kern/49810: netbsd-6-1 branch XEN3_DOM0 kernel crashes on boot

[waddell%caravaninfotech.com@localhost]

>Number:         49810
>Category:       kern
>Synopsis:       netbsd-6-1 branch XEN3_DOM0 kernel crashes on boot
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 03 00:15:00 +0000 2015
>Originator:     Harry Waddell
>Release:        netbsd-6-1 ftom ftp://nyftp.netbsd.org/pub/NetBSD-daily/netbsd-6-1/201503310940Z/
>Organization:
>Environment:
NetBSD  6.1.5_PATCH NetBSD 6.1.5_PATCH (GENERIC) amd64
>Description:
booting the latest netbsd 6.1 branch XEN DOM0 kernel from the daily builds causes a crash on boot. I have found this problem on a 1 year old supermicro server and using a vmware test system. The GENERIC kernel from the same time period boots without any issues. 

I have two screen grabs with the crash back trace at

http://www.extremelymodern.com/netbsd-6-1-branch-xen-crash-on-boot-1.png

and 

http://www.extremelymodern.com/netbsd-6-1-branch-xen-crash-on-boot-2.png

In both cases, xen is xen 4.2 from pkgsrc-2014Q4 branch as of yesterday.
>How-To-Repeat:
boot netbsd-XEN3_DOM0.gz kernel
>Fix: