The problem: After upgrade / update of s15.smythies.com (a test machine, not available on internet), none of the desktop Virtual Machines (VM) would work properly. The server Virtual Machines work, but only in a low resolution console mode.
The solution: (At least in my case.) Use "virsh edit bla_name" and change the machine type from this:
<type arch='x86_64' machine='pc-1.0'>hvm</type>
To this:
<type arch='x86_64' machine='pc-i440fx-1.7'>hvm</type>
The details:
I upgraded my host server from ubuntu 12.04 to 14.04. Afterwards, none of my desktop Virtual Machines (VM's) worked. During login the VM's complained about being unable to detect the graphics card:
Proceeding results in a screen of jibberish:
The VM guest is actually working fine, and I can SSH into it.
I made a new guest VM using the exact same "virst-install" command I had used for the original VM creation on the 12.04 host server, and compared the resulting .xml file. There were 3 or 4 differences, but above machine type change fixes the issue. I used "virsh edit" and changed that line and the guest VM originally created under a 12.04 server host then worked under the 14.04 server host.
This change has been made to 6 VM's (5 are either 14.04 originally or as upgraded from 13.10, and one was a 12.04 Desktop guest VM) and 5 of them are now working. The one is only not working for one log in type out of 5 possible (GNOME; GNOME Classic; GNOME Flashback (Compiz); GNOME Flashback (Metacity); Ubuntu (Default)), and I think is due to another unrelated issue.
I use both TightVNC viewer and UltraVNC viewer from a windows computer for this work, and have tested both viewers for this particular issue.
I use both vmvga or default (cirrus) video, and have tested both for this issue.
Typical VM creation command:
sudo virt-install -n desk_tt -r 8192 --disk path=/media/newhd/desk_tt.img,bus=virtio,size=50 -c trusty-desktop-amd64-20140224.iso --network bridge=br0,model=virtio --video=vmvga --graphics vnc,listen=0.0.0.0 --noautoconsole -v --vcpus=4
References:
The launchpad bug.
The launchpad bug from which the above bug was spun off.
The two xml files differences.
The typical xml file for a 1204 host created guest vm.
The typical xml file for a 1404 host created guest vm.
Hardware Profile for my Ubuntu 14.04 Test Server. (to be updated.)