[Intel-gfx] [PATCH] drm/i915: Allow i915_gem_object_get_page() on userptr as well

[Chris Wilson]

commit 033908aed5a596f6202c848c6bbc8a40fb1a8490
Author: Dave Gordon <david.s.gordon at intel.com>
Date:   Thu Dec 10 18:51:23 2015 +0000

    drm/i915: mark GEM object pages dirty when mapped & written by the CPU

introduced a check into i915_gem_object_get_dirty_pages() that returned
a NULL pointer when called with a bad object, one that was not backed by
shmemfs. This WARN was too strict as we can work on all struct page
backed objects, and resulted in a WARN + GPF for existing userspace. In
order to differentiate the various types of objects, add a new flags field
to the i915_gem_object_ops struct to describe their capabilities, with
the first flag being whether the object has struct pages.

Reported-by: Kristian Høgsberg Kristensen <krh at bitplanet.net>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Dave Gordon <david.s.gordon at intel.com>
Cc: Kristian Høgsberg Kristensen <krh at bitplanet.net>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_drv.h         | 4 ++++
 drivers/gpu/drm/i915/i915_gem.c         | 3 ++-
 drivers/gpu/drm/i915/i915_gem_userptr.c | 3 ++-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 104bd1809936..e6ad06c5c2f5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1994,6 +1994,9 @@ enum hdmi_force_audio {
 #define I915_GTT_OFFSET_NONE ((u32)-1)
 
 struct drm_i915_gem_object_ops {
+	const unsigned int flags;
+#define I915_GEM_OBJECT_HAS_STRUCT_PAGE 0x1
+
 	/* Interface between the GEM object and its backing storage.
 	 * get_pages() is called once prior to the use of the associated set
 	 * of pages before to binding them into the GTT, and put_pages() is
@@ -2009,6 +2012,7 @@ struct drm_i915_gem_object_ops {
 	 */
 	int (*get_pages)(struct drm_i915_gem_object *);
 	void (*put_pages)(struct drm_i915_gem_object *);
+
 	int (*dmabuf_export)(struct drm_i915_gem_object *);
 	void (*release)(struct drm_i915_gem_object *);
 };
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ddc21d4b388d..bb44bad15403 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4425,6 +4425,7 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_object_ops = {
+	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
 	.get_pages = i915_gem_object_get_pages_gtt,
 	.put_pages = i915_gem_object_put_pages_gtt,
 };
@@ -5261,7 +5262,7 @@ i915_gem_object_get_dirty_page(struct drm_i915_gem_object *obj, int n)
 	struct page *page;
 
 	/* Only default objects have per-page dirty tracking */
-	if (WARN_ON(obj->ops != &i915_gem_object_ops))
+	if (WARN_ON((obj->ops->flags & I915_GEM_OBJECT_HAS_STRUCT_PAGE) == 0))
 		return NULL;
 
 	page = i915_gem_object_get_page(obj, n);
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 19fb0bddc1cd..59e45b3a6937 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -789,9 +789,10 @@ i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj)
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
-	.dmabuf_export = i915_gem_userptr_dmabuf_export,
+	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
 	.get_pages = i915_gem_userptr_get_pages,
 	.put_pages = i915_gem_userptr_put_pages,
+	.dmabuf_export = i915_gem_userptr_dmabuf_export,
 	.release = i915_gem_userptr_release,
 };
 
-- 
2.7.0.rc3