Messages in this thread |  | | Date | Thu, 18 Jan 2018 19:46:25 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH 29/35] x86/speculation: Add IPBP support |
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On Thu, Jan 18, 2018 at 12:35:23PM -0600, Josh Poimboeuf wrote: > Maybe I missed the memo, why do we need both X86_FEATURE_IBPB and > X86_FEATURE_AMD_IBPB?
So AMD_IBPB is a different CPUID bit in a different CPUID function and on Intel, IBPB is set only when X86_FEATURE_SPEC_CTRL - see specctrl_init_ibpb() in that same patch.
IOW, CPUID(7).EDAC[26] means both IBRS and IBPB on Intel.
So, in the end of the day, X86_FEATURE_IBPB is the feature bit we'll be testing and X86_FEATURE_AMD_IBPB is used only to set X86_FEATURE_IBPB.
:-)
More confused?
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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