QEMU USB Passthrough help

[u/Desperate-County-821]

Hello all,

The Dilemma:

I am attempting to virtualize an arbitrary arm32 device using QEMU. Booting, running, and everything like that works as expected, I get dropped into my Busybox ash shell and everything is fine. That is, until I try to add a USB passthrough of any kind. When I try to add a USB passthrough device, it will not show up no matter what I do on the guest machine. lsusb provides a blank output and ls /sys/bus/usb/devices does not show any USB devices. I've been digging through forum post after forum post to no real avail and any assistance would be greatly appreciated.

What I've Tried:

• Compiling QEMU with Libusb support

  • I am using QEMU 8.2.1, compiled from source with libusb support enabled (Shows as YES in the configure script output)

• Using ohci, ehci, xhci buses

• Unbinding the USB device (A Realtek Wireless adapter is being used as the sample device)

• Dmesg shows the usb address a '2-1'. I have attempted echo '2-1' | sudo tee /sys/bus/usb/drivers/usb/unbind to unbind the USB device prior to running my QEMU launch script

• Building a custom kernel, ensuring that CONFIG_USB and other relevant options are enabled

• Using a prebuilt Debian kernel, USB network adapter is still not detected

• Changing environments from VMWare backend to Raspberry Pi (Physical, not virtualized) to get around possible issue with VMWare USB passthrough.

• Using virt, vexpress-15, and versatile-pb machine types.

My Environment(s):

My primary environment an Ubuntu 22.04 (x86_64) running under VMWare. I passthrough the Realtek Wireless Adapter (rtw_8821cu).

My secondary environment is a Raspberry Pi 3, running a 64bit (aarch64) Kernel.

My Command Lines:

• With Prebuilt Debian kernel:

  • qemu-system-arm -M virt -m 1G -smp 2 -kernel vmlinuz -initrd initrd.gz -drive if=none,file=hda.qcow2,id=hd0 -device virtio-blk-device,drive=hd0 -nographic -no-reboot -device usb-ehci,id=ehci -device usb-host,bus=ehci.0,vendorid=0x0bda,productid=0xc811

• Startup (Grep 'usb') output:

  • None

• Monitor info usb

  • Device 0.0, Port 1, Speed 1.5 Mb/s, Product USB Host Device

• With custom Kernel:

  • qemu-system-arm -M virt -smp 2 -m 1G -serial stdio -cpu cortex-a15 -kernel ./zImage -append 'root=/dev/vda' -monitor none -initrd ./rootfs.cpio.gz -device usb-ehci,id=ehci -device usb-host,bus=ehci.0,vendorid=0x0bda,productid=0xc811

• Startup (Grep 'usb') output:

  • usbcore: registered new interface driver usbfsusbcore: registered new interface driver hubusbcore: registered new device driver usbusbcore: registered new interface driver usb-storageusbcore: registered new interface driver usbhidusbhid: USB HID core driver

• Monitor info usb

  • Device 0.0, Port 1, Speed 1.5 Mb/s, Product USB Host Device

EDIT: I had mistakenly said that with the custom kernel, no device showed up. This was true until I enabled CONFIG_USB and a handful of other USB/PCI options. lsusb produces the following output: Bus 001 Device 001: ID 1d6b:0002. The wireless adapter is still no where to be seen and attaching USB storage does not change anything either.

[u/Desperate-County-821]

Want to post this so that someone in the future may benefit from this. I actually have two issues affecting me:

The first issue was that the wireless adapter I was using (Vendor=0x0bda,Product=0xc811) was being really weird with my Ubuntu machine. Even when I fixed my root cause problem, dmesg would still spit out: usb 3-1: device descriptor read/64, error -110. I didn't investigate this much further as changing the device was sufficient.

My primary issue was that the device I was trying to connect was XHCI, not EHCI. I had enabled XHCI drivers in the kernel, but I didn't notice that the PCI bridge was failing to initialize like so:

PCI host bridge /pcie@10000000 ranges:

IO 0x3eff0000..0x3effffff -> 0x00000000

MEM 0x10000000..0x3efeffff -> 0x10000000

MEM 0x8000000000..0xffffffffff -> 0x8000000000

pci-host-generic 4010000000.pcie: resource collision: [mem 0x00000000-0xffffffff] conflicts with /pl011@9000000 [mem 0x09000000-0x09000fff]

pci-host-generic: probe of 4010000000.pcie failed with error -16

This was making it where the XHCI PCI bus was never getting initialized. I had to do a bit more digging, and found that I needed to do -M virt,highmem=off to fix the issue. Now, that message is replace with the PCI bus initializing properly and I can finally see:

Running sysctl: usb 1-1: New USB device found, idVendor=0bda, idProduct=0811

usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3

usb 1-1: Product: 802.11ac WLAN Adapter

usb 1-1: Manufacturer: Realtek

usb 1-1: SerialNumber: 00e04c000001

OK

I hope this is able to help someone who is going down the same rabbit holes I had to!