drm/i915/ttm: fix sg_table construction

If we encounter some monster sized local-memory page that exceeds the
maximum sg length (UINT32_MAX), ensure that don't end up with some
misaligned address in the entry that follows, leading to fireworks
later. Also ensure we have some coverage of this in the selftests.

v2(Chris):
  - Use round_down consistently to avoid udiv errors
v3(Nirmoy):
  - Also update the max_segment in the selftest

Fixes: f701b16d4cc5 ("drm/i915/ttm: add i915_sg_from_buddy_resource")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6379
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Nirmoy Das <nirmoy.das@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220711085859.24198-1-matthew.auld@intel.com

2 files changed, 21 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
index 73eb53edb8de..3b18e5905c86 100644
--- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
@@ -451,7 +451,6 @@ out_put:
 
 static int igt_mock_max_segment(void *arg)
 {
-	const unsigned int max_segment = rounddown(UINT_MAX, PAGE_SIZE);
 	struct intel_memory_region *mem = arg;
 	struct drm_i915_private *i915 = mem->i915;
 	struct i915_ttm_buddy_resource *res;
@@ -460,7 +459,10 @@ static int igt_mock_max_segment(void *arg)
 	struct drm_buddy *mm;
 	struct list_head *blocks;
 	struct scatterlist *sg;
+	I915_RND_STATE(prng);
 	LIST_HEAD(objects);
+	unsigned int max_segment;
+	unsigned int ps;
 	u64 size;
 	int err = 0;
 
@@ -472,7 +474,13 @@ static int igt_mock_max_segment(void *arg)
 	 */
 
 	size = SZ_8G;
-	mem = mock_region_create(i915, 0, size, PAGE_SIZE, 0, 0);
+	ps = PAGE_SIZE;
+	if (i915_prandom_u64_state(&prng) & 1)
+		ps = SZ_64K; /* For something like DG2 */
+
+	max_segment = round_down(UINT_MAX, ps);
+
+	mem = mock_region_create(i915, 0, size, ps, 0, 0);
 	if (IS_ERR(mem))
 		return PTR_ERR(mem);
 
@@ -498,12 +506,21 @@ static int igt_mock_max_segment(void *arg)
 	}
 
 	for (sg = obj->mm.pages->sgl; sg; sg = sg_next(sg)) {
+		dma_addr_t daddr = sg_dma_address(sg);
+
 		if (sg->length > max_segment) {
 			pr_err("%s: Created an oversized scatterlist entry, %u > %u\n",
 			       __func__, sg->length, max_segment);
 			err = -EINVAL;
 			goto out_close;
 		}
+
+		if (!IS_ALIGNED(daddr, ps)) {
+			pr_err("%s: Created an unaligned scatterlist entry, addr=%pa, ps=%u\n",
+			       __func__,  &daddr, ps);
+			err = -EINVAL;
+			goto out_close;
+		}
 	}
 
 out_close:
diff --git a/drivers/gpu/drm/i915/selftests/mock_region.c b/drivers/gpu/drm/i915/selftests/mock_region.c
index 670557ce1024..bac21fe84ca5 100644
--- a/drivers/gpu/drm/i915/selftests/mock_region.c
+++ b/drivers/gpu/drm/i915/selftests/mock_region.c
@@ -33,7 +33,8 @@ static int mock_region_get_pages(struct drm_i915_gem_object *obj)
 		return PTR_ERR(obj->mm.res);
 
 	obj->mm.rsgt = intel_region_ttm_resource_to_rsgt(obj->mm.region,
-							 obj->mm.res);
+							 obj->mm.res,
+							 obj->mm.region->min_page_size);
 	if (IS_ERR(obj->mm.rsgt)) {
 		err = PTR_ERR(obj->mm.rsgt);
 		goto err_free_resource;