Re: [Xen-ia64-devel] PATCH: [resent] cleanup + fph handling

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Lundi 24 Avril 2006 11:06, Tian, Kevin a écrit :
> From: Tristan Gingold
>
> >Sent: 2006年4月24日 16:40
> >Hi,
> >
> >
> >this patch moves switch_to macro from xensystem.h and put its body
> >directly in
> >context_switch.  FP saved and restore is slighly optimized: fph is *still*
> >enabled and not anymore disabled.
> >
> >Misc cleanup.
> >
> >Note: not enabling fph before saving fph in context switch does not work.
> >I
> >will look on this issue.  However,  I think it is worth adding this patch.
>
> If you failed at the first context switch, the possible cause is in head.S
> where psr.dfh is initialized as disabled for idle domain. Then the first
> time when you switch from idle to domain0, disabled fp fault occurs
> unless you explicitly enable psr.dfh like in your patch. This is one place
> where psr value doesn't get from hardware exception.
Good idea, but xensetup() initializes fpu and also calls  ia64_fph_enable() !

Tristan.



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