USB passthrough to VM

b0ll0s

New Member
Oct 26, 2025
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Hi all,

Perhaps this question has already been asked multiple times (sorry) but I cannot get it to work.
The situation is as follows; im running a VM (q35) with HAOS installed; I've connected 2 USB devices, a P1 meter and a Arduino Mega (with a RFlink setup).
root@pve:~# lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0403:6001 Future Technology Devices International, Ltd FT232 Serial (UART) IC
Bus 001 Device 008: ID 2341:0042 Arduino SA Mega 2560 R3 (CDC ACM)
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 002: ID 18d1:9302 Google Inc.

root@pve:~# ls -l /dev/serial/by-id
total 0
lrwxrwxrwx 1 root root 13 Oct 26 11:46 usb-Arduino__www.arduino.cc__0042_55037313137351918161-if00 -> ../../ttyACM0
lrwxrwxrwx 1 root root 13 Oct 25 18:10 usb-FTDI_FT232R_USB_UART_AB73R2A7-if00-port0 -> ../../ttyUSB1

The P1 meter (Future Technology Devices International, Ltd FT232 Serial (UART) IC) is configured to be passed through via "Use usb port" and is working fine (also the product is shown in the gui).

When I try to setup the same for the Arduino and I choose the USB port the GUI shows "Unplugged 1-2":
1761485437567.pngWhen I continue with this setup the RFlink is not working when using the following strings in HA; /dev/ttyACM0 or /dev/serial/by-id/usb-Arduino__www.arduino.cc__0042_55037313137351918161-if00 it looks like somehow HA cannot connect to the device. I've also tried to setup the usb via "USB Vendor/Device ID" but also that didn't work.

Now today I also tried the docker setup for HA and when using the following docker compose all is working as expected:
docker run --device /dev/ttyUSB1:/dev/ttyUSB1 --device /dev/ttyACM0:/dev/ttyACM0 -d --name="home-assistant" -v /docker/homeassistant:/config -v /etc/localtime:/etc/localtime:ro --net=host ghcr.io/home-assistant/home-assistant

Of course its nice to see that the docker setup is working as expected but I would like to understand why my initial setup with a VM running HAOS is not working; what im I missing?

Thanks
 
I had a similar issue with a usb modem a few years back, in the end I resorted to passing through a whole usb controller via vfio passthrough, luckily the board had 2 separate iommu groups for the controllers, so the host kept one and guest got the other, problem was solved in that particular case.

Maybe you could do something like this in your case too.