Commit 68fb4757 authored by Like Xu's avatar Like Xu Committed by Paolo Bonzini
Browse files

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: default avatarLike Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20220831085328.45489-5-likexu@tencent.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20220923001355.3741194-4-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent dcbb816a

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -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.

	 */

arch/x86/kvm/pmu.c

+12 −5
Original line number Diff line number Diff line
@@ -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 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc) 
	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;

	}

arch/x86/kvm/pmu.h

+5 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/svm/pmu.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

	}

arch/x86/kvm/vmx/pmu_intel.c

+3 −3
Original line number Diff line number Diff line
@@ -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))