drm/i915/selftests: add sanity selftest for huge-GTT-pages

Now that for all the relevant backends we do randomised testing, we need
to make sure we still sanity check the obvious cases that might blow up,
such that introducing a temporary regression is less likely.  Also
rather than do this for every backend, just limit to our two memory
types: system and local.

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191025153728.23689-7-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/selftests/huge_pages.c

@@ -1342,6 +1342,12 @@ igt_create_internal(struct drm_i915_private *i915, u32 size, u32 flags)
 	return i915_gem_object_create_internal(i915, size);
 }
 
+static struct drm_i915_gem_object *
+igt_create_system(struct drm_i915_private *i915, u32 size, u32 flags)
+{
+	return huge_pages_object(i915, size, size);
+}
+
 static struct drm_i915_gem_object *
 igt_create_local(struct drm_i915_private *i915, u32 size, u32 flags)
 {
@@ -1452,6 +1458,98 @@ static int igt_ppgtt_smoke_huge(void *arg)
 	return err;
 }
 
+static int igt_ppgtt_sanity_check(void *arg)
+{
+	struct i915_gem_context *ctx = arg;
+	struct drm_i915_private *i915 = ctx->i915;
+	unsigned int supported = INTEL_INFO(i915)->page_sizes;
+	struct {
+		igt_create_fn fn;
+		unsigned int flags;
+	} backends[] = {
+		{ igt_create_system, 0,                        },
+		{ igt_create_local,  I915_BO_ALLOC_CONTIGUOUS, },
+	};
+	struct {
+		u32 size;
+		u32 pages;
+	} combos[] = {
+		{ SZ_64K,		SZ_64K		},
+		{ SZ_2M,		SZ_2M		},
+		{ SZ_2M,		SZ_64K		},
+		{ SZ_2M - SZ_64K,	SZ_64K		},
+		{ SZ_2M - SZ_4K,	SZ_64K | SZ_4K	},
+		{ SZ_2M + SZ_4K,	SZ_64K | SZ_4K	},
+		{ SZ_2M + SZ_4K,	SZ_2M  | SZ_4K	},
+		{ SZ_2M + SZ_64K,	SZ_2M  | SZ_64K },
+	};
+	int i, j;
+	int err;
+
+	if (supported == I915_GTT_PAGE_SIZE_4K)
+		return 0;
+
+	/*
+	 * Sanity check that the HW behaves with a limited set of combinations.
+	 * We already have a bunch of randomised testing, which should give us
+	 * a decent amount of variation between runs, however we should keep
+	 * this to limit the chances of introducing a temporary regression, by
+	 * testing the most obvious cases that might make something blow up.
+	 */
+
+	for (i = 0; i < ARRAY_SIZE(backends); ++i) {
+		for (j = 0; j < ARRAY_SIZE(combos); ++j) {
+			struct drm_i915_gem_object *obj;
+			u32 size = combos[j].size;
+			u32 pages = combos[j].pages;
+
+			obj = backends[i].fn(i915, size, backends[i].flags);
+			if (IS_ERR(obj)) {
+				err = PTR_ERR(obj);
+				if (err == -ENODEV) {
+					pr_info("Device lacks local memory, skipping\n");
+					err = 0;
+					break;
+				}
+
+				return err;
+			}
+
+			err = i915_gem_object_pin_pages(obj);
+			if (err) {
+				i915_gem_object_put(obj);
+				goto out;
+			}
+
+			GEM_BUG_ON(pages > obj->base.size);
+			pages = pages & supported;
+
+			if (pages)
+				obj->mm.page_sizes.sg = pages;
+
+			err = igt_write_huge(ctx, obj);
+
+			i915_gem_object_unpin_pages(obj);
+			__i915_gem_object_put_pages(obj, I915_MM_NORMAL);
+			i915_gem_object_put(obj);
+
+			if (err) {
+				pr_err("%s write-huge failed with size=%u pages=%u i=%d, j=%d\n",
+				       __func__, size, pages, i, j);
+				goto out;
+			}
+		}
+
+		cond_resched();
+	}
+
+out:
+	if (err == -ENOMEM)
+		err = 0;
+
+	return err;
+}
+
 static int igt_ppgtt_pin_update(void *arg)
 {
 	struct i915_gem_context *ctx = arg;
@@ -1812,6 +1910,7 @@ int i915_gem_huge_page_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(igt_tmpfs_fallback),
 		SUBTEST(igt_ppgtt_exhaust_huge),
 		SUBTEST(igt_ppgtt_smoke_huge),
+		SUBTEST(igt_ppgtt_sanity_check),
 	};
 	struct drm_file *file;
 	struct i915_gem_context *ctx;