[PATCH 04/20] drm/i915/ringbuffer: Force restore of mm after failed context switch

[Chris Wilson <chris@chris-wilson.co.uk>]

If we interrupt the context switch and unwind, we leave the to_mm
believing that we have cleared the dirty bit for this engine (but the
LRI will never take place). Just in case we immediately reload the same
context, mark this engine as dirty so that we force the LRI to reload
the PD.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 3df802cc3710..93b5f4a8316d 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1591,6 +1591,7 @@ static int switch_context(struct i915_request *rq)
 		to_ctx->ppgtt ?: rq->i915->mm.aliasing_ppgtt;
 	struct i915_gem_context *from_ctx = engine->legacy_active_context;
 	struct i915_hw_ppgtt *from_mm = engine->legacy_active_ppgtt;
+	unsigned int unwind_mm = 0;
 	u32 hw_flags = 0;
 	int ret, i;
 
@@ -1604,7 +1605,11 @@ static int switch_context(struct i915_request *rq)
 		if (ret)
 			goto err;
 
-		to_mm->pd_dirty_rings &= ~intel_engine_flag(engine);
+		if (to_mm->pd_dirty_rings & intel_engine_flag(engine)) {
+			unwind_mm = intel_engine_flag(engine);
+			to_mm->pd_dirty_rings &= ~unwind_mm;
+		}
+
 		engine->legacy_active_ppgtt = to_mm;
 
 		if (to_ctx == from_ctx) {
@@ -1651,6 +1656,8 @@ static int switch_context(struct i915_request *rq)
 err_ctx:
 	engine->legacy_active_context = from_ctx;
 err_mm:
+	if (unwind_mm)
+		to_mm->pd_dirty_rings |= unwind_mm;
 	engine->legacy_active_ppgtt = from_mm;
 err:
 	return ret;
-- 
2.17.1

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