Build multi-buffer xdp using virtnet_build_xdp_buff_mrg().
For the prefilled buffer before xdp is set, we will probably use
vq reset in the future. At the same time, virtio net currently
uses comp pages, and bpf_xdp_frags_increase_tail() needs to calculate
the tailroom of the last frag, which will involve the offset of the
corresponding page and cause a negative value, so we disable tail
increase by not setting xdp_rxq->frag_size.
Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
drivers/net/virtio_net.c | 58 ++++++++++++++++++++++++++++++----------
1 file changed, 44 insertions(+), 14 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 699e376b8f8b..ab01cf3855bc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1036,7 +1036,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
unsigned int metasize = 0;
unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
- unsigned int frame_sz;
+ unsigned int frame_sz, xdp_room;
int err;
head_skb = NULL;
@@ -1057,11 +1057,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
rcu_read_lock();
xdp_prog = rcu_dereference(rq->xdp_prog);
if (xdp_prog) {
+ unsigned int xdp_frags_truesz = 0;
+ struct skb_shared_info *shinfo;
struct xdp_frame *xdpf;
struct page *xdp_page;
struct xdp_buff xdp;
void *data;
u32 act;
+ int i;
/* Transient failure which in theory could occur if
* in-flight packets from before XDP was enabled reach
@@ -1077,14 +1080,16 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
*/
frame_sz = truesize;
- /* This happens when rx buffer size is underestimated
- * or headroom is not enough because of the buffer
- * was refilled before XDP is set. This should only
- * happen for the first several packets, so we don't
- * care much about its performance.
+ /* This happens when headroom is not enough because
+ * of the buffer was prefilled before XDP is set.
+ * This should only happen for the first several packets.
+ * In fact, vq reset can be used here to help us clean up
+ * the prefilled buffers, but many existing devices do not
+ * support it, and we don't want to bother users who are
+ * using xdp normally.
*/
- if (unlikely(num_buf > 1 ||
- headroom < virtnet_get_headroom(vi))) {
+ if (!xdp_prog->aux->xdp_has_frags &&
+ (num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
/* linearize data for XDP */
xdp_page = xdp_linearize_page(rq, &num_buf,
page, offset,
@@ -1095,17 +1100,29 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
if (!xdp_page)
goto err_xdp;
offset = VIRTIO_XDP_HEADROOM;
+ } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
+ xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
+ sizeof(struct skb_shared_info));
+ if (len + xdp_room > PAGE_SIZE)
+ goto err_xdp;
+
+ xdp_page = alloc_page(GFP_ATOMIC);
+ if (!xdp_page)
+ goto err_xdp;
+
+ memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
+ page_address(page) + offset, len);
+ frame_sz = PAGE_SIZE;
+ offset = VIRTIO_XDP_HEADROOM;
} else {
xdp_page = page;
}
- /* Allow consuming headroom but reserve enough space to push
- * the descriptor on if we get an XDP_TX return code.
- */
data = page_address(xdp_page) + offset;
- xdp_init_buff(&xdp, frame_sz - vi->hdr_len, &rq->xdp_rxq);
- xdp_prepare_buff(&xdp, data - VIRTIO_XDP_HEADROOM + vi->hdr_len,
- VIRTIO_XDP_HEADROOM, len - vi->hdr_len, true);
+ err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
+ &num_buf, &xdp_frags_truesz, stats);
+ if (unlikely(err))
+ goto err_xdp_frags;
act = bpf_prog_run_xdp(xdp_prog, &xdp);
stats->xdp_packets++;
@@ -1201,6 +1218,19 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
__free_pages(xdp_page, 0);
goto err_xdp;
}
+err_xdp_frags:
+ if (unlikely(xdp_page != page))
+ __free_pages(xdp_page, 0);
+
+ if (xdp_buff_has_frags(&xdp)) {
+ shinfo = xdp_get_shared_info_from_buff(&xdp);
+ for (i = 0; i < shinfo->nr_frags; i++) {
+ xdp_page = skb_frag_page(&shinfo->frags[i]);
+ put_page(xdp_page);
+ }
+ }
+
+ goto err_xdp;
}
rcu_read_unlock();
--
2.19.1.6.gb485710b
