From: Jason Wang <jasowang@redhat.com>

Date: Fri, 25 Sep 2015 13:21:29 +0800

Subject: [PATCH] virtio: introduce virtqueue_discard()

This patch introduces virtqueue_discard() to discard a descriptor and

unmap the sgs. This will be used by the patch that will discard

descriptor when packet is truncated.

Cc: Michael S. Tsirkin <mst@redhat.com>

Signed-off-by: Jason Wang <jasowang@redhat.com>

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

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

(cherry picked from commit 29b9f5efd78ae0f9cc02dd169b6e80d2c404bade)

---

 hw/virtio/virtio.c         | 7 +++++++

 include/hw/virtio/virtio.h | 2 ++

 2 files changed, 9 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c

index 242aecb..b1f4e16 100644

--- a/hw/virtio/virtio.c

+++ b/hw/virtio/virtio.c

@@ -266,6 +266,13 @@ static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,

                                   0, elem->out_sg[i].iov_len);

 }

+void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,

+                       unsigned int len)

+{

+    vq->last_avail_idx--;

+    virtqueue_unmap_sg(vq, elem, len);

+}

+

 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,

                     unsigned int len, unsigned int idx)

 {

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h

index cccae89..8023bde 100644

--- a/include/hw/virtio/virtio.h

+++ b/include/hw/virtio/virtio.h

@@ -146,6 +146,8 @@ void virtio_del_queue(VirtIODevice *vdev, int n);

 void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,

                     unsigned int len);

 void virtqueue_flush(VirtQueue *vq, unsigned int count);

+void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,

+                       unsigned int len);

 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,

                     unsigned int len, unsigned int idx);