drm/i915: Keep rings pinned while the context is active

Remember to keep the rings pinned as well as the context image until the
GPU is no longer active.

v2: Introduce a ring->pin_count primarily to hide the
mock_ring that doesn't fit into the normal GGTT vma picture.

v3: Order is important in teardown, ringbuffer submission needs to drop
the pin count on the engine->kernel_context before it can gleefully free
its ring.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110946
Fixes: ce476c80b8bf ("drm/i915: Keep contexts pinned until after the next kernel context switch")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190619170135.15281-1-chris@chris-wilson.co.uk

1 files changed, 18 insertions, 9 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 2c454f227c2e..23120901c55f 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -126,6 +126,7 @@ static void intel_context_retire(struct i915_active *active)
 	if (ce->state)
 		__context_unpin_state(ce->state);
 
+	intel_ring_unpin(ce->ring);
 	intel_context_put(ce);
 }
 
@@ -160,27 +161,35 @@ int intel_context_active_acquire(struct intel_context *ce, unsigned long flags)
 
 	intel_context_get(ce);
 
+	err = intel_ring_pin(ce->ring);
+	if (err)
+		goto err_put;
+
 	if (!ce->state)
 		return 0;
 
 	err = __context_pin_state(ce->state, flags);
-	if (err) {
-		i915_active_cancel(&ce->active);
-		intel_context_put(ce);
-		return err;
-	}
+	if (err)
+		goto err_ring;
 
 	/* Preallocate tracking nodes */
 	if (!i915_gem_context_is_kernel(ce->gem_context)) {
 		err = i915_active_acquire_preallocate_barrier(&ce->active,
 							      ce->engine);
-		if (err) {
-			i915_active_release(&ce->active);
-			return err;
-		}
+		if (err)
+			goto err_state;
 	}
 
 	return 0;
+
+err_state:
+	__context_unpin_state(ce->state);
+err_ring:
+	intel_ring_unpin(ce->ring);
+err_put:
+	intel_context_put(ce);
+	i915_active_cancel(&ce->active);
+	return err;
 }
 
 void intel_context_active_release(struct intel_context *ce)