Nested KVM performance evaluation on Ubuntu 20.04 (Focal Fossa) Guest on Virthost CentOS 8.1

Performance appraisal has been done via attempt to set up Ubuntu 20.04 as KVM virtualization host installing Qemu && Libvirt per
https://computingforgeeks.com/install-kvm-hypervisor-on-ubuntu-focal-fossa/

$ sudo apt -y install qemu-kvm libvirt-daemon bridge-utils \
 virtinst libvirt-daemon-system
$ sudo apt -y install virt-top libguestfs-tools \
libosinfo-bin  qemu-system virt-manager

$ sudo modprobe vhost_net 
$ lsmod | grep vhost
vhost_net              24576  0
tun                    49152  1 vhost_net
vhost                  49152  1 vhost_net
tap                    28672  1 vhost_net
$ echo vhost_net | sudo tee -a /etc/modules

At this point default network appears to be created 
Shutdown L1 Guest Ubuntu 20.04 and update it's
XML - profile via virsh console replacing 'host-model' by 'host-passthrough' afterwards restart Ubuntu 20.04 Guest via virsh console either via Virt-Manager. 

Due to default networks on Virthost CentOS 8.1 and L1 Guest appears to be different there is no need to create manually libvirt's network inside Ubuntu 20.04 L1 Guest. I have to notice that Focal Fossa allows to setup KVM-Hypervisor && Libvirtd.service as smoothly as RH's systems

   Create L2 KVM Guest Manjaro Gnome 19.02  inside L1 Guest Ubuntu 20.04
  

    Libvirtd status