Only the plain console is ring 0. You can kill your X server.
With a Cirrus board at least, you can't even fix the result with
a warm reboot. The out-of-memory policy makes it easy to kill X.
"Your Linux box crashed? Oh, just hit the power switch..."
> Possibly it could make better use of irq/dma hooks and stuff - the mode
> restore is trivial - its a single notifier hook and some modules that
> just load/unload notifier hooked routines to save/restore video mode.
Video hardware is not that simple. (of course it should be...)
> Doing all video via the kernel is bad- the intel CPU's are
> very slow when crossing protection and ring boundaries
This is why GGI avoids crossing protection and ring boundaries.
The last time I heard, they had a 2-page sized command queue.
As things are now, the kernel is starting to collect ad-hoc video
drivers for various non-i386 hardware.