Description:
The libvirt have an issue where attempting to start a KVM/QEmu VM with PCI-E Passthrough will cause the libvirtd service to freeze which lead to kernel panic requiring a reboot. Minimal error information can be obtained from either journalctl:

Jul 27 02:56:03 DevMachine libvirtd[1076]: End of file while reading data: Input/output error
Jul 27 02:58:22 DevMachine systemd[1]: Stopping Virtualization daemon... // Attempt to run systemctl stop libvirtd and eventually killall -9 libvirtd
Jul 27 02:59:53 DevMachine systemd[1]: libvirtd.service: State 'stop-sigterm' timed out. Killing.
Jul 27 02:59:53 DevMachine systemd[1]: libvirtd.service: Killing process 1076 (libvirtd) with signal SIGKILL.
Jul 27 03:01:23 DevMachine systemd[1]: libvirtd.service: Processes still around after SIGKILL. Ignoring.
Jul 27 03:02:53 DevMachine systemd[1]: libvirtd.service: State 'stop-final-sigterm' timed out. Killing.
Jul 27 03:02:53 DevMachine systemd[1]: libvirtd.service: Killing process 1076 (libvirtd) with signal SIGKILL.
Jul 27 03:04:23 DevMachine systemd[1]: libvirtd.service: Processes still around after final SIGKILL. Entering failed mode.
Jul 27 03:04:23 DevMachine systemd[1]: libvirtd.service: Failed with result 'timeout'.

Additional info:
Package Versions: libvirt 6.5.0-1

Unable to obtain a more verbose error as it freezes the libvirtd service, it cannot be stopped by running "systemctl stop libvirtd" and require a reboot to resolve a kernel panic. I ended up rolling back the versions by changing the mirrorlist configuration and update packages to version prior to update and the functionality returns for Windows KVM.

Steps to reproduce:

Simply attempt to start Windows KVM with PCI-E Passthrough, version prior to libvirt 6.5.0-1 display no issue and able to start Windows KVM.