echo "ttyS0" >> /etc/securetty

vi /etc/default/grub
# Add console=ttyS0 to the end of kernel line(s) "GRUB_CMDLINE_LINUX"
grub2-mkconfig -o /boot/grub2/grub.cfg
reboot
#vi /etc/sysconfig/init
# Edit ACTIVE_CONSOLES to look like:
#ACTIVE_CONSOLES="/dev/tty[1-6] /dev/ttyS0"

# If on a live system, do the following
#init q

# After that, if on KVM virtual machine, it should be possible to do
virsh console <vm_name>
# and see the console output