linux-kernel - perf r5101c4 counter regression

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Message-ID: <aBpcvG2yBtrrTie-@eldamar.lan>
Date: Tue, 6 May 2025 21:02:20 +0200
From: Salvatore Bonaccorso <carnil@...ian.org>
To: Pasi Kallinen <paxed@....org>, 1104796@...s.debian.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, regressions@...ts.linux.dev,
	Debian Bug Tracking System <submit@...s.debian.org>
Subject: perf r5101c4 counter regression

Hi,

Pasi Kallinen reported in Debian a regression with perf r5101c4
counter, initially it was found in
https://github.com/rr-debugger/rr/issues/3949 but said to be a kernel
problem.

On Tue, May 06, 2025 at 07:18:39PM +0300, Pasi Kallinen wrote:
> Package: src:linux
> Version: 6.12.25-1
> Severity: normal
> X-Debbugs-Cc: debian-amd64@...ts.debian.org, paxed@....org
> User: debian-amd64@...ts.debian.org
> Usertags: amd64
> 
> Dear Maintainer,
> 
> perf stat -e r5101c4 true
> 
> reports "not supported".
> 
> The counters worked in kernel 6.11.10.
> 
> I first noticed this not working when updating to 6.12.22.
> Booting back to 6.11.10, the counters work correctly.

Does this ring a bell?

Would you be able to bisect the changes to identify where the
behaviour changed?

Regards,
Salvatore