[PATCH] hw/virtio: Fix packed virtqueue flush used_idx

[Wafer <wafer@jaguarmicro.com>]

For indirect descriptors the elelm->ndescs was one,
For direct descriptors the elele->ndesc was the numbe of entries.
elem->ndescs = (desc_cache == &indirect_desc_cache) ? 1 : elem_entries;

When flushing multiple elemes,
the used_idx should be added to all the privious numeric entry value.

Signed-off-by: Wafer <wafer@jaguarmicro.com>
---
 hw/virtio/virtio.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d229755eae..44f1d2fcfc 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -957,12 +957,17 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count)
         return;
     }
 
+    /*
+     * When the descriptor's flag was 'INDIRECT', the value of 'ndescs' is one.
+     * When the descriptor's flag was 'chain', the value of 'ndescs'
+     * is the number of entries.
+     */
+    ndescs += vq->used_elems[0].ndescs;
     for (i = 1; i < count; i++) {
-        virtqueue_packed_fill_desc(vq, &vq->used_elems[i], i, false);
+        virtqueue_packed_fill_desc(vq, &vq->used_elems[i], ndescs, false);
         ndescs += vq->used_elems[i].ndescs;
     }
     virtqueue_packed_fill_desc(vq, &vq->used_elems[0], 0, true);
-    ndescs += vq->used_elems[0].ndescs;
 
     vq->inuse -= ndescs;
     vq->used_idx += ndescs;
-- 
2.27.0