Hi Andrew,
On 05/21/2019 04:52 PM, Andrew Murray wrote:
> ARMv8 provides support for chained PMU counters, where an event type
> of 0x001E is set for odd-numbered counters, the event counter will
> increment by one for each overflow of the preceding even-numbered
> counter. Let's emulate this in KVM by creating a 64 bit perf counter
> when a user chains two emulated counters together.
>
> For chained events we only support generating an overflow interrupt
> on the high counter. We use the attributes of the low counter to
> determine the attributes of the perf event.
>
> Suggested-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
> ---
> include/kvm/arm_pmu.h | 2 +
> virt/kvm/arm/pmu.c | 246 ++++++++++++++++++++++++++++++++++++------
> 2 files changed, 215 insertions(+), 33 deletions(-)
>
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index b73f31baca52..8b434745500a 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -22,6 +22,7 @@
> #include <asm/perf_event.h>
>
> #define ARMV8_PMU_CYCLE_IDX (ARMV8_PMU_MAX_COUNTERS - 1)
> +#define ARMV8_PMU_MAX_COUNTER_PAIRS ((ARMV8_PMU_MAX_COUNTERS + 1) >> 1)
>
> #ifdef CONFIG_KVM_ARM_PMU
>
> @@ -34,6 +35,7 @@ struct kvm_pmc {
> struct kvm_pmu {
> int irq_num;
> struct kvm_pmc pmc[ARMV8_PMU_MAX_COUNTERS];
> + DECLARE_BITMAP(chained, ARMV8_PMU_MAX_COUNTER_PAIRS);
> bool ready;
> bool created;
> bool irq_level;
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index ae1e886d4a1a..4b0981c402c6 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -25,28 +25,128 @@
> #include <kvm/arm_vgic.h>
>
> static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx);
> +
> +#define PERF_ATTR_CFG1_KVM_PMU_CHAINED 0x1
> +
> +static struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
> +{
> + struct kvm_pmu *pmu;
> + struct kvm_vcpu_arch *vcpu_arch;
> +
> + pmc -= pmc->idx;
> + pmu = container_of(pmc, struct kvm_pmu, pmc[0]);
> + vcpu_arch = container_of(pmu, struct kvm_vcpu_arch, pmu);
> + return container_of(vcpu_arch, struct kvm_vcpu, arch);
> +}
> +
> /**
> - * kvm_pmu_get_counter_value - get PMU counter value
> + * kvm_pmu_pmc_is_chained - determine if the pmc is chained
> + * @pmc: The PMU counter pointer
> + */
> +static bool kvm_pmu_pmc_is_chained(struct kvm_pmc *pmc)
> +{
> + struct kvm_vcpu *vcpu = kvm_pmc_to_vcpu(pmc);
> +
> + return test_bit(pmc->idx >> 1, vcpu->arch.pmu.chained);
> +}
> +
> +/**
> + * kvm_pmu_pmc_is_high_counter - determine if select_idx is a high/low counter
> + * @select_idx: The counter index
> + */
> +static bool kvm_pmu_pmc_is_high_counter(u64 select_idx)
> +{
> + return select_idx & 0x1;
> +}
> +
> +/**
> + * kvm_pmu_get_canonical_pmc - obtain the canonical pmc
> + * @pmc: The PMU counter pointer
> + *
> + * When a pair of PMCs are chained together we use the low counter (canonical)
> + * to hold the underlying perf event.
> + */
> +static struct kvm_pmc *kvm_pmu_get_canonical_pmc(struct kvm_pmc *pmc)
> +{
> + if (kvm_pmu_pmc_is_chained(pmc) &&
> + kvm_pmu_pmc_is_high_counter(pmc->idx))
> + return pmc - 1;
> +
> + return pmc;
> +}
> +
> +/**
> + * kvm_pmu_idx_has_chain_evtype - determine if the event type is chain
> * @vcpu: The vcpu pointer
> * @select_idx: The counter index
> */
> -u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
> +static bool kvm_pmu_idx_has_chain_evtype(struct kvm_vcpu *vcpu, u64 select_idx)
> {
> - u64 counter, reg, enabled, running;
> - struct kvm_pmu *pmu = &vcpu->arch.pmu;
> - struct kvm_pmc *pmc = &pmu->pmc[select_idx];
> + u64 eventsel, reg;
>
> - reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> - ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx;
> - counter = __vcpu_sys_reg(vcpu, reg);
> + select_idx |= 0x1;
> +
> + if (select_idx == ARMV8_PMU_CYCLE_IDX)
> + return false;
> +
> + reg = PMEVTYPER0_EL0 + select_idx;
> + eventsel = __vcpu_sys_reg(vcpu, reg) & ARMV8_PMU_EVTYPE_EVENT;
> +
> + return armv8pmu_evtype_is_chain(eventsel);
> +}
> +
> +/**
> + * kvm_pmu_get_pair_counter_value - get PMU counter value
> + * @vcpu: The vcpu pointer
> + * @pmc: The PMU counter pointer
> + */
> +static u64 kvm_pmu_get_pair_counter_value(struct kvm_vcpu *vcpu,
> + struct kvm_pmc *pmc)
> +{
> + u64 counter, counter_high, reg, enabled, running;
> +
> + if (kvm_pmu_pmc_is_chained(pmc)) {
> + pmc = kvm_pmu_get_canonical_pmc(pmc);
> + reg = PMEVCNTR0_EL0 + pmc->idx;
> +
> + counter = __vcpu_sys_reg(vcpu, reg);
> + counter_high = __vcpu_sys_reg(vcpu, reg + 1);
> +
> + counter = lower_32_bits(counter) | (counter_high << 32);
> + } else {
> + reg = (pmc->idx == ARMV8_PMU_CYCLE_IDX)
> + ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
> + counter = __vcpu_sys_reg(vcpu, reg);
> + }
>
> - /* The real counter value is equal to the value of counter register plus
> + /*
> + * 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,
> &running);
>
> + return counter;
> +}
> +
> +/**
> + * kvm_pmu_get_counter_value - get PMU counter value
> + * @vcpu: The vcpu pointer
> + * @select_idx: The counter index
> + */
> +u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
> +{
> + u64 counter;
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> + struct kvm_pmc *pmc = &pmu->pmc[select_idx];
> +
> + counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);
> +
> + if (kvm_pmu_pmc_is_chained(pmc) &&
> + kvm_pmu_pmc_is_high_counter(select_idx))
> + counter >>= 32;
> +
> return counter & pmc->bitmask;
> }
>
> @@ -74,6 +174,7 @@ void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
> */
> static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc)
> {
> + pmc = kvm_pmu_get_canonical_pmc(pmc);
> if (pmc->perf_event) {
> perf_event_disable(pmc->perf_event);
> perf_event_release_kernel(pmc->perf_event);
> @@ -91,13 +192,24 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
> {
> u64 counter, reg;
>
> - if (pmc->perf_event) {
> + pmc = kvm_pmu_get_canonical_pmc(pmc);
> + if (!pmc->perf_event)
> + return;
> +
> + if (kvm_pmu_pmc_is_chained(pmc)) {
> + counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);
> +
> + reg = PMEVCNTR0_EL0 + pmc->idx;
> + __vcpu_sys_reg(vcpu, reg) = counter & pmc->bitmask;
> + __vcpu_sys_reg(vcpu, reg + 1) = (counter >> 32) & pmc->bitmask;
> + } else {
> 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_release_perf_event(pmc);
> }
>
> /**
> @@ -115,6 +227,8 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu)
> pmu->pmc[i].idx = i;
> pmu->pmc[i].bitmask = 0xffffffffUL;
> }
> +
> + bitmap_zero(vcpu->arch.pmu.chained, ARMV8_PMU_MAX_COUNTER_PAIRS);
> }
>
> /**
> @@ -154,6 +268,7 @@ 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;
> + struct perf_event *perf_event;
>
> if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) || !val)
> return;
> @@ -163,9 +278,21 @@ void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
> continue;
>
> pmc = &pmu->pmc[i];
> +
> + /*
> + * For high counters of chained events we must recreate the
> + * perf event with the long (64bit) attribute set.
> + */
> + if (kvm_pmu_pmc_is_chained(pmc) &&
> + kvm_pmu_pmc_is_high_counter(i)) {
> + kvm_pmu_create_perf_event(vcpu, i);
> + continue;
> + }
> +
> + pmc = kvm_pmu_get_canonical_pmc(pmc);
But pmc is already a canonical pmc, we don't need to call
kvm_pmu_get_canonical_pmc(). The condition above is the same as the one
use in kvm_pmu_get_canonical_pmc(), so no "non canonical" pmc ever
reaches that point. I would understand putting a comment to clarify that
fact.
> if (pmc->perf_event) {
> perf_event_enable(pmc->perf_event);
> - if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
> + if (perf_event->state != PERF_EVENT_STATE_ACTIVE)
You forgot to set perf_event.
> kvm_debug("fail to enable perf event\n");
> }
> }
> @@ -192,6 +319,18 @@ void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
> continue;
>
> pmc = &pmu->pmc[i];
> +
> + /*
> + * For high counters of chained events we must recreate the
> + * perf event with the long (64bit) attribute unset.
> + */
> + if (kvm_pmu_pmc_is_chained(pmc) &&
> + kvm_pmu_pmc_is_high_counter(i)) {
> + kvm_pmu_create_perf_event(vcpu, i);
> + continue;
> + }
> +
> + pmc = kvm_pmu_get_canonical_pmc(pmc);
Same as the enable case, we know pmc is already canonical, no need to
call the function.
Thanks,
--
Julien Thierry
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