Reproduces on:
libvirt-7.0.0-4.el9.x86_64
qemu-kvm-5.2.0-11.el9.x86_64
kernel-5.11.0-2.el9.x86_64

+++ This bug was initially created as a clone of Bug #1887775 +++

Description of problem:
update interface with <interface type='network'> will fail as the live interface type changed to direct/bridge. The patch
https://www.spinics.net/linux/fedora/libvir/msg203162.html fix the bridge type, but for the direct type and bridge type interface connected to ovs bridge, the issue still exists.

Version-Release number of selected component (if applicable):
libvirt-6.6.0-6.virtcov.el8.x86_64

How reproducible:
100%

Steps to Reproduce:
1. prepare a macvtap network like:

1. virsh net-dumpxml direct-bridge
   <network>
   <name>direct-bridge</name>
   <uuid>ab3c21e0-2282-47e0-8211-e8df2118664f</uuid>
   <forward dev='eno1' mode='bridge'>
   <interface dev='eno1'/>
   <interface dev='eno2'/>
   </forward>
   </network>

and prepare interface xml as:

1. cat interface.xml
   <interface type='network'>
   <source network='direct-bridge'/>
   <mac address='52:54:00:59:cb:11'/>
   <model type='virtio'/>
   </interface>

start the vm.

2. hotplug the interface device, then check the live xml, the interface type changed from <interface type='network'> to <interface type='direct'>

1. virsh attach-device rhel interface.xml
2. virsh dumpxml rhel | grep /interface -B12
   <interface type='direct'>
   <mac address='52:54:00:59:cb:11'/>
   <source network='direct-bridge' portid='a2dac94a-37b2-4fed-a166-b7ffc9931868' dev='eno1' mode='bridge'/>
   <target dev='macvtap0'/>
   <model type='virtio'/>
   <alias name='net0'/>
   <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
   </interface>

3. use the xml with interface type='network' to do the update-device, it failed

1. cat interface.xml
   <interface type='network'>
   <source network='direct-bridge'/>
   <model type='virtio'/>
   <link state='down'/>
   <mac address='52:54:00:59:cb:11'/>
   </interface>
2. virsh update-device rhel interface.xml
   error: Failed to update device from interface.xml
   error: Operation not supported: unable to change config on 'network' network type

Actual results:
in step 3, the live update failed

Expected results:
the live update should pass

Additional info:
This is the similar scenario with https://www.spinics.net/linux/fedora/libvir/msg203162.html

For ovs bridge, the live update will also fail.

— Additional comment from Laine Stump on 2020-10-14 01:48:32 UTC —

It appears that we're comparing the "ActualType" (direct in this case) to the config type of the modified interface ("network" in this case) rather than to the actual type that resolves to. This sounds eerily similar to:

commit bc85c34ea91c46588423fa24e56e09ca5aab31dd
Author: Laine Stump <laine@redhat.com>
Date: Thu May 28 18:04:24 2020 -0400

qemu: don't reject interface update when switching to/from bridged network

which went into upstream before 6.5.0, so should be in the build referenced here (6.6.0). I would guess that either I missed some case, or caused a regression. I can look at it next week.