serial port not working on kvm guest

Hi there,

I have a serial port pci add-on card. It brings 2 extra serial ports.

It is correctly detected by proxmox system (lspci -v shows the new card with the 2 extra ports)

After running 'setserial' on proxmox, I have /dev/ttyS2 correctly set and working: cat /dev/ttyS2 display a correct data flow sent from the serial device connected to it.

I'd like to use this 2 extra serial ports on my kvm vm guest.

So I mapped /dev/ttyS0 (myVM-101) on /dev/ttyS2 (proxmox):
qm -serial0 /dev/ttyS2 101

which created this entry in 101.conf:
serial0: /dev/ttyS2

Unfortunately, this is not working. With this configuration, when I start the vm up,
- cat /dev/ttyS0 returns nothing on the vm
- cat /dev/ttyS2 returns nothing on proxmox ether

Any idea ?