drm/i915: Fix 32b overflow check in gen8_ppgtt_alloc_page_directories

The patch 69876bed7e008f5fe01538a2d47c09f2862129d0: "drm/i915/gen8:
page directories rework allocation" added an overflow warning, but the
mask had an extra 0. Use less typo-prone option suggested by Dave
instead, to check for (start + length) >= 0x100000000ULL.

This check will be unnecessary after gen8_alloc_va_range handles more
than 4 PDPs (48b addressing).

v2: Really check for 32b overflow (Ville)

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index ce91314f2c0c9ebde82e0dc98c1fc680ab73d774..8fee6789fae2dbc3d95af7ec14ca26014f6d29bf 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -756,8 +756,8 @@ static int gen8_ppgtt_alloc_page_directories(struct i915_hw_ppgtt *ppgtt,
 
        WARN_ON(!bitmap_empty(new_pds, GEN8_LEGACY_PDPES));
 
-       /* FIXME: PPGTT container_of won't work for 64b */
-       WARN_ON((start + length) > 0x800000000ULL);
+       /* FIXME: upper bound must not overflow 32 bits  */
+       WARN_ON((start + length) >= (1ULL << 32));
 
        gen8_for_each_pdpe(pd, pdp, start, length, temp, pdpe) {
                if (pd)