Hi Andrew,
On 04/02/2019 16:53, Andrew Murray wrote:
> Emulate chained PMU counters by creating a single 64 bit event counter
> for a pair of chained KVM counters.
>
> Signed-off-by: Andrew Murray <[email protected]>
> ---
> include/kvm/arm_pmu.h | 1 +
> virt/kvm/arm/pmu.c | 321
> +++++++++++++++++++++++++++++++++++++++++---------
> 2 files changed, 269 insertions(+), 53 deletions(-)
>
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index b73f31b..8e691ee 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -29,6 +29,7 @@ struct kvm_pmc {
> u8 idx; /* index into the pmu->pmc array */
> struct perf_event *perf_event;
> u64 bitmask;
> + u64 overflow_count;
> };
>
> struct kvm_pmu {
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index a64aeb2..9318130 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -24,9 +24,25 @@
> #include <kvm/arm_pmu.h>
> #include <kvm/arm_vgic.h>
>
> +#define ARMV8_PMUV3_PERFCTR_CHAIN 0x1E
I find it a bit awkward to have this redefined here.
Maybe we could define a helper in kvm_host.h:
bool kvm_pmu_typer_is_chain(u64 typer);
That would always return false for arm32?
> +static void kvm_pmu_stop_release_perf_event_pair(struct kvm_vcpu *vcpu,
> + u64 pair_low);
> +static void kvm_pmu_stop_release_perf_event(struct kvm_vcpu *vcpu,
> + u64 select_idx);
> +static void kvm_pmu_sync_counter_enable_pair(struct kvm_vcpu *vcpu, u64
> pair_low);
> 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_counter_is_high_word - is select_idx high counter of 64bit event
> + * @pmc: The PMU counter pointer
> + * @select_idx: The counter index
> + */
> +static inline bool kvm_pmu_counter_is_high_word(struct kvm_pmc *pmc)
> +{
> + return ((pmc->perf_event->attr.config1 & 0x1)
> + && (pmc->idx % 2));
> +}
>
> /**
> * kvm_pmu_get_counter_value - get PMU counter value
> @@ -35,22 +51,70 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu,
> struct kvm_pmc *pmc);
> */
> u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
> {
> - u64 counter, reg, enabled, running;
> + u64 counter_idx, reg, enabled, running, incr;
> 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;
> - counter = __vcpu_sys_reg(vcpu, reg);
> + counter_idx = __vcpu_sys_reg(vcpu, reg);
I'm not sure I understand the "_idx" suffix for this variable. This
holds a counter value, not and index. Right?
>
> /* The real counter value is equal to the value of counter register plus
> * the value perf event counts.
> */
> - if (pmc->perf_event)
> - counter += perf_event_read_value(pmc->perf_event, &enabled,
> + if (pmc->perf_event) {
> + incr = perf_event_read_value(pmc->perf_event, &enabled,
> &running);
>
> - return counter & pmc->bitmask;
> + if (kvm_pmu_counter_is_high_word(pmc)) {
> + u64 counter_low, counter;
> +
> + reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> + ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx - 1;
> + counter_low = __vcpu_sys_reg(vcpu, reg);
> + counter = lower_32_bits(counter_low) | (counter_idx <<
> 32);
> + counter_idx = upper_32_bits(counter + incr);
> + } else {
> + counter_idx += incr;
> + }
> + }
> +
> + return counter_idx & pmc->bitmask;
> +}
> +
> +/**
> + * kvm_pmu_counter_is_enabled - is a counter active
> + * @vcpu: The vcpu pointer
> + * @select_idx: The counter index
> + */
> +static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx)
> +{
> + u64 mask = kvm_pmu_valid_counter_mask(vcpu);
> +
> + return (__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) &&
> + (__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & mask & BIT(select_idx));
> +}
> +
> +/**
> + * kvnm_pmu_event_is_chained - is a pair of counters chained and enabled
> + * @vcpu: The vcpu pointer
> + * @select_idx: The low counter index
> + */
> +static bool kvm_pmu_event_is_chained(struct kvm_vcpu *vcpu, u64 pair_low)
> +{
> + u64 eventsel, reg;
> +
> + reg = (pair_low + 1 == ARMV8_PMU_CYCLE_IDX)
> + ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + pair_low + 1;
> + eventsel = __vcpu_sys_reg(vcpu, reg) & ARMV8_PMU_EVTYPE_EVENT;
> + if (eventsel != ARMV8_PMUV3_PERFCTR_CHAIN)
> + return false;
> +
> + if (kvm_pmu_counter_is_enabled(vcpu, pair_low) !=
> + kvm_pmu_counter_is_enabled(vcpu, pair_low + 1))
> + return false;
> +
> + return true;
> }
>
> /**
> @@ -61,29 +125,45 @@ 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];
> + u64 reg, pair_low;
>
> 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);
>
> - kvm_pmu_stop_counter(vcpu, pmc);
> - kvm_pmu_sync_counter_enable(vcpu, select_idx);
> + pair_low = (select_idx % 2) ? select_idx - 1 : select_idx;
> +
> + /* Recreate the perf event to reflect the updated sample_period */
> + if (kvm_pmu_event_is_chained(vcpu, pair_low)) {
> + kvm_pmu_stop_release_perf_event_pair(vcpu, pair_low);
> + kvm_pmu_sync_counter_enable_pair(vcpu, pair_low);
> + } else {
> + kvm_pmu_stop_release_perf_event(vcpu, select_idx);
> + kvm_pmu_sync_counter_enable(vcpu, select_idx);
> + }
> }
>
> /**
> * kvm_pmu_release_perf_event - remove the perf event
> * @pmc: The PMU counter pointer
> */
> -static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc)
> +static void kvm_pmu_release_perf_event(struct kvm_vcpu *vcpu,
> + struct kvm_pmc *pmc)
> {
> - if (pmc->perf_event) {
> - perf_event_disable(pmc->perf_event);
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc_alt;
> + u64 pair_alt;
> +
> + pair_alt = (pmc->idx % 2) ? pmc->idx - 1 : pmc->idx + 1;
> + pmc_alt = &pmu->pmc[pair_alt];
> +
> + if (pmc->perf_event)
> perf_event_release_kernel(pmc->perf_event);
> - pmc->perf_event = NULL;
> - }
> +
> + if (pmc->perf_event == pmc_alt->perf_event)
> + pmc_alt->perf_event = NULL;
> +
> + pmc->perf_event = NULL;
> }
>
> /**
> @@ -91,22 +171,65 @@ static void kvm_pmu_release_perf_event(struct kvm_pmc
> *pmc)
> * @vcpu: The vcpu pointer
> * @pmc: The PMU counter pointer
> *
> - * If this counter has been configured to monitor some event, release it
> here.
> + * If this counter has been configured to monitor some event, stop it here.
> */
> static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
> {
> u64 counter, reg;
>
> if (pmc->perf_event) {
> + perf_event_disable(pmc->perf_event);
> counter = kvm_pmu_get_counter_value(vcpu, pmc->idx);
> reg = (pmc->idx == ARMV8_PMU_CYCLE_IDX)
> ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
> __vcpu_sys_reg(vcpu, reg) = counter;
> - kvm_pmu_release_perf_event(pmc);
> }
> }
>
> /**
> + * kvm_pmu_stop_release_perf_event_pair - stop and release a pair of counters
> + * @vcpu: The vcpu pointer
> + * @pmc_low: The PMU counter pointer for lower word
> + * @pmc_high: The PMU counter pointer for higher word
> + *
> + * As chained counters share the underlying perf event, we stop them
> + * both first before discarding the underlying perf event
> + */
> +static void kvm_pmu_stop_release_perf_event_pair(struct kvm_vcpu *vcpu,
> + u64 idx_low)
> +{
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc_low = &pmu->pmc[idx_low];
> + struct kvm_pmc *pmc_high = &pmu->pmc[idx_low + 1];
> +
> + /* Stopping a counter involves adding the perf event value to the
> + * vcpu sys register value prior to releasing the perf event. As
> + * kvm_pmu_get_counter_value may depend on the low counter value we
> + * must always stop the high counter first
> + */
> + kvm_pmu_stop_counter(vcpu, pmc_high);
> + kvm_pmu_stop_counter(vcpu, pmc_low);
> +
> + kvm_pmu_release_perf_event(vcpu, pmc_high);
> + kvm_pmu_release_perf_event(vcpu, pmc_low);
> +}
> +
> +/**
> + * kvm_pmu_stop_release_perf_event - stop and release a counter
> + * @vcpu: The vcpu pointer
> + * @select_idx: The counter index
> + */
> +static void kvm_pmu_stop_release_perf_event(struct kvm_vcpu *vcpu,
> + u64 select_idx)
> +{
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc = &pmu->pmc[select_idx];
> +
> + kvm_pmu_stop_counter(vcpu, pmc);
> + kvm_pmu_release_perf_event(vcpu, pmc);
> +}
> +
> +/**
> * kvm_pmu_vcpu_reset - reset pmu state for cpu
> * @vcpu: The vcpu pointer
> *
> @@ -117,7 +240,7 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu)
> struct kvm_pmu *pmu = &vcpu->arch.pmu;
>
> for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
> - kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]);
> + kvm_pmu_stop_release_perf_event(vcpu, i);
> pmu->pmc[i].idx = i;
> pmu->pmc[i].bitmask = 0xffffffffUL;
> }
> @@ -134,7 +257,7 @@ void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu)
> struct kvm_pmu *pmu = &vcpu->arch.pmu;
>
> for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
> - kvm_pmu_release_perf_event(&pmu->pmc[i]);
> + kvm_pmu_release_perf_event(vcpu, &pmu->pmc[i]);
> }
>
> u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
> @@ -167,53 +290,115 @@ static void kvm_pmu_enable_counter(struct kvm_vcpu
> *vcpu, u64 select_idx)
> }
>
> /**
> + * 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)
> +{
> + kvm_pmu_enable_counter_mask(vcpu, BIT(select_idx));
> +}
> +
> +/**
> + * kvm_pmu_sync_counter_enable_pair - reenable a pair if they should be
> enabled
> + * @vcpu: The vcpu pointer
> + * @pair_low: The low counter index
> + */
> +static void kvm_pmu_sync_counter_enable_pair(struct kvm_vcpu *vcpu, u64
> pair_low)
> +{
> + kvm_pmu_enable_counter_mask(vcpu, BIT(pair_low) | BIT(pair_low + 1));
> +}
> +
> +/**
> + * kvm_pmu_enable_counter_pair - enable counters pair at a time
> + * @vcpu: The vcpu pointer
> + * @val: counters to enable
> + * @pair_low: The low counter index
> + */
> +static void kvm_pmu_enable_counter_pair(struct kvm_vcpu *vcpu, u64 val,
> + u64 pair_low)
> +{
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc_low = &pmu->pmc[pair_low];
> + struct kvm_pmc *pmc_high = &pmu->pmc[pair_low + 1];
> +
> + if (kvm_pmu_event_is_chained(vcpu, pair_low)) {
> + if (pmc_low->perf_event != pmc_high->perf_event)
> + kvm_pmu_stop_release_perf_event_pair(vcpu, pair_low);
> + }
> +
> + if (val & BIT(pair_low))
> + kvm_pmu_enable_counter(vcpu, pair_low);
> +
> + if (val & BIT(pair_low+1))
Style nit: I think there should be spaces around the '+', might be worth
running checkpatch to check for other style stuff.
> + kvm_pmu_enable_counter(vcpu, pair_low + 1);
> +}
> +
> +/**
> * kvm_pmu_enable_counter_mask - enable selected PMU counters
> * @vcpu: The vcpu pointer
> - * @val: the value guest writes to PMCNTENSET register
> + * @val: the value guest writes to PMCNTENSET register or a subset
> *
> * Call perf_event_enable to start counting the perf event
> */
> void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
> {
> int i;
> + 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) || !val)
> return;
>
> - for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
> - if (!(val & BIT(i)))
> - continue;
> -
> - kvm_pmu_enable_counter(vcpu, i);
> - }
> + for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i += 2)
> + kvm_pmu_enable_counter_pair(vcpu, val & set, i);
> }
>
> /**
> - * kvm_pmu_sync_counter_enable - reenable a counter if it should be enabled
> + * kvm_pmu_disable_counter - disable selected PMU counter
> * @vcpu: The vcpu pointer
> * @select_idx: The counter index
> */
> -static void kvm_pmu_sync_counter_enable(struct kvm_vcpu *vcpu,
> - u64 select_idx)
> +static void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 select_idx)
> {
> - u64 set = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc = &pmu->pmc[select_idx];
>
> - if (set & BIT(select_idx))
> - kvm_pmu_enable_counter_mask(vcpu, BIT(select_idx));
> + if (pmc->perf_event) {
> + perf_event_disable(pmc->perf_event);
> + if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
> + kvm_debug("fail to enable perf event\n");
> + }
> }
>
> /**
> - * kvm_pmu_disable_counter - disable selected PMU counter
> - * @vcpu: The vcpu pointer
> - * @pmc: The counter to disable
> + * kvm_pmu_disable_counter_pair - disable counters pair at a time
> + * @val: counters to disable
> + * @pair_low: The low counter index
> */
> -static void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 select_idx)
> +static void kvm_pmu_disable_counter_pair(struct kvm_vcpu *vcpu, u64 val,
> + u64 pair_low)
> {
> struct kvm_pmu *pmu = &vcpu->arch.pmu;
> - struct kvm_pmc *pmc = &pmu->pmc[select_idx];
> + struct kvm_pmc *pmc_low = &pmu->pmc[pair_low];
> + struct kvm_pmc *pmc_high = &pmu->pmc[pair_low + 1];
> +
> + if (!kvm_pmu_event_is_chained(vcpu, pair_low)) {
> + if (pmc_low->perf_event == pmc_high->perf_event) {
> + if (pmc_low->perf_event) {
> + kvm_pmu_stop_release_perf_event_pair(vcpu,
> + pair_low);
> + kvm_pmu_sync_counter_enable_pair(vcpu,
> pair_low);
> + }
> + }
> + }
>
> - if (pmc->perf_event)
> - perf_event_disable(pmc->perf_event);
> + if (val & BIT(pair_low))
> + kvm_pmu_disable_counter(vcpu, pair_low);
> +
> + if (val & BIT(pair_low + 1))
> + kvm_pmu_disable_counter(vcpu, pair_low + 1);
> }
>
> /**
> @@ -230,12 +415,8 @@ void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu,
> u64 val)
> if (!val)
> return;
>
> - for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
> - if (!(val & BIT(i)))
> - continue;
> -
> - kvm_pmu_disable_counter(vcpu, i);
> - }
> + for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i += 2)
> + kvm_pmu_disable_counter_pair(vcpu, val, i);
> }
>
> static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
> @@ -346,6 +527,17 @@ static void kvm_pmu_perf_overflow(struct perf_event
> *perf_event,
>
> __vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(idx);
>
> + if (kvm_pmu_event_is_chained(vcpu, idx)) {
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc_high = &pmu->pmc[idx + 1];
> +
> + if (!(--pmc_high->overflow_count)) {
> + __vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(idx + 1);
> + pmc_high->overflow_count = U32_MAX + 1UL;
> + }
> +
> + }
> +
> if (kvm_pmu_overflow_status(vcpu)) {
> kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
> kvm_vcpu_kick(vcpu);
> @@ -440,6 +632,10 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu
> *vcpu, u64 select_idx)
> select_idx != ARMV8_PMU_CYCLE_IDX)
> return;
>
> + /* Handled by even event */
> + if (eventsel == ARMV8_PMUV3_PERFCTR_CHAIN)
> + return;
> +
> memset(&attr, 0, sizeof(struct perf_event_attr));
> attr.type = PERF_TYPE_RAW;
> attr.size = sizeof(attr);
> @@ -452,6 +648,9 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu
> *vcpu, u64 select_idx)
> attr.config = (select_idx == ARMV8_PMU_CYCLE_IDX) ?
> ARMV8_PMUV3_PERFCTR_CPU_CYCLES : eventsel;
>
> + if (kvm_pmu_event_is_chained(vcpu, select_idx))
> + attr.config1 |= 0x1;
I'm not very familiar with the usage of perf attributes configs, but is
there any chance we could name this flag? Even if only for the local
file? Something like PERF_ATTR_CFG1_KVM_PMU_CHAINED (unless there is an
existing naming convention for event attributes).
Thanks,
--
Julien Thierry
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