Re: [PATCH drm-misc-next 2/3] drm/gpuva_mgr: generalize dma_resv/extobj handling and GEM validation

Thomas Hellström (Intel)
2023-08-30T19:03:15Z

On 8/30/23 14:49, Danilo Krummrich wrote:
> Hi Thomas,
>
> thanks for having a look!
>
> On Wed, Aug 30, 2023 at 09:27:45AM +0200, Thomas Hellström (Intel) wrote:
>> Hi, Danilo.
>>
>> Some quick comments since I'm doing some Xe work in this area. Will probably
>> get back with more.
>>
>> On 8/20/23 23:53, Danilo Krummrich wrote:
>>> So far the DRM GPUVA manager offers common infrastructure to track GPU VA
>>> allocations and mappings, generically connect GPU VA mappings to their
>>> backing buffers and perform more complex mapping operations on the GPU VA
>>> space.
>>>
>>> However, there are more design patterns commonly used by drivers, which
>>> can potentially be generalized in order to make the DRM GPUVA manager
>>> represent a basic GPU-VM implementation. In this context, this patch aims
>>> at generalizing the following elements.
>>>
>>> 1) Provide a common dma-resv for GEM objects not being used outside of
>>> this GPU-VM.
>>>
>>> 2) Provide tracking of external GEM objects (GEM objects which are
>>> shared with other GPU-VMs).
>>>
>>> 3) Provide functions to efficiently lock all GEM objects dma-resv the
>>> GPU-VM contains mappings of.
>>>
>>> 4) Provide tracking of evicted GEM objects the GPU-VM contains mappings
>>> of, such that validation of evicted GEM objects is accelerated.
>>>
>>> 5) Provide some convinience functions for common patterns.
>>>
>>> Rather than being designed as a "framework", the target is to make all
>>> features appear as a collection of optional helper functions, such that
>>> drivers are free to make use of the DRM GPUVA managers basic
>>> functionality and opt-in for other features without setting any feature
>>> flags, just by making use of the corresponding functions.
>>>
>>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>>> ---
>>> drivers/gpu/drm/drm_gpuva_mgr.c | 688 +++++++++++++++++++++++++++++++-
>>> include/drm/drm_gem.h | 48 ++-
>>> include/drm/drm_gpuva_mgr.h | 302 +++++++++++++-
>>> 3 files changed, 1010 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_gpuva_mgr.c b/drivers/gpu/drm/drm_gpuva_mgr.c
>>> index f86bfad74ff8..69872b205961 100644
>>> --- a/drivers/gpu/drm/drm_gpuva_mgr.c
>>> +++ b/drivers/gpu/drm/drm_gpuva_mgr.c
>>> @@ -655,6 +655,7 @@ drm_gpuva_range_valid(struct drm_gpuva_manager *mgr,
>>> /**
>>> * drm_gpuva_manager_init() - initialize a &drm_gpuva_manager
>>> * @mgr: pointer to the &drm_gpuva_manager to initialize
>>> + * @drm: the drivers &drm_device
>>> * @name: the name of the GPU VA space
>>> * @start_offset: the start offset of the GPU VA space
>>> * @range: the size of the GPU VA space
>>> @@ -669,6 +670,7 @@ drm_gpuva_range_valid(struct drm_gpuva_manager *mgr,
>>> */
>>> void
>>> drm_gpuva_manager_init(struct drm_gpuva_manager *mgr,
>>> + struct drm_device *drm,
>>> const char *name,
>>> u64 start_offset, u64 range,
>>> u64 reserve_offset, u64 reserve_range,
>>> @@ -677,6 +679,11 @@ drm_gpuva_manager_init(struct drm_gpuva_manager *mgr,
>>> mgr->rb.tree = RB_ROOT_CACHED;
>>> INIT_LIST_HEAD(&mgr->rb.list);
>>> + mt_init(&mgr->mt_ext);
>>> +
>>> + INIT_LIST_HEAD(&mgr->evict.list);
>>> + spin_lock_init(&mgr->evict.lock);
>>> +
>>> drm_gpuva_check_overflow(start_offset, range);
>>> mgr->mm_start = start_offset;
>>> mgr->mm_range = range;
>>> @@ -694,6 +701,9 @@ drm_gpuva_manager_init(struct drm_gpuva_manager *mgr,
>>> reserve_range)))
>>> __drm_gpuva_insert(mgr, &mgr->kernel_alloc_node);
>>> }
>>> +
>>> + drm_gem_private_object_init(drm, &mgr->d_obj, 0);
>>> + mgr->resv = mgr->d_obj.resv;
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_manager_init);
>>> @@ -713,10 +723,575 @@ drm_gpuva_manager_destroy(struct drm_gpuva_manager *mgr)
>>> __drm_gpuva_remove(&mgr->kernel_alloc_node);
>>> WARN(!RB_EMPTY_ROOT(&mgr->rb.tree.rb_root),
>>> - "GPUVA tree is not empty, potentially leaking memory.");
>>> + "GPUVA tree is not empty, potentially leaking memory.\n");
>>> +
>>> + mtree_destroy(&mgr->mt_ext);
>>> + WARN(!list_empty(&mgr->evict.list), "Evict list should be empty.\n");
>>> +
>>> + drm_gem_private_object_fini(&mgr->d_obj);
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_manager_destroy);
>>> +/**
>>> + * drm_gpuva_manager_prepare_objects() - prepare all assoiciated BOs
>>> + * @mgr: the &drm_gpuva_manager
>>> + * @num_fences: the amount of &dma_fences to reserve
>>> + *
>>> + * Calls drm_exec_prepare_obj() for all &drm_gem_objects the given
>>> + * &drm_gpuva_manager contains mappings of.
>>> + *
>>> + * Drivers can obtain the corresponding &drm_exec instance through
>>> + * DRM_GPUVA_EXEC(). It is the drivers responsibility to call drm_exec_init()
>>> + * and drm_exec_fini() accordingly.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +int
>>> +drm_gpuva_manager_prepare_objects(struct drm_gpuva_manager *mgr,
>>> + unsigned int num_fences)
>>> +{
>>> + struct drm_exec *exec = DRM_GPUVA_EXEC(mgr);
>>> + MA_STATE(mas, &mgr->mt_ext, 0, 0);
>>> + union {
>>> + void *ptr;
>>> + uintptr_t cnt;
>>> + } ref;
>>> + int ret;
>>> +
>>> + ret = drm_exec_prepare_obj(exec, &mgr->d_obj, num_fences);
>>> + if (ret)
>>> + goto out;
>>> +
>>> + rcu_read_lock();
>> In xe we're protecting the external object list with an outer lock, (same as
>> protecting the mgr itself). Do we need a separate lock for this? In theory
>> as  outlined in the VM_BIND locking document draft, one could probably even
>> use the mgr resv for this, but with more complicated code I guess. Also see
>> the comment below about the data structure chosen.
> The idea is to protect this list with the GPU-VM lock. The locking here is more
> of an implication of the maple tree. Either you use the internal lock of the
> maple tree or RCU respectively, or you give the maple tree an external lock to
> perform lockdep checks on (mt_set_external_lock()). Basically same as here:
>
> https://elixir.bootlin.com/linux/latest/source/drivers/base/regmap/regcache-maple.c#L124

Ah, I suspected it was something along those lines.

>
>>> + mas_for_each(&mas, ref.ptr, ULONG_MAX) {
>>> + struct drm_gem_object *obj;
>>> +
>>> + mas_pause(&mas);
>>> + rcu_read_unlock();
>>> +
>>> + obj = (struct drm_gem_object *)(uintptr_t)mas.index;
>>> + ret = drm_exec_prepare_obj(exec, obj, num_fences);
>>> + if (ret)
>>> + goto out;
>>> +
>>> + rcu_read_lock();
>>> + }
>>> + rcu_read_unlock();
>>> +
>>> +out:
>>> + return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_manager_prepare_objects);
>>> +
>>> +/**
>>> + * drm_gpuva_manager_lock_extra() - lock all dma-resv of all assoiciated BOs
>>> + * @mgr: the &drm_gpuva_manager
>>> + * @fn: callback received by the driver to lock additional dma-resv
>>> + * @priv: private driver data passed to @fn
>>> + * @num_fences: the amount of &dma_fences to reserve
>>> + * @interruptible: sleep interruptible if waiting
>>> + *
>>> + * Acquires all dma-resv locks of all &drm_gem_objects the given
>>> + * &drm_gpuva_manager contains mappings of.
>>> + *
>>> + * Addionally, when calling this function the driver receives the given @fn
>>> + * callback to lock additional dma-resv in the context of the
>>> + * &drm_gpuva_managers &drm_exec instance. Typically, drivers would call
>>> + * drm_exec_prepare_obj() from within this callback.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +int
>>> +drm_gpuva_manager_lock_extra(struct drm_gpuva_manager *mgr,
>>> + int (*fn)(struct drm_gpuva_manager *mgr,
>>> + void *priv, unsigned int num_fences),
>>> + void *priv,
>>> + unsigned int num_fences,
>>> + bool interruptible)
>>> +{
>>> + struct drm_exec *exec = DRM_GPUVA_EXEC(mgr);
>>> + uint32_t flags;
>>> + int ret;
>>> +
>>> + flags = interruptible ? DRM_EXEC_INTERRUPTIBLE_WAIT : 0 |
>>> + DRM_EXEC_IGNORE_DUPLICATES;
>>> +
>>> + drm_exec_init(exec, flags);
>>> +
>>> + drm_exec_until_all_locked(exec) {
>>> + ret = drm_gpuva_manager_prepare_objects(mgr, num_fences);
>>> + drm_exec_retry_on_contention(exec);
>>> + if (ret)
>>> + goto err;
>>> +
>>> + if (fn) {
>>> + ret = fn(mgr, priv, num_fences);
>>> + drm_exec_retry_on_contention(exec);
>>> + if (ret)
>>> + goto err;
>>> + }
>>> + }
>>> +
>>> + return 0;
>>> +
>>> +err:
>>> + drm_exec_fini(exec);
>>> + return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_manager_lock_extra);
>>> +
>>> +static int
>>> +fn_lock_array(struct drm_gpuva_manager *mgr, void *priv,
>>> + unsigned int num_fences)
>>> +{
>>> + struct {
>>> + struct drm_gem_object **objs;
>>> + unsigned int num_objs;
>>> + } *args = priv;
>>> +
>>> + return drm_exec_prepare_array(DRM_GPUVA_EXEC(mgr), args->objs,
>>> + args->num_objs, num_fences);
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuva_manager_lock_array() - lock all dma-resv of all assoiciated BOs
>>> + * @mgr: the &drm_gpuva_manager
>>> + * @objs: additional &drm_gem_objects to lock
>>> + * @num_objs: the number of additional &drm_gem_objects to lock
>>> + * @num_fences: the amount of &dma_fences to reserve
>>> + * @interruptible: sleep interruptible if waiting
>>> + *
>>> + * Acquires all dma-resv locks of all &drm_gem_objects the given
>>> + * &drm_gpuva_manager contains mappings of, plus the ones given through @objs.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +int
>>> +drm_gpuva_manager_lock_array(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object **objs,
>>> + unsigned int num_objs,
>>> + unsigned int num_fences,
>>> + bool interruptible)
>>> +{
>>> + struct {
>>> + struct drm_gem_object **objs;
>>> + unsigned int num_objs;
>>> + } args;
>>> +
>>> + args.objs = objs;
>>> + args.num_objs = num_objs;
>>> +
>>> + return drm_gpuva_manager_lock_extra(mgr, fn_lock_array, &args,
>>> + num_fences, interruptible);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_manager_lock_array);
>>> +
>>> +/**
>>> + * drm_gpuva_manager_validate() - validate all BOs marked as evicted
>>> + * @mgr: the &drm_gpuva_manager to validate evicted BOs
>>> + *
>>> + * Calls the &drm_gpuva_fn_ops.bo_validate callback for all evicted buffer
>>> + * objects being mapped in the given &drm_gpuva_manager.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +int
>>> +drm_gpuva_manager_validate(struct drm_gpuva_manager *mgr)
>>> +{
>>> + const struct drm_gpuva_fn_ops *ops = mgr->ops;
>>> + struct drm_gpuva_gem *vm_bo;
>>> + int ret;
>>> +
>>> + if (unlikely(!ops || !ops->bo_validate))
>>> + return -ENOTSUPP;
>>> +
>>> + /* At this point we should hold all dma-resv locks of all GEM objects
>>> + * associated with this GPU-VM, hence it is safe to walk the list.
>>> + */
>>> + list_for_each_entry(vm_bo, &mgr->evict.list, list.entry.evict) {
>>> + dma_resv_assert_held(vm_bo->obj->resv);
>>> +
>>> + ret = ops->bo_validate(vm_bo->obj);
>>> + if (ret)
>>> + return ret;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_manager_validate);
>>> +
>>> +/**
>>> + * drm_gpuva_manager_resv_add_fence - add fence to private and all extobj
>>> + * dma-resv
>>> + * @mgr: the &drm_gpuva_manager to add a fence to
>>> + * @fence: fence to add
>>> + * @private_usage: private dma-resv usage
>>> + * @extobj_usage: extobj dma-resv usage
>>> + */
>>> +void
>>> +drm_gpuva_manager_resv_add_fence(struct drm_gpuva_manager *mgr,
>>> + struct dma_fence *fence,
>>> + enum dma_resv_usage private_usage,
>>> + enum dma_resv_usage extobj_usage)
>>> +{
>>> + struct drm_exec *exec = DRM_GPUVA_EXEC(mgr);
>>> + struct drm_gem_object *obj;
>>> + unsigned long index;
>>> +
>>> + drm_exec_for_each_locked_object(exec, index, obj) {
>>> + dma_resv_assert_held(obj->resv);
>>> + dma_resv_add_fence(obj->resv, fence,
>>> + drm_gpuva_is_extobj(mgr, obj) ?
>>> + private_usage : extobj_usage);
>>> + }
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_manager_resv_add_fence);
>>> +
>>> +static struct drm_gpuva_gem *
>>> +__drm_gpuva_gem_find(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + struct drm_gpuva_gem *vm_bo;
>>> +
>>> + drm_gem_gpuva_assert_lock_held(obj);
>>> +
>>> + drm_gem_for_each_gpuva_gem(vm_bo, obj)
>>> + if (vm_bo->mgr == mgr)
>>> + return vm_bo;
>>> +
>>> + return NULL;
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuva_gem_create() - create a new instance of struct drm_gpuva_gem
>>> + * @mgr: The &drm_gpuva_manager the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @mgr.
>>> + *
>>> + * If provided by the driver, this function uses the &drm_gpuva_fn_ops
>>> + * vm_bo_alloc() callback to allocate.
>>> + *
>>> + * Returns: a pointer to the &drm_gpuva_gem on success, NULL on failure
>>> + */
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_create(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + const struct drm_gpuva_fn_ops *ops = mgr->ops;
>>> + struct drm_gpuva_gem *vm_bo;
>>> +
>>> + if (ops && ops->vm_bo_alloc)
>>> + vm_bo = ops->vm_bo_alloc();
>>> + else
>>> + vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
>>> +
>>> + if (unlikely(!vm_bo))
>>> + return NULL;
>>> +
>>> + vm_bo->mgr = mgr;
>>> + vm_bo->obj = obj;
>>> +
>>> + kref_init(&vm_bo->kref);
>>> + INIT_LIST_HEAD(&vm_bo->list.gpuva);
>>> + INIT_LIST_HEAD(&vm_bo->list.entry.gem);
>>> + INIT_LIST_HEAD(&vm_bo->list.entry.evict);
>>> +
>>> + drm_gem_object_get(obj);
>>> +
>>> + return vm_bo;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_gem_create);
>>> +
>>> +void
>>> +drm_gpuva_gem_destroy(struct kref *kref)
>>> +{
>>> + struct drm_gpuva_gem *vm_bo = container_of(kref, struct drm_gpuva_gem,
>>> + kref);
>>> + const struct drm_gpuva_fn_ops *ops = vm_bo->mgr->ops;
>>> +
>>> + drm_gem_object_put(vm_bo->obj);
>>> +
>>> + if (ops && ops->vm_bo_free)
>>> + ops->vm_bo_free(vm_bo);
>>> + else
>>> + kfree(vm_bo);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_gem_destroy);
>>> +
>>> +/**
>>> + * drm_gpuva_gem_find() - find the &drm_gpuva_gem for the given
>>> + * &drm_gpuva_manager and &drm_gem_object
>>> + * @mgr: The &drm_gpuva_manager the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @mgr.
>>> + *
>>> + * Find the &drm_gpuva_gem representing the combination of the given
>>> + * &drm_gpuva_manager and &drm_gem_object. If found, increases the reference
>>> + * count of the &drm_gpuva_gem accordingly.
>>> + *
>>> + * Returns: a pointer to the &drm_gpuva_gem on success, NULL on failure
>>> + */
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_find(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + struct drm_gpuva_gem *vm_bo = __drm_gpuva_gem_find(mgr, obj);
>>> +
>>> + return vm_bo ? drm_gpuva_gem_get(vm_bo) : NULL;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_gem_find);
>>> +
>>> +/**
>>> + * drm_gpuva_gem_obtain() - obtains and instance of the &drm_gpuva_gem for the
>>> + * given &drm_gpuva_manager and &drm_gem_object
>>> + * @mgr: The &drm_gpuva_manager the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @mgr.
>>> + *
>>> + * Find the &drm_gpuva_gem representing the combination of the given
>>> + * &drm_gpuva_manager and &drm_gem_object. If found, increases the reference
>>> + * count of the &drm_gpuva_gem accordingly. If not found, allsocates a new
>>> + * &drm_gpuva_gem.
>>> + *
>>> + * Returns: a pointer to the &drm_gpuva_gem on success, an ERR_PTR on failure
>>> + */
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_obtain(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + struct drm_gpuva_gem *vm_bo;
>>> +
>>> + vm_bo = drm_gpuva_gem_find(mgr, obj);
>>> + if (vm_bo)
>>> + return vm_bo;
>>> +
>>> + vm_bo = drm_gpuva_gem_create(mgr, obj);
>>> + if (!vm_bo)
>>> + return ERR_PTR(-ENOMEM);
>>> +
>>> + return vm_bo;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_gem_obtain);
>>> +
>>> +/**
>>> + * drm_gpuva_gem_obtain_prealloc() - obtains and instance of the &drm_gpuva_gem
>>> + * for the given &drm_gpuva_manager and &drm_gem_object
>>> + * @mgr: The &drm_gpuva_manager the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @mgr.
>>> + *
>>> + * Find the &drm_gpuva_gem representing the combination of the given
>>> + * &drm_gpuva_manager and &drm_gem_object. If found, increases the reference
>>> + * count of the found &drm_gpuva_gem accordingly, while the @__vm_bo reference
>>> + * count is decreased. If not found @__vm_bo is returned.
>>> + *
>>> + * Returns: a pointer to the found &drm_gpuva_gem or @__vm_bo if no existing
>>> + * &drm_gpuva_gem was found
>>> + */
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_obtain_prealloc(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj,
>>> + struct drm_gpuva_gem *__vm_bo)
>>> +{
>>> + struct drm_gpuva_gem *vm_bo;
>>> +
>>> + vm_bo = drm_gpuva_gem_find(mgr, obj);
>>> + if (vm_bo) {
>>> + drm_gpuva_gem_put(__vm_bo);
>>> + return vm_bo;
>>> + }
>>> +
>>> + return __vm_bo;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_gem_obtain_prealloc);
>>> +
>>> +static int
>>> +__drm_gpuva_extobj_insert(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj,
>>> + gfp_t gfp)
>>> +{
>>> + MA_STATE(mas, &mgr->mt_ext, 0, 0);
>>> + union {
>>> + struct drm_gem_object *obj;
>>> + uintptr_t index;
>>> + } gem;
>>> + union {
>>> + void *ptr;
>>> + uintptr_t cnt;
>>> + } ref;
>>> + int ret = 0;
>>> +
>>> + gem.obj = obj;
>>> + mas_set(&mas, gem.index);
>>> +
>>> + mas_lock(&mas);
>>> + ref.ptr = mas_walk(&mas);
>>> + if (ref.ptr) {
>>> + ++ref.cnt;
>>> + mas_store(&mas, ref.ptr);
>>> + } else {
>>> + if (unlikely(!gfp)) {
>>> + ret = -EINVAL;
>>> + goto out;
>>> + }
>>> +
>>> + mas_set(&mas, gem.index);
>>> + ref.cnt = 1;
>>> + ret = mas_store_gfp(&mas, ref.ptr, gfp);
>>> + if (likely(!ret))
>>> + drm_gem_object_get(obj);
>>> + }
>>> +out:
>>> + mas_unlock(&mas);
>>> + return ret;
>>> +}
>>> +
>>> +static void
>>> +__drm_gpuva_extobj_remove(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + MA_STATE(mas, &mgr->mt_ext, 0, 0);
>>> + union {
>>> + struct drm_gem_object *obj;
>>> + uintptr_t index;
>>> + } gem;
>>> + union {
>>> + void *ptr;
>>> + uintptr_t cnt;
>>> + } ref;
>>> +
>>> + gem.obj = obj;
>>> + mas_set(&mas, gem.index);
>>> +
>>> + mas_lock(&mas);
>>> + if (unlikely(!(ref.ptr = mas_walk(&mas))))
>>> + goto out;
>>> +
>>> + if (!--ref.cnt) {
>>> + mas_erase(&mas);
>>> + drm_gem_object_put(obj);
>>> + } else {
>>> + mas_store(&mas, ref.ptr);
>>> + }
>>> +out:
>>> + mas_unlock(&mas);
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuva_extobj_insert - insert an external &drm_gem_object
>>> + * @mgr: the &drm_gpuva_manager to insert into
>>> + * @obj: the &drm_gem_object to insert as extobj
>>> + *
>>> + * Insert a &drm_gem_object into the &drm_gpuva_managers external object tree.
>>> + * If the &drm_gem_object already exists in the tree, the reference counter
>>> + * of this external object is increased by one.
>>> + *
>>> + * Drivers should insert the external &drm_gem_object before the dma-fence
>>> + * signalling critical section, e.g. when submitting the job, and before
>>> + * locking all &drm_gem_objects of a GPU-VM, e.g. with drm_gpuva_manager_lock()
>>> + * or its dervates.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +int
>>> +drm_gpuva_extobj_insert(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + return drm_gpuva_is_extobj(mgr, obj) ?
>>> + __drm_gpuva_extobj_insert(mgr, obj, GFP_KERNEL) : 0;
>>> +
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_extobj_insert);
>>> +
>>> +/**
>>> + * drm_gpuva_extobj_get - increase the referecne count of an external
>>> + * &drm_gem_object
>>> + * @mgr: the &drm_gpuva_manager storing the extobj
>>> + * @obj: the &drm_gem_object to representing the extobj
>>> + *
>>> + * Increases the reference count of the extobj represented by @obj.
>>> + *
>>> + * Drivers should call this for every &drm_gpuva backed by a &drm_gem_object
>>> + * being inserted.
>>> + *
>>> + * For &drm_gpuva_op_remap operations drivers should make sure to only take an
>>> + * additional reference if the re-map operation splits an existing &drm_gpuva
>>> + * into two separate ones.
>>> + *
>>> + * See also drm_gpuva_map_get() and drm_gpuva_remap_get().
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +void
>>> +drm_gpuva_extobj_get(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + if (drm_gpuva_is_extobj(mgr, obj))
>>> + WARN(__drm_gpuva_extobj_insert(mgr, obj, 0),
>>> + "Can't increase ref-count of non-existent extobj.");
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_extobj_get);
>>> +
>>> +/**
>>> + * drm_gpuva_extobj_put - decrease the referecne count of an external
>>> + * &drm_gem_object
>>> + * @mgr: the &drm_gpuva_manager storing the extobj
>>> + * @obj: the &drm_gem_object to representing the extobj
>>> + *
>>> + * Decreases the reference count of the extobj represented by @obj.
>>> + *
>>> + * Drivers should call this for every &drm_gpuva backed by a &drm_gem_object
>>> + * being removed from the GPU VA space.
>>> + *
>>> + * See also drm_gpuva_unmap_put().
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +void
>>> +drm_gpuva_extobj_put(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + if (drm_gpuva_is_extobj(mgr, obj))
>>> + __drm_gpuva_extobj_remove(mgr, obj);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_extobj_put);
>>> +
>>> +/**
>>> + * drm_gpuva_gem_evict() - add / remove a &drm_gem_object to / from a
>>> + * &drm_gpuva_managers evicted list
>>> + * @obj: the &drm_gem_object to add or remove
>>> + * @evict: indicates whether the object is evicted
>>> + *
>>> + * Adds a &drm_gem_object to or removes it from all &drm_gpuva_managers evicted
>>> + * list containing a mapping of this &drm_gem_object.
>>> + */
>>> +void
>>> +drm_gpuva_gem_evict(struct drm_gem_object *obj, bool evict)
>>> +{
>>> + struct drm_gpuva_gem *vm_bo;
>>> +
>>> + /* Required for iterating the GEMs GPUVA GEM list. If no driver specific
>>> + * lock has been set, the list is protected with the GEMs dma-resv lock.
>>> + */
>>> + drm_gem_gpuva_assert_lock_held(obj);
>>> +
>>> + /* Required to protect the GPUVA managers evict list against concurrent
>>> + * access through drm_gpuva_manager_validate(). Concurrent insertions to
>>> + * the evict list through different GEM object evictions are protected
>>> + * by the GPUVA managers evict lock.
>>> + */
>>> + dma_resv_assert_held(obj->resv);
>>> +
>>> + drm_gem_for_each_gpuva_gem(vm_bo, obj) {
>>> + struct drm_gpuva_manager *mgr = vm_bo->mgr;
>>> +
>>> + spin_lock(&mgr->evict.lock);
>>> + if (evict)
>>> + list_add_tail(&vm_bo->list.entry.evict,
>>> + &mgr->evict.list);
>>> + else
>>> + list_del_init(&vm_bo->list.entry.evict);
>>> + spin_unlock(&mgr->evict.lock);
>>> + }
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_gem_evict);
>>> +
>>> static int
>>> __drm_gpuva_insert(struct drm_gpuva_manager *mgr,
>>> struct drm_gpuva *va)
>>> @@ -806,15 +1381,20 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
>>> /**
>>> * drm_gpuva_link() - link a &drm_gpuva
>>> * @va: the &drm_gpuva to link
>>> + * @vm_bo: the &drm_gpuva_gem to add the &drm_gpuva to
>>> *
>>> - * This adds the given &va to the GPU VA list of the &drm_gem_object it is
>>> - * associated with.
>>> + * This adds the given &va to the GPU VA list of the &drm_gpuva_gem and the
>>> + * &drm_gpuva_gem to the &drm_gem_object it is associated with.
>>> + *
>>> + * For every &drm_gpuva entry added to the &drm_gpuva_gem an additional
>>> + * reference of the latter is taken.
>>> *
>>> * This function expects the caller to protect the GEM's GPUVA list against
>>> - * concurrent access using the GEMs dma_resv lock.
>>> + * concurrent access using either the GEMs dma_resv lock or a driver specific
>>> + * lock set through drm_gem_gpuva_set_lock().
>>> */
>>> void
>>> -drm_gpuva_link(struct drm_gpuva *va)
>>> +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuva_gem *vm_bo)
>>> {
>>> struct drm_gem_object *obj = va->gem.obj;
>>> @@ -823,7 +1403,10 @@ drm_gpuva_link(struct drm_gpuva *va)
>>> drm_gem_gpuva_assert_lock_held(obj);
>>> - list_add_tail(&va->gem.entry, &obj->gpuva.list);
>>> + drm_gpuva_gem_get(vm_bo);
>>> + list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
>>> + if (list_empty(&vm_bo->list.entry.gem))
>>> + list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>> @@ -834,20 +1417,39 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>> * This removes the given &va from the GPU VA list of the &drm_gem_object it is
>>> * associated with.
>>> *
>>> + * This removes the given &va from the GPU VA list of the &drm_gpuva_gem and
>>> + * the &drm_gpuva_gem from the &drm_gem_object it is associated with in case
>>> + * this call unlinks the last &drm_gpuva from the &drm_gpuva_gem.
>>> + *
>>> + * For every &drm_gpuva entry removed from the &drm_gpuva_gem a reference of
>>> + * the latter is dropped.
>>> + *
>>> * This function expects the caller to protect the GEM's GPUVA list against
>>> - * concurrent access using the GEMs dma_resv lock.
>>> + * concurrent access using either the GEMs dma_resv lock or a driver specific
>>> + * lock set through drm_gem_gpuva_set_lock().
>>> */
>>> void
>>> drm_gpuva_unlink(struct drm_gpuva *va)
>>> {
>>> struct drm_gem_object *obj = va->gem.obj;
>>> + struct drm_gpuva_gem *vm_bo;
>>> if (unlikely(!obj))
>>> return;
>>> drm_gem_gpuva_assert_lock_held(obj);
>>> + vm_bo = __drm_gpuva_gem_find(va->mgr, obj);
>>> + if (WARN(!vm_bo, "GPUVA doesn't seem to be linked.\n"))
>>> + return;
>>> +
>>> list_del_init(&va->gem.entry);
>>> +
>>> + if (list_empty(&vm_bo->list.gpuva)) {
>>> + list_del_init(&vm_bo->list.entry.gem);
>>> + list_del_init(&vm_bo->list.entry.evict);
>>> + }
>>> + drm_gpuva_gem_put(vm_bo);
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
>>> @@ -977,6 +1579,26 @@ drm_gpuva_map(struct drm_gpuva_manager *mgr,
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_map);
>>> +/**
>>> + * drm_gpuva_map_get() - helper to insert a &drm_gpuva according to a
>>> + * &drm_gpuva_op_map
>>> + * @mgr: the &drm_gpuva_manager
>>> + * @va: the &drm_gpuva to insert
>>> + * @op: the &drm_gpuva_op_map to initialize @va with
>>> + *
>>> + * Initializes the @va from the @op and inserts it into the given @mgr and
>>> + * increases the reference count of the corresponding extobj.
>>> + */
>>> +void
>>> +drm_gpuva_map_get(struct drm_gpuva_manager *mgr,
>>> + struct drm_gpuva *va,
>>> + struct drm_gpuva_op_map *op)
>>> +{
>>> + drm_gpuva_map(mgr, va, op);
>>> + drm_gpuva_extobj_get(mgr, va->gem.obj);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_map_get);
>>> +
>>> /**
>>> * drm_gpuva_remap() - helper to remap a &drm_gpuva according to a
>>> * &drm_gpuva_op_remap
>>> @@ -992,10 +1614,10 @@ drm_gpuva_remap(struct drm_gpuva *prev,
>>> struct drm_gpuva *next,
>>> struct drm_gpuva_op_remap *op)
>>> {
>>> - struct drm_gpuva *curr = op->unmap->va;
>>> - struct drm_gpuva_manager *mgr = curr->mgr;
>>> + struct drm_gpuva *va = op->unmap->va;
>>> + struct drm_gpuva_manager *mgr = va->mgr;
>>> - drm_gpuva_remove(curr);
>>> + drm_gpuva_remove(va);
>>> if (op->prev) {
>>> drm_gpuva_init_from_op(prev, op->prev);
>>> @@ -1009,6 +1631,31 @@ drm_gpuva_remap(struct drm_gpuva *prev,
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_remap);
>>> +/**
>>> + * drm_gpuva_remap_get() - helper to remap a &drm_gpuva according to a
>>> + * &drm_gpuva_op_remap
>>> + * @prev: the &drm_gpuva to remap when keeping the start of a mapping
>>> + * @next: the &drm_gpuva to remap when keeping the end of a mapping
>>> + * @op: the &drm_gpuva_op_remap to initialize @prev and @next with
>>> + *
>>> + * Removes the currently mapped &drm_gpuva and remaps it using @prev and/or
>>> + * @next. Additionally, if the re-map splits the existing &drm_gpuva into two
>>> + * separate mappings, increases the reference count of the corresponding extobj.
>>> + */
>>> +void
>>> +drm_gpuva_remap_get(struct drm_gpuva *prev,
>>> + struct drm_gpuva *next,
>>> + struct drm_gpuva_op_remap *op)
>>> +{
>>> + struct drm_gpuva *va = op->unmap->va;
>>> + struct drm_gpuva_manager *mgr = va->mgr;
>>> +
>>> + drm_gpuva_remap(prev, next, op);
>>> + if (op->prev && op->next)
>>> + drm_gpuva_extobj_get(mgr, va->gem.obj);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_remap_get);
>>> +
>>> /**
>>> * drm_gpuva_unmap() - helper to remove a &drm_gpuva according to a
>>> * &drm_gpuva_op_unmap
>>> @@ -1023,6 +1670,24 @@ drm_gpuva_unmap(struct drm_gpuva_op_unmap *op)
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_unmap);
>>> +/**
>>> + * drm_gpuva_unmap_put() - helper to remove a &drm_gpuva according to a
>>> + * &drm_gpuva_op_unmap
>>> + * @op: the &drm_gpuva_op_unmap specifying the &drm_gpuva to remove
>>> + *
>>> + * Removes the &drm_gpuva associated with the &drm_gpuva_op_unmap and decreases
>>> + * the reference count of the corresponding extobj.
>>> + */
>>> +void
>>> +drm_gpuva_unmap_put(struct drm_gpuva_op_unmap *op)
>>> +{
>>> + struct drm_gpuva *va = op->va;
>>> +
>>> + drm_gpuva_unmap(op);
>>> + drm_gpuva_extobj_put(va->mgr, va->gem.obj);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuva_unmap_put);
>>> +
>>> static int
>>> op_map_cb(const struct drm_gpuva_fn_ops *fn, void *priv,
>>> u64 addr, u64 range,
>>> @@ -1663,6 +2328,7 @@ drm_gpuva_gem_unmap_ops_create(struct drm_gpuva_manager *mgr,
>>> {
>>> struct drm_gpuva_ops *ops;
>>> struct drm_gpuva_op *op;
>>> + struct drm_gpuva_gem *vm_bo;
>>> struct drm_gpuva *va;
>>> int ret;
>>> @@ -1674,7 +2340,7 @@ drm_gpuva_gem_unmap_ops_create(struct drm_gpuva_manager *mgr,
>>> INIT_LIST_HEAD(&ops->list);
>>> - drm_gem_for_each_gpuva(va, obj) {
>>> + drm_gem_for_each_gpuva(va, vm_bo, mgr, obj) {
>>> op = gpuva_op_alloc(mgr);
>>> if (!op) {
>>> ret = -ENOMEM;
>>> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
>>> index bc9f6aa2f3fe..783ed3ab440d 100644
>>> --- a/include/drm/drm_gem.h
>>> +++ b/include/drm/drm_gem.h
>>> @@ -571,7 +571,7 @@ int drm_gem_evict(struct drm_gem_object *obj);
>>> * drm_gem_gpuva_init() - initialize the gpuva list of a GEM object
>>> * @obj: the &drm_gem_object
>>> *
>>> - * This initializes the &drm_gem_object's &drm_gpuva list.
>>> + * This initializes the &drm_gem_object's &drm_gpuva_gem list.
>>> *
>>> * Calling this function is only necessary for drivers intending to support the
>>> * &drm_driver_feature DRIVER_GEM_GPUVA.
>>> @@ -584,28 +584,44 @@ static inline void drm_gem_gpuva_init(struct drm_gem_object *obj)
>>> }
>>> /**
>>> - * drm_gem_for_each_gpuva() - iternator to walk over a list of gpuvas
>>> - * @entry__: &drm_gpuva structure to assign to in each iteration step
>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are associated with
>>> + * drm_gem_for_each_gpuva_gem() - iterator to walk over a list of &drm_gpuva_gem
>>> + * @entry__: &drm_gpuva_gem structure to assign to in each iteration step
>>> + * @obj__: the &drm_gem_object the &drm_gpuva_gem to walk are associated with
>>> *
>>> - * This iterator walks over all &drm_gpuva structures associated with the
>>> - * &drm_gpuva_manager.
>>> + * This iterator walks over all &drm_gpuva_gem structures associated with the
>>> + * &drm_gem_object.
>>> */
>>> -#define drm_gem_for_each_gpuva(entry__, obj__) \
>>> - list_for_each_entry(entry__, &(obj__)->gpuva.list, gem.entry)
>>> +#define drm_gem_for_each_gpuva_gem(entry__, obj__) \
>>> + list_for_each_entry(entry__, &(obj__)->gpuva.list, list.entry.gem)
>>> /**
>>> - * drm_gem_for_each_gpuva_safe() - iternator to safely walk over a list of
>>> - * gpuvas
>>> - * @entry__: &drm_gpuva structure to assign to in each iteration step
>>> - * @next__: &next &drm_gpuva to store the next step
>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are associated with
>>> + * drm_gem_for_each_gpuva_gem_safe() - iterator to safely walk over a list of
>>> + * &drm_gpuva_gem
>>> + * @entry__: &drm_gpuva_gemstructure to assign to in each iteration step
>>> + * @next__: &next &drm_gpuva_gem to store the next step
>>> + * @obj__: the &drm_gem_object the &drm_gpuva_gem to walk are associated with
>>> *
>>> - * This iterator walks over all &drm_gpuva structures associated with the
>>> + * This iterator walks over all &drm_gpuva_gem structures associated with the
>>> * &drm_gem_object. It is implemented with list_for_each_entry_safe(), hence
>>> * it is save against removal of elements.
>>> */
>>> -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__) \
>>> - list_for_each_entry_safe(entry__, next__, &(obj__)->gpuva.list, gem.entry)
>>> +#define drm_gem_for_each_gpuva_gem_safe(entry__, next__, obj__) \
>>> + list_for_each_entry_safe(entry__, next__, &(obj__)->gpuva.list, list.entry.gem)
>>> +
>>> +/**
>>> + * drm_gem_for_each_gpuva() - iterator to walk over a list of &drm_gpuva
>>> + * @va__: &drm_gpuva structure to assign to in each iteration step
>>> + * @vm_bo__: the &drm_gpuva_gem representing the @mgr__ and @obj__ combination
>>> + * @mgr__: the &drm_gpuva_manager the &drm_gpuvas to walk are associated with
>>> + * @obj__: the &drm_gem_object the &drm_gpuvas to walk are associated with
>>> + *
>>> + * This iterator walks over all &drm_gpuva structures associated with the
>>> + * &drm_gpuva_manager and &drm_gem_object.
>>> + */
>>> +#define drm_gem_for_each_gpuva(va__, vm_bo__, mgr__, obj__) \
>>> + for (vm_bo__ = drm_gpuva_gem_find(mgr__, obj__), \
>>> + va__ = vm_bo__ ? list_first_entry(&vm_bo__->list.gpuva, typeof(*va__), gem.entry) : NULL; \
>>> + va__ && !list_entry_is_head(va__, &vm_bo__->list.gpuva, gem.entry); \
>>> + va__ = list_next_entry(va__, gem.entry))
>>> #endif /* __DRM_GEM_H__ */
>>> diff --git a/include/drm/drm_gpuva_mgr.h b/include/drm/drm_gpuva_mgr.h
>>> index ed8d50200cc3..693e2da3f425 100644
>>> --- a/include/drm/drm_gpuva_mgr.h
>>> +++ b/include/drm/drm_gpuva_mgr.h
>>> @@ -26,12 +26,16 @@
>>> */
>>> #include <linux/list.h>
>>> +#include <linux/dma-resv.h>
>>> +#include <linux/maple_tree.h>
>>> #include <linux/rbtree.h>
>>> #include <linux/types.h>
>>> #include <drm/drm_gem.h>
>>> +#include <drm/drm_exec.h>
>>> struct drm_gpuva_manager;
>>> +struct drm_gpuva_gem;
>>> struct drm_gpuva_fn_ops;
>>> /**
>>> @@ -140,7 +144,7 @@ struct drm_gpuva {
>>> int drm_gpuva_insert(struct drm_gpuva_manager *mgr, struct drm_gpuva *va);
>>> void drm_gpuva_remove(struct drm_gpuva *va);
>>> -void drm_gpuva_link(struct drm_gpuva *va);
>>> +void drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuva_gem *vm_bo);
>>> void drm_gpuva_unlink(struct drm_gpuva *va);
>>> struct drm_gpuva *drm_gpuva_find(struct drm_gpuva_manager *mgr,
>>> @@ -240,15 +244,137 @@ struct drm_gpuva_manager {
>>> * @ops: &drm_gpuva_fn_ops providing the split/merge steps to drivers
>>> */
>>> const struct drm_gpuva_fn_ops *ops;
>>> +
>>> + /**
>>> + * @d_obj: Dummy GEM object; used internally to pass the GPU VMs
>>> + * dma-resv to &drm_exec.
>>> + */
>>> + struct drm_gem_object d_obj;
>>> +
>>> + /**
>>> + * @resv: the &dma_resv for &drm_gem_objects mapped in this GPU VA
>>> + * space
>>> + */
>>> + struct dma_resv *resv;
>>> +
>>> + /**
>>> + * @exec: the &drm_exec helper to lock external &drm_gem_objects
>>> + */
>>> + struct drm_exec exec;
>>> +
>>> + /**
>>> + * @mt_ext: &maple_tree storing external &drm_gem_objects
>>> + */
>>> + struct maple_tree mt_ext;
>> Why are you using a maple tree here? Insertion and removal is O(log(n))
>> instead of O(1) for a list?
>>
> Having a list of drm_gem_objects directly wouldn't work, as multiple GPU-VMs
> could have mappings of the same extobj.
>
> I considered using the VM_BO abstraction (struct drm_gpuva_gem) as list entry
> instead, which also seems to be the obvious choice. However, there is a locking
> conflict.
>
> A drm_gem_object keeps a list of drm_gpuva_gems, while each drm_gpuva_gem keeps
> a list of drm_gpuvas. Both lists are either protected with the dma-resv lock of
> the corresponding drm_gem_object, or with an external lock provided by the
> driver (see drm_gem_gpuva_set_lock()). The latter is used by drivers performing
> changes on the GPUVA space directly from the fence signalling path.
>
> Now, similar to what drm_gpuva_link() and drm_gpuva_unlink() are doing already,
> we'd want to add a drm_gpuva_gem to the extobj list for the first mapping being
> linked and we'd want to remove it for the last one being unlinked.
>
> (Actually we'd want to add the drm_gpuva_gem object to the extobj list even
> before, because otherwise we'd not acquire it's dma-resv lock of this GEM object
> through drm_gpuva_manager_lock(). But that's trival, we could do that when we
> create the drm_gpuva_gem, which we need to do anyways.)
>
> Anyway, we'd probably want to keep removing the drm_gpuva_gem from the extobj
> list from drm_gpuva_unlink() when the last mapping of this BO is unlinked. In
> order to do so, we'd (as discussed above) either need to hold the outer GPU-VM
> lock or the GPU-VMs dma-resv lock. Both would be illegal in the case
> drm_gpuva_unlink() is called from within the fence signalling path. For drivers
> like XE or Nouveau, we'd at least need to make sure to not mess up the locking
> hierarchy of GPU-VM lock and dma-resv lock of the corresponding BO.
>
> Considering all that, I thought it's probably better to track extobjs separate
> from the drm_gpuva_gem, hence the maple tree choice.

Hm. OK, in Xe we're having a list of the xe_vmas (drm_gpuvas) that point
to external objects, or in the case of multiple mappings to the same gem
object, only one of the drm_gpuvas is in the list. These are protected
by the GPU-VM lock. I don't see a problem with removing those from the
fence signalling path, though?

Although assuming that's a no-go for GPUVA wouldn't an XArray be a
better choice, keeping O(1)?

>
>>> +
>>> + /**
>>> + * @evict: structure holding the evict list and evict list lock
>>> + */
>>> + struct {
>>> + /**
>>> + * @list: &list_head storing &drm_gem_objects currently being
>>> + * evicted
>>> + */
>>> + struct list_head list;
>>> +
>>> + /**
>>> + * @lock: spinlock to protect the evict list against concurrent
>>> + * insertion / removal of different &drm_gpuva_gems
>>> + */
>>> + spinlock_t lock;
>>> + } evict;
>>> };
>>> void drm_gpuva_manager_init(struct drm_gpuva_manager *mgr,
>>> + struct drm_device *drm,
>>> const char *name,
>>> u64 start_offset, u64 range,
>>> u64 reserve_offset, u64 reserve_range,
>>> const struct drm_gpuva_fn_ops *ops);
>>> void drm_gpuva_manager_destroy(struct drm_gpuva_manager *mgr);
>>> +/**
>>> + * DRM_GPUVA_EXEC - returns the &drm_gpuva_managers &drm_exec instance
>>> + * @mgr: the &drm_gpuva_managers to return the &drm_exec instance for
>>> + */
>>> +#define DRM_GPUVA_EXEC(mgr) &(mgr)->exec
>> A struct ww_acquire_ctx and thus a drm_exec is fundamentally per task and
>> should typically be allocated on the stack. Otherwise you'd need to protect
>> the mgr->exec member with an exclusive lock throughout the locking process,
>> and that's not what we want.
> Oh, good point. I think it works in Nouveau, because there it's implicitly
> protected with the job submission lock.
>
>> Did you consider subclassing a drm_exec for drm_gpuva purposes and add
>> needed ops to it: Like so:
> That's a good idea, will take this into V2.

Actually, I'm not fully sure that was a good idea: I've now have a
working version of Xe ported over to drm_exec, having these helpers in
mind and with the intention to start using them as they mature. What I
found, though is that open-coding the drm_exec loop is not all that bad,
but that building blocks that can be called from within the loop are useful:

Like the drm_gpuva_prepare_objects() and an imaginary
drm_gpuva_prepare_gpuva() that locks the vm resv and the resv of the
object (if different and the gpuva points to the object. And
drm_gpuva_prepare_array() although we don't use it within Xe. That means
you can use these building blocks like helpers and avoid the fn()
callback by instead open-coding.

But I guess YMMV.

>
>> struct drm_gpuva_exec_ops {
>>     int (*fn) (struct drm_gpuva_exec *exec, int num_fences);
> Is this the fn argument from drm_gpuva_manager_lock_extra()?
>
>>     int (*bo_validate) (struct drm_gpuva_exec *exec, struct drm_gem_object
>> *obj);
> I guess we could also keep that within the drm_gpuva_fn_ops? This should always
> be the same callback, right?
>
>> };
>>
>> struct drm_gpuva_exec {
>>     const struct drm_gpuva_exec_ops *ops;
>>     struct drm_exec exec;
>>     struct drm_gpuva_manager *mgr;
>> };
>>
>> Although I'd actually expect bo_validate to be part of fn in the typical
>> case. The drm_gpuva_exec would then be allocated by the caller on the stack.
> This doesn't sound like my assumption about fn() above is correct.

Well one important thing in our conversion is that ttm_bo_validate ()
needs to be in the until_all_locked() loop. We want to be able soon to
use sleeping locks for eviction, so a xe_bo_validate() would, at least
temporarily, add locked objects to the drm_exec list of locked objects.
That means everything that may end up calling validate deep within the
call chain needs to be part of the until_all_locked() loop, so our
drm_gpuva_manager_lock_extra() fn callback would include those validates
and look different all the time. Hence that's why open-coding isn't all
that bad...

/Thomas

>
>>
>>> +
>>> +int drm_gpuva_manager_lock_extra(struct drm_gpuva_manager *mgr,
>>> + int (*fn)(struct drm_gpuva_manager *mgr,
>>> + void *priv, unsigned int num_fences),
>>> + void *priv,
>>> + unsigned int num_fences,
>>> + bool interruptible);
>>> +
>>> +int drm_gpuva_manager_lock_array(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object **objs,
>>> + unsigned int num_objs,
>>> + unsigned int num_fences,
>>> + bool interruptible);
>>> +
>>> +/**
>>> + * drm_gpuva_manager_lock() - lock all dma-resv of all assoiciated BOs
>>> + * @mgr: the &drm_gpuva_manager
>>> + * @num_fences: the amount of &dma_fences to reserve
>>> + * @interruptible: sleep interruptible if waiting
>>> + *
>>> + * Acquires all dma-resv locks of all &drm_gem_objects the given
>>> + * &drm_gpuva_manager contains mappings of.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +static inline int
>>> +drm_gpuva_manager_lock(struct drm_gpuva_manager *mgr,
>>> + unsigned int num_fences,
>>> + bool interruptible)
>>> +{
>>> + return drm_gpuva_manager_lock_extra(mgr, NULL, NULL, num_fences,
>>> + interruptible);
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuva_manager_lock() - lock all dma-resv of all assoiciated BOs
>>> + * @mgr: the &drm_gpuva_manager
>>> + *
>>> + * Releases all dma-resv locks of all &drm_gem_objects previously acquired
>>> + * through drm_gpuva_manager_lock() or its variants.
>>> + *
>>> + * Returns: 0 on success, negative error code on failure.
>>> + */
>>> +static inline void
>>> +drm_gpuva_manager_unlock(struct drm_gpuva_manager *mgr)
>>> +{
>>> + drm_exec_fini(&mgr->exec);
>>> +}
>>> +
>>> +int drm_gpuva_manager_validate(struct drm_gpuva_manager *mgr);
>>> +void drm_gpuva_manager_resv_add_fence(struct drm_gpuva_manager *mgr,
>>> + struct dma_fence *fence,
>>> + enum dma_resv_usage private_usage,
>>> + enum dma_resv_usage extobj_usage);
>>> +
>>> +int drm_gpuva_extobj_insert(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj);
>>> +void drm_gpuva_extobj_get(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj);
>>> +void drm_gpuva_extobj_put(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj);
>>> +
>>> +/**
>>> + * drm_gpuva_is_extobj() - indicates whether the given &drm_gem_object is an
>>> + * external object
>>> + * @mgr: the &drm_gpuva_manager to check
>>> + * @obj: the &drm_gem_object to check
>>> + *
>>> + * Returns: true if the &drm_gem_object &dma_resv differs from the
>>> + * &drm_gpuva_managers &dma_resv, false otherwise
>>> + */
>>> +static inline bool drm_gpuva_is_extobj(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + return obj && obj->resv != mgr->resv;
>>> +}
>>> +
>>> static inline struct drm_gpuva *
>>> __drm_gpuva_next(struct drm_gpuva *va)
>>> {
>>> @@ -327,6 +453,138 @@ __drm_gpuva_next(struct drm_gpuva *va)
>>> #define drm_gpuva_for_each_va_safe(va__, next__, mgr__) \
>>> list_for_each_entry_safe(va__, next__, &(mgr__)->rb.list, rb.entry)
>>> +/**
>>> + * struct drm_gpuva_gem - structure representing a &drm_gpuva_manager and
>>> + * &drm_gem_object combination
>>> + *
>>> + * This structure is an abstraction representing a &drm_gpuva_manager and
>>> + * &drm_gem_object combination. It serves as an indirection to accelerate
>>> + * iterating all &drm_gpuvas within a &drm_gpuva_manager backed by the same
>>> + * &drm_gem_object.
>>> + *
>>> + * Furthermore it is used cache evicted GEM objects for a certain GPU-VM to
>>> + * accelerate validation.
>>> + *
>>> + * Typically, drivers want to create an instance of a struct drm_gpuva_gem once
>>> + * a GEM object is mapped first in a GPU-VM and release the instance once the
>>> + * last mapping of the GEM object in this GPU-VM is unmapped.
>>> + */
>>> +struct drm_gpuva_gem {
>>> +
>>> + /**
>>> + * @mgr: The &drm_gpuva_manager the @obj is mapped in.
>>> + */
>>> + struct drm_gpuva_manager *mgr;
>>> +
>>> + /**
>>> + * @obj: The &drm_gem_object being mapped in the @mgr.
>>> + */
>>> + struct drm_gem_object *obj;
>>> +
>>> + /**
>>> + * @kref: The reference count for this &drm_gpuva_gem.
>>> + */
>>> + struct kref kref;
>>> +
>>> + /**
>>> + * @list: Structure containing all &list_heads.
>>> + */
>>> + struct {
>>> + /**
>>> + * @gpuva: The list of linked &drm_gpuvas.
>>> + */
>>> + struct list_head gpuva;
>>> +
>>> + /**
>>> + * @entry: Structure containing all &list_heads serving as
>>> + * entry.
>>> + */
>>> + struct {
>>> + /**
>>> + * @gem: List entry to attach to the &drm_gem_objects
>>> + * gpuva list.
>>> + */
>>> + struct list_head gem;
>>> +
>>> + /**
>>> + * @evict: List entry to attach to the
>>> + * &drm_gpuva_managers evict list.
>>> + */
>>> + struct list_head evict;
>>> + } entry;
>>> + } list;
>>> +};
>>> +
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_obtain(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj);
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_obtain_prealloc(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj,
>>> + struct drm_gpuva_gem *__vm_bo);
>>> +
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_find(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj);
>>> +
>>> +void drm_gpuva_gem_evict(struct drm_gem_object *obj, bool evict);
>>> +
>>> +struct drm_gpuva_gem *
>>> +drm_gpuva_gem_create(struct drm_gpuva_manager *mgr,
>>> + struct drm_gem_object *obj);
>>> +void drm_gpuva_gem_destroy(struct kref *kref);
>>> +
>>> +/**
>>> + * drm_gpuva_gem_get() - acquire a struct drm_gpuva_gem reference
>>> + * @vm_bo: the &drm_gpuva_gem to acquire the reference of
>>> + *
>>> + * This function acquires an additional reference to @vm_bo. It is illegal to
>>> + * call this without already holding a reference. No locks required.
>>> + */
>>> +static inline struct drm_gpuva_gem *
>>> +drm_gpuva_gem_get(struct drm_gpuva_gem *vm_bo)
>>> +{
>>> + kref_get(&vm_bo->kref);
>>> + return vm_bo;
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuva_gem_put() - drop a struct drm_gpuva_gem reference
>>> + * @vm_bo: the &drm_gpuva_gem to release the reference of
>>> + *
>>> + * This releases a reference to @vm_bo.
>>> + */
>>> +static inline void
>>> +drm_gpuva_gem_put(struct drm_gpuva_gem *vm_bo)
>>> +{
>>> + kref_put(&vm_bo->kref, drm_gpuva_gem_destroy);
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuva_gem_for_each_va() - iterator to walk over a list of &drm_gpuva
>>> + * @va__: &drm_gpuva structure to assign to in each iteration step
>>> + * @vm_bo__: the &drm_gpuva_gem the &drm_gpuva to walk are associated with
>>> + *
>>> + * This iterator walks over all &drm_gpuva structures associated with the
>>> + * &drm_gpuva_gem.
>>> + */
>>> +#define drm_gpuva_gem_for_each_va(va__, vm_bo__) \
>>> + list_for_each_entry(va__, &(vm_bo)->list.gpuva, gem.entry)
>>> +
>>> +/**
>>> + * drm_gpuva_gem_for_each_va_safe() - iterator to safely walk over a list of
>>> + * &drm_gpuva
>>> + * @va__: &drm_gpuva structure to assign to in each iteration step
>>> + * @next__: &next &drm_gpuva to store the next step
>>> + * @vm_bo__: the &drm_gpuva_gem the &drm_gpuva to walk are associated with
>>> + *
>>> + * This iterator walks over all &drm_gpuva structures associated with the
>>> + * &drm_gpuva_gem. It is implemented with list_for_each_entry_safe(), hence
>>> + * it is save against removal of elements.
>>> + */
>>> +#define drm_gpuva_gem_for_each_va_safe(va__, next__, vm_bo__) \
>>> + list_for_each_entry_safe(va__, next__, &(vm_bo)->list.gpuva, gem.entry)
>>> +
>>> /**
>>> * enum drm_gpuva_op_type - GPU VA operation type
>>> *
>>> @@ -641,6 +899,30 @@ struct drm_gpuva_fn_ops {
>>> */
>>> void (*op_free)(struct drm_gpuva_op *op);
>>> + /**
>>> + * @vm_bo_alloc: called when the &drm_gpuva_manager allocates
>>> + * a struct drm_gpuva_gem
>>> + *
>>> + * Some drivers may want to embed struct drm_gpuva_gem into driver
>>> + * specific structures. By implementing this callback drivers can
>>> + * allocate memory accordingly.
>>> + *
>>> + * This callback is optional.
>>> + */
>>> + struct drm_gpuva_gem *(*vm_bo_alloc)(void);
>>> +
>>> + /**
>>> + * @vm_bo_free: called when the &drm_gpuva_manager frees a
>>> + * struct drm_gpuva_gem
>>> + *
>>> + * Some drivers may want to embed struct drm_gpuva_gem into driver
>>> + * specific structures. By implementing this callback drivers can
>>> + * free the previously allocated memory accordingly.
>>> + *
>>> + * This callback is optional.
>>> + */
>>> + void (*vm_bo_free)(struct drm_gpuva_gem *vm_bo);
>>> +
>>> /**
>>> * @sm_step_map: called from &drm_gpuva_sm_map to finally insert the
>>> * mapping once all previous steps were completed
>>> @@ -684,6 +966,17 @@ struct drm_gpuva_fn_ops {
>>> * used.
>>> */
>>> int (*sm_step_unmap)(struct drm_gpuva_op *op, void *priv);
>>> +
>>> + /**
>>> + * @bo_validate: called from drm_gpuva_manager_validate()
>>> + *
>>> + * Drivers receive this callback for every evicted &drm_gem_object being
>>> + * mapped in the corresponding &drm_gpuva_manager.
>>> + *
>>> + * Typically, drivers would call their driver specific variant of
>>> + * ttm_bo_validate() from within this callback.
>>> + */
>>> + int (*bo_validate)(struct drm_gem_object *obj);
>>> };
>>> int drm_gpuva_sm_map(struct drm_gpuva_manager *mgr, void *priv,
>>> @@ -696,11 +989,18 @@ int drm_gpuva_sm_unmap(struct drm_gpuva_manager *mgr, void *priv,
>>> void drm_gpuva_map(struct drm_gpuva_manager *mgr,
>>> struct drm_gpuva *va,
>>> struct drm_gpuva_op_map *op);
>>> +void drm_gpuva_map_get(struct drm_gpuva_manager *mgr,
>>> + struct drm_gpuva *va,
>>> + struct drm_gpuva_op_map *op);
>>> void drm_gpuva_remap(struct drm_gpuva *prev,
>>> struct drm_gpuva *next,
>>> struct drm_gpuva_op_remap *op);
>>> +void drm_gpuva_remap_get(struct drm_gpuva *prev,
>>> + struct drm_gpuva *next,
>>> + struct drm_gpuva_op_remap *op);
>>> void drm_gpuva_unmap(struct drm_gpuva_op_unmap *op);
>>> +void drm_gpuva_unmap_put(struct drm_gpuva_op_unmap *op);
>>> #endif /* __DRM_GPUVA_MGR_H__ */