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 2f8a858325a4..f5491bba75fc 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 */ #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) ); /* -- 2.34.1
