drm/i915: Compare user's 64b GTT offset even on 32b

Beware mixing unsigned long constants and 64b values, as on 32b the
constant will be zero extended and discard the high 32b when used as
a mask!

Reported-by: Sergii Romantsov <sergii.romantsov@globallogic.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108282
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181025091823.20571-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gvt/gtt.h

@@ -35,7 +35,6 @@
 #define _GVT_GTT_H_
 
 #define I915_GTT_PAGE_SHIFT         12
-#define I915_GTT_PAGE_MASK		(~(I915_GTT_PAGE_SIZE - 1))
 
 struct intel_vgpu_mm;
 

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -460,7 +460,7 @@ eb_validate_vma(struct i915_execbuffer *eb,
 	 * any non-page-aligned or non-canonical addresses.
 	 */
 	if (unlikely(entry->flags & EXEC_OBJECT_PINNED &&
-		     entry->offset != gen8_canonical_addr(entry->offset & PAGE_MASK)))
+		     entry->offset != gen8_canonical_addr(entry->offset & I915_GTT_PAGE_MASK)))
 		return -EINVAL;
 
 	/* pad_to_size was once a reserved field, so sanitize it */

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -49,6 +49,8 @@
 #define I915_GTT_PAGE_SIZE I915_GTT_PAGE_SIZE_4K
 #define I915_GTT_MAX_PAGE_SIZE I915_GTT_PAGE_SIZE_2M
 
+#define I915_GTT_PAGE_MASK -I915_GTT_PAGE_SIZE
+
 #define I915_GTT_MIN_ALIGNMENT I915_GTT_PAGE_SIZE
 
 #define I915_FENCE_REG_NONE -1