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diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst index 37105aedb2e4..b516164999a8 100644 --- a/Documentation/admin-guide/kernel-parameters.rst +++ b/Documentation/admin-guide/kernel-parameters.rst @@ -198,4378 +198,10 @@ and is between 256 and 4096 characters. It is defined in the file Finally, the [KMG] suffix is commonly described after a number of kernel parameter values. These 'K', 'M', and 'G' letters represent the _binary_ multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30 -bytes respectively. Such letter suffixes can also be entirely omitted:: +bytes respectively. Such letter suffixes can also be entirely omitted: - - acpi= [HW,ACPI,X86,ARM64] - Advanced Configuration and Power Interface - Format: { force | on | off | strict | noirq | rsdt | - copy_dsdt } - force -- enable ACPI if default was off - on -- enable ACPI but allow fallback to DT [arm64] - off -- disable ACPI if default was on - noirq -- do not use ACPI for IRQ routing - strict -- Be less tolerant of platforms that are not - strictly ACPI specification compliant. - rsdt -- prefer RSDT over (default) XSDT - copy_dsdt -- copy DSDT to memory - For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" - are available - - See also Documentation/power/runtime_pm.txt, pci=noacpi - - acpi_apic_instance= [ACPI, IOAPIC] - Format: <int> - 2: use 2nd APIC table, if available - 1,0: use 1st APIC table - default: 0 - - acpi_backlight= [HW,ACPI] - acpi_backlight=vendor - acpi_backlight=video - If set to vendor, prefer vendor specific driver - (e.g. thinkpad_acpi, sony_acpi, etc.) instead - of the ACPI video.ko driver. - - acpi_force_32bit_fadt_addr - force FADT to use 32 bit addresses rather than the - 64 bit X_* addresses. Some firmware have broken 64 - bit addresses for force ACPI ignore these and use - the older legacy 32 bit addresses. - - acpica_no_return_repair [HW, ACPI] - Disable AML predefined validation mechanism - This mechanism can repair the evaluation result to make - the return objects more ACPI specification compliant. - This option is useful for developers to identify the - root cause of an AML interpreter issue when the issue - has something to do with the repair mechanism. - - acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] - acpi.debug_level= [HW,ACPI,ACPI_DEBUG] - Format: <int> - CONFIG_ACPI_DEBUG must be enabled to produce any ACPI - debug output. Bits in debug_layer correspond to a - _COMPONENT in an ACPI source file, e.g., - #define _COMPONENT ACPI_PCI_COMPONENT - Bits in debug_level correspond to a level in - ACPI_DEBUG_PRINT statements, e.g., - ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... - The debug_level mask defaults to "info". See - Documentation/acpi/debug.txt for more information about - debug layers and levels. - - Enable processor driver info messages: - acpi.debug_layer=0x20000000 - Enable PCI/PCI interrupt routing info messages: - acpi.debug_layer=0x400000 - Enable AML "Debug" output, i.e., stores to the Debug - object while interpreting AML: - acpi.debug_layer=0xffffffff acpi.debug_level=0x2 - Enable all messages related to ACPI hardware: - acpi.debug_layer=0x2 acpi.debug_level=0xffffffff - - Some values produce so much output that the system is - unusable. The "log_buf_len" parameter may be useful - if you need to capture more output. - - acpi_enforce_resources= [ACPI] - { strict | lax | no } - Check for resource conflicts between native drivers - and ACPI OperationRegions (SystemIO and SystemMemory - only). IO ports and memory declared in ACPI might be - used by the ACPI subsystem in arbitrary AML code and - can interfere with legacy drivers. - strict (default): access to resources claimed by ACPI - is denied; legacy drivers trying to access reserved - resources will fail to bind to device using them. - lax: access to resources claimed by ACPI is allowed; - legacy drivers trying to access reserved resources - will bind successfully but a warning message is logged. - no: ACPI OperationRegions are not marked as reserved, - no further checks are performed. - - acpi_force_table_verification [HW,ACPI] - Enable table checksum verification during early stage. - By default, this is disabled due to x86 early mapping - size limitation. - - acpi_irq_balance [HW,ACPI] - ACPI will balance active IRQs - default in APIC mode - - acpi_irq_nobalance [HW,ACPI] - ACPI will not move active IRQs (default) - default in PIC mode - - acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA - Format: <irq>,<irq>... - - acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for - use by PCI - Format: <irq>,<irq>... - - acpi_no_auto_serialize [HW,ACPI] - Disable auto-serialization of AML methods - AML control methods that contain the opcodes to create - named objects will be marked as "Serialized" by the - auto-serialization feature. - This feature is enabled by default. - This option allows to turn off the feature. - - acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump - kernels. - - acpi_no_static_ssdt [HW,ACPI] - Disable installation of static SSDTs at early boot time - By default, SSDTs contained in the RSDT/XSDT will be - installed automatically and they will appear under - /sys/firmware/acpi/tables. - This option turns off this feature. - Note that specifying this option does not affect - dynamic table installation which will install SSDT - tables to /sys/firmware/acpi/tables/dynamic. - - acpi_rsdp= [ACPI,EFI,KEXEC] - Pass the RSDP address to the kernel, mostly used - on machines running EFI runtime service to boot the - second kernel for kdump. - - acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS - Format: To spoof as Windows 98: ="Microsoft Windows" - - acpi_rev_override [ACPI] Override the _REV object to return 5 (instead - of 2 which is mandated by ACPI 6) as the supported ACPI - specification revision (when using this switch, it may - be necessary to carry out a cold reboot _twice_ in a - row to make it take effect on the platform firmware). - - acpi_osi= [HW,ACPI] Modify list of supported OS interface strings - acpi_osi="string1" # add string1 - acpi_osi="!string2" # remove string2 - acpi_osi=!* # remove all strings - acpi_osi=! # disable all built-in OS vendor - strings - acpi_osi=!! # enable all built-in OS vendor - strings - acpi_osi= # disable all strings - - 'acpi_osi=!' can be used in combination with single or - multiple 'acpi_osi="string1"' to support specific OS - vendor string(s). Note that such command can only - affect the default state of the OS vendor strings, thus - it cannot affect the default state of the feature group - strings and the current state of the OS vendor strings, - specifying it multiple times through kernel command line - is meaningless. This command is useful when one do not - care about the state of the feature group strings which - should be controlled by the OSPM. - Examples: - 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent - to 'acpi_osi="Windows 2000" acpi_osi=!', they all - can make '_OSI("Windows 2000")' TRUE. - - 'acpi_osi=' cannot be used in combination with other - 'acpi_osi=' command lines, the _OSI method will not - exist in the ACPI namespace. NOTE that such command can - only affect the _OSI support state, thus specifying it - multiple times through kernel command line is also - meaningless. - Examples: - 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' - FALSE. - - 'acpi_osi=!*' can be used in combination with single or - multiple 'acpi_osi="string1"' to support specific - string(s). Note that such command can affect the - current state of both the OS vendor strings and the - feature group strings, thus specifying it multiple times - through kernel command line is meaningful. But it may - still not able to affect the final state of a string if - there are quirks related to this string. This command - is useful when one want to control the state of the - feature group strings to debug BIOS issues related to - the OSPM features. - Examples: - 1. 'acpi_osi="Module Device" acpi_osi=!*' can make - '_OSI("Module Device")' FALSE. - 2. 'acpi_osi=!* acpi_osi="Module Device"' can make - '_OSI("Module Device")' TRUE. - 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is - equivalent to - 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' - and - 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', - they all will make '_OSI("Windows 2000")' TRUE. - - acpi_pm_good [X86] - Override the pmtimer bug detection: force the kernel - to assume that this machine's pmtimer latches its value - and always returns good values. - - acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode - Format: { level | edge | high | low } - - acpi_skip_timer_override [HW,ACPI] - Recognize and ignore IRQ0/pin2 Interrupt Override. - For broken nForce2 BIOS resulting in XT-PIC timer. - - acpi_sleep= [HW,ACPI] Sleep options - Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, - old_ordering, nonvs, sci_force_enable } - See Documentation/power/video.txt for information on - s3_bios and s3_mode. - s3_beep is for debugging; it makes the PC's speaker beep - as soon as the kernel's real-mode entry point is called. - s4_nohwsig prevents ACPI hardware signature from being - used during resume from hibernation. - old_ordering causes the ACPI 1.0 ordering of the _PTS - control method, with respect to putting devices into - low power states, to be enforced (the ACPI 2.0 ordering - of _PTS is used by default). - nonvs prevents the kernel from saving/restoring the - ACPI NVS memory during suspend/hibernation and resume. - sci_force_enable causes the kernel to set SCI_EN directly - on resume from S1/S3 (which is against the ACPI spec, - but some broken systems don't work without it). - - acpi_use_timer_override [HW,ACPI] - Use timer override. For some broken Nvidia NF5 boards - that require a timer override, but don't have HPET - - add_efi_memmap [EFI; X86] Include EFI memory map in - kernel's map of available physical RAM. - - agp= [AGP] - { off | try_unsupported } - off: disable AGP support - try_unsupported: try to drive unsupported chipsets - (may crash computer or cause data corruption) - - ALSA [HW,ALSA] - See Documentation/sound/alsa/alsa-parameters.txt - - alignment= [KNL,ARM] - Allow the default userspace alignment fault handler - behaviour to be specified. Bit 0 enables warnings, - bit 1 enables fixups, and bit 2 sends a segfault. - - align_va_addr= [X86-64] - Align virtual addresses by clearing slice [14:12] when - allocating a VMA at process creation time. This option - gives you up to 3% performance improvement on AMD F15h - machines (where it is enabled by default) for a - CPU-intensive style benchmark, and it can vary highly in - a microbenchmark depending on workload and compiler. - - 32: only for 32-bit processes - 64: only for 64-bit processes - on: enable for both 32- and 64-bit processes - off: disable for both 32- and 64-bit processes - - alloc_snapshot [FTRACE] - Allocate the ftrace snapshot buffer on boot up when the - main buffer is allocated. This is handy if debugging - and you need to use tracing_snapshot() on boot up, and - do not want to use tracing_snapshot_alloc() as it needs - to be done where GFP_KERNEL allocations are allowed. - - amd_iommu= [HW,X86-64] - Pass parameters to the AMD IOMMU driver in the system. - Possible values are: - fullflush - enable flushing of IO/TLB entries when - they are unmapped. Otherwise they are - flushed before they will be reused, which - is a lot of faster - off - do not initialize any AMD IOMMU found in - the system - force_isolation - Force device isolation for all - devices. The IOMMU driver is not - allowed anymore to lift isolation - requirements as needed. This option - does not override iommu=pt - - amd_iommu_dump= [HW,X86-64] - Enable AMD IOMMU driver option to dump the ACPI table - for AMD IOMMU. With this option enabled, AMD IOMMU - driver will print ACPI tables for AMD IOMMU during - IOMMU initialization. - - amd_iommu_intr= [HW,X86-64] - Specifies one of the following AMD IOMMU interrupt - remapping modes: - legacy - Use legacy interrupt remapping mode. - vapic - Use virtual APIC mode, which allows IOMMU - to inject interrupts directly into guest. - This mode requires kvm-amd.avic=1. - (Default when IOMMU HW support is present.) - - amijoy.map= [HW,JOY] Amiga joystick support - Map of devices attached to JOY0DAT and JOY1DAT - Format: <a>,<b> - See also Documentation/input/joystick.txt - - analog.map= [HW,JOY] Analog joystick and gamepad support - Specifies type or capabilities of an analog joystick - connected to one of 16 gameports - Format: <type1>,<type2>,..<type16> - - apc= [HW,SPARC] - Power management functions (SPARCstation-4/5 + deriv.) - Format: noidle - Disable APC CPU standby support. SPARCstation-Fox does - not play well with APC CPU idle - disable it if you have - APC and your system crashes randomly. - - apic= [APIC,X86-32] Advanced Programmable Interrupt Controller - Change the output verbosity whilst booting - Format: { quiet (default) | verbose | debug } - Change the amount of debugging information output - when initialising the APIC and IO-APIC components. - - apic_extnmi= [APIC,X86] External NMI delivery setting - Format: { bsp (default) | all | none } - bsp: External NMI is delivered only to CPU 0 - all: External NMIs are broadcast to all CPUs as a - backup of CPU 0 - none: External NMI is masked for all CPUs. This is - useful so that a dump capture kernel won't be - shot down by NMI - - autoconf= [IPV6] - See Documentation/networking/ipv6.txt. - - show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller - Limit apic dumping. The parameter defines the maximal - number of local apics being dumped. Also it is possible - to set it to "all" by meaning -- no limit here. - Format: { 1 (default) | 2 | ... | all }. - The parameter valid if only apic=debug or - apic=verbose is specified. - Example: apic=debug show_lapic=all - - apm= [APM] Advanced Power Management - See header of arch/x86/kernel/apm_32.c. - - arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards - Format: <io>,<irq>,<nodeID> - - ataflop= [HW,M68k] - - atarimouse= [HW,MOUSE] Atari Mouse - - atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, - EzKey and similar keyboards - - atkbd.reset= [HW] Reset keyboard during initialization - - atkbd.set= [HW] Select keyboard code set - Format: <int> (2 = AT (default), 3 = PS/2) - - atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar - keyboards - - atkbd.softraw= [HW] Choose between synthetic and real raw mode - Format: <bool> (0 = real, 1 = synthetic (default)) - - atkbd.softrepeat= [HW] - Use software keyboard repeat - - audit= [KNL] Enable the audit sub-system - Format: { "0" | "1" } (0 = disabled, 1 = enabled) - 0 - kernel audit is disabled and can not be enabled - until the next reboot - unset - kernel audit is initialized but disabled and - will be fully enabled by the userspace auditd. - 1 - kernel audit is initialized and partially enabled, - storing at most audit_backlog_limit messages in - RAM until it is fully enabled by the userspace - auditd. - Default: unset - - audit_backlog_limit= [KNL] Set the audit queue size limit. - Format: <int> (must be >=0) - Default: 64 - - bau= [X86_UV] Enable the BAU on SGI UV. The default - behavior is to disable the BAU (i.e. bau=0). - Format: { "0" | "1" } - 0 - Disable the BAU. - 1 - Enable the BAU. - unset - Disable the BAU. - - baycom_epp= [HW,AX25] - Format: <io>,<mode> - - baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem - Format: <io>,<mode> - See header of drivers/net/hamradio/baycom_par.c. - - baycom_ser_fdx= [HW,AX25] - BayCom Serial Port AX.25 Modem (Full Duplex Mode) - Format: <io>,<irq>,<mode>[,<baud>] - See header of drivers/net/hamradio/baycom_ser_fdx.c. - - baycom_ser_hdx= [HW,AX25] - BayCom Serial Port AX.25 Modem (Half Duplex Mode) - Format: <io>,<irq>,<mode> - See header of drivers/net/hamradio/baycom_ser_hdx.c. - - blkdevparts= Manual partition parsing of block device(s) for - embedded devices based on command line input. - See Documentation/block/cmdline-partition.txt - - boot_delay= Milliseconds to delay each printk during boot. - Values larger than 10 seconds (10000) are changed to - no delay (0). - Format: integer - - bootmem_debug [KNL] Enable bootmem allocator debug messages. - - bert_disable [ACPI] - Disable BERT OS support on buggy BIOSes. - - bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) - bttv.radio= Most important insmod options are available as - kernel args too. - bttv.pll= See Documentation/video4linux/bttv/Insmod-options - bttv.tuner= - - bulk_remove=off [PPC] This parameter disables the use of the pSeries - firmware feature for flushing multiple hpte entries - at a time. - - c101= [NET] Moxa C101 synchronous serial card - - cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. - Sometimes CPU hardware bugs make them report the cache - size incorrectly. The kernel will attempt work arounds - to fix known problems, but for some CPUs it is not - possible to determine what the correct size should be. - This option provides an override for these situations. - - ca_keys= [KEYS] This parameter identifies a specific key(s) on - the system trusted keyring to be used for certificate - trust validation. - format: { id:<keyid> | builtin } - - cca= [MIPS] Override the kernel pages' cache coherency - algorithm. Accepted values range from 0 to 7 - inclusive. See arch/mips/include/asm/pgtable-bits.h - for platform specific values (SB1, Loongson3 and - others). - - ccw_timeout_log [S390] - See Documentation/s390/CommonIO for details. - - cgroup_disable= [KNL] Disable a particular controller - Format: {name of the controller(s) to disable} - The effects of cgroup_disable=foo are: - - foo isn't auto-mounted if you mount all cgroups in - a single hierarchy - - foo isn't visible as an individually mountable - subsystem - {Currently only "memory" controller deal with this and - cut the overhead, others just disable the usage. So - only cgroup_disable=memory is actually worthy} - - cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1 - Format: { controller[,controller...] | "all" } - Like cgroup_disable, but only applies to cgroup v1; - the blacklisted controllers remain available in cgroup2. - - cgroup.memory= [KNL] Pass options to the cgroup memory controller. - Format: <string> - nosocket -- Disable socket memory accounting. - nokmem -- Disable kernel memory accounting. - - checkreqprot [SELINUX] Set initial checkreqprot flag value. - Format: { "0" | "1" } - See security/selinux/Kconfig help text. - 0 -- check protection applied by kernel (includes - any implied execute protection). - 1 -- check protection requested by application. - Default value is set via a kernel config option. - Value can be changed at runtime via - /selinux/checkreqprot. - - cio_ignore= [S390] - See Documentation/s390/CommonIO for details. - clk_ignore_unused - [CLK] - Prevents the clock framework from automatically gating - clocks that have not been explicitly enabled by a Linux - device driver but are enabled in hardware at reset or - by the bootloader/firmware. Note that this does not - force such clocks to be always-on nor does it reserve - those clocks in any way. This parameter is useful for - debug and development, but should not be needed on a - platform with proper driver support. For more - information, see Documentation/clk.txt. - - clock= [BUGS=X86-32, HW] gettimeofday clocksource override. - [Deprecated] - Forces specified clocksource (if available) to be used - when calculating gettimeofday(). If specified - clocksource is not available, it defaults to PIT. - Format: { pit | tsc | cyclone | pmtmr } - - clocksource= Override the default clocksource - Format: <string> - Override the default clocksource and use the clocksource - with the name specified. - Some clocksource names to choose from, depending on - the platform: - [all] jiffies (this is the base, fallback clocksource) - [ACPI] acpi_pm - [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, - pxa_timer,timer3,32k_counter,timer0_1 - [AVR32] avr32 - [X86-32] pit,hpet,tsc; - scx200_hrt on Geode; cyclone on IBM x440 - [MIPS] MIPS - [PARISC] cr16 - [S390] tod - [SH] SuperH - [SPARC64] tick - [X86-64] hpet,tsc - - clocksource.arm_arch_timer.evtstrm= - [ARM,ARM64] - Format: <bool> - Enable/disable the eventstream feature of the ARM - architected timer so that code using WFE-based polling - loops can be debugged more effectively on production - systems. - - clocksource.arm_arch_timer.fsl-a008585= - [ARM64] - Format: <bool> - Enable/disable the workaround of Freescale/NXP - erratum A-008585. This can be useful for KVM - guests, if the guest device tree doesn't show the - erratum. If unspecified, the workaround is - enabled based on the device tree. - - clearcpuid=BITNUM [X86] - Disable CPUID feature X for the kernel. See - arch/x86/include/asm/cpufeatures.h for the valid bit - numbers. Note the Linux specific bits are not necessarily - stable over kernel options, but the vendor specific - ones should be. - Also note that user programs calling CPUID directly - or using the feature without checking anything - will still see it. This just prevents it from - being used by the kernel or shown in /proc/cpuinfo. - Also note the kernel might malfunction if you disable - some critical bits. - - cma=nn[MG]@[start[MG][-end[MG]]] - [ARM,X86,KNL] - Sets the size of kernel global memory area for - contiguous memory allocations and optionally the - placement constraint by the physical address range of - memory allocations. A value of 0 disables CMA - altogether. For more information, see - include/linux/dma-contiguous.h - - cmo_free_hint= [PPC] Format: { yes | no } - Specify whether pages are marked as being inactive - when they are freed. This is used in CMO environments - to determine OS memory pressure for page stealing by - a hypervisor. - Default: yes - - coherent_pool=nn[KMG] [ARM,KNL] - Sets the size of memory pool for coherent, atomic dma - allocations, by default set to 256K. - - code_bytes [X86] How many bytes of object code to print - in an oops report. - Range: 0 - 8192 - Default: 64 - - com20020= [HW,NET] ARCnet - COM20020 chipset - Format: - <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] - - com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) - Format: <io>[,<irq>] - - com90xx= [HW,NET] - ARCnet - COM90xx chipset (memory-mapped buffers) - Format: <io>[,<irq>[,<memstart>]] - - condev= [HW,S390] console device - conmode= - - console= [KNL] Output console device and options. - - tty<n> Use the virtual console device <n>. - - ttyS<n>[,options] - ttyUSB0[,options] - Use the specified serial port. The options are of - the form "bbbbpnf", where "bbbb" is the baud rate, - "p" is parity ("n", "o", or "e"), "n" is number of - bits, and "f" is flow control ("r" for RTS or - omit it). Default is "9600n8". - - See Documentation/admin-guide/serial-console.rst for more - information. See - Documentation/networking/netconsole.txt for an - alternative. - - uart[8250],io,<addr>[,options] - uart[8250],mmio,<addr>[,options] - uart[8250],mmio16,<addr>[,options] - uart[8250],mmio32,<addr>[,options] - uart[8250],0x<addr>[,options] - Start an early, polled-mode console on the 8250/16550 - UART at the specified I/O port or MMIO address, - switching to the matching ttyS device later. - MMIO inter-register address stride is either 8-bit - (mmio), 16-bit (mmio16), or 32-bit (mmio32). - If none of [io|mmio|mmio16|mmio32], <addr> is assumed - to be equivalent to 'mmio'. 'options' are specified in - the same format described for ttyS above; if unspecified, - the h/w is not re-initialized. - - hvc<n> Use the hypervisor console device <n>. This is for - both Xen and PowerPC hypervisors. - - If the device connected to the port is not a TTY but a braille - device, prepend "brl," before the device type, for instance - console=brl,ttyS0 - For now, only VisioBraille is supported. - - consoleblank= [KNL] The console blank (screen saver) timeout in - seconds. Defaults to 10*60 = 10mins. A value of 0 - disables the blank timer. - - coredump_filter= - [KNL] Change the default value for - /proc/<pid>/coredump_filter. - See also Documentation/filesystems/proc.txt. - - cpuidle.off=1 [CPU_IDLE] - disable the cpuidle sub-system - - cpu_init_udelay=N - [X86] Delay for N microsec between assert and de-assert - of APIC INIT to start processors. This delay occurs - on every CPU online, such as boot, and resume from suspend. - Default: 10000 - - cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver - Format: - <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] - - crashkernel=size[KMG][@offset[KMG]] - [KNL] Using kexec, Linux can switch to a 'crash kernel' - upon panic. This parameter reserves the physical - memory region [offset, offset + size] for that kernel - image. If '@offset' is omitted, then a suitable offset - is selected automatically. Check - Documentation/kdump/kdump.txt for further details. - - crashkernel=range1:size1[,range2:size2,...][@offset] - [KNL] Same as above, but depends on the memory - in the running system. The syntax of range is - start-[end] where start and end are both - a memory unit (amount[KMG]). See also - Documentation/kdump/kdump.txt for an example. - - crashkernel=size[KMG],high - [KNL, x86_64] range could be above 4G. Allow kernel - to allocate physical memory region from top, so could - be above 4G if system have more than 4G ram installed. - Otherwise memory region will be allocated below 4G, if - available. - It will be ignored if crashkernel=X is specified. - crashkernel=size[KMG],low - [KNL, x86_64] range under 4G. When crashkernel=X,high - is passed, kernel could allocate physical memory region - above 4G, that cause second kernel crash on system - that require some amount of low memory, e.g. swiotlb - requires at least 64M+32K low memory, also enough extra - low memory is needed to make sure DMA buffers for 32-bit - devices won't run out. Kernel would try to allocate at - at least 256M below 4G automatically. - This one let user to specify own low range under 4G - for second kernel instead. - 0: to disable low allocation. - It will be ignored when crashkernel=X,high is not used - or memory reserved is below 4G. - - cryptomgr.notests - [KNL] Disable crypto self-tests - - cs89x0_dma= [HW,NET] - Format: <dma> - - cs89x0_media= [HW,NET] - Format: { rj45 | aui | bnc } - - dasd= [HW,NET] - See header of drivers/s390/block/dasd_devmap.c. - - db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port - (one device per port) - Format: <port#>,<type> - See also Documentation/input/joystick-parport.txt - - ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot - time. See Documentation/dynamic-debug-howto.txt for - details. Deprecated, see dyndbg. - - debug [KNL] Enable kernel debugging (events log level). - - debug_locks_verbose= - [KNL] verbose self-tests - Format=<0|1> - Print debugging info while doing the locking API - self-tests. - We default to 0 (no extra messages), setting it to - 1 will print _a lot_ more information - normally - only useful to kernel developers. - - debug_objects [KNL] Enable object debugging - - no_debug_objects - [KNL] Disable object debugging - - debug_guardpage_minorder= - [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this - parameter allows control of the order of pages that will - be intentionally kept free (and hence protected) by the - buddy allocator. Bigger value increase the probability - of catching random memory corruption, but reduce the - amount of memory for normal system use. The maximum - possible value is MAX_ORDER/2. Setting this parameter - to 1 or 2 should be enough to identify most random - memory corruption problems caused by bugs in kernel or - driver code when a CPU writes to (or reads from) a - random memory location. Note that there exists a class - of memory corruptions problems caused by buggy H/W or - F/W or by drivers badly programing DMA (basically when - memory is written at bus level and the CPU MMU is - bypassed) which are not detectable by - CONFIG_DEBUG_PAGEALLOC, hence this option will not help - tracking down these problems. - - debug_pagealloc= - [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this - parameter enables the feature at boot time. In - default, it is disabled. We can avoid allocating huge - chunk of memory for debug pagealloc if we don't enable - it at boot time and the system will work mostly same - with the kernel built without CONFIG_DEBUG_PAGEALLOC. - on: enable the feature - - debugpat [X86] Enable PAT debugging - - decnet.addr= [HW,NET] - Format: <area>[,<node>] - See also Documentation/networking/decnet.txt. - - default_hugepagesz= - [same as hugepagesz=] The size of the default - HugeTLB page size. This is the size represented by - the legacy /proc/ hugepages APIs, used for SHM, and - default size when mounting hugetlbfs filesystems. - Defaults to the default architecture's huge page size - if not specified. - - dhash_entries= [KNL] - Set number of hash buckets for dentry cache. - - disable_1tb_segments [PPC] - Disables the use of 1TB hash page table segments. This - causes the kernel to fall back to 256MB segments which - can be useful when debugging issues that require an SLB - miss to occur. - - disable= [IPV6] - See Documentation/networking/ipv6.txt. - - disable_radix [PPC] - Disable RADIX MMU mode on POWER9 - - disable_cpu_apicid= [X86,APIC,SMP] - Format: <int> - The number of initial APIC ID for the - corresponding CPU to be disabled at boot, - mostly used for the kdump 2nd kernel to - disable BSP to wake up multiple CPUs without - causing system reset or hang due to sending - INIT from AP to BSP. - - disable_ddw [PPC/PSERIES] - Disable Dynamic DMA Window support. Use this if - to workaround buggy firmware. - - disable_ipv6= [IPV6] - See Documentation/networking/ipv6.txt. - - disable_mtrr_cleanup [X86] - The kernel tries to adjust MTRR layout from continuous - to discrete, to make X server driver able to add WB - entry later. This parameter disables that. - - disable_mtrr_trim [X86, Intel and AMD only] - By default the kernel will trim any uncacheable - memory out of your available memory pool based on - MTRR settings. This parameter disables that behavior, - possibly causing your machine to run very slowly. - - disable_timer_pin_1 [X86] - Disable PIN 1 of APIC timer - Can be useful to work around chipset bugs. - - dis_ucode_ldr [X86] Disable the microcode loader. - - dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, - this option disables the debugging code at boot. - - dma_debug_entries=<number> - This option allows to tune the number of preallocated - entries for DMA-API debugging code. One entry is - required per DMA-API allocation. Use this if the - DMA-API debugging code disables itself because the - architectural default is too low. - - dma_debug_driver=<driver_name> - With this option the DMA-API debugging driver - filter feature can be enabled at boot time. Just - pass the driver to filter for as the parameter. - The filter can be disabled or changed to another - driver later using sysfs. - - drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] - Broken monitors, graphic adapters, KVMs and EDIDless - panels may send no or incorrect EDID data sets. - This parameter allows to specify an EDID data sets - in the /lib/firmware directory that are used instead. - Generic built-in EDID data sets are used, if one of - edid/1024x768.bin, edid/1280x1024.bin, - edid/1680x1050.bin, or edid/1920x1080.bin is given - and no file with the same name exists. Details and - instructions how to build your own EDID data are - available in Documentation/EDID/HOWTO.txt. An EDID - data set will only be used for a particular connector, - if its name and a colon are prepended to the EDID - name. Each connector may use a unique EDID data - set by separating the files with a comma. An EDID - data set with no connector name will be used for - any connectors not explicitly specified. - - dscc4.setup= [NET] - - dyndbg[="val"] [KNL,DYNAMIC_DEBUG] - module.dyndbg[="val"] - Enable debug messages at boot time. See - Documentation/dynamic-debug-howto.txt for details. - - nompx [X86] Disables Intel Memory Protection Extensions. - See Documentation/x86/intel_mpx.txt for more - information about the feature. - - nopku [X86] Disable Memory Protection Keys CPU feature found - in some Intel CPUs. - - eagerfpu= [X86] - on enable eager fpu restore - off disable eager fpu restore - auto selects the default scheme, which automatically - enables eagerfpu restore for xsaveopt. - - module.async_probe [KNL] - Enable asynchronous probe on this module. - - early_ioremap_debug [KNL] - Enable debug messages in early_ioremap support. This - is useful for tracking down temporary early mappings - which are not unmapped. - - earlycon= [KNL] Output early console device and options. - - When used with no options, the early console is - determined by the stdout-path property in device - tree's chosen node. - - cdns,<addr>[,options] - Start an early, polled-mode console on a Cadence - (xuartps) serial port at the specified address. Only - supported option is baud rate. If baud rate is not - specified, the serial port must already be setup and - configured. - - uart[8250],io,<addr>[,options] - uart[8250],mmio,<addr>[,options] - uart[8250],mmio32,<addr>[,options] - uart[8250],mmio32be,<addr>[,options] - uart[8250],0x<addr>[,options] - Start an early, polled-mode console on the 8250/16550 - UART at the specified I/O port or MMIO address. - MMIO inter-register address stride is either 8-bit - (mmio) or 32-bit (mmio32 or mmio32be). - If none of [io|mmio|mmio32|mmio32be], <addr> is assumed - to be equivalent to 'mmio'. 'options' are specified - in the same format described for "console=ttyS<n>"; if - unspecified, the h/w is not initialized. - - pl011,<addr> - pl011,mmio32,<addr> - Start an early, polled-mode console on a pl011 serial - port at the specified address. The pl011 serial port - must already be setup and configured. Options are not - yet supported. If 'mmio32' is specified, then only - the driver will use only 32-bit accessors to read/write - the device registers. - - meson,<addr> - Start an early, polled-mode console on a meson serial - port at the specified address. The serial port must - already be setup and configured. Options are not yet - supported. - - msm_serial,<addr> - Start an early, polled-mode console on an msm serial - port at the specified address. The serial port - must already be setup and configured. Options are not - yet supported. - - msm_serial_dm,<addr> - Start an early, polled-mode console on an msm serial - dm port at the specified address. The serial port - must already be setup and configured. Options are not - yet supported. |