linux-kernel - Re: [perf] unchecked MSR access error: WRMSR to 0x3f1

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Message-ID: <9aee2b65-e43a-4fcd-a929-a98269621315@linux.intel.com>
Date: Thu, 19 Jun 2025 12:06:21 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Vince Weaver <vincent.weaver@...ne.edu>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [perf] unchecked MSR access error: WRMSR to 0x3f1



On 2025-06-19 11:17 a.m., Vince Weaver wrote:
> On Wed, 18 Jun 2025, Vince Weaver wrote:
> 
>> On Wed, 18 Jun 2025, Liang, Kan wrote:
>>
>>> No, the error message doesn't say it. Just want to check if you have
>>> extra information. Because the Topdown perf metrics is only supported on
>>> p-core. I want to understand whether the code messes up with e-core.
>>
>> I can't easily tell from the fuzzer as it intentionally switches cores 
>> often.  I guess I could patch the kernel to report CPU when the WRMSR 
>> error triggers.
> 
> I've patched the kernel to get rid of the warn_once() and added a printk
> for smp_processor_id()  (is that what I want to print?)  In any case that 
> reports the warning is happening on CPU1 which is actually a P core, not 
> an atom core.

Thanks for the confirmation.
I've tried fuzzer in some newer machines (later than raptor-lake), but I
haven't reproduce it yet. I will try to find a raptor-lake for more tests.

Thanks,
Kan