drm/i915/gt: Make deferred context allocation explicit

Refactor the backends to handle the deferred context allocation in a
consistent manner, and allow calling it as an explicit first step in
pinning a context for the first time. This should make it easier for
backends to keep track of partially constructed contexts from
initialisation.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190809182518.20486-2-chris@chris-wilson.co.uk

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

@@ -53,6 +53,14 @@ int __intel_context_do_pin(struct intel_context *ce)
 	if (likely(!atomic_read(&ce->pin_count))) {
 		intel_wakeref_t wakeref;
 
+		if (unlikely(!test_bit(CONTEXT_ALLOC_BIT, &ce->flags))) {
+			err = ce->ops->alloc(ce);
+			if (unlikely(err))
+				goto err;
+
+			__set_bit(CONTEXT_ALLOC_BIT, &ce->flags);
+		}
+
 		err = 0;
 		with_intel_runtime_pm(&ce->engine->i915->runtime_pm, wakeref)
 			err = ce->ops->pin(ce);

drivers/gpu/drm/i915/gt/intel_context_types.h

@@ -23,6 +23,8 @@ struct intel_context;
 struct intel_ring;
 
 struct intel_context_ops {
+	int (*alloc)(struct intel_context *ce);
+
 	int (*pin)(struct intel_context *ce);
 	void (*unpin)(struct intel_context *ce);
 
@@ -52,6 +54,9 @@ struct intel_context {
 	struct i915_vma *state;
 	struct intel_ring *ring;
 
+	unsigned long flags;
+#define CONTEXT_ALLOC_BIT 0
+
 	u32 *lrc_reg_state;
 	u64 lrc_desc;
 

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

@@ -219,8 +219,9 @@ static struct virtual_engine *to_virtual_engine(struct intel_engine_cs *engine)
 	return container_of(engine, struct virtual_engine, base);
 }
 
-static int execlists_context_deferred_alloc(struct intel_context *ce,
+static int __execlists_context_alloc(struct intel_context *ce,
 				     struct intel_engine_cs *engine);
+
 static void execlists_init_reg_state(u32 *reg_state,
 				     struct intel_context *ce,
 				     struct intel_engine_cs *engine,
@@ -1614,9 +1615,6 @@ __execlists_context_pin(struct intel_context *ce,
 	void *vaddr;
 	int ret;
 
-	ret = execlists_context_deferred_alloc(ce, engine);
-	if (ret)
-		goto err;
 	GEM_BUG_ON(!ce->state);
 
 	ret = intel_context_active_acquire(ce);
@@ -1655,6 +1653,11 @@ static int execlists_context_pin(struct intel_context *ce)
 	return __execlists_context_pin(ce, ce->engine);
 }
 
+static int execlists_context_alloc(struct intel_context *ce)
+{
+	return __execlists_context_alloc(ce, ce->engine);
+}
+
 static void execlists_context_reset(struct intel_context *ce)
 {
 	/*
@@ -1678,6 +1681,8 @@ static void execlists_context_reset(struct intel_context *ce)
 }
 
 static const struct intel_context_ops execlists_context_ops = {
+	.alloc = execlists_context_alloc,
+
 	.pin = execlists_context_pin,
 	.unpin = execlists_context_unpin,
 
@@ -3075,7 +3080,7 @@ get_timeline(struct i915_gem_context *ctx, struct intel_gt *gt)
 		return intel_timeline_create(gt, NULL);
 }
 
-static int execlists_context_deferred_alloc(struct intel_context *ce,
+static int __execlists_context_alloc(struct intel_context *ce,
 				     struct intel_engine_cs *engine)
 {
 	struct drm_i915_gem_object *ctx_obj;
@@ -3085,9 +3090,7 @@ static int execlists_context_deferred_alloc(struct intel_context *ce,
 	struct intel_timeline *timeline;
 	int ret;
 
-	if (ce->state)
-		return 0;
-
+	GEM_BUG_ON(ce->state);
 	context_size = round_up(engine->context_size, I915_GTT_PAGE_SIZE);
 
 	/*
@@ -3533,6 +3536,12 @@ intel_execlists_create_virtual(struct i915_gem_context *ctx,
 
 	ve->base.flags |= I915_ENGINE_IS_VIRTUAL;
 
+	err = __execlists_context_alloc(&ve->context, siblings[0]);
+	if (err)
+		goto err_put;
+
+	__set_bit(CONTEXT_ALLOC_BIT, &ve->context.flags);
+
 	return &ve->context;
 
 err_put:

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

@@ -1480,16 +1480,16 @@ alloc_context_vma(struct intel_engine_cs *engine)
 	return ERR_PTR(err);
 }
 
-static int ring_context_pin(struct intel_context *ce)
+static int ring_context_alloc(struct intel_context *ce)
 {
 	struct intel_engine_cs *engine = ce->engine;
-	int err;
 
 	/* One ringbuffer to rule them all */
 	GEM_BUG_ON(!engine->buffer);
 	ce->ring = engine->buffer;
 
-	if (!ce->state && engine->context_size) {
+	GEM_BUG_ON(ce->state);
+	if (engine->context_size) {
 		struct i915_vma *vma;
 
 		vma = alloc_context_vma(engine);
@@ -1499,6 +1499,13 @@ static int ring_context_pin(struct intel_context *ce)
 		ce->state = vma;
 	}
 
+	return 0;
+}
+
+static int ring_context_pin(struct intel_context *ce)
+{
+	int err;
+
 	err = intel_context_active_acquire(ce);
 	if (err)
 		return err;
@@ -1520,6 +1527,8 @@ static void ring_context_reset(struct intel_context *ce)
 }
 
 static const struct intel_context_ops ring_context_ops = {
+	.alloc = ring_context_alloc,
+
 	.pin = ring_context_pin,
 	.unpin = ring_context_unpin,
 

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

@@ -147,15 +147,18 @@ static void mock_context_destroy(struct kref *ref)
 	intel_context_free(ce);
 }
 
-static int mock_context_pin(struct intel_context *ce)
+static int mock_context_alloc(struct intel_context *ce)
 {
-	int ret;
-
-	if (!ce->ring) {
 	ce->ring = mock_ring(ce->engine);
 	if (!ce->ring)
 		return -ENOMEM;
-	}
+
+	return 0;
+}
+
+static int mock_context_pin(struct intel_context *ce)
+{
+	int ret;
 
 	ret = intel_context_active_acquire(ce);
 	if (ret)
@@ -166,6 +169,8 @@ static int mock_context_pin(struct intel_context *ce)
 }
 
 static const struct intel_context_ops mock_context_ops = {
+	.alloc = mock_context_alloc,
+
 	.pin = mock_context_pin,
 	.unpin = mock_context_unpin,