On Tue, 12 Sep 2006, Andreas Wrede wrote:
> Try booting xen with 'nosmp' (and maybe 'noapic') on the 'kernel 
> (hd0,a)/xen.gz...' line in grub's menu.lst. Right now NetBSD does not support 
> multiple CPUs to well.

now, I'm running a Debian dom0 and a NetBSD3.1-rc2 domU.  Of course, the 
xen and the hardware is dual cpu;   I put nosmp in the root= line on the 
domU config file.  It seems to work,  a nosmp NetBSD domu with a SMP 
debian dom0.  I'd be interested in the details of how the smp/nosmp nature 
of the xen kernel and the dom0 effect the domU, if anyone has information 
or links.