linux-kernel - Re: [PATCH bpf-next v2] bpf: Allow to use kfunc XDP hints and frags together

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Date:   Fri, 15 Sep 2023 09:21:51 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Larysa Zaremba <larysa.zaremba@...el.com>
Cc:     bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: Re: [PATCH bpf-next v2] bpf: Allow to use kfunc XDP hints and frags together

On Fri, Sep 15, 2023 at 1:45 AM Larysa Zaremba <larysa.zaremba@...el.com> wrote:
>
> There is no fundamental reason, why multi-buffer XDP and XDP kfunc RX hints
> cannot coexist in a single program.
>
> Allow those features to be used together by modifying the flags condition
> for dev-bound-only programs, segments are still prohibited for fully
> offloaded programs, hence additional check.
>
> Suggested-by: Stanislav Fomichev <sdf@...gle.com>
> Link: https://lore.kernel.org/bpf/CAKH8qBuzgtJj=OKMdsxEkyML36VsAuZpcrsXcyqjdKXSJCBq=Q@mail.gmail.com/
> Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>

Acked-by: Stanislav Fomichev <sdf@...gle.com>

Thank you!

> ---
>  kernel/bpf/offload.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> index ee35f33a96d1..9d8e508c9b86 100644
> --- a/kernel/bpf/offload.c
> +++ b/kernel/bpf/offload.c
> @@ -232,7 +232,14 @@ int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
>             attr->prog_type != BPF_PROG_TYPE_XDP)
>                 return -EINVAL;
>
> -       if (attr->prog_flags & ~BPF_F_XDP_DEV_BOUND_ONLY)
> +       if (attr->prog_flags & ~(BPF_F_XDP_DEV_BOUND_ONLY | BPF_F_XDP_HAS_FRAGS))
> +               return -EINVAL;
> +
> +       /* Frags are allowed only if program is dev-bound-only, but not
> +        * if it is requesting bpf offload.
> +        */
> +       if (attr->prog_flags & BPF_F_XDP_HAS_FRAGS &&
> +           !(attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY))
>                 return -EINVAL;
>
>         if (attr->prog_type == BPF_PROG_TYPE_SCHED_CLS &&
> --
> 2.41.0
>