Description of problem:

When I start qemu via libvirt with vnc and websocket defined, it is not possible to live migrate to other host, where other qemu process is running with the same display id. 

Version-Release number of selected component (if applicable):

1.2.16 (and many previous versions)

How reproducible:
Always

Steps to Reproduce:
1. have 2 libvirtd hosts
2. start one qemu guest on each host, with vnc display and websocket definet and with identical display id
3. live migrate one qemu guest from one host to other

Actual results:

migration error is:

error: internal error: early end of file from monitor: possible problem:
            [1] => 2015-06-23T11:54:25.590506Z qemu-system-x86_64: -vnc 0.0.0.0:1,websocket=5700,password: Failed to start VNC server on `(null)': Failed to bind socket: Address already in use

(please note vnc display id=1 and websocket=5700 - where it should be 5701) 


Expected results:

live migration is possible.

Additional info:

in libvirt's xml i have:
(...)
    <graphics type='vnc' port='-1' autoport='yes' websocket='-1' listen='0.0.0.0' passwd='xxx'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
(...)

for first and only qemu process on host, this creates qemu commandline:
(...) -vnc 0.0.0.0:0,websocket=5700,password (...)

for second qemu process on the same host:
(...)  -vnc 0.0.0.0:1,websocket=5701,password (...)

There is no problem with migration, when there is no websocket configuration.

Solution:

I believe, to solve this problem, libvirt has to omit websocket port definition in commandline string ('websocket=5700' => 'websocket') when autoport is defined in domain xml definition.

Martin has sone adittional ideas here:
https://lists.gnu.org/archive/html/qemu-devel/2015-06/msg06752.html

Best regards
Piotr Rybicki