Yes, perhaps it all (including PCI hotplug controller) should be using
something else than hardcoded IO ports, but thats what we have now.
At least it should be documented.
What's the behaviour with a qemu that doesn't support the new port?
We don't strictly support it, but let's do so if we can.
All slots will be marked as hotpluggable (since the "removability" IO port will
registered and return all 1's).