Hi Andrew,
On 04/02/2019 16:53, Andrew Murray wrote:
> The perf event sample_period is currently set based upon the current
> counter value, when PMXEVTYPER is written to and the perf event is created.
> However the user may choose to write the type before the counter value in
> which case sample_period will be set incorrectly. Let's instead decouple
> event creation from PMXEVTYPER and (re)create the event in either
> suitation.
>
> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
> ---
> virt/kvm/arm/pmu.c | 40 +++++++++++++++++++++++++++++++---------
> 1 file changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 6e7c179..95d74ec 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -24,6 +24,7 @@
> #include <kvm/arm_pmu.h>
> #include <kvm/arm_vgic.h>
>
> +static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx);
> /**
> * kvm_pmu_get_counter_value - get PMU counter value
> * @vcpu: The vcpu pointer
> @@ -62,6 +63,9 @@ void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
> 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);
> }
>
> /**
> @@ -378,23 +382,22 @@ static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx)
> }
>
> /**
> - * kvm_pmu_set_counter_event_type - set selected counter to monitor some event
> + * kvm_pmu_create_perf_event - create a perf event for a counter
> * @vcpu: The vcpu pointer
> - * @data: The data guest writes to PMXEVTYPER_EL0
> + * @data: Type of event as per PMXEVTYPER_EL0 format
> * @select_idx: The number of selected counter
> - *
> - * When OS accesses PMXEVTYPER_EL0, that means it wants to set a PMC to count an
> - * event with given hardware event number. Here we call perf_event API to
> - * emulate this action and create a kernel perf event for it.
> */
> -void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
> - u64 select_idx)
> +static void kvm_pmu_create_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, reg, data;
> +
> + reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> + ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + select_idx;
> + data = __vcpu_sys_reg(vcpu, reg);
>
> kvm_pmu_stop_counter(vcpu, pmc);
> eventsel = data & ARMV8_PMU_EVTYPE_EVENT;
> @@ -431,6 +434,25 @@ void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
> pmc->perf_event = event;
> }
>
> +/**
> + * kvm_pmu_set_counter_event_type - set selected counter to monitor some event
> + * @vcpu: The vcpu pointer
> + * @data: The data guest writes to PMXEVTYPER_EL0
> + * @select_idx: The number of selected counter
> + *
> + * When OS accesses PMXEVTYPER_EL0, that means it wants to set a PMC to count an
> + * event with given hardware event number. Here we call perf_event API to
> + * emulate this action and create a kernel perf event for it.
> + */
> +void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
> + u64 select_idx)
> +{
> + u64 event_type = data & ARMV8_PMU_EVTYPE_MASK;
> +> + __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + select_idx) = event_type;
I think there has been a wrong split. In the next patch you add the
check for the cycle counter but I believe it should be already present here.
With that fixed:
Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx>
> + kvm_pmu_create_perf_event(vcpu, select_idx);
> +}
> +
> bool kvm_arm_support_pmu_v3(void)
> {
> /*
>
--
Julien Thierry
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