RE: [Xen-ia64-devel] PATCH: rewrite vcpu_get_psr

[tgingold@xxxxxxx]

Quoting "Xu, Anthony" <anthony.xu@xxxxxxxxx>:

> >Tristan Gingold
> >Sent: 2007Äê5ÔÂ11ÈÕ 13:23
> >To: Alex Williamson
> >Cc: Xen-ia64-devel
> >Subject: Re: [Xen-ia64-devel] PATCH: rewrite vcpu_get_psr
> >
> >> Unfortunately...
> >It's a little bit puzzling.  I didn't think the performace of mov =psr.l was
> >to important!
>
>
>
> +
> +     if (!PSCB(vcpu, metaphysical_mode))
> +             newpsr.i64 |= IA64_PSR_DT | IA64_PSR_RT | IA64_PSR_IT;
>
> -     if (PSCB(vcpu, metaphysical_mode))
> -             newpsr.dt = 0;
>
> Above old code would be translated to
>       if (PSCB(vcpu, metaphysical_mode))
>               newpsr.i64 &= ~IA64_PSR_DT;
I seriously think the old code was wrong (more precisely incorrect).

I have to re-read Dan's paper and linux code, but in PV mode we only correctly
support IT=DT=RT.

(the same should be true for VTi BTW and incidently we can
easily write OS which cannot be virtualized by VTi!)

Tristan.

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