netdev - Re: [xdp-hints] Re: [PATCH bpf-next v7 15/17] net/mlx5e: Introduce wrapper for xdp

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Date:   Thu, 12 Jan 2023 22:09:17 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Stanislav Fomichev <sdf@...gle.com>,
        Tariq Toukan <ttoukan.linux@...il.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        haoluo@...gle.com, jolsa@...nel.org,
        Tariq Toukan <tariqt@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org
Subject: Re: [xdp-hints] Re: [PATCH bpf-next v7 15/17] net/mlx5e: Introduce
 wrapper for xdp_buff

Stanislav Fomichev <sdf@...gle.com> writes:

> On Thu, Jan 12, 2023 at 12:07 AM Tariq Toukan <ttoukan.linux@...il.com> wrote:
>>
>>
>>
>> On 12/01/2023 2:32, Stanislav Fomichev wrote:
>> > From: Toke Høiland-Jørgensen <toke@...hat.com>
>> >
>> > Preparation for implementing HW metadata kfuncs. No functional change.
>> >
>> > Cc: Tariq Toukan <tariqt@...dia.com>
>> > Cc: Saeed Mahameed <saeedm@...dia.com>
>> > Cc: John Fastabend <john.fastabend@...il.com>
>> > Cc: David Ahern <dsahern@...il.com>
>> > Cc: Martin KaFai Lau <martin.lau@...ux.dev>
>> > Cc: Jakub Kicinski <kuba@...nel.org>
>> > Cc: Willem de Bruijn <willemb@...gle.com>
>> > Cc: Jesper Dangaard Brouer <brouer@...hat.com>
>> > Cc: Anatoly Burakov <anatoly.burakov@...el.com>
>> > Cc: Alexander Lobakin <alexandr.lobakin@...el.com>
>> > Cc: Magnus Karlsson <magnus.karlsson@...il.com>
>> > Cc: Maryam Tahhan <mtahhan@...hat.com>
>> > Cc: xdp-hints@...-project.net
>> > Cc: netdev@...r.kernel.org
>> > Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
>> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
>> > ---
>> >   drivers/net/ethernet/mellanox/mlx5/core/en.h  |  1 +
>> >   .../net/ethernet/mellanox/mlx5/core/en/xdp.c  |  3 +-
>> >   .../net/ethernet/mellanox/mlx5/core/en/xdp.h  |  6 +-
>> >   .../ethernet/mellanox/mlx5/core/en/xsk/rx.c   | 25 ++++----
>> >   .../net/ethernet/mellanox/mlx5/core/en_rx.c   | 58 +++++++++----------
>> >   5 files changed, 50 insertions(+), 43 deletions(-)
>> >
>> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
>> > index 2d77fb8a8a01..af663978d1b4 100644
>> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
>> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
>> > @@ -469,6 +469,7 @@ struct mlx5e_txqsq {
>> >   union mlx5e_alloc_unit {
>> >       struct page *page;
>> >       struct xdp_buff *xsk;
>> > +     struct mlx5e_xdp_buff *mxbuf;
>>
>> In XSK files below you mix usage of both alloc_units[page_idx].mxbuf and
>> alloc_units[page_idx].xsk, while both fields share the memory of a union.
>>
>> As struct mlx5e_xdp_buff wraps struct xdp_buff, I think that you just
>> need to change the existing xsk field type from struct xdp_buff *xsk
>> into struct mlx5e_xdp_buff *xsk and align the usage.
>
> Hmmm, good point. I'm actually not sure how it works currently.
> mlx5e_alloc_unit.mxbuf doesn't seem to be initialized anywhere? Toke,
> am I missing something?

It's initialised piecemeal in different places; but yeah, we're mixing
things a bit...

> I'm thinking about something like this:
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h
> b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> index af663978d1b4..2d77fb8a8a01 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> @@ -469,7 +469,6 @@ struct mlx5e_txqsq {
>  union mlx5e_alloc_unit {
>         struct page *page;
>         struct xdp_buff *xsk;
> -       struct mlx5e_xdp_buff *mxbuf;
>  };

Hmm, for consistency with the non-XSK path we should rather go the other
direction and lose the xsk member, moving everything to mxbuf? Let me
give that a shot...

-Toke