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 34e6800dea0eed64c30d97a205c8b86014f307d1..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.
        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
 
                        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