[dpdk-dev] [PATCH] virtio: Fix enqueue/dequeue can't handle chained vring descriptors.

[Ouyang Changchun]

Vring enqueue need consider the 2 cases:
 1. Vring descriptors chained together, the first one is for virtio header, the rest are for real data;
 2. Only one descriptor, virtio header and real data share one single descriptor;

So does vring dequeue.

Signed-off-by: Changchun Ouyang <changchun.ouyang at intel.com>
---
 lib/librte_vhost/vhost_rxtx.c | 60 +++++++++++++++++++++++++++++++------------
 1 file changed, 44 insertions(+), 16 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 510ffe8..3135883 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -59,7 +59,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 	struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
 	uint64_t buff_addr = 0;
 	uint64_t buff_hdr_addr = 0;
-	uint32_t head[MAX_PKT_BURST], packet_len = 0;
+	uint32_t head[MAX_PKT_BURST];
 	uint32_t head_idx, packet_success = 0;
 	uint16_t avail_idx, res_cur_idx;
 	uint16_t res_base_idx, res_end_idx;
@@ -113,6 +113,10 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 	rte_prefetch0(&vq->desc[head[packet_success]]);
 
 	while (res_cur_idx != res_end_idx) {
+		uint32_t offset = 0;
+		uint32_t data_len, len_to_cpy;
+		uint8_t plus_hdr = 0;
+
 		/* Get descriptor from available ring */
 		desc = &vq->desc[head[packet_success]];
 
@@ -125,7 +129,6 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 
 		/* Copy virtio_hdr to packet and increment buffer address */
 		buff_hdr_addr = buff_addr;
-		packet_len = rte_pktmbuf_data_len(buff) + vq->vhost_hlen;
 
 		/*
 		 * If the descriptors are chained the header and data are
@@ -136,24 +139,44 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 			desc = &vq->desc[desc->next];
 			/* Buffer address translation. */
 			buff_addr = gpa_to_vva(dev, desc->addr);
-			desc->len = rte_pktmbuf_data_len(buff);
 		} else {
 			buff_addr += vq->vhost_hlen;
-			desc->len = packet_len;
+			plus_hdr = 1;
 		}
 
+		data_len = rte_pktmbuf_data_len(buff);
+		len_to_cpy = RTE_MIN(data_len, desc->len);
+		do {
+			if (len_to_cpy > 0) {
+				/* Copy mbuf data to buffer */
+				rte_memcpy((void *)(uintptr_t)buff_addr,
+					(const void *)(rte_pktmbuf_mtod(buff, const char *) + offset),
+					len_to_cpy);
+				PRINT_PACKET(dev, (uintptr_t)buff_addr,
+					len_to_cpy, 0);
+
+				desc->len = len_to_cpy + (plus_hdr ? vq->vhost_hlen : 0);
+				offset += len_to_cpy;
+				if (desc->flags & VRING_DESC_F_NEXT) {
+					desc = &vq->desc[desc->next];
+					buff_addr = gpa_to_vva(dev, desc->addr);
+					len_to_cpy = RTE_MIN(data_len - offset, desc->len);
+				} else
+					break;
+			} else {
+				desc->len = 0;
+				if (desc->flags & VRING_DESC_F_NEXT)
+                                        desc = &vq->desc[desc->next];
+				else
+					break;
+			}
+		} while (1);
+
 		/* Update used ring with desc information */
 		vq->used->ring[res_cur_idx & (vq->size - 1)].id =
 							head[packet_success];
-		vq->used->ring[res_cur_idx & (vq->size - 1)].len = packet_len;
-
-		/* Copy mbuf data to buffer */
-		/* FIXME for sg mbuf and the case that desc couldn't hold the mbuf data */
-		rte_memcpy((void *)(uintptr_t)buff_addr,
-			rte_pktmbuf_mtod(buff, const void *),
-			rte_pktmbuf_data_len(buff));
-		PRINT_PACKET(dev, (uintptr_t)buff_addr,
-			rte_pktmbuf_data_len(buff), 0);
+		vq->used->ring[res_cur_idx & (vq->size - 1)].len =
+							offset + vq->vhost_hlen;
 
 		res_cur_idx++;
 		packet_success++;
@@ -583,7 +606,14 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
 		desc = &vq->desc[head[entry_success]];
 
 		/* Discard first buffer as it is the virtio header */
-		desc = &vq->desc[desc->next];
+		if (desc->flags & VRING_DESC_F_NEXT) {
+			desc = &vq->desc[desc->next];
+			vb_offset = 0;
+			vb_avail = desc->len;
+		} else {
+			vb_offset = vq->vhost_hlen;
+			vb_avail = desc->len - vb_offset;
+		}
 
 		/* Buffer address translation. */
 		vb_addr = gpa_to_vva(dev, desc->addr);
@@ -602,8 +632,6 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
 		vq->used->ring[used_idx].id = head[entry_success];
 		vq->used->ring[used_idx].len = 0;
 
-		vb_offset = 0;
-		vb_avail = desc->len;
 		/* Allocate an mbuf and populate the structure. */
 		m = rte_pktmbuf_alloc(mbuf_pool);
 		if (unlikely(m == NULL)) {
-- 
1.8.4.2