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

[Thomas Gleixner]

On Thu, Dec 10 2020 at 14:01, Peter Zijlstra wrote:
> 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.

Core2 is really not something which should prevent making all of this
correct and robust. That'd be not only wrong, that'd be outright insane.

Thanks,

        tglx