How to enable KVM virsh console access

From Debian / Ubuntu guest

sudo systemctl enable --now serial-getty@ttyS0.service

From KVM server

virsh list
Id    Name                           State
----------------------------------------------------
1     freebsd                        running
2     ubuntu-box1                    running
3     ubuntu-box2                    running

Type the following command from KVM host to login to the guest named ubuntu-box1

virsh console ubuntu-box1

OR

virsh console 2

Use CTRL + 5 to exit the console.