libvirt users - Jan 2013 - Unable to connect to vmchannel on host when the VM is started via libvirt

Hi experts,

When I start a VM using "virsh create vm.xml", I'm not able to
connect
to the vmchannel from host. The process libvirtd is running as root
(modified qemu.conf to set user/group to root) already. The connect
just hangs there even after the guest VM is up and running. However,
if I start the VM using kvm directly (with same arguments as libvirtd
in `ps auxwww`), the connect to vmchannel goes though after the guest
VM is up and running.

The problem is observed on ubuntu 12.10 (libvirt 0.9.13), but not
ubuntu 12.04 (libvirt 0.9.8). Anyone knows why is this and how to fix
it? Any suggestion is appreciated.

ubuntu 12.10: Linux linux-01 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9
19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
ubuntu 12.04: Linux linux-06 3.2.0-30-generic #48-Ubuntu SMP Fri Aug
24 16:52:48 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

Content of vm.xml:
<domain type="kvm">
  <uuid>c548c477-af6f-4aee-9e7d-987d6620aa27</uuid>
  <name>instance-00</name>
  <memory>262144</memory>
  <vcpu>1</vcpu>
  <os>
    <type>hvm</type>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
  </features>
  <clock offset="utc">
    <timer name="pit" tickpolicy="delay"/>
    <timer name="rtc" tickpolicy="catchup"/>
  </clock>
  <devices>
    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2"
cache="none"/>
      <source file="/home/user/project/kvm/instance-00/disk"/>
      <target bus="virtio" dev="vda"/>
    </disk>
    <serial type="file">
      <source
path="/home/user/project/kvm/instance-00/console.log"/>
    </serial>
    <serial type="pty"/>
    <channel type="unix">
      <source
path="/home/user/project/kvm/instance-00/vmchannel.sock"
mode="bind"/>
      <target type="virtio"
name="org.qemu.guest_agent.0"/>
    </channel>
    <graphics type="vnc" port="5900"
autoport="no" keymap="en-us"
listen="127.0.0.1"/>
  </devices>
</domain>