[xdp-hints] Re: [PATCH bpf-next V1 2/5] igc: add igc_xdp_buff wrapper for xdp_buff in driver

["Song, Yoong Siang" <yoong.siang.song@intel.com>]

On Monday, April 17, 2023 10:57 PM, Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>Driver specific metadata data for XDP-hints kfuncs are propagated via tail
>extending the struct xdp_buff with a locally scoped driver struct.
>
>Zero-Copy AF_XDP/XSK does similar tricks via struct xdp_buff_xsk. This
>xdp_buff_xsk struct contains a CB area (24 bytes) that can be used for extending
>the locally scoped driver into. The XSK_CHECK_PRIV_TYPE define catch size
>violations build time.
>

Since the main purpose of this patch is to introduce igc_xdp_buff, and
you have another two patches for timestamp and hash,
thus, suggest to move timestamp and hash related code into respective patches. 

>Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
>---
> drivers/net/ethernet/intel/igc/igc.h      |    6 ++++++
> drivers/net/ethernet/intel/igc/igc_main.c |   30 ++++++++++++++++++++++-------
> 2 files changed, 29 insertions(+), 7 deletions(-)
>
>diff --git a/drivers/net/ethernet/intel/igc/igc.h
>b/drivers/net/ethernet/intel/igc/igc.h
>index f7f9e217e7b4..c609a2e648f8 100644
>--- a/drivers/net/ethernet/intel/igc/igc.h
>+++ b/drivers/net/ethernet/intel/igc/igc.h
>@@ -499,6 +499,12 @@ struct igc_rx_buffer {
> 	};
> };
>
>+/* context wrapper around xdp_buff to provide access to descriptor
>+metadata */ struct igc_xdp_buff {
>+	struct xdp_buff xdp;
>+	union igc_adv_rx_desc *rx_desc;

Move rx_desc to 4th patch (Rx hash patch)

>+};
>+
> struct igc_q_vector {
> 	struct igc_adapter *adapter;    /* backlink */
> 	void __iomem *itr_register;
>diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
>b/drivers/net/ethernet/intel/igc/igc_main.c
>index bfa9768d447f..3a844cf5be3f 100644
>--- a/drivers/net/ethernet/intel/igc/igc_main.c
>+++ b/drivers/net/ethernet/intel/igc/igc_main.c
>@@ -2236,6 +2236,8 @@ static bool igc_alloc_rx_buffers_zc(struct igc_ring
>*ring, u16 count)
> 	if (!count)
> 		return ok;
>
>+	XSK_CHECK_PRIV_TYPE(struct igc_xdp_buff);
>+
> 	desc = IGC_RX_DESC(ring, i);
> 	bi = &ring->rx_buffer_info[i];
> 	i -= ring->count;
>@@ -2520,8 +2522,8 @@ static int igc_clean_rx_irq(struct igc_q_vector
>*q_vector, const int budget)
> 		union igc_adv_rx_desc *rx_desc;
> 		struct igc_rx_buffer *rx_buffer;
> 		unsigned int size, truesize;
>+		struct igc_xdp_buff ctx;
> 		ktime_t timestamp = 0;
>-		struct xdp_buff xdp;
> 		int pkt_offset = 0;
> 		void *pktbuf;
>
>@@ -2555,13 +2557,14 @@ 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),
>+			xdp_init_buff(&ctx.xdp, truesize, &rx_ring->xdp_rxq);
>+			xdp_prepare_buff(&ctx.xdp, pktbuf - igc_rx_offset(rx_ring),
> 					 igc_rx_offset(rx_ring) + pkt_offset,
> 					 size, true);
>-			xdp_buff_clear_frags_flag(&xdp);
>+			xdp_buff_clear_frags_flag(&ctx.xdp);
>+			ctx.rx_desc = rx_desc;

Move rx_desc to 4th patch (Rx hash patch)

>
>-			skb = igc_xdp_run_prog(adapter, &xdp);
>+			skb = igc_xdp_run_prog(adapter, &ctx.xdp);
> 		}
>
> 		if (IS_ERR(skb)) {
>@@ -2583,9 +2586,9 @@ 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, &xdp);
>+			skb = igc_build_skb(rx_ring, rx_buffer, &ctx.xdp);
> 		else
>-			skb = igc_construct_skb(rx_ring, rx_buffer, &xdp,
>+			skb = igc_construct_skb(rx_ring, rx_buffer, &ctx.xdp,
> 						timestamp);
>
> 		/* exit if we failed to retrieve a buffer */ @@ -2686,6 +2689,15
>@@ static void igc_dispatch_skb_zc(struct igc_q_vector *q_vector,
> 	napi_gro_receive(&q_vector->napi, skb);  }
>
>+static struct igc_xdp_buff *xsk_buff_to_igc_ctx(struct xdp_buff *xdp) {
>+	/* xdp_buff pointer used by ZC code path is alloc as xdp_buff_xsk. The
>+	 * igc_xdp_buff shares its layout with xdp_buff_xsk and private
>+	 * igc_xdp_buff fields fall into xdp_buff_xsk->cb
>+	 */
>+       return (struct igc_xdp_buff *)xdp; }
>+

Move xsk_buff_to_igc_ctx to 3th patch (timestamp patch), which is first patch
adding xdp_metadata_ops support to igc.

> static int igc_clean_rx_irq_zc(struct igc_q_vector *q_vector, const int budget)  {
> 	struct igc_adapter *adapter = q_vector->adapter; @@ -2704,6 +2716,7
>@@ static int igc_clean_rx_irq_zc(struct igc_q_vector *q_vector, const int
>budget)
> 	while (likely(total_packets < budget)) {
> 		union igc_adv_rx_desc *desc;
> 		struct igc_rx_buffer *bi;
>+		struct igc_xdp_buff *ctx;
> 		ktime_t timestamp = 0;
> 		unsigned int size;
> 		int res;
>@@ -2721,6 +2734,9 @@ static int igc_clean_rx_irq_zc(struct igc_q_vector
>*q_vector, const int budget)
>
> 		bi = &ring->rx_buffer_info[ntc];
>
>+		ctx = xsk_buff_to_igc_ctx(bi->xdp);

Move xsk_buff_to_igc_ctx to 3th patch (timestamp patch), which is first patch
adding xdp_metadata_ops support to igc.

>+		ctx->rx_desc = desc;

Move rx_desc to 4th patch (Rx hash patch)

Thanks & Regards
Siang

>+
> 		if (igc_test_staterr(desc, IGC_RXDADV_STAT_TSIP)) {
> 			timestamp = igc_ptp_rx_pktstamp(q_vector->adapter,
> 							bi->xdp->data);
>