Re: NetBSD and Xen 2.0

[Pavel Cahyna <pcah8322%artax.karlin.mff.cuni.cz@localhost>]

> On Thu, Dec 09, 2004 at 03:55:19PM +0100, Pavel Cahyna wrote:
> > On Wed, 08 Dec 2004 07:06:05 +0000, Christian Limpach wrote:
> > 
> > >> Due to the way Xen works, you need NetBSD/xen in all Domains.
> > > 
> > > This is not true, you can mix NetBSD and Linux domains on the same 
> > > machine.
> > > You can run NetBSD as domain0 on Xen 1.2, which is the Xen version the
> > > NetBSD/xen port in the NetBSD cvs repository (-current as well as -2.0)
> > > works with.  On Xen 2.0, for which there's a NetBSD/xen port in the Xen
> > > bitkeeper repository, you can only run NetBSD in unprivileged domains.
> > 
> > So Xen is not backward-compatible? OS for Xen 1.2 can't be run on 2.0 in
> > unprivileged domains?
> 
> The interface between the guest OS and the "hypervisor" (the Xen kernel
> that controls certain privileged operations) changed in 2.0, even for
> unprivileged domains.  It looks like there is some effort for backwards
> compatibility but not a complete one, so the answer is "you need a
> different NetBSD kernel that supports the 2.0 hypervisor interface". 
> 
> In theory, we could maintain two sets of architecture-dependent code
> to allow a NetBSD kernel to run with xen1 or xen2, but that would be
> pretty ugly and painful.  A single NetBSD "port" that could do either
> hypervisor interface would be...less ugly, but more painful, I think.

OK, since those two versions of Xen are essentially two different virtual
machines it seems, why not have two NetBSD ports: xen and xen2?

Thanks and bye  Pavel