Serial Port COM Passthrough

This article introduces how to passthrough host's serial ports (COM) to virtual machines for use.

Configure Host

View COM devices on the host. Use command setserial to view:

# View onboard serial port devices
$ sudo setserial -g /dev/ttyS[0123]
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x1020, IRQ: 18
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
# View USB serial ports
$ sudo setserial -g /dev/ttyUSB[01]
/dev/ttyUSB0, UART: unknown, Port: 0x0000, IRQ: 0

Find the serial port device path to be passthrough on the host, for example /dev/ttyUSB0

Add the following command line parameters in QEMU to pass this serial port device to the virtual machine:

-chardev tty,path=/dev/ttyUSB0,id=hostusbserial
-device pci-serial,chardev=hostusbserial

Set the above command line parameters for specified hosts through the following climc command:

climc server-add-extra-options <sid> chardev tty,path=/dev/ttyUSB0,id=hostusbserial
climc server-add-extra-options <sid> device pci-serial,chardev=hostusbserial

Restart this virtual machine, and view in the virtual machine details page whether the above parameters have been added to command line parameters.