Proxmox VE 8.2.2 PCI Express USB HUB Issue

[cbl]

Hello,

Issue Description​

I am experiencing an issue with USB passthrough when connecting multiple TTY USB devices through a USB hub attached to a PCI Express port. The setup and problem are as follows:

1. I connect a single TTY USB device to the USB hub and pass it through to an Ubuntu 22.04 VM using the Proxmox web interface (Add > USB Device).
2. The VM starts, and the device appears as /dev/ttyUSB0 and functions correctly.
3. I then connect a second TTY USB device to the same USB hub and pass it to another Ubuntu 22.04 VM.
4. The second VM starts, and the device also appears as /dev/ttyUSB0 and initially works.
5. After a short period, both VMs lose their USB connections. The devices no longer appear in the VMs, and the Proxmox web interface or shell (lsusb, etc.) no longer detects the USB devices.
6. Unplugging and replugging the USB devices does not resolve the issue. The only way to restore functionality is to reboot the Proxmox VE host.

Environment​

• Proxmox VE Version: 8.2.2
• Kernel: Linux pve 6.8.4-2-pve #1 SMP PREEMPT_DYNAMIC PMX 6.8.4-2 (2024-04-10T17:36Z) x86_64 GNU/Linux
• Boot Parameters: BOOT_IMAGE=/boot/vmlinuz-6.8.4-2-pve root=/dev/mapper/pve-root ro quiet usbcore.autosuspend=-1
• Hardware:
  • Motherboard: Supermicro
  • USB Controller: VIA Technologies, Inc. VL805/806 xHCI USB 3.0 Controller (rev 01) at 0000:d8:00.0
  • USB Hub: Connected to a PCI Express port
  • Devices: Multiple development kits with TTY USB connections
• Virtual Machines: Ubuntu 22.04 VMs

I have followed the steps outlined in the Proxmox Wiki for PCI(e) Passthrough to ensure proper configuration, but the issue persists. (https://pve.proxmox.com/wiki/PCI(e)_Passthrough)

I also enabled the IOMMU (VT-d) setting in my motherboard's BIOS settings.

Could you please support me in this issue?

Best regards.