pmu_ctr_read() adds the event count returned by perf_event_read_value() to counter_val, which can accumulate the same count repeatedly across reads. kvm_riscv_vcpu_pmu_ctr_stop() also leaves counter_val stale by not folding the current event count into it. Make reads of perf-backed counters side-effect free, and use perf_event_pause() when stopping a counter to fold the current event count into counter_val while resetting it. This preserves the counter value across stop/start and lets the snapshot path use counter_val directly. Fixes: 0cb74b65d2e5 ("RISC-V: KVM: Implement perf support without sampling") Signed-off-by: SeungJu Cheon --- arch/riscv/kvm/vcpu_pmu.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c index 45dd5233340d..7d50490cc622 100644 --- a/arch/riscv/kvm/vcpu_pmu.c +++ b/arch/riscv/kvm/vcpu_pmu.c @@ -268,12 +268,13 @@ static int pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx, return -EINVAL; pmc->counter_val = kvpmu->fw_event[fevent_code].value; + *out_val = pmc->counter_val; } else if (pmc->perf_event) { - pmc->counter_val += perf_event_read_value(pmc->perf_event, &enabled, &running); + *out_val = pmc->counter_val + + perf_event_read_value(pmc->perf_event, &enabled, &running); } else { return -EINVAL; } - *out_val = pmc->counter_val; return 0; } @@ -641,7 +642,6 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base, { struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu); int i, pmc_index, sbiret = 0; - u64 enabled, running; struct kvm_pmc *pmc; int fevent_code; bool snap_flag_set = flags & SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT; @@ -679,8 +679,11 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base, } } else if (pmc->perf_event) { if (pmc->started) { - /* Stop counting the counter */ - perf_event_disable(pmc->perf_event); + /* + * Stop the counter and fold the live count into counter_val. + * Reset the event value to avoid redundant accumulation. + */ + pmc->counter_val += perf_event_pause(pmc->perf_event, true); pmc->started = false; } else { sbiret = SBI_ERR_ALREADY_STOPPED; @@ -694,9 +697,6 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base, } if (snap_flag_set && !sbiret) { - if (pmc->perf_event) - pmc->counter_val += perf_event_read_value(pmc->perf_event, - &enabled, &running); /* * The counter and overflow indices in the snapshot region are w.r.to * cbase. Modify the set bit in the counter mask instead of the pmc_index -- 2.52.0