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

Mauro Carvalho Chehab
2022-07-13T08:14:04Z

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>
---

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