This enabled the hv_relaxed flag on all my Windows VMs, causing them to no longer boot.  The same thing would happen if I simply booted from the Windows install media.  I would get a screen with a stop error:

Your PC needs to restart.

Please hold down the power button.

Error Code: 0x0000001E

Parameters:

0xFFFFFFFFC0000096

0xFFFFF802C4044EA4

0x00000000000000000

0x00000000000000000

I created a file called /etc/ovirt-engine/osinfo.conf.d/01-windows.properties that had one line:

os.windows_xp.devices.hyperv.enabled.value = false

I restarted ovirt-engine and now I can start my Windows VMs.

Why does this occur?  Is it because I upgraded from 3.4 to 3.5?  Is there something else I'm doing wrong?  I would like to not need this workaround.  Thanks.

Charles