drm/i915/gt: Mark ring->vma as active while pinned

As we use the active state to keep the vma alive while we are reading
its contents during GPU error capture, we need to mark the
ring->vma as active during execution if we want to include the rinbuffer
in the error state.
Reported-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: b1e3177b ("drm/i915: Coordinate i915_active with its own mutex")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200110110402.1231745-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_context.c

@@ -185,6 +185,31 @@ static void __context_unpin_state(struct i915_vma *vma)
 	__i915_vma_unpin(vma);
 }
 
+static int __ring_active(struct intel_ring *ring)
+{
+	int err;
+
+	err = i915_active_acquire(&ring->vma->active);
+	if (err)
+		return err;
+
+	err = intel_ring_pin(ring);
+	if (err)
+		goto err_active;
+
+	return 0;
+
+err_active:
+	i915_active_release(&ring->vma->active);
+	return err;
+}
+
+static void __ring_retire(struct intel_ring *ring)
+{
+	intel_ring_unpin(ring);
+	i915_active_release(&ring->vma->active);
+}
+
 __i915_active_call
 static void __intel_context_retire(struct i915_active *active)
 {
@@ -197,7 +222,7 @@ static void __intel_context_retire(struct i915_active *active)
 		__context_unpin_state(ce->state);
 
 	intel_timeline_unpin(ce->timeline);
-	intel_ring_unpin(ce->ring);
+	__ring_retire(ce->ring);
 
 	intel_context_put(ce);
 }
@@ -211,7 +236,7 @@ static int __intel_context_active(struct i915_active *active)
 
 	intel_context_get(ce);
 
-	err = intel_ring_pin(ce->ring);
+	err = __ring_active(ce->ring);
 	if (err)
 		goto err_put;
 
@@ -231,7 +256,7 @@ static int __intel_context_active(struct i915_active *active)
 err_timeline:
 	intel_timeline_unpin(ce->timeline);
 err_ring:
-	intel_ring_unpin(ce->ring);
+	__ring_retire(ce->ring);
 err_put:
 	intel_context_put(ce);
 	return err;