[PATCH v3 09/19] vhost: Track number of descs in SVQDescState

["Eugenio Pérez" <eperezma@redhat.com>]

A guest's buffer continuos on GPA may need multiple descriptors on
qemu's VA, so SVQ should track its length sepparatedly.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h | 6 ++++++
 hw/virtio/vhost-shadow-virtqueue.c | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index d646c35054..5c7e7cbab6 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -17,6 +17,12 @@
 
 typedef struct SVQDescState {
     VirtQueueElement *elem;
+
+    /*
+     * Number of descriptors exposed to the device. May or may not match
+     * guest's
+     */
+    unsigned int ndescs;
 } SVQDescState;
 
 /* Shadow virtqueue to relay notifications */
diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index d12f5afffb..ae5bd6efa8 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -257,6 +257,7 @@ static int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
     }
 
     svq->desc_state[qemu_head].elem = elem;
+    svq->desc_state[qemu_head].ndescs = ndescs;
     vhost_svq_kick(svq);
     return 0;
 }
@@ -417,8 +418,7 @@ static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
         return NULL;
     }
 
-    num = svq->desc_state[used_elem.id].elem->in_num +
-          svq->desc_state[used_elem.id].elem->out_num;
+    num = svq->desc_state[used_elem.id].ndescs;
     last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
     svq->desc_next[last_used_chain] = svq->free_head;
     svq->free_head = used_elem.id;
-- 
2.31.1