Re: [PATCH RFC] pvh: clearly specify used parameters in vcpu_guest_context

[Mukesh Rathor <mukesh.rathor@oracle.com>]

On Fri, 15 Nov 2013 17:55:09 +0100
Tim Deegan <tim@xen.org> wrote:

> At 16:32 +0000 on 15 Nov (1384529574), Jan Beulich wrote:
> > >>> On 15.11.13 at 16:50, Roger Pau Monne <roger.pau@citrix.com>
> > >>> wrote:
> > > --- a/xen/arch/x86/domain.c
> > > +++ b/xen/arch/x86/domain.c
> > > @@ -704,9 +704,11 @@ int arch_set_info_guest(
> > >          /* PVH 32bitfixme */
> > >          ASSERT(!compat);
> > >  
> > > -        if ( c(ctrlreg[1]) || c(ldt_base) || c(ldt_ents) ||
> > > +        if ( c(ctrlreg[0]) || c(ctrlreg[1]) || c(ctrlreg[2]) ||
> > > +             c(ctrlreg[4]) || c(ldt_base) || c(ldt_ents) ||
> > 
> > I think it should actually be a bug for the guest to request an
> > all blank CR0 or CR4. Minimally CR0.PE, CR0.PG, and CR4.PAE
> > would seem to be a valid requirement to be set.
> 
> I think zero is better.  Guest CRx are explicitly _not_ loaded from 
> these fields so making them look like valid CRx values is just
> confusing.

+1.

> But even better would be to allow all these fields to be set to any
> valid values, and to load the state into the guest vCPU.  I think
> that's going to be more sensible once the current restriction that PVH
> vCPUs are always in long more goes away.

Agree, it can be designed much better when the 32bit guest support
is added.

thanks,
mukesh