[Qemu-discuss] [question] why only one vport in /dev/char/ when I use qemu option "-device virtio-serial, max_ports=2"

[Zhang Haoyu]

Hi, Amit,
I start a VM with the option "-device virtio-serial,max_ports=2", but only one 
vport I can see in /dev/char/,
I read the source, 

guest virtio console driver                                                     
 qemu virtio-serial

virtcons_probe
     |
init_vqs
     |
__send_control_msg(
 VIRTIO_CONSOLE_DEVICE_READY)       =====>                         control_out
                                                                                
                |
                                                                                
         handle_control_message
                                                                                
                |
                                                                                
         QTAILQ_FOREACH(port, &vser->ports, next) {
control_intr                                      <=====                        
           send_control_event(VIRTIO_CONSOLE_PORT_ADD) } 
     |
control_work_handler
     |
add_port
    |
device_create("vport%up%u")

And, I add debug log in virtser_port_device_realize(), find that 
virtser_port_device_realize() was called only once,
i.e., only one port in vser->ports,  why?

How does max_ports option take effection ?

Thanks,
Zhang Haoyu