Currently I am trying to give a physical rs232 port to a Qemu VM.

Currently I use

-chardev serial,path=/dev/ttyUSB0,id=hostusbserial

command argument to do that. However, being an usb-based serial port, sometimes it should be able to handle hot add/removes without a guest restart, too.

Furthermore, any app on guest OS wants to know a serial port number to talk on. In the case of Windows guests, these would be com1-com4, while Linuxes would use /dev/ttyS0-3.

Qemu docs don't reveal too much about it.

Sharing the usb host with device_add usb-host,... works, but it is not a viable option. Thus:

  1. Sharing should happen on the rs232 level,
  2. it should be hotadd-capable,
  3. and somehow I should influence (or, at least see), which serial port will it be on the guest side.

Can I somehow do this with qmp? (Qmp is that qemu monitor, I handle it with telnetting to a tcp port on -monitor telnet:,server,nowait.

  • I am not sure if (1)-(3) are essentially different questions. If needed, I can split the question into this 3 parts. – peterh Jan 30 at 15:25

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