On 1/26/2018 12:49 PM, Borislav Petkov wrote: > On Fri, Jan 26, 2018 at 06:45:18PM +0000, David Woodhouse wrote: >> On Fri, 2018-01-26 at 19:41 +0100, Borislav Petkov wrote: >>> +#define X86_FEATURE_AMD_IBPB (13*32+12) /* "" Indirect Branch >>> Prediction Barrier MSR */ >> >> Stray quotes. > > No no, those quotes are magical. :) > > They don't show the string in /proc/cpuinfo, see > arch/x86/kernel/cpu/mkcapflags.sh > >>> +#define X86_FEATURE_IBRS (13*32+14) /* Indirect Branch >>> Restricted Speculation */ >> >> Please don't call it that. Call it X86_FEATURE_AMD_IBRS and leave >> X86_FEATURE_IBRS to parallel X86_FEATURE_IBPB as the *software* bit >> which is vendor-independent. > > Do we have a X86_FEATURE_IBRS bit? > > If so, then this bit should become > > #define X86_FEATURE_AMD_IBRS (13*32+14) /* "" Speculation Control MSR > only (AMD) */ > > *with* the magic quotes.
So I like the idea of AMD_IBRS/AMD_IBPB/AMD_STIBP and then use the magic quotes as appropriate. We could probably use the magic quotes on AMD_STIBP and set X86_FEATURE_STIBP when we see X86_FEATURE_AMD_STIBP. Just my two cents. Thanks, Tom >
