port-xen/52662: Almost everything crashes on -current kernel

[coypu%sdf.org@localhost]

>Number:         52662
>Category:       port-xen
>Synopsis:       Almost everything crashes on -current kernel
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Oct 28 11:45:00 +0000 2017
>Originator:     coypu
>Release:        NetBSD 8.99.5
>Organization:
>Environment:
NetBSD  8.99.5 NetBSD 8.99.5 (XEN3_DOMU) #3: Sat Oct 28 11:17:52 UTC 2017  lio@lio:/home/lio/obj/sys/arch/amd64/compile/XEN3_DOMU amd64
>Description:
Updating the kernel only
Can make it to userland but:
# service sshd onestart
Starting sshd.
[1]   Segmentation fault (core dumped) RC_PID= _rc_pid=...

...

$ gunzip netbsd-XEN3_DOMU.gz                                                   
Memory fault (core dumped) 

reverting to a kernel from 10 days ago works, also using /rescue
>How-To-Repeat:

>Fix: