KVM: arm64: Enable GICv3 Group-1 sysreg trapping via command-line

[mirror_ubuntu-artful-kernel.git] / Documentation / admin-guide / kernel-parameters.txt

        acpi=           [HW,ACPI,X86,ARM64]
                        Advanced Configuration and Power Interface
                        Format: { force | on | off | strict | noirq | rsdt |
                                  copy_dsdt }
                        force -- enable ACPI if default was off
                        on -- enable ACPI but allow fallback to DT [arm64]
                        off -- disable ACPI if default was on
                        noirq -- do not use ACPI for IRQ routing
                        strict -- Be less tolerant of platforms that are not
                                strictly ACPI specification compliant.
                        rsdt -- prefer RSDT over (default) XSDT
                        copy_dsdt -- copy DSDT to memory
                        For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
                        are available

                        See also Documentation/power/runtime_pm.txt, pci=noacpi

        acpi_apic_instance=     [ACPI, IOAPIC]
                        Format: <int>
                        2: use 2nd APIC table, if available
                        1,0: use 1st APIC table
                        default: 0

        acpi_backlight= [HW,ACPI]
                        acpi_backlight=vendor
                        acpi_backlight=video
                        If set to vendor, prefer vendor specific driver
                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
                        of the ACPI video.ko driver.

        acpi_force_32bit_fadt_addr
                        force FADT to use 32 bit addresses rather than the
                        64 bit X_* addresses. Some firmware have broken 64
                        bit addresses for force ACPI ignore these and use
                        the older legacy 32 bit addresses.

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

        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
                        Format: <int>
                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
                        debug output.  Bits in debug_layer correspond to a
                        _COMPONENT in an ACPI source file, e.g.,
                            #define _COMPONENT ACPI_PCI_COMPONENT
                        Bits in debug_level correspond to a level in
                        ACPI_DEBUG_PRINT statements, e.g.,
                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
                        The debug_level mask defaults to "info".  See
                        Documentation/acpi/debug.txt for more information about
                        debug layers and levels.

                        Enable processor driver info messages:
                            acpi.debug_layer=0x20000000
                        Enable PCI/PCI interrupt routing info messages:
                            acpi.debug_layer=0x400000
                        Enable AML "Debug" output, i.e., stores to the Debug
                        object while interpreting AML:
                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
                        Enable all messages related to ACPI hardware:
                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff

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

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

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

        acpi_irq_balance [HW,ACPI]
                        ACPI will balance active IRQs
                        default in APIC mode

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

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

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

        acpi_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: <int>
                        Support masking of GPEs numbered from 0x00 to 0x7f.

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

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

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

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

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

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

        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
                        acpi_osi="string1"      # add string1
                        acpi_osi="!string2"     # remove string2
                        acpi_osi=!*             # remove all strings
                        acpi_osi=!              # disable all built-in OS vendor
                                                  strings
                        acpi_osi=!!             # enable all built-in OS vendor
                                                  strings
                        acpi_osi=               # disable all strings

                        'acpi_osi=!' can be used in combination with single or
                        multiple 'acpi_osi="string1"' to support specific OS
                        vendor string(s).  Note that such command can only
                        affect the default state of the OS vendor strings, thus
                        it cannot affect the default state of the feature group
                        strings and the current state of the OS vendor strings,
                        specifying it multiple times through kernel command line
                        is meaningless.  This command is useful when one do not
                        care about the state of the feature group strings which
                        should be controlled by the OSPM.
                        Examples:
                          1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
                             to 'acpi_osi="Windows 2000" acpi_osi=!', they all
                             can make '_OSI("Windows 2000")' TRUE.

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

                        'acpi_osi=!*' can be used in combination with single or
                        multiple 'acpi_osi="string1"' to support specific
                        string(s).  Note that such command can affect the
                        current state of both the OS vendor strings and the
                        feature group strings, thus specifying it multiple times
                        through kernel command line is meaningful.  But it may
                        still not able to affect the final state of a string if
                        there are quirks related to this string.  This command
                        is useful when one want to control the state of the
                        feature group strings to debug BIOS issues related to
                        the OSPM features.
                        Examples:
                          1. 'acpi_osi="Module Device" acpi_osi=!*' can make
                             '_OSI("Module Device")' FALSE.
                          2. 'acpi_osi=!* acpi_osi="Module Device"' can make
                             '_OSI("Module Device")' TRUE.
                          3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
                             equivalent to
                             'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
                             and
                             'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
                             they all will make '_OSI("Windows 2000")' TRUE.

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

        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
                        Format: { level | edge | high | low }

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

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

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

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

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

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

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

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

                        32: only for 32-bit processes
                        64: only for 64-bit processes
                        on: enable for both 32- and 64-bit processes
                        off: disable for both 32- and 64-bit processes

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

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

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

        amd_iommu_intr= [HW,X86-64]
                        Specifies one of the following AMD IOMMU interrupt
                        remapping modes:
                        legacy     - Use legacy interrupt remapping mode.
                        vapic      - Use virtual APIC mode, which allows IOMMU
                                     to inject interrupts directly into guest.
                                     This mode requires kvm-amd.avic=1.
                                     (Default when IOMMU HW support is present.)

        amijoy.map=     [HW,JOY] Amiga joystick support
                        Map of devices attached to JOY0DAT and JOY1DAT
                        Format: <a>,<b>
                        See also Documentation/input/joystick.txt

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

        apc=            [HW,SPARC]
                        Power management functions (SPARCstation-4/5 + deriv.)
                        Format: noidle
                        Disable APC CPU standby support. SPARCstation-Fox does
                        not play well with APC CPU idle - disable it if you have
                        APC and your system crashes randomly.

        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
                        Change the output verbosity whilst booting
                        Format: { quiet (default) | verbose | debug }
                        Change the amount of debugging information output
                        when initialising the APIC and IO-APIC components.

        apic_extnmi=    [APIC,X86] External NMI delivery setting
                        Format: { bsp (default) | all | none }
                        bsp:  External NMI is delivered only to CPU 0
                        all:  External NMIs are broadcast to all CPUs as a
                              backup of CPU 0
                        none: External NMI is masked for all CPUs. This is
                              useful so that a dump capture kernel won't be
                              shot down by NMI

        autoconf=       [IPV6]
                        See Documentation/networking/ipv6.txt.

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

        apm=            [APM] Advanced Power Management
                        See header of arch/x86/kernel/apm_32.c.

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

        ataflop=        [HW,M68k]

        atarimouse=     [HW,MOUSE] Atari Mouse

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

        atkbd.reset=    [HW] Reset keyboard during initialization

        atkbd.set=      [HW] Select keyboard code set
                        Format: <int> (2 = AT (default), 3 = PS/2)

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

        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
                        Format: <bool> (0 = real, 1 = synthetic (default))

        atkbd.softrepeat= [HW]
                        Use software keyboard repeat

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

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

        bau=            [X86_UV] Enable the BAU on SGI UV.  The default
                        behavior is to disable the BAU (i.e. bau=0).
                        Format: { "0" | "1" }
                        0 - Disable the BAU.
                        1 - Enable the BAU.
                        unset - Disable the BAU.

        baycom_epp=     [HW,AX25]
                        Format: <io>,<mode>

        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
                        Format: <io>,<mode>
                        See header of drivers/net/hamradio/baycom_par.c.

        baycom_ser_fdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
                        Format: <io>,<irq>,<mode>[,<baud>]
                        See header of drivers/net/hamradio/baycom_ser_fdx.c.

        baycom_ser_hdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
                        Format: <io>,<irq>,<mode>
                        See header of drivers/net/hamradio/baycom_ser_hdx.c.

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

        boot_delay=     Milliseconds to delay each printk during boot.
                        Values larger than 10 seconds (10000) are changed to
                        no delay (0).
                        Format: integer

        bootmem_debug   [KNL] Enable bootmem allocator debug messages.

        bert_disable    [ACPI]
                        Disable BERT OS support on buggy BIOSes.

        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
        bttv.radio=     Most important insmod options are available as
                        kernel args too.
        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
        bttv.tuner=

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

        c101=           [NET] Moxa C101 synchronous serial card

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

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

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

        ccw_timeout_log [S390]
                        See Documentation/s390/CommonIO for details.

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

        cgroup_no_v1=   [KNL] Disable one, multiple, all cgroup controllers in v1
                        Format: { controller[,controller...] | "all" }
                        Like cgroup_disable, but only applies to cgroup v1;
                        the blacklisted controllers remain available in cgroup2.

        cgroup.memory=  [KNL] Pass options to the cgroup memory controller.
                        Format: <string>
                        nosocket -- Disable socket memory accounting.
                        nokmem -- Disable kernel memory accounting.

        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- check protection applied by kernel (includes
                                any implied execute protection).
                        1 -- check protection requested by application.
                        Default value is set via a kernel config option.
                        Value can be changed at runtime via
                                /selinux/checkreqprot.

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

        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
                        [Deprecated]
                        Forces specified clocksource (if available) to be used
                        when calculating gettimeofday(). If specified
                        clocksource is not available, it defaults to PIT.
                        Format: { pit | tsc | cyclone | pmtmr }

        clocksource=    Override the default clocksource
                        Format: <string>
                        Override the default clocksource and use the clocksource
                        with the name specified.
                        Some clocksource names to choose from, depending on
                        the platform:
                        [all] jiffies (this is the base, fallback clocksource)
                        [ACPI] acpi_pm
                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
                                pxa_timer,timer3,32k_counter,timer0_1
                        [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.

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

        com20020=       [HW,NET] ARCnet - COM20020 chipset
                        Format:
                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

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

        com90xx=        [HW,NET]
                        ARCnet - COM90xx chipset (memory-mapped buffers)
                        Format: <io>[,<irq>[,<memstart>]]

        condev=         [HW,S390] console device
        conmode=

        console=        [KNL] Output console device and options.

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

                ttyS<n>[,options]
                ttyUSB0[,options]
                        Use the specified serial port.  The options are of
                        the form "bbbbpnf", where "bbbb" is the baud rate,
                        "p" is parity ("n", "o", or "e"), "n" is number of
                        bits, and "f" is flow control ("r" for RTS or
                        omit it).  Default is "9600n8".

                        See Documentation/admin-guide/serial-console.rst for more
                        information.  See
                        Documentation/networking/netconsole.txt for an
                        alternative.

                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                uart[8250],mmio16,<addr>[,options]
                uart[8250],mmio32,<addr>[,options]
                uart[8250],0x<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address,
                        switching to the matching ttyS device later.
                        MMIO inter-register address stride is either 8-bit
                        (mmio), 16-bit (mmio16), or 32-bit (mmio32).
                        If none of [io|mmio|mmio16|mmio32], <addr> is assumed
                        to be equivalent to 'mmio'. 'options' are specified in
                        the same format described for ttyS above; if unspecified,
                        the h/w is not re-initialized.

                hvc<n>  Use the hypervisor console device <n>. This is for
                        both Xen and PowerPC hypervisors.

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

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

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

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

        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. Check
                        Documentation/kdump/kdump.txt for further details.

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

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

        cryptomgr.notests
                        [KNL] Disable crypto self-tests

        cs89x0_dma=     [HW,NET]
                        Format: <dma>

        cs89x0_media=   [HW,NET]
                        Format: { rj45 | aui | bnc }

        dasd=           [HW,NET]
                        See header of drivers/s390/block/dasd_devmap.c.

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

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

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

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

        debug_objects   [KNL] Enable object debugging

        no_debug_objects
                        [KNL] Disable object debugging

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

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

        debugpat        [X86] Enable PAT debugging

        decnet.addr=    [HW,NET]
                        Format: <area>[,<node>]
                        See also Documentation/networking/decnet.txt.

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

        dhash_entries=  [KNL]
                        Set number of hash buckets for dentry cache.

        disable_1tb_segments [PPC]
                        Disables the use of 1TB hash page table segments. This
                        causes the kernel to fall back to 256MB segments which
                        can be useful when debugging issues that require an SLB
                        miss to occur.

        disable=        [IPV6]
                        See Documentation/networking/ipv6.txt.

        disable_radix   [PPC]
                        Disable RADIX MMU mode on POWER9

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

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

        disable_ipv6=   [IPV6]
                        See Documentation/networking/ipv6.txt.

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

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

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

        dis_ucode_ldr   [X86] Disable the microcode loader.

        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
                        this option disables the debugging code at boot.

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

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

        drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
                        Broken monitors, graphic adapters, KVMs and EDIDless
                        panels may send no or incorrect EDID data sets.
                        This parameter allows to specify an EDID data sets
                        in the /lib/firmware directory that are used instead.
                        Generic built-in EDID data sets are used, if one of
                        edid/1024x768.bin, edid/1280x1024.bin,
                        edid/1680x1050.bin, or edid/1920x1080.bin is given
                        and no file with the same name exists. Details and
                        instructions how to build your own EDID data are
                        available in Documentation/EDID/HOWTO.txt. An EDID
                        data set will only be used for a particular connector,
                        if its name and a colon are prepended to the EDID
                        name. Each connector may use a unique EDID data
                        set by separating the files with a comma.  An EDID
                        data set with no connector name will be used for
                        any connectors not explicitly specified.

        dscc4.setup=    [NET]

        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/dynamic-debug-howto.txt for details.

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

        nopku           [X86] Disable Memory Protection Keys CPU feature found
                        in some Intel CPUs.

        module.async_probe [KNL]
                        Enable asynchronous probe on this module.

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

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

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

                cdns,<addr>[,options]
                        Start an early, polled-mode console on a Cadence
                        (xuartps) serial port at the specified address. Only
                        supported option is baud rate. If baud rate is not
                        specified, the serial port must already be setup and
                        configured.

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

                pl011,<addr>
                pl011,mmio32,<addr>
                        Start an early, polled-mode console on a pl011 serial
                        port at the specified address. The pl011 serial port
                        must already be setup and configured. Options are not
                        yet supported.  If 'mmio32' is specified, then only
                        the driver will use only 32-bit accessors to read/write
                        the device registers.

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

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

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

                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.

        earlyprintk=    [X86,SH,BLACKFIN,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" }
                        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

        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 /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/joystick-parport.txt

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

        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.

        hwthread_map=   [METAG] Comma-separated list of Linux cpu id to
                                hardware thread id mappings.
                                Format: <cpu>:<hwthread>

        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 measurement policy to load during IMA
                        setup.  Specyfing "tcb" as the value, measures all
                        programs exec'd, files mmap'd for exec, and all files
                        opened with the read mode bit set by either the
                        effective uid (euid=0) or uid=0.
                        Format: "tcb"

        ima_tcb         [IMA] Deprecated.  Use ima_policy= instead.
                        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.
                ecs_off [Default Off]
                        By default, extended context tables will be supported if
                        the hardware advertises that it has support both for the
                        extended tables themselves, and also PASID support. With
                        this option set, extended tables will not be used even
                        on hardware which claims to support them.
                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.

        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
                forcesac
                soft
                pt              [x86, IA-64]
                nobypass        [PPC/POWERNV]
                        Disable IOMMU bypass, using IOMMU for PCI devices.

        iommu.passthrough=
                        [ARM64] 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 IOMMU translation for DMA.

        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.

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

        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] Isolate CPUs from the general scheduler.
                        The argument is a cpu list, as described above.

                        This option can be used to specify one or more CPUs
                        to isolate from the general SMP balancing and scheduling
                        algorithms. 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".

                        This option is the preferred way to isolate CPUs. The
                        alternative -- manually setting the CPU mask of all
                        tasks in the system -- can cause problems and
                        suboptimal load balancer performance.

        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/joystick.txt.

        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] | "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. The
                        remaining memory in each node is used for Movable
                        pages. In the event, a node is too small to have both
                        kernelcore and Movable pages, kernelcore pages will
                        take priority and other nodes will have a larger number
                        of Movable pages.  The Movable zone is used for the
                        allocation of pages that may be reclaimed or moved
                        by the page migration subsystem.  This means that
                        HugeTLB pages may not be allocated from this zone.
                        Note that allocations like PTEs-from-HighMem still
                        use the HighMem zone if it exists, and the Normal
                        zone if it does not.

                        Instead of specifying the amount of memory (nn[KMGTPE]),
                        you can specify "mirror" option. In case "mirror"
                        option is specified, mirrored (reliable) memory is used
                        for non-movable allocations and remaining memory is used
                        for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
                        so you can NOT specify nn[KMGTPE] and "mirror" at the same
                        time.

        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.

        kmemcheck=      [X86] Boot-time kmemcheck enable/disable/one-shot mode
                        Valid arguments: 0, 1, 2
                        kmemcheck=0 (disabled)
                        kmemcheck=1 (enabled)
                        kmemcheck=2 (one-shot mode)
                        Default: 2 (one-shot mode)

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

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

        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_group1_trap=
                        [KVM,ARM] Trap guest accesses to GICv3 group-1
                        system registers

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

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

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

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

        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.

        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        Amount of memory to be used when the kernel is not able
                        to see the whole system memory or for test.
                        [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.

        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.

        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

        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.

        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_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/power/states.txt.

        meye.*=         [HW] Set MotionEye Camera parameters
                        See Documentation/video4linux/meye.txt.

        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

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

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

        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.

        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.

        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.

        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]

        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.

        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]
                        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.
                        The CPUs in this range must also be included in the
                        rcu_nocbs= set.

        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] 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.

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

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

        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.

        notsc           [BUGS=X86-32] Disable Time Stamp Counter

        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.

        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.
                        one of ['zone', '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.

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

        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_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:
                earlydump       [X86] 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>@][<domain>:]<bus>:<slot>.<func>[; ...]
                                [<order of align>@]pci:<vendor>:<device>\
                                                [:<subvendor>:<subdevice>][; ...]
                                Specifies alignment and device to reassign
                                aligned memory resources.
                                If <order of align> is not specified,
                                PAGE_SIZE is used as alignment.
                                PCI-PCI bridge can be specified, if resource
                                windows need to be expanded.
                                To specify the alignment for several
                                instances of a device, the PCI vendor,
                                device, subvendor, and subdevice may be
                                specified, e.g., 4096@pci:8086:9c22:103c:198f
                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.
                hpmemsize=nn[KMG]       The fixed amount of bus space which is
                                reserved for hotplug bridge's memory 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.
                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
                                only look for one device below a PCIe downstream
                                port.

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

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

        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/parport.txt.

        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.

        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: [schedule,]<number>
                        Param: "schedule" - profile schedule points.
                        Param: <number> - step/bucket size as a power of 2 for
                                statistical time based profiling.
                        Param: "sleep" - profile D-state sleeping (millisecs).
                                Requires CONFIG_SCHEDSTATS
                        Param: "kvm" - profile VM exits.

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

        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.

        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.

        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.

                        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 "b" for RCU-bh, "p"
                        for RCU-preempt, and "s" for RCU-sched, and "N"
                        is the CPU number.  This reduces OS jitter on the
                        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.  This only has effect
                        when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.

        rcutree.gp_init_delay=  [KNL]
                        Set the number of jiffies to delay each step of
                        RCU grace-period initialization.  This only has
                        effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
                        is set.

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

        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_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().

        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.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().

        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_runnable= [BOOT]
                        Start rcuperf running at boot time.

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

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

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

        rcutorture.cbflood_inter_holdoff= [KNL]
                        Set holdoff time (jiffies) between successive
                        callback-flood tests.

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

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

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

        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.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 (s) 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.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_runnable= [BOOT]
                        Start rcutorture running at boot time.

        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

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

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

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

        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 the kernel to ignore some iomem area

        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.txt

        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 set via kernel config option.
                        If enabled at boot time, /selinux/disable can be used
                        later to disable prior to initial policy load.

        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. Debug options disable
                        merging on their own.
                        For more information see Documentation/vm/slub.txt.

        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.txt.

        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.txt.

        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.txt.

        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.txt.

        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>

        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

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

        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.

        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.

        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.txt

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

                            /sys/kernel/debug/tracing/trace_options

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

                              trace_options=stacktrace

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

        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/vm/transhuge.txt 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.

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

        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.

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

        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 (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

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

        usbhid.jspoll=
                        [USBHID] The interval which joysticks 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.

        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.

        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.txt
                        or other driver-specific files in the
                        Documentation/watchdog/ directory.

        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.

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