With this feature a virtual machine is created and then it is suspended. However the machine cannot be resumed.

That is because when creating the virtual machine, we launch qemu with parameters to create a virtual serial port and then establish a TCP connection to the coin server in order to allow for coin to send data into the serial port. On the receiving end the agent bootstrap process will then listen and act accordingly.

However when resuming a suspended VM, qemu will fail to re-establish that TCP connection for the serial port, because the listening side in coin does not exist anymore. Therefore the VM cannot be resumed.