Maybe this is way off the mark....., but I was just
thinking...
Xvnc and its cousins manage to map an X-screen into a
virtual screen just fine. This is done under unix
without ever touching a video hardware device. Maybe
we could use a method similar to theirs for mapping
the video-window/console space to a virtual screen and
then display that with something native like X or
svgalib. This would get rid of the need to map
anything to hardware--it would only require mapping a
framebuffer. Just thinking you know........
Drew Northup, N1XIM
P.S. If there is anything that you would like me to
check out in this arena, let me know..... I have the
latest released Xvnc source code and can make my way
around in it. The only thing that we would need to do
is to eliminate the dependency on Xfree86 to compile
(for use on non-X [svgalib..., W98, etc.] systems).
--- Ulrich Weigand wrote:
> [snip mapping host frame buffer]
>
> I wasn't thinking of this at all; at the current
> stage, IMO we
> shouldn't touch the real host hardware directly in
> any way.
>
> I was just talking about possible ways to implement
> emulated VGA
> hardware, either by asynchronous means (read out the
> guest frame
> buffer periodically) or by synchronous means (trap
> guest access
> to the frame buffer, like we trap I/O access -- this
> is how Bochs
> does it AFAIK).
>
> > (2) that you can use the dirty bit to check,
> whether
> > the guest wrote to the framebuffer memory.
> > There's no reason that this should imply
> mapping
> > the FB read-only... to the contrary, it avoids
> it.
>
> If you do in fact map the host frame buffer, you
> don't even *need*
> to check whether it was modified -- it is already
> displayed. You
> could use this information to help the asynch frame
> buffer emulation,
> however, so that you can skip updating the video
> display if the guest
> didn't touch the (emulated) guest frame buffer
> during the last tick.
>
> Bye,
> Ulrich
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