Comment 5 for bug 1821595

As far as I can tell QEMU just hands this off to the whpx emulation sub-system:

  https://docs.microsoft.com/en-us/virtualization/api/hypervisor-instruction-emulator/funcs/whvemulatortryemulation

Basically what is happening is the guest has tried to access I/O space and trapped back to QEMU which then passes the instruction back to the whpx support library to decode and emulate.