My 64-bit OS and kernel now has working USB mouse and keyboard! Through my now-working xHCI driver (USB 3.0).
The attached image shows the OS running in QEMU, and me typing some commands with my keyboard and drawing coloured lines with my mouse.
The image also showcases my NVMe driver and filesystem driver working as intended.
Overall I am pretty proud of the progress that I am making, and next up I will be working on getting the xHCI driver to run on real hardware.