On Wed, Jul 29, 2026 at 01:49:16PM +0800, Chenguang Zhao wrote:
> From: Chenguang Zhao <[email protected]>
>
> Replace the driver-local i40e_construct_skb_zc() with the common
> helper xdp_build_skb_from_zc(). On failure, free the xdp buff in
> the caller.
>
> xdp_build_skb_from_zc() already calls skb_record_rx_queue() and
> eth_type_trans(), so pull the remaining descriptor field setup into
> __i40e_process_skb_fields() and use that on the XDP_PASS path.
> Briefly restore the Ethernet header around eth_skb_pad() so padding
> sees the full L2 frame length.
>
> Signed-off-by: Chenguang Zhao <[email protected]>
> ---
> v2:
> - Extract descriptor field setup into __i40e_process_skb_fields() and
> use it on the XDP_PASS path, so skb_record_rx_queue()/eth_type_trans()
> are not repeated after xdp_build_skb_from_zc().
> - Keep a brief __skb_push()/__skb_pull() around eth_skb_pad() so padding
> still sees the full L2 frame length.
>
> v1:
> -
> https://lore.kernel.org/all/[email protected]/
> ---
> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 32 ++++++--
> .../ethernet/intel/i40e/i40e_txrx_common.h | 2 +
> drivers/net/ethernet/intel/i40e/i40e_xsk.c | 76 +++----------------
> 3 files changed, 36 insertions(+), 74 deletions(-)
>
[...]
> static void i40e_handle_xdp_result_zc(struct i40e_ring *rx_ring,
> struct xdp_buff *xdp_buff,
> union i40e_rx_desc *rx_desc,
> @@ -372,21 +309,28 @@ static void i40e_handle_xdp_result_zc(struct i40e_ring
> *rx_ring,
> * BIT(I40E_RXD_QW1_ERROR_SHIFT). This is due to that
> * SBP is *not* set in PRT_SBPVSI (default not set).
> */
> - skb = i40e_construct_skb_zc(rx_ring, xdp_buff);
> + skb = xdp_build_skb_from_zc(xdp_buff);
> if (!skb) {
> + xsk_buff_free(xdp_buff);
> rx_ring->rx_stats.alloc_buff_failed++;
> *rx_packets = 0;
> *rx_bytes = 0;
> return;
> }
>
> + /* xdp_build_skb_from_zc() already ran eth_type_trans() and
> + * skb_record_rx_queue(). Restore the Ethernet header only for
> + * eth_skb_pad(), then pull it back.
> + */
> + __skb_push(skb, ETH_HLEN);
> if (eth_skb_pad(skb)) {
> *rx_packets = 0;
> *rx_bytes = 0;
> return;
> }
> + __skb_pull(skb, ETH_HLEN);
I am pretty sure that eth_skb_pad() is not needed on Rx, network stack handles
small skbs just fine, and no other vendor does this. We were trying to figure
out the historical reasons for eth_skb_pad() being there in the intel drivers,
but with no luck.
>
> - i40e_process_skb_fields(rx_ring, rx_desc, skb);
> + __i40e_process_skb_fields(rx_ring, rx_desc, skb);
> napi_gro_receive(&rx_ring->q_vector->napi, skb);
> return;
> }
> --
> 2.25.1
>
>
