[RFC 03/10] drm/i915/vm_bind: Support private and shared BOs

Christian König christian.koenig at amd.com
Thu Jul 7 13:27:43 UTC 2022


Am 02.07.22 um 00:50 schrieb Niranjana Vishwanathapura:
> Add uapi allowing user to specify a BO as private to a specified VM
> during the BO creation.
> VM private BOs can only be mapped on the specified VM and can't be
> dma_buf exported. VM private BOs share a single common dma_resv object,
> hence has a performance advantage requiring a single dma_resv object
> update in the execbuf path compared to non-private (shared) BOs.

Sounds like you picked up the per VM BO idea from amdgpu here :)

Of hand looks like a good idea, but shouldn't we add a few comments in 
the common documentation about that?

E.g. something like "Multiple buffer objects sometimes share the same 
dma_resv object....." to the dma_resv documentation.

Probably best as a separate patch after this here has landed.

Regards,
Christian.

>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_create.c    | 41 ++++++++++++++++++-
>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c    |  6 +++
>   .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 ++
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c       |  3 ++
>   drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h   | 11 +++++
>   .../drm/i915/gem/i915_gem_vm_bind_object.c    |  9 ++++
>   drivers/gpu/drm/i915/gt/intel_gtt.c           |  4 ++
>   drivers/gpu/drm/i915/gt/intel_gtt.h           |  2 +
>   drivers/gpu/drm/i915/i915_vma.c               |  1 +
>   drivers/gpu/drm/i915/i915_vma_types.h         |  2 +
>   include/uapi/drm/i915_drm.h                   | 30 ++++++++++++++
>   11 files changed, 110 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> index 927a87e5ec59..7e264566b51f 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_create.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> @@ -11,6 +11,7 @@
>   #include "pxp/intel_pxp.h"
>   
>   #include "i915_drv.h"
> +#include "i915_gem_context.h"
>   #include "i915_gem_create.h"
>   #include "i915_trace.h"
>   #include "i915_user_extensions.h"
> @@ -243,6 +244,7 @@ struct create_ext {
>   	unsigned int n_placements;
>   	unsigned int placement_mask;
>   	unsigned long flags;
> +	u32 vm_id;
>   };
>   
>   static void repr_placements(char *buf, size_t size,
> @@ -392,9 +394,24 @@ static int ext_set_protected(struct i915_user_extension __user *base, void *data
>   	return 0;
>   }
>   
> +static int ext_set_vm_private(struct i915_user_extension __user *base,
> +			      void *data)
> +{
> +	struct drm_i915_gem_create_ext_vm_private ext;
> +	struct create_ext *ext_data = data;
> +
> +	if (copy_from_user(&ext, base, sizeof(ext)))
> +		return -EFAULT;
> +
> +	ext_data->vm_id = ext.vm_id;
> +
> +	return 0;
> +}
> +
>   static const i915_user_extension_fn create_extensions[] = {
>   	[I915_GEM_CREATE_EXT_MEMORY_REGIONS] = ext_set_placements,
>   	[I915_GEM_CREATE_EXT_PROTECTED_CONTENT] = ext_set_protected,
> +	[I915_GEM_CREATE_EXT_VM_PRIVATE] = ext_set_vm_private,
>   };
>   
>   /**
> @@ -410,6 +427,7 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
>   	struct drm_i915_private *i915 = to_i915(dev);
>   	struct drm_i915_gem_create_ext *args = data;
>   	struct create_ext ext_data = { .i915 = i915 };
> +	struct i915_address_space *vm = NULL;
>   	struct drm_i915_gem_object *obj;
>   	int ret;
>   
> @@ -423,6 +441,12 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
>   	if (ret)
>   		return ret;
>   
> +	if (ext_data.vm_id) {
> +		vm = i915_gem_vm_lookup(file->driver_priv, ext_data.vm_id);
> +		if (unlikely(!vm))
> +			return -ENOENT;
> +	}
> +
>   	if (!ext_data.n_placements) {
>   		ext_data.placements[0] =
>   			intel_memory_region_by_type(i915, INTEL_MEMORY_SYSTEM);
> @@ -449,8 +473,21 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
>   						ext_data.placements,
>   						ext_data.n_placements,
>   						ext_data.flags);
> -	if (IS_ERR(obj))
> -		return PTR_ERR(obj);
> +	if (IS_ERR(obj)) {
> +		ret = PTR_ERR(obj);
> +		goto vm_put;
> +	}
> +
> +	if (vm) {
> +		obj->base.resv = vm->root_obj->base.resv;
> +		obj->priv_root = i915_gem_object_get(vm->root_obj);
> +		i915_vm_put(vm);
> +	}
>   
>   	return i915_gem_publish(obj, file, &args->size, &args->handle);
> +vm_put:
> +	if (vm)
> +		i915_vm_put(vm);
> +
> +	return ret;
>   }
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> index f5062d0c6333..6433173c3e84 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> @@ -218,6 +218,12 @@ struct dma_buf *i915_gem_prime_export(struct drm_gem_object *gem_obj, int flags)
>   	struct drm_i915_gem_object *obj = to_intel_bo(gem_obj);
>   	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
>   
> +	if (obj->priv_root) {
> +		drm_dbg(obj->base.dev,
> +			"Exporting VM private objects is not allowed\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
>   	exp_info.ops = &i915_dmabuf_ops;
>   	exp_info.size = gem_obj->size;
>   	exp_info.flags = flags;
> 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 5cf36a130061..9fe3395ad4d9 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -241,6 +241,9 @@ struct drm_i915_gem_object {
>   
>   	const struct drm_i915_gem_object_ops *ops;
>   
> +	/* Shared root is object private to a VM; NULL otherwise */
> +	struct drm_i915_gem_object *priv_root;
> +
>   	struct {
>   		/**
>   		 * @vma.lock: protect the list/tree of vmas
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 7e1f8b83077f..f1912b12db00 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -1152,6 +1152,9 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
>   	i915_gem_object_release_memory_region(obj);
>   	mutex_destroy(&obj->ttm.get_io_page.lock);
>   
> +	if (obj->priv_root)
> +		i915_gem_object_put(obj->priv_root);
> +
>   	if (obj->ttm.created) {
>   		/*
>   		 * We freely manage the shrinker LRU outide of the mm.pages life
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> index 642cdb559f17..ee6e4c52e80e 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> @@ -26,6 +26,17 @@ static inline void i915_gem_vm_bind_unlock(struct i915_address_space *vm)
>   	mutex_unlock(&vm->vm_bind_lock);
>   }
>   
> +static inline int i915_gem_vm_priv_lock(struct i915_address_space *vm,
> +					struct i915_gem_ww_ctx *ww)
> +{
> +	return i915_gem_object_lock(vm->root_obj, ww);
> +}
> +
> +static inline void i915_gem_vm_priv_unlock(struct i915_address_space *vm)
> +{
> +	i915_gem_object_unlock(vm->root_obj);
> +}
> +
>   struct i915_vma *
>   i915_gem_vm_bind_lookup_vma(struct i915_address_space *vm, u64 va);
>   void i915_gem_vm_bind_remove(struct i915_vma *vma, bool release_obj);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> index 43ceb4dcca6c..3201204c8e74 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> @@ -85,6 +85,7 @@ void i915_gem_vm_bind_remove(struct i915_vma *vma, bool release_obj)
>   
>   	if (!list_empty(&vma->vm_bind_link)) {
>   		list_del_init(&vma->vm_bind_link);
> +		list_del_init(&vma->non_priv_vm_bind_link);
>   		i915_vm_bind_it_remove(vma, &vma->vm->va);
>   
>   		/* Release object */
> @@ -185,6 +186,11 @@ int i915_gem_vm_bind_obj(struct i915_address_space *vm,
>   		goto put_obj;
>   	}
>   
> +	if (obj->priv_root && obj->priv_root != vm->root_obj) {
> +		ret = -EINVAL;
> +		goto put_obj;
> +	}
> +
>   	ret = i915_gem_vm_bind_lock_interruptible(vm);
>   	if (ret)
>   		goto put_obj;
> @@ -211,6 +217,9 @@ int i915_gem_vm_bind_obj(struct i915_address_space *vm,
>   
>   	list_add_tail(&vma->vm_bind_link, &vm->vm_bound_list);
>   	i915_vm_bind_it_insert(vma, &vm->va);
> +	if (!obj->priv_root)
> +		list_add_tail(&vma->non_priv_vm_bind_link,
> +			      &vm->non_priv_vm_bind_list);
>   
>   	/* Hold object reference until vm_unbind */
>   	i915_gem_object_get(vma->obj);
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
> index 135dc4a76724..df0a8459c3c6 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
> @@ -176,6 +176,7 @@ int i915_vm_lock_objects(struct i915_address_space *vm,
>   void i915_address_space_fini(struct i915_address_space *vm)
>   {
>   	drm_mm_takedown(&vm->mm);
> +	i915_gem_object_put(vm->root_obj);
>   	GEM_BUG_ON(!RB_EMPTY_ROOT(&vm->va.rb_root));
>   	mutex_destroy(&vm->vm_bind_lock);
>   }
> @@ -289,6 +290,9 @@ void i915_address_space_init(struct i915_address_space *vm, int subclass)
>   	INIT_LIST_HEAD(&vm->vm_bind_list);
>   	INIT_LIST_HEAD(&vm->vm_bound_list);
>   	mutex_init(&vm->vm_bind_lock);
> +	INIT_LIST_HEAD(&vm->non_priv_vm_bind_list);
> +	vm->root_obj = i915_gem_object_create_internal(vm->i915, PAGE_SIZE);
> +	GEM_BUG_ON(IS_ERR(vm->root_obj));
>   }
>   
>   void *__px_vaddr(struct drm_i915_gem_object *p)
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
> index d4a6ce65251d..f538ce9115c9 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
> @@ -267,6 +267,8 @@ struct i915_address_space {
>   	struct list_head vm_bound_list;
>   	/* va tree of persistent vmas */
>   	struct rb_root_cached va;
> +	struct list_head non_priv_vm_bind_list;
> +	struct drm_i915_gem_object *root_obj;
>   
>   	/* Global GTT */
>   	bool is_ggtt:1;
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index d324e29cef0a..f0226581d342 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -236,6 +236,7 @@ vma_create(struct drm_i915_gem_object *obj,
>   	mutex_unlock(&vm->mutex);
>   
>   	INIT_LIST_HEAD(&vma->vm_bind_link);
> +	INIT_LIST_HEAD(&vma->non_priv_vm_bind_link);
>   	return vma;
>   
>   err_unlock:
> diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h
> index b6d179bdbfa0..2298b3d6b7c4 100644
> --- a/drivers/gpu/drm/i915/i915_vma_types.h
> +++ b/drivers/gpu/drm/i915/i915_vma_types.h
> @@ -290,6 +290,8 @@ struct i915_vma {
>   	struct list_head vm_link;
>   
>   	struct list_head vm_bind_link; /* Link in persistent VMA list */
> +	/* Link in non-private persistent VMA list */
> +	struct list_head non_priv_vm_bind_link;
>   
>   	/** Interval tree structures for persistent vma */
>   	struct rb_node rb;
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 26cca49717f8..ce1c6592b0d7 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -3542,9 +3542,13 @@ struct drm_i915_gem_create_ext {
>   	 *
>   	 * For I915_GEM_CREATE_EXT_PROTECTED_CONTENT usage see
>   	 * struct drm_i915_gem_create_ext_protected_content.
> +	 *
> +	 * For I915_GEM_CREATE_EXT_VM_PRIVATE usage see
> +	 * struct drm_i915_gem_create_ext_vm_private.
>   	 */
>   #define I915_GEM_CREATE_EXT_MEMORY_REGIONS 0
>   #define I915_GEM_CREATE_EXT_PROTECTED_CONTENT 1
> +#define I915_GEM_CREATE_EXT_VM_PRIVATE 2
>   	__u64 extensions;
>   };
>   
> @@ -3662,6 +3666,32 @@ struct drm_i915_gem_create_ext_protected_content {
>   /* ID of the protected content session managed by i915 when PXP is active */
>   #define I915_PROTECTED_CONTENT_DEFAULT_SESSION 0xf
>   
> +/**
> + * struct drm_i915_gem_create_ext_vm_private - Extension to make the object
> + * private to the specified VM.
> + *
> + * See struct drm_i915_gem_create_ext.
> + *
> + * By default, BOs can be mapped on multiple VMs and can also be dma-buf
> + * exported. Hence these BOs are referred to as Shared BOs.
> + * During each execbuf3 submission, the request fence must be added to the
> + * dma-resv fence list of all shared BOs mapped on the VM.
> + *
> + * Unlike Shared BOs, these VM private BOs can only be mapped on the VM they
> + * are private to and can't be dma-buf exported. All private BOs of a VM share
> + * the dma-resv object. Hence during each execbuf3 submission, they need only
> + * one dma-resv fence list updated. Thus, the fast path (where required
> + * mappings are already bound) submission latency is O(1) w.r.t the number of
> + * VM private BOs.
> + */
> +struct drm_i915_gem_create_ext_vm_private {
> +	/** @base: Extension link. See struct i915_user_extension. */
> +	struct i915_user_extension base;
> +
> +	/** @vm_id: Id of the VM to which the object is private */
> +	__u32 vm_id;
> +};
> +
>   /**
>    * struct drm_i915_gem_vm_bind - VA to object mapping to bind.
>    *



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