Re: [PATCH 2/4] KVM: arm/arm64: re-create event when setting counter value

[Julien Thierry <julien.thierry@arm.com>]

Hi Andrew,

On 22/01/2019 10:49, 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 | 39 ++++++++++++++++++++++++++++++---------
>  1 file changed, 30 insertions(+), 9 deletions(-)
> 
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 531d27f..4464899 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -24,6 +24,8 @@
>  #include <kvm/arm_pmu.h>
>  #include <kvm/arm_vgic.h>
>  
> +static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 data,
> +				      u64 select_idx);
>  /**
>   * kvm_pmu_get_counter_value - get PMU counter value
>   * @vcpu: The vcpu pointer
> @@ -57,11 +59,18 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
>   */
>  void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
>  {
> -	u64 reg;
> +	u64 reg, data;
>  
>  	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);
> +
> +	reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> +	      ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + select_idx;
> +	data = __vcpu_sys_reg(vcpu, reg + select_idx);

I think this should be just "reg" instead of "reg + select_idx".

Cheers,

-- 
Julien Thierry

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