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    Subject[PATCH v14 07/11] KVM: vmx/pmu: Reduce the overhead of LBR pass-through or cancellation
    Date
    When the LBR records msrs has already been pass-through, there is no
    need to call vmx_update_intercept_for_lbr_msrs() again and again, and
    vice versa.

    Signed-off-by: Like Xu <like.xu@linux.intel.com>
    Reviewed-by: Andi Kleen <ak@linux.intel.com>
    ---
    arch/x86/kvm/vmx/pmu_intel.c | 13 +++++++++++++
    arch/x86/kvm/vmx/vmx.h | 3 +++
    2 files changed, 16 insertions(+)

    diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
    index 287fc14f0445..60f395e18446 100644
    --- a/arch/x86/kvm/vmx/pmu_intel.c
    +++ b/arch/x86/kvm/vmx/pmu_intel.c
    @@ -550,6 +550,7 @@ static void intel_pmu_init(struct kvm_vcpu *vcpu)
    vcpu->arch.perf_capabilities = 0;
    lbr_desc->records.nr = 0;
    lbr_desc->event = NULL;
    + lbr_desc->msr_passthrough = false;
    }

    static void intel_pmu_reset(struct kvm_vcpu *vcpu)
    @@ -596,12 +597,24 @@ static void vmx_update_intercept_for_lbr_msrs(struct kvm_vcpu *vcpu, bool set)

    static inline void vmx_disable_lbr_msrs_passthrough(struct kvm_vcpu *vcpu)
    {
    + struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
    +
    + if (!lbr_desc->msr_passthrough)
    + return;
    +
    vmx_update_intercept_for_lbr_msrs(vcpu, true);
    + lbr_desc->msr_passthrough = false;
    }

    static inline void vmx_enable_lbr_msrs_passthrough(struct kvm_vcpu *vcpu)
    {
    + struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
    +
    + if (lbr_desc->msr_passthrough)
    + return;
    +
    vmx_update_intercept_for_lbr_msrs(vcpu, false);
    + lbr_desc->msr_passthrough = true;
    }

    /*
    diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
    index 863bb3fe73d4..4d6a2624a204 100644
    --- a/arch/x86/kvm/vmx/vmx.h
    +++ b/arch/x86/kvm/vmx/vmx.h
    @@ -90,6 +90,9 @@ struct lbr_desc {
    * The records may be inaccurate if the host reclaims the LBR.
    */
    struct perf_event *event;
    +
    + /* True if LBRs are marked as not intercepted in the MSR bitmap */
    + bool msr_passthrough;
    };

    /*
    --
    2.29.2
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