Re: [PATCH] KVM: arm/arm64: vgic: Reevaluate level sensitive interrupts on enable

[Marc Zyngier <maz@kernel.org>]

On Wed,  7 Aug 2019 10:53:20 +0100
Alexandru Elisei <alexandru.elisei@arm.com> wrote:

> A HW mapped level sensitive interrupt asserted by a device will not be put
> into the ap_list if it is disabled at the VGIC level. When it is enabled
> again, it will be inserted into the ap_list and written to a list register
> on guest entry regardless of the state of the device.
> 
> We could argue that this can also happen on real hardware, when the command
> to enable the interrupt reached the GIC before the device had the chance to
> de-assert the interrupt signal; however, we emulate the distributor and
> redistributors in software and we can do better than that.
> 
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
>  virt/kvm/arm/vgic/vgic-mmio.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index 3ba7278fb533..44efc2ff863f 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -113,6 +113,22 @@ void vgic_mmio_write_senable(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
>  		raw_spin_lock_irqsave(&irq->irq_lock, flags);
> +		if (vgic_irq_is_mapped_level(irq)) {
> +			bool was_high = irq->line_level;
> +
> +			/*
> +			 * We need to update the state of the interrupt because
> +			 * the guest might have changed the state of the device
> +			 * while the interrupt was disabled at the VGIC level.
> +			 */
> +			irq->line_level = vgic_get_phys_line_level(irq);
> +			/*
> +			 * Deactivate the physical interrupt so the GIC will let
> +			 * us know when it is asserted again.
> +			 */
> +			if (!irq->active && was_high && !irq->line_level)
> +				vgic_irq_set_phys_active(irq, false);
> +		}
>  		irq->enabled = true;
>  		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
>  


Applied, thanks.

	M.
-- 
Without deviation from the norm, progress is not possible.

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