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    Subject[PATCH 7/7] KVM: x86: add SPEC_CTRL and IBPB_SUPPORT to MSR and CPUID lists
    Date
    Expose them to userspace, now that guests can use them.
    I am not adding cpufeatures here to avoid having a kernel
    that shows spec_ctrl in /proc/cpuinfo and actually has no
    support whatsoever for IBRS/IBPB. Keep the ugly special-casing
    for now, and clean it up once the generic arch/x86/ code
    learns about them.

    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    ---
    arch/x86/kvm/cpuid.c | 24 +++++++++++++++++++++---
    arch/x86/kvm/x86.c | 1 +
    2 files changed, 22 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
    index 767af697c20c..5f43a5940275 100644
    --- a/arch/x86/kvm/cpuid.c
    +++ b/arch/x86/kvm/cpuid.c
    @@ -397,7 +397,12 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,

    /* cpuid 7.0.edx*/
    const u32 kvm_cpuid_7_0_edx_x86_features =
    - KF(AVX512_4VNNIW) | KF(AVX512_4FMAPS);
    + KF(AVX512_4VNNIW) | KF(AVX512_4FMAPS) |
    + KF(SPEC_CTRL) | KF(STIBP);
    +
    + /* cpuid 0x80000008.edx */
    + const u32 kvm_cpuid_80000008_ebx_x86_features =
    + KF(IBPB_SUPPORT);

    /* all calls to cpuid_count() should be made on the same cpu */
    get_cpu();
    @@ -483,7 +488,14 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
    if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
    entry->ecx &= ~F(PKU);
    entry->edx &= kvm_cpuid_7_0_edx_x86_features;
    - entry->edx &= get_scattered_cpuid_leaf(7, 0, CPUID_EDX);
    + /*
    + * FIXME: the special casing of SPEC_CTRL and STIBP
    + * can be removed once they become regular
    + * cpufeatures.
    + */
    + entry->edx &= (
    + get_scattered_cpuid_leaf(7, 0, CPUID_EDX) |
    + KF(SPEC_CTRL) | KF(STIBP));
    } else {
    entry->ebx = 0;
    entry->ecx = 0;
    @@ -651,7 +663,13 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
    if (!g_phys_as)
    g_phys_as = phys_as;
    entry->eax = g_phys_as | (virt_as << 8);
    - entry->ebx = entry->edx = 0;
    + /*
    + * FIXME: mask against cpufeatures, with
    + * get_scattered_cpuid_leaf(0x80000008, 0, CPUID_EBX),
    + * once IBPB_SUPPORT becomes a regular cpufeature.
    + */
    + entry->ebx &= kvm_cpuid_80000008_ebx_x86_features;
    + entry->edx = 0;
    break;
    }
    case 0x80000019:
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index daa1918031df..4abb37d9f4d8 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -1032,6 +1032,7 @@ unsigned int kvm_get_pt_addr_cnt(void)
    MSR_IA32_RTIT_ADDR1_A, MSR_IA32_RTIT_ADDR1_B,
    MSR_IA32_RTIT_ADDR2_A, MSR_IA32_RTIT_ADDR2_B,
    MSR_IA32_RTIT_ADDR3_A, MSR_IA32_RTIT_ADDR3_B,
    + MSR_IA32_SPEC_CTRL,
    };

    static unsigned num_msrs_to_save;
    --
    1.8.3.1
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