virtio: add virtio_detach_element()

During device reset or similar situations a VirtQueueElement needs to be
freed without pushing it onto the used ring or rewinding the virtqueue.
Extract a new function to do this.

Later patches add virtio_detach_element() calls to existing device so
that scatter-gather lists are unmapped and vq->inuse goes back to zero
during device reset.  Currently some devices don't bother and simply
call g_free(elem) which is not a clean way to throw away a
VirtQueueElement.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Ladi Prosek <lprosek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2016-09-19 14:28:03 +01:00 committed by Michael S. Tsirkin
parent af78c91f57
commit 2640d2a5ff
2 changed files with 27 additions and 2 deletions

View file

@ -155,6 +155,8 @@ void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_num);
void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len);
void virtqueue_flush(VirtQueue *vq, unsigned int count);
void virtqueue_detach_element(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len);
void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len);
bool virtqueue_rewind(VirtQueue *vq, unsigned int num);