[Intel-gfx] [PATCH] drm/i915: set ctx->initialized only after RCS

[Chris Wilson]

On Tue, Jan 07, 2014 at 08:10:33AM +0100, Daniel Vetter wrote:
> On Sat, Dec 28, 2013 at 01:31:49PM -0800, Ben Widawsky wrote:
> > The initialized flag is used to specify a context has been initialized
> > and it's context is safe to load, ie. the 3d state is setup properly.
> > With full PPGTT, we emit the address space loads during context switch
> > and this currently marks a context as initialized. With full PPGTT
> > patches, if a client first emits a batch to !RCS, then later, RCS, the
> > code will mistake the context as initialized and try to reload an
> > uninitialized context.
> > 
> > 1. context 1 blit // context initialized
> > 2. context 2 <X operation> // saves context 1 random state
> > 3. context 1 render // loads random state from step 2
> > 
> > It is really easy to hit this with a planned upcoming patch which makes
> > default context reuse possible.
> > 
> > NOTE: This should only effect full PPGTT branches, ie. current
> > drm-intel-nightly.
> > 
> > Thanks to Chris for helping me track this down.
> > 
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> 
> Do we have a testcase for this or a bug report?

Odd, since QA should have hit this...
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre