netdev - Re: [PATCH v3 bpf-next] bpf: make verifier log more relevant by default

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Message-ID: <20201105135338.316e1677@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 5 Nov 2020 13:53:38 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Jiri Benc <jbenc@...hat.com>, Andrii Nakryiko <andriin@...com>,
        bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v3 bpf-next] bpf: make verifier log more relevant by
 default

On Thu, 5 Nov 2020 13:22:12 -0800 Andrii Nakryiko wrote:
> On Thu, Nov 5, 2020 at 8:02 AM Jiri Benc <jbenc@...hat.com> wrote:
> > On Thu, 23 Apr 2020 12:58:50 -0700, Andrii Nakryiko wrote:  
> > > To make BPF verifier verbose log more releavant and easier to use to debug
> > > verification failures, "pop" parts of log that were successfully verified.
> > > This has effect of leaving only verifier logs that correspond to code branches
> > > that lead to verification failure, which in practice should result in much
> > > shorter and more relevant verifier log dumps. This behavior is made the
> > > default behavior and can be overriden to do exhaustive logging by specifying
> > > BPF_LOG_LEVEL2 log level.  
> >
> > This patch broke the test_offload.py selftest:
> >
> > [...]
> > Test TC offloads work...
> > FAIL: Missing or incorrect message from netdevsim in verifier log
> > [...]
> >
> > The selftest expects to receive "[netdevsim] Hello from netdevsim!" in
> > the log (coming from nsim_bpf_verify_insn) but that part of the log is
> > cleared by bpf_vlog_reset added by this patch.  
> 
> Should we just drop check_verifier_log() checks?

Drivers only print error messages when something goes wrong, so the
messages are high priority. IIUC this change was just supposed to
decrease verbosity, right?