Re: [Xen-ia64-devel] SMP-guest status

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Jeudi 20 Avril 2006 15:33, Tian, Kevin a écrit :
> From: Tristan Gingold
>
> >Sent: 2006年4月20日 21:22
> >
> >Le Jeudi 20 Avril 2006 05:47, Alex Williamson a écrit :
> >> On Wed, 2006-04-19 at 11:38 +0200, Tristan Gingold wrote:
> >> > +       /* Fill a platform feature.  ITC are (almost!) synchronized. .
> >> > */
> >> > +       sal_feature->type = SAL_DESC_PLATFORM_FEATURE;
> >> > +       sal_feature->feature_mask =
> >> > IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT;
> >>
> >>    Is the jitter protection in the time interpolator sufficient for
> >> ignoring this?  Drift is really meant to indicate the ITCs are driven
> >> from different time sources so may run at slightly different clock
> >> frequencies.  Seems we should only need to provide that flag to the
> >> guest if the platform firmware set it.  As long as the ITCs are nearly
> >> synchronized, the jitter protection in the ITC interpolator will prevent
> >> time from going backwards.  This would then get rid of the change in
> >> time.c.  Thanks,
> >
> >The change in time.c is just to work around a kernel bug.  Linux kernel
> >requires at least an interpolator. [Hence I think there is no platform
> >without ITC drift].
>
> This is the sal platform feature printed on my tiger4 box:
> SAL Platform features: BusLock
>
> So there's no ITC drift provided. :-)
That's the opposite: the ITC drifts.

Tristan.


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