Re: [Qemu-devel] [PATCH v1 00/16] packed ring virtio-net backend support

[Wei Xu <wexu@redhat.com>]

On Fri, Nov 23, 2018 at 01:57:37PM +0800, Wei Xu wrote:
> On Thu, Nov 22, 2018 at 06:57:31PM +0100, Maxime Coquelin wrote:
> > Hi Wei,
> > 
> > I just tested your series with Tiwei's v3, and it fails
> > with ctrl vq enabled:
> > qemu-system-x86_64: virtio-net ctrl missing headers
> 
> OK, I haven't tried Tiwei's v3 yet, will give it a try.

Hi Maxime,
It is caused by the _F_NEXT flag bit for indirect descriptor as
mentioned by tiwei, this patch is needed to fix it.

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 7487d3d..8e61e6f 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1478,7 +1478,11 @@ static void *virtqueue_packed_pop(VirtQueue *vq, size_t sz)
             i -= vq->vring.num;
         }
 
-        if (desc.flags & VRING_DESC_F_NEXT) {
+        if (cache == &indirect_desc_cache) {
+            if (i == max)
+                break;
+            vring_packed_desc_read(vq->vdev, &desc, cache, i);
+        } else if (desc.flags & VRING_DESC_F_NEXT) {
             vring_packed_desc_read(vq->vdev, &desc, cache, i);
         } else {