kernel-parameters.txt 144.9 KB
Newer Older
1 2
                          Kernel Parameters
                          ~~~~~~~~~~~~~~~~~
L
Linus Torvalds 已提交
3

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
The following is a consolidated list of the kernel parameters as
implemented by the __setup(), core_param() and module_param() macros
and sorted into English Dictionary order (defined as ignoring all
punctuation and sorting digits before letters in a case insensitive
manner), and with descriptions where known.

The kernel parses parameters from the kernel command line up to "--";
if it doesn't recognize a parameter and it doesn't contain a '.', the
parameter gets passed to init: parameters with '=' go into init's
environment, others are passed as command line arguments to init.
Everything after "--" is passed as an argument to init.

Module parameters can be specified in two ways: via the kernel command
line with a module name prefix, or via modprobe, e.g.:

	(kernel command line) usbcore.blinkenlights=1
	(modprobe command line) modprobe usbcore blinkenlights=1

Parameters for modules which are built into the kernel need to be
specified on the kernel command line.  modprobe looks through the
kernel command line (/proc/cmdline) and collects module parameters
when it loads a module, so the kernel command line can be used for
loadable modules too.
L
Linus Torvalds 已提交
27

28 29 30 31 32
Hyphens (dashes) and underscores are equivalent in parameter names, so
	log_buf_len=1M print-fatal-signals=1
can also be entered as
	log-buf-len=1M print_fatal_signals=1

33 34
Double-quotes can be used to protect spaces in values, e.g.:
	param="spaces in here"
35

36 37 38 39 40 41 42
This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
module. Loadable modules, after being loaded into the running kernel, also
reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
parameters may be changed at runtime by the command
"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".

43 44 45 46
The parameters listed below are only valid if certain kernel build options were
enabled and if respective hardware is present. The text in square brackets at
the beginning of each description states the restrictions within which a
parameter is applicable:
L
Linus Torvalds 已提交
47 48

	ACPI	ACPI support is enabled.
C
Chuck Ebbert 已提交
49
	AGP	AGP (Accelerated Graphics Port) is enabled.
L
Linus Torvalds 已提交
50 51 52
	ALSA	ALSA sound support is enabled.
	APIC	APIC support is enabled.
	APM	Advanced Power Management support is enabled.
53
	ARM	ARM architecture is enabled.
H
Haavard Skinnemoen 已提交
54
	AVR32	AVR32 architecture is enabled.
L
Linus Torvalds 已提交
55
	AX25	Appropriate AX.25 support is enabled.
56
	BLACKFIN Blackfin architecture is enabled.
57
	CLK	Common clock infrastructure is enabled.
58
	CMA	Contiguous Memory Area support is enabled.
59 60
	DRM	Direct Rendering Management support is enabled.
	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
L
Linus Torvalds 已提交
61 62 63
	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
	EFI	EFI Partitioning (GPT) is enabled
	EIDE	EIDE/ATAPI support is enabled.
64
	EVM	Extended Verification Module
L
Linus Torvalds 已提交
65
	FB	The frame buffer device is enabled.
66
	FTRACE	Function tracing enabled.
67
	GCOV	GCOV profiling is enabled.
L
Linus Torvalds 已提交
68 69
	HW	Appropriate hardware is enabled.
	IA-64	IA-64 architecture is enabled.
M
Mimi Zohar 已提交
70
	IMA     Integrity measurement architecture is enabled.
L
Linus Torvalds 已提交
71
	IOSCHED	More than one I/O scheduler is enabled.
72
	IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
B
Brian Haley 已提交
73
	IPV6	IPv6 support is enabled.
L
Linus Torvalds 已提交
74 75 76
	ISAPNP	ISA PnP code is enabled.
	ISDN	Appropriate ISDN support is enabled.
	JOY	Appropriate joystick support is enabled.
77
	KGDB	Kernel debugger support is enabled.
78
	KVM	Kernel Virtual Machine support is enabled.
79
	LIBATA  Libata driver is enabled
L
Linus Torvalds 已提交
80 81 82 83 84 85
	LP	Printer support is enabled.
	LOOP	Loopback device support is enabled.
	M68k	M68k architecture is enabled.
			These options have more detailed description inside of
			Documentation/m68k/kernel-options.txt.
	MDA	MDA console support is enabled.
86
	MIPS	MIPS architecture is enabled.
L
Linus Torvalds 已提交
87
	MOUSE	Appropriate mouse support is enabled.
88
	MSI	Message Signaled Interrupts (PCI).
89
	MTD	MTD (Memory Technology Device) support is enabled.
L
Linus Torvalds 已提交
90 91 92 93
	NET	Appropriate network support is enabled.
	NUMA	NUMA support is enabled.
	NFS	Appropriate NFS support is enabled.
	OSS	OSS sound support is enabled.
94 95
	PV_OPS	A paravirtualized kernel is enabled.
	PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
L
Linus Torvalds 已提交
96 97
	PARISC	The PA-RISC architecture is enabled.
	PCI	PCI bus support is enabled.
R
Randy Dunlap 已提交
98
	PCIE	PCI Express support is enabled.
L
Linus Torvalds 已提交
99 100 101 102 103 104 105 106
	PCMCIA	The PCMCIA subsystem is enabled.
	PNP	Plug & Play support is enabled.
	PPC	PowerPC architecture is enabled.
	PPT	Parallel port support is enabled.
	PS2	Appropriate PS/2 support is enabled.
	RAM	RAM disk support is enabled.
	S390	S390 architecture is enabled.
	SCSI	Appropriate SCSI support is enabled.
107 108
			A lot of drivers have their options described inside
			the Documentation/scsi/ sub-directory.
109
	SECURITY Different security models are enabled.
L
Linus Torvalds 已提交
110
	SELINUX SELinux support is enabled.
111
	APPARMOR AppArmor support is enabled.
L
Linus Torvalds 已提交
112
	SERIAL	Serial support is enabled.
113
	SH	SuperH architecture is enabled.
L
Linus Torvalds 已提交
114 115
	SMP	The kernel is an SMP kernel.
	SPARC	Sparc architecture is enabled.
D
David Brownell 已提交
116 117
	SWSUSP	Software suspend (hibernation) is enabled.
	SUSPEND	System suspend states are enabled.
118
	TPM	TPM drivers are enabled.
L
Linus Torvalds 已提交
119
	TS	Appropriate touchscreen support is enabled.
120
	UMS	USB Mass Storage support is enabled.
L
Linus Torvalds 已提交
121 122 123
	USB	USB support is enabled.
	USBHID	USB Human Interface Device support is enabled.
	V4L	Video For Linux support is enabled.
124
	VMMIO   Driver for memory mapped virtio devices is enabled.
L
Linus Torvalds 已提交
125 126 127 128
	VGA	The VGA console has been enabled.
	VT	Virtual terminal support is enabled.
	WDT	Watchdog support is enabled.
	XT	IBM PC/XT MFM hard disk support is enabled.
129
	X86-32	X86-32, aka i386 architecture is enabled.
L
Linus Torvalds 已提交
130 131
	X86-64	X86-64 architecture is enabled.
			More X86-64 boot options can be found in
U
Uwe Hermann 已提交
132
			Documentation/x86/x86_64/boot-options.txt .
133
	X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134
	XEN	Xen support is enabled
L
Linus Torvalds 已提交
135 136 137 138 139 140 141 142 143 144

In addition, the following text indicates that the option:

	BUGS=	Relates to possible processor bugs on the said processor.
	KNL	Is a kernel start-up parameter.
	BOOT	Is a boot loader parameter.

Parameters denoted with BOOT are actually interpreted by the boot
loader, and have no meaning to the kernel directly.
Do not modify the syntax of boot loader parameters without extreme
145
need or coordination with <Documentation/x86/boot.txt>.
L
Linus Torvalds 已提交
146

147
There are also arch-specific kernel-parameters not documented here.
U
Uwe Hermann 已提交
148
See for example <Documentation/x86/x86_64/boot-options.txt>.
149

L
Linus Torvalds 已提交
150 151 152 153 154 155
Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
a trailing = on the name of any parameter states that that parameter will
be entered as an environment variable, whereas its absence indicates that
it will appear as a kernel argument readable via /proc/cmdline by programs
running once the system is up.

156 157 158 159 160 161
The number of kernel parameters is not limited, but the length of the
complete command line (parameters including spaces etc.) is limited to
a fixed number of characters. This limit depends on the architecture
and is between 256 and 4096 characters. It is defined in the file
./include/asm/setup.h as COMMAND_LINE_SIZE.

162 163 164 165 166
Finally, the [KMG] suffix is commonly described after a number of kernel
parameter values. These 'K', 'M', and 'G' letters represent the _binary_
multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
bytes respectively. Such letter suffixes can also be entirely omitted.

167

168
	acpi=		[HW,ACPI,X86,ARM64]
169
			Advanced Configuration and Power Interface
170
			Format: { force | off | strict | noirq | rsdt }
L
Linus Torvalds 已提交
171 172 173
			force -- enable ACPI if default was off
			off -- disable ACPI if default was on
			noirq -- do not use ACPI for IRQ routing
R
Randy Dunlap 已提交
174
			strict -- Be less tolerant of platforms that are not
L
Linus Torvalds 已提交
175
				strictly ACPI specification compliant.
176
			rsdt -- prefer RSDT over (default) XSDT
177
			copy_dsdt -- copy DSDT to memory
178
			For ARM64, ONLY "acpi=off" or "acpi=force" are available
L
Linus Torvalds 已提交
179

P
Paul Bolle 已提交
180
			See also Documentation/power/runtime_pm.txt, pci=noacpi
L
Linus Torvalds 已提交
181

L
Len Brown 已提交
182 183 184 185
	acpi_apic_instance=	[ACPI, IOAPIC]
			Format: <int>
			2: use 2nd APIC table, if available
			1,0: use 1st APIC table
186
			default: 0
L
Len Brown 已提交
187

188 189 190 191 192 193 194
	acpi_backlight=	[HW,ACPI]
			acpi_backlight=vendor
			acpi_backlight=video
			If set to vendor, prefer vendor specific driver
			(e.g. thinkpad_acpi, sony_acpi, etc.) instead
			of the ACPI video.ko driver.

195 196 197 198 199 200 201 202
	acpica_no_return_repair [HW, ACPI]
			Disable AML predefined validation mechanism
			This mechanism can repair the evaluation result to make
			the return objects more ACPI specification compliant.
			This option is useful for developers to identify the
			root cause of an AML interpreter issue when the issue
			has something to do with the repair mechanism.

203 204
	acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
	acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
L
Linus Torvalds 已提交
205
			Format: <int>
206 207 208 209 210 211 212
			CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
			debug output.  Bits in debug_layer correspond to a
			_COMPONENT in an ACPI source file, e.g.,
			    #define _COMPONENT ACPI_PCI_COMPONENT
			Bits in debug_level correspond to a level in
			ACPI_DEBUG_PRINT statements, e.g.,
			    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
213 214 215
			The debug_level mask defaults to "info".  See
			Documentation/acpi/debug.txt for more information about
			debug layers and levels.
216

217 218 219 220
			Enable processor driver info messages:
			    acpi.debug_layer=0x20000000
			Enable PCI/PCI interrupt routing info messages:
			    acpi.debug_layer=0x400000
221 222 223 224 225 226 227 228 229
			Enable AML "Debug" output, i.e., stores to the Debug
			object while interpreting AML:
			    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
			Enable all messages related to ACPI hardware:
			    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff

			Some values produce so much output that the system is
			unusable.  The "log_buf_len" parameter may be useful
			if you need to capture more output.
230

231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246
	acpi_enforce_resources=	[ACPI]
			{ strict | lax | no }
			Check for resource conflicts between native drivers
			and ACPI OperationRegions (SystemIO and SystemMemory
			only). IO ports and memory declared in ACPI might be
			used by the ACPI subsystem in arbitrary AML code and
			can interfere with legacy drivers.
			strict (default): access to resources claimed by ACPI
			is denied; legacy drivers trying to access reserved
			resources will fail to bind to device using them.
			lax: access to resources claimed by ACPI is allowed;
			legacy drivers trying to access reserved resources
			will bind successfully but a warning message is logged.
			no: ACPI OperationRegions are not marked as reserved,
			no further checks are performed.

247 248 249 250 251
	acpi_force_table_verification	[HW,ACPI]
			Enable table checksum verification during early stage.
			By default, this is disabled due to x86 early mapping
			size limitation.

252 253 254 255 256 257 258 259 260 261 262 263 264 265 266
	acpi_irq_balance [HW,ACPI]
			ACPI will balance active IRQs
			default in APIC mode

	acpi_irq_nobalance [HW,ACPI]
			ACPI will not move active IRQs (default)
			default in PIC mode

	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
			Format: <irq>,<irq>...

	acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
			use by PCI
			Format: <irq>,<irq>...

267 268
	acpi_no_auto_serialize	[HW,ACPI]
			Disable auto-serialization of AML methods
269 270 271
			AML control methods that contain the opcodes to create
			named objects will be marked as "Serialized" by the
			auto-serialization feature.
272 273
			This feature is enabled by default.
			This option allows to turn off the feature.
274

275 276 277
	acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
			   kernels.

278 279 280 281 282 283 284 285 286
	acpi_no_static_ssdt	[HW,ACPI]
			Disable installation of static SSDTs at early boot time
			By default, SSDTs contained in the RSDT/XSDT will be
			installed automatically and they will appear under
			/sys/firmware/acpi/tables.
			This option turns off this feature.
			Note that specifying this option does not affect
			dynamic table installation which will install SSDT
			tables to /sys/firmware/acpi/tables/dynamic.
287

288 289 290 291
	acpi_rsdp=	[ACPI,EFI,KEXEC]
			Pass the RSDP address to the kernel, mostly used
			on machines running EFI runtime service to boot the
			second kernel for kdump.
292

293 294 295
	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
			Format: To spoof as Windows 98: ="Microsoft Windows"

296 297 298 299 300 301
	acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
			of 2 which is mandated by ACPI 6) as the supported ACPI
			specification revision (when using this switch, it may
			be necessary to carry out a cold reboot _twice_ in a
			row to make it take effect on the platform firmware).

302
	acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
303 304
			acpi_osi="string1"	# add string1
			acpi_osi="!string2"	# remove string2
305
			acpi_osi=!*		# remove all strings
306 307
			acpi_osi=!		# disable all built-in OS vendor
						  strings
308 309
			acpi_osi=		# disable all strings

310 311 312 313 314 315 316
			'acpi_osi=!' can be used in combination with single or
			multiple 'acpi_osi="string1"' to support specific OS
			vendor string(s).  Note that such command can only
			affect the default state of the OS vendor strings, thus
			it cannot affect the default state of the feature group
			strings and the current state of the OS vendor strings,
			specifying it multiple times through kernel command line
317 318 319
			is meaningless.  This command is useful when one do not
			care about the state of the feature group strings which
			should be controlled by the OSPM.
320 321 322 323 324 325 326 327 328 329 330 331 332 333 334
			Examples:
			  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
			     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
			     can make '_OSI("Windows 2000")' TRUE.

			'acpi_osi=' cannot be used in combination with other
			'acpi_osi=' command lines, the _OSI method will not
			exist in the ACPI namespace.  NOTE that such command can
			only affect the _OSI support state, thus specifying it
			multiple times through kernel command line is also
			meaningless.
			Examples:
			  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
			     FALSE.

335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357
			'acpi_osi=!*' can be used in combination with single or
			multiple 'acpi_osi="string1"' to support specific
			string(s).  Note that such command can affect the
			current state of both the OS vendor strings and the
			feature group strings, thus specifying it multiple times
			through kernel command line is meaningful.  But it may
			still not able to affect the final state of a string if
			there are quirks related to this string.  This command
			is useful when one want to control the state of the
			feature group strings to debug BIOS issues related to
			the OSPM features.
			Examples:
			  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
			     '_OSI("Module Device")' FALSE.
			  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
			     '_OSI("Module Device")' TRUE.
			  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
			     equivalent to
			     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
			     and
			     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
			     they all will make '_OSI("Windows 2000")' TRUE.

358
	acpi_pm_good	[X86]
359 360 361 362
			Override the pmtimer bug detection: force the kernel
			to assume that this machine's pmtimer latches its value
			and always returns good values.

363 364 365 366 367 368 369 370 371
	acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
			Format: { level | edge | high | low }

	acpi_skip_timer_override [HW,ACPI]
			Recognize and ignore IRQ0/pin2 Interrupt Override.
			For broken nForce2 BIOS resulting in XT-PIC timer.

	acpi_sleep=	[HW,ACPI] Sleep options
			Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
372
				  old_ordering, nonvs, sci_force_enable }
373 374 375 376 377 378 379 380 381 382
			See Documentation/power/video.txt for information on
			s3_bios and s3_mode.
			s3_beep is for debugging; it makes the PC's speaker beep
			as soon as the kernel's real-mode entry point is called.
			s4_nohwsig prevents ACPI hardware signature from being
			used during resume from hibernation.
			old_ordering causes the ACPI 1.0 ordering of the _PTS
			control method, with respect to putting devices into
			low power states, to be enforced (the ACPI 2.0 ordering
			of _PTS is used by default).
383 384
			nonvs prevents the kernel from saving/restoring the
			ACPI NVS memory during suspend/hibernation and resume.
385 386 387
			sci_force_enable causes the kernel to set SCI_EN directly
			on resume from S1/S3 (which is against the ACPI spec,
			but some broken systems don't work without it).
388 389 390 391 392 393 394 395

	acpi_use_timer_override [HW,ACPI]
			Use timer override. For some broken Nvidia NF5 boards
			that require a timer override, but don't have HPET

	add_efi_memmap	[EFI; X86] Include EFI memory map in
			kernel's map of available physical RAM.

396 397 398 399 400 401
	agp=		[AGP]
			{ off | try_unsupported }
			off: disable AGP support
			try_unsupported: try to drive unsupported chipsets
				(may crash computer or cause data corruption)

402 403 404
	ALSA		[HW,ALSA]
			See Documentation/sound/alsa/alsa-parameters.txt

405 406 407 408 409
	alignment=	[KNL,ARM]
			Allow the default userspace alignment fault handler
			behaviour to be specified.  Bit 0 enables warnings,
			bit 1 enables fixups, and bit 2 sends a segfault.

410 411 412 413 414 415 416 417
	align_va_addr=	[X86-64]
			Align virtual addresses by clearing slice [14:12] when
			allocating a VMA at process creation time. This option
			gives you up to 3% performance improvement on AMD F15h
			machines (where it is enabled by default) for a
			CPU-intensive style benchmark, and it can vary highly in
			a microbenchmark depending on workload and compiler.

418 419
			32: only for 32-bit processes
			64: only for 64-bit processes
420 421 422
			on: enable for both 32- and 64-bit processes
			off: disable for both 32- and 64-bit processes

423 424 425 426 427 428 429
	alloc_snapshot	[FTRACE]
			Allocate the ftrace snapshot buffer on boot up when the
			main buffer is allocated. This is handy if debugging
			and you need to use tracing_snapshot() on boot up, and
			do not want to use tracing_snapshot_alloc() as it needs
			to be done where GFP_KERNEL allocations are allowed.

430
	amd_iommu=	[HW,X86-64]
431 432
			Pass parameters to the AMD IOMMU driver in the system.
			Possible values are:
433 434 435 436
			fullflush - enable flushing of IO/TLB entries when
				    they are unmapped. Otherwise they are
				    flushed before they will be reused, which
				    is a lot of faster
437 438
			off	  - do not initialize any AMD IOMMU found in
				    the system
439 440 441 442 443
			force_isolation - Force device isolation for all
					  devices. The IOMMU driver is not
					  allowed anymore to lift isolation
					  requirements as needed. This option
					  does not override iommu=pt
444

445 446 447 448 449 450
	amd_iommu_dump=	[HW,X86-64]
			Enable AMD IOMMU driver option to dump the ACPI table
			for AMD IOMMU. With this option enabled, AMD IOMMU
			driver will print ACPI tables for AMD IOMMU during
			IOMMU initialization.

L
Linus Torvalds 已提交
451 452 453
	amijoy.map=	[HW,JOY] Amiga joystick support
			Map of devices attached to JOY0DAT and JOY1DAT
			Format: <a>,<b>
P
Paul Bolle 已提交
454
			See also Documentation/input/joystick.txt
L
Linus Torvalds 已提交
455 456 457 458 459 460

	analog.map=	[HW,JOY] Analog joystick and gamepad support
			Specifies type or capabilities of an analog joystick
			connected to one of 16 gameports
			Format: <type1>,<type2>,..<type16>

R
Randy Dunlap 已提交
461 462
	apc=		[HW,SPARC]
			Power management functions (SPARCstation-4/5 + deriv.)
L
Linus Torvalds 已提交
463 464 465 466 467
			Format: noidle
			Disable APC CPU standby support. SPARCstation-Fox does
			not play well with APC CPU idle - disable it if you have
			APC and your system crashes randomly.

468
	apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
469
			Change the output verbosity whilst booting
L
Linus Torvalds 已提交
470 471 472
			Format: { quiet (default) | verbose | debug }
			Change the amount of debugging information output
			when initialising the APIC and IO-APIC components.
R
Randy Dunlap 已提交
473

B
Brian Haley 已提交
474 475 476
	autoconf=	[IPV6]
			See Documentation/networking/ipv6.txt.

477 478 479 480 481 482 483 484 485
	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
			Limit apic dumping. The parameter defines the maximal
			number of local apics being dumped. Also it is possible
			to set it to "all" by meaning -- no limit here.
			Format: { 1 (default) | 2 | ... | all }.
			The parameter valid if only apic=debug or
			apic=verbose is specified.
			Example: apic=debug show_lapic=all

L
Linus Torvalds 已提交
486
	apm=		[APM] Advanced Power Management
487
			See header of arch/x86/kernel/apm_32.c.
L
Linus Torvalds 已提交
488 489 490 491 492 493 494 495 496 497 498 499 500

	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
			Format: <io>,<irq>,<nodeID>

	ataflop=	[HW,M68k]

	atarimouse=	[HW,MOUSE] Atari Mouse

	atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
			EzKey and similar keyboards

	atkbd.reset=	[HW] Reset keyboard during initialization

R
Randy Dunlap 已提交
501 502
	atkbd.set=	[HW] Select keyboard code set
			Format: <int> (2 = AT (default), 3 = PS/2)
L
Linus Torvalds 已提交
503 504 505 506 507 508

	atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
			keyboards

	atkbd.softraw=	[HW] Choose between synthetic and real raw mode
			Format: <bool> (0 = real, 1 = synthetic (default))
R
Randy Dunlap 已提交
509 510 511

	atkbd.softrepeat= [HW]
			Use software keyboard repeat
L
Linus Torvalds 已提交
512

513 514
	audit=		[KNL] Enable the audit sub-system
			Format: { "0" | "1" } (0 = disabled, 1 = enabled)
515 516 517 518 519 520 521 522
			0 - kernel audit is disabled and can not be enabled
			    until the next reboot
			unset - kernel audit is initialized but disabled and
			    will be fully enabled by the userspace auditd.
			1 - kernel audit is initialized and partially enabled,
			    storing at most audit_backlog_limit messages in
			    RAM until it is fully enabled by the userspace
			    auditd.
523
			Default: unset
524

525 526 527 528
	audit_backlog_limit= [KNL] Set the audit queue size limit.
			Format: <int> (must be >=0)
			Default: 64

L
Linus Torvalds 已提交
529 530
	baycom_epp=	[HW,AX25]
			Format: <io>,<mode>
R
Randy Dunlap 已提交
531

L
Linus Torvalds 已提交
532 533 534 535
	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
			Format: <io>,<mode>
			See header of drivers/net/hamradio/baycom_par.c.

R
Randy Dunlap 已提交
536 537
	baycom_ser_fdx=	[HW,AX25]
			BayCom Serial Port AX.25 Modem (Full Duplex Mode)
L
Linus Torvalds 已提交
538 539 540
			Format: <io>,<irq>,<mode>[,<baud>]
			See header of drivers/net/hamradio/baycom_ser_fdx.c.

R
Randy Dunlap 已提交
541 542
	baycom_ser_hdx=	[HW,AX25]
			BayCom Serial Port AX.25 Modem (Half Duplex Mode)
L
Linus Torvalds 已提交
543 544 545
			Format: <io>,<irq>,<mode>
			See header of drivers/net/hamradio/baycom_ser_hdx.c.

546 547 548 549
	blkdevparts=	Manual partition parsing of block device(s) for
			embedded devices based on command line input.
			See Documentation/block/cmdline-partition.txt

R
Randy Dunlap 已提交
550 551 552 553 554
	boot_delay=	Milliseconds to delay each printk during boot.
			Values larger than 10 seconds (10000) are changed to
			no delay (0).
			Format: integer

555 556
	bootmem_debug	[KNL] Enable bootmem allocator debug messages.

L
Linus Torvalds 已提交
557
	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
R
Randy Dunlap 已提交
558 559
	bttv.radio=	Most important insmod options are available as
			kernel args too.
L
Linus Torvalds 已提交
560
	bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
P
Paul Bolle 已提交
561
	bttv.tuner=
L
Linus Torvalds 已提交
562

563 564 565 566
	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
			firmware feature for flushing multiple hpte entries
			at a time.

L
Linus Torvalds 已提交
567 568
	c101=		[NET] Moxa C101 synchronous serial card

569
	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
L
Linus Torvalds 已提交
570 571 572 573 574 575
			Sometimes CPU hardware bugs make them report the cache
			size incorrectly. The kernel will attempt work arounds
			to fix known problems, but for some CPUs it is not
			possible to determine what the correct size should be.
			This option provides an override for these situations.

576 577 578
	ca_keys=	[KEYS] This parameter identifies a specific key(s) on
			the system trusted keyring to be used for certificate
			trust validation.
579
			format: { id:<keyid> | builtin }
580

581 582 583 584 585 586
	cca=		[MIPS] Override the kernel pages' cache coherency
			algorithm.  Accepted values range from 0 to 7
			inclusive. See arch/mips/include/asm/pgtable-bits.h
			for platform specific values (SB1, Loongson3 and
			others).

587 588
	ccw_timeout_log [S390]
			See Documentation/s390/CommonIO for details.
L
Linus Torvalds 已提交
589

590 591
	cgroup_disable= [KNL] Disable a particular controller
			Format: {name of the controller(s) to disable}
592 593 594 595 596 597 598 599
			The effects of cgroup_disable=foo are:
			- foo isn't auto-mounted if you mount all cgroups in
			  a single hierarchy
			- foo isn't visible as an individually mountable
			  subsystem
			{Currently only "memory" controller deal with this and
			cut the overhead, others just disable the usage. So
			only cgroup_disable=memory is actually worthy}
600

L
Linus Torvalds 已提交
601 602 603
	checkreqprot	[SELINUX] Set initial checkreqprot flag value.
			Format: { "0" | "1" }
			See security/selinux/Kconfig help text.
R
Randy Dunlap 已提交
604 605
			0 -- check protection applied by kernel (includes
				any implied execute protection).
L
Linus Torvalds 已提交
606 607
			1 -- check protection requested by application.
			Default value is set via a kernel config option.
R
Randy Dunlap 已提交
608 609 610
			Value can be changed at runtime via
				/selinux/checkreqprot.

611 612
	cio_ignore=	[S390]
			See Documentation/s390/CommonIO for details.
613 614
	clk_ignore_unused
			[CLK]
615 616 617 618 619 620 621 622 623
			Prevents the clock framework from automatically gating
			clocks that have not been explicitly enabled by a Linux
			device driver but are enabled in hardware at reset or
			by the bootloader/firmware. Note that this does not
			force such clocks to be always-on nor does it reserve
			those clocks in any way. This parameter is useful for
			debug and development, but should not be needed on a
			platform with proper driver support.  For more
			information, see Documentation/clk.txt.
624

625
	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
626
			[Deprecated]
627
			Forces specified clocksource (if available) to be used
628
			when calculating gettimeofday(). If specified
629
			clocksource is not available, it defaults to PIT.
L
Linus Torvalds 已提交
630 631
			Format: { pit | tsc | cyclone | pmtmr }

J
John Stultz 已提交
632
	clocksource=	Override the default clocksource
R
Randy Dunlap 已提交
633 634 635 636 637 638 639 640 641 642
			Format: <string>
			Override the default clocksource and use the clocksource
			with the name specified.
			Some clocksource names to choose from, depending on
			the platform:
			[all] jiffies (this is the base, fallback clocksource)
			[ACPI] acpi_pm
			[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
				pxa_timer,timer3,32k_counter,timer0_1
			[AVR32] avr32
643
			[X86-32] pit,hpet,tsc;
R
Randy Dunlap 已提交
644 645 646 647 648 649 650 651
				scx200_hrt on Geode; cyclone on IBM x440
			[MIPS] MIPS
			[PARISC] cr16
			[S390] tod
			[SH] SuperH
			[SPARC64] tick
			[X86-64] hpet,tsc

652 653
	clearcpuid=BITNUM [X86]
			Disable CPUID feature X for the kernel. See
654 655
			arch/x86/include/asm/cpufeature.h for the valid bit
			numbers. Note the Linux specific bits are not necessarily
656 657 658 659 660 661 662 663 664
			stable over kernel options, but the vendor specific
			ones should be.
			Also note that user programs calling CPUID directly
			or using the feature without checking anything
			will still see it. This just prevents it from
			being used by the kernel or shown in /proc/cpuinfo.
			Also note the kernel might malfunction if you disable
			some critical bits.

665 666 667 668 669
	cma=nn[MG]@[start[MG][-end[MG]]]
			[ARM,X86,KNL]
			Sets the size of kernel global memory area for
			contiguous memory allocations and optionally the
			placement constraint by the physical address range of
J
Jean Delvare 已提交
670 671
			memory allocations. A value of 0 disables CMA
			altogether. For more information, see
672 673
			include/linux/dma-contiguous.h

674 675 676 677 678 679 680
	cmo_free_hint=	[PPC] Format: { yes | no }
			Specify whether pages are marked as being inactive
			when they are freed.  This is used in CMO environments
			to determine OS memory pressure for page stealing by
			a hypervisor.
			Default: yes

681 682
	coherent_pool=nn[KMG]	[ARM,KNL]
			Sets the size of memory pool for coherent, atomic dma
683
			allocations, by default set to 256K.
684

685
	code_bytes	[X86] How many bytes of object code to print
686
			in an oops report.
687 688 689
			Range: 0 - 8192
			Default: 64

L
Linus Torvalds 已提交
690
	com20020=	[HW,NET] ARCnet - COM20020 chipset
R
Randy Dunlap 已提交
691 692
			Format:
			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
L
Linus Torvalds 已提交
693 694 695 696

	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
			Format: <io>[,<irq>]

R
Randy Dunlap 已提交
697 698
	com90xx=	[HW,NET]
			ARCnet - COM90xx chipset (memory-mapped buffers)
L
Linus Torvalds 已提交
699 700 701 702
			Format: <io>[,<irq>[,<memstart>]]

	condev=		[HW,S390] console device
	conmode=
R
Randy Dunlap 已提交
703

L
Linus Torvalds 已提交
704 705 706 707 708
	console=	[KNL] Output console device and options.

		tty<n>	Use the virtual console device <n>.

		ttyS<n>[,options]
709
		ttyUSB0[,options]
L
Linus Torvalds 已提交
710
			Use the specified serial port.  The options are of
711 712 713 714 715 716 717 718 719
			the form "bbbbpnf", where "bbbb" is the baud rate,
			"p" is parity ("n", "o", or "e"), "n" is number of
			bits, and "f" is flow control ("r" for RTS or
			omit it).  Default is "9600n8".

			See Documentation/serial-console.txt for more
			information.  See
			Documentation/networking/netconsole.txt for an
			alternative.
L
Linus Torvalds 已提交
720

721 722
		uart[8250],io,<addr>[,options]
		uart[8250],mmio,<addr>[,options]
723 724
		uart[8250],mmio32,<addr>[,options]
		uart[8250],0x<addr>[,options]
L
Linus Torvalds 已提交
725 726
			Start an early, polled-mode console on the 8250/16550
			UART at the specified I/O port or MMIO address,
727 728 729 730 731 732 733 734
			switching to the matching ttyS device later.
			MMIO inter-register address stride is either 8-bit
			(mmio) or 32-bit (mmio32).
			If none of [io|mmio|mmio32], <addr> is assumed to be
			equivalent to 'mmio'. 'options' are specified in the
			same format described for ttyS above; if unspecified,
			the h/w is not re-initialized.

735 736
		hvc<n>	Use the hypervisor console device <n>. This is for
			both Xen and PowerPC hypervisors.
L
Linus Torvalds 已提交
737

738 739 740 741 742
                If the device connected to the port is not a TTY but a braille
                device, prepend "brl," before the device type, for instance
			console=brl,ttyS0
		For now, only VisioBraille is supported.

743 744 745 746
	consoleblank=	[KNL] The console blank (screen saver) timeout in
			seconds. Defaults to 10*60 = 10mins. A value of 0
			disables the blank timer.

747 748 749 750 751
	coredump_filter=
			[KNL] Change the default value for
			/proc/<pid>/coredump_filter.
			See also Documentation/filesystems/proc.txt.

752 753 754
	cpuidle.off=1	[CPU_IDLE]
			disable the cpuidle sub-system

755 756 757 758 759 760
	cpu_init_udelay=N
			[X86] Delay for N microsec between assert and de-assert
			of APIC INIT to start processors.  This delay occurs
			on every CPU online, such as boot, and resume from suspend.
			Default: 10000

L
Linus Torvalds 已提交
761
	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
R
Randy Dunlap 已提交
762 763
			Format:
			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
L
Linus Torvalds 已提交
764

765 766 767 768 769 770 771
	crashkernel=size[KMG][@offset[KMG]]
			[KNL] Using kexec, Linux can switch to a 'crash kernel'
			upon panic. This parameter reserves the physical
			memory region [offset, offset + size] for that kernel
			image. If '@offset' is omitted, then a suitable offset
			is selected automatically. Check
			Documentation/kdump/kdump.txt for further details.
772

773 774 775 776 777
	crashkernel=range1:size1[,range2:size2,...][@offset]
			[KNL] Same as above, but depends on the memory
			in the running system. The syntax of range is
			start-[end] where start and end are both
			a memory unit (amount[KMG]). See also
778
			Documentation/kdump/kdump.txt for an example.
779

780
	crashkernel=size[KMG],high
781 782 783 784 785 786
			[KNL, x86_64] range could be above 4G. Allow kernel
			to allocate physical memory region from top, so could
			be above 4G if system have more than 4G ram installed.
			Otherwise memory region will be allocated below 4G, if
			available.
			It will be ignored if crashkernel=X is specified.
787 788 789
	crashkernel=size[KMG],low
			[KNL, x86_64] range under 4G. When crashkernel=X,high
			is passed, kernel could allocate physical memory region
790 791
			above 4G, that cause second kernel crash on system
			that require some amount of low memory, e.g. swiotlb
792 793 794 795
			requires at least 64M+32K low memory, also enough extra
			low memory is needed to make sure DMA buffers for 32-bit
			devices won't run out. Kernel would try to allocate at
			at least 256M below 4G automatically.
796 797 798
			This one let user to specify own low range under 4G
			for second kernel instead.
			0: to disable low allocation.
799
			It will be ignored when crashkernel=X,high is not used
800
			or memory reserved is below 4G.
801

L
Linus Torvalds 已提交
802 803 804 805 806
	cs89x0_dma=	[HW,NET]
			Format: <dma>

	cs89x0_media=	[HW,NET]
			Format: { rj45 | aui | bnc }
R
Randy Dunlap 已提交
807 808

	dasd=		[HW,NET]
L
Linus Torvalds 已提交
809 810 811 812 813 814 815
			See header of drivers/s390/block/dasd_devmap.c.

	db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
			(one device per port)
			Format: <port#>,<type>
			See also Documentation/input/joystick-parport.txt

816 817
	ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
			time. See Documentation/dynamic-debug-howto.txt for
818
			details.  Deprecated, see dyndbg.
819

L
Linus Torvalds 已提交
820 821
	debug		[KNL] Enable kernel debugging (events log level).

822 823 824 825 826 827 828 829 830
	debug_locks_verbose=
			[KNL] verbose self-tests
			Format=<0|1>
			Print debugging info while doing the locking API
			self-tests.
			We default to 0 (no extra messages), setting it to
			1 will print _a lot_ more information - normally
			only useful to kernel developers.

831 832
	debug_objects	[KNL] Enable object debugging

833 834 835
	no_debug_objects
			[KNL] Disable object debugging

836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854
	debug_guardpage_minorder=
			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
			parameter allows control of the order of pages that will
			be intentionally kept free (and hence protected) by the
			buddy allocator. Bigger value increase the probability
			of catching random memory corruption, but reduce the
			amount of memory for normal system use. The maximum
			possible value is MAX_ORDER/2.  Setting this parameter
			to 1 or 2 should be enough to identify most random
			memory corruption problems caused by bugs in kernel or
			driver code when a CPU writes to (or reads from) a
			random memory location. Note that there exists a class
			of memory corruptions problems caused by buggy H/W or
			F/W or by drivers badly programing DMA (basically when
			memory is written at bus level and the CPU MMU is
			bypassed) which are not detectable by
			CONFIG_DEBUG_PAGEALLOC, hence this option will not help
			tracking down these problems.

855 856 857 858 859 860 861 862 863
	debug_pagealloc=
			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
			parameter enables the feature at boot time. In
			default, it is disabled. We can avoid allocating huge
			chunk of memory for debug pagealloc if we don't enable
			it at boot time and the system will work mostly same
			with the kernel built without CONFIG_DEBUG_PAGEALLOC.
			on: enable the feature

864 865
	debugpat	[X86] Enable PAT debugging

866
	decnet.addr=	[HW,NET]
L
Linus Torvalds 已提交
867 868 869
			Format: <area>[,<node>]
			See also Documentation/networking/decnet.txt.

870 871 872 873 874 875 876
	default_hugepagesz=
			[same as hugepagesz=] The size of the default
			HugeTLB page size. This is the size represented by
			the legacy /proc/ hugepages APIs, used for SHM, and
			default size when mounting hugetlbfs filesystems.
			Defaults to the default architecture's huge page size
			if not specified.
877

L
Linus Torvalds 已提交
878 879
	dhash_entries=	[KNL]
			Set number of hash buckets for dentry cache.
R
Randy Dunlap 已提交
880

B
Brian Haley 已提交
881 882 883
	disable=	[IPV6]
			See Documentation/networking/ipv6.txt.

884 885 886 887 888 889 890 891 892
	disable_cpu_apicid= [X86,APIC,SMP]
			Format: <int>
			The number of initial APIC ID for the
			corresponding CPU to be disabled at boot,
			mostly used for the kdump 2nd kernel to
			disable BSP to wake up multiple CPUs without
			causing system reset or hang due to sending
			INIT from AP to BSP.

893 894 895 896
	disable_ddw     [PPC/PSERIES]
			Disable Dynamic DMA Window support. Use this if
			to workaround buggy firmware.

B
Brian Haley 已提交
897 898 899
	disable_ipv6=	[IPV6]
			See Documentation/networking/ipv6.txt.

900 901 902
	disable_mtrr_cleanup [X86]
			The kernel tries to adjust MTRR layout from continuous
			to discrete, to make X server driver able to add WB
903
			entry later. This parameter disables that.
904

905
	disable_mtrr_trim [X86, Intel and AMD only]
906 907 908 909 910
			By default the kernel will trim any uncacheable
			memory out of your available memory pool based on
			MTRR settings.  This parameter disables that behavior,
			possibly causing your machine to run very slowly.

911
	disable_timer_pin_1 [X86]
912 913 914
			Disable PIN 1 of APIC timer
			Can be useful to work around chipset bugs.

915 916
	dis_ucode_ldr	[X86] Disable the microcode loader.

917 918 919 920 921 922 923 924 925 926
	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
			this option disables the debugging code at boot.

	dma_debug_entries=<number>
			This option allows to tune the number of preallocated
			entries for DMA-API debugging code. One entry is
			required per DMA-API allocation. Use this if the
			DMA-API debugging code disables itself because the
			architectural default is too low.

927 928 929 930 931 932 933
	dma_debug_driver=<driver_name>
			With this option the DMA-API debugging driver
			filter feature can be enabled at boot time. Just
			pass the driver to filter for as the parameter.
			The filter can be disabled or changed to another
			driver later using sysfs.

934 935 936 937 938 939 940 941 942 943 944 945 946 947 948
	drm_kms_helper.edid_firmware=[<connector>:]<file>
			Broken monitors, graphic adapters and KVMs may
			send no or incorrect EDID data sets. This parameter
			allows to specify an EDID data set in the
			/lib/firmware directory that is used instead.
			Generic built-in EDID data sets are used, if one of
			edid/1024x768.bin, edid/1280x1024.bin,
			edid/1680x1050.bin, or edid/1920x1080.bin is given
			and no file with the same name exists. Details and
			instructions how to build your own EDID data are
			available in Documentation/EDID/HOWTO.txt. An EDID
			data set will only be used for a particular connector,
			if its name and a colon are prepended to the EDID
			name.

L
Linus Torvalds 已提交
949 950
	dscc4.setup=	[NET]

951 952 953 954 955
	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
	module.dyndbg[="val"]
			Enable debug messages at boot time.  See
			Documentation/dynamic-debug-howto.txt for details.

956 957 958 959
	nompx		[X86] Disables Intel Memory Protection Extensions.
			See Documentation/x86/intel_mpx.txt for more
			information about the feature.

960 961 962 963 964 965
	eagerfpu=	[X86]
			on	enable eager fpu restore
			off	disable eager fpu restore
			auto	selects the default scheme, which automatically
				enables eagerfpu restore for xsaveopt.

966 967 968
	module.async_probe [KNL]
			Enable asynchronous probe on this module.

969 970 971 972 973
	early_ioremap_debug [KNL]
			Enable debug messages in early_ioremap support. This
			is useful for tracking down temporary early mappings
			which are not unmapped.

974
	earlycon=	[KNL] Output early console device and options.
975

976 977 978 979
			When used with no options, the early console is
			determined by the stdout-path property in device
			tree's chosen node.

980 981 982 983 984 985
		cdns,<addr>
			Start an early, polled-mode console on a cadence serial
			port at the specified address. The cadence serial port
			must already be setup and configured. Options are not
			yet supported.

986 987
		uart[8250],io,<addr>[,options]
		uart[8250],mmio,<addr>[,options]
988
		uart[8250],mmio32,<addr>[,options]
989
		uart[8250],mmio32be,<addr>[,options]
990
		uart[8250],0x<addr>[,options]
991 992
			Start an early, polled-mode console on the 8250/16550
			UART at the specified I/O port or MMIO address.
993
			MMIO inter-register address stride is either 8-bit
994 995 996 997
			(mmio) or 32-bit (mmio32 or mmio32be).
			If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
			to be equivalent to 'mmio'. 'options' are specified
			in the same format described for "console=ttyS<n>"; if
998
			unspecified, the h/w is not initialized.
999

1000 1001 1002 1003 1004 1005
		pl011,<addr>
			Start an early, polled-mode console on a pl011 serial
			port at the specified address. The pl011 serial port
			must already be setup and configured. Options are not
			yet supported.

1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017
		msm_serial,<addr>
			Start an early, polled-mode console on an msm serial
			port at the specified address. The serial port
			must already be setup and configured. Options are not
			yet supported.

		msm_serial_dm,<addr>
			Start an early, polled-mode console on an msm serial
			dm port at the specified address. The serial port
			must already be setup and configured. Options are not
			yet supported.

1018 1019
		smh	Use ARM semihosting calls for early console.

1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031
		s3c2410,<addr>
		s3c2412,<addr>
		s3c2440,<addr>
		s3c6400,<addr>
		s5pv210,<addr>
		exynos4210,<addr>
			Use early console provided by serial driver available
			on Samsung SoCs, requires selecting proper type and
			a correct base address of the selected UART port. The
			serial port must already be setup and configured.
			Options are not yet supported.

F
Finn Thain 已提交
1032
	earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
L
Linus Torvalds 已提交
1033
			earlyprintk=vga
1034
			earlyprintk=efi
1035
			earlyprintk=xen
L
Linus Torvalds 已提交
1036
			earlyprintk=serial[,ttySn[,baudrate]]
1037
			earlyprintk=serial[,0x...[,baudrate]]
1038
			earlyprintk=ttySn[,baudrate]
1039
			earlyprintk=dbgp[debugController#]
1040
			earlyprintk=pciserial,bus:device.function[,baudrate]
L
Linus Torvalds 已提交
1041

1042 1043 1044 1045
			earlyprintk is useful when the kernel crashes before
			the normal console is initialized. It is not enabled by
			default because it has some cosmetic problems.

R
Randy Dunlap 已提交
1046
			Append ",keep" to not disable it when the real console
L
Linus Torvalds 已提交
1047 1048
			takes over.

1049 1050
			Only one of vga, efi, serial, or usb debug port can
			be used at a time.
L
Linus Torvalds 已提交
1051

1052 1053 1054 1055 1056 1057 1058 1059
			Currently only ttyS0 and ttyS1 may be specified by
			name.  Other I/O ports may be explicitly specified
			on some architectures (x86 and arm at least) by
			replacing ttySn with an I/O port address, like this:
				earlyprintk=serial,0x1008,115200
			You can find the port for a given device in
			/proc/tty/driver/serial:
				2: uart:ST16650V2 port:00001008 irq:18 ...
L
Linus Torvalds 已提交
1060 1061 1062 1063

			Interaction with the standard serial driver is not
			very good.

1064 1065
			The VGA and EFI output is eventually overwritten by
			the real console.
L
Linus Torvalds 已提交
1066

1067 1068
			The xen output can only be used by Xen PV guests.

1069 1070 1071 1072 1073 1074 1075 1076
	edac_report=	[HW,EDAC] Control how to report EDAC event
			Format: {"on" | "off" | "force"}
			on: enable EDAC to report H/W event. May be overridden
			by other higher priority error reporting module.
			off: disable H/W event reporting through EDAC.
			force: enforce the use of EDAC to report H/W event.
			default: on.

1077 1078 1079
	ekgdboc=	[X86,KGDB] Allow early kernel console debugging
			ekgdboc=kbd

L
Lucas De Marchi 已提交
1080
			This is designed to be used in conjunction with
1081 1082
			the boot argument: earlyprintk=vga

L
Linus Torvalds 已提交
1083
	edd=		[EDD]
1084
			Format: {"off" | "on" | "skip[mbr]"}
L
Linus Torvalds 已提交
1085

1086
	efi=		[EFI]
1087
			Format: { "old_map", "nochunk", "noruntime", "debug" }
1088 1089 1090
			old_map [X86-64]: switch to the old ioremap-based EFI
			runtime services mapping. 32-bit still uses this one by
			default.
1091 1092 1093
			nochunk: disable reading files in "chunks" in the EFI
			boot stub, as chunking can cause problems with some
			firmware implementations.
D
Dave Young 已提交
1094
			noruntime : disable EFI runtime services support
1095
			debug: enable misc debug output
1096

1097 1098 1099 1100 1101 1102
	efi_no_storage_paranoia [EFI; X86]
			Using this parameter you can use more than 50% of
			your efi variable storage. Use this parameter only if
			you are really sure that your UEFI does sane gc and
			fulfills the spec otherwise your board may brick.

L
Linus Torvalds 已提交
1103 1104 1105
	eisa_irq_edge=	[PARISC,HW]
			See header of drivers/parisc/eisa.c.

1106
	elanfreq=	[X86-32]
L
Linus Torvalds 已提交
1107
			See comment before function elanfreq_setup() in
1108
			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
L
Linus Torvalds 已提交
1109 1110

	elevator=	[IOSCHED]
1111
			Format: {"cfq" | "deadline" | "noop"}
P
Paul Bolle 已提交
1112
			See Documentation/block/cfq-iosched.txt and
R
Randy Dunlap 已提交
1113 1114
			Documentation/block/deadline-iosched.txt for details.

1115
	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
R
Randy Dunlap 已提交
1116
			Specifies physical address of start of kernel core
1117 1118
			image elf header and optionally the size. Generally
			kexec loader will pass this option to capture kernel.
1119
			See Documentation/kdump/kdump.txt for details.
L
Linus Torvalds 已提交
1120

1121 1122 1123 1124 1125
	enable_mtrr_cleanup [X86]
			The kernel tries to adjust MTRR layout from continuous
			to discrete, to make X server driver able to add WB
			entry later. This parameter enables that.

1126
	enable_timer_pin_1 [X86]
1127 1128 1129 1130 1131
			Enable PIN 1 of APIC timer
			Can be useful to work around chipset bugs
			(in particular on some ATI chipsets).
			The kernel tries to set a reasonable default.

L
Linus Torvalds 已提交
1132 1133 1134 1135 1136 1137 1138 1139
	enforcing	[SELINUX] Set initial enforcing status.
			Format: {"0" | "1"}
			See security/selinux/Kconfig help text.
			0 -- permissive (log only, no denials).
			1 -- enforcing (deny and log).
			Default value is 0.
			Value can be changed at runtime via /selinux/enforce.

1140 1141 1142 1143
	erst_disable	[ACPI]
			Disable Error Record Serialization Table (ERST)
			support.

L
Linus Torvalds 已提交
1144 1145 1146 1147
	ether=		[HW,NET] Ethernet cards parameters
			This option is obsoleted by the "netdev=" option, which
			has equivalent usage. See its documentation for details.

1148 1149 1150 1151 1152
	evm=		[EVM]
			Format: { "fix" }
			Permit 'security.evm' to be updated regardless of
			current integrity status.

1153 1154 1155 1156 1157
	failslab=
	fail_page_alloc=
	fail_make_request=[KNL]
			General fault injection mechanism.
			Format: <interval>,<probability>,<space>,<times>
P
Paul Bolle 已提交
1158
			See also Documentation/fault-injection/.
1159

L
Linus Torvalds 已提交
1160
	floppy=		[HW]
1161
			See Documentation/blockdev/floppy.txt.
L
Linus Torvalds 已提交
1162

1163 1164 1165 1166 1167 1168
	force_pal_cache_flush
			[IA-64] Avoid check_sal_cache_flush which may hang on
			buggy SAL_CACHE_FLUSH implementations. Using this
			parameter will force ia64_sal_cache_flush to call
			ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

1169 1170 1171 1172 1173 1174 1175
	forcepae [X86-32]
			Forcefully enable Physical Address Extension (PAE).
			Many Pentium M systems disable PAE but may have a
			functionally usable PAE implementation.
			Warning: use of this parameter will taint the kernel
			and may cause unknown problems.

1176
	ftrace=[tracer]
1177
			[FTRACE] will set and start the specified tracer
1178 1179 1180
			as early as possible in order to facilitate early
			boot debugging.

1181
	ftrace_dump_on_oops[=orig_cpu]
1182
			[FTRACE] will dump the trace buffers on oops.
1183 1184 1185 1186
			If no parameter is passed, ftrace will dump
			buffers of all CPUs, but if you pass orig_cpu, it will
			dump only the buffer of the CPU that triggered the
			oops.
1187 1188 1189 1190 1191 1192

	ftrace_filter=[function-list]
			[FTRACE] Limit the functions traced by the function
			tracer at boot up. function-list is a comma separated
			list of functions. This list can be changed at run
			time by the set_ftrace_filter file in the debugfs
1193
			tracing directory.
1194 1195 1196 1197 1198 1199

	ftrace_notrace=[function-list]
			[FTRACE] Do not trace the functions specified in
			function-list. This list can be changed at run time
			by the set_ftrace_notrace file in the debugfs
			tracing directory.
1200

1201 1202 1203 1204 1205 1206 1207
	ftrace_graph_filter=[function-list]
			[FTRACE] Limit the top level callers functions traced
			by the function graph tracer at boot up.
			function-list is a comma separated list of functions
			that can be changed at run time by the
			set_graph_function file in the debugfs tracing directory.

1208 1209 1210 1211 1212 1213
	ftrace_graph_notrace=[function-list]
			[FTRACE] Do not trace from the functions specified in
			function-list.  This list is a comma separated list of
			functions that can be changed at run time by the
			set_graph_notrace file in the debugfs tracing directory.

L
Linus Torvalds 已提交
1214 1215 1216 1217 1218 1219 1220 1221
	gamecon.map[2|3]=
			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
			support via parallel port (up to 5 devices per port)
			Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
			See also Documentation/input/joystick-parport.txt

	gamma=		[HW,DRM]

Y
Yinghai Lu 已提交
1222 1223 1224 1225
	gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
			Format: off | on
			default: on

1226 1227 1228 1229 1230 1231
	gcov_persist=	[GCOV] When non-zero (default), profiling data for
			kernel modules is saved and remains accessible via
			debugfs, even when the module is unloaded/reloaded.
			When zero, profiling data is discarded and associated
			debugfs files are removed at module unload time.

L
Linus Torvalds 已提交
1232
	gpt		[EFI] Forces disk with valid GPT signature but
1233 1234 1235
			invalid Protective MBR to be treated as GPT. If the
			primary GPT is corrupted, it enables the backup/alternate
			GPT to be used instead.
L
Linus Torvalds 已提交
1236

1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254
	grcan.enable0=	[HW] Configuration of physical interface 0. Determines
			the "Enable 0" bit of the configuration register.
			Format: 0 | 1
			Default: 0
	grcan.enable1=	[HW] Configuration of physical interface 1. Determines
			the "Enable 0" bit of the configuration register.
			Format: 0 | 1
			Default: 0
	grcan.select=	[HW] Select which physical interface to use.
			Format: 0 | 1
			Default: 0
	grcan.txsize=	[HW] Sets the size of the tx buffer.
			Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
			Default: 1024
	grcan.rxsize=	[HW] Sets the size of the rx buffer.
			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
			Default: 1024

L
Linus Torvalds 已提交
1255 1256
	hashdist=	[KNL,NUMA] Large hashes allocated during boot
			are distributed across NUMA nodes.  Defaults on
1257
			for 64-bit NUMA, off otherwise.
R
Randy Dunlap 已提交
1258
			Format: 0 | 1 (for off | on)
L
Linus Torvalds 已提交
1259 1260 1261 1262 1263 1264

	hcl=		[IA-64] SGI's Hardware Graph compatibility layer

	hd=		[EIDE] (E)IDE hard drive subsystem geometry
			Format: <cyl>,<head>,<sect>

H
Huang Ying 已提交
1265 1266 1267 1268 1269
	hest_disable	[ACPI]
			Disable Hardware Error Source Table (HEST) support;
			corresponding firmware-first mode error processing
			logic will be disabled.

L
Linus Torvalds 已提交
1270 1271 1272 1273 1274
	highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
			size of <nn>. This works even on boxes that have no
			highmem otherwise. This also works to reduce highmem
			size on bigger boxes.

1275 1276 1277 1278
	highres=	[KNL] Enable/disable high resolution timer mode.
			Valid parameters: "on", "off"
			Default: "on"

L
Linus Torvalds 已提交
1279 1280 1281
	hisax=		[HW,ISDN]
			See Documentation/isdn/README.HiSax.

1282 1283 1284 1285 1286 1287 1288 1289 1290 1291
	hlt		[BUGS=ARM,SH]

	hpet=		[X86-32,HPET] option to control HPET usage
			Format: { enable (default) | disable | force |
				verbose }
			disable: disable HPET and use PIT instead
			force: allow force enabled of undocumented chips (ICH4,
				VIA, nVidia)
			verbose: show contents of HPET registers during setup

1292 1293 1294
	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.

1295 1296
	hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
	hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1297 1298 1299 1300
			On x86-64 and powerpc, this option can be specified
			multiple times interleaved with hugepages= to reserve
			huge pages of different sizes. Valid pages sizes on
			x86-64 are 2M (when the CPU supports "pse") and 1G
1301
			(when the CPU supports the "pdpe1gb" cpuinfo flag).
1302

1303 1304
	hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
			       terminal devices. Valid values: 0..8
1305 1306 1307
	hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
			       If specified, z/VM IUCV HVC accepts connections
			       from listed z/VM user IDs only.
1308

J
James Hogan 已提交
1309 1310 1311 1312
	hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
			        hardware thread id mappings.
				Format: <cpu>:<hwthread>

1313 1314 1315 1316 1317 1318
	keep_bootcon	[KNL]
			Do not unregister boot console at start. This is only
			useful for debugging when something happens in the window
			between unregistering the boot console and initializing
			the real console.

1319
	i2c_bus=	[HW] Override the default board specific I2C bus speed
1320 1321
			     or register an additional I2C bus that is not
			     registered from board initialization code.
1322 1323 1324
			     Format:
			     <bus_id>,<clkrate>

1325
	i8042.debug	[HW] Toggle i8042 debug mode
1326 1327 1328 1329
	i8042.unmask_kbd_data
			[HW] Enable printing of interrupt data from the KBD port
			     (disabled by default, and as a pre-condition
			     requires that i8042.debug=1 be enabled)
L
Linus Torvalds 已提交
1330
	i8042.direct	[HW] Put keyboard port into non-translated mode
1331 1332
	i8042.dumbkbd	[HW] Pretend that controller can only read data from
			     keyboard and cannot control its state
L
Linus Torvalds 已提交
1333 1334
			     (Don't attempt to blink the leds)
	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1335
	i8042.nokbd	[HW] Don't check/create keyboard port
J
Jiri Kosina 已提交
1336 1337
	i8042.noloop	[HW] Disable the AUX Loopback command while probing
			     for the AUX port
L
Linus Torvalds 已提交
1338
	i8042.nomux	[HW] Don't check presence of an active multiplexing
1339
			     controller
L
Linus Torvalds 已提交
1340 1341
	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
			     controllers
1342
	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
L
Linus Torvalds 已提交
1343 1344
	i8042.reset	[HW] Reset the controller during init and cleanup
	i8042.unlock	[HW] Unlock (ignore) the keylock
1345
	i8042.kbdreset  [HW] Reset device connected to KBD port
L
Linus Torvalds 已提交
1346 1347 1348

	i810=		[HW,DRM]

1349 1350 1351
	i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
			indicates that the driver is running on unsupported
			hardware.
L
Linus Torvalds 已提交
1352 1353 1354 1355 1356 1357 1358 1359
	i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
			does not match list of supported models.
	i8k.power_status
			[HW] Report power status in /proc/i8k
			(disabled by default)
	i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
			capability is set.

1360
	i915.invert_brightness=
1361 1362
			[DRM] Invert the sense of the variable that is used to
			set the brightness of the panel backlight. Normally a
1363 1364 1365 1366 1367 1368 1369 1370 1371 1372
			brightness value of 0 indicates backlight switched off,
			and the maximum of the brightness value sets the backlight
			to maximum brightness. If this parameter is set to 0
			(default) and the machine requires it, or this parameter
			is set to 1, a brightness value of 0 sets the backlight
			to maximum brightness, and the maximum of the brightness
			value switches the backlight off.
			-1 -- never invert brightness
			 0 -- machine default
			 1 -- force brightness inversion
1373

L
Linus Torvalds 已提交
1374 1375 1376
	icn=		[HW,ISDN]
			Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]

1377 1378
	ide-core.nodma=	[HW] (E)IDE subsystem
			Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1379 1380
			.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
			.cdrom .chs .ignore_cable are additional options
1381
			See Documentation/ide/ide.txt.
L
Linus Torvalds 已提交
1382

1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394
	ide-generic.probe-mask= [HW] (E)IDE subsystem
			Format: <int>
			Probe mask for legacy ISA IDE ports.  Depending on
			platform up to 6 ports are supported, enabled by
			setting corresponding bits in the mask to 1.  The
			default value is 0x0, which has a special meaning.
			On systems that have PCI, it triggers scanning the
			PCI bus for the first and the second port, which
			are then probed.  On systems without PCI the value
			of 0x0 enables probing the two first ports as if it
			was 0x3.

1395 1396 1397
	ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
			Claim all unknown PCI IDE storage controllers.

1398
	idle=		[X86]
1399
			Format: idle=poll, idle=halt, idle=nomwait
1400 1401 1402 1403 1404
			Poll forces a polling idle loop that can slightly
			improve the performance of waking up a idle CPU, but
			will use a lot of power and make the system run hot.
			Not recommended.
			idle=halt: Halt is forced to be used for CPU idle.
Z
Zhao Yakui 已提交
1405
			In such case C2/C3 won't be used again.
1406
			idle=nomwait: Disable mwait for CPU C-states
R
Randy Dunlap 已提交
1407

1408 1409 1410
	ignore_loglevel	[KNL]
			Ignore loglevel setting - this will print /all/
			kernel messages to the console. Useful for debugging.
1411 1412 1413
			We also add it as printk module parameter, so users
			could change it dynamically, usually by
			/sys/module/printk/parameters/ignore_loglevel.
1414

L
Linus Torvalds 已提交
1415 1416 1417
	ihash_entries=	[KNL]
			Set number of hash buckets for inode cache.

M
Mimi Zohar 已提交
1418
	ima_appraise=	[IMA] appraise integrity measurements
1419
			Format: { "off" | "enforce" | "fix" | "log" }
M
Mimi Zohar 已提交
1420 1421
			default: "enforce"

1422 1423 1424 1425
	ima_appraise_tcb [IMA]
			The builtin appraise policy appraises all files
			owned by uid=0.

1426
	ima_hash=	[IMA]
1427 1428
			Format: { md5 | sha1 | rmd160 | sha256 | sha384
				   | sha512 | ... }
1429 1430
			default: "sha1"

1431 1432 1433
			The list of supported hash algorithms is defined
			in crypto/hash_info.h.

M
Mimi Zohar 已提交
1434 1435 1436 1437 1438 1439 1440 1441 1442
	ima_policy=	[IMA]
			The builtin measurement policy to load during IMA
			setup.  Specyfing "tcb" as the value, measures all
			programs exec'd, files mmap'd for exec, and all files
			opened with the read mode bit set by either the
			effective uid (euid=0) or uid=0.
			Format: "tcb"

	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
1443 1444 1445 1446 1447
			Load a policy which meets the needs of the Trusted
			Computing Base.  This means IMA will measure all
			programs exec'd, files mmap'd for exec, and all files
			opened for read by uid=0.

1448 1449
	ima_template=   [IMA]
			Select one of defined IMA measurements template formats.
1450
			Formats: { "ima" | "ima-ng" | "ima-sig" }
1451 1452
			Default: "ima-ng"

1453 1454 1455 1456
	ima_template_fmt=
	                [IMA] Define a custom template format.
			Format: { "field1|...|fieldN" }

1457 1458 1459 1460 1461 1462 1463 1464 1465
	ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
			Format: <min_file_size>
			Set the minimal file size for using asynchronous hash.
			If left unspecified, ahash usage is disabled.

			ahash performance varies for different data sizes on
			different crypto accelerators. This option can be used
			to achieve the best performance for a particular HW.

1466 1467 1468 1469 1470 1471 1472 1473
	ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
			Format: <bufsize>
			Set hashing buffer size. Default: 4k.

			ahash performance varies for different chunk sizes on
			different crypto accelerators. This option can be used
			to achieve best performance for particular HW.

L
Linus Torvalds 已提交
1474 1475 1476 1477 1478 1479 1480 1481 1482
	init=		[KNL]
			Format: <full_path>
			Run specified binary instead of /sbin/init as init
			process.

	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
			for working out where the kernel is dying during
			startup.

1483 1484 1485 1486
	initcall_blacklist=  [KNL] Do not execute a comma-separated list of
			initcall functions.  Useful for debugging built-in
			modules and initcalls.

L
Linus Torvalds 已提交
1487 1488 1489 1490 1491
	initrd=		[BOOT] Specify the location of the initial ramdisk

	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
			Format: <irq>

1492 1493
	int_pln_enable  [x86] Enable power limit notification interrupt

1494 1495 1496 1497 1498
	integrity_audit=[IMA]
			Format: { "0" | "1" }
			0 -- basic integrity auditing messages. (Default)
			1 -- additional integrity auditing messages.

1499
	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1500 1501
		on
			Enable intel iommu driver.
1502 1503 1504 1505 1506 1507 1508 1509
		off
			Disable intel iommu driver.
		igfx_off [Default Off]
			By default, gfx is mapped as normal device. If a gfx
			device has a dedicated DMAR unit, the DMAR unit is
			bypassed by not enabling DMAR with this option. In
			this case, gfx device will use physical address for
			DMA.
1510 1511
		forcedac [x86_64]
			With this option iommu will not optimize to look
1512
			for io virtual address below 32-bit forcing dual
1513
			address cycle on pci bus for cards supporting greater
1514 1515
			than 32-bit addressing. The default is to look
			for translation below 32-bit and if not available
1516
			then look in the higher range.
M
mark gross 已提交
1517 1518 1519 1520
		strict [Default Off]
			With this option on every unmap_single operation will
			result in a hardware IOTLB flush operation as opposed
			to batching them for performance.
1521 1522 1523 1524
		sp_off [Default Off]
			By default, super page will be supported if Intel IOMMU
			has the capability. With this option, super page will
			not be supported.
1525 1526 1527 1528 1529 1530
		ecs_off [Default Off]
			By default, extended context tables will be supported if
			the hardware advertises that it has support both for the
			extended tables themselves, and also PASID support. With
			this option set, extended tables will not be used even
			on hardware which claims to support them.
1531 1532 1533 1534 1535

	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
			0	disables intel_idle and fall back on acpi_idle.
			1 to 6	specify maximum depth of C-state.

1536 1537 1538 1539
	intel_pstate=  [X86]
		       disable
		         Do not enable intel_pstate as the default
		         scaling driver for the supported processors
1540 1541 1542 1543 1544 1545 1546 1547 1548
		       force
			 Enable intel_pstate on systems that prohibit it by default
			 in favor of acpi-cpufreq. Forcing the intel_pstate driver
			 instead of acpi-cpufreq may disable platform features, such
			 as thermal controls and power capping, that rely on ACPI
			 P-States information being indicated to OSPM and therefore
			 should be used with caution. This option does not work with
			 processors that aren't supported by the intel_pstate driver
			 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
D
Dirk Brandewie 已提交
1549 1550 1551
		       no_hwp
		         Do not enable hardware P state control (HWP)
			 if available.
1552 1553 1554
		hwp_only
			Only load intel_pstate on systems which support
			hardware P state control (HWP) if available.
1555

1556 1557 1558 1559
	intremap=	[X86-64, Intel-IOMMU]
			on	enable Interrupt Remapping (default)
			off	disable Interrupt Remapping
			nosid	disable Source ID checking
1560 1561
			no_x2apic_optout
				BIOS x2APIC opt-out request will be ignored
1562

1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
	iomem=		Disable strict checking of access to MMIO memory
		strict	regions from userspace.
		relaxed

	iommu=		[x86]
		off
		force
		noforce
		biomerge
		panic
		nopanic
		merge
		nomerge
		forcesac
		soft
1578
		pt		[x86, IA-64]
1579 1580
		nobypass	[PPC/POWERNV]
			Disable IOMMU bypass, using IOMMU for PCI devices.
1581

1582 1583 1584 1585 1586

	io7=		[HW] IO7 for Marvel based alpha systems
			See comment before marvel_specify_io7 in
			arch/alpha/kernel/core_marvel.c.

1587
	io_delay=	[X86] I/O delay method
1588 1589 1590 1591
		0x80
			Standard port 0x80 based delay
		0xed
			Alternate port 0xed based delay (needed on some systems)
1592
		udelay
1593 1594 1595
			Simple two microseconds delay
		none
			No delay
1596

L
Linus Torvalds 已提交
1597
	ip=		[IP_PNP]
1598
			See Documentation/filesystems/nfs/nfsroot.txt.
L
Linus Torvalds 已提交
1599

A
Alan Cox 已提交
1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610
	irqfixup	[HW]
			When an interrupt is not handled search all handlers
			for it. Intended to get systems with badly broken
			firmware running.

	irqpoll		[HW]
			When an interrupt is not handled search all handlers
			for it. Also check all handlers each timer
			interrupt. Intended to get systems with badly broken
			firmware running.

L
Linus Torvalds 已提交
1611
	isapnp=		[ISAPNP]
R
Randy Dunlap 已提交
1612
			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
L
Linus Torvalds 已提交
1613 1614

	isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1615 1616 1617
			Format:
			<cpu number>,...,<cpu number>
			or
1618 1619
			<cpu number>-<cpu number>
			(must be a positive range in ascending order)
1620 1621
			or a mixture
			<cpu number>,...,<cpu number>-<cpu number>
1622

L
Linus Torvalds 已提交
1623 1624
			This option can be used to specify one or more CPUs
			to isolate from the general SMP balancing and scheduling
1625 1626
			algorithms. You can move a process onto or off an
			"isolated" CPU via the CPU affinity syscalls or cpuset.
L
Linus Torvalds 已提交
1627 1628 1629 1630
			<cpu number> begins at 0 and the maximum value is
			"number of CPUs in system - 1".

			This option is the preferred way to isolate CPUs. The
R
Randy Dunlap 已提交
1631 1632 1633
			alternative -- manually setting the CPU mask of all
			tasks in the system -- can cause problems and
			suboptimal load balancer performance.
L
Linus Torvalds 已提交
1634

R
Randy Dunlap 已提交
1635
	iucv=		[HW,NET]
L
Linus Torvalds 已提交
1636

1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650
	ivrs_ioapic	[HW,X86_64]
			Provide an override to the IOAPIC-ID<->DEVICE-ID
			mapping provided in the IVRS ACPI table. For
			example, to map IOAPIC-ID decimal 10 to
			PCI device 00:14.0 write the parameter as:
				ivrs_ioapic[10]=00:14.0

	ivrs_hpet	[HW,X86_64]
			Provide an override to the HPET-ID<->DEVICE-ID
			mapping provided in the IVRS ACPI table. For
			example, to map HPET-ID decimal 0 to
			PCI device 00:14.0 write the parameter as:
				ivrs_hpet[0]=00:14.0

L
Linus Torvalds 已提交
1651 1652 1653
	js=		[HW,JOY] Analog joystick
			See Documentation/input/joystick.txt.

1654 1655 1656 1657 1658 1659 1660
	kaslr/nokaslr	[X86]
			Enable/disable kernel and module base offset ASLR
			(Address Space Layout Randomization) if built into
			the kernel. When CONFIG_HIBERNATION is selected,
			kASLR is disabled by default. When kASLR is enabled,
			hibernation will be disabled.

1661 1662
	keepinitrd	[HW,ARM]

1663
	kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
M
Mel Gorman 已提交
1664 1665 1666 1667 1668 1669 1670
			specifies the amount of memory usable by the kernel
			for non-movable allocations.  The requested amount is
			spread evenly throughout all nodes in the system. The
			remaining memory in each node is used for Movable
			pages. In the event, a node is too small to have both
			kernelcore and Movable pages, kernelcore pages will
			take priority and other nodes will have a larger number
1671
			of Movable pages.  The Movable zone is used for the
M
Mel Gorman 已提交
1672 1673 1674 1675 1676 1677 1678
			allocation of pages that may be reclaimed or moved
			by the page migration subsystem.  This means that
			HugeTLB pages may not be allocated from this zone.
			Note that allocations like PTEs-from-HighMem still
			use the HighMem zone if it exists, and the Normal
			zone if it does not.

1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689
	kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
			Format: <Controller#>[,poll interval]
			The controller # is the number of the ehci usb debug
			port as it is probed via PCI.  The poll interval is
			optional and is the number seconds in between
			each poll cycle to the debug port in case you need
			the functionality for interrupting the kernel with
			gdb or control-c on the dbgp connection.  When
			not using this parameter you use sysrq-g to break into
			the kernel debugger.

1690
	kgdboc=		[KGDB,HW] kgdb over consoles.
1691 1692
			Requires a tty driver that supports console polling,
			or a supported polling keyboard driver (non-usb).
1693 1694 1695 1696 1697 1698
			 Serial only format: <serial_device>[,baud]
			 keyboard only format: kbd
			 keyboard and serial format: kbd,<serial_device>[,baud]
			Optional Kernel mode setting:
			 kms, kbd format: kms,kbd
			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
J
Jason Wessel 已提交
1699

1700 1701 1702
	kgdbwait	[KGDB] Stop kernel execution and enter the
			kernel debugger at the earliest opportunity.

1703 1704 1705 1706
	kmac=		[MIPS] korina ethernet MAC address.
			Configure the RouterBoard 532 series on-chip
			Ethernet adapter MAC address.

1707 1708 1709
	kmemleak=	[KNL] Boot-time kmemleak enable/disable
			Valid arguments: on, off
			Default: on
1710 1711
			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
			the default is off.
1712

1713 1714 1715 1716 1717 1718 1719
	kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
			Valid arguments: 0, 1, 2
			kmemcheck=0 (disabled)
			kmemcheck=1 (enabled)
			kmemcheck=2 (one-shot mode)
			Default: 2 (one-shot mode)

1720
	kstack=N	[X86] Print N words from the kernel stack
1721 1722
			in oops dumps.

1723 1724 1725
	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
			Default is 0 (don't ignore, but inject #GP)

1726 1727
	kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
			KVM MMU at runtime.
1728 1729 1730
			Default is 0 (off)

	kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1731
			Default is 1 (enabled)
1732 1733 1734

	kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
			for all guests.
1735
			Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748

	kvm-intel.ept=	[KVM,Intel] Disable extended page tables
			(virtualized MMU) support on capable Intel chips.
			Default is 1 (enabled)

	kvm-intel.emulate_invalid_guest_state=
			[KVM,Intel] Enable emulation of invalid guest states
			Default is 0 (disabled)

	kvm-intel.flexpriority=
			[KVM,Intel] Disable FlexPriority feature (TPR shadow).
			Default is 1 (enabled)

1749 1750 1751 1752
	kvm-intel.nested=
			[KVM,Intel] Enable VMX nesting (nVMX).
			Default is 0 (disabled)

1753 1754 1755 1756 1757 1758 1759 1760 1761
	kvm-intel.unrestricted_guest=
			[KVM,Intel] Disable unrestricted guest feature
			(virtualized real and unpaged mode) on capable
			Intel chips. Default is 1 (enabled)

	kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
			feature (tagged TLBs) on capable Intel chips.
			Default is 1 (enabled)

L
Linus Torvalds 已提交
1762 1763
	l2cr=		[PPC]

1764 1765
	l3cr=		[PPC]

1766
	lapic		[X86-32,APIC] Enable the local APIC even if BIOS
R
Randy Dunlap 已提交
1767
			disabled it.
L
Linus Torvalds 已提交
1768

1769 1770 1771 1772
	lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
			value for LAPIC timer one-shot implementation. Default
			back to the programmable timer unit in the LAPIC.

1773
	lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1774
			in C2 power state.
1775

1776 1777 1778 1779
	libata.dma=	[LIBATA] DMA control
			libata.dma=0	  Disable all PATA and SATA DMA
			libata.dma=1	  PATA and SATA Disk DMA only
			libata.dma=2	  ATAPI (CDROM) DMA only
1780
			libata.dma=4	  Compact Flash DMA only
1781 1782
			Combinations also work, so libata.dma=3 enables DMA
			for disks and CDROMs, but not CFs.
1783

1784 1785 1786
	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
			libata.ignore_hpa=0	  keep BIOS limits (default)
			libata.ignore_hpa=1	  ignore limits, using full disk
1787

1788 1789 1790 1791
	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
			when set.
			Format: <int>

1792 1793
	libata.force=	[LIBATA] Force configurations.  The format is comma
			separated list of "[ID:]VAL" where ID is
1794
			PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823
			matching port, link or device.  Basically, it matches
			the ATA ID string printed on console by libata.  If
			the whole ID part is omitted, the last PORT and DEVICE
			values are used.  If ID hasn't been specified yet, the
			configuration applies to all ports, links and devices.

			If only DEVICE is omitted, the parameter applies to
			the port and all links and devices behind it.  DEVICE
			number of 0 either selects the first device or the
			first fan-out link behind PMP device.  It does not
			select the host link.  DEVICE number of 15 selects the
			host link and device attached to it.

			The VAL specifies the configuration to force.  As long
			as there's no ambiguity shortcut notation is allowed.
			For example, both 1.5 and 1.5G would work for 1.5Gbps.
			The following configurations can be forced.

			* Cable type: 40c, 80c, short40c, unk, ign or sata.
			  Any ID with matching PORT is used.

			* SATA link speed limit: 1.5Gbps or 3.0Gbps.

			* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
			  udma[/][16,25,33,44,66,100,133] notation is also
			  allowed.

			* [no]ncq: Turn on or off NCQ.

1824 1825
			* [no]ncqtrim: Turn off queued DSM TRIM.

1826 1827 1828
			* nohrst, nosrst, norst: suppress hard, soft
                          and both resets.

D
Dan Williams 已提交
1829 1830 1831
			* rstonce: only attempt one reset during
			  hot-unplug link recovery

1832 1833
			* dump_id: dump IDENTIFY data.

1834 1835
			* atapi_dmadir: Enable ATAPI DMADIR bridge support

1836 1837
			* disable: Disable this device.

1838 1839 1840
			If there are multiple matching configurations changing
			the same attribute, the last one is used.

Y
Yinghai Lu 已提交
1841
	memblock=debug	[KNL] Enable memblock debug messages.
1842

L
Linus Torvalds 已提交
1843
	load_ramdisk=	[RAM] List of ramdisks to load from floppy
1844
			See Documentation/blockdev/ramdisk.txt.
L
Linus Torvalds 已提交
1845

1846 1847
	lockd.nlm_grace_period=P  [NFS] Assign grace period.
			Format: <integer>
L
Linus Torvalds 已提交
1848

1849 1850 1851 1852 1853 1854 1855 1856
	lockd.nlm_tcpport=N	[NFS] Assign TCP port.
			Format: <integer>

	lockd.nlm_timeout=T	[NFS] Assign timeout value.
			Format: <integer>

	lockd.nlm_udpport=M	[NFS] Assign UDP port.
			Format: <integer>
L
Linus Torvalds 已提交
1857

1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900
	locktorture.nreaders_stress= [KNL]
			Set the number of locking read-acquisition kthreads.
			Defaults to being automatically set based on the
			number of online CPUs.

	locktorture.nwriters_stress= [KNL]
			Set the number of locking write-acquisition kthreads.

	locktorture.onoff_holdoff= [KNL]
			Set time (s) after boot for CPU-hotplug testing.

	locktorture.onoff_interval= [KNL]
			Set time (s) between CPU-hotplug operations, or
			zero to disable CPU-hotplug testing.

	locktorture.shuffle_interval= [KNL]
			Set task-shuffle interval (jiffies).  Shuffling
			tasks allows some CPUs to go into dyntick-idle
			mode during the locktorture test.

	locktorture.shutdown_secs= [KNL]
			Set time (s) after boot system shutdown.  This
			is useful for hands-off automated testing.

	locktorture.stat_interval= [KNL]
			Time (s) between statistics printk()s.

	locktorture.stutter= [KNL]
			Time (s) to stutter testing, for example,
			specifying five seconds causes the test to run for
			five seconds, wait for five seconds, and so on.
			This tests the locking primitive's ability to
			transition abruptly to and from idle.

	locktorture.torture_runnable= [BOOT]
			Start locktorture running at boot time.

	locktorture.torture_type= [KNL]
			Specify the locking implementation to test.

	locktorture.verbose= [KNL]
			Enable additional printk() statements.

L
Linus Torvalds 已提交
1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917
	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
			Format: <irq>

	loglevel=	All Kernel Messages with a loglevel smaller than the
			console loglevel will be printed to the console. It can
			also be changed with klogd or other programs. The
			loglevels are defined as follows:

			0 (KERN_EMERG)		system is unusable
			1 (KERN_ALERT)		action must be taken immediately
			2 (KERN_CRIT)		critical conditions
			3 (KERN_ERR)		error conditions
			4 (KERN_WARNING)	warning conditions
			5 (KERN_NOTICE)		normal but significant condition
			6 (KERN_INFO)		informational
			7 (KERN_DEBUG)		debug-level messages

1918
	log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1919 1920 1921 1922 1923 1924
			in bytes.  n must be a power of two and greater
			than the minimal size. The minimal size is defined
			by LOG_BUF_SHIFT kernel config parameter. There is
			also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
			that allows to increase the default size depending on
			the number of CPUs. See init/Kconfig for more details.
L
Linus Torvalds 已提交
1925

R
Randy Dunlap 已提交
1926 1927 1928 1929 1930
	logo.nologo	[FB] Disables display of the built-in Linux logo.
			This may be used to provide more screen space for
			kernel log messages and is useful when debugging
			kernel boot problems.

L
Linus Torvalds 已提交
1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964
	lp=0		[LP]	Specify parallel ports to use, e.g,
	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
	lp=reset		first parallel port). 'lp=0' disables the
	lp=auto			printer driver. 'lp=reset' (which can be
				specified in addition to the ports) causes
				attached printers to be reset. Using
				lp=port1,port2,... specifies the parallel ports
				to associate lp devices with, starting with
				lp0. A port specification may be 'none' to skip
				that lp device, or a parport name such as
				'parport0'. Specifying 'lp=auto' instead of a
				port specification list means that device IDs
				from each port should be examined, to see if
				an IEEE 1284-compliant printer is attached; if
				so, the driver will manage that printer.
				See also header of drivers/char/lp.c.

	lpj=n		[KNL]
			Sets loops_per_jiffy to given constant, thus avoiding
			time-consuming boot-time autodetection (up to 250 ms per
			CPU). 0 enables autodetection (default). To determine
			the correct value for your kernel, boot with normal
			autodetection and see what value is printed. Note that
			on SMP systems the preset will be applied to all CPUs,
			which is likely to cause problems if your CPUs need
			significantly divergent settings. An incorrect value
			will cause delays in the kernel to be wrong, leading to
			unpredictable I/O errors and other breakage. Although
			unlikely, in the extreme case this might damage your
			hardware.

	ltpc=		[NET]
			Format: <io>,<irq>,<dma>

1965
	machvec=	[IA-64] Force the use of a particular machine-vector
R
Randy Dunlap 已提交
1966 1967
			(machvec) in a generic kernel.
			Example: machvec=hpzx1_swiotlb
L
Linus Torvalds 已提交
1968

1969 1970 1971 1972
	machtype=	[Loongson] Share the same kernel image file between different
			 yeeloong laptop.
			Example: machtype=lemote-yeeloong-2f-7inch

1973 1974
	max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
			than or equal to this physical address is ignored.
L
Linus Torvalds 已提交
1975 1976

	maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1977 1978 1979 1980
			should make use of.  maxcpus=n : n >= 0 limits the
			kernel to using 'n' processors.  n=0 is a special case,
			it is equivalent to "nosmp", which also disables
			the IO APIC.
L
Linus Torvalds 已提交
1981

1982 1983 1984 1985 1986 1987
	max_loop=	[LOOP] The number of loop block devices that get
	(loop.max_loop)	unconditionally pre-created at init time. The default
			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
			of statically allocating a predefined number, loop
			devices can be requested on-demand with the
			/dev/loop-control interface.
B
Bob Picco 已提交
1988

1989
	mce		[X86-32] Machine Check Exception
L
Linus Torvalds 已提交
1990

U
Uwe Hermann 已提交
1991
	mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1992

L
Linus Torvalds 已提交
1993 1994
	md=		[HW] RAID subsystems devices and level
			See Documentation/md.txt.
R
Randy Dunlap 已提交
1995

L
Linus Torvalds 已提交
1996 1997 1998
	mdacon=		[MDA]
			Format: <first>,<last>
			Specifies range of consoles to be captured by the MDA.
R
Randy Dunlap 已提交
1999

L
Linus Torvalds 已提交
2000 2001 2002
	mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
			Amount of memory to be used when the kernel is not able
			to see the whole system memory or for test.
2003 2004 2005 2006
			[X86] Work as limiting max address. Use together
			with memmap= to avoid physical address space collisions.
			Without memmap= PCI devices could be placed at addresses
			belonging to unused RAM.
L
Linus Torvalds 已提交
2007

2008
	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
L
Linus Torvalds 已提交
2009 2010
			memory.

2011 2012 2013 2014
	memchunk=nn[KMG]
			[KNL,SH] Allow user to override the default size for
			per-device physically contiguous DMA buffers.

2015
	memmap=exactmap	[KNL,X86] Enable setting of an exact
L
Linus Torvalds 已提交
2016 2017 2018 2019 2020 2021
			E820 memory map, as specified by the user.
			Such memmap=exactmap lines can be constructed based on
			BIOS output or other requirements. See the memmap=nn@ss
			option description.

	memmap=nn[KMG]@ss[KMG]
2022 2023
			[KNL] Force usage of a specific region of memory.
			Region of memory to be used is from ss to ss+nn.
L
Linus Torvalds 已提交
2024 2025 2026

	memmap=nn[KMG]#ss[KMG]
			[KNL,ACPI] Mark specific memory as ACPI data.
2027
			Region of memory to be marked is from ss to ss+nn.
L
Linus Torvalds 已提交
2028 2029 2030

	memmap=nn[KMG]$ss[KMG]
			[KNL,ACPI] Mark specific memory as reserved.
2031
			Region of memory to be reserved is from ss to ss+nn.
2032 2033 2034 2035
			Example: Exclude memory from 0x18690000-0x1869ffff
			         memmap=64K$0x18690000
			         or
			         memmap=0x10000$0x18690000
L
Linus Torvalds 已提交
2036

2037 2038 2039 2040 2041 2042
	memmap=nn[KMG]!ss[KMG]
			[KNL,X86] Mark specific memory as protected.
			Region of memory to be used, from ss to ss+nn.
			The memory region may be marked as e820 type 12 (0xc)
			and is NVDIMM or ADR memory.

2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065
	memory_corruption_check=0/1 [X86]
			Some BIOSes seem to corrupt the first 64k of
			memory when doing things like suspend/resume.
			Setting this option will scan the memory
			looking for corruption.  Enabling this will
			both detect corruption and prevent the kernel
			from using the memory being corrupted.
			However, its intended as a diagnostic tool; if
			repeatable BIOS-originated corruption always
			affects the same memory, you can use memmap=
			to prevent the kernel from using that memory.

	memory_corruption_check_size=size [X86]
			By default it checks for corruption in the low
			64k, making this memory unavailable for normal
			use.  Use this parameter to scan for
			corruption in more or less memory.

	memory_corruption_check_period=seconds [X86]
			By default it checks for corruption every 60
			seconds.  Use this parameter to check at some
			other rate.  0 disables periodic checking.

2066
	memtest=	[KNL,X86,ARM] Enable memtest
Y
Yinghai Lu 已提交
2067 2068
			Format: <integer>
			default : 0 <disable>
2069 2070 2071 2072 2073 2074
			Specifies the number of memtest passes to be
			performed. Each pass selects another test
			pattern from a given set of patterns. Memtest
			fills the memory with this pattern, validates
			memory contents and reserves bad memory
			regions that are detected.
Y
Yinghai Lu 已提交
2075

L
Linus Torvalds 已提交
2076 2077 2078
	meye.*=		[HW] Set MotionEye Camera parameters
			See Documentation/video4linux/meye.txt.

2079 2080 2081 2082
	mfgpt_irq=	[IA-32] Specify the IRQ to use for the
			Multi-Function General Purpose Timers on AMD Geode
			platforms.

2083 2084 2085 2086 2087
	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
			the BIOS has incorrectly applied a workaround. TinyBIOS
			version 0.98 is known to be affected, 0.99 fixes the
			problem by letting the user disable the workaround.

L
Linus Torvalds 已提交
2088 2089
	mga=		[HW,DRM]

2090 2091 2092
	min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
			physical address is ignored.

2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113
	mini2440=	[ARM,HW,KNL]
			Format:[0..2][b][c][t]
			Default: "0tb"
			MINI2440 configuration specification:
			0 - The attached screen is the 3.5" TFT
			1 - The attached screen is the 7" TFT
			2 - The VGA Shield is attached (1024x768)
			Leaving out the screen size parameter will not load
			the TFT driver, and the framebuffer will be left
			unconfigured.
			b - Enable backlight. The TFT backlight pin will be
			linked to the kernel VESA blanking code and a GPIO
			LED. This parameter is not necessary when using the
			VGA shield.
			c - Enable the s3c camera interface.
			t - Reserved for enabling touchscreen support. The
			touchscreen support is not enabled in the mainstream
			kernel as of 2.6.30, a preliminary port can be found
			in the "bleeding edge" mini2440 support kernel at
			http://repo.or.cz/w/linux-2.6/mini2440.git

2114 2115 2116 2117 2118 2119 2120 2121
	mminit_loglevel=
			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
			parameter allows control of the logging verbosity for
			the additional memory initialisation checks. A value
			of 0 disables mminit logging and a level of 4 will
			log everything. Information is printed at KERN_DEBUG
			so loglevel=8 may also need to be specified.

R
Rusty Russell 已提交
2122 2123 2124
	module.sig_enforce
			[KNL] When CONFIG_MODULE_SIG is set, this means that
			modules without (valid) signatures will fail to load.
2125
			Note that if CONFIG_MODULE_SIG_FORCE is set, that
R
Rusty Russell 已提交
2126 2127
			is always true, so this option does nothing.

L
Linus Torvalds 已提交
2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138
	mousedev.tap_time=
			[MOUSE] Maximum time between finger touching and
			leaving touchpad surface for touch to be considered
			a tap and be reported as a left button click (for
			touchpads working in absolute mode only).
			Format: <msecs>
	mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
			reporting absolute coordinates, such as tablets
	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
			reporting absolute coordinates, such as tablets

2139
	movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2140 2141 2142 2143 2144 2145 2146 2147 2148
			is similar to kernelcore except it specifies the
			amount of memory used for migratable allocations.
			If both kernelcore and movablecore is specified,
			then kernelcore will be at *least* the specified
			value but may be more. If movablecore on its own
			is specified, the administrator must be careful
			that the amount of memory usable for all allocations
			is not too small.

2149 2150 2151
	movable_node	[KNL,X86] Boot-time switch to enable the effects
			of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.

L
Linus Torvalds 已提交
2152 2153 2154
	MTD_Partition=	[MTD]
			Format: <name>,<region-number>,<size>,<offset>

R
Randy Dunlap 已提交
2155 2156
	MTD_Region=	[MTD] Format:
			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
L
Linus Torvalds 已提交
2157 2158

	mtdparts=	[MTD]
2159
			See drivers/mtd/cmdlinepart.c.
L
Linus Torvalds 已提交
2160

2161 2162 2163 2164
	multitce=off	[PPC]  This parameter disables the use of the pSeries
			firmware feature for updating multiple TCE entries
			at a time.

R
Rohit Hagargundgi 已提交
2165 2166 2167 2168 2169 2170 2171 2172 2173 2174
	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration

			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]

			boundary - index of last SLC block on Flex-OneNAND.
				   The remaining blocks are configured as MLC blocks.
			lock	 - Configure if Flex-OneNAND boundary should be locked.
				   Once locked, the boundary cannot be changed.
				   1 indicates lock status, 0 indicates unlock status.

2175 2176 2177 2178 2179
	mtdset=		[ARM]
			ARM/S3C2412 JIVE boot control

			See arch/arm/mach-s3c2412/mach-jive.c

L
Linus Torvalds 已提交
2180
	mtouchusb.raw_coordinates=
R
Randy Dunlap 已提交
2181 2182
			[HW] Make the MicroTouch USB driver use raw coordinates
			('y', default) or cooked coordinates ('n')
L
Linus Torvalds 已提交
2183

2184
	mtrr_chunk_size=nn[KMG] [X86]
2185
			used for mtrr cleanup. It is largest continuous chunk
2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200
			that could hold holes aka. UC entries.

	mtrr_gran_size=nn[KMG] [X86]
			Used for mtrr cleanup. It is granularity of mtrr block.
			Default is 1.
			Large value could prevent small alignment from
			using up MTRRs.

	mtrr_spare_reg_nr=n [X86]
			Format: <integer>
			Range: 0,7 : spare reg number
			Default : 1
			Used for mtrr cleanup. It is spare mtrr entries number.
			Set to 2 or more if your graphical card needs more.

L
Linus Torvalds 已提交
2201 2202 2203 2204 2205 2206
	n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card

	netdev=		[NET] Network devices parameters
			Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
			Note that mem_start is often overloaded to mean
			something different and driver-specific.
R
Randy Dunlap 已提交
2207 2208 2209
			This usage is only documented in each driver source
			file if at all.

2210 2211 2212 2213
	nf_conntrack.acct=
			[NETFILTER] Enable connection tracking flow accounting
			0 to disable accounting
			1 to enable accounting
2214
			Default value is 0.
2215

2216
	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2217
			See Documentation/filesystems/nfs/nfsroot.txt.
L
Linus Torvalds 已提交
2218 2219

	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2220
			See Documentation/filesystems/nfs/nfsroot.txt.
L
Linus Torvalds 已提交
2221

2222 2223 2224
	nfsrootdebug	[NFS] enable nfsroot debugging messages.
			See Documentation/filesystems/nfs/nfsroot.txt.

2225 2226 2227 2228
	nfs.callback_tcpport=
			[NFS] set the TCP port on which the NFSv4 callback
			channel should listen.

2229 2230 2231 2232 2233 2234 2235 2236
	nfs.cache_getent=
			[NFS] sets the pathname to the program which is used
			to update the NFS client cache entries.

	nfs.cache_getent_timeout=
			[NFS] sets the timeout after which an attempt to
			update a cache entry is deemed to have failed.

2237 2238 2239 2240
	nfs.idmap_cache_timeout=
			[NFS] set the maximum lifetime for idmapper cache
			entries.

2241 2242 2243 2244 2245 2246 2247
	nfs.enable_ino64=
			[NFS] enable 64-bit inode numbers.
			If zero, the NFS client will fake up a 32-bit inode
			number for the readdir() and stat() syscalls instead
			of returning the full 64-bit number.
			The default is to return 64-bit inode numbers.

2248 2249 2250 2251 2252 2253 2254 2255
	nfs.max_session_slots=
			[NFSv4.1] Sets the maximum number of session slots
			the client will attempt to negotiate with the server.
			This limits the number of simultaneous RPC requests
			that the client can send to the NFSv4.1 server.
			Note that there is little point in setting this
			value higher than the max_tcp_slot_table_limit.

2256
	nfs.nfs4_disable_idmapping=
2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267
			[NFSv4] When set to the default of '1', this option
			ensures that both the RPC level authentication
			scheme and the NFS level operations agree to use
			numeric uids/gids if the mount is using the
			'sec=sys' security flavour. In effect it is
			disabling idmapping, which can make migration from
			legacy NFSv2/v3 systems to NFSv4 easier.
			Servers that do not support this mode of operation
			will be autodetected by the client, and it will fall
			back to using the idmapper.
			To turn off this behaviour, set the value to '0'.
2268 2269 2270 2271 2272
	nfs.nfs4_unique_id=
			[NFS4] Specify an additional fixed unique ident-
			ification string that NFSv4 clients can insert into
			their nfs_client_id4 string.  This is typically a
			UUID that is generated at system install time.
2273

2274 2275 2276 2277 2278 2279 2280
	nfs.send_implementation_id =
			[NFSv4.1] Send client implementation identification
			information in exchange_id requests.
			If zero, no implementation identification information
			will be sent.
			The default is to send the implementation identification
			information.
2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292
	
	nfs.recover_lost_locks =
			[NFSv4] Attempt to recover locks that were lost due
			to a lease timeout on the server. Please note that
			doing this risks data corruption, since there are
			no guarantees that the file will remain unchanged
			after the locks are lost.
			If you want to enable the kernel legacy behaviour of
			attempting to recover these locks, then set this
			parameter to '1'.
			The default parameter value of '0' causes the kernel
			not to attempt recovery of lost locks.
2293

2294 2295 2296 2297 2298 2299 2300 2301 2302
	nfs4.layoutstats_timer =
			[NFSv4.2] Change the rate at which the kernel sends
			layoutstats to the pNFS metadata server.

			Setting this to value to 0 causes the kernel to use
			whatever value is the default set by the layout
			driver. A non-zero value sets the minimum interval
			in seconds between layoutstats transmissions.

J
J. Bruce Fields 已提交
2303 2304 2305 2306 2307 2308
	nfsd.nfs4_disable_idmapping=
			[NFSv4] When set to the default of '1', the NFSv4
			server will return only numeric uids and gids to
			clients using auth_sys, and will accept numeric uids
			and gids from such clients.  This is intended to ease
			migration from NFSv2/v3.
2309

2310 2311 2312 2313 2314 2315
	objlayoutdriver.osd_login_prog=
			[NFS] [OBJLAYOUT] sets the pathname to the program which
			is used to automatically discover and login into new
			osd-targets. Please see:
			Documentation/filesystems/pnfs.txt for more explanations

P
Paul Mundt 已提交
2316
	nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
H
Haavard Skinnemoen 已提交
2317 2318 2319
			when a NMI is triggered.
			Format: [state][,regs][,debounce][,die]

2320
	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2321
			Format: [panic,][nopanic,][num]
2322
			Valid num: 0 or 1
2323 2324
			0 - turn hardlockup detector in nmi_watchdog off
			1 - turn hardlockup detector in nmi_watchdog on
2325
			When panic is specified, panic when an NMI watchdog
2326
			timeout occurs (or 'nopanic' to override the opposite
2327 2328
			default). To disable both hard and soft lockup detectors,
			please see 'nowatchdog'.
2329 2330
			This is useful when you use a panic=... timeout and
			need the box quickly up again.
L
Linus Torvalds 已提交
2331

2332 2333 2334 2335 2336
	netpoll.carrier_timeout=
			[NET] Specifies amount of time (in seconds) that
			netpoll should wait for a carrier. By default netpoll
			waits 4 seconds.

2337
	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
L
Linus Torvalds 已提交
2338 2339 2340
			emulation library even if a 387 maths coprocessor
			is present.

2341 2342 2343 2344 2345 2346 2347 2348 2349
	no_console_suspend
			[HW] Never suspend the console
			Disable suspending of consoles during suspend and
			hibernate operations.  Once disabled, debugging
			messages can reach various consoles while the rest
			of the system is being put to sleep (ie, while
			debugging driver suspend/resume hooks).  This may
			not work reliably with all consoles, but is known
			to work with serial and VGA consoles.
2350 2351 2352 2353 2354
			To facilitate more flexible debugging, we also add
			console_suspend, a printk module parameter to control
			it. Users could use console_suspend (usually
			/sys/module/printk/parameters/console_suspend) to
			turn on/off it dynamically.
2355

C
Christoph Lameter 已提交
2356 2357 2358
	noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
			caches in the slab allocator.  Saves per-node memory,
			but will impact performance.
2359

R
Randy Dunlap 已提交
2360 2361
	noalign		[KNL,ARM]

L
Linus Torvalds 已提交
2362 2363 2364
	noapic		[SMP,APIC] Tells the kernel to not make use of any
			IOAPICs that may be present in the system.

2365 2366
	noautogroup	Disable scheduler automatic task group creation.

L
Linus Torvalds 已提交
2367 2368 2369 2370
	nobats		[PPC] Do not use BATs for mapping kernel lowmem
			on "Classic" PPC cores.

	nocache		[ARM]
R
Randy Dunlap 已提交
2371

2372 2373
	noclflush	[BUGS=X86] Don't use the CLFLUSH instruction

2374 2375
	nodelayacct	[KNL] Disable per-task delay accounting

L
Linus Torvalds 已提交
2376 2377
	nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.

2378 2379
	nodsp		[SH] Disable hardware DSP at boot time.

2380
	noefi		Disable EFI runtime services support.
2381

L
Linus Torvalds 已提交
2382 2383
	noexec		[IA-64]

2384
	noexec		[X86]
J
Jiri Slaby 已提交
2385
			On X86-32 available only on PAE configured kernels.
L
Linus Torvalds 已提交
2386
			noexec=on: enable non-executable mappings (default)
J
Jiri Slaby 已提交
2387 2388
			noexec=off: disable non-executable mappings

2389 2390 2391 2392
	nosmap		[X86]
			Disable SMAP (Supervisor Mode Access Prevention)
			even if it is supported by processor.

2393
	nosmep		[X86]
2394
			Disable SMEP (Supervisor Mode Execution Prevention)
2395 2396
			even if it is supported by processor.

J
Jiri Slaby 已提交
2397 2398 2399 2400 2401 2402
	noexec32	[X86-64]
			This affects only 32-bit executables.
			noexec32=on: enable non-executable mappings (default)
				read doesn't imply executable mappings
			noexec32=off: disable non-executable mappings
				read implies executable mappings
L
Linus Torvalds 已提交
2403

2404
	nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2405

2406
	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2407 2408
			register save and restore. The kernel will only save
			legacy floating-point registers on task switch.
L
Linus Torvalds 已提交
2409

2410 2411
	nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.

2412 2413 2414 2415
	noxsave		[BUGS=X86] Disables x86 extended register state save
			and restore using xsave. The kernel will fallback to
			enabling legacy floating-point and sse state.

2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430
	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
			register states. The kernel will fall back to use
			xsave to save the states. By using this parameter,
			performance of saving the states is degraded because
			xsave doesn't support modified optimization while
			xsaveopt supports it on xsaveopt enabled systems.

	noxsaves	[X86] Disables xsaves and xrstors used in saving and
			restoring x86 extended register state in compacted
			form of xsave area. The kernel will fall back to use
			xsaveopt and xrstor to save and restore the states
			in standard form of xsave area. By using this
			parameter, xsave area per process might occupy more
			memory on xsaves enabled systems.

2431 2432 2433
	nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
			wfi(ARM) instruction doesn't work correctly and not to
			use it. This is also useful when using JTAG debugger.
R
Randy Dunlap 已提交
2434

2435 2436 2437 2438
	no_file_caps	Tells the kernel not to honor file capabilities.  The
			only way then for a file to be executed with privilege
			is to be setuid root or executed by root.

L
Linus Torvalds 已提交
2439 2440 2441 2442 2443 2444 2445
	nohalt		[IA-64] Tells the kernel not to use the power saving
			function PAL_HALT_LIGHT when idle. This increases
			power-consumption. On the positive side, it reduces
			interrupt wake-up latency, which may improve performance
			in certain environments such as networked servers or
			real-time systems.

2446 2447
	nohibernate	[HIBERNATION] Disable hibernation and resume.

2448 2449 2450 2451
	nohz=		[KNL] Boottime enable/disable dynamic ticks
			Valid arguments: on, off
			Default: on

2452 2453
	nohz_full=	[KNL,BOOT]
			In kernels built with CONFIG_NO_HZ_FULL=y, set
2454
			the specified list of CPUs whose tick will be stopped
2455 2456
			whenever possible. The boot CPU will be forced outside
			the range to maintain the timekeeping.
2457 2458
			The CPUs in this range must also be included in the
			rcu_nocbs= set.
2459

2460 2461
	noiotrap	[SH] Disables trapped I/O port accesses.

2462
	noirqdebug	[X86-32] Disables the code which attempts to detect and
L
Linus Torvalds 已提交
2463 2464
			disable unhandled interrupt sources.

2465
	no_timer_check	[X86,APIC] Disables the code which tests for
2466 2467
			broken timer IRQ sources.

L
Linus Torvalds 已提交
2468 2469 2470 2471 2472
	noisapnp	[ISAPNP] Disables ISA PnP code.

	noinitrd	[RAM] Tells the kernel not to load any configured
			initial RAM disk.

2473 2474
	nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
			remapping.
2475
			[Deprecated - use intremap=off]
2476

L
Linus Torvalds 已提交
2477 2478
	nointroute	[IA-64]

2479
	nojitter	[IA-64] Disables jitter checking for ITC timers.
2480

2481 2482
	no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver

2483 2484 2485
	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
			fault handling.

2486 2487 2488 2489
	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
			steal time is computed, but won't influence scheduler
			behaviour

2490
	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
L
Linus Torvalds 已提交
2491

2492
	nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2493

L
Linus Torvalds 已提交
2494 2495 2496
	noltlbs		[PPC] Do not use large page/tlb entries for kernel
			lowmem mapping on PPC40x.

2497 2498
	nomca		[IA-64] Disable machine check abort handling

2499
	nomce		[X86-32] Disable Machine Check Exception
2500

2501 2502 2503
	nomfgpt		[X86-32] Disable Multi-Function General Purpose
			Timer usage (for AMD Geode machines).

2504 2505 2506 2507
	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
			shutdown the other cpus.  Instead use the REBOOT_VECTOR
			irq.

2508 2509
	nomodule	Disable module load

2510 2511 2512
	nopat		[X86] Disable PAT (page attribute table extension of
			pagetables) support.

2513 2514 2515
	norandmaps	Don't use address space randomization.  Equivalent to
			echo 0 > /proc/sys/kernel/randomize_va_space

2516
	noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2517

2518
	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2519 2520
			with UP alternatives

2521 2522 2523 2524
	nordrand	[X86] Disable kernel use of the RDRAND and
			RDSEED instructions even if they are supported
			by the processor.  RDRAND and RDSEED are still
			available to user space applications.
2525

R
Randy Dunlap 已提交
2526 2527 2528
	noresume	[SWSUSP] Disables resume and restores original swap
			space.

L
Linus Torvalds 已提交
2529 2530 2531 2532 2533 2534
	no-scroll	[VGA] Disables scrollback.
			This is required for the Braillex ib80-piezo Braille
			reader made by F.H. Papenmeier (Germany).

	nosbagart	[IA-64]

2535
	nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2536

2537 2538
	nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
			and disable the IO APIC.  legacy for "maxcpus=0".
L
Linus Torvalds 已提交
2539

2540 2541
	nosoftlockup	[KNL] Disable the soft-lockup detector.

L
Linus Torvalds 已提交
2542 2543
	nosync		[HW,M68K] Disables sync negotiation for all devices.

2544
	notsc		[BUGS=X86-32] Disable Time Stamp Counter
L
Linus Torvalds 已提交
2545 2546 2547

	nousb		[USB] Disable the USB subsystem

2548 2549
	nowatchdog	[KNL] Disable both lockup detectors, i.e.
                        soft-lockup and NMI watchdog (hard-lockup).
2550

L
Linus Torvalds 已提交
2551
	nowb		[ARM]
R
Randy Dunlap 已提交
2552

2553 2554
	nox2apic	[X86-64,APIC] Do not enable x2APIC mode.

2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568
	cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
			CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
			Some features depend on CPU0. Known dependencies are:
			1. Resume from suspend/hibernate depends on CPU0.
			Suspend/hibernate will fail if CPU0 is offline and you
			need to online CPU0 before suspend/hibernate.
			2. PIC interrupts also depend on CPU0. CPU0 can't be
			removed if a PIC interrupt is detected.
			It's said poweroff/reboot may depend on CPU0 on some
			machines although I haven't seen such issues so far
			after CPU0 is offline on a few tested machines.
			If the dependencies are under your control, you can
			turn on cpu0_hotplug.

2569
	nptcg=		[IA-64] Override max number of concurrent global TLB
2570 2571 2572
			purges which is reported from either PAL_VM_SUMMARY or
			SAL PALO.

2573 2574 2575 2576 2577 2578
	nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
			could support.  nr_cpus=n : n >= 1 limits the kernel to
			supporting 'n' processors. Later in runtime you can not
			use hotplug cpu feature to put more cpu back to online.
			just like you compile the kernel NR_CPUS=n

2579 2580
	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.

2581 2582 2583
	numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
			Allowed values are enable and disable

2584 2585 2586 2587 2588
	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
			one of ['zone', 'node', 'default'] can be specified
			This can be set from sysctl after boot.
			See Documentation/sysctl/vm.txt for details.

2589 2590 2591 2592
	ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
			See Documentation/debugging-via-ohci1394.txt for more
			info.

2593 2594 2595 2596 2597 2598 2599
	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
			Rather than timing out after 20 ms if an EC
			command is not properly ACKed, override the length
			of the timeout.  We have interrupts disabled while
			waiting for the ACK, so if this is set too high
			interrupts *may* be lost!

2600 2601 2602 2603 2604
	omap_mux=	[OMAP] Override bootloader pin multiplexing.
			Format: <mux_mode0.mode_name=value>...
			For example, to override I2C bus2:
			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100

L
Linus Torvalds 已提交
2605 2606 2607
	oprofile.timer=	[HW]
			Use timer interrupt instead of performance counters

2608 2609 2610
	oprofile.cpu_type=	Force an oprofile cpu type
			This might be useful if you have an older oprofile
			userland or if you want common events.
2611 2612
			Format: { arch_perfmon }
			arch_perfmon: [X86] Force use of architectural
2613 2614
				perfmon on Intel CPUs instead of the
				CPU specific event set.
2615 2616 2617
			timer: [X86] Force use of architectural NMI
				timer mode (see also oprofile.timer
				for generic hr timer mode)
2618 2619
				[s390] Force legacy basic mode sampling
                                (report cpu_type "timer")
2620

2621 2622 2623
	oops=panic	Always panic on oopses. Default is to just kill the
			process, but there is a small probability of
			deadlocking the machine.
2624 2625 2626
			This will also cause panics on machine check exceptions.
			Useful together with panic=30 to trigger a reboot.

2627 2628 2629
	OSS		[HW,OSS]
			See Documentation/sound/oss/oss-parameters.txt

2630 2631 2632 2633 2634 2635
	page_owner=	[KNL] Boot-time page_owner enabling option.
			Storage of the information about who allocated
			each page is disabled in default. With this switch,
			we can turn it on.
			on: enable the feature

2636
	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2637 2638 2639
			timeout > 0: seconds before rebooting
			timeout = 0: wait forever
			timeout < 0: reboot immediately
L
Linus Torvalds 已提交
2640 2641
			Format: <timeout>

P
Prarit Bhargava 已提交
2642 2643 2644
	panic_on_warn	panic() instead of WARN().  Useful to cause kdump
			on a WARN().

2645 2646 2647 2648 2649 2650 2651 2652
	crash_kexec_post_notifiers
			Run kdump after running panic-notifiers and dumping
			kmsg. This only for the users who doubt kdump always
			succeeds in any situation.
			Note that this also increases risks of kdump failure,
			because some panic notifiers can make the crashed
			kernel more unstable.

L
Linus Torvalds 已提交
2653 2654 2655 2656 2657
	parkbd.port=	[HW] Parallel port number the keyboard adapter is
			connected to, default is 0.
			Format: <parport#>
	parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
			0 for XT, 1 for AT (default is AT).
R
Randy Dunlap 已提交
2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679
			Format: <mode>

	parport=	[HW,PPT] Specify parallel ports. 0 disables.
			Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
			Use 'auto' to force the driver to use any
			IRQ/DMA settings detected (the default is to
			ignore detected IRQ/DMA settings because of
			possible conflicts). You can specify the base
			address, IRQ, and DMA settings; IRQ and DMA
			should be numbers, or 'auto' (for using detected
			settings on that particular port), or 'nofifo'
			(to avoid using a FIFO even if it is detected).
			Parallel ports are assigned in the order they
			are specified on the command line, starting
			with parport0.

	parport_init_mode=	[HW,PPT]
			Configure VIA parallel port to operate in
			a specific mode. This is necessary on Pegasos
			computer where firmware has no options for setting
			up parallel port mode and sets it to spp.
			Currently this function knows 686a and 8231 chips.
L
Linus Torvalds 已提交
2680 2681
			Format: [spp|ps2|epp|ecp|ecpepp]

2682 2683 2684 2685 2686
	pause_on_oops=
			Halt all CPUs after the first oops has been printed for
			the specified number of seconds.  This is to be used if
			your oopses keep scrolling off the screen.

L
Linus Torvalds 已提交
2687 2688 2689 2690
	pcbit=		[HW,ISDN]

	pcd.		[PARIDE]
			See header of drivers/block/paride/pcd.c.
2691
			See also Documentation/blockdev/paride.txt.
L
Linus Torvalds 已提交
2692

R
Randy Dunlap 已提交
2693
	pci=option[,option...]	[PCI] various PCI subsystem options:
2694 2695
		earlydump	[X86] dump PCI config space before the kernel
			        changes anything
2696
		off		[X86] don't probe for the PCI bus
2697
		bios		[X86-32] force use of PCI BIOS, don't access
R
Randy Dunlap 已提交
2698 2699
				the hardware directly. Use this if your machine
				has a non-standard PCI host bridge.
2700
		nobios		[X86-32] disallow use of PCI BIOS, only direct
R
Randy Dunlap 已提交
2701 2702 2703
				hardware access methods are allowed. Use this
				if you experience crashes upon bootup and you
				suspect they are caused by the BIOS.
2704
		conf1		[X86] Force use of PCI Configuration
R
Randy Dunlap 已提交
2705
				Mechanism 1.
2706
		conf2		[X86] Force use of PCI Configuration
R
Randy Dunlap 已提交
2707
				Mechanism 2.
R
Randy Dunlap 已提交
2708 2709 2710
		noaer		[PCIE] If the PCIEAER kernel config parameter is
				enabled, this kernel boot option can be used to
				disable the use of PCIE advanced error reporting.
2711 2712
		nodomains	[PCI] Disable support for multiple PCI
				root domains (aka PCI segments, in ACPI-speak).
2713
		nommconf	[X86] Disable use of MMCONFIG for PCI
2714
				Configuration
2715 2716 2717
		check_enable_amd_mmconf [X86] check for and enable
				properly configured MMIO access to PCI
				config space on AMD family 10h CPU
2718 2719 2720
		nomsi		[MSI] If the PCI_MSI kernel config parameter is
				enabled, this kernel boot option can be used to
				disable the use of MSI interrupts system-wide.
2721 2722 2723
		noioapicquirk	[APIC] Disable all boot interrupt quirks.
				Safety option to keep boot IRQs enabled. This
				should never be necessary.
2724 2725 2726 2727
		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
				primary IO-APIC for bridges that cannot disable
				boot IRQs. This fixes a source of spurious IRQs
				when the system masks IRQs.
2728 2729 2730 2731
		noioapicreroute	[APIC] Disable workaround that uses the
				boot IRQ equivalent of an IRQ that connects to
				a chipset where boot IRQs cannot be disabled.
				The opposite of ioapicreroute.
2732
		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
R
Randy Dunlap 已提交
2733 2734 2735 2736 2737 2738 2739
				routing table. These calls are known to be buggy
				on several machines and they hang the machine
				when used, but on other computers it's the only
				way to get the interrupt routing table. Try
				this option if the kernel is unable to allocate
				IRQs or discover secondary PCI buses on your
				motherboard.
2740
		rom		[X86] Assign address space to expansion ROMs.
R
Randy Dunlap 已提交
2741 2742 2743
				Use with caution as certain devices share
				address decoders between ROMs and other
				resources.
2744
		norom		[X86] Do not assign address space to
2745 2746
				expansion ROMs that do not already have
				BIOS assigned address ranges.
2747 2748
		nobar		[X86] Do not assign address space to the
				BARs that weren't assigned by the BIOS.
2749
		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
R
Randy Dunlap 已提交
2750 2751 2752
				assigned automatically to PCI devices. You can
				make the kernel exclude IRQs of your ISA cards
				this way.
2753
		pirqaddr=0xAAAAA	[X86] Specify the physical address
R
Randy Dunlap 已提交
2754 2755 2756
				of the PIRQ table (normally generated
				by the BIOS) if it is outside the
				F0000h-100000h range.
2757
		lastbus=N	[X86] Scan all buses thru bus #N. Can be
R
Randy Dunlap 已提交
2758 2759 2760
				useful if the kernel is unable to find your
				secondary buses and you want to tell it
				explicitly which ones they are.
2761
		assign-busses	[X86] Always assign all PCI bus
R
Randy Dunlap 已提交
2762 2763
				numbers ourselves, overriding
				whatever the firmware may have done.
2764
		usepirqmask	[X86] Honor the possible IRQ mask stored
R
Randy Dunlap 已提交
2765 2766 2767 2768 2769
				in the BIOS $PIR table. This is needed on
				some systems with broken BIOSes, notably
				some HP Pavilion N5400 and Omnibook XE3
				notebooks. This will have no effect if ACPI
				IRQ routing is enabled.
2770
		noacpi		[X86] Do not use ACPI for IRQ routing
R
Randy Dunlap 已提交
2771
				or for PCI scanning.
2772 2773 2774 2775 2776 2777
		use_crs		[X86] Use PCI host bridge window information
				from ACPI.  On BIOSes from 2008 or later, this
				is enabled by default.  If you need to use this,
				please report a bug.
		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
			        If you need to use this, please report a bug.
R
Randy Dunlap 已提交
2778 2779 2780 2781
		routeirq	Do IRQ routing for all PCI devices.
				This is normally done in pci_enable_device(),
				so this option is a temporary workaround
				for broken drivers that don't call it.
2782 2783
		skip_isa_align	[X86] do not align io start addr, so can
				handle more pci cards
R
Randy Dunlap 已提交
2784 2785 2786 2787 2788
		firmware	[ARM] Do not re-enumerate the bus but instead
				just use the configuration from the
				bootloader. This is currently used on
				IXP2000 systems where the bus has to be
				configured a certain way for adjunct CPUs.
2789 2790 2791 2792 2793
		noearly		[X86] Don't do any early type 1 scanning.
				This might help on some broken boards which
				machine check when some devices' config space
				is read. But various workarounds are disabled
				and some IOMMU drivers will not work.
2794 2795 2796 2797
		bfsort		Sort PCI devices into breadth-first order.
				This sorting is done to get a device
				order compatible with older (<= 2.4) kernels.
		nobfsort	Don't sort PCI devices into breadth-first order.
2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812
		pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
				tuning and use the BIOS-configured MPS defaults.
		pcie_bus_safe	Set every device's MPS to the largest value
				supported by all devices below the root complex.
		pcie_bus_perf	Set device MPS to the largest allowable MPS
				based on its parent bus. Also set MRRS (Max
				Read Request Size) to the largest supported
				value (no larger than the MPS that the device
				or bus can support) for best performance.
		pcie_bus_peer2peer	Set every device's MPS to 128B, which
				every device is guaranteed to support. This
				configuration allows peer-to-peer DMA between
				any pair of devices, possibly at the cost of
				reduced performance.  This also guarantees
				that hot-added devices will work.
2813 2814 2815 2816 2817 2818
		cbiosize=nn[KMG]	The fixed amount of bus space which is
				reserved for the CardBus bridge's IO window.
				The default value is 256 bytes.
		cbmemsize=nn[KMG]	The fixed amount of bus space which is
				reserved for the CardBus bridge's memory
				window. The default value is 64 megabytes.
2819 2820 2821 2822 2823 2824 2825 2826 2827
		resource_alignment=
				Format:
				[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
				Specifies alignment and device to reassign
				aligned memory resources.
				If <order of align> is not specified,
				PAGE_SIZE is used as alignment.
				PCI-PCI bridge can be specified, if resource
				windows need to be expanded.
2828 2829 2830 2831 2832 2833
		ecrc=		Enable/disable PCIe ECRC (transaction layer
				end-to-end CRC checking).
				bios: Use BIOS/firmware settings. This is the
				the default.
				off: Turn ECRC off
				on: Turn ECRC on.
2834 2835 2836 2837 2838 2839
		hpiosize=nn[KMG]	The fixed amount of bus space which is
				reserved for hotplug bridge's IO window.
				Default size is 256 bytes.
		hpmemsize=nn[KMG]	The fixed amount of bus space which is
				reserved for hotplug bridge's memory window.
				Default size is 2 megabytes.
2840 2841 2842 2843 2844 2845 2846
		realloc=	Enable/disable reallocating PCI bridge resources
				if allocations done by BIOS are too small to
				accommodate resources required by all child
				devices.
				off: Turn realloc off
				on: Turn realloc on
		realloc		same as realloc=on
2847
		noari		do not use PCIe ARI.
2848 2849 2850
		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
				only look for one device below a PCIe downstream
				port.
2851

2852 2853 2854 2855 2856 2857
	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
			Management.
		off	Disable ASPM.
		force	Enable ASPM even on devices that claim not to support it.
			WARNING: Forcing ASPM on may cause system lockups.

2858 2859 2860 2861
	pcie_hp=	[PCIE] PCI Express Hotplug driver options:
		nomsi	Do not use MSI for PCI Express Native Hotplug (this
			makes all PCIe ports use INTx for hotplug services).

2862
	pcie_ports=	[PCIE] PCIe ports handling:
2863 2864 2865 2866 2867
		auto	Ask the BIOS whether or not to use native PCIe services
			associated with PCIe ports (PME, hot-plug, AER).  Use
			them only if that is allowed by the BIOS.
		native	Use native PCIe services associated with PCIe ports
			unconditionally.
2868 2869 2870
		compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
			ports driver.

2871
	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2872
		nomsi	Do not use MSI for native PCIe PME signaling (this makes
2873
			all PCIe root ports use INTx for all services).
2874

L
Linus Torvalds 已提交
2875 2876
	pcmv=		[HW,PCMCIA] BadgePAD 4

2877 2878 2879 2880 2881 2882 2883
	pd_ignore_unused
			[PM]
			Keep all power-domains already enabled by bootloader on,
			even if no driver has claimed them. This is useful
			for debug and development, but should not be
			needed on a platform with proper driver support.

L
Linus Torvalds 已提交
2884
	pd.		[PARIDE]
2885
			See Documentation/blockdev/paride.txt.
L
Linus Torvalds 已提交
2886 2887 2888 2889 2890 2891

	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
			boot time.
			Format: { 0 | 1 }
			See arch/parisc/kernel/pdc_chassis.c

2892
	percpu_alloc=	Select which percpu first chunk allocator to use.
2893 2894 2895 2896 2897
			Currently supported values are "embed" and "page".
			Archs may support subset or none of the	selections.
			See comments in mm/percpu.c for details on each
			allocator.  This parameter is primarily	for debugging
			and performance comparison.
2898

L
Linus Torvalds 已提交
2899
	pf.		[PARIDE]
2900
			See Documentation/blockdev/paride.txt.
L
Linus Torvalds 已提交
2901 2902

	pg.		[PARIDE]
2903
			See Documentation/blockdev/paride.txt.
L
Linus Torvalds 已提交
2904 2905

	pirq=		[SMP,APIC] Manual mp-table setup
U
Uwe Hermann 已提交
2906
			See Documentation/x86/i386/IO-APIC.txt.
L
Linus Torvalds 已提交
2907 2908 2909 2910 2911

	plip=		[PPT,NET] Parallel port network link
			Format: { parport<nr> | timid | 0 }
			See also Documentation/parport.txt.

2912
	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2913 2914 2915
			Override pmtimer IOPort with a hex value.
			e.g. pmtmr=0x508

2916 2917 2918 2919 2920 2921
	pnp.debug=1	[PNP]
			Enable PNP debug messages (depends on the
			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
			via /sys/module/pnp/parameters/debug.  We always show
			current resource usage; turning this on also shows
			possible settings and some assignment information.
2922

L
Linus Torvalds 已提交
2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935
	pnpacpi=	[ACPI]
			{ off }

	pnpbios=	[ISAPNP]
			{ on | off | curr | res | no-curr | no-res }

	pnp_reserve_irq=
			[ISAPNP] Exclude IRQs for the autoconfiguration

	pnp_reserve_dma=
			[ISAPNP] Exclude DMAs for the autoconfiguration

	pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
R
Randy Dunlap 已提交
2936
			Ranges are in pairs (I/O port base and size).
L
Linus Torvalds 已提交
2937 2938

	pnp_reserve_mem=
R
Randy Dunlap 已提交
2939 2940
			[ISAPNP] Exclude memory regions for the
			autoconfiguration.
L
Linus Torvalds 已提交
2941 2942
			Ranges are in pairs (memory base and size).

2943 2944 2945 2946 2947 2948
	ports=		[IP_VS_FTP] IPVS ftp helper module
			Default is 21.
			Up to 8 (IP_VS_APP_MAX_PORTS) ports
			may be specified.
			Format: <port>,<port>....

I
Ingo Molnar 已提交
2949 2950
	print-fatal-signals=
			[KNL] debug: print fatal signals
2951 2952 2953 2954 2955 2956 2957 2958 2959

			If enabled, warn about various signal handling
			related application anomalies: too many signals,
			too many POSIX.1 timers, fatal signals causing a
			coredump - etc.

			If you hit the warning due to signal overflow,
			you might want to try "ulimit -i unlimited".

I
Ingo Molnar 已提交
2960 2961
			default: off.

2962 2963 2964 2965 2966 2967
	printk.always_kmsg_dump=
			Trigger kmsg_dump for cases other than kernel oops or
			panics
			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
			default: disabled

2968 2969 2970
	printk.time=	Show timing data prefixed to each printk message line
			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

2971 2972 2973 2974 2975 2976 2977 2978
	processor.max_cstate=	[HW,ACPI]
			Limit processor to maximum C-state
			max_cstate=9 overrides any DMI blacklist limit.

	processor.nocst	[HW,ACPI]
			Ignore the _CST method to determine C-states,
			instead using the legacy FADT method

L
Linus Torvalds 已提交
2979
	profile=	[KNL] Enable kernel profiling via /proc/profile
R
Randy Dunlap 已提交
2980 2981 2982 2983
			Format: [schedule,]<number>
			Param: "schedule" - profile schedule points.
			Param: <number> - step/bucket size as a power of 2 for
				statistical time based profiling.
2984 2985
			Param: "sleep" - profile D-state sleeping (millisecs).
				Requires CONFIG_SCHEDSTATS
2986
			Param: "kvm" - profile VM exits.
L
Linus Torvalds 已提交
2987 2988 2989

	prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
			before loading.
2990
			See Documentation/blockdev/ramdisk.txt.
L
Linus Torvalds 已提交
2991

R
Randy Dunlap 已提交
2992 2993
	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
			probe for; one of (bare|imps|exps|lifebook|any).
L
Linus Torvalds 已提交
2994 2995
	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
			per second.
R
Randy Dunlap 已提交
2996 2997
	psmouse.resetafter=	[HW,MOUSE]
			Try to reset the device after so many bad packets
L
Linus Torvalds 已提交
2998 2999 3000 3001
			(0 = never).
	psmouse.resolution=
			[HW,MOUSE] Set desired mouse resolution, in dpi.
	psmouse.smartscroll=
R
Randy Dunlap 已提交
3002
			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
L
Linus Torvalds 已提交
3003 3004
			0 = disabled, 1 = enabled (default).

3005 3006
	pstore.backend=	Specify the name of the pstore backend to use

L
Linus Torvalds 已提交
3007
	pt.		[PARIDE]
3008
			See Documentation/blockdev/paride.txt.
L
Linus Torvalds 已提交
3009

3010 3011 3012 3013
	pty.legacy_count=
			[KNL] Number of legacy pty's. Overwrites compiled-in
			default number.

3014
	quiet		[KNL] Disable most log messages
R
Randy Dunlap 已提交
3015

L
Linus Torvalds 已提交
3016 3017 3018 3019 3020
	r128=		[HW,DRM]

	raid=		[HW,RAID]
			See Documentation/md.txt.

R
Randy Dunlap 已提交
3021
	ramdisk_blocksize=	[RAM]
3022
			See Documentation/blockdev/ramdisk.txt.
R
Randy Dunlap 已提交
3023

L
Linus Torvalds 已提交
3024
	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
3025
			See Documentation/blockdev/ramdisk.txt.
L
Linus Torvalds 已提交
3026

3027
	rcu_nocbs=	[KNL]
P
Paul E. McKenney 已提交
3028 3029 3030
			In kernels built with CONFIG_RCU_NOCB_CPU=y, set
			the specified list of CPUs to be no-callback CPUs.
			Invocation of these CPUs' RCU callbacks will
3031 3032 3033 3034
			be offloaded to "rcuox/N" kthreads created for
			that purpose, where "x" is "b" for RCU-bh, "p"
			for RCU-preempt, and "s" for RCU-sched, and "N"
			is the CPU number.  This reduces OS jitter on the
P
Paul E. McKenney 已提交
3035 3036 3037 3038
			offloaded CPUs, which can be useful for HPC and
			real-time workloads.  It can also improve energy
			efficiency for asymmetric multiprocessors.

3039
	rcu_nocb_poll	[KNL]
P
Paul E. McKenney 已提交
3040 3041 3042 3043 3044 3045 3046 3047 3048 3049
			Rather than requiring that offloaded CPUs
			(specified by rcu_nocbs= above) explicitly
			awaken the corresponding "rcuoN" kthreads,
			make these kthreads poll for callbacks.
			This improves the real-time response for the
			offloaded CPUs by relieving them of the need to
			wake up the corresponding kthread, but degrades
			energy efficiency by requiring that the kthreads
			periodically wake up to do the polling.

3050
	rcutree.blimit=	[KNL]
3051 3052
			Set maximum number of finished RCU callbacks to
			process in one batch.
D
Dipankar Sarma 已提交
3053

3054 3055 3056 3057 3058
	rcutree.dump_tree=	[KNL]
			Dump the structure of the rcu_node combining tree
			out at early boot.  This is used for diagnostic
			purposes, to verify correct tree setup.

3059 3060 3061 3062 3063
	rcutree.gp_cleanup_delay=	[KNL]
			Set the number of jiffies to delay each step of
			RCU grace-period cleanup.  This only has effect
			when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.

3064 3065 3066
	rcutree.gp_init_delay=	[KNL]
			Set the number of jiffies to delay each step of
			RCU grace-period initialization.  This only has
3067 3068 3069 3070 3071 3072 3073 3074 3075
			effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
			is set.

	rcutree.gp_preinit_delay=	[KNL]
			Set the number of jiffies to delay each step of
			RCU grace-period pre-initialization, that is,
			the propagation of recent CPU-hotplug changes up
			the rcu_node combining tree.  This only has effect
			when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3076

3077 3078 3079 3080 3081
	rcutree.rcu_fanout_exact= [KNL]
			Disable autobalancing of the rcu_node combining
			tree.  This is used by rcutorture, and might
			possibly be useful for architectures having high
			cache-to-cache transfer latencies.
3082

3083
	rcutree.rcu_fanout_leaf= [KNL]
3084 3085 3086 3087
			Increase the number of CPUs assigned to each
			leaf rcu_node structure.  Useful for very large
			systems.

3088 3089 3090 3091 3092 3093
	rcutree.jiffies_till_sched_qs= [KNL]
			Set required age in jiffies for a
			given grace period before RCU starts
			soliciting quiescent-state help from
			rcu_note_context_switch().

3094
	rcutree.jiffies_till_first_fqs= [KNL]
3095 3096 3097 3098 3099
			Set delay from grace-period initialization to
			first attempt to force quiescent states.
			Units are jiffies, minimum value is zero,
			and maximum value is HZ.

3100
	rcutree.jiffies_till_next_fqs= [KNL]
3101 3102 3103 3104
			Set delay between subsequent attempts to force
			quiescent states.  Units are jiffies, minimum
			value is one, and maximum value is HZ.

3105
	rcutree.kthread_prio= 	 [KNL,BOOT]
3106 3107 3108 3109 3110 3111 3112 3113 3114
			Set the SCHED_FIFO priority of the RCU per-CPU
			kthreads (rcuc/N). This value is also used for
			the priority of the RCU boost threads (rcub/N)
			and for the RCU grace-period kthreads (rcu_bh,
			rcu_preempt, and rcu_sched). If RCU_BOOST is
			set, valid values are 1-99 and the default is 1
			(the least-favored priority).  Otherwise, when
			RCU_BOOST is not set, valid values are 0-99 and
			the default is zero (non-realtime operation).
3115

3116 3117 3118 3119 3120 3121 3122
	rcutree.rcu_nocb_leader_stride= [KNL]
			Set the number of NOCB kthread groups, which
			defaults to the square root of the number of
			CPUs.  Larger numbers reduces the wakeup overhead
			on the per-CPU grace-period kthreads, but increases
			that same overhead on each group's leader.

3123
	rcutree.qhimark= [KNL]
3124 3125
			Set threshold of queued RCU callbacks beyond which
			batch limiting is disabled.
D
Dipankar Sarma 已提交
3126

3127
	rcutree.qlowmark= [KNL]
3128 3129
			Set threshold of queued RCU callbacks below which
			batch limiting is re-enabled.
D
Dipankar Sarma 已提交
3130

3131
	rcutree.rcu_idle_gp_delay= [KNL]
3132 3133
			Set wakeup interval for idle CPUs that have
			RCU callbacks (RCU_FAST_NO_HZ=y).
3134

3135
	rcutree.rcu_idle_lazy_gp_delay= [KNL]
3136 3137 3138 3139
			Set wakeup interval for idle CPUs that have
			only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
			Lazy RCU callbacks are those which RCU can
			prove do nothing more than free memory.
3140

3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158
	rcutorture.cbflood_inter_holdoff= [KNL]
			Set holdoff time (jiffies) between successive
			callback-flood tests.

	rcutorture.cbflood_intra_holdoff= [KNL]
			Set holdoff time (jiffies) between successive
			bursts of callbacks within a given callback-flood
			test.

	rcutorture.cbflood_n_burst= [KNL]
			Set the number of bursts making up a given
			callback-flood test.  Set this to zero to
			disable callback-flood testing.

	rcutorture.cbflood_n_per_burst= [KNL]
			Set the number of callbacks to be registered
			in a given burst of a callback-flood test.

3159
	rcutorture.fqs_duration= [KNL]
3160 3161
			Set duration of force_quiescent_state bursts
			in microseconds.
3162

3163
	rcutorture.fqs_holdoff= [KNL]
3164 3165
			Set holdoff time within force_quiescent_state bursts
			in microseconds.
3166

3167
	rcutorture.fqs_stutter= [KNL]
3168 3169 3170 3171 3172 3173
			Set wait time between force_quiescent_state bursts
			in seconds.

	rcutorture.gp_cond= [KNL]
			Use conditional/asynchronous update-side
			primitives, if available.
3174

3175
	rcutorture.gp_exp= [KNL]
3176
			Use expedited update-side primitives, if available.
3177 3178

	rcutorture.gp_normal= [KNL]
3179 3180 3181 3182 3183 3184 3185 3186 3187 3188
			Use normal (non-expedited) asynchronous
			update-side primitives, if available.

	rcutorture.gp_sync= [KNL]
			Use normal (non-expedited) synchronous
			update-side primitives, if available.  If all
			of rcutorture.gp_cond=, rcutorture.gp_exp=,
			rcutorture.gp_normal=, and rcutorture.gp_sync=
			are zero, rcutorture acts as if is interpreted
			they are all non-zero.
3189

3190
	rcutorture.n_barrier_cbs= [KNL]
3191 3192
			Set callbacks/threads for rcu_barrier() testing.

3193
	rcutorture.nfakewriters= [KNL]
3194 3195 3196 3197
			Set number of concurrent RCU writers.  These just
			stress RCU, they don't participate in the actual
			test, hence the "fake".

3198
	rcutorture.nreaders= [KNL]
3199 3200 3201 3202 3203
			Set number of RCU readers.  The value -1 selects
			N-1, where N is the number of CPUs.  A value
			"n" less than -1 selects N-n-2, where N is again
			the number of CPUs.  For example, -2 selects N
			(the number of CPUs), -3 selects N+1, and so on.
3204

3205 3206 3207 3208
	rcutorture.object_debug= [KNL]
			Enable debug-object double-call_rcu() testing.

	rcutorture.onoff_holdoff= [KNL]
3209 3210
			Set time (s) after boot for CPU-hotplug testing.

3211
	rcutorture.onoff_interval= [KNL]
3212 3213 3214
			Set time (s) between CPU-hotplug operations, or
			zero to disable CPU-hotplug testing.

3215
	rcutorture.shuffle_interval= [KNL]
3216 3217 3218 3219
			Set task-shuffle interval (s).  Shuffling tasks
			allows some CPUs to go into dyntick-idle mode
			during the rcutorture test.

3220
	rcutorture.shutdown_secs= [KNL]
3221 3222 3223
			Set time (s) after boot system shutdown.  This
			is useful for hands-off automated testing.

3224
	rcutorture.stall_cpu= [KNL]
3225 3226 3227
			Duration of CPU stall (s) to test RCU CPU stall
			warnings, zero to disable.

3228
	rcutorture.stall_cpu_holdoff= [KNL]
3229 3230
			Time to wait (s) after boot before inducing stall.

3231
	rcutorture.stat_interval= [KNL]
3232 3233
			Time (s) between statistics printk()s.

3234
	rcutorture.stutter= [KNL]
3235 3236 3237 3238 3239
			Time (s) to stutter testing, for example, specifying
			five seconds causes the test to run for five seconds,
			wait for five seconds, and so on.  This tests RCU's
			ability to transition abruptly to and from idle.

3240
	rcutorture.test_boost= [KNL]
3241 3242 3243 3244
			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
			"Maybe" means test if the RCU implementation
			under test support RCU priority boosting.

3245
	rcutorture.test_boost_duration= [KNL]
3246 3247
			Duration (s) of each individual boost test.

3248
	rcutorture.test_boost_interval= [KNL]
3249 3250
			Interval (s) between each boost test.

3251
	rcutorture.test_no_idle_hz= [KNL]
3252 3253 3254
			Test RCU's dyntick-idle handling.  See also the
			rcutorture.shuffle_interval parameter.

3255 3256 3257
	rcutorture.torture_runnable= [BOOT]
			Start rcutorture running at boot time.

3258
	rcutorture.torture_type= [KNL]
3259 3260
			Specify the RCU implementation to test.

3261
	rcutorture.verbose= [KNL]
3262 3263
			Enable additional printk() statements.

3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276
	rcupdate.rcu_expedited= [KNL]
			Use expedited grace-period primitives, for
			example, synchronize_rcu_expedited() instead
			of synchronize_rcu().  This reduces latency,
			but can increase CPU utilization, degrade
			real-time latency, and degrade energy efficiency.

	rcupdate.rcu_cpu_stall_suppress= [KNL]
			Suppress RCU CPU stall warning messages.

	rcupdate.rcu_cpu_stall_timeout= [KNL]
			Set timeout for RCU CPU stall warning messages.

3277 3278 3279 3280 3281
	rcupdate.rcu_task_stall_timeout= [KNL]
			Set timeout in jiffies for RCU task stall warning
			messages.  Disable with a value less than or equal
			to zero.

3282 3283 3284 3285 3286 3287 3288 3289 3290
	rcupdate.rcu_self_test= [KNL]
			Run the RCU early boot self tests

	rcupdate.rcu_self_test_bh= [KNL]
			Run the RCU bh early boot self tests

	rcupdate.rcu_self_test_sched= [KNL]
			Run the RCU sched early boot self tests

3291 3292 3293 3294 3295
	rdinit=		[KNL]
			Format: <full_path>
			Run specified binary instead of /init from the ramdisk,
			used for early userspace startup. See initrd.

3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306
	reboot=		[KNL]
			Format (x86 or x86_64):
				[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
				[[,]s[mp]#### \
				[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
				[[,]f[orce]
			Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
			      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
			      reboot_force is either force or not specified,
			      reboot_cpu is s[mp]#### with #### being the processor
					to be used for rebooting.
L
Linus Torvalds 已提交
3307

3308 3309
	relax_domain_level=
			[KNL, SMP] Set scheduler's default relax_domain_level.
3310
			See Documentation/cgroups/cpusets.txt.
3311

3312 3313 3314 3315 3316 3317 3318
	relative_sleep_states=
			[SUSPEND] Use sleep state labeling where the deepest
			state available other than hibernation is always "mem".
			Format: { "0" | "1" }
			0 -- Traditional sleep state labels.
			1 -- Relative sleep state labels.

L
Linus Torvalds 已提交
3319 3320
	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area

3321
	reservetop=	[X86-32]
3322 3323 3324 3325
			Format: nn[KMG]
			Reserves a hole at the top of the kernel virtual
			address space.

3326 3327 3328 3329 3330
	reservelow=	[X86]
			Format: nn[K]
			Set the amount of memory to reserve for BIOS at
			the bottom of the address space.

3331 3332 3333
	reset_devices	[KNL] Force drivers to reset the underlying device
			during initialization.

R
Randy Dunlap 已提交
3334 3335
	resume=		[SWSUSP]
			Specify the partition device for software suspend
3336 3337
			Format:
			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
L
Linus Torvalds 已提交
3338

3339 3340 3341 3342 3343 3344
	resume_offset=	[SWSUSP]
			Specify the offset from the beginning of the partition
			given by "resume=" at which the swap header is located,
			in <PAGE_SIZE> units (needed only for swap files).
			See  Documentation/power/swsusp-and-swap-files.txt

3345 3346 3347
	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
			read the resume files

3348 3349 3350 3351
	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
			Useful for devices that are detected asynchronously
			(e.g. USB and MMC devices).

3352 3353 3354 3355
	hibernate=	[HIBERNATION]
		noresume	Don't check if there's a hibernation image
				present during boot.
		nocompress	Don't compress/decompress hibernation images.
3356
		no		Disable hibernation and resume.
3357

3358 3359
	retain_initrd	[RAM] Keep initrd memory after extraction

3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371
	rfkill.default_state=
		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
			etc. communication is blocked by default.
		1	Unblocked.

	rfkill.master_switch_mode=
		0	The "airplane mode" button does nothing.
		1	The "airplane mode" button toggles between everything
			blocked and the previous configuration.
		2	The "airplane mode" button toggles between everything
			blocked and everything unblocked.

L
Linus Torvalds 已提交
3372 3373 3374 3375 3376 3377
	rhash_entries=	[KNL,NET]
			Set number of hash buckets for route cache

	ro		[KNL] Mount root device read-only on boot

	root=		[KNL] Root filesystem
3378
			See name_to_dev_t comment in init/do_mounts.c.
L
Linus Torvalds 已提交
3379 3380 3381 3382 3383 3384 3385 3386

	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
			mount the root filesystem

	rootflags=	[KNL] Set root filesystem mount option string

	rootfstype=	[KNL] Set root filesystem type

3387 3388 3389 3390
	rootwait	[KNL] Wait (indefinitely) for root device to show up.
			Useful for devices that are detected asynchronously
			(e.g. USB and MMC devices).

3391 3392 3393 3394 3395
	rproc_mem=nn[KMG][@address]
			[KNL,ARM,CMA] Remoteproc physical memory block.
			Memory area to be used by remote processor image,
			managed by CMA.

L
Linus Torvalds 已提交
3396 3397 3398 3399
	rw		[KNL] Mount root device read-write on boot

	S		[KNL] Run init in single mode

3400 3401 3402 3403 3404 3405 3406
	s390_iommu=	[HW,S390]
			Set s390 IOTLB flushing mode
		strict
			With strict flushing every unmap operation will result in
			an IOTLB flush. Default is lazy flushing before reuse,
			which is faster.

L
Linus Torvalds 已提交
3407 3408 3409 3410
	sa1100ir	[NET]
			See drivers/net/irda/sa1100_ir.c.

	sbni=		[NET] Granch SBNI12 leased line adapter
R
Randy Dunlap 已提交
3411

3412 3413
	sched_debug	[KNL] Enables verbose scheduler debug messages.

M
Mike Galbraith 已提交
3414 3415 3416 3417 3418 3419 3420 3421 3422
	skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
			xtime_lock contention on larger systems, and/or RCU lock
			contention on all systems with CONFIG_MAXSMP set.
			Format: { "0" | "1" }
			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
			1 -- enable.
			Note: increases power consumption, thus should only be
			enabled if running jitter sensitive (HPC/RT) workloads.

3423 3424 3425 3426 3427 3428 3429
	security=	[SECURITY] Choose a security module to enable at boot.
			If this boot parameter is not specified, only the first
			security module asking for security registration will be
			loaded. An invalid security module name will be treated
			as if no module has been chosen.

	selinux=	[SELINUX] Disable or enable SELinux at boot time.
L
Linus Torvalds 已提交
3430 3431 3432 3433 3434 3435 3436 3437
			Format: { "0" | "1" }
			See security/selinux/Kconfig help text.
			0 -- disable.
			1 -- enable.
			Default value is set via kernel config option.
			If enabled at boot time, /selinux/disable can be used
			later to disable prior to initial policy load.

3438 3439 3440 3441 3442 3443 3444
	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
			Format: { "0" | "1" }
			See security/apparmor/Kconfig help text
			0 -- disable.
			1 -- enable.
			Default value is set via kernel config option.

3445
	serialnumber	[BUGS=X86-32]
L
Linus Torvalds 已提交
3446 3447 3448

	shapers=	[NET]
			Maximal number of shapers.
R
Randy Dunlap 已提交
3449

Y
Yinghai Lu 已提交
3450 3451 3452 3453 3454 3455
	show_msr=	[x86] show boot-time MSR settings
			Format: { <integer> }
			Show boot-time (BIOS-initialized) MSR settings.
			The parameter means the number of CPUs to show,
			for example 1 means boot CPU only.

L
Linus Torvalds 已提交
3456 3457
	simeth=		[IA-64]
	simscsi=
R
Randy Dunlap 已提交
3458

L
Linus Torvalds 已提交
3459 3460
	slram=		[HW,MTD]

3461 3462 3463 3464 3465 3466 3467
	slab_nomerge	[MM]
			Disable merging of slabs with similar size. May be
			necessary if there is some reason to distinguish
			allocs to different slabs. Debug options disable
			merging on their own.
			For more information see Documentation/vm/slub.txt.

3468 3469 3470 3471 3472 3473
	slab_max_order=	[MM, SLAB]
			Determines the maximum allowed order for slabs.
			A high setting may cause OOMs due to memory
			fragmentation.  Defaults to 1 for systems with
			more than 32MB of RAM, 0 otherwise.

3474 3475 3476 3477 3478 3479 3480
	slub_debug[=options[,slabs]]	[MM, SLUB]
			Enabling slub_debug allows one to determine the
			culprit if slab objects become corrupted. Enabling
			slub_debug can create guard zones around objects and
			may poison objects when not in use. Also tracks the
			last alloc / free. For more information see
			Documentation/vm/slub.txt.
C
Christoph Lameter 已提交
3481 3482

	slub_max_order= [MM, SLUB]
3483 3484 3485 3486
			Determines the maximum allowed order for slabs.
			A high setting may cause OOMs due to memory
			fragmentation. For more information see
			Documentation/vm/slub.txt.
C
Christoph Lameter 已提交
3487 3488

	slub_min_objects=	[MM, SLUB]
3489 3490 3491 3492 3493 3494
			The minimum number of objects per slab. SLUB will
			increase the slab order up to slub_max_order to
			generate a sufficiently large slab able to contain
			the number of objects indicated. The higher the number
			of objects the smaller the overhead of tracking slabs
			and the less frequently locks need to be acquired.
C
Christoph Lameter 已提交
3495 3496 3497
			For more information see Documentation/vm/slub.txt.

	slub_min_order=	[MM, SLUB]
3498
			Determines the minimum page order for slabs. Must be
3499
			lower than slub_max_order.
C
Christoph Lameter 已提交
3500 3501 3502
			For more information see Documentation/vm/slub.txt.

	slub_nomerge	[MM, SLUB]
3503 3504
			Same with slab_nomerge. This is supported for legacy.
			See slab_nomerge for more information.
C
Christoph Lameter 已提交
3505

L
Linus Torvalds 已提交
3506 3507 3508
	smart2=		[HW]
			Format: <io1>[,<io2>[,...,<io8>]]

B
Bjorn Helgaas 已提交
3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519
	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
	smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
	smsc-ircc2.ircc_irq=	[HW] IRQ line
	smsc-ircc2.ircc_dma=	[HW] DMA channel
	smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
				0: Toshiba Satellite 1800 (GP data pin select)
				1: Fast pin select (default)
				2: ATC IRMode

I
Ingo Molnar 已提交
3520 3521
	softlockup_panic=
			[KNL] Should the soft-lockup detector generate panics.
3522
			Format: <integer>
I
Ingo Molnar 已提交
3523

3524 3525 3526 3527 3528
	softlockup_all_cpu_backtrace=
			[KNL] Should the soft-lockup detector generate
			backtraces on all cpus.
			Format: <integer>

L
Linus Torvalds 已提交
3529
	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
P
Paul Bolle 已提交
3530
			See Documentation/laptops/sonypi.txt
L
Linus Torvalds 已提交
3531 3532 3533 3534 3535 3536

	spia_io_base=	[HW,MTD]
	spia_fio_base=
	spia_pedr=
	spia_peddr=

3537 3538 3539
	stacktrace	[FTRACE]
			Enabled the stack tracer on boot up.

3540 3541 3542 3543 3544 3545 3546 3547
	stacktrace_filter=[function-list]
			[FTRACE] Limit the functions that the stack tracer
			will trace at boot up. function-list is a comma separated
			list of functions. This list can be changed at run
			time by the stack_trace_filter file in the debugfs
			tracing directory. Note, this enables stack tracing
			and the stacktrace above is not needed.

L
Linus Torvalds 已提交
3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560
	sti=		[PARISC,HW]
			Format: <num>
			Set the STI (builtin display/keyboard on the HP-PARISC
			machines) console (graphic card) which should be used
			as the initial boot-console.
			See also comment in drivers/video/console/sticore.c.

	sti_font=	[HW]
			See comment in drivers/video/console/sticore.c.

	stifb=		[HW]
			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]

3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572
	sunrpc.min_resvport=
	sunrpc.max_resvport=
			[NFS,SUNRPC]
			SunRPC servers often require that client requests
			originate from a privileged port (i.e. a port in the
			range 0 < portnr < 1024).
			An administrator who wishes to reserve some of these
			ports for other uses may adjust the range that the
			kernel's sunrpc client considers to be privileged
			using these two parameters to set the minimum and
			maximum port values.

3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588
	sunrpc.pool_mode=
			[NFS]
			Control how the NFS server code allocates CPUs to
			service thread pools.  Depending on how many NICs
			you have and where their interrupts are bound, this
			option will affect which CPUs will do NFS serving.
			Note: this parameter cannot be changed while the
			NFS server is running.

			auto	    the server chooses an appropriate mode
				    automatically using heuristics
			global	    a single global pool contains all CPUs
			percpu	    one pool for each CPU
			pernode	    one pool for each NUMA node (equivalent
				    to global on non-NUMA machines)

3589 3590 3591 3592 3593 3594 3595 3596 3597
	sunrpc.tcp_slot_table_entries=
	sunrpc.udp_slot_table_entries=
			[NFS,SUNRPC]
			Sets the upper limit on the number of simultaneous
			RPC calls that can be sent from the client to a
			server. Increasing these values may allow you to
			improve throughput, but will also increase the
			amount of memory reserved for use by the client.

3598 3599 3600 3601 3602 3603 3604
	suspend.pm_test_delay=
			[SUSPEND]
			Sets the number of seconds to remain in a suspend test
			mode before resuming the system (see
			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
			is set. Default value is 5.

3605
	swapaccount=[0|1]
3606 3607 3608 3609
			[KNL] Enable accounting of swap in memory resource
			controller if no parameter or 1 is given or disable
			it if 0 is given (See Documentation/cgroups/memory.txt)

J
Jiri Kosina 已提交
3610 3611 3612 3613 3614
	swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
			Format: { <int> | force }
			<int> -- Number of I/O TLB slabs
			force -- force using of bounce buffers even if they
			         wouldn't be automatically used by the kernel
R
Randy Dunlap 已提交
3615

L
Linus Torvalds 已提交
3616 3617
	switches=	[HW,M68k]

3618 3619 3620 3621 3622 3623 3624 3625 3626
	sysfs.deprecated=0|1 [KNL]
			Enable/disable old style sysfs layout for old udev
			on older distributions. When this option is enabled
			very new udev will not work anymore. When this option
			is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
			in older udev will not work anymore.
			Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
			the kernel configuration.

3627 3628 3629 3630 3631 3632
	sysrq_always_enabled
			[KNL]
			Ignore sysrq setting - this boot parameter will
			neutralize any effect of /proc/sys/kernel/sysrq.
			Useful for debugging.

3633 3634 3635 3636 3637 3638 3639
	tcpmhash_entries= [KNL,NET]
			Set the number of tcp_metrics_hash slots.
			Default value is 8192 or 16384 depending on total
			ram pages. This is used to specify the TCP metrics
			cache size. See Documentation/networking/ip-sysctl.txt
			"tcp_no_metrics_save" section for more details.

L
Linus Torvalds 已提交
3640 3641
	tdfx=		[HW,DRM]

3642
	test_suspend=	[SUSPEND][,N]
D
David Brownell 已提交
3643
			Specify "mem" (for Suspend-to-RAM) or "standby" (for
3644 3645 3646 3647 3648
			standby suspend) or "freeze" (for suspend type freeze)
			as the system sleep state during system startup with
			the optional capability to repeat N number of times.
			The system is woken from this state using a
			wakeup-capable RTC alarm.
D
David Brownell 已提交
3649

L
Linus Torvalds 已提交
3650 3651 3652
	thash_entries=	[KNL,NET]
			Set number of hash buckets for TCP connection

3653 3654 3655 3656
	thermal.act=	[HW,ACPI]
			-1: disable all active trip points in all thermal zones
			<degrees C>: override all lowest active trip points

3657 3658
	thermal.crt=	[HW,ACPI]
			-1: disable all critical trip points in all thermal zones
3659
			<degrees C>: override all critical trip points
3660

3661 3662 3663 3664
	thermal.nocrt=	[HW,ACPI]
			Set to disable actions on ACPI thermal zone
			critical and hot trip points.

3665 3666 3667
	thermal.off=	[HW,ACPI]
			1: disable ACPI thermal control

3668 3669
	thermal.psv=	[HW,ACPI]
			-1: disable all passive trip points
3670 3671
			<degrees C>: override all passive trip points to this
			value
3672

3673 3674 3675 3676 3677
	thermal.tzp=	[HW,ACPI]
			Specify global default ACPI thermal zone polling rate
			<deci-seconds>: poll all this frequency
			0: no polling (default)

3678 3679
	threadirqs	[KNL]
			Force threading of all interrupt handlers except those
3680
			marked explicitly IRQF_NO_THREAD.
3681

3682 3683 3684 3685 3686 3687 3688 3689 3690
	tmem		[KNL,XEN]
			Enable the Transcendent memory driver if built-in.

	tmem.cleancache=0|1 [KNL, XEN]
			Default is on (1). Disable the usage of the cleancache
			API to send anonymous pages to the hypervisor.

	tmem.frontswap=0|1 [KNL, XEN]
			Default is on (1). Disable the usage of the frontswap
3691 3692
			API to send swap pages to the hypervisor. If disabled
			the selfballooning and selfshrinking are force disabled.
3693 3694 3695 3696 3697 3698 3699 3700 3701 3702

	tmem.selfballooning=0|1 [KNL, XEN]
			Default is on (1). Disable the driving of swap pages
			to the hypervisor.

	tmem.selfshrinking=0|1 [KNL, XEN]
			Default is on (1). Partial swapoff that immediately
			transfers pages from Xen hypervisor back to the
			kernel based on different criteria.

3703 3704 3705
	topology=	[S390]
			Format: {off | on}
			Specify if the kernel should make use of the cpu
3706 3707
			topology information if the hardware supports this.
			The scheduler will make use of this information and
3708
			e.g. base its process migration decisions on it.
H
Heiko Carstens 已提交
3709
			Default is on.
3710

3711 3712 3713 3714 3715 3716
	topology_updates= [KNL, PPC, NUMA]
			Format: {off}
			Specify if the kernel should ignore (off)
			topology updates sent by the hypervisor to this
			LPAR.

L
Linus Torvalds 已提交
3717 3718
	tp720=		[HW,PS2]

3719 3720 3721 3722 3723 3724 3725 3726 3727
	tpm_suspend_pcr=[HW,TPM]
			Format: integer pcr id
			Specify that at suspend time, the tpm driver
			should extend the specified pcr with zeros,
			as a workaround for some chips which fail to
			flush the last written pcr on TPM_SaveState.
			This will guarantee that all the other pcrs
			are saved.

3728
	trace_buf_size=nn[KMG]
3729
			[FTRACE] will set tracing buffer size on each cpu.
3730

3731 3732 3733 3734 3735
	trace_event=[event-list]
			[FTRACE] Set and start specified trace events in order
			to facilitate early boot debugging.
			See also Documentation/trace/events.txt

3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751
	trace_options=[option-list]
			[FTRACE] Enable or disable tracer options at boot.
			The option-list is a comma delimited list of options
			that can be enabled or disabled just as if you were
			to echo the option name into

			    /sys/kernel/debug/tracing/trace_options

			For example, to enable stacktrace option (to dump the
			stack trace of each event), add to the command line:

			      trace_options=stacktrace

			See also Documentation/trace/ftrace.txt "trace options"
			section.

3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769
	tp_printk[FTRACE]
			Have the tracepoints sent to printk as well as the
			tracing ring buffer. This is useful for early boot up
			where the system hangs or reboots and does not give the
			option for reading the tracing buffer or performing a
			ftrace_dump_on_oops.

			To turn off having tracepoints sent to printk,
			 echo 0 > /proc/sys/kernel/tracepoint_printk
			Note, echoing 1 into this file without the
			tracepoint_printk kernel cmdline option has no effect.

			** CAUTION **

			Having tracepoints sent to printk() and activating high
			frequency tracepoints such as irq or sched, can cause
			the system to live lock.

3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782
	traceoff_on_warning
			[FTRACE] enable this option to disable tracing when a
			warning is hit. This turns off "tracing_on". Tracing can
			be enabled again by echoing '1' into the "tracing_on"
			file located in /sys/kernel/debug/tracing/

			This option is useful, as it disables the trace before
			the WARNING dump is called, which prevents the trace to
			be filled with content caused by the warning output.

			This option can also be set at run time via the sysctl
			option:  kernel/traceoff_on_warning

3783 3784 3785 3786 3787 3788 3789
	transparent_hugepage=
			[KNL]
			Format: [always|madvise|never]
			Can be used to control the default behavior of the system
			with respect to transparent hugepages.
			See Documentation/vm/transhuge.txt for more details.

3790
	tsc=		Disable clocksource stability checks for TSC.
3791 3792
			Format: <string>
			[x86] reliable: mark tsc clocksource as reliable, this
3793 3794 3795 3796
			disables clocksource verification at runtime, as well
			as the stability checks done at bootup.	Used to enable
			high-resolution timer mode on older hardware, and in
			virtualized environment.
V
Venkatesh Pallipadi 已提交
3797 3798 3799 3800
			[x86] noirqtime: Do not use TSC to do irq accounting.
			Used to run time disable IRQ_TIME_ACCOUNTING on any
			platforms where RDTSC is slow and this accounting
			can add overhead.
3801

R
Randy Dunlap 已提交
3802 3803 3804 3805
	turbografx.map[2|3]=	[HW,JOY]
			TurboGraFX parallel port interface
			Format:
			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
L
Linus Torvalds 已提交
3806 3807
			See also Documentation/input/joystick-parport.txt

C
Christian Kujau 已提交
3808 3809 3810 3811 3812
	udbg-immortal	[PPC] When debugging early kernel crashes that
			happen after console_init() and before a proper 
			console driver takes over, this boot options might
			help "seeing" what's going on.

3813 3814 3815
	uhash_entries=	[KNL,NET]
			Set number of hash buckets for UDP/UDP-Lite connections

3816 3817 3818 3819 3820 3821 3822 3823
	uhci-hcd.ignore_oc=
			[USB] Ignore overcurrent events (default N).
			Some badly-designed motherboards generate lots of
			bogus events, for ports that aren't wired to
			anything.  Set this parameter to avoid log spamming.
			Note that genuine overcurrent events won't be
			reported either.

3824
	unknown_nmi_panic
3825
			[X86] Cause panic on unknown NMI.
3826

3827 3828 3829 3830 3831
	usbcore.authorized_default=
			[USB] Default USB device authorization:
			(default -1 = authorized except for wireless USB,
			0 = not authorized, 1 = authorized)

3832 3833 3834 3835 3836
	usbcore.autosuspend=
			[USB] The autosuspend time delay (in seconds) used
			for newly-detected USB devices (default 2).  This
			is the time required before an idle device will be
			autosuspended.  Devices for which the delay is set
3837
			to a negative value won't be autosuspended at all.
3838

3839 3840 3841 3842 3843 3844 3845 3846 3847 3848
	usbcore.usbfs_snoop=
			[USB] Set to log all usbfs traffic (default 0 = off).

	usbcore.blinkenlights=
			[USB] Set to cycle leds on hubs (default 0 = off).

	usbcore.old_scheme_first=
			[USB] Start with the old device initialization
			scheme (default 0 = off).

3849 3850 3851 3852
	usbcore.usbfs_memory_mb=
			[USB] Memory limit (in MB) for buffers allocated by
			usbfs (default = 16, 0 = max = 2047).

3853 3854 3855 3856 3857 3858 3859 3860 3861
	usbcore.use_both_schemes=
			[USB] Try the other device initialization scheme
			if the first one fails (default 1 = enabled).

	usbcore.initial_descriptor_timeout=
			[USB] Specifies timeout for the initial 64-byte
                        USB_REQ_GET_DESCRIPTOR request in milliseconds
			(default 5000 = 5.0 seconds).

L
Linus Torvalds 已提交
3862 3863
	usbhid.mousepoll=
			[USBHID] The interval which mice are to be polled at.
R
Randy Dunlap 已提交
3864

3865 3866
	usb-storage.delay_use=
			[UMS] The delay in seconds before a new device is
3867
			scanned for Logical Units (default 1).
3868 3869 3870 3871 3872 3873 3874 3875 3876

	usb-storage.quirks=
			[UMS] A list of quirks entries to supplement or
			override the built-in unusual_devs list.  List
			entries are separated by commas.  Each entry has
			the form VID:PID:Flags where VID and PID are Vendor
			and Product ID values (4-digit hex numbers) and
			Flags is a set of characters, each corresponding
			to a common usb-storage quirk flag as follows:
3877 3878
				a = SANE_SENSE (collect more than 18 bytes
					of sense data);
A
Alan Stern 已提交
3879 3880
				b = BAD_SENSE (don't collect more than 18
					bytes of sense data);
3881 3882
				c = FIX_CAPACITY (decrease the reported
					device capacity by one sector);
3883 3884 3885 3886
				d = NO_READ_DISC_INFO (don't use
					READ_DISC_INFO command);
				e = NO_READ_CAPACITY_16 (don't use
					READ_CAPACITY_16 command);
H
Hans de Goede 已提交
3887 3888
				f = NO_REPORT_OPCODES (don't use report opcodes
					command, uas only);
3889 3890
				g = MAX_SECTORS_240 (don't transfer more than
					240 sectors at a time, uas only);
3891 3892 3893
				h = CAPACITY_HEURISTICS (decrease the
					reported device capacity by one
					sector if the number is odd);
3894 3895 3896 3897 3898 3899
				i = IGNORE_DEVICE (don't bind to this
					device);
				l = NOT_LOCKABLE (don't try to lock and
					unlock ejectable media);
				m = MAX_SECTORS_64 (don't transfer more
					than 64 sectors = 32 KB at a time);
A
Alan Stern 已提交
3900 3901
				n = INITIAL_READ10 (force a retry of the
					initial READ(10) command);
3902 3903
				o = CAPACITY_OK (accept the capacity
					reported by the device);
3904 3905
				p = WRITE_CACHE (the device cache is ON
					by default);
3906 3907 3908 3909
				r = IGNORE_RESIDUE (the device reports
					bogus residue values);
				s = SINGLE_LUN (the device has only one
					Logical Unit);
3910 3911
				t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
					commands, uas only);
3912
				u = IGNORE_UAS (don't bind to the uas driver);
3913 3914 3915 3916
				w = NO_WP_DETECT (don't test whether the
					medium is write-protected).
			Example: quirks=0419:aaf5:rl,0421:0433:rc

3917 3918 3919 3920 3921 3922 3923 3924 3925 3926
	user_debug=	[KNL,ARM]
			Format: <int>
			See arch/arm/Kconfig.debug help text.
				 1 - undefined instruction events
				 2 - system calls
				 4 - invalid data aborts
				 8 - SIGSEGV faults
				16 - SIGBUS faults
			Example: user_debug=31

3927 3928 3929 3930 3931 3932 3933
	userpte=
			[X86] Flags controlling user PTE allocations.

				nohigh = do not allocate PTE pages in
					HIGHMEM regardless of setting
					of CONFIG_HIGHPTE.

3934
	vdso=		[X86,SH]
3935 3936 3937
			On X86_32, this is an alias for vdso32=.  Otherwise:

			vdso=1: enable VDSO (the default)
3938 3939
			vdso=0: disable VDSO mapping

3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952
	vdso32=		[X86] Control the 32-bit vDSO
			vdso32=1: enable 32-bit VDSO
			vdso32=0 or vdso32=2: disable 32-bit VDSO

			See the help text for CONFIG_COMPAT_VDSO for more
			details.  If CONFIG_COMPAT_VDSO is set, the default is
			vdso32=0; otherwise, the default is vdso32=1.

			For compatibility with older kernels, vdso32=2 is an
			alias for vdso32=0.

			Try vdso32=0 if you encounter an error that says:
			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
R
Roland McGrath 已提交
3953

3954 3955 3956
	vector=		[IA-64,SMP]
			vector=percpu: enable percpu vector domain

L
Linus Torvalds 已提交
3957 3958 3959
	video=		[FB] Frame buffer configuration
			See Documentation/fb/modedb.txt.

3960 3961 3962 3963 3964 3965 3966
	video.brightness_switch_enabled= [0,1]
			If set to 1, on receiving an ACPI notify event
			generated by hotkey, video driver will adjust brightness
			level and then send out the event to user space through
			the allocated input device; If set to 0, video driver
			will only send out the event without touching backlight
			brightness level.
3967
			default: 1
3968

3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984
	virtio_mmio.device=
			[VMMIO] Memory mapped virtio (platform) device.

				<size>@<baseaddr>:<irq>[:<id>]
			where:
				<size>     := size (can use standard suffixes
						like K, M and G)
				<baseaddr> := physical base address
				<irq>      := interrupt number (as passed to
						request_irq())
				<id>       := (optional) platform device id
			example:
				virtio_mmio.device=1K@0x100b0000:48:7

			Can be used multiple times for multiple devices.

3985
	vga=		[BOOT,X86-32] Select a particular video mode
3986
			See Documentation/x86/boot.txt and
R
Randy Dunlap 已提交
3987
			Documentation/svga.txt.
L
Linus Torvalds 已提交
3988 3989 3990 3991
			Use vga=ask for menu.
			This is actually a boot loader parameter; the value is
			passed to the kernel using a special protocol.

R
Randy Dunlap 已提交
3992
	vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
L
Linus Torvalds 已提交
3993 3994 3995 3996 3997
			size of <nn>. This can be used to increase the
			minimum size (128MB on x86). It can also be used to
			decrease the size and leave more room for directly
			mapped kernel RAM.

3998 3999
	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
			Format: <command>
L
Linus Torvalds 已提交
4000

4001 4002 4003 4004 4005
	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
			Format: <command>

	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
			Format: <command>
R
Randy Dunlap 已提交
4006

4007 4008 4009 4010 4011 4012 4013 4014
	vsyscall=	[X86-64]
			Controls the behavior of vsyscalls (i.e. calls to
			fixed addresses of 0xffffffffff600x00 from legacy
			code).  Most statically-linked binaries and older
			versions of glibc use these calls.  Because these
			functions are at fixed addresses, they make nice
			targets for exploits that can control RIP.

A
Andy Lutomirski 已提交
4015 4016
			emulate     [default] Vsyscalls turn into traps and are
			            emulated reasonably safely.
4017

A
Andy Lutomirski 已提交
4018
			native      Vsyscalls are native syscall instructions.
4019 4020 4021 4022 4023 4024 4025 4026 4027
			            This is a little bit faster than trapping
			            and makes a few dynamic recompilers work
			            better than they would in emulation mode.
			            It also makes exploits much easier to write.

			none        Vsyscalls don't work at all.  This makes
			            them quite hard to use for exploits but
			            might break your system.

4028 4029 4030 4031
	vt.color=	[VT] Default text color.
			Format: 0xYX, X = foreground, Y = background.
			Default: 0x07 = light gray on black.

4032 4033 4034 4035 4036
	vt.cur_default=	[VT] Default cursor shape.
			Format: 0xCCBBAA, where AA, BB, and CC are the same as
			the parameters of the <Esc>[?A;B;Cc escape sequence;
			see VGA-softcursor.txt. Default: 2 = underline.

4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061
	vt.default_blu=	[VT]
			Format: <blue0>,<blue1>,<blue2>,...,<blue15>
			Change the default blue palette of the console.
			This is a 16-member array composed of values
			ranging from 0-255.

	vt.default_grn=	[VT]
			Format: <green0>,<green1>,<green2>,...,<green15>
			Change the default green palette of the console.
			This is a 16-member array composed of values
			ranging from 0-255.

	vt.default_red=	[VT]
			Format: <red0>,<red1>,<red2>,...,<red15>
			Change the default red palette of the console.
			This is a 16-member array composed of values
			ranging from 0-255.

	vt.default_utf8=
			[VT]
			Format=<0|1>
			Set system-wide default UTF-8 mode for all tty's.
			Default is 1, i.e. UTF-8 mode is enabled for all
			newly opened terminals.

4062 4063 4064 4065 4066 4067 4068 4069 4070
	vt.global_cursor_default=
			[VT]
			Format=<-1|0|1>
			Set system-wide default for whether a cursor
			is shown on new VTs. Default is -1,
			i.e. cursors will be created by default unless
			overridden by individual drivers. 0 will hide
			cursors, 1 will display them.

4071 4072 4073 4074 4075 4076
	vt.italic=	[VT] Default color for italic text; 0-15.
			Default: 2 = green.

	vt.underline=	[VT] Default color for underlined text; 0-15.
			Default: 3 = cyan.

4077 4078 4079 4080
	watchdog timers	[HW,WDT] For information on watchdog timers,
			see Documentation/watchdog/watchdog-parameters.txt
			or other driver-specific files in the
			Documentation/watchdog/ directory.
L
Linus Torvalds 已提交
4081

4082 4083 4084 4085 4086 4087 4088 4089 4090
	workqueue.disable_numa
			By default, all work items queued to unbound
			workqueues are affine to the NUMA nodes they're
			issued on, which results in better behavior in
			general.  If NUMA affinity needs to be disabled for
			whatever reason, this option can be used.  Note
			that this also can be controlled per-workqueue for
			workqueues visible under /sys/bus/workqueue/.

4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105
	workqueue.power_efficient
			Per-cpu workqueues are generally preferred because
			they show better performance thanks to cache
			locality; unfortunately, per-cpu workqueues tend to
			be more power hungry than unbound workqueues.

			Enabling this makes the per-cpu workqueues which
			were observed to contribute significantly to power
			consumption unbound, leading to measurably lower
			power usage at the cost of small performance
			overhead.

			The default value of this parameter is determined by
			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.

4106 4107 4108 4109
	x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
			default x2apic cluster mode on platforms
			supporting x2apic.

4110 4111
	x86_intel_mid_timer= [X86-32,APBT]
			Choose timer option for x86 Intel MID platform.
4112 4113
			Two valid options are apbt timer only and lapic timer
			plus one apbt timer for broadcast timer.
4114
			x86_intel_mid_timer=apbt_only | lapic_and_apbt
4115

4116 4117 4118 4119 4120 4121 4122
	xen_512gb_limit		[KNL,X86-64,XEN]
			Restricts the kernel running paravirtualized under Xen
			to use only up to 512 GB of RAM. The reason to do so is
			crash analysis tools and Xen tools for doing domain
			save/restore/migration must be enabled to handle larger
			domains.

4123 4124 4125 4126 4127 4128 4129
	xen_emul_unplug=		[HW,X86,XEN]
			Unplug Xen emulated devices
			Format: [unplug0,][unplug1]
			ide-disks -- unplug primary master IDE devices
			aux-ide-disks -- unplug non-primary-master IDE devices
			nics -- unplug network devices
			all -- unplug all emulated devices (NICs and IDE disks)
4130 4131 4132
			unnecessary -- unplugging emulated devices is
				unnecessary even if the host did not respond to
				the unplug protocol
4133
			never -- do not unplug even if version check succeeds
4134

4135 4136 4137 4138
	xen_nopvspin	[X86,XEN]
			Disables the ticketlock slowpath using Xen PV
			optimizations.

4139 4140 4141 4142
	xen_nopv	[X86]
			Disables the PV optimizations forcing the HVM guest to
			run as generic HVM guest with no PV drivers.

L
Linus Torvalds 已提交
4143
	xirc2ps_cs=	[NET,PCMCIA]
R
Randy Dunlap 已提交
4144 4145
			Format:
			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
L
Linus Torvalds 已提交
4146

R
Randy Dunlap 已提交
4147
______________________________________________________________________
L
Linus Torvalds 已提交
4148 4149 4150 4151

TODO:

	Add more DRM drivers.