[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [RFC PATCH v1 08/15] x86/cpufeatures: Add a CPU feature bit for MSR immediate form instructions
The immediate form of MSR access instructions are primarily motivated by performance, not code size: by having the MSR number in an immediate, it is available *much* earlier in the pipeline, which allows the hardware much more leeway about how a particular MSR is handled. Use a scattered CPU feature bit for MSR immediate form instructions. Suggested-by: Borislav Petkov <bp@xxxxxxxxx> Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx> --- arch/x86/include/asm/cpufeatures.h | 19 ++++++++++--------- arch/x86/kernel/cpu/scattered.c | 1 + 2 files changed, 11 insertions(+), 9 deletions(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 6c2c152d8a67..a742a3d34712 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -472,15 +472,16 @@ * * Reuse free bits when adding new feature flags! */ -#define X86_FEATURE_AMD_LBR_PMC_FREEZE (21*32+ 0) /* "amd_lbr_pmc_freeze" AMD LBR and PMC Freeze */ -#define X86_FEATURE_CLEAR_BHB_LOOP (21*32+ 1) /* Clear branch history at syscall entry using SW loop */ -#define X86_FEATURE_BHI_CTRL (21*32+ 2) /* BHI_DIS_S HW control available */ -#define X86_FEATURE_CLEAR_BHB_HW (21*32+ 3) /* BHI_DIS_S HW control enabled */ -#define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */ -#define X86_FEATURE_AMD_FAST_CPPC (21*32 + 5) /* Fast CPPC */ -#define X86_FEATURE_AMD_HETEROGENEOUS_CORES (21*32 + 6) /* Heterogeneous Core Topology */ -#define X86_FEATURE_AMD_WORKLOAD_CLASS (21*32 + 7) /* Workload Classification */ -#define X86_FEATURE_PREFER_YMM (21*32 + 8) /* Avoid ZMM registers due to downclocking */ +#define X86_FEATURE_AMD_LBR_PMC_FREEZE (21*32+ 0) /* "amd_lbr_pmc_freeze" AMD LBR and PMC Freeze */ +#define X86_FEATURE_CLEAR_BHB_LOOP (21*32+ 1) /* Clear branch history at syscall entry using SW loop */ +#define X86_FEATURE_BHI_CTRL (21*32+ 2) /* BHI_DIS_S HW control available */ +#define X86_FEATURE_CLEAR_BHB_HW (21*32+ 3) /* BHI_DIS_S HW control enabled */ +#define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */ +#define X86_FEATURE_AMD_FAST_CPPC (21*32+ 5) /* Fast CPPC */ +#define X86_FEATURE_AMD_HETEROGENEOUS_CORES (21*32+ 6) /* Heterogeneous Core Topology */ +#define X86_FEATURE_AMD_WORKLOAD_CLASS (21*32+ 7) /* Workload Classification */ +#define X86_FEATURE_PREFER_YMM (21*32+ 8) /* Avoid ZMM registers due to downclocking */ +#define X86_FEATURE_MSR_IMM (21*32+ 9) /* MSR immediate form instructions */ /* * BUG word(s) diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c index 16f3ca30626a..9eda656e9793 100644 --- a/arch/x86/kernel/cpu/scattered.c +++ b/arch/x86/kernel/cpu/scattered.c @@ -27,6 +27,7 @@ static const struct cpuid_bit cpuid_bits[] = { { X86_FEATURE_APERFMPERF, CPUID_ECX, 0, 0x00000006, 0 }, { X86_FEATURE_EPB, CPUID_ECX, 3, 0x00000006, 0 }, { X86_FEATURE_INTEL_PPIN, CPUID_EBX, 0, 0x00000007, 1 }, + { X86_FEATURE_MSR_IMM, CPUID_ECX, 5, 0x00000007, 1 }, { X86_FEATURE_RRSBA_CTRL, CPUID_EDX, 2, 0x00000007, 2 }, { X86_FEATURE_BHI_CTRL, CPUID_EDX, 4, 0x00000007, 2 }, { X86_FEATURE_CQM_LLC, CPUID_EDX, 1, 0x0000000f, 0 }, -- 2.49.0
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