Merge tag 'docs-5.12' of git://git.lwn.net/linux
[sfrench/cifs-2.6.git] / Documentation / admin-guide / kernel-parameters.txt
index e938ccf3dad31a667b301afbb174a5ad4b8677ed..52f8233f8bb8efbad5d05f2bfb55e927f95de469 100644 (file)
        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
                        Format: <io>,<irq>,<nodeID>
 
+       arm64.nobti     [ARM64] Unconditionally disable Branch Target
+                       Identification support
+
+       arm64.nopauth   [ARM64] Unconditionally disable Pointer Authentication
+                       support
+
        ataflop=        [HW,M68k]
 
        atarimouse=     [HW,MOUSE] Atari Mouse
                        insecure, please do not use on production kernels.
 
        debug_locks_verbose=
-                       [KNL] verbose self-tests
-                       Format=<0|1>
+                       [KNL] verbose locking self-tests
+                       Format: <int>
                        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.
+                       Bitmask for the various LOCKTYPE_ tests. Defaults to 0
+                       (no extra messages), setting it to -1 (all bits set)
+                       will print _a_lot_ more information - normally only
+                       useful to lockdep developers.
 
        debug_objects   [KNL] Enable object debugging
 
                        causing system reset or hang due to sending
                        INIT from AP to BSP.
 
-       perf_v4_pmi=    [X86,INTEL]
-                       Format: <bool>
-                       Disable Intel PMU counter freezing feature.
-                       The feature only exists starting from
-                       Arch Perfmon v4 (Skylake and newer).
-
        disable_ddw     [PPC/PSERIES]
                        Disable Dynamic DMA Window support. Use this
                        to workaround buggy firmware.
        ima_policy=     [IMA]
                        The builtin policies to load during IMA setup.
                        Format: "tcb | appraise_tcb | secure_boot |
-                                fail_securely"
+                                fail_securely | critical_data"
 
                        The "tcb" policy measures all programs exec'd, files
                        mmap'd for exec, and all files opened with the read
                        filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
                        flag.
 
+                       The "critical_data" policy measures kernel integrity
+                       critical data.
+
        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
        kvm-arm.mode=
                        [KVM,ARM] Select one of KVM/arm64's modes of operation.
 
+                       nvhe: Standard nVHE-based mode, without support for
+                             protected guests.
+
                        protected: nVHE-based mode with support for guests whose
                                   state is kept private from the host.
                                   Not valid if the kernel is running in EL2.
                        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.
                        Format: {"off"}
                        Disable Hardware Transactional Memory
 
+       preempt=        [KNL]
+                       Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
+                       none - Limited to cond_resched() calls
+                       voluntary - Limited to cond_resched() and might_sleep() calls
+                       full - Any section that isn't explicitly preempt disabled
+                              can be preempted anytime.
+
        print-fatal-signals=
                        [KNL] debug: print fatal signals
 
                        value, meaning that RCU_SOFTIRQ is used by default.
                        Specify rcutree.use_softirq=0 to use rcuc kthreads.
 
+                       But note that CONFIG_PREEMPT_RT=y kernels disable
+                       this kernel boot parameter, forcibly setting it
+                       to zero.
+
        rcutree.rcu_fanout_exact= [KNL]
                        Disable autobalancing of the rcu_node combining
                        tree.  This is used by rcutorture, and might
                        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
                        stress RCU, they don't participate in the actual
                        test, hence the "fake".
 
+       rcutorture.nocbs_nthreads= [KNL]
+                       Set number of RCU callback-offload togglers.
+                       Zero (the default) disables toggling.
+
+       rcutorture.nocbs_toggle= [KNL]
+                       Set the delay in milliseconds between successive
+                       callback-offload toggling attempts.
+
        rcutorture.nreaders= [KNL]
                        Set number of RCU readers.  The value -1 selects
                        N-1, where N is the number of CPUs.  A value
                        only normal grace-period primitives.  No effect
                        on CONFIG_TINY_RCU kernels.
 
+                       But note that CONFIG_PREEMPT_RT=y kernels enables
+                       this kernel boot parameter, forcibly setting
+                       it to the value one, that is, converting any
+                       post-boot attempt at an expedited RCU grace
+                       period to instead use normal non-expedited
+                       grace-period processing.
+
        rcupdate.rcu_task_ipi_delay= [KNL]
                        Set time in jiffies during which RCU tasks will
                        avoid sending IPIs, starting with the beginning
        refscale.verbose= [KNL]
                        Enable additional printk() statements.
 
+       refscale.verbose_batched= [KNL]
+                       Batch the additional printk() statements.  If zero
+                       (the default) or negative, print everything.  Otherwise,
+                       print every Nth verbose statement, where N is the value
+                       specified.
+
        relax_domain_level=
                        [KNL, SMP] Set scheduler's default relax_domain_level.
                        See Documentation/admin-guide/cgroup-v1/cpusets.rst.
                        are running concurrently, especially on systems
                        with rotating-rust storage.
 
+       torture.verbose_sleep_frequency= [KNL]
+                       Specifies how many verbose printk()s should be
+                       emitted between each sleep.  The default of zero
+                       disables verbose-printk() sleeping.
+
+       torture.verbose_sleep_duration= [KNL]
+                       Duration of each verbose-printk() sleep in jiffies.
+
        tp720=          [HW,PS2]
 
        tpm_suspend_pcr=[HW,TPM]
                        This option is obsoleted by the "nopv" option, which
                        has equivalent effect for XEN platform.
 
+       xen_no_vector_callback
+                       [KNL,X86,XEN] Disable the vector callback for Xen
+                       event channel interrupts.
+
        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