Fedora 40 vm, bluetooth (USB) passthrough

planetf1

New Member
Jun 19, 2024
10
2
3
I am using Proxmox 8.2.4 on a N100 based miniPC with 16GB ram. Kernel is Linux 6.8.12-1-pve.

The unit only has one full-time VM, a Fedora 40 guest with 8GB ram.
Bios is UEFI, machine q35 (iommu=intel). I have the n100 GPU passed through

I also have 1 USB devices passed through (usb3) - bluetooth, audio. lsusb begins:
```
Bus 009 Device 002: ID 0bda:c821 Realtek Semiconductor Corp. Bluetooth Radio
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 224 Wireless
bDeviceSubClass 1 Radio Frequency
bDeviceProtocol 1 Bluetooth
bMaxPacketSize0 64
idVendor 0x0bda Realtek Semiconductor Corp.
idProduct 0xc821 Bluetooth Radio
bcdDevice 1.10
iManufacturer 1 Realtek
iProduct 2 Bluetooth Radio
```
I have a logitech keyboard (K850) and a related mouse that can connect to multiple devices.

The issue is that after a while I find that I can no longer connect via bluetooth

On the vm bluetooth looks ok - I don't see any errors just:
```
[ 16.291920] Bluetooth: RFCOMM TTY layer initialized
[ 16.291931] Bluetooth: RFCOMM socket layer initialized
[ 16.291938] Bluetooth: RFCOMM ver 1.11
[ 19.495100] Bluetooth: hci0: unexpected cc 0x0c7c length: 1 < 3
[ 20.079243] input: MX Ergo Mouse as /devices/virtual/misc/uhid/0005:046D:B01D.0002/input/input6
[ 20.079571] hid-generic 0005:046D:B01D.0002: input,hidraw1: BLUETOOTH HID v0.22 Mouse [MX Ergo] on c0:4b:24:35:7e:22
[ 20.191953] input: Logitech MX Ergo Multi-Device Trackball as /devices/virtual/misc/uhid/0005:046D:B01D.0002/input/input8
[ 20.192312] logitech-hidpp-device 0005:046D:B01D.0002: input,hidraw1: BLUETOOTH HID v0.22 Mouse [Logitech MX Ergo Multi-Device Trackball ] on c0:4b:24:35:7e:22
[ 20.213849] logitech-hidpp-device 0005:046D:B01D.0002: HID++ 4.5 device connected.
[ 23.394164] Bluetooth: hci0: unexpected cc 0x0c7c length: 1 < 3
[ 25.823997] input: Keyboard K850 Keyboard as /devices/virtual/misc/uhid/0005:046D:B34D.0003/input/input9
```

I can always connect after boot, but an hour or two later - probably not (but sometimes it works)

I did try ensuring the proxmox host doesn't touch bluetooth with:
```
root@pv3:/etc/modprobe.d# cat bluetooth-blacklist.conf
blacklist bluetooth
blacklist btbcm
blacklist btintel
blacklist btrtl
blacklist btusb
```

but this didn't seem to make a difference.

This could simply be an issue with fedora in the vm, but I'm wondering if there's anything else around passthrough I need to check?
 

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