virtio_net: xsk: rx: support fill with xsk buffer

Implement the logic of filling rq with XSK buffers.

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/20240708112537.96291-9-xuanzhuo@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/virtio_net.c

@@ -354,6 +354,8 @@ struct receive_queue {
 
 	/* xdp rxq used by xsk */
 	struct xdp_rxq_info xsk_rxq_info;
+
+	struct xdp_buff **xsk_buffs;
 };
 
 /* This structure can contain rss message with maximum settings for indirection table and keysize
@@ -1054,6 +1056,53 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
 	}
 }
 
+static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
+{
+	sg->dma_address = addr;
+	sg->length = len;
+}
+
+static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue *rq,
+				   struct xsk_buff_pool *pool, gfp_t gfp)
+{
+	struct xdp_buff **xsk_buffs;
+	dma_addr_t addr;
+	int err = 0;
+	u32 len, i;
+	int num;
+
+	xsk_buffs = rq->xsk_buffs;
+
+	num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free);
+	if (!num)
+		return -ENOMEM;
+
+	len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len;
+
+	for (i = 0; i < num; ++i) {
+		/* Use the part of XDP_PACKET_HEADROOM as the virtnet hdr space.
+		 * We assume XDP_PACKET_HEADROOM is larger than hdr->len.
+		 * (see function virtnet_xsk_pool_enable)
+		 */
+		addr = xsk_buff_xdp_get_dma(xsk_buffs[i]) - vi->hdr_len;
+
+		sg_init_table(rq->sg, 1);
+		sg_fill_dma(rq->sg, addr, len);
+
+		err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, xsk_buffs[i], gfp);
+		if (err)
+			goto err;
+	}
+
+	return num;
+
+err:
+	for (; i < num; ++i)
+		xsk_buff_free(xsk_buffs[i]);
+
+	return err;
+}
+
 static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
@@ -2245,7 +2294,11 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
 			  gfp_t gfp)
 {
 	int err;
-	bool oom;
+
+	if (rq->xsk_pool) {
+		err = virtnet_add_recvbuf_xsk(vi, rq, rq->xsk_pool, gfp);
+		goto kick;
+	}
 
 	do {
 		if (vi->mergeable_rx_bufs)
@@ -2255,10 +2308,11 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
 		else
 			err = add_recvbuf_small(vi, rq, gfp);
 
-		oom = err == -ENOMEM;
 		if (err)
 			break;
 	} while (rq->vq->num_free);
+
+kick:
 	if (virtqueue_kick_prepare(rq->vq) && virtqueue_notify(rq->vq)) {
 		unsigned long flags;
 
@@ -2267,7 +2321,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
 		u64_stats_update_end_irqrestore(&rq->stats.syncp, flags);
 	}
 
-	return !oom;
+	return err != -ENOMEM;
 }
 
 static void skb_recv_done(struct virtqueue *rvq)
@@ -5104,7 +5158,7 @@ static int virtnet_xsk_pool_enable(struct net_device *dev,
 	struct receive_queue *rq;
 	struct device *dma_dev;
 	struct send_queue *sq;
-	int err;
+	int err, size;
 
 	if (vi->hdr_len > xsk_pool_get_headroom(pool))
 		return -EINVAL;
@@ -5135,6 +5189,12 @@ static int virtnet_xsk_pool_enable(struct net_device *dev,
 	if (!dma_dev)
 		return -EINVAL;
 
+	size = virtqueue_get_vring_size(rq->vq);
+
+	rq->xsk_buffs = kvcalloc(size, sizeof(*rq->xsk_buffs), GFP_KERNEL);
+	if (!rq->xsk_buffs)
+		return -ENOMEM;
+
 	err = xsk_pool_dma_map(pool, dma_dev, 0);
 	if (err)
 		goto err_xsk_map;
@@ -5169,6 +5229,8 @@ static int virtnet_xsk_pool_disable(struct net_device *dev, u16 qid)
 
 	xsk_pool_dma_unmap(pool, 0);
 
+	kvfree(rq->xsk_buffs);
+
 	return err;
 }