On Tue, Nov 26, 2024 at 1:45 AM Maksim Davydov <davydov-max@xxxxxxxxxxxxxx> wrote: > > It seems helpful to expose to userspace some speculation control features > from 0x80000008_EBX function: > * 16 bit. IBRS always on. Indicates whether processor prefers that > IBRS is always on. It simplifies speculation managing. > * 18 bit. IBRS is preferred over software solution. Indicates that > software mitigations can be replaced with more performant IBRS. > * 19 bit. IBRS provides Same Mode Protection. Indicates that when IBRS > is set indirect branch predictions are not influenced by any prior > indirect branches. > * 29 bit. BTC_NO. Indicates that processor isn't affected by branch type > confusion. It's used during mitigations setting up. > * 30 bit. IBPB clears return address predictor. It's used during > mitigations setting up. > > Signed-off-by: Maksim Davydov <davydov-max@xxxxxxxxxxxxxx> > --- > arch/x86/include/asm/cpufeatures.h | 3 +++ > arch/x86/kvm/cpuid.c | 5 +++-- > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h > index f6be4fd2ead0..ba371d364c58 100644 > --- a/arch/x86/include/asm/cpufeatures.h > +++ b/arch/x86/include/asm/cpufeatures.h > @@ -340,7 +340,10 @@ > #define X86_FEATURE_AMD_IBPB (13*32+12) /* Indirect Branch Prediction Barrier */ > #define X86_FEATURE_AMD_IBRS (13*32+14) /* Indirect Branch Restricted Speculation */ > #define X86_FEATURE_AMD_STIBP (13*32+15) /* Single Thread Indirect Branch Predictors */ > +#define X86_FEATURE_AMD_IBRS_ALWAYS_ON (13*32+16) /* Indirect Branch Restricted Speculation always-on preferred */ > #define X86_FEATURE_AMD_STIBP_ALWAYS_ON (13*32+17) /* Single Thread Indirect Branch Predictors always-on preferred */ > +#define X86_FEATURE_AMD_IBRS_PREFERRED (13*32+18) /* Indirect Branch Restricted Speculation is preferred over SW solution */ > +#define X86_FEATURE_AMD_IBRS_SMP (13*32+19) /* Indirect Branch Restricted Speculation provides Same Mode Protection */ "SMP" is an unfortunate overloading of an acronym with another well-known meaning. Perhaps "SAME_MODE"? > #define X86_FEATURE_AMD_PPIN (13*32+23) /* "amd_ppin" Protected Processor Inventory Number */ > #define X86_FEATURE_AMD_SSBD (13*32+24) /* Speculative Store Bypass Disable */ > #define X86_FEATURE_VIRT_SSBD (13*32+25) /* "virt_ssbd" Virtualized Speculative Store Bypass Disable */ > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 30ce1bcfc47f..5b2d52913b18 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -754,8 +754,9 @@ void kvm_set_cpu_caps(void) > kvm_cpu_cap_mask(CPUID_8000_0008_EBX, > F(CLZERO) | F(XSAVEERPTR) | > F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) | > - F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON) | > - F(AMD_PSFD) > + F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_IBRS_ALWAYS_ON) | > + F(AMD_STIBP_ALWAYS_ON) | F(AMD_IBRS_PREFERRED) | > + F(AMD_IBRS_SMP) | F(AMD_PSFD) | F(BTC_NO) | F(AMD_IBPB_RET) > ); Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
