[Mesa-dev] [PATCH] i965: Allow 48-bit addressing on Gen8+.

[Kenneth Graunke]

On Wednesday, February 28, 2018 2:21:24 PM PST Emil Velikov wrote:
> On 27 February 2018 at 00:05, Kenneth Graunke <kenneth at whitecape.org> wrote:
> 
> > --- a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
> > +++ b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
> > @@ -203,12 +203,23 @@ brw_emit_surface_state(struct brw_context *brw,
> >         * FIXME: move to the point of assignment.
> >         */
> >        assert((aux_offset & 0xfff) == 0);
> > -      uint32_t *aux_addr = state + brw->isl_dev.ss.aux_addr_offset;
> > -      *aux_addr = brw_state_reloc(&brw->batch,
> > -                                  *surf_offset +
> > -                                  brw->isl_dev.ss.aux_addr_offset,
> > -                                  aux_bo, *aux_addr,
> > -                                  reloc_flags);
> > +
> > +      if (devinfo->gen >= 8) {
> > +         uint64_t *aux_addr = state + brw->isl_dev.ss.aux_addr_offset;
> > +         *aux_addr = brw_state_reloc(&brw->batch,
> > +                                     *surf_offset +
> > +                                     brw->isl_dev.ss.aux_addr_offset,
> > +                                     aux_bo, *aux_addr,
> > +                                     reloc_flags);
> > +      } else {
> > +         uint32_t *aux_addr = state + brw->isl_dev.ss.aux_addr_offset;
> > +         *aux_addr = brw_state_reloc(&brw->batch,
> > +                                     *surf_offset +
> > +                                     brw->isl_dev.ss.aux_addr_offset,
> > +                                     aux_bo, *aux_addr,
> > +                                     reloc_flags);
> > +
> Hmm something looks funky here - is there another patch for
> brw_state_reloc somewhere?
> Currently it's declared as
> 
> uint64_t
> brw_state_reloc(struct intel_batchbuffer *batch, uint32_t
> state_offset,
>                 struct brw_bo *target, uint32_t target_offset,
>                 unsigned int reloc_flags);
> 
> So the new hunk a) caters for *aux_addr hitting an arithmetic
> overflow, or b) stores the full 64bit return value of the function
> only to discard it.
> If a) is the intended behaviour an explicit note might be a good idea.
> 
> HTH
> Emil

Pointers are 32-bit on Gen4-7.5 and 64-bit on Gen8+.  We changed
brw_state_reloc to return a uint64_t a while back, to handle the new
large size on new platforms.  On old platforms we need to write a 32-bit
value, and the high 32-bits of the value returned is 0.
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