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>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 58a562b..afadbc4 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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.
         */

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index be8ce5a..3054b35 100644 (file)
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -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;
        }

diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 5cc5721..85ff3c0 100644 (file)
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -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);

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 9d65cd0..c4b322f 100644 (file)
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -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;
        }

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index b7c3a98..6c80dff 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -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))