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

Christoffer Dall
2017-05-06T18:55:48Z

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
>