[Qemu-devel] [PULL 21/22] virtio: introduce virtqueue_discard()

["Michael S. Tsirkin" <mst@redhat.com>]

From: Jason Wang <jasowang@redhat.com>

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>
---
 include/hw/virtio/virtio.h | 2 ++
 hw/virtio/virtio.c         | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 6201ee8..9d09115 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);
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d6a2bca..c9bf10c 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)
 {
-- 
MST