The glibc version that's included with Oracle Linux 9 checks for compatibility between a system's CPU and new architectures that are supported. A system might pass the compatibility check. However, the CPU flags that are set on the system after passing the check might be unknown to the KVM virtual machines that are hosted on that system. Consequently, the VMs panic when they're booted.

To work around this issue, run the following command:

virsh edit vm-name

Then, add the following declaration in the virtual machine's XML file:

<cpu mode='host-model' check='partial'/>

The check parameter's partial setting sets libvirt to check the VM's CPU specification before starting a domain. However, the rest of the checking remains on the hypervisor, which can still provide a different virtual CPU.

(Bug ID 34224821)

After reboot, the virbr0 network interface might be missing, which can prevent virtual machines from automatically starting up after boot.

The libvirt daemons on Oracle Linux 9 are modular to handle atomic features within the virtualization environment and are started and run as required, and stopped after two minutes of inactivity. The daemon responsible for setting up the networking interfaces for libvirt is virtnetworkd. This service isn't automatically started when a virtual machine is started.

To work around this issue, enable the virtnetworkd service so that the service starts at boot:

sudo systemctl enable --now virtnetworkd

(Bug ID 34237540)