linux-kernel - Re: [PATCH 6.14 000/197] 6.14.7-rc1 review

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Message-ID: <6cratgkqkq4lnln65bqjiqn4vle7uhtlvnmi5r2v3l4lug3g5p@n55v6sogh6x2>
Date: Thu, 15 May 2025 20:04:06 +0800
From: Shung-Hsi Yu <shung-hsi.yu@...e.com>
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, patches@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org, linux@...ck-us.net, shuah@...nel.org, 
	patches@...nelci.org, lkft-triage@...ts.linaro.org, pavel@...x.de, 
	jonathanh@...dia.com, f.fainelli@...il.com, sudipm.mukherjee@...il.com, 
	srw@...dewatkins.net, rwarsow@....de, conor@...nel.org, hargar@...rosoft.com, 
	broonie@...nel.org, Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, 
	Ihor Solodrai <ihor.solodrai@...ux.dev>, Kees Cook <kees@...nel.org>, 
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 6.14 000/197] 6.14.7-rc1 review

On Wed, May 14, 2025 at 09:17:45PM -0700, Pawan Gupta wrote:
> On Wed, May 14, 2025 at 07:49:29PM +0800, Shung-Hsi Yu wrote:
> > On Mon, May 12, 2025 at 07:37:30PM +0200, Greg Kroah-Hartman wrote:
> > > This is the start of the stable review cycle for the 6.14.7 release.
> > > There are 197 patches in this series, all will be posted as a response
> > > to this one.  If anyone has any issues with these being applied, please
> > > let me know.
> > 
> > Running included BPF selftests with a BPF CI fork (i.e. running on
> > GitHub Action x86-64 machines), I observe that that running the BPF
> > selftests now takes about 2x the time (from ~25m to ~50m), and
> > verif_scale_loop3_fail is timing out, taking more than 6 minutes to run
> > compare to the usual single digit second runtime. See [1] for the log.
...
> > Compare to a day before when such behavior wasn't observed[2], the main
> > difference being these additional patches:
...
> Not sure why but this commit seems to related to the failure.
> 
> Below is log of bisecting v6.14.6 and v6.14.7-rc2 with the test:
> 
>   ./tools/testing/selftests/bpf/vmtest.sh -i -- timeout 20 ./test_progs -t verif_scale_loop3_fail
> 
> # good: [e2d3e1fdb530198317501eb7ded4f3a5fb6c881c] Linux 6.14.6
> git bisect good e2d3e1fdb530198317501eb7ded4f3a5fb6c881c
...
> git bisect bad 336f780075f36e0d1181ce44d6d4197e4a22babc
> # bad: [665f26e5de2325e3bca107b632bc2ccac1b9806a] mm: vmalloc: support more granular vrealloc() sizing
> git bisect bad 665f26e5de2325e3bca107b632bc2ccac1b9806a
> # first bad commit: [665f26e5de2325e3bca107b632bc2ccac1b9806a] mm: vmalloc: support more granular vrealloc() sizing

Thanks! Just dawn on me after seeing this that I should try 6.15-rc6 as
well (which has 665f26e5de23), turns out it also reproduce there. I'll
report regression in a separate mail. 

> ...
> > No patches touch BPF's core component, and while the
> > verif_scale_loop3_fail test did time out, the verifier is still
> > correctly rejecting it, so shouldn't have anything to do with
> > kernel/bpf/. The x86/arm64 BPF patches only affect JIT output, and only
> > for cBPF.
> > 
> > In comparison, with 6.12.29-rc1 I don't observe any timeout or increase
> > in runtime[3]. Below is a diff comparing the applied patches in
> > 6.12.29-rc1 and 6.14.7-rc1. Seems like 6.14.7-rc1 does not have the
> > CALL_NOSPEC patches, but I cannot tell whether that is what makes the
> > difference.
> 
> Thats because CALL_NOSPEC patches were already part of v6.14.

Ah yes indeed, sorry about the negligence.