UPDATE 16/04/2015
For now http://www.slideshare.net/xen_com_mgr...
is supposed to work only with nova networking per Anthony PERARD
Neutron appears to be an issue.
Please, view details of troubleshooting and diagnostic obtained (thanks to Ian Campbell) :-
http://lists.xen.org/archives/html/xe...
END UPDATE

After devstack install (via master) with local.conf :-

[[local|localrc]]
HOST_IP=192.168.1.57
ADMIN_PASSWORD=secret
DATABASE_PASSWORD=$ADMIN_PASSWORD
RABBIT_PASSWORD=$ADMIN_PASSWORD
SERVICE_PASSWORD=$ADMIN_PASSWORD
SERVICE_TOKEN=a682f596-76f3-11e3-b3b2-e716f9080d50

FLOATING_RANGE=192.168.10.0/24
FLAT_INTERFACE=eth0
Q_FLOATING_ALLOCATION_POOL=start=192.168.10.150,end=192.168.10.254
PUBLIC_NETWORK_GATEWAY=192.168.10.15

# Useful logging options for debugging:
DEST=/opt/stack
LOGFILE=$DEST/logs/stack.sh.log
SCREEN_LOGDIR=$DEST/logs/screen

# The default fixed range (10.0.0.0/24) conflicted with an address
# range I was using locally.
FIXED_RANGE=10.254.1.0/24
NETWORK_GATEWAY=10.254.1.1

# Services
disable_service n-net
enable_service n-cauth
enable_service q-svc
enable_service q-agt
enable_service q-dhcp
enable_service q-l3
enable_service q-meta
enable_service horizon
disable_service tempest

# This is a Xen Project host:
LIBVIRT_TYPE=xen

Upgraded Libvirt && restarted libvirt-bin

root@ubuntu-system:~# virsh --connect xen:///
Welcome to virsh, the virtualization interactive terminal.

Type:  'help' for help with commands
       'quit' to quit

virsh # version
Compiled against library: libvirt 1.2.14
Using library: libvirt 1.2.14
Using API: Xen 1.2.14
Running hypervisor: Xen 4.4.0

Per page 19 of http://www.slideshare.net/xen_com_mgr...

xen.gz command line tuned
ubuntu@ubuntu-system:~/devstack$ nova image-meta cirros-0.3.2-x86_64-uec set vm_mode=HVM
ubuntu@ubuntu-system:~/devstack$ nova image-meta cirros-0.3.2-x86_64-uec delete vm_mode

Attempt to launch instance ( nova-compute is up ) error in n-sch.log from Nova side

root@ubuntu-system:/var/log/libvirt/libxl# ls -l
total 32
-rw-r--r-- 1 root root 30700 Apr 12 03:47 libxl-driver.log

Verify log file and see

libxl: debug: libxl_dm.c:1320:libxl__spawn_local_dm: Spawning device-model /usr/bin/qemu-system-i386 with arguments:
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   /usr/bin/qemu-system-i386
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -xen-domid
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   2
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -chardev
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   socket,id=libxl-cmd,path=/var/run/xen/qmp-libxl-2,server,nowait
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -mon
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   chardev=libxl-cmd,mode=control
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -nodefaults
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -xen-attach
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -name
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   instance-00000002
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -vnc
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   127.0.0.1:1
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -display
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   none
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -k
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   en-us
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -machine
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   xenpv
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   -m
libxl: debug: libxl_dm.c:1322:libxl__spawn_local_dm:   513
libxl: debug: libxl_event.c:570:libxl__ev_xswatch_register: watch w=0x7f36cc001990 wpath=/local/domain/0/device-model/2/state token=3/3: register slotnum=3
libxl ...