netdev - Re: [PATCH v14 bpf-next 00/18] mvneta: introduce XDP multi-buffer support

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Message-ID: <20210929122229.1d0c4960@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 29 Sep 2021 12:22:29 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Lorenz Bauer <lmb@...udflare.com>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>, Lorenzo Bianconi <lorenzo@...nel.org>,
        bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, shayagr@...zon.com,
        John Fastabend <john.fastabend@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Saeed Mahameed <saeed@...nel.org>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        tirthendu.sarkar@...el.com
Subject: Re: [PATCH v14 bpf-next 00/18] mvneta: introduce XDP multi-buffer
 support

On Wed, 29 Sep 2021 11:54:46 -0700 Alexei Starovoitov wrote:
> I'm missing something. Why do we need a separate flush() helper?
> Can't we do:
> char buf[64], *p;
> p = xdp_mb_pointer(ctx, flags, off, len, buf);
> read/write p[]
> if (p == buf)
>     xdp_store_bytes(ctx, off, buf, len, flags);

Sure we can. That's what I meant by "leave the checking to the program".
It's bike shedding at this point.