Merge tag 'x86-bugs-2022-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux-block.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8090130b544b0701237a7b657a29c83c000a60f4..bba2f27d73582e2f9df6bd095b26531848e68e1f 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3176,6 +3176,7 @@
                                               srbds=off [X86,INTEL]
                                               no_entry_flush [PPC]
                                               no_uaccess_flush [PPC]
+                                              mmio_stale_data=off [X86]
 
                                Exceptions:
                                               This does not have any effect on
@@ -3197,6 +3198,7 @@
                                Equivalent to: l1tf=flush,nosmt [X86]
                                               mds=full,nosmt [X86]
                                               tsx_async_abort=full,nosmt [X86]
+                                              mmio_stale_data=full,nosmt [X86]
 
        mminit_loglevel=
                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
@@ -3206,6 +3208,40 @@
                        log everything. Information is printed at KERN_DEBUG
                        so loglevel=8 may also need to be specified.
 
+       mmio_stale_data=
+                       [X86,INTEL] Control mitigation for the Processor
+                       MMIO Stale Data vulnerabilities.
+
+                       Processor MMIO Stale Data is a class of
+                       vulnerabilities that may expose data after an MMIO
+                       operation. Exposed data could originate or end in
+                       the same CPU buffers as affected by MDS and TAA.
+                       Therefore, similar to MDS and TAA, the mitigation
+                       is to clear the affected CPU buffers.
+
+                       This parameter controls the mitigation. The
+                       options are:
+
+                       full       - Enable mitigation on vulnerable CPUs
+
+                       full,nosmt - Enable mitigation and disable SMT on
+                                    vulnerable CPUs.
+
+                       off        - Unconditionally disable mitigation
+
+                       On MDS or TAA affected machines,
+                       mmio_stale_data=off can be prevented by an active
+                       MDS or TAA mitigation as these vulnerabilities are
+                       mitigated with the same mechanism so in order to
+                       disable this mitigation, you need to specify
+                       mds=off and tsx_async_abort=off too.
+
+                       Not specifying this option is equivalent to
+                       mmio_stale_data=full.
+
+                       For details see:
+                       Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
+
        module.sig_enforce
                        [KNL] When CONFIG_MODULE_SIG is set, this means that
                        modules without (valid) signatures will fail to load.