Hi Andrew,
On 22/01/2019 10:49, 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@xxxxxxx>
> ---
> virt/kvm/arm/pmu.c | 114 ++++++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 78 insertions(+), 36 deletions(-)
>
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 4464899..1921ca9 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -24,8 +24,11 @@
> #include <kvm/arm_pmu.h>
> #include <kvm/arm_vgic.h>
>
> -static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 data,
> - u64 select_idx);
> +static void kvm_pmu_reenable_enabled_single(struct kvm_vcpu *vcpu, u64 pair);
> +static void kvm_pmu_counter_create_enabled_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
> @@ -59,18 +62,16 @@ 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, data;
> + 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);
>
> - reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> - ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + select_idx;
> - data = __vcpu_sys_reg(vcpu, reg + select_idx);
> -
> - /* Recreate the perf event to reflect the updated sample_period */
> - kvm_pmu_create_perf_event(vcpu, data, select_idx);
> + kvm_pmu_stop_counter(vcpu, pmc);
Shouldn't this be before we do the write to __vcpu_sys_reg()?
> + kvm_pmu_reenable_enabled_single(vcpu, select_idx);
> }
>
> /**
> @@ -88,6 +89,7 @@ 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.
> @@ -150,6 +152,25 @@ u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
> }
>
> /**
> + * kvm_pmu_enable_counter_single - create/enable a unpaired counter
> + * @vcpu: The vcpu pointer
> + * @select_idx: The counter index
> + */
> +static void kvm_pmu_enable_counter_single(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_counter_create_enabled_perf_event(vcpu, select_idx);
> + } else if (pmc->perf_event) {
"else" is enough here, no need for "else if" :) .
Actually, after we call kvm_pmu_counter_create_enabled_perf_event() we
know that pmc->perf_event != NULL.
Shouldn't we execute the code below unconditionally?
> + 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 - enable selected PMU counter
> * @vcpu: The vcpu pointer
> * @val: the value guest writes to PMCNTENSET register
> @@ -159,8 +180,6 @@ u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
> void kvm_pmu_enable_counter(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;
> @@ -169,16 +188,44 @@ void kvm_pmu_enable_counter(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_single(vcpu, i);
> }
> }
>
> /**
> + * kvm_pmu_reenable_enabled_single - reenable a counter if it should be enabled
> + * @vcpu: The vcpu pointer
> + * @select_idx: The counter index
> + */
> +static void kvm_pmu_reenable_enabled_single(struct kvm_vcpu *vcpu,
> + u64 select_idx)
Not completely convinced by the name. kvm_pmu_sync_counter_status() ?
Or maybe have the callers check whether they actually need to
disable/enable and not have this function.
> +{
> + u64 mask = kvm_pmu_valid_counter_mask(vcpu);
> + u64 set = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & mask;
> +
> + if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E))
> + return;
> +
> + if (set & BIT(select_idx))
> + kvm_pmu_enable_counter_single(vcpu, select_idx);
> +}
> +
> +/**
> + * kvm_pmu_disable_counter - disable selected PMU counter
> + * @vcpu: The vcpu pointer
> + * @pmc: The counter to dissable
> + */
> +static void kvm_pmu_disable_counter_single(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 - disable selected PMU counter
> * @vcpu: The vcpu pointer
> * @val: the value guest writes to PMCNTENCLR register
> @@ -188,8 +235,6 @@ void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val)
> void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val)
> {
> int i;
> - struct kvm_pmu *pmu = &vcpu->arch.pmu;
> - struct kvm_pmc *pmc;
>
> if (!val)
> return;
> @@ -198,9 +243,7 @@ void kvm_pmu_disable_counter(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_single(vcpu, i);
> }
> }
>
> @@ -382,28 +425,22 @@ 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
> * @vcpu: The vcpu pointer
> - * @data: Type of event as per PMXEVTYPER_EL0 format
> * @select_idx: The number of selected counter
> */
> -static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 data,
> - u64 select_idx)
> +static void kvm_pmu_counter_create_enabled_perf_event(struct kvm_vcpu *vcpu,
> + u64 select_idx)
> {
> struct kvm_pmu *pmu = &vcpu->arch.pmu;
> struct kvm_pmc *pmc = &pmu->pmc[select_idx];
> struct perf_event *event;
> struct perf_event_attr attr;
> - u64 eventsel, counter;
> + u64 eventsel, counter, data;
> +
> + data = __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + select_idx);
Should we worry about the case select_idx == ARMV8_PMU_CYCLE_IDX?
>
> - kvm_pmu_stop_counter(vcpu, pmc);
> eventsel = data & ARMV8_PMU_EVTYPE_EVENT;
>
> /* Software increment event does't need to be backed by a perf event */
> @@ -415,7 +452,6 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 data,
> attr.type = PERF_TYPE_RAW;
> attr.size = sizeof(attr);
> attr.pinned = 1;
> - attr.disabled = !kvm_pmu_counter_is_enabled(vcpu, select_idx);
> attr.exclude_user = data & ARMV8_PMU_EXCLUDE_EL0 ? 1 : 0;
> attr.exclude_kernel = data & ARMV8_PMU_EXCLUDE_EL1 ? 1 : 0;
> attr.exclude_hv = 1; /* Don't count EL2 events */
> @@ -451,7 +487,13 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 data,
> void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
> u64 select_idx)
> {
> - kvm_pmu_create_perf_event(vcpu, data, select_idx);
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc = &pmu->pmc[select_idx];
> + u64 event_type = data & ARMV8_PMU_EVTYPE_MASK;
> +
> + kvm_pmu_stop_counter(vcpu, pmc);
> + __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + select_idx) = event_type;
Why don't we take into account the select_idx == ARMV8_PMU_CYCLE_IDX
case into account anymore?
> + kvm_pmu_reenable_enabled_single(vcpu, select_idx);
> }
>
> bool kvm_arm_support_pmu_v3(void)
>
Cheers,
--
Julien Thierry
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