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From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Wed, 11 Sep 2019 14:07:38 -0700
Message-ID: <CABCJKufCwjXQ6a4oLjywDmxY2apUZ1yop-5+qty82bfwV-QTAA@mail.gmail.com>
Subject: Re: [PATCH] bpf: validate bpf_func when BPF_JIT is enabled
To:     =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= <toke@redhat.com>
Cc:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
        Yonghong Song <yhs@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Kees Cook <keescook@chromium.org>, Martin Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jesper Dangaard Brouer <brouer@redhat.com>
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On Wed, Sep 11, 2019 at 5:09 AM Toke H=C3=B8iland-J=C3=B8rgensen <toke@redh=
at.com> wrote:
>
> Bj=C3=B6rn T=C3=B6pel <bjorn.topel@intel.com> writes:
> > I ran the "xdp_rxq_info" sample with and without Sami's patch:
>
> Thanks for doing this!

Yes, thanks for testing this Bj=C3=B6rn!

> Or (1/22998700 - 1/23923874) * 10**9 =3D=3D 1.7 nanoseconds of overhead.
>
> I guess that is not *too* bad; but it's still chipping away at
> performance; anything we could do to lower the overhead?

The check is already rather minimal, but I could move this to a static
inline function to help ensure the compiler doesn't generate an
additional function call for this. I'm also fine with gating this
behind a separate config option, but I'm not sure if that's worth it.
Any thoughts?

Sami