lxc don't work

I tried lxc, but failed to start nova-compute service. The error message and related info are as below.

nova-compute.log

2011-03-17 17:53:27,462 DEBUG nova.virt.libvirt_conn [-] libvirt lxc:/// connecting from (pid=28609) _get_connection /usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py:198
2011-03-17 17:53:27,475 ERROR nova.exception [-] Exception wasn't caught
(nova.exception): TRACE: Traceback (most recent call last):
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/exception.py", line 120, in _wrap
(nova.exception): TRACE: return f(*args, **kw)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/compute/manager.py", line 793, in update_available_resource
(nova.exception): TRACE: return self.driver.update_available_resource(context, self.host)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 1096, in update_available_resource
(nova.exception): TRACE: 'cpu_info': self.get_cpu_info()}
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 1012, in get_cpu_info
(nova.exception): TRACE: cpu_info['model'] = xml.xpathEval('//host/cpu/model')[0].getContent()
(nova.exception): TRACE: IndexError: list index out of range
(nova.exception): TRACE:
2011-03-17 17:53:27,476 CRITICAL nova [-] list index out of range
(nova): TRACE: Traceback (most recent call last):
(nova): TRACE: File "/usr/bin/nova-compute", line 48, in <module>
(nova): TRACE: service.serve()
(nova): TRACE: File "/usr/lib/pymodules/python2.6/nova/service.py", line 284, in serve
(nova): TRACE: x.start()
(nova): TRACE: File "/usr/lib/pymodules/python2.6/nova/service.py", line 96, in start
(nova): TRACE: self.manager.update_available_resource(ctxt)
(nova): TRACE: File "/usr/lib/pymodules/python2.6/nova/exception.py", line 126, in _wrap
(nova): TRACE: raise Error(str(e))
(nova): TRACE: Error: list index out of range
(nova): TRACE:

The version of nova-api: 2011.2~bzr815-0ubuntu0ppa1~maverick1

The patch of lxc was downloaded from https://code.launchpad.net/~zulcss/nova/nova-lxc/+merge/51469/+preview-diff/+files/preview.diff

/etc/nova.conf:
--sql_connection=mysql://root:nova@ubuntu7/nova
--s3_host=ubuntu7
--rabbit_host=192.168.32.202
--cc_host=192.168.32.202
--ec2_url=http://192.168.32.202:8773/services/Cloud

--daemonize=1

--dhcpbridge_flagfile=/etc/nova/nova.conf
--dhcpbridge=/usr/bin/nova-dhcpbridge

--FAKE_subdomain=ec2

--ca_path=/var/lib/nova/CA
--keys_path=/var/lib/nova/keys
--networks_path=/var/lib/nova/networks
--instances_path=/var/lib/nova/instances
--images_path=/var/lib/nova/images
--buckets_path=/var/lib/nova/buckets

--libvirt_type=lxc

--network_manager=nova.network.manager.VlanManager

--vlan_interface=eth0

--logdir=/var/log/nova
--verbose
--volume_group=ubuntu7
--fixed_range=192.168.2.64/26
--network_size=64
--lock_path=/home/nii/tmp