Re: [PATCH v2 1/3] KVM: x86: implement KVM_{GET|SET}_TSC_STATE

[Peter Zijlstra]

On Thu, Dec 10, 2020 at 01:22:02PM +0100, Paolo Bonzini wrote:
> On 10/12/20 13:14, Peter Zijlstra wrote:
> > On Thu, Dec 10, 2020 at 12:42:36PM +0100, Paolo Bonzini wrote:
> > > On 07/12/20 18:41, Thomas Gleixner wrote:
> > > > Right this happens still occasionally, but for quite some time this is
> > > > 100% firmware sillyness and not a fundamental property of the hardware
> > > > anymore.
> > > 
> > > It's still a fundamental property of old hardware.  Last time I tried to
> > > kill support for processors earlier than Core 2, I had to revert it. That's
> > > older than Nehalem.
> > 
> > Core2 doesn't use TSC for timekeeping anyway. KVM shouldn't either.
> 
> On Core2, KVM guests pass TSC through kvmclock in order to get something
> usable and not incredibly slow.

Which is incredibly wrong.