1 acpi= [HW,ACPI,X86,ARM64]
2 Advanced Configuration and Power Interface
3 Format: { force | on | off | strict | noirq | rsdt |
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
10 strictly ACPI specification compliant.
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
16 See also Documentation/power/runtime_pm.txt, pci=noacpi
18 acpi_apic_instance= [ACPI, IOAPIC]
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
24 acpi_backlight= [HW,ACPI]
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
31 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
37 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
59 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
63 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
69 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
73 acpi_enforce_resources= [ACPI]
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
89 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
94 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
107 Format: <irq>,<irq>...
109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
114 This facility can be used to prevent such uncontrolled
118 acpi_no_auto_serialize [HW,ACPI]
119 Disable auto-serialization of AML methods
120 AML control methods that contain the opcodes to create
121 named objects will be marked as "Serialized" by the
122 auto-serialization feature.
123 This feature is enabled by default.
124 This option allows to turn off the feature.
126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
129 acpi_no_static_ssdt [HW,ACPI]
130 Disable installation of static SSDTs at early boot time
131 By default, SSDTs contained in the RSDT/XSDT will be
132 installed automatically and they will appear under
133 /sys/firmware/acpi/tables.
134 This option turns off this feature.
135 Note that specifying this option does not affect
136 dynamic table installation which will install SSDT
137 tables to /sys/firmware/acpi/tables/dynamic.
139 acpi_rsdp= [ACPI,EFI,KEXEC]
140 Pass the RSDP address to the kernel, mostly used
141 on machines running EFI runtime service to boot the
142 second kernel for kdump.
144 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
145 Format: To spoof as Windows 98: ="Microsoft Windows"
147 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
148 of 2 which is mandated by ACPI 6) as the supported ACPI
149 specification revision (when using this switch, it may
150 be necessary to carry out a cold reboot _twice_ in a
151 row to make it take effect on the platform firmware).
153 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
154 acpi_osi="string1" # add string1
155 acpi_osi="!string2" # remove string2
156 acpi_osi=!* # remove all strings
157 acpi_osi=! # disable all built-in OS vendor
159 acpi_osi=!! # enable all built-in OS vendor
161 acpi_osi= # disable all strings
163 'acpi_osi=!' can be used in combination with single or
164 multiple 'acpi_osi="string1"' to support specific OS
165 vendor string(s). Note that such command can only
166 affect the default state of the OS vendor strings, thus
167 it cannot affect the default state of the feature group
168 strings and the current state of the OS vendor strings,
169 specifying it multiple times through kernel command line
170 is meaningless. This command is useful when one do not
171 care about the state of the feature group strings which
172 should be controlled by the OSPM.
174 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
175 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
176 can make '_OSI("Windows 2000")' TRUE.
178 'acpi_osi=' cannot be used in combination with other
179 'acpi_osi=' command lines, the _OSI method will not
180 exist in the ACPI namespace. NOTE that such command can
181 only affect the _OSI support state, thus specifying it
182 multiple times through kernel command line is also
185 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
188 'acpi_osi=!*' can be used in combination with single or
189 multiple 'acpi_osi="string1"' to support specific
190 string(s). Note that such command can affect the
191 current state of both the OS vendor strings and the
192 feature group strings, thus specifying it multiple times
193 through kernel command line is meaningful. But it may
194 still not able to affect the final state of a string if
195 there are quirks related to this string. This command
196 is useful when one want to control the state of the
197 feature group strings to debug BIOS issues related to
200 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
201 '_OSI("Module Device")' FALSE.
202 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
203 '_OSI("Module Device")' TRUE.
204 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
209 they all will make '_OSI("Windows 2000")' TRUE.
212 Override the pmtimer bug detection: force the kernel
213 to assume that this machine's pmtimer latches its value
214 and always returns good values.
216 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
217 Format: { level | edge | high | low }
219 acpi_skip_timer_override [HW,ACPI]
220 Recognize and ignore IRQ0/pin2 Interrupt Override.
221 For broken nForce2 BIOS resulting in XT-PIC timer.
223 acpi_sleep= [HW,ACPI] Sleep options
224 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
225 old_ordering, nonvs, sci_force_enable, nobl }
226 See Documentation/power/video.txt for information on
228 s3_beep is for debugging; it makes the PC's speaker beep
229 as soon as the kernel's real-mode entry point is called.
230 s4_nohwsig prevents ACPI hardware signature from being
231 used during resume from hibernation.
232 old_ordering causes the ACPI 1.0 ordering of the _PTS
233 control method, with respect to putting devices into
234 low power states, to be enforced (the ACPI 2.0 ordering
235 of _PTS is used by default).
236 nonvs prevents the kernel from saving/restoring the
237 ACPI NVS memory during suspend/hibernation and resume.
238 sci_force_enable causes the kernel to set SCI_EN directly
239 on resume from S1/S3 (which is against the ACPI spec,
240 but some broken systems don't work without it).
241 nobl causes the internal blacklist of systems known to
242 behave incorrectly in some ways with respect to system
243 suspend and resume to be ignored (use wisely).
245 acpi_use_timer_override [HW,ACPI]
246 Use timer override. For some broken Nvidia NF5 boards
247 that require a timer override, but don't have HPET
249 add_efi_memmap [EFI; X86] Include EFI memory map in
250 kernel's map of available physical RAM.
253 { off | try_unsupported }
254 off: disable AGP support
255 try_unsupported: try to drive unsupported chipsets
256 (may crash computer or cause data corruption)
259 See Documentation/sound/alsa/alsa-parameters.txt
262 Allow the default userspace alignment fault handler
263 behaviour to be specified. Bit 0 enables warnings,
264 bit 1 enables fixups, and bit 2 sends a segfault.
266 align_va_addr= [X86-64]
267 Align virtual addresses by clearing slice [14:12] when
268 allocating a VMA at process creation time. This option
269 gives you up to 3% performance improvement on AMD F15h
270 machines (where it is enabled by default) for a
271 CPU-intensive style benchmark, and it can vary highly in
272 a microbenchmark depending on workload and compiler.
274 32: only for 32-bit processes
275 64: only for 64-bit processes
276 on: enable for both 32- and 64-bit processes
277 off: disable for both 32- and 64-bit processes
279 alloc_snapshot [FTRACE]
280 Allocate the ftrace snapshot buffer on boot up when the
281 main buffer is allocated. This is handy if debugging
282 and you need to use tracing_snapshot() on boot up, and
283 do not want to use tracing_snapshot_alloc() as it needs
284 to be done where GFP_KERNEL allocations are allowed.
286 amd_iommu= [HW,X86-64]
287 Pass parameters to the AMD IOMMU driver in the system.
289 fullflush - enable flushing of IO/TLB entries when
290 they are unmapped. Otherwise they are
291 flushed before they will be reused, which
293 off - do not initialize any AMD IOMMU found in
295 force_isolation - Force device isolation for all
296 devices. The IOMMU driver is not
297 allowed anymore to lift isolation
298 requirements as needed. This option
299 does not override iommu=pt
301 amd_iommu_dump= [HW,X86-64]
302 Enable AMD IOMMU driver option to dump the ACPI table
303 for AMD IOMMU. With this option enabled, AMD IOMMU
304 driver will print ACPI tables for AMD IOMMU during
305 IOMMU initialization.
307 amd_iommu_intr= [HW,X86-64]
308 Specifies one of the following AMD IOMMU interrupt
310 legacy - Use legacy interrupt remapping mode.
311 vapic - Use virtual APIC mode, which allows IOMMU
312 to inject interrupts directly into guest.
313 This mode requires kvm-amd.avic=1.
314 (Default when IOMMU HW support is present.)
316 amijoy.map= [HW,JOY] Amiga joystick support
317 Map of devices attached to JOY0DAT and JOY1DAT
319 See also Documentation/input/joydev/joystick.rst
321 analog.map= [HW,JOY] Analog joystick and gamepad support
322 Specifies type or capabilities of an analog joystick
323 connected to one of 16 gameports
324 Format: <type1>,<type2>,..<type16>
327 Power management functions (SPARCstation-4/5 + deriv.)
329 Disable APC CPU standby support. SPARCstation-Fox does
330 not play well with APC CPU idle - disable it if you have
331 APC and your system crashes randomly.
333 apic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Change the output verbosity whilst booting
335 Format: { quiet (default) | verbose | debug }
336 Change the amount of debugging information output
337 when initialising the APIC and IO-APIC components.
338 For X86-32, this can also be used to specify an APIC
340 Format: apic=driver_name
341 Examples: apic=bigsmp
343 apic_extnmi= [APIC,X86] External NMI delivery setting
344 Format: { bsp (default) | all | none }
345 bsp: External NMI is delivered only to CPU 0
346 all: External NMIs are broadcast to all CPUs as a
348 none: External NMI is masked for all CPUs. This is
349 useful so that a dump capture kernel won't be
353 See Documentation/networking/ipv6.txt.
355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
364 apm= [APM] Advanced Power Management
365 See header of arch/x86/kernel/apm_32.c.
367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
372 atarimouse= [HW,MOUSE] Atari Mouse
374 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
375 EzKey and similar keyboards
377 atkbd.reset= [HW] Reset keyboard during initialization
379 atkbd.set= [HW] Select keyboard code set
380 Format: <int> (2 = AT (default), 3 = PS/2)
382 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 atkbd.softraw= [HW] Choose between synthetic and real raw mode
386 Format: <bool> (0 = real, 1 = synthetic (default))
388 atkbd.softrepeat= [HW]
389 Use software keyboard repeat
391 audit= [KNL] Enable the audit sub-system
392 Format: { "0" | "1" | "off" | "on" }
393 0 | off - kernel audit is disabled and can not be
394 enabled until the next reboot
395 unset - kernel audit is initialized but disabled and
396 will be fully enabled by the userspace auditd.
397 1 | on - kernel audit is initialized and partially
398 enabled, storing at most audit_backlog_limit
399 messages in RAM until it is fully enabled by the
403 audit_backlog_limit= [KNL] Set the audit queue size limit.
404 Format: <int> (must be >=0)
407 bau= [X86_UV] Enable the BAU on SGI UV. The default
408 behavior is to disable the BAU (i.e. bau=0).
409 Format: { "0" | "1" }
412 unset - Disable the BAU.
414 baycom_epp= [HW,AX25]
417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
419 See header of drivers/net/hamradio/baycom_par.c.
421 baycom_ser_fdx= [HW,AX25]
422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
423 Format: <io>,<irq>,<mode>[,<baud>]
424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
426 baycom_ser_hdx= [HW,AX25]
427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
428 Format: <io>,<irq>,<mode>
429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
431 blkdevparts= Manual partition parsing of block device(s) for
432 embedded devices based on command line input.
433 See Documentation/block/cmdline-partition.txt
435 boot_delay= Milliseconds to delay each printk during boot.
436 Values larger than 10 seconds (10000) are changed to
440 bootmem_debug [KNL] Enable bootmem allocator debug messages.
443 Disable BERT OS support on buggy BIOSes.
445 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
446 bttv.radio= Most important insmod options are available as
448 bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
451 bulk_remove=off [PPC] This parameter disables the use of the pSeries
452 firmware feature for flushing multiple hpte entries
455 c101= [NET] Moxa C101 synchronous serial card
457 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
458 Sometimes CPU hardware bugs make them report the cache
459 size incorrectly. The kernel will attempt work arounds
460 to fix known problems, but for some CPUs it is not
461 possible to determine what the correct size should be.
462 This option provides an override for these situations.
464 ca_keys= [KEYS] This parameter identifies a specific key(s) on
465 the system trusted keyring to be used for certificate
467 format: { id:<keyid> | builtin }
469 cca= [MIPS] Override the kernel pages' cache coherency
470 algorithm. Accepted values range from 0 to 7
471 inclusive. See arch/mips/include/asm/pgtable-bits.h
472 for platform specific values (SB1, Loongson3 and
475 ccw_timeout_log [S390]
476 See Documentation/s390/CommonIO for details.
478 cgroup_disable= [KNL] Disable a particular controller
479 Format: {name of the controller(s) to disable}
480 The effects of cgroup_disable=foo are:
481 - foo isn't auto-mounted if you mount all cgroups in
483 - foo isn't visible as an individually mountable
485 {Currently only "memory" controller deal with this and
486 cut the overhead, others just disable the usage. So
487 only cgroup_disable=memory is actually worthy}
489 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
490 Format: { controller[,controller...] | "all" }
491 Like cgroup_disable, but only applies to cgroup v1;
492 the blacklisted controllers remain available in cgroup2.
494 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
496 nosocket -- Disable socket memory accounting.
497 nokmem -- Disable kernel memory accounting.
499 checkreqprot [SELINUX] Set initial checkreqprot flag value.
500 Format: { "0" | "1" }
501 See security/selinux/Kconfig help text.
502 0 -- check protection applied by kernel (includes
503 any implied execute protection).
504 1 -- check protection requested by application.
505 Default value is set via a kernel config option.
506 Value can be changed at runtime via
507 /selinux/checkreqprot.
510 See Documentation/s390/CommonIO for details.
513 Prevents the clock framework from automatically gating
514 clocks that have not been explicitly enabled by a Linux
515 device driver but are enabled in hardware at reset or
516 by the bootloader/firmware. Note that this does not
517 force such clocks to be always-on nor does it reserve
518 those clocks in any way. This parameter is useful for
519 debug and development, but should not be needed on a
520 platform with proper driver support. For more
521 information, see Documentation/clk.txt.
523 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
525 Forces specified clocksource (if available) to be used
526 when calculating gettimeofday(). If specified
527 clocksource is not available, it defaults to PIT.
528 Format: { pit | tsc | cyclone | pmtmr }
530 clocksource= Override the default clocksource
532 Override the default clocksource and use the clocksource
533 with the name specified.
534 Some clocksource names to choose from, depending on
536 [all] jiffies (this is the base, fallback clocksource)
538 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
539 pxa_timer,timer3,32k_counter,timer0_1
540 [X86-32] pit,hpet,tsc;
541 scx200_hrt on Geode; cyclone on IBM x440
549 clocksource.arm_arch_timer.evtstrm=
552 Enable/disable the eventstream feature of the ARM
553 architected timer so that code using WFE-based polling
554 loops can be debugged more effectively on production
557 clearcpuid=BITNUM [X86]
558 Disable CPUID feature X for the kernel. See
559 arch/x86/include/asm/cpufeatures.h for the valid bit
560 numbers. Note the Linux specific bits are not necessarily
561 stable over kernel options, but the vendor specific
563 Also note that user programs calling CPUID directly
564 or using the feature without checking anything
565 will still see it. This just prevents it from
566 being used by the kernel or shown in /proc/cpuinfo.
567 Also note the kernel might malfunction if you disable
570 cma=nn[MG]@[start[MG][-end[MG]]]
572 Sets the size of kernel global memory area for
573 contiguous memory allocations and optionally the
574 placement constraint by the physical address range of
575 memory allocations. A value of 0 disables CMA
576 altogether. For more information, see
577 include/linux/dma-contiguous.h
579 cmo_free_hint= [PPC] Format: { yes | no }
580 Specify whether pages are marked as being inactive
581 when they are freed. This is used in CMO environments
582 to determine OS memory pressure for page stealing by
586 coherent_pool=nn[KMG] [ARM,KNL]
587 Sets the size of memory pool for coherent, atomic dma
588 allocations, by default set to 256K.
590 code_bytes [X86] How many bytes of object code to print
595 com20020= [HW,NET] ARCnet - COM20020 chipset
597 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
599 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
603 ARCnet - COM90xx chipset (memory-mapped buffers)
604 Format: <io>[,<irq>[,<memstart>]]
606 condev= [HW,S390] console device
609 console= [KNL] Output console device and options.
611 tty<n> Use the virtual console device <n>.
615 Use the specified serial port. The options are of
616 the form "bbbbpnf", where "bbbb" is the baud rate,
617 "p" is parity ("n", "o", or "e"), "n" is number of
618 bits, and "f" is flow control ("r" for RTS or
619 omit it). Default is "9600n8".
621 See Documentation/admin-guide/serial-console.rst for more
623 Documentation/networking/netconsole.txt for an
626 uart[8250],io,<addr>[,options]
627 uart[8250],mmio,<addr>[,options]
628 uart[8250],mmio16,<addr>[,options]
629 uart[8250],mmio32,<addr>[,options]
630 uart[8250],0x<addr>[,options]
631 Start an early, polled-mode console on the 8250/16550
632 UART at the specified I/O port or MMIO address,
633 switching to the matching ttyS device later.
634 MMIO inter-register address stride is either 8-bit
635 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
636 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
637 to be equivalent to 'mmio'. 'options' are specified in
638 the same format described for ttyS above; if unspecified,
639 the h/w is not re-initialized.
641 hvc<n> Use the hypervisor console device <n>. This is for
642 both Xen and PowerPC hypervisors.
644 If the device connected to the port is not a TTY but a braille
645 device, prepend "brl," before the device type, for instance
647 For now, only VisioBraille is supported.
650 [KNL] Change console messages format
652 By default we print messages on consoles in
653 "[time stamp] text\n" format (time stamp may not be
654 printed, depending on CONFIG_PRINTK_TIME or
655 `printk_time' param).
657 Switch to syslog format: "<%u>[time stamp] text\n"
658 IOW, each message will have a facility and loglevel
659 prefix. The format is similar to one used by syslog()
660 syscall, or to executing "dmesg -S --raw" or to reading
663 consoleblank= [KNL] The console blank (screen saver) timeout in
664 seconds. A value of 0 disables the blank timer.
668 [KNL] Change the default value for
669 /proc/<pid>/coredump_filter.
670 See also Documentation/filesystems/proc.txt.
672 coresight_cpu_debug.enable
675 Enable/disable the CPU sampling based debugging.
676 0: default value, disable debugging
677 1: enable debugging at boot time
679 cpuidle.off=1 [CPU_IDLE]
680 disable the cpuidle sub-system
682 cpufreq.off=1 [CPU_FREQ]
683 disable the cpufreq sub-system
686 [X86] Delay for N microsec between assert and de-assert
687 of APIC INIT to start processors. This delay occurs
688 on every CPU online, such as boot, and resume from suspend.
691 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
693 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
695 crashkernel=size[KMG][@offset[KMG]]
696 [KNL] Using kexec, Linux can switch to a 'crash kernel'
697 upon panic. This parameter reserves the physical
698 memory region [offset, offset + size] for that kernel
699 image. If '@offset' is omitted, then a suitable offset
700 is selected automatically. Check
701 Documentation/kdump/kdump.txt for further details.
703 crashkernel=range1:size1[,range2:size2,...][@offset]
704 [KNL] Same as above, but depends on the memory
705 in the running system. The syntax of range is
706 start-[end] where start and end are both
707 a memory unit (amount[KMG]). See also
708 Documentation/kdump/kdump.txt for an example.
710 crashkernel=size[KMG],high
711 [KNL, x86_64] range could be above 4G. Allow kernel
712 to allocate physical memory region from top, so could
713 be above 4G if system have more than 4G ram installed.
714 Otherwise memory region will be allocated below 4G, if
716 It will be ignored if crashkernel=X is specified.
717 crashkernel=size[KMG],low
718 [KNL, x86_64] range under 4G. When crashkernel=X,high
719 is passed, kernel could allocate physical memory region
720 above 4G, that cause second kernel crash on system
721 that require some amount of low memory, e.g. swiotlb
722 requires at least 64M+32K low memory, also enough extra
723 low memory is needed to make sure DMA buffers for 32-bit
724 devices won't run out. Kernel would try to allocate at
725 at least 256M below 4G automatically.
726 This one let user to specify own low range under 4G
727 for second kernel instead.
728 0: to disable low allocation.
729 It will be ignored when crashkernel=X,high is not used
730 or memory reserved is below 4G.
733 [KNL] Disable crypto self-tests
738 cs89x0_media= [HW,NET]
739 Format: { rj45 | aui | bnc }
742 See header of drivers/s390/block/dasd_devmap.c.
744 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
745 (one device per port)
746 Format: <port#>,<type>
747 See also Documentation/input/devices/joystick-parport.rst
749 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
751 Documentation/admin-guide/dynamic-debug-howto.rst for
752 details. Deprecated, see dyndbg.
754 debug [KNL] Enable kernel debugging (events log level).
757 [KNL] verbose self-tests
759 Print debugging info while doing the locking API
761 We default to 0 (no extra messages), setting it to
762 1 will print _a lot_ more information - normally
763 only useful to kernel developers.
765 debug_objects [KNL] Enable object debugging
768 [KNL] Disable object debugging
770 debug_guardpage_minorder=
771 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
772 parameter allows control of the order of pages that will
773 be intentionally kept free (and hence protected) by the
774 buddy allocator. Bigger value increase the probability
775 of catching random memory corruption, but reduce the
776 amount of memory for normal system use. The maximum
777 possible value is MAX_ORDER/2. Setting this parameter
778 to 1 or 2 should be enough to identify most random
779 memory corruption problems caused by bugs in kernel or
780 driver code when a CPU writes to (or reads from) a
781 random memory location. Note that there exists a class
782 of memory corruptions problems caused by buggy H/W or
783 F/W or by drivers badly programing DMA (basically when
784 memory is written at bus level and the CPU MMU is
785 bypassed) which are not detectable by
786 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
787 tracking down these problems.
790 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
791 parameter enables the feature at boot time. In
792 default, it is disabled. We can avoid allocating huge
793 chunk of memory for debug pagealloc if we don't enable
794 it at boot time and the system will work mostly same
795 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
796 on: enable the feature
798 debugpat [X86] Enable PAT debugging
800 decnet.addr= [HW,NET]
801 Format: <area>[,<node>]
802 See also Documentation/networking/decnet.txt.
805 [same as hugepagesz=] The size of the default
806 HugeTLB page size. This is the size represented by
807 the legacy /proc/ hugepages APIs, used for SHM, and
808 default size when mounting hugetlbfs filesystems.
809 Defaults to the default architecture's huge page size
813 Set number of hash buckets for dentry cache.
815 disable_1tb_segments [PPC]
816 Disables the use of 1TB hash page table segments. This
817 causes the kernel to fall back to 256MB segments which
818 can be useful when debugging issues that require an SLB
822 See Documentation/networking/ipv6.txt.
825 Disable RADIX MMU mode on POWER9
827 disable_cpu_apicid= [X86,APIC,SMP]
829 The number of initial APIC ID for the
830 corresponding CPU to be disabled at boot,
831 mostly used for the kdump 2nd kernel to
832 disable BSP to wake up multiple CPUs without
833 causing system reset or hang due to sending
836 disable_ddw [PPC/PSERIES]
837 Disable Dynamic DMA Window support. Use this if
838 to workaround buggy firmware.
841 See Documentation/networking/ipv6.txt.
843 disable_mtrr_cleanup [X86]
844 The kernel tries to adjust MTRR layout from continuous
845 to discrete, to make X server driver able to add WB
846 entry later. This parameter disables that.
848 disable_mtrr_trim [X86, Intel and AMD only]
849 By default the kernel will trim any uncacheable
850 memory out of your available memory pool based on
851 MTRR settings. This parameter disables that behavior,
852 possibly causing your machine to run very slowly.
854 disable_timer_pin_1 [X86]
855 Disable PIN 1 of APIC timer
856 Can be useful to work around chipset bugs.
858 dis_ucode_ldr [X86] Disable the microcode loader.
860 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
861 this option disables the debugging code at boot.
863 dma_debug_entries=<number>
864 This option allows to tune the number of preallocated
865 entries for DMA-API debugging code. One entry is
866 required per DMA-API allocation. Use this if the
867 DMA-API debugging code disables itself because the
868 architectural default is too low.
870 dma_debug_driver=<driver_name>
871 With this option the DMA-API debugging driver
872 filter feature can be enabled at boot time. Just
873 pass the driver to filter for as the parameter.
874 The filter can be disabled or changed to another
875 driver later using sysfs.
877 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
878 Broken monitors, graphic adapters, KVMs and EDIDless
879 panels may send no or incorrect EDID data sets.
880 This parameter allows to specify an EDID data sets
881 in the /lib/firmware directory that are used instead.
882 Generic built-in EDID data sets are used, if one of
883 edid/1024x768.bin, edid/1280x1024.bin,
884 edid/1680x1050.bin, or edid/1920x1080.bin is given
885 and no file with the same name exists. Details and
886 instructions how to build your own EDID data are
887 available in Documentation/EDID/HOWTO.txt. An EDID
888 data set will only be used for a particular connector,
889 if its name and a colon are prepended to the EDID
890 name. Each connector may use a unique EDID data
891 set by separating the files with a comma. An EDID
892 data set with no connector name will be used for
893 any connectors not explicitly specified.
898 Format: {"off" | "known"}
899 Control how the dt_cpu_ftrs device-tree binding is
900 used for CPU feature discovery and setup (if it
902 off: Do not use it, fall back to legacy cpu table.
903 known: Do not pass through unknown features to guests
904 or userspace, only those that the kernel is aware of.
906 dump_apple_properties [X86]
907 Dump name and content of EFI device properties on
908 x86 Macs. Useful for driver authors to determine
909 what data is available or for reverse-engineering.
911 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
912 module.dyndbg[="val"]
913 Enable debug messages at boot time. See
914 Documentation/admin-guide/dynamic-debug-howto.rst
917 nompx [X86] Disables Intel Memory Protection Extensions.
918 See Documentation/x86/intel_mpx.txt for more
919 information about the feature.
921 nopku [X86] Disable Memory Protection Keys CPU feature found
924 module.async_probe [KNL]
925 Enable asynchronous probe on this module.
927 early_ioremap_debug [KNL]
928 Enable debug messages in early_ioremap support. This
929 is useful for tracking down temporary early mappings
930 which are not unmapped.
932 earlycon= [KNL] Output early console device and options.
934 [ARM64] The early console is determined by the
935 stdout-path property in device tree's chosen node,
936 or determined by the ACPI SPCR table.
938 [X86] When used with no options the early console is
939 determined by the ACPI SPCR table.
941 cdns,<addr>[,options]
942 Start an early, polled-mode console on a Cadence
943 (xuartps) serial port at the specified address. Only
944 supported option is baud rate. If baud rate is not
945 specified, the serial port must already be setup and
948 uart[8250],io,<addr>[,options]
949 uart[8250],mmio,<addr>[,options]
950 uart[8250],mmio32,<addr>[,options]
951 uart[8250],mmio32be,<addr>[,options]
952 uart[8250],0x<addr>[,options]
953 Start an early, polled-mode console on the 8250/16550
954 UART at the specified I/O port or MMIO address.
955 MMIO inter-register address stride is either 8-bit
956 (mmio) or 32-bit (mmio32 or mmio32be).
957 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
958 to be equivalent to 'mmio'. 'options' are specified
959 in the same format described for "console=ttyS<n>"; if
960 unspecified, the h/w is not initialized.
964 Start an early, polled-mode console on a pl011 serial
965 port at the specified address. The pl011 serial port
966 must already be setup and configured. Options are not
967 yet supported. If 'mmio32' is specified, then only
968 the driver will use only 32-bit accessors to read/write
969 the device registers.
972 Start an early, polled-mode console on a meson serial
973 port at the specified address. The serial port must
974 already be setup and configured. Options are not yet
978 Start an early, polled-mode console on an msm serial
979 port at the specified address. The serial port
980 must already be setup and configured. Options are not
984 Start an early, polled-mode console on an msm serial
985 dm port at the specified address. The serial port
986 must already be setup and configured. Options are not
990 Start an early, polled-mode console on a serial port
991 of an Actions Semi SoC, such as S500 or S900, at the
992 specified address. The serial port must already be
993 setup and configured. Options are not yet supported.
995 smh Use ARM semihosting calls for early console.
1003 Use early console provided by serial driver available
1004 on Samsung SoCs, requires selecting proper type and
1005 a correct base address of the selected UART port. The
1006 serial port must already be setup and configured.
1007 Options are not yet supported.
1010 Start an early, polled-mode console on a lantiq serial
1011 (lqasc) port at the specified address. The serial port
1012 must already be setup and configured. Options are not
1017 Use early console provided by Freescale LP UART driver
1018 found on Freescale Vybrid and QorIQ LS1021A processors.
1019 A valid base address must be provided, and the serial
1020 port must already be setup and configured.
1023 Start an early, polled-mode console on the
1024 Armada 3700 serial port at the specified
1025 address. The serial port must already be setup
1026 and configured. Options are not yet supported.
1028 earlyprintk= [X86,SH,ARM,M68k,S390]
1033 earlyprintk=serial[,ttySn[,baudrate]]
1034 earlyprintk=serial[,0x...[,baudrate]]
1035 earlyprintk=ttySn[,baudrate]
1036 earlyprintk=dbgp[debugController#]
1037 earlyprintk=pciserial,bus:device.function[,baudrate]
1038 earlyprintk=xdbc[xhciController#]
1040 earlyprintk is useful when the kernel crashes before
1041 the normal console is initialized. It is not enabled by
1042 default because it has some cosmetic problems.
1044 Append ",keep" to not disable it when the real console
1047 Only one of vga, efi, serial, or usb debug port can
1050 Currently only ttyS0 and ttyS1 may be specified by
1051 name. Other I/O ports may be explicitly specified
1052 on some architectures (x86 and arm at least) by
1053 replacing ttySn with an I/O port address, like this:
1054 earlyprintk=serial,0x1008,115200
1055 You can find the port for a given device in
1056 /proc/tty/driver/serial:
1057 2: uart:ST16650V2 port:00001008 irq:18 ...
1059 Interaction with the standard serial driver is not
1062 The VGA and EFI output is eventually overwritten by
1065 The xen output can only be used by Xen PV guests.
1067 The sclp output can only be used on s390.
1069 edac_report= [HW,EDAC] Control how to report EDAC event
1070 Format: {"on" | "off" | "force"}
1071 on: enable EDAC to report H/W event. May be overridden
1072 by other higher priority error reporting module.
1073 off: disable H/W event reporting through EDAC.
1074 force: enforce the use of EDAC to report H/W event.
1077 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1080 This is designed to be used in conjunction with
1081 the boot argument: earlyprintk=vga
1084 Format: {"off" | "on" | "skip[mbr]"}
1087 Format: { "old_map", "nochunk", "noruntime", "debug" }
1088 old_map [X86-64]: switch to the old ioremap-based EFI
1089 runtime services mapping. 32-bit still uses this one by
1091 nochunk: disable reading files in "chunks" in the EFI
1092 boot stub, as chunking can cause problems with some
1093 firmware implementations.
1094 noruntime : disable EFI runtime services support
1095 debug: enable misc debug output
1097 efi_no_storage_paranoia [EFI; X86]
1098 Using this parameter you can use more than 50% of
1099 your efi variable storage. Use this parameter only if
1100 you are really sure that your UEFI does sane gc and
1101 fulfills the spec otherwise your board may brick.
1103 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1104 Add arbitrary attribute to specific memory range by
1105 updating original EFI memory map.
1106 Region of memory which aa attribute is added to is
1108 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1109 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1110 attribute is added to range 0x100000000-0x180000000 and
1111 0x10a0000000-0x1120000000.
1113 Using this parameter you can do debugging of EFI memmap
1114 related feature. For example, you can do debugging of
1115 Address Range Mirroring feature even if your box
1118 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1119 that is to be dynamically loaded by Linux. If there are
1120 multiple variables with the same name but with different
1121 vendor GUIDs, all of them will be loaded. See
1122 Documentation/acpi/ssdt-overlays.txt for details.
1125 eisa_irq_edge= [PARISC,HW]
1126 See header of drivers/parisc/eisa.c.
1129 See comment before function elanfreq_setup() in
1130 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1133 Format: {"cfq" | "deadline" | "noop"}
1134 See Documentation/block/cfq-iosched.txt and
1135 Documentation/block/deadline-iosched.txt for details.
1137 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1138 Specifies physical address of start of kernel core
1139 image elf header and optionally the size. Generally
1140 kexec loader will pass this option to capture kernel.
1141 See Documentation/kdump/kdump.txt for details.
1143 enable_mtrr_cleanup [X86]
1144 The kernel tries to adjust MTRR layout from continuous
1145 to discrete, to make X server driver able to add WB
1146 entry later. This parameter enables that.
1148 enable_timer_pin_1 [X86]
1149 Enable PIN 1 of APIC timer
1150 Can be useful to work around chipset bugs
1151 (in particular on some ATI chipsets).
1152 The kernel tries to set a reasonable default.
1154 enforcing [SELINUX] Set initial enforcing status.
1156 See security/selinux/Kconfig help text.
1157 0 -- permissive (log only, no denials).
1158 1 -- enforcing (deny and log).
1160 Value can be changed at runtime via /selinux/enforce.
1163 Disable Error Record Serialization Table (ERST)
1166 ether= [HW,NET] Ethernet cards parameters
1167 This option is obsoleted by the "netdev=" option, which
1168 has equivalent usage. See its documentation for details.
1172 Permit 'security.evm' to be updated regardless of
1173 current integrity status.
1177 fail_make_request=[KNL]
1178 General fault injection mechanism.
1179 Format: <interval>,<probability>,<space>,<times>
1180 See also Documentation/fault-injection/.
1183 See Documentation/blockdev/floppy.txt.
1185 force_pal_cache_flush
1186 [IA-64] Avoid check_sal_cache_flush which may hang on
1187 buggy SAL_CACHE_FLUSH implementations. Using this
1188 parameter will force ia64_sal_cache_flush to call
1189 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1192 Forcefully enable Physical Address Extension (PAE).
1193 Many Pentium M systems disable PAE but may have a
1194 functionally usable PAE implementation.
1195 Warning: use of this parameter will taint the kernel
1196 and may cause unknown problems.
1199 [FTRACE] will set and start the specified tracer
1200 as early as possible in order to facilitate early
1203 ftrace_dump_on_oops[=orig_cpu]
1204 [FTRACE] will dump the trace buffers on oops.
1205 If no parameter is passed, ftrace will dump
1206 buffers of all CPUs, but if you pass orig_cpu, it will
1207 dump only the buffer of the CPU that triggered the
1210 ftrace_filter=[function-list]
1211 [FTRACE] Limit the functions traced by the function
1212 tracer at boot up. function-list is a comma separated
1213 list of functions. This list can be changed at run
1214 time by the set_ftrace_filter file in the debugfs
1217 ftrace_notrace=[function-list]
1218 [FTRACE] Do not trace the functions specified in
1219 function-list. This list can be changed at run time
1220 by the set_ftrace_notrace file in the debugfs
1223 ftrace_graph_filter=[function-list]
1224 [FTRACE] Limit the top level callers functions traced
1225 by the function graph tracer at boot up.
1226 function-list is a comma separated list of functions
1227 that can be changed at run time by the
1228 set_graph_function file in the debugfs tracing directory.
1230 ftrace_graph_notrace=[function-list]
1231 [FTRACE] Do not trace from the functions specified in
1232 function-list. This list is a comma separated list of
1233 functions that can be changed at run time by the
1234 set_graph_notrace file in the debugfs tracing directory.
1236 ftrace_graph_max_depth=<uint>
1237 [FTRACE] Used with the function graph tracer. This is
1238 the max depth it will trace into a function. This value
1239 can be changed at run time by the max_graph_depth file
1240 in the tracefs tracing directory. default: 0 (no limit)
1243 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1244 support via parallel port (up to 5 devices per port)
1245 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1246 See also Documentation/input/devices/joystick-parport.rst
1250 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1254 gcov_persist= [GCOV] When non-zero (default), profiling data for
1255 kernel modules is saved and remains accessible via
1256 debugfs, even when the module is unloaded/reloaded.
1257 When zero, profiling data is discarded and associated
1258 debugfs files are removed at module unload time.
1260 goldfish [X86] Enable the goldfish android emulator platform.
1261 Don't use this when you are not running on the
1264 gpt [EFI] Forces disk with valid GPT signature but
1265 invalid Protective MBR to be treated as GPT. If the
1266 primary GPT is corrupted, it enables the backup/alternate
1267 GPT to be used instead.
1269 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1270 the "Enable 0" bit of the configuration register.
1273 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1274 the "Enable 0" bit of the configuration register.
1277 grcan.select= [HW] Select which physical interface to use.
1280 grcan.txsize= [HW] Sets the size of the tx buffer.
1281 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1283 grcan.rxsize= [HW] Sets the size of the rx buffer.
1284 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1287 gpio-mockup.gpio_mockup_ranges
1288 [HW] Sets the ranges of gpiochip of for this device.
1289 Format: <start1>,<end1>,<start2>,<end2>...
1291 hardlockup_all_cpu_backtrace=
1292 [KNL] Should the hard-lockup detector generate
1293 backtraces on all cpus.
1296 hashdist= [KNL,NUMA] Large hashes allocated during boot
1297 are distributed across NUMA nodes. Defaults on
1298 for 64-bit NUMA, off otherwise.
1299 Format: 0 | 1 (for off | on)
1301 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1303 hd= [EIDE] (E)IDE hard drive subsystem geometry
1304 Format: <cyl>,<head>,<sect>
1307 Disable Hardware Error Source Table (HEST) support;
1308 corresponding firmware-first mode error processing
1309 logic will be disabled.
1311 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1312 size of <nn>. This works even on boxes that have no
1313 highmem otherwise. This also works to reduce highmem
1314 size on bigger boxes.
1316 highres= [KNL] Enable/disable high resolution timer mode.
1317 Valid parameters: "on", "off"
1321 See Documentation/isdn/README.HiSax.
1325 hpet= [X86-32,HPET] option to control HPET usage
1326 Format: { enable (default) | disable | force |
1328 disable: disable HPET and use PIT instead
1329 force: allow force enabled of undocumented chips (ICH4,
1331 verbose: show contents of HPET registers during setup
1333 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1334 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1336 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1337 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1338 On x86-64 and powerpc, this option can be specified
1339 multiple times interleaved with hugepages= to reserve
1340 huge pages of different sizes. Valid pages sizes on
1341 x86-64 are 2M (when the CPU supports "pse") and 1G
1342 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1344 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1345 terminal devices. Valid values: 0..8
1346 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1347 If specified, z/VM IUCV HVC accepts connections
1348 from listed z/VM user IDs only.
1351 Do not unregister boot console at start. This is only
1352 useful for debugging when something happens in the window
1353 between unregistering the boot console and initializing
1356 i2c_bus= [HW] Override the default board specific I2C bus speed
1357 or register an additional I2C bus that is not
1358 registered from board initialization code.
1362 i8042.debug [HW] Toggle i8042 debug mode
1363 i8042.unmask_kbd_data
1364 [HW] Enable printing of interrupt data from the KBD port
1365 (disabled by default, and as a pre-condition
1366 requires that i8042.debug=1 be enabled)
1367 i8042.direct [HW] Put keyboard port into non-translated mode
1368 i8042.dumbkbd [HW] Pretend that controller can only read data from
1369 keyboard and cannot control its state
1370 (Don't attempt to blink the leds)
1371 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1372 i8042.nokbd [HW] Don't check/create keyboard port
1373 i8042.noloop [HW] Disable the AUX Loopback command while probing
1375 i8042.nomux [HW] Don't check presence of an active multiplexing
1377 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1379 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1380 i8042.reset [HW] Reset the controller during init, cleanup and
1381 suspend-to-ram transitions, only during s2r
1382 transitions, or never reset
1383 Format: { 1 | Y | y | 0 | N | n }
1384 1, Y, y: always reset controller
1385 0, N, n: don't ever reset controller
1386 Default: only on s2r transitions on x86; most other
1387 architectures force reset to be always executed
1388 i8042.unlock [HW] Unlock (ignore) the keylock
1389 i8042.kbdreset [HW] Reset device connected to KBD port
1393 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1394 indicates that the driver is running on unsupported
1396 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1397 does not match list of supported models.
1399 [HW] Report power status in /proc/i8k
1400 (disabled by default)
1401 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1404 i915.invert_brightness=
1405 [DRM] Invert the sense of the variable that is used to
1406 set the brightness of the panel backlight. Normally a
1407 brightness value of 0 indicates backlight switched off,
1408 and the maximum of the brightness value sets the backlight
1409 to maximum brightness. If this parameter is set to 0
1410 (default) and the machine requires it, or this parameter
1411 is set to 1, a brightness value of 0 sets the backlight
1412 to maximum brightness, and the maximum of the brightness
1413 value switches the backlight off.
1414 -1 -- never invert brightness
1415 0 -- machine default
1416 1 -- force brightness inversion
1419 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1421 ide-core.nodma= [HW] (E)IDE subsystem
1422 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1423 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1424 .cdrom .chs .ignore_cable are additional options
1425 See Documentation/ide/ide.txt.
1427 ide-generic.probe-mask= [HW] (E)IDE subsystem
1429 Probe mask for legacy ISA IDE ports. Depending on
1430 platform up to 6 ports are supported, enabled by
1431 setting corresponding bits in the mask to 1. The
1432 default value is 0x0, which has a special meaning.
1433 On systems that have PCI, it triggers scanning the
1434 PCI bus for the first and the second port, which
1435 are then probed. On systems without PCI the value
1436 of 0x0 enables probing the two first ports as if it
1439 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1440 Claim all unknown PCI IDE storage controllers.
1443 Format: idle=poll, idle=halt, idle=nomwait
1444 Poll forces a polling idle loop that can slightly
1445 improve the performance of waking up a idle CPU, but
1446 will use a lot of power and make the system run hot.
1448 idle=halt: Halt is forced to be used for CPU idle.
1449 In such case C2/C3 won't be used again.
1450 idle=nomwait: Disable mwait for CPU C-states
1452 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1453 Format: { strict | legacy | 2008 | relaxed }
1456 Choose which programs will be accepted for execution
1457 based on the IEEE 754 NaN encoding(s) supported by
1458 the FPU and the NaN encoding requested with the value
1459 of an ELF file header flag individually set by each
1460 binary. Hardware implementations are permitted to
1461 support either or both of the legacy and the 2008 NaN
1464 Available settings are as follows:
1465 strict accept binaries that request a NaN encoding
1466 supported by the FPU
1467 legacy only accept legacy-NaN binaries, if supported
1469 2008 only accept 2008-NaN binaries, if supported
1471 relaxed accept any binaries regardless of whether
1472 supported by the FPU
1474 The FPU emulator is always able to support both NaN
1475 encodings, so if no FPU hardware is present or it has
1476 been disabled with 'nofpu', then the settings of
1477 'legacy' and '2008' strap the emulator accordingly,
1478 'relaxed' straps the emulator for both legacy-NaN and
1479 2008-NaN, whereas 'strict' enables legacy-NaN only on
1480 legacy processors and both NaN encodings on MIPS32 or
1483 The setting for ABS.fmt/NEG.fmt instruction execution
1484 mode generally follows that for the NaN encoding,
1485 except where unsupported by hardware.
1487 ignore_loglevel [KNL]
1488 Ignore loglevel setting - this will print /all/
1489 kernel messages to the console. Useful for debugging.
1490 We also add it as printk module parameter, so users
1491 could change it dynamically, usually by
1492 /sys/module/printk/parameters/ignore_loglevel.
1495 Ignore RLIMIT_DATA setting for data mappings,
1496 print warning at first misuse. Can be changed via
1497 /sys/module/kernel/parameters/ignore_rlimit_data.
1499 ihash_entries= [KNL]
1500 Set number of hash buckets for inode cache.
1502 ima_appraise= [IMA] appraise integrity measurements
1503 Format: { "off" | "enforce" | "fix" | "log" }
1506 ima_appraise_tcb [IMA]
1507 The builtin appraise policy appraises all files
1510 ima_canonical_fmt [IMA]
1511 Use the canonical format for the binary runtime
1512 measurements, instead of host native format.
1515 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1519 The list of supported hash algorithms is defined
1520 in crypto/hash_info.h.
1523 The builtin policies to load during IMA setup.
1524 Format: "tcb | appraise_tcb | secure_boot |
1527 The "tcb" policy measures all programs exec'd, files
1528 mmap'd for exec, and all files opened with the read
1529 mode bit set by either the effective uid (euid=0) or
1532 The "appraise_tcb" policy appraises the integrity of
1533 all files owned by root. (This is the equivalent
1534 of ima_appraise_tcb.)
1536 The "secure_boot" policy appraises the integrity
1537 of files (eg. kexec kernel image, kernel modules,
1538 firmware, policy, etc) based on file signatures.
1540 The "fail_securely" policy forces file signature
1541 verification failure also on privileged mounted
1542 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1545 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1546 Load a policy which meets the needs of the Trusted
1547 Computing Base. This means IMA will measure all
1548 programs exec'd, files mmap'd for exec, and all files
1549 opened for read by uid=0.
1552 Select one of defined IMA measurements template formats.
1553 Formats: { "ima" | "ima-ng" | "ima-sig" }
1557 [IMA] Define a custom template format.
1558 Format: { "field1|...|fieldN" }
1560 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1561 Format: <min_file_size>
1562 Set the minimal file size for using asynchronous hash.
1563 If left unspecified, ahash usage is disabled.
1565 ahash performance varies for different data sizes on
1566 different crypto accelerators. This option can be used
1567 to achieve the best performance for a particular HW.
1569 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1571 Set hashing buffer size. Default: 4k.
1573 ahash performance varies for different chunk sizes on
1574 different crypto accelerators. This option can be used
1575 to achieve best performance for particular HW.
1579 Run specified binary instead of /sbin/init as init
1582 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1583 for working out where the kernel is dying during
1586 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1587 initcall functions. Useful for debugging built-in
1588 modules and initcalls.
1590 initrd= [BOOT] Specify the location of the initial ramdisk
1592 init_pkru= [x86] Specify the default memory protection keys rights
1593 register contents for all processes. 0x55555554 by
1594 default (disallow access to all but pkey 0). Can
1595 override in debugfs after boot.
1597 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1600 int_pln_enable [x86] Enable power limit notification interrupt
1602 integrity_audit=[IMA]
1603 Format: { "0" | "1" }
1604 0 -- basic integrity auditing messages. (Default)
1605 1 -- additional integrity auditing messages.
1607 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1609 Enable intel iommu driver.
1611 Disable intel iommu driver.
1612 igfx_off [Default Off]
1613 By default, gfx is mapped as normal device. If a gfx
1614 device has a dedicated DMAR unit, the DMAR unit is
1615 bypassed by not enabling DMAR with this option. In
1616 this case, gfx device will use physical address for
1619 With this option iommu will not optimize to look
1620 for io virtual address below 32-bit forcing dual
1621 address cycle on pci bus for cards supporting greater
1622 than 32-bit addressing. The default is to look
1623 for translation below 32-bit and if not available
1624 then look in the higher range.
1625 strict [Default Off]
1626 With this option on every unmap_single operation will
1627 result in a hardware IOTLB flush operation as opposed
1628 to batching them for performance.
1629 sp_off [Default Off]
1630 By default, super page will be supported if Intel IOMMU
1631 has the capability. With this option, super page will
1633 ecs_off [Default Off]
1634 By default, extended context tables will be supported if
1635 the hardware advertises that it has support both for the
1636 extended tables themselves, and also PASID support. With
1637 this option set, extended tables will not be used even
1638 on hardware which claims to support them.
1639 tboot_noforce [Default Off]
1640 Do not force the Intel IOMMU enabled under tboot.
1641 By default, tboot will force Intel IOMMU on, which
1642 could harm performance of some high-throughput
1643 devices like 40GBit network cards, even if identity
1645 Note that using this option lowers the security
1646 provided by tboot because it makes the system
1647 vulnerable to DMA attacks.
1649 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1650 0 disables intel_idle and fall back on acpi_idle.
1651 1 to 9 specify maximum depth of C-state.
1655 Do not enable intel_pstate as the default
1656 scaling driver for the supported processors
1658 Use intel_pstate as a scaling driver, but configure it
1659 to work with generic cpufreq governors (instead of
1660 enabling its internal governor). This mode cannot be
1661 used along with the hardware-managed P-states (HWP)
1664 Enable intel_pstate on systems that prohibit it by default
1665 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1666 instead of acpi-cpufreq may disable platform features, such
1667 as thermal controls and power capping, that rely on ACPI
1668 P-States information being indicated to OSPM and therefore
1669 should be used with caution. This option does not work with
1670 processors that aren't supported by the intel_pstate driver
1671 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1673 Do not enable hardware P state control (HWP)
1676 Only load intel_pstate on systems which support
1677 hardware P state control (HWP) if available.
1679 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1680 Description Table, specifies preferred power management
1681 profile as "Enterprise Server" or "Performance Server",
1682 then this feature is turned on by default.
1684 Allow per-logical-CPU P-State performance control limits using
1685 cpufreq sysfs interface
1687 intremap= [X86-64, Intel-IOMMU]
1688 on enable Interrupt Remapping (default)
1689 off disable Interrupt Remapping
1690 nosid disable Source ID checking
1692 BIOS x2APIC opt-out request will be ignored
1693 nopost disable Interrupt Posting
1695 iomem= Disable strict checking of access to MMIO memory
1696 strict regions from userspace.
1711 nobypass [PPC/POWERNV]
1712 Disable IOMMU bypass, using IOMMU for PCI devices.
1715 [ARM64] Configure DMA to bypass the IOMMU by default.
1716 Format: { "0" | "1" }
1717 0 - Use IOMMU translation for DMA.
1718 1 - Bypass the IOMMU for DMA.
1719 unset - Use IOMMU translation for DMA.
1721 io7= [HW] IO7 for Marvel based alpha systems
1722 See comment before marvel_specify_io7 in
1723 arch/alpha/kernel/core_marvel.c.
1725 io_delay= [X86] I/O delay method
1727 Standard port 0x80 based delay
1729 Alternate port 0xed based delay (needed on some systems)
1731 Simple two microseconds delay
1736 See Documentation/filesystems/nfs/nfsroot.txt.
1738 irqaffinity= [SMP] Set the default irq affinity mask
1739 The argument is a cpu list, as described above.
1741 irqchip.gicv2_force_probe=
1744 Force the kernel to look for the second 4kB page
1745 of a GICv2 controller even if the memory range
1746 exposed by the device tree is too small.
1748 irqchip.gicv3_nolpi=
1750 Force the kernel to ignore the availability of
1751 LPIs (and by consequence ITSs). Intended for system
1752 that use the kernel as a bootloader, and thus want
1753 to let secondary kernels in charge of setting up
1757 When an interrupt is not handled search all handlers
1758 for it. Intended to get systems with badly broken
1762 When an interrupt is not handled search all handlers
1763 for it. Also check all handlers each timer
1764 interrupt. Intended to get systems with badly broken
1768 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1770 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
1771 [Deprecated - use cpusets instead]
1772 Format: [flag-list,]<cpu-list>
1774 Specify one or more CPUs to isolate from disturbances
1775 specified in the flag list (default: domain):
1778 Disable the tick when a single task runs.
1780 A residual 1Hz tick is offloaded to workqueues, which you
1781 need to affine to housekeeping through the global
1782 workqueue's affinity configured via the
1783 /sys/devices/virtual/workqueue/cpumask sysfs file, or
1784 by using the 'domain' flag described below.
1786 NOTE: by default the global workqueue runs on all CPUs,
1787 so to protect individual CPUs the 'cpumask' file has to
1788 be configured manually after bootup.
1791 Isolate from the general SMP balancing and scheduling
1792 algorithms. Note that performing domain isolation this way
1793 is irreversible: it's not possible to bring back a CPU to
1794 the domains once isolated through isolcpus. It's strongly
1795 advised to use cpusets instead to disable scheduler load
1796 balancing through the "cpuset.sched_load_balance" file.
1797 It offers a much more flexible interface where CPUs can
1798 move in and out of an isolated set anytime.
1800 You can move a process onto or off an "isolated" CPU via
1801 the CPU affinity syscalls or cpuset.
1802 <cpu number> begins at 0 and the maximum value is
1803 "number of CPUs in system - 1".
1805 The format of <cpu-list> is described above.
1811 ivrs_ioapic [HW,X86_64]
1812 Provide an override to the IOAPIC-ID<->DEVICE-ID
1813 mapping provided in the IVRS ACPI table. For
1814 example, to map IOAPIC-ID decimal 10 to
1815 PCI device 00:14.0 write the parameter as:
1816 ivrs_ioapic[10]=00:14.0
1818 ivrs_hpet [HW,X86_64]
1819 Provide an override to the HPET-ID<->DEVICE-ID
1820 mapping provided in the IVRS ACPI table. For
1821 example, to map HPET-ID decimal 0 to
1822 PCI device 00:14.0 write the parameter as:
1823 ivrs_hpet[0]=00:14.0
1825 ivrs_acpihid [HW,X86_64]
1826 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1827 mapping provided in the IVRS ACPI table. For
1828 example, to map UART-HID:UID AMD0020:0 to
1829 PCI device 00:14.5 write the parameter as:
1830 ivrs_acpihid[00:14.5]=AMD0020:0
1832 js= [HW,JOY] Analog joystick
1833 See Documentation/input/joydev/joystick.rst.
1836 When CONFIG_RANDOMIZE_BASE is set, this disables
1837 kernel and module base offset ASLR (Address Space
1838 Layout Randomization).
1841 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1842 report on every invalid memory access. Without this
1843 parameter KASAN will print report only for the first
1848 kernelcore= [KNL,X86,IA-64,PPC]
1849 Format: nn[KMGTPE] | nn% | "mirror"
1850 This parameter specifies the amount of memory usable by
1851 the kernel for non-movable allocations. The requested
1852 amount is spread evenly throughout all nodes in the
1853 system as ZONE_NORMAL. The remaining memory is used for
1854 movable memory in its own zone, ZONE_MOVABLE. In the
1855 event, a node is too small to have both ZONE_NORMAL and
1856 ZONE_MOVABLE, kernelcore memory will take priority and
1857 other nodes will have a larger ZONE_MOVABLE.
1859 ZONE_MOVABLE is used for the allocation of pages that
1860 may be reclaimed or moved by the page migration
1861 subsystem. Note that allocations like PTEs-from-HighMem
1862 still use the HighMem zone if it exists, and the Normal
1863 zone if it does not.
1865 It is possible to specify the exact amount of memory in
1866 the form of "nn[KMGTPE]", a percentage of total system
1867 memory in the form of "nn%", or "mirror". If "mirror"
1868 option is specified, mirrored (reliable) memory is used
1869 for non-movable allocations and remaining memory is used
1870 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
1871 are exclusive, so you cannot specify multiple forms.
1873 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1874 Format: <Controller#>[,poll interval]
1875 The controller # is the number of the ehci usb debug
1876 port as it is probed via PCI. The poll interval is
1877 optional and is the number seconds in between
1878 each poll cycle to the debug port in case you need
1879 the functionality for interrupting the kernel with
1880 gdb or control-c on the dbgp connection. When
1881 not using this parameter you use sysrq-g to break into
1882 the kernel debugger.
1884 kgdboc= [KGDB,HW] kgdb over consoles.
1885 Requires a tty driver that supports console polling,
1886 or a supported polling keyboard driver (non-usb).
1887 Serial only format: <serial_device>[,baud]
1888 keyboard only format: kbd
1889 keyboard and serial format: kbd,<serial_device>[,baud]
1890 Optional Kernel mode setting:
1891 kms, kbd format: kms,kbd
1892 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1894 kgdbwait [KGDB] Stop kernel execution and enter the
1895 kernel debugger at the earliest opportunity.
1897 kmac= [MIPS] korina ethernet MAC address.
1898 Configure the RouterBoard 532 series on-chip
1899 Ethernet adapter MAC address.
1901 kmemleak= [KNL] Boot-time kmemleak enable/disable
1902 Valid arguments: on, off
1904 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1907 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1908 Default is 0 (don't ignore, but inject #GP)
1910 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
1911 Default is false (don't support).
1913 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1917 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1918 Default is 1 (enabled)
1920 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1922 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1924 kvm-arm.vgic_v3_group0_trap=
1925 [KVM,ARM] Trap guest accesses to GICv3 group-0
1928 kvm-arm.vgic_v3_group1_trap=
1929 [KVM,ARM] Trap guest accesses to GICv3 group-1
1932 kvm-arm.vgic_v3_common_trap=
1933 [KVM,ARM] Trap guest accesses to GICv3 common
1936 kvm-arm.vgic_v4_enable=
1937 [KVM,ARM] Allow use of GICv4 for direct injection of
1940 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1941 (virtualized MMU) support on capable Intel chips.
1942 Default is 1 (enabled)
1944 kvm-intel.emulate_invalid_guest_state=
1945 [KVM,Intel] Enable emulation of invalid guest states
1946 Default is 0 (disabled)
1948 kvm-intel.flexpriority=
1949 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1950 Default is 1 (enabled)
1953 [KVM,Intel] Enable VMX nesting (nVMX).
1954 Default is 0 (disabled)
1956 kvm-intel.unrestricted_guest=
1957 [KVM,Intel] Disable unrestricted guest feature
1958 (virtualized real and unpaged mode) on capable
1959 Intel chips. Default is 1 (enabled)
1961 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1962 feature (tagged TLBs) on capable Intel chips.
1963 Default is 1 (enabled)
1969 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1972 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1973 value for LAPIC timer one-shot implementation. Default
1974 back to the programmable timer unit in the LAPIC.
1976 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1979 libata.dma= [LIBATA] DMA control
1980 libata.dma=0 Disable all PATA and SATA DMA
1981 libata.dma=1 PATA and SATA Disk DMA only
1982 libata.dma=2 ATAPI (CDROM) DMA only
1983 libata.dma=4 Compact Flash DMA only
1984 Combinations also work, so libata.dma=3 enables DMA
1985 for disks and CDROMs, but not CFs.
1987 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1988 libata.ignore_hpa=0 keep BIOS limits (default)
1989 libata.ignore_hpa=1 ignore limits, using full disk
1991 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1995 libata.force= [LIBATA] Force configurations. The format is comma
1996 separated list of "[ID:]VAL" where ID is
1997 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1998 matching port, link or device. Basically, it matches
1999 the ATA ID string printed on console by libata. If
2000 the whole ID part is omitted, the last PORT and DEVICE
2001 values are used. If ID hasn't been specified yet, the
2002 configuration applies to all ports, links and devices.
2004 If only DEVICE is omitted, the parameter applies to
2005 the port and all links and devices behind it. DEVICE
2006 number of 0 either selects the first device or the
2007 first fan-out link behind PMP device. It does not
2008 select the host link. DEVICE number of 15 selects the
2009 host link and device attached to it.
2011 The VAL specifies the configuration to force. As long
2012 as there's no ambiguity shortcut notation is allowed.
2013 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2014 The following configurations can be forced.
2016 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2017 Any ID with matching PORT is used.
2019 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2021 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2022 udma[/][16,25,33,44,66,100,133] notation is also
2025 * [no]ncq: Turn on or off NCQ.
2027 * [no]ncqtrim: Turn off queued DSM TRIM.
2029 * nohrst, nosrst, norst: suppress hard, soft
2032 * rstonce: only attempt one reset during
2033 hot-unplug link recovery
2035 * dump_id: dump IDENTIFY data.
2037 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2039 * disable: Disable this device.
2041 If there are multiple matching configurations changing
2042 the same attribute, the last one is used.
2044 memblock=debug [KNL] Enable memblock debug messages.
2046 load_ramdisk= [RAM] List of ramdisks to load from floppy
2047 See Documentation/blockdev/ramdisk.txt.
2049 lockd.nlm_grace_period=P [NFS] Assign grace period.
2052 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2055 lockd.nlm_timeout=T [NFS] Assign timeout value.
2058 lockd.nlm_udpport=M [NFS] Assign UDP port.
2061 locktorture.nreaders_stress= [KNL]
2062 Set the number of locking read-acquisition kthreads.
2063 Defaults to being automatically set based on the
2064 number of online CPUs.
2066 locktorture.nwriters_stress= [KNL]
2067 Set the number of locking write-acquisition kthreads.
2069 locktorture.onoff_holdoff= [KNL]
2070 Set time (s) after boot for CPU-hotplug testing.
2072 locktorture.onoff_interval= [KNL]
2073 Set time (s) between CPU-hotplug operations, or
2074 zero to disable CPU-hotplug testing.
2076 locktorture.shuffle_interval= [KNL]
2077 Set task-shuffle interval (jiffies). Shuffling
2078 tasks allows some CPUs to go into dyntick-idle
2079 mode during the locktorture test.
2081 locktorture.shutdown_secs= [KNL]
2082 Set time (s) after boot system shutdown. This
2083 is useful for hands-off automated testing.
2085 locktorture.stat_interval= [KNL]
2086 Time (s) between statistics printk()s.
2088 locktorture.stutter= [KNL]
2089 Time (s) to stutter testing, for example,
2090 specifying five seconds causes the test to run for
2091 five seconds, wait for five seconds, and so on.
2092 This tests the locking primitive's ability to
2093 transition abruptly to and from idle.
2095 locktorture.torture_type= [KNL]
2096 Specify the locking implementation to test.
2098 locktorture.verbose= [KNL]
2099 Enable additional printk() statements.
2101 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2104 loglevel= All Kernel Messages with a loglevel smaller than the
2105 console loglevel will be printed to the console. It can
2106 also be changed with klogd or other programs. The
2107 loglevels are defined as follows:
2109 0 (KERN_EMERG) system is unusable
2110 1 (KERN_ALERT) action must be taken immediately
2111 2 (KERN_CRIT) critical conditions
2112 3 (KERN_ERR) error conditions
2113 4 (KERN_WARNING) warning conditions
2114 5 (KERN_NOTICE) normal but significant condition
2115 6 (KERN_INFO) informational
2116 7 (KERN_DEBUG) debug-level messages
2118 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2119 in bytes. n must be a power of two and greater
2120 than the minimal size. The minimal size is defined
2121 by LOG_BUF_SHIFT kernel config parameter. There is
2122 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2123 that allows to increase the default size depending on
2124 the number of CPUs. See init/Kconfig for more details.
2126 logo.nologo [FB] Disables display of the built-in Linux logo.
2127 This may be used to provide more screen space for
2128 kernel log messages and is useful when debugging
2129 kernel boot problems.
2131 lp=0 [LP] Specify parallel ports to use, e.g,
2132 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2133 lp=reset first parallel port). 'lp=0' disables the
2134 lp=auto printer driver. 'lp=reset' (which can be
2135 specified in addition to the ports) causes
2136 attached printers to be reset. Using
2137 lp=port1,port2,... specifies the parallel ports
2138 to associate lp devices with, starting with
2139 lp0. A port specification may be 'none' to skip
2140 that lp device, or a parport name such as
2141 'parport0'. Specifying 'lp=auto' instead of a
2142 port specification list means that device IDs
2143 from each port should be examined, to see if
2144 an IEEE 1284-compliant printer is attached; if
2145 so, the driver will manage that printer.
2146 See also header of drivers/char/lp.c.
2149 Sets loops_per_jiffy to given constant, thus avoiding
2150 time-consuming boot-time autodetection (up to 250 ms per
2151 CPU). 0 enables autodetection (default). To determine
2152 the correct value for your kernel, boot with normal
2153 autodetection and see what value is printed. Note that
2154 on SMP systems the preset will be applied to all CPUs,
2155 which is likely to cause problems if your CPUs need
2156 significantly divergent settings. An incorrect value
2157 will cause delays in the kernel to be wrong, leading to
2158 unpredictable I/O errors and other breakage. Although
2159 unlikely, in the extreme case this might damage your
2163 Format: <io>,<irq>,<dma>
2165 machvec= [IA-64] Force the use of a particular machine-vector
2166 (machvec) in a generic kernel.
2167 Example: machvec=hpzx1_swiotlb
2169 machtype= [Loongson] Share the same kernel image file between different
2171 Example: machtype=lemote-yeeloong-2f-7inch
2173 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2174 than or equal to this physical address is ignored.
2176 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2177 will bring up during bootup. maxcpus=n : n >= 0 limits
2178 the kernel to bring up 'n' processors. Surely after
2179 bootup you can bring up the other plugged cpu by executing
2180 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2181 only takes effect during system bootup.
2182 While n=0 is a special case, it is equivalent to "nosmp",
2183 which also disables the IO APIC.
2185 max_loop= [LOOP] The number of loop block devices that get
2186 (loop.max_loop) unconditionally pre-created at init time. The default
2187 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2188 of statically allocating a predefined number, loop
2189 devices can be requested on-demand with the
2190 /dev/loop-control interface.
2192 mce [X86-32] Machine Check Exception
2194 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2196 md= [HW] RAID subsystems devices and level
2197 See Documentation/admin-guide/md.rst.
2200 Format: <first>,<last>
2201 Specifies range of consoles to be captured by the MDA.
2203 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2204 Amount of memory to be used when the kernel is not able
2205 to see the whole system memory or for test.
2206 [X86] Work as limiting max address. Use together
2207 with memmap= to avoid physical address space collisions.
2208 Without memmap= PCI devices could be placed at addresses
2209 belonging to unused RAM.
2211 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2215 [KNL,SH] Allow user to override the default size for
2216 per-device physically contiguous DMA buffers.
2218 memhp_default_state=online/offline
2219 [KNL] Set the initial state for the memory hotplug
2220 onlining policy. If not specified, the default value is
2221 set according to the
2222 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2224 See Documentation/memory-hotplug.txt.
2226 memmap=exactmap [KNL,X86] Enable setting of an exact
2227 E820 memory map, as specified by the user.
2228 Such memmap=exactmap lines can be constructed based on
2229 BIOS output or other requirements. See the memmap=nn@ss
2232 memmap=nn[KMG]@ss[KMG]
2233 [KNL] Force usage of a specific region of memory.
2234 Region of memory to be used is from ss to ss+nn.
2235 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2236 which limits max address to nn[KMG].
2237 Multiple different regions can be specified,
2240 memmap=100M@2G,100M#3G,1G!1024G
2242 memmap=nn[KMG]#ss[KMG]
2243 [KNL,ACPI] Mark specific memory as ACPI data.
2244 Region of memory to be marked is from ss to ss+nn.
2246 memmap=nn[KMG]$ss[KMG]
2247 [KNL,ACPI] Mark specific memory as reserved.
2248 Region of memory to be reserved is from ss to ss+nn.
2249 Example: Exclude memory from 0x18690000-0x1869ffff
2250 memmap=64K$0x18690000
2252 memmap=0x10000$0x18690000
2253 Some bootloaders may need an escape character before '$',
2254 like Grub2, otherwise '$' and the following number
2257 memmap=nn[KMG]!ss[KMG]
2258 [KNL,X86] Mark specific memory as protected.
2259 Region of memory to be used, from ss to ss+nn.
2260 The memory region may be marked as e820 type 12 (0xc)
2261 and is NVDIMM or ADR memory.
2263 memmap=<size>%<offset>-<oldtype>+<newtype>
2264 [KNL,ACPI] Convert memory within the specified region
2265 from <oldtype> to <newtype>. If "-<oldtype>" is left
2266 out, the whole region will be marked as <newtype>,
2267 even if previously unavailable. If "+<newtype>" is left
2268 out, matching memory will be removed. Types are
2269 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
2270 3 = ACPI, 12 = PRAM.
2272 memory_corruption_check=0/1 [X86]
2273 Some BIOSes seem to corrupt the first 64k of
2274 memory when doing things like suspend/resume.
2275 Setting this option will scan the memory
2276 looking for corruption. Enabling this will
2277 both detect corruption and prevent the kernel
2278 from using the memory being corrupted.
2279 However, its intended as a diagnostic tool; if
2280 repeatable BIOS-originated corruption always
2281 affects the same memory, you can use memmap=
2282 to prevent the kernel from using that memory.
2284 memory_corruption_check_size=size [X86]
2285 By default it checks for corruption in the low
2286 64k, making this memory unavailable for normal
2287 use. Use this parameter to scan for
2288 corruption in more or less memory.
2290 memory_corruption_check_period=seconds [X86]
2291 By default it checks for corruption every 60
2292 seconds. Use this parameter to check at some
2293 other rate. 0 disables periodic checking.
2295 memtest= [KNL,X86,ARM] Enable memtest
2297 default : 0 <disable>
2298 Specifies the number of memtest passes to be
2299 performed. Each pass selects another test
2300 pattern from a given set of patterns. Memtest
2301 fills the memory with this pattern, validates
2302 memory contents and reserves bad memory
2303 regions that are detected.
2305 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2306 Valid arguments: on, off
2307 Default (depends on kernel configuration option):
2308 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2309 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2310 mem_encrypt=on: Activate SME
2311 mem_encrypt=off: Do not activate SME
2313 Refer to Documentation/x86/amd-memory-encryption.txt
2314 for details on when memory encryption can be activated.
2316 mem_sleep_default= [SUSPEND] Default system suspend mode:
2317 s2idle - Suspend-To-Idle
2318 shallow - Power-On Suspend or equivalent (if supported)
2319 deep - Suspend-To-RAM or equivalent (if supported)
2320 See Documentation/admin-guide/pm/sleep-states.rst.
2322 meye.*= [HW] Set MotionEye Camera parameters
2323 See Documentation/media/v4l-drivers/meye.rst.
2325 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2326 Multi-Function General Purpose Timers on AMD Geode
2329 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2330 the BIOS has incorrectly applied a workaround. TinyBIOS
2331 version 0.98 is known to be affected, 0.99 fixes the
2332 problem by letting the user disable the workaround.
2336 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2337 physical address is ignored.
2339 mini2440= [ARM,HW,KNL]
2340 Format:[0..2][b][c][t]
2342 MINI2440 configuration specification:
2343 0 - The attached screen is the 3.5" TFT
2344 1 - The attached screen is the 7" TFT
2345 2 - The VGA Shield is attached (1024x768)
2346 Leaving out the screen size parameter will not load
2347 the TFT driver, and the framebuffer will be left
2349 b - Enable backlight. The TFT backlight pin will be
2350 linked to the kernel VESA blanking code and a GPIO
2351 LED. This parameter is not necessary when using the
2353 c - Enable the s3c camera interface.
2354 t - Reserved for enabling touchscreen support. The
2355 touchscreen support is not enabled in the mainstream
2356 kernel as of 2.6.30, a preliminary port can be found
2357 in the "bleeding edge" mini2440 support kernel at
2358 http://repo.or.cz/w/linux-2.6/mini2440.git
2361 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2362 parameter allows control of the logging verbosity for
2363 the additional memory initialisation checks. A value
2364 of 0 disables mminit logging and a level of 4 will
2365 log everything. Information is printed at KERN_DEBUG
2366 so loglevel=8 may also need to be specified.
2369 [KNL] When CONFIG_MODULE_SIG is set, this means that
2370 modules without (valid) signatures will fail to load.
2371 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2372 is always true, so this option does nothing.
2374 module_blacklist= [KNL] Do not load a comma-separated list of
2375 modules. Useful for debugging problem modules.
2378 [MOUSE] Maximum time between finger touching and
2379 leaving touchpad surface for touch to be considered
2380 a tap and be reported as a left button click (for
2381 touchpads working in absolute mode only).
2383 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2384 reporting absolute coordinates, such as tablets
2385 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2386 reporting absolute coordinates, such as tablets
2388 movablecore= [KNL,X86,IA-64,PPC]
2389 Format: nn[KMGTPE] | nn%
2390 This parameter is the complement to kernelcore=, it
2391 specifies the amount of memory used for migratable
2392 allocations. If both kernelcore and movablecore is
2393 specified, then kernelcore will be at *least* the
2394 specified value but may be more. If movablecore on its
2395 own is specified, the administrator must be careful
2396 that the amount of memory usable for all allocations
2399 movable_node [KNL] Boot-time switch to make hotplugable memory
2400 NUMA nodes to be movable. This means that the memory
2401 of such nodes will be usable only for movable
2402 allocations which rules out almost all kernel
2403 allocations. Use with caution!
2405 MTD_Partition= [MTD]
2406 Format: <name>,<region-number>,<size>,<offset>
2408 MTD_Region= [MTD] Format:
2409 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2412 See drivers/mtd/cmdlinepart.c.
2414 multitce=off [PPC] This parameter disables the use of the pSeries
2415 firmware feature for updating multiple TCE entries
2418 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2420 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2422 boundary - index of last SLC block on Flex-OneNAND.
2423 The remaining blocks are configured as MLC blocks.
2424 lock - Configure if Flex-OneNAND boundary should be locked.
2425 Once locked, the boundary cannot be changed.
2426 1 indicates lock status, 0 indicates unlock status.
2429 ARM/S3C2412 JIVE boot control
2431 See arch/arm/mach-s3c2412/mach-jive.c
2433 mtouchusb.raw_coordinates=
2434 [HW] Make the MicroTouch USB driver use raw coordinates
2435 ('y', default) or cooked coordinates ('n')
2437 mtrr_chunk_size=nn[KMG] [X86]
2438 used for mtrr cleanup. It is largest continuous chunk
2439 that could hold holes aka. UC entries.
2441 mtrr_gran_size=nn[KMG] [X86]
2442 Used for mtrr cleanup. It is granularity of mtrr block.
2444 Large value could prevent small alignment from
2447 mtrr_spare_reg_nr=n [X86]
2449 Range: 0,7 : spare reg number
2451 Used for mtrr cleanup. It is spare mtrr entries number.
2452 Set to 2 or more if your graphical card needs more.
2454 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2456 netdev= [NET] Network devices parameters
2457 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2458 Note that mem_start is often overloaded to mean
2459 something different and driver-specific.
2460 This usage is only documented in each driver source
2464 [NETFILTER] Enable connection tracking flow accounting
2465 0 to disable accounting
2466 1 to enable accounting
2469 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2470 See Documentation/filesystems/nfs/nfsroot.txt.
2472 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2473 See Documentation/filesystems/nfs/nfsroot.txt.
2475 nfsrootdebug [NFS] enable nfsroot debugging messages.
2476 See Documentation/filesystems/nfs/nfsroot.txt.
2478 nfs.callback_nr_threads=
2479 [NFSv4] set the total number of threads that the
2480 NFS client will assign to service NFSv4 callback
2483 nfs.callback_tcpport=
2484 [NFS] set the TCP port on which the NFSv4 callback
2485 channel should listen.
2488 [NFS] sets the pathname to the program which is used
2489 to update the NFS client cache entries.
2491 nfs.cache_getent_timeout=
2492 [NFS] sets the timeout after which an attempt to
2493 update a cache entry is deemed to have failed.
2495 nfs.idmap_cache_timeout=
2496 [NFS] set the maximum lifetime for idmapper cache
2500 [NFS] enable 64-bit inode numbers.
2501 If zero, the NFS client will fake up a 32-bit inode
2502 number for the readdir() and stat() syscalls instead
2503 of returning the full 64-bit number.
2504 The default is to return 64-bit inode numbers.
2506 nfs.max_session_cb_slots=
2507 [NFSv4.1] Sets the maximum number of session
2508 slots the client will assign to the callback
2509 channel. This determines the maximum number of
2510 callbacks the client will process in parallel for
2511 a particular server.
2513 nfs.max_session_slots=
2514 [NFSv4.1] Sets the maximum number of session slots
2515 the client will attempt to negotiate with the server.
2516 This limits the number of simultaneous RPC requests
2517 that the client can send to the NFSv4.1 server.
2518 Note that there is little point in setting this
2519 value higher than the max_tcp_slot_table_limit.
2521 nfs.nfs4_disable_idmapping=
2522 [NFSv4] When set to the default of '1', this option
2523 ensures that both the RPC level authentication
2524 scheme and the NFS level operations agree to use
2525 numeric uids/gids if the mount is using the
2526 'sec=sys' security flavour. In effect it is
2527 disabling idmapping, which can make migration from
2528 legacy NFSv2/v3 systems to NFSv4 easier.
2529 Servers that do not support this mode of operation
2530 will be autodetected by the client, and it will fall
2531 back to using the idmapper.
2532 To turn off this behaviour, set the value to '0'.
2534 [NFS4] Specify an additional fixed unique ident-
2535 ification string that NFSv4 clients can insert into
2536 their nfs_client_id4 string. This is typically a
2537 UUID that is generated at system install time.
2539 nfs.send_implementation_id =
2540 [NFSv4.1] Send client implementation identification
2541 information in exchange_id requests.
2542 If zero, no implementation identification information
2544 The default is to send the implementation identification
2547 nfs.recover_lost_locks =
2548 [NFSv4] Attempt to recover locks that were lost due
2549 to a lease timeout on the server. Please note that
2550 doing this risks data corruption, since there are
2551 no guarantees that the file will remain unchanged
2552 after the locks are lost.
2553 If you want to enable the kernel legacy behaviour of
2554 attempting to recover these locks, then set this
2556 The default parameter value of '0' causes the kernel
2557 not to attempt recovery of lost locks.
2559 nfs4.layoutstats_timer =
2560 [NFSv4.2] Change the rate at which the kernel sends
2561 layoutstats to the pNFS metadata server.
2563 Setting this to value to 0 causes the kernel to use
2564 whatever value is the default set by the layout
2565 driver. A non-zero value sets the minimum interval
2566 in seconds between layoutstats transmissions.
2568 nfsd.nfs4_disable_idmapping=
2569 [NFSv4] When set to the default of '1', the NFSv4
2570 server will return only numeric uids and gids to
2571 clients using auth_sys, and will accept numeric uids
2572 and gids from such clients. This is intended to ease
2573 migration from NFSv2/v3.
2575 nmi_debug= [KNL,SH] Specify one or more actions to take
2576 when a NMI is triggered.
2577 Format: [state][,regs][,debounce][,die]
2579 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2580 Format: [panic,][nopanic,][num]
2582 0 - turn hardlockup detector in nmi_watchdog off
2583 1 - turn hardlockup detector in nmi_watchdog on
2584 When panic is specified, panic when an NMI watchdog
2585 timeout occurs (or 'nopanic' to override the opposite
2586 default). To disable both hard and soft lockup detectors,
2587 please see 'nowatchdog'.
2588 This is useful when you use a panic=... timeout and
2589 need the box quickly up again.
2591 These settings can be accessed at runtime via
2592 the nmi_watchdog and hardlockup_panic sysctls.
2594 netpoll.carrier_timeout=
2595 [NET] Specifies amount of time (in seconds) that
2596 netpoll should wait for a carrier. By default netpoll
2599 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2600 emulation library even if a 387 maths coprocessor
2604 [HW] Never suspend the console
2605 Disable suspending of consoles during suspend and
2606 hibernate operations. Once disabled, debugging
2607 messages can reach various consoles while the rest
2608 of the system is being put to sleep (ie, while
2609 debugging driver suspend/resume hooks). This may
2610 not work reliably with all consoles, but is known
2611 to work with serial and VGA consoles.
2612 To facilitate more flexible debugging, we also add
2613 console_suspend, a printk module parameter to control
2614 it. Users could use console_suspend (usually
2615 /sys/module/printk/parameters/console_suspend) to
2616 turn on/off it dynamically.
2618 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2619 caches in the slab allocator. Saves per-node memory,
2620 but will impact performance.
2624 noaltinstr [S390] Disables alternative instructions patching
2625 (CPU alternatives feature).
2627 noapic [SMP,APIC] Tells the kernel to not make use of any
2628 IOAPICs that may be present in the system.
2630 noautogroup Disable scheduler automatic task group creation.
2632 nobats [PPC] Do not use BATs for mapping kernel lowmem
2633 on "Classic" PPC cores.
2637 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2639 nodelayacct [KNL] Disable per-task delay accounting
2641 nodsp [SH] Disable hardware DSP at boot time.
2643 noefi Disable EFI runtime services support.
2648 On X86-32 available only on PAE configured kernels.
2649 noexec=on: enable non-executable mappings (default)
2650 noexec=off: disable non-executable mappings
2653 Disable SMAP (Supervisor Mode Access Prevention)
2654 even if it is supported by processor.
2657 Disable SMEP (Supervisor Mode Execution Prevention)
2658 even if it is supported by processor.
2661 This affects only 32-bit executables.
2662 noexec32=on: enable non-executable mappings (default)
2663 read doesn't imply executable mappings
2664 noexec32=off: disable non-executable mappings
2665 read implies executable mappings
2667 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2669 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2670 register save and restore. The kernel will only save
2671 legacy floating-point registers on task switch.
2673 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2675 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2676 Equivalent to smt=1.
2678 nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2
2679 (indirect branch prediction) vulnerability. System may
2680 allow data leaks with this option, which is equivalent
2683 noxsave [BUGS=X86] Disables x86 extended register state save
2684 and restore using xsave. The kernel will fallback to
2685 enabling legacy floating-point and sse state.
2687 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2688 register states. The kernel will fall back to use
2689 xsave to save the states. By using this parameter,
2690 performance of saving the states is degraded because
2691 xsave doesn't support modified optimization while
2692 xsaveopt supports it on xsaveopt enabled systems.
2694 noxsaves [X86] Disables xsaves and xrstors used in saving and
2695 restoring x86 extended register state in compacted
2696 form of xsave area. The kernel will fall back to use
2697 xsaveopt and xrstor to save and restore the states
2698 in standard form of xsave area. By using this
2699 parameter, xsave area per process might occupy more
2700 memory on xsaves enabled systems.
2702 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2703 wfi(ARM) instruction doesn't work correctly and not to
2704 use it. This is also useful when using JTAG debugger.
2706 no_file_caps Tells the kernel not to honor file capabilities. The
2707 only way then for a file to be executed with privilege
2708 is to be setuid root or executed by root.
2710 nohalt [IA-64] Tells the kernel not to use the power saving
2711 function PAL_HALT_LIGHT when idle. This increases
2712 power-consumption. On the positive side, it reduces
2713 interrupt wake-up latency, which may improve performance
2714 in certain environments such as networked servers or
2717 nohibernate [HIBERNATION] Disable hibernation and resume.
2719 nohz= [KNL] Boottime enable/disable dynamic ticks
2720 Valid arguments: on, off
2723 nohz_full= [KNL,BOOT,SMP,ISOL]
2724 The argument is a cpu list, as described above.
2725 In kernels built with CONFIG_NO_HZ_FULL=y, set
2726 the specified list of CPUs whose tick will be stopped
2727 whenever possible. The boot CPU will be forced outside
2728 the range to maintain the timekeeping. Any CPUs
2729 in this list will have their RCU callbacks offloaded,
2730 just as if they had also been called out in the
2731 rcu_nocbs= boot parameter.
2733 noiotrap [SH] Disables trapped I/O port accesses.
2735 noirqdebug [X86-32] Disables the code which attempts to detect and
2736 disable unhandled interrupt sources.
2738 no_timer_check [X86,APIC] Disables the code which tests for
2739 broken timer IRQ sources.
2741 noisapnp [ISAPNP] Disables ISA PnP code.
2743 noinitrd [RAM] Tells the kernel not to load any configured
2746 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2748 [Deprecated - use intremap=off]
2752 noinvpcid [X86] Disable the INVPCID cpu feature.
2754 nojitter [IA-64] Disables jitter checking for ITC timers.
2756 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2758 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2762 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2763 clock and use the default one.
2765 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2766 steal time is computed, but won't influence scheduler
2769 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2771 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2773 noltlbs [PPC] Do not use large page/tlb entries for kernel
2774 lowmem mapping on PPC40x and PPC8xx
2776 nomca [IA-64] Disable machine check abort handling
2778 nomce [X86-32] Disable Machine Check Exception
2780 nomfgpt [X86-32] Disable Multi-Function General Purpose
2781 Timer usage (for AMD Geode machines).
2783 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2784 shutdown the other cpus. Instead use the REBOOT_VECTOR
2787 nomodule Disable module load
2789 nopat [X86] Disable PAT (page attribute table extension of
2790 pagetables) support.
2792 nopcid [X86-64] Disable the PCID cpu feature.
2794 norandmaps Don't use address space randomization. Equivalent to
2795 echo 0 > /proc/sys/kernel/randomize_va_space
2797 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2798 with UP alternatives
2800 nordrand [X86] Disable kernel use of the RDRAND and
2801 RDSEED instructions even if they are supported
2802 by the processor. RDRAND and RDSEED are still
2803 available to user space applications.
2805 noresume [SWSUSP] Disables resume and restores original swap
2808 no-scroll [VGA] Disables scrollback.
2809 This is required for the Braillex ib80-piezo Braille
2810 reader made by F.H. Papenmeier (Germany).
2814 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2816 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2817 and disable the IO APIC. legacy for "maxcpus=0".
2819 nosoftlockup [KNL] Disable the soft-lockup detector.
2821 nosync [HW,M68K] Disables sync negotiation for all devices.
2823 notsc [BUGS=X86-32] Disable Time Stamp Counter
2825 nowatchdog [KNL] Disable both lockup detectors, i.e.
2826 soft-lockup and NMI watchdog (hard-lockup).
2830 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2832 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2833 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2834 Some features depend on CPU0. Known dependencies are:
2835 1. Resume from suspend/hibernate depends on CPU0.
2836 Suspend/hibernate will fail if CPU0 is offline and you
2837 need to online CPU0 before suspend/hibernate.
2838 2. PIC interrupts also depend on CPU0. CPU0 can't be
2839 removed if a PIC interrupt is detected.
2840 It's said poweroff/reboot may depend on CPU0 on some
2841 machines although I haven't seen such issues so far
2842 after CPU0 is offline on a few tested machines.
2843 If the dependencies are under your control, you can
2844 turn on cpu0_hotplug.
2846 nps_mtm_hs_ctr= [KNL,ARC]
2847 This parameter sets the maximum duration, in
2848 cycles, each HW thread of the CTOP can run
2849 without interruptions, before HW switches it.
2850 The actual maximum duration is 16 times this
2852 Format: integer between 1 and 255
2855 nptcg= [IA-64] Override max number of concurrent global TLB
2856 purges which is reported from either PAL_VM_SUMMARY or
2859 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2860 could support. nr_cpus=n : n >= 1 limits the kernel to
2861 support 'n' processors. It could be larger than the
2862 number of already plugged CPU during bootup, later in
2863 runtime you can physically add extra cpu until it reaches
2864 n. So during boot up some boot time memory for per-cpu
2865 variables need be pre-allocated for later physical cpu
2868 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2870 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2871 Allowed values are enable and disable
2873 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2874 'node', 'default' can be specified
2875 This can be set from sysctl after boot.
2876 See Documentation/sysctl/vm.txt for details.
2878 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2879 See Documentation/debugging-via-ohci1394.txt for more
2882 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2883 Rather than timing out after 20 ms if an EC
2884 command is not properly ACKed, override the length
2885 of the timeout. We have interrupts disabled while
2886 waiting for the ACK, so if this is set too high
2887 interrupts *may* be lost!
2889 omap_mux= [OMAP] Override bootloader pin multiplexing.
2890 Format: <mux_mode0.mode_name=value>...
2891 For example, to override I2C bus2:
2892 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2894 oprofile.timer= [HW]
2895 Use timer interrupt instead of performance counters
2897 oprofile.cpu_type= Force an oprofile cpu type
2898 This might be useful if you have an older oprofile
2899 userland or if you want common events.
2900 Format: { arch_perfmon }
2901 arch_perfmon: [X86] Force use of architectural
2902 perfmon on Intel CPUs instead of the
2903 CPU specific event set.
2904 timer: [X86] Force use of architectural NMI
2905 timer mode (see also oprofile.timer
2906 for generic hr timer mode)
2908 oops=panic Always panic on oopses. Default is to just kill the
2909 process, but there is a small probability of
2910 deadlocking the machine.
2911 This will also cause panics on machine check exceptions.
2912 Useful together with panic=30 to trigger a reboot.
2915 See Documentation/sound/oss/oss-parameters.txt
2917 page_owner= [KNL] Boot-time page_owner enabling option.
2918 Storage of the information about who allocated
2919 each page is disabled in default. With this switch,
2921 on: enable the feature
2923 page_poison= [KNL] Boot-time parameter changing the state of
2924 poisoning on the buddy allocator.
2925 off: turn off poisoning
2926 on: turn on poisoning
2928 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2929 timeout > 0: seconds before rebooting
2930 timeout = 0: wait forever
2931 timeout < 0: reboot immediately
2934 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2937 crash_kexec_post_notifiers
2938 Run kdump after running panic-notifiers and dumping
2939 kmsg. This only for the users who doubt kdump always
2940 succeeds in any situation.
2941 Note that this also increases risks of kdump failure,
2942 because some panic notifiers can make the crashed
2943 kernel more unstable.
2945 parkbd.port= [HW] Parallel port number the keyboard adapter is
2946 connected to, default is 0.
2948 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2949 0 for XT, 1 for AT (default is AT).
2952 parport= [HW,PPT] Specify parallel ports. 0 disables.
2953 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2954 Use 'auto' to force the driver to use any
2955 IRQ/DMA settings detected (the default is to
2956 ignore detected IRQ/DMA settings because of
2957 possible conflicts). You can specify the base
2958 address, IRQ, and DMA settings; IRQ and DMA
2959 should be numbers, or 'auto' (for using detected
2960 settings on that particular port), or 'nofifo'
2961 (to avoid using a FIFO even if it is detected).
2962 Parallel ports are assigned in the order they
2963 are specified on the command line, starting
2966 parport_init_mode= [HW,PPT]
2967 Configure VIA parallel port to operate in
2968 a specific mode. This is necessary on Pegasos
2969 computer where firmware has no options for setting
2970 up parallel port mode and sets it to spp.
2971 Currently this function knows 686a and 8231 chips.
2972 Format: [spp|ps2|epp|ecp|ecpepp]
2975 Halt all CPUs after the first oops has been printed for
2976 the specified number of seconds. This is to be used if
2977 your oopses keep scrolling off the screen.
2982 See header of drivers/block/paride/pcd.c.
2983 See also Documentation/blockdev/paride.txt.
2985 pci=option[,option...] [PCI] various PCI subsystem options:
2986 earlydump [X86] dump PCI config space before the kernel
2988 off [X86] don't probe for the PCI bus
2989 bios [X86-32] force use of PCI BIOS, don't access
2990 the hardware directly. Use this if your machine
2991 has a non-standard PCI host bridge.
2992 nobios [X86-32] disallow use of PCI BIOS, only direct
2993 hardware access methods are allowed. Use this
2994 if you experience crashes upon bootup and you
2995 suspect they are caused by the BIOS.
2996 conf1 [X86] Force use of PCI Configuration Access
2997 Mechanism 1 (config address in IO port 0xCF8,
2998 data in IO port 0xCFC, both 32-bit).
2999 conf2 [X86] Force use of PCI Configuration Access
3000 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
3001 the function, IO port 0xCFA, also 8-bit, sets
3002 bus number. The config space is then accessed
3003 through ports 0xC000-0xCFFF).
3004 See http://wiki.osdev.org/PCI for more info
3005 on the configuration access mechanisms.
3006 noaer [PCIE] If the PCIEAER kernel config parameter is
3007 enabled, this kernel boot option can be used to
3008 disable the use of PCIE advanced error reporting.
3009 nodomains [PCI] Disable support for multiple PCI
3010 root domains (aka PCI segments, in ACPI-speak).
3011 nommconf [X86] Disable use of MMCONFIG for PCI
3013 check_enable_amd_mmconf [X86] check for and enable
3014 properly configured MMIO access to PCI
3015 config space on AMD family 10h CPU
3016 nomsi [MSI] If the PCI_MSI kernel config parameter is
3017 enabled, this kernel boot option can be used to
3018 disable the use of MSI interrupts system-wide.
3019 noioapicquirk [APIC] Disable all boot interrupt quirks.
3020 Safety option to keep boot IRQs enabled. This
3021 should never be necessary.
3022 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3023 primary IO-APIC for bridges that cannot disable
3024 boot IRQs. This fixes a source of spurious IRQs
3025 when the system masks IRQs.
3026 noioapicreroute [APIC] Disable workaround that uses the
3027 boot IRQ equivalent of an IRQ that connects to
3028 a chipset where boot IRQs cannot be disabled.
3029 The opposite of ioapicreroute.
3030 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3031 routing table. These calls are known to be buggy
3032 on several machines and they hang the machine
3033 when used, but on other computers it's the only
3034 way to get the interrupt routing table. Try
3035 this option if the kernel is unable to allocate
3036 IRQs or discover secondary PCI buses on your
3038 rom [X86] Assign address space to expansion ROMs.
3039 Use with caution as certain devices share
3040 address decoders between ROMs and other
3042 norom [X86] Do not assign address space to
3043 expansion ROMs that do not already have
3044 BIOS assigned address ranges.
3045 nobar [X86] Do not assign address space to the
3046 BARs that weren't assigned by the BIOS.
3047 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3048 assigned automatically to PCI devices. You can
3049 make the kernel exclude IRQs of your ISA cards
3051 pirqaddr=0xAAAAA [X86] Specify the physical address
3052 of the PIRQ table (normally generated
3053 by the BIOS) if it is outside the
3054 F0000h-100000h range.
3055 lastbus=N [X86] Scan all buses thru bus #N. Can be
3056 useful if the kernel is unable to find your
3057 secondary buses and you want to tell it
3058 explicitly which ones they are.
3059 assign-busses [X86] Always assign all PCI bus
3060 numbers ourselves, overriding
3061 whatever the firmware may have done.
3062 usepirqmask [X86] Honor the possible IRQ mask stored
3063 in the BIOS $PIR table. This is needed on
3064 some systems with broken BIOSes, notably
3065 some HP Pavilion N5400 and Omnibook XE3
3066 notebooks. This will have no effect if ACPI
3067 IRQ routing is enabled.
3068 noacpi [X86] Do not use ACPI for IRQ routing
3069 or for PCI scanning.
3070 use_crs [X86] Use PCI host bridge window information
3071 from ACPI. On BIOSes from 2008 or later, this
3072 is enabled by default. If you need to use this,
3073 please report a bug.
3074 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3075 If you need to use this, please report a bug.
3076 routeirq Do IRQ routing for all PCI devices.
3077 This is normally done in pci_enable_device(),
3078 so this option is a temporary workaround
3079 for broken drivers that don't call it.
3080 skip_isa_align [X86] do not align io start addr, so can
3081 handle more pci cards
3082 noearly [X86] Don't do any early type 1 scanning.
3083 This might help on some broken boards which
3084 machine check when some devices' config space
3085 is read. But various workarounds are disabled
3086 and some IOMMU drivers will not work.
3087 bfsort Sort PCI devices into breadth-first order.
3088 This sorting is done to get a device
3089 order compatible with older (<= 2.4) kernels.
3090 nobfsort Don't sort PCI devices into breadth-first order.
3091 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3092 tuning and use the BIOS-configured MPS defaults.
3093 pcie_bus_safe Set every device's MPS to the largest value
3094 supported by all devices below the root complex.
3095 pcie_bus_perf Set device MPS to the largest allowable MPS
3096 based on its parent bus. Also set MRRS (Max
3097 Read Request Size) to the largest supported
3098 value (no larger than the MPS that the device
3099 or bus can support) for best performance.
3100 pcie_bus_peer2peer Set every device's MPS to 128B, which
3101 every device is guaranteed to support. This
3102 configuration allows peer-to-peer DMA between
3103 any pair of devices, possibly at the cost of
3104 reduced performance. This also guarantees
3105 that hot-added devices will work.
3106 cbiosize=nn[KMG] The fixed amount of bus space which is
3107 reserved for the CardBus bridge's IO window.
3108 The default value is 256 bytes.
3109 cbmemsize=nn[KMG] The fixed amount of bus space which is
3110 reserved for the CardBus bridge's memory
3111 window. The default value is 64 megabytes.
3114 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3115 [<order of align>@]pci:<vendor>:<device>\
3116 [:<subvendor>:<subdevice>][; ...]
3117 Specifies alignment and device to reassign
3118 aligned memory resources.
3119 If <order of align> is not specified,
3120 PAGE_SIZE is used as alignment.
3121 PCI-PCI bridge can be specified, if resource
3122 windows need to be expanded.
3123 To specify the alignment for several
3124 instances of a device, the PCI vendor,
3125 device, subvendor, and subdevice may be
3126 specified, e.g., 4096@pci:8086:9c22:103c:198f
3127 ecrc= Enable/disable PCIe ECRC (transaction layer
3128 end-to-end CRC checking).
3129 bios: Use BIOS/firmware settings. This is the
3133 hpiosize=nn[KMG] The fixed amount of bus space which is
3134 reserved for hotplug bridge's IO window.
3135 Default size is 256 bytes.
3136 hpmemsize=nn[KMG] The fixed amount of bus space which is
3137 reserved for hotplug bridge's memory window.
3138 Default size is 2 megabytes.
3139 hpbussize=nn The minimum amount of additional bus numbers
3140 reserved for buses below a hotplug bridge.
3142 realloc= Enable/disable reallocating PCI bridge resources
3143 if allocations done by BIOS are too small to
3144 accommodate resources required by all child
3146 off: Turn realloc off
3148 realloc same as realloc=on
3149 noari do not use PCIe ARI.
3150 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3151 only look for one device below a PCIe downstream
3153 big_root_window Try to add a big 64bit memory window to the PCIe
3154 root complex on AMD CPUs. Some GFX hardware
3155 can resize a BAR to allow access to all VRAM.
3156 Adding the window is slightly risky (it may
3157 conflict with unreported devices), so this
3160 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3163 force Enable ASPM even on devices that claim not to support it.
3164 WARNING: Forcing ASPM on may cause system lockups.
3166 pcie_ports= [PCIE] PCIe port services handling:
3167 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
3168 even if the platform doesn't give the OS permission to
3169 use them. This may cause conflicts if the platform
3170 also tries to use these services.
3171 compat Disable native PCIe services (PME, AER, DPC, PCIe
3174 pcie_port_pm= [PCIE] PCIe port power management handling:
3175 off Disable power management of all PCIe ports
3176 force Forcibly enable power management of all PCIe ports
3178 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3179 nomsi Do not use MSI for native PCIe PME signaling (this makes
3180 all PCIe root ports use INTx for all services).
3182 pcmv= [HW,PCMCIA] BadgePAD 4
3186 Keep all power-domains already enabled by bootloader on,
3187 even if no driver has claimed them. This is useful
3188 for debug and development, but should not be
3189 needed on a platform with proper driver support.
3192 See Documentation/blockdev/paride.txt.
3194 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3197 See arch/parisc/kernel/pdc_chassis.c
3199 percpu_alloc= Select which percpu first chunk allocator to use.
3200 Currently supported values are "embed" and "page".
3201 Archs may support subset or none of the selections.
3202 See comments in mm/percpu.c for details on each
3203 allocator. This parameter is primarily for debugging
3204 and performance comparison.
3207 See Documentation/blockdev/paride.txt.
3210 See Documentation/blockdev/paride.txt.
3212 pirq= [SMP,APIC] Manual mp-table setup
3213 See Documentation/x86/i386/IO-APIC.txt.
3215 plip= [PPT,NET] Parallel port network link
3216 Format: { parport<nr> | timid | 0 }
3217 See also Documentation/admin-guide/parport.rst.
3219 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3220 Override pmtimer IOPort with a hex value.
3224 Enable PNP debug messages (depends on the
3225 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3226 via /sys/module/pnp/parameters/debug. We always show
3227 current resource usage; turning this on also shows
3228 possible settings and some assignment information.
3234 { on | off | curr | res | no-curr | no-res }
3237 [ISAPNP] Exclude IRQs for the autoconfiguration
3240 [ISAPNP] Exclude DMAs for the autoconfiguration
3242 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3243 Ranges are in pairs (I/O port base and size).
3246 [ISAPNP] Exclude memory regions for the
3248 Ranges are in pairs (memory base and size).
3250 ports= [IP_VS_FTP] IPVS ftp helper module
3252 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3254 Format: <port>,<port>....
3256 powersave=off [PPC] This option disables power saving features.
3257 It specifically disables cpuidle and sets the
3258 platform machine description specific power_save
3259 function to NULL. On Idle the CPU just reduces
3262 ppc_strict_facility_enable
3263 [PPC] This option catches any kernel floating point,
3264 Altivec, VSX and SPE outside of regions specifically
3265 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3266 There is some performance impact when enabling this.
3270 Disable Hardware Transactional Memory
3272 print-fatal-signals=
3273 [KNL] debug: print fatal signals
3275 If enabled, warn about various signal handling
3276 related application anomalies: too many signals,
3277 too many POSIX.1 timers, fatal signals causing a
3280 If you hit the warning due to signal overflow,
3281 you might want to try "ulimit -i unlimited".
3285 printk.always_kmsg_dump=
3286 Trigger kmsg_dump for cases other than kernel oops or
3288 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3291 printk.devkmsg={on,off,ratelimit}
3292 Control writing to /dev/kmsg.
3293 on - unlimited logging to /dev/kmsg from userspace
3294 off - logging to /dev/kmsg disabled
3295 ratelimit - ratelimit the logging
3298 printk.time= Show timing data prefixed to each printk message line
3299 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3301 processor.max_cstate= [HW,ACPI]
3302 Limit processor to maximum C-state
3303 max_cstate=9 overrides any DMI blacklist limit.
3305 processor.nocst [HW,ACPI]
3306 Ignore the _CST method to determine C-states,
3307 instead using the legacy FADT method
3309 profile= [KNL] Enable kernel profiling via /proc/profile
3310 Format: [<profiletype>,]<number>
3311 Param: <profiletype>: "schedule", "sleep", or "kvm"
3312 [defaults to kernel profiling]
3313 Param: "schedule" - profile schedule points.
3314 Param: "sleep" - profile D-state sleeping (millisecs).
3315 Requires CONFIG_SCHEDSTATS
3316 Param: "kvm" - profile VM exits.
3317 Param: <number> - step/bucket size as a power of 2 for
3318 statistical time based profiling.
3320 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3322 See Documentation/blockdev/ramdisk.txt.
3324 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3325 probe for; one of (bare|imps|exps|lifebook|any).
3326 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3328 psmouse.resetafter= [HW,MOUSE]
3329 Try to reset the device after so many bad packets
3332 [HW,MOUSE] Set desired mouse resolution, in dpi.
3333 psmouse.smartscroll=
3334 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3335 0 = disabled, 1 = enabled (default).
3337 pstore.backend= Specify the name of the pstore backend to use
3340 See Documentation/blockdev/paride.txt.
3342 pti= [X86_64] Control Page Table Isolation of user and
3343 kernel address spaces. Disabling this feature
3344 removes hardening, but improves performance of
3345 system calls and interrupts.
3347 on - unconditionally enable
3348 off - unconditionally disable
3349 auto - kernel detects whether your CPU model is
3350 vulnerable to issues that PTI mitigates
3352 Not specifying this option is equivalent to pti=auto.
3355 Equivalent to pti=off
3358 [KNL] Number of legacy pty's. Overwrites compiled-in
3361 quiet [KNL] Disable most log messages
3366 See Documentation/admin-guide/md.rst.
3368 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3369 See Documentation/blockdev/ramdisk.txt.
3371 ras=option[,option,...] [KNL] RAS-specific options
3374 Disable the Correctable Errors Collector,
3375 see CONFIG_RAS_CEC help text.
3378 The argument is a cpu list, as described above.
3380 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3381 the specified list of CPUs to be no-callback CPUs.
3382 Invocation of these CPUs' RCU callbacks will
3383 be offloaded to "rcuox/N" kthreads created for
3384 that purpose, where "x" is "b" for RCU-bh, "p"
3385 for RCU-preempt, and "s" for RCU-sched, and "N"
3386 is the CPU number. This reduces OS jitter on the
3387 offloaded CPUs, which can be useful for HPC and
3388 real-time workloads. It can also improve energy
3389 efficiency for asymmetric multiprocessors.
3392 Rather than requiring that offloaded CPUs
3393 (specified by rcu_nocbs= above) explicitly
3394 awaken the corresponding "rcuoN" kthreads,
3395 make these kthreads poll for callbacks.
3396 This improves the real-time response for the
3397 offloaded CPUs by relieving them of the need to
3398 wake up the corresponding kthread, but degrades
3399 energy efficiency by requiring that the kthreads
3400 periodically wake up to do the polling.
3402 rcutree.blimit= [KNL]
3403 Set maximum number of finished RCU callbacks to
3404 process in one batch.
3406 rcutree.dump_tree= [KNL]
3407 Dump the structure of the rcu_node combining tree
3408 out at early boot. This is used for diagnostic
3409 purposes, to verify correct tree setup.
3411 rcutree.gp_cleanup_delay= [KNL]
3412 Set the number of jiffies to delay each step of
3413 RCU grace-period cleanup.
3415 rcutree.gp_init_delay= [KNL]
3416 Set the number of jiffies to delay each step of
3417 RCU grace-period initialization.
3419 rcutree.gp_preinit_delay= [KNL]
3420 Set the number of jiffies to delay each step of
3421 RCU grace-period pre-initialization, that is,
3422 the propagation of recent CPU-hotplug changes up
3423 the rcu_node combining tree.
3425 rcutree.rcu_fanout_exact= [KNL]
3426 Disable autobalancing of the rcu_node combining
3427 tree. This is used by rcutorture, and might
3428 possibly be useful for architectures having high
3429 cache-to-cache transfer latencies.
3431 rcutree.rcu_fanout_leaf= [KNL]
3432 Change the number of CPUs assigned to each
3433 leaf rcu_node structure. Useful for very
3434 large systems, which will choose the value 64,
3435 and for NUMA systems with large remote-access
3436 latencies, which will choose a value aligned
3437 with the appropriate hardware boundaries.
3439 rcutree.jiffies_till_sched_qs= [KNL]
3440 Set required age in jiffies for a
3441 given grace period before RCU starts
3442 soliciting quiescent-state help from
3443 rcu_note_context_switch().
3445 rcutree.jiffies_till_first_fqs= [KNL]
3446 Set delay from grace-period initialization to
3447 first attempt to force quiescent states.
3448 Units are jiffies, minimum value is zero,
3449 and maximum value is HZ.
3451 rcutree.jiffies_till_next_fqs= [KNL]
3452 Set delay between subsequent attempts to force
3453 quiescent states. Units are jiffies, minimum
3454 value is one, and maximum value is HZ.
3456 rcutree.kthread_prio= [KNL,BOOT]
3457 Set the SCHED_FIFO priority of the RCU per-CPU
3458 kthreads (rcuc/N). This value is also used for
3459 the priority of the RCU boost threads (rcub/N)
3460 and for the RCU grace-period kthreads (rcu_bh,
3461 rcu_preempt, and rcu_sched). If RCU_BOOST is
3462 set, valid values are 1-99 and the default is 1
3463 (the least-favored priority). Otherwise, when
3464 RCU_BOOST is not set, valid values are 0-99 and
3465 the default is zero (non-realtime operation).
3467 rcutree.rcu_nocb_leader_stride= [KNL]
3468 Set the number of NOCB kthread groups, which
3469 defaults to the square root of the number of
3470 CPUs. Larger numbers reduces the wakeup overhead
3471 on the per-CPU grace-period kthreads, but increases
3472 that same overhead on each group's leader.
3474 rcutree.qhimark= [KNL]
3475 Set threshold of queued RCU callbacks beyond which
3476 batch limiting is disabled.
3478 rcutree.qlowmark= [KNL]
3479 Set threshold of queued RCU callbacks below which
3480 batch limiting is re-enabled.
3482 rcutree.rcu_idle_gp_delay= [KNL]
3483 Set wakeup interval for idle CPUs that have
3484 RCU callbacks (RCU_FAST_NO_HZ=y).
3486 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3487 Set wakeup interval for idle CPUs that have
3488 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3489 Lazy RCU callbacks are those which RCU can
3490 prove do nothing more than free memory.
3492 rcutree.rcu_kick_kthreads= [KNL]
3493 Cause the grace-period kthread to get an extra
3494 wake_up() if it sleeps three times longer than
3495 it should at force-quiescent-state time.
3496 This wake_up() will be accompanied by a
3497 WARN_ONCE() splat and an ftrace_dump().
3499 rcuperf.gp_async= [KNL]
3500 Measure performance of asynchronous
3501 grace-period primitives such as call_rcu().
3503 rcuperf.gp_async_max= [KNL]
3504 Specify the maximum number of outstanding
3505 callbacks per writer thread. When a writer
3506 thread exceeds this limit, it invokes the
3507 corresponding flavor of rcu_barrier() to allow
3508 previously posted callbacks to drain.
3510 rcuperf.gp_exp= [KNL]
3511 Measure performance of expedited synchronous
3512 grace-period primitives.
3514 rcuperf.holdoff= [KNL]
3515 Set test-start holdoff period. The purpose of
3516 this parameter is to delay the start of the
3517 test until boot completes in order to avoid
3520 rcuperf.nreaders= [KNL]
3521 Set number of RCU readers. The value -1 selects
3522 N, where N is the number of CPUs. A value
3523 "n" less than -1 selects N-n+1, where N is again
3524 the number of CPUs. For example, -2 selects N
3525 (the number of CPUs), -3 selects N+1, and so on.
3526 A value of "n" less than or equal to -N selects
3529 rcuperf.nwriters= [KNL]
3530 Set number of RCU writers. The values operate
3531 the same as for rcuperf.nreaders.
3532 N, where N is the number of CPUs
3534 rcuperf.perf_type= [KNL]
3535 Specify the RCU implementation to test.
3537 rcuperf.shutdown= [KNL]
3538 Shut the system down after performance tests
3539 complete. This is useful for hands-off automated
3542 rcuperf.verbose= [KNL]
3543 Enable additional printk() statements.
3545 rcuperf.writer_holdoff= [KNL]
3546 Write-side holdoff between grace periods,
3547 in microseconds. The default of zero says
3550 rcutorture.cbflood_inter_holdoff= [KNL]
3551 Set holdoff time (jiffies) between successive
3552 callback-flood tests.
3554 rcutorture.cbflood_intra_holdoff= [KNL]
3555 Set holdoff time (jiffies) between successive
3556 bursts of callbacks within a given callback-flood
3559 rcutorture.cbflood_n_burst= [KNL]
3560 Set the number of bursts making up a given
3561 callback-flood test. Set this to zero to
3562 disable callback-flood testing.
3564 rcutorture.cbflood_n_per_burst= [KNL]
3565 Set the number of callbacks to be registered
3566 in a given burst of a callback-flood test.
3568 rcutorture.fqs_duration= [KNL]
3569 Set duration of force_quiescent_state bursts
3572 rcutorture.fqs_holdoff= [KNL]
3573 Set holdoff time within force_quiescent_state bursts
3576 rcutorture.fqs_stutter= [KNL]
3577 Set wait time between force_quiescent_state bursts
3580 rcutorture.gp_cond= [KNL]
3581 Use conditional/asynchronous update-side
3582 primitives, if available.
3584 rcutorture.gp_exp= [KNL]
3585 Use expedited update-side primitives, if available.
3587 rcutorture.gp_normal= [KNL]
3588 Use normal (non-expedited) asynchronous
3589 update-side primitives, if available.
3591 rcutorture.gp_sync= [KNL]
3592 Use normal (non-expedited) synchronous
3593 update-side primitives, if available. If all
3594 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3595 rcutorture.gp_normal=, and rcutorture.gp_sync=
3596 are zero, rcutorture acts as if is interpreted
3597 they are all non-zero.
3599 rcutorture.n_barrier_cbs= [KNL]
3600 Set callbacks/threads for rcu_barrier() testing.
3602 rcutorture.nfakewriters= [KNL]
3603 Set number of concurrent RCU writers. These just
3604 stress RCU, they don't participate in the actual
3605 test, hence the "fake".
3607 rcutorture.nreaders= [KNL]
3608 Set number of RCU readers. The value -1 selects
3609 N-1, where N is the number of CPUs. A value
3610 "n" less than -1 selects N-n-2, where N is again
3611 the number of CPUs. For example, -2 selects N
3612 (the number of CPUs), -3 selects N+1, and so on.
3614 rcutorture.object_debug= [KNL]
3615 Enable debug-object double-call_rcu() testing.
3617 rcutorture.onoff_holdoff= [KNL]
3618 Set time (s) after boot for CPU-hotplug testing.
3620 rcutorture.onoff_interval= [KNL]
3621 Set time (s) between CPU-hotplug operations, or
3622 zero to disable CPU-hotplug testing.
3624 rcutorture.shuffle_interval= [KNL]
3625 Set task-shuffle interval (s). Shuffling tasks
3626 allows some CPUs to go into dyntick-idle mode
3627 during the rcutorture test.
3629 rcutorture.shutdown_secs= [KNL]
3630 Set time (s) after boot system shutdown. This
3631 is useful for hands-off automated testing.
3633 rcutorture.stall_cpu= [KNL]
3634 Duration of CPU stall (s) to test RCU CPU stall
3635 warnings, zero to disable.
3637 rcutorture.stall_cpu_holdoff= [KNL]
3638 Time to wait (s) after boot before inducing stall.
3640 rcutorture.stall_cpu_irqsoff= [KNL]
3641 Disable interrupts while stalling if set.
3643 rcutorture.stat_interval= [KNL]
3644 Time (s) between statistics printk()s.
3646 rcutorture.stutter= [KNL]
3647 Time (s) to stutter testing, for example, specifying
3648 five seconds causes the test to run for five seconds,
3649 wait for five seconds, and so on. This tests RCU's
3650 ability to transition abruptly to and from idle.
3652 rcutorture.test_boost= [KNL]
3653 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3654 "Maybe" means test if the RCU implementation
3655 under test support RCU priority boosting.
3657 rcutorture.test_boost_duration= [KNL]
3658 Duration (s) of each individual boost test.
3660 rcutorture.test_boost_interval= [KNL]
3661 Interval (s) between each boost test.
3663 rcutorture.test_no_idle_hz= [KNL]
3664 Test RCU's dyntick-idle handling. See also the
3665 rcutorture.shuffle_interval parameter.
3667 rcutorture.torture_type= [KNL]
3668 Specify the RCU implementation to test.
3670 rcutorture.verbose= [KNL]
3671 Enable additional printk() statements.
3673 rcupdate.rcu_cpu_stall_suppress= [KNL]
3674 Suppress RCU CPU stall warning messages.
3676 rcupdate.rcu_cpu_stall_timeout= [KNL]
3677 Set timeout for RCU CPU stall warning messages.
3679 rcupdate.rcu_expedited= [KNL]
3680 Use expedited grace-period primitives, for
3681 example, synchronize_rcu_expedited() instead
3682 of synchronize_rcu(). This reduces latency,
3683 but can increase CPU utilization, degrade
3684 real-time latency, and degrade energy efficiency.
3685 No effect on CONFIG_TINY_RCU kernels.
3687 rcupdate.rcu_normal= [KNL]
3688 Use only normal grace-period primitives,
3689 for example, synchronize_rcu() instead of
3690 synchronize_rcu_expedited(). This improves
3691 real-time latency, CPU utilization, and
3692 energy efficiency, but can expose users to
3693 increased grace-period latency. This parameter
3694 overrides rcupdate.rcu_expedited. No effect on
3695 CONFIG_TINY_RCU kernels.
3697 rcupdate.rcu_normal_after_boot= [KNL]
3698 Once boot has completed (that is, after
3699 rcu_end_inkernel_boot() has been invoked), use
3700 only normal grace-period primitives. No effect
3701 on CONFIG_TINY_RCU kernels.
3703 rcupdate.rcu_task_stall_timeout= [KNL]
3704 Set timeout in jiffies for RCU task stall warning
3705 messages. Disable with a value less than or equal
3708 rcupdate.rcu_self_test= [KNL]
3709 Run the RCU early boot self tests
3711 rcupdate.rcu_self_test_bh= [KNL]
3712 Run the RCU bh early boot self tests
3714 rcupdate.rcu_self_test_sched= [KNL]
3715 Run the RCU sched early boot self tests
3719 Run specified binary instead of /init from the ramdisk,
3720 used for early userspace startup. See initrd.
3723 Turn on/off individual RDT features. List is:
3724 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
3726 E.g. to turn on cmt and turn off mba use:
3730 Format (x86 or x86_64):
3731 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3733 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3735 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3736 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3737 reboot_force is either force or not specified,
3738 reboot_cpu is s[mp]#### with #### being the processor
3739 to be used for rebooting.
3742 [KNL, SMP] Set scheduler's default relax_domain_level.
3743 See Documentation/cgroup-v1/cpusets.txt.
3745 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
3746 Format: <base1>,<size1>[,<base2>,<size2>,...]
3747 Reserve I/O ports or memory so the kernel won't use
3748 them. If <base> is less than 0x10000, the region
3749 is assumed to be I/O ports; otherwise it is memory.
3751 reservetop= [X86-32]
3753 Reserves a hole at the top of the kernel virtual
3758 Set the amount of memory to reserve for BIOS at
3759 the bottom of the address space.
3761 reset_devices [KNL] Force drivers to reset the underlying device
3762 during initialization.
3765 Specify the partition device for software suspend
3767 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3769 resume_offset= [SWSUSP]
3770 Specify the offset from the beginning of the partition
3771 given by "resume=" at which the swap header is located,
3772 in <PAGE_SIZE> units (needed only for swap files).
3773 See Documentation/power/swsusp-and-swap-files.txt
3775 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3776 read the resume files
3778 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3779 Useful for devices that are detected asynchronously
3780 (e.g. USB and MMC devices).
3782 hibernate= [HIBERNATION]
3783 noresume Don't check if there's a hibernation image
3784 present during boot.
3785 nocompress Don't compress/decompress hibernation images.
3786 no Disable hibernation and resume.
3787 protect_image Turn on image protection during restoration
3788 (that will set all pages holding image data
3789 during restoration read-only).
3791 retain_initrd [RAM] Keep initrd memory after extraction
3793 rfkill.default_state=
3794 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3795 etc. communication is blocked by default.
3798 rfkill.master_switch_mode=
3799 0 The "airplane mode" button does nothing.
3800 1 The "airplane mode" button toggles between everything
3801 blocked and the previous configuration.
3802 2 The "airplane mode" button toggles between everything
3803 blocked and everything unblocked.
3805 rhash_entries= [KNL,NET]
3806 Set number of hash buckets for route cache
3809 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3812 ro [KNL] Mount root device read-only on boot
3815 on Mark read-only kernel memory as read-only (default).
3816 off Leave read-only kernel memory writable for debugging.
3819 Enable the uart passthrough on the designated usb port
3820 on Rockchip SoCs. When active, the signals of the
3821 debug-uart get routed to the D+ and D- pins of the usb
3822 port and the regular usb controller gets disabled.
3824 root= [KNL] Root filesystem
3825 See name_to_dev_t comment in init/do_mounts.c.
3827 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3828 mount the root filesystem
3830 rootflags= [KNL] Set root filesystem mount option string
3832 rootfstype= [KNL] Set root filesystem type
3834 rootwait [KNL] Wait (indefinitely) for root device to show up.
3835 Useful for devices that are detected asynchronously
3836 (e.g. USB and MMC devices).
3838 rproc_mem=nn[KMG][@address]
3839 [KNL,ARM,CMA] Remoteproc physical memory block.
3840 Memory area to be used by remote processor image,
3843 rw [KNL] Mount root device read-write on boot
3845 S [KNL] Run init in single mode
3847 s390_iommu= [HW,S390]
3848 Set s390 IOTLB flushing mode
3850 With strict flushing every unmap operation will result in
3851 an IOTLB flush. Default is lazy flushing before reuse,
3855 See drivers/net/irda/sa1100_ir.c.
3857 sbni= [NET] Granch SBNI12 leased line adapter
3859 sched_debug [KNL] Enables verbose scheduler debug messages.
3861 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3862 Allowed values are enable and disable. This feature
3863 incurs a small amount of overhead in the scheduler
3864 but is useful for debugging and performance tuning.
3866 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3867 xtime_lock contention on larger systems, and/or RCU lock
3868 contention on all systems with CONFIG_MAXSMP set.
3869 Format: { "0" | "1" }
3870 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3872 Note: increases power consumption, thus should only be
3873 enabled if running jitter sensitive (HPC/RT) workloads.
3875 security= [SECURITY] Choose a security module to enable at boot.
3876 If this boot parameter is not specified, only the first
3877 security module asking for security registration will be
3878 loaded. An invalid security module name will be treated
3879 as if no module has been chosen.
3881 selinux= [SELINUX] Disable or enable SELinux at boot time.
3882 Format: { "0" | "1" }
3883 See security/selinux/Kconfig help text.
3886 Default value is set via kernel config option.
3887 If enabled at boot time, /selinux/disable can be used
3888 later to disable prior to initial policy load.
3890 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3891 Format: { "0" | "1" }
3892 See security/apparmor/Kconfig help text
3895 Default value is set via kernel config option.
3897 serialnumber [BUGS=X86-32]
3900 Maximal number of shapers.
3908 Disable merging of slabs with similar size. May be
3909 necessary if there is some reason to distinguish
3910 allocs to different slabs, especially in hardened
3911 environments where the risk of heap overflows and
3912 layout control by attackers can usually be
3913 frustrated by disabling merging. This will reduce
3914 most of the exposure of a heap attack to a single
3915 cache (risks via metadata attacks are mostly
3916 unchanged). Debug options disable merging on their
3918 For more information see Documentation/vm/slub.txt.
3920 slab_max_order= [MM, SLAB]
3921 Determines the maximum allowed order for slabs.
3922 A high setting may cause OOMs due to memory
3923 fragmentation. Defaults to 1 for systems with
3924 more than 32MB of RAM, 0 otherwise.
3926 slub_debug[=options[,slabs]] [MM, SLUB]
3927 Enabling slub_debug allows one to determine the
3928 culprit if slab objects become corrupted. Enabling
3929 slub_debug can create guard zones around objects and
3930 may poison objects when not in use. Also tracks the
3931 last alloc / free. For more information see
3932 Documentation/vm/slub.txt.
3934 slub_memcg_sysfs= [MM, SLUB]
3935 Determines whether to enable sysfs directories for
3936 memory cgroup sub-caches. 1 to enable, 0 to disable.
3937 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3938 Enabling this can lead to a very high number of debug
3939 directories and files being created under
3942 slub_max_order= [MM, SLUB]
3943 Determines the maximum allowed order for slabs.
3944 A high setting may cause OOMs due to memory
3945 fragmentation. For more information see
3946 Documentation/vm/slub.txt.
3948 slub_min_objects= [MM, SLUB]
3949 The minimum number of objects per slab. SLUB will
3950 increase the slab order up to slub_max_order to
3951 generate a sufficiently large slab able to contain
3952 the number of objects indicated. The higher the number
3953 of objects the smaller the overhead of tracking slabs
3954 and the less frequently locks need to be acquired.
3955 For more information see Documentation/vm/slub.txt.
3957 slub_min_order= [MM, SLUB]
3958 Determines the minimum page order for slabs. Must be
3959 lower than slub_max_order.
3960 For more information see Documentation/vm/slub.txt.
3962 slub_nomerge [MM, SLUB]
3963 Same with slab_nomerge. This is supported for legacy.
3964 See slab_nomerge for more information.
3967 Format: <io1>[,<io2>[,...,<io8>]]
3969 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3970 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3971 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3972 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3973 smsc-ircc2.ircc_irq= [HW] IRQ line
3974 smsc-ircc2.ircc_dma= [HW] DMA channel
3975 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3976 0: Toshiba Satellite 1800 (GP data pin select)
3977 1: Fast pin select (default)
3980 smt [KNL,S390] Set the maximum number of threads (logical
3981 CPUs) to use per physical CPU on systems capable of
3982 symmetric multithreading (SMT). Will be capped to the
3983 actual hardware limit.
3985 Default: -1 (no limit)
3988 [KNL] Should the soft-lockup detector generate panics.
3991 A nonzero value instructs the soft-lockup detector
3992 to panic the machine when a soft-lockup occurs. This
3993 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
3994 which is the respective build-time switch to that
3997 softlockup_all_cpu_backtrace=
3998 [KNL] Should the soft-lockup detector generate
3999 backtraces on all cpus.
4002 sonypi.*= [HW] Sony Programmable I/O Control Device driver
4003 See Documentation/laptops/sonypi.txt
4005 spectre_v2= [X86] Control mitigation of Spectre variant 2
4006 (indirect branch speculation) vulnerability.
4008 on - unconditionally enable
4009 off - unconditionally disable
4010 auto - kernel detects whether your CPU model is
4013 Selecting 'on' will, and 'auto' may, choose a
4014 mitigation method at run time according to the
4015 CPU, the available microcode, the setting of the
4016 CONFIG_RETPOLINE configuration option, and the
4017 compiler with which the kernel was built.
4019 Specific mitigations can also be selected manually:
4021 retpoline - replace indirect branches
4022 retpoline,generic - google's original retpoline
4023 retpoline,amd - AMD-specific minimal thunk
4025 Not specifying this option is equivalent to
4028 spia_io_base= [HW,MTD]
4033 srcutree.counter_wrap_check [KNL]
4034 Specifies how frequently to check for
4035 grace-period sequence counter wrap for the
4036 srcu_data structure's ->srcu_gp_seq_needed field.
4037 The greater the number of bits set in this kernel
4038 parameter, the less frequently counter wrap will
4039 be checked for. Note that the bottom two bits
4042 srcutree.exp_holdoff [KNL]
4043 Specifies how many nanoseconds must elapse
4044 since the end of the last SRCU grace period for
4045 a given srcu_struct until the next normal SRCU
4046 grace period will be considered for automatic
4047 expediting. Set to zero to disable automatic
4050 stack_guard_gap= [MM]
4051 override the default stack gap protection. The value
4052 is in page units and it defines how many pages prior
4053 to (for stacks growing down) resp. after (for stacks
4054 growing up) the main stack are reserved for no other
4055 mapping. Default value is 256 pages.
4058 Enabled the stack tracer on boot up.
4060 stacktrace_filter=[function-list]
4061 [FTRACE] Limit the functions that the stack tracer
4062 will trace at boot up. function-list is a comma separated
4063 list of functions. This list can be changed at run
4064 time by the stack_trace_filter file in the debugfs
4065 tracing directory. Note, this enables stack tracing
4066 and the stacktrace above is not needed.
4070 Set the STI (builtin display/keyboard on the HP-PARISC
4071 machines) console (graphic card) which should be used
4072 as the initial boot-console.
4073 See also comment in drivers/video/console/sticore.c.
4076 See comment in drivers/video/console/sticore.c.
4079 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
4081 sunrpc.min_resvport=
4082 sunrpc.max_resvport=
4084 SunRPC servers often require that client requests
4085 originate from a privileged port (i.e. a port in the
4086 range 0 < portnr < 1024).
4087 An administrator who wishes to reserve some of these
4088 ports for other uses may adjust the range that the
4089 kernel's sunrpc client considers to be privileged
4090 using these two parameters to set the minimum and
4091 maximum port values.
4093 sunrpc.svc_rpc_per_connection_limit=
4095 Limit the number of requests that the server will
4096 process in parallel from a single connection.
4097 The default value is 0 (no limit).
4101 Control how the NFS server code allocates CPUs to
4102 service thread pools. Depending on how many NICs
4103 you have and where their interrupts are bound, this
4104 option will affect which CPUs will do NFS serving.
4105 Note: this parameter cannot be changed while the
4106 NFS server is running.
4108 auto the server chooses an appropriate mode
4109 automatically using heuristics
4110 global a single global pool contains all CPUs
4111 percpu one pool for each CPU
4112 pernode one pool for each NUMA node (equivalent
4113 to global on non-NUMA machines)
4115 sunrpc.tcp_slot_table_entries=
4116 sunrpc.udp_slot_table_entries=
4118 Sets the upper limit on the number of simultaneous
4119 RPC calls that can be sent from the client to a
4120 server. Increasing these values may allow you to
4121 improve throughput, but will also increase the
4122 amount of memory reserved for use by the client.
4124 suspend.pm_test_delay=
4126 Sets the number of seconds to remain in a suspend test
4127 mode before resuming the system (see
4128 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4129 is set. Default value is 5.
4132 [KNL] Enable accounting of swap in memory resource
4133 controller if no parameter or 1 is given or disable
4134 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4136 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
4137 Format: { <int> | force | noforce }
4138 <int> -- Number of I/O TLB slabs
4139 force -- force using of bounce buffers even if they
4140 wouldn't be automatically used by the kernel
4141 noforce -- Never use bounce buffers (for debugging)
4145 sysfs.deprecated=0|1 [KNL]
4146 Enable/disable old style sysfs layout for old udev
4147 on older distributions. When this option is enabled
4148 very new udev will not work anymore. When this option
4149 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4150 in older udev will not work anymore.
4151 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4152 the kernel configuration.
4154 sysrq_always_enabled
4156 Ignore sysrq setting - this boot parameter will
4157 neutralize any effect of /proc/sys/kernel/sysrq.
4158 Useful for debugging.
4160 tcpmhash_entries= [KNL,NET]
4161 Set the number of tcp_metrics_hash slots.
4162 Default value is 8192 or 16384 depending on total
4163 ram pages. This is used to specify the TCP metrics
4164 cache size. See Documentation/networking/ip-sysctl.txt
4165 "tcp_no_metrics_save" section for more details.
4169 test_suspend= [SUSPEND][,N]
4170 Specify "mem" (for Suspend-to-RAM) or "standby" (for
4171 standby suspend) or "freeze" (for suspend type freeze)
4172 as the system sleep state during system startup with
4173 the optional capability to repeat N number of times.
4174 The system is woken from this state using a
4175 wakeup-capable RTC alarm.
4177 thash_entries= [KNL,NET]
4178 Set number of hash buckets for TCP connection
4180 thermal.act= [HW,ACPI]
4181 -1: disable all active trip points in all thermal zones
4182 <degrees C>: override all lowest active trip points
4184 thermal.crt= [HW,ACPI]
4185 -1: disable all critical trip points in all thermal zones
4186 <degrees C>: override all critical trip points
4188 thermal.nocrt= [HW,ACPI]
4189 Set to disable actions on ACPI thermal zone
4190 critical and hot trip points.
4192 thermal.off= [HW,ACPI]
4193 1: disable ACPI thermal control
4195 thermal.psv= [HW,ACPI]
4196 -1: disable all passive trip points
4197 <degrees C>: override all passive trip points to this
4200 thermal.tzp= [HW,ACPI]
4201 Specify global default ACPI thermal zone polling rate
4202 <deci-seconds>: poll all this frequency
4203 0: no polling (default)
4206 Force threading of all interrupt handlers except those
4207 marked explicitly IRQF_NO_THREAD.
4210 Enable the Transcendent memory driver if built-in.
4212 tmem.cleancache=0|1 [KNL, XEN]
4213 Default is on (1). Disable the usage of the cleancache
4214 API to send anonymous pages to the hypervisor.
4216 tmem.frontswap=0|1 [KNL, XEN]
4217 Default is on (1). Disable the usage of the frontswap
4218 API to send swap pages to the hypervisor. If disabled
4219 the selfballooning and selfshrinking are force disabled.
4221 tmem.selfballooning=0|1 [KNL, XEN]
4222 Default is on (1). Disable the driving of swap pages
4225 tmem.selfshrinking=0|1 [KNL, XEN]
4226 Default is on (1). Partial swapoff that immediately
4227 transfers pages from Xen hypervisor back to the
4228 kernel based on different criteria.
4232 Specify if the kernel should make use of the cpu
4233 topology information if the hardware supports this.
4234 The scheduler will make use of this information and
4235 e.g. base its process migration decisions on it.
4238 topology_updates= [KNL, PPC, NUMA]
4240 Specify if the kernel should ignore (off)
4241 topology updates sent by the hypervisor to this
4246 tpm_suspend_pcr=[HW,TPM]
4247 Format: integer pcr id
4248 Specify that at suspend time, the tpm driver
4249 should extend the specified pcr with zeros,
4250 as a workaround for some chips which fail to
4251 flush the last written pcr on TPM_SaveState.
4252 This will guarantee that all the other pcrs
4255 trace_buf_size=nn[KMG]
4256 [FTRACE] will set tracing buffer size on each cpu.
4258 trace_event=[event-list]
4259 [FTRACE] Set and start specified trace events in order
4260 to facilitate early boot debugging. The event-list is a
4261 comma separated list of trace events to enable. See
4262 also Documentation/trace/events.txt
4264 trace_options=[option-list]
4265 [FTRACE] Enable or disable tracer options at boot.
4266 The option-list is a comma delimited list of options
4267 that can be enabled or disabled just as if you were
4268 to echo the option name into
4270 /sys/kernel/debug/tracing/trace_options
4272 For example, to enable stacktrace option (to dump the
4273 stack trace of each event), add to the command line:
4275 trace_options=stacktrace
4277 See also Documentation/trace/ftrace.txt "trace options"
4281 Have the tracepoints sent to printk as well as the
4282 tracing ring buffer. This is useful for early boot up
4283 where the system hangs or reboots and does not give the
4284 option for reading the tracing buffer or performing a
4285 ftrace_dump_on_oops.
4287 To turn off having tracepoints sent to printk,
4288 echo 0 > /proc/sys/kernel/tracepoint_printk
4289 Note, echoing 1 into this file without the
4290 tracepoint_printk kernel cmdline option has no effect.
4294 Having tracepoints sent to printk() and activating high
4295 frequency tracepoints such as irq or sched, can cause
4296 the system to live lock.
4299 [FTRACE] enable this option to disable tracing when a
4300 warning is hit. This turns off "tracing_on". Tracing can
4301 be enabled again by echoing '1' into the "tracing_on"
4302 file located in /sys/kernel/debug/tracing/
4304 This option is useful, as it disables the trace before
4305 the WARNING dump is called, which prevents the trace to
4306 be filled with content caused by the warning output.
4308 This option can also be set at run time via the sysctl
4309 option: kernel/traceoff_on_warning
4311 transparent_hugepage=
4313 Format: [always|madvise|never]
4314 Can be used to control the default behavior of the system
4315 with respect to transparent hugepages.
4316 See Documentation/vm/transhuge.txt for more details.
4318 tsc= Disable clocksource stability checks for TSC.
4320 [x86] reliable: mark tsc clocksource as reliable, this
4321 disables clocksource verification at runtime, as well
4322 as the stability checks done at bootup. Used to enable
4323 high-resolution timer mode on older hardware, and in
4324 virtualized environment.
4325 [x86] noirqtime: Do not use TSC to do irq accounting.
4326 Used to run time disable IRQ_TIME_ACCOUNTING on any
4327 platforms where RDTSC is slow and this accounting
4329 [x86] unstable: mark the TSC clocksource as unstable, this
4330 marks the TSC unconditionally unstable at bootup and
4331 avoids any further wobbles once the TSC watchdog notices.
4333 turbografx.map[2|3]= [HW,JOY]
4334 TurboGraFX parallel port interface
4336 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4337 See also Documentation/input/devices/joystick-parport.rst
4339 udbg-immortal [PPC] When debugging early kernel crashes that
4340 happen after console_init() and before a proper
4341 console driver takes over, this boot options might
4342 help "seeing" what's going on.
4344 uhash_entries= [KNL,NET]
4345 Set number of hash buckets for UDP/UDP-Lite connections
4348 [USB] Ignore overcurrent events (default N).
4349 Some badly-designed motherboards generate lots of
4350 bogus events, for ports that aren't wired to
4351 anything. Set this parameter to avoid log spamming.
4352 Note that genuine overcurrent events won't be
4356 [X86] Cause panic on unknown NMI.
4358 usbcore.authorized_default=
4359 [USB] Default USB device authorization:
4360 (default -1 = authorized except for wireless USB,
4361 0 = not authorized, 1 = authorized)
4363 usbcore.autosuspend=
4364 [USB] The autosuspend time delay (in seconds) used
4365 for newly-detected USB devices (default 2). This
4366 is the time required before an idle device will be
4367 autosuspended. Devices for which the delay is set
4368 to a negative value won't be autosuspended at all.
4370 usbcore.usbfs_snoop=
4371 [USB] Set to log all usbfs traffic (default 0 = off).
4373 usbcore.usbfs_snoop_max=
4374 [USB] Maximum number of bytes to snoop in each URB
4377 usbcore.blinkenlights=
4378 [USB] Set to cycle leds on hubs (default 0 = off).
4380 usbcore.old_scheme_first=
4381 [USB] Start with the old device initialization
4382 scheme (default 0 = off).
4384 usbcore.usbfs_memory_mb=
4385 [USB] Memory limit (in MB) for buffers allocated by
4386 usbfs (default = 16, 0 = max = 2047).
4388 usbcore.use_both_schemes=
4389 [USB] Try the other device initialization scheme
4390 if the first one fails (default 1 = enabled).
4392 usbcore.initial_descriptor_timeout=
4393 [USB] Specifies timeout for the initial 64-byte
4394 USB_REQ_GET_DESCRIPTOR request in milliseconds
4395 (default 5000 = 5.0 seconds).
4397 usbcore.nousb [USB] Disable the USB subsystem
4400 [USB] A list of quirk entries to augment the built-in
4401 usb core quirk list. List entries are separated by
4402 commas. Each entry has the form
4403 VendorID:ProductID:Flags. The IDs are 4-digit hex
4404 numbers and Flags is a set of letters. Each letter
4405 will change the built-in quirk; setting it if it is
4406 clear and clearing it if it is set. The letters have
4407 the following meanings:
4408 a = USB_QUIRK_STRING_FETCH_255 (string
4409 descriptors must not be fetched using
4411 b = USB_QUIRK_RESET_RESUME (device can't resume
4412 correctly so reset it instead);
4413 c = USB_QUIRK_NO_SET_INTF (device can't handle
4414 Set-Interface requests);
4415 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
4416 handle its Configuration or Interface
4418 e = USB_QUIRK_RESET (device can't be reset
4419 (e.g morph devices), don't use reset);
4420 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
4421 more interface descriptions than the
4422 bNumInterfaces count, and can't handle
4423 talking to these interfaces);
4424 g = USB_QUIRK_DELAY_INIT (device needs a pause
4425 during initialization, after we read
4426 the device descriptor);
4427 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
4428 high speed and super speed interrupt
4429 endpoints, the USB 2.0 and USB 3.0 spec
4430 require the interval in microframes (1
4431 microframe = 125 microseconds) to be
4432 calculated as interval = 2 ^
4434 Devices with this quirk report their
4435 bInterval as the result of this
4436 calculation instead of the exponent
4437 variable used in the calculation);
4438 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
4439 handle device_qualifier descriptor
4441 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
4442 generates spurious wakeup, ignore
4443 remote wakeup capability);
4444 k = USB_QUIRK_NO_LPM (device can't handle Link
4446 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
4447 (Device reports its bInterval as linear
4448 frames instead of the USB 2.0
4450 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
4451 to be disconnected before suspend to
4452 prevent spurious wakeup);
4453 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
4454 pause after every control message);
4455 Example: quirks=0781:5580:bk,0a5c:5834:gij
4458 [USBHID] The interval which mice are to be polled at.
4461 [USBHID] The interval which joysticks are to be polled at.
4464 [USBHID] The interval which keyboards are to be polled at.
4466 usb-storage.delay_use=
4467 [UMS] The delay in seconds before a new device is
4468 scanned for Logical Units (default 1).
4471 [UMS] A list of quirks entries to supplement or
4472 override the built-in unusual_devs list. List
4473 entries are separated by commas. Each entry has
4474 the form VID:PID:Flags where VID and PID are Vendor
4475 and Product ID values (4-digit hex numbers) and
4476 Flags is a set of characters, each corresponding
4477 to a common usb-storage quirk flag as follows:
4478 a = SANE_SENSE (collect more than 18 bytes
4480 b = BAD_SENSE (don't collect more than 18
4481 bytes of sense data);
4482 c = FIX_CAPACITY (decrease the reported
4483 device capacity by one sector);
4484 d = NO_READ_DISC_INFO (don't use
4485 READ_DISC_INFO command);
4486 e = NO_READ_CAPACITY_16 (don't use
4487 READ_CAPACITY_16 command);
4488 f = NO_REPORT_OPCODES (don't use report opcodes
4490 g = MAX_SECTORS_240 (don't transfer more than
4491 240 sectors at a time, uas only);
4492 h = CAPACITY_HEURISTICS (decrease the
4493 reported device capacity by one
4494 sector if the number is odd);
4495 i = IGNORE_DEVICE (don't bind to this
4497 j = NO_REPORT_LUNS (don't use report luns
4499 l = NOT_LOCKABLE (don't try to lock and
4500 unlock ejectable media);
4501 m = MAX_SECTORS_64 (don't transfer more
4502 than 64 sectors = 32 KB at a time);
4503 n = INITIAL_READ10 (force a retry of the
4504 initial READ(10) command);
4505 o = CAPACITY_OK (accept the capacity
4506 reported by the device);
4507 p = WRITE_CACHE (the device cache is ON
4509 r = IGNORE_RESIDUE (the device reports
4510 bogus residue values);
4511 s = SINGLE_LUN (the device has only one
4513 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4514 commands, uas only);
4515 u = IGNORE_UAS (don't bind to the uas driver);
4516 w = NO_WP_DETECT (don't test whether the
4517 medium is write-protected).
4518 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4519 even if the device claims no cache)
4520 Example: quirks=0419:aaf5:rl,0421:0433:rc
4522 user_debug= [KNL,ARM]
4524 See arch/arm/Kconfig.debug help text.
4525 1 - undefined instruction events
4527 4 - invalid data aborts
4530 Example: user_debug=31
4533 [X86] Flags controlling user PTE allocations.
4535 nohigh = do not allocate PTE pages in
4536 HIGHMEM regardless of setting
4540 On X86_32, this is an alias for vdso32=. Otherwise:
4542 vdso=1: enable VDSO (the default)
4543 vdso=0: disable VDSO mapping
4545 vdso32= [X86] Control the 32-bit vDSO
4546 vdso32=1: enable 32-bit VDSO
4547 vdso32=0 or vdso32=2: disable 32-bit VDSO
4549 See the help text for CONFIG_COMPAT_VDSO for more
4550 details. If CONFIG_COMPAT_VDSO is set, the default is
4551 vdso32=0; otherwise, the default is vdso32=1.
4553 For compatibility with older kernels, vdso32=2 is an
4556 Try vdso32=0 if you encounter an error that says:
4557 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4560 vector=percpu: enable percpu vector domain
4562 video= [FB] Frame buffer configuration
4563 See Documentation/fb/modedb.txt.
4565 video.brightness_switch_enabled= [0,1]
4566 If set to 1, on receiving an ACPI notify event
4567 generated by hotkey, video driver will adjust brightness
4568 level and then send out the event to user space through
4569 the allocated input device; If set to 0, video driver
4570 will only send out the event without touching backlight
4575 [VMMIO] Memory mapped virtio (platform) device.
4577 <size>@<baseaddr>:<irq>[:<id>]
4579 <size> := size (can use standard suffixes
4581 <baseaddr> := physical base address
4582 <irq> := interrupt number (as passed to
4584 <id> := (optional) platform device id
4586 virtio_mmio.device=1K@0x100b0000:48:7
4588 Can be used multiple times for multiple devices.
4590 vga= [BOOT,X86-32] Select a particular video mode
4591 See Documentation/x86/boot.txt and
4592 Documentation/svga.txt.
4593 Use vga=ask for menu.
4594 This is actually a boot loader parameter; the value is
4595 passed to the kernel using a special protocol.
4597 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4598 size of <nn>. This can be used to increase the
4599 minimum size (128MB on x86). It can also be used to
4600 decrease the size and leave more room for directly
4603 vmcp_cma=nn[MG] [KNL,S390]
4604 Sets the memory size reserved for contiguous memory
4605 allocations for the vmcp device driver.
4607 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4610 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4613 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4617 Controls the behavior of vsyscalls (i.e. calls to
4618 fixed addresses of 0xffffffffff600x00 from legacy
4619 code). Most statically-linked binaries and older
4620 versions of glibc use these calls. Because these
4621 functions are at fixed addresses, they make nice
4622 targets for exploits that can control RIP.
4624 emulate [default] Vsyscalls turn into traps and are
4625 emulated reasonably safely.
4627 native Vsyscalls are native syscall instructions.
4628 This is a little bit faster than trapping
4629 and makes a few dynamic recompilers work
4630 better than they would in emulation mode.
4631 It also makes exploits much easier to write.
4633 none Vsyscalls don't work at all. This makes
4634 them quite hard to use for exploits but
4635 might break your system.
4637 vt.color= [VT] Default text color.
4638 Format: 0xYX, X = foreground, Y = background.
4639 Default: 0x07 = light gray on black.
4641 vt.cur_default= [VT] Default cursor shape.
4642 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4643 the parameters of the <Esc>[?A;B;Cc escape sequence;
4644 see VGA-softcursor.txt. Default: 2 = underline.
4646 vt.default_blu= [VT]
4647 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4648 Change the default blue palette of the console.
4649 This is a 16-member array composed of values
4652 vt.default_grn= [VT]
4653 Format: <green0>,<green1>,<green2>,...,<green15>
4654 Change the default green palette of the console.
4655 This is a 16-member array composed of values
4658 vt.default_red= [VT]
4659 Format: <red0>,<red1>,<red2>,...,<red15>
4660 Change the default red palette of the console.
4661 This is a 16-member array composed of values
4667 Set system-wide default UTF-8 mode for all tty's.
4668 Default is 1, i.e. UTF-8 mode is enabled for all
4669 newly opened terminals.
4671 vt.global_cursor_default=
4674 Set system-wide default for whether a cursor
4675 is shown on new VTs. Default is -1,
4676 i.e. cursors will be created by default unless
4677 overridden by individual drivers. 0 will hide
4678 cursors, 1 will display them.
4680 vt.italic= [VT] Default color for italic text; 0-15.
4683 vt.underline= [VT] Default color for underlined text; 0-15.
4686 watchdog timers [HW,WDT] For information on watchdog timers,
4687 see Documentation/watchdog/watchdog-parameters.txt
4688 or other driver-specific files in the
4689 Documentation/watchdog/ directory.
4691 workqueue.watchdog_thresh=
4692 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4693 warn stall conditions and dump internal state to
4694 help debugging. 0 disables workqueue stall
4695 detection; otherwise, it's the stall threshold
4696 duration in seconds. The default value is 30 and
4697 it can be updated at runtime by writing to the
4698 corresponding sysfs file.
4700 workqueue.disable_numa
4701 By default, all work items queued to unbound
4702 workqueues are affine to the NUMA nodes they're
4703 issued on, which results in better behavior in
4704 general. If NUMA affinity needs to be disabled for
4705 whatever reason, this option can be used. Note
4706 that this also can be controlled per-workqueue for
4707 workqueues visible under /sys/bus/workqueue/.
4709 workqueue.power_efficient
4710 Per-cpu workqueues are generally preferred because
4711 they show better performance thanks to cache
4712 locality; unfortunately, per-cpu workqueues tend to
4713 be more power hungry than unbound workqueues.
4715 Enabling this makes the per-cpu workqueues which
4716 were observed to contribute significantly to power
4717 consumption unbound, leading to measurably lower
4718 power usage at the cost of small performance
4721 The default value of this parameter is determined by
4722 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4724 workqueue.debug_force_rr_cpu
4725 Workqueue used to implicitly guarantee that work
4726 items queued without explicit CPU specified are put
4727 on the local CPU. This guarantee is no longer true
4728 and while local CPU is still preferred work items
4729 may be put on foreign CPUs. This debug option
4730 forces round-robin CPU selection to flush out
4731 usages which depend on the now broken guarantee.
4732 When enabled, memory and cache locality will be
4735 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4736 default x2apic cluster mode on platforms
4739 x86_intel_mid_timer= [X86-32,APBT]
4740 Choose timer option for x86 Intel MID platform.
4741 Two valid options are apbt timer only and lapic timer
4742 plus one apbt timer for broadcast timer.
4743 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4745 xen_512gb_limit [KNL,X86-64,XEN]
4746 Restricts the kernel running paravirtualized under Xen
4747 to use only up to 512 GB of RAM. The reason to do so is
4748 crash analysis tools and Xen tools for doing domain
4749 save/restore/migration must be enabled to handle larger
4752 xen_emul_unplug= [HW,X86,XEN]
4753 Unplug Xen emulated devices
4754 Format: [unplug0,][unplug1]
4755 ide-disks -- unplug primary master IDE devices
4756 aux-ide-disks -- unplug non-primary-master IDE devices
4757 nics -- unplug network devices
4758 all -- unplug all emulated devices (NICs and IDE disks)
4759 unnecessary -- unplugging emulated devices is
4760 unnecessary even if the host did not respond to
4762 never -- do not unplug even if version check succeeds
4764 xen_nopvspin [X86,XEN]
4765 Disables the ticketlock slowpath using Xen PV
4769 Disables the PV optimizations forcing the HVM guest to
4770 run as generic HVM guest with no PV drivers.
4772 xirc2ps_cs= [NET,PCMCIA]
4774 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
git.samba.org / sfrench / cifs-2.6.git / blob