Re: [PATCH 22/23] Hack in dirty logging for VGA

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2009-07-07 at 18:48 +0300, Avi Kivity wrote:
> On 07/07/2009 05:17 PM, Alexander Graf wrote:
> > I haven't implemented dirty logging yet, but without things are just way too
> > slow. So for the time being I hacked in a dummy function that always tells
> > userspace we're dirty in VGA regions.
> >
> > Please don't apply this. This patch is for reference only.
> >
> >    
> 
> ia64 has the same problem; you can deal with this in userspace.

Well... also depending on what we are trying to emulate it might not be
worth at all presenting some kind of legacy VGA device. For example,
PowerMacs are physically incapable of generating the appropriate cycles
on the bus.

We are probably better off exposing pseudo PCI graphics device that is
reflected by a display node in the device-tree with enough information
populated there for offb to be able to pick it up initially, and then
have the option of paravirt drivers for accelerating it or making it
capable of switching modes etc... That's pretty much what we did with
MacOnLinux in fact.

Also, MOL kept track of dirtied pages in the fb as well to speed up
refresh.

Cheers,
Ben.