1 acpi= [HW,ACPI,X86,ARM64] 2 Advanced Configuration and Power Interface 3 Format: { force | on | off | strict | noirq | rsdt | 4 copy_dsdt } 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" 14 are available 15 16 See also Documentation/power/runtime_pm.txt, pci=noacpi 17 18 acpi_apic_instance= [ACPI, IOAPIC] 19 Format: <int> 20 2: use 2nd APIC table, if available 21 1,0: use 1st APIC table 22 default: 0 23 24 acpi_backlight= [HW,ACPI] 25 acpi_backlight=vendor 26 acpi_backlight=video 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. 30 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. 36 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. 44 45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 47 Format: <int> 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. 58 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 68 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. 72 73 acpi_enforce_resources= [ACPI] 74 { strict | lax | no } 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. 88 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 92 size limitation. 93 94 acpi_irq_balance [HW,ACPI] 95 ACPI will balance active IRQs 96 default in APIC mode 97 98 acpi_irq_nobalance [HW,ACPI] 99 ACPI will not move active IRQs (default) 100 default in PIC mode 101 102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 103 Format: <irq>,<irq>... 104 105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 106 use by PCI 107 Format: <irq>,<irq>... 108 109 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 113 the GPE dispatcher. 114 This facility can be used to prevent such uncontrolled 115 GPE floodings. 116 Format: <int> 117 Support masking of GPEs numbered from 0x00 to 0x7f. 118 119 acpi_no_auto_serialize [HW,ACPI] 120 Disable auto-serialization of AML methods 121 AML control methods that contain the opcodes to create 122 named objects will be marked as "Serialized" by the 123 auto-serialization feature. 124 This feature is enabled by default. 125 This option allows to turn off the feature. 126 127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump 128 kernels. 129 130 acpi_no_static_ssdt [HW,ACPI] 131 Disable installation of static SSDTs at early boot time 132 By default, SSDTs contained in the RSDT/XSDT will be 133 installed automatically and they will appear under 134 /sys/firmware/acpi/tables. 135 This option turns off this feature. 136 Note that specifying this option does not affect 137 dynamic table installation which will install SSDT 138 tables to /sys/firmware/acpi/tables/dynamic. 139 140 acpi_rsdp= [ACPI,EFI,KEXEC] 141 Pass the RSDP address to the kernel, mostly used 142 on machines running EFI runtime service to boot the 143 second kernel for kdump. 144 145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 146 Format: To spoof as Windows 98: ="Microsoft Windows" 147 148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead 149 of 2 which is mandated by ACPI 6) as the supported ACPI 150 specification revision (when using this switch, it may 151 be necessary to carry out a cold reboot _twice_ in a 152 row to make it take effect on the platform firmware). 153 154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 155 acpi_osi="string1" # add string1 156 acpi_osi="!string2" # remove string2 157 acpi_osi=!* # remove all strings 158 acpi_osi=! # disable all built-in OS vendor 159 strings 160 acpi_osi=!! # enable all built-in OS vendor 161 strings 162 acpi_osi= # disable all strings 163 164 'acpi_osi=!' can be used in combination with single or 165 multiple 'acpi_osi="string1"' to support specific OS 166 vendor string(s). Note that such command can only 167 affect the default state of the OS vendor strings, thus 168 it cannot affect the default state of the feature group 169 strings and the current state of the OS vendor strings, 170 specifying it multiple times through kernel command line 171 is meaningless. This command is useful when one do not 172 care about the state of the feature group strings which 173 should be controlled by the OSPM. 174 Examples: 175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent 176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all 177 can make '_OSI("Windows 2000")' TRUE. 178 179 'acpi_osi=' cannot be used in combination with other 180 'acpi_osi=' command lines, the _OSI method will not 181 exist in the ACPI namespace. NOTE that such command can 182 only affect the _OSI support state, thus specifying it 183 multiple times through kernel command line is also 184 meaningless. 185 Examples: 186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' 187 FALSE. 188 189 'acpi_osi=!*' can be used in combination with single or 190 multiple 'acpi_osi="string1"' to support specific 191 string(s). Note that such command can affect the 192 current state of both the OS vendor strings and the 193 feature group strings, thus specifying it multiple times 194 through kernel command line is meaningful. But it may 195 still not able to affect the final state of a string if 196 there are quirks related to this string. This command 197 is useful when one want to control the state of the 198 feature group strings to debug BIOS issues related to 199 the OSPM features. 200 Examples: 201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make 202 '_OSI("Module Device")' FALSE. 203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make 204 '_OSI("Module Device")' TRUE. 205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is 206 equivalent to 207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' 208 and 209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', 210 they all will make '_OSI("Windows 2000")' TRUE. 211 212 acpi_pm_good [X86] 213 Override the pmtimer bug detection: force the kernel 214 to assume that this machine's pmtimer latches its value 215 and always returns good values. 216 217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 218 Format: { level | edge | high | low } 219 220 acpi_skip_timer_override [HW,ACPI] 221 Recognize and ignore IRQ0/pin2 Interrupt Override. 222 For broken nForce2 BIOS resulting in XT-PIC timer. 223 224 acpi_sleep= [HW,ACPI] Sleep options 225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 226 old_ordering, nonvs, sci_force_enable } 227 See Documentation/power/video.txt for information on 228 s3_bios and s3_mode. 229 s3_beep is for debugging; it makes the PC's speaker beep 230 as soon as the kernel's real-mode entry point is called. 231 s4_nohwsig prevents ACPI hardware signature from being 232 used during resume from hibernation. 233 old_ordering causes the ACPI 1.0 ordering of the _PTS 234 control method, with respect to putting devices into 235 low power states, to be enforced (the ACPI 2.0 ordering 236 of _PTS is used by default). 237 nonvs prevents the kernel from saving/restoring the 238 ACPI NVS memory during suspend/hibernation and resume. 239 sci_force_enable causes the kernel to set SCI_EN directly 240 on resume from S1/S3 (which is against the ACPI spec, 241 but some broken systems don't work without it). 242 243 acpi_use_timer_override [HW,ACPI] 244 Use timer override. For some broken Nvidia NF5 boards 245 that require a timer override, but don't have HPET 246 247 add_efi_memmap [EFI; X86] Include EFI memory map in 248 kernel's map of available physical RAM. 249 250 agp= [AGP] 251 { off | try_unsupported } 252 off: disable AGP support 253 try_unsupported: try to drive unsupported chipsets 254 (may crash computer or cause data corruption) 255 256 ALSA [HW,ALSA] 257 See Documentation/sound/alsa/alsa-parameters.txt 258 259 alignment= [KNL,ARM] 260 Allow the default userspace alignment fault handler 261 behaviour to be specified. Bit 0 enables warnings, 262 bit 1 enables fixups, and bit 2 sends a segfault. 263 264 align_va_addr= [X86-64] 265 Align virtual addresses by clearing slice [14:12] when 266 allocating a VMA at process creation time. This option 267 gives you up to 3% performance improvement on AMD F15h 268 machines (where it is enabled by default) for a 269 CPU-intensive style benchmark, and it can vary highly in 270 a microbenchmark depending on workload and compiler. 271 272 32: only for 32-bit processes 273 64: only for 64-bit processes 274 on: enable for both 32- and 64-bit processes 275 off: disable for both 32- and 64-bit processes 276 277 alloc_snapshot [FTRACE] 278 Allocate the ftrace snapshot buffer on boot up when the 279 main buffer is allocated. This is handy if debugging 280 and you need to use tracing_snapshot() on boot up, and 281 do not want to use tracing_snapshot_alloc() as it needs 282 to be done where GFP_KERNEL allocations are allowed. 283 284 amd_iommu= [HW,X86-64] 285 Pass parameters to the AMD IOMMU driver in the system. 286 Possible values are: 287 fullflush - enable flushing of IO/TLB entries when 288 they are unmapped. Otherwise they are 289 flushed before they will be reused, which 290 is a lot of faster 291 off - do not initialize any AMD IOMMU found in 292 the system 293 force_isolation - Force device isolation for all 294 devices. The IOMMU driver is not 295 allowed anymore to lift isolation 296 requirements as needed. This option 297 does not override iommu=pt 298 299 amd_iommu_dump= [HW,X86-64] 300 Enable AMD IOMMU driver option to dump the ACPI table 301 for AMD IOMMU. With this option enabled, AMD IOMMU 302 driver will print ACPI tables for AMD IOMMU during 303 IOMMU initialization. 304 305 amd_iommu_intr= [HW,X86-64] 306 Specifies one of the following AMD IOMMU interrupt 307 remapping modes: 308 legacy - Use legacy interrupt remapping mode. 309 vapic - Use virtual APIC mode, which allows IOMMU 310 to inject interrupts directly into guest. 311 This mode requires kvm-amd.avic=1. 312 (Default when IOMMU HW support is present.) 313 314 amijoy.map= [HW,JOY] Amiga joystick support 315 Map of devices attached to JOY0DAT and JOY1DAT 316 Format: <a>,<b> 317 See also Documentation/input/joystick.txt 318 319 analog.map= [HW,JOY] Analog joystick and gamepad support 320 Specifies type or capabilities of an analog joystick 321 connected to one of 16 gameports 322 Format: <type1>,<type2>,..<type16> 323 324 apc= [HW,SPARC] 325 Power management functions (SPARCstation-4/5 + deriv.) 326 Format: noidle 327 Disable APC CPU standby support. SPARCstation-Fox does 328 not play well with APC CPU idle - disable it if you have 329 APC and your system crashes randomly. 330 331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller 332 Change the output verbosity whilst booting 333 Format: { quiet (default) | verbose | debug } 334 Change the amount of debugging information output 335 when initialising the APIC and IO-APIC components. 336 337 apic_extnmi= [APIC,X86] External NMI delivery setting 338 Format: { bsp (default) | all | none } 339 bsp: External NMI is delivered only to CPU 0 340 all: External NMIs are broadcast to all CPUs as a 341 backup of CPU 0 342 none: External NMI is masked for all CPUs. This is 343 useful so that a dump capture kernel won't be 344 shot down by NMI 345 346 autoconf= [IPV6] 347 See Documentation/networking/ipv6.txt. 348 349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 350 Limit apic dumping. The parameter defines the maximal 351 number of local apics being dumped. Also it is possible 352 to set it to "all" by meaning -- no limit here. 353 Format: { 1 (default) | 2 | ... | all }. 354 The parameter valid if only apic=debug or 355 apic=verbose is specified. 356 Example: apic=debug show_lapic=all 357 358 apm= [APM] Advanced Power Management 359 See header of arch/x86/kernel/apm_32.c. 360 361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 362 Format: <io>,<irq>,<nodeID> 363 364 ataflop= [HW,M68k] 365 366 atarimouse= [HW,MOUSE] Atari Mouse 367 368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 369 EzKey and similar keyboards 370 371 atkbd.reset= [HW] Reset keyboard during initialization 372 373 atkbd.set= [HW] Select keyboard code set 374 Format: <int> (2 = AT (default), 3 = PS/2) 375 376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 377 keyboards 378 379 atkbd.softraw= [HW] Choose between synthetic and real raw mode 380 Format: <bool> (0 = real, 1 = synthetic (default)) 381 382 atkbd.softrepeat= [HW] 383 Use software keyboard repeat 384 385 audit= [KNL] Enable the audit sub-system 386 Format: { "0" | "1" } (0 = disabled, 1 = enabled) 387 0 - kernel audit is disabled and can not be enabled 388 until the next reboot 389 unset - kernel audit is initialized but disabled and 390 will be fully enabled by the userspace auditd. 391 1 - kernel audit is initialized and partially enabled, 392 storing at most audit_backlog_limit messages in 393 RAM until it is fully enabled by the userspace 394 auditd. 395 Default: unset 396 397 audit_backlog_limit= [KNL] Set the audit queue size limit. 398 Format: <int> (must be >=0) 399 Default: 64 400 401 bau= [X86_UV] Enable the BAU on SGI UV. The default 402 behavior is to disable the BAU (i.e. bau=0). 403 Format: { "0" | "1" } 404 0 - Disable the BAU. 405 1 - Enable the BAU. 406 unset - Disable the BAU. 407 408 baycom_epp= [HW,AX25] 409 Format: <io>,<mode> 410 411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 412 Format: <io>,<mode> 413 See header of drivers/net/hamradio/baycom_par.c. 414 415 baycom_ser_fdx= [HW,AX25] 416 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 417 Format: <io>,<irq>,<mode>[,<baud>] 418 See header of drivers/net/hamradio/baycom_ser_fdx.c. 419 420 baycom_ser_hdx= [HW,AX25] 421 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 422 Format: <io>,<irq>,<mode> 423 See header of drivers/net/hamradio/baycom_ser_hdx.c. 424 425 blkdevparts= Manual partition parsing of block device(s) for 426 embedded devices based on command line input. 427 See Documentation/block/cmdline-partition.txt 428 429 boot_delay= Milliseconds to delay each printk during boot. 430 Values larger than 10 seconds (10000) are changed to 431 no delay (0). 432 Format: integer 433 434 bootmem_debug [KNL] Enable bootmem allocator debug messages. 435 436 bert_disable [ACPI] 437 Disable BERT OS support on buggy BIOSes. 438 439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 440 bttv.radio= Most important insmod options are available as 441 kernel args too. 442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 443 bttv.tuner= 444 445 bulk_remove=off [PPC] This parameter disables the use of the pSeries 446 firmware feature for flushing multiple hpte entries 447 at a time. 448 449 c101= [NET] Moxa C101 synchronous serial card 450 451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 452 Sometimes CPU hardware bugs make them report the cache 453 size incorrectly. The kernel will attempt work arounds 454 to fix known problems, but for some CPUs it is not 455 possible to determine what the correct size should be. 456 This option provides an override for these situations. 457 458 ca_keys= [KEYS] This parameter identifies a specific key(s) on 459 the system trusted keyring to be used for certificate 460 trust validation. 461 format: { id:<keyid> | builtin } 462 463 cca= [MIPS] Override the kernel pages' cache coherency 464 algorithm. Accepted values range from 0 to 7 465 inclusive. See arch/mips/include/asm/pgtable-bits.h 466 for platform specific values (SB1, Loongson3 and 467 others). 468 469 ccw_timeout_log [S390] 470 See Documentation/s390/CommonIO for details. 471 472 cgroup_disable= [KNL] Disable a particular controller 473 Format: {name of the controller(s) to disable} 474 The effects of cgroup_disable=foo are: 475 - foo isn't auto-mounted if you mount all cgroups in 476 a single hierarchy 477 - foo isn't visible as an individually mountable 478 subsystem 479 {Currently only "memory" controller deal with this and 480 cut the overhead, others just disable the usage. So 481 only cgroup_disable=memory is actually worthy} 482 483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1 484 Format: { controller[,controller...] | "all" } 485 Like cgroup_disable, but only applies to cgroup v1; 486 the blacklisted controllers remain available in cgroup2. 487 488 cgroup.memory= [KNL] Pass options to the cgroup memory controller. 489 Format: <string> 490 nosocket -- Disable socket memory accounting. 491 nokmem -- Disable kernel memory accounting. 492 493 checkreqprot [SELINUX] Set initial checkreqprot flag value. 494 Format: { "0" | "1" } 495 See security/selinux/Kconfig help text. 496 0 -- check protection applied by kernel (includes 497 any implied execute protection). 498 1 -- check protection requested by application. 499 Default value is set via a kernel config option. 500 Value can be changed at runtime via 501 /selinux/checkreqprot. 502 503 cio_ignore= [S390] 504 See Documentation/s390/CommonIO for details. 505 clk_ignore_unused 506 [CLK] 507 Prevents the clock framework from automatically gating 508 clocks that have not been explicitly enabled by a Linux 509 device driver but are enabled in hardware at reset or 510 by the bootloader/firmware. Note that this does not 511 force such clocks to be always-on nor does it reserve 512 those clocks in any way. This parameter is useful for 513 debug and development, but should not be needed on a 514 platform with proper driver support. For more 515 information, see Documentation/clk.txt. 516 517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 518 [Deprecated] 519 Forces specified clocksource (if available) to be used 520 when calculating gettimeofday(). If specified 521 clocksource is not available, it defaults to PIT. 522 Format: { pit | tsc | cyclone | pmtmr } 523 524 clocksource= Override the default clocksource 525 Format: <string> 526 Override the default clocksource and use the clocksource 527 with the name specified. 528 Some clocksource names to choose from, depending on 529 the platform: 530 [all] jiffies (this is the base, fallback clocksource) 531 [ACPI] acpi_pm 532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 533 pxa_timer,timer3,32k_counter,timer0_1 534 [AVR32] avr32 535 [X86-32] pit,hpet,tsc; 536 scx200_hrt on Geode; cyclone on IBM x440 537 [MIPS] MIPS 538 [PARISC] cr16 539 [S390] tod 540 [SH] SuperH 541 [SPARC64] tick 542 [X86-64] hpet,tsc 543 544 clocksource.arm_arch_timer.evtstrm= 545 [ARM,ARM64] 546 Format: <bool> 547 Enable/disable the eventstream feature of the ARM 548 architected timer so that code using WFE-based polling 549 loops can be debugged more effectively on production 550 systems. 551 552 clearcpuid=BITNUM [X86] 553 Disable CPUID feature X for the kernel. See 554 arch/x86/include/asm/cpufeatures.h for the valid bit 555 numbers. Note the Linux specific bits are not necessarily 556 stable over kernel options, but the vendor specific 557 ones should be. 558 Also note that user programs calling CPUID directly 559 or using the feature without checking anything 560 will still see it. This just prevents it from 561 being used by the kernel or shown in /proc/cpuinfo. 562 Also note the kernel might malfunction if you disable 563 some critical bits. 564 565 cma=nn[MG]@[start[MG][-end[MG]]] 566 [ARM,X86,KNL] 567 Sets the size of kernel global memory area for 568 contiguous memory allocations and optionally the 569 placement constraint by the physical address range of 570 memory allocations. A value of 0 disables CMA 571 altogether. For more information, see 572 include/linux/dma-contiguous.h 573 574 cmo_free_hint= [PPC] Format: { yes | no } 575 Specify whether pages are marked as being inactive 576 when they are freed. This is used in CMO environments 577 to determine OS memory pressure for page stealing by 578 a hypervisor. 579 Default: yes 580 581 coherent_pool=nn[KMG] [ARM,KNL] 582 Sets the size of memory pool for coherent, atomic dma 583 allocations, by default set to 256K. 584 585 code_bytes [X86] How many bytes of object code to print 586 in an oops report. 587 Range: 0 - 8192 588 Default: 64 589 590 com20020= [HW,NET] ARCnet - COM20020 chipset 591 Format: 592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 593 594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 595 Format: <io>[,<irq>] 596 597 com90xx= [HW,NET] 598 ARCnet - COM90xx chipset (memory-mapped buffers) 599 Format: <io>[,<irq>[,<memstart>]] 600 601 condev= [HW,S390] console device 602 conmode= 603 604 console= [KNL] Output console device and options. 605 606 tty<n> Use the virtual console device <n>. 607 608 ttyS<n>[,options] 609 ttyUSB0[,options] 610 Use the specified serial port. The options are of 611 the form "bbbbpnf", where "bbbb" is the baud rate, 612 "p" is parity ("n", "o", or "e"), "n" is number of 613 bits, and "f" is flow control ("r" for RTS or 614 omit it). Default is "9600n8". 615 616 See Documentation/admin-guide/serial-console.rst for more 617 information. See 618 Documentation/networking/netconsole.txt for an 619 alternative. 620 621 uart[8250],io,<addr>[,options] 622 uart[8250],mmio,<addr>[,options] 623 uart[8250],mmio16,<addr>[,options] 624 uart[8250],mmio32,<addr>[,options] 625 uart[8250],0x<addr>[,options] 626 Start an early, polled-mode console on the 8250/16550 627 UART at the specified I/O port or MMIO address, 628 switching to the matching ttyS device later. 629 MMIO inter-register address stride is either 8-bit 630 (mmio), 16-bit (mmio16), or 32-bit (mmio32). 631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed 632 to be equivalent to 'mmio'. 'options' are specified in 633 the same format described for ttyS above; if unspecified, 634 the h/w is not re-initialized. 635 636 hvc<n> Use the hypervisor console device <n>. This is for 637 both Xen and PowerPC hypervisors. 638 639 If the device connected to the port is not a TTY but a braille 640 device, prepend "brl," before the device type, for instance 641 console=brl,ttyS0 642 For now, only VisioBraille is supported. 643 644 consoleblank= [KNL] The console blank (screen saver) timeout in 645 seconds. Defaults to 10*60 = 10mins. A value of 0 646 disables the blank timer. 647 648 coredump_filter= 649 [KNL] Change the default value for 650 /proc/<pid>/coredump_filter. 651 See also Documentation/filesystems/proc.txt. 652 653 cpuidle.off=1 [CPU_IDLE] 654 disable the cpuidle sub-system 655 656 cpu_init_udelay=N 657 [X86] Delay for N microsec between assert and de-assert 658 of APIC INIT to start processors. This delay occurs 659 on every CPU online, such as boot, and resume from suspend. 660 Default: 10000 661 662 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 663 Format: 664 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 665 666 crashkernel=size[KMG][@offset[KMG]] 667 [KNL] Using kexec, Linux can switch to a 'crash kernel' 668 upon panic. This parameter reserves the physical 669 memory region [offset, offset + size] for that kernel 670 image. If '@offset' is omitted, then a suitable offset 671 is selected automatically. Check 672 Documentation/kdump/kdump.txt for further details. 673 674 crashkernel=range1:size1[,range2:size2,...][@offset] 675 [KNL] Same as above, but depends on the memory 676 in the running system. The syntax of range is 677 start-[end] where start and end are both 678 a memory unit (amount[KMG]). See also 679 Documentation/kdump/kdump.txt for an example. 680 681 crashkernel=size[KMG],high 682 [KNL, x86_64] range could be above 4G. Allow kernel 683 to allocate physical memory region from top, so could 684 be above 4G if system have more than 4G ram installed. 685 Otherwise memory region will be allocated below 4G, if 686 available. 687 It will be ignored if crashkernel=X is specified. 688 crashkernel=size[KMG],low 689 [KNL, x86_64] range under 4G. When crashkernel=X,high 690 is passed, kernel could allocate physical memory region 691 above 4G, that cause second kernel crash on system 692 that require some amount of low memory, e.g. swiotlb 693 requires at least 64M+32K low memory, also enough extra 694 low memory is needed to make sure DMA buffers for 32-bit 695 devices won't run out. Kernel would try to allocate at 696 at least 256M below 4G automatically. 697 This one let user to specify own low range under 4G 698 for second kernel instead. 699 0: to disable low allocation. 700 It will be ignored when crashkernel=X,high is not used 701 or memory reserved is below 4G. 702 703 cryptomgr.notests 704 [KNL] Disable crypto self-tests 705 706 cs89x0_dma= [HW,NET] 707 Format: <dma> 708 709 cs89x0_media= [HW,NET] 710 Format: { rj45 | aui | bnc } 711 712 dasd= [HW,NET] 713 See header of drivers/s390/block/dasd_devmap.c. 714 715 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 716 (one device per port) 717 Format: <port#>,<type> 718 See also Documentation/input/joystick-parport.txt 719 720 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot 721 time. See Documentation/dynamic-debug-howto.txt for 722 details. Deprecated, see dyndbg. 723 724 debug [KNL] Enable kernel debugging (events log level). 725 726 debug_locks_verbose= 727 [KNL] verbose self-tests 728 Format=<0|1> 729 Print debugging info while doing the locking API 730 self-tests. 731 We default to 0 (no extra messages), setting it to 732 1 will print _a lot_ more information - normally 733 only useful to kernel developers. 734 735 debug_objects [KNL] Enable object debugging 736 737 no_debug_objects 738 [KNL] Disable object debugging 739 740 debug_guardpage_minorder= 741 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 742 parameter allows control of the order of pages that will 743 be intentionally kept free (and hence protected) by the 744 buddy allocator. Bigger value increase the probability 745 of catching random memory corruption, but reduce the 746 amount of memory for normal system use. The maximum 747 possible value is MAX_ORDER/2. Setting this parameter 748 to 1 or 2 should be enough to identify most random 749 memory corruption problems caused by bugs in kernel or 750 driver code when a CPU writes to (or reads from) a 751 random memory location. Note that there exists a class 752 of memory corruptions problems caused by buggy H/W or 753 F/W or by drivers badly programing DMA (basically when 754 memory is written at bus level and the CPU MMU is 755 bypassed) which are not detectable by 756 CONFIG_DEBUG_PAGEALLOC, hence this option will not help 757 tracking down these problems. 758 759 debug_pagealloc= 760 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this 761 parameter enables the feature at boot time. In 762 default, it is disabled. We can avoid allocating huge 763 chunk of memory for debug pagealloc if we don't enable 764 it at boot time and the system will work mostly same 765 with the kernel built without CONFIG_DEBUG_PAGEALLOC. 766 on: enable the feature 767 768 debugpat [X86] Enable PAT debugging 769 770 decnet.addr= [HW,NET] 771 Format: <area>[,<node>] 772 See also Documentation/networking/decnet.txt. 773 774 default_hugepagesz= 775 [same as hugepagesz=] The size of the default 776 HugeTLB page size. This is the size represented by 777 the legacy /proc/ hugepages APIs, used for SHM, and 778 default size when mounting hugetlbfs filesystems. 779 Defaults to the default architecture's huge page size 780 if not specified. 781 782 dhash_entries= [KNL] 783 Set number of hash buckets for dentry cache. 784 785 disable_1tb_segments [PPC] 786 Disables the use of 1TB hash page table segments. This 787 causes the kernel to fall back to 256MB segments which 788 can be useful when debugging issues that require an SLB 789 miss to occur. 790 791 disable= [IPV6] 792 See Documentation/networking/ipv6.txt. 793 794 disable_radix [PPC] 795 Disable RADIX MMU mode on POWER9 796 797 disable_cpu_apicid= [X86,APIC,SMP] 798 Format: <int> 799 The number of initial APIC ID for the 800 corresponding CPU to be disabled at boot, 801 mostly used for the kdump 2nd kernel to 802 disable BSP to wake up multiple CPUs without 803 causing system reset or hang due to sending 804 INIT from AP to BSP. 805 806 disable_ddw [PPC/PSERIES] 807 Disable Dynamic DMA Window support. Use this if 808 to workaround buggy firmware. 809 810 disable_ipv6= [IPV6] 811 See Documentation/networking/ipv6.txt. 812 813 disable_mtrr_cleanup [X86] 814 The kernel tries to adjust MTRR layout from continuous 815 to discrete, to make X server driver able to add WB 816 entry later. This parameter disables that. 817 818 disable_mtrr_trim [X86, Intel and AMD only] 819 By default the kernel will trim any uncacheable 820 memory out of your available memory pool based on 821 MTRR settings. This parameter disables that behavior, 822 possibly causing your machine to run very slowly. 823 824 disable_timer_pin_1 [X86] 825 Disable PIN 1 of APIC timer 826 Can be useful to work around chipset bugs. 827 828 dis_ucode_ldr [X86] Disable the microcode loader. 829 830 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 831 this option disables the debugging code at boot. 832 833 dma_debug_entries=<number> 834 This option allows to tune the number of preallocated 835 entries for DMA-API debugging code. One entry is 836 required per DMA-API allocation. Use this if the 837 DMA-API debugging code disables itself because the 838 architectural default is too low. 839 840 dma_debug_driver=<driver_name> 841 With this option the DMA-API debugging driver 842 filter feature can be enabled at boot time. Just 843 pass the driver to filter for as the parameter. 844 The filter can be disabled or changed to another 845 driver later using sysfs. 846 847 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] 848 Broken monitors, graphic adapters, KVMs and EDIDless 849 panels may send no or incorrect EDID data sets. 850 This parameter allows to specify an EDID data sets 851 in the /lib/firmware directory that are used instead. 852 Generic built-in EDID data sets are used, if one of 853 edid/1024x768.bin, edid/1280x1024.bin, 854 edid/1680x1050.bin, or edid/1920x1080.bin is given 855 and no file with the same name exists. Details and 856 instructions how to build your own EDID data are 857 available in Documentation/EDID/HOWTO.txt. An EDID 858 data set will only be used for a particular connector, 859 if its name and a colon are prepended to the EDID 860 name. Each connector may use a unique EDID data 861 set by separating the files with a comma. An EDID 862 data set with no connector name will be used for 863 any connectors not explicitly specified. 864 865 dscc4.setup= [NET] 866 867 dump_apple_properties [X86] 868 Dump name and content of EFI device properties on 869 x86 Macs. Useful for driver authors to determine 870 what data is available or for reverse-engineering. 871 872 dyndbg[="val"] [KNL,DYNAMIC_DEBUG] 873 module.dyndbg[="val"] 874 Enable debug messages at boot time. See 875 Documentation/dynamic-debug-howto.txt for details. 876 877 nompx [X86] Disables Intel Memory Protection Extensions. 878 See Documentation/x86/intel_mpx.txt for more 879 information about the feature. 880 881 nopku [X86] Disable Memory Protection Keys CPU feature found 882 in some Intel CPUs. 883 884 module.async_probe [KNL] 885 Enable asynchronous probe on this module. 886 887 early_ioremap_debug [KNL] 888 Enable debug messages in early_ioremap support. This 889 is useful for tracking down temporary early mappings 890 which are not unmapped. 891 892 earlycon= [KNL] Output early console device and options. 893 894 When used with no options, the early console is 895 determined by the stdout-path property in device 896 tree's chosen node. 897 898 cdns,<addr>[,options] 899 Start an early, polled-mode console on a Cadence 900 (xuartps) serial port at the specified address. Only 901 supported option is baud rate. If baud rate is not 902 specified, the serial port must already be setup and 903 configured. 904 905 uart[8250],io,<addr>[,options] 906 uart[8250],mmio,<addr>[,options] 907 uart[8250],mmio32,<addr>[,options] 908 uart[8250],mmio32be,<addr>[,options] 909 uart[8250],0x<addr>[,options] 910 Start an early, polled-mode console on the 8250/16550 911 UART at the specified I/O port or MMIO address. 912 MMIO inter-register address stride is either 8-bit 913 (mmio) or 32-bit (mmio32 or mmio32be). 914 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed 915 to be equivalent to 'mmio'. 'options' are specified 916 in the same format described for "console=ttyS<n>"; if 917 unspecified, the h/w is not initialized. 918 919 pl011,<addr> 920 pl011,mmio32,<addr> 921 Start an early, polled-mode console on a pl011 serial 922 port at the specified address. The pl011 serial port 923 must already be setup and configured. Options are not 924 yet supported. If 'mmio32' is specified, then only 925 the driver will use only 32-bit accessors to read/write 926 the device registers. 927 928 meson,<addr> 929 Start an early, polled-mode console on a meson serial 930 port at the specified address. The serial port must 931 already be setup and configured. Options are not yet 932 supported. 933 934 msm_serial,<addr> 935 Start an early, polled-mode console on an msm serial 936 port at the specified address. The serial port 937 must already be setup and configured. Options are not 938 yet supported. 939 940 msm_serial_dm,<addr> 941 Start an early, polled-mode console on an msm serial 942 dm port at the specified address. The serial port 943 must already be setup and configured. Options are not 944 yet supported. 945 946 smh Use ARM semihosting calls for early console. 947 948 s3c2410,<addr> 949 s3c2412,<addr> 950 s3c2440,<addr> 951 s3c6400,<addr> 952 s5pv210,<addr> 953 exynos4210,<addr> 954 Use early console provided by serial driver available 955 on Samsung SoCs, requires selecting proper type and 956 a correct base address of the selected UART port. The 957 serial port must already be setup and configured. 958 Options are not yet supported. 959 960 lantiq,<addr> 961 Start an early, polled-mode console on a lantiq serial 962 (lqasc) port at the specified address. The serial port 963 must already be setup and configured. Options are not 964 yet supported. 965 966 lpuart,<addr> 967 lpuart32,<addr> 968 Use early console provided by Freescale LP UART driver 969 found on Freescale Vybrid and QorIQ LS1021A processors. 970 A valid base address must be provided, and the serial 971 port must already be setup and configured. 972 973 armada3700_uart,<addr> 974 Start an early, polled-mode console on the 975 Armada 3700 serial port at the specified 976 address. The serial port must already be setup 977 and configured. Options are not yet supported. 978 979 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390] 980 earlyprintk=vga 981 earlyprintk=efi 982 earlyprintk=sclp 983 earlyprintk=xen 984 earlyprintk=serial[,ttySn[,baudrate]] 985 earlyprintk=serial[,0x...[,baudrate]] 986 earlyprintk=ttySn[,baudrate] 987 earlyprintk=dbgp[debugController#] 988 earlyprintk=pciserial,bus:device.function[,baudrate] 989 990 earlyprintk is useful when the kernel crashes before 991 the normal console is initialized. It is not enabled by 992 default because it has some cosmetic problems. 993 994 Append ",keep" to not disable it when the real console 995 takes over. 996 997 Only one of vga, efi, serial, or usb debug port can 998 be used at a time. 999 1000 Currently only ttyS0 and ttyS1 may be specified by 1001 name. Other I/O ports may be explicitly specified 1002 on some architectures (x86 and arm at least) by 1003 replacing ttySn with an I/O port address, like this: 1004 earlyprintk=serial,0x1008,115200 1005 You can find the port for a given device in 1006 /proc/tty/driver/serial: 1007 2: uart:ST16650V2 port:00001008 irq:18 ... 1008 1009 Interaction with the standard serial driver is not 1010 very good. 1011 1012 The VGA and EFI output is eventually overwritten by 1013 the real console. 1014 1015 The xen output can only be used by Xen PV guests. 1016 1017 The sclp output can only be used on s390. 1018 1019 edac_report= [HW,EDAC] Control how to report EDAC event 1020 Format: {"on" | "off" | "force"} 1021 on: enable EDAC to report H/W event. May be overridden 1022 by other higher priority error reporting module. 1023 off: disable H/W event reporting through EDAC. 1024 force: enforce the use of EDAC to report H/W event. 1025 default: on. 1026 1027 ekgdboc= [X86,KGDB] Allow early kernel console debugging 1028 ekgdboc=kbd 1029 1030 This is designed to be used in conjunction with 1031 the boot argument: earlyprintk=vga 1032 1033 edd= [EDD] 1034 Format: {"off" | "on" | "skip[mbr]"} 1035 1036 efi= [EFI] 1037 Format: { "old_map", "nochunk", "noruntime", "debug" } 1038 old_map [X86-64]: switch to the old ioremap-based EFI 1039 runtime services mapping. 32-bit still uses this one by 1040 default. 1041 nochunk: disable reading files in "chunks" in the EFI 1042 boot stub, as chunking can cause problems with some 1043 firmware implementations. 1044 noruntime : disable EFI runtime services support 1045 debug: enable misc debug output 1046 1047 efi_no_storage_paranoia [EFI; X86] 1048 Using this parameter you can use more than 50% of 1049 your efi variable storage. Use this parameter only if 1050 you are really sure that your UEFI does sane gc and 1051 fulfills the spec otherwise your board may brick. 1052 1053 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] 1054 Add arbitrary attribute to specific memory range by 1055 updating original EFI memory map. 1056 Region of memory which aa attribute is added to is 1057 from ss to ss+nn. 1058 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 1059 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) 1060 attribute is added to range 0x100000000-0x180000000 and 1061 0x10a0000000-0x1120000000. 1062 1063 Using this parameter you can do debugging of EFI memmap 1064 related feature. For example, you can do debugging of 1065 Address Range Mirroring feature even if your box 1066 doesn't support it. 1067 1068 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT 1069 that is to be dynamically loaded by Linux. If there are 1070 multiple variables with the same name but with different 1071 vendor GUIDs, all of them will be loaded. See 1072 Documentation/acpi/ssdt-overlays.txt for details. 1073 1074 1075 eisa_irq_edge= [PARISC,HW] 1076 See header of drivers/parisc/eisa.c. 1077 1078 elanfreq= [X86-32] 1079 See comment before function elanfreq_setup() in 1080 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 1081 1082 elevator= [IOSCHED] 1083 Format: {"cfq" | "deadline" | "noop"} 1084 See Documentation/block/cfq-iosched.txt and 1085 Documentation/block/deadline-iosched.txt for details. 1086 1087 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] 1088 Specifies physical address of start of kernel core 1089 image elf header and optionally the size. Generally 1090 kexec loader will pass this option to capture kernel. 1091 See Documentation/kdump/kdump.txt for details. 1092 1093 enable_mtrr_cleanup [X86] 1094 The kernel tries to adjust MTRR layout from continuous 1095 to discrete, to make X server driver able to add WB 1096 entry later. This parameter enables that. 1097 1098 enable_timer_pin_1 [X86] 1099 Enable PIN 1 of APIC timer 1100 Can be useful to work around chipset bugs 1101 (in particular on some ATI chipsets). 1102 The kernel tries to set a reasonable default. 1103 1104 enforcing [SELINUX] Set initial enforcing status. 1105 Format: {"0" | "1"} 1106 See security/selinux/Kconfig help text. 1107 0 -- permissive (log only, no denials). 1108 1 -- enforcing (deny and log). 1109 Default value is 0. 1110 Value can be changed at runtime via /selinux/enforce. 1111 1112 erst_disable [ACPI] 1113 Disable Error Record Serialization Table (ERST) 1114 support. 1115 1116 ether= [HW,NET] Ethernet cards parameters 1117 This option is obsoleted by the "netdev=" option, which 1118 has equivalent usage. See its documentation for details. 1119 1120 evm= [EVM] 1121 Format: { "fix" } 1122 Permit 'security.evm' to be updated regardless of 1123 current integrity status. 1124 1125 failslab= 1126 fail_page_alloc= 1127 fail_make_request=[KNL] 1128 General fault injection mechanism. 1129 Format: <interval>,<probability>,<space>,<times> 1130 See also Documentation/fault-injection/. 1131 1132 floppy= [HW] 1133 See Documentation/blockdev/floppy.txt. 1134 1135 force_pal_cache_flush 1136 [IA-64] Avoid check_sal_cache_flush which may hang on 1137 buggy SAL_CACHE_FLUSH implementations. Using this 1138 parameter will force ia64_sal_cache_flush to call 1139 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 1140 1141 forcepae [X86-32] 1142 Forcefully enable Physical Address Extension (PAE). 1143 Many Pentium M systems disable PAE but may have a 1144 functionally usable PAE implementation. 1145 Warning: use of this parameter will taint the kernel 1146 and may cause unknown problems. 1147 1148 ftrace=[tracer] 1149 [FTRACE] will set and start the specified tracer 1150 as early as possible in order to facilitate early 1151 boot debugging. 1152 1153 ftrace_dump_on_oops[=orig_cpu] 1154 [FTRACE] will dump the trace buffers on oops. 1155 If no parameter is passed, ftrace will dump 1156 buffers of all CPUs, but if you pass orig_cpu, it will 1157 dump only the buffer of the CPU that triggered the 1158 oops. 1159 1160 ftrace_filter=[function-list] 1161 [FTRACE] Limit the functions traced by the function 1162 tracer at boot up. function-list is a comma separated 1163 list of functions. This list can be changed at run 1164 time by the set_ftrace_filter file in the debugfs 1165 tracing directory. 1166 1167 ftrace_notrace=[function-list] 1168 [FTRACE] Do not trace the functions specified in 1169 function-list. This list can be changed at run time 1170 by the set_ftrace_notrace file in the debugfs 1171 tracing directory. 1172 1173 ftrace_graph_filter=[function-list] 1174 [FTRACE] Limit the top level callers functions traced 1175 by the function graph tracer at boot up. 1176 function-list is a comma separated list of functions 1177 that can be changed at run time by the 1178 set_graph_function file in the debugfs tracing directory. 1179 1180 ftrace_graph_notrace=[function-list] 1181 [FTRACE] Do not trace from the functions specified in 1182 function-list. This list is a comma separated list of 1183 functions that can be changed at run time by the 1184 set_graph_notrace file in the debugfs tracing directory. 1185 1186 gamecon.map[2|3]= 1187 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 1188 support via parallel port (up to 5 devices per port) 1189 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 1190 See also Documentation/input/joystick-parport.txt 1191 1192 gamma= [HW,DRM] 1193 1194 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 1195 Format: off | on 1196 default: on 1197 1198 gcov_persist= [GCOV] When non-zero (default), profiling data for 1199 kernel modules is saved and remains accessible via 1200 debugfs, even when the module is unloaded/reloaded. 1201 When zero, profiling data is discarded and associated 1202 debugfs files are removed at module unload time. 1203 1204 goldfish [X86] Enable the goldfish android emulator platform. 1205 Don't use this when you are not running on the 1206 android emulator 1207 1208 gpt [EFI] Forces disk with valid GPT signature but 1209 invalid Protective MBR to be treated as GPT. If the 1210 primary GPT is corrupted, it enables the backup/alternate 1211 GPT to be used instead. 1212 1213 grcan.enable0= [HW] Configuration of physical interface 0. Determines 1214 the "Enable 0" bit of the configuration register. 1215 Format: 0 | 1 1216 Default: 0 1217 grcan.enable1= [HW] Configuration of physical interface 1. Determines 1218 the "Enable 0" bit of the configuration register. 1219 Format: 0 | 1 1220 Default: 0 1221 grcan.select= [HW] Select which physical interface to use. 1222 Format: 0 | 1 1223 Default: 0 1224 grcan.txsize= [HW] Sets the size of the tx buffer. 1225 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. 1226 Default: 1024 1227 grcan.rxsize= [HW] Sets the size of the rx buffer. 1228 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. 1229 Default: 1024 1230 1231 gpio-mockup.gpio_mockup_ranges 1232 [HW] Sets the ranges of gpiochip of for this device. 1233 Format: <start1>,<end1>,<start2>,<end2>... 1234 1235 hardlockup_all_cpu_backtrace= 1236 [KNL] Should the hard-lockup detector generate 1237 backtraces on all cpus. 1238 Format: <integer> 1239 1240 hashdist= [KNL,NUMA] Large hashes allocated during boot 1241 are distributed across NUMA nodes. Defaults on 1242 for 64-bit NUMA, off otherwise. 1243 Format: 0 | 1 (for off | on) 1244 1245 hcl= [IA-64] SGI's Hardware Graph compatibility layer 1246 1247 hd= [EIDE] (E)IDE hard drive subsystem geometry 1248 Format: <cyl>,<head>,<sect> 1249 1250 hest_disable [ACPI] 1251 Disable Hardware Error Source Table (HEST) support; 1252 corresponding firmware-first mode error processing 1253 logic will be disabled. 1254 1255 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 1256 size of <nn>. This works even on boxes that have no 1257 highmem otherwise. This also works to reduce highmem 1258 size on bigger boxes. 1259 1260 highres= [KNL] Enable/disable high resolution timer mode. 1261 Valid parameters: "on", "off" 1262 Default: "on" 1263 1264 hisax= [HW,ISDN] 1265 See Documentation/isdn/README.HiSax. 1266 1267 hlt [BUGS=ARM,SH] 1268 1269 hpet= [X86-32,HPET] option to control HPET usage 1270 Format: { enable (default) | disable | force | 1271 verbose } 1272 disable: disable HPET and use PIT instead 1273 force: allow force enabled of undocumented chips (ICH4, 1274 VIA, nVidia) 1275 verbose: show contents of HPET registers during setup 1276 1277 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET 1278 registers. Default set by CONFIG_HPET_MMAP_DEFAULT. 1279 1280 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 1281 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 1282 On x86-64 and powerpc, this option can be specified 1283 multiple times interleaved with hugepages= to reserve 1284 huge pages of different sizes. Valid pages sizes on 1285 x86-64 are 2M (when the CPU supports "pse") and 1G 1286 (when the CPU supports the "pdpe1gb" cpuinfo flag). 1287 1288 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 1289 terminal devices. Valid values: 0..8 1290 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 1291 If specified, z/VM IUCV HVC accepts connections 1292 from listed z/VM user IDs only. 1293 1294 hwthread_map= [METAG] Comma-separated list of Linux cpu id to 1295 hardware thread id mappings. 1296 Format: <cpu>:<hwthread> 1297 1298 keep_bootcon [KNL] 1299 Do not unregister boot console at start. This is only 1300 useful for debugging when something happens in the window 1301 between unregistering the boot console and initializing 1302 the real console. 1303 1304 i2c_bus= [HW] Override the default board specific I2C bus speed 1305 or register an additional I2C bus that is not 1306 registered from board initialization code. 1307 Format: 1308 <bus_id>,<clkrate> 1309 1310 i8042.debug [HW] Toggle i8042 debug mode 1311 i8042.unmask_kbd_data 1312 [HW] Enable printing of interrupt data from the KBD port 1313 (disabled by default, and as a pre-condition 1314 requires that i8042.debug=1 be enabled) 1315 i8042.direct [HW] Put keyboard port into non-translated mode 1316 i8042.dumbkbd [HW] Pretend that controller can only read data from 1317 keyboard and cannot control its state 1318 (Don't attempt to blink the leds) 1319 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 1320 i8042.nokbd [HW] Don't check/create keyboard port 1321 i8042.noloop [HW] Disable the AUX Loopback command while probing 1322 for the AUX port 1323 i8042.nomux [HW] Don't check presence of an active multiplexing 1324 controller 1325 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 1326 controllers 1327 i8042.notimeout [HW] Ignore timeout condition signalled by controller 1328 i8042.reset [HW] Reset the controller during init, cleanup and 1329 suspend-to-ram transitions, only during s2r 1330 transitions, or never reset 1331 Format: { 1 | Y | y | 0 | N | n } 1332 1, Y, y: always reset controller 1333 0, N, n: don't ever reset controller 1334 Default: only on s2r transitions on x86; most other 1335 architectures force reset to be always executed 1336 i8042.unlock [HW] Unlock (ignore) the keylock 1337 i8042.kbdreset [HW] Reset device connected to KBD port 1338 1339 i810= [HW,DRM] 1340 1341 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 1342 indicates that the driver is running on unsupported 1343 hardware. 1344 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 1345 does not match list of supported models. 1346 i8k.power_status 1347 [HW] Report power status in /proc/i8k 1348 (disabled by default) 1349 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 1350 capability is set. 1351 1352 i915.invert_brightness= 1353 [DRM] Invert the sense of the variable that is used to 1354 set the brightness of the panel backlight. Normally a 1355 brightness value of 0 indicates backlight switched off, 1356 and the maximum of the brightness value sets the backlight 1357 to maximum brightness. If this parameter is set to 0 1358 (default) and the machine requires it, or this parameter 1359 is set to 1, a brightness value of 0 sets the backlight 1360 to maximum brightness, and the maximum of the brightness 1361 value switches the backlight off. 1362 -1 -- never invert brightness 1363 0 -- machine default 1364 1 -- force brightness inversion 1365 1366 icn= [HW,ISDN] 1367 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 1368 1369 ide-core.nodma= [HW] (E)IDE subsystem 1370 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 1371 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 1372 .cdrom .chs .ignore_cable are additional options 1373 See Documentation/ide/ide.txt. 1374 1375 ide-generic.probe-mask= [HW] (E)IDE subsystem 1376 Format: <int> 1377 Probe mask for legacy ISA IDE ports. Depending on 1378 platform up to 6 ports are supported, enabled by 1379 setting corresponding bits in the mask to 1. The 1380 default value is 0x0, which has a special meaning. 1381 On systems that have PCI, it triggers scanning the 1382 PCI bus for the first and the second port, which 1383 are then probed. On systems without PCI the value 1384 of 0x0 enables probing the two first ports as if it 1385 was 0x3. 1386 1387 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 1388 Claim all unknown PCI IDE storage controllers. 1389 1390 idle= [X86] 1391 Format: idle=poll, idle=halt, idle=nomwait 1392 Poll forces a polling idle loop that can slightly 1393 improve the performance of waking up a idle CPU, but 1394 will use a lot of power and make the system run hot. 1395 Not recommended. 1396 idle=halt: Halt is forced to be used for CPU idle. 1397 In such case C2/C3 won't be used again. 1398 idle=nomwait: Disable mwait for CPU C-states 1399 1400 ieee754= [MIPS] Select IEEE Std 754 conformance mode 1401 Format: { strict | legacy | 2008 | relaxed } 1402 Default: strict 1403 1404 Choose which programs will be accepted for execution 1405 based on the IEEE 754 NaN encoding(s) supported by 1406 the FPU and the NaN encoding requested with the value 1407 of an ELF file header flag individually set by each 1408 binary. Hardware implementations are permitted to 1409 support either or both of the legacy and the 2008 NaN 1410 encoding mode. 1411 1412 Available settings are as follows: 1413 strict accept binaries that request a NaN encoding 1414 supported by the FPU 1415 legacy only accept legacy-NaN binaries, if supported 1416 by the FPU 1417 2008 only accept 2008-NaN binaries, if supported 1418 by the FPU 1419 relaxed accept any binaries regardless of whether 1420 supported by the FPU 1421 1422 The FPU emulator is always able to support both NaN 1423 encodings, so if no FPU hardware is present or it has 1424 been disabled with 'nofpu', then the settings of 1425 'legacy' and '2008' strap the emulator accordingly, 1426 'relaxed' straps the emulator for both legacy-NaN and 1427 2008-NaN, whereas 'strict' enables legacy-NaN only on 1428 legacy processors and both NaN encodings on MIPS32 or 1429 MIPS64 CPUs. 1430 1431 The setting for ABS.fmt/NEG.fmt instruction execution 1432 mode generally follows that for the NaN encoding, 1433 except where unsupported by hardware. 1434 1435 ignore_loglevel [KNL] 1436 Ignore loglevel setting - this will print /all/ 1437 kernel messages to the console. Useful for debugging. 1438 We also add it as printk module parameter, so users 1439 could change it dynamically, usually by 1440 /sys/module/printk/parameters/ignore_loglevel. 1441 1442 ignore_rlimit_data 1443 Ignore RLIMIT_DATA setting for data mappings, 1444 print warning at first misuse. Can be changed via 1445 /sys/module/kernel/parameters/ignore_rlimit_data. 1446 1447 ihash_entries= [KNL] 1448 Set number of hash buckets for inode cache. 1449 1450 ima_appraise= [IMA] appraise integrity measurements 1451 Format: { "off" | "enforce" | "fix" | "log" } 1452 default: "enforce" 1453 1454 ima_appraise_tcb [IMA] 1455 The builtin appraise policy appraises all files 1456 owned by uid=0. 1457 1458 ima_canonical_fmt [IMA] 1459 Use the canonical format for the binary runtime 1460 measurements, instead of host native format. 1461 1462 ima_hash= [IMA] 1463 Format: { md5 | sha1 | rmd160 | sha256 | sha384 1464 | sha512 | ... } 1465 default: "sha1" 1466 1467 The list of supported hash algorithms is defined 1468 in crypto/hash_info.h. 1469 1470 ima_policy= [IMA] 1471 The builtin measurement policy to load during IMA 1472 setup. Specyfing "tcb" as the value, measures all 1473 programs exec'd, files mmap'd for exec, and all files 1474 opened with the read mode bit set by either the 1475 effective uid (euid=0) or uid=0. 1476 Format: "tcb" 1477 1478 ima_tcb [IMA] Deprecated. Use ima_policy= instead. 1479 Load a policy which meets the needs of the Trusted 1480 Computing Base. This means IMA will measure all 1481 programs exec'd, files mmap'd for exec, and all files 1482 opened for read by uid=0. 1483 1484 ima_template= [IMA] 1485 Select one of defined IMA measurements template formats. 1486 Formats: { "ima" | "ima-ng" | "ima-sig" } 1487 Default: "ima-ng" 1488 1489 ima_template_fmt= 1490 [IMA] Define a custom template format. 1491 Format: { "field1|...|fieldN" } 1492 1493 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage 1494 Format: <min_file_size> 1495 Set the minimal file size for using asynchronous hash. 1496 If left unspecified, ahash usage is disabled. 1497 1498 ahash performance varies for different data sizes on 1499 different crypto accelerators. This option can be used 1500 to achieve the best performance for a particular HW. 1501 1502 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 1503 Format: <bufsize> 1504 Set hashing buffer size. Default: 4k. 1505 1506 ahash performance varies for different chunk sizes on 1507 different crypto accelerators. This option can be used 1508 to achieve best performance for particular HW. 1509 1510 init= [KNL] 1511 Format: <full_path> 1512 Run specified binary instead of /sbin/init as init 1513 process. 1514 1515 initcall_debug [KNL] Trace initcalls as they are executed. Useful 1516 for working out where the kernel is dying during 1517 startup. 1518 1519 initcall_blacklist= [KNL] Do not execute a comma-separated list of 1520 initcall functions. Useful for debugging built-in 1521 modules and initcalls. 1522 1523 initrd= [BOOT] Specify the location of the initial ramdisk 1524 1525 init_pkru= [x86] Specify the default memory protection keys rights 1526 register contents for all processes. 0x55555554 by 1527 default (disallow access to all but pkey 0). Can 1528 override in debugfs after boot. 1529 1530 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 1531 Format: <irq> 1532 1533 int_pln_enable [x86] Enable power limit notification interrupt 1534 1535 integrity_audit=[IMA] 1536 Format: { "0" | "1" } 1537 0 -- basic integrity auditing messages. (Default) 1538 1 -- additional integrity auditing messages. 1539 1540 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 1541 on 1542 Enable intel iommu driver. 1543 off 1544 Disable intel iommu driver. 1545 igfx_off [Default Off] 1546 By default, gfx is mapped as normal device. If a gfx 1547 device has a dedicated DMAR unit, the DMAR unit is 1548 bypassed by not enabling DMAR with this option. In 1549 this case, gfx device will use physical address for 1550 DMA. 1551 forcedac [x86_64] 1552 With this option iommu will not optimize to look 1553 for io virtual address below 32-bit forcing dual 1554 address cycle on pci bus for cards supporting greater 1555 than 32-bit addressing. The default is to look 1556 for translation below 32-bit and if not available 1557 then look in the higher range. 1558 strict [Default Off] 1559 With this option on every unmap_single operation will 1560 result in a hardware IOTLB flush operation as opposed 1561 to batching them for performance. 1562 sp_off [Default Off] 1563 By default, super page will be supported if Intel IOMMU 1564 has the capability. With this option, super page will 1565 not be supported. 1566 ecs_off [Default Off] 1567 By default, extended context tables will be supported if 1568 the hardware advertises that it has support both for the 1569 extended tables themselves, and also PASID support. With 1570 this option set, extended tables will not be used even 1571 on hardware which claims to support them. 1572 1573 intel_idle.max_cstate= [KNL,HW,ACPI,X86] 1574 0 disables intel_idle and fall back on acpi_idle. 1575 1 to 9 specify maximum depth of C-state. 1576 1577 intel_pstate= [X86] 1578 disable 1579 Do not enable intel_pstate as the default 1580 scaling driver for the supported processors 1581 passive 1582 Use intel_pstate as a scaling driver, but configure it 1583 to work with generic cpufreq governors (instead of 1584 enabling its internal governor). This mode cannot be 1585 used along with the hardware-managed P-states (HWP) 1586 feature. 1587 force 1588 Enable intel_pstate on systems that prohibit it by default 1589 in favor of acpi-cpufreq. Forcing the intel_pstate driver 1590 instead of acpi-cpufreq may disable platform features, such 1591 as thermal controls and power capping, that rely on ACPI 1592 P-States information being indicated to OSPM and therefore 1593 should be used with caution. This option does not work with 1594 processors that aren't supported by the intel_pstate driver 1595 or on platforms that use pcc-cpufreq instead of acpi-cpufreq. 1596 no_hwp 1597 Do not enable hardware P state control (HWP) 1598 if available. 1599 hwp_only 1600 Only load intel_pstate on systems which support 1601 hardware P state control (HWP) if available. 1602 support_acpi_ppc 1603 Enforce ACPI _PPC performance limits. If the Fixed ACPI 1604 Description Table, specifies preferred power management 1605 profile as "Enterprise Server" or "Performance Server", 1606 then this feature is turned on by default. 1607 per_cpu_perf_limits 1608 Allow per-logical-CPU P-State performance control limits using 1609 cpufreq sysfs interface 1610 1611 intremap= [X86-64, Intel-IOMMU] 1612 on enable Interrupt Remapping (default) 1613 off disable Interrupt Remapping 1614 nosid disable Source ID checking 1615 no_x2apic_optout 1616 BIOS x2APIC opt-out request will be ignored 1617 nopost disable Interrupt Posting 1618 1619 iomem= Disable strict checking of access to MMIO memory 1620 strict regions from userspace. 1621 relaxed 1622 1623 iommu= [x86] 1624 off 1625 force 1626 noforce 1627 biomerge 1628 panic 1629 nopanic 1630 merge 1631 nomerge 1632 forcesac 1633 soft 1634 pt [x86, IA-64] 1635 nobypass [PPC/POWERNV] 1636 Disable IOMMU bypass, using IOMMU for PCI devices. 1637 1638 1639 io7= [HW] IO7 for Marvel based alpha systems 1640 See comment before marvel_specify_io7 in 1641 arch/alpha/kernel/core_marvel.c. 1642 1643 io_delay= [X86] I/O delay method 1644 0x80 1645 Standard port 0x80 based delay 1646 0xed 1647 Alternate port 0xed based delay (needed on some systems) 1648 udelay 1649 Simple two microseconds delay 1650 none 1651 No delay 1652 1653 ip= [IP_PNP] 1654 See Documentation/filesystems/nfs/nfsroot.txt. 1655 1656 irqaffinity= [SMP] Set the default irq affinity mask 1657 The argument is a cpu list, as described above. 1658 1659 irqfixup [HW] 1660 When an interrupt is not handled search all handlers 1661 for it. Intended to get systems with badly broken 1662 firmware running. 1663 1664 irqpoll [HW] 1665 When an interrupt is not handled search all handlers 1666 for it. Also check all handlers each timer 1667 interrupt. Intended to get systems with badly broken 1668 firmware running. 1669 1670 isapnp= [ISAPNP] 1671 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1672 1673 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1674 The argument is a cpu list, as described above. 1675 1676 This option can be used to specify one or more CPUs 1677 to isolate from the general SMP balancing and scheduling 1678 algorithms. You can move a process onto or off an 1679 "isolated" CPU via the CPU affinity syscalls or cpuset. 1680 <cpu number> begins at 0 and the maximum value is 1681 "number of CPUs in system - 1". 1682 1683 This option is the preferred way to isolate CPUs. The 1684 alternative -- manually setting the CPU mask of all 1685 tasks in the system -- can cause problems and 1686 suboptimal load balancer performance. 1687 1688 iucv= [HW,NET] 1689 1690 ivrs_ioapic [HW,X86_64] 1691 Provide an override to the IOAPIC-ID<->DEVICE-ID 1692 mapping provided in the IVRS ACPI table. For 1693 example, to map IOAPIC-ID decimal 10 to 1694 PCI device 00:14.0 write the parameter as: 1695 ivrs_ioapic[10]=00:14.0 1696 1697 ivrs_hpet [HW,X86_64] 1698 Provide an override to the HPET-ID<->DEVICE-ID 1699 mapping provided in the IVRS ACPI table. For 1700 example, to map HPET-ID decimal 0 to 1701 PCI device 00:14.0 write the parameter as: 1702 ivrs_hpet[0]=00:14.0 1703 1704 ivrs_acpihid [HW,X86_64] 1705 Provide an override to the ACPI-HID:UID<->DEVICE-ID 1706 mapping provided in the IVRS ACPI table. For 1707 example, to map UART-HID:UID AMD0020:0 to 1708 PCI device 00:14.5 write the parameter as: 1709 ivrs_acpihid[00:14.5]=AMD0020:0 1710 1711 js= [HW,JOY] Analog joystick 1712 See Documentation/input/joystick.txt. 1713 1714 nokaslr [KNL] 1715 When CONFIG_RANDOMIZE_BASE is set, this disables 1716 kernel and module base offset ASLR (Address Space 1717 Layout Randomization). 1718 1719 keepinitrd [HW,ARM] 1720 1721 kernelcore= [KNL,X86,IA-64,PPC] 1722 Format: nn[KMGTPE] | "mirror" 1723 This parameter 1724 specifies the amount of memory usable by the kernel 1725 for non-movable allocations. The requested amount is 1726 spread evenly throughout all nodes in the system. The 1727 remaining memory in each node is used for Movable 1728 pages. In the event, a node is too small to have both 1729 kernelcore and Movable pages, kernelcore pages will 1730 take priority and other nodes will have a larger number 1731 of Movable pages. The Movable zone is used for the 1732 allocation of pages that may be reclaimed or moved 1733 by the page migration subsystem. This means that 1734 HugeTLB pages may not be allocated from this zone. 1735 Note that allocations like PTEs-from-HighMem still 1736 use the HighMem zone if it exists, and the Normal 1737 zone if it does not. 1738 1739 Instead of specifying the amount of memory (nn[KMGTPE]), 1740 you can specify "mirror" option. In case "mirror" 1741 option is specified, mirrored (reliable) memory is used 1742 for non-movable allocations and remaining memory is used 1743 for Movable pages. nn[KMGTPE] and "mirror" are exclusive, 1744 so you can NOT specify nn[KMGTPE] and "mirror" at the same 1745 time. 1746 1747 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 1748 Format: <Controller#>[,poll interval] 1749 The controller # is the number of the ehci usb debug 1750 port as it is probed via PCI. The poll interval is 1751 optional and is the number seconds in between 1752 each poll cycle to the debug port in case you need 1753 the functionality for interrupting the kernel with 1754 gdb or control-c on the dbgp connection. When 1755 not using this parameter you use sysrq-g to break into 1756 the kernel debugger. 1757 1758 kgdboc= [KGDB,HW] kgdb over consoles. 1759 Requires a tty driver that supports console polling, 1760 or a supported polling keyboard driver (non-usb). 1761 Serial only format: <serial_device>[,baud] 1762 keyboard only format: kbd 1763 keyboard and serial format: kbd,<serial_device>[,baud] 1764 Optional Kernel mode setting: 1765 kms, kbd format: kms,kbd 1766 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 1767 1768 kgdbwait [KGDB] Stop kernel execution and enter the 1769 kernel debugger at the earliest opportunity. 1770 1771 kmac= [MIPS] korina ethernet MAC address. 1772 Configure the RouterBoard 532 series on-chip 1773 Ethernet adapter MAC address. 1774 1775 kmemleak= [KNL] Boot-time kmemleak enable/disable 1776 Valid arguments: on, off 1777 Default: on 1778 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, 1779 the default is off. 1780 1781 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode 1782 Valid arguments: 0, 1, 2 1783 kmemcheck=0 (disabled) 1784 kmemcheck=1 (enabled) 1785 kmemcheck=2 (one-shot mode) 1786 Default: 2 (one-shot mode) 1787 1788 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1789 Default is 0 (don't ignore, but inject #GP) 1790 1791 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit 1792 KVM MMU at runtime. 1793 Default is 0 (off) 1794 1795 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1796 Default is 1 (enabled) 1797 1798 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 1799 for all guests. 1800 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. 1801 1802 kvm-intel.ept= [KVM,Intel] Disable extended page tables 1803 (virtualized MMU) support on capable Intel chips. 1804 Default is 1 (enabled) 1805 1806 kvm-intel.emulate_invalid_guest_state= 1807 [KVM,Intel] Enable emulation of invalid guest states 1808 Default is 0 (disabled) 1809 1810 kvm-intel.flexpriority= 1811 [KVM,Intel] Disable FlexPriority feature (TPR shadow). 1812 Default is 1 (enabled) 1813 1814 kvm-intel.nested= 1815 [KVM,Intel] Enable VMX nesting (nVMX). 1816 Default is 0 (disabled) 1817 1818 kvm-intel.unrestricted_guest= 1819 [KVM,Intel] Disable unrestricted guest feature 1820 (virtualized real and unpaged mode) on capable 1821 Intel chips. Default is 1 (enabled) 1822 1823 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 1824 feature (tagged TLBs) on capable Intel chips. 1825 Default is 1 (enabled) 1826 1827 l2cr= [PPC] 1828 1829 l3cr= [PPC] 1830 1831 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1832 disabled it. 1833 1834 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline 1835 value for LAPIC timer one-shot implementation. Default 1836 back to the programmable timer unit in the LAPIC. 1837 1838 lapic_timer_c2_ok [X86,APIC] trust the local apic timer 1839 in C2 power state. 1840 1841 libata.dma= [LIBATA] DMA control 1842 libata.dma=0 Disable all PATA and SATA DMA 1843 libata.dma=1 PATA and SATA Disk DMA only 1844 libata.dma=2 ATAPI (CDROM) DMA only 1845 libata.dma=4 Compact Flash DMA only 1846 Combinations also work, so libata.dma=3 enables DMA 1847 for disks and CDROMs, but not CFs. 1848 1849 libata.ignore_hpa= [LIBATA] Ignore HPA limit 1850 libata.ignore_hpa=0 keep BIOS limits (default) 1851 libata.ignore_hpa=1 ignore limits, using full disk 1852 1853 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1854 when set. 1855 Format: <int> 1856 1857 libata.force= [LIBATA] Force configurations. The format is comma 1858 separated list of "[ID:]VAL" where ID is 1859 PORT[.DEVICE]. PORT and DEVICE are decimal numbers 1860 matching port, link or device. Basically, it matches 1861 the ATA ID string printed on console by libata. If 1862 the whole ID part is omitted, the last PORT and DEVICE 1863 values are used. If ID hasn't been specified yet, the 1864 configuration applies to all ports, links and devices. 1865 1866 If only DEVICE is omitted, the parameter applies to 1867 the port and all links and devices behind it. DEVICE 1868 number of 0 either selects the first device or the 1869 first fan-out link behind PMP device. It does not 1870 select the host link. DEVICE number of 15 selects the 1871 host link and device attached to it. 1872 1873 The VAL specifies the configuration to force. As long 1874 as there's no ambiguity shortcut notation is allowed. 1875 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1876 The following configurations can be forced. 1877 1878 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1879 Any ID with matching PORT is used. 1880 1881 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1882 1883 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1884 udma[/][16,25,33,44,66,100,133] notation is also 1885 allowed. 1886 1887 * [no]ncq: Turn on or off NCQ. 1888 1889 * [no]ncqtrim: Turn off queued DSM TRIM. 1890 1891 * nohrst, nosrst, norst: suppress hard, soft 1892 and both resets. 1893 1894 * rstonce: only attempt one reset during 1895 hot-unplug link recovery 1896 1897 * dump_id: dump IDENTIFY data. 1898 1899 * atapi_dmadir: Enable ATAPI DMADIR bridge support 1900 1901 * disable: Disable this device. 1902 1903 If there are multiple matching configurations changing 1904 the same attribute, the last one is used. 1905 1906 memblock=debug [KNL] Enable memblock debug messages. 1907 1908 load_ramdisk= [RAM] List of ramdisks to load from floppy 1909 See Documentation/blockdev/ramdisk.txt. 1910 1911 lockd.nlm_grace_period=P [NFS] Assign grace period. 1912 Format: <integer> 1913 1914 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1915 Format: <integer> 1916 1917 lockd.nlm_timeout=T [NFS] Assign timeout value. 1918 Format: <integer> 1919 1920 lockd.nlm_udpport=M [NFS] Assign UDP port. 1921 Format: <integer> 1922 1923 locktorture.nreaders_stress= [KNL] 1924 Set the number of locking read-acquisition kthreads. 1925 Defaults to being automatically set based on the 1926 number of online CPUs. 1927 1928 locktorture.nwriters_stress= [KNL] 1929 Set the number of locking write-acquisition kthreads. 1930 1931 locktorture.onoff_holdoff= [KNL] 1932 Set time (s) after boot for CPU-hotplug testing. 1933 1934 locktorture.onoff_interval= [KNL] 1935 Set time (s) between CPU-hotplug operations, or 1936 zero to disable CPU-hotplug testing. 1937 1938 locktorture.shuffle_interval= [KNL] 1939 Set task-shuffle interval (jiffies). Shuffling 1940 tasks allows some CPUs to go into dyntick-idle 1941 mode during the locktorture test. 1942 1943 locktorture.shutdown_secs= [KNL] 1944 Set time (s) after boot system shutdown. This 1945 is useful for hands-off automated testing. 1946 1947 locktorture.stat_interval= [KNL] 1948 Time (s) between statistics printk()s. 1949 1950 locktorture.stutter= [KNL] 1951 Time (s) to stutter testing, for example, 1952 specifying five seconds causes the test to run for 1953 five seconds, wait for five seconds, and so on. 1954 This tests the locking primitive's ability to 1955 transition abruptly to and from idle. 1956 1957 locktorture.torture_runnable= [BOOT] 1958 Start locktorture running at boot time. 1959 1960 locktorture.torture_type= [KNL] 1961 Specify the locking implementation to test. 1962 1963 locktorture.verbose= [KNL] 1964 Enable additional printk() statements. 1965 1966 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1967 Format: <irq> 1968 1969 loglevel= All Kernel Messages with a loglevel smaller than the 1970 console loglevel will be printed to the console. It can 1971 also be changed with klogd or other programs. The 1972 loglevels are defined as follows: 1973 1974 0 (KERN_EMERG) system is unusable 1975 1 (KERN_ALERT) action must be taken immediately 1976 2 (KERN_CRIT) critical conditions 1977 3 (KERN_ERR) error conditions 1978 4 (KERN_WARNING) warning conditions 1979 5 (KERN_NOTICE) normal but significant condition 1980 6 (KERN_INFO) informational 1981 7 (KERN_DEBUG) debug-level messages 1982 1983 log_buf_len=n[KMG] Sets the size of the printk ring buffer, 1984 in bytes. n must be a power of two and greater 1985 than the minimal size. The minimal size is defined 1986 by LOG_BUF_SHIFT kernel config parameter. There is 1987 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter 1988 that allows to increase the default size depending on 1989 the number of CPUs. See init/Kconfig for more details. 1990 1991 logo.nologo [FB] Disables display of the built-in Linux logo. 1992 This may be used to provide more screen space for 1993 kernel log messages and is useful when debugging 1994 kernel boot problems. 1995 1996 lp=0 [LP] Specify parallel ports to use, e.g, 1997 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1998 lp=reset first parallel port). 'lp=0' disables the 1999 lp=auto printer driver. 'lp=reset' (which can be 2000 specified in addition to the ports) causes 2001 attached printers to be reset. Using 2002 lp=port1,port2,... specifies the parallel ports 2003 to associate lp devices with, starting with 2004 lp0. A port specification may be 'none' to skip 2005 that lp device, or a parport name such as 2006 'parport0'. Specifying 'lp=auto' instead of a 2007 port specification list means that device IDs 2008 from each port should be examined, to see if 2009 an IEEE 1284-compliant printer is attached; if 2010 so, the driver will manage that printer. 2011 See also header of drivers/char/lp.c. 2012 2013 lpj=n [KNL] 2014 Sets loops_per_jiffy to given constant, thus avoiding 2015 time-consuming boot-time autodetection (up to 250 ms per 2016 CPU). 0 enables autodetection (default). To determine 2017 the correct value for your kernel, boot with normal 2018 autodetection and see what value is printed. Note that 2019 on SMP systems the preset will be applied to all CPUs, 2020 which is likely to cause problems if your CPUs need 2021 significantly divergent settings. An incorrect value 2022 will cause delays in the kernel to be wrong, leading to 2023 unpredictable I/O errors and other breakage. Although 2024 unlikely, in the extreme case this might damage your 2025 hardware. 2026 2027 ltpc= [NET] 2028 Format: <io>,<irq>,<dma> 2029 2030 machvec= [IA-64] Force the use of a particular machine-vector 2031 (machvec) in a generic kernel. 2032 Example: machvec=hpzx1_swiotlb 2033 2034 machtype= [Loongson] Share the same kernel image file between different 2035 yeeloong laptop. 2036 Example: machtype=lemote-yeeloong-2f-7inch 2037 2038 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 2039 than or equal to this physical address is ignored. 2040 2041 maxcpus= [SMP] Maximum number of processors that an SMP kernel 2042 will bring up during bootup. maxcpus=n : n >= 0 limits 2043 the kernel to bring up 'n' processors. Surely after 2044 bootup you can bring up the other plugged cpu by executing 2045 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus 2046 only takes effect during system bootup. 2047 While n=0 is a special case, it is equivalent to "nosmp", 2048 which also disables the IO APIC. 2049 2050 max_loop= [LOOP] The number of loop block devices that get 2051 (loop.max_loop) unconditionally pre-created at init time. The default 2052 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead 2053 of statically allocating a predefined number, loop 2054 devices can be requested on-demand with the 2055 /dev/loop-control interface. 2056 2057 mce [X86-32] Machine Check Exception 2058 2059 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 2060 2061 md= [HW] RAID subsystems devices and level 2062 See Documentation/admin-guide/md.rst. 2063 2064 mdacon= [MDA] 2065 Format: <first>,<last> 2066 Specifies range of consoles to be captured by the MDA. 2067 2068 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 2069 Amount of memory to be used when the kernel is not able 2070 to see the whole system memory or for test. 2071 [X86] Work as limiting max address. Use together 2072 with memmap= to avoid physical address space collisions. 2073 Without memmap= PCI devices could be placed at addresses 2074 belonging to unused RAM. 2075 2076 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 2077 memory. 2078 2079 memchunk=nn[KMG] 2080 [KNL,SH] Allow user to override the default size for 2081 per-device physically contiguous DMA buffers. 2082 2083 memhp_default_state=online/offline 2084 [KNL] Set the initial state for the memory hotplug 2085 onlining policy. If not specified, the default value is 2086 set according to the 2087 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config 2088 option. 2089 See Documentation/memory-hotplug.txt. 2090 2091 memmap=exactmap [KNL,X86] Enable setting of an exact 2092 E820 memory map, as specified by the user. 2093 Such memmap=exactmap lines can be constructed based on 2094 BIOS output or other requirements. See the memmap=nn@ss 2095 option description. 2096 2097 memmap=nn[KMG]@ss[KMG] 2098 [KNL] Force usage of a specific region of memory. 2099 Region of memory to be used is from ss to ss+nn. 2100 2101 memmap=nn[KMG]#ss[KMG] 2102 [KNL,ACPI] Mark specific memory as ACPI data. 2103 Region of memory to be marked is from ss to ss+nn. 2104 2105 memmap=nn[KMG]$ss[KMG] 2106 [KNL,ACPI] Mark specific memory as reserved. 2107 Region of memory to be reserved is from ss to ss+nn. 2108 Example: Exclude memory from 0x18690000-0x1869ffff 2109 memmap=64K$0x18690000 2110 or 2111 memmap=0x10000$0x18690000 2112 2113 memmap=nn[KMG]!ss[KMG] 2114 [KNL,X86] Mark specific memory as protected. 2115 Region of memory to be used, from ss to ss+nn. 2116 The memory region may be marked as e820 type 12 (0xc) 2117 and is NVDIMM or ADR memory. 2118 2119 memory_corruption_check=0/1 [X86] 2120 Some BIOSes seem to corrupt the first 64k of 2121 memory when doing things like suspend/resume. 2122 Setting this option will scan the memory 2123 looking for corruption. Enabling this will 2124 both detect corruption and prevent the kernel 2125 from using the memory being corrupted. 2126 However, its intended as a diagnostic tool; if 2127 repeatable BIOS-originated corruption always 2128 affects the same memory, you can use memmap= 2129 to prevent the kernel from using that memory. 2130 2131 memory_corruption_check_size=size [X86] 2132 By default it checks for corruption in the low 2133 64k, making this memory unavailable for normal 2134 use. Use this parameter to scan for 2135 corruption in more or less memory. 2136 2137 memory_corruption_check_period=seconds [X86] 2138 By default it checks for corruption every 60 2139 seconds. Use this parameter to check at some 2140 other rate. 0 disables periodic checking. 2141 2142 memtest= [KNL,X86,ARM] Enable memtest 2143 Format: <integer> 2144 default : 0 <disable> 2145 Specifies the number of memtest passes to be 2146 performed. Each pass selects another test 2147 pattern from a given set of patterns. Memtest 2148 fills the memory with this pattern, validates 2149 memory contents and reserves bad memory 2150 regions that are detected. 2151 2152 mem_sleep_default= [SUSPEND] Default system suspend mode: 2153 s2idle - Suspend-To-Idle 2154 shallow - Power-On Suspend or equivalent (if supported) 2155 deep - Suspend-To-RAM or equivalent (if supported) 2156 See Documentation/power/states.txt. 2157 2158 meye.*= [HW] Set MotionEye Camera parameters 2159 See Documentation/video4linux/meye.txt. 2160 2161 mfgpt_irq= [IA-32] Specify the IRQ to use for the 2162 Multi-Function General Purpose Timers on AMD Geode 2163 platforms. 2164 2165 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 2166 the BIOS has incorrectly applied a workaround. TinyBIOS 2167 version 0.98 is known to be affected, 0.99 fixes the 2168 problem by letting the user disable the workaround. 2169 2170 mga= [HW,DRM] 2171 2172 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 2173 physical address is ignored. 2174 2175 mini2440= [ARM,HW,KNL] 2176 Format:[0..2][b][c][t] 2177 Default: "0tb" 2178 MINI2440 configuration specification: 2179 0 - The attached screen is the 3.5" TFT 2180 1 - The attached screen is the 7" TFT 2181 2 - The VGA Shield is attached (1024x768) 2182 Leaving out the screen size parameter will not load 2183 the TFT driver, and the framebuffer will be left 2184 unconfigured. 2185 b - Enable backlight. The TFT backlight pin will be 2186 linked to the kernel VESA blanking code and a GPIO 2187 LED. This parameter is not necessary when using the 2188 VGA shield. 2189 c - Enable the s3c camera interface. 2190 t - Reserved for enabling touchscreen support. The 2191 touchscreen support is not enabled in the mainstream 2192 kernel as of 2.6.30, a preliminary port can be found 2193 in the "bleeding edge" mini2440 support kernel at 2194 http://repo.or.cz/w/linux-2.6/mini2440.git 2195 2196 mminit_loglevel= 2197 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 2198 parameter allows control of the logging verbosity for 2199 the additional memory initialisation checks. A value 2200 of 0 disables mminit logging and a level of 4 will 2201 log everything. Information is printed at KERN_DEBUG 2202 so loglevel=8 may also need to be specified. 2203 2204 module.sig_enforce 2205 [KNL] When CONFIG_MODULE_SIG is set, this means that 2206 modules without (valid) signatures will fail to load. 2207 Note that if CONFIG_MODULE_SIG_FORCE is set, that 2208 is always true, so this option does nothing. 2209 2210 module_blacklist= [KNL] Do not load a comma-separated list of 2211 modules. Useful for debugging problem modules. 2212 2213 mousedev.tap_time= 2214 [MOUSE] Maximum time between finger touching and 2215 leaving touchpad surface for touch to be considered 2216 a tap and be reported as a left button click (for 2217 touchpads working in absolute mode only). 2218 Format: <msecs> 2219 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 2220 reporting absolute coordinates, such as tablets 2221 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 2222 reporting absolute coordinates, such as tablets 2223 2224 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 2225 is similar to kernelcore except it specifies the 2226 amount of memory used for migratable allocations. 2227 If both kernelcore and movablecore is specified, 2228 then kernelcore will be at *least* the specified 2229 value but may be more. If movablecore on its own 2230 is specified, the administrator must be careful 2231 that the amount of memory usable for all allocations 2232 is not too small. 2233 2234 movable_node [KNL] Boot-time switch to enable the effects 2235 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details. 2236 2237 MTD_Partition= [MTD] 2238 Format: <name>,<region-number>,<size>,<offset> 2239 2240 MTD_Region= [MTD] Format: 2241 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 2242 2243 mtdparts= [MTD] 2244 See drivers/mtd/cmdlinepart.c. 2245 2246 multitce=off [PPC] This parameter disables the use of the pSeries 2247 firmware feature for updating multiple TCE entries 2248 at a time. 2249 2250 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 2251 2252 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 2253 2254 boundary - index of last SLC block on Flex-OneNAND. 2255 The remaining blocks are configured as MLC blocks. 2256 lock - Configure if Flex-OneNAND boundary should be locked. 2257 Once locked, the boundary cannot be changed. 2258 1 indicates lock status, 0 indicates unlock status. 2259 2260 mtdset= [ARM] 2261 ARM/S3C2412 JIVE boot control 2262 2263 See arch/arm/mach-s3c2412/mach-jive.c 2264 2265 mtouchusb.raw_coordinates= 2266 [HW] Make the MicroTouch USB driver use raw coordinates 2267 ('y', default) or cooked coordinates ('n') 2268 2269 mtrr_chunk_size=nn[KMG] [X86] 2270 used for mtrr cleanup. It is largest continuous chunk 2271 that could hold holes aka. UC entries. 2272 2273 mtrr_gran_size=nn[KMG] [X86] 2274 Used for mtrr cleanup. It is granularity of mtrr block. 2275 Default is 1. 2276 Large value could prevent small alignment from 2277 using up MTRRs. 2278 2279 mtrr_spare_reg_nr=n [X86] 2280 Format: <integer> 2281 Range: 0,7 : spare reg number 2282 Default : 1 2283 Used for mtrr cleanup. It is spare mtrr entries number. 2284 Set to 2 or more if your graphical card needs more. 2285 2286 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 2287 2288 netdev= [NET] Network devices parameters 2289 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 2290 Note that mem_start is often overloaded to mean 2291 something different and driver-specific. 2292 This usage is only documented in each driver source 2293 file if at all. 2294 2295 nf_conntrack.acct= 2296 [NETFILTER] Enable connection tracking flow accounting 2297 0 to disable accounting 2298 1 to enable accounting 2299 Default value is 0. 2300 2301 nfsaddrs= [NFS] Deprecated. Use ip= instead. 2302 See Documentation/filesystems/nfs/nfsroot.txt. 2303 2304 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 2305 See Documentation/filesystems/nfs/nfsroot.txt. 2306 2307 nfsrootdebug [NFS] enable nfsroot debugging messages. 2308 See Documentation/filesystems/nfs/nfsroot.txt. 2309 2310 nfs.callback_nr_threads= 2311 [NFSv4] set the total number of threads that the 2312 NFS client will assign to service NFSv4 callback 2313 requests. 2314 2315 nfs.callback_tcpport= 2316 [NFS] set the TCP port on which the NFSv4 callback 2317 channel should listen. 2318 2319 nfs.cache_getent= 2320 [NFS] sets the pathname to the program which is used 2321 to update the NFS client cache entries. 2322 2323 nfs.cache_getent_timeout= 2324 [NFS] sets the timeout after which an attempt to 2325 update a cache entry is deemed to have failed. 2326 2327 nfs.idmap_cache_timeout= 2328 [NFS] set the maximum lifetime for idmapper cache 2329 entries. 2330 2331 nfs.enable_ino64= 2332 [NFS] enable 64-bit inode numbers. 2333 If zero, the NFS client will fake up a 32-bit inode 2334 number for the readdir() and stat() syscalls instead 2335 of returning the full 64-bit number. 2336 The default is to return 64-bit inode numbers. 2337 2338 nfs.max_session_cb_slots= 2339 [NFSv4.1] Sets the maximum number of session 2340 slots the client will assign to the callback 2341 channel. This determines the maximum number of 2342 callbacks the client will process in parallel for 2343 a particular server. 2344 2345 nfs.max_session_slots= 2346 [NFSv4.1] Sets the maximum number of session slots 2347 the client will attempt to negotiate with the server. 2348 This limits the number of simultaneous RPC requests 2349 that the client can send to the NFSv4.1 server. 2350 Note that there is little point in setting this 2351 value higher than the max_tcp_slot_table_limit. 2352 2353 nfs.nfs4_disable_idmapping= 2354 [NFSv4] When set to the default of '1', this option 2355 ensures that both the RPC level authentication 2356 scheme and the NFS level operations agree to use 2357 numeric uids/gids if the mount is using the 2358 'sec=sys' security flavour. In effect it is 2359 disabling idmapping, which can make migration from 2360 legacy NFSv2/v3 systems to NFSv4 easier. 2361 Servers that do not support this mode of operation 2362 will be autodetected by the client, and it will fall 2363 back to using the idmapper. 2364 To turn off this behaviour, set the value to '0'. 2365 nfs.nfs4_unique_id= 2366 [NFS4] Specify an additional fixed unique ident- 2367 ification string that NFSv4 clients can insert into 2368 their nfs_client_id4 string. This is typically a 2369 UUID that is generated at system install time. 2370 2371 nfs.send_implementation_id = 2372 [NFSv4.1] Send client implementation identification 2373 information in exchange_id requests. 2374 If zero, no implementation identification information 2375 will be sent. 2376 The default is to send the implementation identification 2377 information. 2378 2379 nfs.recover_lost_locks = 2380 [NFSv4] Attempt to recover locks that were lost due 2381 to a lease timeout on the server. Please note that 2382 doing this risks data corruption, since there are 2383 no guarantees that the file will remain unchanged 2384 after the locks are lost. 2385 If you want to enable the kernel legacy behaviour of 2386 attempting to recover these locks, then set this 2387 parameter to '1'. 2388 The default parameter value of '0' causes the kernel 2389 not to attempt recovery of lost locks. 2390 2391 nfs4.layoutstats_timer = 2392 [NFSv4.2] Change the rate at which the kernel sends 2393 layoutstats to the pNFS metadata server. 2394 2395 Setting this to value to 0 causes the kernel to use 2396 whatever value is the default set by the layout 2397 driver. A non-zero value sets the minimum interval 2398 in seconds between layoutstats transmissions. 2399 2400 nfsd.nfs4_disable_idmapping= 2401 [NFSv4] When set to the default of '1', the NFSv4 2402 server will return only numeric uids and gids to 2403 clients using auth_sys, and will accept numeric uids 2404 and gids from such clients. This is intended to ease 2405 migration from NFSv2/v3. 2406 2407 objlayoutdriver.osd_login_prog= 2408 [NFS] [OBJLAYOUT] sets the pathname to the program which 2409 is used to automatically discover and login into new 2410 osd-targets. Please see: 2411 Documentation/filesystems/pnfs.txt for more explanations 2412 2413 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take 2414 when a NMI is triggered. 2415 Format: [state][,regs][,debounce][,die] 2416 2417 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 2418 Format: [panic,][nopanic,][num] 2419 Valid num: 0 or 1 2420 0 - turn hardlockup detector in nmi_watchdog off 2421 1 - turn hardlockup detector in nmi_watchdog on 2422 When panic is specified, panic when an NMI watchdog 2423 timeout occurs (or 'nopanic' to override the opposite 2424 default). To disable both hard and soft lockup detectors, 2425 please see 'nowatchdog'. 2426 This is useful when you use a panic=... timeout and 2427 need the box quickly up again. 2428 2429 netpoll.carrier_timeout= 2430 [NET] Specifies amount of time (in seconds) that 2431 netpoll should wait for a carrier. By default netpoll 2432 waits 4 seconds. 2433 2434 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 2435 emulation library even if a 387 maths coprocessor 2436 is present. 2437 2438 no_console_suspend 2439 [HW] Never suspend the console 2440 Disable suspending of consoles during suspend and 2441 hibernate operations. Once disabled, debugging 2442 messages can reach various consoles while the rest 2443 of the system is being put to sleep (ie, while 2444 debugging driver suspend/resume hooks). This may 2445 not work reliably with all consoles, but is known 2446 to work with serial and VGA consoles. 2447 To facilitate more flexible debugging, we also add 2448 console_suspend, a printk module parameter to control 2449 it. Users could use console_suspend (usually 2450 /sys/module/printk/parameters/console_suspend) to 2451 turn on/off it dynamically. 2452 2453 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 2454 caches in the slab allocator. Saves per-node memory, 2455 but will impact performance. 2456 2457 noalign [KNL,ARM] 2458 2459 noapic [SMP,APIC] Tells the kernel to not make use of any 2460 IOAPICs that may be present in the system. 2461 2462 noautogroup Disable scheduler automatic task group creation. 2463 2464 nobats [PPC] Do not use BATs for mapping kernel lowmem 2465 on "Classic" PPC cores. 2466 2467 nocache [ARM] 2468 2469 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 2470 2471 nodelayacct [KNL] Disable per-task delay accounting 2472 2473 nodsp [SH] Disable hardware DSP at boot time. 2474 2475 noefi Disable EFI runtime services support. 2476 2477 noexec [IA-64] 2478 2479 noexec [X86] 2480 On X86-32 available only on PAE configured kernels. 2481 noexec=on: enable non-executable mappings (default) 2482 noexec=off: disable non-executable mappings 2483 2484 nosmap [X86] 2485 Disable SMAP (Supervisor Mode Access Prevention) 2486 even if it is supported by processor. 2487 2488 nosmep [X86] 2489 Disable SMEP (Supervisor Mode Execution Prevention) 2490 even if it is supported by processor. 2491 2492 noexec32 [X86-64] 2493 This affects only 32-bit executables. 2494 noexec32=on: enable non-executable mappings (default) 2495 read doesn't imply executable mappings 2496 noexec32=off: disable non-executable mappings 2497 read implies executable mappings 2498 2499 nofpu [MIPS,SH] Disable hardware FPU at boot time. 2500 2501 nofxsr [BUGS=X86-32] Disables x86 floating point extended 2502 register save and restore. The kernel will only save 2503 legacy floating-point registers on task switch. 2504 2505 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings. 2506 2507 nosmt [KNL,S390] Disable symmetric multithreading (SMT). 2508 Equivalent to smt=1. 2509 2510 noxsave [BUGS=X86] Disables x86 extended register state save 2511 and restore using xsave. The kernel will fallback to 2512 enabling legacy floating-point and sse state. 2513 2514 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended 2515 register states. The kernel will fall back to use 2516 xsave to save the states. By using this parameter, 2517 performance of saving the states is degraded because 2518 xsave doesn't support modified optimization while 2519 xsaveopt supports it on xsaveopt enabled systems. 2520 2521 noxsaves [X86] Disables xsaves and xrstors used in saving and 2522 restoring x86 extended register state in compacted 2523 form of xsave area. The kernel will fall back to use 2524 xsaveopt and xrstor to save and restore the states 2525 in standard form of xsave area. By using this 2526 parameter, xsave area per process might occupy more 2527 memory on xsaves enabled systems. 2528 2529 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 2530 wfi(ARM) instruction doesn't work correctly and not to 2531 use it. This is also useful when using JTAG debugger. 2532 2533 no_file_caps Tells the kernel not to honor file capabilities. The 2534 only way then for a file to be executed with privilege 2535 is to be setuid root or executed by root. 2536 2537 nohalt [IA-64] Tells the kernel not to use the power saving 2538 function PAL_HALT_LIGHT when idle. This increases 2539 power-consumption. On the positive side, it reduces 2540 interrupt wake-up latency, which may improve performance 2541 in certain environments such as networked servers or 2542 real-time systems. 2543 2544 nohibernate [HIBERNATION] Disable hibernation and resume. 2545 2546 nohz= [KNL] Boottime enable/disable dynamic ticks 2547 Valid arguments: on, off 2548 Default: on 2549 2550 nohz_full= [KNL,BOOT] 2551 The argument is a cpu list, as described above. 2552 In kernels built with CONFIG_NO_HZ_FULL=y, set 2553 the specified list of CPUs whose tick will be stopped 2554 whenever possible. The boot CPU will be forced outside 2555 the range to maintain the timekeeping. 2556 The CPUs in this range must also be included in the 2557 rcu_nocbs= set. 2558 2559 noiotrap [SH] Disables trapped I/O port accesses. 2560 2561 noirqdebug [X86-32] Disables the code which attempts to detect and 2562 disable unhandled interrupt sources. 2563 2564 no_timer_check [X86,APIC] Disables the code which tests for 2565 broken timer IRQ sources. 2566 2567 noisapnp [ISAPNP] Disables ISA PnP code. 2568 2569 noinitrd [RAM] Tells the kernel not to load any configured 2570 initial RAM disk. 2571 2572 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 2573 remapping. 2574 [Deprecated - use intremap=off] 2575 2576 nointroute [IA-64] 2577 2578 noinvpcid [X86] Disable the INVPCID cpu feature. 2579 2580 nojitter [IA-64] Disables jitter checking for ITC timers. 2581 2582 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver 2583 2584 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page 2585 fault handling. 2586 2587 no-vmw-sched-clock 2588 [X86,PV_OPS] Disable paravirtualized VMware scheduler 2589 clock and use the default one. 2590 2591 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting. 2592 steal time is computed, but won't influence scheduler 2593 behaviour 2594 2595 nolapic [X86-32,APIC] Do not enable or use the local APIC. 2596 2597 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 2598 2599 noltlbs [PPC] Do not use large page/tlb entries for kernel 2600 lowmem mapping on PPC40x and PPC8xx 2601 2602 nomca [IA-64] Disable machine check abort handling 2603 2604 nomce [X86-32] Disable Machine Check Exception 2605 2606 nomfgpt [X86-32] Disable Multi-Function General Purpose 2607 Timer usage (for AMD Geode machines). 2608 2609 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to 2610 shutdown the other cpus. Instead use the REBOOT_VECTOR 2611 irq. 2612 2613 nomodule Disable module load 2614 2615 nopat [X86] Disable PAT (page attribute table extension of 2616 pagetables) support. 2617 2618 norandmaps Don't use address space randomization. Equivalent to 2619 echo 0 > /proc/sys/kernel/randomize_va_space 2620 2621 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops 2622 2623 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 2624 with UP alternatives 2625 2626 nordrand [X86] Disable kernel use of the RDRAND and 2627 RDSEED instructions even if they are supported 2628 by the processor. RDRAND and RDSEED are still 2629 available to user space applications. 2630 2631 noresume [SWSUSP] Disables resume and restores original swap 2632 space. 2633 2634 no-scroll [VGA] Disables scrollback. 2635 This is required for the Braillex ib80-piezo Braille 2636 reader made by F.H. Papenmeier (Germany). 2637 2638 nosbagart [IA-64] 2639 2640 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 2641 2642 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 2643 and disable the IO APIC. legacy for "maxcpus=0". 2644 2645 nosoftlockup [KNL] Disable the soft-lockup detector. 2646 2647 nosync [HW,M68K] Disables sync negotiation for all devices. 2648 2649 notsc [BUGS=X86-32] Disable Time Stamp Counter 2650 2651 nowatchdog [KNL] Disable both lockup detectors, i.e. 2652 soft-lockup and NMI watchdog (hard-lockup). 2653 2654 nowb [ARM] 2655 2656 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 2657 2658 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when 2659 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. 2660 Some features depend on CPU0. Known dependencies are: 2661 1. Resume from suspend/hibernate depends on CPU0. 2662 Suspend/hibernate will fail if CPU0 is offline and you 2663 need to online CPU0 before suspend/hibernate. 2664 2. PIC interrupts also depend on CPU0. CPU0 can't be 2665 removed if a PIC interrupt is detected. 2666 It's said poweroff/reboot may depend on CPU0 on some 2667 machines although I haven't seen such issues so far 2668 after CPU0 is offline on a few tested machines. 2669 If the dependencies are under your control, you can 2670 turn on cpu0_hotplug. 2671 2672 nptcg= [IA-64] Override max number of concurrent global TLB 2673 purges which is reported from either PAL_VM_SUMMARY or 2674 SAL PALO. 2675 2676 nr_cpus= [SMP] Maximum number of processors that an SMP kernel 2677 could support. nr_cpus=n : n >= 1 limits the kernel to 2678 support 'n' processors. It could be larger than the 2679 number of already plugged CPU during bootup, later in 2680 runtime you can physically add extra cpu until it reaches 2681 n. So during boot up some boot time memory for per-cpu 2682 variables need be pre-allocated for later physical cpu 2683 hot plugging. 2684 2685 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 2686 2687 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. 2688 Allowed values are enable and disable 2689 2690 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 2691 one of ['zone', 'node', 'default'] can be specified 2692 This can be set from sysctl after boot. 2693 See Documentation/sysctl/vm.txt for details. 2694 2695 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 2696 See Documentation/debugging-via-ohci1394.txt for more 2697 info. 2698 2699 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 2700 Rather than timing out after 20 ms if an EC 2701 command is not properly ACKed, override the length 2702 of the timeout. We have interrupts disabled while 2703 waiting for the ACK, so if this is set too high 2704 interrupts *may* be lost! 2705 2706 omap_mux= [OMAP] Override bootloader pin multiplexing. 2707 Format: <mux_mode0.mode_name=value>... 2708 For example, to override I2C bus2: 2709 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 2710 2711 oprofile.timer= [HW] 2712 Use timer interrupt instead of performance counters 2713 2714 oprofile.cpu_type= Force an oprofile cpu type 2715 This might be useful if you have an older oprofile 2716 userland or if you want common events. 2717 Format: { arch_perfmon } 2718 arch_perfmon: [X86] Force use of architectural 2719 perfmon on Intel CPUs instead of the 2720 CPU specific event set. 2721 timer: [X86] Force use of architectural NMI 2722 timer mode (see also oprofile.timer 2723 for generic hr timer mode) 2724 2725 oops=panic Always panic on oopses. Default is to just kill the 2726 process, but there is a small probability of 2727 deadlocking the machine. 2728 This will also cause panics on machine check exceptions. 2729 Useful together with panic=30 to trigger a reboot. 2730 2731 OSS [HW,OSS] 2732 See Documentation/sound/oss/oss-parameters.txt 2733 2734 page_owner= [KNL] Boot-time page_owner enabling option. 2735 Storage of the information about who allocated 2736 each page is disabled in default. With this switch, 2737 we can turn it on. 2738 on: enable the feature 2739 2740 page_poison= [KNL] Boot-time parameter changing the state of 2741 poisoning on the buddy allocator. 2742 off: turn off poisoning 2743 on: turn on poisoning 2744 2745 panic= [KNL] Kernel behaviour on panic: delay <timeout> 2746 timeout > 0: seconds before rebooting 2747 timeout = 0: wait forever 2748 timeout < 0: reboot immediately 2749 Format: <timeout> 2750 2751 panic_on_warn panic() instead of WARN(). Useful to cause kdump 2752 on a WARN(). 2753 2754 crash_kexec_post_notifiers 2755 Run kdump after running panic-notifiers and dumping 2756 kmsg. This only for the users who doubt kdump always 2757 succeeds in any situation. 2758 Note that this also increases risks of kdump failure, 2759 because some panic notifiers can make the crashed 2760 kernel more unstable. 2761 2762 parkbd.port= [HW] Parallel port number the keyboard adapter is 2763 connected to, default is 0. 2764 Format: <parport#> 2765 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 2766 0 for XT, 1 for AT (default is AT). 2767 Format: <mode> 2768 2769 parport= [HW,PPT] Specify parallel ports. 0 disables. 2770 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 2771 Use 'auto' to force the driver to use any 2772 IRQ/DMA settings detected (the default is to 2773 ignore detected IRQ/DMA settings because of 2774 possible conflicts). You can specify the base 2775 address, IRQ, and DMA settings; IRQ and DMA 2776 should be numbers, or 'auto' (for using detected 2777 settings on that particular port), or 'nofifo' 2778 (to avoid using a FIFO even if it is detected). 2779 Parallel ports are assigned in the order they 2780 are specified on the command line, starting 2781 with parport0. 2782 2783 parport_init_mode= [HW,PPT] 2784 Configure VIA parallel port to operate in 2785 a specific mode. This is necessary on Pegasos 2786 computer where firmware has no options for setting 2787 up parallel port mode and sets it to spp. 2788 Currently this function knows 686a and 8231 chips. 2789 Format: [spp|ps2|epp|ecp|ecpepp] 2790 2791 pause_on_oops= 2792 Halt all CPUs after the first oops has been printed for 2793 the specified number of seconds. This is to be used if 2794 your oopses keep scrolling off the screen. 2795 2796 pcbit= [HW,ISDN] 2797 2798 pcd. [PARIDE] 2799 See header of drivers/block/paride/pcd.c. 2800 See also Documentation/blockdev/paride.txt. 2801 2802 pci=option[,option...] [PCI] various PCI subsystem options: 2803 earlydump [X86] dump PCI config space before the kernel 2804 changes anything 2805 off [X86] don't probe for the PCI bus 2806 bios [X86-32] force use of PCI BIOS, don't access 2807 the hardware directly. Use this if your machine 2808 has a non-standard PCI host bridge. 2809 nobios [X86-32] disallow use of PCI BIOS, only direct 2810 hardware access methods are allowed. Use this 2811 if you experience crashes upon bootup and you 2812 suspect they are caused by the BIOS. 2813 conf1 [X86] Force use of PCI Configuration Access 2814 Mechanism 1 (config address in IO port 0xCF8, 2815 data in IO port 0xCFC, both 32-bit). 2816 conf2 [X86] Force use of PCI Configuration Access 2817 Mechanism 2 (IO port 0xCF8 is an 8-bit port for 2818 the function, IO port 0xCFA, also 8-bit, sets 2819 bus number. The config space is then accessed 2820 through ports 0xC000-0xCFFF). 2821 See http://wiki.osdev.org/PCI for more info 2822 on the configuration access mechanisms. 2823 noaer [PCIE] If the PCIEAER kernel config parameter is 2824 enabled, this kernel boot option can be used to 2825 disable the use of PCIE advanced error reporting. 2826 nodomains [PCI] Disable support for multiple PCI 2827 root domains (aka PCI segments, in ACPI-speak). 2828 nommconf [X86] Disable use of MMCONFIG for PCI 2829 Configuration 2830 check_enable_amd_mmconf [X86] check for and enable 2831 properly configured MMIO access to PCI 2832 config space on AMD family 10h CPU 2833 nomsi [MSI] If the PCI_MSI kernel config parameter is 2834 enabled, this kernel boot option can be used to 2835 disable the use of MSI interrupts system-wide. 2836 noioapicquirk [APIC] Disable all boot interrupt quirks. 2837 Safety option to keep boot IRQs enabled. This 2838 should never be necessary. 2839 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 2840 primary IO-APIC for bridges that cannot disable 2841 boot IRQs. This fixes a source of spurious IRQs 2842 when the system masks IRQs. 2843 noioapicreroute [APIC] Disable workaround that uses the 2844 boot IRQ equivalent of an IRQ that connects to 2845 a chipset where boot IRQs cannot be disabled. 2846 The opposite of ioapicreroute. 2847 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 2848 routing table. These calls are known to be buggy 2849 on several machines and they hang the machine 2850 when used, but on other computers it's the only 2851 way to get the interrupt routing table. Try 2852 this option if the kernel is unable to allocate 2853 IRQs or discover secondary PCI buses on your 2854 motherboard. 2855 rom [X86] Assign address space to expansion ROMs. 2856 Use with caution as certain devices share 2857 address decoders between ROMs and other 2858 resources. 2859 norom [X86] Do not assign address space to 2860 expansion ROMs that do not already have 2861 BIOS assigned address ranges. 2862 nobar [X86] Do not assign address space to the 2863 BARs that weren't assigned by the BIOS. 2864 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 2865 assigned automatically to PCI devices. You can 2866 make the kernel exclude IRQs of your ISA cards 2867 this way. 2868 pirqaddr=0xAAAAA [X86] Specify the physical address 2869 of the PIRQ table (normally generated 2870 by the BIOS) if it is outside the 2871 F0000h-100000h range. 2872 lastbus=N [X86] Scan all buses thru bus #N. Can be 2873 useful if the kernel is unable to find your 2874 secondary buses and you want to tell it 2875 explicitly which ones they are. 2876 assign-busses [X86] Always assign all PCI bus 2877 numbers ourselves, overriding 2878 whatever the firmware may have done. 2879 usepirqmask [X86] Honor the possible IRQ mask stored 2880 in the BIOS $PIR table. This is needed on 2881 some systems with broken BIOSes, notably 2882 some HP Pavilion N5400 and Omnibook XE3 2883 notebooks. This will have no effect if ACPI 2884 IRQ routing is enabled. 2885 noacpi [X86] Do not use ACPI for IRQ routing 2886 or for PCI scanning. 2887 use_crs [X86] Use PCI host bridge window information 2888 from ACPI. On BIOSes from 2008 or later, this 2889 is enabled by default. If you need to use this, 2890 please report a bug. 2891 nocrs [X86] Ignore PCI host bridge windows from ACPI. 2892 If you need to use this, please report a bug. 2893 routeirq Do IRQ routing for all PCI devices. 2894 This is normally done in pci_enable_device(), 2895 so this option is a temporary workaround 2896 for broken drivers that don't call it. 2897 skip_isa_align [X86] do not align io start addr, so can 2898 handle more pci cards 2899 noearly [X86] Don't do any early type 1 scanning. 2900 This might help on some broken boards which 2901 machine check when some devices' config space 2902 is read. But various workarounds are disabled 2903 and some IOMMU drivers will not work. 2904 bfsort Sort PCI devices into breadth-first order. 2905 This sorting is done to get a device 2906 order compatible with older (<= 2.4) kernels. 2907 nobfsort Don't sort PCI devices into breadth-first order. 2908 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) 2909 tuning and use the BIOS-configured MPS defaults. 2910 pcie_bus_safe Set every device's MPS to the largest value 2911 supported by all devices below the root complex. 2912 pcie_bus_perf Set device MPS to the largest allowable MPS 2913 based on its parent bus. Also set MRRS (Max 2914 Read Request Size) to the largest supported 2915 value (no larger than the MPS that the device 2916 or bus can support) for best performance. 2917 pcie_bus_peer2peer Set every device's MPS to 128B, which 2918 every device is guaranteed to support. This 2919 configuration allows peer-to-peer DMA between 2920 any pair of devices, possibly at the cost of 2921 reduced performance. This also guarantees 2922 that hot-added devices will work. 2923 cbiosize=nn[KMG] The fixed amount of bus space which is 2924 reserved for the CardBus bridge's IO window. 2925 The default value is 256 bytes. 2926 cbmemsize=nn[KMG] The fixed amount of bus space which is 2927 reserved for the CardBus bridge's memory 2928 window. The default value is 64 megabytes. 2929 resource_alignment= 2930 Format: 2931 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] 2932 [<order of align>@]pci:<vendor>:<device>\ 2933 [:<subvendor>:<subdevice>][; ...] 2934 Specifies alignment and device to reassign 2935 aligned memory resources. 2936 If <order of align> is not specified, 2937 PAGE_SIZE is used as alignment. 2938 PCI-PCI bridge can be specified, if resource 2939 windows need to be expanded. 2940 To specify the alignment for several 2941 instances of a device, the PCI vendor, 2942 device, subvendor, and subdevice may be 2943 specified, e.g., 4096@pci:8086:9c22:103c:198f 2944 ecrc= Enable/disable PCIe ECRC (transaction layer 2945 end-to-end CRC checking). 2946 bios: Use BIOS/firmware settings. This is the 2947 the default. 2948 off: Turn ECRC off 2949 on: Turn ECRC on. 2950 hpiosize=nn[KMG] The fixed amount of bus space which is 2951 reserved for hotplug bridge's IO window. 2952 Default size is 256 bytes. 2953 hpmemsize=nn[KMG] The fixed amount of bus space which is 2954 reserved for hotplug bridge's memory window. 2955 Default size is 2 megabytes. 2956 hpbussize=nn The minimum amount of additional bus numbers 2957 reserved for buses below a hotplug bridge. 2958 Default is 1. 2959 realloc= Enable/disable reallocating PCI bridge resources 2960 if allocations done by BIOS are too small to 2961 accommodate resources required by all child 2962 devices. 2963 off: Turn realloc off 2964 on: Turn realloc on 2965 realloc same as realloc=on 2966 noari do not use PCIe ARI. 2967 pcie_scan_all Scan all possible PCIe devices. Otherwise we 2968 only look for one device below a PCIe downstream 2969 port. 2970 2971 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 2972 Management. 2973 off Disable ASPM. 2974 force Enable ASPM even on devices that claim not to support it. 2975 WARNING: Forcing ASPM on may cause system lockups. 2976 2977 pcie_hp= [PCIE] PCI Express Hotplug driver options: 2978 nomsi Do not use MSI for PCI Express Native Hotplug (this 2979 makes all PCIe ports use INTx for hotplug services). 2980 2981 pcie_ports= [PCIE] PCIe ports handling: 2982 auto Ask the BIOS whether or not to use native PCIe services 2983 associated with PCIe ports (PME, hot-plug, AER). Use 2984 them only if that is allowed by the BIOS. 2985 native Use native PCIe services associated with PCIe ports 2986 unconditionally. 2987 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe 2988 ports driver. 2989 2990 pcie_port_pm= [PCIE] PCIe port power management handling: 2991 off Disable power management of all PCIe ports 2992 force Forcibly enable power management of all PCIe ports 2993 2994 pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 2995 nomsi Do not use MSI for native PCIe PME signaling (this makes 2996 all PCIe root ports use INTx for all services). 2997 2998 pcmv= [HW,PCMCIA] BadgePAD 4 2999 3000 pd_ignore_unused 3001 [PM] 3002 Keep all power-domains already enabled by bootloader on, 3003 even if no driver has claimed them. This is useful 3004 for debug and development, but should not be 3005 needed on a platform with proper driver support. 3006 3007 pd. [PARIDE] 3008 See Documentation/blockdev/paride.txt. 3009 3010 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 3011 boot time. 3012 Format: { 0 | 1 } 3013 See arch/parisc/kernel/pdc_chassis.c 3014 3015 percpu_alloc= Select which percpu first chunk allocator to use. 3016 Currently supported values are "embed" and "page". 3017 Archs may support subset or none of the selections. 3018 See comments in mm/percpu.c for details on each 3019 allocator. This parameter is primarily for debugging 3020 and performance comparison. 3021 3022 pf. [PARIDE] 3023 See Documentation/blockdev/paride.txt. 3024 3025 pg. [PARIDE] 3026 See Documentation/blockdev/paride.txt. 3027 3028 pirq= [SMP,APIC] Manual mp-table setup 3029 See Documentation/x86/i386/IO-APIC.txt. 3030 3031 plip= [PPT,NET] Parallel port network link 3032 Format: { parport<nr> | timid | 0 } 3033 See also Documentation/parport.txt. 3034 3035 pmtmr= [X86] Manual setup of pmtmr I/O Port. 3036 Override pmtimer IOPort with a hex value. 3037 e.g. pmtmr=0x508 3038 3039 pnp.debug=1 [PNP] 3040 Enable PNP debug messages (depends on the 3041 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time 3042 via /sys/module/pnp/parameters/debug. We always show 3043 current resource usage; turning this on also shows 3044 possible settings and some assignment information. 3045 3046 pnpacpi= [ACPI] 3047 { off } 3048 3049 pnpbios= [ISAPNP] 3050 { on | off | curr | res | no-curr | no-res } 3051 3052 pnp_reserve_irq= 3053 [ISAPNP] Exclude IRQs for the autoconfiguration 3054 3055 pnp_reserve_dma= 3056 [ISAPNP] Exclude DMAs for the autoconfiguration 3057 3058 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 3059 Ranges are in pairs (I/O port base and size). 3060 3061 pnp_reserve_mem= 3062 [ISAPNP] Exclude memory regions for the 3063 autoconfiguration. 3064 Ranges are in pairs (memory base and size). 3065 3066 ports= [IP_VS_FTP] IPVS ftp helper module 3067 Default is 21. 3068 Up to 8 (IP_VS_APP_MAX_PORTS) ports 3069 may be specified. 3070 Format: <port>,<port>.... 3071 3072 powersave=off [PPC] This option disables power saving features. 3073 It specifically disables cpuidle and sets the 3074 platform machine description specific power_save 3075 function to NULL. On Idle the CPU just reduces 3076 execution priority. 3077 3078 ppc_strict_facility_enable 3079 [PPC] This option catches any kernel floating point, 3080 Altivec, VSX and SPE outside of regions specifically 3081 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). 3082 There is some performance impact when enabling this. 3083 3084 print-fatal-signals= 3085 [KNL] debug: print fatal signals 3086 3087 If enabled, warn about various signal handling 3088 related application anomalies: too many signals, 3089 too many POSIX.1 timers, fatal signals causing a 3090 coredump - etc. 3091 3092 If you hit the warning due to signal overflow, 3093 you might want to try "ulimit -i unlimited". 3094 3095 default: off. 3096 3097 printk.always_kmsg_dump= 3098 Trigger kmsg_dump for cases other than kernel oops or 3099 panics 3100 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3101 default: disabled 3102 3103 printk.devkmsg={on,off,ratelimit} 3104 Control writing to /dev/kmsg. 3105 on - unlimited logging to /dev/kmsg from userspace 3106 off - logging to /dev/kmsg disabled 3107 ratelimit - ratelimit the logging 3108 Default: ratelimit 3109 3110 printk.time= Show timing data prefixed to each printk message line 3111 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 3112 3113 processor.max_cstate= [HW,ACPI] 3114 Limit processor to maximum C-state 3115 max_cstate=9 overrides any DMI blacklist limit. 3116 3117 processor.nocst [HW,ACPI] 3118 Ignore the _CST method to determine C-states, 3119 instead using the legacy FADT method 3120 3121 profile= [KNL] Enable kernel profiling via /proc/profile 3122 Format: [schedule,]<number> 3123 Param: "schedule" - profile schedule points. 3124 Param: <number> - step/bucket size as a power of 2 for 3125 statistical time based profiling. 3126 Param: "sleep" - profile D-state sleeping (millisecs). 3127 Requires CONFIG_SCHEDSTATS 3128 Param: "kvm" - profile VM exits. 3129 3130 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 3131 before loading. 3132 See Documentation/blockdev/ramdisk.txt. 3133 3134 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 3135 probe for; one of (bare|imps|exps|lifebook|any). 3136 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 3137 per second. 3138 psmouse.resetafter= [HW,MOUSE] 3139 Try to reset the device after so many bad packets 3140 (0 = never). 3141 psmouse.resolution= 3142 [HW,MOUSE] Set desired mouse resolution, in dpi. 3143 psmouse.smartscroll= 3144 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 3145 0 = disabled, 1 = enabled (default). 3146 3147 pstore.backend= Specify the name of the pstore backend to use 3148 3149 pt. [PARIDE] 3150 See Documentation/blockdev/paride.txt. 3151 3152 pty.legacy_count= 3153 [KNL] Number of legacy pty's. Overwrites compiled-in 3154 default number. 3155 3156 quiet [KNL] Disable most log messages 3157 3158 r128= [HW,DRM] 3159 3160 raid= [HW,RAID] 3161 See Documentation/admin-guide/md.rst. 3162 3163 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 3164 See Documentation/blockdev/ramdisk.txt. 3165 3166 rcu_nocbs= [KNL] 3167 The argument is a cpu list, as described above. 3168 3169 In kernels built with CONFIG_RCU_NOCB_CPU=y, set 3170 the specified list of CPUs to be no-callback CPUs. 3171 Invocation of these CPUs' RCU callbacks will 3172 be offloaded to "rcuox/N" kthreads created for 3173 that purpose, where "x" is "b" for RCU-bh, "p" 3174 for RCU-preempt, and "s" for RCU-sched, and "N" 3175 is the CPU number. This reduces OS jitter on the 3176 offloaded CPUs, which can be useful for HPC and 3177 real-time workloads. It can also improve energy 3178 efficiency for asymmetric multiprocessors. 3179 3180 rcu_nocb_poll [KNL] 3181 Rather than requiring that offloaded CPUs 3182 (specified by rcu_nocbs= above) explicitly 3183 awaken the corresponding "rcuoN" kthreads, 3184 make these kthreads poll for callbacks. 3185 This improves the real-time response for the 3186 offloaded CPUs by relieving them of the need to 3187 wake up the corresponding kthread, but degrades 3188 energy efficiency by requiring that the kthreads 3189 periodically wake up to do the polling. 3190 3191 rcutree.blimit= [KNL] 3192 Set maximum number of finished RCU callbacks to 3193 process in one batch. 3194 3195 rcutree.dump_tree= [KNL] 3196 Dump the structure of the rcu_node combining tree 3197 out at early boot. This is used for diagnostic 3198 purposes, to verify correct tree setup. 3199 3200 rcutree.gp_cleanup_delay= [KNL] 3201 Set the number of jiffies to delay each step of 3202 RCU grace-period cleanup. This only has effect 3203 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set. 3204 3205 rcutree.gp_init_delay= [KNL] 3206 Set the number of jiffies to delay each step of 3207 RCU grace-period initialization. This only has 3208 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT 3209 is set. 3210 3211 rcutree.gp_preinit_delay= [KNL] 3212 Set the number of jiffies to delay each step of 3213 RCU grace-period pre-initialization, that is, 3214 the propagation of recent CPU-hotplug changes up 3215 the rcu_node combining tree. This only has effect 3216 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set. 3217 3218 rcutree.rcu_fanout_exact= [KNL] 3219 Disable autobalancing of the rcu_node combining 3220 tree. This is used by rcutorture, and might 3221 possibly be useful for architectures having high 3222 cache-to-cache transfer latencies. 3223 3224 rcutree.rcu_fanout_leaf= [KNL] 3225 Change the number of CPUs assigned to each 3226 leaf rcu_node structure. Useful for very 3227 large systems, which will choose the value 64, 3228 and for NUMA systems with large remote-access 3229 latencies, which will choose a value aligned 3230 with the appropriate hardware boundaries. 3231 3232 rcutree.jiffies_till_sched_qs= [KNL] 3233 Set required age in jiffies for a 3234 given grace period before RCU starts 3235 soliciting quiescent-state help from 3236 rcu_note_context_switch(). 3237 3238 rcutree.jiffies_till_first_fqs= [KNL] 3239 Set delay from grace-period initialization to 3240 first attempt to force quiescent states. 3241 Units are jiffies, minimum value is zero, 3242 and maximum value is HZ. 3243 3244 rcutree.jiffies_till_next_fqs= [KNL] 3245 Set delay between subsequent attempts to force 3246 quiescent states. Units are jiffies, minimum 3247 value is one, and maximum value is HZ. 3248 3249 rcutree.kthread_prio= [KNL,BOOT] 3250 Set the SCHED_FIFO priority of the RCU per-CPU 3251 kthreads (rcuc/N). This value is also used for 3252 the priority of the RCU boost threads (rcub/N) 3253 and for the RCU grace-period kthreads (rcu_bh, 3254 rcu_preempt, and rcu_sched). If RCU_BOOST is 3255 set, valid values are 1-99 and the default is 1 3256 (the least-favored priority). Otherwise, when 3257 RCU_BOOST is not set, valid values are 0-99 and 3258 the default is zero (non-realtime operation). 3259 3260 rcutree.rcu_nocb_leader_stride= [KNL] 3261 Set the number of NOCB kthread groups, which 3262 defaults to the square root of the number of 3263 CPUs. Larger numbers reduces the wakeup overhead 3264 on the per-CPU grace-period kthreads, but increases 3265 that same overhead on each group's leader. 3266 3267 rcutree.qhimark= [KNL] 3268 Set threshold of queued RCU callbacks beyond which 3269 batch limiting is disabled. 3270 3271 rcutree.qlowmark= [KNL] 3272 Set threshold of queued RCU callbacks below which 3273 batch limiting is re-enabled. 3274 3275 rcutree.rcu_idle_gp_delay= [KNL] 3276 Set wakeup interval for idle CPUs that have 3277 RCU callbacks (RCU_FAST_NO_HZ=y). 3278 3279 rcutree.rcu_idle_lazy_gp_delay= [KNL] 3280 Set wakeup interval for idle CPUs that have 3281 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). 3282 Lazy RCU callbacks are those which RCU can 3283 prove do nothing more than free memory. 3284 3285 rcutree.rcu_kick_kthreads= [KNL] 3286 Cause the grace-period kthread to get an extra 3287 wake_up() if it sleeps three times longer than 3288 it should at force-quiescent-state time. 3289 This wake_up() will be accompanied by a 3290 WARN_ONCE() splat and an ftrace_dump(). 3291 3292 rcuperf.gp_exp= [KNL] 3293 Measure performance of expedited synchronous 3294 grace-period primitives. 3295 3296 rcuperf.holdoff= [KNL] 3297 Set test-start holdoff period. The purpose of 3298 this parameter is to delay the start of the 3299 test until boot completes in order to avoid 3300 interference. 3301 3302 rcuperf.nreaders= [KNL] 3303 Set number of RCU readers. The value -1 selects 3304 N, where N is the number of CPUs. A value 3305 "n" less than -1 selects N-n+1, where N is again 3306 the number of CPUs. For example, -2 selects N 3307 (the number of CPUs), -3 selects N+1, and so on. 3308 A value of "n" less than or equal to -N selects 3309 a single reader. 3310 3311 rcuperf.nwriters= [KNL] 3312 Set number of RCU writers. The values operate 3313 the same as for rcuperf.nreaders. 3314 N, where N is the number of CPUs 3315 3316 rcuperf.perf_runnable= [BOOT] 3317 Start rcuperf running at boot time. 3318 3319 rcuperf.shutdown= [KNL] 3320 Shut the system down after performance tests 3321 complete. This is useful for hands-off automated 3322 testing. 3323 3324 rcuperf.perf_type= [KNL] 3325 Specify the RCU implementation to test. 3326 3327 rcuperf.verbose= [KNL] 3328 Enable additional printk() statements. 3329 3330 rcutorture.cbflood_inter_holdoff= [KNL] 3331 Set holdoff time (jiffies) between successive 3332 callback-flood tests. 3333 3334 rcutorture.cbflood_intra_holdoff= [KNL] 3335 Set holdoff time (jiffies) between successive 3336 bursts of callbacks within a given callback-flood 3337 test. 3338 3339 rcutorture.cbflood_n_burst= [KNL] 3340 Set the number of bursts making up a given 3341 callback-flood test. Set this to zero to 3342 disable callback-flood testing. 3343 3344 rcutorture.cbflood_n_per_burst= [KNL] 3345 Set the number of callbacks to be registered 3346 in a given burst of a callback-flood test. 3347 3348 rcutorture.fqs_duration= [KNL] 3349 Set duration of force_quiescent_state bursts 3350 in microseconds. 3351 3352 rcutorture.fqs_holdoff= [KNL] 3353 Set holdoff time within force_quiescent_state bursts 3354 in microseconds. 3355 3356 rcutorture.fqs_stutter= [KNL] 3357 Set wait time between force_quiescent_state bursts 3358 in seconds. 3359 3360 rcutorture.gp_cond= [KNL] 3361 Use conditional/asynchronous update-side 3362 primitives, if available. 3363 3364 rcutorture.gp_exp= [KNL] 3365 Use expedited update-side primitives, if available. 3366 3367 rcutorture.gp_normal= [KNL] 3368 Use normal (non-expedited) asynchronous 3369 update-side primitives, if available. 3370 3371 rcutorture.gp_sync= [KNL] 3372 Use normal (non-expedited) synchronous 3373 update-side primitives, if available. If all 3374 of rcutorture.gp_cond=, rcutorture.gp_exp=, 3375 rcutorture.gp_normal=, and rcutorture.gp_sync= 3376 are zero, rcutorture acts as if is interpreted 3377 they are all non-zero. 3378 3379 rcutorture.n_barrier_cbs= [KNL] 3380 Set callbacks/threads for rcu_barrier() testing. 3381 3382 rcutorture.nfakewriters= [KNL] 3383 Set number of concurrent RCU writers. These just 3384 stress RCU, they don't participate in the actual 3385 test, hence the "fake". 3386 3387 rcutorture.nreaders= [KNL] 3388 Set number of RCU readers. The value -1 selects 3389 N-1, where N is the number of CPUs. A value 3390 "n" less than -1 selects N-n-2, where N is again 3391 the number of CPUs. For example, -2 selects N 3392 (the number of CPUs), -3 selects N+1, and so on. 3393 3394 rcutorture.object_debug= [KNL] 3395 Enable debug-object double-call_rcu() testing. 3396 3397 rcutorture.onoff_holdoff= [KNL] 3398 Set time (s) after boot for CPU-hotplug testing. 3399 3400 rcutorture.onoff_interval= [KNL] 3401 Set time (s) between CPU-hotplug operations, or 3402 zero to disable CPU-hotplug testing. 3403 3404 rcutorture.shuffle_interval= [KNL] 3405 Set task-shuffle interval (s). Shuffling tasks 3406 allows some CPUs to go into dyntick-idle mode 3407 during the rcutorture test. 3408 3409 rcutorture.shutdown_secs= [KNL] 3410 Set time (s) after boot system shutdown. This 3411 is useful for hands-off automated testing. 3412 3413 rcutorture.stall_cpu= [KNL] 3414 Duration of CPU stall (s) to test RCU CPU stall 3415 warnings, zero to disable. 3416 3417 rcutorture.stall_cpu_holdoff= [KNL] 3418 Time to wait (s) after boot before inducing stall. 3419 3420 rcutorture.stat_interval= [KNL] 3421 Time (s) between statistics printk()s. 3422 3423 rcutorture.stutter= [KNL] 3424 Time (s) to stutter testing, for example, specifying 3425 five seconds causes the test to run for five seconds, 3426 wait for five seconds, and so on. This tests RCU's 3427 ability to transition abruptly to and from idle. 3428 3429 rcutorture.test_boost= [KNL] 3430 Test RCU priority boosting? 0=no, 1=maybe, 2=yes. 3431 "Maybe" means test if the RCU implementation 3432 under test support RCU priority boosting. 3433 3434 rcutorture.test_boost_duration= [KNL] 3435 Duration (s) of each individual boost test. 3436 3437 rcutorture.test_boost_interval= [KNL] 3438 Interval (s) between each boost test. 3439 3440 rcutorture.test_no_idle_hz= [KNL] 3441 Test RCU's dyntick-idle handling. See also the 3442 rcutorture.shuffle_interval parameter. 3443 3444 rcutorture.torture_runnable= [BOOT] 3445 Start rcutorture running at boot time. 3446 3447 rcutorture.torture_type= [KNL] 3448 Specify the RCU implementation to test. 3449 3450 rcutorture.verbose= [KNL] 3451 Enable additional printk() statements. 3452 3453 rcupdate.rcu_cpu_stall_suppress= [KNL] 3454 Suppress RCU CPU stall warning messages. 3455 3456 rcupdate.rcu_cpu_stall_timeout= [KNL] 3457 Set timeout for RCU CPU stall warning messages. 3458 3459 rcupdate.rcu_expedited= [KNL] 3460 Use expedited grace-period primitives, for 3461 example, synchronize_rcu_expedited() instead 3462 of synchronize_rcu(). This reduces latency, 3463 but can increase CPU utilization, degrade 3464 real-time latency, and degrade energy efficiency. 3465 No effect on CONFIG_TINY_RCU kernels. 3466 3467 rcupdate.rcu_normal= [KNL] 3468 Use only normal grace-period primitives, 3469 for example, synchronize_rcu() instead of 3470 synchronize_rcu_expedited(). This improves 3471 real-time latency, CPU utilization, and 3472 energy efficiency, but can expose users to 3473 increased grace-period latency. This parameter 3474 overrides rcupdate.rcu_expedited. No effect on 3475 CONFIG_TINY_RCU kernels. 3476 3477 rcupdate.rcu_normal_after_boot= [KNL] 3478 Once boot has completed (that is, after 3479 rcu_end_inkernel_boot() has been invoked), use 3480 only normal grace-period primitives. No effect 3481 on CONFIG_TINY_RCU kernels. 3482 3483 rcupdate.rcu_task_stall_timeout= [KNL] 3484 Set timeout in jiffies for RCU task stall warning 3485 messages. Disable with a value less than or equal 3486 to zero. 3487 3488 rcupdate.rcu_self_test= [KNL] 3489 Run the RCU early boot self tests 3490 3491 rcupdate.rcu_self_test_bh= [KNL] 3492 Run the RCU bh early boot self tests 3493 3494 rcupdate.rcu_self_test_sched= [KNL] 3495 Run the RCU sched early boot self tests 3496 3497 rdinit= [KNL] 3498 Format: <full_path> 3499 Run specified binary instead of /init from the ramdisk, 3500 used for early userspace startup. See initrd. 3501 3502 reboot= [KNL] 3503 Format (x86 or x86_64): 3504 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ 3505 [[,]s[mp]#### \ 3506 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ 3507 [[,]f[orce] 3508 Where reboot_mode is one of warm (soft) or cold (hard) or gpio, 3509 reboot_type is one of bios, acpi, kbd, triple, efi, or pci, 3510 reboot_force is either force or not specified, 3511 reboot_cpu is s[mp]#### with #### being the processor 3512 to be used for rebooting. 3513 3514 relax_domain_level= 3515 [KNL, SMP] Set scheduler's default relax_domain_level. 3516 See Documentation/cgroup-v1/cpusets.txt. 3517 3518 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 3519 3520 reservetop= [X86-32] 3521 Format: nn[KMG] 3522 Reserves a hole at the top of the kernel virtual 3523 address space. 3524 3525 reservelow= [X86] 3526 Format: nn[K] 3527 Set the amount of memory to reserve for BIOS at 3528 the bottom of the address space. 3529 3530 reset_devices [KNL] Force drivers to reset the underlying device 3531 during initialization. 3532 3533 resume= [SWSUSP] 3534 Specify the partition device for software suspend 3535 Format: 3536 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} 3537 3538 resume_offset= [SWSUSP] 3539 Specify the offset from the beginning of the partition 3540 given by "resume=" at which the swap header is located, 3541 in <PAGE_SIZE> units (needed only for swap files). 3542 See Documentation/power/swsusp-and-swap-files.txt 3543 3544 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to 3545 read the resume files 3546 3547 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. 3548 Useful for devices that are detected asynchronously 3549 (e.g. USB and MMC devices). 3550 3551 hibernate= [HIBERNATION] 3552 noresume Don't check if there's a hibernation image 3553 present during boot. 3554 nocompress Don't compress/decompress hibernation images. 3555 no Disable hibernation and resume. 3556 protect_image Turn on image protection during restoration 3557 (that will set all pages holding image data 3558 during restoration read-only). 3559 3560 retain_initrd [RAM] Keep initrd memory after extraction 3561 3562 rfkill.default_state= 3563 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, 3564 etc. communication is blocked by default. 3565 1 Unblocked. 3566 3567 rfkill.master_switch_mode= 3568 0 The "airplane mode" button does nothing. 3569 1 The "airplane mode" button toggles between everything 3570 blocked and the previous configuration. 3571 2 The "airplane mode" button toggles between everything 3572 blocked and everything unblocked. 3573 3574 rhash_entries= [KNL,NET] 3575 Set number of hash buckets for route cache 3576 3577 ring3mwait=disable 3578 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported 3579 CPUs. 3580 3581 ro [KNL] Mount root device read-only on boot 3582 3583 rodata= [KNL] 3584 on Mark read-only kernel memory as read-only (default). 3585 off Leave read-only kernel memory writable for debugging. 3586 3587 rockchip.usb_uart 3588 Enable the uart passthrough on the designated usb port 3589 on Rockchip SoCs. When active, the signals of the 3590 debug-uart get routed to the D+ and D- pins of the usb 3591 port and the regular usb controller gets disabled. 3592 3593 root= [KNL] Root filesystem 3594 See name_to_dev_t comment in init/do_mounts.c. 3595 3596 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 3597 mount the root filesystem 3598 3599 rootflags= [KNL] Set root filesystem mount option string 3600 3601 rootfstype= [KNL] Set root filesystem type 3602 3603 rootwait [KNL] Wait (indefinitely) for root device to show up. 3604 Useful for devices that are detected asynchronously 3605 (e.g. USB and MMC devices). 3606 3607 rproc_mem=nn[KMG][@address] 3608 [KNL,ARM,CMA] Remoteproc physical memory block. 3609 Memory area to be used by remote processor image, 3610 managed by CMA. 3611 3612 rw [KNL] Mount root device read-write on boot 3613 3614 S [KNL] Run init in single mode 3615 3616 s390_iommu= [HW,S390] 3617 Set s390 IOTLB flushing mode 3618 strict 3619 With strict flushing every unmap operation will result in 3620 an IOTLB flush. Default is lazy flushing before reuse, 3621 which is faster. 3622 3623 sa1100ir [NET] 3624 See drivers/net/irda/sa1100_ir.c. 3625 3626 sbni= [NET] Granch SBNI12 leased line adapter 3627 3628 sched_debug [KNL] Enables verbose scheduler debug messages. 3629 3630 schedstats= [KNL,X86] Enable or disable scheduled statistics. 3631 Allowed values are enable and disable. This feature 3632 incurs a small amount of overhead in the scheduler 3633 but is useful for debugging and performance tuning. 3634 3635 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate 3636 xtime_lock contention on larger systems, and/or RCU lock 3637 contention on all systems with CONFIG_MAXSMP set. 3638 Format: { "0" | "1" } 3639 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" 3640 1 -- enable. 3641 Note: increases power consumption, thus should only be 3642 enabled if running jitter sensitive (HPC/RT) workloads. 3643 3644 security= [SECURITY] Choose a security module to enable at boot. 3645 If this boot parameter is not specified, only the first 3646 security module asking for security registration will be 3647 loaded. An invalid security module name will be treated 3648 as if no module has been chosen. 3649 3650 selinux= [SELINUX] Disable or enable SELinux at boot time. 3651 Format: { "0" | "1" } 3652 See security/selinux/Kconfig help text. 3653 0 -- disable. 3654 1 -- enable. 3655 Default value is set via kernel config option. 3656 If enabled at boot time, /selinux/disable can be used 3657 later to disable prior to initial policy load. 3658 3659 apparmor= [APPARMOR] Disable or enable AppArmor at boot time 3660 Format: { "0" | "1" } 3661 See security/apparmor/Kconfig help text 3662 0 -- disable. 3663 1 -- enable. 3664 Default value is set via kernel config option. 3665 3666 serialnumber [BUGS=X86-32] 3667 3668 shapers= [NET] 3669 Maximal number of shapers. 3670 3671 simeth= [IA-64] 3672 simscsi= 3673 3674 slram= [HW,MTD] 3675 3676 slab_nomerge [MM] 3677 Disable merging of slabs with similar size. May be 3678 necessary if there is some reason to distinguish 3679 allocs to different slabs. Debug options disable 3680 merging on their own. 3681 For more information see Documentation/vm/slub.txt. 3682 3683 slab_max_order= [MM, SLAB] 3684 Determines the maximum allowed order for slabs. 3685 A high setting may cause OOMs due to memory 3686 fragmentation. Defaults to 1 for systems with 3687 more than 32MB of RAM, 0 otherwise. 3688 3689 slub_debug[=options[,slabs]] [MM, SLUB] 3690 Enabling slub_debug allows one to determine the 3691 culprit if slab objects become corrupted. Enabling 3692 slub_debug can create guard zones around objects and 3693 may poison objects when not in use. Also tracks the 3694 last alloc / free. For more information see 3695 Documentation/vm/slub.txt. 3696 3697 slub_memcg_sysfs= [MM, SLUB] 3698 Determines whether to enable sysfs directories for 3699 memory cgroup sub-caches. 1 to enable, 0 to disable. 3700 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON. 3701 Enabling this can lead to a very high number of debug 3702 directories and files being created under 3703 /sys/kernel/slub. 3704 3705 slub_max_order= [MM, SLUB] 3706 Determines the maximum allowed order for slabs. 3707 A high setting may cause OOMs due to memory 3708 fragmentation. For more information see 3709 Documentation/vm/slub.txt. 3710 3711 slub_min_objects= [MM, SLUB] 3712 The minimum number of objects per slab. SLUB will 3713 increase the slab order up to slub_max_order to 3714 generate a sufficiently large slab able to contain 3715 the number of objects indicated. The higher the number 3716 of objects the smaller the overhead of tracking slabs 3717 and the less frequently locks need to be acquired. 3718 For more information see Documentation/vm/slub.txt. 3719 3720 slub_min_order= [MM, SLUB] 3721 Determines the minimum page order for slabs. Must be 3722 lower than slub_max_order. 3723 For more information see Documentation/vm/slub.txt. 3724 3725 slub_nomerge [MM, SLUB] 3726 Same with slab_nomerge. This is supported for legacy. 3727 See slab_nomerge for more information. 3728 3729 smart2= [HW] 3730 Format: <io1>[,<io2>[,...,<io8>]] 3731 3732 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 3733 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 3734 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 3735 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 3736 smsc-ircc2.ircc_irq= [HW] IRQ line 3737 smsc-ircc2.ircc_dma= [HW] DMA channel 3738 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 3739 0: Toshiba Satellite 1800 (GP data pin select) 3740 1: Fast pin select (default) 3741 2: ATC IRMode 3742 3743 smt [KNL,S390] Set the maximum number of threads (logical 3744 CPUs) to use per physical CPU on systems capable of 3745 symmetric multithreading (SMT). Will be capped to the 3746 actual hardware limit. 3747 Format: <integer> 3748 Default: -1 (no limit) 3749 3750 softlockup_panic= 3751 [KNL] Should the soft-lockup detector generate panics. 3752 Format: <integer> 3753 3754 softlockup_all_cpu_backtrace= 3755 [KNL] Should the soft-lockup detector generate 3756 backtraces on all cpus. 3757 Format: <integer> 3758 3759 sonypi.*= [HW] Sony Programmable I/O Control Device driver 3760 See Documentation/laptops/sonypi.txt 3761 3762 spia_io_base= [HW,MTD] 3763 spia_fio_base= 3764 spia_pedr= 3765 spia_peddr= 3766 3767 stacktrace [FTRACE] 3768 Enabled the stack tracer on boot up. 3769 3770 stacktrace_filter=[function-list] 3771 [FTRACE] Limit the functions that the stack tracer 3772 will trace at boot up. function-list is a comma separated 3773 list of functions. This list can be changed at run 3774 time by the stack_trace_filter file in the debugfs 3775 tracing directory. Note, this enables stack tracing 3776 and the stacktrace above is not needed. 3777 3778 sti= [PARISC,HW] 3779 Format: <num> 3780 Set the STI (builtin display/keyboard on the HP-PARISC 3781 machines) console (graphic card) which should be used 3782 as the initial boot-console. 3783 See also comment in drivers/video/console/sticore.c. 3784 3785 sti_font= [HW] 3786 See comment in drivers/video/console/sticore.c. 3787 3788 stifb= [HW] 3789 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 3790 3791 sunrpc.min_resvport= 3792 sunrpc.max_resvport= 3793 [NFS,SUNRPC] 3794 SunRPC servers often require that client requests 3795 originate from a privileged port (i.e. a port in the 3796 range 0 < portnr < 1024). 3797 An administrator who wishes to reserve some of these 3798 ports for other uses may adjust the range that the 3799 kernel's sunrpc client considers to be privileged 3800 using these two parameters to set the minimum and 3801 maximum port values. 3802 3803 sunrpc.svc_rpc_per_connection_limit= 3804 [NFS,SUNRPC] 3805 Limit the number of requests that the server will 3806 process in parallel from a single connection. 3807 The default value is 0 (no limit). 3808 3809 sunrpc.pool_mode= 3810 [NFS] 3811 Control how the NFS server code allocates CPUs to 3812 service thread pools. Depending on how many NICs 3813 you have and where their interrupts are bound, this 3814 option will affect which CPUs will do NFS serving. 3815 Note: this parameter cannot be changed while the 3816 NFS server is running. 3817 3818 auto the server chooses an appropriate mode 3819 automatically using heuristics 3820 global a single global pool contains all CPUs 3821 percpu one pool for each CPU 3822 pernode one pool for each NUMA node (equivalent 3823 to global on non-NUMA machines) 3824 3825 sunrpc.tcp_slot_table_entries= 3826 sunrpc.udp_slot_table_entries= 3827 [NFS,SUNRPC] 3828 Sets the upper limit on the number of simultaneous 3829 RPC calls that can be sent from the client to a 3830 server. Increasing these values may allow you to 3831 improve throughput, but will also increase the 3832 amount of memory reserved for use by the client. 3833 3834 suspend.pm_test_delay= 3835 [SUSPEND] 3836 Sets the number of seconds to remain in a suspend test 3837 mode before resuming the system (see 3838 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG 3839 is set. Default value is 5. 3840 3841 swapaccount=[0|1] 3842 [KNL] Enable accounting of swap in memory resource 3843 controller if no parameter or 1 is given or disable 3844 it if 0 is given (See Documentation/cgroup-v1/memory.txt) 3845 3846 swiotlb= [ARM,IA-64,PPC,MIPS,X86] 3847 Format: { <int> | force | noforce } 3848 <int> -- Number of I/O TLB slabs 3849 force -- force using of bounce buffers even if they 3850 wouldn't be automatically used by the kernel 3851 noforce -- Never use bounce buffers (for debugging) 3852 3853 switches= [HW,M68k] 3854 3855 sysfs.deprecated=0|1 [KNL] 3856 Enable/disable old style sysfs layout for old udev 3857 on older distributions. When this option is enabled 3858 very new udev will not work anymore. When this option 3859 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) 3860 in older udev will not work anymore. 3861 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in 3862 the kernel configuration. 3863 3864 sysrq_always_enabled 3865 [KNL] 3866 Ignore sysrq setting - this boot parameter will 3867 neutralize any effect of /proc/sys/kernel/sysrq. 3868 Useful for debugging. 3869 3870 tcpmhash_entries= [KNL,NET] 3871 Set the number of tcp_metrics_hash slots. 3872 Default value is 8192 or 16384 depending on total 3873 ram pages. This is used to specify the TCP metrics 3874 cache size. See Documentation/networking/ip-sysctl.txt 3875 "tcp_no_metrics_save" section for more details. 3876 3877 tdfx= [HW,DRM] 3878 3879 test_suspend= [SUSPEND][,N] 3880 Specify "mem" (for Suspend-to-RAM) or "standby" (for 3881 standby suspend) or "freeze" (for suspend type freeze) 3882 as the system sleep state during system startup with 3883 the optional capability to repeat N number of times. 3884 The system is woken from this state using a 3885 wakeup-capable RTC alarm. 3886 3887 thash_entries= [KNL,NET] 3888 Set number of hash buckets for TCP connection 3889 3890 thermal.act= [HW,ACPI] 3891 -1: disable all active trip points in all thermal zones 3892 <degrees C>: override all lowest active trip points 3893 3894 thermal.crt= [HW,ACPI] 3895 -1: disable all critical trip points in all thermal zones 3896 <degrees C>: override all critical trip points 3897 3898 thermal.nocrt= [HW,ACPI] 3899 Set to disable actions on ACPI thermal zone 3900 critical and hot trip points. 3901 3902 thermal.off= [HW,ACPI] 3903 1: disable ACPI thermal control 3904 3905 thermal.psv= [HW,ACPI] 3906 -1: disable all passive trip points 3907 <degrees C>: override all passive trip points to this 3908 value 3909 3910 thermal.tzp= [HW,ACPI] 3911 Specify global default ACPI thermal zone polling rate 3912 <deci-seconds>: poll all this frequency 3913 0: no polling (default) 3914 3915 threadirqs [KNL] 3916 Force threading of all interrupt handlers except those 3917 marked explicitly IRQF_NO_THREAD. 3918 3919 tmem [KNL,XEN] 3920 Enable the Transcendent memory driver if built-in. 3921 3922 tmem.cleancache=0|1 [KNL, XEN] 3923 Default is on (1). Disable the usage of the cleancache 3924 API to send anonymous pages to the hypervisor. 3925 3926 tmem.frontswap=0|1 [KNL, XEN] 3927 Default is on (1). Disable the usage of the frontswap 3928 API to send swap pages to the hypervisor. If disabled 3929 the selfballooning and selfshrinking are force disabled. 3930 3931 tmem.selfballooning=0|1 [KNL, XEN] 3932 Default is on (1). Disable the driving of swap pages 3933 to the hypervisor. 3934 3935 tmem.selfshrinking=0|1 [KNL, XEN] 3936 Default is on (1). Partial swapoff that immediately 3937 transfers pages from Xen hypervisor back to the 3938 kernel based on different criteria. 3939 3940 topology= [S390] 3941 Format: {off | on} 3942 Specify if the kernel should make use of the cpu 3943 topology information if the hardware supports this. 3944 The scheduler will make use of this information and 3945 e.g. base its process migration decisions on it. 3946 Default is on. 3947 3948 topology_updates= [KNL, PPC, NUMA] 3949 Format: {off} 3950 Specify if the kernel should ignore (off) 3951 topology updates sent by the hypervisor to this 3952 LPAR. 3953 3954 tp720= [HW,PS2] 3955 3956 tpm_suspend_pcr=[HW,TPM] 3957 Format: integer pcr id 3958 Specify that at suspend time, the tpm driver 3959 should extend the specified pcr with zeros, 3960 as a workaround for some chips which fail to 3961 flush the last written pcr on TPM_SaveState. 3962 This will guarantee that all the other pcrs 3963 are saved. 3964 3965 trace_buf_size=nn[KMG] 3966 [FTRACE] will set tracing buffer size on each cpu. 3967 3968 trace_event=[event-list] 3969 [FTRACE] Set and start specified trace events in order 3970 to facilitate early boot debugging. The event-list is a 3971 comma separated list of trace events to enable. See 3972 also Documentation/trace/events.txt 3973 3974 trace_options=[option-list] 3975 [FTRACE] Enable or disable tracer options at boot. 3976 The option-list is a comma delimited list of options 3977 that can be enabled or disabled just as if you were 3978 to echo the option name into 3979 3980 /sys/kernel/debug/tracing/trace_options 3981 3982 For example, to enable stacktrace option (to dump the 3983 stack trace of each event), add to the command line: 3984 3985 trace_options=stacktrace 3986 3987 See also Documentation/trace/ftrace.txt "trace options" 3988 section. 3989 3990 tp_printk[FTRACE] 3991 Have the tracepoints sent to printk as well as the 3992 tracing ring buffer. This is useful for early boot up 3993 where the system hangs or reboots and does not give the 3994 option for reading the tracing buffer or performing a 3995 ftrace_dump_on_oops. 3996 3997 To turn off having tracepoints sent to printk, 3998 echo 0 > /proc/sys/kernel/tracepoint_printk 3999 Note, echoing 1 into this file without the 4000 tracepoint_printk kernel cmdline option has no effect. 4001 4002 ** CAUTION ** 4003 4004 Having tracepoints sent to printk() and activating high 4005 frequency tracepoints such as irq or sched, can cause 4006 the system to live lock. 4007 4008 traceoff_on_warning 4009 [FTRACE] enable this option to disable tracing when a 4010 warning is hit. This turns off "tracing_on". Tracing can 4011 be enabled again by echoing '1' into the "tracing_on" 4012 file located in /sys/kernel/debug/tracing/ 4013 4014 This option is useful, as it disables the trace before 4015 the WARNING dump is called, which prevents the trace to 4016 be filled with content caused by the warning output. 4017 4018 This option can also be set at run time via the sysctl 4019 option: kernel/traceoff_on_warning 4020 4021 transparent_hugepage= 4022 [KNL] 4023 Format: [always|madvise|never] 4024 Can be used to control the default behavior of the system 4025 with respect to transparent hugepages. 4026 See Documentation/vm/transhuge.txt for more details. 4027 4028 tsc= Disable clocksource stability checks for TSC. 4029 Format: <string> 4030 [x86] reliable: mark tsc clocksource as reliable, this 4031 disables clocksource verification at runtime, as well 4032 as the stability checks done at bootup. Used to enable 4033 high-resolution timer mode on older hardware, and in 4034 virtualized environment. 4035 [x86] noirqtime: Do not use TSC to do irq accounting. 4036 Used to run time disable IRQ_TIME_ACCOUNTING on any 4037 platforms where RDTSC is slow and this accounting 4038 can add overhead. 4039 4040 turbografx.map[2|3]= [HW,JOY] 4041 TurboGraFX parallel port interface 4042 Format: 4043 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 4044 See also Documentation/input/joystick-parport.txt 4045 4046 udbg-immortal [PPC] When debugging early kernel crashes that 4047 happen after console_init() and before a proper 4048 console driver takes over, this boot options might 4049 help "seeing" what's going on. 4050 4051 uhash_entries= [KNL,NET] 4052 Set number of hash buckets for UDP/UDP-Lite connections 4053 4054 uhci-hcd.ignore_oc= 4055 [USB] Ignore overcurrent events (default N). 4056 Some badly-designed motherboards generate lots of 4057 bogus events, for ports that aren't wired to 4058 anything. Set this parameter to avoid log spamming. 4059 Note that genuine overcurrent events won't be 4060 reported either. 4061 4062 unknown_nmi_panic 4063 [X86] Cause panic on unknown NMI. 4064 4065 usbcore.authorized_default= 4066 [USB] Default USB device authorization: 4067 (default -1 = authorized except for wireless USB, 4068 0 = not authorized, 1 = authorized) 4069 4070 usbcore.autosuspend= 4071 [USB] The autosuspend time delay (in seconds) used 4072 for newly-detected USB devices (default 2). This 4073 is the time required before an idle device will be 4074 autosuspended. Devices for which the delay is set 4075 to a negative value won't be autosuspended at all. 4076 4077 usbcore.usbfs_snoop= 4078 [USB] Set to log all usbfs traffic (default 0 = off). 4079 4080 usbcore.usbfs_snoop_max= 4081 [USB] Maximum number of bytes to snoop in each URB 4082 (default = 65536). 4083 4084 usbcore.blinkenlights= 4085 [USB] Set to cycle leds on hubs (default 0 = off). 4086 4087 usbcore.old_scheme_first= 4088 [USB] Start with the old device initialization 4089 scheme (default 0 = off). 4090 4091 usbcore.usbfs_memory_mb= 4092 [USB] Memory limit (in MB) for buffers allocated by 4093 usbfs (default = 16, 0 = max = 2047). 4094 4095 usbcore.use_both_schemes= 4096 [USB] Try the other device initialization scheme 4097 if the first one fails (default 1 = enabled). 4098 4099 usbcore.initial_descriptor_timeout= 4100 [USB] Specifies timeout for the initial 64-byte 4101 USB_REQ_GET_DESCRIPTOR request in milliseconds 4102 (default 5000 = 5.0 seconds). 4103 4104 usbcore.nousb [USB] Disable the USB subsystem 4105 4106 usbhid.mousepoll= 4107 [USBHID] The interval which mice are to be polled at. 4108 4109 usb-storage.delay_use= 4110 [UMS] The delay in seconds before a new device is 4111 scanned for Logical Units (default 1). 4112 4113 usb-storage.quirks= 4114 [UMS] A list of quirks entries to supplement or 4115 override the built-in unusual_devs list. List 4116 entries are separated by commas. Each entry has 4117 the form VID:PID:Flags where VID and PID are Vendor 4118 and Product ID values (4-digit hex numbers) and 4119 Flags is a set of characters, each corresponding 4120 to a common usb-storage quirk flag as follows: 4121 a = SANE_SENSE (collect more than 18 bytes 4122 of sense data); 4123 b = BAD_SENSE (don't collect more than 18 4124 bytes of sense data); 4125 c = FIX_CAPACITY (decrease the reported 4126 device capacity by one sector); 4127 d = NO_READ_DISC_INFO (don't use 4128 READ_DISC_INFO command); 4129 e = NO_READ_CAPACITY_16 (don't use 4130 READ_CAPACITY_16 command); 4131 f = NO_REPORT_OPCODES (don't use report opcodes 4132 command, uas only); 4133 g = MAX_SECTORS_240 (don't transfer more than 4134 240 sectors at a time, uas only); 4135 h = CAPACITY_HEURISTICS (decrease the 4136 reported device capacity by one 4137 sector if the number is odd); 4138 i = IGNORE_DEVICE (don't bind to this 4139 device); 4140 j = NO_REPORT_LUNS (don't use report luns 4141 command, uas only); 4142 l = NOT_LOCKABLE (don't try to lock and 4143 unlock ejectable media); 4144 m = MAX_SECTORS_64 (don't transfer more 4145 than 64 sectors = 32 KB at a time); 4146 n = INITIAL_READ10 (force a retry of the 4147 initial READ(10) command); 4148 o = CAPACITY_OK (accept the capacity 4149 reported by the device); 4150 p = WRITE_CACHE (the device cache is ON 4151 by default); 4152 r = IGNORE_RESIDUE (the device reports 4153 bogus residue values); 4154 s = SINGLE_LUN (the device has only one 4155 Logical Unit); 4156 t = NO_ATA_1X (don't allow ATA(12) and ATA(16) 4157 commands, uas only); 4158 u = IGNORE_UAS (don't bind to the uas driver); 4159 w = NO_WP_DETECT (don't test whether the 4160 medium is write-protected). 4161 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE 4162 even if the device claims no cache) 4163 Example: quirks=0419:aaf5:rl,0421:0433:rc 4164 4165 user_debug= [KNL,ARM] 4166 Format: <int> 4167 See arch/arm/Kconfig.debug help text. 4168 1 - undefined instruction events 4169 2 - system calls 4170 4 - invalid data aborts 4171 8 - SIGSEGV faults 4172 16 - SIGBUS faults 4173 Example: user_debug=31 4174 4175 userpte= 4176 [X86] Flags controlling user PTE allocations. 4177 4178 nohigh = do not allocate PTE pages in 4179 HIGHMEM regardless of setting 4180 of CONFIG_HIGHPTE. 4181 4182 vdso= [X86,SH] 4183 On X86_32, this is an alias for vdso32=. Otherwise: 4184 4185 vdso=1: enable VDSO (the default) 4186 vdso=0: disable VDSO mapping 4187 4188 vdso32= [X86] Control the 32-bit vDSO 4189 vdso32=1: enable 32-bit VDSO 4190 vdso32=0 or vdso32=2: disable 32-bit VDSO 4191 4192 See the help text for CONFIG_COMPAT_VDSO for more 4193 details. If CONFIG_COMPAT_VDSO is set, the default is 4194 vdso32=0; otherwise, the default is vdso32=1. 4195 4196 For compatibility with older kernels, vdso32=2 is an 4197 alias for vdso32=0. 4198 4199 Try vdso32=0 if you encounter an error that says: 4200 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! 4201 4202 vector= [IA-64,SMP] 4203 vector=percpu: enable percpu vector domain 4204 4205 video= [FB] Frame buffer configuration 4206 See Documentation/fb/modedb.txt. 4207 4208 video.brightness_switch_enabled= [0,1] 4209 If set to 1, on receiving an ACPI notify event 4210 generated by hotkey, video driver will adjust brightness 4211 level and then send out the event to user space through 4212 the allocated input device; If set to 0, video driver 4213 will only send out the event without touching backlight 4214 brightness level. 4215 default: 1 4216 4217 virtio_mmio.device= 4218 [VMMIO] Memory mapped virtio (platform) device. 4219 4220 <size>@<baseaddr>:<irq>[:<id>] 4221 where: 4222 <size> := size (can use standard suffixes 4223 like K, M and G) 4224 <baseaddr> := physical base address 4225 <irq> := interrupt number (as passed to 4226 request_irq()) 4227 <id> := (optional) platform device id 4228 example: 4229 virtio_mmio.device=1K@0x100b0000:48:7 4230 4231 Can be used multiple times for multiple devices. 4232 4233 vga= [BOOT,X86-32] Select a particular video mode 4234 See Documentation/x86/boot.txt and 4235 Documentation/svga.txt. 4236 Use vga=ask for menu. 4237 This is actually a boot loader parameter; the value is 4238 passed to the kernel using a special protocol. 4239 4240 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 4241 size of <nn>. This can be used to increase the 4242 minimum size (128MB on x86). It can also be used to 4243 decrease the size and leave more room for directly 4244 mapped kernel RAM. 4245 4246 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 4247 Format: <command> 4248 4249 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 4250 Format: <command> 4251 4252 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 4253 Format: <command> 4254 4255 vsyscall= [X86-64] 4256 Controls the behavior of vsyscalls (i.e. calls to 4257 fixed addresses of 0xffffffffff600x00 from legacy 4258 code). Most statically-linked binaries and older 4259 versions of glibc use these calls. Because these 4260 functions are at fixed addresses, they make nice 4261 targets for exploits that can control RIP. 4262 4263 emulate [default] Vsyscalls turn into traps and are 4264 emulated reasonably safely. 4265 4266 native Vsyscalls are native syscall instructions. 4267 This is a little bit faster than trapping 4268 and makes a few dynamic recompilers work 4269 better than they would in emulation mode. 4270 It also makes exploits much easier to write. 4271 4272 none Vsyscalls don't work at all. This makes 4273 them quite hard to use for exploits but 4274 might break your system. 4275 4276 vt.color= [VT] Default text color. 4277 Format: 0xYX, X = foreground, Y = background. 4278 Default: 0x07 = light gray on black. 4279 4280 vt.cur_default= [VT] Default cursor shape. 4281 Format: 0xCCBBAA, where AA, BB, and CC are the same as 4282 the parameters of the <Esc>[?A;B;Cc escape sequence; 4283 see VGA-softcursor.txt. Default: 2 = underline. 4284 4285 vt.default_blu= [VT] 4286 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 4287 Change the default blue palette of the console. 4288 This is a 16-member array composed of values 4289 ranging from 0-255. 4290 4291 vt.default_grn= [VT] 4292 Format: <green0>,<green1>,<green2>,...,<green15> 4293 Change the default green palette of the console. 4294 This is a 16-member array composed of values 4295 ranging from 0-255. 4296 4297 vt.default_red= [VT] 4298 Format: <red0>,<red1>,<red2>,...,<red15> 4299 Change the default red palette of the console. 4300 This is a 16-member array composed of values 4301 ranging from 0-255. 4302 4303 vt.default_utf8= 4304 [VT] 4305 Format=<0|1> 4306 Set system-wide default UTF-8 mode for all tty's. 4307 Default is 1, i.e. UTF-8 mode is enabled for all 4308 newly opened terminals. 4309 4310 vt.global_cursor_default= 4311 [VT] 4312 Format=<-1|0|1> 4313 Set system-wide default for whether a cursor 4314 is shown on new VTs. Default is -1, 4315 i.e. cursors will be created by default unless 4316 overridden by individual drivers. 0 will hide 4317 cursors, 1 will display them. 4318 4319 vt.italic= [VT] Default color for italic text; 0-15. 4320 Default: 2 = green. 4321 4322 vt.underline= [VT] Default color for underlined text; 0-15. 4323 Default: 3 = cyan. 4324 4325 watchdog timers [HW,WDT] For information on watchdog timers, 4326 see Documentation/watchdog/watchdog-parameters.txt 4327 or other driver-specific files in the 4328 Documentation/watchdog/ directory. 4329 4330 workqueue.watchdog_thresh= 4331 If CONFIG_WQ_WATCHDOG is configured, workqueue can 4332 warn stall conditions and dump internal state to 4333 help debugging. 0 disables workqueue stall 4334 detection; otherwise, it's the stall threshold 4335 duration in seconds. The default value is 30 and 4336 it can be updated at runtime by writing to the 4337 corresponding sysfs file. 4338 4339 workqueue.disable_numa 4340 By default, all work items queued to unbound 4341 workqueues are affine to the NUMA nodes they're 4342 issued on, which results in better behavior in 4343 general. If NUMA affinity needs to be disabled for 4344 whatever reason, this option can be used. Note 4345 that this also can be controlled per-workqueue for 4346 workqueues visible under /sys/bus/workqueue/. 4347 4348 workqueue.power_efficient 4349 Per-cpu workqueues are generally preferred because 4350 they show better performance thanks to cache 4351 locality; unfortunately, per-cpu workqueues tend to 4352 be more power hungry than unbound workqueues. 4353 4354 Enabling this makes the per-cpu workqueues which 4355 were observed to contribute significantly to power 4356 consumption unbound, leading to measurably lower 4357 power usage at the cost of small performance 4358 overhead. 4359 4360 The default value of this parameter is determined by 4361 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. 4362 4363 workqueue.debug_force_rr_cpu 4364 Workqueue used to implicitly guarantee that work 4365 items queued without explicit CPU specified are put 4366 on the local CPU. This guarantee is no longer true 4367 and while local CPU is still preferred work items 4368 may be put on foreign CPUs. This debug option 4369 forces round-robin CPU selection to flush out 4370 usages which depend on the now broken guarantee. 4371 When enabled, memory and cache locality will be 4372 impacted. 4373 4374 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 4375 default x2apic cluster mode on platforms 4376 supporting x2apic. 4377 4378 x86_intel_mid_timer= [X86-32,APBT] 4379 Choose timer option for x86 Intel MID platform. 4380 Two valid options are apbt timer only and lapic timer 4381 plus one apbt timer for broadcast timer. 4382 x86_intel_mid_timer=apbt_only | lapic_and_apbt 4383 4384 xen_512gb_limit [KNL,X86-64,XEN] 4385 Restricts the kernel running paravirtualized under Xen 4386 to use only up to 512 GB of RAM. The reason to do so is 4387 crash analysis tools and Xen tools for doing domain 4388 save/restore/migration must be enabled to handle larger 4389 domains. 4390 4391 xen_emul_unplug= [HW,X86,XEN] 4392 Unplug Xen emulated devices 4393 Format: [unplug0,][unplug1] 4394 ide-disks -- unplug primary master IDE devices 4395 aux-ide-disks -- unplug non-primary-master IDE devices 4396 nics -- unplug network devices 4397 all -- unplug all emulated devices (NICs and IDE disks) 4398 unnecessary -- unplugging emulated devices is 4399 unnecessary even if the host did not respond to 4400 the unplug protocol 4401 never -- do not unplug even if version check succeeds 4402 4403 xen_nopvspin [X86,XEN] 4404 Disables the ticketlock slowpath using Xen PV 4405 optimizations. 4406 4407 xen_nopv [X86] 4408 Disables the PV optimizations forcing the HVM guest to 4409 run as generic HVM guest with no PV drivers. 4410 4411 xirc2ps_cs= [NET,PCMCIA] 4412 Format: 4413 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 4414