[Mesa-dev] [PATCH 02/17] i965/miptree: Zero-initialize CCS_D buffers

[Nanley Chery]

On Thu, May 03, 2018 at 12:40:49PM -0700, Jason Ekstrand wrote:
> Good catch. Rb
> 

Thanks!

> On May 3, 2018 12:04:59 Nanley Chery <nanleychery at gmail.com> wrote:
> 
> > Before this patch, the aux_state was actually AUX_INVALID because the BO
> > was never defined. This was fine on single slice miptrees because we
> > would fast-clear the resource right after creation. For multi-slice
> > miptrees on SKL+ however, this results in undefined behavior when
> > accessing a non-base slice. Here's a specific example:
> > 
> > 1) Fast clear level 0
> >   * Undefined CCS_D buffer allocated in "PASS_THROUGH" state.
> >   * Level 0 transitions to the CLEAR state.
> > 2) Render to level 1
> >   * Level 1 may have a 2-bit pattern of 2's.
> >   * Rendering with a 2 in the CCS is undefined.
> > 
> > Cc: <mesa-stable at lists.freedesktop.org>
> > ---
> > src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 10 ++++------
> > 1 file changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > index 377efae32c9..182a896e23a 100644
> > --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > @@ -1806,13 +1806,11 @@ intel_miptree_alloc_ccs(struct brw_context *brw,
> >     * A CCS value of 0 indicates that the corresponding block is in the
> >     * pass-through state which is what we want.
> >     *
> > -    * For CCS_D, on the other hand, we don't care as we're about to perform a
> > -    * fast-clear operation.  In that case, being hot in caches more useful.
> > +    * For CCS_D, do the same thing. On gen9+, this avoids having any undefined
> > +    * bits in the aux buffer.
> >     */
> > -   const uint32_t alloc_flags = mt->aux_usage == ISL_AUX_USAGE_CCS_E ?
> > -                                BO_ALLOC_ZEROED : BO_ALLOC_BUSY;
> > -   mt->aux_buf = intel_alloc_aux_buffer(brw, "ccs-miptree",
> > -                                        &temp_ccs_surf, alloc_flags, mt);
> > +   mt->aux_buf = intel_alloc_aux_buffer(brw, "ccs-miptree", &temp_ccs_surf,
> > +                                        BO_ALLOC_ZEROED, mt);
> >    if (!mt->aux_buf) {
> >       free(aux_state);
> >       return false;
> > --
> > 2.16.2
> > 
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> 
> 
>