[PATCH v14 09/11] KVM: vmx/pmu: Release guest LBR event via lazy release mechanism

Like Xu
2021-02-01T06:35:16Z

The vPMU uses GUEST_LBR_IN_USE_IDX (bit 58) in 'pmu->pmc_in_use' to
indicate whether a guest LBR event is still needed by the vcpu. If the
vcpu no longer accesses LBR related registers within a scheduling time
slice, and the enable bit of LBR has been unset, vPMU will treat the
guest LBR event as a bland event of a vPMC counter and release it
as usual. Also, the pass-through state of LBR records msrs is cancelled.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
arch/x86/kvm/pmu.c | 3 +++
arch/x86/kvm/pmu.h | 1 +
arch/x86/kvm/vmx/pmu_intel.c | 21 ++++++++++++++++++++-
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 405890c723a1..136dc2f3c5d3 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -476,6 +476,9 @@ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)
pmc_stop_counter(pmc);
}

+ if (kvm_x86_ops.pmu_ops->cleanup)
+ kvm_x86_ops.pmu_ops->cleanup(vcpu);
+
bitmap_zero(pmu->pmc_in_use, X86_PMC_IDX_MAX);
}

diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 742a4e98df8c..7b30bc967af3 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -40,6 +40,7 @@ struct kvm_pmu_ops {
void (*init)(struct kvm_vcpu *vcpu);
void (*reset)(struct kvm_vcpu *vcpu);
void (*deliver_pmi)(struct kvm_vcpu *vcpu);
+ void (*cleanup)(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 51edd9c1adfa..23cd31b849f4 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -288,8 +288,10 @@ int intel_pmu_create_guest_lbr_event(struct kvm_vcpu *vcpu)
PERF_SAMPLE_BRANCH_USER,
};

- if (unlikely(lbr_desc->event))
+ if (unlikely(lbr_desc->event)) {
+ __set_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use);
return 0;
+ }

event = perf_event_create_kernel_counter(&attr, -1,
current, NULL, NULL);
@@ -300,6 +302,7 @@ int intel_pmu_create_guest_lbr_event(struct kvm_vcpu *vcpu)
}
lbr_desc->event = event;
pmu->event_count++;
+ __set_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use);
return 0;
}

@@ -332,9 +335,11 @@ static bool intel_pmu_handle_lbr_msrs_access(struct kvm_vcpu *vcpu,
rdmsrl(index, msr_info->data);
else
wrmsrl(index, msr_info->data);
+ __set_bit(INTEL_PMC_IDX_FIXED_VLBR, vcpu_to_pmu(vcpu)->pmc_in_use);
local_irq_enable();
return true;
}
+ clear_bit(INTEL_PMC_IDX_FIXED_VLBR, vcpu_to_pmu(vcpu)->pmc_in_use);
local_irq_enable();

dummy:
@@ -463,6 +468,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
struct kvm_cpuid_entry2 *entry;
union cpuid10_eax eax;
union cpuid10_edx edx;
+ struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);

pmu->nr_arch_gp_counters = 0;
pmu->nr_arch_fixed_counters = 0;
@@ -482,6 +488,8 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
return;

perf_get_x86_pmu_capability(&x86_pmu);
+ if (lbr_desc->records.nr)
+ bitmap_set(pmu->all_valid_pmc_idx, INTEL_PMC_IDX_FIXED_VLBR, 1);

pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
x86_pmu.num_counters_gp);
@@ -658,17 +666,21 @@ static inline void vmx_enable_lbr_msrs_passthrough(struct kvm_vcpu *vcpu)
*/
void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
{
+ struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);

if (!lbr_desc->event) {
vmx_disable_lbr_msrs_passthrough(vcpu);
if (vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR)
goto warn;
+ if (test_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use))
+ goto warn;
return;
}

if (lbr_desc->event->state < PERF_EVENT_STATE_ACTIVE) {
vmx_disable_lbr_msrs_passthrough(vcpu);
+ __clear_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use);
goto warn;
} else
vmx_enable_lbr_msrs_passthrough(vcpu);
@@ -680,6 +692,12 @@ void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
vcpu->vcpu_id);
}

+static void intel_pmu_cleanup(struct kvm_vcpu *vcpu)
+{
+ if (!(vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR))
+ intel_pmu_release_guest_lbr_event(vcpu);
+}
+
struct kvm_pmu_ops intel_pmu_ops = {
.find_arch_event = intel_find_arch_event,
.find_fixed_event = intel_find_fixed_event,
@@ -695,4 +713,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
.init = intel_pmu_init,
.reset = intel_pmu_reset,
.deliver_pmi = intel_pmu_deliver_pmi,
+ .cleanup = intel_pmu_cleanup,
};
--
2.29.2