From: Jim Mattson <jmattson@xxxxxxxxxx> commit ff898623af2ed564300752bba83a680a1e4fec8d upstream. 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[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> Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/cpufeatures.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -216,7 +216,7 @@ #define X86_FEATURE_SPEC_STORE_BYPASS_DISABLE ( 7*32+23) /* "" Disable Speculative Store Bypass. */ #define X86_FEATURE_LS_CFG_SSBD ( 7*32+24) /* "" AMD SSBD implementation via LS_CFG MSR */ #define X86_FEATURE_IBRS ( 7*32+25) /* Indirect Branch Restricted Speculation */ -#define X86_FEATURE_IBPB ( 7*32+26) /* Indirect Branch Prediction Barrier */ +#define X86_FEATURE_IBPB ( 7*32+26) /* "ibpb" Indirect Branch Prediction Barrier without a guaranteed RSB flush */ #define X86_FEATURE_STIBP ( 7*32+27) /* Single Thread Indirect Branch Predictors */ #define X86_FEATURE_ZEN ( 7*32+28) /* "" CPU is AMD family 0x17 (Zen) */ #define X86_FEATURE_L1TF_PTEINV ( 7*32+29) /* "" L1TF workaround PTE inversion */ @@ -306,6 +306,7 @@ #define X86_FEATURE_VIRT_SSBD (13*32+25) /* Virtualized Speculative Store Bypass Disable */ #define X86_FEATURE_AMD_SSB_NO (13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */ #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 */ /* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */ #define X86_FEATURE_DTHERM (14*32+ 0) /* Digital Thermal Sensor */ Patches currently in stable-queue which might be from jmattson@xxxxxxxxxx are queue-4.19/x86-cpufeatures-define-x86_feature_amd_ibpb_ret.patch
