Re: [Intel-gfx] [PATCH v2 37/39] drm/i915: document struct drm_i915_gem_object

Rodrigo Vivi
2022-08-09T10:08:54Z

On Wed, Jul 13, 2022 at 09:12:25AM +0100, Mauro Carvalho Chehab wrote:
> This is a large struct used to describe gem objects. It is
> currently partially documented. Finish its documentation, filling
> the gaps from git logs.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/39] at: https://lore.kernel.org/all/cover.1657699522.git.mchehab@kernel.org/
>
> .../gpu/drm/i915/gem/i915_gem_object_types.h | 200 ++++++++++++++----
> 1 file changed, 158 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> index ceed0d220ce3..8c09e493590d 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -233,6 +233,9 @@ struct i915_gem_object_page_iter {
> struct mutex lock; /* protects this cache */
> };
>
> +/**
> + * struct drm_i915_gem_object - describes an i915 GEM object
> + */
> struct drm_i915_gem_object {
> /*
> * We might have reason to revisit the below since it wastes
> @@ -241,12 +244,16 @@ struct drm_i915_gem_object {
> * when accessing it.
> */
> union {
> + /** @base: GEM base object */
> struct drm_gem_object base;
> + /** @__do_not_access: TTM buffer object */
> struct ttm_buffer_object __do_not_access;
> };
>
> + /** @ops: pointer to GEM object ops */
> const struct drm_i915_gem_object_ops *ops;
>
> + /** @vma: struct containing VMA list, tree and lock */
> struct {
> /**
> * @vma.lock: protect the list/tree of vmas
> @@ -280,10 +287,12 @@ struct drm_i915_gem_object {
> *
> * If this object is closed, we need to remove all of its VMA from
> * the fast lookup index in associated contexts; @lut_list provides
> - * this translation from object to context->handles_vma.
> + * this translation from object to ``context->handles_vma``.
> */
> struct list_head lut_list;
> - spinlock_t lut_lock; /* guards lut_list */
> +
> + /** @lut_lock: guards @lut_list */
> + spinlock_t lut_lock;
>
> /**
> * @obj_link: Link into @i915_gem_ww_ctx.obj_list
> @@ -294,42 +303,88 @@ struct drm_i915_gem_object {
> */
> struct list_head obj_link;
> /**
> - * @shared_resv_from: The object shares the resv from this vm.
> + * @shares_resv_from: The object shares the resv from this vm.
> */
> struct i915_address_space *shares_resv_from;
>
> union {
> + /** @rcu: head used when freeing objects with RCU */
> struct rcu_head rcu;
> + /** @freed: list of GEM freed objects */
> struct llist_node freed;
> };
>
> /**
> - * Whether the object is currently in the GGTT mmap.
> + * @userfault_count: a value bigger than zero means that the object
> + * was mmapped into userspace.
> + *
> + * Used when the object is currently in the GGTT mmap.
> */
> unsigned int userfault_count;
> + /**
> + * @userfault_link: list of all objects that were
> + * mmapped into userspace.
> + *
> + * Used when the object is currently in the GGTT mmap.
> + */
> struct list_head userfault_link;
>
> + /** @mmo: struct containing mmo offsets and lock */
> struct {
> - spinlock_t lock; /* Protects access to mmo offsets */
> + /** @mmo.lock: protects access to @mmo.offsets */
> + spinlock_t lock;
> + /** @mmo.offsets: rbtree list of mmo offsets */
> struct rb_root offsets;
> } mmo;
>
> + /* private: used on selftest only */
> I915_SELFTEST_DECLARE(struct list_head st_link);
> + /* public: */
>
> + /**
> + * @flags: object flags. Current flags are:
> + *
> + * %I915_BO_ALLOC_CONTIGUOUS:
> + * Object requires to be allocated as a contiguous block
> + * %I915_BO_ALLOC_VOLATILE:
> + * Volatile objects are marked as %DONTNEED while pinned, therefore
> + * once unpinned the backing store can be discarded.
> + * This is limited to kernel internal objects.
> + * %I915_BO_ALLOC_CPU_CLEAR:
> + * Some internal device local-memory objects may have an option
> + * to CPU clear the pages upon gathering the backing store.
> + * Note that this might be before the blitter is usable, which
> + * is the case for some internal GuC objects.
> + * %I915_BO_ALLOC_USER:
> + * Make sure the object is cleared before any user access.
> + * %I915_BO_ALLOC_PM_VOLATILE:
> + * Object is allowed to lose its contents on suspend / resume,
> + * even if pinned
> + * %I915_BO_ALLOC_PM_EARLY:
> + * Object needs to be restored early using memcpy during resume
> + * %I915_BO_ALLOC_GPU_ONLY:
> + * Object is likely never accessed by the CPU. This will
> + * prioritise the BO to be allocated in the non-mappable portion
> + * of lmem. This is merely a hint, and if dealing with userspace
> + * objects the CPU fault handler is free to ignore this.
> + * %I915_BO_READONLY:
> + * User has created object as read-only
> + * %I915_BO_PROTECTED:
> + * User has created protected. All protected objects and
> + * contexts will be considered invalid when the PXP session
> + * is destroyed and all new submissions using them will be
> + * rejected. All intel contexts within the invalidated gem
> + * contexts will be marked banned. Userspace can detect that
> + * an invalidation has occurred via the %RESET_STATS ioctl,
> + * where we report it the same way as a ban due to a hang.
> + */
> unsigned long flags;
> #define I915_BO_ALLOC_CONTIGUOUS BIT(0)
> #define I915_BO_ALLOC_VOLATILE BIT(1)
> #define I915_BO_ALLOC_CPU_CLEAR BIT(2)
> #define I915_BO_ALLOC_USER BIT(3)
> -/* Object is allowed to lose its contents on suspend / resume, even if pinned */
> #define I915_BO_ALLOC_PM_VOLATILE BIT(4)
> -/* Object needs to be restored early using memcpy during resume */
> #define I915_BO_ALLOC_PM_EARLY BIT(5)
> -/*
> - * Object is likely never accessed by the CPU. This will prioritise the BO to be
> - * allocated in the non-mappable portion of lmem. This is merely a hint, and if
> - * dealing with userspace objects the CPU fault handler is free to ignore this.
> - */
> #define I915_BO_ALLOC_GPU_ONLY BIT(6)
> #define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS | \
> I915_BO_ALLOC_VOLATILE | \
> @@ -343,15 +398,21 @@ struct drm_i915_gem_object {
> #define I915_BO_PROTECTED BIT(9)
> #define I915_BO_WAS_BOUND_BIT 10
> /**
> - * @mem_flags - Mutable placement-related flags
> + * @mem_flags: Mutable placement-related flags
> *
> * These are flags that indicate specifics of the memory region
> * the object is currently in. As such they are only stable
> * either under the object lock or if the object is pinned.
> + * There are two flags:
> + *
> + * %I915_BO_FLAG_STRUCT_PAGE:
> + * Object backed by struct pages
> + * %I915_BO_FLAG_IOMEM:
> + * Object backed by IO memory
> */
> unsigned int mem_flags;
> -#define I915_BO_FLAG_STRUCT_PAGE BIT(0) /* Object backed by struct pages */
> -#define I915_BO_FLAG_IOMEM BIT(1) /* Object backed by IO memory */
> +#define I915_BO_FLAG_STRUCT_PAGE BIT(0)
> +#define I915_BO_FLAG_IOMEM BIT(1)
> /**
> * @cache_level: The desired GTT caching level.
> *
> @@ -400,7 +461,7 @@ struct drm_i915_gem_object {
> *
> * Supported values:
> *
> - * I915_BO_CACHE_COHERENT_FOR_READ:
> + * %I915_BO_CACHE_COHERENT_FOR_READ:
> *
> * On shared LLC platforms, we use this for special scanout surfaces,
> * where the display engine is not coherent with the CPU cache. As such
> @@ -423,7 +484,7 @@ struct drm_i915_gem_object {
> *
> * cache_coherent = 0
> *
> - * I915_BO_CACHE_COHERENT_FOR_WRITE:
> + * %I915_BO_CACHE_COHERENT_FOR_WRITE:
> *
> * When writing through the CPU cache, the GPU is still coherent. Note
> * that this also implies I915_BO_CACHE_COHERENT_FOR_READ.
> @@ -509,23 +570,29 @@ struct drm_i915_gem_object {
> */
> u16 write_domain;
>
> + /** @frontbuffer: pointer to the object's frontbuffer */
> struct intel_frontbuffer __rcu *frontbuffer;
>
> - /** Current tiling stride for the object, if it's tiled. */
> + /**
> + * @tiling_and_stride: current tiling stride for the object,
> + * if it's tiled.
> + */
> unsigned int tiling_and_stride;
> #define FENCE_MINIMUM_STRIDE 128 /* See i915_tiling_ok() */
> #define TILING_MASK (FENCE_MINIMUM_STRIDE - 1)
> #define STRIDE_MASK (~TILING_MASK)
>
> + /** @mm: struct containing mm-specific fields */
> struct {
> - /*
> - * Protects the pages and their use. Do not use directly, but
> - * instead go through the pin/unpin interfaces.
> + /**
> + * @mm.pages_pin_count: protects the pages and their use. Do
> + * not use directly, but instead go through the pin/unpin
> + * interfaces.
> */
> atomic_t pages_pin_count;
>
> /**
> - * @shrink_pin: Prevents the pages from being made visible to
> + * @mm.shrink_pin: Prevents the pages from being made visible to
> * the shrinker, while the shrink_pin is non-zero. Most users
> * should pretty much never have to care about this, outside of
> * some special use cases.
> @@ -536,7 +603,7 @@ struct drm_i915_gem_object {
> * __i915_gem_object_set_pages(). They will then be removed the
> * shrinker list once the pages are released.
> *
> - * The @shrink_pin is incremented by calling
> + * The @mm.shrink_pin is incremented by calling
> * i915_gem_object_make_unshrinkable(), which will also remove
> * the object from the shrinker list, if the pin count was zero.
> *
> @@ -548,13 +615,13 @@ struct drm_i915_gem_object {
> atomic_t shrink_pin;
>
> /**
> - * @ttm_shrinkable: True when the object is using shmem pages
> + * @mm.ttm_shrinkable: True when the object is using shmem pages
> * underneath. Protected by the object lock.
> */
> bool ttm_shrinkable;
>
> /**
> - * @unknown_state: Indicate that the object is effectively
> + * @mm.unknown_state: Indicate that the object is effectively
> * borked. This is write-once and set if we somehow encounter a
> * fatal error when moving/clearing the pages, and we are not
> * able to fallback to memcpy/memset, like on small-BAR systems.
> @@ -572,94 +639,143 @@ struct drm_i915_gem_object {
> bool unknown_state;
>
> /**
> - * Priority list of potential placements for this object.
> + * @mm.placements: priority list of potential placements for
> + * this object.
> */
> struct intel_memory_region **placements;
> + /**
> + * @mm.n_placements: Size of @mm.placements.
> + */
> int n_placements;
>
> /**
> - * Memory region for this object.
> + * @mm.region: memory region for this object.
> */
> struct intel_memory_region *region;
>
> /**
> - * Memory manager resource allocated for this object. Only
> - * needed for the mock region.
> + * @mm.res: Memory manager resource allocated for this object.
> + * Only needed for the mock region.
> */
> struct ttm_resource *res;
>
> /**
> - * Element within memory_region->objects or region->purgeable
> - * if the object is marked as DONTNEED. Access is protected by
> - * region->obj_lock.
> + * @mm.region_link: element within memory_region->objects or
> + * ``region->purgeable`` if the object is marked as %DONTNEED.
> + * Access is protected by ``region->obj_lock``.
> */
> struct list_head region_link;
>
> + /** @mm.rsgt: refcounted sg-tables */
> struct i915_refct_sgt *rsgt;
> + /** @mm.pages: pages pointer for GGTT entries */
> struct sg_table *pages;
> + /**
> + * @mm.mapping: mapped pages of the object into kernel space.
> + * can be %NULL if unmapped.
> + */
> void *mapping;
>
> + /**
> + * @mm.page_sizes: Page sizes of the pages.
> + */
> struct i915_page_sizes page_sizes;
>
> + /* private: used on selftest only */
> I915_SELFTEST_DECLARE(unsigned int page_mask);
> + /* public: */
>
> + /** @mm.get_page: */
> struct i915_gem_object_page_iter get_page;
> + /** @mm.get_dma_page: */
> struct i915_gem_object_page_iter get_dma_page;
>
> /**
> - * Element within i915->mm.shrink_list or i915->mm.purge_list,
> - * locked by i915->mm.obj_lock.
> + * @mm.link: element within ``i915->mm.shrink_list`` or
> + * ``i915->mm.purge_list``, locked by ``i915->mm.obj_lock``.
> */
> struct list_head link;
>
> /**
> - * Advice: are the backing pages purgeable?
> + * @mm.madv: Advice: are the backing pages purgeable?
> */
> unsigned int madv:2;
>
> /**
> - * This is set if the object has been written to since the
> - * pages were last acquired.
> + * @mm.dirty: this is set if the object has been written to
> + * since the pages were last acquired.
> */
> bool dirty:1;
> } mm;
>
> + /** @ttm: struct containing TTM specific fields */
> struct {
> + /** @ttm.cached_io_rsgt: cached refcounted sg-tables */
> struct i915_refct_sgt *cached_io_rsgt;
> + /** @ttm.get_io_page: rbtree iterator to get IO pages */
> struct i915_gem_object_page_iter get_io_page;
> + /** @ttm.backup: list of LMEM objects backed up at suspend */
> struct drm_i915_gem_object *backup;
> + /** @ttm.created: indicate that object as created with TTM */
> bool created:1;
> } ttm;
>
> - /*
> - * Record which PXP key instance this object was created against (if
> - * any), so we can use it to determine if the encryption is valid by
> - * comparing against the current key instance.
> + /**
> + * @pxp_key_instance: rRecord which PXP key instance this object was
> + * created against (if any), so we can use it to determine if the
> + * encryption is valid by comparing against the current key instance.
> */
> u32 pxp_key_instance;
>
> - /** Record of address bit 17 of each page at last unbind. */
> + /** @bit_17: Record of address bit 17 of each page at last unbind. */
> unsigned long *bit_17;
>
> union {
> #ifdef CONFIG_MMU_NOTIFIER
> + /**
> + * @userptr: Struct which supports userptr data
> + * Only used when %CONFIG_MMU_NOTIFIER is enabled
> + */
> struct i915_gem_userptr {
> + /** @userptr.ptr: pointer to the user-mapped ptr */
> uintptr_t ptr;
> + /** @userptr.notifier_seq: */
> unsigned long notifier_seq;
>
> + /** @userptr.notifier: data used by MMU notifier */
> struct mmu_interval_notifier notifier;
> + /** @userptr.pvec: S/G pages used by userptr */
> struct page **pvec;
> + /**
> + * @userptr.page_ref: number of page references
> + * incremented when pages are in usage.
> + *
> + */
> int page_ref;
> } userptr;
> #endif
>
> + /**
> + * @stolen: Used to identify an object allocated from
> + * stolen memory.
> + */
> struct drm_mm_node *stolen;
>
> + /**
> + * @bo_offset: The range start.
> + * Used only by TTM.
> + */
> resource_size_t bo_offset;
>
> + /** @scratch: physical size of huge gem object */
> unsigned long scratch;
> + /** @encode: gen8 PDE encode address */
> u64 encode;
>
> + /**
> + * @gvt_info: contains a pointer to ``dmabuf_obj->info``
> + * Used only by gvt.
> + */
> void *gvt_info;
> };
> };
> --
> 2.36.1
>