Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into sta…

…ging

virtio: fixes

some bugfixes for virtio
balloon is still broken wrt migration

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Tue 23 Aug 2016 17:33:11 BST
# gpg:                using RSA key 0x281F0DB8D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"
# Primary key fingerprint: 0270 606B 6F3C DF3D 0B17  0970 C350 3912 AFBE 8E67
#      Subkey fingerprint: 5D09 FD08 71C8 F85B 94CA  8A0D 281F 0DB8 D28D 5469

* remotes/mst/tags/for_upstream:
  virtio: decrement vq->inuse in virtqueue_discard()
  virtio: recalculate vq->inuse after migration

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/virtio/virtio.c

@@ -268,6 +268,7 @@ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
                        unsigned int len)
 {
     vq->last_avail_idx--;
+    vq->inuse--;
     virtqueue_unmap_sg(vq, elem, len);
 }
 
@@ -1648,6 +1649,21 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
             }
             vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]);
             vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]);
+
+            /*
+             * Some devices migrate VirtQueueElements that have been popped
+             * from the avail ring but not yet returned to the used ring.
+             */
+            vdev->vq[i].inuse = vdev->vq[i].last_avail_idx -
+                                vdev->vq[i].used_idx;
+            if (vdev->vq[i].inuse > vdev->vq[i].vring.num) {
+                error_report("VQ %d size 0x%x < last_avail_idx 0x%x - "
+                             "used_idx 0x%x",
+                             i, vdev->vq[i].vring.num,
+                             vdev->vq[i].last_avail_idx,
+                             vdev->vq[i].used_idx);
+                return -1;
+            }
         }
     }