
3071 [KNL] Number of legacy pty's. Overwrites compiled-in
3072 default number.
3073
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003074 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003075
Linus Torvalds1da177e2005-04-16 15:20:36 -07003076 r128= [HW,DRM]
3077
3078 raid= [HW,RAID]
3079 See Documentation/md.txt.
3080
Linus Torvalds1da177e2005-04-16 15:20:36 -07003081 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003082 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003083
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003084 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003085 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3086 the specified list of CPUs to be no-callback CPUs.
3087 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003088 be offloaded to "rcuox/N" kthreads created for
3089 that purpose, where "x" is "b" for RCU-bh, "p"
3090 for RCU-preempt, and "s" for RCU-sched, and "N"
3091 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003092 offloaded CPUs, which can be useful for HPC and
3093 real-time workloads. It can also improve energy
3094 efficiency for asymmetric multiprocessors.
3095
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003096 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003097 Rather than requiring that offloaded CPUs
3098 (specified by rcu_nocbs= above) explicitly
3099 awaken the corresponding "rcuoN" kthreads,
3100 make these kthreads poll for callbacks.
3101 This improves the real-time response for the
3102 offloaded CPUs by relieving them of the need to
3103 wake up the corresponding kthread, but degrades
3104 energy efficiency by requiring that the kthreads
3105 periodically wake up to do the polling.
3106
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003107 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003108 Set maximum number of finished RCU callbacks to
3109 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003110
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003111 rcutree.dump_tree= [KNL]
3112 Dump the structure of the rcu_node combining tree
3113 out at early boot. This is used for diagnostic
3114 purposes, to verify correct tree setup.
3115
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003116 rcutree.gp_cleanup_delay= [KNL]
3117 Set the number of jiffies to delay each step of
3118 RCU grace-period cleanup. This only has effect
3119 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3120
Paul E. McKenney37745d22015-01-22 18:24:08 -08003121 rcutree.gp_init_delay= [KNL]
3122 Set the number of jiffies to delay each step of
3123 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003124 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3125 is set.
3126
3127 rcutree.gp_preinit_delay= [KNL]
3128 Set the number of jiffies to delay each step of
3129 RCU grace-period pre-initialization, that is,
3130 the propagation of recent CPU-hotplug changes up
3131 the rcu_node combining tree. This only has effect
3132 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003133
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003134 rcutree.rcu_fanout_exact= [KNL]
3135 Disable autobalancing of the rcu_node combining
3136 tree. This is used by rcutorture, and might
3137 possibly be useful for architectures having high
3138 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003139
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003140 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003141 Change the number of CPUs assigned to each
3142 leaf rcu_node structure. Useful for very
3143 large systems, which will choose the value 64,
3144 and for NUMA systems with large remote-access
3145 latencies, which will choose a value aligned
3146 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003147
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003148 rcutree.jiffies_till_sched_qs= [KNL]
3149 Set required age in jiffies for a
3150 given grace period before RCU starts
3151 soliciting quiescent-state help from
3152 rcu_note_context_switch().
3153
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003154 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003155 Set delay from grace-period initialization to
3156 first attempt to force quiescent states.
3157 Units are jiffies, minimum value is zero,
3158 and maximum value is HZ.
3159
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003160 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003161 Set delay between subsequent attempts to force
3162 quiescent states. Units are jiffies, minimum
3163 value is one, and maximum value is HZ.
3164
Clark Williams21871d72014-09-12 21:21:09 -05003165 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003166 Set the SCHED_FIFO priority of the RCU per-CPU
3167 kthreads (rcuc/N). This value is also used for
3168 the priority of the RCU boost threads (rcub/N)
3169 and for the RCU grace-period kthreads (rcu_bh,
3170 rcu_preempt, and rcu_sched). If RCU_BOOST is
3171 set, valid values are 1-99 and the default is 1
3172 (the least-favored priority). Otherwise, when
3173 RCU_BOOST is not set, valid values are 0-99 and
3174 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003175
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003176 rcutree.rcu_nocb_leader_stride= [KNL]
3177 Set the number of NOCB kthread groups, which
3178 defaults to the square root of the number of
3179 CPUs. Larger numbers reduces the wakeup overhead
3180 on the per-CPU grace-period kthreads, but increases
3181 that same overhead on each group's leader.
3182
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003183 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003184 Set threshold of queued RCU callbacks beyond which
3185 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003186
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003187 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003188 Set threshold of queued RCU callbacks below which
3189 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003190
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003191 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003192 Set wakeup interval for idle CPUs that have
3193 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003194
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003195 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003196 Set wakeup interval for idle CPUs that have
3197 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3198 Lazy RCU callbacks are those which RCU can
3199 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003200
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003201 rcutorture.cbflood_inter_holdoff= [KNL]
3202 Set holdoff time (jiffies) between successive
3203 callback-flood tests.
3204
3205 rcutorture.cbflood_intra_holdoff= [KNL]
3206 Set holdoff time (jiffies) between successive
3207 bursts of callbacks within a given callback-flood
3208 test.
3209
3210 rcutorture.cbflood_n_burst= [KNL]
3211 Set the number of bursts making up a given
3212 callback-flood test. Set this to zero to
3213 disable callback-flood testing.
3214
3215 rcutorture.cbflood_n_per_burst= [KNL]
3216 Set the number of callbacks to be registered
3217 in a given burst of a callback-flood test.
3218
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003219 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003220 Set duration of force_quiescent_state bursts
3221 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003222
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003223 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003224 Set holdoff time within force_quiescent_state bursts
3225 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003226
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003227 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003228 Set wait time between force_quiescent_state bursts
3229 in seconds.
3230
3231 rcutorture.gp_cond= [KNL]
3232 Use conditional/asynchronous update-side
3233 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003234
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003235 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003236 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003237
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003238 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003239 Use normal (non-expedited) asynchronous
3240 update-side primitives, if available.
3241
3242 rcutorture.gp_sync= [KNL]
3243 Use normal (non-expedited) synchronous
3244 update-side primitives, if available. If all
3245 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3246 rcutorture.gp_normal=, and rcutorture.gp_sync=
3247 are zero, rcutorture acts as if is interpreted
3248 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003249
3250 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003251 Set callbacks/threads for rcu_barrier() testing.
3252
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003253 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003254 Set number of concurrent RCU writers. These just
3255 stress RCU, they don't participate in the actual
3256 test, hence the "fake".
3257
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003258 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003259 Set number of RCU readers. The value -1 selects
3260 N-1, where N is the number of CPUs. A value
3261 "n" less than -1 selects N-n-2, where N is again
3262 the number of CPUs. For example, -2 selects N
3263 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003264
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003265 rcutorture.object_debug= [KNL]
3266 Enable debug-object double-call_rcu() testing.
3267
3268 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003269 Set time (s) after boot for CPU-hotplug testing.
3270
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003271 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003272 Set time (s) between CPU-hotplug operations, or
3273 zero to disable CPU-hotplug testing.
3274
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003275 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003276 Set task-shuffle interval (s). Shuffling tasks
3277 allows some CPUs to go into dyntick-idle mode
3278 during the rcutorture test.
3279
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003280 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003281 Set time (s) after boot system shutdown. This
3282 is useful for hands-off automated testing.
3283
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003284 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003285 Duration of CPU stall (s) to test RCU CPU stall
3286 warnings, zero to disable.
3287
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003288 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003289 Time to wait (s) after boot before inducing stall.
3290
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003291 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003292 Time (s) between statistics printk()s.
3293
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003294 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003295 Time (s) to stutter testing, for example, specifying
3296 five seconds causes the test to run for five seconds,
3297 wait for five seconds, and so on. This tests RCU's
3298 ability to transition abruptly to and from idle.
3299
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003300 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003301 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3302 "Maybe" means test if the RCU implementation
3303 under test support RCU priority boosting.
3304
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003305 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003306 Duration (s) of each individual boost test.
3307
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003308 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003309 Interval (s) between each boost test.
3310
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003311 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003312 Test RCU's dyntick-idle handling. See also the
3313 rcutorture.shuffle_interval parameter.
3314
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003315 rcutorture.torture_runnable= [BOOT]
3316 Start rcutorture running at boot time.
3317
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003318 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003319 Specify the RCU implementation to test.
3320
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003321 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003322 Enable additional printk() statements.
3323
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003324 rcupdate.rcu_cpu_stall_suppress= [KNL]
3325 Suppress RCU CPU stall warning messages.
3326
3327 rcupdate.rcu_cpu_stall_timeout= [KNL]
3328 Set timeout for RCU CPU stall warning messages.
3329
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003330 rcupdate.rcu_expedited= [KNL]
3331 Use expedited grace-period primitives, for
3332 example, synchronize_rcu_expedited() instead
3333 of synchronize_rcu(). This reduces latency,
3334 but can increase CPU utilization, degrade
3335 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003336 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003337
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003338 rcupdate.rcu_normal= [KNL]
3339 Use only normal grace-period primitives,
3340 for example, synchronize_rcu() instead of
3341 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003342 real-time latency, CPU utilization, and
3343 energy efficiency, but can expose users to
3344 increased grace-period latency. This parameter
3345 overrides rcupdate.rcu_expedited. No effect on
3346 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003347
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003348 rcupdate.rcu_normal_after_boot= [KNL]
3349 Once boot has completed (that is, after
3350 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003351 only normal grace-period primitives. No effect
3352 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003353
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003354 rcupdate.rcu_task_stall_timeout= [KNL]
3355 Set timeout in jiffies for RCU task stall warning
3356 messages. Disable with a value less than or equal
3357 to zero.
3358
Pranith Kumar74860fe2014-09-19 11:34:09 -04003359 rcupdate.rcu_self_test= [KNL]
3360 Run the RCU early boot self tests
3361
3362 rcupdate.rcu_self_test_bh= [KNL]
3363 Run the RCU bh early boot self tests
3364
3365 rcupdate.rcu_self_test_sched= [KNL]
3366 Run the RCU sched early boot self tests
3367
Olof Johanssonffdfc402005-09-06 15:17:19 -07003368 rdinit= [KNL]
3369 Format: <full_path>
3370 Run specified binary instead of /init from the ramdisk,
3371 used for early userspace startup. See initrd.
3372
Robin Holt1b3a5d02013-07-08 16:01:42 -07003373 reboot= [KNL]
3374 Format (x86 or x86_64):
3375 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3376 [[,]s[mp]#### \
3377 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3378 [[,]f[orce]
3379 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3380 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3381 reboot_force is either force or not specified,
3382 reboot_cpu is s[mp]#### with #### being the processor
3383 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003384
Paul Jackson46b6d942008-07-04 10:00:09 -07003385 relax_domain_level=
3386 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003387 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003388
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003389 relative_sleep_states=
3390 [SUSPEND] Use sleep state labeling where the deepest
3391 state available other than hibernation is always "mem".
3392 Format: { "0" | "1" }
3393 0 -- Traditional sleep state labels.
3394 1 -- Relative sleep state labels.
3395
Linus Torvalds1da177e2005-04-16 15:20:36 -07003396 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3397
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003398 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003399 Format: nn[KMG]
3400 Reserves a hole at the top of the kernel virtual
3401 address space.
3402
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003403 reservelow= [X86]
3404 Format: nn[K]
3405 Set the amount of memory to reserve for BIOS at
3406 the bottom of the address space.
3407
Vivek Goyal7e962872006-09-27 01:50:44 -07003408 reset_devices [KNL] Force drivers to reset the underlying device
3409 during initialization.
3410
Randy Dunlapa9913042005-10-23 12:57:11 -07003411 resume= [SWSUSP]
3412 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003413 Format:
3414 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003415
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003416 resume_offset= [SWSUSP]
3417 Specify the offset from the beginning of the partition
3418 given by "resume=" at which the swap header is located,
3419 in <PAGE_SIZE> units (needed only for swap files).
3420 See Documentation/power/swsusp-and-swap-files.txt
3421
Barry Songf126f732011-10-10 23:38:41 +02003422 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3423 read the resume files
3424
Barry Song6f8d7022011-10-06 20:34:46 +02003425 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3426 Useful for devices that are detected asynchronously
3427 (e.g. USB and MMC devices).
3428
Bojan Smojverf996fc92010-09-09 23:06:23 +02003429 hibernate= [HIBERNATION]
3430 noresume Don't check if there's a hibernation image
3431 present during boot.
3432 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003433 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003434
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003435 retain_initrd [RAM] Keep initrd memory after extraction
3436
Andrew Clausen0efbb782015-01-09 20:24:55 +00003437 rfkill.default_state=
3438 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3439 etc. communication is blocked by default.
3440 1 Unblocked.
3441
3442 rfkill.master_switch_mode=
3443 0 The "airplane mode" button does nothing.
3444 1 The "airplane mode" button toggles between everything
3445 blocked and the previous configuration.
3446 2 The "airplane mode" button toggles between everything
3447 blocked and everything unblocked.
3448
Linus Torvalds1da177e2005-04-16 15:20:36 -07003449 rhash_entries= [KNL,NET]
3450 Set number of hash buckets for route cache
3451
Linus Torvalds1da177e2005-04-16 15:20:36 -07003452 ro [KNL] Mount root device read-only on boot
3453
3454 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003455 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003456
3457 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3458 mount the root filesystem
3459
3460 rootflags= [KNL] Set root filesystem mount option string
3461
3462 rootfstype= [KNL] Set root filesystem type
3463
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003464 rootwait [KNL] Wait (indefinitely) for root device to show up.
3465 Useful for devices that are detected asynchronously
3466 (e.g. USB and MMC devices).
3467
Robert Tivy5c71d612013-03-28 18:41:46 -07003468 rproc_mem=nn[KMG][@address]
3469 [KNL,ARM,CMA] Remoteproc physical memory block.
3470 Memory area to be used by remote processor image,
3471 managed by CMA.
3472
Linus Torvalds1da177e2005-04-16 15:20:36 -07003473 rw [KNL] Mount root device read-write on boot
3474
3475 S [KNL] Run init in single mode
3476
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003477 s390_iommu= [HW,S390]
3478 Set s390 IOTLB flushing mode
3479 strict
3480 With strict flushing every unmap operation will result in
3481 an IOTLB flush. Default is lazy flushing before reuse,
3482 which is faster.
3483
Linus Torvalds1da177e2005-04-16 15:20:36 -07003484 sa1100ir [NET]
3485 See drivers/net/irda/sa1100_ir.c.
3486
Linus Torvalds1da177e2005-04-16 15:20:36 -07003487 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003488
Mike Travisf6630112009-11-17 18:22:15 -06003489 sched_debug [KNL] Enables verbose scheduler debug messages.
3490
Mike Galbraith5307c952012-05-08 12:20:58 +02003491 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3492 xtime_lock contention on larger systems, and/or RCU lock
3493 contention on all systems with CONFIG_MAXSMP set.
3494 Format: { "0" | "1" }
3495 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3496 1 -- enable.
3497 Note: increases power consumption, thus should only be
3498 enabled if running jitter sensitive (HPC/RT) workloads.
3499
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003500 security= [SECURITY] Choose a security module to enable at boot.
3501 If this boot parameter is not specified, only the first
3502 security module asking for security registration will be
3503 loaded. An invalid security module name will be treated
3504 as if no module has been chosen.
3505
3506 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003507 Format: { "0" | "1" }
3508 See security/selinux/Kconfig help text.
3509 0 -- disable.
3510 1 -- enable.
3511 Default value is set via kernel config option.
3512 If enabled at boot time, /selinux/disable can be used
3513 later to disable prior to initial policy load.
3514
John Johansenc1c124e2010-07-29 14:48:09 -07003515 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3516 Format: { "0" | "1" }
3517 See security/apparmor/Kconfig help text
3518 0 -- disable.
3519 1 -- enable.
3520 Default value is set via kernel config option.
3521
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003522 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003523
Linus Torvalds1da177e2005-04-16 15:20:36 -07003524 shapers= [NET]
3525 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003526
Yinghai Lub05f78f2008-08-22 01:32:50 -07003527 show_msr= [x86] show boot-time MSR settings
3528 Format: { <integer> }
3529 Show boot-time (BIOS-initialized) MSR settings.
3530 The parameter means the number of CPUs to show,
3531 for example 1 means boot CPU only.
3532
Linus Torvalds1da177e2005-04-16 15:20:36 -07003533 simeth= [IA-64]
3534 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003535
Linus Torvalds1da177e2005-04-16 15:20:36 -07003536 slram= [HW,MTD]
3537
Joonsoo Kim423c9292014-10-09 15:26:22 -07003538 slab_nomerge [MM]
3539 Disable merging of slabs with similar size. May be
3540 necessary if there is some reason to distinguish
3541 allocs to different slabs. Debug options disable
3542 merging on their own.
3543 For more information see Documentation/vm/slub.txt.
3544
David Rientjes3df1ccc2011-10-18 22:09:28 -07003545 slab_max_order= [MM, SLAB]
3546 Determines the maximum allowed order for slabs.
3547 A high setting may cause OOMs due to memory
3548 fragmentation. Defaults to 1 for systems with
3549 more than 32MB of RAM, 0 otherwise.
3550
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003551 slub_debug[=options[,slabs]] [MM, SLUB]
3552 Enabling slub_debug allows one to determine the
3553 culprit if slab objects become corrupted. Enabling
3554 slub_debug can create guard zones around objects and
3555 may poison objects when not in use. Also tracks the
3556 last alloc / free. For more information see
3557 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003558
3559 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003560 Determines the maximum allowed order for slabs.
3561 A high setting may cause OOMs due to memory
3562 fragmentation. For more information see
3563 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003564
3565 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003566 The minimum number of objects per slab. SLUB will
3567 increase the slab order up to slub_max_order to
3568 generate a sufficiently large slab able to contain
3569 the number of objects indicated. The higher the number
3570 of objects the smaller the overhead of tracking slabs
3571 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003572 For more information see Documentation/vm/slub.txt.
3573
3574 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003575 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003576 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003577 For more information see Documentation/vm/slub.txt.
3578
3579 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003580 Same with slab_nomerge. This is supported for legacy.
3581 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003582
Linus Torvalds1da177e2005-04-16 15:20:36 -07003583 smart2= [HW]
3584 Format: <io1>[,<io2>[,...,<io8>]]
3585
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003586 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3587 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3588 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3589 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3590 smsc-ircc2.ircc_irq= [HW] IRQ line
3591 smsc-ircc2.ircc_dma= [HW] DMA channel
3592 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3593 0: Toshiba Satellite 1800 (GP data pin select)
3594 1: Fast pin select (default)
3595 2: ATC IRMode
3596
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003597 softlockup_panic=
3598 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003599 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003600
Aaron Tomlined235872014-06-23 13:22:05 -07003601 softlockup_all_cpu_backtrace=
3602 [KNL] Should the soft-lockup detector generate
3603 backtraces on all cpus.
3604 Format: <integer>
3605
Linus Torvalds1da177e2005-04-16 15:20:36 -07003606 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003607 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003608
Linus Torvalds1da177e2005-04-16 15:20:36 -07003609 spia_io_base= [HW,MTD]
3610 spia_fio_base=
3611 spia_pedr=
3612 spia_peddr=
3613
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003614 stacktrace [FTRACE]
3615 Enabled the stack tracer on boot up.
3616
Steven Rostedt762e1202011-12-19 22:01:00 -05003617 stacktrace_filter=[function-list]
3618 [FTRACE] Limit the functions that the stack tracer
3619 will trace at boot up. function-list is a comma separated
3620 list of functions. This list can be changed at run
3621 time by the stack_trace_filter file in the debugfs
3622 tracing directory. Note, this enables stack tracing
3623 and the stacktrace above is not needed.
3624
Linus Torvalds1da177e2005-04-16 15:20:36 -07003625 sti= [PARISC,HW]
3626 Format: <num>
3627 Set the STI (builtin display/keyboard on the HP-PARISC
3628 machines) console (graphic card) which should be used
3629 as the initial boot-console.
3630 See also comment in drivers/video/console/sticore.c.
3631
3632 sti_font= [HW]
3633 See comment in drivers/video/console/sticore.c.
3634
3635 stifb= [HW]
3636 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3637
Trond Myklebustcbf11072009-08-09 15:06:19 -04003638 sunrpc.min_resvport=
3639 sunrpc.max_resvport=
3640 [NFS,SUNRPC]
3641 SunRPC servers often require that client requests
3642 originate from a privileged port (i.e. a port in the
3643 range 0 < portnr < 1024).
3644 An administrator who wishes to reserve some of these
3645 ports for other uses may adjust the range that the
3646 kernel's sunrpc client considers to be privileged
3647 using these two parameters to set the minimum and
3648 maximum port values.
3649
Greg Banks42a7fc42007-03-06 01:42:23 -08003650 sunrpc.pool_mode=
3651 [NFS]
3652 Control how the NFS server code allocates CPUs to
3653 service thread pools. Depending on how many NICs
3654 you have and where their interrupts are bound, this
3655 option will affect which CPUs will do NFS serving.
3656 Note: this parameter cannot be changed while the
3657 NFS server is running.
3658
3659 auto the server chooses an appropriate mode
3660 automatically using heuristics
3661 global a single global pool contains all CPUs
3662 percpu one pool for each CPU
3663 pernode one pool for each NUMA node (equivalent
3664 to global on non-NUMA machines)
3665
Trond Myklebustcbf11072009-08-09 15:06:19 -04003666 sunrpc.tcp_slot_table_entries=
3667 sunrpc.udp_slot_table_entries=
3668 [NFS,SUNRPC]
3669 Sets the upper limit on the number of simultaneous
3670 RPC calls that can be sent from the client to a
3671 server. Increasing these values may allow you to
3672 improve throughput, but will also increase the
3673 amount of memory reserved for use by the client.
3674
Brian Norris1d4a9c12015-02-22 21:16:49 -08003675 suspend.pm_test_delay=
3676 [SUSPEND]
3677 Sets the number of seconds to remain in a suspend test
3678 mode before resuming the system (see
3679 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3680 is set. Default value is 5.
3681
Michal Hocko07555ac2013-08-22 16:35:46 -07003682 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003683 [KNL] Enable accounting of swap in memory resource
3684 controller if no parameter or 1 is given or disable
3685 it if 0 is given (See Documentation/cgroups/memory.txt)
3686
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003687 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3688 Format: { <int> | force }
3689 <int> -- Number of I/O TLB slabs
3690 force -- force using of bounce buffers even if they
3691 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003692
Linus Torvalds1da177e2005-04-16 15:20:36 -07003693 switches= [HW,M68k]
3694
Andi Kleene52eec12010-09-08 16:54:17 +02003695 sysfs.deprecated=0|1 [KNL]
3696 Enable/disable old style sysfs layout for old udev
3697 on older distributions. When this option is enabled
3698 very new udev will not work anymore. When this option
3699 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3700 in older udev will not work anymore.
3701 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3702 the kernel configuration.
3703
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003704 sysrq_always_enabled
3705 [KNL]
3706 Ignore sysrq setting - this boot parameter will
3707 neutralize any effect of /proc/sys/kernel/sysrq.
3708 Useful for debugging.
3709
Fabian Frederick747029a2014-11-06 19:46:50 +01003710 tcpmhash_entries= [KNL,NET]
3711 Set the number of tcp_metrics_hash slots.
3712 Default value is 8192 or 16384 depending on total
3713 ram pages. This is used to specify the TCP metrics
3714 cache size. See Documentation/networking/ip-sysctl.txt
3715 "tcp_no_metrics_save" section for more details.
3716
Linus Torvalds1da177e2005-04-16 15:20:36 -07003717 tdfx= [HW,DRM]
3718
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003719 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003720 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003721 standby suspend) or "freeze" (for suspend type freeze)
3722 as the system sleep state during system startup with
3723 the optional capability to repeat N number of times.
3724 The system is woken from this state using a
3725 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003726
Linus Torvalds1da177e2005-04-16 15:20:36 -07003727 thash_entries= [KNL,NET]
3728 Set number of hash buckets for TCP connection
3729
Len Brownf8707ec2007-08-12 00:12:54 -04003730 thermal.act= [HW,ACPI]
3731 -1: disable all active trip points in all thermal zones
3732 <degrees C>: override all lowest active trip points
3733
Len Brownc52a7412007-08-14 15:49:32 -04003734 thermal.crt= [HW,ACPI]
3735 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003736 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003737
Len Brownf5487142007-08-12 00:12:44 -04003738 thermal.nocrt= [HW,ACPI]
3739 Set to disable actions on ACPI thermal zone
3740 critical and hot trip points.
3741
Len Brown72b33ef2007-08-12 00:12:17 -04003742 thermal.off= [HW,ACPI]
3743 1: disable ACPI thermal control
3744
Len Browna70cdc52007-08-12 00:12:35 -04003745 thermal.psv= [HW,ACPI]
3746 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003747 <degrees C>: override all passive trip points to this
3748 value
Len Browna70cdc52007-08-12 00:12:35 -04003749
Len Brown730ff342007-08-12 00:12:26 -04003750 thermal.tzp= [HW,ACPI]
3751 Specify global default ACPI thermal zone polling rate
3752 <deci-seconds>: poll all this frequency
3753 0: no polling (default)
3754
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003755 threadirqs [KNL]
3756 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003757 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003758
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003759 tmem [KNL,XEN]
3760 Enable the Transcendent memory driver if built-in.
3761
3762 tmem.cleancache=0|1 [KNL, XEN]
3763 Default is on (1). Disable the usage of the cleancache
3764 API to send anonymous pages to the hypervisor.
3765
3766 tmem.frontswap=0|1 [KNL, XEN]
3767 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003768 API to send swap pages to the hypervisor. If disabled
3769 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003770
3771 tmem.selfballooning=0|1 [KNL, XEN]
3772 Default is on (1). Disable the driving of swap pages
3773 to the hypervisor.
3774
3775 tmem.selfshrinking=0|1 [KNL, XEN]
3776 Default is on (1). Partial swapoff that immediately
3777 transfers pages from Xen hypervisor back to the
3778 kernel based on different criteria.
3779
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003780 topology= [S390]
3781 Format: {off | on}
3782 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003783 topology information if the hardware supports this.
3784 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003785 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003786 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003787
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003788 topology_updates= [KNL, PPC, NUMA]
3789 Format: {off}
3790 Specify if the kernel should ignore (off)
3791 topology updates sent by the hypervisor to this
3792 LPAR.
3793
Linus Torvalds1da177e2005-04-16 15:20:36 -07003794 tp720= [HW,PS2]
3795
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003796 tpm_suspend_pcr=[HW,TPM]
3797 Format: integer pcr id
3798 Specify that at suspend time, the tpm driver
3799 should extend the specified pcr with zeros,
3800 as a workaround for some chips which fail to
3801 flush the last written pcr on TPM_SaveState.
3802 This will guarantee that all the other pcrs
3803 are saved.
3804
Li Zefan9d612be2009-06-24 17:33:15 +08003805 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003806 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003807
Li Zefan020e5f82009-07-01 10:47:05 +08003808 trace_event=[event-list]
3809 [FTRACE] Set and start specified trace events in order
3810 to facilitate early boot debugging.
3811 See also Documentation/trace/events.txt
3812
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003813 trace_options=[option-list]
3814 [FTRACE] Enable or disable tracer options at boot.
3815 The option-list is a comma delimited list of options
3816 that can be enabled or disabled just as if you were
3817 to echo the option name into
3818
3819 /sys/kernel/debug/tracing/trace_options
3820
3821 For example, to enable stacktrace option (to dump the
3822 stack trace of each event), add to the command line:
3823
3824 trace_options=stacktrace
3825
3826 See also Documentation/trace/ftrace.txt "trace options"
3827 section.
3828
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003829 tp_printk[FTRACE]
3830 Have the tracepoints sent to printk as well as the
3831 tracing ring buffer. This is useful for early boot up
3832 where the system hangs or reboots and does not give the
3833 option for reading the tracing buffer or performing a
3834 ftrace_dump_on_oops.
3835
3836 To turn off having tracepoints sent to printk,
3837 echo 0 > /proc/sys/kernel/tracepoint_printk
3838 Note, echoing 1 into this file without the
3839 tracepoint_printk kernel cmdline option has no effect.
3840
3841 ** CAUTION **
3842
3843 Having tracepoints sent to printk() and activating high
3844 frequency tracepoints such as irq or sched, can cause
3845 the system to live lock.
3846
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003847 traceoff_on_warning
3848 [FTRACE] enable this option to disable tracing when a
3849 warning is hit. This turns off "tracing_on". Tracing can
3850 be enabled again by echoing '1' into the "tracing_on"
3851 file located in /sys/kernel/debug/tracing/
3852
3853 This option is useful, as it disables the trace before
3854 the WARNING dump is called, which prevents the trace to
3855 be filled with content caused by the warning output.
3856
3857 This option can also be set at run time via the sysctl
3858 option: kernel/traceoff_on_warning
3859
Jiri Kosinafcf4d8212012-03-21 16:34:02 -07003860 transparent_hugepage=
3861 [KNL]
3862 Format: [always|madvise|never]
3863 Can be used to control the default behavior of the system
3864 with respect to transparent hugepages.
3865 See Documentation/vm/transhuge.txt for more details.
3866
john stultzd3b8f882009-08-17 16:40:47 -07003867 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003868 Format: <string>
3869 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003870 disables clocksource verification at runtime, as well
3871 as the stability checks done at bootup. Used to enable
3872 high-resolution timer mode on older hardware, and in
3873 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003874 [x86] noirqtime: Do not use TSC to do irq accounting.
3875 Used to run time disable IRQ_TIME_ACCOUNTING on any
3876 platforms where RDTSC is slow and this accounting
3877 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003878
Randy Dunlapa9913042005-10-23 12:57:11 -07003879 turbografx.map[2|3]= [HW,JOY]
3880 TurboGraFX parallel port interface
3881 Format:
3882 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003883 See also Documentation/input/joystick-parport.txt
3884
Christian Kujaub6935f82011-05-31 15:22:05 +00003885 udbg-immortal [PPC] When debugging early kernel crashes that
3886 happen after console_init() and before a proper
3887 console driver takes over, this boot options might
3888 help "seeing" what's going on.
3889
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003890 uhash_entries= [KNL,NET]
3891 Set number of hash buckets for UDP/UDP-Lite connections
3892
Alan Stern5f8364b2006-12-05 16:29:55 -05003893 uhci-hcd.ignore_oc=
3894 [USB] Ignore overcurrent events (default N).
3895 Some badly-designed motherboards generate lots of
3896 bogus events, for ports that aren't wired to
3897 anything. Set this parameter to avoid log spamming.
3898 Note that genuine overcurrent events won't be
3899 reported either.
3900
Simon Arlotte3a61b02008-07-19 23:32:54 +01003901 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003902 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003903
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003904 usbcore.authorized_default=
3905 [USB] Default USB device authorization:
3906 (default -1 = authorized except for wireless USB,
3907 0 = not authorized, 1 = authorized)
3908
Alan Sternb5e795f2007-02-20 15:00:53 -05003909 usbcore.autosuspend=
3910 [USB] The autosuspend time delay (in seconds) used
3911 for newly-detected USB devices (default 2). This
3912 is the time required before an idle device will be
3913 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003914 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003915
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003916 usbcore.usbfs_snoop=
3917 [USB] Set to log all usbfs traffic (default 0 = off).
3918
Alan Stern0290cc92015-11-20 13:53:22 -05003919 usbcore.usbfs_snoop_max=
3920 [USB] Maximum number of bytes to snoop in each URB
3921 (default = 65536).
3922
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003923 usbcore.blinkenlights=
3924 [USB] Set to cycle leds on hubs (default 0 = off).
3925
3926 usbcore.old_scheme_first=
3927 [USB] Start with the old device initialization
3928 scheme (default 0 = off).
3929
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003930 usbcore.usbfs_memory_mb=
3931 [USB] Memory limit (in MB) for buffers allocated by
3932 usbfs (default = 16, 0 = max = 2047).
3933
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003934 usbcore.use_both_schemes=
3935 [USB] Try the other device initialization scheme
3936 if the first one fails (default 1 = enabled).
3937
3938 usbcore.initial_descriptor_timeout=
3939 [USB] Specifies timeout for the initial 64-byte
3940 USB_REQ_GET_DESCRIPTOR request in milliseconds
3941 (default 5000 = 5.0 seconds).
3942
Oliver Neukum40d58142015-12-03 15:03:32 +01003943 usbcore.nousb [USB] Disable the USB subsystem
3944
Linus Torvalds1da177e2005-04-16 15:20:36 -07003945 usbhid.mousepoll=
3946 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003947
Alan Sternd4f373e2008-11-10 14:07:45 -05003948 usb-storage.delay_use=
3949 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00003950 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05003951
3952 usb-storage.quirks=
3953 [UMS] A list of quirks entries to supplement or
3954 override the built-in unusual_devs list. List
3955 entries are separated by commas. Each entry has
3956 the form VID:PID:Flags where VID and PID are Vendor
3957 and Product ID values (4-digit hex numbers) and
3958 Flags is a set of characters, each corresponding
3959 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003960 a = SANE_SENSE (collect more than 18 bytes
3961 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003962 b = BAD_SENSE (don't collect more than 18
3963 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003964 c = FIX_CAPACITY (decrease the reported
3965 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003966 d = NO_READ_DISC_INFO (don't use
3967 READ_DISC_INFO command);
3968 e = NO_READ_CAPACITY_16 (don't use
3969 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003970 f = NO_REPORT_OPCODES (don't use report opcodes
3971 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02003972 g = MAX_SECTORS_240 (don't transfer more than
3973 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003974 h = CAPACITY_HEURISTICS (decrease the
3975 reported device capacity by one
3976 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003977 i = IGNORE_DEVICE (don't bind to this
3978 device);
3979 l = NOT_LOCKABLE (don't try to lock and
3980 unlock ejectable media);
3981 m = MAX_SECTORS_64 (don't transfer more
3982 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003983 n = INITIAL_READ10 (force a retry of the
3984 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003985 o = CAPACITY_OK (accept the capacity
3986 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003987 p = WRITE_CACHE (the device cache is ON
3988 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003989 r = IGNORE_RESIDUE (the device reports
3990 bogus residue values);
3991 s = SINGLE_LUN (the device has only one
3992 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003993 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3994 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003995 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003996 w = NO_WP_DETECT (don't test whether the
3997 medium is write-protected).
3998 Example: quirks=0419:aaf5:rl,0421:0433:rc
3999
Stephen Boydac1667d2011-08-13 12:34:50 -07004000 user_debug= [KNL,ARM]
4001 Format: <int>
4002 See arch/arm/Kconfig.debug help text.
4003 1 - undefined instruction events
4004 2 - system calls
4005 4 - invalid data aborts
4006 8 - SIGSEGV faults
4007 16 - SIGBUS faults
4008 Example: user_debug=31
4009
Ian Campbell14315592010-02-17 10:38:10 +00004010 userpte=
4011 [X86] Flags controlling user PTE allocations.
4012
4013 nohigh = do not allocate PTE pages in
4014 HIGHMEM regardless of setting
4015 of CONFIG_HIGHPTE.
4016
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304017 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004018 On X86_32, this is an alias for vdso32=. Otherwise:
4019
4020 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004021 vdso=0: disable VDSO mapping
4022
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004023 vdso32= [X86] Control the 32-bit vDSO
4024 vdso32=1: enable 32-bit VDSO
4025 vdso32=0 or vdso32=2: disable 32-bit VDSO
4026
4027 See the help text for CONFIG_COMPAT_VDSO for more
4028 details. If CONFIG_COMPAT_VDSO is set, the default is
4029 vdso32=0; otherwise, the default is vdso32=1.
4030
4031 For compatibility with older kernels, vdso32=2 is an
4032 alias for vdso32=0.
4033
4034 Try vdso32=0 if you encounter an error that says:
4035 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004036
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004037 vector= [IA-64,SMP]
4038 vector=percpu: enable percpu vector domain
4039
Linus Torvalds1da177e2005-04-16 15:20:36 -07004040 video= [FB] Frame buffer configuration
4041 See Documentation/fb/modedb.txt.
4042
Aaron Lu3afe6da2013-06-20 15:08:55 +08004043 video.brightness_switch_enabled= [0,1]
4044 If set to 1, on receiving an ACPI notify event
4045 generated by hotkey, video driver will adjust brightness
4046 level and then send out the event to user space through
4047 the allocated input device; If set to 0, video driver
4048 will only send out the event without touching backlight
4049 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004050 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004051
Pawel Moll81a054c2012-05-09 18:30:16 +01004052 virtio_mmio.device=
4053 [VMMIO] Memory mapped virtio (platform) device.
4054
4055 <size>@<baseaddr>:<irq>[:<id>]
4056 where:
4057 <size> := size (can use standard suffixes
4058 like K, M and G)
4059 <baseaddr> := physical base address
4060 <irq> := interrupt number (as passed to
4061 request_irq())
4062 <id> := (optional) platform device id
4063 example:
4064 virtio_mmio.device=1K@0x100b0000:48:7
4065
4066 Can be used multiple times for multiple devices.
4067
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004068 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004069 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004070 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004071 Use vga=ask for menu.
4072 This is actually a boot loader parameter; the value is
4073 passed to the kernel using a special protocol.
4074
Randy Dunlapa9913042005-10-23 12:57:11 -07004075 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004076 size of <nn>. This can be used to increase the
4077 minimum size (128MB on x86). It can also be used to
4078 decrease the size and leave more room for directly
4079 mapped kernel RAM.
4080
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004081 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4082 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004083
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004084 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4085 Format: <command>
4086
4087 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4088 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004089
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004090 vsyscall= [X86-64]
4091 Controls the behavior of vsyscalls (i.e. calls to
4092 fixed addresses of 0xffffffffff600x00 from legacy
4093 code). Most statically-linked binaries and older
4094 versions of glibc use these calls. Because these
4095 functions are at fixed addresses, they make nice
4096 targets for exploits that can control RIP.
4097
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004098 emulate [default] Vsyscalls turn into traps and are
4099 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004100
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004101 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004102 This is a little bit faster than trapping
4103 and makes a few dynamic recompilers work
4104 better than they would in emulation mode.
4105 It also makes exploits much easier to write.
4106
4107 none Vsyscalls don't work at all. This makes
4108 them quite hard to use for exploits but
4109 might break your system.
4110
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004111 vt.color= [VT] Default text color.
4112 Format: 0xYX, X = foreground, Y = background.
4113 Default: 0x07 = light gray on black.
4114
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004115 vt.cur_default= [VT] Default cursor shape.
4116 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4117 the parameters of the <Esc>[?A;B;Cc escape sequence;
4118 see VGA-softcursor.txt. Default: 2 = underline.
4119
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004120 vt.default_blu= [VT]
4121 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4122 Change the default blue palette of the console.
4123 This is a 16-member array composed of values
4124 ranging from 0-255.
4125
4126 vt.default_grn= [VT]
4127 Format: <green0>,<green1>,<green2>,...,<green15>
4128 Change the default green palette of the console.
4129 This is a 16-member array composed of values
4130 ranging from 0-255.
4131
4132 vt.default_red= [VT]
4133 Format: <red0>,<red1>,<red2>,...,<red15>
4134 Change the default red palette of the console.
4135 This is a 16-member array composed of values
4136 ranging from 0-255.
4137
4138 vt.default_utf8=
4139 [VT]
4140 Format=<0|1>
4141 Set system-wide default UTF-8 mode for all tty's.
4142 Default is 1, i.e. UTF-8 mode is enabled for all
4143 newly opened terminals.
4144
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004145 vt.global_cursor_default=
4146 [VT]
4147 Format=<-1|0|1>
4148 Set system-wide default for whether a cursor
4149 is shown on new VTs. Default is -1,
4150 i.e. cursors will be created by default unless
4151 overridden by individual drivers. 0 will hide
4152 cursors, 1 will display them.
4153
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004154 vt.italic= [VT] Default color for italic text; 0-15.
4155 Default: 2 = green.
4156
4157 vt.underline= [VT] Default color for underlined text; 0-15.
4158 Default: 3 = cyan.
4159
Randy Dunlap4724ba572010-05-03 11:42:52 -07004160 watchdog timers [HW,WDT] For information on watchdog timers,
4161 see Documentation/watchdog/watchdog-parameters.txt
4162 or other driver-specific files in the
4163 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004164
Tejun Heo82607adc2015-12-08 11:28:04 -05004165 workqueue.watchdog_thresh=
4166 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4167 warn stall conditions and dump internal state to
4168 help debugging. 0 disables workqueue stall
4169 detection; otherwise, it's the stall threshold
4170 duration in seconds. The default value is 30 and
4171 it can be updated at runtime by writing to the
4172 corresponding sysfs file.
4173
Tejun Heod55262c2013-04-01 11:23:38 -07004174 workqueue.disable_numa
4175 By default, all work items queued to unbound
4176 workqueues are affine to the NUMA nodes they're
4177 issued on, which results in better behavior in
4178 general. If NUMA affinity needs to be disabled for
4179 whatever reason, this option can be used. Note
4180 that this also can be controlled per-workqueue for
4181 workqueues visible under /sys/bus/workqueue/.
4182
Viresh Kumarcee22a12013-04-08 16:45:40 +05304183 workqueue.power_efficient
4184 Per-cpu workqueues are generally preferred because
4185 they show better performance thanks to cache
4186 locality; unfortunately, per-cpu workqueues tend to
4187 be more power hungry than unbound workqueues.
4188
4189 Enabling this makes the per-cpu workqueues which
4190 were observed to contribute significantly to power
4191 consumption unbound, leading to measurably lower
4192 power usage at the cost of small performance
4193 overhead.
4194
4195 The default value of this parameter is determined by
4196 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4197
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004198 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4199 default x2apic cluster mode on platforms
4200 supporting x2apic.
4201
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004202 x86_intel_mid_timer= [X86-32,APBT]
4203 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004204 Two valid options are apbt timer only and lapic timer
4205 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004206 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004207
Juergen Grossc70727a2015-07-17 06:51:36 +02004208 xen_512gb_limit [KNL,X86-64,XEN]
4209 Restricts the kernel running paravirtualized under Xen
4210 to use only up to 512 GB of RAM. The reason to do so is
4211 crash analysis tools and Xen tools for doing domain
4212 save/restore/migration must be enabled to handle larger
4213 domains.
4214
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004215 xen_emul_unplug= [HW,X86,XEN]
4216 Unplug Xen emulated devices
4217 Format: [unplug0,][unplug1]
4218 ide-disks -- unplug primary master IDE devices
4219 aux-ide-disks -- unplug non-primary-master IDE devices
4220 nics -- unplug network devices
4221 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004222 unnecessary -- unplugging emulated devices is
4223 unnecessary even if the host did not respond to
4224 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004225 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004226
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004227 xen_nopvspin [X86,XEN]
4228 Disables the ticketlock slowpath using Xen PV
4229 optimizations.
4230
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004231 xen_nopv [X86]
4232 Disables the PV optimizations forcing the HVM guest to
4233 run as generic HVM guest with no PV drivers.
4234
Linus Torvalds1da177e2005-04-16 15:20:36 -07004235 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004236 Format:
4237 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004238
Randy Dunlapa9913042005-10-23 12:57:11 -07004239______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004240
4241TODO:
4242
Linus Torvalds1da177e2005-04-16 15:20:36 -07004243 Add more DRM drivers.