Re: [Bug 218792] Guest call trace with mwait enabled

Sean Christopherson
2025-08-08T22:59:31Z

On Fri, Aug 08, 2025, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=218792
>
> Len Brown (lenb@kernel.org) changed:
>
> What |Removed |Added
> ----------------------------------------------------------------------------
> CC| |lenb@kernel.org
>
> --- Comment #6 from Len Brown (lenb@kernel.org) ---
> Re: intel_idle
>
> I agree that the SDM doesn't guarantee this MSR exists
> based on the presence of PC10.
>
> I'm not opposed to _safe().
>
> but...
>
> Why is this "platform" advertising PC10 (or any MWAIT C-states) to intel_idle
> in the first place?

Because letting the guest execute MONITOR/MWAIT natively, and thus get into deeper
sleep states, is advantageous for all the same reasons bare metal CPUs want to
get into deep sleep states, e.g. to let active cores hit higher turbo bins.