On Thu, Oct 30, 2014 at 5:18 PM, Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> wrote: > Global GTT doesn't have pat_sel[2:0] so it always point to pat_sel = 000; > So the only way to avoid screen corruptions is setting PAT 0 to Uncached. > > MOCS can still be used though. But if userspace is trusting PTE for > cache selection the safest thing to do is to let caches disabled. > > BSpec: "For GGTT, there is NO pat_sel[2:0] from the entry, > so RTL will always use the value corresponding to pat_sel = 000" > > Reference: https://bugs.freedesktop.org/show_bug.cgi?id=85576 > Cc: James Ausmus <james.ausmus@xxxxxxxxx> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Ok, I think this is -fixes + cc: stable material, but we need to be a bit more elaborate on the commit message: - System agent ggtt writes (i.e. cpu gtt mmaps) already work before this patch, i.e. the same uncached + snooping access like on gen6/7 seems to be in effect. - So this just fixes blitter/render access. Again it looks like it's not just uncached access, but uncached + snooping. So we can still hold onto all our assumptions wrt cpu clflushing on LLC machines. I think this should be both in the commit message and code. Chris, please correct if I've summarized this wrongly. Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
