this is happening on the xen OBS build worker machines
CPU model name      : Dual-Core AMD Opteron(tm) Processor 8214
(no vme, that's actually why these boxes are running xen while everything else
does kvm)

booting a xen vm goes up to this point:
[    2.421079] emc: device handler registered
[    2.421462] rdac: device handler registered
[    2.435194] device-mapper: uevent: version 1.0.3
[    2.435392] device-mapper: ioctl: 4.34.0-ioctl (2015-10-28) initialised:
dm-devel@redhat.com
[    2.455299] device-mapper: multipath: version 1.11.0 loaded
[    3.070552] loop: unknown parameter 'lbs' ignored
[    3.220213] loop: module loaded
[    3.316259] fuse init (API version 7.23)
[    3.373081] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[    3.524229] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
[  117.136041] random: nonblocking pool is initialized
---------------------
and there it hangs.

The same setup works on leap42.1 (kernel 4.1.21-14-xen, xen-4.5.2_06)
on leap42.2 (kernel 4.4.22-1-default, xen-4.7.0_12) I get the stuck VM
This happens with every single guest, regardless if 32 or 64bit.

config file:
kernel = "/boot/vmlinuz"
ramdisk = "/boot/initrd"
memory = 1500
vcpus = 4
root = "/dev/hda1 ro"
extra = "init=/bin/bash console=ttyS0 panic=1 udev_timeout=10"
on_poweroff = "destroy"
on_reboot = "destroy"
on_crash = "destroy"


xl call:
xl create -c /var/tmp/build.xen.conf-ShCtQtZiH name="\"build_Z\"" "disk=[
\"phy:/dev/dm-2,hda1,w\", \"phy:/dev/dm-3,hda2,w\" ]" "extra=\"panic=1
init=/.build/build rd.driver.pre=binfmt_misc elevator=noop console=ttyS0
udev_timeout=10 rd.debug rdudevdebug rd.shell\""