Re: [Xen-users] Xen 3.1 - 32 vs 64 bit hypervisor

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Fri, Jun 08, 2007 at 05:38:33PM +0100, Mark Williamson wrote:
> > > That said, in principle it ought to be alright.  32-on-64 even fully
> > > supports glibc's TLS, which even 32-on-32 doesn't (this is because of
> > > slightly arcane implementation details in x86.  Really.  The mind
> > > boggles.).
> >
> > I won't ask as I don't need my brain exploded on Friday afternoon ;-)
> 
> Well, it's really very simple.  Basically what happens is *bang* *bang* 
> *splat*[1]
> 
> OK, maybe you were right :-)
> 
> > > If you're running a 64-bit Xen, I think you also have the potential to
> > > run 64-bit paravirt guests, and 64-bit HVM guests in addition to all the
> > > stuff you could run on 32-bit Xen.
> >
> > Yes that is certainly of future interest.
> >
> > > At some point it should be possible to run a 32-bit dom0, but I'm not
> > > sure if that's allowed yet.
> >
> > Well that is how I tested it so I guess it is possible ;-)
> 
> Well, more particularly, I don't know if a 32-bit dom0 will boot 64-bit 
> guests, which may or may not matter for you.  I think it's on the roadmap.

Pretty sure it will. Back before 3.1.0 was released I was running 32-bit
Dom0 with 64-bit HV. IIRC I booted a 64-bit guest too. The only dep between
dom0 and guest is the front/back drivers & they're now 64-bit invariant
so AFAICT it shouldn't matter whether Dom0 is 32 or 64-bit wrt to guests,
as long as the HV is 64-bit.

Dan.
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