Re: [PATCH v2] kvm: x86: emulate monitor and mwait instructions as nop

Eduardo Habkost
2014-06-05T14:40:51Z

On Wed, Jun 04, 2014 at 10:44:48PM +0200, Borislav Petkov wrote:
> On Wed, Jun 04, 2014 at 06:34:04PM +0200, Paolo Bonzini wrote:
> > That should be the purpose of KVM_GET_EMULATED_CPUID, so MWAIT could be
> > added in __do_cpuid_ent_emulated. However, the corresponding QEMU patches
> > were never included. Borislav, can you refresh them?
>
> /me goes and swaps in all the details from the discussion at that
> time.... tries to decipher what the whole story was about...
>
> Well, AFAIR - the operative word being "remember" - Eduardo had a
> problem with diffentiating between emulated features and real hw
> features and what was being filtered out... here's where the thread
> starts:
>
> http://lkml.kernel.org/r/20130923162856.GC7264@otherpad.lan.raisama.net
>
> I think we remained at that someone, maybe he, would have to clean all
> that discrepancy before we do the emulated gunk. Let me CC him.

I didn't work on it because of other tasks, and because the
GET_SUPPORTED_CPUID code on QEMU needed some cleanup first. Now it
should be easy to implement GET_EMULATED_CPUID support in the same way
the "migratable" property was implemented[1]. I will send a patch today.

[1] See tree at
https://github.com/ehabkost/qemu-hacks/tree/work/qom-cpu-fixes

--
Eduardo