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

On Wed, 23 Sep 2020 at 17:24, Andrii Nakryiko [off-list ref] wrote:

On Wed, Sep 23, 2020 at 9:12 AM Lorenz Bauer [off-list ref] wrote:

quoted

On Fri, 18 Sep 2020 at 04:26, Alexei Starovoitov
[off-list ref] wrote:
[...]

quoted

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.

Yeah, that is very possible. Keep in mind though that our internal
version has since become more complex, and also has a more
comprehensive test suite. I wasn't sounding the alarms, it's just an
FYI that I appreciate the work that went into this and have taken a
look, but that I need to do some more digging :)

-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

www.cloudflare.com