On Fri, 13 Apr 2018 11:01:49 +0800
Jason Wang <jasowang@redhat.com> wrote:
> When IOMMU is enabled, we store virtqueue metadata as iova (though it
> may has _phys suffix) and access them through dma helpers. Any
> translation failures could be reported by IOMMU.
>
> In this case, trying to validate iova against gpa won't work and will
> cause a false error reporting. So this patch bypasses the ring
> verification if IOMMU is enabled which is similar to the behavior
> before 0ca1fd2d6878 that calls vhost_memory_map() which is a nop when
> IOMMU is enabled.
>
> Fixes: 0ca1fd2d6878 ("vhost: Simplify ring verification checks")
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Looks like candidat for 2.12 if it's not too late?
> ---
> hw/virtio/vhost.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index f51bf57..9d5850a 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -342,6 +342,10 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
> "used ring"
> };
>
> + if (vhost_dev_has_iommu(dev)) {
> + return 0;
> + }
> +
> for (i = 0; i < dev->nvqs; ++i) {
> struct vhost_virtqueue *vq = dev->vqs + i;
>