[xdp-hints] Re: [PATCH bpf-next v2 6/8] mlx4: Introduce mlx4_xdp_buff wrapper for xdp_buff

[Tariq Toukan <ttoukan.linux@gmail.com>]

On 11/21/2022 8:25 PM, Stanislav Fomichev wrote:
> No functional changes. Boilerplate to allow stuffing more data after xdp_buff.
> 
> Cc: Tariq Toukan <tariqt@nvidia.com>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Martin KaFai Lau <martin.lau@linux.dev>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> Cc: Anatoly Burakov <anatoly.burakov@intel.com>
> Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
> Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
> Cc: Maryam Tahhan <mtahhan@redhat.com>
> Cc: xdp-hints@xdp-project.net
> Cc: netdev@vger.kernel.org
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---
>   drivers/net/ethernet/mellanox/mlx4/en_rx.c | 26 +++++++++++++---------
>   1 file changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 8f762fc170b3..467356633172 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -661,17 +661,21 @@ static int check_csum(struct mlx4_cqe *cqe, struct sk_buff *skb, void *va,
>   #define MLX4_CQE_STATUS_IP_ANY (MLX4_CQE_STATUS_IPV4)
>   #endif
>   
> +struct mlx4_xdp_buff {
> +	struct xdp_buff xdp;
> +};
> +
>   int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int budget)
>   {
>   	struct mlx4_en_priv *priv = netdev_priv(dev);
>   	int factor = priv->cqe_factor;
>   	struct mlx4_en_rx_ring *ring;
> +	struct mlx4_xdp_buff this would helpmxbuf;

as it doesn't go through an init function (only mxbuf.xdp does), better 
init to zero.

>   	struct bpf_prog *xdp_prog;
>   	int cq_ring = cq->ring;
>   	bool doorbell_pending;
>   	bool xdp_redir_flush;
>   	struct mlx4_cqe *cqe;
> -	struct xdp_buff xdp;
>   	int polled = 0;
>   	int index;
>   
> @@ -681,7 +685,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
>   	ring = priv->rx_ring[cq_ring];
>   
>   	xdp_prog = rcu_dereference_bh(ring->xdp_prog);
> -	xdp_init_buff(&xdp, priv->frag_info[0].frag_stride, &ring->xdp_rxq);
> +	xdp_init_buff(&mxbuf.xdp, priv->frag_info[0].frag_stride, &ring->xdp_rxq);
>   	doorbell_pending = false;
>   	xdp_redir_flush = false;
>   
> @@ -776,24 +780,24 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
>   						priv->frag_info[0].frag_size,
>   						DMA_FROM_DEVICE);
>   
> -			xdp_prepare_buff(&xdp, va - frags[0].page_offset,
> +			xdp_prepare_buff(&mxbuf.xdp, va - frags[0].page_offset,
>   					 frags[0].page_offset, length, false);
> -			orig_data = xdp.data;
> +			orig_data = mxbuf.xdp.data;
>   
> -			act = bpf_prog_run_xdp(xdp_prog, &xdp);
> +			act = bpf_prog_run_xdp(xdp_prog, &mxbuf.xdp);
>   
> -			length = xdp.data_end - xdp.data;
> -			if (xdp.data != orig_data) {
> -				frags[0].page_offset = xdp.data -
> -					xdp.data_hard_start;
> -				va = xdp.data;
> +			length = mxbuf.xdp.data_end - mxbuf.xdp.data;
> +			if (mxbuf.xdp.data != orig_data) {
> +				frags[0].page_offset = mxbuf.xdp.data -
> +					mxbuf.xdp.data_hard_start;
> +				va = mxbuf.xdp.data;
>   			}
>   
>   			switch (act) {
>   			case XDP_PASS:
>   				break;
>   			case XDP_REDIRECT:
> -				if (likely(!xdp_do_redirect(dev, &xdp, xdp_prog))) {
> +				if (likely(!xdp_do_redirect(dev, &mxbuf.xdp, xdp_prog))) {
>   					ring->xdp_redirect++;
>   					xdp_redir_flush = true;
>   					frags[0].page = NULL;