netdev - Re: [PATCH net-next 01/33] xdp: add frame size to xdp

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Date:   Fri, 24 Apr 2020 16:00:53 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, sameehj@...zon.com
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, zorik@...zon.com, akiyano@...zon.com,
        gtzalik@...zon.com, Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        David Ahern <dsahern@...il.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        steffen.klassert@...unet.com
Subject: Re: [PATCH net-next 01/33] xdp: add frame size to xdp_buff

Jesper Dangaard Brouer <brouer@...hat.com> writes:

> XDP have evolved to support several frame sizes, but xdp_buff was not
> updated with this information. The frame size (frame_sz) member of
> xdp_buff is introduced to know the real size of the memory the frame is
> delivered in.
>
> When introducing this also make it clear that some tailroom is
> reserved/required when creating SKBs using build_skb().
>
> It would also have been an option to introduce a pointer to
> data_hard_end (with reserved offset). The advantage with frame_sz is
> that (like rxq) drivers only need to setup/assign this value once per
> NAPI cycle. Due to XDP-generic (and some drivers) it's not possible to
> store frame_sz inside xdp_rxq_info, because it's varies per packet as it
> can be based/depend on packet length.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>

With one possible nit below:

Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>

> ---
>  include/net/xdp.h |   13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 40c6d3398458..1ccf7df98bee 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -6,6 +6,8 @@
>  #ifndef __LINUX_NET_XDP_H__
>  #define __LINUX_NET_XDP_H__
>  
> +#include <linux/skbuff.h> /* skb_shared_info */
> +
>  /**
>   * DOC: XDP RX-queue information
>   *
> @@ -70,8 +72,19 @@ struct xdp_buff {
>  	void *data_hard_start;
>  	unsigned long handle;
>  	struct xdp_rxq_info *rxq;
> +	u32 frame_sz; /* frame size to deduct data_hard_end/reserved tailroom*/

I think maybe you want to s/deduct/deduce/ here?

-Toke