drm/i915: Fix pages pin counting around swizzle quirk

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.

v2: Consistently use atomics (not mix atomics and helpers) within the
lowlevel get_pages routines. This makes the atomic operations much
clearer.

Fixes: 1233e2db199d ("drm/i915: Move object backing storage manipulation")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161104103001.27643-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1f995ce..0dbf38c 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2324,12 +2324,6 @@ 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:
@@ -2362,12 +2356,21 @@ 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)
 {
        struct sg_table *pages;
 
+       GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
+
        if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
                DRM_DEBUG("Attempting to obtain a purgeable object\n");
                return -EFAULT;
@@ -2396,16 +2399,14 @@ 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;
-       }
+       if (unlikely(!obj->mm.pages)) {
+               err = ____i915_gem_object_get_pages(obj);
+               if (err)
+                       goto unlock;
 
-       GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
-
-       err = ____i915_gem_object_get_pages(obj);
-       if (!err)
-               atomic_set_release(&obj->mm.pages_pin_count, 1);
+               smp_mb__before_atomic();
+       }
+       atomic_inc(&obj->mm.pages_pin_count);
 
 unlock:
        mutex_unlock(&obj->mm.lock);
@@ -2476,12 +2477,14 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 
        pinned = true;
        if (!atomic_inc_not_zero(&obj->mm.pages_pin_count)) {
-               ret = ____i915_gem_object_get_pages(obj);
-               if (ret)
-                       goto err_unlock;
+               if (unlikely(!obj->mm.pages)) {
+                       ret = ____i915_gem_object_get_pages(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();
+               }
+               atomic_inc(&obj->mm.pages_pin_count);
                pinned = false;
        }
        GEM_BUG_ON(!obj->mm.pages);
@@ -2933,7 +2936,7 @@ 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 */
@@ -3167,6 +3170,7 @@ search_free:
        list_move_tail(&obj->global_link, &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;
 
@@ -4100,6 +4104,7 @@ 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 cad6de6..7531bca 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3711,6 +3711,13 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
 {
        int ret = 0;
 
+       /* The vma->pages are only valid within the lifespan of the borrowed
+        * obj->mm.pages. When the obj->mm.pages sg_table is regenerated, so
+        * must be the vma->pages. A simple rule is that vma->pages must only
+        * be accessed when the obj->mm.pages are pinned.
+        */
+       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 1577e78..251d51b 100644 (file)
--- 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;
                                }