Re: progress on xen3 HVM support

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Mon, Oct 16, 2006 at 11:41:11AM +1000, Daniel Carosone wrote:
> On Mon, Oct 16, 2006 at 03:34:09AM +0200, Hubert Feyrer wrote:
> > 
> > I'm not following Xen as close as I'd like to, and as such your posting 
> > raised two questions for me that I was able to google. Maybe you can 
> > confirm my understanding:
> > 
> > 1) HVM = Hardware Virtual Machine, a Common Interface for VT-x/VT-i and
> >          AMD SVM CPUs[1]
> > 
> > 2) Qemu-dm = Qemu[2] Device Model - a modified(?) Qemu that's used to
> >              emulate instruction sets for real-mode support[3] - I guess
> >              to run Xen inside Xen
> 
> Mostly, I think, to run BIOS code for native operating systems inside
> Xen HVM domains.  And/or to provide the emulated devices (like VGA
> cards) that the BIOS and native code will poke at.

It's only used to emulate devices (disks, network, audio, usb, ...)
The 32/64bit code can run native on the CPU (this is the point of the
Virtual Machine extentions). AMD SVM can also run 16 bit code but
for Intel VT this has to be emuled and this is done by the hypervisor.
This is probably why I couldn't boot native NetBSD: some 16bit instructions
we use are not emuled by the hypervisor.

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           
Manuel.Bouyer%lip6.fr@localhost
     NetBSD: 26 ans d'experience feront toujours la difference
--