[RFC PATCH 5/9] virtio_net: build xdp_buff with multi buffers

Heng Qi
2022-11-22T07:44:08Z

Support xdp for multi buffer packets.

Putting the first buffer as the linear part for xdp_buff,
and the rest of the buffers as non-linear fragments to struct
skb_shared_info in the tailroom belonging to xdp_buff.

Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
drivers/net/virtio_net.c | 74 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 74 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index cd65f85d5075..20784b1d8236 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -911,6 +911,80 @@ static struct sk_buff *receive_big(struct net_device *dev,
return NULL;
}

+static int virtnet_build_xdp_buff(struct net_device *dev,
+ struct virtnet_info *vi,
+ struct receive_queue *rq,
+ struct xdp_buff *xdp,
+ void *buf,
+ unsigned int len,
+ unsigned int frame_sz,
+ u16 *num_buf,
+ unsigned int *xdp_frags_truesize,
+ struct virtnet_rq_stats *stats)
+{
+ unsigned int tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+ struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
+ unsigned int truesize, headroom;
+ struct skb_shared_info *shinfo;
+ unsigned int xdp_frags_truesz = 0;
+ unsigned int cur_frag_size;
+ struct page *page;
+ skb_frag_t *frag;
+ int offset;
+ void *ctx;
+
+ xdp_init_buff(xdp, frame_sz, &rq->xdp_rxq);
+ xdp_prepare_buff(xdp, buf - VIRTIO_XDP_HEADROOM,
+ VIRTIO_XDP_HEADROOM + vi->hdr_len, len - vi->hdr_len, true);
+ shinfo = xdp_get_shared_info_from_buff(xdp);
+ shinfo->nr_frags = 0;
+ shinfo->xdp_frags_size = 0;
+
+ if ((*num_buf - 1) > MAX_SKB_FRAGS)
+ return -EINVAL;
+
+ while ((--*num_buf) >= 1) {
+ buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
+ if (unlikely(!buf)) {
+ pr_debug("%s: rx error: %d buffers out of %d missing\n",
+ dev->name, *num_buf,
+ virtio16_to_cpu(vi->vdev, hdr->num_buffers));
+ dev->stats.rx_length_errors++;
+ return -EINVAL;
+ }
+
+ if (!xdp_buff_has_frags(xdp))
+ xdp_buff_set_frags_flag(xdp);
+
+ stats->bytes += len;
+ page = virt_to_head_page(buf);
+ offset = buf - page_address(page);
+ truesize = mergeable_ctx_to_truesize(ctx);
+ headroom = mergeable_ctx_to_headroom(ctx);
+
+ cur_frag_size = truesize + (headroom ? (headroom + tailroom) : 0);
+ xdp_frags_truesz += cur_frag_size;
+ if (unlikely(len > truesize || cur_frag_size > PAGE_SIZE)) {
+ pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
+ dev->name, len, (unsigned long)ctx);
+ dev->stats.rx_length_errors++;
+ return -EINVAL;
+ }
+
+ frag = &shinfo->frags[shinfo->nr_frags++];
+ __skb_frag_set_page(frag, page);
+ skb_frag_off_set(frag, offset);
+ skb_frag_size_set(frag, len);
+ if (page_is_pfmemalloc(page))
+ xdp_buff_set_frag_pfmemalloc(xdp);
+
+ shinfo->xdp_frags_size += len;
+ }
+
+ *xdp_frags_truesize = xdp_frags_truesz;
+ return 0;
+}
+
static struct sk_buff *receive_mergeable(struct net_device *dev,
struct virtnet_info *vi,
struct receive_queue *rq,
--
2.19.1.6.gb485710b