drm/i915: Create a full object for mock_ring, v2.

This allows us to finally get rid of all the assumptions that vma->obj
is NULL.

Changes since v1:
- Ensure the mock_ring vma is pinned to prevent a fault.
- Pin it high to avoid failure in evict_for_vma selftest.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211117142024.1043017-3-matthew.auld@intel.com

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

@@ -35,9 +35,31 @@ static void mock_timeline_unpin(struct intel_timeline *tl)
 	atomic_dec(&tl->pin_count);
 }
 
+static struct i915_vma *create_ring_vma(struct i915_ggtt *ggtt, int size)
+{
+	struct i915_address_space *vm = &ggtt->vm;
+	struct drm_i915_private *i915 = vm->i915;
+	struct drm_i915_gem_object *obj;
+	struct i915_vma *vma;
+
+	obj = i915_gem_object_create_internal(i915, size);
+	if (IS_ERR(obj))
+		return ERR_CAST(obj);
+
+	vma = i915_vma_instance(obj, vm, NULL);
+	if (IS_ERR(vma))
+		goto err;
+
+	return vma;
+
+err:
+	i915_gem_object_put(obj);
+	return vma;
+}
+
 static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 {
-	const unsigned long sz = PAGE_SIZE / 2;
+	const unsigned long sz = PAGE_SIZE;
 	struct intel_ring *ring;
 
 	ring = kzalloc(sizeof(*ring) + sz, GFP_KERNEL);
@@ -50,15 +72,11 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 	ring->vaddr = (void *)(ring + 1);
 	atomic_set(&ring->pin_count, 1);
 
-	ring->vma = i915_vma_alloc();
-	if (!ring->vma) {
+	ring->vma = create_ring_vma(engine->gt->ggtt, PAGE_SIZE);
+	if (IS_ERR(ring->vma)) {
 		kfree(ring);
 		return NULL;
 	}
-	i915_active_init(&ring->vma->active, NULL, NULL, 0);
-	__set_bit(I915_VMA_GGTT_BIT, __i915_vma_flags(ring->vma));
-	__set_bit(DRM_MM_NODE_ALLOCATED_BIT, &ring->vma->node.flags);
-	ring->vma->node.size = sz;
 
 	intel_ring_update_space(ring);
 
@@ -67,8 +85,7 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 
 static void mock_ring_free(struct intel_ring *ring)
 {
-	i915_active_fini(&ring->vma->active);
-	i915_vma_free(ring->vma);
+	i915_vma_put(ring->vma);
 
 	kfree(ring);
 }
@@ -125,6 +142,7 @@ static void mock_context_unpin(struct intel_context *ce)
 
 static void mock_context_post_unpin(struct intel_context *ce)
 {
+	i915_vma_unpin(ce->ring->vma);
 }
 
 static void mock_context_destroy(struct kref *ref)
@@ -169,7 +187,7 @@ static int mock_context_alloc(struct intel_context *ce)
 static int mock_context_pre_pin(struct intel_context *ce,
 				struct i915_gem_ww_ctx *ww, void **unused)
 {
-	return 0;
+	return i915_vma_pin_ww(ce->ring->vma, ww, 0, 0, PIN_GLOBAL | PIN_HIGH);
 }
 
 static int mock_context_pin(struct intel_context *ce, void *unused)