netdev - Re: [PATCH bpf 1/7] xdp: remove the xdp_attachment_flags

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Message-ID: <87o8j99aip.fsf@toke.dk>
Date:   Fri, 04 Dec 2020 10:38:06 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andriin@...com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Romain Perier <romain.perier@...il.com>,
        Allen Pais <apais@...ux.microsoft.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Simon Horman <simon.horman@...ronome.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Jiri Benc <jbenc@...hat.com>, oss-drivers@...ronome.com,
        linux-omap@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf 1/7] xdp: remove the xdp_attachment_flags_ok() callback

Jakub Kicinski <kuba@...nel.org> writes:

> On Thu, 03 Dec 2020 22:35:18 +0100 Toke Høiland-Jørgensen wrote:
>> Since we offloaded and non-offloaded programs can co-exist there doesn't
>> really seem to be any reason for the check anyway, and it's only used in
>> three drivers so let's just get rid of the callback entirely.
>
> I don't remember exactly now, but I think the concern was that using 
> the unspecified mode is pretty ambiguous when interface has multiple
> programs attached.

Right. I did scratch my head a bit for why the check was there in the
first place, but that makes sense, actually :)

So how about we disallow unload without specifying a mode, but only if
more than one program is loaded? Since the core code tracks all the
programs now, this could just be enforced there and we would avoid all
the weird interactions with the drivers trying to enforce it...

-Toke