Re: [PATCH v3 44/59] KVM: arm/arm64: GICv4: Handle MOVI applied to a VLPI

Christoffer Dall
2017-08-28T18:16:13Z

On Mon, Jul 31, 2017 at 06:26:22PM +0100, Marc Zyngier wrote:
> When the guest issues a MOVI, we need to tell the physical ITS
> that we're now targetting a new vcpu. This is done by extracting
> the current mapping, updating the target, and reapplying the
> mapping. The core ITS code should do the right thing.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> virt/kvm/arm/vgic/vgic-its.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 79bac93d3e7d..aaad577ce328 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -706,6 +706,19 @@ static int vgic_its_cmd_handle_movi(struct kvm *kvm, struct vgic_its *its,
> ite->irq->target_vcpu = vcpu;
> spin_unlock(&ite->irq->irq_lock);
>
> + if (ite->irq->hw) {
> + struct its_vlpi_map map;
> + int ret;
> +
> + ret = its_get_vlpi(ite->irq->host_irq, &map);
> + if (ret)
> + return ret;
> +
> + map.vpe_idx = vcpu->vcpu_id;
> +
> + return its_map_vlpi(ite->irq->host_irq, &map);

Since you're not holding the irq_lock across these two calls, would it
be possible that the forwarding was removed through some other call path
here, and could you end up passing an invalid host_irq to its_map_vlpi?

Thanks,
-Christoffer

> + }
> +
> return 0;
> }
>
> --
> 2.11.0
>