Merge tag 'driver-core-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...
[platform/kernel/linux-rpi.git] / Documentation / admin-guide / kernel-parameters.txt
index 692b636..da949b2 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
                        kernel/dma/contiguous.c
 
        cma_pernuma=nn[MG]
-                       [ARM64,KNL]
+                       [ARM64,KNL,CMA]
                        Sets the size of kernel per-numa memory area for
                        contiguous memory allocations. A value of 0 disables
                        per-numa CMA altogether. And If this option is not
                        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.
        hpet_mmap=      [X86, HPET_MMAP] Allow userspace to mmap HPET
                        registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
 
-       hugetlb_cma=    [HW] The size of a cma area used for allocation
+       hugetlb_cma=    [HW,CMA] The size of a CMA area used for allocation
                        of gigantic hugepages.
                        Format: nn[KMGTPE]
 
-                       Reserve a cma area of given size and allocate gigantic
-                       hugepages using the cma allocator. If enabled, the
+                       Reserve a CMA area of given size and allocate gigantic
+                       hugepages using the CMA allocator. If enabled, the
                        boot-time allocation of gigantic hugepages is skipped.
 
        hugepages=      [HW] Number of HugeTLB pages to allocate at boot.
                        In such case C2/C3 won't be used again.
                        idle=nomwait: Disable mwait for CPU C-states
 
+       idxd.sva=       [HW]
+                       Format: <bool>
+                       Allow force disabling of Shared Virtual Memory (SVA)
+                       support for the idxd driver. By default it is set to
+                       true (1).
+
        ieee754=        [MIPS] Select IEEE Std 754 conformance mode
                        Format: { strict | legacy | 2008 | relaxed }
                        Default: strict
        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.
                        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.
+       nohlt           [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
+                       in do_idle() and not use the arch_cpu_idle()
+                       implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
+                       to be effective. This is useful on platforms where the
+                       sleep(SH) or wfi(ARM,ARM64) instructions do not work
+                       correctly or when doing power measurements to evalute
+                       the impact of the sleep instructions. 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
                        in certain environments such as networked servers or
                        real-time systems.
 
+       no_hash_pointers
+                       Force pointers printed to the console or buffers to be
+                       unhashed.  By default, when a pointer is printed via %p
+                       format string, that pointer is "hashed", i.e. obscured
+                       by hashing the pointer value.  This is a security feature
+                       that hides actual kernel addresses from unprivileged
+                       users, but it also makes debugging the kernel more
+                       difficult since unequal pointers can no longer be
+                       compared.  However, if this command-line option is
+                       specified, then all normal pointers will have their true
+                       value printed.  Pointers printed via %pK may still be
+                       hashed.  This option should only be specified when
+                       debugging the kernel.  Please do not use on production
+                       kernels.
+
        nohibernate     [HIBERNATION] Disable hibernation and resume.
 
        nohz=           [KNL] Boottime enable/disable dynamic ticks
                        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]