Re: [PATCH v12 09/11] x86/tsc: prepare for early sched_clock

[Thomas Gleixner]

On Thu, 28 Jun 2018, Pavel Tatashin wrote:
> On Thu, Jun 28, 2018 at 11:23 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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.

Thanks,

	tglx