From: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Date: Mon, 15 Nov 2021 21:36:30 +0100
> Enabling the XDP bpf_prog access to data_meta area is a very small
> change. Hint passing 'true' to xdp_prepare_buff().
>
> The SKB layers can also access data_meta area, which required more
> driver changes to support. Reviewers, notice the igc driver have two
> different functions that can create SKBs, depending on driver config.
>
> Hint for testers, ethtool priv-flags legacy-rx enables
> the function igc_construct_skb()
>
> ethtool --set-priv-flags DEV legacy-rx on
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> ---
> drivers/net/ethernet/intel/igc/igc_main.c | 29 +++++++++++++++++++----------
> 1 file changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 76b0a7311369..b516f1b301b4 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -1718,24 +1718,26 @@ static void igc_add_rx_frag(struct igc_ring *rx_ring,
>
> static struct sk_buff *igc_build_skb(struct igc_ring *rx_ring,
> struct igc_rx_buffer *rx_buffer,
> - union igc_adv_rx_desc *rx_desc,
> - unsigned int size)
> + struct xdp_buff *xdp)
> {
> - void *va = page_address(rx_buffer->page) + rx_buffer->page_offset;
> + unsigned int size = xdp->data_end - xdp->data;
> unsigned int truesize = igc_get_rx_frame_truesize(rx_ring, size);
> + unsigned int metasize = xdp->data - xdp->data_meta;
> struct sk_buff *skb;
>
> /* prefetch first cache line of first page */
> - net_prefetch(va);
> + net_prefetch(xdp->data);
I'd prefer prefetching xdp->data_meta here. GRO layer accesses it.
Maximum meta size for now is 32, so at least 96 bytes of the frame
will stil be prefetched.
>
> /* build an skb around the page buffer */
> - skb = build_skb(va - IGC_SKB_PAD, truesize);
> + skb = build_skb(xdp->data_hard_start, truesize);
> if (unlikely(!skb))
> return NULL;
>
> /* update pointers within the skb to store the data */
> - skb_reserve(skb, IGC_SKB_PAD);
> + skb_reserve(skb, xdp->data - xdp->data_hard_start);
> __skb_put(skb, size);
> + if (metasize)
> + skb_metadata_set(skb, metasize);
>
> igc_rx_buffer_flip(rx_buffer, truesize);
> return skb;
> @@ -1746,6 +1748,7 @@ static struct sk_buff *igc_construct_skb(struct igc_ring *rx_ring,
> struct xdp_buff *xdp,
> ktime_t timestamp)
> {
> + unsigned int metasize = xdp->data - xdp->data_meta;
> unsigned int size = xdp->data_end - xdp->data;
> unsigned int truesize = igc_get_rx_frame_truesize(rx_ring, size);
> void *va = xdp->data;
> @@ -1756,7 +1759,7 @@ static struct sk_buff *igc_construct_skb(struct igc_ring *rx_ring,
> net_prefetch(va);
...here as well.
>
> /* allocate a skb to store the frags */
> - skb = napi_alloc_skb(&rx_ring->q_vector->napi, IGC_RX_HDR_LEN);
> + skb = napi_alloc_skb(&rx_ring->q_vector->napi, IGC_RX_HDR_LEN + metasize);
> if (unlikely(!skb))
> return NULL;
>
> @@ -1769,7 +1772,13 @@ static struct sk_buff *igc_construct_skb(struct igc_ring *rx_ring,
> headlen = eth_get_headlen(skb->dev, va, IGC_RX_HDR_LEN);
>
> /* align pull length to size of long to optimize memcpy performance */
> - memcpy(__skb_put(skb, headlen), va, ALIGN(headlen, sizeof(long)));
> + memcpy(__skb_put(skb, headlen + metasize), xdp->data_meta,
> + ALIGN(headlen + metasize, sizeof(long)));
> +
> + if (metasize) {
> + skb_metadata_set(skb, metasize);
> + __skb_pull(skb, metasize);
> + }
>
> /* update all of the pointers */
> size -= headlen;
> @@ -2354,7 +2363,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
> if (!skb) {
> xdp_init_buff(&xdp, truesize, &rx_ring->xdp_rxq);
> xdp_prepare_buff(&xdp, pktbuf - igc_rx_offset(rx_ring),
> - igc_rx_offset(rx_ring) + pkt_offset, size, false);
> + igc_rx_offset(rx_ring) + pkt_offset, size, true);
>
> skb = igc_xdp_run_prog(adapter, &xdp);
> }
> @@ -2378,7 +2387,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
> } else if (skb)
> igc_add_rx_frag(rx_ring, rx_buffer, skb, size);
> else if (ring_uses_build_skb(rx_ring))
> - skb = igc_build_skb(rx_ring, rx_buffer, rx_desc, size);
> + skb = igc_build_skb(rx_ring, rx_buffer, &xdp);
> else
> skb = igc_construct_skb(rx_ring, rx_buffer, &xdp,
> timestamp);
Thanks!
Al
