Can we run Xorg as unprivileged with this?
We already do on macppc and sparc(64), although arguably we probably
shouldn't allow mapping PCI resources without INSECURE.
Probably? There's no `probably' about it, to me. But then, I also
think the X server has no business mapping PCI resources, per se, at
all; it should be going through the display device's driver, which will
constrain what userland can map to what userland has business mapping -
and will do so regardless of the bus type; the X server also has no
business caring whether the display device is behind PCI, ISA, SBus,
Qbus, or something else. That's what drivers are for: to insulate
userland from that mess.
Of course, this may be considered a heretical point of view. But I
still maintain that moving a device driver's job into userland is a
very wrong thing to do in multiple respects.