bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Yonghong Song <yhs@fb.com>, bpf <bpf@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>, Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next] selftests/bpf: change llvm flag -mcpu=probe to -mcpu=v3
Date: Wed, 19 Feb 2020 15:17:35 -0800	[thread overview]
Message-ID: <CAADnVQ+CtuOkpidngFxEXWU_efLOv9_ozj=eSgNo1os1w3b8Sw@mail.gmail.com> (raw)
In-Reply-To: <CAADnVQLWJ+F8w0g9XaLbNHZEXKbcQeXt+AiAZX7gMX=L_PWrhw@mail.gmail.com>

On Wed, Feb 19, 2020 at 9:06 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Wed, Feb 19, 2020 at 8:56 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
> >
> > On 2/19/20 1:42 AM, Yonghong Song wrote:
> > > The latest llvm supports cpu version v3, which is cpu version v1
> > > plus some additional 64bit jmp insns and 32bit jmp insn support.
> > >
> > > In selftests/bpf Makefile, the llvm flag -mcpu=probe did runtime
> > > probe into the host system. Depending on compilation environments,
> > > it is possible that runtime probe may fail, e.g., due to
> > > memlock issue. This will cause generated code with cpu version v1.
> >
> > But those are tiny BPF progs that LLVM is probing. If memlock is not
> > sufficient, should it try to bump the limit with the diff needed and
> > only if that fails as well then it bails out to v1.
>
> with hundred parallel clangs running and all stamping on the same rlimit
> I don't think bumping that limit can work.
> Also building on older kernel should still do v3, since build should
> produce selftest binaries for the same vmlinux as this kernel tree.
> We hit this issue with github/libbpf CI. The vm used to do the build
> was too old. So far we cannot build vmlinux out of latest tree,
> boot into it and only then build selftests inside. It's too complex
> for CI system.
> So we build vmlinux and build selftests in that CI's VM, and then boot into it
> and run selftests.
> Upgrading VM is an easy fix for now, but the issue will cause the problems
> later. So imo fixing selftests build to predictable -mcpu=v3 is the
> most sensible way.

Applied. Thanks

  reply	other threads:[~2020-02-19 23:17 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-19  0:42 [PATCH bpf-next] selftests/bpf: change llvm flag -mcpu=probe to -mcpu=v3 Yonghong Song
2020-02-19  7:34 ` Andrii Nakryiko
2020-02-19 16:56 ` Daniel Borkmann
2020-02-19 17:04   ` Yonghong Song
2020-02-19 17:06   ` Alexei Starovoitov
2020-02-19 23:17     ` Alexei Starovoitov [this message]
2020-02-20  0:15       ` Daniel Borkmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAADnVQ+CtuOkpidngFxEXWU_efLOv9_ozj=eSgNo1os1w3b8Sw@mail.gmail.com' \
    --to=alexei.starovoitov@gmail.com \
    --cc=ast@fb.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=kernel-team@fb.com \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).