linux-kernel - Re: [RFC net-next 5/9] ice: apply XDP offloading fixup when building skb

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Date: Fri, 21 Jun 2024 11:20:46 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Yan Zhai <yan@...udflare.com>
CC: <netdev@...r.kernel.org>, Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Björn Töpel <bjorn@...nel.org>, Magnus Karlsson
	<magnus.karlsson@...el.com>, Maciej Fijalkowski
	<maciej.fijalkowski@...el.com>, Jonathan Lemon <jonathan.lemon@...il.com>,
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, <intel-wired-lan@...ts.osuosl.org>,
	<linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [RFC net-next 5/9] ice: apply XDP offloading fixup when building
 skb

From: Yan Zhai <yan@...udflare.com>
Date: Thu, 20 Jun 2024 15:19:22 -0700

> Add a common point to transfer offloading info from XDP context to skb.
> 
> Signed-off-by: Yan Zhai <yan@...udflare.com>
> Signed-off-by: Jesper Dangaard Brouer <hawk@...nel.org>
> ---
>  drivers/net/ethernet/intel/ice/ice_txrx.c | 2 ++
>  drivers/net/ethernet/intel/ice/ice_xsk.c  | 6 +++++-
>  include/net/xdp_sock_drv.h                | 2 +-
>  3 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> index 8bb743f78fcb..a247306837ed 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> @@ -1222,6 +1222,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
>  
>  			hard_start = page_address(rx_buf->page) + rx_buf->page_offset -
>  				     offset;
> +			xdp_init_buff_minimal(xdp);

Two lines below, you have this:

	xdp_buff_clear_frags_flag(xdp);

Which clears frags bit in xdp->flags. I.e. since you always clear flags
here, this call becomes redundant.
But I'd say that `xdp->flags = 0` really wants to be moved from
xdp_init_buff() to xdp_prepare_buff().

>  			xdp_prepare_buff(xdp, hard_start, offset, size, !!offset);
>  #if (PAGE_SIZE > 4096)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
> @@ -1287,6 +1288,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
>  
>  		/* populate checksum, VLAN, and protocol */
>  		ice_process_skb_fields(rx_ring, rx_desc, skb);
> +		xdp_buff_fixup_skb_offloading(xdp, skb);
>  
>  		ice_trace(clean_rx_irq_indicate, rx_ring, rx_desc, skb);
>  		/* send completed skb up the stack */
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index a65955eb23c0..367658acaab8 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -845,8 +845,10 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
>  	xdp_prog = READ_ONCE(rx_ring->xdp_prog);
>  	xdp_ring = rx_ring->xdp_ring;
>  
> -	if (ntc != rx_ring->first_desc)
> +	if (ntc != rx_ring->first_desc) {
>  		first = *ice_xdp_buf(rx_ring, rx_ring->first_desc);
> +		xdp_init_buff_minimal(first);

xdp_buff_set_size() always clears flags, this is redundant.

> +	}
>  
>  	while (likely(total_rx_packets < (unsigned int)budget)) {
>  		union ice_32b_rx_flex_desc *rx_desc;
> @@ -920,6 +922,7 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
>  			break;
>  		}
>  
> +		xdp = first;
>  		first = NULL;
>  		rx_ring->first_desc = ntc;
>  
> @@ -934,6 +937,7 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
>  		vlan_tci = ice_get_vlan_tci(rx_desc);
>  
>  		ice_process_skb_fields(rx_ring, rx_desc, skb);
> +		xdp_buff_fixup_skb_offloading(xdp, skb);
>  		ice_receive_skb(rx_ring, skb, vlan_tci);
>  	}
>  
> diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
> index 0a5dca2b2b3f..02243dc064c2 100644
> --- a/include/net/xdp_sock_drv.h
> +++ b/include/net/xdp_sock_drv.h
> @@ -181,7 +181,7 @@ static inline void xsk_buff_set_size(struct xdp_buff *xdp, u32 size)
>  	xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
>  	xdp->data_meta = xdp->data;
>  	xdp->data_end = xdp->data + size;
> -	xdp->flags = 0;
> +	xdp_init_buff_minimal(xdp);

Why is this done in the patch prefixed with "ice:"?

>  }
>  
>  static inline dma_addr_t xsk_buff_raw_get_dma(struct xsk_buff_pool *pool,

Thanks,
Olek