cpu/speculation: Add 'mitigations=' cmdline option

[mirror_ubuntu-bionic-kernel.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index eb2b0ca22bd120477564f8f73f769142a1db4740..811a524411a8a0f03d8a0a181926be02785d98bc 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2423,6 +2423,30 @@
                        in the "bleeding edge" mini2440 support kernel at
                        http://repo.or.cz/w/linux-2.6/mini2440.git
 
+       mitigations=
+                       Control optional mitigations for CPU vulnerabilities.
+                       This is a set of curated, arch-independent options, each
+                       of which is an aggregation of existing arch-specific
+                       options.
+
+                       off
+                               Disable all optional CPU mitigations.  This
+                               improves system performance, but it may also
+                               expose users to several CPU vulnerabilities.
+
+                       auto (default)
+                               Mitigate all CPU vulnerabilities, but leave SMT
+                               enabled, even if it's vulnerable.  This is for
+                               users who don't want to be surprised by SMT
+                               getting disabled across kernel upgrades, or who
+                               have other ways of avoiding SMT-based attacks.
+                               This is the default behavior.
+
+                       auto,nosmt
+                               Mitigate all CPU vulnerabilities, disabling SMT
+                               if needed.  This is for users who always want to
+                               be fully mitigated, even if it means losing SMT.
+
        mminit_loglevel=
                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
                        parameter allows control of the logging verbosity for