Commit bccdef6b authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Michael S. Tsirkin
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virtio: recalculate vq->inuse after migration 



The vq->inuse field is not migrated.  Many devices don't hold
VirtQueueElements across migration so it doesn't matter that vq->inuse
starts at 0 on the destination QEMU.

At least virtio-serial, virtio-blk, and virtio-balloon migrate while
holding VirtQueueElements.  For these devices we need to recalculate
vq->inuse upon load so the value is correct.

Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 6bbbb0ac

hw/virtio/virtio.c

+15 −0
Original line number Diff line number Diff line
@@ -1648,6 +1648,21 @@ 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;

            }

        }

    }