Merge branches 'x86/early-printk', 'x86/microcode' and 'core/objtool' into x86/urgent...
[sfrench/cifs-2.6.git] / Documentation / admin-guide / kernel-parameters.txt
index 9871e649ffeffe8798cd20a1450377a4f4777fca..81d1d5a7472804e50a663480ef92dc67abc71ab5 100644 (file)
                        causing system reset or hang due to sending
                        INIT from AP to BSP.
 
+       disable_counter_freezing [HW]
+                       Disable Intel PMU counter freezing feature.
+                       The feature only exists starting from
+                       Arch Perfmon v4 (Skylake and newer).
+
        disable_ddw     [PPC/PSERIES]
                        Disable Dynamic DMA Window support. Use this if
                        to workaround buggy firmware.
                        earlyprintk=serial[,0x...[,baudrate]]
                        earlyprintk=ttySn[,baudrate]
                        earlyprintk=dbgp[debugController#]
-                       earlyprintk=pciserial,bus:device.function[,baudrate]
+                       earlyprintk=pciserial[,force],bus:device.function[,baudrate]
                        earlyprintk=xdbc[xhciController#]
 
                        earlyprintk is useful when the kernel crashes before
 
                        The sclp output can only be used on s390.
 
+                       The optional "force" to "pciserial" enables use of a
+                       PCI device even when its classcode is not of the
+                       UART class.
+
        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
        hvc_iucv_allow= [S390]  Comma-separated list of z/VM user IDs.
                                If specified, z/VM IUCV HVC accepts connections
                                from listed z/VM user IDs only.
+
+       hv_nopvspin     [X86,HYPER_V] Disables the paravirt spinlock optimizations
+                                     which allow the hypervisor to 'idle' the
+                                     guest on lock contention.
+
        keep_bootcon    [KNL]
                        Do not unregister boot console at start. This is only
                        useful for debugging when something happens in the window
                nobypass        [PPC/POWERNV]
                        Disable IOMMU bypass, using IOMMU for PCI devices.
 
+       iommu.strict=   [ARM64] Configure TLB invalidation behaviour
+                       Format: { "0" | "1" }
+                       0 - Lazy mode.
+                         Request that DMA unmap operations use deferred
+                         invalidation of hardware TLBs, for increased
+                         throughput at the cost of reduced device isolation.
+                         Will fall back to strict mode if not supported by
+                         the relevant IOMMU driver.
+                       1 - Strict mode (default).
+                         DMA unmap operations invalidate IOMMU hardware TLBs
+                         synchronously.
+
        iommu.passthrough=
                        [ARM64] 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.
+                       unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
 
        io7=            [HW] IO7 for Marvel based alpha systems
                        See comment before marvel_specify_io7 in
        ltpc=           [NET]
                        Format: <io>,<irq>,<dma>
 
+       lsm.debug       [SECURITY] Enable LSM initialization debugging output.
+
        machvec=        [IA-64] Force the use of a particular machine-vector
                        (machvec) in a generic kernel.
                        Example: machvec=hpzx1_swiotlb
                        seconds.  Use this parameter to check at some
                        other rate.  0 disables periodic checking.
 
-       memtest=        [KNL,X86,ARM] Enable memtest
+       memtest=        [KNL,X86,ARM,PPC] Enable memtest
                        Format: <integer>
                        default : 0 <disable>
                        Specifies the number of memtest passes to be
        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
                        See Documentation/blockdev/ramdisk.txt.
 
+       random.trust_cpu={on,off}
+                       [KNL] Enable or disable trusting the use of the
+                       CPU's random number generator (if available) to
+                       fully seed the kernel's CRNG. Default is controlled
+                       by CONFIG_RANDOM_TRUST_CPU.
+
        ras=option[,option,...] [KNL] RAS-specific options
 
                cec_disable     [X86]
 
                        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.
+                       Invocation of these CPUs' RCU callbacks will be
+                       offloaded to "rcuox/N" kthreads created for that
+                       purpose, where "x" is "p" for RCU-preempt, and
+                       "s" for RCU-sched, and "N" is the CPU number.
+                       This reduces OS jitter on the offloaded CPUs,
+                       which can be useful for HPC and real-time
+                       workloads.  It can also improve energy efficiency
+                       for asymmetric multiprocessors.
 
        rcu_nocb_poll   [KNL]
                        Rather than requiring that offloaded CPUs
                        Set required age in jiffies for a
                        given grace period before RCU starts
                        soliciting quiescent-state help from
-                       rcu_note_context_switch().
+                       rcu_note_context_switch().  If not specified, the
+                       kernel will calculate a value based on the most
+                       recent settings of rcutree.jiffies_till_first_fqs
+                       and rcutree.jiffies_till_next_fqs.
+                       This calculated value may be viewed in
+                       rcutree.jiffies_to_sched_qs.  Any attempt to
+                       set rcutree.jiffies_to_sched_qs will be
+                       cheerfully overwritten.
 
        rcutree.jiffies_till_first_fqs= [KNL]
                        Set delay from grace-period initialization to
        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,
 
        usbcore.old_scheme_first=
                        [USB] Start with the old device initialization
-                       scheme (default 0 = off).
+                       scheme,  applies only to low and full-speed devices
+                        (default 0 = off).
 
        usbcore.usbfs_memory_mb=
                        [USB] Memory limit (in MB) for buffers allocated by
                        This is actually a boot loader parameter; the value is
                        passed to the kernel using a special protocol.
 
+       vm_debug[=options]      [KNL] Available with CONFIG_DEBUG_VM=y.
+                       May slow down system boot speed, especially when
+                       enabled on systems with a large amount of memory.
+                       All options are enabled by default, and this
+                       interface is meant to allow for selectively
+                       enabling or disabling specific virtual memory
+                       debugging features.
+
+                       Available options are:
+                         P     Enable page structure init time poisoning
+                         -     Disable all of the above options
+
        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
                        size of <nn>. This can be used to increase the
                        minimum size (128MB on x86). It can also be used to
                        Disables the PV optimizations forcing the HVM guest to
                        run as generic HVM guest with no PV drivers.
 
+       xen_scrub_pages=        [XEN]
+                       Boolean option to control scrubbing pages before giving them back
+                       to Xen, for use by other domains. Can be also changed at runtime
+                       with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
+                       Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
+
        xirc2ps_cs=     [NET,PCMCIA]
                        Format:
                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]