4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chris Wilson chris@chris-wilson.co.uk
[ Upstream commit 8516673a996870ea0ceb337ee4f83c33c5ec3111 ]
Before accessing the GGTT we must flush the PTE writes and make them visible to the chipset, or else the indirect access may end up in the wrong page. In commit 3497971a71d8 ("agp/intel: Flush chipset writes after updating a single PTE"), we noticed corruption of the uploads for pwrite and for capturing GPU error states, but it was presumed that the explicit calls to intel_gtt_chipset_flush() were sufficient for the execbuffer path. However, we have not been flushing the chipset between the PTE writes and access via the GTT itself.
For simplicity, do the flush after any PTE update rather than try and batch the flushes on a just-in-time basis.
References: 3497971a71d8 ("agp/intel: Flush chipset writes after updating a single PTE") Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: Mika Kuoppala mika.kuoppala@intel.com Cc: drm-intel-fixes@lists.freedesktop.org Reviewed-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20171208214616.30147-1-chris@c... Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/agp/intel-gtt.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/char/agp/intel-gtt.c +++ b/drivers/char/agp/intel-gtt.c @@ -859,6 +859,8 @@ void intel_gtt_insert_sg_entries(struct } } wmb(); + if (intel_private.driver->chipset_flush) + intel_private.driver->chipset_flush(); } EXPORT_SYMBOL(intel_gtt_insert_sg_entries);