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KVM: x86/pmu: Defer reprogram_counter() to kvm_pmu_handle_event() 

Batch reprogramming PMU counters by setting KVM_REQ_PMU and thus
deferring reprogramming kvm_pmu_handle_event() to avoid reprogramming
a counter multiple times during a single VM-Exit.

Deferring programming will also allow KVM to fix a bug where immediately
reprogramming a counter can result in sleeping (taking a mutex) while
interrupts are disabled in the VM-Exit fastpath.

Introduce kvm_pmu_request_counter_reprogam() to make it obvious that
KVM is _requesting_ a reprogram and not actually doing the reprogram.

Opportunistically refine related comments to avoid misunderstandings.

Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20220831085328.45489-5-likexu@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220923001355.3741194-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Like Xu 2022-09-23 00:13:54 +00:00 committed by Paolo Bonzini
parent dcbb816a28
commit 68fb4757e8
5 changed files with 22 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/kvm_host.h
View File

@ -496,6 +496,7 @@ struct kvm_pmc {
struct perf_event *perf_event;
struct kvm_vcpu *vcpu;
/*
* only for creating or reusing perf_event,
* eventsel value for general purpose counters,
* ctrl value for fixed counters.
*/

17
arch/x86/kvm/pmu.c
View File

@ -101,7 +101,11 @@ static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi)
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
bool skip_pmi = false;
/* Ignore counters that have been reprogrammed already. */
/*
* Ignore overflow events for counters that are scheduled to be
* reprogrammed, e.g. if a PMI for the previous event races with KVM's
* handling of a related guest WRMSR.
*/
if (test_and_set_bit(pmc->idx, pmu->reprogram_pmi))
return;
@ -292,7 +296,7 @@ out:
return allow_event;
}
void reprogram_counter(struct kvm_pmc *pmc)
static void reprogram_counter(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
u64 eventsel = pmc->eventsel;
@ -345,7 +349,6 @@ void reprogram_counter(struct kvm_pmc *pmc)
reprogram_complete:
clear_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->reprogram_pmi);
}
EXPORT_SYMBOL_GPL(reprogram_counter);
void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
{
@ -355,10 +358,11 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
for_each_set_bit(bit, pmu->reprogram_pmi, X86_PMC_IDX_MAX) {
struct kvm_pmc *pmc = static_call(kvm_x86_pmu_pmc_idx_to_pmc)(pmu, bit);
if (unlikely(!pmc || !pmc->perf_event)) {
if (unlikely(!pmc)) {
clear_bit(bit, pmu->reprogram_pmi);
continue;
}
reprogram_counter(pmc);
}
@ -552,12 +556,15 @@ static inline bool eventsel_match_perf_hw_id(struct kvm_pmc *pmc,
static inline bool cpl_is_matched(struct kvm_pmc *pmc)
{
bool select_os, select_user;
u64 config = pmc->current_config;
u64 config;
if (pmc_is_gp(pmc)) {
config = pmc->eventsel;
select_os = config & ARCH_PERFMON_EVENTSEL_OS;
select_user = config & ARCH_PERFMON_EVENTSEL_USR;
} else {
config = fixed_ctrl_field(pmc_to_pmu(pmc)->fixed_ctr_ctrl,
pmc->idx - INTEL_PMC_IDX_FIXED);
select_os = config & 0x1;
select_user = config & 0x2;
}

6
arch/x86/kvm/pmu.h
View File

@ -183,7 +183,11 @@ static inline void kvm_init_pmu_capability(void)
KVM_PMC_MAX_FIXED);
}
void reprogram_counter(struct kvm_pmc *pmc);
static inline void kvm_pmu_request_counter_reprogam(struct kvm_pmc *pmc)
{
set_bit(pmc->idx, pmc_to_pmu(pmc)->reprogram_pmi);
kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
}
void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu);
void kvm_pmu_handle_event(struct kvm_vcpu *vcpu);

2
arch/x86/kvm/svm/pmu.c
View File

@ -159,7 +159,7 @@ static int amd_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
data &= ~pmu->reserved_bits;
if (data != pmc->eventsel) {
pmc->eventsel = data;
reprogram_counter(pmc);
kvm_pmu_request_counter_reprogam(pmc);
}
return 0;
}

6
arch/x86/kvm/vmx/pmu_intel.c
View File

@ -52,7 +52,7 @@ static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
pmc = get_fixed_pmc(pmu, MSR_CORE_PERF_FIXED_CTR0 + i);
__set_bit(INTEL_PMC_IDX_FIXED + i, pmu->pmc_in_use);
reprogram_counter(pmc);
kvm_pmu_request_counter_reprogam(pmc);
}
}
@ -76,7 +76,7 @@ static void reprogram_counters(struct kvm_pmu *pmu, u64 diff)
for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX) {
pmc = intel_pmc_idx_to_pmc(pmu, bit);
if (pmc)
reprogram_counter(pmc);
kvm_pmu_request_counter_reprogam(pmc);
}
}
@ -477,7 +477,7 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
reserved_bits ^= HSW_IN_TX_CHECKPOINTED;
if (!(data & reserved_bits)) {
pmc->eventsel = data;
reprogram_counter(pmc);
kvm_pmu_request_counter_reprogam(pmc);
return 0;
}
} else if (intel_pmu_handle_lbr_msrs_access(vcpu, msr_info, false))