Add serial console device using virt-manager

1. Add serial console device

Click "Add Hardware", then new "Serieal" device specifying options like:
===
Device type: unix
Source path: /tmp/s0
===

2. Listen on this "serial" device on host

# nc -U /tmp/s0

3. Two ways to add kernel parameters

The kernel parameter to add - "console=ttyS0"

- temporary setting on boot

Press "e" on grub booting item, add it at the end of kernel parameter list.

- persistent setting

Edit /boot/grub/grub.conf inside the guest, and do the same thing as the above way.