Comment 1 for bug 1713328

Well, with your "-serial" setup, you've put the guest serial console on the telnet port, so there is nothing to switch on the host console here via the CTRL-a c key combination, i.e. this is the expected behavior. What exactly were you trying to do here? Access the serial console via two ways, one time via telnet and one time via the host console? AFAIK that's not possible.