linux-kernel - Re: [PATCH bpf-next] xsk: Simplify xp_aligned_validate

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Message-ID: <CAJ8uoz11tOSUK0+45K=L9q-yj3gyMCDJVPsOjawE+Wjbe2FSTQ@mail.gmail.com>
Date:   Wed, 12 Apr 2023 14:23:34 +0200
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Kal Conley <kal.conley@...tris.com>
Cc:     Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next] xsk: Simplify xp_aligned_validate_desc implementation

On Mon, 10 Apr 2023 at 14:24, Kal Conley <kal.conley@...tris.com> wrote:
>
> Perform the chunk boundary check like the page boundary check in
> xp_desc_crosses_non_contig_pg(). This simplifies the implementation and
> reduces the number of branches.

Thanks for this simplification Kal. Just to check, does your change
pass the xsk selftests, especially the INV_DESC test? If so, then you
have my ack below.

Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>

> Signed-off-by: Kal Conley <kal.conley@...tris.com>
> ---
>  net/xdp/xsk_queue.h | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index dea4f378327d..6d40a77fccbe 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -133,16 +133,12 @@ static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
>  static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
>                                             struct xdp_desc *desc)
>  {
> -       u64 chunk, chunk_end;
> +       u64 offset = desc->addr & (pool->chunk_size - 1);
>
> -       chunk = xp_aligned_extract_addr(pool, desc->addr);
> -       if (likely(desc->len)) {
> -               chunk_end = xp_aligned_extract_addr(pool, desc->addr + desc->len - 1);
> -               if (chunk != chunk_end)
> -                       return false;
> -       }
> +       if (offset + desc->len > pool->chunk_size)
> +               return false;
>
> -       if (chunk >= pool->addrs_cnt)
> +       if (desc->addr >= pool->addrs_cnt)
>                 return false;
>
>         if (desc->options)
> --
> 2.39.2
>