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

[Vince Weaver]

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.

Vince Weaver
vincent.weaver@xxxxxxxxx