netdev - Re: [PATCH v8 bpf-next 0/7] bpf: tailcalls in BPF subprograms

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Date:   Wed, 23 Sep 2020 09:24:29 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Andrii Nakryiko <andriin@...com>,
        Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH v8 bpf-next 0/7] bpf: tailcalls in BPF subprograms

On Wed, Sep 23, 2020 at 9:12 AM Lorenz Bauer <lmb@...udflare.com> wrote:
>
> On Fri, 18 Sep 2020 at 04:26, Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> [...]
> >
> > Lorenz,
> > if you can test it on cloudflare progs would be awesome.
>
> Our programs all bpf_tail_call from the topmost function, so no calls
> from subprogs. I stripped out our FORCE_INLINE flag, recompiled and
> ran our testsuite. cls_redirect.c (also in the kernel selftests) has a
> test failure that I currently can't explain, but I don't have the time
> to look at it in detail right now.
>

I've already converted test_cls_redirect.c in selftest to have
__noinline variant. And it works fine. There are only 4 helper
functions that can't be converted to a sub-program (pkt_parse_ipv4,
pkt_parse_ipv6, and three buffer manipulation helpers) because they
are accepting a pointer to a stack from a calling function, which
won't work with subprograms. But all the other functions were
trivially converted to __noinline and keep working.

> Hopefully I can get back to this next week.
>
> Best
> Lorenz
>
> --
> Lorenz Bauer  |  Systems Engineer
> 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK
>
> www.cloudflare.com