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Kim Phillips authored
AMD's "Technical Guidance for Mitigating Branch Type Confusion, Rev. 1.0 2022-07-12" whitepaper, under section 6.1.2 "IBPB On Privileged Mode Entry / SMT Safety" says: Similar to the Jmp2Ret mitigation, if the code on the sibling thread cannot be trusted, software should set STIBP to 1 or disable SMT to ensure SMT safety when using this mitigation. So, like already being done for retbleed=unret, and now also for retbleed=ibpb, force STIBP on machines that have it, and report its SMT vulnerability status accordingly. [ bp: Remove the "we" and remove "[AMD]" applicability parameter which doesn't work here. ] Fixes: 3ebc1700 ("x86/bugs: Add retbleed=ibpb") Signed-off-by:
Kim Phillips <kim.phillips@amd.com> Signed-off-by:
Borislav Petkov <bp@suse.de> Cc: stable@vger.kernel.org # 5.10, 5.15, 5.19 Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 Link: https://lore.kernel.org/r/20220804192201.439596-1-kim.phillips@amd.com
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