RHEL8 内核参数 Kernel-4.18.0-240.15.1.el8_3_kernel-parameters

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.rst, 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_mask_gpe=    [HW,ACPI]
        Due to the existence of _Lxx/_Exx, some GPEs triggered
        by unsupported hardware/firmware features can result in
        GPE floodings that cannot be automatically disabled by
        the GPE dispatcher.
        This facility can be used to prevent such uncontrolled
        GPE floodings.
        Format: <byte>

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_no_watchdog    [HW,ACPI,WDT]
        Ignore the ACPI-based watchdog interface (WDAT) and let
        a native driver control the watchdog device instead.

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, nobl }
        See Documentation/power/video.rst 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).
        nobl causes the internal blacklist of systems known to
        behave incorrectly in some ways with respect to system
        suspend and resume to be ignored (use wisely).

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-configuration.rst

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/joydev/joystick.rst

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] 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.
        For X86-32, this can also be used to specify an APIC
        driver name.
        Format: apic=driver_name
        Examples: apic=bigsmp

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" | "off" | "on" }
        0 | off - 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 | on - 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/media/v4l-drivers/bttv.rst
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/common_io.rst 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 cgroup controllers and named hierarchies in v1
        Format: { { controller | "all" | "named" }
                  [,{ controller | "all" | "named" }...] }
        Like cgroup_disable, but only applies to cgroup v1;
        the blacklisted controllers remain available in cgroup2.
        "all" blacklists all controllers and "named" disables
        named mounts. Specifying both "all" and "named" disables
        all v1 hierarchies.

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
            /sys/fs/selinux/checkreqprot.

cio_ignore=    [S390]
        See Documentation/s390/common_io.rst 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/driver-api/clk.rst.

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
        [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.

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.

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.

console_msg_format=
        [KNL] Change console messages format
    default
        By default we print messages on consoles in
        "[time stamp] text\n" format (time stamp may not be
        printed, depending on CONFIG_PRINTK_TIME or
        `printk_time' param).
    syslog
        Switch to syslog format: "<%u>[time stamp] text\n"
        IOW, each message will have a facility and loglevel
        prefix. The format is similar to one used by syslog()
        syscall, or to executing "dmesg -S --raw" or to reading
        from /proc/kmsg.

consoleblank=    [KNL] The console blank (screen saver) timeout in
        seconds. A value of 0 disables the blank timer.
        Defaults to 0.

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

coresight_cpu_debug.enable
        [ARM,ARM64]
        Format: <bool>
        Enable/disable the CPU sampling based debugging.
        0: default value, disable debugging
        1: enable debugging at boot time

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

cpuidle.governor=
        [CPU_IDLE] Name of the cpuidle governor to use.

cpufreq.off=1    [CPU_FREQ]
        disable the cpufreq 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.
        [KNL, x86_64] select a region under 4G first, and
        fall back to reserve region above 4G when '@offset'
        hasn't been specified.
        See 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/devices/joystick-parport.rst

ddebug_query=    [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
        time. See
        Documentation/admin-guide/dynamic-debug-howto.rst for
        details.  Deprecated, see dyndbg.

debug        [KNL] Enable kernel debugging (events log level).

debug_boot_weak_hash
        [KNL] Enable printing [hashed] pointers early in the
        boot sequence.  If enabled, we use a weak hash instead
        of siphash to hash pointers.  Use this option if you are
        seeing instances of '(___ptrval___)') and need to see a
        value (hashed pointer) instead. Cryptographically
        insecure, please do not use on production kernels.

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=
        [HW] The size of the default HugeTLB page. This is
        the size represented by the legacy /proc/ hugepages
        APIs.  In addition, this is the default hugetlb size
        used for shmget(), mmap() and mounting hugetlbfs
        filesystems.  If not specified, defaults to the
        architecture's default huge page size.  Huge page
        sizes are architecture dependent.  See also
        Documentation/admin-guide/mm/hugetlbpage.rst.
        Format: size[KMG]

deferred_probe_timeout=
        [KNL] Debugging option to set a timeout in seconds for
        deferred probe to give up waiting on dependencies to
        probe. Only specific dependencies (subsystems or
        drivers) that have opted in will be ignored. A timeout of 0
        will timeout at the end of initcalls. This option will also
        dump out devices still on the deferred probe list after
        retrying.

dfltcc=        [HW,S390]
        Format: { on | off | def_only | inf_only | always }
        on:       s390 zlib hardware support for compression on
                  level 1 and decompression (default)
        off:      No s390 zlib hardware support
        def_only: s390 zlib hardware support for deflate
                  only (compression on level 1)
        inf_only: s390 zlib hardware support for inflate
                  only (decompression)
        always:   Same as 'on' but ignores the selected compression
                  level always using hardware support (used for debugging)

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.

hardened_usercopy=
                    [KNL] Under CONFIG_HARDENED_USERCOPY, whether
                    hardening is enabled for this boot. Hardened
                    usercopy checking is used to protect the kernel
                    from reading or writing beyond known memory
                    allocation boundaries as a proactive defense
                    against bounds-checking flaws in the kernel's
                    copy_to_user()/copy_from_user() interface.
            on      Perform hardened usercopy checks (default).
            off     Disable hardened usercopy checks.

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.

perf_v4_pmi=    [X86,INTEL]
        Format: <bool>
        Disable Intel PMU counter freezing feature.
        The feature only exists starting from
        Arch Perfmon v4 (Skylake and newer).

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.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]

dt_cpu_ftrs=    [PPC]
        Format: {"off" | "known"}
        Control how the dt_cpu_ftrs device-tree binding is
        used for CPU feature discovery and setup (if it
        exists).
        off: Do not use it, fall back to legacy cpu table.
        known: Do not pass through unknown features to guests
        or userspace, only those that the kernel is aware of.

dump_apple_properties    [X86]
        Dump name and content of EFI device properties on
        x86 Macs.  Useful for driver authors to determine
        what data is available or for reverse-engineering.

dyndbg[="val"]        [KNL,DYNAMIC_DEBUG]
module.dyndbg[="val"]
        Enable debug messages at boot time.  See
        Documentation/admin-guide/dynamic-debug-howto.rst
        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.

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.

        [ARM64] The early console is determined by the
        stdout-path property in device tree's chosen node,
        or determined by the ACPI SPCR table.

        [X86] When used with no options the early console is
        determined by the ACPI SPCR table.

    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.

    owl,<addr>
        Start an early, polled-mode console on a serial port
        of an Actions Semi SoC, such as S500 or S900, at the
        specified address. The serial port must already be
        setup and configured. Options are not yet supported.

    smh    Use ARM semihosting calls for early console.

    s3c2410,<addr>
    s3c2412,<addr>
    s3c2440,<addr>
    s3c6400,<addr>
    s5pv210,<addr>
    exynos4210,<addr>
        Use early console provided by serial driver available
        on Samsung SoCs, requires selecting proper type and
        a correct base address of the selected UART port. The
        serial port must already be setup and configured.
        Options are not yet supported.

    lantiq,<addr>
        Start an early, polled-mode console on a lantiq serial
        (lqasc) port at the specified address. The serial port
        must already be setup and configured. Options are not
        yet supported.

    lpuart,<addr>
    lpuart32,<addr>
        Use early console provided by Freescale LP UART driver
        found on Freescale Vybrid and QorIQ LS1021A processors.
        A valid base address must be provided, and the serial
        port must already be setup and configured.

    ar3700_uart,<addr>
        Start an early, polled-mode console on the
        Armada 3700 serial port at the specified
        address. The serial port must already be setup
        and configured. Options are not yet supported.

    qcom_geni,<addr>
        Start an early, polled-mode console on a Qualcomm
        Generic Interface (GENI) based serial port at the
        specified address. The serial port must already be
        setup and configured. Options are not yet supported.

earlyprintk=    [X86,SH,ARM,M68k,S390]
        earlyprintk=vga
        earlyprintk=efi
        earlyprintk=sclp
        earlyprintk=xen
        earlyprintk=serial[,ttySn[,baudrate]]
        earlyprintk=serial[,0x...[,baudrate]]
        earlyprintk=ttySn[,baudrate]
        earlyprintk=dbgp[debugController#]
        earlyprintk=pciserial,bus:device.function[,baudrate]
        earlyprintk=xdbc[xhciController#]

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

        Append ",keep" to not disable it when the real console
        takes over.

        Only one of vga, efi, serial, or usb debug port can
        be used at a time.

        Currently only ttyS0 and ttyS1 may be specified by
        name.  Other I/O ports may be explicitly specified
        on some architectures (x86 and arm at least) by
        replacing ttySn with an I/O port address, like this:
            earlyprintk=serial,0x1008,115200
        You can find the port for a given device in
        /proc/tty/driver/serial:
            2: uart:ST16650V2 port:00001008 irq:18 ...

        Interaction with the standard serial driver is not
        very good.

        The VGA and EFI output is eventually overwritten by
        the real console.

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

        The sclp output can only be used on s390.

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

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

        This is designed to be used in conjunction with
        the boot argument: earlyprintk=vga

edd=        [EDD]
        Format: {"off" | "on" | "skip[mbr]"}

efi=        [EFI]
        Format: { "old_map", "nochunk", "noruntime", "debug",
              "nosoftreserve" }
        old_map [X86-64]: switch to the old ioremap-based EFI
        runtime services mapping. 32-bit still uses this one by
        default.
        nochunk: disable reading files in "chunks" in the EFI
        boot stub, as chunking can cause problems with some
        firmware implementations.
        noruntime : disable EFI runtime services support
        debug: enable misc debug output
        nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
        attribute may cause the kernel to reserve the
        memory range for a memory mapping driver to
        claim. Specify efi=nosoftreserve to disable this
        reservation and treat the memory by its base type
        (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").

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

efi_fake_mem=    nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
        Add arbitrary attribute to specific memory range by
        updating original EFI memory map.
        Region of memory which aa attribute is added to is
        from ss to ss+nn.
        If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
        is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
        attribute is added to range 0x100000000-0x180000000 and
        0x10a0000000-0x1120000000.

        Using this parameter you can do debugging of EFI memmap
        related feature. For example, you can do debugging of
        Address Range Mirroring feature even if your box
        doesn't support it.

efivar_ssdt=    [EFI; X86] Name of an EFI variable that contains an SSDT
        that is to be dynamically loaded by Linux. If there are
        multiple variables with the same name but with different
        vendor GUIDs, all of them will be loaded. See
        Documentation/acpi/ssdt-overlays.txt for details.


eisa_irq_edge=    [PARISC,HW]
        See header of drivers/parisc/eisa.c.

elanfreq=    [X86-32]
        See comment before function elanfreq_setup() in
        arch/x86/kernel/cpu/cpufreq/elanfreq.c.

elevator=    [IOSCHED]
        Format: {"cfq" | "deadline" | "noop"}
        See Documentation/block/cfq-iosched.txt and
        Documentation/block/deadline-iosched.txt for details.

elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
        Specifies physical address of start of kernel core
        image elf header and optionally the size. Generally
        kexec loader will pass this option to capture kernel.
        See Documentation/kdump/kdump.txt for details.

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

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

enforcing    [SELINUX] Set initial enforcing status.
        Format: {"0" | "1"}
        See security/selinux/Kconfig help text.
        0 -- permissive (log only, no denials).
        1 -- enforcing (deny and log).
        Default value is 0.
        Value can be changed at runtime via
        /sys/fs/selinux/enforce.

erst_disable    [ACPI]
        Disable Error Record Serialization Table (ERST)
        support.

ether=        [HW,NET] Ethernet cards parameters
        This option is obsoleted by the "netdev=" option, which
        has equivalent usage. See its documentation for details.

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

failslab=
fail_page_alloc=
fail_make_request=[KNL]
        General fault injection mechanism.
        Format: <interval>,<probability>,<space>,<times>
        See also Documentation/fault-injection/.

floppy=        [HW]
        See Documentation/blockdev/floppy.txt.

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

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

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

ftrace_dump_on_oops[=orig_cpu]
        [FTRACE] will dump the trace buffers on oops.
        If no parameter is passed, ftrace will dump
        buffers of all CPUs, but if you pass orig_cpu, it will
        dump only the buffer of the CPU that triggered the
        oops.

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

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

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

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

ftrace_graph_max_depth=<uint>
        [FTRACE] Used with the function graph tracer. This is
        the max depth it will trace into a function. This value
        can be changed at run time by the max_graph_depth file
        in the tracefs tracing directory. default: 0 (no limit)

gamecon.map[2|3]=
        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
        support via parallel port (up to 5 devices per port)
        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
        See also Documentation/input/devices/joystick-parport.rst

gamma=        [HW,DRM]

gart_fix_e820=    [X86_64] disable the fix e820 for K8 GART
        Format: off | on
        default: on

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

goldfish    [X86] Enable the goldfish android emulator platform.
        Don't use this when you are not running on the
        android emulator

gpt        [EFI] Forces disk with valid GPT signature but
        invalid Protective MBR to be treated as GPT. If the
        primary GPT is corrupted, it enables the backup/alternate
        GPT to be used instead.

grcan.enable0=    [HW] Configuration of physical interface 0. Determines
        the "Enable 0" bit of the configuration register.
        Format: 0 | 1
        Default: 0
grcan.enable1=    [HW] Configuration of physical interface 1. Determines
        the "Enable 0" bit of the configuration register.
        Format: 0 | 1
        Default: 0
grcan.select=    [HW] Select which physical interface to use.
        Format: 0 | 1
        Default: 0
grcan.txsize=    [HW] Sets the size of the tx buffer.
        Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
        Default: 1024
grcan.rxsize=    [HW] Sets the size of the rx buffer.
        Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
        Default: 1024

gpio-mockup.gpio_mockup_ranges
        [HW] Sets the ranges of gpiochip of for this device.
        Format: <start1>,<end1>,<start2>,<end2>...

hardlockup_all_cpu_backtrace=
        [KNL] Should the hard-lockup detector generate
        backtraces on all cpus.
        Format: <integer>

hashdist=    [KNL,NUMA] Large hashes allocated during boot
        are distributed across NUMA nodes.  Defaults on
        for 64-bit NUMA, off otherwise.
        Format: 0 | 1 (for off | on)

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

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

hest_disable    [ACPI]
        Disable Hardware Error Source Table (HEST) support;
        corresponding firmware-first mode error processing
        logic will be disabled.

highmem=nn[KMG]    [KNL,BOOT] forces the highmem zone to have an exact
        size of <nn>. This works even on boxes that have no
        highmem otherwise. This also works to reduce highmem
        size on bigger boxes.

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

hisax=        [HW,ISDN]
        See Documentation/isdn/README.HiSax.

hlt        [BUGS=ARM,SH]

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

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

hugepages=    [HW] Number of HugeTLB pages to allocate at boot.
        If this follows hugepagesz (below), it specifies
        the number of pages of hugepagesz to be allocated.
        If this is the first HugeTLB parameter on the command
        line, it specifies the number of pages to allocate for
        the default huge page size.  See also
        Documentation/admin-guide/mm/hugetlbpage.rst.
        Format: <integer>

hugepagesz=
        [HW] The size of the HugeTLB pages.  This is used in
        conjunction with hugepages (above) to allocate huge
        pages of a specific size at boot.  The pair
        hugepagesz=X hugepages=Y can be specified once for
        each supported huge page size. Huge page sizes are
        architecture dependent.  See also
        Documentation/admin-guide/mm/hugetlbpage.rst.
        Format: size[KMG]

hung_task_panic=
        [KNL] Should the hung task detector generate panics.
        Format: <integer>

        A nonzero value instructs the kernel to panic when a
        hung task is detected. The default value is controlled
        by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
        option. The value selected by this boot parameter can
        be changed later by the kernel.hung_task_panic sysctl.

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

hv_nopvspin    [X86,HYPER_V] Disables the paravirt spinlock optimizations
                  which allow the hypervisor to 'idle' the
                  guest on lock contention.

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

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

i8042.debug    [HW] Toggle i8042 debug mode
i8042.unmask_kbd_data
        [HW] Enable printing of interrupt data from the KBD port
             (disabled by default, and as a pre-condition
             requires that i8042.debug=1 be enabled)
i8042.direct    [HW] Put keyboard port into non-translated mode
i8042.dumbkbd    [HW] Pretend that controller can only read data from
             keyboard and cannot control its state
             (Don't attempt to blink the leds)
i8042.noaux    [HW] Don't check for auxiliary (== mouse) port
i8042.nokbd    [HW] Don't check/create keyboard port
i8042.noloop    [HW] Disable the AUX Loopback command while probing
             for the AUX port
i8042.nomux    [HW] Don't check presence of an active multiplexing
             controller
i8042.nopnp    [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
             controllers
i8042.notimeout    [HW] Ignore timeout condition signalled by controller
i8042.reset    [HW] Reset the controller during init, cleanup and
             suspend-to-ram transitions, only during s2r
             transitions, or never reset
        Format: { 1 | Y | y | 0 | N | n }
        1, Y, y: always reset controller
        0, N, n: don't ever reset controller
        Default: only on s2r transitions on x86; most other
        architectures force reset to be always executed
i8042.unlock    [HW] Unlock (ignore) the keylock
i8042.kbdreset    [HW] Reset device connected to KBD port

i810=        [HW,DRM]

i8k.ignore_dmi    [HW] Continue probing hardware even if DMI data
        indicates that the driver is running on unsupported
        hardware.
i8k.force    [HW] Activate i8k driver even if SMM BIOS signature
        does not match list of supported models.
i8k.power_status
        [HW] Report power status in /proc/i8k
        (disabled by default)
i8k.restricted    [HW] Allow controlling fans only if SYS_ADMIN
        capability is set.

i915.invert_brightness=
        [DRM] Invert the sense of the variable that is used to
        set the brightness of the panel backlight. Normally a
        brightness value of 0 indicates backlight switched off,
        and the maximum of the brightness value sets the backlight
        to maximum brightness. If this parameter is set to 0
        (default) and the machine requires it, or this parameter
        is set to 1, a brightness value of 0 sets the backlight
        to maximum brightness, and the maximum of the brightness
        value switches the backlight off.
        -1 -- never invert brightness
         0 -- machine default
         1 -- force brightness inversion

icn=        [HW,ISDN]
        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]

ide-core.nodma=    [HW] (E)IDE subsystem
        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
        .cdrom .chs .ignore_cable are additional options
        See Documentation/ide/ide.txt.

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

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

idle=        [X86]
        Format: idle=poll, idle=halt, idle=nomwait
        Poll forces a polling idle loop that can slightly
        improve the performance of waking up a idle CPU, but
        will use a lot of power and make the system run hot.
        Not recommended.
        idle=halt: Halt is forced to be used for CPU idle.
        In such case C2/C3 won't be used again.
        idle=nomwait: Disable mwait for CPU C-states

ieee754=    [MIPS] Select IEEE Std 754 conformance mode
        Format: { strict | legacy | 2008 | relaxed }
        Default: strict

        Choose which programs will be accepted for execution
        based on the IEEE 754 NaN encoding(s) supported by
        the FPU and the NaN encoding requested with the value
        of an ELF file header flag individually set by each
        binary.  Hardware implementations are permitted to
        support either or both of the legacy and the 2008 NaN
        encoding mode.

        Available settings are as follows:
        strict    accept binaries that request a NaN encoding
            supported by the FPU
        legacy    only accept legacy-NaN binaries, if supported
            by the FPU
        2008    only accept 2008-NaN binaries, if supported
            by the FPU
        relaxed    accept any binaries regardless of whether
            supported by the FPU

        The FPU emulator is always able to support both NaN
        encodings, so if no FPU hardware is present or it has
        been disabled with 'nofpu', then the settings of
        'legacy' and '2008' strap the emulator accordingly,
        'relaxed' straps the emulator for both legacy-NaN and
        2008-NaN, whereas 'strict' enables legacy-NaN only on
        legacy processors and both NaN encodings on MIPS32 or
        MIPS64 CPUs.

        The setting for ABS.fmt/NEG.fmt instruction execution
        mode generally follows that for the NaN encoding,
        except where unsupported by hardware.

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

ignore_rlimit_data
        Ignore RLIMIT_DATA setting for data mappings,
        print warning at first misuse.  Can be changed via
        /sys/module/kernel/parameters/ignore_rlimit_data.

ihash_entries=    [KNL]
        Set number of hash buckets for inode cache.

ima_appraise=    [IMA] appraise integrity measurements
        Format: { "off" | "enforce" | "fix" | "log" }
        default: "enforce"

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

ima_canonical_fmt [IMA]
        Use the canonical format for the binary runtime
        measurements, instead of host native format.

ima_hash=    [IMA]
        Format: { md5 | sha1 | rmd160 | sha256 | sha384
               | sha512 | ... }
        default: "sha1"

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

ima_policy=    [IMA]
        The builtin policies to load during IMA setup.
        Format: "tcb | appraise_tcb | secure_boot |
             fail_securely"

        The "tcb" policy measures all programs exec'd, files
        mmap'd for exec, and all files opened with the read
        mode bit set by either the effective uid (euid=0) or
        uid=0.

        The "appraise_tcb" policy appraises the integrity of
        all files owned by root. (This is the equivalent
        of ima_appraise_tcb.)

        The "secure_boot" policy appraises the integrity
        of files (eg. kexec kernel image, kernel modules,
        firmware, policy, etc) based on file signatures.

        The "fail_securely" policy forces file signature
        verification failure also on privileged mounted
        filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
        flag.

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

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

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

ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
        Format: <min_file_size>
        Set the minimal file size for using asynchronous hash.
        If left unspecified, ahash usage is disabled.

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

ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
        Format: <bufsize>
        Set hashing buffer size. Default: 4k.

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

init=        [KNL]
        Format: <full_path>
        Run specified binary instead of /sbin/init as init
        process.

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

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

initrd=        [BOOT] Specify the location of the initial ramdisk

init_pkru=    [x86] Specify the default memory protection keys rights
        register contents for all processes.  0x55555554 by
        default (disallow access to all but pkey 0).  Can
        override in debugfs after boot.

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

int_pln_enable    [x86] Enable power limit notification interrupt

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

intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
    on
        Enable intel iommu driver.
    off
        Disable intel iommu driver.
    igfx_off [Default Off]
        By default, gfx is mapped as normal device. If a gfx
        device has a dedicated DMAR unit, the DMAR unit is
        bypassed by not enabling DMAR with this option. In
        this case, gfx device will use physical address for
        DMA.
    forcedac [x86_64]
        With this option iommu will not optimize to look
        for io virtual address below 32-bit forcing dual
        address cycle on pci bus for cards supporting greater
        than 32-bit addressing. The default is to look
        for translation below 32-bit and if not available
        then look in the higher range.
    strict [Default Off]
        With this option on every unmap_single operation will
        result in a hardware IOTLB flush operation as opposed
        to batching them for performance.
    sp_off [Default Off]
        By default, super page will be supported if Intel IOMMU
        has the capability. With this option, super page will
        not be supported.
    sm_on [Default Off]
        By default, scalable mode will be disabled even if the
        hardware advertises that it has support for the scalable
        mode translation. With this option set, scalable mode
        will be used on hardware which claims to support it.
    tboot_noforce [Default Off]
        Do not force the Intel IOMMU enabled under tboot.
        By default, tboot will force Intel IOMMU on, which
        could harm performance of some high-throughput
        devices like 40GBit network cards, even if identity
        mapping is enabled.
        Note that using this option lowers the security
        provided by tboot because it makes the system
        vulnerable to DMA attacks.
    nobounce [Default off]
        Disable bounce buffer for unstrusted devices such as
        the Thunderbolt devices. This will treat the untrusted
        devices as the trusted ones, hence might expose security
        risks of DMA attacks.

intel_idle.max_cstate=    [KNL,HW,ACPI,X86]
        0    disables intel_idle and fall back on acpi_idle.
        1 to 9    specify maximum depth of C-state.

intel_pstate=    [X86]
        disable
          Do not enable intel_pstate as the default
          scaling driver for the supported processors
        passive
          Use intel_pstate as a scaling driver, but configure it
          to work with generic cpufreq governors (instead of
          enabling its internal governor).  This mode cannot be
          used along with the hardware-managed P-states (HWP)
          feature.
        force
          Enable intel_pstate on systems that prohibit it by default
          in favor of acpi-cpufreq. Forcing the intel_pstate driver
          instead of acpi-cpufreq may disable platform features, such
          as thermal controls and power capping, that rely on ACPI
          P-States information being indicated to OSPM and therefore
          should be used with caution. This option does not work with
          processors that aren't supported by the intel_pstate driver
          or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
        no_hwp
          Do not enable hardware P state control (HWP)
          if available.
        hwp_only
          Only load intel_pstate on systems which support
          hardware P state control (HWP) if available.
        support_acpi_ppc
          Enforce ACPI _PPC performance limits. If the Fixed ACPI
          Description Table, specifies preferred power management
          profile as "Enterprise Server" or "Performance Server",
          then this feature is turned on by default.
        per_cpu_perf_limits
          Allow per-logical-CPU P-State performance control limits using
          cpufreq sysfs interface

intremap=    [X86-64, Intel-IOMMU]
        on    enable Interrupt Remapping (default)
        off    disable Interrupt Remapping
        nosid    disable Source ID checking
        no_x2apic_optout
            BIOS x2APIC opt-out request will be ignored
        nopost    disable Interrupt Posting

iomem=        Disable strict checking of access to MMIO memory
    strict    regions from userspace.
    relaxed

iommu=        [x86]
    off
    force
    noforce
    biomerge
    panic
    nopanic
    merge
    nomerge
    soft
    pt        [x86]
    nopt        [x86]
    nobypass    [PPC/POWERNV]
        Disable IOMMU bypass, using IOMMU for PCI devices.

iommu.strict=    [ARM64] Configure TLB invalidation behaviour
        Format: { "0" | "1" }
        0 - Lazy mode.
          Request that DMA unmap operations use deferred
          invalidation of hardware TLBs, for increased
          throughput at the cost of reduced device isolation.
          Will fall back to strict mode if not supported by
          the relevant IOMMU driver.
        1 - Strict mode (default).
          DMA unmap operations invalidate IOMMU hardware TLBs
          synchronously.

iommu.passthrough=
        [ARM64, X86] Configure DMA to bypass the IOMMU by default.
        Format: { "0" | "1" }
        0 - Use IOMMU translation for DMA.
        1 - Bypass the IOMMU for DMA.
        unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.

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

io_delay=    [X86] I/O delay method
    0x80
        Standard port 0x80 based delay
    0xed
        Alternate port 0xed based delay (needed on some systems)
    udelay
        Simple two microseconds delay
    none
        No delay

ip=        [IP_PNP]
        See Documentation/filesystems/nfs/nfsroot.txt.

ipcmni_extend    [KNL] Extend the maximum number of unique System V
        IPC identifiers from 32,768 to 16,777,216.

irqaffinity=    [SMP] Set the default irq affinity mask
        The argument is a cpu list, as described above.

irqchip.gicv2_force_probe=
        [ARM, ARM64]
        Format: <bool>
        Force the kernel to look for the second 4kB page
        of a GICv2 controller even if the memory range
        exposed by the device tree is too small.

irqchip.gicv3_nolpi=
        [ARM, ARM64]
        Force the kernel to ignore the availability of
        LPIs (and by consequence ITSs). Intended for system
        that use the kernel as a bootloader, and thus want
        to let secondary kernels in charge of setting up
        LPIs.

irqchip.gicv3_pseudo_nmi= [ARM64]
        Enables support for pseudo-NMIs in the kernel. This
        requires the kernel to be built with
        CONFIG_ARM64_PSEUDO_NMI.

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

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

isapnp=        [ISAPNP]
        Format: <RDP>,<reset>,<pci_scan>,<verbosity>

isolcpus=    [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
        [Deprecated - use cpusets instead]
        Format: [flag-list,]<cpu-list>

        Specify one or more CPUs to isolate from disturbances
        specified in the flag list (default: domain):

        nohz
          Disable the tick when a single task runs.

          A residual 1Hz tick is offloaded to workqueues, which you
          need to affine to housekeeping through the global
          workqueue's affinity configured via the
          /sys/devices/virtual/workqueue/cpumask sysfs file, or
          by using the 'domain' flag described below.

          NOTE: by default the global workqueue runs on all CPUs,
          so to protect individual CPUs the 'cpumask' file has to
          be configured manually after bootup.

        domain
          Isolate from the general SMP balancing and scheduling
          algorithms. Note that performing domain isolation this way
          is irreversible: it's not possible to bring back a CPU to
          the domains once isolated through isolcpus. It's strongly
          advised to use cpusets instead to disable scheduler load
          balancing through the "cpuset.sched_load_balance" file.
          It offers a much more flexible interface where CPUs can
          move in and out of an isolated set anytime.

          You can move a process onto or off an "isolated" CPU via
          the CPU affinity syscalls or cpuset.
          <cpu number> begins at 0 and the maximum value is
          "number of CPUs in system - 1".

        managed_irq

          Isolate from being targeted by managed interrupts
          which have an interrupt mask containing isolated
          CPUs. The affinity of managed interrupts is
          handled by the kernel and cannot be changed via
          the /proc/irq/* interfaces.

          This isolation is best effort and only effective
          if the automatically assigned interrupt mask of a
          device queue contains isolated and housekeeping
          CPUs. If housekeeping CPUs are online then such
          interrupts are directed to the housekeeping CPU
          so that IO submitted on the housekeeping CPU
          cannot disturb the isolated CPU.

          If a queue's affinity mask contains only isolated
          CPUs then this parameter has no effect on the
          interrupt routing decision, though interrupts are
          only delivered when tasks running on those
          isolated CPUs submit IO. IO submitted on
          housekeeping CPUs has no influence on those
          queues.

        The format of <cpu-list> is described above.

iucv=        [HW,NET]

ivrs_ioapic    [HW,X86_64]
        Provide an override to the IOAPIC-ID<->DEVICE-ID
        mapping provided in the IVRS ACPI table. For
        example, to map IOAPIC-ID decimal 10 to
        PCI device 00:14.0 write the parameter as:
            ivrs_ioapic[10]=00:14.0

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

ivrs_acpihid    [HW,X86_64]
        Provide an override to the ACPI-HID:UID<->DEVICE-ID
        mapping provided in the IVRS ACPI table. For
        example, to map UART-HID:UID AMD0020:0 to
        PCI device 00:14.5 write the parameter as:
            ivrs_acpihid[00:14.5]=AMD0020:0

js=        [HW,JOY] Analog joystick
        See Documentation/input/joydev/joystick.rst.

nokaslr        [KNL]
        When CONFIG_RANDOMIZE_BASE is set, this disables
        kernel and module base offset ASLR (Address Space
        Layout Randomization).

kasan_multi_shot
        [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
        report on every invalid memory access. Without this
        parameter KASAN will print report only for the first
        invalid access.

keepinitrd    [HW,ARM]

kernelcore=    [KNL,X86,IA-64,PPC]
        Format: nn[KMGTPE] | nn% | "mirror"
        This parameter specifies the amount of memory usable by
        the kernel for non-movable allocations.  The requested
        amount is spread evenly throughout all nodes in the
        system as ZONE_NORMAL.  The remaining memory is used for
        movable memory in its own zone, ZONE_MOVABLE.  In the
        event, a node is too small to have both ZONE_NORMAL and
        ZONE_MOVABLE, kernelcore memory will take priority and
        other nodes will have a larger ZONE_MOVABLE.

        ZONE_MOVABLE is used for the allocation of pages that
        may be reclaimed or moved by the page migration
        subsystem.  Note that allocations like PTEs-from-HighMem
        still use the HighMem zone if it exists, and the Normal
        zone if it does not.

        It is possible to specify the exact amount of memory in
        the form of "nn[KMGTPE]", a percentage of total system
        memory in the form of "nn%", or "mirror".  If "mirror"
        option is specified, mirrored (reliable) memory is used
        for non-movable allocations and remaining memory is used
        for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
        are exclusive, so you cannot specify multiple forms.

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

kgdboc=        [KGDB,HW] kgdb over consoles.
        Requires a tty driver that supports console polling,
        or a supported polling keyboard driver (non-usb).
         Serial only format: <serial_device>[,baud]
         keyboard only format: kbd
         keyboard and serial format: kbd,<serial_device>[,baud]
        Optional Kernel mode setting:
         kms, kbd format: kms,kbd
         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]

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

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

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

kpti=        [ARM64] Control page table isolation of user
        and kernel address spaces.
        Default: enabled on cores which need mitigation.
        0: force disabled
        1: force enabled

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

kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
               Default is false (don't support).

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

kvm.nx_huge_pages=
        [KVM] Controls the software workaround for the
        X86_BUG_ITLB_MULTIHIT bug.
        force    : Always deploy workaround.
        off    : Never deploy workaround.
        auto    : Deploy workaround based on the presence of
              X86_BUG_ITLB_MULTIHIT.

        Default is 'auto'.

        If the software workaround is enabled for the host,
        guests do need not to enable it for nested guests.

kvm.nx_huge_pages_recovery_ratio=
        [KVM] Controls how many 4KiB pages are periodically zapped
        back to huge pages.  0 disables the recovery, otherwise if
        the value is N KVM will zap 1/Nth of the 4KiB pages every
        minute.  The default is 60.

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

kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
        for all guests.
        Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.

kvm-arm.vgic_v3_group0_trap=
        [KVM,ARM] Trap guest accesses to GICv3 group-0
        system registers

kvm-arm.vgic_v3_group1_trap=
        [KVM,ARM] Trap guest accesses to GICv3 group-1
        system registers

kvm-arm.vgic_v3_common_trap=
        [KVM,ARM] Trap guest accesses to GICv3 common
        system registers

kvm-arm.vgic_v4_enable=
        [KVM,ARM] Allow use of GICv4 for direct injection of
        LPIs.

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

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

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

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

kvm-intel.unrestricted_guest=
        [KVM,Intel] Disable unrestricted guest feature
        (virtualized real and unpaged mode) on capable
        Intel chips. Default is 1 (enabled)

kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
        CVE-2018-3620.

        Valid arguments: never, cond, always

        always: L1D cache flush on every VMENTER.
        cond:    Flush L1D on VMENTER only when the code between
            VMEXIT and VMENTER can leak host memory.
        never:    Disables the mitigation

        Default is cond (do L1 cache flush in specific instances)

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

l1tf=           [X86] Control mitigation of the L1TF vulnerability on
              affected CPUs

        The kernel PTE inversion protection is unconditionally
        enabled and cannot be disabled.

        full
            Provides all available mitigations for the
            L1TF vulnerability. Disables SMT and
            enables all mitigations in the
            hypervisors, i.e. unconditional L1D flush.

            SMT control and L1D flush control via the
            sysfs interface is still possible after
            boot.  Hypervisors will issue a warning
            when the first VM is started in a
            potentially insecure configuration,
            i.e. SMT enabled or L1D flush disabled.

        full,force
            Same as 'full', but disables SMT and L1D
            flush runtime control. Implies the
            'nosmt=force' command line option.
            (i.e. sysfs control of SMT is disabled.)

        flush
            Leaves SMT enabled and enables the default
            hypervisor mitigation, i.e. conditional
            L1D flush.

            SMT control and L1D flush control via the
            sysfs interface is still possible after
            boot.  Hypervisors will issue a warning
            when the first VM is started in a
            potentially insecure configuration,
            i.e. SMT enabled or L1D flush disabled.

        flush,nosmt

            Disables SMT and enables the default
            hypervisor mitigation.

            SMT control and L1D flush control via the
            sysfs interface is still possible after
            boot.  Hypervisors will issue a warning
            when the first VM is started in a
            potentially insecure configuration,
            i.e. SMT enabled or L1D flush disabled.

        flush,nowarn
            Same as 'flush', but hypervisors will not
            warn when a VM is started in a potentially
            insecure configuration.

        off
            Disables hypervisor mitigations and doesn't
            emit any warnings.
            It also drops the swap size and available
            RAM limit restriction on both hypervisor and
            bare metal.

        Default is 'flush'.

        For details see: Documentation/admin-guide/hw-vuln/l1tf.rst

l2cr=        [PPC]

l3cr=        [PPC]

lapic        [X86-32,APIC] Enable the local APIC even if BIOS
        disabled it.

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

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

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

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

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

libata.force=    [LIBATA] Force configurations.  The format is comma
        separated list of "[ID:]VAL" where ID is
        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
        matching port, link or device.  Basically, it matches
        the ATA ID string printed on console by libata.  If
        the whole ID part is omitted, the last PORT and DEVICE
        values are used.  If ID hasn't been specified yet, the
        configuration applies to all ports, links and devices.

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

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

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

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

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

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

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

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

        * rstonce: only attempt one reset during
          hot-unplug link recovery

        * dump_id: dump IDENTIFY data.

        * atapi_dmadir: Enable ATAPI DMADIR bridge support

        * disable: Disable this device.

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

memblock=debug    [KNL] Enable memblock debug messages.

load_ramdisk=    [RAM] List of ramdisks to load from floppy
        See Documentation/blockdev/ramdisk.txt.

lockd.nlm_grace_period=P  [NFS] Assign grace period.
        Format: <integer>

lockd.nlm_tcpport=N    [NFS] Assign TCP port.
        Format: <integer>

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

lockd.nlm_udpport=M    [NFS] Assign UDP port.
        Format: <integer>

locktorture.nreaders_stress= [KNL]
        Set the number of locking read-acquisition kthreads.
        Defaults to being automatically set based on the
        number of online CPUs.

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

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

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

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

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

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

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

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

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

logibm.irq=    [HW,MOUSE] Logitech Bus Mouse Driver
        Format: <irq>

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

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

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

logo.nologo    [FB] Disables display of the built-in Linux logo.
        This may be used to provide more screen space for
        kernel log messages and is useful when debugging
        kernel boot problems.

lp=0        [LP]    Specify parallel ports to use, e.g,
lp=port[,port...]    lp=none,parport0 (lp0 not configured, lp1 uses
lp=reset        first parallel port). 'lp=0' disables the
lp=auto            printer driver. 'lp=reset' (which can be
            specified in addition to the ports) causes
            attached printers to be reset. Using
            lp=port1,port2,... specifies the parallel ports
            to associate lp devices with, starting with
            lp0. A port specification may be 'none' to skip
            that lp device, or a parport name such as
            'parport0'. Specifying 'lp=auto' instead of a
            port specification list means that device IDs
            from each port should be examined, to see if
            an IEEE 1284-compliant printer is attached; if
            so, the driver will manage that printer.
            See also header of drivers/char/lp.c.

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

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

machvec=    [IA-64] Force the use of a particular machine-vector
        (machvec) in a generic kernel.
        Example: machvec=hpzx1_swiotlb

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

max_addr=nn[KMG]    [KNL,BOOT,ia64] All physical memory greater
        than or equal to this physical address is ignored.

maxcpus=    [SMP] Maximum number of processors that    an SMP kernel
        will bring up during bootup.  maxcpus=n : n >= 0 limits
        the kernel to bring up 'n' processors. Surely after
        bootup you can bring up the other plugged cpu by executing
        "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
        only takes effect during system bootup.
        While n=0 is a special case, it is equivalent to "nosmp",
        which also disables the IO APIC.

max_loop=    [LOOP] The number of loop block devices that get
(loop.max_loop)    unconditionally pre-created at init time. The default
        number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
        of statically allocating a predefined number, loop
        devices can be requested on-demand with the
        /dev/loop-control interface.

mce        [X86-32] Machine Check Exception

mce=option    [X86-64] See Documentation/x86/x86_64/boot-options.txt

md=        [HW] RAID subsystems devices and level
        See Documentation/admin-guide/md.rst.

mdacon=        [MDA]
        Format: <first>,<last>
        Specifies range of consoles to be captured by the MDA.

mds=        [X86,INTEL]
        Control mitigation for the Micro-architectural Data
        Sampling (MDS) vulnerability.

        Certain CPUs are vulnerable to an exploit against CPU
        internal buffers which can forward information to a
        disclosure gadget under certain conditions.

        In vulnerable processors, the speculatively
        forwarded data can be used in a cache side channel
        attack, to access data to which the attacker does
        not have direct access.

        This parameter controls the MDS mitigation. The
        options are:

        full       - Enable MDS mitigation on vulnerable CPUs
        full,nosmt - Enable MDS mitigation and disable
                 SMT on vulnerable CPUs
        off        - Unconditionally disable MDS mitigation

        On TAA-affected machines, mds=off can be prevented by
        an active TAA mitigation as both vulnerabilities are
        mitigated with the same mechanism so in order to disable
        this mitigation, you need to specify tsx_async_abort=off
        too.

        Not specifying this option is equivalent to
        mds=full.

        For details see: Documentation/admin-guide/hw-vuln/mds.rst

mem=nn[KMG]    [KNL,BOOT] Force usage of a specific amount of memory
        Amount of memory to be used in cases as follows:

        1 for test;
        2 when the kernel is not able to see the whole system memory;
        3 memory that lies after 'mem=' boundary is excluded from
         the hypervisor, then assigned to KVM guests.

        [X86] Work as limiting max address. Use together
        with memmap= to avoid physical address space collisions.
        Without memmap= PCI devices could be placed at addresses
        belonging to unused RAM.

        Note that this only takes effects during boot time since
        in above case 3, memory may need be hot added after boot
        if system memory of hypervisor is not sufficient.

mem=nopentium    [BUGS=X86-32] Disable usage of 4MB pages for kernel
        memory.

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

memhp_default_state=online/offline
        [KNL] Set the initial state for the memory hotplug
        onlining policy. If not specified, the default value is
        set according to the
        CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
        option.
        See Documentation/memory-hotplug.txt.

memmap=exactmap    [KNL,X86] Enable setting of an exact
        E820 memory map, as specified by the user.
        Such memmap=exactmap lines can be constructed based on
        BIOS output or other requirements. See the memmap=nn@ss
        option description.

memmap=nn[KMG]@ss[KMG]
        [KNL] Force usage of a specific region of memory.
        Region of memory to be used is from ss to ss+nn.
        If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
        which limits max address to nn[KMG].
        Multiple different regions can be specified,
        comma delimited.
        Example:
            memmap=100M@2G,100M#3G,1G!1024G

memmap=nn[KMG]#ss[KMG]
        [KNL,ACPI] Mark specific memory as ACPI data.
        Region of memory to be marked is from ss to ss+nn.

memmap=nn[KMG]$ss[KMG]
        [KNL,ACPI] Mark specific memory as reserved.
        Region of memory to be reserved is from ss to ss+nn.
        Example: Exclude memory from 0x18690000-0x1869ffff
                 memmap=64K$0x18690000
                 or
                 memmap=0x10000$0x18690000
        Some bootloaders may need an escape character before '$',
        like Grub2, otherwise '$' and the following number
        will be eaten.

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

memmap=<size>%<offset>-<oldtype>+<newtype>
        [KNL,ACPI] Convert memory within the specified region
        from <oldtype> to <newtype>. If "-<oldtype>" is left
        out, the whole region will be marked as <newtype>,
        even if previously unavailable. If "+<newtype>" is left
        out, matching memory will be removed. Types are
        specified as e820 types, e.g., 1 = RAM, 2 = reserved,
        3 = ACPI, 12 = PRAM.

memory_corruption_check=0/1 [X86]
        Some BIOSes seem to corrupt the first 64k of
        memory when doing things like suspend/resume.
        Setting this option will scan the memory
        looking for corruption.  Enabling this will
        both detect corruption and prevent the kernel
        from using the memory being corrupted.
        However, its intended as a diagnostic tool; if
        repeatable BIOS-originated corruption always
        affects the same memory, you can use memmap=
        to prevent the kernel from using that memory.

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

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

memtest=    [KNL,X86,ARM] Enable memtest
        Format: <integer>
        default : 0 <disable>
        Specifies the number of memtest passes to be
        performed. Each pass selects another test
        pattern from a given set of patterns. Memtest
        fills the memory with this pattern, validates
        memory contents and reserves bad memory
        regions that are detected.

mem_encrypt=    [X86-64] AMD Secure Memory Encryption (SME) control
        Valid arguments: on, off
        Default (depends on kernel configuration option):
          on  (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
          off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
        mem_encrypt=on:        Activate SME
        mem_encrypt=off:    Do not activate SME

        Refer to Documentation/virt/kvm/amd-memory-encryption.txt
        for details on when memory encryption can be activated.

mem_sleep_default=    [SUSPEND] Default system suspend mode:
        s2idle  - Suspend-To-Idle
        shallow - Power-On Suspend or equivalent (if supported)
        deep    - Suspend-To-RAM or equivalent (if supported)
        See Documentation/admin-guide/pm/sleep-states.rst.

meye.*=        [HW] Set MotionEye Camera parameters
        See Documentation/media/v4l-drivers/meye.rst.

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

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

mga=        [HW,DRM]

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

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

mitigations=
        [X86,PPC,S390,ARM64] Control optional mitigations for
        CPU vulnerabilities.  This is a set of curated,
        arch-independent options, each of which is an
        aggregation of existing arch-specific options.

        off
            Disable all optional CPU mitigations.  This
            improves system performance, but it may also
            expose users to several CPU vulnerabilities.
            Equivalent to: nopti [X86,PPC]
                       kpti=0 [ARM64]
                       nospectre_v1 [X86,PPC]
                       nobp=0 [S390]
                       nospectre_v2 [X86,PPC,S390,ARM64]
                       spectre_v2_user=off [X86]
                       spec_store_bypass_disable=off [X86,PPC]
                       ssbd=force-off [ARM64]
                       l1tf=off [X86]
                       mds=off [X86]
                       tsx_async_abort=off [X86]
                       kvm.nx_huge_pages=off [X86]

            Exceptions:
                       This does not have any effect on
                       kvm.nx_huge_pages when
                       kvm.nx_huge_pages=force.

        auto (default)
            Mitigate all CPU vulnerabilities, but leave SMT
            enabled, even if it's vulnerable.  This is for
            users who don't want to be surprised by SMT
            getting disabled across kernel upgrades, or who
            have other ways of avoiding SMT-based attacks.
            Equivalent to: (default behavior)

        auto,nosmt
            Mitigate all CPU vulnerabilities, disabling SMT
            if needed.  This is for users who always want to
            be fully mitigated, even if it means losing SMT.
            Equivalent to: l1tf=flush,nosmt [X86]
                       mds=full,nosmt [X86]
                       tsx_async_abort=full,nosmt [X86]

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

module.sig_enforce
        [KNL] When CONFIG_MODULE_SIG is set, this means that
        modules without (valid) signatures will fail to load.
        Note that if CONFIG_MODULE_SIG_FORCE is set, that
        is always true, so this option does nothing.

module_blacklist=  [KNL] Do not load a comma-separated list of
        modules.  Useful for debugging problem modules.

mousedev.tap_time=
        [MOUSE] Maximum time between finger touching and
        leaving touchpad surface for touch to be considered
        a tap and be reported as a left button click (for
        touchpads working in absolute mode only).
        Format: <msecs>
mousedev.xres=    [MOUSE] Horizontal screen resolution, used for devices
        reporting absolute coordinates, such as tablets
mousedev.yres=    [MOUSE] Vertical screen resolution, used for devices
        reporting absolute coordinates, such as tablets

movablecore=    [KNL,X86,IA-64,PPC]
        Format: nn[KMGTPE] | nn%
        This parameter is the complement to kernelcore=, it
        specifies the amount of memory used for migratable
        allocations.  If both kernelcore and movablecore is
        specified, then kernelcore will be at *least* the
        specified value but may be more.  If movablecore on its
        own is specified, the administrator must be careful
        that the amount of memory usable for all allocations
        is not too small.

movable_node    [KNL] Boot-time switch to make hotplugable memory
        NUMA nodes to be movable. This means that the memory
        of such nodes will be usable only for movable
        allocations which rules out almost all kernel
        allocations. Use with caution!

MTD_Partition=    [MTD]
        Format: <name>,<region-number>,<size>,<offset>

MTD_Region=    [MTD] Format:
        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]

mtdparts=    [MTD]
        See drivers/mtd/cmdlinepart.c.

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

onenand.bdry=    [HW,MTD] Flex-OneNAND Boundary Configuration

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

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

mtdset=        [ARM]
        ARM/S3C2412 JIVE boot control

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

mtouchusb.raw_coordinates=
        [HW] Make the MicroTouch USB driver use raw coordinates
        ('y', default) or cooked coordinates ('n')

mtrr_chunk_size=nn[KMG] [X86]
        used for mtrr cleanup. It is largest continuous chunk
        that could hold holes aka. UC entries.

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

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

n2=        [NET] SDL Inc. RISCom/N2 synchronous serial card

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

nf_conntrack.acct=
        [NETFILTER] Enable connection tracking flow accounting
        0 to disable accounting
        1 to enable accounting
        Default value is 0.

nfsaddrs=    [NFS] Deprecated.  Use ip= instead.
        See Documentation/filesystems/nfs/nfsroot.txt.

nfsroot=    [NFS] nfs root filesystem for disk-less boxes.
        See Documentation/filesystems/nfs/nfsroot.txt.

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

nfs.callback_nr_threads=
        [NFSv4] set the total number of threads that the
        NFS client will assign to service NFSv4 callback
        requests.

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

nfs.cache_getent=
        [NFS] sets the pathname to the program which is used
        to update the NFS client cache entries.

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

nfs.idmap_cache_timeout=
        [NFS] set the maximum lifetime for idmapper cache
        entries.

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

nfs.max_session_cb_slots=
        [NFSv4.1] Sets the maximum number of session
        slots the client will assign to the callback
        channel. This determines the maximum number of
        callbacks the client will process in parallel for
        a particular server.

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

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

nfs.send_implementation_id =
        [NFSv4.1] Send client implementation identification
        information in exchange_id requests.
        If zero, no implementation identification information
        will be sent.
        The default is to send the implementation identification
        information.

nfs.recover_lost_locks =
        [NFSv4] Attempt to recover locks that were lost due
        to a lease timeout on the server. Please note that
        doing this risks data corruption, since there are
        no guarantees that the file will remain unchanged
        after the locks are lost.
        If you want to enable the kernel legacy behaviour of
        attempting to recover these locks, then set this
        parameter to '1'.
        The default parameter value of '0' causes the kernel
        not to attempt recovery of lost locks.

nfs4.layoutstats_timer =
        [NFSv4.2] Change the rate at which the kernel sends
        layoutstats to the pNFS metadata server.

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

nfsd.nfs4_disable_idmapping=
        [NFSv4] When set to the default of '1', the NFSv4
        server will return only numeric uids and gids to
        clients using auth_sys, and will accept numeric uids
        and gids from such clients.  This is intended to ease
        migration from NFSv2/v3.

nmi_debug=    [KNL,SH] Specify one or more actions to take
        when a NMI is triggered.
        Format: [state][,regs][,debounce][,die]

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

        These settings can be accessed at runtime via
        the nmi_watchdog and hardlockup_panic sysctls.

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

no387        [BUGS=X86-32] Tells the kernel to use the 387 maths
        emulation library even if a 387 maths coprocessor
        is present.

no5lvl        [X86-64] Disable 5-level paging mode. Forces
        kernel to use 4-level paging instead.

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

novmcoredd    [KNL,KDUMP]
        Disable device dump. Device dump allows drivers to
        append dump data to vmcore so you can collect driver
        specified debug info.  Drivers can append the data
        without any limit and this data is stored in memory,
        so this may cause significant memory stress.  Disabling
        device dump can help save memory but the driver debug
        data will be no longer available.  This parameter
        is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
        is set.

noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
        caches in the slab allocator.  Saves per-node memory,
        but will impact performance.

noalign        [KNL,ARM]

noaltinstr    [S390] Disables alternative instructions patching
        (CPU alternatives feature).

noapic        [SMP,APIC] Tells the kernel to not make use of any
        IOAPICs that may be present in the system.

noautogroup    Disable scheduler automatic task group creation.

nobats        [PPC] Do not use BATs for mapping kernel lowmem
        on "Classic" PPC cores.

nocache        [ARM]

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

nodelayacct    [KNL] Disable per-task delay accounting

nodsp        [SH] Disable hardware DSP at boot time.

noefi        Disable EFI runtime services support.

noexec        [IA-64]

noexec        [X86]
        On X86-32 available only on PAE configured kernels.
        noexec=on: enable non-executable mappings (default)
        noexec=off: disable non-executable mappings

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

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

noexec32    [X86-64]
        This affects only 32-bit executables.
        noexec32=on: enable non-executable mappings (default)
            read doesn't imply executable mappings
        noexec32=off: disable non-executable mappings
            read implies executable mappings

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

nofxsr        [BUGS=X86-32] Disables x86 floating point extended
        register save and restore. The kernel will only save
        legacy floating-point registers on task switch.

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

nosmt        [KNL,S390] Disable symmetric multithreading (SMT).
        Equivalent to smt=1.

        [KNL,x86] Disable symmetric multithreading (SMT).
        nosmt=force: Force disable SMT, cannot be undone
                 via the sysfs control file.

nospectre_v1    [X86] Disable mitigations for Spectre Variant 1
        (bounds check bypass). With this option data leaks are
        possible in the system.

nospectre_v2    [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
        the Spectre variant 2 (indirect branch prediction)
        vulnerability. System may allow data leaks with this
        option.

nospec_store_bypass_disable
        [HW] Disable all mitigations for the Speculative Store Bypass vulnerability

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

noxsaveopt    [X86] Disables xsaveopt used in saving x86 extended
        register states. The kernel will fall back to use
        xsave to save the states. By using this parameter,
        performance of saving the states is degraded because
        xsave doesn't support modified optimization while
        xsaveopt supports it on xsaveopt enabled systems.

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

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

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

nohalt        [IA-64] Tells the kernel not to use the power saving
        function PAL_HALT_LIGHT when idle. This increases
        power-consumption. On the positive side, it reduces
        interrupt wake-up latency, which may improve performance
        in certain environments such as networked servers or
        real-time systems.

nohibernate    [HIBERNATION] Disable hibernation and resume.

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

nohz_full=    [KNL,BOOT,SMP,ISOL]
        The argument is a cpu list, as described above.
        In kernels built with CONFIG_NO_HZ_FULL=y, set
        the specified list of CPUs whose tick will be stopped
        whenever possible. The boot CPU will be forced outside
        the range to maintain the timekeeping.  Any CPUs
        in this list will have their RCU callbacks offloaded,
        just as if they had also been called out in the
        rcu_nocbs= boot parameter.

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

noirqdebug    [X86-32] Disables the code which attempts to detect and
        disable unhandled interrupt sources.

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

noisapnp    [ISAPNP] Disables ISA PnP code.

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

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

nointroute    [IA-64]

noinvpcid    [X86] Disable the INVPCID cpu feature.

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

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

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

no-vmw-sched-clock
        [X86,PV_OPS] Disable paravirtualized VMware scheduler
        clock and use the default one.

no-steal-acc    [X86,KVM,ARM64] Disable paravirtualized steal time
        accounting. steal time is computed, but won't
        influence scheduler behaviour

nolapic        [X86-32,APIC] Do not enable or use the local APIC.

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

noltlbs        [PPC] Do not use large page/tlb entries for kernel
        lowmem mapping on PPC40x and PPC8xx

nomca        [IA-64] Disable machine check abort handling

nomce        [X86-32] Disable Machine Check Exception

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

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

nomodule    Disable module load

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

nopcid        [X86-64] Disable the PCID cpu feature.

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

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

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

noresume    [SWSUSP] Disables resume and restores original swap
        space.

no-scroll    [VGA] Disables scrollback.
        This is required for the Braillex ib80-piezo Braille
        reader made by F.H. Papenmeier (Germany).

nosbagart    [IA-64]

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

nosmp        [SMP] Tells an SMP kernel to act as a UP kernel,
        and disable the IO APIC.  legacy for "maxcpus=0".

nosoftlockup    [KNL] Disable the soft-lockup detector.

nosync        [HW,M68K] Disables sync negotiation for all devices.

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

nowb        [ARM]

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

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

nps_mtm_hs_ctr=    [KNL,ARC]
        This parameter sets the maximum duration, in
        cycles, each HW thread of the CTOP can run
        without interruptions, before HW switches it.
        The actual maximum duration is 16 times this
        parameter's value.
        Format: integer between 1 and 255
        Default: 255

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

nr_cpus=    [SMP] Maximum number of processors that    an SMP kernel
        could support.  nr_cpus=n : n >= 1 limits the kernel to
        support 'n' processors. It could be larger than the
        number of already plugged CPU during bootup, later in
        runtime you can physically add extra cpu until it reaches
        n. So during boot up some boot time memory for per-cpu
        variables need be pre-allocated for later physical cpu
        hot plugging.

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

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

numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
        'node', 'default' can be specified
        This can be set from sysctl after boot.
        See Documentation/sysctl/vm.txt for details.

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

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

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

oprofile.timer=    [HW]
        Use timer interrupt instead of performance counters

oprofile.cpu_type=    Force an oprofile cpu type
        This might be useful if you have an older oprofile
        userland or if you want common events.
        Format: { arch_perfmon }
        arch_perfmon: [X86] Force use of architectural
            perfmon on Intel CPUs instead of the
            CPU specific event set.
        timer: [X86] Force use of architectural NMI
            timer mode (see also oprofile.timer
            for generic hr timer mode)

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

page_alloc.shuffle=
        [KNL] Boolean flag to control whether the page allocator
        should randomize its free lists. The randomization may
        be automatically enabled if the kernel detects it is
        running on a platform with a direct-mapped memory-side
        cache, and this parameter can be used to
        override/disable that behavior. The state of the flag
        can be read from sysfs at:
        /sys/module/page_alloc/parameters/shuffle.

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

page_poison=    [KNL] Boot-time parameter changing the state of
        poisoning on the buddy allocator.
        off: turn off poisoning
        on: turn on poisoning

panic=        [KNL] Kernel behaviour on panic: delay <timeout>
        timeout > 0: seconds before rebooting
        timeout = 0: wait forever
        timeout < 0: reboot immediately
        Format: <timeout>

panic_print=    Bitmask for printing system info when panic happens.
        User can chose combination of the following bits:
        bit 0: print all tasks info
        bit 1: print system memory info
        bit 2: print timer info
        bit 3: print locks info if CONFIG_LOCKDEP is on
        bit 4: print ftrace buffer
        bit 5: print all printk messages in buffer

panic_on_taint=    Bitmask for conditionally calling panic() in add_taint()
        Format: <hex>[,nousertaint]
        Hexadecimal bitmask representing the set of TAINT flags
        that will cause the kernel to panic when add_taint() is
        called with any of the flags in this set.
        The optional switch "nousertaint" can be utilized to
        prevent userspace forced crashes by writing to sysctl
        /proc/sys/kernel/tainted any flagset matching with the
        bitmask set on panic_on_taint.
        See Documentation/admin-guide/tainted-kernels.rst for
        extra details on the taint flags that users can pick
        to compose the bitmask to assign to panic_on_taint.

panic_on_warn    panic() instead of WARN().  Useful to cause kdump
        on a WARN().

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

parkbd.port=    [HW] Parallel port number the keyboard adapter is
        connected to, default is 0.
        Format: <parport#>
parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
        0 for XT, 1 for AT (default is AT).
        Format: <mode>

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

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

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

pcbit=        [HW,ISDN]

pcd.        [PARIDE]
        See header of drivers/block/paride/pcd.c.
        See also Documentation/blockdev/paride.txt.

pci=option[,option...]    [PCI] various PCI subsystem options.

            Some options herein operate on a specific device
            or a set of devices (<pci_dev>). These are
            specified in one of the following formats:

            [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
            pci:<vendor>:<device>[:<subvendor>:<subdevice>]

            Note: the first format specifies a PCI
            bus/device/function address which may change
            if new hardware is inserted, if motherboard
            firmware changes, or due to changes caused
            by other kernel parameters. If the
            domain is left unspecified, it is
            taken to be zero. Optionally, a path
            to a device through multiple device/function
            addresses can be specified after the base
            address (this is more robust against
            renumbering issues).  The second format
            selects devices using IDs from the
            configuration space which may match multiple
            devices in the system.

    earlydump    dump PCI config space before the kernel
            changes anything
    off        [X86] don't probe for the PCI bus
    bios        [X86-32] force use of PCI BIOS, don't access
            the hardware directly. Use this if your machine
            has a non-standard PCI host bridge.
    nobios        [X86-32] disallow use of PCI BIOS, only direct
            hardware access methods are allowed. Use this
            if you experience crashes upon bootup and you
            suspect they are caused by the BIOS.
    conf1        [X86] Force use of PCI Configuration Access
            Mechanism 1 (config address in IO port 0xCF8,
            data in IO port 0xCFC, both 32-bit).
    conf2        [X86] Force use of PCI Configuration Access
            Mechanism 2 (IO port 0xCF8 is an 8-bit port for
            the function, IO port 0xCFA, also 8-bit, sets
            bus number. The config space is then accessed
            through ports 0xC000-0xCFFF).
            See http://wiki.osdev.org/PCI for more info
            on the configuration access mechanisms.
    noaer        [PCIE] If the PCIEAER kernel config parameter is
            enabled, this kernel boot option can be used to
            disable the use of PCIE advanced error reporting.
    nodomains    [PCI] Disable support for multiple PCI
            root domains (aka PCI segments, in ACPI-speak).
    nommconf    [X86] Disable use of MMCONFIG for PCI
            Configuration
    check_enable_amd_mmconf [X86] check for and enable
            properly configured MMIO access to PCI
            config space on AMD family 10h CPU
    nomsi        [MSI] If the PCI_MSI kernel config parameter is
            enabled, this kernel boot option can be used to
            disable the use of MSI interrupts system-wide.
    noioapicquirk    [APIC] Disable all boot interrupt quirks.
            Safety option to keep boot IRQs enabled. This
            should never be necessary.
    ioapicreroute    [APIC] Enable rerouting of boot IRQs to the
            primary IO-APIC for bridges that cannot disable
            boot IRQs. This fixes a source of spurious IRQs
            when the system masks IRQs.
    noioapicreroute    [APIC] Disable workaround that uses the
            boot IRQ equivalent of an IRQ that connects to
            a chipset where boot IRQs cannot be disabled.
            The opposite of ioapicreroute.
    biosirq        [X86-32] Use PCI BIOS calls to get the interrupt
            routing table. These calls are known to be buggy
            on several machines and they hang the machine
            when used, but on other computers it's the only
            way to get the interrupt routing table. Try
            this option if the kernel is unable to allocate
            IRQs or discover secondary PCI buses on your
            motherboard.
    rom        [X86] Assign address space to expansion ROMs.
            Use with caution as certain devices share
            address decoders between ROMs and other
            resources.
    norom        [X86] Do not assign address space to
            expansion ROMs that do not already have
            BIOS assigned address ranges.
    nobar        [X86] Do not assign address space to the
            BARs that weren't assigned by the BIOS.
    irqmask=0xMMMM    [X86] Set a bit mask of IRQs allowed to be
            assigned automatically to PCI devices. You can
            make the kernel exclude IRQs of your ISA cards
            this way.
    pirqaddr=0xAAAAA    [X86] Specify the physical address
            of the PIRQ table (normally generated
            by the BIOS) if it is outside the
            F0000h-100000h range.
    lastbus=N    [X86] Scan all buses thru bus #N. Can be
            useful if the kernel is unable to find your
            secondary buses and you want to tell it
            explicitly which ones they are.
    assign-busses    [X86] Always assign all PCI bus
            numbers ourselves, overriding
            whatever the firmware may have done.
    usepirqmask    [X86] Honor the possible IRQ mask stored
            in the BIOS $PIR table. This is needed on
            some systems with broken BIOSes, notably
            some HP Pavilion N5400 and Omnibook XE3
            notebooks. This will have no effect if ACPI
            IRQ routing is enabled.
    noacpi        [X86] Do not use ACPI for IRQ routing
            or for PCI scanning.
    use_crs        [X86] Use PCI host bridge window information
            from ACPI.  On BIOSes from 2008 or later, this
            is enabled by default.  If you need to use this,
            please report a bug.
    nocrs        [X86] Ignore PCI host bridge windows from ACPI.
            If you need to use this, please report a bug.
    routeirq    Do IRQ routing for all PCI devices.
            This is normally done in pci_enable_device(),
            so this option is a temporary workaround
            for broken drivers that don't call it.
    skip_isa_align    [X86] do not align io start addr, so can
            handle more pci cards
    noearly        [X86] Don't do any early type 1 scanning.
            This might help on some broken boards which
            machine check when some devices' config space
            is read. But various workarounds are disabled
            and some IOMMU drivers will not work.
    bfsort        Sort PCI devices into breadth-first order.
            This sorting is done to get a device
            order compatible with older (<= 2.4) kernels.
    nobfsort    Don't sort PCI devices into breadth-first order.
    pcie_bus_tune_off    Disable PCIe MPS (Max Payload Size)
            tuning and use the BIOS-configured MPS defaults.
    pcie_bus_safe    Set every device's MPS to the largest value
            supported by all devices below the root complex.
    pcie_bus_perf    Set device MPS to the largest allowable MPS
            based on its parent bus. Also set MRRS (Max
            Read Request Size) to the largest supported
            value (no larger than the MPS that the device
            or bus can support) for best performance.
    pcie_bus_peer2peer    Set every device's MPS to 128B, which
            every device is guaranteed to support. This
            configuration allows peer-to-peer DMA between
            any pair of devices, possibly at the cost of
            reduced performance.  This also guarantees
            that hot-added devices will work.
    cbiosize=nn[KMG]    The fixed amount of bus space which is
            reserved for the CardBus bridge's IO window.
            The default value is 256 bytes.
    cbmemsize=nn[KMG]    The fixed amount of bus space which is
            reserved for the CardBus bridge's memory
            window. The default value is 64 megabytes.
    resource_alignment=
            Format:
            [<order of align>@]<pci_dev>[; ...]
            Specifies alignment and device to reassign
            aligned memory resources. How to
            specify the device is described above.
            If <order of align> is not specified,
            PAGE_SIZE is used as alignment.
            A PCI-PCI bridge can be specified if resource
            windows need to be expanded.
            To specify the alignment for several
            instances of a device, the PCI vendor,
            device, subvendor, and subdevice may be
            specified, e.g., 12@pci:8086:9c22:103c:198f
            for 4096-byte alignment.
    ecrc=        Enable/disable PCIe ECRC (transaction layer
            end-to-end CRC checking).
            bios: Use BIOS/firmware settings. This is the
            the default.
            off: Turn ECRC off
            on: Turn ECRC on.
    hpiosize=nn[KMG]    The fixed amount of bus space which is
            reserved for hotplug bridge's IO window.
            Default size is 256 bytes.
    hpmmiosize=nn[KMG]    The fixed amount of bus space which is
            reserved for hotplug bridge's MMIO window.
            Default size is 2 megabytes.
    hpmmioprefsize=nn[KMG]    The fixed amount of bus space which is
            reserved for hotplug bridge's MMIO_PREF window.
            Default size is 2 megabytes.
    hpmemsize=nn[KMG]    The fixed amount of bus space which is
            reserved for hotplug bridge's MMIO and
            MMIO_PREF window.
            Default size is 2 megabytes.
    hpbussize=nn    The minimum amount of additional bus numbers
            reserved for buses below a hotplug bridge.
            Default is 1.
    realloc=    Enable/disable reallocating PCI bridge resources
            if allocations done by BIOS are too small to
            accommodate resources required by all child
            devices.
            off: Turn realloc off
            on: Turn realloc on
    realloc        same as realloc=on
    noari        do not use PCIe ARI.
    noats        [PCIE, Intel-IOMMU, AMD-IOMMU]
            do not use PCIe ATS (and IOMMU device IOTLB).
    pcie_scan_all    Scan all possible PCIe devices.  Otherwise we
            only look for one device below a PCIe downstream
            port.
    big_root_window    Try to add a big 64bit memory window to the PCIe
            root complex on AMD CPUs. Some GFX hardware
            can resize a BAR to allow access to all VRAM.
            Adding the window is slightly risky (it may
            conflict with unreported devices), so this
            taints the kernel.
    disable_acs_redir=<pci_dev>[; ...]
            Specify one or more PCI devices (in the format
            specified above) separated by semicolons.
            Each device specified will have the PCI ACS
            redirect capabilities forced off which will
            allow P2P traffic between devices through
            bridges without forcing it upstream. Note:
            this removes isolation between devices and
            may put more devices in an IOMMU group.
    force_floating    [S390] Force usage of floating interrupts.
    nomio        [S390] Do not use MIO instructions.

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

pcie_ports=    [PCIE] PCIe port services handling:
    native    Use native PCIe services (PME, AER, DPC, PCIe hotplug)
        even if the platform doesn't give the OS permission to
        use them.  This may cause conflicts if the platform
        also tries to use these services.
    dpc-native    Use native PCIe service for DPC only.  May
            cause conflicts if firmware uses AER or DPC.
    compat    Disable native PCIe services (PME, AER, DPC, PCIe
        hotplug).

pcie_port_pm=    [PCIE] PCIe port power management handling:
    off    Disable power management of all PCIe ports
    force    Forcibly enable power management of all PCIe ports

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

pcmv=        [HW,PCMCIA] BadgePAD 4

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

pd.        [PARIDE]
        See Documentation/blockdev/paride.txt.

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

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

pf.        [PARIDE]
        See Documentation/blockdev/paride.txt.

pg.        [PARIDE]
        See Documentation/blockdev/paride.txt.

pirq=        [SMP,APIC] Manual mp-table setup
        See Documentation/x86/i386/IO-APIC.txt.

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

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

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

pnpacpi=    [ACPI]
        { off }

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

pnp_reserve_irq=
        [ISAPNP] Exclude IRQs for the autoconfiguration

pnp_reserve_dma=
        [ISAPNP] Exclude DMAs for the autoconfiguration

pnp_reserve_io=    [ISAPNP] Exclude I/O ports for the autoconfiguration
        Ranges are in pairs (I/O port base and size).

pnp_reserve_mem=
        [ISAPNP] Exclude memory regions for the
        autoconfiguration.
        Ranges are in pairs (memory base and size).

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

powersave=off    [PPC] This option disables power saving features.
        It specifically disables cpuidle and sets the
        platform machine description specific power_save
        function to NULL. On Idle the CPU just reduces
        execution priority.

ppc_strict_facility_enable
        [PPC] This option catches any kernel floating point,
        Altivec, VSX and SPE outside of regions specifically
        allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
        There is some performance impact when enabling this.

ppc_tm=        [PPC]
        Format: {"off"}
        Disable Hardware Transactional Memory

print-fatal-signals=
        [KNL] debug: print fatal signals

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

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

        default: off.

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

printk.devkmsg={on,off,ratelimit}
        Control writing to /dev/kmsg.
        on - unlimited logging to /dev/kmsg from userspace
        off - logging to /dev/kmsg disabled
        ratelimit - ratelimit the logging
        Default: ratelimit

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

processor.max_cstate=    [HW,ACPI]
        Limit processor to maximum C-state
        max_cstate=9 overrides any DMI blacklist limit.

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

profile=    [KNL] Enable kernel profiling via /proc/profile
        Format: [<profiletype>,]<number>
        Param: <profiletype>: "schedule", "sleep", or "kvm"
            [defaults to kernel profiling]
        Param: "schedule" - profile schedule points.
        Param: "sleep" - profile D-state sleeping (millisecs).
            Requires CONFIG_SCHEDSTATS
        Param: "kvm" - profile VM exits.
        Param: <number> - step/bucket size as a power of 2 for
            statistical time based profiling.

prompt_ramdisk=    [RAM] List of RAM disks to prompt for floppy disk
        before loading.
        See Documentation/blockdev/ramdisk.txt.

prot_virt=    [S390] enable hosting protected virtual machines
        isolated from the hypervisor (if hardware supports
        that).
        Format: <bool>

psi=        [KNL] Enable or disable pressure stall information
        tracking.
        Format: <bool>

psmouse.proto=    [HW,MOUSE] Highest PS2 mouse protocol extension to
        probe for; one of (bare|imps|exps|lifebook|any).
psmouse.rate=    [HW,MOUSE] Set desired mouse report rate, in reports
        per second.
psmouse.resetafter=    [HW,MOUSE]
        Try to reset the device after so many bad packets
        (0 = never).
psmouse.resolution=
        [HW,MOUSE] Set desired mouse resolution, in dpi.
psmouse.smartscroll=
        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
        0 = disabled, 1 = enabled (default).

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

pt.        [PARIDE]
        See Documentation/blockdev/paride.txt.

pti=        [X86_64] Control Page Table Isolation of user and
        kernel address spaces.  Disabling this feature
        removes hardening, but improves performance of
        system calls and interrupts.

        on   - unconditionally enable
        off  - unconditionally disable
        auto - kernel detects whether your CPU model is
               vulnerable to issues that PTI mitigates

        Not specifying this option is equivalent to pti=auto.

nopti        [X86_64]
        Equivalent to pti=off

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

quiet        [KNL] Disable most log messages

r128=        [HW,DRM]

raid=        [HW,RAID]
        See Documentation/admin-guide/md.rst.

ramdisk_size=    [RAM] Sizes of RAM disks in kilobytes
        See Documentation/blockdev/ramdisk.txt.

random.trust_cpu={on,off}
        [KNL] Enable or disable trusting the use of the
        CPU's random number generator (if available) to
        fully seed the kernel's CRNG. Default is controlled
        by CONFIG_RANDOM_TRUST_CPU.

ras=option[,option,...]    [KNL] RAS-specific options

    cec_disable    [X86]
            Disable the Correctable Errors Collector,
            see CONFIG_RAS_CEC help text.

rcu_nocbs=    [KNL]
        The argument is a cpu list, as described above,
        except that the string "all" can be used to
        specify every CPU on the system.

        In kernels built with CONFIG_RCU_NOCB_CPU=y, set
        the specified list of CPUs to be no-callback CPUs.
        Invocation of these CPUs' RCU callbacks will be
        offloaded to "rcuox/N" kthreads created for that
        purpose, where "x" is "p" for RCU-preempt, and
        "s" for RCU-sched, and "N" is the CPU number.
        This reduces OS jitter on the offloaded CPUs,
        which can be useful for HPC and real-time
        workloads.  It can also improve energy efficiency
        for asymmetric multiprocessors.

rcu_nocb_poll    [KNL]
        Rather than requiring that offloaded CPUs
        (specified by rcu_nocbs= above) explicitly
        awaken the corresponding "rcuoN" kthreads,
        make these kthreads poll for callbacks.
        This improves the real-time response for the
        offloaded CPUs by relieving them of the need to
        wake up the corresponding kthread, but degrades
        energy efficiency by requiring that the kthreads
        periodically wake up to do the polling.

rcutree.blimit=    [KNL]
        Set maximum number of finished RCU callbacks to
        process in one batch.

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

rcutree.gp_cleanup_delay=    [KNL]
        Set the number of jiffies to delay each step of
        RCU grace-period cleanup.

rcutree.gp_init_delay=    [KNL]
        Set the number of jiffies to delay each step of
        RCU grace-period initialization.

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

rcutree.use_softirq=    [KNL]
        If set to zero, move all RCU_SOFTIRQ processing to
        per-CPU rcuc kthreads.  Defaults to a non-zero
        value, meaning that RCU_SOFTIRQ is used by default.
        Specify rcutree.use_softirq=0 to use rcuc kthreads.

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

rcutree.rcu_fanout_leaf= [KNL]
        Change the number of CPUs assigned to each
        leaf rcu_node structure.  Useful for very
        large systems, which will choose the value 64,
        and for NUMA systems with large remote-access
        latencies, which will choose a value aligned
        with the appropriate hardware boundaries.

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

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

rcutree.jiffies_till_sched_qs= [KNL]
        Set required age in jiffies for a
        given grace period before RCU starts
        soliciting quiescent-state help from
        rcu_note_context_switch() and cond_resched().
        If not specified, the kernel will calculate
        a value based on the most recent settings
        of rcutree.jiffies_till_first_fqs
        and rcutree.jiffies_till_next_fqs.
        This calculated value may be viewed in
        rcutree.jiffies_to_sched_qs.  Any attempt to set
        rcutree.jiffies_to_sched_qs will be cheerfully
        overwritten.

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

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

rcutree.qhimark= [KNL]
        Set threshold of queued RCU callbacks beyond which
        batch limiting is disabled.

rcutree.qlowmark= [KNL]
        Set threshold of queued RCU callbacks below which
        batch limiting is re-enabled.

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

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

rcutree.rcu_kick_kthreads= [KNL]
        Cause the grace-period kthread to get an extra
        wake_up() if it sleeps three times longer than
        it should at force-quiescent-state time.
        This wake_up() will be accompanied by a
        WARN_ONCE() splat and an ftrace_dump().

rcutree.sysrq_rcu= [KNL]
        Commandeer a sysrq key to dump out Tree RCU's
        rcu_node tree with an eye towards determining
        why a new grace period has not yet started.

rcuperf.gp_async= [KNL]
        Measure performance of asynchronous
        grace-period primitives such as call_rcu().

rcuperf.gp_async_max= [KNL]
        Specify the maximum number of outstanding
        callbacks per writer thread.  When a writer
        thread exceeds this limit, it invokes the
        corresponding flavor of rcu_barrier() to allow
        previously posted callbacks to drain.

rcuperf.gp_exp= [KNL]
        Measure performance of expedited synchronous
        grace-period primitives.

rcuperf.holdoff= [KNL]
        Set test-start holdoff period.  The purpose of
        this parameter is to delay the start of the
        test until boot completes in order to avoid
        interference.

rcuperf.nreaders= [KNL]
        Set number of RCU readers.  The value -1 selects
        N, where N is the number of CPUs.  A value
        "n" less than -1 selects N-n+1, where N is again
        the number of CPUs.  For example, -2 selects N
        (the number of CPUs), -3 selects N+1, and so on.
        A value of "n" less than or equal to -N selects
        a single reader.

rcuperf.nwriters= [KNL]
        Set number of RCU writers.  The values operate
        the same as for rcuperf.nreaders.
        N, where N is the number of CPUs

rcuperf.perf_type= [KNL]
        Specify the RCU implementation to test.

rcuperf.shutdown= [KNL]
        Shut the system down after performance tests
        complete.  This is useful for hands-off automated
        testing.

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

rcuperf.writer_holdoff= [KNL]
        Write-side holdoff between grace periods,
        in microseconds.  The default of zero says
        no holdoff.

rcutorture.fqs_duration= [KNL]
        Set duration of force_quiescent_state bursts
        in microseconds.

rcutorture.fqs_holdoff= [KNL]
        Set holdoff time within force_quiescent_state bursts
        in microseconds.

rcutorture.fqs_stutter= [KNL]
        Set wait time between force_quiescent_state bursts
        in seconds.

rcutorture.fwd_progress= [KNL]
        Enable RCU grace-period forward-progress testing
        for the types of RCU supporting this notion.

rcutorture.fwd_progress_div= [KNL]
        Specify the fraction of a CPU-stall-warning
        period to do tight-loop forward-progress testing.

rcutorture.fwd_progress_holdoff= [KNL]
        Number of seconds to wait between successive
        forward-progress tests.

rcutorture.fwd_progress_need_resched= [KNL]
        Enclose cond_resched() calls within checks for
        need_resched() during tight-loop forward-progress
        testing.

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

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

rcutorture.gp_normal= [KNL]
        Use normal (non-expedited) asynchronous
        update-side primitives, if available.

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

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

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

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

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

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

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

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

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

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

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

rcutorture.stall_cpu_irqsoff= [KNL]
        Disable interrupts while stalling if set.

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

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

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

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

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

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

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

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

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

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

rcupdate.rcu_expedited= [KNL]
        Use expedited grace-period primitives, for
        example, synchronize_rcu_expedited() instead
        of synchronize_rcu().  This reduces latency,
        but can increase CPU utilization, degrade
        real-time latency, and degrade energy efficiency.
        No effect on CONFIG_TINY_RCU kernels.

rcupdate.rcu_normal= [KNL]
        Use only normal grace-period primitives,
        for example, synchronize_rcu() instead of
        synchronize_rcu_expedited().  This improves
        real-time latency, CPU utilization, and
        energy efficiency, but can expose users to
        increased grace-period latency.  This parameter
        overrides rcupdate.rcu_expedited.  No effect on
        CONFIG_TINY_RCU kernels.

rcupdate.rcu_normal_after_boot= [KNL]
        Once boot has completed (that is, after
        rcu_end_inkernel_boot() has been invoked), use
        only normal grace-period primitives.  No effect
        on CONFIG_TINY_RCU kernels.

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

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

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

rdt=        [HW,X86,RDT]
        Turn on/off individual RDT features. List is:
        cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
        mba.
        E.g. to turn on cmt and turn off mba use:
            rdt=cmt,!mba

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

relax_domain_level=
        [KNL, SMP] Set scheduler's default relax_domain_level.
        See Documentation/cgroup-v1/cpusets.txt.

reserve=    [KNL,BUGS] Force kernel to ignore I/O ports or memory
        Format: <base1>,<size1>[,<base2>,<size2>,...]
        Reserve I/O ports or memory so the kernel won't use
        them.  If <base> is less than 0x10000, the region
        is assumed to be I/O ports; otherwise it is memory.

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

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

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

resume=        [SWSUSP]
        Specify the partition device for software suspend
        Format:
        {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}

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

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

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

hibernate=    [HIBERNATION]
    noresume    Don't check if there's a hibernation image
            present during boot.
    nocompress    Don't compress/decompress hibernation images.
    no        Disable hibernation and resume.
    protect_image    Turn on image protection during restoration
            (that will set all pages holding image data
            during restoration read-only).

retain_initrd    [RAM] Keep initrd memory after extraction

rfkill.default_state=
    0    "airplane mode".  All wifi, bluetooth, wimax, gps, fm,
        etc. communication is blocked by default.
    1    Unblocked.

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

rhash_entries=    [KNL,NET]
        Set number of hash buckets for route cache

ring3mwait=disable
        [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
        CPUs.

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

rodata=        [KNL]
    on    Mark read-only kernel memory as read-only (default).
    off    Leave read-only kernel memory writable for debugging.

rockchip.usb_uart
        Enable the uart passthrough on the designated usb port
        on Rockchip SoCs. When active, the signals of the
        debug-uart get routed to the D+ and D- pins of the usb
        port and the regular usb controller gets disabled.

root=        [KNL] Root filesystem
        See name_to_dev_t comment in init/do_mounts.c.

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

rootflags=    [KNL] Set root filesystem mount option string

rootfstype=    [KNL] Set root filesystem type

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

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

rw        [KNL] Mount root device read-write on boot

S        [KNL] Run init in single mode

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

sa1100ir    [NET]
        See drivers/net/irda/sa1100_ir.c.

sbni=        [NET] Granch SBNI12 leased line adapter

sched_debug    [KNL] Enables verbose scheduler debug messages.

schedstats=    [KNL,X86] Enable or disable scheduled statistics.
        Allowed values are enable and disable. This feature
        incurs a small amount of overhead in the scheduler
        but is useful for debugging and performance tuning.

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

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

selinux=    [SELINUX] Disable or enable SELinux at boot time.
        Format: { "0" | "1" }
        See security/selinux/Kconfig help text.
        0 -- disable.
        1 -- enable.
        Default value is 1.

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

serialnumber    [BUGS=X86-32]

shapers=    [NET]
        Maximal number of shapers.

simeth=        [IA-64]
simscsi=

slram=        [HW,MTD]

slab_nomerge    [MM]
        Disable merging of slabs with similar size. May be
        necessary if there is some reason to distinguish
        allocs to different slabs, especially in hardened
        environments where the risk of heap overflows and
        layout control by attackers can usually be
        frustrated by disabling merging. This will reduce
        most of the exposure of a heap attack to a single
        cache (risks via metadata attacks are mostly
        unchanged). Debug options disable merging on their
        own.
        For more information see Documentation/vm/slub.rst.

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

slub_debug[=options[,slabs]]    [MM, SLUB]
        Enabling slub_debug allows one to determine the
        culprit if slab objects become corrupted. Enabling
        slub_debug can create guard zones around objects and
        may poison objects when not in use. Also tracks the
        last alloc / free. For more information see
        Documentation/vm/slub.rst.

slub_memcg_sysfs=    [MM, SLUB]
        Determines whether to enable sysfs directories for
        memory cgroup sub-caches. 1 to enable, 0 to disable.
        The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
        Enabling this can lead to a very high number of    debug
        directories and files being created under
        /sys/kernel/slub.

slub_max_order= [MM, SLUB]
        Determines the maximum allowed order for slabs.
        A high setting may cause OOMs due to memory
        fragmentation. For more information see
        Documentation/vm/slub.rst.

slub_min_objects=    [MM, SLUB]
        The minimum number of objects per slab. SLUB will
        increase the slab order up to slub_max_order to
        generate a sufficiently large slab able to contain
        the number of objects indicated. The higher the number
        of objects the smaller the overhead of tracking slabs
        and the less frequently locks need to be acquired.
        For more information see Documentation/vm/slub.rst.

slub_min_order=    [MM, SLUB]
        Determines the minimum page order for slabs. Must be
        lower than slub_max_order.
        For more information see Documentation/vm/slub.rst.

slub_nomerge    [MM, SLUB]
        Same with slab_nomerge. This is supported for legacy.
        See slab_nomerge for more information.

smart2=        [HW]
        Format: <io1>[,<io2>[,...,<io8>]]

smsc-ircc2.nopnp    [HW] Don't use PNP to discover SMC devices
smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
smsc-ircc2.ircc_irq=    [HW] IRQ line
smsc-ircc2.ircc_dma=    [HW] DMA channel
smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
            0: Toshiba Satellite 1800 (GP data pin select)
            1: Fast pin select (default)
            2: ATC IRMode

smt        [KNL,S390] Set the maximum number of threads (logical
        CPUs) to use per physical CPU on systems capable of
        symmetric multithreading (SMT). Will be capped to the
        actual hardware limit.
        Format: <integer>
        Default: -1 (no limit)

softlockup_panic=
        [KNL] Should the soft-lockup detector generate panics.
        Format: <integer>

        A nonzero value instructs the soft-lockup detector
        to panic the machine when a soft-lockup occurs. This
        is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
        which is the respective build-time switch to that
        functionality.

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

sonypi.*=    [HW] Sony Programmable I/O Control Device driver
        See Documentation/laptops/sonypi.txt

spectre_v2=    [X86] Control mitigation of Spectre variant 2
        (indirect branch speculation) vulnerability.
        The default operation protects the kernel from
        user space attacks.

        on   - unconditionally enable, implies
               spectre_v2_user=on
        off  - unconditionally disable, implies
               spectre_v2_user=off
        auto - kernel detects whether your CPU model is
               vulnerable

        Selecting 'on' will, and 'auto' may, choose a
        mitigation method at run time according to the
        CPU, the available microcode, the setting of the
        CONFIG_RETPOLINE configuration option, and the
        compiler with which the kernel was built.

        Selecting 'on' will also enable the mitigation
        against user space to user space task attacks.

        Selecting 'off' will disable both the kernel and
        the user space protections.

        Specific mitigations can also be selected manually:

        retpoline      - replace indirect branches
        retpoline,generic - google's original retpoline
        retpoline,amd     - AMD-specific minimal thunk
        ibrs          - use IBRS to protect kernel
        ibrs_always      - use IBRS to protect both kernel
                    and userland
        retpoline,ibrs_user
                  - replace indirect branches
                    with retpolines and use
                    IBRS to protect userland

        Not specifying this option is equivalent to
        spectre_v2=auto.

spectre_v2_user=
        [X86] Control mitigation of Spectre variant 2
            (indirect branch speculation) vulnerability between
            user space tasks

        on    - Unconditionally enable mitigations. Is
              enforced by spectre_v2=on

        off     - Unconditionally disable mitigations. Is
              enforced by spectre_v2=off

        prctl   - Indirect branch speculation is enabled,
              but mitigation can be enabled via prctl
              per thread.  The mitigation control state
              is inherited on fork.

        prctl,ibpb
            - Like "prctl" above, but only STIBP is
              controlled per thread. IBPB is issued
              always when switching between different user
              space processes.

        seccomp
            - Same as "prctl" above, but all seccomp
              threads will enable the mitigation unless
              they explicitly opt out.

        seccomp,ibpb
            - Like "seccomp" above, but only STIBP is
              controlled per thread. IBPB is issued
              always when switching between different
              user space processes.

        auto    - Kernel selects the mitigation depending on
              the available CPU features and vulnerability.

        Default mitigation:
        If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"

        Not specifying this option is equivalent to
        spectre_v2_user=auto.

spec_store_bypass_disable=
        [HW] Control Speculative Store Bypass (SSB) Disable mitigation
        (Speculative Store Bypass vulnerability)

        Certain CPUs are vulnerable to an exploit against a
        a common industry wide performance optimization known
        as "Speculative Store Bypass" in which recent stores
        to the same memory location may not be observed by
        later loads during speculative execution. The idea
        is that such stores are unlikely and that they can
        be detected prior to instruction retirement at the
        end of a particular speculation execution window.

        In vulnerable processors, the speculatively forwarded
        store can be used in a cache side channel attack, for
        example to read memory to which the attacker does not
        directly have access (e.g. inside sandboxed code).

        This parameter controls whether the Speculative Store
        Bypass optimization is used.

        on      - Unconditionally disable Speculative Store Bypass
        off     - Unconditionally enable Speculative Store Bypass
        auto    - Kernel detects whether the CPU model contains an
              implementation of Speculative Store Bypass and
              picks the most appropriate mitigation. If the
              CPU is not vulnerable, "off" is selected. If the
              CPU is vulnerable the default mitigation is
              architecture and Kconfig dependent. See below.
        prctl   - Control Speculative Store Bypass per thread
              via prctl. Speculative Store Bypass is enabled
              for a process by default. The state of the control
              is inherited on fork.
        seccomp - Same as "prctl" above, but all seccomp threads
              will disable SSB unless they explicitly opt out.

        Not specifying this option is equivalent to
        spec_store_bypass_disable=auto.

        Default mitigations:
        X86:    If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"

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

split_lock_detect=
        [X86] Enable split lock detection

        When enabled (and if hardware support is present), atomic
        instructions that access data across cache line
        boundaries will result in an alignment check exception.

        off    - not enabled

        warn    - the kernel will emit rate limited warnings
              about applications triggering the #AC
              exception. This mode is the default on CPUs
              that supports split lock detection.

        fatal    - the kernel will send SIGBUS to applications
              that trigger the #AC exception.

        If an #AC exception is hit in the kernel or in
        firmware (i.e. not while executing in user mode)
        the kernel will oops in either "warn" or "fatal"
        mode.

srbds=        [X86,INTEL]
        Control the Special Register Buffer Data Sampling
        (SRBDS) mitigation.

        Certain CPUs are vulnerable to an MDS-like
        exploit which can leak bits from the random
        number generator.

        By default, this issue is mitigated by
        microcode.  However, the microcode fix can cause
        the RDRAND and RDSEED instructions to become
        much slower.  Among other effects, this will
        result in reduced throughput from /dev/urandom.

        The microcode mitigation can be disabled with
        the following option:

        off:    Disable mitigation and remove
            performance impact to RDRAND and RDSEED

srcutree.counter_wrap_check [KNL]
        Specifies how frequently to check for
        grace-period sequence counter wrap for the
        srcu_data structure's ->srcu_gp_seq_needed field.
        The greater the number of bits set in this kernel
        parameter, the less frequently counter wrap will
        be checked for.  Note that the bottom two bits
        are ignored.

srcutree.exp_holdoff [KNL]
        Specifies how many nanoseconds must elapse
        since the end of the last SRCU grace period for
        a given srcu_struct until the next normal SRCU
        grace period will be considered for automatic
        expediting.  Set to zero to disable automatic
        expediting.

ssbd=        [ARM64,HW]
        Speculative Store Bypass Disable control

        On CPUs that are vulnerable to the Speculative
        Store Bypass vulnerability and offer a
        firmware based mitigation, this parameter
        indicates how the mitigation should be used:

        force-on:  Unconditionally enable mitigation for
               for both kernel and userspace
        force-off: Unconditionally disable mitigation for
               for both kernel and userspace
        kernel:    Always enable mitigation in the
               kernel, and offer a prctl interface
               to allow userspace to register its
               interest in being mitigated too.

stack_guard_gap=    [MM]
        override the default stack gap protection. The value
        is in page units and it defines how many pages prior
        to (for stacks growing down) resp. after (for stacks
        growing up) the main stack are reserved for no other
        mapping. Default value is 256 pages.

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

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

sti=        [PARISC,HW]
        Format: <num>
        Set the STI (builtin display/keyboard on the HP-PARISC
        machines) console (graphic card) which should be used
        as the initial boot-console.
        See also comment in drivers/video/console/sticore.c.

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

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

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

sunrpc.svc_rpc_per_connection_limit=
        [NFS,SUNRPC]
        Limit the number of requests that the server will
        process in parallel from a single connection.
        The default value is 0 (no limit).

sunrpc.pool_mode=
        [NFS]
        Control how the NFS server code allocates CPUs to
        service thread pools.  Depending on how many NICs
        you have and where their interrupts are bound, this
        option will affect which CPUs will do NFS serving.
        Note: this parameter cannot be changed while the
        NFS server is running.

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

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

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

svm=        [PPC]
        Format: { on | off | y | n | 1 | 0 }
        This parameter controls use of the Protected
        Execution Facility on pSeries.

swapaccount=[0|1]
        [KNL] Enable accounting of swap in memory resource
        controller if no parameter or 1 is given or disable
        it if 0 is given (See Documentation/cgroup-v1/memory.txt)

swiotlb=    [ARM,IA-64,PPC,MIPS,X86]
        Format: { <int> | force | noforce }
        <int> -- Number of I/O TLB slabs
        force -- force using of bounce buffers even if they
                 wouldn't be automatically used by the kernel
        noforce -- Never use bounce buffers (for debugging)

switches=    [HW,M68k]

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

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

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

tdfx=        [HW,DRM]

test_suspend=    [SUSPEND][,N]
        Specify "mem" (for Suspend-to-RAM) or "standby" (for
        standby suspend) or "freeze" (for suspend type freeze)
        as the system sleep state during system startup with
        the optional capability to repeat N number of times.
        The system is woken from this state using a
        wakeup-capable RTC alarm.

thash_entries=    [KNL,NET]
        Set number of hash buckets for TCP connection

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

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

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

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

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

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

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

tmem        [KNL,XEN]
        Enable the Transcendent memory driver if built-in.

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

tmem.frontswap=0|1 [KNL, XEN]
        Default is on (1). Disable the usage of the frontswap
        API to send swap pages to the hypervisor. If disabled
        the selfballooning and selfshrinking are force disabled.

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

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

topology=    [S390]
        Format: {off | on}
        Specify if the kernel should make use of the cpu
        topology information if the hardware supports this.
        The scheduler will make use of this information and
        e.g. base its process migration decisions on it.
        Default is on.

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

tp720=        [HW,PS2]

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

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

trace_event=[event-list]
        [FTRACE] Set and start specified trace events in order
        to facilitate early boot debugging. The event-list is a
        comma separated list of trace events to enable. See
        also Documentation/trace/events.rst

trace_options=[option-list]
        [FTRACE] Enable or disable tracer options at boot.
        The option-list is a comma delimited list of options
        that can be enabled or disabled just as if you were
        to echo the option name into

            /sys/kernel/debug/tracing/trace_options

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

              trace_options=stacktrace

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

tp_printk[FTRACE]
        Have the tracepoints sent to printk as well as the
        tracing ring buffer. This is useful for early boot up
        where the system hangs or reboots and does not give the
        option for reading the tracing buffer or performing a
        ftrace_dump_on_oops.

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

        ** CAUTION **

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

traceoff_on_warning
        [FTRACE] enable this option to disable tracing when a
        warning is hit. This turns off "tracing_on". Tracing can
        be enabled again by echoing '1' into the "tracing_on"
        file located in /sys/kernel/debug/tracing/

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

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

transparent_hugepage=
        [KNL]
        Format: [always|madvise|never]
        Can be used to control the default behavior of the system
        with respect to transparent hugepages.
        See Documentation/admin-guide/mm/transhuge.rst
        for more details.

tsc=        Disable clocksource stability checks for TSC.
        Format: <string>
        [x86] reliable: mark tsc clocksource as reliable, this
        disables clocksource verification at runtime, as well
        as the stability checks done at bootup.    Used to enable
        high-resolution timer mode on older hardware, and in
        virtualized environment.
        [x86] noirqtime: Do not use TSC to do irq accounting.
        Used to run time disable IRQ_TIME_ACCOUNTING on any
        platforms where RDTSC is slow and this accounting
        can add overhead.
        [x86] unstable: mark the TSC clocksource as unstable, this
        marks the TSC unconditionally unstable at bootup and
        avoids any further wobbles once the TSC watchdog notices.
        [x86] nowatchdog: disable clocksource watchdog. Used
        in situations with strict latency requirements (where
        interruptions from clocksource watchdog are not
        acceptable).

tsx=        [X86] Control Transactional Synchronization
        Extensions (TSX) feature in Intel processors that
        support TSX control.

        This parameter controls the TSX feature. The options are:

        on    - Enable TSX on the system. Although there are
            mitigations for all known security vulnerabilities,
            TSX has been known to be an accelerator for
            several previous speculation-related CVEs, and
            so there may be unknown    security risks associated
            with leaving it enabled.

        off    - Disable TSX on the system. (Note that this
            option takes effect only on newer CPUs which are
            not vulnerable to MDS, i.e., have
            MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
            the new IA32_TSX_CTRL MSR through a microcode
            update. This new MSR allows for the reliable
            deactivation of the TSX functionality.)

        auto    - Disable TSX if X86_BUG_TAA is present,
              otherwise enable TSX on the system.

        Not specifying this option is equivalent to tsx=off.

        See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
        for more details.

tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
        Abort (TAA) vulnerability.

        Similar to Micro-architectural Data Sampling (MDS)
        certain CPUs that support Transactional
        Synchronization Extensions (TSX) are vulnerable to an
        exploit against CPU internal buffers which can forward
        information to a disclosure gadget under certain
        conditions.

        In vulnerable processors, the speculatively forwarded
        data can be used in a cache side channel attack, to
        access data to which the attacker does not have direct
        access.

        This parameter controls the TAA mitigation.  The
        options are:

        full       - Enable TAA mitigation on vulnerable CPUs
                 if TSX is enabled.

        full,nosmt - Enable TAA mitigation and disable SMT on
                 vulnerable CPUs. If TSX is disabled, SMT
                 is not disabled because CPU is not
                 vulnerable to cross-thread TAA attacks.
        off        - Unconditionally disable TAA mitigation

        On MDS-affected machines, tsx_async_abort=off can be
        prevented by an active MDS mitigation as both vulnerabilities
        are mitigated with the same mechanism so in order to disable
        this mitigation, you need to specify mds=off too.

        Not specifying this option is equivalent to
        tsx_async_abort=full.  On CPUs which are MDS affected
        and deploy MDS mitigation, TAA mitigation is not
        required and doesn't provide any additional
        mitigation.

        For details see:
        Documentation/admin-guide/hw-vuln/tsx_async_abort.rst

turbografx.map[2|3]=    [HW,JOY]
        TurboGraFX parallel port interface
        Format:
        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
        See also Documentation/input/devices/joystick-parport.rst

udbg-immortal    [PPC] When debugging early kernel crashes that
        happen after console_init() and before a proper
        console driver takes over, this boot options might
        help "seeing" what's going on.

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

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

unknown_nmi_panic
        [X86] Cause panic on unknown NMI.

unprivileged_bpf_disabled=
        Format: { "0" | "1" }
        Sets the initial value of
        kernel.unprivileged_bpf_disabled sysctl knob.
        0 - unprivileged bpf() syscall access is enabled.
        1 - unprivileged bpf() syscall access is disabled.
        Default value is 1.

usbcore.authorized_default=
        [USB] Default USB device authorization:
        (default -1 = authorized except for wireless USB,
        0 = not authorized, 1 = authorized, 2 = authorized
        if device connected to internal port)

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

usbcore.usbfs_snoop=
        [USB] Set to log all usbfs traffic (default 0 = off).

usbcore.usbfs_snoop_max=
        [USB] Maximum number of bytes to snoop in each URB
        (default = 65536).

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

usbcore.old_scheme_first=
        [USB] Start with the old device initialization
        scheme,  applies only to low and full-speed devices
         (default 0 = off).

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

usbcore.use_both_schemes=
        [USB] Try the other device initialization scheme
        if the first one fails (default 1 = enabled).

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

usbcore.nousb    [USB] Disable the USB subsystem

usbcore.quirks=
        [USB] A list of quirk entries to augment the built-in
        usb core quirk list. List entries are separated by
        commas. Each entry has the form
        VendorID:ProductID:Flags. The IDs are 4-digit hex
        numbers and Flags is a set of letters. Each letter
        will change the built-in quirk; setting it if it is
        clear and clearing it if it is set. The letters have
        the following meanings:
            a = USB_QUIRK_STRING_FETCH_255 (string
                descriptors must not be fetched using
                a 255-byte read);
            b = USB_QUIRK_RESET_RESUME (device can't resume
                correctly so reset it instead);
            c = USB_QUIRK_NO_SET_INTF (device can't handle
                Set-Interface requests);
            d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
                handle its Configuration or Interface
                strings);
            e = USB_QUIRK_RESET (device can't be reset
                (e.g morph devices), don't use reset);
            f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
                more interface descriptions than the
                bNumInterfaces count, and can't handle
                talking to these interfaces);
            g = USB_QUIRK_DELAY_INIT (device needs a pause
                during initialization, after we read
                the device descriptor);
            h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
                high speed and super speed interrupt
                endpoints, the USB 2.0 and USB 3.0 spec
                require the interval in microframes (1
                microframe = 125 microseconds) to be
                calculated as interval = 2 ^
                (bInterval-1).
                Devices with this quirk report their
                bInterval as the result of this
                calculation instead of the exponent
                variable used in the calculation);
            i = USB_QUIRK_DEVICE_QUALIFIER (device can't
                handle device_qualifier descriptor
                requests);
            j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
                generates spurious wakeup, ignore
                remote wakeup capability);
            k = USB_QUIRK_NO_LPM (device can't handle Link
                Power Management);
            l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
                (Device reports its bInterval as linear
                frames instead of the USB 2.0
                calculation);
            m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
                to be disconnected before suspend to
                prevent spurious wakeup);
            n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
                pause after every control message);
            o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
                delay after resetting its port);
        Example: quirks=0781:5580:bk,0a5c:5834:gij

usbhid.mousepoll=
        [USBHID] The interval which mice are to be polled at.

usbhid.jspoll=
        [USBHID] The interval which joysticks are to be polled at.

usbhid.kbpoll=
        [USBHID] The interval which keyboards are to be polled at.

usb-storage.delay_use=
        [UMS] The delay in seconds before a new device is
        scanned for Logical Units (default 1).

usb-storage.quirks=
        [UMS] A list of quirks entries to supplement or
        override the built-in unusual_devs list.  List
        entries are separated by commas.  Each entry has
        the form VID:PID:Flags where VID and PID are Vendor
        and Product ID values (4-digit hex numbers) and
        Flags is a set of characters, each corresponding
        to a common usb-storage quirk flag as follows:
            a = SANE_SENSE (collect more than 18 bytes
                of sense data);
            b = BAD_SENSE (don't collect more than 18
                bytes of sense data);
            c = FIX_CAPACITY (decrease the reported
                device capacity by one sector);
            d = NO_READ_DISC_INFO (don't use
                READ_DISC_INFO command);
            e = NO_READ_CAPACITY_16 (don't use
                READ_CAPACITY_16 command);
            f = NO_REPORT_OPCODES (don't use report opcodes
                command, uas only);
            g = MAX_SECTORS_240 (don't transfer more than
                240 sectors at a time, uas only);
            h = CAPACITY_HEURISTICS (decrease the
                reported device capacity by one
                sector if the number is odd);
            i = IGNORE_DEVICE (don't bind to this
                device);
            j = NO_REPORT_LUNS (don't use report luns
                command, uas only);
            l = NOT_LOCKABLE (don't try to lock and
                unlock ejectable media);
            m = MAX_SECTORS_64 (don't transfer more
                than 64 sectors = 32 KB at a time);
            n = INITIAL_READ10 (force a retry of the
                initial READ(10) command);
            o = CAPACITY_OK (accept the capacity
                reported by the device);
            p = WRITE_CACHE (the device cache is ON
                by default);
            r = IGNORE_RESIDUE (the device reports
                bogus residue values);
            s = SINGLE_LUN (the device has only one
                Logical Unit);
            t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
                commands, uas only);
            u = IGNORE_UAS (don't bind to the uas driver);
            w = NO_WP_DETECT (don't test whether the
                medium is write-protected).
            y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
                even if the device claims no cache)
        Example: quirks=0419:aaf5:rl,0421:0433:rc

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

userpte=
        [X86] Flags controlling user PTE allocations.

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

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

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

vdso32=        [X86] Control the 32-bit vDSO
        vdso32=1: enable 32-bit VDSO
        vdso32=0 or vdso32=2: disable 32-bit VDSO

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

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

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

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

video=        [FB] Frame buffer configuration
        See Documentation/fb/modedb.txt.

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

virtio_mmio.device=
        [VMMIO] Memory mapped virtio (platform) device.

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

        Can be used multiple times for multiple devices.

vga=        [BOOT,X86-32] Select a particular video mode
        See Documentation/x86/boot.txt and
        Documentation/svga.txt.
        Use vga=ask for menu.
        This is actually a boot loader parameter; the value is
        passed to the kernel using a special protocol.

vm_debug[=options]    [KNL] Available with CONFIG_DEBUG_VM=y.
        May slow down system boot speed, especially when
        enabled on systems with a large amount of memory.
        All options are enabled by default, and this
        interface is meant to allow for selectively
        enabling or disabling specific virtual memory
        debugging features.

        Available options are:
          P    Enable page structure init time poisoning
          -    Disable all of the above options

vmalloc=nn[KMG]    [KNL,BOOT] Forces the vmalloc area to have an exact
        size of <nn>. This can be used to increase the
        minimum size (128MB on x86). It can also be used to
        decrease the size and leave more room for directly
        mapped kernel RAM.

vmcp_cma=nn[MG]    [KNL,S390]
        Sets the memory size reserved for contiguous memory
        allocations for the vmcp device driver.

vmhalt=        [KNL,S390] Perform z/VM CP command after system halt.
        Format: <command>

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

vmpoff=        [KNL,S390] Perform z/VM CP command after power off.
        Format: <command>

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

        emulate     [default] Vsyscalls turn into traps and are
                    emulated reasonably safely.

        native      Vsyscalls are native syscall instructions.
                    This is a little bit faster than trapping
                    and makes a few dynamic recompilers work
                    better than they would in emulation mode.
                    It also makes exploits much easier to write.

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

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

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

vt.default_blu=    [VT]
        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
        Change the default blue palette of the console.
        This is a 16-member array composed of values
        ranging from 0-255.

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

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

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

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

vt.italic=    [VT] Default color for italic text; 0-15.
        Default: 2 = green.

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

watchdog timers    [HW,WDT] For information on watchdog timers,
        see Documentation/watchdog/watchdog-parameters.rst
        or other driver-specific files in the
        Documentation/watchdog/ directory.

watchdog_thresh=
        This parameter allows early boot to change the
        value of the watchdog timeout threshold from the default
        of 10 seconds to avoid hard lockups.  Example:
        watchdog_thresh=30
        Default: 10

workqueue.watchdog_thresh=
        If CONFIG_WQ_WATCHDOG is configured, workqueue can
        warn stall conditions and dump internal state to
        help debugging.  0 disables workqueue stall
        detection; otherwise, it's the stall threshold
        duration in seconds.  The default value is 30 and
        it can be updated at runtime by writing to the
        corresponding sysfs file.

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

workqueue.power_efficient
        Per-cpu workqueues are generally preferred because
        they show better performance thanks to cache
        locality; unfortunately, per-cpu workqueues tend to
        be more power hungry than unbound workqueues.

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

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

workqueue.debug_force_rr_cpu
        Workqueue used to implicitly guarantee that work
        items queued without explicit CPU specified are put
        on the local CPU.  This guarantee is no longer true
        and while local CPU is still preferred work items
        may be put on foreign CPUs.  This debug option
        forces round-robin CPU selection to flush out
        usages which depend on the now broken guarantee.
        When enabled, memory and cache locality will be
        impacted.

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

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

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

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

xen_nopvspin    [X86,XEN]
        Disables the ticketlock slowpath using Xen PV
        optimizations.

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

nopv=        [X86,XEN,KVM,HYPER_V,VMWARE]
        Disables the PV optimizations forcing the guest to run
        as generic guest with no PV drivers. Currently support
        XEN HVM, KVM, HYPER_V and VMWARE guest.

xirc2ps_cs=    [NET,PCMCIA]
        Format:
        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]

xhci-hcd.quirks        [USB,KNL]
        A hex value specifying bitmask with supplemental xhci
        host controller quirks. Meaning of each bit can be
        consulted in header drivers/usb/host/xhci.h.