6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jim Mattson jmattson@google.com
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@chromium.org Signed-off-by: Jim Mattson jmattson@google.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Reviewed-by: Tom Lendacky thomas.lendacky@amd.com Reviewed-by: Thomas Gleixner tglx@linutronix.de Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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) /* "" Generic flag for all Zen and newer */ #define X86_FEATURE_L1TF_PTEINV ( 7*32+29) /* "" L1TF workaround PTE inversion */ @@ -347,6 +347,7 @@ #define X86_FEATURE_CPPC (13*32+27) /* 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) /* Branch Sampling available */
/* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */