Created attachment 1268910 [details]
libvirtd.log on source and target host, qemu log on target host

Description of problem:
Libvirtd can not report clear error when migration start but failed with some reason.

Version-Release number of selected component (if applicable):
libvirt-3.2.0-1.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Prepare guest xml with unix guest agent, and specify the socket path :
   <channel type='unix'>
      <source mode='bind' path='/test/agent'/>
      <target type='virtio' name='org.qemu.guest_agent.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='2'/>
    </channel>

2.# mkdir /test

3. Change the owner and selinux context of the directory:
# chown qemu:qemu /test

# chcon system_u:object_r:qemu_var_run_t:s0 /test/

4. Define&start guest:
 # virsh define rhel7.3-min.xml
 # virsh start rhel7.3-min

5.Do migration:
# virsh migrate rhel7.3-min qemu+ssh://10.66.4.148/system --live --verbose --migrateuri tcp://10.66.4.148
root.4.148's password:
error: invalid argument: monitor must not be NULL

Actual results:
Migration failed with unclear error.

Expected results:
Migration failed with error:
error: internal error: process exited while connecting to monitor: 2017-04-05T05:43:26.542618Z qemu-kvm: -chardev socket,id=charchannel1,path=/test/agent,server,nowait: Failed to bind socket to /test/agent: No such file or directory


Additional info:
1.Check the libvirtd.log on source host, could see the migration has started;
2.The issue can also reproduced with other scenario, such as the source file not found on the target host;
3.It works well with libvirt-3.1.0-2.el7.x86_64