netdev - RE: [PATCH v12 bpf-next 06/18] net: marvell: rely on xdp_update_skb_shared

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Message-ID: <612ebe4548da_6b87208fa@john-XPS-13-9370.notmuch>
Date:   Tue, 31 Aug 2021 16:41:57 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, shayagr@...zon.com,
        john.fastabend@...il.com, dsahern@...nel.org, brouer@...hat.com,
        echaudro@...hat.com, jasowang@...hat.com,
        alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com, toke@...hat.com
Subject: RE: [PATCH v12 bpf-next 06/18] net: marvell: rely on
 xdp_update_skb_shared_info utility routine

Lorenzo Bianconi wrote:
> Rely on xdp_update_skb_shared_info routine in order to avoid
> resetting frags array in skb_shared_info structure building
> the skb in mvneta_swbm_build_skb(). Frags array is expected to
> be initialized by the receiving driver building the xdp_buff
> and here we just need to update memory metadata.
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---

Acked-by: John Fastabend <john.fastabend@...il.com>

>  drivers/net/ethernet/marvell/mvneta.c | 35 +++++++++++++++------------
>  1 file changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index cbf614d6b993..b996eb49d813 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2304,11 +2304,19 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
>  		skb_frag_size_set(frag, data_len);
>  		__skb_frag_set_page(frag, page);
>  
> -		if (!xdp_buff_is_mb(xdp))
> +		if (!xdp_buff_is_mb(xdp)) {
> +			sinfo->xdp_frags_size = *size;
>  			xdp_buff_set_mb(xdp);
> +		}
> +		if (page_is_pfmemalloc(page))
> +			xdp_buff_set_frag_pfmemalloc(xdp);
>  	} else {
>  		page_pool_put_full_page(rxq->page_pool, page, true);
>  	}
> +
> +	/* last fragment */
> +	if (len == *size)
> +		sinfo->xdp_frags_tsize = sinfo->nr_frags * PAGE_SIZE;
>  	*size -= len;
>  }
>  
> @@ -2316,13 +2324,18 @@ static struct sk_buff *
>  mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
>  		      struct xdp_buff *xdp, u32 desc_status)
>  {
> -	struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> +	unsigned int size, truesize;
>  	struct sk_buff *skb;
>  	u8 num_frags;
> -	int i;
>  
> -	if (unlikely(xdp_buff_is_mb(xdp)))
> +	if (unlikely(xdp_buff_is_mb(xdp))) {

Just curious does the mvneta hardware support header split? If we
get to that point then we can drop the unlikely.

> +		struct skb_shared_info *sinfo;
> +
> +		sinfo = xdp_get_shared_info_from_buff(xdp);
> +		truesize = sinfo->xdp_frags_tsize;
> +		size = sinfo->xdp_frags_size;
>  		num_frags = sinfo->nr_frags;
> +	}
>  
>  	skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
>  	if (!skb)
> @@ -2334,18 +2347,10 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
>  	skb_put(skb, xdp->data_end - xdp->data);
>  	skb->ip_summed = mvneta_rx_csum(pp, desc_status);
>  
> -	if (likely(!xdp_buff_is_mb(xdp)))
> -		goto out;
> -
> -	for (i = 0; i < num_frags; i++) {
> -		skb_frag_t *frag = &sinfo->frags[i];
> -
> -		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
> -				skb_frag_page(frag), skb_frag_off(frag),
> -				skb_frag_size(frag), PAGE_SIZE);
> -	}
> +	if (unlikely(xdp_buff_is_mb(xdp)))
> +		xdp_update_skb_shared_info(skb, num_frags, size, truesize,
> +					   xdp_buff_is_frag_pfmemalloc(xdp));
>  
> -out:
>  	return skb;
>  }
>  
> -- 
> 2.31.1
>