[dpdk-stable] [DPDK] vhost: fix zmbuf buffer id invalid

[Marvin Liu <yong.liu@intel.com>]

zc mbufs should save buffer id when doing dequeue zcopy. There's no guarantee
that local queue avail index equal to buffer index.

Fixes: d1eafb532268 ("vhost: add packed ring zcopy batch and single dequeue")
Cc: stable@dpdk.org

Signed-off-by: Marvin Liu <yong.liu@intel.com>
Reported-by: Yinan Wang <yinan.wang@intel.com>
---
 lib/librte_vhost/virtio_net.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 37c47c7dc..210415904 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -2004,7 +2004,7 @@ virtio_dev_tx_batch_packed_zmbuf(struct virtio_net *dev,
 
 	vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
 		zmbufs[i]->mbuf = pkts[i];
-		zmbufs[i]->desc_idx = avail_idx + i;
+		zmbufs[i]->desc_idx = ids[i];
 		zmbufs[i]->desc_count = 1;
 	}
 
@@ -2045,7 +2045,7 @@ virtio_dev_tx_single_packed_zmbuf(struct virtio_net *dev,
 		return -1;
 	}
 	zmbuf->mbuf = *pkts;
-	zmbuf->desc_idx = vq->last_avail_idx;
+	zmbuf->desc_idx = buf_id;
 	zmbuf->desc_count = desc_count;
 
 	rte_mbuf_refcnt_update(*pkts, 1);
-- 
2.17.1