From ec26f8052ecc7915453eebc942063021b901b8f6 Mon Sep 17 00:00:00 2001 From: Babu Moger Date: Thu, 4 May 2023 15:53:08 -0500 Subject: [PATCH] target/i386: Add a couple of feature bits in 8000_0008_EBX Add the following feature bits. amd-psfd : Predictive Store Forwarding Disable: PSF is a hardware-based micro-architectural optimization designed to improve the performance of code execution by predicting address dependencies between loads and stores. While SSBD (Speculative Store Bypass Disable) disables both PSF and speculative store bypass, PSFD only disables PSF. PSFD may be desirable for the software which is concerned with the speculative behavior of PSF but desires a smaller performance impact than setting SSBD. Depends on the following kernel commit: b73a54321ad8 ("KVM: x86: Expose Predictive Store Forwarding Disable") stibp-always-on : Single Thread Indirect Branch Prediction mode has enhanced performance and may be left always on. The documentation for the features are available in the links below. a. Processor Programming Reference (PPR) for AMD Family 19h Model 01h, Revision B1 Processors b. SECURITY ANALYSIS OF AMD PREDICTIVE STORE FORWARDING Signed-off-by: Babu Moger Acked-by: Michael S. Tsirkin Link: https://www.amd.com/system/files/documents/security-analysis-predictive-store-forwarding.pdf Link: https://www.amd.com/system/files/TechDocs/55898_B1_pub_0.50.zip Message-Id: <20230504205313.225073-4-babu.moger@amd.com> Signed-off-by: Paolo Bonzini (cherry picked from commit bb039a230e6a7920d71d21fa9afee2653a678c48) References: jsc#PED-7366 Signed-off-by: Dario Faggioli --- target/i386/cpu.c | 4 ++-- target/i386/cpu.h | 4 ++++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index da3602af9c..ad3ad03a5e 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -909,10 +909,10 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = { NULL, NULL, NULL, NULL, NULL, "wbnoinvd", NULL, NULL, "ibpb", NULL, "ibrs", "amd-stibp", - NULL, NULL, NULL, NULL, + NULL, "stibp-always-on", NULL, NULL, NULL, NULL, NULL, NULL, "amd-ssbd", "virt-ssbd", "amd-no-ssb", NULL, - NULL, NULL, NULL, NULL, + "amd-psfd", NULL, NULL, NULL, }, .cpuid = { .eax = 0x80000008, .reg = R_EBX, }, .tcg_features = 0, diff --git a/target/i386/cpu.h b/target/i386/cpu.h index b75108d6a3..095168aafe 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -916,8 +916,12 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w, #define CPUID_8000_0008_EBX_IBRS (1U << 14) /* Single Thread Indirect Branch Predictors */ #define CPUID_8000_0008_EBX_STIBP (1U << 15) +/* STIBP mode has enhanced performance and may be left always on */ +#define CPUID_8000_0008_EBX_STIBP_ALWAYS_ON (1U << 17) /* Speculative Store Bypass Disable */ #define CPUID_8000_0008_EBX_AMD_SSBD (1U << 24) +/* Predictive Store Forwarding Disable */ +#define CPUID_8000_0008_EBX_AMD_PSFD (1U << 28) #define CPUID_XSAVE_XSAVEOPT (1U << 0) #define CPUID_XSAVE_XSAVEC (1U << 1)