Re: [SeaBIOS] [PATCH] tsc: use kvmclock for calibration

[Avi Kivity]

On 08/09/2012 09:59 PM, Marcelo Tosatti wrote:
> > > wrmsr(msr, 0);
> > > if (time.version < 2 || time.tsc_to_system_mul == 0)
> > >    return 0;
> > > /* go figure tsc frequency */
> > > khz = pvclock_tsc_khz(&time);
> > > dprintf(1, "Using kvmclock, msr 0x%x, tsc %d MHz\n",
> > >        msr, (u32)khz / 1000);
> > > return khz;
> >
> > That's a meaningless number.  You can be migrated to a cpu or a machine
> > with very different tsc.
>
> Thats why there exists hardware tsc frequency scaling and the software
> equivalent for that on kvm.

The hardware is only available on a minority of processors in the field.
 The software equivalent isn't there.