Re: [PATCH v2 3/5] KVM: arm/arm64: re-create event when setting counter value

[Andrew Murray <andrew.murray@arm.com>]

On Wed, Feb 13, 2019 at 02:28:51PM +0000, Suzuki K Poulose 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 <andrew.murray@arm.com>
> > ---
> >   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
> 
> nit: data no longer exists.
> 

Thanks for the review,

Andrew Murray

> 
> > - *
> > - * 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)
> >   {
> 
> With the comment from Julien addressed,
> 
> Reviewed-by: Suzuki K Poulose <suzuki.poulse@arm.com>

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel