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SubjectRe: [PATCH v12 09/11] x86/tsc: prepare for early sched_clock
On Fri, Jun 29, 2018 at 09:30:10AM +0200, Thomas Gleixner wrote:
> On Thu, 28 Jun 2018, Pavel Tatashin wrote:
> > On Thu, Jun 28, 2018 at 11:23 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> > Hi Thomas,
> >
> > In addition to above, we have xen hvm:
> >
> > setup_arch()
> > ...
> > init_hypervisor_platform();
> > x86_init.hyper.init_platform();
> > xen_hvm_guest_init()
> > xen_hvm_init_time_ops();
>
> Duh. Missed that completely.
>
> > ...
> > tsc_early_delay_calibrate();
> > tsc_khz = x86_platform.calibrate_tsc(); == xen_tsc_khz()
> > ...
> >
> > Which works early.
> >
> > So, what should we do with xen, which seems to be the only platform
> > that would provide different tsc frequency early and late, because of
> > different calibration method?
>
> Fix it? I have no idea why XEN has two variants of the scheme and I neither
> have a clue why the KVM clock stuff is late.

Added Juergen (Xen).
>
> Thanks,
>
> tglx
>

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