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@lists.debian.org, paxed@alt.org User: debian-amd64@lists.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