man = ttm_manager_type(&xe->ttm, XE_PL_TT);
mem_regions->mem_regions[0].mem_class = DRM_XE_MEM_REGION_CLASS_SYSMEM;
+ /*
+ * The instance needs to be a unique number that represents the index
+ * in the placement mask used at xe_gem_create_ioctl() for the
+ * xe_bo_create() placement.
+ */
mem_regions->mem_regions[0].instance = 0;
mem_regions->mem_regions[0].min_page_size = PAGE_SIZE;
mem_regions->mem_regions[0].total_size = man->size << PAGE_SHIFT;
gt_list->gt_list[id].tile_id = gt_to_tile(gt)->id;
gt_list->gt_list[id].gt_id = gt->info.id;
gt_list->gt_list[id].reference_clock = gt->info.reference_clock;
+ /*
+ * The mem_regions indexes in the mask below need to
+ * directly identify the struct
+ * drm_xe_query_mem_regions' instance constructed at
+ * query_mem_regions()
+ *
+ * For our current platforms:
+ * Bit 0 -> System Memory
+ * Bit 1 -> VRAM0 on Tile0
+ * Bit 2 -> VRAM1 on Tile1
+ * However the uAPI is generic and it's userspace's
+ * responsibility to check the mem_class, without any
+ * assumption.
+ */
if (!IS_DGFX(xe))
gt_list->gt_list[id].near_mem_regions = 0x1;
else
*/
__u16 mem_class;
/**
- * @instance: The instance for this region.
- *
- * The @mem_class and @instance taken together will always give
- * a unique pair.
+ * @instance: The unique ID for this region, which serves as the
+ * index in the placement bitmask used as argument for
+ * &DRM_IOCTL_XE_GEM_CREATE
*/
__u16 instance;
/**
* @near_mem_regions: Bit mask of instances from
* drm_xe_query_mem_regions that are nearest to the current engines
* of this GT.
+ * Each index in this mask refers directly to the struct
+ * drm_xe_query_mem_regions' instance, no assumptions should
+ * be made about order. The type of each region is described
+ * by struct drm_xe_query_mem_regions' mem_class.
*/
__u64 near_mem_regions;
/**
* In general, they have extra indirections when compared to the
* @near_mem_regions. For a discrete device this could mean system
* memory and memory living in a different tile.
+ * Each index in this mask refers directly to the struct
+ * drm_xe_query_mem_regions' instance, no assumptions should
+ * be made about order. The type of each region is described
+ * by struct drm_xe_query_mem_regions' mem_class.
*/
__u64 far_mem_regions;
/** @reserved: Reserved */
*/
__u64 size;
- /** @placement: A mask of memory instances of where BO can be placed. */
+ /**
+ * @placement: A mask of memory instances of where BO can be placed.
+ * Each index in this mask refers directly to the struct
+ * drm_xe_query_mem_regions' instance, no assumptions should
+ * be made about order. The type of each region is described
+ * by struct drm_xe_query_mem_regions' mem_class.
+ */
__u32 placement;
#define DRM_XE_GEM_CREATE_FLAG_DEFER_BACKING (1 << 0)