From: Halil Pasic Date: Mon, 19 Dec 2016 15:44:44 +0000 (+0100) Subject: virtio: fix vq->inuse recalc after migr X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e66bcc408146730958d1a840bda85d7ad51e0cd7;p=qemu.git virtio: fix vq->inuse recalc after migr Correct recalculation of vq->inuse after migration for the corner case where the avail_idx has already wrapped but used_idx not yet. Also change the type of the VirtQueue.inuse to unsigned int. This is done to be consistent with other members representing sizes (VRing.num), and because C99 guarantees max ring size < UINT_MAX but does not guarantee max ring size < INT_MAX. Signed-off-by: Halil Pasic Fixes: bccdef6b ("virtio: recalculate vq->inuse after migration") CC: qemu-stable@nongnu.org Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefan Hajnoczi --- diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 933a3d749a..8357218ae6 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -93,7 +93,7 @@ struct VirtQueue uint16_t queue_index; - int inuse; + unsigned int inuse; uint16_t vector; VirtIOHandleOutput handle_output; @@ -1878,9 +1878,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id) /* * Some devices migrate VirtQueueElements that have been popped * from the avail ring but not yet returned to the used ring. + * Since max ring size < UINT16_MAX it's safe to use modulo + * UINT16_MAX + 1 subtraction. */ - vdev->vq[i].inuse = vdev->vq[i].last_avail_idx - - vdev->vq[i].used_idx; + vdev->vq[i].inuse = (uint16_t)(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",