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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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700586 bttv.radio= Most important insmod options are available as
587 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700588 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200589 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000591 bulk_remove=off [PPC] This parameter disables the use of the pSeries
592 firmware feature for flushing multiple hpte entries
593 at a time.
594
Linus Torvalds1da177e2005-04-16 15:20:36 -0700595 c101= [NET] Moxa C101 synchronous serial card
596
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700597 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598 Sometimes CPU hardware bugs make them report the cache
599 size incorrectly. The kernel will attempt work arounds
600 to fix known problems, but for some CPUs it is not
601 possible to determine what the correct size should be.
602 This option provides an override for these situations.
603
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300604 ca_keys= [KEYS] This parameter identifies a specific key(s) on
605 the system trusted keyring to be used for certificate
606 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300607 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300608
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700609 cca= [MIPS] Override the kernel pages' cache coherency
610 algorithm. Accepted values range from 0 to 7
611 inclusive. See arch/mips/include/asm/pgtable-bits.h
612 for platform specific values (SB1, Loongson3 and
613 others).
614
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100615 ccw_timeout_log [S390]
616 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617
Paul Menage8bab8dd2008-04-04 14:29:57 -0700618 cgroup_disable= [KNL] Disable a particular controller
619 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800620 The effects of cgroup_disable=foo are:
621 - foo isn't auto-mounted if you mount all cgroups in
622 a single hierarchy
623 - foo isn't visible as an individually mountable
624 subsystem
625 {Currently only "memory" controller deal with this and
626 cut the overhead, others just disable the usage. So
627 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700628
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500629 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
630 Format: { controller[,controller...] | "all" }
631 Like cgroup_disable, but only applies to cgroup v1;
632 the blacklisted controllers remain available in cgroup2.
633
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800634 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
635 Format: <string>
636 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800637 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800638
Linus Torvalds1da177e2005-04-16 15:20:36 -0700639 checkreqprot [SELINUX] Set initial checkreqprot flag value.
640 Format: { "0" | "1" }
641 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700642 0 -- check protection applied by kernel (includes
643 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644 1 -- check protection requested by application.
645 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700646 Value can be changed at runtime via
647 /selinux/checkreqprot.
648
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100649 cio_ignore= [S390]
650 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700651 clk_ignore_unused
652 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700653 Prevents the clock framework from automatically gating
654 clocks that have not been explicitly enabled by a Linux
655 device driver but are enabled in hardware at reset or
656 by the bootloader/firmware. Note that this does not
657 force such clocks to be always-on nor does it reserve
658 those clocks in any way. This parameter is useful for
659 debug and development, but should not be needed on a
660 platform with proper driver support. For more
661 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100662
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700663 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700664 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200665 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700666 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200667 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 Format: { pit | tsc | cyclone | pmtmr }
669
John Stultz592913e2010-07-13 17:56:20 -0700670 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700671 Format: <string>
672 Override the default clocksource and use the clocksource
673 with the name specified.
674 Some clocksource names to choose from, depending on
675 the platform:
676 [all] jiffies (this is the base, fallback clocksource)
677 [ACPI] acpi_pm
678 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
679 pxa_timer,timer3,32k_counter,timer0_1
680 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700681 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700682 scx200_hrt on Geode; cyclone on IBM x440
683 [MIPS] MIPS
684 [PARISC] cr16
685 [S390] tod
686 [SH] SuperH
687 [SPARC64] tick
688 [X86-64] hpet,tsc
689
Andi Kleenac72e782008-01-30 13:33:21 +0100690 clearcpuid=BITNUM [X86]
691 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100692 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800693 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100694 stable over kernel options, but the vendor specific
695 ones should be.
696 Also note that user programs calling CPUID directly
697 or using the feature without checking anything
698 will still see it. This just prevents it from
699 being used by the kernel or shown in /proc/cpuinfo.
700 Also note the kernel might malfunction if you disable
701 some critical bits.
702
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700703 cma=nn[MG]@[start[MG][-end[MG]]]
704 [ARM,X86,KNL]
705 Sets the size of kernel global memory area for
706 contiguous memory allocations and optionally the
707 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700708 memory allocations. A value of 0 disables CMA
709 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100710 include/linux/dma-contiguous.h
711
Robert Jennings14f966e2009-04-15 05:55:32 +0000712 cmo_free_hint= [PPC] Format: { yes | no }
713 Specify whether pages are marked as being inactive
714 when they are freed. This is used in CMO environments
715 to determine OS memory pressure for page stealing by
716 a hypervisor.
717 Default: yes
718
Marek Szyprowskic7909502011-12-29 13:09:51 +0100719 coherent_pool=nn[KMG] [ARM,KNL]
720 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200721 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100722
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530723 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100724 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100725 Range: 0 - 8192
726 Default: 64
727
Linus Torvalds1da177e2005-04-16 15:20:36 -0700728 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700729 Format:
730 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731
732 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
733 Format: <io>[,<irq>]
734
Randy Dunlapa9913042005-10-23 12:57:11 -0700735 com90xx= [HW,NET]
736 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737 Format: <io>[,<irq>[,<memstart>]]
738
739 condev= [HW,S390] console device
740 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700741
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742 console= [KNL] Output console device and options.
743
744 tty<n> Use the virtual console device <n>.
745
746 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800747 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800749 the form "bbbbpnf", where "bbbb" is the baud rate,
750 "p" is parity ("n", "o", or "e"), "n" is number of
751 bits, and "f" is flow control ("r" for RTS or
752 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800754 See Documentation/serial-console.txt for more
755 information. See
756 Documentation/networking/netconsole.txt for an
757 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700758
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700759 uart[8250],io,<addr>[,options]
760 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900761 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400762 uart[8250],mmio32,<addr>[,options]
763 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764 Start an early, polled-mode console on the 8250/16550
765 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400766 switching to the matching ttyS device later.
767 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900768 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
769 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
770 to be equivalent to 'mmio'. 'options' are specified in
771 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400772 the h/w is not re-initialized.
773
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500774 hvc<n> Use the hypervisor console device <n>. This is for
775 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700777 If the device connected to the port is not a TTY but a braille
778 device, prepend "brl," before the device type, for instance
779 console=brl,ttyS0
780 For now, only VisioBraille is supported.
781
Daniel Mackf324edc2009-06-16 15:33:52 -0700782 consoleblank= [KNL] The console blank (screen saver) timeout in
783 seconds. Defaults to 10*60 = 10mins. A value of 0
784 disables the blank timer.
785
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800786 coredump_filter=
787 [KNL] Change the default value for
788 /proc/<pid>/coredump_filter.
789 See also Documentation/filesystems/proc.txt.
790
Len Brown62027ae2011-04-01 18:13:10 -0400791 cpuidle.off=1 [CPU_IDLE]
792 disable the cpuidle sub-system
793
Len Brownd68921f2015-05-11 17:27:09 -0400794 cpu_init_udelay=N
795 [X86] Delay for N microsec between assert and de-assert
796 of APIC INIT to start processors. This delay occurs
797 on every CPU online, such as boot, and resume from suspend.
798 Default: 10000
799
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700801 Format:
802 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700803
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800804 crashkernel=size[KMG][@offset[KMG]]
805 [KNL] Using kexec, Linux can switch to a 'crash kernel'
806 upon panic. This parameter reserves the physical
807 memory region [offset, offset + size] for that kernel
808 image. If '@offset' is omitted, then a suitable offset
809 is selected automatically. Check
810 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700811
Bernhard Wallefb391592007-10-18 23:41:02 -0700812 crashkernel=range1:size1[,range2:size2,...][@offset]
813 [KNL] Same as above, but depends on the memory
814 in the running system. The syntax of range is
815 start-[end] where start and end are both
816 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800817 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700818
Yinghai Luadbc7422013-04-15 22:23:48 -0700819 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700820 [KNL, x86_64] range could be above 4G. Allow kernel
821 to allocate physical memory region from top, so could
822 be above 4G if system have more than 4G ram installed.
823 Otherwise memory region will be allocated below 4G, if
824 available.
825 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700826 crashkernel=size[KMG],low
827 [KNL, x86_64] range under 4G. When crashkernel=X,high
828 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700829 above 4G, that cause second kernel crash on system
830 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800831 requires at least 64M+32K low memory, also enough extra
832 low memory is needed to make sure DMA buffers for 32-bit
833 devices won't run out. Kernel would try to allocate at
834 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700835 This one let user to specify own low range under 4G
836 for second kernel instead.
837 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700838 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700839 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700840
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100841 cryptomgr.notests
842 [KNL] Disable crypto self-tests
843
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844 cs89x0_dma= [HW,NET]
845 Format: <dma>
846
847 cs89x0_media= [HW,NET]
848 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700849
Randy Dunlapa9913042005-10-23 12:57:11 -0700850 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700851 See header of drivers/s390/block/dasd_devmap.c.
852
853 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
854 (one device per port)
855 Format: <port#>,<type>
856 See also Documentation/input/joystick-parport.txt
857
Thomas Renningera648ec02010-08-06 16:11:02 +0200858 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
859 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600860 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200861
Linus Torvalds1da177e2005-04-16 15:20:36 -0700862 debug [KNL] Enable kernel debugging (events log level).
863
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700864 debug_locks_verbose=
865 [KNL] verbose self-tests
866 Format=<0|1>
867 Print debugging info while doing the locking API
868 self-tests.
869 We default to 0 (no extra messages), setting it to
870 1 will print _a lot_ more information - normally
871 only useful to kernel developers.
872
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700873 debug_objects [KNL] Enable object debugging
874
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500875 no_debug_objects
876 [KNL] Disable object debugging
877
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800878 debug_guardpage_minorder=
879 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
880 parameter allows control of the order of pages that will
881 be intentionally kept free (and hence protected) by the
882 buddy allocator. Bigger value increase the probability
883 of catching random memory corruption, but reduce the
884 amount of memory for normal system use. The maximum
885 possible value is MAX_ORDER/2. Setting this parameter
886 to 1 or 2 should be enough to identify most random
887 memory corruption problems caused by bugs in kernel or
888 driver code when a CPU writes to (or reads from) a
889 random memory location. Note that there exists a class
890 of memory corruptions problems caused by buggy H/W or
891 F/W or by drivers badly programing DMA (basically when
892 memory is written at bus level and the CPU MMU is
893 bypassed) which are not detectable by
894 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
895 tracking down these problems.
896
Joonsoo Kim031bc572014-12-12 16:55:52 -0800897 debug_pagealloc=
898 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
899 parameter enables the feature at boot time. In
900 default, it is disabled. We can avoid allocating huge
901 chunk of memory for debug pagealloc if we don't enable
902 it at boot time and the system will work mostly same
903 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
904 on: enable the feature
905
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200906 debugpat [X86] Enable PAT debugging
907
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200908 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909 Format: <area>[,<node>]
910 See also Documentation/networking/decnet.txt.
911
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700912 default_hugepagesz=
913 [same as hugepagesz=] The size of the default
914 HugeTLB page size. This is the size represented by
915 the legacy /proc/ hugepages APIs, used for SHM, and
916 default size when mounting hugetlbfs filesystems.
917 Defaults to the default architecture's huge page size
918 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700919
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920 dhash_entries= [KNL]
921 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700922
Brian Haleyb0f83b22010-02-04 13:36:50 -0800923 disable= [IPV6]
924 See Documentation/networking/ipv6.txt.
925
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900926 disable_cpu_apicid= [X86,APIC,SMP]
927 Format: <int>
928 The number of initial APIC ID for the
929 corresponding CPU to be disabled at boot,
930 mostly used for the kdump 2nd kernel to
931 disable BSP to wake up multiple CPUs without
932 causing system reset or hang due to sending
933 INIT from AP to BSP.
934
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000935 disable_ddw [PPC/PSERIES]
936 Disable Dynamic DMA Window support. Use this if
937 to workaround buggy firmware.
938
Brian Haleyb0f83b22010-02-04 13:36:50 -0800939 disable_ipv6= [IPV6]
940 See Documentation/networking/ipv6.txt.
941
Yinghai Lu95ffa242008-04-29 03:52:33 -0700942 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700943 The kernel tries to adjust MTRR layout from continuous
944 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700945 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700946
Yinghai Lu093af8d2008-01-30 13:33:32 +0100947 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100948 By default the kernel will trim any uncacheable
949 memory out of your available memory pool based on
950 MTRR settings. This parameter disables that behavior,
951 possibly causing your machine to run very slowly.
952
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530953 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700954 Disable PIN 1 of APIC timer
955 Can be useful to work around chipset bugs.
956
Prarit Bhargavace14c582015-08-25 13:34:53 -0400957 dis_ucode_ldr [X86] Disable the microcode loader.
958
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700959 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
960 this option disables the debugging code at boot.
961
962 dma_debug_entries=<number>
963 This option allows to tune the number of preallocated
964 entries for DMA-API debugging code. One entry is
965 required per DMA-API allocation. Use this if the
966 DMA-API debugging code disables itself because the
967 architectural default is too low.
968
Joerg Roedel1745de52009-05-22 21:49:51 +0200969 dma_debug_driver=<driver_name>
970 With this option the DMA-API debugging driver
971 filter feature can be enabled at boot time. Just
972 pass the driver to filter for as the parameter.
973 The filter can be disabled or changed to another
974 driver later using sysfs.
975
Bob Paauwe96206e22015-08-27 10:04:13 -0700976 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
977 Broken monitors, graphic adapters, KVMs and EDIDless
978 panels may send no or incorrect EDID data sets.
979 This parameter allows to specify an EDID data sets
980 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100981 Generic built-in EDID data sets are used, if one of
982 edid/1024x768.bin, edid/1280x1024.bin,
983 edid/1680x1050.bin, or edid/1920x1080.bin is given
984 and no file with the same name exists. Details and
985 instructions how to build your own EDID data are
986 available in Documentation/EDID/HOWTO.txt. An EDID
987 data set will only be used for a particular connector,
988 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700989 name. Each connector may use a unique EDID data
990 set by separating the files with a comma. An EDID
991 data set with no connector name will be used for
992 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100993
Linus Torvalds1da177e2005-04-16 15:20:36 -0700994 dscc4.setup= [NET]
995
Jim Cromie29e36c92012-04-27 14:30:41 -0600996 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
997 module.dyndbg[="val"]
998 Enable debug messages at boot time. See
999 Documentation/dynamic-debug-howto.txt for details.
1000
Dave Hansen8c3641e2015-06-07 11:37:02 -07001001 nompx [X86] Disables Intel Memory Protection Extensions.
1002 See Documentation/x86/intel_mpx.txt for more
1003 information about the feature.
1004
Dave Hansen06976942016-02-12 13:02:29 -08001005 nopku [X86] Disable Memory Protection Keys CPU feature found
1006 in some Intel CPUs.
1007
Borislav Petkovf29ba612015-03-27 16:15:18 +01001008 eagerfpu= [X86]
1009 on enable eager fpu restore
1010 off disable eager fpu restore
1011 auto selects the default scheme, which automatically
1012 enables eagerfpu restore for xsaveopt.
1013
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -07001014 module.async_probe [KNL]
1015 Enable asynchronous probe on this module.
1016
Mark Salter56aeeba2014-04-07 15:39:53 -07001017 early_ioremap_debug [KNL]
1018 Enable debug messages in early_ioremap support. This
1019 is useful for tracking down temporary early mappings
1020 which are not unmapped.
1021
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001022 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -05001023
Scott Wood5664f762015-09-14 19:54:07 -05001024 When used with no options, the early console is
1025 determined by the stdout-path property in device
1026 tree's chosen node.
1027
Michal Simek6fa62fc2014-09-10 12:43:02 +02001028 cdns,<addr>
1029 Start an early, polled-mode console on a cadence serial
1030 port at the specified address. The cadence serial port
1031 must already be setup and configured. Options are not
1032 yet supported.
1033
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001034 uart[8250],io,<addr>[,options]
1035 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -07001036 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +03001037 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -04001038 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001039 Start an early, polled-mode console on the 8250/16550
1040 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -07001041 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +03001042 (mmio) or 32-bit (mmio32 or mmio32be).
1043 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1044 to be equivalent to 'mmio'. 'options' are specified
1045 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001046 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001047
Rob Herring0d3c6732014-04-18 17:19:57 -05001048 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -06001049 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -05001050 Start an early, polled-mode console on a pl011 serial
1051 port at the specified address. The pl011 serial port
1052 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -06001053 yet supported. If 'mmio32' is specified, then only
1054 the driver will use only 32-bit accessors to read/write
1055 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -05001056
Andreas Färber736d5532016-03-06 12:21:24 +01001057 meson,<addr>
1058 Start an early, polled-mode console on a meson serial
1059 port at the specified address. The serial port must
1060 already be setup and configured. Options are not yet
1061 supported.
1062
Stephen Boyd0efe7292014-09-15 17:22:51 -07001063 msm_serial,<addr>
1064 Start an early, polled-mode console on an msm serial
1065 port at the specified address. The serial port
1066 must already be setup and configured. Options are not
1067 yet supported.
1068
1069 msm_serial_dm,<addr>
1070 Start an early, polled-mode console on an msm serial
1071 dm port at the specified address. The serial port
1072 must already be setup and configured. Options are not
1073 yet supported.
1074
Rob Herringd50d7262014-04-18 17:19:58 -05001075 smh Use ARM semihosting calls for early console.
1076
Tomasz Figab94ba032015-01-23 14:47:41 +01001077 s3c2410,<addr>
1078 s3c2412,<addr>
1079 s3c2440,<addr>
1080 s3c6400,<addr>
1081 s5pv210,<addr>
1082 exynos4210,<addr>
1083 Use early console provided by serial driver available
1084 on Samsung SoCs, requires selecting proper type and
1085 a correct base address of the selected UART port. The
1086 serial port must already be setup and configured.
1087 Options are not yet supported.
1088
Stefan Agner1d59b382015-10-17 00:45:55 -07001089 lpuart,<addr>
1090 lpuart32,<addr>
1091 Use early console provided by Freescale LP UART driver
1092 found on Freescale Vybrid and QorIQ LS1021A processors.
1093 A valid base address must be provided, and the serial
1094 port must already be setup and configured.
1095
Wilson Ding30530792016-02-16 19:14:53 +01001096 armada3700_uart,<addr>
1097 Start an early, polled-mode console on the
1098 Armada 3700 serial port at the specified
1099 address. The serial port must already be setup
1100 and configured. Options are not yet supported.
1101
Finn Thain7913ad12014-04-12 23:48:56 +10001102 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001104 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001105 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001107 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001108 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001109 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001110 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111
Dave Hansen147ea092013-04-10 14:03:38 -07001112 earlyprintk is useful when the kernel crashes before
1113 the normal console is initialized. It is not enabled by
1114 default because it has some cosmetic problems.
1115
Randy Dunlapa9913042005-10-23 12:57:11 -07001116 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001117 takes over.
1118
Matt Fleming72548e82013-10-04 09:36:56 +01001119 Only one of vga, efi, serial, or usb debug port can
1120 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121
Dave Hansen147ea092013-04-10 14:03:38 -07001122 Currently only ttyS0 and ttyS1 may be specified by
1123 name. Other I/O ports may be explicitly specified
1124 on some architectures (x86 and arm at least) by
1125 replacing ttySn with an I/O port address, like this:
1126 earlyprintk=serial,0x1008,115200
1127 You can find the port for a given device in
1128 /proc/tty/driver/serial:
1129 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130
1131 Interaction with the standard serial driver is not
1132 very good.
1133
Matt Fleming72548e82013-10-04 09:36:56 +01001134 The VGA and EFI output is eventually overwritten by
1135 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001137 The xen output can only be used by Xen PV guests.
1138
Chen, Gongc700f012013-12-06 01:17:08 -05001139 edac_report= [HW,EDAC] Control how to report EDAC event
1140 Format: {"on" | "off" | "force"}
1141 on: enable EDAC to report H/W event. May be overridden
1142 by other higher priority error reporting module.
1143 off: disable H/W event reporting through EDAC.
1144 force: enforce the use of EDAC to report H/W event.
1145 default: on.
1146
Jason Wessel97311912010-05-20 21:04:30 -05001147 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1148 ekgdboc=kbd
1149
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001150 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001151 the boot argument: earlyprintk=vga
1152
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001154 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001155
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001156 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001157 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001158 old_map [X86-64]: switch to the old ioremap-based EFI
1159 runtime services mapping. 32-bit still uses this one by
1160 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001161 nochunk: disable reading files in "chunks" in the EFI
1162 boot stub, as chunking can cause problems with some
1163 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001164 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001165 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001166
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001167 efi_no_storage_paranoia [EFI; X86]
1168 Using this parameter you can use more than 50% of
1169 your efi variable storage. Use this parameter only if
1170 you are really sure that your UEFI does sane gc and
1171 fulfills the spec otherwise your board may brick.
1172
Taku Izumi0f96a992015-09-30 23:01:56 +09001173 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1174 Add arbitrary attribute to specific memory range by
1175 updating original EFI memory map.
1176 Region of memory which aa attribute is added to is
1177 from ss to ss+nn.
1178 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1179 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1180 attribute is added to range 0x100000000-0x180000000 and
1181 0x10a0000000-0x1120000000.
1182
1183 Using this parameter you can do debugging of EFI memmap
1184 related feature. For example, you can do debugging of
1185 Address Range Mirroring feature even if your box
1186 doesn't support it.
1187
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188 eisa_irq_edge= [PARISC,HW]
1189 See header of drivers/parisc/eisa.c.
1190
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001191 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001192 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001193 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194
1195 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001196 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001197 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001198 Documentation/block/deadline-iosched.txt for details.
1199
Michael Holzheud3bf37952011-10-30 15:16:37 +01001200 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001201 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001202 image elf header and optionally the size. Generally
1203 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001204 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001206 enable_mtrr_cleanup [X86]
1207 The kernel tries to adjust MTRR layout from continuous
1208 to discrete, to make X server driver able to add WB
1209 entry later. This parameter enables that.
1210
Randy Dunlapca1eda22009-05-06 16:02:58 -07001211 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001212 Enable PIN 1 of APIC timer
1213 Can be useful to work around chipset bugs
1214 (in particular on some ATI chipsets).
1215 The kernel tries to set a reasonable default.
1216
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217 enforcing [SELINUX] Set initial enforcing status.
1218 Format: {"0" | "1"}
1219 See security/selinux/Kconfig help text.
1220 0 -- permissive (log only, no denials).
1221 1 -- enforcing (deny and log).
1222 Default value is 0.
1223 Value can be changed at runtime via /selinux/enforce.
1224
Huang Yinga08f82d2010-05-18 14:35:21 +08001225 erst_disable [ACPI]
1226 Disable Error Record Serialization Table (ERST)
1227 support.
1228
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 ether= [HW,NET] Ethernet cards parameters
1230 This option is obsoleted by the "netdev=" option, which
1231 has equivalent usage. See its documentation for details.
1232
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001233 evm= [EVM]
1234 Format: { "fix" }
1235 Permit 'security.evm' to be updated regardless of
1236 current integrity status.
1237
Akinobu Mitade1ba092006-12-08 02:39:42 -08001238 failslab=
1239 fail_page_alloc=
1240 fail_make_request=[KNL]
1241 General fault injection mechanism.
1242 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001243 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001244
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001246 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247
Alex Chiangf13ae302008-05-08 14:03:23 -06001248 force_pal_cache_flush
1249 [IA-64] Avoid check_sal_cache_flush which may hang on
1250 buggy SAL_CACHE_FLUSH implementations. Using this
1251 parameter will force ia64_sal_cache_flush to call
1252 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1253
Chris Bainbridge69f23662014-03-07 18:40:42 +07001254 forcepae [X86-32]
1255 Forcefully enable Physical Address Extension (PAE).
1256 Many Pentium M systems disable PAE but may have a
1257 functionally usable PAE implementation.
1258 Warning: use of this parameter will taint the kernel
1259 and may cause unknown problems.
1260
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001261 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001262 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001263 as early as possible in order to facilitate early
1264 boot debugging.
1265
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001266 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001267 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001268 If no parameter is passed, ftrace will dump
1269 buffers of all CPUs, but if you pass orig_cpu, it will
1270 dump only the buffer of the CPU that triggered the
1271 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001272
1273 ftrace_filter=[function-list]
1274 [FTRACE] Limit the functions traced by the function
1275 tracer at boot up. function-list is a comma separated
1276 list of functions. This list can be changed at run
1277 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001278 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001279
1280 ftrace_notrace=[function-list]
1281 [FTRACE] Do not trace the functions specified in
1282 function-list. This list can be changed at run time
1283 by the set_ftrace_notrace file in the debugfs
1284 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001285
Stefan Assmann369bc182009-10-12 22:17:21 +02001286 ftrace_graph_filter=[function-list]
1287 [FTRACE] Limit the top level callers functions traced
1288 by the function graph tracer at boot up.
1289 function-list is a comma separated list of functions
1290 that can be changed at run time by the
1291 set_graph_function file in the debugfs tracing directory.
1292
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001293 ftrace_graph_notrace=[function-list]
1294 [FTRACE] Do not trace from the functions specified in
1295 function-list. This list is a comma separated list of
1296 functions that can be changed at run time by the
1297 set_graph_notrace file in the debugfs tracing directory.
1298
Linus Torvalds1da177e2005-04-16 15:20:36 -07001299 gamecon.map[2|3]=
1300 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1301 support via parallel port (up to 5 devices per port)
1302 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1303 See also Documentation/input/joystick-parport.txt
1304
1305 gamma= [HW,DRM]
1306
Yinghai Luaaf23042008-01-30 13:33:09 +01001307 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1308 Format: off | on
1309 default: on
1310
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001311 gcov_persist= [GCOV] When non-zero (default), profiling data for
1312 kernel modules is saved and remains accessible via
1313 debugfs, even when the module is unloaded/reloaded.
1314 When zero, profiling data is discarded and associated
1315 debugfs files are removed at module unload time.
1316
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001318 invalid Protective MBR to be treated as GPT. If the
1319 primary GPT is corrupted, it enables the backup/alternate
1320 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001322 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1323 the "Enable 0" bit of the configuration register.
1324 Format: 0 | 1
1325 Default: 0
1326 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1327 the "Enable 0" bit of the configuration register.
1328 Format: 0 | 1
1329 Default: 0
1330 grcan.select= [HW] Select which physical interface to use.
1331 Format: 0 | 1
1332 Default: 0
1333 grcan.txsize= [HW] Sets the size of the tx buffer.
1334 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1335 Default: 1024
1336 grcan.rxsize= [HW] Sets the size of the rx buffer.
1337 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1338 Default: 1024
1339
Jiri Kosina55537872015-11-05 18:44:41 -08001340 hardlockup_all_cpu_backtrace=
1341 [KNL] Should the hard-lockup detector generate
1342 backtraces on all cpus.
1343 Format: <integer>
1344
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 hashdist= [KNL,NUMA] Large hashes allocated during boot
1346 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001347 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001348 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349
1350 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1351
1352 hd= [EIDE] (E)IDE hard drive subsystem geometry
1353 Format: <cyl>,<head>,<sect>
1354
Huang Yingea8c0712010-05-18 14:35:15 +08001355 hest_disable [ACPI]
1356 Disable Hardware Error Source Table (HEST) support;
1357 corresponding firmware-first mode error processing
1358 logic will be disabled.
1359
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1361 size of <nn>. This works even on boxes that have no
1362 highmem otherwise. This also works to reduce highmem
1363 size on bigger boxes.
1364
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001365 highres= [KNL] Enable/disable high resolution timer mode.
1366 Valid parameters: "on", "off"
1367 Default: "on"
1368
Linus Torvalds1da177e2005-04-16 15:20:36 -07001369 hisax= [HW,ISDN]
1370 See Documentation/isdn/README.HiSax.
1371
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001372 hlt [BUGS=ARM,SH]
1373
1374 hpet= [X86-32,HPET] option to control HPET usage
1375 Format: { enable (default) | disable | force |
1376 verbose }
1377 disable: disable HPET and use PIT instead
1378 force: allow force enabled of undocumented chips (ICH4,
1379 VIA, nVidia)
1380 verbose: show contents of HPET registers during setup
1381
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001382 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1383 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1384
Andi Kleenb4718e62008-07-23 21:27:51 -07001385 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1386 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001387 On x86-64 and powerpc, this option can be specified
1388 multiple times interleaved with hugepages= to reserve
1389 huge pages of different sizes. Valid pages sizes on
1390 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001391 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001392
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001393 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1394 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001395 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1396 If specified, z/VM IUCV HVC accepts connections
1397 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001398
James Hoganfdabf522012-10-09 11:00:27 +01001399 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1400 hardware thread id mappings.
1401 Format: <cpu>:<hwthread>
1402
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001403 keep_bootcon [KNL]
1404 Do not unregister boot console at start. This is only
1405 useful for debugging when something happens in the window
1406 between unregistering the boot console and initializing
1407 the real console.
1408
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001409 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001410 or register an additional I2C bus that is not
1411 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001412 Format:
1413 <bus_id>,<clkrate>
1414
Jiri Kosina36d95732008-10-06 02:51:09 -04001415 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001416 i8042.unmask_kbd_data
1417 [HW] Enable printing of interrupt data from the KBD port
1418 (disabled by default, and as a pre-condition
1419 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001421 i8042.dumbkbd [HW] Pretend that controller can only read data from
1422 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423 (Don't attempt to blink the leds)
1424 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001425 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001426 i8042.noloop [HW] Disable the AUX Loopback command while probing
1427 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001428 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001429 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001430 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1431 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001432 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001433 i8042.reset [HW] Reset the controller during init and cleanup
1434 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001435 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436
1437 i810= [HW,DRM]
1438
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001439 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1440 indicates that the driver is running on unsupported
1441 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1443 does not match list of supported models.
1444 i8k.power_status
1445 [HW] Report power status in /proc/i8k
1446 (disabled by default)
1447 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1448 capability is set.
1449
Carsten Emde4dca20e2012-03-15 15:56:26 +01001450 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001451 [DRM] Invert the sense of the variable that is used to
1452 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001453 brightness value of 0 indicates backlight switched off,
1454 and the maximum of the brightness value sets the backlight
1455 to maximum brightness. If this parameter is set to 0
1456 (default) and the machine requires it, or this parameter
1457 is set to 1, a brightness value of 0 sets the backlight
1458 to maximum brightness, and the maximum of the brightness
1459 value switches the backlight off.
1460 -1 -- never invert brightness
1461 0 -- machine default
1462 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001463
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 icn= [HW,ISDN]
1465 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1466
David Fries0af80c02009-02-25 20:28:21 +01001467 ide-core.nodma= [HW] (E)IDE subsystem
1468 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001469 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1470 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001471 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001473 ide-generic.probe-mask= [HW] (E)IDE subsystem
1474 Format: <int>
1475 Probe mask for legacy ISA IDE ports. Depending on
1476 platform up to 6 ports are supported, enabled by
1477 setting corresponding bits in the mask to 1. The
1478 default value is 0x0, which has a special meaning.
1479 On systems that have PCI, it triggers scanning the
1480 PCI bus for the first and the second port, which
1481 are then probed. On systems without PCI the value
1482 of 0x0 enables probing the two first ports as if it
1483 was 0x3.
1484
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001485 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1486 Claim all unknown PCI IDE storage controllers.
1487
Andi Kleenf039b752007-05-02 19:27:12 +02001488 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001489 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001490 Poll forces a polling idle loop that can slightly
1491 improve the performance of waking up a idle CPU, but
1492 will use a lot of power and make the system run hot.
1493 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001494 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001495 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001496 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001497
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001498 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1499 Format: { strict | legacy | 2008 | relaxed }
1500 Default: strict
1501
1502 Choose which programs will be accepted for execution
1503 based on the IEEE 754 NaN encoding(s) supported by
1504 the FPU and the NaN encoding requested with the value
1505 of an ELF file header flag individually set by each
1506 binary. Hardware implementations are permitted to
1507 support either or both of the legacy and the 2008 NaN
1508 encoding mode.
1509
1510 Available settings are as follows:
1511 strict accept binaries that request a NaN encoding
1512 supported by the FPU
1513 legacy only accept legacy-NaN binaries, if supported
1514 by the FPU
1515 2008 only accept 2008-NaN binaries, if supported
1516 by the FPU
1517 relaxed accept any binaries regardless of whether
1518 supported by the FPU
1519
1520 The FPU emulator is always able to support both NaN
1521 encodings, so if no FPU hardware is present or it has
1522 been disabled with 'nofpu', then the settings of
1523 'legacy' and '2008' strap the emulator accordingly,
1524 'relaxed' straps the emulator for both legacy-NaN and
1525 2008-NaN, whereas 'strict' enables legacy-NaN only on
1526 legacy processors and both NaN encodings on MIPS32 or
1527 MIPS64 CPUs.
1528
1529 The setting for ABS.fmt/NEG.fmt instruction execution
1530 mode generally follows that for the NaN encoding,
1531 except where unsupported by hardware.
1532
Ingo Molnar792908222006-12-06 20:40:51 -08001533 ignore_loglevel [KNL]
1534 Ignore loglevel setting - this will print /all/
1535 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001536 We also add it as printk module parameter, so users
1537 could change it dynamically, usually by
1538 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001539
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001540 ignore_rlimit_data
1541 Ignore RLIMIT_DATA setting for data mappings,
1542 print warning at first misuse. Can be changed via
1543 /sys/module/kernel/parameters/ignore_rlimit_data.
1544
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545 ihash_entries= [KNL]
1546 Set number of hash buckets for inode cache.
1547
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001548 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001549 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001550 default: "enforce"
1551
Mimi Zohar07f6a792011-03-09 22:25:48 -05001552 ima_appraise_tcb [IMA]
1553 The builtin appraise policy appraises all files
1554 owned by uid=0.
1555
Mimi Zohar3323eec92009-02-04 09:06:58 -05001556 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001557 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1558 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001559 default: "sha1"
1560
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001561 The list of supported hash algorithms is defined
1562 in crypto/hash_info.h.
1563
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001564 ima_policy= [IMA]
1565 The builtin measurement policy to load during IMA
1566 setup. Specyfing "tcb" as the value, measures all
1567 programs exec'd, files mmap'd for exec, and all files
1568 opened with the read mode bit set by either the
1569 effective uid (euid=0) or uid=0.
1570 Format: "tcb"
1571
1572 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001573 Load a policy which meets the needs of the Trusted
1574 Computing Base. This means IMA will measure all
1575 programs exec'd, files mmap'd for exec, and all files
1576 opened for read by uid=0.
1577
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001578 ima_template= [IMA]
1579 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001580 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001581 Default: "ima-ng"
1582
Roberto Sassuc2426d22014-10-13 14:08:42 +02001583 ima_template_fmt=
1584 [IMA] Define a custom template format.
1585 Format: { "field1|...|fieldN" }
1586
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001587 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1588 Format: <min_file_size>
1589 Set the minimal file size for using asynchronous hash.
1590 If left unspecified, ahash usage is disabled.
1591
1592 ahash performance varies for different data sizes on
1593 different crypto accelerators. This option can be used
1594 to achieve the best performance for a particular HW.
1595
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001596 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1597 Format: <bufsize>
1598 Set hashing buffer size. Default: 4k.
1599
1600 ahash performance varies for different chunk sizes on
1601 different crypto accelerators. This option can be used
1602 to achieve best performance for particular HW.
1603
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604 init= [KNL]
1605 Format: <full_path>
1606 Run specified binary instead of /sbin/init as init
1607 process.
1608
1609 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1610 for working out where the kernel is dying during
1611 startup.
1612
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001613 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1614 initcall functions. Useful for debugging built-in
1615 modules and initcalls.
1616
Linus Torvalds1da177e2005-04-16 15:20:36 -07001617 initrd= [BOOT] Specify the location of the initial ramdisk
1618
1619 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1620 Format: <irq>
1621
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001622 int_pln_enable [x86] Enable power limit notification interrupt
1623
Mimi Zohard726d8d2013-03-18 14:48:02 -04001624 integrity_audit=[IMA]
1625 Format: { "0" | "1" }
1626 0 -- basic integrity auditing messages. (Default)
1627 1 -- additional integrity auditing messages.
1628
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001629 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001630 on
1631 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001632 off
1633 Disable intel iommu driver.
1634 igfx_off [Default Off]
1635 By default, gfx is mapped as normal device. If a gfx
1636 device has a dedicated DMAR unit, the DMAR unit is
1637 bypassed by not enabling DMAR with this option. In
1638 this case, gfx device will use physical address for
1639 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001640 forcedac [x86_64]
1641 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001642 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001643 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001644 than 32-bit addressing. The default is to look
1645 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001646 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001647 strict [Default Off]
1648 With this option on every unmap_single operation will
1649 result in a hardware IOTLB flush operation as opposed
1650 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001651 sp_off [Default Off]
1652 By default, super page will be supported if Intel IOMMU
1653 has the capability. With this option, super page will
1654 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001655 ecs_off [Default Off]
1656 By default, extended context tables will be supported if
1657 the hardware advertises that it has support both for the
1658 extended tables themselves, and also PASID support. With
1659 this option set, extended tables will not be used even
1660 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001661
1662 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1663 0 disables intel_idle and fall back on acpi_idle.
1664 1 to 6 specify maximum depth of C-state.
1665
Dirk Brandewie6be26492013-02-15 22:55:10 +01001666 intel_pstate= [X86]
1667 disable
1668 Do not enable intel_pstate as the default
1669 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001670 force
1671 Enable intel_pstate on systems that prohibit it by default
1672 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1673 instead of acpi-cpufreq may disable platform features, such
1674 as thermal controls and power capping, that rely on ACPI
1675 P-States information being indicated to OSPM and therefore
1676 should be used with caution. This option does not work with
1677 processors that aren't supported by the intel_pstate driver
1678 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001679 no_hwp
1680 Do not enable hardware P state control (HWP)
1681 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001682 hwp_only
1683 Only load intel_pstate on systems which support
1684 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001685 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001686 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1687 Description Table, specifies preferred power management
1688 profile as "Enterprise Server" or "Performance Server",
1689 then this feature is turned on by default.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001690
Chris Wrightd1423d52010-07-20 11:06:49 -07001691 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001692 on enable Interrupt Remapping (default)
1693 off disable Interrupt Remapping
1694 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001695 no_x2apic_optout
1696 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001697 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001698
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001699 iomem= Disable strict checking of access to MMIO memory
1700 strict regions from userspace.
1701 relaxed
1702
1703 iommu= [x86]
1704 off
1705 force
1706 noforce
1707 biomerge
1708 panic
1709 nopanic
1710 merge
1711 nomerge
1712 forcesac
1713 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001714 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001715 nobypass [PPC/POWERNV]
1716 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001717
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001718
1719 io7= [HW] IO7 for Marvel based alpha systems
1720 See comment before marvel_specify_io7 in
1721 arch/alpha/kernel/core_marvel.c.
1722
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301723 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001724 0x80
1725 Standard port 0x80 based delay
1726 0xed
1727 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001728 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001729 Simple two microseconds delay
1730 none
1731 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001732
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001734 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001736 irqaffinity= [SMP] Set the default irq affinity mask
1737 Format:
1738 <cpu number>,...,<cpu number>
1739 or
1740 <cpu number>-<cpu number>
1741 (must be a positive range in ascending order)
1742 or a mixture
1743 <cpu number>,...,<cpu number>-<cpu number>
1744
Alan Cox200803d2005-06-28 20:45:18 -07001745 irqfixup [HW]
1746 When an interrupt is not handled search all handlers
1747 for it. Intended to get systems with badly broken
1748 firmware running.
1749
1750 irqpoll [HW]
1751 When an interrupt is not handled search all handlers
1752 for it. Also check all handlers each timer
1753 interrupt. Intended to get systems with badly broken
1754 firmware running.
1755
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001757 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758
1759 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001760 Format:
1761 <cpu number>,...,<cpu number>
1762 or
Li Zefanb225d442008-11-06 12:53:39 -08001763 <cpu number>-<cpu number>
1764 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001765 or a mixture
1766 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001767
Linus Torvalds1da177e2005-04-16 15:20:36 -07001768 This option can be used to specify one or more CPUs
1769 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001770 algorithms. You can move a process onto or off an
1771 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772 <cpu number> begins at 0 and the maximum value is
1773 "number of CPUs in system - 1".
1774
1775 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001776 alternative -- manually setting the CPU mask of all
1777 tasks in the system -- can cause problems and
1778 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001779
Randy Dunlapa9913042005-10-23 12:57:11 -07001780 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001782 ivrs_ioapic [HW,X86_64]
1783 Provide an override to the IOAPIC-ID<->DEVICE-ID
1784 mapping provided in the IVRS ACPI table. For
1785 example, to map IOAPIC-ID decimal 10 to
1786 PCI device 00:14.0 write the parameter as:
1787 ivrs_ioapic[10]=00:14.0
1788
1789 ivrs_hpet [HW,X86_64]
1790 Provide an override to the HPET-ID<->DEVICE-ID
1791 mapping provided in the IVRS ACPI table. For
1792 example, to map HPET-ID decimal 0 to
1793 PCI device 00:14.0 write the parameter as:
1794 ivrs_hpet[0]=00:14.0
1795
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001796 ivrs_acpihid [HW,X86_64]
1797 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1798 mapping provided in the IVRS ACPI table. For
1799 example, to map UART-HID:UID AMD0020:0 to
1800 PCI device 00:14.5 write the parameter as:
1801 ivrs_acpihid[00:14.5]=AMD0020:0
1802
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803 js= [HW,JOY] Analog joystick
1804 See Documentation/input/joystick.txt.
1805
Kees Cook24f2e022014-06-13 13:30:36 -07001806 kaslr/nokaslr [X86]
1807 Enable/disable kernel and module base offset ASLR
1808 (Address Space Layout Randomization) if built into
1809 the kernel. When CONFIG_HIBERNATION is selected,
1810 kASLR is disabled by default. When kASLR is enabled,
1811 hibernation will be disabled.
1812
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001813 keepinitrd [HW,ARM]
1814
Taku Izumi342332e2016-03-15 14:55:22 -07001815 kernelcore= [KNL,X86,IA-64,PPC]
1816 Format: nn[KMGTPE] | "mirror"
1817 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001818 specifies the amount of memory usable by the kernel
1819 for non-movable allocations. The requested amount is
1820 spread evenly throughout all nodes in the system. The
1821 remaining memory in each node is used for Movable
1822 pages. In the event, a node is too small to have both
1823 kernelcore and Movable pages, kernelcore pages will
1824 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001825 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001826 allocation of pages that may be reclaimed or moved
1827 by the page migration subsystem. This means that
1828 HugeTLB pages may not be allocated from this zone.
1829 Note that allocations like PTEs-from-HighMem still
1830 use the HighMem zone if it exists, and the Normal
1831 zone if it does not.
1832
Taku Izumi342332e2016-03-15 14:55:22 -07001833 Instead of specifying the amount of memory (nn[KMGTPE]),
1834 you can specify "mirror" option. In case "mirror"
1835 option is specified, mirrored (reliable) memory is used
1836 for non-movable allocations and remaining memory is used
1837 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1838 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1839 time.
1840
Jason Wessel4fe1da42010-05-20 21:04:31 -05001841 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1842 Format: <Controller#>[,poll interval]
1843 The controller # is the number of the ehci usb debug
1844 port as it is probed via PCI. The poll interval is
1845 optional and is the number seconds in between
1846 each poll cycle to the debug port in case you need
1847 the functionality for interrupting the kernel with
1848 gdb or control-c on the dbgp connection. When
1849 not using this parameter you use sysrq-g to break into
1850 the kernel debugger.
1851
Jason Wessel84c08fd2010-05-20 21:04:24 -05001852 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001853 Requires a tty driver that supports console polling,
1854 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001855 Serial only format: <serial_device>[,baud]
1856 keyboard only format: kbd
1857 keyboard and serial format: kbd,<serial_device>[,baud]
1858 Optional Kernel mode setting:
1859 kms, kbd format: kms,kbd
1860 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001861
Jason Wessel84c08fd2010-05-20 21:04:24 -05001862 kgdbwait [KGDB] Stop kernel execution and enter the
1863 kernel debugger at the earliest opportunity.
1864
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001865 kmac= [MIPS] korina ethernet MAC address.
1866 Configure the RouterBoard 532 series on-chip
1867 Ethernet adapter MAC address.
1868
Catalin Marinas04f70332009-06-11 13:22:39 +01001869 kmemleak= [KNL] Boot-time kmemleak enable/disable
1870 Valid arguments: on, off
1871 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001872 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1873 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001874
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001875 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1876 Valid arguments: 0, 1, 2
1877 kmemcheck=0 (disabled)
1878 kmemcheck=1 (enabled)
1879 kmemcheck=2 (one-shot mode)
1880 Default: 2 (one-shot mode)
1881
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301882 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001883 in oops dumps.
1884
Andre Przywarafef07aa2009-07-10 14:20:35 +02001885 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1886 Default is 0 (don't ignore, but inject #GP)
1887
Xiao Guangronga182d872010-09-20 22:17:48 +08001888 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1889 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001890 Default is 0 (off)
1891
Andre Przywarafef07aa2009-07-10 14:20:35 +02001892 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001893 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001894
1895 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1896 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001897 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001898
Andre Przywarafef07aa2009-07-10 14:20:35 +02001899 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1900 (virtualized MMU) support on capable Intel chips.
1901 Default is 1 (enabled)
1902
1903 kvm-intel.emulate_invalid_guest_state=
1904 [KVM,Intel] Enable emulation of invalid guest states
1905 Default is 0 (disabled)
1906
1907 kvm-intel.flexpriority=
1908 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1909 Default is 1 (enabled)
1910
Sasha Levine1a72ae2011-08-09 14:28:35 +03001911 kvm-intel.nested=
1912 [KVM,Intel] Enable VMX nesting (nVMX).
1913 Default is 0 (disabled)
1914
Andre Przywarafef07aa2009-07-10 14:20:35 +02001915 kvm-intel.unrestricted_guest=
1916 [KVM,Intel] Disable unrestricted guest feature
1917 (virtualized real and unpaged mode) on capable
1918 Intel chips. Default is 1 (enabled)
1919
1920 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1921 feature (tagged TLBs) on capable Intel chips.
1922 Default is 1 (enabled)
1923
Linus Torvalds1da177e2005-04-16 15:20:36 -07001924 l2cr= [PPC]
1925
Robert Brosea78bfbf2008-03-29 07:20:23 +11001926 l3cr= [PPC]
1927
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001928 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001929 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001930
Suresh Siddha279f1462012-10-22 14:37:58 -07001931 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1932 value for LAPIC timer one-shot implementation. Default
1933 back to the programmable timer unit in the LAPIC.
1934
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301935 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001936 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001937
FD Camifcb71f62008-01-06 19:08:56 +01001938 libata.dma= [LIBATA] DMA control
1939 libata.dma=0 Disable all PATA and SATA DMA
1940 libata.dma=1 PATA and SATA Disk DMA only
1941 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001942 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001943 Combinations also work, so libata.dma=3 enables DMA
1944 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001945
Michael Prokop20308872009-08-06 00:14:10 +02001946 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1947 libata.ignore_hpa=0 keep BIOS limits (default)
1948 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001949
Dave Jones78e70c22007-09-27 11:50:13 -04001950 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1951 when set.
1952 Format: <int>
1953
Tejun Heo33267322008-02-13 09:15:09 +09001954 libata.force= [LIBATA] Force configurations. The format is comma
1955 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001956 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001957 matching port, link or device. Basically, it matches
1958 the ATA ID string printed on console by libata. If
1959 the whole ID part is omitted, the last PORT and DEVICE
1960 values are used. If ID hasn't been specified yet, the
1961 configuration applies to all ports, links and devices.
1962
1963 If only DEVICE is omitted, the parameter applies to
1964 the port and all links and devices behind it. DEVICE
1965 number of 0 either selects the first device or the
1966 first fan-out link behind PMP device. It does not
1967 select the host link. DEVICE number of 15 selects the
1968 host link and device attached to it.
1969
1970 The VAL specifies the configuration to force. As long
1971 as there's no ambiguity shortcut notation is allowed.
1972 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1973 The following configurations can be forced.
1974
1975 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1976 Any ID with matching PORT is used.
1977
1978 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1979
1980 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1981 udma[/][16,25,33,44,66,100,133] notation is also
1982 allowed.
1983
1984 * [no]ncq: Turn on or off NCQ.
1985
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001986 * [no]ncqtrim: Turn off queued DSM TRIM.
1987
Tejun Heo05944bd2008-08-13 20:19:09 +09001988 * nohrst, nosrst, norst: suppress hard, soft
1989 and both resets.
1990
Dan Williamsca6d43b2012-06-21 23:41:41 -07001991 * rstonce: only attempt one reset during
1992 hot-unplug link recovery
1993
Tejun Heo43c9c592010-05-23 12:59:11 +02001994 * dump_id: dump IDENTIFY data.
1995
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001996 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1997
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001998 * disable: Disable this device.
1999
Tejun Heo33267322008-02-13 09:15:09 +09002000 If there are multiple matching configurations changing
2001 the same attribute, the last one is used.
2002
Yinghai Lu95f72d12010-07-12 14:36:09 +10002003 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002004
Linus Torvalds1da177e2005-04-16 15:20:36 -07002005 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002006 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002007
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002008 lockd.nlm_grace_period=P [NFS] Assign grace period.
2009 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002010
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002011 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2012 Format: <integer>
2013
2014 lockd.nlm_timeout=T [NFS] Assign timeout value.
2015 Format: <integer>
2016
2017 lockd.nlm_udpport=M [NFS] Assign UDP port.
2018 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002019
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07002020 locktorture.nreaders_stress= [KNL]
2021 Set the number of locking read-acquisition kthreads.
2022 Defaults to being automatically set based on the
2023 number of online CPUs.
2024
2025 locktorture.nwriters_stress= [KNL]
2026 Set the number of locking write-acquisition kthreads.
2027
2028 locktorture.onoff_holdoff= [KNL]
2029 Set time (s) after boot for CPU-hotplug testing.
2030
2031 locktorture.onoff_interval= [KNL]
2032 Set time (s) between CPU-hotplug operations, or
2033 zero to disable CPU-hotplug testing.
2034
2035 locktorture.shuffle_interval= [KNL]
2036 Set task-shuffle interval (jiffies). Shuffling
2037 tasks allows some CPUs to go into dyntick-idle
2038 mode during the locktorture test.
2039
2040 locktorture.shutdown_secs= [KNL]
2041 Set time (s) after boot system shutdown. This
2042 is useful for hands-off automated testing.
2043
2044 locktorture.stat_interval= [KNL]
2045 Time (s) between statistics printk()s.
2046
2047 locktorture.stutter= [KNL]
2048 Time (s) to stutter testing, for example,
2049 specifying five seconds causes the test to run for
2050 five seconds, wait for five seconds, and so on.
2051 This tests the locking primitive's ability to
2052 transition abruptly to and from idle.
2053
2054 locktorture.torture_runnable= [BOOT]
2055 Start locktorture running at boot time.
2056
2057 locktorture.torture_type= [KNL]
2058 Specify the locking implementation to test.
2059
2060 locktorture.verbose= [KNL]
2061 Enable additional printk() statements.
2062
Linus Torvalds1da177e2005-04-16 15:20:36 -07002063 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2064 Format: <irq>
2065
2066 loglevel= All Kernel Messages with a loglevel smaller than the
2067 console loglevel will be printed to the console. It can
2068 also be changed with klogd or other programs. The
2069 loglevels are defined as follows:
2070
2071 0 (KERN_EMERG) system is unusable
2072 1 (KERN_ALERT) action must be taken immediately
2073 2 (KERN_CRIT) critical conditions
2074 3 (KERN_ERR) error conditions
2075 4 (KERN_WARNING) warning conditions
2076 5 (KERN_NOTICE) normal but significant condition
2077 6 (KERN_INFO) informational
2078 7 (KERN_DEBUG) debug-level messages
2079
Randy Dunlapc756d082011-02-20 20:08:35 -08002080 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07002081 in bytes. n must be a power of two and greater
2082 than the minimal size. The minimal size is defined
2083 by LOG_BUF_SHIFT kernel config parameter. There is
2084 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2085 that allows to increase the default size depending on
2086 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087
Randy Dunlapaccaa242007-10-16 01:29:37 -07002088 logo.nologo [FB] Disables display of the built-in Linux logo.
2089 This may be used to provide more screen space for
2090 kernel log messages and is useful when debugging
2091 kernel boot problems.
2092
Linus Torvalds1da177e2005-04-16 15:20:36 -07002093 lp=0 [LP] Specify parallel ports to use, e.g,
2094 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2095 lp=reset first parallel port). 'lp=0' disables the
2096 lp=auto printer driver. 'lp=reset' (which can be
2097 specified in addition to the ports) causes
2098 attached printers to be reset. Using
2099 lp=port1,port2,... specifies the parallel ports
2100 to associate lp devices with, starting with
2101 lp0. A port specification may be 'none' to skip
2102 that lp device, or a parport name such as
2103 'parport0'. Specifying 'lp=auto' instead of a
2104 port specification list means that device IDs
2105 from each port should be examined, to see if
2106 an IEEE 1284-compliant printer is attached; if
2107 so, the driver will manage that printer.
2108 See also header of drivers/char/lp.c.
2109
2110 lpj=n [KNL]
2111 Sets loops_per_jiffy to given constant, thus avoiding
2112 time-consuming boot-time autodetection (up to 250 ms per
2113 CPU). 0 enables autodetection (default). To determine
2114 the correct value for your kernel, boot with normal
2115 autodetection and see what value is printed. Note that
2116 on SMP systems the preset will be applied to all CPUs,
2117 which is likely to cause problems if your CPUs need
2118 significantly divergent settings. An incorrect value
2119 will cause delays in the kernel to be wrong, leading to
2120 unpredictable I/O errors and other breakage. Although
2121 unlikely, in the extreme case this might damage your
2122 hardware.
2123
2124 ltpc= [NET]
2125 Format: <io>,<irq>,<dma>
2126
Randy Dunlap16290242011-08-13 12:34:52 -07002127 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002128 (machvec) in a generic kernel.
2129 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002130
Wu Zhangjin3209e702009-07-02 23:27:12 +08002131 machtype= [Loongson] Share the same kernel image file between different
2132 yeeloong laptop.
2133 Example: machtype=lemote-yeeloong-2f-7inch
2134
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002135 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2136 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002137
2138 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04002139 should make use of. maxcpus=n : n >= 0 limits the
2140 kernel to using 'n' processors. n=0 is a special case,
2141 it is equivalent to "nosmp", which also disables
2142 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002143
Kay Sieversd134b002011-07-31 22:08:04 +02002144 max_loop= [LOOP] The number of loop block devices that get
2145 (loop.max_loop) unconditionally pre-created at init time. The default
2146 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2147 of statically allocating a predefined number, loop
2148 devices can be requested on-demand with the
2149 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002150
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002151 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152
Uwe Hermann71cced62008-10-20 09:32:21 -07002153 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002154
Linus Torvalds1da177e2005-04-16 15:20:36 -07002155 md= [HW] RAID subsystems devices and level
2156 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002157
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158 mdacon= [MDA]
2159 Format: <first>,<last>
2160 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002161
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2163 Amount of memory to be used when the kernel is not able
2164 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002165 [X86] Work as limiting max address. Use together
2166 with memmap= to avoid physical address space collisions.
2167 Without memmap= PCI devices could be placed at addresses
2168 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002169
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002170 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171 memory.
2172
Paul Mundt6902aa82008-09-21 17:14:42 +09002173 memchunk=nn[KMG]
2174 [KNL,SH] Allow user to override the default size for
2175 per-device physically contiguous DMA buffers.
2176
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002177 memhp_default_state=online/offline
2178 [KNL] Set the initial state for the memory hotplug
2179 onlining policy. If not specified, the default value is
2180 set according to the
2181 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2182 option.
2183 See Documentation/memory-hotplug.txt.
2184
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302185 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186 E820 memory map, as specified by the user.
2187 Such memmap=exactmap lines can be constructed based on
2188 BIOS output or other requirements. See the memmap=nn@ss
2189 option description.
2190
2191 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002192 [KNL] Force usage of a specific region of memory.
2193 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002194
2195 memmap=nn[KMG]#ss[KMG]
2196 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002197 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002198
2199 memmap=nn[KMG]$ss[KMG]
2200 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002201 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002202 Example: Exclude memory from 0x18690000-0x1869ffff
2203 memmap=64K$0x18690000
2204 or
2205 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002206
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002207 memmap=nn[KMG]!ss[KMG]
2208 [KNL,X86] Mark specific memory as protected.
2209 Region of memory to be used, from ss to ss+nn.
2210 The memory region may be marked as e820 type 12 (0xc)
2211 and is NVDIMM or ADR memory.
2212
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002213 memory_corruption_check=0/1 [X86]
2214 Some BIOSes seem to corrupt the first 64k of
2215 memory when doing things like suspend/resume.
2216 Setting this option will scan the memory
2217 looking for corruption. Enabling this will
2218 both detect corruption and prevent the kernel
2219 from using the memory being corrupted.
2220 However, its intended as a diagnostic tool; if
2221 repeatable BIOS-originated corruption always
2222 affects the same memory, you can use memmap=
2223 to prevent the kernel from using that memory.
2224
2225 memory_corruption_check_size=size [X86]
2226 By default it checks for corruption in the low
2227 64k, making this memory unavailable for normal
2228 use. Use this parameter to scan for
2229 corruption in more or less memory.
2230
2231 memory_corruption_check_period=seconds [X86]
2232 By default it checks for corruption every 60
2233 seconds. Use this parameter to check at some
2234 other rate. 0 disables periodic checking.
2235
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002236 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002237 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002238 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002239 Specifies the number of memtest passes to be
2240 performed. Each pass selects another test
2241 pattern from a given set of patterns. Memtest
2242 fills the memory with this pattern, validates
2243 memory contents and reserves bad memory
2244 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002245
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 meye.*= [HW] Set MotionEye Camera parameters
2247 See Documentation/video4linux/meye.txt.
2248
Andres Salomon8f368812007-10-12 23:04:06 +02002249 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2250 Multi-Function General Purpose Timers on AMD Geode
2251 platforms.
2252
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002253 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2254 the BIOS has incorrectly applied a workaround. TinyBIOS
2255 version 0.98 is known to be affected, 0.99 fixes the
2256 problem by letting the user disable the workaround.
2257
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258 mga= [HW,DRM]
2259
Randy Dunlap1c207f92008-11-19 15:36:16 -08002260 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2261 physical address is ignored.
2262
Michel Pollet39f45d72009-05-20 11:10:31 +01002263 mini2440= [ARM,HW,KNL]
2264 Format:[0..2][b][c][t]
2265 Default: "0tb"
2266 MINI2440 configuration specification:
2267 0 - The attached screen is the 3.5" TFT
2268 1 - The attached screen is the 7" TFT
2269 2 - The VGA Shield is attached (1024x768)
2270 Leaving out the screen size parameter will not load
2271 the TFT driver, and the framebuffer will be left
2272 unconfigured.
2273 b - Enable backlight. The TFT backlight pin will be
2274 linked to the kernel VESA blanking code and a GPIO
2275 LED. This parameter is not necessary when using the
2276 VGA shield.
2277 c - Enable the s3c camera interface.
2278 t - Reserved for enabling touchscreen support. The
2279 touchscreen support is not enabled in the mainstream
2280 kernel as of 2.6.30, a preliminary port can be found
2281 in the "bleeding edge" mini2440 support kernel at
2282 http://repo.or.cz/w/linux-2.6/mini2440.git
2283
Mel Gorman6b74ab92008-07-23 21:26:49 -07002284 mminit_loglevel=
2285 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2286 parameter allows control of the logging verbosity for
2287 the additional memory initialisation checks. A value
2288 of 0 disables mminit logging and a level of 4 will
2289 log everything. Information is printed at KERN_DEBUG
2290 so loglevel=8 may also need to be specified.
2291
Rusty Russell106a4ee2012-09-26 10:09:40 +01002292 module.sig_enforce
2293 [KNL] When CONFIG_MODULE_SIG is set, this means that
2294 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002295 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002296 is always true, so this option does nothing.
2297
Linus Torvalds1da177e2005-04-16 15:20:36 -07002298 mousedev.tap_time=
2299 [MOUSE] Maximum time between finger touching and
2300 leaving touchpad surface for touch to be considered
2301 a tap and be reported as a left button click (for
2302 touchpads working in absolute mode only).
2303 Format: <msecs>
2304 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2305 reporting absolute coordinates, such as tablets
2306 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2307 reporting absolute coordinates, such as tablets
2308
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302309 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002310 is similar to kernelcore except it specifies the
2311 amount of memory used for migratable allocations.
2312 If both kernelcore and movablecore is specified,
2313 then kernelcore will be at *least* the specified
2314 value but may be more. If movablecore on its own
2315 is specified, the administrator must be careful
2316 that the amount of memory usable for all allocations
2317 is not too small.
2318
Tang Chenc5320922013-11-12 15:08:10 -08002319 movable_node [KNL,X86] Boot-time switch to enable the effects
2320 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2321
Linus Torvalds1da177e2005-04-16 15:20:36 -07002322 MTD_Partition= [MTD]
2323 Format: <name>,<region-number>,<size>,<offset>
2324
Randy Dunlapa9913042005-10-23 12:57:11 -07002325 MTD_Region= [MTD] Format:
2326 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002327
2328 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002329 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002330
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002331 multitce=off [PPC] This parameter disables the use of the pSeries
2332 firmware feature for updating multiple TCE entries
2333 at a time.
2334
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002335 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2336
2337 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2338
2339 boundary - index of last SLC block on Flex-OneNAND.
2340 The remaining blocks are configured as MLC blocks.
2341 lock - Configure if Flex-OneNAND boundary should be locked.
2342 Once locked, the boundary cannot be changed.
2343 1 indicates lock status, 0 indicates unlock status.
2344
Ben Dooks9db829f2008-07-03 11:24:29 +01002345 mtdset= [ARM]
2346 ARM/S3C2412 JIVE boot control
2347
2348 See arch/arm/mach-s3c2412/mach-jive.c
2349
Linus Torvalds1da177e2005-04-16 15:20:36 -07002350 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002351 [HW] Make the MicroTouch USB driver use raw coordinates
2352 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002353
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002354 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002355 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002356 that could hold holes aka. UC entries.
2357
2358 mtrr_gran_size=nn[KMG] [X86]
2359 Used for mtrr cleanup. It is granularity of mtrr block.
2360 Default is 1.
2361 Large value could prevent small alignment from
2362 using up MTRRs.
2363
2364 mtrr_spare_reg_nr=n [X86]
2365 Format: <integer>
2366 Range: 0,7 : spare reg number
2367 Default : 1
2368 Used for mtrr cleanup. It is spare mtrr entries number.
2369 Set to 2 or more if your graphical card needs more.
2370
Linus Torvalds1da177e2005-04-16 15:20:36 -07002371 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2372
Linus Torvalds1da177e2005-04-16 15:20:36 -07002373 netdev= [NET] Network devices parameters
2374 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2375 Note that mem_start is often overloaded to mean
2376 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002377 This usage is only documented in each driver source
2378 file if at all.
2379
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002380 nf_conntrack.acct=
2381 [NETFILTER] Enable connection tracking flow accounting
2382 0 to disable accounting
2383 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002384 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002385
Chuck Lever306a0752010-09-17 10:54:37 -04002386 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002387 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388
2389 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002390 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002391
Chuck Lever306a0752010-09-17 10:54:37 -04002392 nfsrootdebug [NFS] enable nfsroot debugging messages.
2393 See Documentation/filesystems/nfs/nfsroot.txt.
2394
Trond Myklebusta72b4422006-01-03 09:55:41 +01002395 nfs.callback_tcpport=
2396 [NFS] set the TCP port on which the NFSv4 callback
2397 channel should listen.
2398
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002399 nfs.cache_getent=
2400 [NFS] sets the pathname to the program which is used
2401 to update the NFS client cache entries.
2402
2403 nfs.cache_getent_timeout=
2404 [NFS] sets the timeout after which an attempt to
2405 update a cache entry is deemed to have failed.
2406
Trond Myklebust58df0952006-01-03 09:55:57 +01002407 nfs.idmap_cache_timeout=
2408 [NFS] set the maximum lifetime for idmapper cache
2409 entries.
2410
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002411 nfs.enable_ino64=
2412 [NFS] enable 64-bit inode numbers.
2413 If zero, the NFS client will fake up a 32-bit inode
2414 number for the readdir() and stat() syscalls instead
2415 of returning the full 64-bit number.
2416 The default is to return 64-bit inode numbers.
2417
Trond Myklebustef159e92012-02-06 19:50:40 -05002418 nfs.max_session_slots=
2419 [NFSv4.1] Sets the maximum number of session slots
2420 the client will attempt to negotiate with the server.
2421 This limits the number of simultaneous RPC requests
2422 that the client can send to the NFSv4.1 server.
2423 Note that there is little point in setting this
2424 value higher than the max_tcp_slot_table_limit.
2425
Trond Myklebustb064eca22011-02-22 15:44:32 -08002426 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002427 [NFSv4] When set to the default of '1', this option
2428 ensures that both the RPC level authentication
2429 scheme and the NFS level operations agree to use
2430 numeric uids/gids if the mount is using the
2431 'sec=sys' security flavour. In effect it is
2432 disabling idmapping, which can make migration from
2433 legacy NFSv2/v3 systems to NFSv4 easier.
2434 Servers that do not support this mode of operation
2435 will be autodetected by the client, and it will fall
2436 back to using the idmapper.
2437 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002438 nfs.nfs4_unique_id=
2439 [NFS4] Specify an additional fixed unique ident-
2440 ification string that NFSv4 clients can insert into
2441 their nfs_client_id4 string. This is typically a
2442 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002443
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002444 nfs.send_implementation_id =
2445 [NFSv4.1] Send client implementation identification
2446 information in exchange_id requests.
2447 If zero, no implementation identification information
2448 will be sent.
2449 The default is to send the implementation identification
2450 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002451
2452 nfs.recover_lost_locks =
2453 [NFSv4] Attempt to recover locks that were lost due
2454 to a lease timeout on the server. Please note that
2455 doing this risks data corruption, since there are
2456 no guarantees that the file will remain unchanged
2457 after the locks are lost.
2458 If you want to enable the kernel legacy behaviour of
2459 attempting to recover these locks, then set this
2460 parameter to '1'.
2461 The default parameter value of '0' causes the kernel
2462 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002463
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002464 nfs4.layoutstats_timer =
2465 [NFSv4.2] Change the rate at which the kernel sends
2466 layoutstats to the pNFS metadata server.
2467
2468 Setting this to value to 0 causes the kernel to use
2469 whatever value is the default set by the layout
2470 driver. A non-zero value sets the minimum interval
2471 in seconds between layoutstats transmissions.
2472
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002473 nfsd.nfs4_disable_idmapping=
2474 [NFSv4] When set to the default of '1', the NFSv4
2475 server will return only numeric uids and gids to
2476 clients using auth_sys, and will accept numeric uids
2477 and gids from such clients. This is intended to ease
2478 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002479
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002480 objlayoutdriver.osd_login_prog=
2481 [NFS] [OBJLAYOUT] sets the pathname to the program which
2482 is used to automatically discover and login into new
2483 osd-targets. Please see:
2484 Documentation/filesystems/pnfs.txt for more explanations
2485
Paul Mundt1e1030d2009-09-01 17:38:32 +09002486 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002487 when a NMI is triggered.
2488 Format: [state][,regs][,debounce][,die]
2489
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302490 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002491 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002492 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002493 0 - turn hardlockup detector in nmi_watchdog off
2494 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002495 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002496 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002497 default). To disable both hard and soft lockup detectors,
2498 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002499 This is useful when you use a panic=... timeout and
2500 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002501
Anton Vorontsovbff38772009-07-08 11:10:56 -07002502 netpoll.carrier_timeout=
2503 [NET] Specifies amount of time (in seconds) that
2504 netpoll should wait for a carrier. By default netpoll
2505 waits 4 seconds.
2506
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002507 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508 emulation library even if a 387 maths coprocessor
2509 is present.
2510
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002511 no_console_suspend
2512 [HW] Never suspend the console
2513 Disable suspending of consoles during suspend and
2514 hibernate operations. Once disabled, debugging
2515 messages can reach various consoles while the rest
2516 of the system is being put to sleep (ie, while
2517 debugging driver suspend/resume hooks). This may
2518 not work reliably with all consoles, but is known
2519 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002520 To facilitate more flexible debugging, we also add
2521 console_suspend, a printk module parameter to control
2522 it. Users could use console_suspend (usually
2523 /sys/module/printk/parameters/console_suspend) to
2524 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002525
Christoph Lameterc1aee212007-05-31 00:40:47 -07002526 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2527 caches in the slab allocator. Saves per-node memory,
2528 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002529
Randy Dunlapa9913042005-10-23 12:57:11 -07002530 noalign [KNL,ARM]
2531
Linus Torvalds1da177e2005-04-16 15:20:36 -07002532 noapic [SMP,APIC] Tells the kernel to not make use of any
2533 IOAPICs that may be present in the system.
2534
Mike Galbraith5091faa2010-11-30 14:18:03 +01002535 noautogroup Disable scheduler automatic task group creation.
2536
Linus Torvalds1da177e2005-04-16 15:20:36 -07002537 nobats [PPC] Do not use BATs for mapping kernel lowmem
2538 on "Classic" PPC cores.
2539
2540 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002541
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002542 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2543
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002544 nodelayacct [KNL] Disable per-task delay accounting
2545
Linus Torvalds1da177e2005-04-16 15:20:36 -07002546 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2547
Paul Mundt6902aa82008-09-21 17:14:42 +09002548 nodsp [SH] Disable hardware DSP at boot time.
2549
Dave Youngb2e0a542014-08-14 17:15:26 +08002550 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002551
Linus Torvalds1da177e2005-04-16 15:20:36 -07002552 noexec [IA-64]
2553
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302554 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002555 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002556 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002557 noexec=off: disable non-executable mappings
2558
H. Peter Anvin52b61792012-09-21 12:43:13 -07002559 nosmap [X86]
2560 Disable SMAP (Supervisor Mode Access Prevention)
2561 even if it is supported by processor.
2562
Fenghua Yude5397a2011-05-11 16:51:05 -07002563 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002564 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002565 even if it is supported by processor.
2566
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002567 noexec32 [X86-64]
2568 This affects only 32-bit executables.
2569 noexec32=on: enable non-executable mappings (default)
2570 read doesn't imply executable mappings
2571 noexec32=off: disable non-executable mappings
2572 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002573
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002574 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002575
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002576 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002577 register save and restore. The kernel will only save
2578 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002579
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002580 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2581
Sascha Silbe52c48c52016-04-05 12:53:38 +02002582 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2583 Equivalent to smt=1.
2584
Suresh Siddha0c752a92009-05-22 12:17:45 -07002585 noxsave [BUGS=X86] Disables x86 extended register state save
2586 and restore using xsave. The kernel will fallback to
2587 enabling legacy floating-point and sse state.
2588
Fenghua Yub6f42a42014-05-29 11:12:31 -07002589 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2590 register states. The kernel will fall back to use
2591 xsave to save the states. By using this parameter,
2592 performance of saving the states is degraded because
2593 xsave doesn't support modified optimization while
2594 xsaveopt supports it on xsaveopt enabled systems.
2595
2596 noxsaves [X86] Disables xsaves and xrstors used in saving and
2597 restoring x86 extended register state in compacted
2598 form of xsave area. The kernel will fall back to use
2599 xsaveopt and xrstor to save and restore the states
2600 in standard form of xsave area. By using this
2601 parameter, xsave area per process might occupy more
2602 memory on xsaves enabled systems.
2603
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002604 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2605 wfi(ARM) instruction doesn't work correctly and not to
2606 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002607
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002608 no_file_caps Tells the kernel not to honor file capabilities. The
2609 only way then for a file to be executed with privilege
2610 is to be setuid root or executed by root.
2611
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612 nohalt [IA-64] Tells the kernel not to use the power saving
2613 function PAL_HALT_LIGHT when idle. This increases
2614 power-consumption. On the positive side, it reduces
2615 interrupt wake-up latency, which may improve performance
2616 in certain environments such as networked servers or
2617 real-time systems.
2618
Kees Cooka6e15a32014-06-13 13:30:35 -07002619 nohibernate [HIBERNATION] Disable hibernation and resume.
2620
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002621 nohz= [KNL] Boottime enable/disable dynamic ticks
2622 Valid arguments: on, off
2623 Default: on
2624
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002625 nohz_full= [KNL,BOOT]
2626 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002627 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002628 whenever possible. The boot CPU will be forced outside
2629 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002630 The CPUs in this range must also be included in the
2631 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002632
Paul Mundteeee7852009-04-02 12:31:16 +09002633 noiotrap [SH] Disables trapped I/O port accesses.
2634
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002635 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636 disable unhandled interrupt sources.
2637
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302638 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002639 broken timer IRQ sources.
2640
Linus Torvalds1da177e2005-04-16 15:20:36 -07002641 noisapnp [ISAPNP] Disables ISA PnP code.
2642
2643 noinitrd [RAM] Tells the kernel not to load any configured
2644 initial RAM disk.
2645
Weidong Han03ea8152009-04-17 16:42:15 +08002646 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2647 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002648 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002649
Linus Torvalds1da177e2005-04-16 15:20:36 -07002650 nointroute [IA-64]
2651
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002652 noinvpcid [X86] Disable the INVPCID cpu feature.
2653
Randy Dunlap16290242011-08-13 12:34:52 -07002654 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002655
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002656 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2657
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002658 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2659 fault handling.
2660
Glauber Costad910f5c2011-07-11 15:28:19 -04002661 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2662 steal time is computed, but won't influence scheduler
2663 behaviour
2664
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002665 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002666
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002667 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002668
Linus Torvalds1da177e2005-04-16 15:20:36 -07002669 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002670 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002671
Horms312f1f02006-02-22 09:57:55 +09002672 nomca [IA-64] Disable machine check abort handling
2673
Masanari Iida13696e02015-05-16 02:16:43 +09002674 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002675
Andres Salomon83d73842007-10-12 23:04:06 +02002676 nomfgpt [X86-32] Disable Multi-Function General Purpose
2677 Timer usage (for AMD Geode machines).
2678
Don Zickusbda62632011-10-13 15:14:27 -04002679 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2680 shutdown the other cpus. Instead use the REBOOT_VECTOR
2681 irq.
2682
Dave Young02608be2012-02-01 10:33:14 +08002683 nomodule Disable module load
2684
Jiri Kosina016ddd92010-01-18 17:05:40 +01002685 nopat [X86] Disable PAT (page attribute table extension of
2686 pagetables) support.
2687
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002688 norandmaps Don't use address space randomization. Equivalent to
2689 echo 0 > /proc/sys/kernel/randomize_va_space
2690
Jiri Kosinabbff2162010-08-11 18:34:09 +02002691 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002692
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002693 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002694 with UP alternatives
2695
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002696 nordrand [X86] Disable kernel use of the RDRAND and
2697 RDSEED instructions even if they are supported
2698 by the processor. RDRAND and RDSEED are still
2699 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002700
Randy Dunlapa9913042005-10-23 12:57:11 -07002701 noresume [SWSUSP] Disables resume and restores original swap
2702 space.
2703
Linus Torvalds1da177e2005-04-16 15:20:36 -07002704 no-scroll [VGA] Disables scrollback.
2705 This is required for the Braillex ib80-piezo Braille
2706 reader made by F.H. Papenmeier (Germany).
2707
2708 nosbagart [IA-64]
2709
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002710 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002711
Len Brown61ec7562007-08-16 03:34:22 -04002712 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2713 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714
Dave Jones97842212007-07-15 23:41:05 -07002715 nosoftlockup [KNL] Disable the soft-lockup detector.
2716
Linus Torvalds1da177e2005-04-16 15:20:36 -07002717 nosync [HW,M68K] Disables sync negotiation for all devices.
2718
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002719 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002721 nowatchdog [KNL] Disable both lockup detectors, i.e.
2722 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002723
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002725
Weidong Han2b2fd872009-04-17 16:42:12 +08002726 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2727
Fenghua Yuf78cff42012-11-13 11:32:38 -08002728 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2729 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2730 Some features depend on CPU0. Known dependencies are:
2731 1. Resume from suspend/hibernate depends on CPU0.
2732 Suspend/hibernate will fail if CPU0 is offline and you
2733 need to online CPU0 before suspend/hibernate.
2734 2. PIC interrupts also depend on CPU0. CPU0 can't be
2735 removed if a PIC interrupt is detected.
2736 It's said poweroff/reboot may depend on CPU0 on some
2737 machines although I haven't seen such issues so far
2738 after CPU0 is offline on a few tested machines.
2739 If the dependencies are under your control, you can
2740 turn on cpu0_hotplug.
2741
Randy Dunlap16290242011-08-13 12:34:52 -07002742 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002743 purges which is reported from either PAL_VM_SUMMARY or
2744 SAL PALO.
2745
Yinghai Lu2b633e32010-02-10 01:20:37 -08002746 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2747 could support. nr_cpus=n : n >= 1 limits the kernel to
2748 supporting 'n' processors. Later in runtime you can not
2749 use hotplug cpu feature to put more cpu back to online.
2750 just like you compile the kernel NR_CPUS=n
2751
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002752 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2753
Mel Gorman1a687c22012-11-22 11:16:36 +00002754 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2755 Allowed values are enable and disable
2756
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002757 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2758 one of ['zone', 'node', 'default'] can be specified
2759 This can be set from sysctl after boot.
2760 See Documentation/sysctl/vm.txt for details.
2761
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002762 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2763 See Documentation/debugging-via-ohci1394.txt for more
2764 info.
2765
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002766 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2767 Rather than timing out after 20 ms if an EC
2768 command is not properly ACKed, override the length
2769 of the timeout. We have interrupts disabled while
2770 waiting for the ACK, so if this is set too high
2771 interrupts *may* be lost!
2772
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002773 omap_mux= [OMAP] Override bootloader pin multiplexing.
2774 Format: <mux_mode0.mode_name=value>...
2775 For example, to override I2C bus2:
2776 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2777
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778 oprofile.timer= [HW]
2779 Use timer interrupt instead of performance counters
2780
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002781 oprofile.cpu_type= Force an oprofile cpu type
2782 This might be useful if you have an older oprofile
2783 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002784 Format: { arch_perfmon }
2785 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002786 perfmon on Intel CPUs instead of the
2787 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002788 timer: [X86] Force use of architectural NMI
2789 timer mode (see also oprofile.timer
2790 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002791 [s390] Force legacy basic mode sampling
2792 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002793
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002794 oops=panic Always panic on oopses. Default is to just kill the
2795 process, but there is a small probability of
2796 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002797 This will also cause panics on machine check exceptions.
2798 Useful together with panic=30 to trigger a reboot.
2799
Randy Dunlapbcfde332010-06-07 17:10:38 -07002800 OSS [HW,OSS]
2801 See Documentation/sound/oss/oss-parameters.txt
2802
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002803 page_owner= [KNL] Boot-time page_owner enabling option.
2804 Storage of the information about who allocated
2805 each page is disabled in default. With this switch,
2806 we can turn it on.
2807 on: enable the feature
2808
Laura Abbott8823b1d2016-03-15 14:56:27 -07002809 page_poison= [KNL] Boot-time parameter changing the state of
2810 poisoning on the buddy allocator.
2811 off: turn off poisoning
2812 on: turn on poisoning
2813
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002814 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002815 timeout > 0: seconds before rebooting
2816 timeout = 0: wait forever
2817 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002818 Format: <timeout>
2819
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002820 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2821 on a WARN().
2822
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002823 crash_kexec_post_notifiers
2824 Run kdump after running panic-notifiers and dumping
2825 kmsg. This only for the users who doubt kdump always
2826 succeeds in any situation.
2827 Note that this also increases risks of kdump failure,
2828 because some panic notifiers can make the crashed
2829 kernel more unstable.
2830
Linus Torvalds1da177e2005-04-16 15:20:36 -07002831 parkbd.port= [HW] Parallel port number the keyboard adapter is
2832 connected to, default is 0.
2833 Format: <parport#>
2834 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2835 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002836 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002837
Randy Dunlapa9913042005-10-23 12:57:11 -07002838 parport= [HW,PPT] Specify parallel ports. 0 disables.
2839 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2840 Use 'auto' to force the driver to use any
2841 IRQ/DMA settings detected (the default is to
2842 ignore detected IRQ/DMA settings because of
2843 possible conflicts). You can specify the base
2844 address, IRQ, and DMA settings; IRQ and DMA
2845 should be numbers, or 'auto' (for using detected
2846 settings on that particular port), or 'nofifo'
2847 (to avoid using a FIFO even if it is detected).
2848 Parallel ports are assigned in the order they
2849 are specified on the command line, starting
2850 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002851
Randy Dunlapa9913042005-10-23 12:57:11 -07002852 parport_init_mode= [HW,PPT]
2853 Configure VIA parallel port to operate in
2854 a specific mode. This is necessary on Pegasos
2855 computer where firmware has no options for setting
2856 up parallel port mode and sets it to spp.
2857 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002858 Format: [spp|ps2|epp|ecp|ecpepp]
2859
Andrew Mortondd287792006-03-23 03:00:57 -08002860 pause_on_oops=
2861 Halt all CPUs after the first oops has been printed for
2862 the specified number of seconds. This is to be used if
2863 your oopses keep scrolling off the screen.
2864
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865 pcbit= [HW,ISDN]
2866
2867 pcd. [PARIDE]
2868 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002869 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002870
Randy Dunlapa9913042005-10-23 12:57:11 -07002871 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002872 earlydump [X86] dump PCI config space before the kernel
2873 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002874 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002875 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002876 the hardware directly. Use this if your machine
2877 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002878 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002879 hardware access methods are allowed. Use this
2880 if you experience crashes upon bootup and you
2881 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002882 conf1 [X86] Force use of PCI Configuration Access
2883 Mechanism 1 (config address in IO port 0xCF8,
2884 data in IO port 0xCFC, both 32-bit).
2885 conf2 [X86] Force use of PCI Configuration Access
2886 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2887 the function, IO port 0xCFA, also 8-bit, sets
2888 bus number. The config space is then accessed
2889 through ports 0xC000-0xCFFF).
2890 See http://wiki.osdev.org/PCI for more info
2891 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002892 noaer [PCIE] If the PCIEAER kernel config parameter is
2893 enabled, this kernel boot option can be used to
2894 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002895 nodomains [PCI] Disable support for multiple PCI
2896 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302897 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002898 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002899 check_enable_amd_mmconf [X86] check for and enable
2900 properly configured MMIO access to PCI
2901 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002902 nomsi [MSI] If the PCI_MSI kernel config parameter is
2903 enabled, this kernel boot option can be used to
2904 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002905 noioapicquirk [APIC] Disable all boot interrupt quirks.
2906 Safety option to keep boot IRQs enabled. This
2907 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002908 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2909 primary IO-APIC for bridges that cannot disable
2910 boot IRQs. This fixes a source of spurious IRQs
2911 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002912 noioapicreroute [APIC] Disable workaround that uses the
2913 boot IRQ equivalent of an IRQ that connects to
2914 a chipset where boot IRQs cannot be disabled.
2915 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002916 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002917 routing table. These calls are known to be buggy
2918 on several machines and they hang the machine
2919 when used, but on other computers it's the only
2920 way to get the interrupt routing table. Try
2921 this option if the kernel is unable to allocate
2922 IRQs or discover secondary PCI buses on your
2923 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002924 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002925 Use with caution as certain devices share
2926 address decoders between ROMs and other
2927 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002928 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002929 expansion ROMs that do not already have
2930 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002931 nobar [X86] Do not assign address space to the
2932 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002933 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002934 assigned automatically to PCI devices. You can
2935 make the kernel exclude IRQs of your ISA cards
2936 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002937 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002938 of the PIRQ table (normally generated
2939 by the BIOS) if it is outside the
2940 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002941 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002942 useful if the kernel is unable to find your
2943 secondary buses and you want to tell it
2944 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002945 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002946 numbers ourselves, overriding
2947 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002948 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002949 in the BIOS $PIR table. This is needed on
2950 some systems with broken BIOSes, notably
2951 some HP Pavilion N5400 and Omnibook XE3
2952 notebooks. This will have no effect if ACPI
2953 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002954 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002955 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002956 use_crs [X86] Use PCI host bridge window information
2957 from ACPI. On BIOSes from 2008 or later, this
2958 is enabled by default. If you need to use this,
2959 please report a bug.
2960 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2961 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002962 routeirq Do IRQ routing for all PCI devices.
2963 This is normally done in pci_enable_device(),
2964 so this option is a temporary workaround
2965 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002966 skip_isa_align [X86] do not align io start addr, so can
2967 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02002968 noearly [X86] Don't do any early type 1 scanning.
2969 This might help on some broken boards which
2970 machine check when some devices' config space
2971 is read. But various workarounds are disabled
2972 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002973 bfsort Sort PCI devices into breadth-first order.
2974 This sorting is done to get a device
2975 order compatible with older (<= 2.4) kernels.
2976 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002977 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2978 tuning and use the BIOS-configured MPS defaults.
2979 pcie_bus_safe Set every device's MPS to the largest value
2980 supported by all devices below the root complex.
2981 pcie_bus_perf Set device MPS to the largest allowable MPS
2982 based on its parent bus. Also set MRRS (Max
2983 Read Request Size) to the largest supported
2984 value (no larger than the MPS that the device
2985 or bus can support) for best performance.
2986 pcie_bus_peer2peer Set every device's MPS to 128B, which
2987 every device is guaranteed to support. This
2988 configuration allows peer-to-peer DMA between
2989 any pair of devices, possibly at the cost of
2990 reduced performance. This also guarantees
2991 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002992 cbiosize=nn[KMG] The fixed amount of bus space which is
2993 reserved for the CardBus bridge's IO window.
2994 The default value is 256 bytes.
2995 cbmemsize=nn[KMG] The fixed amount of bus space which is
2996 reserved for the CardBus bridge's memory
2997 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002998 resource_alignment=
2999 Format:
3000 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3001 Specifies alignment and device to reassign
3002 aligned memory resources.
3003 If <order of align> is not specified,
3004 PAGE_SIZE is used as alignment.
3005 PCI-PCI bridge can be specified, if resource
3006 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06003007 ecrc= Enable/disable PCIe ECRC (transaction layer
3008 end-to-end CRC checking).
3009 bios: Use BIOS/firmware settings. This is the
3010 the default.
3011 off: Turn ECRC off
3012 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08003013 hpiosize=nn[KMG] The fixed amount of bus space which is
3014 reserved for hotplug bridge's IO window.
3015 Default size is 256 bytes.
3016 hpmemsize=nn[KMG] The fixed amount of bus space which is
3017 reserved for hotplug bridge's memory window.
3018 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08003019 realloc= Enable/disable reallocating PCI bridge resources
3020 if allocations done by BIOS are too small to
3021 accommodate resources required by all child
3022 devices.
3023 off: Turn realloc off
3024 on: Turn realloc on
3025 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01003026 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06003027 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3028 only look for one device below a PCIe downstream
3029 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003030
Chuck Ebberte5665a42008-09-24 20:40:34 -04003031 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3032 Management.
3033 off Disable ASPM.
3034 force Enable ASPM even on devices that claim not to support it.
3035 WARNING: Forcing ASPM on may cause system lockups.
3036
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05003037 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3038 nomsi Do not use MSI for PCI Express Native Hotplug (this
3039 makes all PCIe ports use INTx for hotplug services).
3040
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003041 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003042 auto Ask the BIOS whether or not to use native PCIe services
3043 associated with PCIe ports (PME, hot-plug, AER). Use
3044 them only if that is allowed by the BIOS.
3045 native Use native PCIe services associated with PCIe ports
3046 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003047 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3048 ports driver.
3049
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003050 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003051 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003052 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003053
Linus Torvalds1da177e2005-04-16 15:20:36 -07003054 pcmv= [HW,PCMCIA] BadgePAD 4
3055
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303056 pd_ignore_unused
3057 [PM]
3058 Keep all power-domains already enabled by bootloader on,
3059 even if no driver has claimed them. This is useful
3060 for debug and development, but should not be
3061 needed on a platform with proper driver support.
3062
Linus Torvalds1da177e2005-04-16 15:20:36 -07003063 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003064 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003065
3066 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3067 boot time.
3068 Format: { 0 | 1 }
3069 See arch/parisc/kernel/pdc_chassis.c
3070
Tejun Heof58dc012009-08-14 15:00:50 +09003071 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003072 Currently supported values are "embed" and "page".
3073 Archs may support subset or none of the selections.
3074 See comments in mm/percpu.c for details on each
3075 allocator. This parameter is primarily for debugging
3076 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003077
Linus Torvalds1da177e2005-04-16 15:20:36 -07003078 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003079 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003080
3081 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003082 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003083
3084 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003085 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003086
3087 plip= [PPT,NET] Parallel port network link
3088 Format: { parport<nr> | timid | 0 }
3089 See also Documentation/parport.txt.
3090
Randy Dunlap16290242011-08-13 12:34:52 -07003091 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003092 Override pmtimer IOPort with a hex value.
3093 e.g. pmtmr=0x508
3094
Bjorn Helgaas96242112011-08-11 12:14:05 -06003095 pnp.debug=1 [PNP]
3096 Enable PNP debug messages (depends on the
3097 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3098 via /sys/module/pnp/parameters/debug. We always show
3099 current resource usage; turning this on also shows
3100 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003101
Linus Torvalds1da177e2005-04-16 15:20:36 -07003102 pnpacpi= [ACPI]
3103 { off }
3104
3105 pnpbios= [ISAPNP]
3106 { on | off | curr | res | no-curr | no-res }
3107
3108 pnp_reserve_irq=
3109 [ISAPNP] Exclude IRQs for the autoconfiguration
3110
3111 pnp_reserve_dma=
3112 [ISAPNP] Exclude DMAs for the autoconfiguration
3113
3114 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003115 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003116
3117 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003118 [ISAPNP] Exclude memory regions for the
3119 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003120 Ranges are in pairs (memory base and size).
3121
Randy Dunlap4af94f32009-04-17 18:30:28 -07003122 ports= [IP_VS_FTP] IPVS ftp helper module
3123 Default is 21.
3124 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3125 may be specified.
3126 Format: <port>,<port>....
3127
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003128 ppc_strict_facility_enable
3129 [PPC] This option catches any kernel floating point,
3130 Altivec, VSX and SPE outside of regions specifically
3131 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3132 There is some performance impact when enabling this.
3133
Ingo Molnar45807a12007-07-15 23:40:10 -07003134 print-fatal-signals=
3135 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003136
3137 If enabled, warn about various signal handling
3138 related application anomalies: too many signals,
3139 too many POSIX.1 timers, fatal signals causing a
3140 coredump - etc.
3141
3142 If you hit the warning due to signal overflow,
3143 you might want to try "ulimit -i unlimited".
3144
Ingo Molnar45807a12007-07-15 23:40:10 -07003145 default: off.
3146
Matthew Garrettc22ab332012-03-05 14:59:10 -08003147 printk.always_kmsg_dump=
3148 Trigger kmsg_dump for cases other than kernel oops or
3149 panics
3150 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3151 default: disabled
3152
Randy Dunlape84845c2007-07-15 23:40:25 -07003153 printk.time= Show timing data prefixed to each printk message line
3154 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3155
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003156 processor.max_cstate= [HW,ACPI]
3157 Limit processor to maximum C-state
3158 max_cstate=9 overrides any DMI blacklist limit.
3159
3160 processor.nocst [HW,ACPI]
3161 Ignore the _CST method to determine C-states,
3162 instead using the legacy FADT method
3163
Linus Torvalds1da177e2005-04-16 15:20:36 -07003164 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003165 Format: [schedule,]<number>
3166 Param: "schedule" - profile schedule points.
3167 Param: <number> - step/bucket size as a power of 2 for
3168 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003169 Param: "sleep" - profile D-state sleeping (millisecs).
3170 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003171 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003172
Linus Torvalds1da177e2005-04-16 15:20:36 -07003173 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3174 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003175 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003176
Randy Dunlapa9913042005-10-23 12:57:11 -07003177 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3178 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003179 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3180 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003181 psmouse.resetafter= [HW,MOUSE]
3182 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003183 (0 = never).
3184 psmouse.resolution=
3185 [HW,MOUSE] Set desired mouse resolution, in dpi.
3186 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003187 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003188 0 = disabled, 1 = enabled (default).
3189
Matthew Garrettdee28e72011-07-21 16:57:55 -04003190 pstore.backend= Specify the name of the pstore backend to use
3191
Linus Torvalds1da177e2005-04-16 15:20:36 -07003192 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003193 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003194
Kay Sieversdc8c8582007-08-15 12:25:38 +02003195 pty.legacy_count=
3196 [KNL] Number of legacy pty's. Overwrites compiled-in
3197 default number.
3198
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003199 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003200
Linus Torvalds1da177e2005-04-16 15:20:36 -07003201 r128= [HW,DRM]
3202
3203 raid= [HW,RAID]
3204 See Documentation/md.txt.
3205
Linus Torvalds1da177e2005-04-16 15:20:36 -07003206 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003207 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003208
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003209 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003210 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3211 the specified list of CPUs to be no-callback CPUs.
3212 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003213 be offloaded to "rcuox/N" kthreads created for
3214 that purpose, where "x" is "b" for RCU-bh, "p"
3215 for RCU-preempt, and "s" for RCU-sched, and "N"
3216 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003217 offloaded CPUs, which can be useful for HPC and
3218 real-time workloads. It can also improve energy
3219 efficiency for asymmetric multiprocessors.
3220
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003221 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003222 Rather than requiring that offloaded CPUs
3223 (specified by rcu_nocbs= above) explicitly
3224 awaken the corresponding "rcuoN" kthreads,
3225 make these kthreads poll for callbacks.
3226 This improves the real-time response for the
3227 offloaded CPUs by relieving them of the need to
3228 wake up the corresponding kthread, but degrades
3229 energy efficiency by requiring that the kthreads
3230 periodically wake up to do the polling.
3231
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003232 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003233 Set maximum number of finished RCU callbacks to
3234 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003235
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003236 rcutree.dump_tree= [KNL]
3237 Dump the structure of the rcu_node combining tree
3238 out at early boot. This is used for diagnostic
3239 purposes, to verify correct tree setup.
3240
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003241 rcutree.gp_cleanup_delay= [KNL]
3242 Set the number of jiffies to delay each step of
3243 RCU grace-period cleanup. This only has effect
3244 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3245
Paul E. McKenney37745d22015-01-22 18:24:08 -08003246 rcutree.gp_init_delay= [KNL]
3247 Set the number of jiffies to delay each step of
3248 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003249 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3250 is set.
3251
3252 rcutree.gp_preinit_delay= [KNL]
3253 Set the number of jiffies to delay each step of
3254 RCU grace-period pre-initialization, that is,
3255 the propagation of recent CPU-hotplug changes up
3256 the rcu_node combining tree. This only has effect
3257 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003258
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003259 rcutree.rcu_fanout_exact= [KNL]
3260 Disable autobalancing of the rcu_node combining
3261 tree. This is used by rcutorture, and might
3262 possibly be useful for architectures having high
3263 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003264
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003265 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003266 Change the number of CPUs assigned to each
3267 leaf rcu_node structure. Useful for very
3268 large systems, which will choose the value 64,
3269 and for NUMA systems with large remote-access
3270 latencies, which will choose a value aligned
3271 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003272
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003273 rcutree.jiffies_till_sched_qs= [KNL]
3274 Set required age in jiffies for a
3275 given grace period before RCU starts
3276 soliciting quiescent-state help from
3277 rcu_note_context_switch().
3278
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003279 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003280 Set delay from grace-period initialization to
3281 first attempt to force quiescent states.
3282 Units are jiffies, minimum value is zero,
3283 and maximum value is HZ.
3284
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003285 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003286 Set delay between subsequent attempts to force
3287 quiescent states. Units are jiffies, minimum
3288 value is one, and maximum value is HZ.
3289
Clark Williams21871d72014-09-12 21:21:09 -05003290 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003291 Set the SCHED_FIFO priority of the RCU per-CPU
3292 kthreads (rcuc/N). This value is also used for
3293 the priority of the RCU boost threads (rcub/N)
3294 and for the RCU grace-period kthreads (rcu_bh,
3295 rcu_preempt, and rcu_sched). If RCU_BOOST is
3296 set, valid values are 1-99 and the default is 1
3297 (the least-favored priority). Otherwise, when
3298 RCU_BOOST is not set, valid values are 0-99 and
3299 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003300
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003301 rcutree.rcu_nocb_leader_stride= [KNL]
3302 Set the number of NOCB kthread groups, which
3303 defaults to the square root of the number of
3304 CPUs. Larger numbers reduces the wakeup overhead
3305 on the per-CPU grace-period kthreads, but increases
3306 that same overhead on each group's leader.
3307
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003308 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003309 Set threshold of queued RCU callbacks beyond which
3310 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003311
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003312 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003313 Set threshold of queued RCU callbacks below which
3314 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003315
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003316 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003317 Set wakeup interval for idle CPUs that have
3318 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003319
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003320 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003321 Set wakeup interval for idle CPUs that have
3322 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3323 Lazy RCU callbacks are those which RCU can
3324 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003325
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003326 rcuperf.gp_exp= [KNL]
3327 Measure performance of expedited synchronous
3328 grace-period primitives.
3329
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003330 rcuperf.holdoff= [KNL]
3331 Set test-start holdoff period. The purpose of
3332 this parameter is to delay the start of the
3333 test until boot completes in order to avoid
3334 interference.
3335
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003336 rcuperf.nreaders= [KNL]
3337 Set number of RCU readers. The value -1 selects
3338 N, where N is the number of CPUs. A value
3339 "n" less than -1 selects N-n+1, where N is again
3340 the number of CPUs. For example, -2 selects N
3341 (the number of CPUs), -3 selects N+1, and so on.
3342 A value of "n" less than or equal to -N selects
3343 a single reader.
3344
3345 rcuperf.nwriters= [KNL]
3346 Set number of RCU writers. The values operate
3347 the same as for rcuperf.nreaders.
3348 N, where N is the number of CPUs
3349
3350 rcuperf.perf_runnable= [BOOT]
3351 Start rcuperf running at boot time.
3352
3353 rcuperf.shutdown= [KNL]
3354 Shut the system down after performance tests
3355 complete. This is useful for hands-off automated
3356 testing.
3357
3358 rcuperf.perf_type= [KNL]
3359 Specify the RCU implementation to test.
3360
3361 rcuperf.verbose= [KNL]
3362 Enable additional printk() statements.
3363
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003364 rcutorture.cbflood_inter_holdoff= [KNL]
3365 Set holdoff time (jiffies) between successive
3366 callback-flood tests.
3367
3368 rcutorture.cbflood_intra_holdoff= [KNL]
3369 Set holdoff time (jiffies) between successive
3370 bursts of callbacks within a given callback-flood
3371 test.
3372
3373 rcutorture.cbflood_n_burst= [KNL]
3374 Set the number of bursts making up a given
3375 callback-flood test. Set this to zero to
3376 disable callback-flood testing.
3377
3378 rcutorture.cbflood_n_per_burst= [KNL]
3379 Set the number of callbacks to be registered
3380 in a given burst of a callback-flood test.
3381
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003382 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003383 Set duration of force_quiescent_state bursts
3384 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003385
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003386 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003387 Set holdoff time within force_quiescent_state bursts
3388 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003389
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003390 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003391 Set wait time between force_quiescent_state bursts
3392 in seconds.
3393
3394 rcutorture.gp_cond= [KNL]
3395 Use conditional/asynchronous update-side
3396 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003397
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003398 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003399 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003400
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003401 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003402 Use normal (non-expedited) asynchronous
3403 update-side primitives, if available.
3404
3405 rcutorture.gp_sync= [KNL]
3406 Use normal (non-expedited) synchronous
3407 update-side primitives, if available. If all
3408 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3409 rcutorture.gp_normal=, and rcutorture.gp_sync=
3410 are zero, rcutorture acts as if is interpreted
3411 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003412
3413 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003414 Set callbacks/threads for rcu_barrier() testing.
3415
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003416 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003417 Set number of concurrent RCU writers. These just
3418 stress RCU, they don't participate in the actual
3419 test, hence the "fake".
3420
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003421 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003422 Set number of RCU readers. The value -1 selects
3423 N-1, where N is the number of CPUs. A value
3424 "n" less than -1 selects N-n-2, where N is again
3425 the number of CPUs. For example, -2 selects N
3426 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003427
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003428 rcutorture.object_debug= [KNL]
3429 Enable debug-object double-call_rcu() testing.
3430
3431 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003432 Set time (s) after boot for CPU-hotplug testing.
3433
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003434 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003435 Set time (s) between CPU-hotplug operations, or
3436 zero to disable CPU-hotplug testing.
3437
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003438 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003439 Set task-shuffle interval (s). Shuffling tasks
3440 allows some CPUs to go into dyntick-idle mode
3441 during the rcutorture test.
3442
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003443 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003444 Set time (s) after boot system shutdown. This
3445 is useful for hands-off automated testing.
3446
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003447 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003448 Duration of CPU stall (s) to test RCU CPU stall
3449 warnings, zero to disable.
3450
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003451 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003452 Time to wait (s) after boot before inducing stall.
3453
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003454 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003455 Time (s) between statistics printk()s.
3456
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003457 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003458 Time (s) to stutter testing, for example, specifying
3459 five seconds causes the test to run for five seconds,
3460 wait for five seconds, and so on. This tests RCU's
3461 ability to transition abruptly to and from idle.
3462
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003463 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003464 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3465 "Maybe" means test if the RCU implementation
3466 under test support RCU priority boosting.
3467
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003468 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003469 Duration (s) of each individual boost test.
3470
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003471 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003472 Interval (s) between each boost test.
3473
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003474 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003475 Test RCU's dyntick-idle handling. See also the
3476 rcutorture.shuffle_interval parameter.
3477
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003478 rcutorture.torture_runnable= [BOOT]
3479 Start rcutorture running at boot time.
3480
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003481 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003482 Specify the RCU implementation to test.
3483
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003484 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003485 Enable additional printk() statements.
3486
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003487 rcupdate.rcu_cpu_stall_suppress= [KNL]
3488 Suppress RCU CPU stall warning messages.
3489
3490 rcupdate.rcu_cpu_stall_timeout= [KNL]
3491 Set timeout for RCU CPU stall warning messages.
3492
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003493 rcupdate.rcu_expedited= [KNL]
3494 Use expedited grace-period primitives, for
3495 example, synchronize_rcu_expedited() instead
3496 of synchronize_rcu(). This reduces latency,
3497 but can increase CPU utilization, degrade
3498 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003499 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003500
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003501 rcupdate.rcu_normal= [KNL]
3502 Use only normal grace-period primitives,
3503 for example, synchronize_rcu() instead of
3504 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003505 real-time latency, CPU utilization, and
3506 energy efficiency, but can expose users to
3507 increased grace-period latency. This parameter
3508 overrides rcupdate.rcu_expedited. No effect on
3509 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003510
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003511 rcupdate.rcu_normal_after_boot= [KNL]
3512 Once boot has completed (that is, after
3513 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003514 only normal grace-period primitives. No effect
3515 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003516
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003517 rcupdate.rcu_task_stall_timeout= [KNL]
3518 Set timeout in jiffies for RCU task stall warning
3519 messages. Disable with a value less than or equal
3520 to zero.
3521
Pranith Kumar74860fe2014-09-19 11:34:09 -04003522 rcupdate.rcu_self_test= [KNL]
3523 Run the RCU early boot self tests
3524
3525 rcupdate.rcu_self_test_bh= [KNL]
3526 Run the RCU bh early boot self tests
3527
3528 rcupdate.rcu_self_test_sched= [KNL]
3529 Run the RCU sched early boot self tests
3530
Olof Johanssonffdfc402005-09-06 15:17:19 -07003531 rdinit= [KNL]
3532 Format: <full_path>
3533 Run specified binary instead of /init from the ramdisk,
3534 used for early userspace startup. See initrd.
3535
Robin Holt1b3a5d02013-07-08 16:01:42 -07003536 reboot= [KNL]
3537 Format (x86 or x86_64):
3538 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3539 [[,]s[mp]#### \
3540 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3541 [[,]f[orce]
3542 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3543 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3544 reboot_force is either force or not specified,
3545 reboot_cpu is s[mp]#### with #### being the processor
3546 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003547
Paul Jackson46b6d942008-07-04 10:00:09 -07003548 relax_domain_level=
3549 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003550 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003551
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003552 relative_sleep_states=
3553 [SUSPEND] Use sleep state labeling where the deepest
3554 state available other than hibernation is always "mem".
3555 Format: { "0" | "1" }
3556 0 -- Traditional sleep state labels.
3557 1 -- Relative sleep state labels.
3558
Linus Torvalds1da177e2005-04-16 15:20:36 -07003559 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3560
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003561 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003562 Format: nn[KMG]
3563 Reserves a hole at the top of the kernel virtual
3564 address space.
3565
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003566 reservelow= [X86]
3567 Format: nn[K]
3568 Set the amount of memory to reserve for BIOS at
3569 the bottom of the address space.
3570
Vivek Goyal7e962872006-09-27 01:50:44 -07003571 reset_devices [KNL] Force drivers to reset the underlying device
3572 during initialization.
3573
Randy Dunlapa9913042005-10-23 12:57:11 -07003574 resume= [SWSUSP]
3575 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003576 Format:
3577 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003578
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003579 resume_offset= [SWSUSP]
3580 Specify the offset from the beginning of the partition
3581 given by "resume=" at which the swap header is located,
3582 in <PAGE_SIZE> units (needed only for swap files).
3583 See Documentation/power/swsusp-and-swap-files.txt
3584
Barry Songf126f732011-10-10 23:38:41 +02003585 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3586 read the resume files
3587
Barry Song6f8d7022011-10-06 20:34:46 +02003588 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3589 Useful for devices that are detected asynchronously
3590 (e.g. USB and MMC devices).
3591
Bojan Smojverf996fc92010-09-09 23:06:23 +02003592 hibernate= [HIBERNATION]
3593 noresume Don't check if there's a hibernation image
3594 present during boot.
3595 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003596 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003597
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003598 retain_initrd [RAM] Keep initrd memory after extraction
3599
Andrew Clausen0efbb782015-01-09 20:24:55 +00003600 rfkill.default_state=
3601 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3602 etc. communication is blocked by default.
3603 1 Unblocked.
3604
3605 rfkill.master_switch_mode=
3606 0 The "airplane mode" button does nothing.
3607 1 The "airplane mode" button toggles between everything
3608 blocked and the previous configuration.
3609 2 The "airplane mode" button toggles between everything
3610 blocked and everything unblocked.
3611
Linus Torvalds1da177e2005-04-16 15:20:36 -07003612 rhash_entries= [KNL,NET]
3613 Set number of hash buckets for route cache
3614
Linus Torvalds1da177e2005-04-16 15:20:36 -07003615 ro [KNL] Mount root device read-only on boot
3616
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003617 rodata= [KNL]
3618 on Mark read-only kernel memory as read-only (default).
3619 off Leave read-only kernel memory writable for debugging.
3620
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003621 rockchip.usb_uart
3622 Enable the uart passthrough on the designated usb port
3623 on Rockchip SoCs. When active, the signals of the
3624 debug-uart get routed to the D+ and D- pins of the usb
3625 port and the regular usb controller gets disabled.
3626
Linus Torvalds1da177e2005-04-16 15:20:36 -07003627 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003628 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003629
3630 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3631 mount the root filesystem
3632
3633 rootflags= [KNL] Set root filesystem mount option string
3634
3635 rootfstype= [KNL] Set root filesystem type
3636
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003637 rootwait [KNL] Wait (indefinitely) for root device to show up.
3638 Useful for devices that are detected asynchronously
3639 (e.g. USB and MMC devices).
3640
Robert Tivy5c71d612013-03-28 18:41:46 -07003641 rproc_mem=nn[KMG][@address]
3642 [KNL,ARM,CMA] Remoteproc physical memory block.
3643 Memory area to be used by remote processor image,
3644 managed by CMA.
3645
Linus Torvalds1da177e2005-04-16 15:20:36 -07003646 rw [KNL] Mount root device read-write on boot
3647
3648 S [KNL] Run init in single mode
3649
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003650 s390_iommu= [HW,S390]
3651 Set s390 IOTLB flushing mode
3652 strict
3653 With strict flushing every unmap operation will result in
3654 an IOTLB flush. Default is lazy flushing before reuse,
3655 which is faster.
3656
Linus Torvalds1da177e2005-04-16 15:20:36 -07003657 sa1100ir [NET]
3658 See drivers/net/irda/sa1100_ir.c.
3659
Linus Torvalds1da177e2005-04-16 15:20:36 -07003660 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003661
Mike Travisf6630112009-11-17 18:22:15 -06003662 sched_debug [KNL] Enables verbose scheduler debug messages.
3663
Mel Gormancb251762016-02-05 09:08:36 +00003664 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3665 Allowed values are enable and disable. This feature
3666 incurs a small amount of overhead in the scheduler
3667 but is useful for debugging and performance tuning.
3668
Mike Galbraith5307c952012-05-08 12:20:58 +02003669 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3670 xtime_lock contention on larger systems, and/or RCU lock
3671 contention on all systems with CONFIG_MAXSMP set.
3672 Format: { "0" | "1" }
3673 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3674 1 -- enable.
3675 Note: increases power consumption, thus should only be
3676 enabled if running jitter sensitive (HPC/RT) workloads.
3677
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003678 security= [SECURITY] Choose a security module to enable at boot.
3679 If this boot parameter is not specified, only the first
3680 security module asking for security registration will be
3681 loaded. An invalid security module name will be treated
3682 as if no module has been chosen.
3683
3684 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003685 Format: { "0" | "1" }
3686 See security/selinux/Kconfig help text.
3687 0 -- disable.
3688 1 -- enable.
3689 Default value is set via kernel config option.
3690 If enabled at boot time, /selinux/disable can be used
3691 later to disable prior to initial policy load.
3692
John Johansenc1c124e2010-07-29 14:48:09 -07003693 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3694 Format: { "0" | "1" }
3695 See security/apparmor/Kconfig help text
3696 0 -- disable.
3697 1 -- enable.
3698 Default value is set via kernel config option.
3699
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003700 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003701
Linus Torvalds1da177e2005-04-16 15:20:36 -07003702 shapers= [NET]
3703 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003704
Yinghai Lub05f78f2008-08-22 01:32:50 -07003705 show_msr= [x86] show boot-time MSR settings
3706 Format: { <integer> }
3707 Show boot-time (BIOS-initialized) MSR settings.
3708 The parameter means the number of CPUs to show,
3709 for example 1 means boot CPU only.
3710
Linus Torvalds1da177e2005-04-16 15:20:36 -07003711 simeth= [IA-64]
3712 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003713
Linus Torvalds1da177e2005-04-16 15:20:36 -07003714 slram= [HW,MTD]
3715
Joonsoo Kim423c9292014-10-09 15:26:22 -07003716 slab_nomerge [MM]
3717 Disable merging of slabs with similar size. May be
3718 necessary if there is some reason to distinguish
3719 allocs to different slabs. Debug options disable
3720 merging on their own.
3721 For more information see Documentation/vm/slub.txt.
3722
David Rientjes3df1ccc2011-10-18 22:09:28 -07003723 slab_max_order= [MM, SLAB]
3724 Determines the maximum allowed order for slabs.
3725 A high setting may cause OOMs due to memory
3726 fragmentation. Defaults to 1 for systems with
3727 more than 32MB of RAM, 0 otherwise.
3728
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003729 slub_debug[=options[,slabs]] [MM, SLUB]
3730 Enabling slub_debug allows one to determine the
3731 culprit if slab objects become corrupted. Enabling
3732 slub_debug can create guard zones around objects and
3733 may poison objects when not in use. Also tracks the
3734 last alloc / free. For more information see
3735 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003736
3737 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003738 Determines the maximum allowed order for slabs.
3739 A high setting may cause OOMs due to memory
3740 fragmentation. For more information see
3741 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003742
3743 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003744 The minimum number of objects per slab. SLUB will
3745 increase the slab order up to slub_max_order to
3746 generate a sufficiently large slab able to contain
3747 the number of objects indicated. The higher the number
3748 of objects the smaller the overhead of tracking slabs
3749 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003750 For more information see Documentation/vm/slub.txt.
3751
3752 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003753 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003754 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003755 For more information see Documentation/vm/slub.txt.
3756
3757 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003758 Same with slab_nomerge. This is supported for legacy.
3759 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003760
Linus Torvalds1da177e2005-04-16 15:20:36 -07003761 smart2= [HW]
3762 Format: <io1>[,<io2>[,...,<io8>]]
3763
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003764 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3765 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3766 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3767 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3768 smsc-ircc2.ircc_irq= [HW] IRQ line
3769 smsc-ircc2.ircc_dma= [HW] DMA channel
3770 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3771 0: Toshiba Satellite 1800 (GP data pin select)
3772 1: Fast pin select (default)
3773 2: ATC IRMode
3774
Sascha Silbe52c48c52016-04-05 12:53:38 +02003775 smt [KNL,S390] Set the maximum number of threads (logical
3776 CPUs) to use per physical CPU on systems capable of
3777 symmetric multithreading (SMT). Will be capped to the
3778 actual hardware limit.
3779 Format: <integer>
3780 Default: -1 (no limit)
3781
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003782 softlockup_panic=
3783 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003784 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003785
Aaron Tomlined235872014-06-23 13:22:05 -07003786 softlockup_all_cpu_backtrace=
3787 [KNL] Should the soft-lockup detector generate
3788 backtraces on all cpus.
3789 Format: <integer>
3790
Linus Torvalds1da177e2005-04-16 15:20:36 -07003791 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003792 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003793
Linus Torvalds1da177e2005-04-16 15:20:36 -07003794 spia_io_base= [HW,MTD]
3795 spia_fio_base=
3796 spia_pedr=
3797 spia_peddr=
3798
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003799 stacktrace [FTRACE]
3800 Enabled the stack tracer on boot up.
3801
Steven Rostedt762e1202011-12-19 22:01:00 -05003802 stacktrace_filter=[function-list]
3803 [FTRACE] Limit the functions that the stack tracer
3804 will trace at boot up. function-list is a comma separated
3805 list of functions. This list can be changed at run
3806 time by the stack_trace_filter file in the debugfs
3807 tracing directory. Note, this enables stack tracing
3808 and the stacktrace above is not needed.
3809
Linus Torvalds1da177e2005-04-16 15:20:36 -07003810 sti= [PARISC,HW]
3811 Format: <num>
3812 Set the STI (builtin display/keyboard on the HP-PARISC
3813 machines) console (graphic card) which should be used
3814 as the initial boot-console.
3815 See also comment in drivers/video/console/sticore.c.
3816
3817 sti_font= [HW]
3818 See comment in drivers/video/console/sticore.c.
3819
3820 stifb= [HW]
3821 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3822
Trond Myklebustcbf11072009-08-09 15:06:19 -04003823 sunrpc.min_resvport=
3824 sunrpc.max_resvport=
3825 [NFS,SUNRPC]
3826 SunRPC servers often require that client requests
3827 originate from a privileged port (i.e. a port in the
3828 range 0 < portnr < 1024).
3829 An administrator who wishes to reserve some of these
3830 ports for other uses may adjust the range that the
3831 kernel's sunrpc client considers to be privileged
3832 using these two parameters to set the minimum and
3833 maximum port values.
3834
Greg Banks42a7fc42007-03-06 01:42:23 -08003835 sunrpc.pool_mode=
3836 [NFS]
3837 Control how the NFS server code allocates CPUs to
3838 service thread pools. Depending on how many NICs
3839 you have and where their interrupts are bound, this
3840 option will affect which CPUs will do NFS serving.
3841 Note: this parameter cannot be changed while the
3842 NFS server is running.
3843
3844 auto the server chooses an appropriate mode
3845 automatically using heuristics
3846 global a single global pool contains all CPUs
3847 percpu one pool for each CPU
3848 pernode one pool for each NUMA node (equivalent
3849 to global on non-NUMA machines)
3850
Trond Myklebustcbf11072009-08-09 15:06:19 -04003851 sunrpc.tcp_slot_table_entries=
3852 sunrpc.udp_slot_table_entries=
3853 [NFS,SUNRPC]
3854 Sets the upper limit on the number of simultaneous
3855 RPC calls that can be sent from the client to a
3856 server. Increasing these values may allow you to
3857 improve throughput, but will also increase the
3858 amount of memory reserved for use by the client.
3859
Brian Norris1d4a9c12015-02-22 21:16:49 -08003860 suspend.pm_test_delay=
3861 [SUSPEND]
3862 Sets the number of seconds to remain in a suspend test
3863 mode before resuming the system (see
3864 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3865 is set. Default value is 5.
3866
Michal Hocko07555ac2013-08-22 16:35:46 -07003867 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003868 [KNL] Enable accounting of swap in memory resource
3869 controller if no parameter or 1 is given or disable
3870 it if 0 is given (See Documentation/cgroups/memory.txt)
3871
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003872 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3873 Format: { <int> | force }
3874 <int> -- Number of I/O TLB slabs
3875 force -- force using of bounce buffers even if they
3876 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003877
Linus Torvalds1da177e2005-04-16 15:20:36 -07003878 switches= [HW,M68k]
3879
Andi Kleene52eec12010-09-08 16:54:17 +02003880 sysfs.deprecated=0|1 [KNL]
3881 Enable/disable old style sysfs layout for old udev
3882 on older distributions. When this option is enabled
3883 very new udev will not work anymore. When this option
3884 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3885 in older udev will not work anymore.
3886 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3887 the kernel configuration.
3888
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003889 sysrq_always_enabled
3890 [KNL]
3891 Ignore sysrq setting - this boot parameter will
3892 neutralize any effect of /proc/sys/kernel/sysrq.
3893 Useful for debugging.
3894
Fabian Frederick747029a2014-11-06 19:46:50 +01003895 tcpmhash_entries= [KNL,NET]
3896 Set the number of tcp_metrics_hash slots.
3897 Default value is 8192 or 16384 depending on total
3898 ram pages. This is used to specify the TCP metrics
3899 cache size. See Documentation/networking/ip-sysctl.txt
3900 "tcp_no_metrics_save" section for more details.
3901
Linus Torvalds1da177e2005-04-16 15:20:36 -07003902 tdfx= [HW,DRM]
3903
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003904 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003905 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003906 standby suspend) or "freeze" (for suspend type freeze)
3907 as the system sleep state during system startup with
3908 the optional capability to repeat N number of times.
3909 The system is woken from this state using a
3910 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003911
Linus Torvalds1da177e2005-04-16 15:20:36 -07003912 thash_entries= [KNL,NET]
3913 Set number of hash buckets for TCP connection
3914
Len Brownf8707ec2007-08-12 00:12:54 -04003915 thermal.act= [HW,ACPI]
3916 -1: disable all active trip points in all thermal zones
3917 <degrees C>: override all lowest active trip points
3918
Len Brownc52a7412007-08-14 15:49:32 -04003919 thermal.crt= [HW,ACPI]
3920 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003921 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003922
Len Brownf5487142007-08-12 00:12:44 -04003923 thermal.nocrt= [HW,ACPI]
3924 Set to disable actions on ACPI thermal zone
3925 critical and hot trip points.
3926
Len Brown72b33ef2007-08-12 00:12:17 -04003927 thermal.off= [HW,ACPI]
3928 1: disable ACPI thermal control
3929
Len Browna70cdc52007-08-12 00:12:35 -04003930 thermal.psv= [HW,ACPI]
3931 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003932 <degrees C>: override all passive trip points to this
3933 value
Len Browna70cdc52007-08-12 00:12:35 -04003934
Len Brown730ff342007-08-12 00:12:26 -04003935 thermal.tzp= [HW,ACPI]
3936 Specify global default ACPI thermal zone polling rate
3937 <deci-seconds>: poll all this frequency
3938 0: no polling (default)
3939
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003940 threadirqs [KNL]
3941 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003942 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003943
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003944 tmem [KNL,XEN]
3945 Enable the Transcendent memory driver if built-in.
3946
3947 tmem.cleancache=0|1 [KNL, XEN]
3948 Default is on (1). Disable the usage of the cleancache
3949 API to send anonymous pages to the hypervisor.
3950
3951 tmem.frontswap=0|1 [KNL, XEN]
3952 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003953 API to send swap pages to the hypervisor. If disabled
3954 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003955
3956 tmem.selfballooning=0|1 [KNL, XEN]
3957 Default is on (1). Disable the driving of swap pages
3958 to the hypervisor.
3959
3960 tmem.selfshrinking=0|1 [KNL, XEN]
3961 Default is on (1). Partial swapoff that immediately
3962 transfers pages from Xen hypervisor back to the
3963 kernel based on different criteria.
3964
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003965 topology= [S390]
3966 Format: {off | on}
3967 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003968 topology information if the hardware supports this.
3969 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003970 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003971 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003972
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003973 topology_updates= [KNL, PPC, NUMA]
3974 Format: {off}
3975 Specify if the kernel should ignore (off)
3976 topology updates sent by the hypervisor to this
3977 LPAR.
3978
Linus Torvalds1da177e2005-04-16 15:20:36 -07003979 tp720= [HW,PS2]
3980
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003981 tpm_suspend_pcr=[HW,TPM]
3982 Format: integer pcr id
3983 Specify that at suspend time, the tpm driver
3984 should extend the specified pcr with zeros,
3985 as a workaround for some chips which fail to
3986 flush the last written pcr on TPM_SaveState.
3987 This will guarantee that all the other pcrs
3988 are saved.
3989
Li Zefan9d612be2009-06-24 17:33:15 +08003990 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003991 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003992
Li Zefan020e5f82009-07-01 10:47:05 +08003993 trace_event=[event-list]
3994 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07003995 to facilitate early boot debugging. The event-list is a
3996 comma separated list of trace events to enable. See
3997 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08003998
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003999 trace_options=[option-list]
4000 [FTRACE] Enable or disable tracer options at boot.
4001 The option-list is a comma delimited list of options
4002 that can be enabled or disabled just as if you were
4003 to echo the option name into
4004
4005 /sys/kernel/debug/tracing/trace_options
4006
4007 For example, to enable stacktrace option (to dump the
4008 stack trace of each event), add to the command line:
4009
4010 trace_options=stacktrace
4011
4012 See also Documentation/trace/ftrace.txt "trace options"
4013 section.
4014
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05004015 tp_printk[FTRACE]
4016 Have the tracepoints sent to printk as well as the
4017 tracing ring buffer. This is useful for early boot up
4018 where the system hangs or reboots and does not give the
4019 option for reading the tracing buffer or performing a
4020 ftrace_dump_on_oops.
4021
4022 To turn off having tracepoints sent to printk,
4023 echo 0 > /proc/sys/kernel/tracepoint_printk
4024 Note, echoing 1 into this file without the
4025 tracepoint_printk kernel cmdline option has no effect.
4026
4027 ** CAUTION **
4028
4029 Having tracepoints sent to printk() and activating high
4030 frequency tracepoints such as irq or sched, can cause
4031 the system to live lock.
4032
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004033 traceoff_on_warning
4034 [FTRACE] enable this option to disable tracing when a
4035 warning is hit. This turns off "tracing_on". Tracing can
4036 be enabled again by echoing '1' into the "tracing_on"
4037 file located in /sys/kernel/debug/tracing/
4038
4039 This option is useful, as it disables the trace before
4040 the WARNING dump is called, which prevents the trace to
4041 be filled with content caused by the warning output.
4042
4043 This option can also be set at run time via the sysctl
4044 option: kernel/traceoff_on_warning
4045
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004046 transparent_hugepage=
4047 [KNL]
4048 Format: [always|madvise|never]
4049 Can be used to control the default behavior of the system
4050 with respect to transparent hugepages.
4051 See Documentation/vm/transhuge.txt for more details.
4052
john stultzd3b8f882009-08-17 16:40:47 -07004053 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004054 Format: <string>
4055 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004056 disables clocksource verification at runtime, as well
4057 as the stability checks done at bootup. Used to enable
4058 high-resolution timer mode on older hardware, and in
4059 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004060 [x86] noirqtime: Do not use TSC to do irq accounting.
4061 Used to run time disable IRQ_TIME_ACCOUNTING on any
4062 platforms where RDTSC is slow and this accounting
4063 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004064
Randy Dunlapa9913042005-10-23 12:57:11 -07004065 turbografx.map[2|3]= [HW,JOY]
4066 TurboGraFX parallel port interface
4067 Format:
4068 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004069 See also Documentation/input/joystick-parport.txt
4070
Christian Kujaub6935f82011-05-31 15:22:05 +00004071 udbg-immortal [PPC] When debugging early kernel crashes that
4072 happen after console_init() and before a proper
4073 console driver takes over, this boot options might
4074 help "seeing" what's going on.
4075
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004076 uhash_entries= [KNL,NET]
4077 Set number of hash buckets for UDP/UDP-Lite connections
4078
Alan Stern5f8364b2006-12-05 16:29:55 -05004079 uhci-hcd.ignore_oc=
4080 [USB] Ignore overcurrent events (default N).
4081 Some badly-designed motherboards generate lots of
4082 bogus events, for ports that aren't wired to
4083 anything. Set this parameter to avoid log spamming.
4084 Note that genuine overcurrent events won't be
4085 reported either.
4086
Simon Arlotte3a61b02008-07-19 23:32:54 +01004087 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004088 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004089
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004090 usbcore.authorized_default=
4091 [USB] Default USB device authorization:
4092 (default -1 = authorized except for wireless USB,
4093 0 = not authorized, 1 = authorized)
4094
Alan Sternb5e795f2007-02-20 15:00:53 -05004095 usbcore.autosuspend=
4096 [USB] The autosuspend time delay (in seconds) used
4097 for newly-detected USB devices (default 2). This
4098 is the time required before an idle device will be
4099 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004100 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004101
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004102 usbcore.usbfs_snoop=
4103 [USB] Set to log all usbfs traffic (default 0 = off).
4104
Alan Stern0290cc92015-11-20 13:53:22 -05004105 usbcore.usbfs_snoop_max=
4106 [USB] Maximum number of bytes to snoop in each URB
4107 (default = 65536).
4108
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004109 usbcore.blinkenlights=
4110 [USB] Set to cycle leds on hubs (default 0 = off).
4111
4112 usbcore.old_scheme_first=
4113 [USB] Start with the old device initialization
4114 scheme (default 0 = off).
4115
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004116 usbcore.usbfs_memory_mb=
4117 [USB] Memory limit (in MB) for buffers allocated by
4118 usbfs (default = 16, 0 = max = 2047).
4119
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004120 usbcore.use_both_schemes=
4121 [USB] Try the other device initialization scheme
4122 if the first one fails (default 1 = enabled).
4123
4124 usbcore.initial_descriptor_timeout=
4125 [USB] Specifies timeout for the initial 64-byte
4126 USB_REQ_GET_DESCRIPTOR request in milliseconds
4127 (default 5000 = 5.0 seconds).
4128
Oliver Neukum40d58142015-12-03 15:03:32 +01004129 usbcore.nousb [USB] Disable the USB subsystem
4130
Linus Torvalds1da177e2005-04-16 15:20:36 -07004131 usbhid.mousepoll=
4132 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004133
Alan Sternd4f373e2008-11-10 14:07:45 -05004134 usb-storage.delay_use=
4135 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004136 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004137
4138 usb-storage.quirks=
4139 [UMS] A list of quirks entries to supplement or
4140 override the built-in unusual_devs list. List
4141 entries are separated by commas. Each entry has
4142 the form VID:PID:Flags where VID and PID are Vendor
4143 and Product ID values (4-digit hex numbers) and
4144 Flags is a set of characters, each corresponding
4145 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004146 a = SANE_SENSE (collect more than 18 bytes
4147 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004148 b = BAD_SENSE (don't collect more than 18
4149 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004150 c = FIX_CAPACITY (decrease the reported
4151 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004152 d = NO_READ_DISC_INFO (don't use
4153 READ_DISC_INFO command);
4154 e = NO_READ_CAPACITY_16 (don't use
4155 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004156 f = NO_REPORT_OPCODES (don't use report opcodes
4157 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004158 g = MAX_SECTORS_240 (don't transfer more than
4159 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004160 h = CAPACITY_HEURISTICS (decrease the
4161 reported device capacity by one
4162 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004163 i = IGNORE_DEVICE (don't bind to this
4164 device);
Hans de Goede13630742016-04-12 12:27:09 +02004165 j = NO_REPORT_LUNS (don't use report luns
4166 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004167 l = NOT_LOCKABLE (don't try to lock and
4168 unlock ejectable media);
4169 m = MAX_SECTORS_64 (don't transfer more
4170 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004171 n = INITIAL_READ10 (force a retry of the
4172 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004173 o = CAPACITY_OK (accept the capacity
4174 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004175 p = WRITE_CACHE (the device cache is ON
4176 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004177 r = IGNORE_RESIDUE (the device reports
4178 bogus residue values);
4179 s = SINGLE_LUN (the device has only one
4180 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004181 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4182 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004183 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004184 w = NO_WP_DETECT (don't test whether the
4185 medium is write-protected).
4186 Example: quirks=0419:aaf5:rl,0421:0433:rc
4187
Stephen Boydac1667d2011-08-13 12:34:50 -07004188 user_debug= [KNL,ARM]
4189 Format: <int>
4190 See arch/arm/Kconfig.debug help text.
4191 1 - undefined instruction events
4192 2 - system calls
4193 4 - invalid data aborts
4194 8 - SIGSEGV faults
4195 16 - SIGBUS faults
4196 Example: user_debug=31
4197
Ian Campbell14315592010-02-17 10:38:10 +00004198 userpte=
4199 [X86] Flags controlling user PTE allocations.
4200
4201 nohigh = do not allocate PTE pages in
4202 HIGHMEM regardless of setting
4203 of CONFIG_HIGHPTE.
4204
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304205 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004206 On X86_32, this is an alias for vdso32=. Otherwise:
4207
4208 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004209 vdso=0: disable VDSO mapping
4210
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004211 vdso32= [X86] Control the 32-bit vDSO
4212 vdso32=1: enable 32-bit VDSO
4213 vdso32=0 or vdso32=2: disable 32-bit VDSO
4214
4215 See the help text for CONFIG_COMPAT_VDSO for more
4216 details. If CONFIG_COMPAT_VDSO is set, the default is
4217 vdso32=0; otherwise, the default is vdso32=1.
4218
4219 For compatibility with older kernels, vdso32=2 is an
4220 alias for vdso32=0.
4221
4222 Try vdso32=0 if you encounter an error that says:
4223 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004224
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004225 vector= [IA-64,SMP]
4226 vector=percpu: enable percpu vector domain
4227
Linus Torvalds1da177e2005-04-16 15:20:36 -07004228 video= [FB] Frame buffer configuration
4229 See Documentation/fb/modedb.txt.
4230
Aaron Lu3afe6da2013-06-20 15:08:55 +08004231 video.brightness_switch_enabled= [0,1]
4232 If set to 1, on receiving an ACPI notify event
4233 generated by hotkey, video driver will adjust brightness
4234 level and then send out the event to user space through
4235 the allocated input device; If set to 0, video driver
4236 will only send out the event without touching backlight
4237 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004238 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004239
Pawel Moll81a054c2012-05-09 18:30:16 +01004240 virtio_mmio.device=
4241 [VMMIO] Memory mapped virtio (platform) device.
4242
4243 <size>@<baseaddr>:<irq>[:<id>]
4244 where:
4245 <size> := size (can use standard suffixes
4246 like K, M and G)
4247 <baseaddr> := physical base address
4248 <irq> := interrupt number (as passed to
4249 request_irq())
4250 <id> := (optional) platform device id
4251 example:
4252 virtio_mmio.device=1K@0x100b0000:48:7
4253
4254 Can be used multiple times for multiple devices.
4255
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004256 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004257 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004258 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004259 Use vga=ask for menu.
4260 This is actually a boot loader parameter; the value is
4261 passed to the kernel using a special protocol.
4262
Randy Dunlapa9913042005-10-23 12:57:11 -07004263 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004264 size of <nn>. This can be used to increase the
4265 minimum size (128MB on x86). It can also be used to
4266 decrease the size and leave more room for directly
4267 mapped kernel RAM.
4268
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004269 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4270 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004271
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004272 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4273 Format: <command>
4274
4275 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4276 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004277
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004278 vsyscall= [X86-64]
4279 Controls the behavior of vsyscalls (i.e. calls to
4280 fixed addresses of 0xffffffffff600x00 from legacy
4281 code). Most statically-linked binaries and older
4282 versions of glibc use these calls. Because these
4283 functions are at fixed addresses, they make nice
4284 targets for exploits that can control RIP.
4285
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004286 emulate [default] Vsyscalls turn into traps and are
4287 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004288
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004289 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004290 This is a little bit faster than trapping
4291 and makes a few dynamic recompilers work
4292 better than they would in emulation mode.
4293 It also makes exploits much easier to write.
4294
4295 none Vsyscalls don't work at all. This makes
4296 them quite hard to use for exploits but
4297 might break your system.
4298
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004299 vt.color= [VT] Default text color.
4300 Format: 0xYX, X = foreground, Y = background.
4301 Default: 0x07 = light gray on black.
4302
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004303 vt.cur_default= [VT] Default cursor shape.
4304 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4305 the parameters of the <Esc>[?A;B;Cc escape sequence;
4306 see VGA-softcursor.txt. Default: 2 = underline.
4307
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004308 vt.default_blu= [VT]
4309 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4310 Change the default blue palette of the console.
4311 This is a 16-member array composed of values
4312 ranging from 0-255.
4313
4314 vt.default_grn= [VT]
4315 Format: <green0>,<green1>,<green2>,...,<green15>
4316 Change the default green palette of the console.
4317 This is a 16-member array composed of values
4318 ranging from 0-255.
4319
4320 vt.default_red= [VT]
4321 Format: <red0>,<red1>,<red2>,...,<red15>
4322 Change the default red palette of the console.
4323 This is a 16-member array composed of values
4324 ranging from 0-255.
4325
4326 vt.default_utf8=
4327 [VT]
4328 Format=<0|1>
4329 Set system-wide default UTF-8 mode for all tty's.
4330 Default is 1, i.e. UTF-8 mode is enabled for all
4331 newly opened terminals.
4332
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004333 vt.global_cursor_default=
4334 [VT]
4335 Format=<-1|0|1>
4336 Set system-wide default for whether a cursor
4337 is shown on new VTs. Default is -1,
4338 i.e. cursors will be created by default unless
4339 overridden by individual drivers. 0 will hide
4340 cursors, 1 will display them.
4341
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004342 vt.italic= [VT] Default color for italic text; 0-15.
4343 Default: 2 = green.
4344
4345 vt.underline= [VT] Default color for underlined text; 0-15.
4346 Default: 3 = cyan.
4347
Randy Dunlap4724ba572010-05-03 11:42:52 -07004348 watchdog timers [HW,WDT] For information on watchdog timers,
4349 see Documentation/watchdog/watchdog-parameters.txt
4350 or other driver-specific files in the
4351 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004352
Tejun Heo82607adc2015-12-08 11:28:04 -05004353 workqueue.watchdog_thresh=
4354 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4355 warn stall conditions and dump internal state to
4356 help debugging. 0 disables workqueue stall
4357 detection; otherwise, it's the stall threshold
4358 duration in seconds. The default value is 30 and
4359 it can be updated at runtime by writing to the
4360 corresponding sysfs file.
4361
Tejun Heod55262c2013-04-01 11:23:38 -07004362 workqueue.disable_numa
4363 By default, all work items queued to unbound
4364 workqueues are affine to the NUMA nodes they're
4365 issued on, which results in better behavior in
4366 general. If NUMA affinity needs to be disabled for
4367 whatever reason, this option can be used. Note
4368 that this also can be controlled per-workqueue for
4369 workqueues visible under /sys/bus/workqueue/.
4370
Viresh Kumarcee22a12013-04-08 16:45:40 +05304371 workqueue.power_efficient
4372 Per-cpu workqueues are generally preferred because
4373 they show better performance thanks to cache
4374 locality; unfortunately, per-cpu workqueues tend to
4375 be more power hungry than unbound workqueues.
4376
4377 Enabling this makes the per-cpu workqueues which
4378 were observed to contribute significantly to power
4379 consumption unbound, leading to measurably lower
4380 power usage at the cost of small performance
4381 overhead.
4382
4383 The default value of this parameter is determined by
4384 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4385
Tejun Heof303fcc2016-02-09 17:59:38 -05004386 workqueue.debug_force_rr_cpu
4387 Workqueue used to implicitly guarantee that work
4388 items queued without explicit CPU specified are put
4389 on the local CPU. This guarantee is no longer true
4390 and while local CPU is still preferred work items
4391 may be put on foreign CPUs. This debug option
4392 forces round-robin CPU selection to flush out
4393 usages which depend on the now broken guarantee.
4394 When enabled, memory and cache locality will be
4395 impacted.
4396
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004397 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4398 default x2apic cluster mode on platforms
4399 supporting x2apic.
4400
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004401 x86_intel_mid_timer= [X86-32,APBT]
4402 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004403 Two valid options are apbt timer only and lapic timer
4404 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004405 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004406
Juergen Grossc70727a2015-07-17 06:51:36 +02004407 xen_512gb_limit [KNL,X86-64,XEN]
4408 Restricts the kernel running paravirtualized under Xen
4409 to use only up to 512 GB of RAM. The reason to do so is
4410 crash analysis tools and Xen tools for doing domain
4411 save/restore/migration must be enabled to handle larger
4412 domains.
4413
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004414 xen_emul_unplug= [HW,X86,XEN]
4415 Unplug Xen emulated devices
4416 Format: [unplug0,][unplug1]
4417 ide-disks -- unplug primary master IDE devices
4418 aux-ide-disks -- unplug non-primary-master IDE devices
4419 nics -- unplug network devices
4420 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004421 unnecessary -- unplugging emulated devices is
4422 unnecessary even if the host did not respond to
4423 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004424 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004425
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004426 xen_nopvspin [X86,XEN]
4427 Disables the ticketlock slowpath using Xen PV
4428 optimizations.
4429
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004430 xen_nopv [X86]
4431 Disables the PV optimizations forcing the HVM guest to
4432 run as generic HVM guest with no PV drivers.
4433
Linus Torvalds1da177e2005-04-16 15:20:36 -07004434 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004435 Format:
4436 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004437
Randy Dunlapa9913042005-10-23 12:57:11 -07004438______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004439
4440TODO:
4441
Linus Torvalds1da177e2005-04-16 15:20:36 -07004442 Add more DRM drivers.