From e66bcc408146730958d1a840bda85d7ad51e0cd7 Mon Sep 17 00:00:00 2001 From: Halil Pasic Date: Mon, 19 Dec 2016 16:44:44 +0100 Subject: 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 --- hw/virtio/virtio.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'hw') diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 933a3d7..8357218 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", -- cgit v1.1