Re: [PATCH v3 10/10] KVM: arm/arm64: PMU: remove request-less vcpu kick

[Christoffer Dall <cdall@linaro.org>]

On Wed, May 03, 2017 at 06:06:35PM +0200, Andrew Jones wrote:
> Refactor PMU overflow handling in order to remove the request-less
> vcpu kick.  Now, since kvm_vgic_inject_irq() uses vcpu requests,
> there should be no chance that a kick sent at just the wrong time
> (between the VCPU's call to kvm_pmu_flush_hwstate() and before it
> enters guest mode) results in a failure for the guest to see updated
> GIC state until its next exit some time later for some other reason.
> 
> Signed-off-by: Andrew Jones <drjones@redhat.com>

Reviewed-by: Christoffer Dall <cdall@linaro.org>

> ---
>  virt/kvm/arm/pmu.c | 40 +++++++++++++++++++---------------------
>  1 file changed, 19 insertions(+), 21 deletions(-)
> 
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 4b43e7f3b158..2451607dc25e 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -203,6 +203,23 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
>  	return reg;
>  }
>  
> +static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_pmu *pmu = &vcpu->arch.pmu;
> +	bool overflow = !!kvm_pmu_overflow_status(vcpu);
> +
> +	if (pmu->irq_level == overflow)
> +		return;
> +
> +	pmu->irq_level = overflow;
> +
> +	if (likely(irqchip_in_kernel(vcpu->kvm))) {
> +		int ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> +					      pmu->irq_num, overflow);
> +		WARN_ON(ret);
> +	}
> +}
> +
>  /**
>   * kvm_pmu_overflow_set - set PMU overflow interrupt
>   * @vcpu: The vcpu pointer
> @@ -210,37 +227,18 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
>   */
>  void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
>  {
> -	u64 reg;
> -
>  	if (val == 0)
>  		return;
>  
>  	vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
> -	reg = kvm_pmu_overflow_status(vcpu);
> -	if (reg != 0)
> -		kvm_vcpu_kick(vcpu);
> +	kvm_pmu_check_overflow(vcpu);
>  }
>  
>  static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
>  {
> -	struct kvm_pmu *pmu = &vcpu->arch.pmu;
> -	bool overflow;
> -
>  	if (!kvm_arm_pmu_v3_ready(vcpu))
>  		return;
> -
> -	overflow = !!kvm_pmu_overflow_status(vcpu);
> -	if (pmu->irq_level == overflow)
> -		return;
> -
> -	pmu->irq_level = overflow;
> -
> -	if (likely(irqchip_in_kernel(vcpu->kvm))) {
> -		int ret;
> -		ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
> -					  pmu->irq_num, overflow);
> -		WARN_ON(ret);
> -	}
> +	kvm_pmu_check_overflow(vcpu);
>  }
>  
>  bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)
> -- 
> 2.9.3
>