drm/i915: Take reservation lock around i915_vma_pin.

We previously complained when ww == NULL.

This function is now only used in selftests to pin an object,
and ww locking is now fixed.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
[danvet: Resolve conflict because we don't have a set-domain refactor,
see
https://lore.kernel.org/intel-gfx/20210203090205.25818-8-chris@chris-wilson.co.uk/

The really worrying thing here is that the above patch had a change in
arguments for i915_gem_object_set_to_gtt_domain(), without any
explanation. I decided to just faithfully apply Maarten's change but
not the argument change which was in Maarten's context diff.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210323155059.628690-26-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c

@@ -200,17 +200,15 @@ static int gpu_set(struct context *ctx, unsigned long offset, u32 v)
 	u32 *cs;
 	int err;
 
+	vma = i915_gem_object_ggtt_pin(ctx->obj, NULL, 0, 0, 0);
+	if (IS_ERR(vma))
+		return PTR_ERR(vma);
+
 	i915_gem_object_lock(ctx->obj, NULL);
 	err = i915_gem_object_set_to_gtt_domain(ctx->obj, true);
 	if (err)
 		goto out_unlock;
 
-	vma = i915_gem_object_ggtt_pin(ctx->obj, NULL, 0, 0, 0);
-	if (IS_ERR(vma)) {
-		err = PTR_ERR(vma);
-		goto out_unlock;
-	}
-
 	rq = intel_engine_create_kernel_request(ctx->engine);
 	if (IS_ERR(rq)) {
 		err = PTR_ERR(rq);

drivers/gpu/drm/i915/i915_gem.c

@@ -928,7 +928,11 @@ i915_gem_object_ggtt_pin_ww(struct drm_i915_gem_object *obj,
 			return ERR_PTR(ret);
 	}
 
-	ret = i915_vma_pin_ww(vma, ww, size, alignment, flags | PIN_GLOBAL);
+	if (ww)
+		ret = i915_vma_pin_ww(vma, ww, size, alignment, flags | PIN_GLOBAL);
+	else
+		ret = i915_vma_pin(vma, size, alignment, flags | PIN_GLOBAL);
+
 	if (ret)
 		return ERR_PTR(ret);
 

drivers/gpu/drm/i915/i915_vma.c

@@ -863,9 +863,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 	int err;
 
 #ifdef CONFIG_PROVE_LOCKING
-	if (debug_locks && lockdep_is_held(&vma->vm->i915->drm.struct_mutex))
-		WARN_ON(!ww);
-	if (debug_locks && ww && vma->resv)
+	if (debug_locks && !WARN_ON(!ww) && vma->resv)
 		assert_vma_held(vma);
 #endif
 

drivers/gpu/drm/i915/i915_vma.h

@@ -246,10 +246,22 @@ i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,
 static inline int __must_check
 i915_vma_pin(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 {
-#ifdef CONFIG_LOCKDEP
-	WARN_ON_ONCE(vma->resv && dma_resv_held(vma->resv));
-#endif
-	return i915_vma_pin_ww(vma, NULL, size, alignment, flags);
+	struct i915_gem_ww_ctx ww;
+	int err;
+
+	i915_gem_ww_ctx_init(&ww, true);
+retry:
+	err = i915_gem_object_lock(vma->obj, &ww);
+	if (!err)
+		err = i915_vma_pin_ww(vma, &ww, size, alignment, flags);
+	if (err == -EDEADLK) {
+		err = i915_gem_ww_ctx_backoff(&ww);
+		if (!err)
+			goto retry;
+	}
+	i915_gem_ww_ctx_fini(&ww);
+
+	return err;
 }
 
 int i915_ggtt_pin(struct i915_vma *vma, struct i915_gem_ww_ctx *ww,