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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-11-26 21:11:01 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-11-26 21:11:01 +0300 |
| commit | 53a07a148fd05dc6d317745688270bc79fe73121 (patch) | |
| tree | bbe1eca87d45a6d96e38e6821f84d478466d403a /Documentation | |
| parent | da42761df5ceed2f8b0527bc4c1b2760be45ddb9 (diff) | |
| parent | cd5a2aa89e847bdda7b62029d94e95488d73f6b2 (diff) | |
| download | linux-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.rst | 7 | ||||
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/tsx_async_abort.rst | 5 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 11 |
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 |