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target/i386: Expose bits related to SRSO vulnerability

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Add following bits related Speculative Return Stack Overflow (SRSO).
Guests can make use of these bits if supported.

These bits are reported via CPUID Fn8000_0021_EAX.
===================================================================
Bit Feature Description
===================================================================
27  SBPB                Indicates support for the Selective Branch Predictor Barrier.
28  IBPB_BRTYPE         MSR_PRED_CMD[IBPB] flushes all branch type predictions.
29  SRSO_NO             Not vulnerable to SRSO.
30  SRSO_USER_KERNEL_NO Not vulnerable to SRSO at the user-kernel boundary.
===================================================================

Link: https://www.amd.com/content/dam/amd/en/documents/corporate/cr/speculative-return-stack-overflow-whitepaper.pdf
Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/programmer-references/57238.zip
Signed-off-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/dadbd70c38f4e165418d193918a3747bd715c5f4.1729807947.git.babu.moger@amd.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Babu Moger 2024-10-24 17:18:23 -05:00 committed by Paolo Bonzini
parent 209b0ac120
commit 2ec282b8ea
2 changed files with 12 additions and 4 deletions
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2
target/i386/cpu.c
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@ -1221,7 +1221,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL,
NULL, NULL, NULL, "sbpb",
"ibpb-brtype", NULL, NULL, NULL,
"ibpb-brtype", "srso-no", "srso-user-kernel-no", NULL,
},
.cpuid = { .eax = 0x80000021, .reg = R_EAX, },
.tcg_features = 0,

8
target/i386/cpu.h
View File

@ -1022,6 +1022,14 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
#define CPUID_8000_0021_EAX_NULL_SEL_CLR_BASE (1U << 6)
/* Automatic IBRS */
#define CPUID_8000_0021_EAX_AUTO_IBRS (1U << 8)
/* Selective Branch Predictor Barrier */
#define CPUID_8000_0021_EAX_SBPB (1U << 27)
/* IBPB includes branch type prediction flushing */
#define CPUID_8000_0021_EAX_IBPB_BRTYPE (1U << 28)
/* Not vulnerable to Speculative Return Stack Overflow */
#define CPUID_8000_0021_EAX_SRSO_NO (1U << 29)
/* Not vulnerable to SRSO at the user-kernel boundary */
#define CPUID_8000_0021_EAX_SRSO_USER_KERNEL_NO (1U << 30)
/* Performance Monitoring Version 2 */
#define CPUID_8000_0022_EAX_PERFMON_V2 (1U << 0)