[PATCH 3/5] drm/i915/gt: Discard stale context state from across idling

[Chris Wilson]

Before we idle, on parking, we switch to the kernel context such that we
have a scratch context loaded while the GPU idle, protecting any
precious user state. Be paranoid and assume that the idle state may have
been trashed, and reset the kernel_context image after idling.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_pm.c | 6 ++++++
 drivers/gpu/drm/i915/gt/intel_gt_pm.c     | 8 --------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index 010620b78202..b9444ce29a3a 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -20,6 +20,7 @@ static int __engine_unpark(struct intel_wakeref *wf)
 {
 	struct intel_engine_cs *engine =
 		container_of(wf, typeof(*engine), wakeref);
+	struct intel_context *ce;
 	void *map;
 
 	ENGINE_TRACE(engine, "\n");
@@ -34,6 +35,11 @@ static int __engine_unpark(struct intel_wakeref *wf)
 	if (!IS_ERR_OR_NULL(map))
 		engine->pinned_default_state = map;
 
+	/* Discard stale context state from across idling */
+	ce = engine->kernel_context;
+	if (ce)
+		ce->ops->reset(ce);
+
 	if (engine->unpark)
 		engine->unpark(engine);
 
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
index 3cda837d64c9..2a0058acea65 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
@@ -209,16 +209,8 @@ int intel_gt_resume(struct intel_gt *gt)
 	intel_llc_enable(&gt->llc);
 
 	for_each_engine(engine, gt, id) {
-		struct intel_context *ce;
-
 		intel_engine_pm_get(engine);
 
-		ce = engine->kernel_context;
-		if (ce) {
-			GEM_BUG_ON(!intel_context_is_pinned(ce));
-			ce->ops->reset(ce);
-		}
-
 		engine->serial++; /* kernel context lost */
 		err = engine->resume(engine);
 
-- 
2.24.1