Re: [Qemu-devel] [RFC] qemu VGA endian swap low level drawing changes

[Alexander Graf]

On 01.07.14 10:20, Gerd Hoffmann wrote:
> On Mo, 2014-06-30 at 22:32 +1000, Benjamin Herrenschmidt wrote:
> > On Mon, 2014-06-30 at 13:14 +0200, Gerd Hoffmann wrote:
> > >    Hi,
> > >
> > > >  From what I can tell, we only ever call the cursor drawing callback on
> > > > non-shared surfaces. Should I deduce that the HW cursor emulation simply
> > > > doesn't work when using shared surfaces ? Or is there another path I
> > > > have missed to handle it ?
> > > Hmm.  Looks like hw-cursor-on-shared-surface broken indeed.  Need to dig
> > > out a guest which actually uses it & go figure when testing your patch
> > > series ...
> > I don't think I broke it much more than it already was but then I
> > couldn't find a guest using it. I've tried the plain cirrus DDX in X and
> > it didn't have any problem... maybe windows ?
> Nope.  windows xp doesn't use it.  Anything newer doesn't ship with
> cirrus drivers any more (and uses vesa bios support).
>
> Looking at the code the cirrus hardware cursor supports two colors only
> (and some funky xor mode).  Guess it simply doesn't cut it as you can't
> have your cursors drop shadows with that, so guests are ignoring it.

Windows NT 4 might use it. I remember that I had issues running NT4 with 
Cirrus emulation a while back.

> > Right. A quick fix would be to add a flag to force always using a shadow
> > surface and set it in cirrus ... I'm not sure anybody will notice the
> > performance difference.
> I suspect we can rip out hw cursor emulation and nobody will notice the
> difference either ...

Very likely ;). Though I think we're better off keeping it around to 
make sure we're still compatible with ancient guests (Windows 3.1 might 
use it too). Making it slow however shouldn't make any difference at all.


Alex