[Intel-gfx] [PATCH] drm/i915: Fix pages pin counting around swizzle quirk

[Chris Wilson]

commit bc0629a76726 ("drm/i915: Track pages pinned due to swizzling
quirk") fixed one problem, but revealed a whole lot more. The root cause
of the pin count mismatch for the swizzle quirk (for L-shaped memory on
gen3/4) was that we were incrementing the pages_pin_count upon getting
the backing pages but then overwriting the pages_pin_count to set it to
1 afterwards. With a little bit of adjustment to satisfy the GEM_BUG_ON
sanitychecks, the fix is to replace the explicit atomic_set with an
atomic_inc.

Fixes: 1233e2db199d ("drm/i915: Move object backing storage manipulation")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c        | 40 ++++++++++++++++++----------------
 drivers/gpu/drm/i915/i915_gem_gtt.c    |  1 +
 drivers/gpu/drm/i915/i915_gem_tiling.c |  1 +
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 993fb90da104..5fe7562aefbd 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2386,12 +2386,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	if (i915_gem_object_needs_bit17_swizzle(obj))
 		i915_gem_object_do_bit_17_swizzle(obj, st);
 
-	if (i915_gem_object_is_tiled(obj) &&
-	    dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
-		__i915_gem_object_pin_pages(obj);
-		obj->mm.quirked = true;
-	}
-
 	return st;
 
 err_pages:
@@ -2424,6 +2418,13 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 	obj->mm.get_page.sg_idx = 0;
 
 	obj->mm.pages = pages;
+
+	if (i915_gem_object_is_tiled(obj) &&
+	    to_i915(obj->base.dev)->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
+		GEM_BUG_ON(obj->mm.quirked);
+		__i915_gem_object_pin_pages(obj);
+		obj->mm.quirked = true;
+	}
 }
 
 static int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
@@ -2458,17 +2459,16 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	if (err)
 		return err;
 
-	if (likely(obj->mm.pages)) {
-		__i915_gem_object_pin_pages(obj);
-		goto unlock;
-	}
-
-	GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
+	if (unlikely(!obj->mm.pages)) {
+		GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
+		err = ____i915_gem_object_get_pages(obj);
+		if (err)
+			goto unlock;
 
-	err = ____i915_gem_object_get_pages(obj);
-	if (!err)
-		atomic_set_release(&obj->mm.pages_pin_count, 1);
+		smp_mb__before_atomic();
+	}
 
+	__i915_gem_object_pin_pages(obj);
 unlock:
 	mutex_unlock(&obj->mm.lock);
 	return err;
@@ -2542,8 +2542,8 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 		if (ret)
 			goto err_unlock;
 
-		GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count));
-		atomic_set_release(&obj->mm.pages_pin_count, 1);
+		smp_mb__before_atomic();
+		__i915_gem_object_pin_pages(obj);
 		pinned = false;
 	}
 	GEM_BUG_ON(!obj->mm.pages);
@@ -2578,7 +2578,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 	return ptr;
 
 err_unpin:
-	atomic_dec(&obj->mm.pages_pin_count);
+	__i915_gem_object_unpin_pages(obj);
 err_unlock:
 	ptr = ERR_PTR(ret);
 	goto out_unlock;
@@ -2996,7 +2996,7 @@ int i915_vma_unbind(struct i915_vma *vma)
 		goto destroy;
 
 	GEM_BUG_ON(obj->bind_count == 0);
-	GEM_BUG_ON(!obj->mm.pages);
+	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
 
 	if (i915_vma_is_map_and_fenceable(vma)) {
 		/* release the fence reg _after_ flushing */
@@ -3230,6 +3230,7 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 	list_move_tail(&obj->global_list, &dev_priv->mm.bound_list);
 	list_move_tail(&vma->vm_link, &vma->vm->inactive_list);
 	obj->bind_count++;
+	GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count) < obj->bind_count);
 
 	return 0;
 
@@ -4282,6 +4283,7 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 			obj->mm.quirked = false;
 		}
 		if (args->madv == I915_MADV_WILLNEED) {
+			GEM_BUG_ON(obj->mm.quirked);
 			__i915_gem_object_pin_pages(obj);
 			obj->mm.quirked = true;
 		}
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index dfc40f16f149..4dc1a463ef4c 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3707,6 +3707,7 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
 {
 	int ret = 0;
 
+	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(vma->obj));
 	if (vma->pages)
 		return 0;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 1577e7810cd6..251d51b01174 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -269,6 +269,7 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
 					obj->mm.quirked = false;
 				}
 				if (!i915_gem_object_is_tiled(obj)) {
+					GEM_BUG_ON(!obj->mm.quirked);
 					__i915_gem_object_pin_pages(obj);
 					obj->mm.quirked = true;
 				}
-- 
2.10.2