From: Mel Gorman <mgorman@techsingularity.net>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@infradead.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Michal Suchanek <msuchanek@suse.de>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
LKML <linux-kernel@vger.kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Hritik Vijay <hritikxx8@gmail.com>,
Linux-BPF <bpf@vger.kernel.org>,
Linux-Net <netdev@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH v2] mm/page_alloc: Work around a pahole limitation with zero-sized struct pagesets
Date: Thu, 27 May 2021 15:54:41 +0100 [thread overview]
Message-ID: <20210527145441.GE30378@techsingularity.net> (raw)
In-Reply-To: <CAEf4BzartMG36AGs-7LkQdpgrB6TYyTJ8PQhjkQWiTN=7sO1Bw@mail.gmail.com>
On Thu, May 27, 2021 at 07:37:05AM -0700, Andrii Nakryiko wrote:
> > This patch checks for older versions of pahole and only allows
> > DEBUG_INFO_BTF_MODULES if pahole supports zero-sized per-cpu structures.
> > DEBUG_INFO_BTF is still allowed as a KVM boot test passed with pahole
>
> Unfortunately this won't work. The problem is that vmlinux BTF is
> corrupted, which results in module BTFs to be rejected as well, as
> they depend on it.
>
> But vmlinux BTF corruption makes BPF subsystem completely unusable. So
> even though kernel boots, nothing BPF-related works. So we'd need to
> add dependency for DEBUG_INFO_BTF on pahole 1.22+.
>
While bpf usage would be broken, the kernel will boot and the effect
should be transparent to any kernel build based on "make oldconfig".
CONFIG_DEBUG_INFO_BTF defaults N so if that is forced out, it will be
easily missed by a distribution kernel maintainer.
Yes, users of BPF will be affected and it may generate bug reports but
the fix will be to build with a working pahole. Breaking boot on the other
hand is a lot more visible and hacking around this with a non-zero struct
size has been shot down.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-05-27 14:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 12:02 Mel Gorman
2021-05-27 14:37 ` Andrii Nakryiko
2021-05-27 14:54 ` Mel Gorman [this message]
2021-05-27 16:36 ` Andrii Nakryiko
2021-05-27 17:27 ` Mel Gorman
2021-05-27 22:25 ` Andrii Nakryiko
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=20210527145441.GE30378@techsingularity.net \
--to=mgorman@techsingularity.net \
--cc=acme@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=andrii.nakryiko@gmail.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=hch@infradead.org \
--cc=hritikxx8@gmail.com \
--cc=john.fastabend@gmail.com \
--cc=jolsa@kernel.org \
--cc=kafai@fb.com \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=msuchanek@suse.de \
--cc=netdev@vger.kernel.org \
--cc=songliubraving@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