[Mesa-dev] [PATCH v2 3/3] i965: if DEBUG_OUT_OF_BOUND_CHK is up, check that noise padding for each bo used in batchbuffer is correct

[Chris Wilson]

Quoting Rogovin, Kevin (2017-12-13 11:19:10)
> Hi,
> 
> > Actually that's not strictly true. Since you only do a pread here, it will only synchronize against the last declared write to the bo.
> > There's no guaranteed sync with the last batch for a set of read-only bo.
> > Similarly, because of no domain tracking, it won't also ensure that the bo is cache coherent before the read back.
> 
> Futz. Would then doing brw_bo_map() with flags having value MAP_READ be sufficient then? This is what function
> brw_get_buffer_subdata() of intel_buffer_objects.c does to copy BO contents to application supplied buffer.

Yes. I would also pencil in a note to do a map_range, or at least
MAP_INCOHERENT flag to avoid the gen_invalidate_range and do the
cache invalidation manually (for !llc).
-Chris