Merge tag 'docs-4.12-2' of git://git.lwn.net/linux
[sfrench/cifs-2.6.git] / Documentation / admin-guide / kernel-parameters.txt
index 230b03caee5587df8d8e5801c795437785a7b412..15f79c27748df1611b1643b77ca68e2a5e7cfaab 100644 (file)
                        extended tables themselves, and also PASID support. With
                        this option set, extended tables will not be used even
                        on hardware which claims to support them.
+               tboot_noforce [Default Off]
+                       Do not force the Intel IOMMU enabled under tboot.
+                       By default, tboot will force Intel IOMMU on, which
+                       could harm performance of some high-throughput
+                       devices like 40GBit network cards, even if identity
+                       mapping is enabled.
+                       Note that using this option lowers the security
+                       provided by tboot because it makes the system
+                       vulnerable to DMA attacks.
 
        intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
                        0       disables intel_idle and fall back on acpi_idle.
                nobypass        [PPC/POWERNV]
                        Disable IOMMU bypass, using IOMMU for PCI devices.
 
+       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.
 
        io7=            [HW] IO7 for Marvel based alpha systems
                        See comment before marvel_specify_io7 in
                        and gids from such clients.  This is intended to ease
                        migration from NFSv2/v3.
 
-       objlayoutdriver.osd_login_prog=
-                       [NFS] [OBJLAYOUT] sets the pathname to the program which
-                       is used to automatically discover and login into new
-                       osd-targets. Please see:
-                       Documentation/filesystems/pnfs.txt for more explanations
-
        nmi_debug=      [KNL,SH] Specify one or more actions to take
                        when a NMI is triggered.
                        Format: [state][,regs][,debounce][,die]
        spia_pedr=
        spia_peddr=
 
+       srcutree.exp_holdoff [KNL]
+                       Specifies how many nanoseconds must elapse
+                       since the end of the last SRCU grace period for
+                       a given srcu_struct until the next normal SRCU
+                       grace period will be considered for automatic
+                       expediting.  Set to zero to disable automatic
+                       expediting.
+
        stacktrace      [FTRACE]
                        Enabled the stack tracer on boot up.