On Tue, Feb 05, 2019 at 12:21:25PM +0000, Julien Thierry wrote:
> 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 <[email protected]>
> > ---
> > 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 <[email protected]>
Thanks for spotting this and for the review.
Thanks,
Andrew Murray
>
> > + kvm_pmu_create_perf_event(vcpu, select_idx);
> > +}
> > +
> > bool kvm_arm_support_pmu_v3(void)
> > {
> > /*
> >
>
> --
> Julien Thierry
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