Merge tag 'docs-4.16' of git://git.lwn.net/linux
[sfrench/cifs-2.6.git] / Documentation / admin-guide / kernel-parameters.txt
index dfb7c35b582678cb78ed6ae477b137b48dcd497a..dc63e5bddf7836aed4f3d3e5b77edf4c469bc7d4 100644 (file)
                        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
 
        acpi_sleep=     [HW,ACPI] Sleep options
                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
-                                 old_ordering, nonvs, sci_force_enable }
+                                 old_ordering, nonvs, sci_force_enable, nobl }
                        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
                        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).
+                       nobl causes the internal blacklist of systems known to
+                       behave incorrectly in some ways with respect to system
+                       suspend and resume to be ignored (use wisely).
 
        acpi_use_timer_override [HW,ACPI]
                        Use timer override. For some broken Nvidia NF5 boards
                        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
+       apic=           [APIC,X86] 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.
+                       For X86-32, this can also be used to specify an APIC
+                       driver name.
+                       Format: apic=driver_name
+                       Examples: apic=bigsmp
 
        apic_extnmi=    [APIC,X86] External NMI delivery setting
                        Format: { bsp (default) | all | none }
                        It will be ignored when crashkernel=X,high is not used
                        or memory reserved is below 4G.
 
-       crossrelease_fullstack
-                       [KNL] Allow to record full stack trace in cross-release
-
        cryptomgr.notests
                         [KNL] Disable crypto self-tests
 
        isapnp=         [ISAPNP]
                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 
-       isolcpus=       [KNL,SMP] Isolate a given set of CPUs from disturbance.
+       isolcpus=       [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
                        [Deprecated - use cpusets instead]
                        Format: [flag-list,]<cpu-list>
 
                        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.
 
        nosmt           [KNL,S390] Disable symmetric multithreading (SMT).
                        Equivalent to smt=1.
 
+       nospectre_v2    [X86] Disable all mitigations for the Spectre variant 2
+                       (indirect branch prediction) vulnerability. System may
+                       allow data leaks with this option, which is equivalent
+                       to spectre_v2=off.
+
        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.
                        Valid arguments: on, off
                        Default: on
 
-       nohz_full=      [KNL,BOOT]
+       nohz_full=      [KNL,BOOT,SMP,ISOL]
                        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
                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
                                only look for one device below a PCIe downstream
                                port.
+               big_root_window Try to add a big 64bit memory window to the PCIe
+                               root complex on AMD CPUs. Some GFX hardware
+                               can resize a BAR to allow access to all VRAM.
+                               Adding the window is slightly risky (it may
+                               conflict with unreported devices), so this
+                               taints the kernel.
 
        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
                        Management.
        pt.             [PARIDE]
                        See Documentation/blockdev/paride.txt.
 
+       pti=            [X86_64] Control Page Table Isolation of user and
+                       kernel address spaces.  Disabling this feature
+                       removes hardening, but improves performance of
+                       system calls and interrupts.
+
+                       on   - unconditionally enable
+                       off  - unconditionally disable
+                       auto - kernel detects whether your CPU model is
+                              vulnerable to issues that PTI mitigates
+
+                       Not specifying this option is equivalent to pti=auto.
+
+       nopti           [X86_64]
+                       Equivalent to pti=off
+
        pty.legacy_count=
                        [KNL] Number of legacy pty's. Overwrites compiled-in
                        default number.
                        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.perf_type= [KNL]
                        Specify the RCU implementation to test.
 
                        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.
 
 
        rdt=            [HW,X86,RDT]
                        Turn on/off individual RDT features. List is:
-                       cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, mba.
+                       cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
+                       mba.
                        E.g. to turn on cmt and turn off mba use:
                                rdt=cmt,!mba
 
        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
                        See Documentation/laptops/sonypi.txt
 
+       spectre_v2=     [X86] Control mitigation of Spectre variant 2
+                       (indirect branch speculation) vulnerability.
+
+                       on   - unconditionally enable
+                       off  - unconditionally disable
+                       auto - kernel detects whether your CPU model is
+                              vulnerable
+
+                       Selecting 'on' will, and 'auto' may, choose a
+                       mitigation method at run time according to the
+                       CPU, the available microcode, the setting of the
+                       CONFIG_RETPOLINE configuration option, and the
+                       compiler with which the kernel was built.
+
+                       Specific mitigations can also be selected manually:
+
+                       retpoline         - replace indirect branches
+                       retpoline,generic - google's original retpoline
+                       retpoline,amd     - AMD-specific minimal thunk
+
+                       Not specifying this option is equivalent to
+                       spectre_v2=auto.
+
        spia_io_base=   [HW,MTD]
        spia_fio_base=
        spia_pedr=