Qemu unable to init server

I've been trying to set up GPU passthrough on my laptop running Arch.

I followed a bunch of different guides, but they all fail at the same point for me - when I actually try to run qemu, it says

Unable to init server: Could not connect: Connection Refused
gtk initialization failed

Here's the output of my graphics card:

01:00.0 3D controller [0302]: NVIDIA Corporation GM107M [GeForce GTX 950M] [10de:139a] (rev a2)
	Kernel driver in use: vfio-pci
	Kernel modules: nouveau, nvidia_drm, nvidia

It's controlled by vfio-pci, so I got everything up to here working, but now I can't start qemu.

I followed these guides:

https://bufferoverflow.io/gpu-passthrough/

https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF