drm/i915/selftests: Report ENOMEM clearly for an allocation failure

If we can not run the drunk_hole test because we couldn't allocate the
memory for the permutation array (even after we tried trimming the
size), report a clear ENOMEM. Similary, if we are asked to operate on a
hole too small for ourselves, make it skip quietly.

v2: Avoid malloc(0) since that returns ZERO_SIZE_PTR not NULL.
v3: Fixup similar construction for lowlevel_hole
v4: Use u64 >> 1 to avoid 64b div.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171117101732.4335-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171117162945.16390-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
index 3dcf886..6491cf0 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
@@ -216,13 +216,21 @@ static int lowlevel_hole(struct drm_i915_private *i915,
                hole_size = (hole_end - hole_start) >> size;
                if (hole_size > KMALLOC_MAX_SIZE / sizeof(u32))
                        hole_size = KMALLOC_MAX_SIZE / sizeof(u32);
-               count = hole_size;
+               count = hole_size >> 1;
+               if (!count) {
+                       pr_debug("%s: hole is too small [%llx - %llx] >> %d: %lld\n",
+                                __func__, hole_start, hole_end, size, hole_size);
+                       break;
+               }
+
                do {
-                       count >>= 1;
                        order = i915_random_order(count, &prng);
-               } while (!order && count);
-               if (!order)
-                       break;
+                       if (order)
+                               break;
+               } while (count >>= 1);
+               if (!count)
+                       return -ENOMEM;
+               GEM_BUG_ON(!order);
 
                GEM_BUG_ON(count * BIT_ULL(size) > vm->total);
                GEM_BUG_ON(hole_start + count * BIT_ULL(size) > hole_end);
@@ -704,13 +712,21 @@ static int drunk_hole(struct drm_i915_private *i915,
                hole_size = (hole_end - hole_start) >> size;
                if (hole_size > KMALLOC_MAX_SIZE / sizeof(u32))
                        hole_size = KMALLOC_MAX_SIZE / sizeof(u32);
-               count = hole_size;
+               count = hole_size >> 1;
+               if (!count) {
+                       pr_debug("%s: hole is too small [%llx - %llx] >> %d: %lld\n",
+                                __func__, hole_start, hole_end, size, hole_size);
+                       break;
+               }
+
                do {
-                       count >>= 1;
                        order = i915_random_order(count, &prng);
-               } while (!order && count);
-               if (!order)
-                       break;
+                       if (order)
+                               break;
+               } while (count >>= 1);
+               if (!count)
+                       return -ENOMEM;
+               GEM_BUG_ON(!order);
 
                /* Ignore allocation failures (i.e. don't report them as
                 * a test failure) as we are purposefully allocating very