[vioserial] Serial port does not show up in Windows 11 aarch64 VM

[MarkusPettersson98]

Hello, and thank you for these amazing drivers!

I've encountered a problem while experimenting with Windows on ARM VMs in QEMU. For the life of me, I can not manage to setup a serial port between the host and the guest VM. I use the following command to launch QEMU:

qemu-system-aarch64 \
  -M virt -m 8G -cpu host -smp 8 \
  -bios <QEMU_EFI.fd> \
  -accel hvf \
  -device ramfb \
  -device qemu-xhci -device usb-kbd -device usb-tablet \
  -nic user,model=virtio-net-pci \
  -drive file=<Windows11-aarch64 image> \
  -drive if=none,id=virtio-drivers,format=raw,media=cdrom,file=<virtio-win.iso> \
  -device usb-storage,drive=virtio-drivers \
  -device virtio-serial-pci -serial pty

When I boot into the Windows installation, no serial port is detected in the device manager. Using chgport I can see one generic device which is not detected if I remove the virtio-serial-pci device, but due to it showing up as a generic device I suspect that there is some kind of driver issue.. I've installed the latest virtio-0.1.266 drivers in the VM.

The host is an M1 mac running macOS 15.1. I can provide more information if needed, but initially I just want to know if I'm completely off the mark here and if I need to invoke QEMU with other parameters to get things working. For reference, -device virtio-serial-pci -serial pty works fine to get a working serial port between my host and an x86 Windows 11 guest.

Thanks!