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    Subject[PATCH v12 11/16] KVM: x86: Add XSAVE Support for Architectural LBR
    Date
    From: Like Xu <like.xu@linux.intel.com>

    On processors supporting XSAVES and XRSTORS, Architectural LBR XSAVE
    support is enumerated from CPUID.(EAX=0DH, ECX=1):ECX[bit 15].
    The detailed sub-leaf for Arch LBR is enumerated in CPUID.(0DH, 0FH).

    XSAVES provides a faster means than RDMSR for guest to read all LBRs.
    When guest IA32_XSS[bit 15] is set, the Arch LBR state can be saved using
    XSAVES and restored by XRSTORS with the appropriate RFBM.

    Signed-off-by: Like Xu <like.xu@linux.intel.com>
    Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
    ---
    arch/x86/kvm/vmx/vmx.c | 4 ++++
    arch/x86/kvm/x86.c | 2 +-
    2 files changed, 5 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    index 7238628acb90..1b7194b9b6bc 100644
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -7546,6 +7546,10 @@ static __init void vmx_set_cpu_caps(void)
    kvm_cpu_cap_check_and_set(X86_FEATURE_DS);
    kvm_cpu_cap_check_and_set(X86_FEATURE_DTES64);
    }
    + if (!cpu_has_vmx_arch_lbr()) {
    + kvm_cpu_cap_clear(X86_FEATURE_ARCH_LBR);
    + supported_xss &= ~XFEATURE_MASK_LBR;
    + }

    if (!enable_sgx) {
    kvm_cpu_cap_clear(X86_FEATURE_SGX);
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 90b3129a2fbe..637ecd19c646 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -224,7 +224,7 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
    | XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
    | XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)

    -#define KVM_SUPPORTED_XSS 0
    +#define KVM_SUPPORTED_XSS XFEATURE_MASK_LBR

    u64 __read_mostly host_efer;
    EXPORT_SYMBOL_GPL(host_efer);
    --
    2.27.0
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