More Xen troubles in -current: booting DOMUs fails strangely

[Johan Ihrén <johani%johani.org@localhost>]

This is a rather old box with an Intel Core 2 Quad CPU. This DOM0 runs 5.1 and 
5.99.43 with Xen 3.3.2nb1 just fine, and -current (5.99.55) also boots nicely 
(apart from all the pmap_kenter_pa messages to the console). 

However, when upgrading the DOM0 to 5.99.55 (amd64) the DOMUs (i386pae, not 
upgraded) no longer boot.

I.e. while running 5.99.43:

# xm create -c foo.conf

works fine, and connects me to the console of the booting DOMU "foo". But 
upgrading the kernel to 5.99.55 from today (July 21) leads to the same command 
hanging for a while and then the message:

Error: Device 0 (vif) could not be connected. Hotplug scripts not working.
Error: Domain 'foo' does not exist.

Note that there have been zero changes to the NetBSD userland (only kernel 
upgraded), Xen stuff, it's the same Xen version, python packages, DOMU config 
and DOMU image as before. The only thing that has changed is the DOM0 kernel.

But, to be fair, upgrading the userland doesn't change anything, DOMUs still 
don't boot.

As no one else has reported any problems I realize that this cannot be a 
general problem. But I have zero ideas what may be wrong here.

Any ideas?

Regards,

Johan