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
(cherry picked from commit bc99f1209f19fefa3ee11e77464ccfae541f4291)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 4c25d9b..d30ebca 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -620,10 +620,15 @@ i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
                         struct ttm_resource *res)
 {
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
+       u64 page_alignment;
 
        if (!i915_ttm_gtt_binds_lmem(res))
                return i915_ttm_tt_get_st(bo->ttm);
 
+       page_alignment = bo->page_alignment << PAGE_SHIFT;
+       if (!page_alignment)
+               page_alignment = obj->mm.region->min_page_size;
+
        /*
         * If CPU mapping differs, we need to add the ttm_tt pages to
         * the resulting st. Might make sense for GGTT.
@@ -634,7 +639,8 @@ i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
                        struct i915_refct_sgt *rsgt;
 
                        rsgt = intel_region_ttm_resource_to_rsgt(obj->mm.region,
-                                                                res);
+                                                                res,
+                                                                page_alignment);
                        if (IS_ERR(rsgt))
                                return rsgt;
 
@@ -643,7 +649,8 @@ i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
                return i915_refct_sgt_get(obj->ttm.cached_io_rsgt);
        }
 
-       return intel_region_ttm_resource_to_rsgt(obj->mm.region, res);
+       return intel_region_ttm_resource_to_rsgt(obj->mm.region, res,
+                                                page_alignment);
 }
 
 static int i915_ttm_truncate(struct drm_i915_gem_object *obj)

diff --git a/drivers/gpu/drm/i915/i915_scatterlist.c b/drivers/gpu/drm/i915/i915_scatterlist.c
index 159571b..f63b50b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_scatterlist.c
+++ b/drivers/gpu/drm/i915/i915_scatterlist.c
@@ -68,6 +68,7 @@ void i915_refct_sgt_init(struct i915_refct_sgt *rsgt, size_t size)
  * drm_mm_node
  * @node: The drm_mm_node.
  * @region_start: An offset to add to the dma addresses of the sg list.
+ * @page_alignment: Required page alignment for each sg entry. Power of two.
  *
  * Create a struct sg_table, initializing it from a struct drm_mm_node,
  * taking a maximum segment length into account, splitting into segments
@@ -77,15 +78,18 @@ void i915_refct_sgt_init(struct i915_refct_sgt *rsgt, size_t size)
  * error code cast to an error pointer on failure.
  */
 struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
-                                             u64 region_start)
+                                             u64 region_start,
+                                             u64 page_alignment)
 {
-       const u64 max_segment = SZ_1G; /* Do we have a limit on this? */
+       const u64 max_segment = round_down(UINT_MAX, page_alignment);
        u64 segment_pages = max_segment >> PAGE_SHIFT;
        u64 block_size, offset, prev_end;
        struct i915_refct_sgt *rsgt;
        struct sg_table *st;
        struct scatterlist *sg;
 
+       GEM_BUG_ON(!max_segment);
+
        rsgt = kmalloc(sizeof(*rsgt), GFP_KERNEL);
        if (!rsgt)
                return ERR_PTR(-ENOMEM);
@@ -112,6 +116,8 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
                                sg = __sg_next(sg);
 
                        sg_dma_address(sg) = region_start + offset;
+                       GEM_BUG_ON(!IS_ALIGNED(sg_dma_address(sg),
+                                              page_alignment));
                        sg_dma_len(sg) = 0;
                        sg->length = 0;
                        st->nents++;
@@ -138,6 +144,7 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
  * i915_buddy_block list
  * @res: The struct i915_ttm_buddy_resource.
  * @region_start: An offset to add to the dma addresses of the sg list.
+ * @page_alignment: Required page alignment for each sg entry. Power of two.
  *
  * Create a struct sg_table, initializing it from struct i915_buddy_block list,
  * taking a maximum segment length into account, splitting into segments
@@ -147,11 +154,12 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
  * error code cast to an error pointer on failure.
  */
 struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
-                                                    u64 region_start)
+                                                    u64 region_start,
+                                                    u64 page_alignment)
 {
        struct i915_ttm_buddy_resource *bman_res = to_ttm_buddy_resource(res);
        const u64 size = res->num_pages << PAGE_SHIFT;
-       const u64 max_segment = rounddown(UINT_MAX, PAGE_SIZE);
+       const u64 max_segment = round_down(UINT_MAX, page_alignment);
        struct drm_buddy *mm = bman_res->mm;
        struct list_head *blocks = &bman_res->blocks;
        struct drm_buddy_block *block;
@@ -161,6 +169,7 @@ struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
        resource_size_t prev_end;
 
        GEM_BUG_ON(list_empty(blocks));
+       GEM_BUG_ON(!max_segment);
 
        rsgt = kmalloc(sizeof(*rsgt), GFP_KERNEL);
        if (!rsgt)
@@ -191,6 +200,8 @@ struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
                                        sg = __sg_next(sg);
 
                                sg_dma_address(sg) = region_start + offset;
+                               GEM_BUG_ON(!IS_ALIGNED(sg_dma_address(sg),
+                                                      page_alignment));
                                sg_dma_len(sg) = 0;
                                sg->length = 0;
                                st->nents++;

diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h
index 12c6a16..b13e4cd 100644 (file)
--- a/drivers/gpu/drm/i915/i915_scatterlist.h
+++ b/drivers/gpu/drm/i915/i915_scatterlist.h
@@ -213,9 +213,11 @@ static inline void __i915_refct_sgt_init(struct i915_refct_sgt *rsgt,
 void i915_refct_sgt_init(struct i915_refct_sgt *rsgt, size_t size);
 
 struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
-                                             u64 region_start);
+                                             u64 region_start,
+                                             u64 page_alignment);
 
 struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
-                                                    u64 region_start);
+                                                    u64 region_start,
+                                                    u64 page_alignment);
 
 #endif

diff --git a/drivers/gpu/drm/i915/intel_region_ttm.c b/drivers/gpu/drm/i915/intel_region_ttm.c
index 62ff774..6873808 100644 (file)
--- a/drivers/gpu/drm/i915/intel_region_ttm.c
+++ b/drivers/gpu/drm/i915/intel_region_ttm.c
@@ -152,6 +152,7 @@ int intel_region_ttm_fini(struct intel_memory_region *mem)
  * Convert an opaque TTM resource manager resource to a refcounted sg_table.
  * @mem: The memory region.
  * @res: The resource manager resource obtained from the TTM resource manager.
+ * @page_alignment: Required page alignment for each sg entry. Power of two.
  *
  * The gem backends typically use sg-tables for operations on the underlying
  * io_memory. So provide a way for the backends to translate the
@@ -161,16 +162,19 @@ int intel_region_ttm_fini(struct intel_memory_region *mem)
  */
 struct i915_refct_sgt *
 intel_region_ttm_resource_to_rsgt(struct intel_memory_region *mem,
-                                 struct ttm_resource *res)
+                                 struct ttm_resource *res,
+                                 u64 page_alignment)
 {
        if (mem->is_range_manager) {
                struct ttm_range_mgr_node *range_node =
                        to_ttm_range_mgr_node(res);
 
                return i915_rsgt_from_mm_node(&range_node->mm_nodes[0],
-                                             mem->region.start);
+                                             mem->region.start,
+                                             page_alignment);
        } else {
-               return i915_rsgt_from_buddy_resource(res, mem->region.start);
+               return i915_rsgt_from_buddy_resource(res, mem->region.start,
+                                                    page_alignment);
        }
 }
 

diff --git a/drivers/gpu/drm/i915/intel_region_ttm.h b/drivers/gpu/drm/i915/intel_region_ttm.h
index cf9d86d..98fba51 100644 (file)
--- a/drivers/gpu/drm/i915/intel_region_ttm.h
+++ b/drivers/gpu/drm/i915/intel_region_ttm.h
@@ -24,7 +24,8 @@ int intel_region_ttm_fini(struct intel_memory_region *mem);
 
 struct i915_refct_sgt *
 intel_region_ttm_resource_to_rsgt(struct intel_memory_region *mem,
-                                 struct ttm_resource *res);
+                                 struct ttm_resource *res,
+                                 u64 page_alignment);
 
 void intel_region_ttm_resource_free(struct intel_memory_region *mem,
                                    struct ttm_resource *res);

diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
index 73eb53e..3b18e59 100644 (file)
--- 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 670557c..bac21fe 100644 (file)
--- 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;