[PATCH v6 08/11] net/virtio: add support for mergeable buffers with packed virtqueues

[Jens Freimann <jfreimann@redhat.com>]

Implement support for receiving merged buffers in virtio when packed
virtqueues are enabled.

Signed-off-by: Jens Freimann <jfreimann@redhat.com>
---
 drivers/net/virtio/virtio_ethdev.c |   8 +-
 drivers/net/virtio/virtio_rxtx.c   | 117 ++++++++++++++++++++++++++---
 drivers/net/virtio/virtqueue.h     |   1 +
 3 files changed, 113 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index f03cf04a9..c4ef095ed 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1322,12 +1322,12 @@ set_rxtx_funcs(struct rte_eth_dev *eth_dev)
 {
 	struct virtio_hw *hw = eth_dev->data->dev_private;
 
-	/*
-	 * workarount for packed vqs which don't support
-	 * mrg_rxbuf at this point
-	 */
 	if (vtpci_packed_queue(hw)) {
+		if (vtpci_with_feature(hw, VIRTIO_NET_F_MRG_RXBUF)) {
+			eth_dev->rx_pkt_burst = &virtio_recv_mergeable_pkts;
+		} else {
 		eth_dev->rx_pkt_burst = &virtio_recv_pkts_packed;
+		}
 	} else if (hw->use_simple_rx) {
 		PMD_INIT_LOG(INFO, "virtio: using simple Rx path on port %u",
 			eth_dev->data->port_id);
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 90a0e306f..35c375cd5 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -90,6 +90,80 @@ vq_ring_free_chain(struct virtqueue *vq, uint16_t desc_idx)
 	dp->next = VQ_RING_DESC_CHAIN_END;
 }
 
+static void
+virtio_refill_packed(struct virtqueue *vq, uint16_t used_idx,
+		     struct virtnet_rx *rxvq)
+{
+	struct vq_desc_extra *dxp;
+	struct vring_desc_packed *descs = vq->vq_ring.desc_packed;
+	struct vring_desc_packed *desc;
+	struct rte_mbuf *nmb;
+
+	nmb = rte_mbuf_raw_alloc(rxvq->mpool);
+	if (unlikely(nmb == NULL)) {
+		struct rte_eth_dev *dev
+			= &rte_eth_devices[rxvq->port_id];
+		dev->data->rx_mbuf_alloc_failed++;
+		return;
+	}
+
+	desc = &descs[used_idx];
+
+	dxp = &vq->vq_descx[used_idx];
+
+	dxp->cookie = nmb;
+	dxp->ndescs = 1;
+
+	desc->addr = VIRTIO_MBUF_ADDR(nmb, vq) +
+		RTE_PKTMBUF_HEADROOM - vq->hw->vtnet_hdr_size;
+	desc->len = nmb->buf_len - RTE_PKTMBUF_HEADROOM +
+		vq->hw->vtnet_hdr_size;
+	desc->flags |= VRING_DESC_F_WRITE;
+}
+
+static uint16_t
+virtqueue_dequeue_burst_rx_packed(struct virtqueue *vq,
+				  struct rte_mbuf **rx_pkts,
+				  uint32_t *len,
+				  uint16_t num,
+				  struct virtnet_rx *rx_queue)
+{
+	struct rte_mbuf *cookie;
+	uint16_t used_idx;
+	uint16_t id;
+	struct vring_desc_packed *desc;
+	uint16_t i;
+
+	for (i = 0; i < num; i++) {
+		used_idx = vq->vq_used_cons_idx;
+		desc = &vq->vq_ring.desc_packed[used_idx];
+		if (!desc_is_used(desc, &vq->vq_ring))
+			return i;
+		len[i] = desc->len;
+		id = desc[used_idx].index;
+		cookie = (struct rte_mbuf *)vq->vq_descx[id].cookie;
+
+		if (unlikely(cookie == NULL)) {
+			PMD_DRV_LOG(ERR, "vring descriptor with no mbuf cookie at %u",
+				vq->vq_used_cons_idx);
+			break;
+		}
+		rte_prefetch0(cookie);
+		rte_packet_prefetch(rte_pktmbuf_mtod(cookie, void *));
+		rx_pkts[i] = cookie;
+
+		virtio_refill_packed(vq, used_idx, rx_queue);
+
+		if (++vq->vq_used_cons_idx >= vq->vq_nentries) {
+			vq->vq_used_cons_idx = 0;
+			vq->vq_ring.used_wrap_counter ^= 1;
+		}
+		vq->vq_descx[id].cookie = NULL;
+	}
+
+	return i;
+}
+
 static uint16_t
 virtqueue_dequeue_burst_rx(struct virtqueue *vq, struct rte_mbuf **rx_pkts,
 			   uint32_t *len, uint16_t num)
@@ -1476,12 +1550,16 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 	uint16_t extra_idx;
 	uint32_t seg_res;
 	uint32_t hdr_size;
+	uint32_t rx_num = 0;
 
 	nb_rx = 0;
 	if (unlikely(hw->started == 0))
 		return nb_rx;
 
-	nb_used = VIRTQUEUE_NUSED(vq);
+	if (vtpci_packed_queue(vq->hw))
+		nb_used = VIRTIO_MBUF_BURST_SZ;
+	else
+		nb_used = VIRTQUEUE_NUSED(vq);
 
 	virtio_rmb();
 
@@ -1494,13 +1572,21 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 	seg_res = 0;
 	hdr_size = hw->vtnet_hdr_size;
 
+	vq->vq_used_idx = vq->vq_used_cons_idx;
+
 	while (i < nb_used) {
 		struct virtio_net_hdr_mrg_rxbuf *header;
 
 		if (nb_rx == nb_pkts)
 			break;
 
-		num = virtqueue_dequeue_burst_rx(vq, rcv_pkts, len, 1);
+		if (vtpci_packed_queue(vq->hw))
+			num = virtqueue_dequeue_burst_rx_packed(vq, rcv_pkts,
+				len, 1, (struct virtnet_rx *)rx_queue);
+		else
+			num = virtqueue_dequeue_burst_rx(vq, rcv_pkts, len, 1);
+		if (num == 0)
+			return nb_rx;
 		if (num != 1)
 			continue;
 
@@ -1552,12 +1638,15 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 			 */
 			uint16_t  rcv_cnt =
 				RTE_MIN(seg_res, RTE_DIM(rcv_pkts));
-			if (likely(VIRTQUEUE_NUSED(vq) >= rcv_cnt)) {
-				uint32_t rx_num =
-					virtqueue_dequeue_burst_rx(vq,
-					rcv_pkts, len, rcv_cnt);
-				i += rx_num;
-				rcv_cnt = rx_num;
+			if (vtpci_packed_queue(vq->hw)) {
+				if (likely(vq->vq_free_cnt >= rcv_cnt)) {	
+					rx_num = virtqueue_dequeue_burst_rx_packed(vq,
+						     rcv_pkts, len, rcv_cnt,
+						     (struct virtnet_rx *)rx_queue);
+				}
+			} else if (likely(VIRTQUEUE_NUSED(vq) >= rcv_cnt)) {
+				rx_num = virtqueue_dequeue_burst_rx(vq,
+					      rcv_pkts, len, rcv_cnt);
 			} else {
 				PMD_RX_LOG(ERR,
 					   "No enough segments for packet.");
@@ -1566,6 +1655,8 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 				rxvq->stats.errors++;
 				break;
 			}
+			i += rx_num;
+			rcv_cnt = rx_num;
 
 			extra_idx = 0;
 
@@ -1599,6 +1690,15 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 
 	rxvq->stats.packets += nb_rx;
 
+	if (vtpci_packed_queue(vq->hw)) {
+		if (unlikely(virtqueue_kick_prepare_packed(vq)) &&
+		    likely(nb_rx)) {
+			virtqueue_notify(vq);
+			PMD_RX_LOG(DEBUG, "Notified");
+		}
+		return nb_rx;
+	}
+
 	/* Allocate new mbuf for the used descriptor */
 	while (likely(!virtqueue_full(vq))) {
 		new_mbuf = rte_mbuf_raw_alloc(rxvq->mpool);
@@ -1618,7 +1718,6 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 
 	if (likely(nb_enqueued)) {
 		vq_update_avail_idx(vq);
-
 		if (unlikely(virtqueue_kick_prepare(vq))) {
 			virtqueue_notify(vq);
 			PMD_RX_LOG(DEBUG, "Notified");
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index ffa2d8f92..15df6a050 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -171,6 +171,7 @@ struct virtqueue {
 	 * trails vq_ring.used->idx.
 	 */
 	uint16_t vq_used_cons_idx;
+	uint16_t vq_used_idx;
 	uint16_t vq_nentries;  /**< vring desc numbers */
 	uint16_t vq_free_cnt;  /**< num of desc available */
 	uint16_t vq_avail_idx; /**< sync until needed */
-- 
2.17.1