Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests

Michael S. Tsirkin
2017-03-22T13:35:18Z

On Tue, Mar 21, 2017 at 05:02:25PM -0700, Nadav Amit wrote:
>
> > On Mar 21, 2017, at 3:51 PM, Gabriel Somlo <gsomlo@gmail.com> wrote:
> >
> > And I get the exact same results on the MacBookAir4,2 (which exhibits
> > no freezing or extreme sluggishness when running OS X 10.7 smp with
> > Michael's KVM MWAIT-in-L1 patch)...
>
> Sorry for my confusion. I didn’t read the entire thread and thought that
> the problem is spurious wake-ups.
>
> Since that is not the case, I would just suggest two things that you can
> freely ignore:
>
> 1. According to the SDM, when an interrupt is delivered, the interrupt
> is only delivered on the following instruction, so you may consider
> skipping the MWAIT first.
>
> 2. Perhaps the CPU changes for some reason GUEST_ACTIVITY_STATE (which
> is not according to the SDM).
>
> That is it. No more BS from me.
>
> Nadav

Intersting. I found this errata:
A REP STOS/MOVS to a MONITOR/MWAIT Address Range May Prevent Triggering of
the Monitoring Hardware

Could the macbook CPU be affected?

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MST