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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)
Alex Thorlton1c532e02016-03-31 14:18:29 -0500134 X86_UV SGI UV support is enabled.
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100135 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136
137In addition, the following text indicates that the option:
138
139 BUGS= Relates to possible processor bugs on the said processor.
140 KNL Is a kernel start-up parameter.
141 BOOT Is a boot loader parameter.
142
143Parameters denoted with BOOT are actually interpreted by the boot
144loader, and have no meaning to the kernel directly.
145Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500146need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147
Karsten Weiss55588702007-02-13 13:26:21 +0100148There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700149See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100150
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
152a trailing = on the name of any parameter states that that parameter will
153be entered as an environment variable, whereas its absence indicates that
154it will appear as a kernel argument readable via /proc/cmdline by programs
155running once the system is up.
156
jens m. noedler9c4751f2006-09-29 02:00:27 -0700157The number of kernel parameters is not limited, but the length of the
158complete command line (parameters including spaces etc.) is limited to
159a fixed number of characters. This limit depends on the architecture
160and is between 256 and 4096 characters. It is defined in the file
161./include/asm/setup.h as COMMAND_LINE_SIZE.
162
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800163Finally, the [KMG] suffix is commonly described after a number of kernel
164parameter values. These 'K', 'M', and 'G' letters represent the _binary_
165multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
166bytes respectively. Such letter suffixes can also be entirely omitted.
167
jens m. noedler9c4751f2006-09-29 02:00:27 -0700168
Al Stoneb10d79f2015-03-24 14:02:41 +0000169 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800170 Advanced Configuration and Power Interface
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +0200171 Format: { force | on | off | strict | noirq | rsdt |
Rami Rosene58d1542015-09-26 19:27:57 +0300172 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 force -- enable ACPI if default was off
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +0200174 on -- enable ACPI but allow fallback to DT [arm64]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 off -- disable ACPI if default was on
176 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700177 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800179 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800180 copy_dsdt -- copy DSDT to memory
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +0200181 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
182 are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
Paul Bolle395cf962011-08-15 02:02:26 +0200184 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185
Len Browna1fdcc02007-03-11 03:26:14 -0400186 acpi_apic_instance= [ACPI, IOAPIC]
187 Format: <int>
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400190 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400191
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
194 acpi_backlight=video
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
198
Colin Ian Kingb2ca5da2016-01-21 17:05:47 +0000199 acpi_force_32bit_fadt_addr
200 force FADT to use 32 bit addresses rather than the
201 64 bit X_* addresses. Some firmware have broken 64
202 bit addresses for force ACPI ignore these and use
203 the older legacy 32 bit addresses.
204
Dominik Brodowskief694492015-05-14 15:31:28 +0200205 acpica_no_return_repair [HW, ACPI]
206 Disable AML predefined validation mechanism
207 This mechanism can repair the evaluation result to make
208 the return objects more ACPI specification compliant.
209 This option is useful for developers to identify the
210 root cause of an AML interpreter issue when the issue
211 has something to do with the repair mechanism.
212
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700213 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
214 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700216 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
217 debug output. Bits in debug_layer correspond to a
218 _COMPONENT in an ACPI source file, e.g.,
219 #define _COMPONENT ACPI_PCI_COMPONENT
220 Bits in debug_level correspond to a level in
221 ACPI_DEBUG_PRINT statements, e.g.,
222 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600223 The debug_level mask defaults to "info". See
224 Documentation/acpi/debug.txt for more information about
225 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600227 Enable processor driver info messages:
228 acpi.debug_layer=0x20000000
229 Enable PCI/PCI interrupt routing info messages:
230 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700231 Enable AML "Debug" output, i.e., stores to the Debug
232 object while interpreting AML:
233 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700234 Enable all messages related to ACPI hardware:
235 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200236
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700237 Some values produce so much output that the system is
238 unusable. The "log_buf_len" parameter may be useful
239 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800240
Dominik Brodowskief694492015-05-14 15:31:28 +0200241 acpi_enforce_resources= [ACPI]
242 { strict | lax | no }
243 Check for resource conflicts between native drivers
244 and ACPI OperationRegions (SystemIO and SystemMemory
245 only). IO ports and memory declared in ACPI might be
246 used by the ACPI subsystem in arbitrary AML code and
247 can interfere with legacy drivers.
248 strict (default): access to resources claimed by ACPI
249 is denied; legacy drivers trying to access reserved
250 resources will fail to bind to device using them.
251 lax: access to resources claimed by ACPI is allowed;
252 legacy drivers trying to access reserved resources
253 will bind successfully but a warning message is logged.
254 no: ACPI OperationRegions are not marked as reserved,
255 no further checks are performed.
256
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800257 acpi_force_table_verification [HW,ACPI]
258 Enable table checksum verification during early stage.
259 By default, this is disabled due to x86 early mapping
260 size limitation.
261
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700262 acpi_irq_balance [HW,ACPI]
263 ACPI will balance active IRQs
264 default in APIC mode
265
266 acpi_irq_nobalance [HW,ACPI]
267 ACPI will not move active IRQs (default)
268 default in PIC mode
269
270 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
271 Format: <irq>,<irq>...
272
273 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
274 use by PCI
275 Format: <irq>,<irq>...
276
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800277 acpi_no_auto_serialize [HW,ACPI]
278 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800279 AML control methods that contain the opcodes to create
280 named objects will be marked as "Serialized" by the
281 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800282 This feature is enabled by default.
283 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800284
Dominik Brodowskief694492015-05-14 15:31:28 +0200285 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
286 kernels.
287
Lv Zhenga94e88c2014-04-04 12:39:11 +0800288 acpi_no_static_ssdt [HW,ACPI]
289 Disable installation of static SSDTs at early boot time
290 By default, SSDTs contained in the RSDT/XSDT will be
291 installed automatically and they will appear under
292 /sys/firmware/acpi/tables.
293 This option turns off this feature.
294 Note that specifying this option does not affect
295 dynamic table installation which will install SSDT
296 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700297
Dominik Brodowskief694492015-05-14 15:31:28 +0200298 acpi_rsdp= [ACPI,EFI,KEXEC]
299 Pass the RSDP address to the kernel, mostly used
300 on machines running EFI runtime service to boot the
301 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800302
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700303 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
304 Format: To spoof as Windows 98: ="Microsoft Windows"
305
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200306 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
307 of 2 which is mandated by ACPI 6) as the supported ACPI
308 specification revision (when using this switch, it may
309 be necessary to carry out a cold reboot _twice_ in a
310 row to make it take effect on the platform firmware).
311
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700312 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800313 acpi_osi="string1" # add string1
314 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800315 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800316 acpi_osi=! # disable all built-in OS vendor
317 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800318 acpi_osi=!! # enable all built-in OS vendor
319 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700320 acpi_osi= # disable all strings
321
Lv Zheng5dc17982013-07-22 16:08:25 +0800322 'acpi_osi=!' can be used in combination with single or
323 multiple 'acpi_osi="string1"' to support specific OS
324 vendor string(s). Note that such command can only
325 affect the default state of the OS vendor strings, thus
326 it cannot affect the default state of the feature group
327 strings and the current state of the OS vendor strings,
328 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800329 is meaningless. This command is useful when one do not
330 care about the state of the feature group strings which
331 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800332 Examples:
333 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
334 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
335 can make '_OSI("Windows 2000")' TRUE.
336
337 'acpi_osi=' cannot be used in combination with other
338 'acpi_osi=' command lines, the _OSI method will not
339 exist in the ACPI namespace. NOTE that such command can
340 only affect the _OSI support state, thus specifying it
341 multiple times through kernel command line is also
342 meaningless.
343 Examples:
344 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
345 FALSE.
346
Lv Zheng741d8122013-07-22 16:08:36 +0800347 'acpi_osi=!*' can be used in combination with single or
348 multiple 'acpi_osi="string1"' to support specific
349 string(s). Note that such command can affect the
350 current state of both the OS vendor strings and the
351 feature group strings, thus specifying it multiple times
352 through kernel command line is meaningful. But it may
353 still not able to affect the final state of a string if
354 there are quirks related to this string. This command
355 is useful when one want to control the state of the
356 feature group strings to debug BIOS issues related to
357 the OSPM features.
358 Examples:
359 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
360 '_OSI("Module Device")' FALSE.
361 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
362 '_OSI("Module Device")' TRUE.
363 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
364 equivalent to
365 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
366 and
367 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
368 they all will make '_OSI("Windows 2000")' TRUE.
369
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530370 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700371 Override the pmtimer bug detection: force the kernel
372 to assume that this machine's pmtimer latches its value
373 and always returns good values.
374
Randy Dunlap4af94f32009-04-17 18:30:28 -0700375 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
376 Format: { level | edge | high | low }
377
Randy Dunlap4af94f32009-04-17 18:30:28 -0700378 acpi_skip_timer_override [HW,ACPI]
379 Recognize and ignore IRQ0/pin2 Interrupt Override.
380 For broken nForce2 BIOS resulting in XT-PIC timer.
381
382 acpi_sleep= [HW,ACPI] Sleep options
383 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200384 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700385 See Documentation/power/video.txt for information on
386 s3_bios and s3_mode.
387 s3_beep is for debugging; it makes the PC's speaker beep
388 as soon as the kernel's real-mode entry point is called.
389 s4_nohwsig prevents ACPI hardware signature from being
390 used during resume from hibernation.
391 old_ordering causes the ACPI 1.0 ordering of the _PTS
392 control method, with respect to putting devices into
393 low power states, to be enforced (the ACPI 2.0 ordering
394 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200395 nonvs prevents the kernel from saving/restoring the
396 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800397 sci_force_enable causes the kernel to set SCI_EN directly
398 on resume from S1/S3 (which is against the ACPI spec,
399 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700400
401 acpi_use_timer_override [HW,ACPI]
402 Use timer override. For some broken Nvidia NF5 boards
403 that require a timer override, but don't have HPET
404
Randy Dunlap4af94f32009-04-17 18:30:28 -0700405 add_efi_memmap [EFI; X86] Include EFI memory map in
406 kernel's map of available physical RAM.
407
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700408 agp= [AGP]
409 { off | try_unsupported }
410 off: disable AGP support
411 try_unsupported: try to drive unsupported chipsets
412 (may crash computer or cause data corruption)
413
Randy Dunlapbcfde332010-06-07 17:10:38 -0700414 ALSA [HW,ALSA]
415 See Documentation/sound/alsa/alsa-parameters.txt
416
Russell Kingd944d542010-02-20 16:13:29 +0000417 alignment= [KNL,ARM]
418 Allow the default userspace alignment fault handler
419 behaviour to be specified. Bit 0 enables warnings,
420 bit 1 enables fixups, and bit 2 sends a segfault.
421
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200422 align_va_addr= [X86-64]
423 Align virtual addresses by clearing slice [14:12] when
424 allocating a VMA at process creation time. This option
425 gives you up to 3% performance improvement on AMD F15h
426 machines (where it is enabled by default) for a
427 CPU-intensive style benchmark, and it can vary highly in
428 a microbenchmark depending on workload and compiler.
429
Borislav Petkov8360ee22011-11-21 12:10:19 +0100430 32: only for 32-bit processes
431 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200432 on: enable for both 32- and 64-bit processes
433 off: disable for both 32- and 64-bit processes
434
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500435 alloc_snapshot [FTRACE]
436 Allocate the ftrace snapshot buffer on boot up when the
437 main buffer is allocated. This is handy if debugging
438 and you need to use tracing_snapshot() on boot up, and
439 do not want to use tracing_snapshot_alloc() as it needs
440 to be done where GFP_KERNEL allocations are allowed.
441
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100442 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200443 Pass parameters to the AMD IOMMU driver in the system.
444 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900445 fullflush - enable flushing of IO/TLB entries when
446 they are unmapped. Otherwise they are
447 flushed before they will be reused, which
448 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200449 off - do not initialize any AMD IOMMU found in
450 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100451 force_isolation - Force device isolation for all
452 devices. The IOMMU driver is not
453 allowed anymore to lift isolation
454 requirements as needed. This option
455 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900456
Shuah Khanc099cf12012-05-24 15:58:25 -0600457 amd_iommu_dump= [HW,X86-64]
458 Enable AMD IOMMU driver option to dump the ACPI table
459 for AMD IOMMU. With this option enabled, AMD IOMMU
460 driver will print ACPI tables for AMD IOMMU during
461 IOMMU initialization.
462
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 amijoy.map= [HW,JOY] Amiga joystick support
464 Map of devices attached to JOY0DAT and JOY1DAT
465 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200466 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467
468 analog.map= [HW,JOY] Analog joystick and gamepad support
469 Specifies type or capabilities of an analog joystick
470 connected to one of 16 gameports
471 Format: <type1>,<type2>,..<type16>
472
Randy Dunlapa9913042005-10-23 12:57:11 -0700473 apc= [HW,SPARC]
474 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 Format: noidle
476 Disable APC CPU standby support. SPARCstation-Fox does
477 not play well with APC CPU idle - disable it if you have
478 APC and your system crashes randomly.
479
Randy Dunlapca1eda22009-05-06 16:02:58 -0700480 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700481 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482 Format: { quiet (default) | verbose | debug }
483 Change the amount of debugging information output
484 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700485
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100486 apic_extnmi= [APIC,X86] External NMI delivery setting
487 Format: { bsp (default) | all | none }
488 bsp: External NMI is delivered only to CPU 0
489 all: External NMIs are broadcast to all CPUs as a
490 backup of CPU 0
491 none: External NMI is masked for all CPUs. This is
492 useful so that a dump capture kernel won't be
493 shot down by NMI
494
Brian Haleyb0f83b22010-02-04 13:36:50 -0800495 autoconf= [IPV6]
496 See Documentation/networking/ipv6.txt.
497
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400498 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
499 Limit apic dumping. The parameter defines the maximal
500 number of local apics being dumped. Also it is possible
501 to set it to "all" by meaning -- no limit here.
502 Format: { 1 (default) | 2 | ... | all }.
503 The parameter valid if only apic=debug or
504 apic=verbose is specified.
505 Example: apic=debug show_lapic=all
506
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700508 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
511 Format: <io>,<irq>,<nodeID>
512
513 ataflop= [HW,M68k]
514
515 atarimouse= [HW,MOUSE] Atari Mouse
516
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
518 EzKey and similar keyboards
519
520 atkbd.reset= [HW] Reset keyboard during initialization
521
Randy Dunlapa9913042005-10-23 12:57:11 -0700522 atkbd.set= [HW] Select keyboard code set
523 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524
525 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
526 keyboards
527
528 atkbd.softraw= [HW] Choose between synthetic and real raw mode
529 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700530
531 atkbd.softrepeat= [HW]
532 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400534 audit= [KNL] Enable the audit sub-system
535 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500536 0 - kernel audit is disabled and can not be enabled
537 until the next reboot
538 unset - kernel audit is initialized but disabled and
539 will be fully enabled by the userspace auditd.
540 1 - kernel audit is initialized and partially enabled,
541 storing at most audit_backlog_limit messages in
542 RAM until it is fully enabled by the userspace
543 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400544 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400545
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400546 audit_backlog_limit= [KNL] Set the audit queue size limit.
547 Format: <int> (must be >=0)
548 Default: 64
549
Alex Thorlton1c532e02016-03-31 14:18:29 -0500550 bau= [X86_UV] Enable the BAU on SGI UV. The default
551 behavior is to disable the BAU (i.e. bau=0).
552 Format: { "0" | "1" }
553 0 - Disable the BAU.
554 1 - Enable the BAU.
555 unset - Disable the BAU.
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 baycom_epp= [HW,AX25]
558 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700559
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
561 Format: <io>,<mode>
562 See header of drivers/net/hamradio/baycom_par.c.
563
Randy Dunlapa9913042005-10-23 12:57:11 -0700564 baycom_ser_fdx= [HW,AX25]
565 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566 Format: <io>,<irq>,<mode>[,<baud>]
567 See header of drivers/net/hamradio/baycom_ser_fdx.c.
568
Randy Dunlapa9913042005-10-23 12:57:11 -0700569 baycom_ser_hdx= [HW,AX25]
570 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 Format: <io>,<irq>,<mode>
572 See header of drivers/net/hamradio/baycom_ser_hdx.c.
573
Paul Gortmaker080506a2013-09-30 13:45:19 -0700574 blkdevparts= Manual partition parsing of block device(s) for
575 embedded devices based on command line input.
576 See Documentation/block/cmdline-partition.txt
577
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700578 boot_delay= Milliseconds to delay each printk during boot.
579 Values larger than 10 seconds (10000) are changed to
580 no delay (0).
581 Format: integer
582
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700583 bootmem_debug [KNL] Enable bootmem allocator debug messages.
584
Huang Yinga3e2acc2016-06-29 13:04:29 -0700585 bert_disable [ACPI]
586 Disable BERT OS support on buggy BIOSes.
587
Linus Torvalds1da177e2005-04-16 15:20:36 -0700588 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700589 bttv.radio= Most important insmod options are available as
590 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200592 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000594 bulk_remove=off [PPC] This parameter disables the use of the pSeries
595 firmware feature for flushing multiple hpte entries
596 at a time.
597
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598 c101= [NET] Moxa C101 synchronous serial card
599
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700600 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 Sometimes CPU hardware bugs make them report the cache
602 size incorrectly. The kernel will attempt work arounds
603 to fix known problems, but for some CPUs it is not
604 possible to determine what the correct size should be.
605 This option provides an override for these situations.
606
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300607 ca_keys= [KEYS] This parameter identifies a specific key(s) on
608 the system trusted keyring to be used for certificate
609 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300610 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300611
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700612 cca= [MIPS] Override the kernel pages' cache coherency
613 algorithm. Accepted values range from 0 to 7
614 inclusive. See arch/mips/include/asm/pgtable-bits.h
615 for platform specific values (SB1, Loongson3 and
616 others).
617
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100618 ccw_timeout_log [S390]
619 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620
Paul Menage8bab8dd2008-04-04 14:29:57 -0700621 cgroup_disable= [KNL] Disable a particular controller
622 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800623 The effects of cgroup_disable=foo are:
624 - foo isn't auto-mounted if you mount all cgroups in
625 a single hierarchy
626 - foo isn't visible as an individually mountable
627 subsystem
628 {Currently only "memory" controller deal with this and
629 cut the overhead, others just disable the usage. So
630 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700631
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500632 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
633 Format: { controller[,controller...] | "all" }
634 Like cgroup_disable, but only applies to cgroup v1;
635 the blacklisted controllers remain available in cgroup2.
636
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800637 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
638 Format: <string>
639 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800640 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800641
Linus Torvalds1da177e2005-04-16 15:20:36 -0700642 checkreqprot [SELINUX] Set initial checkreqprot flag value.
643 Format: { "0" | "1" }
644 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700645 0 -- check protection applied by kernel (includes
646 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647 1 -- check protection requested by application.
648 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700649 Value can be changed at runtime via
650 /selinux/checkreqprot.
651
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100652 cio_ignore= [S390]
653 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700654 clk_ignore_unused
655 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700656 Prevents the clock framework from automatically gating
657 clocks that have not been explicitly enabled by a Linux
658 device driver but are enabled in hardware at reset or
659 by the bootloader/firmware. Note that this does not
660 force such clocks to be always-on nor does it reserve
661 those clocks in any way. This parameter is useful for
662 debug and development, but should not be needed on a
663 platform with proper driver support. For more
664 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100665
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700666 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700667 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200668 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700669 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200670 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671 Format: { pit | tsc | cyclone | pmtmr }
672
John Stultz592913e2010-07-13 17:56:20 -0700673 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700674 Format: <string>
675 Override the default clocksource and use the clocksource
676 with the name specified.
677 Some clocksource names to choose from, depending on
678 the platform:
679 [all] jiffies (this is the base, fallback clocksource)
680 [ACPI] acpi_pm
681 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
682 pxa_timer,timer3,32k_counter,timer0_1
683 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700684 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700685 scx200_hrt on Geode; cyclone on IBM x440
686 [MIPS] MIPS
687 [PARISC] cr16
688 [S390] tod
689 [SH] SuperH
690 [SPARC64] tick
691 [X86-64] hpet,tsc
692
Will Deacon46fd5c62016-06-27 17:30:13 +0100693 clocksource.arm_arch_timer.evtstrm=
694 [ARM,ARM64]
695 Format: <bool>
696 Enable/disable the eventstream feature of the ARM
697 architected timer so that code using WFE-based polling
698 loops can be debugged more effectively on production
699 systems.
700
Scott Woodf6dc1572016-09-22 03:35:17 -0500701 clocksource.arm_arch_timer.fsl-a008585=
702 [ARM64]
703 Format: <bool>
704 Enable/disable the workaround of Freescale/NXP
705 erratum A-008585. This can be useful for KVM
706 guests, if the guest device tree doesn't show the
707 erratum. If unspecified, the workaround is
708 enabled based on the device tree.
709
Andi Kleenac72e782008-01-30 13:33:21 +0100710 clearcpuid=BITNUM [X86]
711 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100712 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800713 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100714 stable over kernel options, but the vendor specific
715 ones should be.
716 Also note that user programs calling CPUID directly
717 or using the feature without checking anything
718 will still see it. This just prevents it from
719 being used by the kernel or shown in /proc/cpuinfo.
720 Also note the kernel might malfunction if you disable
721 some critical bits.
722
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700723 cma=nn[MG]@[start[MG][-end[MG]]]
724 [ARM,X86,KNL]
725 Sets the size of kernel global memory area for
726 contiguous memory allocations and optionally the
727 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700728 memory allocations. A value of 0 disables CMA
729 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100730 include/linux/dma-contiguous.h
731
Robert Jennings14f966e2009-04-15 05:55:32 +0000732 cmo_free_hint= [PPC] Format: { yes | no }
733 Specify whether pages are marked as being inactive
734 when they are freed. This is used in CMO environments
735 to determine OS memory pressure for page stealing by
736 a hypervisor.
737 Default: yes
738
Marek Szyprowskic7909502011-12-29 13:09:51 +0100739 coherent_pool=nn[KMG] [ARM,KNL]
740 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200741 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100742
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530743 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100744 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100745 Range: 0 - 8192
746 Default: 64
747
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700749 Format:
750 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700751
752 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
753 Format: <io>[,<irq>]
754
Randy Dunlapa9913042005-10-23 12:57:11 -0700755 com90xx= [HW,NET]
756 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 Format: <io>[,<irq>[,<memstart>]]
758
759 condev= [HW,S390] console device
760 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700761
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762 console= [KNL] Output console device and options.
763
764 tty<n> Use the virtual console device <n>.
765
766 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800767 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800769 the form "bbbbpnf", where "bbbb" is the baud rate,
770 "p" is parity ("n", "o", or "e"), "n" is number of
771 bits, and "f" is flow control ("r" for RTS or
772 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800774 See Documentation/serial-console.txt for more
775 information. See
776 Documentation/networking/netconsole.txt for an
777 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700778
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700779 uart[8250],io,<addr>[,options]
780 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900781 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400782 uart[8250],mmio32,<addr>[,options]
783 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700784 Start an early, polled-mode console on the 8250/16550
785 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400786 switching to the matching ttyS device later.
787 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900788 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
789 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
790 to be equivalent to 'mmio'. 'options' are specified in
791 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400792 the h/w is not re-initialized.
793
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500794 hvc<n> Use the hypervisor console device <n>. This is for
795 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700796
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700797 If the device connected to the port is not a TTY but a braille
798 device, prepend "brl," before the device type, for instance
799 console=brl,ttyS0
800 For now, only VisioBraille is supported.
801
Daniel Mackf324edc2009-06-16 15:33:52 -0700802 consoleblank= [KNL] The console blank (screen saver) timeout in
803 seconds. Defaults to 10*60 = 10mins. A value of 0
804 disables the blank timer.
805
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800806 coredump_filter=
807 [KNL] Change the default value for
808 /proc/<pid>/coredump_filter.
809 See also Documentation/filesystems/proc.txt.
810
Len Brown62027ae2011-04-01 18:13:10 -0400811 cpuidle.off=1 [CPU_IDLE]
812 disable the cpuidle sub-system
813
Len Brownd68921f2015-05-11 17:27:09 -0400814 cpu_init_udelay=N
815 [X86] Delay for N microsec between assert and de-assert
816 of APIC INIT to start processors. This delay occurs
817 on every CPU online, such as boot, and resume from suspend.
818 Default: 10000
819
Linus Torvalds1da177e2005-04-16 15:20:36 -0700820 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700821 Format:
822 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800824 crashkernel=size[KMG][@offset[KMG]]
825 [KNL] Using kexec, Linux can switch to a 'crash kernel'
826 upon panic. This parameter reserves the physical
827 memory region [offset, offset + size] for that kernel
828 image. If '@offset' is omitted, then a suitable offset
829 is selected automatically. Check
830 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700831
Bernhard Wallefb391592007-10-18 23:41:02 -0700832 crashkernel=range1:size1[,range2:size2,...][@offset]
833 [KNL] Same as above, but depends on the memory
834 in the running system. The syntax of range is
835 start-[end] where start and end are both
836 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800837 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700838
Yinghai Luadbc7422013-04-15 22:23:48 -0700839 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700840 [KNL, x86_64] range could be above 4G. Allow kernel
841 to allocate physical memory region from top, so could
842 be above 4G if system have more than 4G ram installed.
843 Otherwise memory region will be allocated below 4G, if
844 available.
845 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700846 crashkernel=size[KMG],low
847 [KNL, x86_64] range under 4G. When crashkernel=X,high
848 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700849 above 4G, that cause second kernel crash on system
850 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800851 requires at least 64M+32K low memory, also enough extra
852 low memory is needed to make sure DMA buffers for 32-bit
853 devices won't run out. Kernel would try to allocate at
854 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700855 This one let user to specify own low range under 4G
856 for second kernel instead.
857 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700858 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700859 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700860
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100861 cryptomgr.notests
862 [KNL] Disable crypto self-tests
863
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 cs89x0_dma= [HW,NET]
865 Format: <dma>
866
867 cs89x0_media= [HW,NET]
868 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700869
Randy Dunlapa9913042005-10-23 12:57:11 -0700870 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 See header of drivers/s390/block/dasd_devmap.c.
872
873 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
874 (one device per port)
875 Format: <port#>,<type>
876 See also Documentation/input/joystick-parport.txt
877
Thomas Renningera648ec02010-08-06 16:11:02 +0200878 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
879 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600880 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200881
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 debug [KNL] Enable kernel debugging (events log level).
883
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700884 debug_locks_verbose=
885 [KNL] verbose self-tests
886 Format=<0|1>
887 Print debugging info while doing the locking API
888 self-tests.
889 We default to 0 (no extra messages), setting it to
890 1 will print _a lot_ more information - normally
891 only useful to kernel developers.
892
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700893 debug_objects [KNL] Enable object debugging
894
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500895 no_debug_objects
896 [KNL] Disable object debugging
897
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800898 debug_guardpage_minorder=
899 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
900 parameter allows control of the order of pages that will
901 be intentionally kept free (and hence protected) by the
902 buddy allocator. Bigger value increase the probability
903 of catching random memory corruption, but reduce the
904 amount of memory for normal system use. The maximum
905 possible value is MAX_ORDER/2. Setting this parameter
906 to 1 or 2 should be enough to identify most random
907 memory corruption problems caused by bugs in kernel or
908 driver code when a CPU writes to (or reads from) a
909 random memory location. Note that there exists a class
910 of memory corruptions problems caused by buggy H/W or
911 F/W or by drivers badly programing DMA (basically when
912 memory is written at bus level and the CPU MMU is
913 bypassed) which are not detectable by
914 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
915 tracking down these problems.
916
Joonsoo Kim031bc572014-12-12 16:55:52 -0800917 debug_pagealloc=
918 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
919 parameter enables the feature at boot time. In
920 default, it is disabled. We can avoid allocating huge
921 chunk of memory for debug pagealloc if we don't enable
922 it at boot time and the system will work mostly same
923 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
924 on: enable the feature
925
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200926 debugpat [X86] Enable PAT debugging
927
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200928 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929 Format: <area>[,<node>]
930 See also Documentation/networking/decnet.txt.
931
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700932 default_hugepagesz=
933 [same as hugepagesz=] The size of the default
934 HugeTLB page size. This is the size represented by
935 the legacy /proc/ hugepages APIs, used for SHM, and
936 default size when mounting hugetlbfs filesystems.
937 Defaults to the default architecture's huge page size
938 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700939
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940 dhash_entries= [KNL]
941 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700942
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000943 disable_1tb_segments [PPC]
944 Disables the use of 1TB hash page table segments. This
945 causes the kernel to fall back to 256MB segments which
946 can be useful when debugging issues that require an SLB
947 miss to occur.
948
Brian Haleyb0f83b22010-02-04 13:36:50 -0800949 disable= [IPV6]
950 See Documentation/networking/ipv6.txt.
951
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530952 disable_radix [PPC]
953 Disable RADIX MMU mode on POWER9
954
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900955 disable_cpu_apicid= [X86,APIC,SMP]
956 Format: <int>
957 The number of initial APIC ID for the
958 corresponding CPU to be disabled at boot,
959 mostly used for the kdump 2nd kernel to
960 disable BSP to wake up multiple CPUs without
961 causing system reset or hang due to sending
962 INIT from AP to BSP.
963
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000964 disable_ddw [PPC/PSERIES]
965 Disable Dynamic DMA Window support. Use this if
966 to workaround buggy firmware.
967
Brian Haleyb0f83b22010-02-04 13:36:50 -0800968 disable_ipv6= [IPV6]
969 See Documentation/networking/ipv6.txt.
970
Yinghai Lu95ffa242008-04-29 03:52:33 -0700971 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700972 The kernel tries to adjust MTRR layout from continuous
973 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700974 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700975
Yinghai Lu093af8d2008-01-30 13:33:32 +0100976 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100977 By default the kernel will trim any uncacheable
978 memory out of your available memory pool based on
979 MTRR settings. This parameter disables that behavior,
980 possibly causing your machine to run very slowly.
981
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530982 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700983 Disable PIN 1 of APIC timer
984 Can be useful to work around chipset bugs.
985
Prarit Bhargavace14c582015-08-25 13:34:53 -0400986 dis_ucode_ldr [X86] Disable the microcode loader.
987
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700988 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
989 this option disables the debugging code at boot.
990
991 dma_debug_entries=<number>
992 This option allows to tune the number of preallocated
993 entries for DMA-API debugging code. One entry is
994 required per DMA-API allocation. Use this if the
995 DMA-API debugging code disables itself because the
996 architectural default is too low.
997
Joerg Roedel1745de52009-05-22 21:49:51 +0200998 dma_debug_driver=<driver_name>
999 With this option the DMA-API debugging driver
1000 filter feature can be enabled at boot time. Just
1001 pass the driver to filter for as the parameter.
1002 The filter can be disabled or changed to another
1003 driver later using sysfs.
1004
Bob Paauwe96206e22015-08-27 10:04:13 -07001005 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1006 Broken monitors, graphic adapters, KVMs and EDIDless
1007 panels may send no or incorrect EDID data sets.
1008 This parameter allows to specify an EDID data sets
1009 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +01001010 Generic built-in EDID data sets are used, if one of
1011 edid/1024x768.bin, edid/1280x1024.bin,
1012 edid/1680x1050.bin, or edid/1920x1080.bin is given
1013 and no file with the same name exists. Details and
1014 instructions how to build your own EDID data are
1015 available in Documentation/EDID/HOWTO.txt. An EDID
1016 data set will only be used for a particular connector,
1017 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -07001018 name. Each connector may use a unique EDID data
1019 set by separating the files with a comma. An EDID
1020 data set with no connector name will be used for
1021 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +01001022
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023 dscc4.setup= [NET]
1024
Jim Cromie29e36c92012-04-27 14:30:41 -06001025 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1026 module.dyndbg[="val"]
1027 Enable debug messages at boot time. See
1028 Documentation/dynamic-debug-howto.txt for details.
1029
Dave Hansen8c3641e2015-06-07 11:37:02 -07001030 nompx [X86] Disables Intel Memory Protection Extensions.
1031 See Documentation/x86/intel_mpx.txt for more
1032 information about the feature.
1033
Dave Hansen06976942016-02-12 13:02:29 -08001034 nopku [X86] Disable Memory Protection Keys CPU feature found
1035 in some Intel CPUs.
1036
Borislav Petkovf29ba612015-03-27 16:15:18 +01001037 eagerfpu= [X86]
1038 on enable eager fpu restore
1039 off disable eager fpu restore
1040 auto selects the default scheme, which automatically
1041 enables eagerfpu restore for xsaveopt.
1042
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -07001043 module.async_probe [KNL]
1044 Enable asynchronous probe on this module.
1045
Mark Salter56aeeba2014-04-07 15:39:53 -07001046 early_ioremap_debug [KNL]
1047 Enable debug messages in early_ioremap support. This
1048 is useful for tracking down temporary early mappings
1049 which are not unmapped.
1050
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001051 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -05001052
Scott Wood5664f762015-09-14 19:54:07 -05001053 When used with no options, the early console is
1054 determined by the stdout-path property in device
1055 tree's chosen node.
1056
Michal Simek6fa62fc2014-09-10 12:43:02 +02001057 cdns,<addr>
1058 Start an early, polled-mode console on a cadence serial
1059 port at the specified address. The cadence serial port
1060 must already be setup and configured. Options are not
1061 yet supported.
1062
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001063 uart[8250],io,<addr>[,options]
1064 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -07001065 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +03001066 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -04001067 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001068 Start an early, polled-mode console on the 8250/16550
1069 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -07001070 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +03001071 (mmio) or 32-bit (mmio32 or mmio32be).
1072 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1073 to be equivalent to 'mmio'. 'options' are specified
1074 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001075 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001076
Rob Herring0d3c6732014-04-18 17:19:57 -05001077 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -06001078 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -05001079 Start an early, polled-mode console on a pl011 serial
1080 port at the specified address. The pl011 serial port
1081 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -06001082 yet supported. If 'mmio32' is specified, then only
1083 the driver will use only 32-bit accessors to read/write
1084 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -05001085
Andreas Färber736d5532016-03-06 12:21:24 +01001086 meson,<addr>
1087 Start an early, polled-mode console on a meson serial
1088 port at the specified address. The serial port must
1089 already be setup and configured. Options are not yet
1090 supported.
1091
Stephen Boyd0efe7292014-09-15 17:22:51 -07001092 msm_serial,<addr>
1093 Start an early, polled-mode console on an msm serial
1094 port at the specified address. The serial port
1095 must already be setup and configured. Options are not
1096 yet supported.
1097
1098 msm_serial_dm,<addr>
1099 Start an early, polled-mode console on an msm serial
1100 dm port at the specified address. The serial port
1101 must already be setup and configured. Options are not
1102 yet supported.
1103
Rob Herringd50d7262014-04-18 17:19:58 -05001104 smh Use ARM semihosting calls for early console.
1105
Tomasz Figab94ba032015-01-23 14:47:41 +01001106 s3c2410,<addr>
1107 s3c2412,<addr>
1108 s3c2440,<addr>
1109 s3c6400,<addr>
1110 s5pv210,<addr>
1111 exynos4210,<addr>
1112 Use early console provided by serial driver available
1113 on Samsung SoCs, requires selecting proper type and
1114 a correct base address of the selected UART port. The
1115 serial port must already be setup and configured.
1116 Options are not yet supported.
1117
Stefan Agner1d59b382015-10-17 00:45:55 -07001118 lpuart,<addr>
1119 lpuart32,<addr>
1120 Use early console provided by Freescale LP UART driver
1121 found on Freescale Vybrid and QorIQ LS1021A processors.
1122 A valid base address must be provided, and the serial
1123 port must already be setup and configured.
1124
Wilson Ding30530792016-02-16 19:14:53 +01001125 armada3700_uart,<addr>
1126 Start an early, polled-mode console on the
1127 Armada 3700 serial port at the specified
1128 address. The serial port must already be setup
1129 and configured. Options are not yet supported.
1130
Finn Thain7913ad12014-04-12 23:48:56 +10001131 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001133 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001134 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001136 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001137 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001138 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001139 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140
Dave Hansen147ea092013-04-10 14:03:38 -07001141 earlyprintk is useful when the kernel crashes before
1142 the normal console is initialized. It is not enabled by
1143 default because it has some cosmetic problems.
1144
Randy Dunlapa9913042005-10-23 12:57:11 -07001145 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146 takes over.
1147
Matt Fleming72548e82013-10-04 09:36:56 +01001148 Only one of vga, efi, serial, or usb debug port can
1149 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001150
Dave Hansen147ea092013-04-10 14:03:38 -07001151 Currently only ttyS0 and ttyS1 may be specified by
1152 name. Other I/O ports may be explicitly specified
1153 on some architectures (x86 and arm at least) by
1154 replacing ttySn with an I/O port address, like this:
1155 earlyprintk=serial,0x1008,115200
1156 You can find the port for a given device in
1157 /proc/tty/driver/serial:
1158 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159
1160 Interaction with the standard serial driver is not
1161 very good.
1162
Matt Fleming72548e82013-10-04 09:36:56 +01001163 The VGA and EFI output is eventually overwritten by
1164 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001166 The xen output can only be used by Xen PV guests.
1167
Chen, Gongc700f012013-12-06 01:17:08 -05001168 edac_report= [HW,EDAC] Control how to report EDAC event
1169 Format: {"on" | "off" | "force"}
1170 on: enable EDAC to report H/W event. May be overridden
1171 by other higher priority error reporting module.
1172 off: disable H/W event reporting through EDAC.
1173 force: enforce the use of EDAC to report H/W event.
1174 default: on.
1175
Jason Wessel97311912010-05-20 21:04:30 -05001176 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1177 ekgdboc=kbd
1178
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001179 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001180 the boot argument: earlyprintk=vga
1181
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001183 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001185 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001186 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001187 old_map [X86-64]: switch to the old ioremap-based EFI
1188 runtime services mapping. 32-bit still uses this one by
1189 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001190 nochunk: disable reading files in "chunks" in the EFI
1191 boot stub, as chunking can cause problems with some
1192 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001193 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001194 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001195
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001196 efi_no_storage_paranoia [EFI; X86]
1197 Using this parameter you can use more than 50% of
1198 your efi variable storage. Use this parameter only if
1199 you are really sure that your UEFI does sane gc and
1200 fulfills the spec otherwise your board may brick.
1201
Taku Izumi0f96a992015-09-30 23:01:56 +09001202 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1203 Add arbitrary attribute to specific memory range by
1204 updating original EFI memory map.
1205 Region of memory which aa attribute is added to is
1206 from ss to ss+nn.
1207 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1208 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1209 attribute is added to range 0x100000000-0x180000000 and
1210 0x10a0000000-0x1120000000.
1211
1212 Using this parameter you can do debugging of EFI memmap
1213 related feature. For example, you can do debugging of
1214 Address Range Mirroring feature even if your box
1215 doesn't support it.
1216
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001217 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1218 that is to be dynamically loaded by Linux. If there are
1219 multiple variables with the same name but with different
1220 vendor GUIDs, all of them will be loaded. See
1221 Documentation/acpi/ssdt-overlays.txt for details.
1222
1223
Linus Torvalds1da177e2005-04-16 15:20:36 -07001224 eisa_irq_edge= [PARISC,HW]
1225 See header of drivers/parisc/eisa.c.
1226
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001227 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001228 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001229 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230
1231 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001232 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001233 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001234 Documentation/block/deadline-iosched.txt for details.
1235
Michael Holzheud3bf37952011-10-30 15:16:37 +01001236 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001237 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001238 image elf header and optionally the size. Generally
1239 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001240 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001242 enable_mtrr_cleanup [X86]
1243 The kernel tries to adjust MTRR layout from continuous
1244 to discrete, to make X server driver able to add WB
1245 entry later. This parameter enables that.
1246
Randy Dunlapca1eda22009-05-06 16:02:58 -07001247 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001248 Enable PIN 1 of APIC timer
1249 Can be useful to work around chipset bugs
1250 (in particular on some ATI chipsets).
1251 The kernel tries to set a reasonable default.
1252
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253 enforcing [SELINUX] Set initial enforcing status.
1254 Format: {"0" | "1"}
1255 See security/selinux/Kconfig help text.
1256 0 -- permissive (log only, no denials).
1257 1 -- enforcing (deny and log).
1258 Default value is 0.
1259 Value can be changed at runtime via /selinux/enforce.
1260
Huang Yinga08f82d2010-05-18 14:35:21 +08001261 erst_disable [ACPI]
1262 Disable Error Record Serialization Table (ERST)
1263 support.
1264
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265 ether= [HW,NET] Ethernet cards parameters
1266 This option is obsoleted by the "netdev=" option, which
1267 has equivalent usage. See its documentation for details.
1268
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001269 evm= [EVM]
1270 Format: { "fix" }
1271 Permit 'security.evm' to be updated regardless of
1272 current integrity status.
1273
Akinobu Mitade1ba092006-12-08 02:39:42 -08001274 failslab=
1275 fail_page_alloc=
1276 fail_make_request=[KNL]
1277 General fault injection mechanism.
1278 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001279 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001280
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001282 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001283
Alex Chiangf13ae302008-05-08 14:03:23 -06001284 force_pal_cache_flush
1285 [IA-64] Avoid check_sal_cache_flush which may hang on
1286 buggy SAL_CACHE_FLUSH implementations. Using this
1287 parameter will force ia64_sal_cache_flush to call
1288 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1289
Chris Bainbridge69f23662014-03-07 18:40:42 +07001290 forcepae [X86-32]
1291 Forcefully enable Physical Address Extension (PAE).
1292 Many Pentium M systems disable PAE but may have a
1293 functionally usable PAE implementation.
1294 Warning: use of this parameter will taint the kernel
1295 and may cause unknown problems.
1296
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001297 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001298 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001299 as early as possible in order to facilitate early
1300 boot debugging.
1301
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001302 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001303 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001304 If no parameter is passed, ftrace will dump
1305 buffers of all CPUs, but if you pass orig_cpu, it will
1306 dump only the buffer of the CPU that triggered the
1307 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001308
1309 ftrace_filter=[function-list]
1310 [FTRACE] Limit the functions traced by the function
1311 tracer at boot up. function-list is a comma separated
1312 list of functions. This list can be changed at run
1313 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001314 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001315
1316 ftrace_notrace=[function-list]
1317 [FTRACE] Do not trace the functions specified in
1318 function-list. This list can be changed at run time
1319 by the set_ftrace_notrace file in the debugfs
1320 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001321
Stefan Assmann369bc182009-10-12 22:17:21 +02001322 ftrace_graph_filter=[function-list]
1323 [FTRACE] Limit the top level callers functions traced
1324 by the function graph tracer at boot up.
1325 function-list is a comma separated list of functions
1326 that can be changed at run time by the
1327 set_graph_function file in the debugfs tracing directory.
1328
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001329 ftrace_graph_notrace=[function-list]
1330 [FTRACE] Do not trace from the functions specified in
1331 function-list. This list is a comma separated list of
1332 functions that can be changed at run time by the
1333 set_graph_notrace file in the debugfs tracing directory.
1334
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335 gamecon.map[2|3]=
1336 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1337 support via parallel port (up to 5 devices per port)
1338 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1339 See also Documentation/input/joystick-parport.txt
1340
1341 gamma= [HW,DRM]
1342
Yinghai Luaaf23042008-01-30 13:33:09 +01001343 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1344 Format: off | on
1345 default: on
1346
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001347 gcov_persist= [GCOV] When non-zero (default), profiling data for
1348 kernel modules is saved and remains accessible via
1349 debugfs, even when the module is unloaded/reloaded.
1350 When zero, profiling data is discarded and associated
1351 debugfs files are removed at module unload time.
1352
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001354 invalid Protective MBR to be treated as GPT. If the
1355 primary GPT is corrupted, it enables the backup/alternate
1356 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001358 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1359 the "Enable 0" bit of the configuration register.
1360 Format: 0 | 1
1361 Default: 0
1362 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1363 the "Enable 0" bit of the configuration register.
1364 Format: 0 | 1
1365 Default: 0
1366 grcan.select= [HW] Select which physical interface to use.
1367 Format: 0 | 1
1368 Default: 0
1369 grcan.txsize= [HW] Sets the size of the tx buffer.
1370 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1371 Default: 1024
1372 grcan.rxsize= [HW] Sets the size of the rx buffer.
1373 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1374 Default: 1024
1375
Jiri Kosina55537872015-11-05 18:44:41 -08001376 hardlockup_all_cpu_backtrace=
1377 [KNL] Should the hard-lockup detector generate
1378 backtraces on all cpus.
1379 Format: <integer>
1380
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381 hashdist= [KNL,NUMA] Large hashes allocated during boot
1382 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001383 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001384 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001385
1386 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1387
1388 hd= [EIDE] (E)IDE hard drive subsystem geometry
1389 Format: <cyl>,<head>,<sect>
1390
Huang Yingea8c0712010-05-18 14:35:15 +08001391 hest_disable [ACPI]
1392 Disable Hardware Error Source Table (HEST) support;
1393 corresponding firmware-first mode error processing
1394 logic will be disabled.
1395
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1397 size of <nn>. This works even on boxes that have no
1398 highmem otherwise. This also works to reduce highmem
1399 size on bigger boxes.
1400
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001401 highres= [KNL] Enable/disable high resolution timer mode.
1402 Valid parameters: "on", "off"
1403 Default: "on"
1404
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405 hisax= [HW,ISDN]
1406 See Documentation/isdn/README.HiSax.
1407
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001408 hlt [BUGS=ARM,SH]
1409
1410 hpet= [X86-32,HPET] option to control HPET usage
1411 Format: { enable (default) | disable | force |
1412 verbose }
1413 disable: disable HPET and use PIT instead
1414 force: allow force enabled of undocumented chips (ICH4,
1415 VIA, nVidia)
1416 verbose: show contents of HPET registers during setup
1417
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001418 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1419 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1420
Andi Kleenb4718e62008-07-23 21:27:51 -07001421 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1422 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001423 On x86-64 and powerpc, this option can be specified
1424 multiple times interleaved with hugepages= to reserve
1425 huge pages of different sizes. Valid pages sizes on
1426 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001427 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001428
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001429 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1430 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001431 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1432 If specified, z/VM IUCV HVC accepts connections
1433 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001434
James Hoganfdabf522012-10-09 11:00:27 +01001435 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1436 hardware thread id mappings.
1437 Format: <cpu>:<hwthread>
1438
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001439 keep_bootcon [KNL]
1440 Do not unregister boot console at start. This is only
1441 useful for debugging when something happens in the window
1442 between unregistering the boot console and initializing
1443 the real console.
1444
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001445 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001446 or register an additional I2C bus that is not
1447 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001448 Format:
1449 <bus_id>,<clkrate>
1450
Jiri Kosina36d95732008-10-06 02:51:09 -04001451 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001452 i8042.unmask_kbd_data
1453 [HW] Enable printing of interrupt data from the KBD port
1454 (disabled by default, and as a pre-condition
1455 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001457 i8042.dumbkbd [HW] Pretend that controller can only read data from
1458 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459 (Don't attempt to blink the leds)
1460 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001461 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001462 i8042.noloop [HW] Disable the AUX Loopback command while probing
1463 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001465 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1467 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001468 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001469 i8042.reset [HW] Reset the controller during init and cleanup
1470 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001471 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472
1473 i810= [HW,DRM]
1474
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001475 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1476 indicates that the driver is running on unsupported
1477 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1479 does not match list of supported models.
1480 i8k.power_status
1481 [HW] Report power status in /proc/i8k
1482 (disabled by default)
1483 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1484 capability is set.
1485
Carsten Emde4dca20e2012-03-15 15:56:26 +01001486 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001487 [DRM] Invert the sense of the variable that is used to
1488 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001489 brightness value of 0 indicates backlight switched off,
1490 and the maximum of the brightness value sets the backlight
1491 to maximum brightness. If this parameter is set to 0
1492 (default) and the machine requires it, or this parameter
1493 is set to 1, a brightness value of 0 sets the backlight
1494 to maximum brightness, and the maximum of the brightness
1495 value switches the backlight off.
1496 -1 -- never invert brightness
1497 0 -- machine default
1498 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001499
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 icn= [HW,ISDN]
1501 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1502
David Fries0af80c02009-02-25 20:28:21 +01001503 ide-core.nodma= [HW] (E)IDE subsystem
1504 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001505 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1506 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001507 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001509 ide-generic.probe-mask= [HW] (E)IDE subsystem
1510 Format: <int>
1511 Probe mask for legacy ISA IDE ports. Depending on
1512 platform up to 6 ports are supported, enabled by
1513 setting corresponding bits in the mask to 1. The
1514 default value is 0x0, which has a special meaning.
1515 On systems that have PCI, it triggers scanning the
1516 PCI bus for the first and the second port, which
1517 are then probed. On systems without PCI the value
1518 of 0x0 enables probing the two first ports as if it
1519 was 0x3.
1520
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001521 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1522 Claim all unknown PCI IDE storage controllers.
1523
Andi Kleenf039b752007-05-02 19:27:12 +02001524 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001525 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001526 Poll forces a polling idle loop that can slightly
1527 improve the performance of waking up a idle CPU, but
1528 will use a lot of power and make the system run hot.
1529 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001530 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001531 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001532 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001533
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001534 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1535 Format: { strict | legacy | 2008 | relaxed }
1536 Default: strict
1537
1538 Choose which programs will be accepted for execution
1539 based on the IEEE 754 NaN encoding(s) supported by
1540 the FPU and the NaN encoding requested with the value
1541 of an ELF file header flag individually set by each
1542 binary. Hardware implementations are permitted to
1543 support either or both of the legacy and the 2008 NaN
1544 encoding mode.
1545
1546 Available settings are as follows:
1547 strict accept binaries that request a NaN encoding
1548 supported by the FPU
1549 legacy only accept legacy-NaN binaries, if supported
1550 by the FPU
1551 2008 only accept 2008-NaN binaries, if supported
1552 by the FPU
1553 relaxed accept any binaries regardless of whether
1554 supported by the FPU
1555
1556 The FPU emulator is always able to support both NaN
1557 encodings, so if no FPU hardware is present or it has
1558 been disabled with 'nofpu', then the settings of
1559 'legacy' and '2008' strap the emulator accordingly,
1560 'relaxed' straps the emulator for both legacy-NaN and
1561 2008-NaN, whereas 'strict' enables legacy-NaN only on
1562 legacy processors and both NaN encodings on MIPS32 or
1563 MIPS64 CPUs.
1564
1565 The setting for ABS.fmt/NEG.fmt instruction execution
1566 mode generally follows that for the NaN encoding,
1567 except where unsupported by hardware.
1568
Ingo Molnar792908222006-12-06 20:40:51 -08001569 ignore_loglevel [KNL]
1570 Ignore loglevel setting - this will print /all/
1571 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001572 We also add it as printk module parameter, so users
1573 could change it dynamically, usually by
1574 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001575
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001576 ignore_rlimit_data
1577 Ignore RLIMIT_DATA setting for data mappings,
1578 print warning at first misuse. Can be changed via
1579 /sys/module/kernel/parameters/ignore_rlimit_data.
1580
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581 ihash_entries= [KNL]
1582 Set number of hash buckets for inode cache.
1583
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001584 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001585 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001586 default: "enforce"
1587
Mimi Zohar07f6a792011-03-09 22:25:48 -05001588 ima_appraise_tcb [IMA]
1589 The builtin appraise policy appraises all files
1590 owned by uid=0.
1591
Mimi Zohar3323eec2009-02-04 09:06:58 -05001592 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001593 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1594 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001595 default: "sha1"
1596
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001597 The list of supported hash algorithms is defined
1598 in crypto/hash_info.h.
1599
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001600 ima_policy= [IMA]
1601 The builtin measurement policy to load during IMA
1602 setup. Specyfing "tcb" as the value, measures all
1603 programs exec'd, files mmap'd for exec, and all files
1604 opened with the read mode bit set by either the
1605 effective uid (euid=0) or uid=0.
1606 Format: "tcb"
1607
1608 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001609 Load a policy which meets the needs of the Trusted
1610 Computing Base. This means IMA will measure all
1611 programs exec'd, files mmap'd for exec, and all files
1612 opened for read by uid=0.
1613
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001614 ima_template= [IMA]
1615 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001616 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001617 Default: "ima-ng"
1618
Roberto Sassuc2426d22014-10-13 14:08:42 +02001619 ima_template_fmt=
1620 [IMA] Define a custom template format.
1621 Format: { "field1|...|fieldN" }
1622
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001623 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1624 Format: <min_file_size>
1625 Set the minimal file size for using asynchronous hash.
1626 If left unspecified, ahash usage is disabled.
1627
1628 ahash performance varies for different data sizes on
1629 different crypto accelerators. This option can be used
1630 to achieve the best performance for a particular HW.
1631
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001632 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1633 Format: <bufsize>
1634 Set hashing buffer size. Default: 4k.
1635
1636 ahash performance varies for different chunk sizes on
1637 different crypto accelerators. This option can be used
1638 to achieve best performance for particular HW.
1639
Linus Torvalds1da177e2005-04-16 15:20:36 -07001640 init= [KNL]
1641 Format: <full_path>
1642 Run specified binary instead of /sbin/init as init
1643 process.
1644
1645 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1646 for working out where the kernel is dying during
1647 startup.
1648
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001649 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1650 initcall functions. Useful for debugging built-in
1651 modules and initcalls.
1652
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 initrd= [BOOT] Specify the location of the initial ramdisk
1654
1655 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1656 Format: <irq>
1657
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001658 int_pln_enable [x86] Enable power limit notification interrupt
1659
Mimi Zohard726d8d2013-03-18 14:48:02 -04001660 integrity_audit=[IMA]
1661 Format: { "0" | "1" }
1662 0 -- basic integrity auditing messages. (Default)
1663 1 -- additional integrity auditing messages.
1664
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001665 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001666 on
1667 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001668 off
1669 Disable intel iommu driver.
1670 igfx_off [Default Off]
1671 By default, gfx is mapped as normal device. If a gfx
1672 device has a dedicated DMAR unit, the DMAR unit is
1673 bypassed by not enabling DMAR with this option. In
1674 this case, gfx device will use physical address for
1675 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001676 forcedac [x86_64]
1677 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001678 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001679 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001680 than 32-bit addressing. The default is to look
1681 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001682 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001683 strict [Default Off]
1684 With this option on every unmap_single operation will
1685 result in a hardware IOTLB flush operation as opposed
1686 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001687 sp_off [Default Off]
1688 By default, super page will be supported if Intel IOMMU
1689 has the capability. With this option, super page will
1690 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001691 ecs_off [Default Off]
1692 By default, extended context tables will be supported if
1693 the hardware advertises that it has support both for the
1694 extended tables themselves, and also PASID support. With
1695 this option set, extended tables will not be used even
1696 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001697
1698 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1699 0 disables intel_idle and fall back on acpi_idle.
1700 1 to 6 specify maximum depth of C-state.
1701
Dirk Brandewie6be26492013-02-15 22:55:10 +01001702 intel_pstate= [X86]
1703 disable
1704 Do not enable intel_pstate as the default
1705 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001706 force
1707 Enable intel_pstate on systems that prohibit it by default
1708 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1709 instead of acpi-cpufreq may disable platform features, such
1710 as thermal controls and power capping, that rely on ACPI
1711 P-States information being indicated to OSPM and therefore
1712 should be used with caution. This option does not work with
1713 processors that aren't supported by the intel_pstate driver
1714 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001715 no_hwp
1716 Do not enable hardware P state control (HWP)
1717 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001718 hwp_only
1719 Only load intel_pstate on systems which support
1720 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001721 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001722 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1723 Description Table, specifies preferred power management
1724 profile as "Enterprise Server" or "Performance Server",
1725 then this feature is turned on by default.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001726
Chris Wrightd1423d52010-07-20 11:06:49 -07001727 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001728 on enable Interrupt Remapping (default)
1729 off disable Interrupt Remapping
1730 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001731 no_x2apic_optout
1732 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001733 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001734
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001735 iomem= Disable strict checking of access to MMIO memory
1736 strict regions from userspace.
1737 relaxed
1738
1739 iommu= [x86]
1740 off
1741 force
1742 noforce
1743 biomerge
1744 panic
1745 nopanic
1746 merge
1747 nomerge
1748 forcesac
1749 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001750 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001751 nobypass [PPC/POWERNV]
1752 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001753
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001754
1755 io7= [HW] IO7 for Marvel based alpha systems
1756 See comment before marvel_specify_io7 in
1757 arch/alpha/kernel/core_marvel.c.
1758
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301759 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001760 0x80
1761 Standard port 0x80 based delay
1762 0xed
1763 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001764 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001765 Simple two microseconds delay
1766 none
1767 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001768
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001770 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001771
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001772 irqaffinity= [SMP] Set the default irq affinity mask
1773 Format:
1774 <cpu number>,...,<cpu number>
1775 or
1776 <cpu number>-<cpu number>
1777 (must be a positive range in ascending order)
1778 or a mixture
1779 <cpu number>,...,<cpu number>-<cpu number>
1780
Alan Cox200803d2005-06-28 20:45:18 -07001781 irqfixup [HW]
1782 When an interrupt is not handled search all handlers
1783 for it. Intended to get systems with badly broken
1784 firmware running.
1785
1786 irqpoll [HW]
1787 When an interrupt is not handled search all handlers
1788 for it. Also check all handlers each timer
1789 interrupt. Intended to get systems with badly broken
1790 firmware running.
1791
Linus Torvalds1da177e2005-04-16 15:20:36 -07001792 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001793 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001794
1795 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001796 Format:
1797 <cpu number>,...,<cpu number>
1798 or
Li Zefanb225d442008-11-06 12:53:39 -08001799 <cpu number>-<cpu number>
1800 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001801 or a mixture
1802 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001803
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804 This option can be used to specify one or more CPUs
1805 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001806 algorithms. You can move a process onto or off an
1807 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001808 <cpu number> begins at 0 and the maximum value is
1809 "number of CPUs in system - 1".
1810
1811 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001812 alternative -- manually setting the CPU mask of all
1813 tasks in the system -- can cause problems and
1814 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001815
Randy Dunlapa9913042005-10-23 12:57:11 -07001816 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001817
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001818 ivrs_ioapic [HW,X86_64]
1819 Provide an override to the IOAPIC-ID<->DEVICE-ID
1820 mapping provided in the IVRS ACPI table. For
1821 example, to map IOAPIC-ID decimal 10 to
1822 PCI device 00:14.0 write the parameter as:
1823 ivrs_ioapic[10]=00:14.0
1824
1825 ivrs_hpet [HW,X86_64]
1826 Provide an override to the HPET-ID<->DEVICE-ID
1827 mapping provided in the IVRS ACPI table. For
1828 example, to map HPET-ID decimal 0 to
1829 PCI device 00:14.0 write the parameter as:
1830 ivrs_hpet[0]=00:14.0
1831
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001832 ivrs_acpihid [HW,X86_64]
1833 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1834 mapping provided in the IVRS ACPI table. For
1835 example, to map UART-HID:UID AMD0020:0 to
1836 PCI device 00:14.5 write the parameter as:
1837 ivrs_acpihid[00:14.5]=AMD0020:0
1838
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839 js= [HW,JOY] Analog joystick
1840 See Documentation/input/joystick.txt.
1841
Kees Cook65fe9352016-06-13 15:10:02 -07001842 nokaslr [KNL]
1843 When CONFIG_RANDOMIZE_BASE is set, this disables
1844 kernel and module base offset ASLR (Address Space
1845 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001846
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001847 keepinitrd [HW,ARM]
1848
Taku Izumi342332e2016-03-15 14:55:22 -07001849 kernelcore= [KNL,X86,IA-64,PPC]
1850 Format: nn[KMGTPE] | "mirror"
1851 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001852 specifies the amount of memory usable by the kernel
1853 for non-movable allocations. The requested amount is
1854 spread evenly throughout all nodes in the system. The
1855 remaining memory in each node is used for Movable
1856 pages. In the event, a node is too small to have both
1857 kernelcore and Movable pages, kernelcore pages will
1858 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001859 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001860 allocation of pages that may be reclaimed or moved
1861 by the page migration subsystem. This means that
1862 HugeTLB pages may not be allocated from this zone.
1863 Note that allocations like PTEs-from-HighMem still
1864 use the HighMem zone if it exists, and the Normal
1865 zone if it does not.
1866
Taku Izumi342332e2016-03-15 14:55:22 -07001867 Instead of specifying the amount of memory (nn[KMGTPE]),
1868 you can specify "mirror" option. In case "mirror"
1869 option is specified, mirrored (reliable) memory is used
1870 for non-movable allocations and remaining memory is used
1871 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1872 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1873 time.
1874
Jason Wessel4fe1da42010-05-20 21:04:31 -05001875 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1876 Format: <Controller#>[,poll interval]
1877 The controller # is the number of the ehci usb debug
1878 port as it is probed via PCI. The poll interval is
1879 optional and is the number seconds in between
1880 each poll cycle to the debug port in case you need
1881 the functionality for interrupting the kernel with
1882 gdb or control-c on the dbgp connection. When
1883 not using this parameter you use sysrq-g to break into
1884 the kernel debugger.
1885
Jason Wessel84c08fd2010-05-20 21:04:24 -05001886 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001887 Requires a tty driver that supports console polling,
1888 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001889 Serial only format: <serial_device>[,baud]
1890 keyboard only format: kbd
1891 keyboard and serial format: kbd,<serial_device>[,baud]
1892 Optional Kernel mode setting:
1893 kms, kbd format: kms,kbd
1894 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001895
Jason Wessel84c08fd2010-05-20 21:04:24 -05001896 kgdbwait [KGDB] Stop kernel execution and enter the
1897 kernel debugger at the earliest opportunity.
1898
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001899 kmac= [MIPS] korina ethernet MAC address.
1900 Configure the RouterBoard 532 series on-chip
1901 Ethernet adapter MAC address.
1902
Catalin Marinas04f70332009-06-11 13:22:39 +01001903 kmemleak= [KNL] Boot-time kmemleak enable/disable
1904 Valid arguments: on, off
1905 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001906 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1907 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001908
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001909 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1910 Valid arguments: 0, 1, 2
1911 kmemcheck=0 (disabled)
1912 kmemcheck=1 (enabled)
1913 kmemcheck=2 (one-shot mode)
1914 Default: 2 (one-shot mode)
1915
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301916 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001917 in oops dumps.
1918
Andre Przywarafef07aa2009-07-10 14:20:35 +02001919 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1920 Default is 0 (don't ignore, but inject #GP)
1921
Xiao Guangronga182d872010-09-20 22:17:48 +08001922 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1923 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001924 Default is 0 (off)
1925
Andre Przywarafef07aa2009-07-10 14:20:35 +02001926 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001927 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001928
1929 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1930 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001931 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001932
Andre Przywarafef07aa2009-07-10 14:20:35 +02001933 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1934 (virtualized MMU) support on capable Intel chips.
1935 Default is 1 (enabled)
1936
1937 kvm-intel.emulate_invalid_guest_state=
1938 [KVM,Intel] Enable emulation of invalid guest states
1939 Default is 0 (disabled)
1940
1941 kvm-intel.flexpriority=
1942 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1943 Default is 1 (enabled)
1944
Sasha Levine1a72ae2011-08-09 14:28:35 +03001945 kvm-intel.nested=
1946 [KVM,Intel] Enable VMX nesting (nVMX).
1947 Default is 0 (disabled)
1948
Andre Przywarafef07aa2009-07-10 14:20:35 +02001949 kvm-intel.unrestricted_guest=
1950 [KVM,Intel] Disable unrestricted guest feature
1951 (virtualized real and unpaged mode) on capable
1952 Intel chips. Default is 1 (enabled)
1953
1954 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1955 feature (tagged TLBs) on capable Intel chips.
1956 Default is 1 (enabled)
1957
Linus Torvalds1da177e2005-04-16 15:20:36 -07001958 l2cr= [PPC]
1959
Robert Brosea78bfbf2008-03-29 07:20:23 +11001960 l3cr= [PPC]
1961
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001962 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001963 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001964
Suresh Siddha279f1462012-10-22 14:37:58 -07001965 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1966 value for LAPIC timer one-shot implementation. Default
1967 back to the programmable timer unit in the LAPIC.
1968
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301969 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001970 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001971
FD Camifcb71f62008-01-06 19:08:56 +01001972 libata.dma= [LIBATA] DMA control
1973 libata.dma=0 Disable all PATA and SATA DMA
1974 libata.dma=1 PATA and SATA Disk DMA only
1975 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001976 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001977 Combinations also work, so libata.dma=3 enables DMA
1978 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001979
Michael Prokop20308872009-08-06 00:14:10 +02001980 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1981 libata.ignore_hpa=0 keep BIOS limits (default)
1982 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001983
Dave Jones78e70c22007-09-27 11:50:13 -04001984 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1985 when set.
1986 Format: <int>
1987
Tejun Heo33267322008-02-13 09:15:09 +09001988 libata.force= [LIBATA] Force configurations. The format is comma
1989 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001990 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001991 matching port, link or device. Basically, it matches
1992 the ATA ID string printed on console by libata. If
1993 the whole ID part is omitted, the last PORT and DEVICE
1994 values are used. If ID hasn't been specified yet, the
1995 configuration applies to all ports, links and devices.
1996
1997 If only DEVICE is omitted, the parameter applies to
1998 the port and all links and devices behind it. DEVICE
1999 number of 0 either selects the first device or the
2000 first fan-out link behind PMP device. It does not
2001 select the host link. DEVICE number of 15 selects the
2002 host link and device attached to it.
2003
2004 The VAL specifies the configuration to force. As long
2005 as there's no ambiguity shortcut notation is allowed.
2006 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2007 The following configurations can be forced.
2008
2009 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2010 Any ID with matching PORT is used.
2011
2012 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2013
2014 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2015 udma[/][16,25,33,44,66,100,133] notation is also
2016 allowed.
2017
2018 * [no]ncq: Turn on or off NCQ.
2019
Martin K. Petersend7b16e42015-05-04 21:54:18 -04002020 * [no]ncqtrim: Turn off queued DSM TRIM.
2021
Tejun Heo05944bd2008-08-13 20:19:09 +09002022 * nohrst, nosrst, norst: suppress hard, soft
2023 and both resets.
2024
Dan Williamsca6d43b2012-06-21 23:41:41 -07002025 * rstonce: only attempt one reset during
2026 hot-unplug link recovery
2027
Tejun Heo43c9c592010-05-23 12:59:11 +02002028 * dump_id: dump IDENTIFY data.
2029
Vincent Pelletier966fbe12013-05-21 22:30:58 +02002030 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2031
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08002032 * disable: Disable this device.
2033
Tejun Heo33267322008-02-13 09:15:09 +09002034 If there are multiple matching configurations changing
2035 the same attribute, the last one is used.
2036
Yinghai Lu95f72d12010-07-12 14:36:09 +10002037 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08002038
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002040 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002042 lockd.nlm_grace_period=P [NFS] Assign grace period.
2043 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002045 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2046 Format: <integer>
2047
2048 lockd.nlm_timeout=T [NFS] Assign timeout value.
2049 Format: <integer>
2050
2051 lockd.nlm_udpport=M [NFS] Assign UDP port.
2052 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07002054 locktorture.nreaders_stress= [KNL]
2055 Set the number of locking read-acquisition kthreads.
2056 Defaults to being automatically set based on the
2057 number of online CPUs.
2058
2059 locktorture.nwriters_stress= [KNL]
2060 Set the number of locking write-acquisition kthreads.
2061
2062 locktorture.onoff_holdoff= [KNL]
2063 Set time (s) after boot for CPU-hotplug testing.
2064
2065 locktorture.onoff_interval= [KNL]
2066 Set time (s) between CPU-hotplug operations, or
2067 zero to disable CPU-hotplug testing.
2068
2069 locktorture.shuffle_interval= [KNL]
2070 Set task-shuffle interval (jiffies). Shuffling
2071 tasks allows some CPUs to go into dyntick-idle
2072 mode during the locktorture test.
2073
2074 locktorture.shutdown_secs= [KNL]
2075 Set time (s) after boot system shutdown. This
2076 is useful for hands-off automated testing.
2077
2078 locktorture.stat_interval= [KNL]
2079 Time (s) between statistics printk()s.
2080
2081 locktorture.stutter= [KNL]
2082 Time (s) to stutter testing, for example,
2083 specifying five seconds causes the test to run for
2084 five seconds, wait for five seconds, and so on.
2085 This tests the locking primitive's ability to
2086 transition abruptly to and from idle.
2087
2088 locktorture.torture_runnable= [BOOT]
2089 Start locktorture running at boot time.
2090
2091 locktorture.torture_type= [KNL]
2092 Specify the locking implementation to test.
2093
2094 locktorture.verbose= [KNL]
2095 Enable additional printk() statements.
2096
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2098 Format: <irq>
2099
2100 loglevel= All Kernel Messages with a loglevel smaller than the
2101 console loglevel will be printed to the console. It can
2102 also be changed with klogd or other programs. The
2103 loglevels are defined as follows:
2104
2105 0 (KERN_EMERG) system is unusable
2106 1 (KERN_ALERT) action must be taken immediately
2107 2 (KERN_CRIT) critical conditions
2108 3 (KERN_ERR) error conditions
2109 4 (KERN_WARNING) warning conditions
2110 5 (KERN_NOTICE) normal but significant condition
2111 6 (KERN_INFO) informational
2112 7 (KERN_DEBUG) debug-level messages
2113
Randy Dunlapc756d082011-02-20 20:08:35 -08002114 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07002115 in bytes. n must be a power of two and greater
2116 than the minimal size. The minimal size is defined
2117 by LOG_BUF_SHIFT kernel config parameter. There is
2118 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2119 that allows to increase the default size depending on
2120 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121
Randy Dunlapaccaa242007-10-16 01:29:37 -07002122 logo.nologo [FB] Disables display of the built-in Linux logo.
2123 This may be used to provide more screen space for
2124 kernel log messages and is useful when debugging
2125 kernel boot problems.
2126
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127 lp=0 [LP] Specify parallel ports to use, e.g,
2128 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2129 lp=reset first parallel port). 'lp=0' disables the
2130 lp=auto printer driver. 'lp=reset' (which can be
2131 specified in addition to the ports) causes
2132 attached printers to be reset. Using
2133 lp=port1,port2,... specifies the parallel ports
2134 to associate lp devices with, starting with
2135 lp0. A port specification may be 'none' to skip
2136 that lp device, or a parport name such as
2137 'parport0'. Specifying 'lp=auto' instead of a
2138 port specification list means that device IDs
2139 from each port should be examined, to see if
2140 an IEEE 1284-compliant printer is attached; if
2141 so, the driver will manage that printer.
2142 See also header of drivers/char/lp.c.
2143
2144 lpj=n [KNL]
2145 Sets loops_per_jiffy to given constant, thus avoiding
2146 time-consuming boot-time autodetection (up to 250 ms per
2147 CPU). 0 enables autodetection (default). To determine
2148 the correct value for your kernel, boot with normal
2149 autodetection and see what value is printed. Note that
2150 on SMP systems the preset will be applied to all CPUs,
2151 which is likely to cause problems if your CPUs need
2152 significantly divergent settings. An incorrect value
2153 will cause delays in the kernel to be wrong, leading to
2154 unpredictable I/O errors and other breakage. Although
2155 unlikely, in the extreme case this might damage your
2156 hardware.
2157
2158 ltpc= [NET]
2159 Format: <io>,<irq>,<dma>
2160
Randy Dunlap16290242011-08-13 12:34:52 -07002161 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002162 (machvec) in a generic kernel.
2163 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002164
Wu Zhangjin3209e702009-07-02 23:27:12 +08002165 machtype= [Loongson] Share the same kernel image file between different
2166 yeeloong laptop.
2167 Example: machtype=lemote-yeeloong-2f-7inch
2168
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002169 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2170 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171
2172 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04002173 should make use of. maxcpus=n : n >= 0 limits the
2174 kernel to using 'n' processors. n=0 is a special case,
2175 it is equivalent to "nosmp", which also disables
2176 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002177
Kay Sieversd134b002011-07-31 22:08:04 +02002178 max_loop= [LOOP] The number of loop block devices that get
2179 (loop.max_loop) unconditionally pre-created at init time. The default
2180 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2181 of statically allocating a predefined number, loop
2182 devices can be requested on-demand with the
2183 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002184
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002185 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186
Uwe Hermann71cced62008-10-20 09:32:21 -07002187 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002188
Linus Torvalds1da177e2005-04-16 15:20:36 -07002189 md= [HW] RAID subsystems devices and level
2190 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002191
Linus Torvalds1da177e2005-04-16 15:20:36 -07002192 mdacon= [MDA]
2193 Format: <first>,<last>
2194 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002195
Linus Torvalds1da177e2005-04-16 15:20:36 -07002196 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2197 Amount of memory to be used when the kernel is not able
2198 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002199 [X86] Work as limiting max address. Use together
2200 with memmap= to avoid physical address space collisions.
2201 Without memmap= PCI devices could be placed at addresses
2202 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002203
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002204 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002205 memory.
2206
Paul Mundt6902aa82008-09-21 17:14:42 +09002207 memchunk=nn[KMG]
2208 [KNL,SH] Allow user to override the default size for
2209 per-device physically contiguous DMA buffers.
2210
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002211 memhp_default_state=online/offline
2212 [KNL] Set the initial state for the memory hotplug
2213 onlining policy. If not specified, the default value is
2214 set according to the
2215 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2216 option.
2217 See Documentation/memory-hotplug.txt.
2218
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302219 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002220 E820 memory map, as specified by the user.
2221 Such memmap=exactmap lines can be constructed based on
2222 BIOS output or other requirements. See the memmap=nn@ss
2223 option description.
2224
2225 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002226 [KNL] Force usage of a specific region of memory.
2227 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002228
2229 memmap=nn[KMG]#ss[KMG]
2230 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002231 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232
2233 memmap=nn[KMG]$ss[KMG]
2234 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002235 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002236 Example: Exclude memory from 0x18690000-0x1869ffff
2237 memmap=64K$0x18690000
2238 or
2239 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002241 memmap=nn[KMG]!ss[KMG]
2242 [KNL,X86] Mark specific memory as protected.
2243 Region of memory to be used, from ss to ss+nn.
2244 The memory region may be marked as e820 type 12 (0xc)
2245 and is NVDIMM or ADR memory.
2246
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002247 memory_corruption_check=0/1 [X86]
2248 Some BIOSes seem to corrupt the first 64k of
2249 memory when doing things like suspend/resume.
2250 Setting this option will scan the memory
2251 looking for corruption. Enabling this will
2252 both detect corruption and prevent the kernel
2253 from using the memory being corrupted.
2254 However, its intended as a diagnostic tool; if
2255 repeatable BIOS-originated corruption always
2256 affects the same memory, you can use memmap=
2257 to prevent the kernel from using that memory.
2258
2259 memory_corruption_check_size=size [X86]
2260 By default it checks for corruption in the low
2261 64k, making this memory unavailable for normal
2262 use. Use this parameter to scan for
2263 corruption in more or less memory.
2264
2265 memory_corruption_check_period=seconds [X86]
2266 By default it checks for corruption every 60
2267 seconds. Use this parameter to check at some
2268 other rate. 0 disables periodic checking.
2269
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002270 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002271 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002272 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002273 Specifies the number of memtest passes to be
2274 performed. Each pass selects another test
2275 pattern from a given set of patterns. Memtest
2276 fills the memory with this pattern, validates
2277 memory contents and reserves bad memory
2278 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002279
Linus Torvalds1da177e2005-04-16 15:20:36 -07002280 meye.*= [HW] Set MotionEye Camera parameters
2281 See Documentation/video4linux/meye.txt.
2282
Andres Salomon8f368812007-10-12 23:04:06 +02002283 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2284 Multi-Function General Purpose Timers on AMD Geode
2285 platforms.
2286
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002287 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2288 the BIOS has incorrectly applied a workaround. TinyBIOS
2289 version 0.98 is known to be affected, 0.99 fixes the
2290 problem by letting the user disable the workaround.
2291
Linus Torvalds1da177e2005-04-16 15:20:36 -07002292 mga= [HW,DRM]
2293
Randy Dunlap1c207f952008-11-19 15:36:16 -08002294 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2295 physical address is ignored.
2296
Michel Pollet39f45d72009-05-20 11:10:31 +01002297 mini2440= [ARM,HW,KNL]
2298 Format:[0..2][b][c][t]
2299 Default: "0tb"
2300 MINI2440 configuration specification:
2301 0 - The attached screen is the 3.5" TFT
2302 1 - The attached screen is the 7" TFT
2303 2 - The VGA Shield is attached (1024x768)
2304 Leaving out the screen size parameter will not load
2305 the TFT driver, and the framebuffer will be left
2306 unconfigured.
2307 b - Enable backlight. The TFT backlight pin will be
2308 linked to the kernel VESA blanking code and a GPIO
2309 LED. This parameter is not necessary when using the
2310 VGA shield.
2311 c - Enable the s3c camera interface.
2312 t - Reserved for enabling touchscreen support. The
2313 touchscreen support is not enabled in the mainstream
2314 kernel as of 2.6.30, a preliminary port can be found
2315 in the "bleeding edge" mini2440 support kernel at
2316 http://repo.or.cz/w/linux-2.6/mini2440.git
2317
Mel Gorman6b74ab92008-07-23 21:26:49 -07002318 mminit_loglevel=
2319 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2320 parameter allows control of the logging verbosity for
2321 the additional memory initialisation checks. A value
2322 of 0 disables mminit logging and a level of 4 will
2323 log everything. Information is printed at KERN_DEBUG
2324 so loglevel=8 may also need to be specified.
2325
Rusty Russell106a4ee2012-09-26 10:09:40 +01002326 module.sig_enforce
2327 [KNL] When CONFIG_MODULE_SIG is set, this means that
2328 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002329 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002330 is always true, so this option does nothing.
2331
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302332 module_blacklist= [KNL] Do not load a comma-separated list of
2333 modules. Useful for debugging problem modules.
2334
Linus Torvalds1da177e2005-04-16 15:20:36 -07002335 mousedev.tap_time=
2336 [MOUSE] Maximum time between finger touching and
2337 leaving touchpad surface for touch to be considered
2338 a tap and be reported as a left button click (for
2339 touchpads working in absolute mode only).
2340 Format: <msecs>
2341 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2342 reporting absolute coordinates, such as tablets
2343 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2344 reporting absolute coordinates, such as tablets
2345
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302346 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002347 is similar to kernelcore except it specifies the
2348 amount of memory used for migratable allocations.
2349 If both kernelcore and movablecore is specified,
2350 then kernelcore will be at *least* the specified
2351 value but may be more. If movablecore on its own
2352 is specified, the administrator must be careful
2353 that the amount of memory usable for all allocations
2354 is not too small.
2355
Tang Chenc5320922013-11-12 15:08:10 -08002356 movable_node [KNL,X86] Boot-time switch to enable the effects
2357 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2358
Linus Torvalds1da177e2005-04-16 15:20:36 -07002359 MTD_Partition= [MTD]
2360 Format: <name>,<region-number>,<size>,<offset>
2361
Randy Dunlapa9913042005-10-23 12:57:11 -07002362 MTD_Region= [MTD] Format:
2363 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002364
2365 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002366 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002367
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002368 multitce=off [PPC] This parameter disables the use of the pSeries
2369 firmware feature for updating multiple TCE entries
2370 at a time.
2371
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002372 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2373
2374 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2375
2376 boundary - index of last SLC block on Flex-OneNAND.
2377 The remaining blocks are configured as MLC blocks.
2378 lock - Configure if Flex-OneNAND boundary should be locked.
2379 Once locked, the boundary cannot be changed.
2380 1 indicates lock status, 0 indicates unlock status.
2381
Ben Dooks9db829f2008-07-03 11:24:29 +01002382 mtdset= [ARM]
2383 ARM/S3C2412 JIVE boot control
2384
2385 See arch/arm/mach-s3c2412/mach-jive.c
2386
Linus Torvalds1da177e2005-04-16 15:20:36 -07002387 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002388 [HW] Make the MicroTouch USB driver use raw coordinates
2389 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002390
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002391 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002392 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002393 that could hold holes aka. UC entries.
2394
2395 mtrr_gran_size=nn[KMG] [X86]
2396 Used for mtrr cleanup. It is granularity of mtrr block.
2397 Default is 1.
2398 Large value could prevent small alignment from
2399 using up MTRRs.
2400
2401 mtrr_spare_reg_nr=n [X86]
2402 Format: <integer>
2403 Range: 0,7 : spare reg number
2404 Default : 1
2405 Used for mtrr cleanup. It is spare mtrr entries number.
2406 Set to 2 or more if your graphical card needs more.
2407
Linus Torvalds1da177e2005-04-16 15:20:36 -07002408 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2409
Linus Torvalds1da177e2005-04-16 15:20:36 -07002410 netdev= [NET] Network devices parameters
2411 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2412 Note that mem_start is often overloaded to mean
2413 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002414 This usage is only documented in each driver source
2415 file if at all.
2416
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002417 nf_conntrack.acct=
2418 [NETFILTER] Enable connection tracking flow accounting
2419 0 to disable accounting
2420 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002421 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002422
Chuck Lever306a0752010-09-17 10:54:37 -04002423 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002424 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002425
2426 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002427 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002428
Chuck Lever306a0752010-09-17 10:54:37 -04002429 nfsrootdebug [NFS] enable nfsroot debugging messages.
2430 See Documentation/filesystems/nfs/nfsroot.txt.
2431
Trond Myklebusta72b4422006-01-03 09:55:41 +01002432 nfs.callback_tcpport=
2433 [NFS] set the TCP port on which the NFSv4 callback
2434 channel should listen.
2435
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002436 nfs.cache_getent=
2437 [NFS] sets the pathname to the program which is used
2438 to update the NFS client cache entries.
2439
2440 nfs.cache_getent_timeout=
2441 [NFS] sets the timeout after which an attempt to
2442 update a cache entry is deemed to have failed.
2443
Trond Myklebust58df0952006-01-03 09:55:57 +01002444 nfs.idmap_cache_timeout=
2445 [NFS] set the maximum lifetime for idmapper cache
2446 entries.
2447
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002448 nfs.enable_ino64=
2449 [NFS] enable 64-bit inode numbers.
2450 If zero, the NFS client will fake up a 32-bit inode
2451 number for the readdir() and stat() syscalls instead
2452 of returning the full 64-bit number.
2453 The default is to return 64-bit inode numbers.
2454
Trond Myklebustef159e92012-02-06 19:50:40 -05002455 nfs.max_session_slots=
2456 [NFSv4.1] Sets the maximum number of session slots
2457 the client will attempt to negotiate with the server.
2458 This limits the number of simultaneous RPC requests
2459 that the client can send to the NFSv4.1 server.
2460 Note that there is little point in setting this
2461 value higher than the max_tcp_slot_table_limit.
2462
Trond Myklebustb064eca22011-02-22 15:44:32 -08002463 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002464 [NFSv4] When set to the default of '1', this option
2465 ensures that both the RPC level authentication
2466 scheme and the NFS level operations agree to use
2467 numeric uids/gids if the mount is using the
2468 'sec=sys' security flavour. In effect it is
2469 disabling idmapping, which can make migration from
2470 legacy NFSv2/v3 systems to NFSv4 easier.
2471 Servers that do not support this mode of operation
2472 will be autodetected by the client, and it will fall
2473 back to using the idmapper.
2474 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002475 nfs.nfs4_unique_id=
2476 [NFS4] Specify an additional fixed unique ident-
2477 ification string that NFSv4 clients can insert into
2478 their nfs_client_id4 string. This is typically a
2479 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002480
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002481 nfs.send_implementation_id =
2482 [NFSv4.1] Send client implementation identification
2483 information in exchange_id requests.
2484 If zero, no implementation identification information
2485 will be sent.
2486 The default is to send the implementation identification
2487 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002488
2489 nfs.recover_lost_locks =
2490 [NFSv4] Attempt to recover locks that were lost due
2491 to a lease timeout on the server. Please note that
2492 doing this risks data corruption, since there are
2493 no guarantees that the file will remain unchanged
2494 after the locks are lost.
2495 If you want to enable the kernel legacy behaviour of
2496 attempting to recover these locks, then set this
2497 parameter to '1'.
2498 The default parameter value of '0' causes the kernel
2499 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002500
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002501 nfs4.layoutstats_timer =
2502 [NFSv4.2] Change the rate at which the kernel sends
2503 layoutstats to the pNFS metadata server.
2504
2505 Setting this to value to 0 causes the kernel to use
2506 whatever value is the default set by the layout
2507 driver. A non-zero value sets the minimum interval
2508 in seconds between layoutstats transmissions.
2509
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002510 nfsd.nfs4_disable_idmapping=
2511 [NFSv4] When set to the default of '1', the NFSv4
2512 server will return only numeric uids and gids to
2513 clients using auth_sys, and will accept numeric uids
2514 and gids from such clients. This is intended to ease
2515 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002516
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002517 objlayoutdriver.osd_login_prog=
2518 [NFS] [OBJLAYOUT] sets the pathname to the program which
2519 is used to automatically discover and login into new
2520 osd-targets. Please see:
2521 Documentation/filesystems/pnfs.txt for more explanations
2522
Paul Mundt1e1030d2009-09-01 17:38:32 +09002523 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002524 when a NMI is triggered.
2525 Format: [state][,regs][,debounce][,die]
2526
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302527 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002528 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002529 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002530 0 - turn hardlockup detector in nmi_watchdog off
2531 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002532 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002533 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002534 default). To disable both hard and soft lockup detectors,
2535 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002536 This is useful when you use a panic=... timeout and
2537 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002538
Anton Vorontsovbff38772009-07-08 11:10:56 -07002539 netpoll.carrier_timeout=
2540 [NET] Specifies amount of time (in seconds) that
2541 netpoll should wait for a carrier. By default netpoll
2542 waits 4 seconds.
2543
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002544 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002545 emulation library even if a 387 maths coprocessor
2546 is present.
2547
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002548 no_console_suspend
2549 [HW] Never suspend the console
2550 Disable suspending of consoles during suspend and
2551 hibernate operations. Once disabled, debugging
2552 messages can reach various consoles while the rest
2553 of the system is being put to sleep (ie, while
2554 debugging driver suspend/resume hooks). This may
2555 not work reliably with all consoles, but is known
2556 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002557 To facilitate more flexible debugging, we also add
2558 console_suspend, a printk module parameter to control
2559 it. Users could use console_suspend (usually
2560 /sys/module/printk/parameters/console_suspend) to
2561 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002562
Christoph Lameterc1aee212007-05-31 00:40:47 -07002563 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2564 caches in the slab allocator. Saves per-node memory,
2565 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002566
Randy Dunlapa9913042005-10-23 12:57:11 -07002567 noalign [KNL,ARM]
2568
Linus Torvalds1da177e2005-04-16 15:20:36 -07002569 noapic [SMP,APIC] Tells the kernel to not make use of any
2570 IOAPICs that may be present in the system.
2571
Mike Galbraith5091faa2010-11-30 14:18:03 +01002572 noautogroup Disable scheduler automatic task group creation.
2573
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 nobats [PPC] Do not use BATs for mapping kernel lowmem
2575 on "Classic" PPC cores.
2576
2577 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002578
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002579 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2580
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002581 nodelayacct [KNL] Disable per-task delay accounting
2582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2584
Paul Mundt6902aa82008-09-21 17:14:42 +09002585 nodsp [SH] Disable hardware DSP at boot time.
2586
Dave Youngb2e0a542014-08-14 17:15:26 +08002587 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002588
Linus Torvalds1da177e2005-04-16 15:20:36 -07002589 noexec [IA-64]
2590
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302591 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002592 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002594 noexec=off: disable non-executable mappings
2595
H. Peter Anvin52b61792012-09-21 12:43:13 -07002596 nosmap [X86]
2597 Disable SMAP (Supervisor Mode Access Prevention)
2598 even if it is supported by processor.
2599
Fenghua Yude5397a2011-05-11 16:51:05 -07002600 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002601 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002602 even if it is supported by processor.
2603
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002604 noexec32 [X86-64]
2605 This affects only 32-bit executables.
2606 noexec32=on: enable non-executable mappings (default)
2607 read doesn't imply executable mappings
2608 noexec32=off: disable non-executable mappings
2609 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002610
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002611 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002612
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002613 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002614 register save and restore. The kernel will only save
2615 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002616
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002617 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2618
Sascha Silbe52c48c52016-04-05 12:53:38 +02002619 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2620 Equivalent to smt=1.
2621
Suresh Siddha0c752a92009-05-22 12:17:45 -07002622 noxsave [BUGS=X86] Disables x86 extended register state save
2623 and restore using xsave. The kernel will fallback to
2624 enabling legacy floating-point and sse state.
2625
Fenghua Yub6f42a42014-05-29 11:12:31 -07002626 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2627 register states. The kernel will fall back to use
2628 xsave to save the states. By using this parameter,
2629 performance of saving the states is degraded because
2630 xsave doesn't support modified optimization while
2631 xsaveopt supports it on xsaveopt enabled systems.
2632
2633 noxsaves [X86] Disables xsaves and xrstors used in saving and
2634 restoring x86 extended register state in compacted
2635 form of xsave area. The kernel will fall back to use
2636 xsaveopt and xrstor to save and restore the states
2637 in standard form of xsave area. By using this
2638 parameter, xsave area per process might occupy more
2639 memory on xsaves enabled systems.
2640
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002641 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2642 wfi(ARM) instruction doesn't work correctly and not to
2643 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002644
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002645 no_file_caps Tells the kernel not to honor file capabilities. The
2646 only way then for a file to be executed with privilege
2647 is to be setuid root or executed by root.
2648
Linus Torvalds1da177e2005-04-16 15:20:36 -07002649 nohalt [IA-64] Tells the kernel not to use the power saving
2650 function PAL_HALT_LIGHT when idle. This increases
2651 power-consumption. On the positive side, it reduces
2652 interrupt wake-up latency, which may improve performance
2653 in certain environments such as networked servers or
2654 real-time systems.
2655
Kees Cooka6e15a32014-06-13 13:30:35 -07002656 nohibernate [HIBERNATION] Disable hibernation and resume.
2657
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002658 nohz= [KNL] Boottime enable/disable dynamic ticks
2659 Valid arguments: on, off
2660 Default: on
2661
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002662 nohz_full= [KNL,BOOT]
2663 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002664 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002665 whenever possible. The boot CPU will be forced outside
2666 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002667 The CPUs in this range must also be included in the
2668 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002669
Paul Mundteeee7852009-04-02 12:31:16 +09002670 noiotrap [SH] Disables trapped I/O port accesses.
2671
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002672 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002673 disable unhandled interrupt sources.
2674
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302675 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002676 broken timer IRQ sources.
2677
Linus Torvalds1da177e2005-04-16 15:20:36 -07002678 noisapnp [ISAPNP] Disables ISA PnP code.
2679
2680 noinitrd [RAM] Tells the kernel not to load any configured
2681 initial RAM disk.
2682
Weidong Han03ea8152009-04-17 16:42:15 +08002683 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2684 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002685 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002686
Linus Torvalds1da177e2005-04-16 15:20:36 -07002687 nointroute [IA-64]
2688
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002689 noinvpcid [X86] Disable the INVPCID cpu feature.
2690
Randy Dunlap16290242011-08-13 12:34:52 -07002691 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002692
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002693 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2694
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002695 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2696 fault handling.
2697
Glauber Costad910f5c2011-07-11 15:28:19 -04002698 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2699 steal time is computed, but won't influence scheduler
2700 behaviour
2701
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002702 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002703
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002704 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002705
Linus Torvalds1da177e2005-04-16 15:20:36 -07002706 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002707 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708
Horms312f1f02006-02-22 09:57:55 +09002709 nomca [IA-64] Disable machine check abort handling
2710
Masanari Iida13696e02015-05-16 02:16:43 +09002711 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002712
Andres Salomon83d73842007-10-12 23:04:06 +02002713 nomfgpt [X86-32] Disable Multi-Function General Purpose
2714 Timer usage (for AMD Geode machines).
2715
Don Zickusbda62632011-10-13 15:14:27 -04002716 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2717 shutdown the other cpus. Instead use the REBOOT_VECTOR
2718 irq.
2719
Dave Young02608be2012-02-01 10:33:14 +08002720 nomodule Disable module load
2721
Jiri Kosina016ddd92010-01-18 17:05:40 +01002722 nopat [X86] Disable PAT (page attribute table extension of
2723 pagetables) support.
2724
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002725 norandmaps Don't use address space randomization. Equivalent to
2726 echo 0 > /proc/sys/kernel/randomize_va_space
2727
Jiri Kosinabbff2162010-08-11 18:34:09 +02002728 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002729
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002730 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002731 with UP alternatives
2732
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002733 nordrand [X86] Disable kernel use of the RDRAND and
2734 RDSEED instructions even if they are supported
2735 by the processor. RDRAND and RDSEED are still
2736 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002737
Randy Dunlapa9913042005-10-23 12:57:11 -07002738 noresume [SWSUSP] Disables resume and restores original swap
2739 space.
2740
Linus Torvalds1da177e2005-04-16 15:20:36 -07002741 no-scroll [VGA] Disables scrollback.
2742 This is required for the Braillex ib80-piezo Braille
2743 reader made by F.H. Papenmeier (Germany).
2744
2745 nosbagart [IA-64]
2746
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002747 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002748
Len Brown61ec7562007-08-16 03:34:22 -04002749 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2750 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002751
Dave Jones97842212007-07-15 23:41:05 -07002752 nosoftlockup [KNL] Disable the soft-lockup detector.
2753
Linus Torvalds1da177e2005-04-16 15:20:36 -07002754 nosync [HW,M68K] Disables sync negotiation for all devices.
2755
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002756 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002757
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002758 nowatchdog [KNL] Disable both lockup detectors, i.e.
2759 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002760
Linus Torvalds1da177e2005-04-16 15:20:36 -07002761 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002762
Weidong Han2b2fd872009-04-17 16:42:12 +08002763 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2764
Fenghua Yuf78cff42012-11-13 11:32:38 -08002765 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2766 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2767 Some features depend on CPU0. Known dependencies are:
2768 1. Resume from suspend/hibernate depends on CPU0.
2769 Suspend/hibernate will fail if CPU0 is offline and you
2770 need to online CPU0 before suspend/hibernate.
2771 2. PIC interrupts also depend on CPU0. CPU0 can't be
2772 removed if a PIC interrupt is detected.
2773 It's said poweroff/reboot may depend on CPU0 on some
2774 machines although I haven't seen such issues so far
2775 after CPU0 is offline on a few tested machines.
2776 If the dependencies are under your control, you can
2777 turn on cpu0_hotplug.
2778
Randy Dunlap16290242011-08-13 12:34:52 -07002779 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002780 purges which is reported from either PAL_VM_SUMMARY or
2781 SAL PALO.
2782
Yinghai Lu2b633e32010-02-10 01:20:37 -08002783 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2784 could support. nr_cpus=n : n >= 1 limits the kernel to
2785 supporting 'n' processors. Later in runtime you can not
2786 use hotplug cpu feature to put more cpu back to online.
2787 just like you compile the kernel NR_CPUS=n
2788
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002789 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2790
Mel Gorman1a687c22012-11-22 11:16:36 +00002791 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2792 Allowed values are enable and disable
2793
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002794 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2795 one of ['zone', 'node', 'default'] can be specified
2796 This can be set from sysctl after boot.
2797 See Documentation/sysctl/vm.txt for details.
2798
Randy Dunlap7c4be252009-01-06 14:42:44 -08002799 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2800 See Documentation/debugging-via-ohci1394.txt for more
2801 info.
2802
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002803 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2804 Rather than timing out after 20 ms if an EC
2805 command is not properly ACKed, override the length
2806 of the timeout. We have interrupts disabled while
2807 waiting for the ACK, so if this is set too high
2808 interrupts *may* be lost!
2809
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002810 omap_mux= [OMAP] Override bootloader pin multiplexing.
2811 Format: <mux_mode0.mode_name=value>...
2812 For example, to override I2C bus2:
2813 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2814
Linus Torvalds1da177e2005-04-16 15:20:36 -07002815 oprofile.timer= [HW]
2816 Use timer interrupt instead of performance counters
2817
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002818 oprofile.cpu_type= Force an oprofile cpu type
2819 This might be useful if you have an older oprofile
2820 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002821 Format: { arch_perfmon }
2822 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002823 perfmon on Intel CPUs instead of the
2824 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002825 timer: [X86] Force use of architectural NMI
2826 timer mode (see also oprofile.timer
2827 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002828
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002829 oops=panic Always panic on oopses. Default is to just kill the
2830 process, but there is a small probability of
2831 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002832 This will also cause panics on machine check exceptions.
2833 Useful together with panic=30 to trigger a reboot.
2834
Randy Dunlapbcfde332010-06-07 17:10:38 -07002835 OSS [HW,OSS]
2836 See Documentation/sound/oss/oss-parameters.txt
2837
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002838 page_owner= [KNL] Boot-time page_owner enabling option.
2839 Storage of the information about who allocated
2840 each page is disabled in default. With this switch,
2841 we can turn it on.
2842 on: enable the feature
2843
Laura Abbott8823b1d2016-03-15 14:56:27 -07002844 page_poison= [KNL] Boot-time parameter changing the state of
2845 poisoning on the buddy allocator.
2846 off: turn off poisoning
2847 on: turn on poisoning
2848
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002849 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002850 timeout > 0: seconds before rebooting
2851 timeout = 0: wait forever
2852 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002853 Format: <timeout>
2854
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002855 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2856 on a WARN().
2857
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002858 crash_kexec_post_notifiers
2859 Run kdump after running panic-notifiers and dumping
2860 kmsg. This only for the users who doubt kdump always
2861 succeeds in any situation.
2862 Note that this also increases risks of kdump failure,
2863 because some panic notifiers can make the crashed
2864 kernel more unstable.
2865
Linus Torvalds1da177e2005-04-16 15:20:36 -07002866 parkbd.port= [HW] Parallel port number the keyboard adapter is
2867 connected to, default is 0.
2868 Format: <parport#>
2869 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2870 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002871 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002872
Randy Dunlapa9913042005-10-23 12:57:11 -07002873 parport= [HW,PPT] Specify parallel ports. 0 disables.
2874 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2875 Use 'auto' to force the driver to use any
2876 IRQ/DMA settings detected (the default is to
2877 ignore detected IRQ/DMA settings because of
2878 possible conflicts). You can specify the base
2879 address, IRQ, and DMA settings; IRQ and DMA
2880 should be numbers, or 'auto' (for using detected
2881 settings on that particular port), or 'nofifo'
2882 (to avoid using a FIFO even if it is detected).
2883 Parallel ports are assigned in the order they
2884 are specified on the command line, starting
2885 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002886
Randy Dunlapa9913042005-10-23 12:57:11 -07002887 parport_init_mode= [HW,PPT]
2888 Configure VIA parallel port to operate in
2889 a specific mode. This is necessary on Pegasos
2890 computer where firmware has no options for setting
2891 up parallel port mode and sets it to spp.
2892 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002893 Format: [spp|ps2|epp|ecp|ecpepp]
2894
Andrew Mortondd287792006-03-23 03:00:57 -08002895 pause_on_oops=
2896 Halt all CPUs after the first oops has been printed for
2897 the specified number of seconds. This is to be used if
2898 your oopses keep scrolling off the screen.
2899
Linus Torvalds1da177e2005-04-16 15:20:36 -07002900 pcbit= [HW,ISDN]
2901
2902 pcd. [PARIDE]
2903 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002904 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002905
Randy Dunlapa9913042005-10-23 12:57:11 -07002906 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002907 earlydump [X86] dump PCI config space before the kernel
2908 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002909 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002910 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002911 the hardware directly. Use this if your machine
2912 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002913 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002914 hardware access methods are allowed. Use this
2915 if you experience crashes upon bootup and you
2916 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002917 conf1 [X86] Force use of PCI Configuration Access
2918 Mechanism 1 (config address in IO port 0xCF8,
2919 data in IO port 0xCFC, both 32-bit).
2920 conf2 [X86] Force use of PCI Configuration Access
2921 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2922 the function, IO port 0xCFA, also 8-bit, sets
2923 bus number. The config space is then accessed
2924 through ports 0xC000-0xCFFF).
2925 See http://wiki.osdev.org/PCI for more info
2926 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002927 noaer [PCIE] If the PCIEAER kernel config parameter is
2928 enabled, this kernel boot option can be used to
2929 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002930 nodomains [PCI] Disable support for multiple PCI
2931 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302932 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002933 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002934 check_enable_amd_mmconf [X86] check for and enable
2935 properly configured MMIO access to PCI
2936 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002937 nomsi [MSI] If the PCI_MSI kernel config parameter is
2938 enabled, this kernel boot option can be used to
2939 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002940 noioapicquirk [APIC] Disable all boot interrupt quirks.
2941 Safety option to keep boot IRQs enabled. This
2942 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002943 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2944 primary IO-APIC for bridges that cannot disable
2945 boot IRQs. This fixes a source of spurious IRQs
2946 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002947 noioapicreroute [APIC] Disable workaround that uses the
2948 boot IRQ equivalent of an IRQ that connects to
2949 a chipset where boot IRQs cannot be disabled.
2950 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002951 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002952 routing table. These calls are known to be buggy
2953 on several machines and they hang the machine
2954 when used, but on other computers it's the only
2955 way to get the interrupt routing table. Try
2956 this option if the kernel is unable to allocate
2957 IRQs or discover secondary PCI buses on your
2958 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002959 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002960 Use with caution as certain devices share
2961 address decoders between ROMs and other
2962 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002963 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002964 expansion ROMs that do not already have
2965 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002966 nobar [X86] Do not assign address space to the
2967 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002968 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002969 assigned automatically to PCI devices. You can
2970 make the kernel exclude IRQs of your ISA cards
2971 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002972 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002973 of the PIRQ table (normally generated
2974 by the BIOS) if it is outside the
2975 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002976 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002977 useful if the kernel is unable to find your
2978 secondary buses and you want to tell it
2979 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002980 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002981 numbers ourselves, overriding
2982 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002983 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002984 in the BIOS $PIR table. This is needed on
2985 some systems with broken BIOSes, notably
2986 some HP Pavilion N5400 and Omnibook XE3
2987 notebooks. This will have no effect if ACPI
2988 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002989 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002990 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002991 use_crs [X86] Use PCI host bridge window information
2992 from ACPI. On BIOSes from 2008 or later, this
2993 is enabled by default. If you need to use this,
2994 please report a bug.
2995 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2996 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002997 routeirq Do IRQ routing for all PCI devices.
2998 This is normally done in pci_enable_device(),
2999 so this option is a temporary workaround
3000 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07003001 skip_isa_align [X86] do not align io start addr, so can
3002 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02003003 noearly [X86] Don't do any early type 1 scanning.
3004 This might help on some broken boards which
3005 machine check when some devices' config space
3006 is read. But various workarounds are disabled
3007 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003008 bfsort Sort PCI devices into breadth-first order.
3009 This sorting is done to get a device
3010 order compatible with older (<= 2.4) kernels.
3011 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08003012 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3013 tuning and use the BIOS-configured MPS defaults.
3014 pcie_bus_safe Set every device's MPS to the largest value
3015 supported by all devices below the root complex.
3016 pcie_bus_perf Set device MPS to the largest allowable MPS
3017 based on its parent bus. Also set MRRS (Max
3018 Read Request Size) to the largest supported
3019 value (no larger than the MPS that the device
3020 or bus can support) for best performance.
3021 pcie_bus_peer2peer Set every device's MPS to 128B, which
3022 every device is guaranteed to support. This
3023 configuration allows peer-to-peer DMA between
3024 any pair of devices, possibly at the cost of
3025 reduced performance. This also guarantees
3026 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08003027 cbiosize=nn[KMG] The fixed amount of bus space which is
3028 reserved for the CardBus bridge's IO window.
3029 The default value is 256 bytes.
3030 cbmemsize=nn[KMG] The fixed amount of bus space which is
3031 reserved for the CardBus bridge's memory
3032 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003033 resource_alignment=
3034 Format:
3035 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00003036 [<order of align>@]pci:<vendor>:<device>\
3037 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003038 Specifies alignment and device to reassign
3039 aligned memory resources.
3040 If <order of align> is not specified,
3041 PAGE_SIZE is used as alignment.
3042 PCI-PCI bridge can be specified, if resource
3043 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06003044 ecrc= Enable/disable PCIe ECRC (transaction layer
3045 end-to-end CRC checking).
3046 bios: Use BIOS/firmware settings. This is the
3047 the default.
3048 off: Turn ECRC off
3049 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08003050 hpiosize=nn[KMG] The fixed amount of bus space which is
3051 reserved for hotplug bridge's IO window.
3052 Default size is 256 bytes.
3053 hpmemsize=nn[KMG] The fixed amount of bus space which is
3054 reserved for hotplug bridge's memory window.
3055 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06003056 hpbussize=nn The minimum amount of additional bus numbers
3057 reserved for buses below a hotplug bridge.
3058 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08003059 realloc= Enable/disable reallocating PCI bridge resources
3060 if allocations done by BIOS are too small to
3061 accommodate resources required by all child
3062 devices.
3063 off: Turn realloc off
3064 on: Turn realloc on
3065 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01003066 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06003067 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3068 only look for one device below a PCIe downstream
3069 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003070
Chuck Ebberte5665a42008-09-24 20:40:34 -04003071 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3072 Management.
3073 off Disable ASPM.
3074 force Enable ASPM even on devices that claim not to support it.
3075 WARNING: Forcing ASPM on may cause system lockups.
3076
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05003077 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3078 nomsi Do not use MSI for PCI Express Native Hotplug (this
3079 makes all PCIe ports use INTx for hotplug services).
3080
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003081 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003082 auto Ask the BIOS whether or not to use native PCIe services
3083 associated with PCIe ports (PME, hot-plug, AER). Use
3084 them only if that is allowed by the BIOS.
3085 native Use native PCIe services associated with PCIe ports
3086 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003087 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3088 ports driver.
3089
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03003090 pcie_port_pm= [PCIE] PCIe port power management handling:
3091 off Disable power management of all PCIe ports
3092 force Forcibly enable power management of all PCIe ports
3093
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003094 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003095 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003096 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003097
Linus Torvalds1da177e2005-04-16 15:20:36 -07003098 pcmv= [HW,PCMCIA] BadgePAD 4
3099
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303100 pd_ignore_unused
3101 [PM]
3102 Keep all power-domains already enabled by bootloader on,
3103 even if no driver has claimed them. This is useful
3104 for debug and development, but should not be
3105 needed on a platform with proper driver support.
3106
Linus Torvalds1da177e2005-04-16 15:20:36 -07003107 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003108 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003109
3110 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3111 boot time.
3112 Format: { 0 | 1 }
3113 See arch/parisc/kernel/pdc_chassis.c
3114
Tejun Heof58dc012009-08-14 15:00:50 +09003115 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003116 Currently supported values are "embed" and "page".
3117 Archs may support subset or none of the selections.
3118 See comments in mm/percpu.c for details on each
3119 allocator. This parameter is primarily for debugging
3120 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003121
Linus Torvalds1da177e2005-04-16 15:20:36 -07003122 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003123 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003124
3125 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003126 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003127
3128 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003129 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003130
3131 plip= [PPT,NET] Parallel port network link
3132 Format: { parport<nr> | timid | 0 }
3133 See also Documentation/parport.txt.
3134
Randy Dunlap16290242011-08-13 12:34:52 -07003135 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003136 Override pmtimer IOPort with a hex value.
3137 e.g. pmtmr=0x508
3138
Bjorn Helgaas96242112011-08-11 12:14:05 -06003139 pnp.debug=1 [PNP]
3140 Enable PNP debug messages (depends on the
3141 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3142 via /sys/module/pnp/parameters/debug. We always show
3143 current resource usage; turning this on also shows
3144 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003145
Linus Torvalds1da177e2005-04-16 15:20:36 -07003146 pnpacpi= [ACPI]
3147 { off }
3148
3149 pnpbios= [ISAPNP]
3150 { on | off | curr | res | no-curr | no-res }
3151
3152 pnp_reserve_irq=
3153 [ISAPNP] Exclude IRQs for the autoconfiguration
3154
3155 pnp_reserve_dma=
3156 [ISAPNP] Exclude DMAs for the autoconfiguration
3157
3158 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003159 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003160
3161 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003162 [ISAPNP] Exclude memory regions for the
3163 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003164 Ranges are in pairs (memory base and size).
3165
Randy Dunlap4af94f32009-04-17 18:30:28 -07003166 ports= [IP_VS_FTP] IPVS ftp helper module
3167 Default is 21.
3168 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3169 may be specified.
3170 Format: <port>,<port>....
3171
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003172 ppc_strict_facility_enable
3173 [PPC] This option catches any kernel floating point,
3174 Altivec, VSX and SPE outside of regions specifically
3175 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3176 There is some performance impact when enabling this.
3177
Ingo Molnar45807a12007-07-15 23:40:10 -07003178 print-fatal-signals=
3179 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003180
3181 If enabled, warn about various signal handling
3182 related application anomalies: too many signals,
3183 too many POSIX.1 timers, fatal signals causing a
3184 coredump - etc.
3185
3186 If you hit the warning due to signal overflow,
3187 you might want to try "ulimit -i unlimited".
3188
Ingo Molnar45807a12007-07-15 23:40:10 -07003189 default: off.
3190
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003191 printk.always_kmsg_dump=
3192 Trigger kmsg_dump for cases other than kernel oops or
3193 panics
3194 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3195 default: disabled
3196
Borislav Petkov750afe72016-08-02 14:04:07 -07003197 printk.devkmsg={on,off,ratelimit}
3198 Control writing to /dev/kmsg.
3199 on - unlimited logging to /dev/kmsg from userspace
3200 off - logging to /dev/kmsg disabled
3201 ratelimit - ratelimit the logging
3202 Default: ratelimit
3203
Randy Dunlape84845c2007-07-15 23:40:25 -07003204 printk.time= Show timing data prefixed to each printk message line
3205 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3206
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003207 processor.max_cstate= [HW,ACPI]
3208 Limit processor to maximum C-state
3209 max_cstate=9 overrides any DMI blacklist limit.
3210
3211 processor.nocst [HW,ACPI]
3212 Ignore the _CST method to determine C-states,
3213 instead using the legacy FADT method
3214
Linus Torvalds1da177e2005-04-16 15:20:36 -07003215 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003216 Format: [schedule,]<number>
3217 Param: "schedule" - profile schedule points.
3218 Param: <number> - step/bucket size as a power of 2 for
3219 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003220 Param: "sleep" - profile D-state sleeping (millisecs).
3221 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003222 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003223
Linus Torvalds1da177e2005-04-16 15:20:36 -07003224 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3225 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003226 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003227
Randy Dunlapa9913042005-10-23 12:57:11 -07003228 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3229 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003230 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3231 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003232 psmouse.resetafter= [HW,MOUSE]
3233 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003234 (0 = never).
3235 psmouse.resolution=
3236 [HW,MOUSE] Set desired mouse resolution, in dpi.
3237 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003238 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003239 0 = disabled, 1 = enabled (default).
3240
Matthew Garrettdee28e72011-07-21 16:57:55 -04003241 pstore.backend= Specify the name of the pstore backend to use
3242
Linus Torvalds1da177e2005-04-16 15:20:36 -07003243 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003244 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003245
Kay Sieversdc8c8582007-08-15 12:25:38 +02003246 pty.legacy_count=
3247 [KNL] Number of legacy pty's. Overwrites compiled-in
3248 default number.
3249
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003250 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003251
Linus Torvalds1da177e2005-04-16 15:20:36 -07003252 r128= [HW,DRM]
3253
3254 raid= [HW,RAID]
3255 See Documentation/md.txt.
3256
Linus Torvalds1da177e2005-04-16 15:20:36 -07003257 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003258 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003259
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003260 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003261 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3262 the specified list of CPUs to be no-callback CPUs.
3263 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003264 be offloaded to "rcuox/N" kthreads created for
3265 that purpose, where "x" is "b" for RCU-bh, "p"
3266 for RCU-preempt, and "s" for RCU-sched, and "N"
3267 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003268 offloaded CPUs, which can be useful for HPC and
3269 real-time workloads. It can also improve energy
3270 efficiency for asymmetric multiprocessors.
3271
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003272 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003273 Rather than requiring that offloaded CPUs
3274 (specified by rcu_nocbs= above) explicitly
3275 awaken the corresponding "rcuoN" kthreads,
3276 make these kthreads poll for callbacks.
3277 This improves the real-time response for the
3278 offloaded CPUs by relieving them of the need to
3279 wake up the corresponding kthread, but degrades
3280 energy efficiency by requiring that the kthreads
3281 periodically wake up to do the polling.
3282
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003283 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003284 Set maximum number of finished RCU callbacks to
3285 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003286
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003287 rcutree.dump_tree= [KNL]
3288 Dump the structure of the rcu_node combining tree
3289 out at early boot. This is used for diagnostic
3290 purposes, to verify correct tree setup.
3291
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003292 rcutree.gp_cleanup_delay= [KNL]
3293 Set the number of jiffies to delay each step of
3294 RCU grace-period cleanup. This only has effect
3295 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3296
Paul E. McKenney37745d22015-01-22 18:24:08 -08003297 rcutree.gp_init_delay= [KNL]
3298 Set the number of jiffies to delay each step of
3299 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003300 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3301 is set.
3302
3303 rcutree.gp_preinit_delay= [KNL]
3304 Set the number of jiffies to delay each step of
3305 RCU grace-period pre-initialization, that is,
3306 the propagation of recent CPU-hotplug changes up
3307 the rcu_node combining tree. This only has effect
3308 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003309
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003310 rcutree.rcu_fanout_exact= [KNL]
3311 Disable autobalancing of the rcu_node combining
3312 tree. This is used by rcutorture, and might
3313 possibly be useful for architectures having high
3314 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003315
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003316 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003317 Change the number of CPUs assigned to each
3318 leaf rcu_node structure. Useful for very
3319 large systems, which will choose the value 64,
3320 and for NUMA systems with large remote-access
3321 latencies, which will choose a value aligned
3322 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003323
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003324 rcutree.jiffies_till_sched_qs= [KNL]
3325 Set required age in jiffies for a
3326 given grace period before RCU starts
3327 soliciting quiescent-state help from
3328 rcu_note_context_switch().
3329
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003330 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003331 Set delay from grace-period initialization to
3332 first attempt to force quiescent states.
3333 Units are jiffies, minimum value is zero,
3334 and maximum value is HZ.
3335
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003336 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003337 Set delay between subsequent attempts to force
3338 quiescent states. Units are jiffies, minimum
3339 value is one, and maximum value is HZ.
3340
Clark Williams21871d72014-09-12 21:21:09 -05003341 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003342 Set the SCHED_FIFO priority of the RCU per-CPU
3343 kthreads (rcuc/N). This value is also used for
3344 the priority of the RCU boost threads (rcub/N)
3345 and for the RCU grace-period kthreads (rcu_bh,
3346 rcu_preempt, and rcu_sched). If RCU_BOOST is
3347 set, valid values are 1-99 and the default is 1
3348 (the least-favored priority). Otherwise, when
3349 RCU_BOOST is not set, valid values are 0-99 and
3350 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003351
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003352 rcutree.rcu_nocb_leader_stride= [KNL]
3353 Set the number of NOCB kthread groups, which
3354 defaults to the square root of the number of
3355 CPUs. Larger numbers reduces the wakeup overhead
3356 on the per-CPU grace-period kthreads, but increases
3357 that same overhead on each group's leader.
3358
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003359 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003360 Set threshold of queued RCU callbacks beyond which
3361 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003362
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003363 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003364 Set threshold of queued RCU callbacks below which
3365 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003366
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003367 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003368 Set wakeup interval for idle CPUs that have
3369 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003370
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003371 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003372 Set wakeup interval for idle CPUs that have
3373 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3374 Lazy RCU callbacks are those which RCU can
3375 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003376
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003377 rcuperf.gp_exp= [KNL]
3378 Measure performance of expedited synchronous
3379 grace-period primitives.
3380
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003381 rcuperf.holdoff= [KNL]
3382 Set test-start holdoff period. The purpose of
3383 this parameter is to delay the start of the
3384 test until boot completes in order to avoid
3385 interference.
3386
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003387 rcuperf.nreaders= [KNL]
3388 Set number of RCU readers. The value -1 selects
3389 N, where N is the number of CPUs. A value
3390 "n" less than -1 selects N-n+1, where N is again
3391 the number of CPUs. For example, -2 selects N
3392 (the number of CPUs), -3 selects N+1, and so on.
3393 A value of "n" less than or equal to -N selects
3394 a single reader.
3395
3396 rcuperf.nwriters= [KNL]
3397 Set number of RCU writers. The values operate
3398 the same as for rcuperf.nreaders.
3399 N, where N is the number of CPUs
3400
3401 rcuperf.perf_runnable= [BOOT]
3402 Start rcuperf running at boot time.
3403
3404 rcuperf.shutdown= [KNL]
3405 Shut the system down after performance tests
3406 complete. This is useful for hands-off automated
3407 testing.
3408
3409 rcuperf.perf_type= [KNL]
3410 Specify the RCU implementation to test.
3411
3412 rcuperf.verbose= [KNL]
3413 Enable additional printk() statements.
3414
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003415 rcutorture.cbflood_inter_holdoff= [KNL]
3416 Set holdoff time (jiffies) between successive
3417 callback-flood tests.
3418
3419 rcutorture.cbflood_intra_holdoff= [KNL]
3420 Set holdoff time (jiffies) between successive
3421 bursts of callbacks within a given callback-flood
3422 test.
3423
3424 rcutorture.cbflood_n_burst= [KNL]
3425 Set the number of bursts making up a given
3426 callback-flood test. Set this to zero to
3427 disable callback-flood testing.
3428
3429 rcutorture.cbflood_n_per_burst= [KNL]
3430 Set the number of callbacks to be registered
3431 in a given burst of a callback-flood test.
3432
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003433 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003434 Set duration of force_quiescent_state bursts
3435 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003436
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003437 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003438 Set holdoff time within force_quiescent_state bursts
3439 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003440
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003441 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003442 Set wait time between force_quiescent_state bursts
3443 in seconds.
3444
3445 rcutorture.gp_cond= [KNL]
3446 Use conditional/asynchronous update-side
3447 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003448
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003449 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003450 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003451
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003452 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003453 Use normal (non-expedited) asynchronous
3454 update-side primitives, if available.
3455
3456 rcutorture.gp_sync= [KNL]
3457 Use normal (non-expedited) synchronous
3458 update-side primitives, if available. If all
3459 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3460 rcutorture.gp_normal=, and rcutorture.gp_sync=
3461 are zero, rcutorture acts as if is interpreted
3462 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003463
3464 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003465 Set callbacks/threads for rcu_barrier() testing.
3466
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003467 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003468 Set number of concurrent RCU writers. These just
3469 stress RCU, they don't participate in the actual
3470 test, hence the "fake".
3471
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003472 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003473 Set number of RCU readers. The value -1 selects
3474 N-1, where N is the number of CPUs. A value
3475 "n" less than -1 selects N-n-2, where N is again
3476 the number of CPUs. For example, -2 selects N
3477 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003478
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003479 rcutorture.object_debug= [KNL]
3480 Enable debug-object double-call_rcu() testing.
3481
3482 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003483 Set time (s) after boot for CPU-hotplug testing.
3484
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003485 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003486 Set time (s) between CPU-hotplug operations, or
3487 zero to disable CPU-hotplug testing.
3488
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003489 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003490 Set task-shuffle interval (s). Shuffling tasks
3491 allows some CPUs to go into dyntick-idle mode
3492 during the rcutorture test.
3493
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003494 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003495 Set time (s) after boot system shutdown. This
3496 is useful for hands-off automated testing.
3497
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003498 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003499 Duration of CPU stall (s) to test RCU CPU stall
3500 warnings, zero to disable.
3501
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003502 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003503 Time to wait (s) after boot before inducing stall.
3504
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003505 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003506 Time (s) between statistics printk()s.
3507
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003508 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003509 Time (s) to stutter testing, for example, specifying
3510 five seconds causes the test to run for five seconds,
3511 wait for five seconds, and so on. This tests RCU's
3512 ability to transition abruptly to and from idle.
3513
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003514 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003515 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3516 "Maybe" means test if the RCU implementation
3517 under test support RCU priority boosting.
3518
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003519 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003520 Duration (s) of each individual boost test.
3521
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003522 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003523 Interval (s) between each boost test.
3524
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003525 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003526 Test RCU's dyntick-idle handling. See also the
3527 rcutorture.shuffle_interval parameter.
3528
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003529 rcutorture.torture_runnable= [BOOT]
3530 Start rcutorture running at boot time.
3531
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003532 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003533 Specify the RCU implementation to test.
3534
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003535 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003536 Enable additional printk() statements.
3537
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003538 rcupdate.rcu_cpu_stall_suppress= [KNL]
3539 Suppress RCU CPU stall warning messages.
3540
3541 rcupdate.rcu_cpu_stall_timeout= [KNL]
3542 Set timeout for RCU CPU stall warning messages.
3543
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003544 rcupdate.rcu_expedited= [KNL]
3545 Use expedited grace-period primitives, for
3546 example, synchronize_rcu_expedited() instead
3547 of synchronize_rcu(). This reduces latency,
3548 but can increase CPU utilization, degrade
3549 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003550 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003551
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003552 rcupdate.rcu_normal= [KNL]
3553 Use only normal grace-period primitives,
3554 for example, synchronize_rcu() instead of
3555 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003556 real-time latency, CPU utilization, and
3557 energy efficiency, but can expose users to
3558 increased grace-period latency. This parameter
3559 overrides rcupdate.rcu_expedited. No effect on
3560 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003561
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003562 rcupdate.rcu_normal_after_boot= [KNL]
3563 Once boot has completed (that is, after
3564 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003565 only normal grace-period primitives. No effect
3566 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003567
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003568 rcupdate.rcu_task_stall_timeout= [KNL]
3569 Set timeout in jiffies for RCU task stall warning
3570 messages. Disable with a value less than or equal
3571 to zero.
3572
Pranith Kumar74860fe2014-09-19 11:34:09 -04003573 rcupdate.rcu_self_test= [KNL]
3574 Run the RCU early boot self tests
3575
3576 rcupdate.rcu_self_test_bh= [KNL]
3577 Run the RCU bh early boot self tests
3578
3579 rcupdate.rcu_self_test_sched= [KNL]
3580 Run the RCU sched early boot self tests
3581
Olof Johanssonffdfc402005-09-06 15:17:19 -07003582 rdinit= [KNL]
3583 Format: <full_path>
3584 Run specified binary instead of /init from the ramdisk,
3585 used for early userspace startup. See initrd.
3586
Robin Holt1b3a5d02013-07-08 16:01:42 -07003587 reboot= [KNL]
3588 Format (x86 or x86_64):
3589 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3590 [[,]s[mp]#### \
3591 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3592 [[,]f[orce]
3593 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3594 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3595 reboot_force is either force or not specified,
3596 reboot_cpu is s[mp]#### with #### being the processor
3597 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003598
Paul Jackson46b6d942008-07-04 10:00:09 -07003599 relax_domain_level=
3600 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003601 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003602
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003603 relative_sleep_states=
3604 [SUSPEND] Use sleep state labeling where the deepest
3605 state available other than hibernation is always "mem".
3606 Format: { "0" | "1" }
3607 0 -- Traditional sleep state labels.
3608 1 -- Relative sleep state labels.
3609
Linus Torvalds1da177e2005-04-16 15:20:36 -07003610 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3611
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003612 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003613 Format: nn[KMG]
3614 Reserves a hole at the top of the kernel virtual
3615 address space.
3616
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003617 reservelow= [X86]
3618 Format: nn[K]
3619 Set the amount of memory to reserve for BIOS at
3620 the bottom of the address space.
3621
Vivek Goyal7e962872006-09-27 01:50:44 -07003622 reset_devices [KNL] Force drivers to reset the underlying device
3623 during initialization.
3624
Randy Dunlapa9913042005-10-23 12:57:11 -07003625 resume= [SWSUSP]
3626 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003627 Format:
3628 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003629
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003630 resume_offset= [SWSUSP]
3631 Specify the offset from the beginning of the partition
3632 given by "resume=" at which the swap header is located,
3633 in <PAGE_SIZE> units (needed only for swap files).
3634 See Documentation/power/swsusp-and-swap-files.txt
3635
Barry Songf126f732011-10-10 23:38:41 +02003636 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3637 read the resume files
3638
Barry Song6f8d7022011-10-06 20:34:46 +02003639 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3640 Useful for devices that are detected asynchronously
3641 (e.g. USB and MMC devices).
3642
Bojan Smojverf996fc92010-09-09 23:06:23 +02003643 hibernate= [HIBERNATION]
3644 noresume Don't check if there's a hibernation image
3645 present during boot.
3646 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003647 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003648 protect_image Turn on image protection during restoration
3649 (that will set all pages holding image data
3650 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003651
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003652 retain_initrd [RAM] Keep initrd memory after extraction
3653
Andrew Clausen0efbb782015-01-09 20:24:55 +00003654 rfkill.default_state=
3655 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3656 etc. communication is blocked by default.
3657 1 Unblocked.
3658
3659 rfkill.master_switch_mode=
3660 0 The "airplane mode" button does nothing.
3661 1 The "airplane mode" button toggles between everything
3662 blocked and the previous configuration.
3663 2 The "airplane mode" button toggles between everything
3664 blocked and everything unblocked.
3665
Linus Torvalds1da177e2005-04-16 15:20:36 -07003666 rhash_entries= [KNL,NET]
3667 Set number of hash buckets for route cache
3668
Linus Torvalds1da177e2005-04-16 15:20:36 -07003669 ro [KNL] Mount root device read-only on boot
3670
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003671 rodata= [KNL]
3672 on Mark read-only kernel memory as read-only (default).
3673 off Leave read-only kernel memory writable for debugging.
3674
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003675 rockchip.usb_uart
3676 Enable the uart passthrough on the designated usb port
3677 on Rockchip SoCs. When active, the signals of the
3678 debug-uart get routed to the D+ and D- pins of the usb
3679 port and the regular usb controller gets disabled.
3680
Linus Torvalds1da177e2005-04-16 15:20:36 -07003681 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003682 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003683
3684 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3685 mount the root filesystem
3686
3687 rootflags= [KNL] Set root filesystem mount option string
3688
3689 rootfstype= [KNL] Set root filesystem type
3690
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003691 rootwait [KNL] Wait (indefinitely) for root device to show up.
3692 Useful for devices that are detected asynchronously
3693 (e.g. USB and MMC devices).
3694
Robert Tivy5c71d612013-03-28 18:41:46 -07003695 rproc_mem=nn[KMG][@address]
3696 [KNL,ARM,CMA] Remoteproc physical memory block.
3697 Memory area to be used by remote processor image,
3698 managed by CMA.
3699
Linus Torvalds1da177e2005-04-16 15:20:36 -07003700 rw [KNL] Mount root device read-write on boot
3701
3702 S [KNL] Run init in single mode
3703
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003704 s390_iommu= [HW,S390]
3705 Set s390 IOTLB flushing mode
3706 strict
3707 With strict flushing every unmap operation will result in
3708 an IOTLB flush. Default is lazy flushing before reuse,
3709 which is faster.
3710
Linus Torvalds1da177e2005-04-16 15:20:36 -07003711 sa1100ir [NET]
3712 See drivers/net/irda/sa1100_ir.c.
3713
Linus Torvalds1da177e2005-04-16 15:20:36 -07003714 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003715
Mike Travisf6630112009-11-17 18:22:15 -06003716 sched_debug [KNL] Enables verbose scheduler debug messages.
3717
Mel Gormancb251762016-02-05 09:08:36 +00003718 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3719 Allowed values are enable and disable. This feature
3720 incurs a small amount of overhead in the scheduler
3721 but is useful for debugging and performance tuning.
3722
Mike Galbraith5307c952012-05-08 12:20:58 +02003723 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3724 xtime_lock contention on larger systems, and/or RCU lock
3725 contention on all systems with CONFIG_MAXSMP set.
3726 Format: { "0" | "1" }
3727 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3728 1 -- enable.
3729 Note: increases power consumption, thus should only be
3730 enabled if running jitter sensitive (HPC/RT) workloads.
3731
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003732 security= [SECURITY] Choose a security module to enable at boot.
3733 If this boot parameter is not specified, only the first
3734 security module asking for security registration will be
3735 loaded. An invalid security module name will be treated
3736 as if no module has been chosen.
3737
3738 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003739 Format: { "0" | "1" }
3740 See security/selinux/Kconfig help text.
3741 0 -- disable.
3742 1 -- enable.
3743 Default value is set via kernel config option.
3744 If enabled at boot time, /selinux/disable can be used
3745 later to disable prior to initial policy load.
3746
John Johansenc1c124e2010-07-29 14:48:09 -07003747 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3748 Format: { "0" | "1" }
3749 See security/apparmor/Kconfig help text
3750 0 -- disable.
3751 1 -- enable.
3752 Default value is set via kernel config option.
3753
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003754 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003755
Linus Torvalds1da177e2005-04-16 15:20:36 -07003756 shapers= [NET]
3757 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003758
Yinghai Lub05f78f2008-08-22 01:32:50 -07003759 show_msr= [x86] show boot-time MSR settings
3760 Format: { <integer> }
3761 Show boot-time (BIOS-initialized) MSR settings.
3762 The parameter means the number of CPUs to show,
3763 for example 1 means boot CPU only.
3764
Linus Torvalds1da177e2005-04-16 15:20:36 -07003765 simeth= [IA-64]
3766 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003767
Linus Torvalds1da177e2005-04-16 15:20:36 -07003768 slram= [HW,MTD]
3769
Joonsoo Kim423c9292014-10-09 15:26:22 -07003770 slab_nomerge [MM]
3771 Disable merging of slabs with similar size. May be
3772 necessary if there is some reason to distinguish
3773 allocs to different slabs. Debug options disable
3774 merging on their own.
3775 For more information see Documentation/vm/slub.txt.
3776
David Rientjes3df1ccc2011-10-18 22:09:28 -07003777 slab_max_order= [MM, SLAB]
3778 Determines the maximum allowed order for slabs.
3779 A high setting may cause OOMs due to memory
3780 fragmentation. Defaults to 1 for systems with
3781 more than 32MB of RAM, 0 otherwise.
3782
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003783 slub_debug[=options[,slabs]] [MM, SLUB]
3784 Enabling slub_debug allows one to determine the
3785 culprit if slab objects become corrupted. Enabling
3786 slub_debug can create guard zones around objects and
3787 may poison objects when not in use. Also tracks the
3788 last alloc / free. For more information see
3789 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003790
3791 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003792 Determines the maximum allowed order for slabs.
3793 A high setting may cause OOMs due to memory
3794 fragmentation. For more information see
3795 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003796
3797 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003798 The minimum number of objects per slab. SLUB will
3799 increase the slab order up to slub_max_order to
3800 generate a sufficiently large slab able to contain
3801 the number of objects indicated. The higher the number
3802 of objects the smaller the overhead of tracking slabs
3803 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003804 For more information see Documentation/vm/slub.txt.
3805
3806 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003807 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003808 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003809 For more information see Documentation/vm/slub.txt.
3810
3811 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003812 Same with slab_nomerge. This is supported for legacy.
3813 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003814
Linus Torvalds1da177e2005-04-16 15:20:36 -07003815 smart2= [HW]
3816 Format: <io1>[,<io2>[,...,<io8>]]
3817
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003818 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3819 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3820 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3821 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3822 smsc-ircc2.ircc_irq= [HW] IRQ line
3823 smsc-ircc2.ircc_dma= [HW] DMA channel
3824 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3825 0: Toshiba Satellite 1800 (GP data pin select)
3826 1: Fast pin select (default)
3827 2: ATC IRMode
3828
Sascha Silbe52c48c52016-04-05 12:53:38 +02003829 smt [KNL,S390] Set the maximum number of threads (logical
3830 CPUs) to use per physical CPU on systems capable of
3831 symmetric multithreading (SMT). Will be capped to the
3832 actual hardware limit.
3833 Format: <integer>
3834 Default: -1 (no limit)
3835
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003836 softlockup_panic=
3837 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003838 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003839
Aaron Tomlined235872014-06-23 13:22:05 -07003840 softlockup_all_cpu_backtrace=
3841 [KNL] Should the soft-lockup detector generate
3842 backtraces on all cpus.
3843 Format: <integer>
3844
Linus Torvalds1da177e2005-04-16 15:20:36 -07003845 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003846 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003847
Linus Torvalds1da177e2005-04-16 15:20:36 -07003848 spia_io_base= [HW,MTD]
3849 spia_fio_base=
3850 spia_pedr=
3851 spia_peddr=
3852
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003853 stacktrace [FTRACE]
3854 Enabled the stack tracer on boot up.
3855
Steven Rostedt762e1202011-12-19 22:01:00 -05003856 stacktrace_filter=[function-list]
3857 [FTRACE] Limit the functions that the stack tracer
3858 will trace at boot up. function-list is a comma separated
3859 list of functions. This list can be changed at run
3860 time by the stack_trace_filter file in the debugfs
3861 tracing directory. Note, this enables stack tracing
3862 and the stacktrace above is not needed.
3863
Linus Torvalds1da177e2005-04-16 15:20:36 -07003864 sti= [PARISC,HW]
3865 Format: <num>
3866 Set the STI (builtin display/keyboard on the HP-PARISC
3867 machines) console (graphic card) which should be used
3868 as the initial boot-console.
3869 See also comment in drivers/video/console/sticore.c.
3870
3871 sti_font= [HW]
3872 See comment in drivers/video/console/sticore.c.
3873
3874 stifb= [HW]
3875 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3876
Trond Myklebustcbf11072009-08-09 15:06:19 -04003877 sunrpc.min_resvport=
3878 sunrpc.max_resvport=
3879 [NFS,SUNRPC]
3880 SunRPC servers often require that client requests
3881 originate from a privileged port (i.e. a port in the
3882 range 0 < portnr < 1024).
3883 An administrator who wishes to reserve some of these
3884 ports for other uses may adjust the range that the
3885 kernel's sunrpc client considers to be privileged
3886 using these two parameters to set the minimum and
3887 maximum port values.
3888
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003889 sunrpc.svc_rpc_per_connection_limit=
3890 [NFS,SUNRPC]
3891 Limit the number of requests that the server will
3892 process in parallel from a single connection.
3893 The default value is 0 (no limit).
3894
Greg Banks42a7fc42007-03-06 01:42:23 -08003895 sunrpc.pool_mode=
3896 [NFS]
3897 Control how the NFS server code allocates CPUs to
3898 service thread pools. Depending on how many NICs
3899 you have and where their interrupts are bound, this
3900 option will affect which CPUs will do NFS serving.
3901 Note: this parameter cannot be changed while the
3902 NFS server is running.
3903
3904 auto the server chooses an appropriate mode
3905 automatically using heuristics
3906 global a single global pool contains all CPUs
3907 percpu one pool for each CPU
3908 pernode one pool for each NUMA node (equivalent
3909 to global on non-NUMA machines)
3910
Trond Myklebustcbf11072009-08-09 15:06:19 -04003911 sunrpc.tcp_slot_table_entries=
3912 sunrpc.udp_slot_table_entries=
3913 [NFS,SUNRPC]
3914 Sets the upper limit on the number of simultaneous
3915 RPC calls that can be sent from the client to a
3916 server. Increasing these values may allow you to
3917 improve throughput, but will also increase the
3918 amount of memory reserved for use by the client.
3919
Brian Norris1d4a9c12015-02-22 21:16:49 -08003920 suspend.pm_test_delay=
3921 [SUSPEND]
3922 Sets the number of seconds to remain in a suspend test
3923 mode before resuming the system (see
3924 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3925 is set. Default value is 5.
3926
Michal Hocko07555ac2013-08-22 16:35:46 -07003927 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003928 [KNL] Enable accounting of swap in memory resource
3929 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003930 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08003931
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003932 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3933 Format: { <int> | force }
3934 <int> -- Number of I/O TLB slabs
3935 force -- force using of bounce buffers even if they
3936 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003937
Linus Torvalds1da177e2005-04-16 15:20:36 -07003938 switches= [HW,M68k]
3939
Andi Kleene52eec12010-09-08 16:54:17 +02003940 sysfs.deprecated=0|1 [KNL]
3941 Enable/disable old style sysfs layout for old udev
3942 on older distributions. When this option is enabled
3943 very new udev will not work anymore. When this option
3944 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3945 in older udev will not work anymore.
3946 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3947 the kernel configuration.
3948
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003949 sysrq_always_enabled
3950 [KNL]
3951 Ignore sysrq setting - this boot parameter will
3952 neutralize any effect of /proc/sys/kernel/sysrq.
3953 Useful for debugging.
3954
Fabian Frederick747029a2014-11-06 19:46:50 +01003955 tcpmhash_entries= [KNL,NET]
3956 Set the number of tcp_metrics_hash slots.
3957 Default value is 8192 or 16384 depending on total
3958 ram pages. This is used to specify the TCP metrics
3959 cache size. See Documentation/networking/ip-sysctl.txt
3960 "tcp_no_metrics_save" section for more details.
3961
Linus Torvalds1da177e2005-04-16 15:20:36 -07003962 tdfx= [HW,DRM]
3963
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003964 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003965 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003966 standby suspend) or "freeze" (for suspend type freeze)
3967 as the system sleep state during system startup with
3968 the optional capability to repeat N number of times.
3969 The system is woken from this state using a
3970 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003971
Linus Torvalds1da177e2005-04-16 15:20:36 -07003972 thash_entries= [KNL,NET]
3973 Set number of hash buckets for TCP connection
3974
Len Brownf8707ec2007-08-12 00:12:54 -04003975 thermal.act= [HW,ACPI]
3976 -1: disable all active trip points in all thermal zones
3977 <degrees C>: override all lowest active trip points
3978
Len Brownc52a7412007-08-14 15:49:32 -04003979 thermal.crt= [HW,ACPI]
3980 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003981 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003982
Len Brownf5487142007-08-12 00:12:44 -04003983 thermal.nocrt= [HW,ACPI]
3984 Set to disable actions on ACPI thermal zone
3985 critical and hot trip points.
3986
Len Brown72b33ef2007-08-12 00:12:17 -04003987 thermal.off= [HW,ACPI]
3988 1: disable ACPI thermal control
3989
Len Browna70cdc52007-08-12 00:12:35 -04003990 thermal.psv= [HW,ACPI]
3991 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003992 <degrees C>: override all passive trip points to this
3993 value
Len Browna70cdc52007-08-12 00:12:35 -04003994
Len Brown730ff342007-08-12 00:12:26 -04003995 thermal.tzp= [HW,ACPI]
3996 Specify global default ACPI thermal zone polling rate
3997 <deci-seconds>: poll all this frequency
3998 0: no polling (default)
3999
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004000 threadirqs [KNL]
4001 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09004002 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004003
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004004 tmem [KNL,XEN]
4005 Enable the Transcendent memory driver if built-in.
4006
4007 tmem.cleancache=0|1 [KNL, XEN]
4008 Default is on (1). Disable the usage of the cleancache
4009 API to send anonymous pages to the hypervisor.
4010
4011 tmem.frontswap=0|1 [KNL, XEN]
4012 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04004013 API to send swap pages to the hypervisor. If disabled
4014 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004015
4016 tmem.selfballooning=0|1 [KNL, XEN]
4017 Default is on (1). Disable the driving of swap pages
4018 to the hypervisor.
4019
4020 tmem.selfshrinking=0|1 [KNL, XEN]
4021 Default is on (1). Partial swapoff that immediately
4022 transfers pages from Xen hypervisor back to the
4023 kernel based on different criteria.
4024
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004025 topology= [S390]
4026 Format: {off | on}
4027 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07004028 topology information if the hardware supports this.
4029 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004030 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02004031 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004032
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07004033 topology_updates= [KNL, PPC, NUMA]
4034 Format: {off}
4035 Specify if the kernel should ignore (off)
4036 topology updates sent by the hypervisor to this
4037 LPAR.
4038
Linus Torvalds1da177e2005-04-16 15:20:36 -07004039 tp720= [HW,PS2]
4040
Rajiv Andrade225a9be2010-03-25 00:55:32 -03004041 tpm_suspend_pcr=[HW,TPM]
4042 Format: integer pcr id
4043 Specify that at suspend time, the tpm driver
4044 should extend the specified pcr with zeros,
4045 as a workaround for some chips which fail to
4046 flush the last written pcr on TPM_SaveState.
4047 This will guarantee that all the other pcrs
4048 are saved.
4049
Li Zefan9d612be2009-06-24 17:33:15 +08004050 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09004051 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09004052
Li Zefan020e5f82009-07-01 10:47:05 +08004053 trace_event=[event-list]
4054 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07004055 to facilitate early boot debugging. The event-list is a
4056 comma separated list of trace events to enable. See
4057 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08004058
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04004059 trace_options=[option-list]
4060 [FTRACE] Enable or disable tracer options at boot.
4061 The option-list is a comma delimited list of options
4062 that can be enabled or disabled just as if you were
4063 to echo the option name into
4064
4065 /sys/kernel/debug/tracing/trace_options
4066
4067 For example, to enable stacktrace option (to dump the
4068 stack trace of each event), add to the command line:
4069
4070 trace_options=stacktrace
4071
4072 See also Documentation/trace/ftrace.txt "trace options"
4073 section.
4074
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05004075 tp_printk[FTRACE]
4076 Have the tracepoints sent to printk as well as the
4077 tracing ring buffer. This is useful for early boot up
4078 where the system hangs or reboots and does not give the
4079 option for reading the tracing buffer or performing a
4080 ftrace_dump_on_oops.
4081
4082 To turn off having tracepoints sent to printk,
4083 echo 0 > /proc/sys/kernel/tracepoint_printk
4084 Note, echoing 1 into this file without the
4085 tracepoint_printk kernel cmdline option has no effect.
4086
4087 ** CAUTION **
4088
4089 Having tracepoints sent to printk() and activating high
4090 frequency tracepoints such as irq or sched, can cause
4091 the system to live lock.
4092
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004093 traceoff_on_warning
4094 [FTRACE] enable this option to disable tracing when a
4095 warning is hit. This turns off "tracing_on". Tracing can
4096 be enabled again by echoing '1' into the "tracing_on"
4097 file located in /sys/kernel/debug/tracing/
4098
4099 This option is useful, as it disables the trace before
4100 the WARNING dump is called, which prevents the trace to
4101 be filled with content caused by the warning output.
4102
4103 This option can also be set at run time via the sysctl
4104 option: kernel/traceoff_on_warning
4105
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004106 transparent_hugepage=
4107 [KNL]
4108 Format: [always|madvise|never]
4109 Can be used to control the default behavior of the system
4110 with respect to transparent hugepages.
4111 See Documentation/vm/transhuge.txt for more details.
4112
john stultzd3b8f882009-08-17 16:40:47 -07004113 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004114 Format: <string>
4115 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004116 disables clocksource verification at runtime, as well
4117 as the stability checks done at bootup. Used to enable
4118 high-resolution timer mode on older hardware, and in
4119 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004120 [x86] noirqtime: Do not use TSC to do irq accounting.
4121 Used to run time disable IRQ_TIME_ACCOUNTING on any
4122 platforms where RDTSC is slow and this accounting
4123 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004124
Randy Dunlapa9913042005-10-23 12:57:11 -07004125 turbografx.map[2|3]= [HW,JOY]
4126 TurboGraFX parallel port interface
4127 Format:
4128 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004129 See also Documentation/input/joystick-parport.txt
4130
Christian Kujaub6935f82011-05-31 15:22:05 +00004131 udbg-immortal [PPC] When debugging early kernel crashes that
4132 happen after console_init() and before a proper
4133 console driver takes over, this boot options might
4134 help "seeing" what's going on.
4135
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004136 uhash_entries= [KNL,NET]
4137 Set number of hash buckets for UDP/UDP-Lite connections
4138
Alan Stern5f8364b2006-12-05 16:29:55 -05004139 uhci-hcd.ignore_oc=
4140 [USB] Ignore overcurrent events (default N).
4141 Some badly-designed motherboards generate lots of
4142 bogus events, for ports that aren't wired to
4143 anything. Set this parameter to avoid log spamming.
4144 Note that genuine overcurrent events won't be
4145 reported either.
4146
Simon Arlotte3a61b02008-07-19 23:32:54 +01004147 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004148 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004149
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004150 usbcore.authorized_default=
4151 [USB] Default USB device authorization:
4152 (default -1 = authorized except for wireless USB,
4153 0 = not authorized, 1 = authorized)
4154
Alan Sternb5e795f2007-02-20 15:00:53 -05004155 usbcore.autosuspend=
4156 [USB] The autosuspend time delay (in seconds) used
4157 for newly-detected USB devices (default 2). This
4158 is the time required before an idle device will be
4159 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004160 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004161
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004162 usbcore.usbfs_snoop=
4163 [USB] Set to log all usbfs traffic (default 0 = off).
4164
Alan Stern0290cc92015-11-20 13:53:22 -05004165 usbcore.usbfs_snoop_max=
4166 [USB] Maximum number of bytes to snoop in each URB
4167 (default = 65536).
4168
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004169 usbcore.blinkenlights=
4170 [USB] Set to cycle leds on hubs (default 0 = off).
4171
4172 usbcore.old_scheme_first=
4173 [USB] Start with the old device initialization
4174 scheme (default 0 = off).
4175
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004176 usbcore.usbfs_memory_mb=
4177 [USB] Memory limit (in MB) for buffers allocated by
4178 usbfs (default = 16, 0 = max = 2047).
4179
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004180 usbcore.use_both_schemes=
4181 [USB] Try the other device initialization scheme
4182 if the first one fails (default 1 = enabled).
4183
4184 usbcore.initial_descriptor_timeout=
4185 [USB] Specifies timeout for the initial 64-byte
4186 USB_REQ_GET_DESCRIPTOR request in milliseconds
4187 (default 5000 = 5.0 seconds).
4188
Oliver Neukum40d58142015-12-03 15:03:32 +01004189 usbcore.nousb [USB] Disable the USB subsystem
4190
Linus Torvalds1da177e2005-04-16 15:20:36 -07004191 usbhid.mousepoll=
4192 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004193
Alan Sternd4f373e2008-11-10 14:07:45 -05004194 usb-storage.delay_use=
4195 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004196 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004197
4198 usb-storage.quirks=
4199 [UMS] A list of quirks entries to supplement or
4200 override the built-in unusual_devs list. List
4201 entries are separated by commas. Each entry has
4202 the form VID:PID:Flags where VID and PID are Vendor
4203 and Product ID values (4-digit hex numbers) and
4204 Flags is a set of characters, each corresponding
4205 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004206 a = SANE_SENSE (collect more than 18 bytes
4207 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004208 b = BAD_SENSE (don't collect more than 18
4209 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004210 c = FIX_CAPACITY (decrease the reported
4211 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004212 d = NO_READ_DISC_INFO (don't use
4213 READ_DISC_INFO command);
4214 e = NO_READ_CAPACITY_16 (don't use
4215 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004216 f = NO_REPORT_OPCODES (don't use report opcodes
4217 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004218 g = MAX_SECTORS_240 (don't transfer more than
4219 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004220 h = CAPACITY_HEURISTICS (decrease the
4221 reported device capacity by one
4222 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004223 i = IGNORE_DEVICE (don't bind to this
4224 device);
Hans de Goede13630742016-04-12 12:27:09 +02004225 j = NO_REPORT_LUNS (don't use report luns
4226 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004227 l = NOT_LOCKABLE (don't try to lock and
4228 unlock ejectable media);
4229 m = MAX_SECTORS_64 (don't transfer more
4230 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004231 n = INITIAL_READ10 (force a retry of the
4232 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004233 o = CAPACITY_OK (accept the capacity
4234 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004235 p = WRITE_CACHE (the device cache is ON
4236 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004237 r = IGNORE_RESIDUE (the device reports
4238 bogus residue values);
4239 s = SINGLE_LUN (the device has only one
4240 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004241 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4242 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004243 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004244 w = NO_WP_DETECT (don't test whether the
4245 medium is write-protected).
4246 Example: quirks=0419:aaf5:rl,0421:0433:rc
4247
Stephen Boydac1667d2011-08-13 12:34:50 -07004248 user_debug= [KNL,ARM]
4249 Format: <int>
4250 See arch/arm/Kconfig.debug help text.
4251 1 - undefined instruction events
4252 2 - system calls
4253 4 - invalid data aborts
4254 8 - SIGSEGV faults
4255 16 - SIGBUS faults
4256 Example: user_debug=31
4257
Ian Campbell14315592010-02-17 10:38:10 +00004258 userpte=
4259 [X86] Flags controlling user PTE allocations.
4260
4261 nohigh = do not allocate PTE pages in
4262 HIGHMEM regardless of setting
4263 of CONFIG_HIGHPTE.
4264
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304265 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004266 On X86_32, this is an alias for vdso32=. Otherwise:
4267
4268 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004269 vdso=0: disable VDSO mapping
4270
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004271 vdso32= [X86] Control the 32-bit vDSO
4272 vdso32=1: enable 32-bit VDSO
4273 vdso32=0 or vdso32=2: disable 32-bit VDSO
4274
4275 See the help text for CONFIG_COMPAT_VDSO for more
4276 details. If CONFIG_COMPAT_VDSO is set, the default is
4277 vdso32=0; otherwise, the default is vdso32=1.
4278
4279 For compatibility with older kernels, vdso32=2 is an
4280 alias for vdso32=0.
4281
4282 Try vdso32=0 if you encounter an error that says:
4283 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004284
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004285 vector= [IA-64,SMP]
4286 vector=percpu: enable percpu vector domain
4287
Linus Torvalds1da177e2005-04-16 15:20:36 -07004288 video= [FB] Frame buffer configuration
4289 See Documentation/fb/modedb.txt.
4290
Aaron Lu3afe6da2013-06-20 15:08:55 +08004291 video.brightness_switch_enabled= [0,1]
4292 If set to 1, on receiving an ACPI notify event
4293 generated by hotkey, video driver will adjust brightness
4294 level and then send out the event to user space through
4295 the allocated input device; If set to 0, video driver
4296 will only send out the event without touching backlight
4297 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004298 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004299
Pawel Moll81a054c2012-05-09 18:30:16 +01004300 virtio_mmio.device=
4301 [VMMIO] Memory mapped virtio (platform) device.
4302
4303 <size>@<baseaddr>:<irq>[:<id>]
4304 where:
4305 <size> := size (can use standard suffixes
4306 like K, M and G)
4307 <baseaddr> := physical base address
4308 <irq> := interrupt number (as passed to
4309 request_irq())
4310 <id> := (optional) platform device id
4311 example:
4312 virtio_mmio.device=1K@0x100b0000:48:7
4313
4314 Can be used multiple times for multiple devices.
4315
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004316 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004317 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004318 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004319 Use vga=ask for menu.
4320 This is actually a boot loader parameter; the value is
4321 passed to the kernel using a special protocol.
4322
Randy Dunlapa9913042005-10-23 12:57:11 -07004323 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004324 size of <nn>. This can be used to increase the
4325 minimum size (128MB on x86). It can also be used to
4326 decrease the size and leave more room for directly
4327 mapped kernel RAM.
4328
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004329 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4330 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004331
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004332 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4333 Format: <command>
4334
4335 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4336 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004337
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004338 vsyscall= [X86-64]
4339 Controls the behavior of vsyscalls (i.e. calls to
4340 fixed addresses of 0xffffffffff600x00 from legacy
4341 code). Most statically-linked binaries and older
4342 versions of glibc use these calls. Because these
4343 functions are at fixed addresses, they make nice
4344 targets for exploits that can control RIP.
4345
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004346 emulate [default] Vsyscalls turn into traps and are
4347 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004348
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004349 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004350 This is a little bit faster than trapping
4351 and makes a few dynamic recompilers work
4352 better than they would in emulation mode.
4353 It also makes exploits much easier to write.
4354
4355 none Vsyscalls don't work at all. This makes
4356 them quite hard to use for exploits but
4357 might break your system.
4358
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004359 vt.color= [VT] Default text color.
4360 Format: 0xYX, X = foreground, Y = background.
4361 Default: 0x07 = light gray on black.
4362
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004363 vt.cur_default= [VT] Default cursor shape.
4364 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4365 the parameters of the <Esc>[?A;B;Cc escape sequence;
4366 see VGA-softcursor.txt. Default: 2 = underline.
4367
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004368 vt.default_blu= [VT]
4369 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4370 Change the default blue palette of the console.
4371 This is a 16-member array composed of values
4372 ranging from 0-255.
4373
4374 vt.default_grn= [VT]
4375 Format: <green0>,<green1>,<green2>,...,<green15>
4376 Change the default green palette of the console.
4377 This is a 16-member array composed of values
4378 ranging from 0-255.
4379
4380 vt.default_red= [VT]
4381 Format: <red0>,<red1>,<red2>,...,<red15>
4382 Change the default red palette of the console.
4383 This is a 16-member array composed of values
4384 ranging from 0-255.
4385
4386 vt.default_utf8=
4387 [VT]
4388 Format=<0|1>
4389 Set system-wide default UTF-8 mode for all tty's.
4390 Default is 1, i.e. UTF-8 mode is enabled for all
4391 newly opened terminals.
4392
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004393 vt.global_cursor_default=
4394 [VT]
4395 Format=<-1|0|1>
4396 Set system-wide default for whether a cursor
4397 is shown on new VTs. Default is -1,
4398 i.e. cursors will be created by default unless
4399 overridden by individual drivers. 0 will hide
4400 cursors, 1 will display them.
4401
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004402 vt.italic= [VT] Default color for italic text; 0-15.
4403 Default: 2 = green.
4404
4405 vt.underline= [VT] Default color for underlined text; 0-15.
4406 Default: 3 = cyan.
4407
Randy Dunlap4724ba572010-05-03 11:42:52 -07004408 watchdog timers [HW,WDT] For information on watchdog timers,
4409 see Documentation/watchdog/watchdog-parameters.txt
4410 or other driver-specific files in the
4411 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004412
Tejun Heo82607adc2015-12-08 11:28:04 -05004413 workqueue.watchdog_thresh=
4414 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4415 warn stall conditions and dump internal state to
4416 help debugging. 0 disables workqueue stall
4417 detection; otherwise, it's the stall threshold
4418 duration in seconds. The default value is 30 and
4419 it can be updated at runtime by writing to the
4420 corresponding sysfs file.
4421
Tejun Heod55262c2013-04-01 11:23:38 -07004422 workqueue.disable_numa
4423 By default, all work items queued to unbound
4424 workqueues are affine to the NUMA nodes they're
4425 issued on, which results in better behavior in
4426 general. If NUMA affinity needs to be disabled for
4427 whatever reason, this option can be used. Note
4428 that this also can be controlled per-workqueue for
4429 workqueues visible under /sys/bus/workqueue/.
4430
Viresh Kumarcee22a12013-04-08 16:45:40 +05304431 workqueue.power_efficient
4432 Per-cpu workqueues are generally preferred because
4433 they show better performance thanks to cache
4434 locality; unfortunately, per-cpu workqueues tend to
4435 be more power hungry than unbound workqueues.
4436
4437 Enabling this makes the per-cpu workqueues which
4438 were observed to contribute significantly to power
4439 consumption unbound, leading to measurably lower
4440 power usage at the cost of small performance
4441 overhead.
4442
4443 The default value of this parameter is determined by
4444 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4445
Tejun Heof303fccb2016-02-09 17:59:38 -05004446 workqueue.debug_force_rr_cpu
4447 Workqueue used to implicitly guarantee that work
4448 items queued without explicit CPU specified are put
4449 on the local CPU. This guarantee is no longer true
4450 and while local CPU is still preferred work items
4451 may be put on foreign CPUs. This debug option
4452 forces round-robin CPU selection to flush out
4453 usages which depend on the now broken guarantee.
4454 When enabled, memory and cache locality will be
4455 impacted.
4456
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004457 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4458 default x2apic cluster mode on platforms
4459 supporting x2apic.
4460
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004461 x86_intel_mid_timer= [X86-32,APBT]
4462 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004463 Two valid options are apbt timer only and lapic timer
4464 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004465 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004466
Juergen Grossc70727a2015-07-17 06:51:36 +02004467 xen_512gb_limit [KNL,X86-64,XEN]
4468 Restricts the kernel running paravirtualized under Xen
4469 to use only up to 512 GB of RAM. The reason to do so is
4470 crash analysis tools and Xen tools for doing domain
4471 save/restore/migration must be enabled to handle larger
4472 domains.
4473
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004474 xen_emul_unplug= [HW,X86,XEN]
4475 Unplug Xen emulated devices
4476 Format: [unplug0,][unplug1]
4477 ide-disks -- unplug primary master IDE devices
4478 aux-ide-disks -- unplug non-primary-master IDE devices
4479 nics -- unplug network devices
4480 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004481 unnecessary -- unplugging emulated devices is
4482 unnecessary even if the host did not respond to
4483 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004484 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004485
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004486 xen_nopvspin [X86,XEN]
4487 Disables the ticketlock slowpath using Xen PV
4488 optimizations.
4489
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004490 xen_nopv [X86]
4491 Disables the PV optimizations forcing the HVM guest to
4492 run as generic HVM guest with no PV drivers.
4493
Linus Torvalds1da177e2005-04-16 15:20:36 -07004494 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004495 Format:
4496 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004497
Randy Dunlapa9913042005-10-23 12:57:11 -07004498______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004499
4500TODO:
4501
Linus Torvalds1da177e2005-04-16 15:20:36 -07004502 Add more DRM drivers.