AMD's initial implementation of IBPB did not clear the return address predictor. Beginning with Zen4, AMD's IBPB *does* clear the return address predictor. This behavior is enumerated by CPUID.80000008H:EBX.IBPB_RET[bit 30]. Define X86_FEATURE_AMD_IBPB_RET for use in KVM_GET_SUPPORTED_CPUID, when determining cross-vendor capabilities. Suggested-by: Venkatesh Srinivas <venkateshs@xxxxxxxxxxxx> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx> --- arch/x86/include/asm/cpufeatures.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index dd4682857c12..e5bcb428dcf9 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -348,6 +348,7 @@ #define X86_FEATURE_CPPC (13*32+27) /* "cppc" Collaborative Processor Performance Control */ #define X86_FEATURE_AMD_PSFD (13*32+28) /* Predictive Store Forwarding Disable */ #define X86_FEATURE_BTC_NO (13*32+29) /* Not vulnerable to Branch Type Confusion */ +#define X86_FEATURE_AMD_IBPB_RET (13*32+30) /* IBPB clears return address predictor */ #define X86_FEATURE_BRS (13*32+31) /* "brs" Branch Sampling available */ /* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */ -- 2.46.0.184.g6999bdac58-goog
