RE: [Xen-users] 32bit DomU on 64-bit Xen

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Lionel Bouton
> Sent: 24 October 2006 18:22
> To: Petersson, Mats
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] 32bit DomU on 64-bit Xen
> 
> Petersson, Mats wrote the following on 24.10.2006 17:46 :
> >  
> >
> >   
> >> -----Original Message-----
> >> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> >> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> >> Lionel Bouton
> >> Sent: 24 October 2006 16:14
> >> To: xen-users@xxxxxxxxxxxxxxxxxxx
> >> Subject: [Xen-users] 32bit DomuU on 64-bit Xen
> >>
> >> Hi,
> >>
> >> from what I could find digging around, it is ok to run a 
> 32-bit DomU 
> >> with a 64bit Xen/Dom0 as long as you use linux32 to avoid 
> the package 
> >> utilities from trying to install 64 bit packages in the DomUs.
> >>     
> >
> > Ehm, no you CAN NOT run 32-bit DomU on a 64-bit Xen/Dom0, 
> because all
> > kernel modes must be the same (32-bit no PAE, 32-bit PAE or 64-bit).
> >   
> 
> What I thought was possible is to start the 32-bit DomU with a 64-bit 
> kernel and use a custom initrd to call linux32 before 
> /sbin/init -> the 
> whole DomU could still be 32-bit, but the kernel would be 64-bit. I'm 
> wondering if there could be problems with some userland 
> system utilities 
> like iptables though.

And the benefit of this is?

I believe iptables is one of the things that you can't run the 32-bit
version on a 64-bit kernel - although I'm not sure... When googling on
the subject, I found that there was a patch submitted in early January
2006 to "fix" this problem - whether that patch got accepted and works
is a different question - I didn't look at it further... 

> 
> Can't this work?

All user-mode code that doesn't make assumptions about the kernel or
uses pre-compiled 32-bit kernel modeuls can be run on 64-bit kernel -
but again, what is the benefit of running a complete 32-bit installation
that is NOT part of a packaged distribution, when there is a (hopefully)
some distribution that comes with the complete 64-bit set of "guaranteed
by the distributor to work together" parts - ok, so it may not ALWAYS
work as the distributor says, but if you mix'n'match your own version of
32+64-bit parts, it's almost guaranteed that you're going to have SOME
problems - at least the main distributors do put SOME effort into making
sure what they distribut works... 

All compatibility problems caused by the kernel being 64-bit would still
remain. The only point I can see is that you save some diskspace by only
installing 32-bit .so's, but with a limited installation of 64-bit
tools, you'd not fill enough diskspace to REALLY make a huge difference.


I just don't get the point, so if you could enlighten me as to why you
would want to do this, I'll look further at any reason why it
would/would not work... 

--
Mats
> 
> Lionel
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
> 
> 
> 




_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users