[Mesa-dev] [PATCH 04/11] st/mesa: Use Array._DrawVAO in st_atom_array.c.

[Erik Faye-Lund]

On Tue, 2018-11-27 at 07:11 +0100, Mathias Fröhlich wrote:
> Hi Erik,
> 
> > > On Monday, 26 November 2018 19:39:50 CET Erik Faye-Lund wrote:
> > > > I know this is *very* late notice, but this commit broke Super
> > > > Tux
> > > > Kart
> > > > on VirGL. Both the player-models as as well as the level data
> > > > renders
> > > > with gibberish vertex positions since this commit.
> > > > 
> > > > The fix that Rob Clark did on top does not fix the problem (and
> > > > shouldn't have; VirGL doesn't use NIR).
> > > 
> > > Do you have any idea how I can reproduce that issue with the
> > > least
> > > effort?
> > > 
> > 
> > Sadly, no. I run a qemu VM where I run super tux cart. It's a
> > rather
> > convoluted setup, I'm afraid. If you're interested in that Robert
> > Foss
> > has written an article about how to set something like this up
> > here:
> > https://memcpy.io/virtualizing-gpu-access.html
> > 
> > ...But I totally understand if this is asking a bit too much. I can
> > help out with any information you need...
> 
> Thanks!
> That, just means that looking into has to wait at least until the
> weekend.
> Probably even later.
> 
> And thanks for looking up the constants.
> The effective binding computation depends on these and may change
> the set up combined buffer objects. So these are interesting to know.
> 
> I have been putting a lot of internal verification into the code
> paths
> especially _mesa_update_vao_derived_arrays contains a larger
> #ifndef NDEBUG part that may tell us if there is something
> unexpected.
> 
> I assume you did run also with asserts enabled in the build?

Yes, I ran with asserts on, and none triggered.

> I can observe some flicker in supertuxcart on i965. The nvidia blob
> seems
> not to flicker here. Also when running through valgrind I don't get
> that flicker
> on i965. Is that flashing - initially looked like a lighting effect
> of the game to
> me - what you observe too?

No, the models are completely garbled. You can find some example
screenshots here:

https://gitlab.freedesktop.org/virgl/virglrenderer/issues/59

> Also what are the game options? Are shaders enabled in some way?

I'm playing with the default settings. I'm not sure what you mean with
"are shaders enabled"; VirGL is a gallium-driver, everything uses
shaders.

> What does change if you change the game settings?
> May be that gives us some hints?
> 

I've tried setting both the lowest and highest graphics settings in the
game, and I get the same problem. This seems to happen regardless of
graphics settings.