drm/i915: Avoid overflow in computing pot_hole loop termination

When using the mock_ppgtt selftest, the GTT is large enough to cause an
overflow in pot_hole() when adding 2 pages to the address. Avoid the
overflow by computing the final valid address and iterating up to that
address.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170214092344.12330-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
index 5af9339087b7c27a773864faa57ea5c25fdc609b..468f0992db39b071c66fde525436a4948e8a4027 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
@@ -615,7 +615,7 @@ static int pot_hole(struct drm_i915_private *i915,
                u64 addr;
 
                for (addr = round_up(hole_start + I915_GTT_PAGE_SIZE, step) - I915_GTT_PAGE_SIZE;
-                    addr + vma->size <= hole_end;
+                    addr <= round_down(hole_end - 2*I915_GTT_PAGE_SIZE, step) - I915_GTT_PAGE_SIZE;
                     addr += step) {
                        err = i915_vma_pin(vma, 0, 0, addr | flags);
                        if (err) {