On Thu, Feb 14, 2019 at 11:36:02AM +0000, Suzuki K Poulose wrote: > Hi Andrew, > > On 04/02/2019 16:53, Andrew Murray wrote: > > To prevent re-creating perf events everytime the counter registers > > are changed, let's instead lazily create the event when the event > > is first enabled and destroy it when it changes. > > > > Signed-off-by: Andrew Murray <andrew.murray at arm.com> > > --- > > virt/kvm/arm/pmu.c | 96 ++++++++++++++++++++++++++++++++++++++---------------- > > 1 file changed, 68 insertions(+), 28 deletions(-) > > > > diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c > > index 95d74ec..a64aeb2 100644 > > --- a/virt/kvm/arm/pmu.c > > +++ b/virt/kvm/arm/pmu.c > > @@ -24,7 +24,10 @@ > > #include <kvm/arm_pmu.h> > > #include <kvm/arm_vgic.h> > > +static void kvm_pmu_sync_counter_enable(struct kvm_vcpu *vcpu, u64 select_idx); > > static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx); > > +static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc); > > + > > /** > > * kvm_pmu_get_counter_value - get PMU counter value > > * @vcpu: The vcpu pointer > > @@ -59,13 +62,15 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx) > > void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val) > > { > > u64 reg; > > + struct kvm_pmu *pmu = &vcpu->arch.pmu; > > + struct kvm_pmc *pmc = &pmu->pmc[select_idx]; > > reg = (select_idx == ARMV8_PMU_CYCLE_IDX) > > ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx; > > __vcpu_sys_reg(vcpu, reg) += (s64)val - kvm_pmu_get_counter_value(vcpu, select_idx); > > - /* Recreate the perf event to reflect the updated sample_period */ > > - kvm_pmu_create_perf_event(vcpu, select_idx); > > + kvm_pmu_stop_counter(vcpu, pmc); > > + kvm_pmu_sync_counter_enable(vcpu, select_idx); > > } > > /** > > @@ -83,6 +88,7 @@ static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc) > > /** > > * kvm_pmu_stop_counter - stop PMU counter > > + * @vcpu: The vcpu pointer > > * @pmc: The PMU counter pointer > > * > > * If this counter has been configured to monitor some event, release it here. > > @@ -143,6 +149,24 @@ u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu) > > } > > /** > > + * kvm_pmu_enable_counter - create/enable a counter > > + * @vcpu: The vcpu pointer > > + * @select_idx: The counter index > > + */ > > +static void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 select_idx) > > +{ > > + struct kvm_pmu *pmu = &vcpu->arch.pmu; > > + struct kvm_pmc *pmc = &pmu->pmc[select_idx]; > > + > > + if (!pmc->perf_event) > > + kvm_pmu_create_perf_event(vcpu, select_idx); > > + > > + perf_event_enable(pmc->perf_event); > > + if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE) > > + kvm_debug("failed to enable perf event\n"); > > +} > > + > > +/** > > * kvm_pmu_enable_counter_mask - enable selected PMU counters > > * @vcpu: The vcpu pointer > > * @val: the value guest writes to PMCNTENSET register > > @@ -152,8 +176,6 @@ u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu) > > void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val) > > { > > int i; > > - struct kvm_pmu *pmu = &vcpu->arch.pmu; > > - struct kvm_pmc *pmc; > > if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) || !val) > > return; > > @@ -162,16 +184,39 @@ void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val) > > if (!(val & BIT(i))) > > continue; > > - pmc = &pmu->pmc[i]; > > - if (pmc->perf_event) { > > - perf_event_enable(pmc->perf_event); > > - if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE) > > - kvm_debug("fail to enable perf event\n"); > > - } > > + kvm_pmu_enable_counter(vcpu, i); > > } > > } > > /** > > + * kvm_pmu_sync_counter_enable - reenable a counter if it should be enabled > > + * @vcpu: The vcpu pointer > > + * @select_idx: The counter index > > + */ > > +static void kvm_pmu_sync_counter_enable(struct kvm_vcpu *vcpu, > > + u64 select_idx) > > +{ > > + u64 set = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0); > > + > > + if (set & BIT(select_idx)) > > + kvm_pmu_enable_counter_mask(vcpu, BIT(select_idx)); > > I think there is a problem here. We could be creating an event for a > counter beyond what is supported by the CPU. i.e, we don't > seem to validate that the mask we are creating is within the > kvm_pmu_valid_counter_mask(). The other callers seem to verify this. > I guess it may be better to add a check for this in the > kvm_pmu_enable_counter_mask(). Actually I think this is OK. This function is only called by kvm_pmu_set_counter_event_type and kvm_pmu_set_counter_value - both these functions are called from arch/arm64/kvm/sys_regs.c which ensures that pmu_counter_idx_valid is true (which is same as kvm_pmu_valid_counter_mask). This does become a problem in the next patch when we add chained counters however we then add the check against kvm_pmu_valid_counter_mask (see kvm_pmu_enable_counter_mask). > > minor nit: Feel free to ignore. If we move the check for PMCNTENSET_EL0 to > pmu_enable_counter_mask() we could get rid of the above function. Anyways, > we should only be enabling the counters set in PMCNTENSET_EL0. > This does seem acceptable, however the next patch adds a kvm_pmu_sync_counter_pair function, which does add some additional value. So whilst kvm_pmu_sync_counter_enable may seem redundant here it is built upon later. > > > +} > > + > > +/** > > + * kvm_pmu_disable_counter - disable selected PMU counter > > + * @vcpu: The vcpu pointer > > + * @pmc: The counter to disable > > + */ > > +static void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 select_idx) > > +{ > > + struct kvm_pmu *pmu = &vcpu->arch.pmu; > > + struct kvm_pmc *pmc = &pmu->pmc[select_idx]; > > + > > + if (pmc->perf_event) > > + perf_event_disable(pmc->perf_event); > > +} > > + > > +/** > > * kvm_pmu_disable_counter_mask - disable selected PMU counters > > * @vcpu: The vcpu pointer > > * @val: the value guest writes to PMCNTENCLR register > > @@ -181,8 +226,6 @@ void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val) > > void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val) > > { > > int i; > > - struct kvm_pmu *pmu = &vcpu->arch.pmu; > > - struct kvm_pmc *pmc; > > if (!val) > > return; > > @@ -191,9 +234,7 @@ void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val) > > if (!(val & BIT(i))) > > continue; > > - pmc = &pmu->pmc[i]; > > - if (pmc->perf_event) > > - perf_event_disable(pmc->perf_event); > > + kvm_pmu_disable_counter(vcpu, i); > > } > > } > > @@ -375,16 +416,9 @@ void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val) > > } > > } > > -static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx) > > -{ > > - return (__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) && > > - (__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & BIT(select_idx)); > > -} > > - > > /** > > - * kvm_pmu_create_perf_event - create a perf event for a counter > > + * kvm_pmu_counter_create_enabled_perf_event - create a perf event for a counter > > nit: Name hasn't changed. Also, please could update that, the events are always > created disabled and they are only enabled lazily. Thanks, Andrew Murray > > Reset looks fines. > > Suzuki