Re: [PATCH net] i40e: xsk: fix multi-buffer XDP_PASS skb construction
From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Date: 2026-07-14 13:08:14
Also in:
intel-wired-lan
On Tue, Jul 14, 2026 at 10:51:12AM +0800, Chenguang Zhao wrote:
From: Chenguang Zhao <redacted>
When AF_XDP ZC receives a multi-buffer frame and the XDP program
returns XDP_PASS, i40e_construct_skb_zc() copies frags into a new
skb. The copy used skb_frag_page() as the memcpy source (page
metadata instead of packet data) and passed a virtual address to
__skb_fill_page_desc_noacc(), which expects a struct page *.
Use skb_frag_address() for the copy, attach frags with
skb_add_rx_frag() so len/data_len/truesize are updated, and on
dev_alloc_page() failure free the skb via the shared out path so
xsk_buff_free() still runs and previously attached pages are
released by kfree_skb.
Fixes: 1c9ba9c14658 ("i40e: xsk: add RX multi-buffer support")
Signed-off-by: Chenguang Zhao <redacted>
---
- Fix memcpy source: use skb_frag_address() instead of skb_frag_page(),
which was copying page metadata rather than packet data.
- Fix frag attachment: pass the allocated struct page * to the skb frag
helper instead of the page virtual address.
- Use skb_add_rx_frag() so skb->len, data_len and truesize are updated
when attaching copied frags.
- On mid-loop dev_alloc_page() failure, go through the shared out path
so previously attached pages are released via kfree_skb and
xsk_buff_free() is still called.Hi! I assume this is a fix, so you should include your target tree in patch subject (net) plus Fixes: tag. However, could you take a look if we could use xdp_build_skb_from_zc() and wipe out i40e_construct_skb_zc() altogether?
quoted hunk ↗ jump to hunk
drivers/net/ethernet/intel/i40e/i40e_xsk.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c index 9f47388eaba5..a4247710c85b 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c +++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c@@ -318,22 +318,19 @@ static struct sk_buff *i40e_construct_skb_zc(struct i40e_ring *rx_ring, goto out; for (int i = 0; i < nr_frags; i++) { - struct skb_shared_info *skinfo = skb_shinfo(skb); skb_frag_t *frag = &sinfo->frags[i]; + unsigned int frag_size = skb_frag_size(frag); struct page *page; - void *addr; page = dev_alloc_page(); if (!page) { dev_kfree_skb(skb); - return NULL; + skb = NULL; + goto out; } - addr = page_to_virt(page); - memcpy(addr, skb_frag_page(frag), skb_frag_size(frag)); - - __skb_fill_page_desc_noacc(skinfo, skinfo->nr_frags++, - addr, 0, skb_frag_size(frag)); + memcpy(page_to_virt(page), skb_frag_address(frag), frag_size); + skb_add_rx_frag(skb, i, page, 0, frag_size, PAGE_SIZE); } out:-- 2.25.1