virtio_net: xsk: rx: support recv merge mode

Support AF-XDP for merge mode.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20240708112537.96291-11-xuanzhuo@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: fengidri

drivers/net/virtio_net.c

@@ -504,6 +504,10 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
 			       struct virtnet_rq_stats *stats);
 static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue *rq,
 				 struct sk_buff *skb, u8 flags);
+static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
+					       struct sk_buff *curr_skb,
+					       struct page *page, void *buf,
+					       int len, int truesize);
 
 static bool is_xdp_frame(void *ptr)
 {
@@ -984,6 +988,11 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
 
 	rq = &vi->rq[i];
 
+	if (rq->xsk_pool) {
+		xsk_buff_free((struct xdp_buff *)buf);
+		return;
+	}
+
 	if (!vi->big_packets || vi->mergeable_rx_bufs)
 		virtnet_rq_unmap(rq, buf, 0);
 
@@ -1152,6 +1161,139 @@ static struct sk_buff *virtnet_receive_xsk_small(struct net_device *dev, struct
 	}
 }
 
+static void xsk_drop_follow_bufs(struct net_device *dev,
+				 struct receive_queue *rq,
+				 u32 num_buf,
+				 struct virtnet_rq_stats *stats)
+{
+	struct xdp_buff *xdp;
+	u32 len;
+
+	while (num_buf-- > 1) {
+		xdp = virtqueue_get_buf(rq->vq, &len);
+		if (unlikely(!xdp)) {
+			pr_debug("%s: rx error: %d buffers missing\n",
+				 dev->name, num_buf);
+			DEV_STATS_INC(dev, rx_length_errors);
+			break;
+		}
+		u64_stats_add(&stats->bytes, len);
+		xsk_buff_free(xdp);
+	}
+}
+
+static int xsk_append_merge_buffer(struct virtnet_info *vi,
+				   struct receive_queue *rq,
+				   struct sk_buff *head_skb,
+				   u32 num_buf,
+				   struct virtio_net_hdr_mrg_rxbuf *hdr,
+				   struct virtnet_rq_stats *stats)
+{
+	struct sk_buff *curr_skb;
+	struct xdp_buff *xdp;
+	u32 len, truesize;
+	struct page *page;
+	void *buf;
+
+	curr_skb = head_skb;
+
+	while (--num_buf) {
+		buf = virtqueue_get_buf(rq->vq, &len);
+		if (unlikely(!buf)) {
+			pr_debug("%s: rx error: %d buffers out of %d missing\n",
+				 vi->dev->name, num_buf,
+				 virtio16_to_cpu(vi->vdev,
+						 hdr->num_buffers));
+			DEV_STATS_INC(vi->dev, rx_length_errors);
+			return -EINVAL;
+		}
+
+		u64_stats_add(&stats->bytes, len);
+
+		xdp = buf_to_xdp(vi, rq, buf, len);
+		if (!xdp)
+			goto err;
+
+		buf = napi_alloc_frag(len);
+		if (!buf) {
+			xsk_buff_free(xdp);
+			goto err;
+		}
+
+		memcpy(buf, xdp->data - vi->hdr_len, len);
+
+		xsk_buff_free(xdp);
+
+		page = virt_to_page(buf);
+
+		truesize = len;
+
+		curr_skb  = virtnet_skb_append_frag(head_skb, curr_skb, page,
+						    buf, len, truesize);
+		if (!curr_skb) {
+			put_page(page);
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	xsk_drop_follow_bufs(vi->dev, rq, num_buf, stats);
+	return -EINVAL;
+}
+
+static struct sk_buff *virtnet_receive_xsk_merge(struct net_device *dev, struct virtnet_info *vi,
+						 struct receive_queue *rq, struct xdp_buff *xdp,
+						 unsigned int *xdp_xmit,
+						 struct virtnet_rq_stats *stats)
+{
+	struct virtio_net_hdr_mrg_rxbuf *hdr;
+	struct bpf_prog *prog;
+	struct sk_buff *skb;
+	u32 ret, num_buf;
+
+	hdr = xdp->data - vi->hdr_len;
+	num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
+
+	ret = XDP_PASS;
+	rcu_read_lock();
+	prog = rcu_dereference(rq->xdp_prog);
+	/* TODO: support multi buffer. */
+	if (prog && num_buf == 1)
+		ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit, stats);
+	rcu_read_unlock();
+
+	switch (ret) {
+	case XDP_PASS:
+		skb = xsk_construct_skb(rq, xdp);
+		if (!skb)
+			goto drop_bufs;
+
+		if (xsk_append_merge_buffer(vi, rq, skb, num_buf, hdr, stats)) {
+			dev_kfree_skb(skb);
+			goto drop;
+		}
+
+		return skb;
+
+	case XDP_TX:
+	case XDP_REDIRECT:
+		return NULL;
+
+	default:
+		/* drop packet */
+		xsk_buff_free(xdp);
+	}
+
+drop_bufs:
+	xsk_drop_follow_bufs(dev, rq, num_buf, stats);
+
+drop:
+	u64_stats_inc(&stats->drops);
+	return NULL;
+}
+
 static void virtnet_receive_xsk_buf(struct virtnet_info *vi, struct receive_queue *rq,
 				    void *buf, u32 len,
 				    unsigned int *xdp_xmit,
@@ -1181,6 +1323,8 @@ static void virtnet_receive_xsk_buf(struct virtnet_info *vi, struct receive_queu
 
 	if (!vi->mergeable_rx_bufs)
 		skb = virtnet_receive_xsk_small(dev, vi, rq, xdp, xdp_xmit, stats);
+	else
+		skb = virtnet_receive_xsk_merge(dev, vi, rq, xdp, xdp_xmit, stats);
 
 	if (skb)
 		virtnet_receive_done(vi, rq, skb, flags);