[dpdk-dev] [PATCH v2] vhost: fix mbuf alloc failure

[Sivaprasad Tummala <Sivaprasad.Tummala@intel.com>]

vhost buffer allocation is successful for packets that fit
into a linear buffer. If it fails, vhost library is expected
to drop the current packet and skip to the next.

The patch fixes the error scenario by skipping to next packet.
Note: Drop counters are not currently supported.

Fixes: c3ff0ac70acb ("vhost: improve performance by supporting large buffer")
Cc: stable@dpdk.org
Cc: fbl@sysclose.org

---
v2:
 * fixed review comments - Maxime Coquelin
 * fixed mbuf alloc errors for packed virtqueues - Maxime Coquelin
 * fixed mbuf copy errors - Flavio Leitner

Signed-off-by: Sivaprasad Tummala <Sivaprasad.Tummala@intel.com>
---
 lib/librte_vhost/virtio_net.c | 50 ++++++++++++++++++++++++++---------
 1 file changed, 37 insertions(+), 13 deletions(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 1fc30c681..764c514fd 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -1674,6 +1674,7 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 {
 	uint16_t i;
 	uint16_t free_entries;
+	uint16_t dropped = 0;
 
 	if (unlikely(dev->dequeue_zero_copy)) {
 		struct zcopy_mbuf *zmbuf, *next;
@@ -1737,13 +1738,31 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			update_shadow_used_ring_split(vq, head_idx, 0);
 
 		pkts[i] = virtio_dev_pktmbuf_alloc(dev, mbuf_pool, buf_len);
-		if (unlikely(pkts[i] == NULL))
+		if (unlikely(pkts[i] == NULL)) {
+			/*
+			 * mbuf allocation fails for jumbo packets when external
+			 * buffer allocation is not allowed and linear buffer
+			 * is required. Drop this packet.
+			 */
+#ifdef RTE_LIBRTE_VHOST_DEBUG
+			VHOST_LOG_DATA(ERR,
+				"Failed to allocate memory for mbuf. Packet dropped!\n");
+#endif
+			dropped += 1;
+			i++;
 			break;
+		}
 
 		err = copy_desc_to_mbuf(dev, vq, buf_vec, nr_vec, pkts[i],
 				mbuf_pool);
 		if (unlikely(err)) {
 			rte_pktmbuf_free(pkts[i]);
+#ifdef RTE_LIBRTE_VHOST_DEBUG
+			VHOST_LOG_DATA(ERR,
+				"Failed to copy desc to mbuf. Packet dropped!\n");
+#endif
+			dropped += 1;
+			i++;
 			break;
 		}
 
@@ -1753,6 +1772,8 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			zmbuf = get_zmbuf(vq);
 			if (!zmbuf) {
 				rte_pktmbuf_free(pkts[i]);
+				dropped += 1;
+				i++;
 				break;
 			}
 			zmbuf->mbuf = pkts[i];
@@ -1782,7 +1803,7 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		}
 	}
 
-	return i;
+	return (i - dropped);
 }
 
 static __rte_always_inline int
@@ -1946,21 +1967,24 @@ virtio_dev_tx_single_packed(struct virtio_net *dev,
 			    struct rte_mbuf **pkts)
 {
 
-	uint16_t buf_id, desc_count;
+	uint16_t buf_id, desc_count = 0;
+	int ret;
 
-	if (vhost_dequeue_single_packed(dev, vq, mbuf_pool, pkts, &buf_id,
-					&desc_count))
-		return -1;
+	ret = vhost_dequeue_single_packed(dev, vq, mbuf_pool, pkts, &buf_id,
+					&desc_count);
 
-	if (virtio_net_is_inorder(dev))
-		vhost_shadow_dequeue_single_packed_inorder(vq, buf_id,
-							   desc_count);
-	else
-		vhost_shadow_dequeue_single_packed(vq, buf_id, desc_count);
+	if (likely(desc_count > 0)) {
+		if (virtio_net_is_inorder(dev))
+			vhost_shadow_dequeue_single_packed_inorder(vq, buf_id,
+								   desc_count);
+		else
+			vhost_shadow_dequeue_single_packed(vq, buf_id,
+					desc_count);
 
-	vq_inc_last_avail_packed(vq, desc_count);
+		vq_inc_last_avail_packed(vq, desc_count);
+	}
 
-	return 0;
+	return ret;
 }
 
 static __rte_always_inline int
-- 
2.17.1