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authorLinus Torvalds <torvalds@linux-foundation.org>2019-11-26 21:11:01 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-11-26 21:11:01 +0300
commit53a07a148fd05dc6d317745688270bc79fe73121 (patch)
treebbe1eca87d45a6d96e38e6821f84d478466d403a /Documentation
parentda42761df5ceed2f8b0527bc4c1b2760be45ddb9 (diff)
parentcd5a2aa89e847bdda7b62029d94e95488d73f6b2 (diff)
downloadlinux-53a07a148fd05dc6d317745688270bc79fe73121.tar.xz
Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 PTI updates from Ingo Molnar: "Fix reporting bugs of the MDS and TAA mitigation status, if one or both are set via a boot option. No change to mitigation behavior intended" * 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/speculation: Fix redundant MDS mitigation message x86/speculation: Fix incorrect MDS/TAA mitigation status
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/hw-vuln/mds.rst7
-rw-r--r--Documentation/admin-guide/hw-vuln/tsx_async_abort.rst5
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt11
3 files changed, 20 insertions, 3 deletions
diff --git a/Documentation/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst
index e3a796c0d3a2..2d19c9f4c1fe 100644
--- a/Documentation/admin-guide/hw-vuln/mds.rst
+++ b/Documentation/admin-guide/hw-vuln/mds.rst
@@ -265,8 +265,11 @@ time with the option "mds=". The valid arguments for this option are:
============ =============================================================
-Not specifying this option is equivalent to "mds=full".
-
+Not specifying this option is equivalent to "mds=full". For processors
+that are affected by both TAA (TSX Asynchronous Abort) and MDS,
+specifying just "mds=off" without an accompanying "tsx_async_abort=off"
+will have no effect as the same mitigation is used for both
+vulnerabilities.
Mitigation selection guide
--------------------------
diff --git a/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst b/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
index fddbd7579c53..af6865b822d2 100644
--- a/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
+++ b/Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
@@ -174,7 +174,10 @@ the option "tsx_async_abort=". The valid arguments for this option are:
CPU is not vulnerable to cross-thread TAA attacks.
============ =============================================================
-Not specifying this option is equivalent to "tsx_async_abort=full".
+Not specifying this option is equivalent to "tsx_async_abort=full". For
+processors that are affected by both TAA and MDS, specifying just
+"tsx_async_abort=off" without an accompanying "mds=off" will have no
+effect as the same mitigation is used for both vulnerabilities.
The kernel command line also allows to control the TSX feature using the
parameter "tsx=" on CPUs which support TSX control. MSR_IA32_TSX_CTRL is used
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9b847f06cb19..a0a4732eedbb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2473,6 +2473,12 @@
SMT on vulnerable CPUs
off - Unconditionally disable MDS mitigation
+ On TAA-affected machines, mds=off can be prevented by
+ an active TAA mitigation as both vulnerabilities are
+ mitigated with the same mechanism so in order to disable
+ this mitigation, you need to specify tsx_async_abort=off
+ too.
+
Not specifying this option is equivalent to
mds=full.
@@ -4931,6 +4937,11 @@
vulnerable to cross-thread TAA attacks.
off - Unconditionally disable TAA mitigation
+ On MDS-affected machines, tsx_async_abort=off can be
+ prevented by an active MDS mitigation as both vulnerabilities
+ are mitigated with the same mechanism so in order to disable
+ this mitigation, you need to specify mds=off too.
+
Not specifying this option is equivalent to
tsx_async_abort=full. On CPUs which are MDS affected
and deploy MDS mitigation, TAA mitigation is not