Re: [PATCH] KVM: arm/arm64: VGIC: Kick new VCPU on interrupt migration

[Christoffer Dall <christoffer.dall@arm.com>]

On Tue, Apr 17, 2018 at 11:23:49AM +0100, Andre Przywara wrote:
> When vgic_prune_ap_list() finds an interrupt that needs to be migrated
> to a new VCPU, we should notify this VCPU of the pending interrupt,
> since it requires immediate action.
> Kick this VCPU once we have added the new IRQ to the list, but only
> after dropping the locks.
> 
> Reported-by: Stefano Stabellini <sstabellini@kernel.org>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>

Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>

> ---
>  virt/kvm/arm/vgic/vgic.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index e74baec76361..4b6d72939c42 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -594,6 +594,7 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
>  
>  	list_for_each_entry_safe(irq, tmp, &vgic_cpu->ap_list_head, ap_list) {
>  		struct kvm_vcpu *target_vcpu, *vcpuA, *vcpuB;
> +		bool target_vcpu_needs_kick = false;
>  
>  		spin_lock(&irq->irq_lock);
>  
> @@ -664,11 +665,18 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
>  			list_del(&irq->ap_list);
>  			irq->vcpu = target_vcpu;
>  			list_add_tail(&irq->ap_list, &new_cpu->ap_list_head);
> +			target_vcpu_needs_kick = true;
>  		}
>  
>  		spin_unlock(&irq->irq_lock);
>  		spin_unlock(&vcpuB->arch.vgic_cpu.ap_list_lock);
>  		spin_unlock_irqrestore(&vcpuA->arch.vgic_cpu.ap_list_lock, flags);
> +
> +		if (target_vcpu_needs_kick) {
> +			kvm_make_request(KVM_REQ_IRQ_PENDING, target_vcpu);
> +			kvm_vcpu_kick(target_vcpu);
> +		}
> +
>  		goto retry;
>  	}
>  
> -- 
> 2.14.1
>