diff options
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 29 |
1 files changed, 21 insertions, 8 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 5e9147fe8968..523b19624026 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5209,20 +5209,33 @@ Speculative Code Execution with Return Instructions) vulnerability. + AMD-based UNRET and IBPB mitigations alone do not stop + sibling threads from influencing the predictions of other + sibling threads. For that reason, STIBP is used on pro- + cessors that support it, and mitigate SMT on processors + that don't. + off - no mitigation auto - automatically select a migitation auto,nosmt - automatically select a mitigation, disabling SMT if necessary for the full mitigation (only on Zen1 and older without STIBP). - ibpb - mitigate short speculation windows on - basic block boundaries too. Safe, highest - perf impact. - unret - force enable untrained return thunks, - only effective on AMD f15h-f17h - based systems. - unret,nosmt - like unret, will disable SMT when STIBP - is not available. + ibpb - On AMD, mitigate short speculation + windows on basic block boundaries too. + Safe, highest perf impact. It also + enables STIBP if present. Not suitable + on Intel. + ibpb,nosmt - Like "ibpb" above but will disable SMT + when STIBP is not available. This is + the alternative for systems which do not + have STIBP. + unret - Force enable untrained return thunks, + only effective on AMD f15h-f17h based + systems. + unret,nosmt - Like unret, but will disable SMT when STIBP + is not available. This is the alternative for + systems which do not have STIBP. Selecting 'auto' will choose a mitigation method at run time according to the CPU. |