[PATCH v12 09/11] KVM: vmx/pmu: Emulate legacy freezing LBRs on virtual PMI

[Like Xu]

The current vPMU only supports Architecture Version 2. According to
Intel SDM "17.4.7 Freezing LBR and Performance Counters on PMI", if
IA32_DEBUGCTL.Freeze_LBR_On_PMI = 1, the LBR is frozen on the virtual
PMI and the KVM would emulate to clear the LBR bit (bit 0) in
IA32_DEBUGCTL. Also guest needs to re-enable IA32_DEBUGCTL.LBR
to resume recording branches.

Signed-off-by: Like Xu <like...@linux.intel.com>
---
 arch/x86/kvm/pmu.c           |  5 ++++-
 arch/x86/kvm/pmu.h           |  1 +
 arch/x86/kvm/vmx/pmu_intel.c | 31 +++++++++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index b86346903f2e..5053f4238218 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -378,8 +378,11 @@ int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 
*data)
 
 void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
 {
-       if (lapic_in_kernel(vcpu))
+       if (lapic_in_kernel(vcpu)) {
+               if (kvm_x86_ops.pmu_ops->deliver_pmi)
+                       kvm_x86_ops.pmu_ops->deliver_pmi(vcpu);
                kvm_apic_local_deliver(vcpu->arch.apic, APIC_LVTPC);
+       }
 }
 
 bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index ab85eed8a6cc..095b84392b89 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -37,6 +37,7 @@ struct kvm_pmu_ops {
        void (*refresh)(struct kvm_vcpu *vcpu);
        void (*init)(struct kvm_vcpu *vcpu);
        void (*reset)(struct kvm_vcpu *vcpu);
+       void (*deliver_pmi)(struct kvm_vcpu *vcpu);
 };
 
 static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index a78c440ebff2..85a675004cbb 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -641,6 +641,36 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
        intel_pmu_free_lbr_event(vcpu);
 }
 
+/*
+ * Emulate LBR_On_PMI behavior for 1 < pmu.version < 4.
+ *
+ * If Freeze_LBR_On_PMI = 1, the LBR is frozen on PMI and
+ * the KVM emulates to clear the LBR bit (bit 0) in IA32_DEBUGCTL.
+ *
+ * Guest needs to re-enable LBR to resume branches recording.
+ */
+static void intel_pmu_legacy_freezing_lbrs_on_pmi(struct kvm_vcpu *vcpu)
+{
+       u64 data;
+
+       data = vmcs_read64(GUEST_IA32_DEBUGCTL);
+       if (data & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI) {
+               data &= ~DEBUGCTLMSR_LBR;
+               vmcs_write64(GUEST_IA32_DEBUGCTL, data);
+       }
+}
+
+static void intel_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
+{
+       u8 version = vcpu_to_pmu(vcpu)->version;
+
+       if (!lbr_is_enabled(vcpu))
+               return;
+
+       if (version > 1 && version < 4)
+               intel_pmu_legacy_freezing_lbrs_on_pmi(vcpu);
+}
+
 struct kvm_pmu_ops intel_pmu_ops = {
        .find_arch_event = intel_find_arch_event,
        .find_fixed_event = intel_find_fixed_event,
@@ -655,4 +685,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
        .refresh = intel_pmu_refresh,
        .init = intel_pmu_init,
        .reset = intel_pmu_reset,
+       .deliver_pmi = intel_pmu_deliver_pmi,
 };
-- 
2.21.3