[PATCH 1/2] vhost: fix memory leak in Virtio Tx split path

[Maxime Coquelin <maxime.coquelin@redhat.com>]

When vIOMMU is enabled and Virtio device is bound to kernel
driver in guest, rte_vhost_dequeue_burst() will often return
early because of IOTLB misses.

This patch fixes a mbuf leak occurring in this case.

Fixes: 242695f6122a ("vhost: allocate and free packets in bulk in Tx split")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/vhost/virtio_net.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 280d4845f8..db9985c9b9 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -3120,11 +3120,8 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 						VHOST_ACCESS_RO) < 0))
 			break;
 
-		update_shadow_used_ring_split(vq, head_idx, 0);
-
 		if (unlikely(buf_len <= dev->vhost_hlen)) {
-			dropped += 1;
-			i++;
+			dropped = 1;
 			break;
 		}
 
@@ -3143,8 +3140,7 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 					buf_len, mbuf_pool->name);
 				allocerr_warned = true;
 			}
-			dropped += 1;
-			i++;
+			dropped = 1;
 			break;
 		}
 
@@ -3155,17 +3151,17 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 				VHOST_DATA_LOG(dev->ifname, ERR, "failed to copy desc to mbuf.");
 				allocerr_warned = true;
 			}
-			dropped += 1;
-			i++;
+			dropped = 1;
 			break;
 		}
 
+		update_shadow_used_ring_split(vq, head_idx, 0);
 	}
 
-	if (dropped)
-		rte_pktmbuf_free_bulk(&pkts[i - 1], count - i + 1);
+	if (unlikely(count != i))
+		rte_pktmbuf_free_bulk(&pkts[i], count - i);
 
-	vq->last_avail_idx += i;
+	vq->last_avail_idx += i + dropped;
 
 	do_data_copy_dequeue(vq);
 	if (unlikely(i < count))
@@ -3175,7 +3171,7 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		vhost_vring_call_split(dev, vq);
 	}
 
-	return (i - dropped);
+	return i;
 }
 
 __rte_noinline
-- 
2.43.0