netdev - Re: [PATCH] bpf: return EOPNOTSUPP when JIT is needed and not possible

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Message-ID: <20211209182349.038ac2b8@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 9 Dec 2021 18:23:49 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Ido Schimmel <idosch@...sch.org>,
        John Fastabend <john.fastabend@...il.com>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: return EOPNOTSUPP when JIT is needed and not
 possible

On Fri, 10 Dec 2021 00:03:40 +0100 Daniel Borkmann wrote:
> > Similar issue was discussed in the past. See:
> > https://lore.kernel.org/netdev/20191204.125135.750458923752225025.davem@davemloft.net/  
> 
> With regards to ENOTSUPP exposure, if the consensus is that we should fix all
> occurences over to EOPNOTSUPP even if they've been exposed for quite some time
> (Jakub?), 

Did you mean me? :) In case you did - I think we should avoid it 
for new code but changing existing now seems risky. Alexei and Andrii
would know best but quick search of code bases at work reveals some
scripts looking for ENOTSUPP.

Thadeu, what motivated the change?

If we're getting those changes fixes based on checkpatch output maybe 
there is a way to mute the checkpatch warnings when it's not run on a 
diff?

> we could give this patch a try maybe via bpf-next and see if anyone complains.
> 
> Thadeu, I think you also need to fix up BPF selftests as test_verifier, to mention
> one example (there are also bunch of others under tools/testing/selftests/), is
> checking for ENOTSUPP specifically..