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virtio-net: construct multi-buffer xdp in mergeable

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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@linux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Heng Qi 2023-01-14 16:22:25 +08:00 committed by David S. Miller
parent ef75cb51f1
commit 22174f79a4
1 changed files with 44 additions and 14 deletions
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58
drivers/net/virtio_net.c
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@ -1043,7 +1043,7 @@ 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;
@ -1064,11 +1064,14 @@ 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
@ -1084,14 +1087,16 @@ 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,
@ -1102,17 +1107,29 @@ 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++;
@ -1208,6 +1225,19 @@ 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();