Subject: [PATCH 1/1] KVM: ARM64: Fix the issues when PMCCFILTR is configured

From: [email-masked] (cov at codeaurora.org)
Date: Wed, 02 Nov 2016 22:11:16 -0600

Hi Wei,

On 2016-11-02 14:55, Wei Huang wrote:
> KVM calls kvm_pmu_set_counter_event_type() when PMCCFILTR is 
> configured.
> But this function can't deals with PMCCFILTR correctly because the 
> evtCount
> bit of PMCCFILTR, which is reserved 0, conflits with the SW_INCR event
> type of other PMXEVTYPER<n> registers. To fix it, when eventsel == 0, 
> KVM
> shouldn't return immediately, but instead it needs to check further if
> select_idx is ARMV8_PMU_CYCLE_IDX.
> 
> Another issue is that KVM shouldn't copy the eventsel bits of 
> PMCCFILTER
> directly to attr.config. Istead it shoudl convert the request to
> perf_event of type 0x11 (i.e. the "cpu cycle" event type).
> 
> Signed-off-by: Wei Huang <[email-masked]>
> ---
>  virt/kvm/arm/pmu.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 6e9c40e..13cc812 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -379,7 +379,8 @@ void kvm_pmu_set_counter_event_type(struct
> kvm_vcpu *vcpu, u64 data,
>  	eventsel = data & ARMV8_PMU_EVTYPE_EVENT;
> 
>  	/* Software increment event does't need to be backed by a perf event 
> */
> -	if (eventsel == ARMV8_PMU_EVTYPE_EVENT_SW_INCR)
> +	if (eventsel == ARMV8_PMU_EVTYPE_EVENT_SW_INCR &&
> +	    select_idx != ARMV8_PMU_CYCLE_IDX)
>  		return;
> 
>  	memset(&attr, 0, sizeof(struct perf_event_attr));
> @@ -391,7 +392,7 @@ void kvm_pmu_set_counter_event_type(struct
> kvm_vcpu *vcpu, u64 data,
>  	attr.exclude_kernel = data & ARMV8_PMU_EXCLUDE_EL1 ? 1 : 0;
>  	attr.exclude_hv = 1; /* Don't count EL2 events */
>  	attr.exclude_host = 1; /* Don't count host events */
> -	attr.config = eventsel;
> +	attr.config = (select_idx == ARMV8_PMU_CYCLE_IDX) ? 0x011 : eventsel;

Nit: Is there some way you could use ARMV8_PMUV3_PERFCTR_CPU_CYCLES 
currently
defined in arch/arm64/kernel/perf_event.c?

Thanks,
Cov