1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/gma500/gtt.c b/drivers/gpu/drm/gma500/gtt.c
index db2e823e8951..54e5c9e1e6fa 100644
--- a/drivers/gpu/drm/gma500/gtt.c
+++ b/drivers/gpu/drm/gma500/gtt.c
@@ -39,6 +39,10 @@ static inline uint32_t psb_gtt_mask_pte(uint32_t pfn, int type)
 {
         uint32_t mask = PSB_PTE_VALID;
 
+        /* Ensure we explode rather than put an invalid low mapping of
+           a high mapping page into the gtt */
+        BUG_ON(pfn & ~(0xFFFFFFFF >> PAGE_SHIFT));
+
         if (type & PSB_MMU_CACHED_MEMORY)
                 mask |= PSB_PTE_CACHED;
         if (type & PSB_MMU_RO_MEMORY)