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KVM: vmx/pmu: Emulate legacy freezing LBRs on virtual PMI 

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.xu@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Message-Id: <20210201051039.255478-9-like.xu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Like Xu 2021-02-01 13:10:36 +08:00 committed by Paolo Bonzini
parent 9254beaafd
commit e6209a3bef
5 changed files with 39 additions and 3 deletions
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5
arch/x86/kvm/pmu.c
View File

@ -383,8 +383,11 @@ 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)

1
arch/x86/kvm/pmu.h
View File

@ -39,6 +39,7 @@ 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)

4
arch/x86/kvm/vmx/capabilities.h
View File

@ -21,6 +21,8 @@ extern int __read_mostly pt_mode;
#define PMU_CAP_FW_WRITES (1ULL << 13)
#define PMU_CAP_LBR_FMT 0x3f
#define DEBUGCTLMSR_LBR_MASK (DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI)
struct nested_vmx_msrs {
/*
* We only store the "true" versions of the VMX capability MSRs. We
@ -390,7 +392,7 @@ static inline u64 vmx_supported_debugctl(void)
u64 debugctl = 0;
if (vmx_get_perf_capabilities() & PMU_CAP_LBR_FMT)
debugctl |= DEBUGCTLMSR_LBR;
debugctl |= DEBUGCTLMSR_LBR_MASK;
return debugctl;
}

30
arch/x86/kvm/vmx/pmu_intel.c
View File

@ -586,6 +586,35 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
intel_pmu_release_guest_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 = 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 (!intel_pmu_lbr_is_enabled(vcpu))
return;
if (version > 1 && version < 4)
intel_pmu_legacy_freezing_lbrs_on_pmi(vcpu);
}
static void vmx_update_intercept_for_lbr_msrs(struct kvm_vcpu *vcpu, bool set)
{
struct x86_pmu_lbr *lbr = vcpu_to_lbr_records(vcpu);
@ -672,4 +701,5 @@ 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
arch/x86/kvm/vmx/vmx.c
View File

@ -1963,7 +1963,7 @@ static u64 vcpu_supported_debugctl(struct kvm_vcpu *vcpu)
u64 debugctl = vmx_supported_debugctl();
if (!intel_pmu_lbr_is_enabled(vcpu))
debugctl &= ~DEBUGCTLMSR_LBR;
debugctl &= ~DEBUGCTLMSR_LBR_MASK;
return debugctl;
}