Re: [Patch] Skip cpu_calibrate for kernel running under hypervisors.

Borislav Petkov
2010-08-17T07:05:25Z

From: "H. Peter Anvin" <hpa@zytor.com>
Date: Mon, Aug 16, 2010 at 11:30:48PM -0700

> On 08/16/2010 10:51 PM, Alok Kataria wrote:
> >>
> >> I'm somewhat reluctant to take this one, since it assumes all the
> >> hypervisors act the same. This seems rather inherently wrong. In fact,
> >> the whole statement is fishy as heck... instead of being dependent on
> >> AMD and so on,
> >
> > The check about being on AMD is something that was already there.
> >
>
> I know it was... and calibrate_cpu() seems to be an AMD-specific
> function, but that's rather crappy. I'm thinking that perhaps we should
> make it an x86_init function, then the AMD CPU detection can install it
> and the vmware hypervisor detection can uninstall it.

Btw, can we revisit this AMD-specific issue? IIUC, Alok you're seeing
a mismatch between the calibrated TSC value and the cpu frequency even
on cpus which have the CONSTANT_TSC bit set, i.e. their TSC is counting
with P0 frequency. Can you please elaborate more on what systems you're
seeing this (cpu family, chipset, etc)?

Thanks.

--
Regards/Gruss,
Boris.