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Date:   Thu, 6 Jul 2023 10:49:43 +0200
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From:   =?UTF-8?Q?Thomas_Hellstr=c3=b6m_=28Intel=29?= 
        <thomas_os@shipmail.org>
Subject: Re: [PATCH drm-next v6 02/13] drm: manager to keep track of GPUs VA
 mappings
To:     Danilo Krummrich <dakr@redhat.com>, airlied@gmail.com,
        daniel@ffwll.ch, tzimmermann@suse.de, mripard@kernel.org,
        corbet@lwn.net, christian.koenig@amd.com, bskeggs@redhat.com,
        Liam.Howlett@oracle.com, matthew.brost@intel.com,
        boris.brezillon@collabora.com, alexdeucher@gmail.com,
        ogabbay@kernel.org, bagasdotme@gmail.com, willy@infradead.org,
        jason@jlekstrand.net
Cc:     linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Donald Robson <donald.robson@imgtec.com>,
        Dave Airlie <airlied@redhat.com>
References: <20230629222651.3196-1-dakr@redhat.com>
 <20230629222651.3196-3-dakr@redhat.com>
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Hi, Danilo

Some review comments below:

On 6/30/23 00:25, Danilo Krummrich wrote:
> Add infrastructure to keep track of GPU virtual address (VA) mappings
> with a decicated VA space manager implementation.
>
> New UAPIs, motivated by Vulkan sparse memory bindings graphics drivers
> start implementing, allow userspace applications to request multiple and
> arbitrary GPU VA mappings of buffer objects. The DRM GPU VA manager is
> intended to serve the following purposes in this context.
>
> 1) Provide infrastructure to track GPU VA allocations and mappings,
>     making use of the maple_tree.

It looks like we're not using the maple tree anymore, but rather an 
instantiation of an interval tree.

(Perhaps as a follow-up it makes sense to provide a pre-instantiated 
common u64 version of the interval tree in addition to the unsigned long 
one since it appears to be used in multiple places in graphics drivers).

> 2) Generically connect GPU VA mappings to their backing buffers, in
>     particular DRM GEM objects.
>
> 3) Provide a common implementation to perform more complex mapping
>     operations on the GPU VA space. In particular splitting and merging
>     of GPU VA mappings, e.g. for intersecting mapping requests or partial
>     unmap requests.
>
> Tested-by: Donald Robson<donald.robson@imgtec.com>
> Reviewed-by: Boris Brezillon<boris.brezillon@collabora.com>
> Suggested-by: Dave Airlie<airlied@redhat.com>
> Signed-off-by: Danilo Krummrich<dakr@redhat.com>
> ---
>   Documentation/gpu/drm-mm.rst    |   36 +
>   drivers/gpu/drm/Makefile        |    1 +
>   drivers/gpu/drm/drm_gem.c       |    3 +
>   drivers/gpu/drm/drm_gpuva_mgr.c | 1743 +++++++++++++++++++++++++++++++
>   include/drm/drm_drv.h           |    6 +
>   include/drm/drm_gem.h           |   52 +
>   include/drm/drm_gpuva_mgr.h     |  756 ++++++++++++++
>   7 files changed, 2597 insertions(+)
>   create mode 100644 drivers/gpu/drm/drm_gpuva_mgr.c
>   create mode 100644 include/drm/drm_gpuva_mgr.h
>
> diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst
> index a52e6f4117d6..3d5dc9dc1bfe 100644
> --- a/Documentation/gpu/drm-mm.rst
> +++ b/Documentation/gpu/drm-mm.rst
> @@ -466,6 +466,42 @@ DRM MM Range Allocator Function References
>   .. kernel-doc:: drivers/gpu/drm/drm_mm.c
>      :export:
>   
> +DRM GPU VA Manager
> +==================
> +
> +Overview
> +--------
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gpuva_mgr.c
> +   :doc: Overview
> +
> +Split and Merge
> +---------------
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gpuva_mgr.c
> +   :doc: Split and Merge
> +
> +Locking
> +-------
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gpuva_mgr.c
> +   :doc: Locking
> +
> +Examples
> +--------
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gpuva_mgr.c
> +   :doc: Examples
> +
> +DRM GPU VA Manager Function References
> +--------------------------------------
> +
> +.. kernel-doc:: include/drm/drm_gpuva_mgr.h
> +   :internal:
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gpuva_mgr.c
> +   :export:
> +
>   DRM Buddy Allocator
>   ===================
>   
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 414855e2a463..6d6c9dec66e8 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -45,6 +45,7 @@ drm-y := \
>   	drm_vblank.o \
>   	drm_vblank_work.o \
>   	drm_vma_manager.o \
> +	drm_gpuva_mgr.o \
>   	drm_writeback.o
>   drm-$(CONFIG_DRM_LEGACY) += \
>   	drm_agpsupport.o \
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 1a5a2cd0d4ec..cd878ebddbd0 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -164,6 +164,9 @@ void drm_gem_private_object_init(struct drm_device *dev,
>   	if (!obj->resv)
>   		obj->resv = &obj->_resv;
>   
> +	if (drm_core_check_feature(dev, DRIVER_GEM_GPUVA))
> +		drm_gem_gpuva_init(obj);
> +
>   	drm_vma_node_reset(&obj->vma_node);
>   	INIT_LIST_HEAD(&obj->lru_node);
>   }
> diff --git a/drivers/gpu/drm/drm_gpuva_mgr.c b/drivers/gpu/drm/drm_gpuva_mgr.c
> new file mode 100644
> index 000000000000..4414990c05cc
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_gpuva_mgr.c
> @@ -0,0 +1,1743 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
SPDX-License is GPL-2.0 but below looks like MIT. Can we use "GPL-2.0 OR 
MIT" or does something restrict it to GPL-only?
> + * Copyright (c) 2022 Red Hat.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + * Authors:
> + *     Danilo Krummrich<dakr@redhat.com>
> + *
> + */
> +
> +#include <drm/drm_gpuva_mgr.h>
> +
> +#include <linux/interval_tree_generic.h>
> +#include <linux/mm.h>
> +
> +/**
> + * DOC: Overview
> + *
> + * The DRM GPU VA Manager, represented by struct drm_gpuva_manager keeps track
> + * of a GPU's virtual address (VA) space and manages the corresponding virtual
> + * mappings represented by &drm_gpuva objects. It also keeps track of the
> + * mapping's backing &drm_gem_object buffers.
> + *
> + * &drm_gem_object buffers maintain a list of &drm_gpuva objects representing
> + * all existent GPU VA mappings using this &drm_gem_object as backing buffer.
> + *
> + * GPU VAs can be flagged as sparse, such that drivers may use GPU VAs to also
> + * keep track of sparse PTEs in order to support Vulkan 'Sparse Resources'.
> + *
> + * The GPU VA manager internally uses a rb-tree to manage the
> + * &drm_gpuva mappings within a GPU's virtual address space.
> + *
> + * The &drm_gpuva_manager contains a special &drm_gpuva representing the
> + * portion of VA space reserved by the kernel. This node is initialized together
> + * with the GPU VA manager instance and removed when the GPU VA manager is
> + * destroyed.
> + *
> + * In a typical application drivers would embed struct drm_gpuva_manager and
> + * struct drm_gpuva within their own driver specific structures, there won't be
> + * any memory allocations of it's own nor memory allocations of &drm_gpuva
s/it's/its/
> + * entries.
> + *
> + * The data structures needed to store &drm_gpuvas within the &drm_gpuva_manager
> + * are contained within struct drm_gpuva already. Hence, for inserting
> + * &drm_gpuva entries from within dma-fence signalling critical sections it is
> + * enough to pre-allocate the &drm_gpuva structures.
> + */
> +
> +/**
> + * DOC: Split and Merge
> + *
> + * Besides it's capability to manage and represent a GPU VA space, the
s/it's/its/
> + * &drm_gpuva_manager also provides functions to let the &drm_gpuva_manager
> + * calculate a sequence of operations to satisfy a given map or unmap request.
> + *
> + * Therefore the DRM GPU VA manager provides an algorithm implementing splitting
> + * and merging of existent GPU VA mappings with the ones that are requested to
> + * be mapped or unmapped. This feature is required by the Vulkan API to
> + * implement Vulkan 'Sparse Memory Bindings' - drivers UAPIs often refer to this
> + * as VM BIND.
> + *
> + * Drivers can call drm_gpuva_sm_map() to receive a sequence of callbacks
> + * containing map, unmap and remap operations for a given newly requested
> + * mapping. The sequence of callbacks represents the set of operations to
> + * execute in order to integrate the new mapping cleanly into the current state
> + * of the GPU VA space.
> + *
> + * Depending on how the new GPU VA mapping intersects with the existent mappings
> + * of the GPU VA space the &drm_gpuva_fn_ops callbacks contain an arbitrary
> + * amount of unmap operations, a maximum of two remap operations and a single
> + * map operation. The caller might receive no callback at all if no operation is
> + * required, e.g. if the requested mapping already exists in the exact same way.
> + *
> + * The single map operation represents the original map operation requested by
> + * the caller.
> + *
> + * &drm_gpuva_op_unmap contains a 'keep' field, which indicates whether the
> + * &drm_gpuva to unmap is physically contiguous with the original mapping
> + * request. Optionally, if 'keep' is set, drivers may keep the actual page table
> + * entries for this &drm_gpuva, adding the missing page table entries only and
> + * update the &drm_gpuva_manager's view of things accordingly.
> + *
> + * Drivers may do the same optimization, namely delta page table updates, also
> + * for remap operations. This is possible since &drm_gpuva_op_remap consists of
> + * one unmap operation and one or two map operations, such that drivers can
> + * derive the page table update delta accordingly.
> + *
> + * Note that there can't be more than two existent mappings to split up, one at
> + * the beginning and one at the end of the new mapping, hence there is a
> + * maximum of two remap operations.
> + *
> + * Analogous to drm_gpuva_sm_map() drm_gpuva_sm_unmap() uses &drm_gpuva_fn_ops
> + * to call back into the driver in order to unmap a range of GPU VA space. The
> + * logic behind this function is way simpler though: For all existent mappings
> + * enclosed by the given range unmap operations are created. For mappings which
> + * are only partically located within the given range, remap operations are
> + * created such that those mappings are split up and re-mapped partically.
> + *
> + * As an alternative to drm_gpuva_sm_map() and drm_gpuva_sm_unmap(),
> + * drm_gpuva_sm_map_ops_create() and drm_gpuva_sm_unmap_ops_create() can be used
> + * to directly obtain an instance of struct drm_gpuva_ops containing a list of
> + * &drm_gpuva_op, which can be iterated with drm_gpuva_for_each_op(). This list
> + * contains the &drm_gpuva_ops analogous to the callbacks one would receive when
> + * calling drm_gpuva_sm_map() or drm_gpuva_sm_unmap(). While this way requires
> + * more memory (to allocate the &drm_gpuva_ops), it provides drivers a way to
> + * iterate the &drm_gpuva_op multiple times, e.g. once in a context where memory
> + * allocations are possible (e.g. to allocate GPU page tables) and once in the
> + * dma-fence signalling critical path.
> + *
> + * To update the &drm_gpuva_manager's view of the GPU VA space
> + * drm_gpuva_insert() and drm_gpuva_remove() may be used. These functions can
> + * safely be used from &drm_gpuva_fn_ops callbacks originating from
> + * drm_gpuva_sm_map() or drm_gpuva_sm_unmap(). However, it might be more
> + * convenient to use the provided helper functions drm_gpuva_map(),
> + * drm_gpuva_remap() and drm_gpuva_unmap() instead.
> + *
> + * The following diagram depicts the basic relationships of existent GPU VA
> + * mappings, a newly requested mapping and the resulting mappings as implemented
> + * by drm_gpuva_sm_map() - it doesn't cover any arbitrary combinations of these.
> + *
> + * 1) Requested mapping is identical. Replace it, but indicate the backing PTEs
> + *    could be kept.
> + *
> + *    ::
> + *
> + *	     0     a     1
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	     0     a     1
> + *	req: |-----------| (bo_offset=n)
> + *
> + *	     0     a     1
> + *	new: |-----------| (bo_offset=n)
> + *
> + *
> + * 2) Requested mapping is identical, except for the BO offset, hence replace
> + *    the mapping.
> + *
> + *    ::
> + *
> + *	     0     a     1
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	     0     a     1
> + *	req: |-----------| (bo_offset=m)
> + *
> + *	     0     a     1
> + *	new: |-----------| (bo_offset=m)
> + *
> + *
> + * 3) Requested mapping is identical, except for the backing BO, hence replace
> + *    the mapping.
> + *
> + *    ::
> + *
> + *	     0     a     1
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	     0     b     1
> + *	req: |-----------| (bo_offset=n)
> + *
> + *	     0     b     1
> + *	new: |-----------| (bo_offset=n)
> + *
> + *
> + * 4) Existent mapping is a left aligned subset of the requested one, hence
> + *    replace the existent one.
> + *
> + *    ::
> + *
> + *	     0  a  1
> + *	old: |-----|       (bo_offset=n)
> + *
> + *	     0     a     2
> + *	req: |-----------| (bo_offset=n)
> + *
> + *	     0     a     2
> + *	new: |-----------| (bo_offset=n)
> + *
> + *    .. note::
> + *       We expect to see the same result for a request with a different BO
> + *       and/or non-contiguous BO offset.
> + *
> + *
> + * 5) Requested mapping's range is a left aligned subset of the existent one,
> + *    but backed by a different BO. Hence, map the requested mapping and split
> + *    the existent one adjusting it's BO offset.
Typo: s/it's/its/ above and in multiple places below.
> + *
> + *    ::
> + *
> + *	     0     a     2
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	     0  b  1
> + *	req: |-----|       (bo_offset=n)
> + *
> + *	     0  b  1  a' 2
> + *	new: |-----|-----| (b.bo_offset=n, a.bo_offset=n+1)
> + *
> + *    .. note::
> + *       We expect to see the same result for a request with a different BO
> + *       and/or non-contiguous BO offset.
> + *
> + *
> + * 6) Existent mapping is a superset of the requested mapping. Split it up, but
> + *    indicate that the backing PTEs could be kept.
> + *
> + *    ::
> + *
> + *	     0     a     2
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	     0  a  1
> + *	req: |-----|       (bo_offset=n)
> + *
> + *	     0  a  1  a' 2
> + *	new: |-----|-----| (a.bo_offset=n, a'.bo_offset=n+1)
> + *
> + *
> + * 7) Requested mapping's range is a right aligned subset of the existent one,
> + *    but backed by a different BO. Hence, map the requested mapping and split
> + *    the existent one, without adjusting the BO offset.
> + *
> + *    ::
> + *
> + *	     0     a     2
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	           1  b  2
> + *	req:       |-----| (bo_offset=m)
> + *
> + *	     0  a  1  b  2
> + *	new: |-----|-----| (a.bo_offset=n,b.bo_offset=m)
> + *
> + *
> + * 8) Existent mapping is a superset of the requested mapping. Split it up, but
> + *    indicate that the backing PTEs could be kept.
> + *
> + *    ::
> + *
> + *	      0     a     2
> + *	old: |-----------| (bo_offset=n)
> + *
> + *	           1  a  2
> + *	req:       |-----| (bo_offset=n+1)
> + *
> + *	     0  a' 1  a  2
> + *	new: |-----|-----| (a'.bo_offset=n, a.bo_offset=n+1)
> + *
> + *
> + * 9) Existent mapping is overlapped at the end by the requested mapping backed
> + *    by a different BO. Hence, map the requested mapping and split up the
> + *    existent one, without adjusting the BO offset.
> + *
> + *    ::
> + *
> + *	     0     a     2
> + *	old: |-----------|       (bo_offset=n)
> + *
> + *	           1     b     3
> + *	req:       |-----------| (bo_offset=m)
> + *
> + *	     0  a  1     b     3
> + *	new: |-----|-----------| (a.bo_offset=n,b.bo_offset=m)
> + *
> + *
> + * 10) Existent mapping is overlapped by the requested mapping, both having the
> + *     same backing BO with a contiguous offset. Indicate the backing PTEs of
> + *     the old mapping could be kept.
> + *
> + *     ::
> + *
> + *	      0     a     2
> + *	 old: |-----------|       (bo_offset=n)
> + *
> + *	            1     a     3
> + *	 req:       |-----------| (bo_offset=n+1)
> + *
> + *	      0  a' 1     a     3
> + *	 new: |-----|-----------| (a'.bo_offset=n, a.bo_offset=n+1)
> + *
> + *
> + * 11) Requested mapping's range is a centered subset of the existent one
> + *     having a different backing BO. Hence, map the requested mapping and split
> + *     up the existent one in two mappings, adjusting the BO offset of the right
> + *     one accordingly.
> + *
> + *     ::
> + *
> + *	      0        a        3
> + *	 old: |-----------------| (bo_offset=n)
> + *
> + *	            1  b  2
> + *	 req:       |-----|       (bo_offset=m)
> + *
> + *	      0  a  1  b  2  a' 3
> + *	 new: |-----|-----|-----| (a.bo_offset=n,b.bo_offset=m,a'.bo_offset=n+2)
> + *
> + *
> + * 12) Requested mapping is a contiguous subset of the existent one. Split it
> + *     up, but indicate that the backing PTEs could be kept.
> + *
> + *     ::
> + *
> + *	      0        a        3
> + *	 old: |-----------------| (bo_offset=n)
> + *
> + *	            1  a  2
> + *	 req:       |-----|       (bo_offset=n+1)
> + *
> + *	      0  a' 1  a  2 a'' 3
> + *	 old: |-----|-----|-----| (a'.bo_offset=n, a.bo_offset=n+1, a''.bo_offset=n+2)
> + *
> + *
> + * 13) Existent mapping is a right aligned subset of the requested one, hence
> + *     replace the existent one.
> + *
> + *     ::
> + *
> + *	            1  a  2
> + *	 old:       |-----| (bo_offset=n+1)
> + *
> + *	      0     a     2
> + *	 req: |-----------| (bo_offset=n)
> + *
> + *	      0     a     2
> + *	 new: |-----------| (bo_offset=n)
> + *
> + *     .. note::
> + *        We expect to see the same result for a request with a different bo
> + *        and/or non-contiguous bo_offset.
> + *
> + *
> + * 14) Existent mapping is a centered subset of the requested one, hence
> + *     replace the existent one.
> + *
> + *     ::
> + *
> + *	            1  a  2
> + *	 old:       |-----| (bo_offset=n+1)
> + *
> + *	      0        a       3
> + *	 req: |----------------| (bo_offset=n)
> + *
> + *	      0        a       3
> + *	 new: |----------------| (bo_offset=n)
> + *
> + *     .. note::
> + *        We expect to see the same result for a request with a different bo
> + *        and/or non-contiguous bo_offset.
> + *
> + *
> + * 15) Existent mappings is overlapped at the beginning by the requested mapping
> + *     backed by a different BO. Hence, map the requested mapping and split up
> + *     the existent one, adjusting it's BO offset accordingly.
> + *
> + *     ::
> + *
> + *	            1     a     3
> + *	 old:       |-----------| (bo_offset=n)
> + *
> + *	      0     b     2
> + *	 req: |-----------|       (bo_offset=m)
> + *
> + *	      0     b     2  a' 3
> + *	 new: |-----------|-----| (b.bo_offset=m,a.bo_offset=n+2)
> + */
> +
> +/**
> + * DOC: Locking
> + *
> + * Generally, the GPU VA manager does not take care of locking itself, it is
> + * the drivers responsibility to take care about locking. Drivers might want to
> + * protect the following operations: inserting, removing and iterating
> + * &drm_gpuva objects as well as generating all kinds of operations, such as
> + * split / merge or prefetch.
> + *
> + * The GPU VA manager also does not take care of the locking of the backing
> + * &drm_gem_object buffers GPU VA lists by itself; drivers are responsible to
> + * enforce mutual exclusion using either the GEMs dma_resv lock or alternatively
> + * a driver specific external lock by setting the @DRM_GPUVA_MANAGER_LOCK_EXTERN
> + * flag.

Is the external lock used or anticipated by any WIP implementation? If 
not I suggest to leave it out until there is a user.

> + *
> + * For the latter, functions such as drm_gpuva_link() or drm_gpuva_unlink()
> + * contain lockdep checks to indicate locking issues. For this to work drivers
> + * must provide (in case the @DRM_GPUVA_MANAGER_LOCK_EXTERN flag is set) their
> + * external lock with drm_gpuva_manager_set_ext_lock() after initialization.
> + */
> +
> +/**
> + * DOC: Examples
> + *
> + * This section gives two examples on how to let the DRM GPUVA Manager generate
> + * &drm_gpuva_op in order to satisfy a given map or unmap request and how to
> + * make use of them.
> + *
> + * The below code is strictly limited to illustrate the generic usage pattern.
> + * To maintain simplicitly, it doesn't make use of any abstractions for common
> + * code, different (asyncronous) stages with fence signalling critical paths,
> + * any other helpers or error handling in terms of freeing memory and dropping
> + * previously taken locks.
> + *
> + * 1) Obtain a list of &drm_gpuva_op to create a new mapping::
> + *
> + *	// Allocates a new &drm_gpuva.
> + *	struct drm_gpuva * driver_gpuva_alloc(void);
> + *
> + *	// Typically drivers would embedd the &drm_gpuva_manager and &drm_gpuva
> + *	// structure in individual driver structures and lock the dma-resv with
> + *	// drm_exec or similar helpers.
> + *	int driver_mapping_create(struct drm_gpuva_manager *mgr,
> + *				  u64 addr, u64 range,
> + *				  struct drm_gem_object *obj, u64 offset)
> + *	{
> + *		struct drm_gpuva_ops *ops;
> + *		struct drm_gpuva_op *op
> + *
> + *		driver_lock_va_space();
> + *		ops = drm_gpuva_sm_map_ops_create(mgr, addr, range,
> + *						  obj, offset);
> + *		if (IS_ERR(ops))
> + *			return PTR_ERR(ops);
> + *
> + *		drm_gpuva_for_each_op(op, ops) {
> + *			struct drm_gpuva *va;
> + *
> + *			switch (op->op) {
> + *			case DRM_GPUVA_OP_MAP:
> + *				va = driver_gpuva_alloc();
> + *				if (!va)
> + *					; // unwind previous VA space updates,
> + *					  // free memory and unlock
> + *
> + *				driver_vm_map();
> + *				drm_gpuva_map(mgr, va, &op->map);
> + *				drm_gpuva_link(va);
> + *			
> + *				break;
> + *			case DRM_GPUVA_OP_REMAP: {
> + *				struct drm_gpuva *prev = NULL, *next = NULL;
> + *
> + *				va = op->remap.unmap->va;
> + *
> + *				if (op->remap.prev) {
> + *					prev = driver_gpuva_alloc();
> + *					if (!prev)
> + *						; // unwind previous VA space
> + *						  // updates, free memory and
> + *						  // unlock
> + *				}
> + *
> + *				if (op->remap.next) {
> + *					next = driver_gpuva_alloc();
> + *					if (!next)
> + *						; // unwind previous VA space
> + *						  // updates, free memory and
> + *						  // unlock
> + *				}
> + *
> + *				driver_vm_remap();
> + *				drm_gpuva_remap(prev, next, &op->remap);
> + *
> + *				drm_gpuva_unlink(va);
> + *				if (prev)
> + *					drm_gpuva_link(prev);
> + *				if (next)
> + *					drm_gpuva_link(next);
> + *
> + *				break;
> + *			}
> + *			case DRM_GPUVA_OP_UNMAP:
> + *				va = op->unmap->va;
> + *
> + *				driver_vm_unmap();
> + *				drm_gpuva_unlink(va);
> + *				drm_gpuva_unmap(&op->unmap);
> + *
> + *				break;
> + *			default:
> + *				break;
> + *			}
> + *		}
> + *		driver_unlock_va_space();
> + *
> + *		return 0;
> + *	}
> + *
> + * 2) Receive a callback for each &drm_gpuva_op to create a new mapping::
> + *
> + *	struct driver_context {
> + *		struct drm_gpuva_manager *mgr;
> + *		struct drm_gpuva *new_va;
> + *		struct drm_gpuva *prev_va;
> + *		struct drm_gpuva *next_va;
> + *	};
> + *
> + *	// ops to pass to drm_gpuva_manager_init()
> + *	static const struct drm_gpuva_fn_ops driver_gpuva_ops = {
> + *		.sm_step_map = driver_gpuva_map,
> + *		.sm_step_remap = driver_gpuva_remap,
> + *		.sm_step_unmap = driver_gpuva_unmap,
> + *	};
> + *
> + *	// Typically drivers would embedd the &drm_gpuva_manager and &drm_gpuva
> + *	// structure in individual driver structures and lock the dma-resv with
> + *	// drm_exec or similar helpers.
> + *	int driver_mapping_create(struct drm_gpuva_manager *mgr,
> + *				  u64 addr, u64 range,
> + *				  struct drm_gem_object *obj, u64 offset)
> + *	{
> + *		struct driver_context ctx;
> + *		struct drm_gpuva_ops *ops;
> + *		struct drm_gpuva_op *op;
> + *		int ret = 0;
> + *
> + *		ctx.mgr = mgr;
> + *
> + *		ctx.new_va = kzalloc(sizeof(*ctx.new_va), GFP_KERNEL);
> + *		ctx.prev_va = kzalloc(sizeof(*ctx.prev_va), GFP_KERNEL);
> + *		ctx.next_va = kzalloc(sizeof(*ctx.next_va), GFP_KERNEL);
> + *		if (!ctx.new_va || !ctx.prev_va || !ctx.next_va) {
> + *			ret = -ENOMEM;
> + *			goto out;
> + *		}
> + *
> + *		driver_lock_va_space();
> + *		ret = drm_gpuva_sm_map(mgr, &ctx, addr, range, obj, offset);
> + *		driver_unlock_va_space();
> + *
> + *	out:
> + *		kfree(ctx.new_va);
> + *		kfree(ctx.prev_va);
> + *		kfree(ctx.next_va);
> + *		return ret;
> + *	}
> + *
> + *	int driver_gpuva_map(struct drm_gpuva_op *op, void *__ctx)
> + *	{
> + *		struct driver_context *ctx = __ctx;
> + *
> + *		drm_gpuva_map(ctx->mgr, ctx->new_va, &op->map);
> + *
> + *		drm_gpuva_link(ctx->new_va);
> + *
> + *		// prevent the new GPUVA from being freed in
> + *		// driver_mapping_create()
> + *		ctx->new_va = NULL;
> + *
> + *		return 0;
> + *	}
> + *
> + *	int driver_gpuva_remap(struct drm_gpuva_op *op, void *__ctx)
> + *	{
> + *		struct driver_context *ctx = __ctx;
> + *
> + *		drm_gpuva_remap(ctx->prev_va, ctx->next_va, &op->remap);
> + *
> + *		drm_gpuva_unlink(op->remap.unmap->va);
> + *		kfree(op->remap.unmap->va);
> + *
> + *		if (op->remap.prev) {
> + *			drm_gpuva_link(ctx->prev_va);
> + *			ctx->prev_va = NULL;
> + *		}
> + *
> + *		if (op->remap.next) {
> + *			drm_gpuva_link(ctx->next_va);
> + *			ctx->next_va = NULL;
> + *		}
> + *
> + *		return 0;
> + *	}
> + *
> + *	int driver_gpuva_unmap(struct drm_gpuva_op *op, void *__ctx)
> + *	{
> + *		drm_gpuva_unlink(op->unmap.va);
> + *		drm_gpuva_unmap(&op->unmap);
> + *		kfree(op->unmap.va);
> + *
> + *		return 0;
> + *	}
> + */
> +
> +#define to_drm_gpuva(__node)	container_of((__node), struct drm_gpuva, rb.node)
> +
> +#define GPUVA_START(node) ((node)->va.addr)
> +#define GPUVA_LAST(node) ((node)->va.addr + (node)->va.range - 1)
> +
> +/* We do not actually use drm_gpuva_it_next(), tell the compiler to not complain
> + * about this.
> + */
> +INTERVAL_TREE_DEFINE(struct drm_gpuva, rb.node, u64, rb.__subtree_last,
> +		     GPUVA_START, GPUVA_LAST, static __attribute__((unused)),

Would  s/__attribute__((unused))/__maybe_unused/ work here?

> +		     drm_gpuva_it)
> +
> +static int __drm_gpuva_insert(struct drm_gpuva_manager *mgr,
> +			      struct drm_gpuva *va);
> +static void __drm_gpuva_remove(struct drm_gpuva *va);
> +
> +static inline bool
"static inline" is typically used only in header files, since the 
compiler should be smart enough to inline if beneficial. Prefer 
"static". Also in multiple places below.
> +drm_gpuva_check_overflow(u64 addr, u64 range)
> +{
> +	u64 end;
> +
> +	return WARN(check_add_overflow(addr, range, &end),
> +		    "GPUVA address limited to %lu bytes.\n", sizeof(end));
> +}
> +
> +static inline bool
> +drm_gpuva_in_mm_range(struct drm_gpuva_manager *mgr, u64 addr, u64 range)
> +{
> +	u64 end = addr + range;
> +	u64 mm_start = mgr->mm_start;
> +	u64 mm_end = mm_start + mgr->mm_range;
> +
> +	return addr >= mm_start && end <= mm_end;
> +}
> +
> +static inline bool
> +drm_gpuva_in_kernel_node(struct drm_gpuva_manager *mgr, u64 addr, u64 range)
> +{
> +	u64 end = addr + range;
> +	u64 kstart = mgr->kernel_alloc_node.va.addr;
> +	u64 krange = mgr->kernel_alloc_node.va.range;
> +	u64 kend = kstart + krange;
> +
> +	return krange && addr < kend && kstart < end;
> +}
> +
> +static inline bool
> +drm_gpuva_range_valid(struct drm_gpuva_manager *mgr,
> +		      u64 addr, u64 range)
> +{
> +
> +	return !drm_gpuva_check_overflow(addr, range) &&
> +	       drm_gpuva_in_mm_range(mgr, addr, range) &&
> +	       !drm_gpuva_in_kernel_node(mgr, addr, range);
> +}
> +
> +/**
> + * drm_gpuva_manager_init - initialize a &drm_gpuva_manager
Function kerneldoc names should end with "()": drm_gpuva_manager_init(). 
General comment across the patch.
> + * @mgr: pointer to the &drm_gpuva_manager to initialize
> + * @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
> + * @reserve_offset: the start of the kernel reserved GPU VA area
> + * @reserve_range: the size of the kernel reserved GPU VA area
> + * @ops: &drm_gpuva_fn_ops called on &drm_gpuva_sm_map / &drm_gpuva_sm_unmap
> + * @flags: the feature flags for the &drm_gpuva_manager
> + *
> + * The &drm_gpuva_manager must be initialized with this function before use.
> + *
> + * Note that @mgr must be cleared to 0 before calling this function. The given
> + * &name is expected to be managed by the surrounding driver structures.
> + */
> +void
> +drm_gpuva_manager_init(struct drm_gpuva_manager *mgr,
> +		       const char *name,
> +		       u64 start_offset, u64 range,
> +		       u64 reserve_offset, u64 reserve_range,
> +		       const struct drm_gpuva_fn_ops *ops,
> +		       enum drm_gpuva_manager_flags flags)
> +{
> +	mgr->rb.tree = RB_ROOT_CACHED;
> +	INIT_LIST_HEAD(&mgr->rb.list);
> +
> +	drm_gpuva_check_overflow(start_offset, range);
> +	mgr->mm_start = start_offset;
> +	mgr->mm_range = range;
> +
> +	mgr->name = name ? name : "unknown";
> +	mgr->flags = flags;
> +	mgr->ops = ops;
> +
> +	memset(&mgr->kernel_alloc_node, 0, sizeof(struct drm_gpuva));
> +
> +	if (reserve_range) {
> +		mgr->kernel_alloc_node.va.addr = reserve_offset;
> +		mgr->kernel_alloc_node.va.range = reserve_range;
> +
> +		if (likely(!drm_gpuva_check_overflow(reserve_offset,
> +						     reserve_range)))
> +			__drm_gpuva_insert(mgr, &mgr->kernel_alloc_node);
> +	}
> +
> +}
> +EXPORT_SYMBOL(drm_gpuva_manager_init);
> +
> +/**
> + * drm_gpuva_manager_destroy - cleanup a &drm_gpuva_manager
> + * @mgr: pointer to the &drm_gpuva_manager to clean up
> + *
> + * Note that it is a bug to call this function on a manager that still
> + * holds GPU VA mappings.
> + */
> +void
> +drm_gpuva_manager_destroy(struct drm_gpuva_manager *mgr)
> +{
> +	mgr->name = NULL;
> +
> +	if (mgr->kernel_alloc_node.va.range)
> +		__drm_gpuva_remove(&mgr->kernel_alloc_node);
> +
> +	WARN(!RB_EMPTY_ROOT(&mgr->rb.tree.rb_root),
> +	     "GPUVA tree is not empty, potentially leaking memory.");
> +}
> +EXPORT_SYMBOL(drm_gpuva_manager_destroy);
> +
> +static int
> +__drm_gpuva_insert(struct drm_gpuva_manager *mgr,
> +		   struct drm_gpuva *va)
> +{
> +	struct rb_node *node;
> +	struct list_head *head;
> +
> +	if (drm_gpuva_it_iter_first(&mgr->rb.tree,
> +				    GPUVA_START(va),
> +				    GPUVA_LAST(va)))
> +		return -EEXIST;
> +
> +	va->mgr = mgr;
> +
> +	drm_gpuva_it_insert(va, &mgr->rb.tree);
> +
> +	node = rb_prev(&va->rb.node);
> +	if (node)
> +		head = &(to_drm_gpuva(node))->rb.entry;
> +	else
> +		head = &mgr->rb.list;
> +
> +	list_add(&va->rb.entry, head);
> +
> +	return 0;
> +}
> +
> +/**
> + * drm_gpuva_insert - insert a &drm_gpuva
> + * @mgr: the &drm_gpuva_manager to insert the &drm_gpuva in
> + * @va: the &drm_gpuva to insert
> + *
> + * Insert a &drm_gpuva with a given address and range into a
> + * &drm_gpuva_manager.
> + *
> + * It is safe to use this function using the safe versions of iterating the GPU
> + * VA space, such as drm_gpuva_for_each_va_safe() and
> + * drm_gpuva_for_each_va_range_safe().
> + *
> + * Returns: 0 on success, negative error code on failure.
> + */
> +int
> +drm_gpuva_insert(struct drm_gpuva_manager *mgr,
> +		 struct drm_gpuva *va)
> +{
> +	u64 addr = va->va.addr;
> +	u64 range = va->va.range;
> +
> +	if (unlikely(!drm_gpuva_range_valid(mgr, addr, range)))
> +		return -EINVAL;
> +
> +	return __drm_gpuva_insert(mgr, va);
> +}
> +EXPORT_SYMBOL(drm_gpuva_insert);
> +
> +static void
> +__drm_gpuva_remove(struct drm_gpuva *va)
> +{
> +	drm_gpuva_it_remove(va, &va->mgr->rb.tree);
> +	list_del_init(&va->rb.entry);
> +}
> +
> +/**
> + * drm_gpuva_remove - remove a &drm_gpuva
> + * @va: the &drm_gpuva to remove
> + *
> + * This removes the given &va from the underlaying tree.
> + *
> + * It is safe to use this function using the safe versions of iterating the GPU
> + * VA space, such as drm_gpuva_for_each_va_safe() and
> + * drm_gpuva_for_each_va_range_safe().
> + */
> +void
> +drm_gpuva_remove(struct drm_gpuva *va)
> +{
> +	struct drm_gpuva_manager *mgr = va->mgr;
> +
> +	if (unlikely(va == &mgr->kernel_alloc_node)) {
> +		WARN(1, "Can't destroy kernel reserved node.\n");
> +		return;
> +	}
> +
> +	__drm_gpuva_remove(va);
> +}
> +EXPORT_SYMBOL(drm_gpuva_remove);
> +
> +/**
> + * drm_gpuva_link - link a &drm_gpuva
> + * @va: the &drm_gpuva to link
> + *
> + * This adds the given &va to the GPU VA list of the &drm_gem_object it is
> + * associated with.
> + *
> + * This function expects the caller to protect the GEM's GPUVA list against
> + * concurrent access using the GEMs dma_resv lock.
> + */
> +void
> +drm_gpuva_link(struct drm_gpuva *va)
> +{
> +	struct drm_gpuva_manager *mgr = va->mgr;
> +	struct drm_gem_object *obj = va->gem.obj;
> +
> +	if (unlikely(!obj))
> +		return;
> +
> +	if (drm_gpuva_manager_external_lock(mgr))
> +		drm_gpuva_manager_ext_assert_held(mgr);
> +	else
> +		dma_resv_assert_held(obj->resv);
> +
> +	list_add_tail(&va->gem.entry, &obj->gpuva.list);
> +}
> +EXPORT_SYMBOL(drm_gpuva_link);
> +
> +/**
> + * drm_gpuva_unlink - unlink a &drm_gpuva
> + * @va: the &drm_gpuva to unlink
> + *
> + * This removes the given &va from the GPU VA list of the &drm_gem_object it is
> + * associated with.
> + *
> + * This function expects the caller to protect the GEM's GPUVA list against
> + * concurrent access using the GEMs dma_resv lock.
> + */
> +void
> +drm_gpuva_unlink(struct drm_gpuva *va)
> +{
> +	struct drm_gpuva_manager *mgr = va->mgr;
> +	struct drm_gem_object *obj = va->gem.obj;
> +
> +	if (unlikely(!obj))
> +		return;
> +
> +	if (drm_gpuva_manager_external_lock(mgr))
> +		drm_gpuva_manager_ext_assert_held(mgr);
> +	else
> +		dma_resv_assert_held(obj->resv);
> +
> +	list_del_init(&va->gem.entry);
> +}
> +EXPORT_SYMBOL(drm_gpuva_unlink);
> +
> +/**
> + * drm_gpuva_find_first - find the first &drm_gpuva in the given range
> + * @mgr: the &drm_gpuva_manager to search in
> + * @addr: the &drm_gpuvas address
> + * @range: the &drm_gpuvas range
> + *
> + * Returns: the first &drm_gpuva within the given range
> + */
> +struct drm_gpuva *
> +drm_gpuva_find_first(struct drm_gpuva_manager *mgr,
> +		     u64 addr, u64 range)
> +{
> +	u64 last = addr + range - 1;
> +
> +	return drm_gpuva_it_iter_first(&mgr->rb.tree, addr, last);
> +}
> +EXPORT_SYMBOL(drm_gpuva_find_first);
> +
> +/**
> + * drm_gpuva_find - find a &drm_gpuva
> + * @mgr: the &drm_gpuva_manager to search in
> + * @addr: the &drm_gpuvas address
> + * @range: the &drm_gpuvas range
> + *
> + * Returns: the &drm_gpuva at a given &addr and with a given &range
> + */
> +struct drm_gpuva *
> +drm_gpuva_find(struct drm_gpuva_manager *mgr,
> +	       u64 addr, u64 range)
> +{
> +	struct drm_gpuva *va;
> +
> +	va = drm_gpuva_find_first(mgr, addr, range);
> +	if (!va)
> +		goto out;
> +
> +	if (va->va.addr != addr ||
> +	    va->va.range != range)
> +		goto out;
> +
> +	return va;
> +
> +out:
> +	return NULL;
> +}
> +EXPORT_SYMBOL(drm_gpuva_find);
> +
> +/**
> + * drm_gpuva_find_prev - find the &drm_gpuva before the given address
> + * @mgr: the &drm_gpuva_manager to search in
> + * @start: the given GPU VA's start address
> + *
> + * Find the adjacent &drm_gpuva before the GPU VA with given &start address.
> + *
> + * Note that if there is any free space between the GPU VA mappings no mapping
> + * is returned.
> + *
> + * Returns: a pointer to the found &drm_gpuva or NULL if none was found
> + */
> +struct drm_gpuva *
> +drm_gpuva_find_prev(struct drm_gpuva_manager *mgr, u64 start)
> +{
> +	if (!drm_gpuva_range_valid(mgr, start - 1, 1))
> +		return NULL;
> +
> +	return drm_gpuva_it_iter_first(&mgr->rb.tree, start - 1, start);
> +}
> +EXPORT_SYMBOL(drm_gpuva_find_prev);
> +
> +/**
> + * drm_gpuva_find_next - find the &drm_gpuva after the given address
> + * @mgr: the &drm_gpuva_manager to search in
> + * @end: the given GPU VA's end address
> + *
> + * Find the adjacent &drm_gpuva after the GPU VA with given &end address.
> + *
> + * Note that if there is any free space between the GPU VA mappings no mapping
> + * is returned.
> + *
> + * Returns: a pointer to the found &drm_gpuva or NULL if none was found
> + */
> +struct drm_gpuva *
> +drm_gpuva_find_next(struct drm_gpuva_manager *mgr, u64 end)
> +{
> +	if (!drm_gpuva_range_valid(mgr, end, 1))
> +		return NULL;
> +
> +	return drm_gpuva_it_iter_first(&mgr->rb.tree, end, end + 1);
> +}
> +EXPORT_SYMBOL(drm_gpuva_find_next);
> +
> +/**
> + * drm_gpuva_interval_empty - indicate whether a given interval of the VA space
> + * is empty
> + * @mgr: the &drm_gpuva_manager to check the range for
> + * @addr: the start address of the range
> + * @range: the range of the interval
> + *
> + * Returns: true if the interval is empty, false otherwise
> + */
> +bool
> +drm_gpuva_interval_empty(struct drm_gpuva_manager *mgr, u64 addr, u64 range)
> +{
> +	return !drm_gpuva_find_first(mgr, addr, range);
> +}
> +EXPORT_SYMBOL(drm_gpuva_interval_empty);
> +
> +/**
> + * drm_gpuva_map - 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.
> + */
> +void
> +drm_gpuva_map(struct drm_gpuva_manager *mgr,
> +	      struct drm_gpuva *va,
> +	      struct drm_gpuva_op_map *op)
> +{
> +	drm_gpuva_init_from_op(va, op);
> +	drm_gpuva_insert(mgr, va);
> +}
> +EXPORT_SYMBOL(drm_gpuva_map);
> +
> +/**
> + * drm_gpuva_remap - 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.
> + */
> +void
> +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_op_map *map;
> +
> +	drm_gpuva_remove(curr);
> +
> +	if ((map = op->prev)) {
> +		drm_gpuva_init_from_op(prev, map);
> +		drm_gpuva_insert(mgr, prev);
> +	}
> +
> +	if ((map = op->next)) {
> +		drm_gpuva_init_from_op(next, map);
> +		drm_gpuva_insert(mgr, next);
> +	}
> +}
> +EXPORT_SYMBOL(drm_gpuva_remap);
> +
> +/**
> + * drm_gpuva_unmap - 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.
> + */
> +void
> +drm_gpuva_unmap(struct drm_gpuva_op_unmap *op)
> +{
> +	drm_gpuva_remove(op->va);
> +}
> +EXPORT_SYMBOL(drm_gpuva_unmap);
> +
> +static int
> +op_map_cb(const struct drm_gpuva_fn_ops *fn, void *priv,
> +	  u64 addr, u64 range,
> +	  struct drm_gem_object *obj, u64 offset)
> +{
> +	struct drm_gpuva_op op = {};
> +
> +	op.op = DRM_GPUVA_OP_MAP;
> +	op.map.va.addr = addr;
> +	op.map.va.range = range;
> +	op.map.gem.obj = obj;
> +	op.map.gem.offset = offset;
> +
> +	return fn->sm_step_map(&op, priv);
> +}
> +
> +static int
> +op_remap_cb(const struct drm_gpuva_fn_ops *fn, void *priv,
> +	    struct drm_gpuva_op_map *prev,
> +	    struct drm_gpuva_op_map *next,
> +	    struct drm_gpuva_op_unmap *unmap)
> +{
> +	struct drm_gpuva_op op = {};
> +	struct drm_gpuva_op_remap *r;
> +
> +	op.op = DRM_GPUVA_OP_REMAP;
> +	r = &op.remap;
> +	r->prev = prev;
> +	r->next = next;
> +	r->unmap = unmap;
> +
> +	return fn->sm_step_remap(&op, priv);
> +}
> +
> +static int
> +op_unmap_cb(const struct drm_gpuva_fn_ops *fn, void *priv,
> +	    struct drm_gpuva *va, bool merge)
> +{
> +	struct drm_gpuva_op op = {};
> +
> +	op.op = DRM_GPUVA_OP_UNMAP;
> +	op.unmap.va = va;
> +	op.unmap.keep = merge;
> +
> +	return fn->sm_step_unmap(&op, priv);
> +}
> +
> +static int
> +__drm_gpuva_sm_map(struct drm_gpuva_manager *mgr,
> +		   const struct drm_gpuva_fn_ops *ops, void *priv,
> +		   u64 req_addr, u64 req_range,
> +		   struct drm_gem_object *req_obj, u64 req_offset)
> +{
> +	struct drm_gpuva *va, *next, *prev = NULL;
> +	u64 req_end = req_addr + req_range;
> +	int ret;
> +
> +	if (unlikely(!drm_gpuva_range_valid(mgr, req_addr, req_range)))
> +		return -EINVAL;
> +
> +	drm_gpuva_for_each_va_range_safe(va, next, mgr, req_addr, req_end) {
> +		struct drm_gem_object *obj = va->gem.obj;
> +		u64 offset = va->gem.offset;
> +		u64 addr = va->va.addr;
> +		u64 range = va->va.range;
> +		u64 end = addr + range;
> +		bool merge = !!va->gem.obj;
> +
> +		if (addr == req_addr) {
> +			merge &= obj == req_obj &&
> +				 offset == req_offset;
> +
> +			if (end == req_end) {
> +				ret = op_unmap_cb(ops, priv, va, merge);
> +				if (ret)
> +					return ret;
> +				break;
> +			}
> +
> +			if (end < req_end) {
> +				ret = op_unmap_cb(ops, priv, va, merge);
> +				if (ret)
> +					return ret;
> +				goto next;
> +			}
> +
> +			if (end > req_end) {
> +				struct drm_gpuva_op_map n = {
> +					.va.addr = req_end,
> +					.va.range = range - req_range,
> +					.gem.obj = obj,
> +					.gem.offset = offset + req_range,
> +				};
> +				struct drm_gpuva_op_unmap u = {
> +					.va = va,
> +					.keep = merge,
> +				};
> +
> +				ret = op_remap_cb(ops, priv, NULL, &n, &u);
> +				if (ret)
> +					return ret;
> +				break;
> +			}
> +		} else if (addr < req_addr) {
> +			u64 ls_range = req_addr - addr;
> +			struct drm_gpuva_op_map p = {
> +				.va.addr = addr,
> +				.va.range = ls_range,
> +				.gem.obj = obj,
> +				.gem.offset = offset,
> +			};
> +			struct drm_gpuva_op_unmap u = { .va = va };
> +
> +			merge &= obj == req_obj &&
> +				 offset + ls_range == req_offset;
> +			u.keep = merge;
> +
> +			if (end == req_end) {
> +				ret = op_remap_cb(ops, priv, &p, NULL, &u);
> +				if (ret)
> +					return ret;
> +				break;
> +			}
> +
> +			if (end < req_end) {
> +				ret = op_remap_cb(ops, priv, &p, NULL, &u);
> +				if (ret)
> +					return ret;
> +				goto next;
> +			}
> +
> +			if (end > req_end) {
> +				struct drm_gpuva_op_map n = {
> +					.va.addr = req_end,
> +					.va.range = end - req_end,
> +					.gem.obj = obj,
> +					.gem.offset = offset + ls_range +
> +						      req_range,
> +				};
> +
> +				ret = op_remap_cb(ops, priv, &p, &n, &u);
> +				if (ret)
> +					return ret;
> +				break;
> +			}
> +		} else if (addr > req_addr) {
> +			merge &= obj == req_obj &&
> +				 offset == req_offset +
> +					   (addr - req_addr);
> +
> +			if (end == req_end) {
> +				ret = op_unmap_cb(ops, priv, va, merge);
> +				if (ret)
> +					return ret;
> +				break;
> +			}
> +
> +			if (end < req_end) {
> +				ret = op_unmap_cb(ops, priv, va, merge);
> +				if (ret)
> +					return ret;
> +				goto next;
> +			}
> +
> +			if (end > req_end) {
> +				struct drm_gpuva_op_map n = {
> +					.va.addr = req_end,
> +					.va.range = end - req_end,
> +					.gem.obj = obj,
> +					.gem.offset = offset + req_end - addr,
> +				};
> +				struct drm_gpuva_op_unmap u = {
> +					.va = va,
> +					.keep = merge,
> +				};
> +
> +				ret = op_remap_cb(ops, priv, NULL, &n, &u);
> +				if (ret)
> +					return ret;
> +				break;
> +			}
> +		}
> +next:
> +		prev = va;
> +	}
> +
> +	return op_map_cb(ops, priv,
> +			 req_addr, req_range,
> +			 req_obj, req_offset);
> +}
> +
> +static int
> +__drm_gpuva_sm_unmap(struct drm_gpuva_manager *mgr,
> +		     const struct drm_gpuva_fn_ops *ops, void *priv,
> +		     u64 req_addr, u64 req_range)
> +{
> +	struct drm_gpuva *va, *next;
> +	u64 req_end = req_addr + req_range;
> +	int ret;
> +
> +	if (unlikely(!drm_gpuva_range_valid(mgr, req_addr, req_range)))
> +		return -EINVAL;
> +
> +	drm_gpuva_for_each_va_range_safe(va, next, mgr, req_addr, req_end) {
> +		struct drm_gpuva_op_map prev = {}, next = {};
> +		bool prev_split = false, next_split = false;
> +		struct drm_gem_object *obj = va->gem.obj;
> +		u64 offset = va->gem.offset;
> +		u64 addr = va->va.addr;
> +		u64 range = va->va.range;
> +		u64 end = addr + range;
> +
> +		if (addr < req_addr) {
> +			prev.va.addr = addr;
> +			prev.va.range = req_addr - addr;
> +			prev.gem.obj = obj;
> +			prev.gem.offset = offset;
> +
> +			prev_split = true;
> +		}
> +
> +		if (end > req_end) {
> +			next.va.addr = req_end;
> +			next.va.range = end - req_end;
> +			next.gem.obj = obj;
> +			next.gem.offset = offset + (req_end - addr);
> +
> +			next_split = true;
> +		}
> +
> +		if (prev_split || next_split) {
> +			struct drm_gpuva_op_unmap unmap = { .va = va };
> +
> +			ret = op_remap_cb(ops, priv,
> +					  prev_split ? &prev : NULL,
> +					  next_split ? &next : NULL,
> +					  &unmap);
> +			if (ret)
> +				return ret;
> +		} else {
> +			ret = op_unmap_cb(ops, priv, va, false);
> +			if (ret)
> +				return ret;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * drm_gpuva_sm_map - creates the &drm_gpuva_op split/merge steps
> + * @mgr: the &drm_gpuva_manager representing the GPU VA space
> + * @req_addr: the start address of the new mapping
> + * @req_range: the range of the new mapping
> + * @req_obj: the &drm_gem_object to map
> + * @req_offset: the offset within the &drm_gem_object
> + * @priv: pointer to a driver private data structure
> + *
> + * This function iterates the given range of the GPU VA space. It utilizes the
> + * &drm_gpuva_fn_ops to call back into the driver providing the split and merge
> + * steps.
> + *
> + * Drivers may use these callbacks to update the GPU VA space right away within
> + * the callback. In case the driver decides to copy and store the operations for
> + * later processing neither this function nor &drm_gpuva_sm_unmap is allowed to
> + * be called before the &drm_gpuva_manager's view of the GPU VA space was
> + * updated with the previous set of operations. To update the
> + * &drm_gpuva_manager's view of the GPU VA space drm_gpuva_insert(),
> + * drm_gpuva_destroy_locked() and/or drm_gpuva_destroy_unlocked() should be
> + * used.
> + *
> + * A sequence of callbacks can contain map, unmap and remap operations, but
> + * the sequence of callbacks might also be empty if no operation is required,
> + * e.g. if the requested mapping already exists in the exact same way.
> + *
> + * There can be an arbitrary amount of unmap operations, a maximum of two remap
> + * operations and a single map operation. The latter one represents the original
> + * map operation requested by the caller.
> + *
> + * Returns: 0 on success or a negative error code
> + */
> +int
> +drm_gpuva_sm_map(struct drm_gpuva_manager *mgr, void *priv,
> +		 u64 req_addr, u64 req_range,
> +		 struct drm_gem_object *req_obj, u64 req_offset)
> +{
> +	const struct drm_gpuva_fn_ops *ops = mgr->ops;
> +
> +	if (unlikely(!(ops && ops->sm_step_map &&
> +		       ops->sm_step_remap &&
> +		       ops->sm_step_unmap)))
> +		return -EINVAL;
> +
> +	return __drm_gpuva_sm_map(mgr, ops, priv,
> +				  req_addr, req_range,
> +				  req_obj, req_offset);
> +}
> +EXPORT_SYMBOL(drm_gpuva_sm_map);
> +
> +/**
> + * drm_gpuva_sm_unmap - creates the &drm_gpuva_ops to split on unmap
> + * @mgr: the &drm_gpuva_manager representing the GPU VA space
> + * @priv: pointer to a driver private data structure
> + * @req_addr: the start address of the range to unmap
> + * @req_range: the range of the mappings to unmap
> + *
> + * This function iterates the given range of the GPU VA space. It utilizes the
> + * &drm_gpuva_fn_ops to call back into the driver providing the operations to
> + * unmap and, if required, split existent mappings.
> + *
> + * Drivers may use these callbacks to update the GPU VA space right away within
> + * the callback. In case the driver decides to copy and store the operations for
> + * later processing neither this function nor &drm_gpuva_sm_map is allowed to be
> + * called before the &drm_gpuva_manager's view of the GPU VA space was updated
> + * with the previous set of operations. To update the &drm_gpuva_manager's view
> + * of the GPU VA space drm_gpuva_insert(), drm_gpuva_destroy_locked() and/or
> + * drm_gpuva_destroy_unlocked() should be used.
> + *
> + * A sequence of callbacks can contain unmap and remap operations, depending on
> + * whether there are actual overlapping mappings to split.
> + *
> + * There can be an arbitrary amount of unmap operations and a maximum of two
> + * remap operations.
> + *
> + * Returns: 0 on success or a negative error code
> + */
> +int
> +drm_gpuva_sm_unmap(struct drm_gpuva_manager *mgr, void *priv,
> +		   u64 req_addr, u64 req_range)
> +{
> +	const struct drm_gpuva_fn_ops *ops = mgr->ops;
> +
> +	if (unlikely(!(ops && ops->sm_step_remap &&
> +		       ops->sm_step_unmap)))
> +		return -EINVAL;
> +
> +	return __drm_gpuva_sm_unmap(mgr, ops, priv,
> +				    req_addr, req_range);
> +}
> +EXPORT_SYMBOL(drm_gpuva_sm_unmap);
> +
> +static struct drm_gpuva_op *
> +gpuva_op_alloc(struct drm_gpuva_manager *mgr)
> +{
> +	const struct drm_gpuva_fn_ops *fn = mgr->ops;
> +	struct drm_gpuva_op *op;
> +
> +	if (fn && fn->op_alloc)
> +		op = fn->op_alloc();
> +	else
> +		op = kzalloc(sizeof(*op), GFP_KERNEL);
> +
> +	if (unlikely(!op))
> +		return NULL;
> +
> +	return op;
> +}
> +
> +static void
> +gpuva_op_free(struct drm_gpuva_manager *mgr,
> +	      struct drm_gpuva_op *op)
> +{
> +	const struct drm_gpuva_fn_ops *fn = mgr->ops;
> +
> +	if (fn && fn->op_free)
> +		fn->op_free(op);
> +	else
> +		kfree(op);
> +}
> +
> +static int
> +drm_gpuva_sm_step(struct drm_gpuva_op *__op,
> +		  void *priv)
> +{
> +	struct {
> +		struct drm_gpuva_manager *mgr;
> +		struct drm_gpuva_ops *ops;
> +	} *args = priv;
> +	struct drm_gpuva_manager *mgr = args->mgr;
> +	struct drm_gpuva_ops *ops = args->ops;
> +	struct drm_gpuva_op *op;
> +
> +	op = gpuva_op_alloc(mgr);
> +	if (unlikely(!op))
> +		goto err;
> +
> +	memcpy(op, __op, sizeof(*op));
> +
> +	if (op->op == DRM_GPUVA_OP_REMAP) {
> +		struct drm_gpuva_op_remap *__r = &__op->remap;
> +		struct drm_gpuva_op_remap *r = &op->remap;
> +
> +		r->unmap = kmemdup(__r->unmap, sizeof(*r->unmap),
> +				   GFP_KERNEL);
> +		if (unlikely(!r->unmap))
> +			goto err_free_op;
> +
> +		if (__r->prev) {
> +			r->prev = kmemdup(__r->prev, sizeof(*r->prev),
> +					  GFP_KERNEL);
> +			if (unlikely(!r->prev))
> +				goto err_free_unmap;
> +		}
> +
> +		if (__r->next) {
> +			r->next = kmemdup(__r->next, sizeof(*r->next),
> +					  GFP_KERNEL);
> +			if (unlikely(!r->next))
> +				goto err_free_prev;
> +		}
> +	}
> +
> +	list_add_tail(&op->entry, &ops->list);
> +
> +	return 0;
> +
> +err_free_unmap:
> +	kfree(op->remap.unmap);
> +err_free_prev:
> +	kfree(op->remap.prev);
> +err_free_op:
> +	gpuva_op_free(mgr, op);
> +err:
> +	return -ENOMEM;
> +}
> +
> +static const struct drm_gpuva_fn_ops gpuva_list_ops = {
> +	.sm_step_map = drm_gpuva_sm_step,
> +	.sm_step_remap = drm_gpuva_sm_step,
> +	.sm_step_unmap = drm_gpuva_sm_step,
> +};
> +
> +/**
> + * drm_gpuva_sm_map_ops_create - creates the &drm_gpuva_ops to split and merge
> + * @mgr: the &drm_gpuva_manager representing the GPU VA space
> + * @req_addr: the start address of the new mapping
> + * @req_range: the range of the new mapping
> + * @req_obj: the &drm_gem_object to map
> + * @req_offset: the offset within the &drm_gem_object
> + *
> + * This function creates a list of operations to perform splitting and merging
> + * of existent mapping(s) with the newly requested one.
> + *
> + * The list can be iterated with &drm_gpuva_for_each_op and must be processed
> + * in the given order. It can contain map, unmap and remap operations, but it
> + * also can be empty if no operation is required, e.g. if the requested mapping
> + * already exists is the exact same way.
> + *
> + * There can be an arbitrary amount of unmap operations, a maximum of two remap
> + * operations and a single map operation. The latter one represents the original
> + * map operation requested by the caller.
> + *
> + * Note that before calling this function again with another mapping request it
> + * is necessary to update the &drm_gpuva_manager's view of the GPU VA space. The
> + * previously obtained operations must be either processed or abandoned. To
> + * update the &drm_gpuva_manager's view of the GPU VA space drm_gpuva_insert(),
> + * drm_gpuva_destroy_locked() and/or drm_gpuva_destroy_unlocked() should be
> + * used.
> + *
> + * After the caller finished processing the returned &drm_gpuva_ops, they must
> + * be freed with &drm_gpuva_ops_free.
> + *
> + * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR on failure
> + */
> +struct drm_gpuva_ops *
> +drm_gpuva_sm_map_ops_create(struct drm_gpuva_manager *mgr,
> +			    u64 req_addr, u64 req_range,
> +			    struct drm_gem_object *req_obj, u64 req_offset)
> +{
> +	struct drm_gpuva_ops *ops;
> +	struct {
> +		struct drm_gpuva_manager *mgr;
> +		struct drm_gpuva_ops *ops;
> +	} args;
> +	int ret;
> +
> +	ops = kzalloc(sizeof(*ops), GFP_KERNEL);
> +	if (unlikely(!ops))
> +		return ERR_PTR(-ENOMEM);
> +
> +	INIT_LIST_HEAD(&ops->list);
> +
> +	args.mgr = mgr;
> +	args.ops = ops;
> +
> +	ret = __drm_gpuva_sm_map(mgr, &gpuva_list_ops, &args,
> +				 req_addr, req_range,
> +				 req_obj, req_offset);
> +	if (ret)
> +		goto err_free_ops;
> +
> +	return ops;
> +
> +err_free_ops:
> +	drm_gpuva_ops_free(mgr, ops);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL(drm_gpuva_sm_map_ops_create);
> +
> +/**
> + * drm_gpuva_sm_unmap_ops_create - creates the &drm_gpuva_ops to split on unmap
> + * @mgr: the &drm_gpuva_manager representing the GPU VA space
> + * @req_addr: the start address of the range to unmap
> + * @req_range: the range of the mappings to unmap
> + *
> + * This function creates a list of operations to perform unmapping and, if
> + * required, splitting of the mappings overlapping the unmap range.
> + *
> + * The list can be iterated with &drm_gpuva_for_each_op and must be processed
> + * in the given order. It can contain unmap and remap operations, depending on
> + * whether there are actual overlapping mappings to split.
> + *
> + * There can be an arbitrary amount of unmap operations and a maximum of two
> + * remap operations.
> + *
> + * Note that before calling this function again with another range to unmap it
> + * is necessary to update the &drm_gpuva_manager's view of the GPU VA space. The
> + * previously obtained operations must be processed or abandoned. To update the
> + * &drm_gpuva_manager's view of the GPU VA space drm_gpuva_insert(),
> + * drm_gpuva_destroy_locked() and/or drm_gpuva_destroy_unlocked() should be
> + * used.
> + *
> + * After the caller finished processing the returned &drm_gpuva_ops, they must
> + * be freed with &drm_gpuva_ops_free.
> + *
> + * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR on failure
> + */
> +struct drm_gpuva_ops *
> +drm_gpuva_sm_unmap_ops_create(struct drm_gpuva_manager *mgr,
> +			      u64 req_addr, u64 req_range)
> +{
> +	struct drm_gpuva_ops *ops;
> +	struct {
> +		struct drm_gpuva_manager *mgr;
> +		struct drm_gpuva_ops *ops;
> +	} args;
> +	int ret;
> +
> +	ops = kzalloc(sizeof(*ops), GFP_KERNEL);
> +	if (unlikely(!ops))
> +		return ERR_PTR(-ENOMEM);
> +
> +	INIT_LIST_HEAD(&ops->list);
> +
> +	args.mgr = mgr;
> +	args.ops = ops;
> +
> +	ret = __drm_gpuva_sm_unmap(mgr, &gpuva_list_ops, &args,
> +				   req_addr, req_range);
> +	if (ret)
> +		goto err_free_ops;
> +
> +	return ops;
> +
> +err_free_ops:
> +	drm_gpuva_ops_free(mgr, ops);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL(drm_gpuva_sm_unmap_ops_create);
> +
> +/**
> + * drm_gpuva_prefetch_ops_create - creates the &drm_gpuva_ops to prefetch
> + * @mgr: the &drm_gpuva_manager representing the GPU VA space
> + * @addr: the start address of the range to prefetch
> + * @range: the range of the mappings to prefetch
> + *
> + * This function creates a list of operations to perform prefetching.
> + *
> + * The list can be iterated with &drm_gpuva_for_each_op and must be processed
> + * in the given order. It can contain prefetch operations.
> + *
> + * There can be an arbitrary amount of prefetch operations.
> + *
> + * After the caller finished processing the returned &drm_gpuva_ops, they must
> + * be freed with &drm_gpuva_ops_free.
> + *
> + * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR on failure
> + */
> +struct drm_gpuva_ops *
> +drm_gpuva_prefetch_ops_create(struct drm_gpuva_manager *mgr,
> +			      u64 addr, u64 range)
> +{
> +	struct drm_gpuva_ops *ops;
> +	struct drm_gpuva_op *op;
> +	struct drm_gpuva *va;
> +	u64 end = addr + range;
> +	int ret;
> +
> +	ops = kzalloc(sizeof(*ops), GFP_KERNEL);
> +	if (!ops)
> +		return ERR_PTR(-ENOMEM);
> +
> +	INIT_LIST_HEAD(&ops->list);
> +
> +	drm_gpuva_for_each_va_range(va, mgr, addr, end) {
> +		op = gpuva_op_alloc(mgr);
> +		if (!op) {
> +			ret = -ENOMEM;
> +			goto err_free_ops;
> +		}
> +
> +		op->op = DRM_GPUVA_OP_PREFETCH;
> +		op->prefetch.va = va;
> +		list_add_tail(&op->entry, &ops->list);
> +	}
> +
> +	return ops;
> +
> +err_free_ops:
> +	drm_gpuva_ops_free(mgr, ops);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL(drm_gpuva_prefetch_ops_create);
> +
> +/**
> + * drm_gpuva_gem_unmap_ops_create - creates the &drm_gpuva_ops to unmap a GEM
> + * @mgr: the &drm_gpuva_manager representing the GPU VA space
> + * @obj: the &drm_gem_object to unmap
> + *
> + * This function creates a list of operations to perform unmapping for every
> + * GPUVA attached to a GEM.
> + *
> + * The list can be iterated with &drm_gpuva_for_each_op and consists out of an
> + * arbitrary amount of unmap operations.
> + *
> + * After the caller finished processing the returned &drm_gpuva_ops, they must
> + * be freed with &drm_gpuva_ops_free.
> + *
> + * It is the callers responsibility to protect the GEMs GPUVA list against
> + * concurrent access using the GEMs dma_resv lock.
> + *
> + * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR on failure
> + */
> +struct drm_gpuva_ops *
> +drm_gpuva_gem_unmap_ops_create(struct drm_gpuva_manager *mgr,
> +			       struct drm_gem_object *obj)
> +{
> +	struct drm_gpuva_ops *ops;
> +	struct drm_gpuva_op *op;
> +	struct drm_gpuva *va;
> +	int ret;
> +
> +	if (drm_gpuva_manager_external_lock(mgr))
> +		drm_gpuva_manager_ext_assert_held(mgr);
> +	else
> +		dma_resv_assert_held(obj->resv);
> +
> +	ops = kzalloc(sizeof(*ops), GFP_KERNEL);
> +	if (!ops)
> +		return ERR_PTR(-ENOMEM);
> +
> +	INIT_LIST_HEAD(&ops->list);
> +
> +	drm_gem_for_each_gpuva(va, obj) {
> +		op = gpuva_op_alloc(mgr);
> +		if (!op) {
> +			ret = -ENOMEM;
> +			goto err_free_ops;
> +		}
> +
> +		op->op = DRM_GPUVA_OP_UNMAP;
> +		op->unmap.va = va;
> +		list_add_tail(&op->entry, &ops->list);
> +	}
> +
> +	return ops;
> +
> +err_free_ops:
> +	drm_gpuva_ops_free(mgr, ops);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL(drm_gpuva_gem_unmap_ops_create);
> +
> +
> +/**
> + * drm_gpuva_ops_free - free the given &drm_gpuva_ops
> + * @mgr: the &drm_gpuva_manager the ops were created for
> + * @ops: the &drm_gpuva_ops to free
> + *
> + * Frees the given &drm_gpuva_ops structure including all the ops associated
> + * with it.
> + */
> +void
> +drm_gpuva_ops_free(struct drm_gpuva_manager *mgr,
> +		   struct drm_gpuva_ops *ops)
> +{
> +	struct drm_gpuva_op *op, *next;
> +
> +	drm_gpuva_for_each_op_safe(op, next, ops) {
> +		list_del(&op->entry);
> +
> +		if (op->op == DRM_GPUVA_OP_REMAP) {
> +			kfree(op->remap.prev);
> +			kfree(op->remap.next);
> +			kfree(op->remap.unmap);
> +		}
> +
> +		gpuva_op_free(mgr, op);
> +	}
> +
> +	kfree(ops);
> +}
> +EXPORT_SYMBOL(drm_gpuva_ops_free);
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 89e2706cac56..04dbe223b1a5 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -104,6 +104,12 @@ enum drm_driver_feature {
>   	 * acceleration should be handled by two drivers that are connected using auxiliary bus.
>   	 */
>   	DRIVER_COMPUTE_ACCEL            = BIT(7),
> +	/**
> +	 * @DRIVER_GEM_GPUVA:
> +	 *
> +	 * Driver supports user defined GPU VA bindings for GEM objects.
> +	 */
> +	DRIVER_GEM_GPUVA		= BIT(8),
>   
>   	/* IMPORTANT: Below are all the legacy flags, add new ones above. */
>   
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index bbc721870c13..5ec8148a30ee 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -36,6 +36,8 @@
>   
>   #include <linux/kref.h>
>   #include <linux/dma-resv.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
>   
>   #include <drm/drm_vma_manager.h>
>   
> @@ -379,6 +381,18 @@ struct drm_gem_object {
>   	 */
>   	struct dma_resv _resv;
>   
> +	/**
> +	 * @gpuva:
> +	 *
> +	 * Provides the list of GPU VAs attached to this GEM object.
> +	 *
> +	 * Drivers should lock list accesses with the GEMs &dma_resv lock
> +	 * (&drm_gem_object.resv).
> +	 */
> +	struct {
> +		struct list_head list;
> +	} gpuva;
> +
>   	/**
>   	 * @funcs:
>   	 *
> @@ -526,4 +540,42 @@ unsigned long drm_gem_lru_scan(struct drm_gem_lru *lru,
>   
>   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.
> + *
> + * Calling this function is only necessary for drivers intending to support the
> + * &drm_driver_feature DRIVER_GEM_GPUVA.
> + */
> +static inline void drm_gem_gpuva_init(struct drm_gem_object *obj)
> +{
> +	INIT_LIST_HEAD(&obj->gpuva.list);
> +}
> +
> +/**
> + * drm_gem_for_each_gpuva - iternator to walk over a list of gpuvas

s/iternator/iterator/. (multiple places) Although since "iterator" 
typically refers to an object being iterated over, perhaps

"drm_gem_for_each_gpuva() - iterate over a list of gpuvas", (general 
comment across the patch).

> + * @entry: &drm_gpuva structure to assign to in each iteration step
> + * @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.
> + */
> +#define drm_gem_for_each_gpuva(entry__, obj__) \
> +	list_for_each_entry(entry__, &(obj__)->gpuva.list, gem.entry)
> +
> +/**
> + * 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
> + *
> + * This iterator walks over all &drm_gpuva 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)
> +
>   #endif /* __DRM_GEM_H__ */
> diff --git a/include/drm/drm_gpuva_mgr.h b/include/drm/drm_gpuva_mgr.h
> new file mode 100644
> index 000000000000..4f23aaf726dd
> --- /dev/null
> +++ b/include/drm/drm_gpuva_mgr.h
> @@ -0,0 +1,756 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __DRM_GPUVA_MGR_H__
> +#define __DRM_GPUVA_MGR_H__
> +
> +/*
> + * Copyright (c) 2022 Red Hat.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#include <linux/list.h>
> +#include <linux/rbtree.h>
> +#include <linux/types.h>
> +
> +#include <drm/drm_gem.h>
> +
> +struct drm_gpuva_manager;
> +struct drm_gpuva_fn_ops;
> +
> +/**
> + * enum drm_gpuva_flags - flags for struct drm_gpuva
> + */
> +enum drm_gpuva_flags {
> +	/**
> +	 * @DRM_GPUVA_INVALIDATED:
> +	 *
> +	 * Flag indicating that the &drm_gpuva's backing GEM is invalidated.
> +	 */
> +	DRM_GPUVA_INVALIDATED = (1 << 0),
> +
> +	/**
> +	 * @DRM_GPUVA_SPARSE:
> +	 *
> +	 * Flag indicating that the &drm_gpuva is a sparse mapping.
> +	 */
> +	DRM_GPUVA_SPARSE = (1 << 1),
> +
> +	/**
> +	 * @DRM_GPUVA_USERBITS: user defined bits
> +	 */
> +	DRM_GPUVA_USERBITS = (1 << 2),
> +};
> +
> +/**
> + * struct drm_gpuva - structure to track a GPU VA mapping
> + *
> + * This structure represents a GPU VA mapping and is associated with a
> + * &drm_gpuva_manager.
> + *
> + * Typically, this structure is embedded in bigger driver structures.
> + */
> +struct drm_gpuva {
> +	/**
> +	 * @mgr: the &drm_gpuva_manager this object is associated with
> +	 */
> +	struct drm_gpuva_manager *mgr;
> +
> +	/**
> +	 * @flags: the &drm_gpuva_flags for this mapping
> +	 */
> +	enum drm_gpuva_flags flags;
> +
> +	/**
> +	 * @va: structure containing the address and range of the &drm_gpuva
> +	 */
> +	struct {
> +		/**
> +		 * @addr: the start address
> +		 */
> +		u64 addr;
> +
> +		/*
> +		 * @range: the range
> +		 */
> +		u64 range;
> +	} va;
> +
> +	/**
> +	 * @gem: structure containing the &drm_gem_object and it's offset
> +	 */
> +	struct {
> +		/**
> +		 * @offset: the offset within the &drm_gem_object
> +		 */
> +		u64 offset;
> +
> +		/**
> +		 * @obj: the mapped &drm_gem_object
> +		 */
> +		struct drm_gem_object *obj;
> +
> +		/**
> +		 * @entry: the &list_head to attach this object to a &drm_gem_object
> +		 */
> +		struct list_head entry;
> +	} gem;
> +
> +	/**
> +	 * @rb: structure containing data to store &drm_gpuvas in a rb-tree
> +	 */
> +	struct {
> +		/**
> +		 * @rb: the rb-tree node
> +		 */
> +		struct rb_node node;
> +
> +		/**
> +		 * @entry: The &list_head to additionally connect &drm_gpuvas
> +		 * in the same order they appear in the interval tree. This is
> +		 * useful to keep iterating &drm_gpuvas from a start node found
> +		 * through the rb-tree while doing modifications on the rb-tree
> +		 * itself.
> +		 */
> +		struct list_head entry;
> +
> +		/**
> +		 * @__subtree_last: needed by the interval tree, holding last-in-subtree
> +		 */
> +		u64 __subtree_last;
> +	} rb;
> +};
> +
> +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_unlink(struct drm_gpuva *va);
> +
> +struct drm_gpuva *drm_gpuva_find(struct drm_gpuva_manager *mgr,
> +				 u64 addr, u64 range);
> +struct drm_gpuva *drm_gpuva_find_first(struct drm_gpuva_manager *mgr,
> +				       u64 addr, u64 range);
> +struct drm_gpuva *drm_gpuva_find_prev(struct drm_gpuva_manager *mgr, u64 start);
> +struct drm_gpuva *drm_gpuva_find_next(struct drm_gpuva_manager *mgr, u64 end);
> +
> +bool drm_gpuva_interval_empty(struct drm_gpuva_manager *mgr, u64 addr, u64 range);
> +
> +static inline void drm_gpuva_init(struct drm_gpuva *va, u64 addr, u64 range,
> +				  struct drm_gem_object *obj, u64 offset)
> +{
> +	va->va.addr = addr;
> +	va->va.range = range;
> +	va->gem.obj = obj;
> +	va->gem.offset = offset;
> +}
> +
> +/**
> + * drm_gpuva_invalidate - sets whether the backing GEM of this &drm_gpuva is
> + * invalidated
> + * @va: the &drm_gpuva to set the invalidate flag for
> + * @invalidate: indicates whether the &drm_gpuva is invalidated
> + */
> +static inline void drm_gpuva_invalidate(struct drm_gpuva *va, bool invalidate)
> +{
> +	if (invalidate)
> +		va->flags |= DRM_GPUVA_INVALIDATED;
> +	else
> +		va->flags &= ~DRM_GPUVA_INVALIDATED;
> +}
> +
> +/**
> + * drm_gpuva_invalidated - indicates whether the backing BO of this &drm_gpuva
> + * is invalidated
> + * @va: the &drm_gpuva to check
> + */
> +static inline bool drm_gpuva_invalidated(struct drm_gpuva *va)
> +{
> +	return va->flags & DRM_GPUVA_INVALIDATED;
> +}
> +
> +#ifdef CONFIG_LOCKDEP
> +typedef struct lockdep_map *lockdep_map_p;
> +#define drm_gpuva_manager_ext_assert_held(mgr)		\
> +	lockdep_assert(lock_is_held((mgr)->ext_lock) != LOCK_STATE_NOT_HELD)
> +/**
> + * drm_gpuva_manager_set_ext_lock - set the external lock according to
> + * @DRM_GPUVA_MANAGER_LOCK_EXTERN
> + * @mgr: the &drm_gpuva_manager to set the lock for
> + * @lock: the lock to set
> + *
> + * If @DRM_GPUVA_MANAGER_LOCK_EXTERN is set, drivers need to call this function
> + * to provide the lock used to lock linking and unlinking of &drm_gpuvas to the
> + * &drm_gem_objects GPUVA list.
> + */
> +#define drm_gpuva_manager_set_ext_lock(mgr, lock)	\
> +	(mgr)->ext_lock = &(lock)->dep_map
> +#else
> +typedef struct { /* nothing */ } lockdep_map_p;
> +#define drm_gpuva_manager_ext_assert_held(mgr)		do { (void)(mgr); } while (0)
> +#define drm_gpuva_manager_set_ext_lock(mgr, lock)	do { } while (0)
> +#endif
> +
> +/**
> + * enum drm_gpuva_manager_flags - the feature flags for the &drm_gpuva_manager
> + */
> +enum drm_gpuva_manager_flags {
> +	/**
> +	 * @DRM_GPUVA_MANAGER_LOCK_EXTERN:
> +	 *
> +	 * Indicates the driver has it's own external lock for linking and
> +	 * unlinking &drm_gpuvas to the &drm_gem_objects GPUVA list.
> +	 *
> +	 * When setting this flag it is rquired to set a lock via
> +	 * drm_gpuva_set_ext_lock().
> +	 */
> +	DRM_GPUVA_MANAGER_LOCK_EXTERN = (1 << 0),
> +};
> +
> +/**
> + * struct drm_gpuva_manager - DRM GPU VA Manager
> + *
> + * The DRM GPU VA Manager keeps track of a GPU's virtual address space by using
> + * &maple_tree structures. Typically, this structure is embedded in bigger
> + * driver structures.
> + *
> + * Drivers can pass addresses and ranges in an arbitrary unit, e.g. bytes or
> + * pages.
> + *
> + * There should be one manager instance per GPU virtual address space.
> + */
> +struct drm_gpuva_manager {
> +	/**
> +	 * @name: the name of the DRM GPU VA space
> +	 */
> +	const char *name;
> +
> +	/**
> +	 * @flags: the feature flags of the &drm_gpuva_manager
> +	 */
> +	enum drm_gpuva_manager_flags flags;
> +
> +	/**
> +	 * @mm_start: start of the VA space
> +	 */
> +	u64 mm_start;
> +
> +	/**
> +	 * @mm_range: length of the VA space
> +	 */
> +	u64 mm_range;
> +
> +	/**
> +	 * @rb: structures to track &drm_gpuva entries
> +	 */
> +	struct {
> +		/**
> +		 * @tree: the rb-tree to track GPU VA mappings
> +		 */
> +		struct rb_root_cached tree;
> +
> +		/**
> +		 * @list: the &list_head to track GPU VA mappings
> +		 */
> +		struct list_head list;
> +	} rb;
> +
> +	/**
> +	 * @kernel_alloc_node:
> +	 *
> +	 * &drm_gpuva representing the address space cutout reserved for
> +	 * the kernel
> +	 */
> +	struct drm_gpuva kernel_alloc_node;
> +
> +	/**
> +	 * @ops: &drm_gpuva_fn_ops providing the split/merge steps to drivers
> +	 */
> +	const struct drm_gpuva_fn_ops *ops;
> +
> +	/**
> +	 * @ext_lock: &lockdep_map according to @DRM_GPUVA_MANAGER_LOCK_EXTERN
> +	 */
> +	lockdep_map_p ext_lock;
> +};
> +
> +void drm_gpuva_manager_init(struct drm_gpuva_manager *mgr,
> +			    const char *name,
> +			    u64 start_offset, u64 range,
> +			    u64 reserve_offset, u64 reserve_range,
> +			    const struct drm_gpuva_fn_ops *ops,
> +			    enum drm_gpuva_manager_flags flags);
> +void drm_gpuva_manager_destroy(struct drm_gpuva_manager *mgr);
> +
> +/**
> + * drm_gpuva_manager_external_lock - indicates whether the
> + * @DRM_GPUVA_MANAGER_LOCK_EXTERN flag is set
> + * @mgr: the &drm_gpuva_manager to check the flag for
> + */
> +static inline bool drm_gpuva_manager_external_lock(struct drm_gpuva_manager *mgr)
> +{
> +	return mgr->flags & DRM_GPUVA_MANAGER_LOCK_EXTERN;
> +}
> +
> +/**
> + * drm_gpuva_for_each_va_range - iternator to walk over a range of &drm_gpuvas
> + * @va__: &drm_gpuva structure to assign to in each iteration step
> + * @mgr__: &drm_gpuva_manager to walk over
> + * @start__: starting offset, the first gpuva will overlap this
> + * @end__: ending offset, the last gpuva will start before this (but may
> + * overlap)
> + *
> + * This iterator walks over all &drm_gpuvas in the &drm_gpuva_manager that lie
> + * between @start__ and @end__. It is implemented similarly to list_for_each(),
> + * but is using the &drm_gpuva_manager's internal interval tree to accelerate
> + * the search for the starting &drm_gpuva, and hence isn't safe against removal
> + * of elements. It assumes that @end__ is within (or is the upper limit of) the
> + * &drm_gpuva_manager. This iterator does not skip over the &drm_gpuva_manager's
> + * @kernel_alloc_node.
> + */
> +#define drm_gpuva_for_each_va_range(va__, mgr__, start__, end__) \
> +	for (va__ = drm_gpuva_find_first((mgr__), (start__), (end__)); \
> +	     va__ && (va__->va.addr < (end__)) && \
> +	     !list_entry_is_head(va__, &(mgr__)->rb.list, rb.entry); \
> +	     va__ = list_next_entry(va__, rb.entry))
> +
> +/**
> + * drm_gpuva_for_each_va_range_safe - iternator to safely walk over a range of
> + * &drm_gpuvas
> + * @va__: &drm_gpuva to assign to in each iteration step
> + * @next__: another &drm_gpuva to use as temporary storage
> + * @mgr__: &drm_gpuva_manager to walk over
> + * @start__: starting offset, the first gpuva will overlap this
> + * @end__: ending offset, the last gpuva will start before this (but may
> + * overlap)
> + *
> + * This iterator walks over all &drm_gpuvas in the &drm_gpuva_manager that lie
> + * between @start__ and @end__. It is implemented similarly to
> + * list_for_each_safe(), but is using the &drm_gpuva_manager's internal interval
> + * tree to accelerate the search for the starting &drm_gpuva, and hence is safe
> + * against removal of elements. It assumes that @end__ is within (or is the
> + * upper limit of) the &drm_gpuva_manager. This iterator does not skip over the
> + * &drm_gpuva_manager's @kernel_alloc_node.
> + */
> +#define drm_gpuva_for_each_va_range_safe(va__, next__, mgr__, start__, end__) \
> +	for (va__ = drm_gpuva_find_first((mgr__), (start__), (end__)), \
> +	     next__ = va ? list_next_entry(va__, rb.entry) : NULL; \
> +	     va__ && (va__->va.addr < (end__)) && \
> +	     !list_entry_is_head(va__, &(mgr__)->rb.list, rb.entry); \
> +	     va__ = next__, next__ = list_next_entry(va__, rb.entry))
> +
> +/**
> + * drm_gpuva_for_each_va - iternator to walk over all &drm_gpuvas
> + * @va__: &drm_gpuva to assign to in each iteration step
> + * @mgr__: &drm_gpuva_manager to walk over
> + *
> + * This iterator walks over all &drm_gpuva structures associated with the given
> + * &drm_gpuva_manager.
> + */
> +#define drm_gpuva_for_each_va(va__, mgr__) \
> +	list_for_each_entry(va__, &(mgr__)->rb.list, rb.entry)
> +
> +/**
> + * drm_gpuva_for_each_va_safe - iternator to safely walk over all &drm_gpuvas
> + * @va__: &drm_gpuva to assign to in each iteration step
> + * @next__: another &drm_gpuva to use as temporary storage
> + * @mgr__: &drm_gpuva_manager to walk over
> + *
> + * This iterator walks over all &drm_gpuva structures associated with the given
> + * &drm_gpuva_manager. It is implemented with list_for_each_entry_safe(), and
> + * hence safe against the removal of elements.
> + */
> +#define drm_gpuva_for_each_va_safe(va__, next__, mgr__) \
> +	list_for_each_entry_safe(va__, next__, &(mgr__)->rb.list, rb.entry)
> +
> +/**
> + * enum drm_gpuva_op_type - GPU VA operation type
> + *
> + * Operations to alter the GPU VA mappings tracked by the &drm_gpuva_manager.
> + */
> +enum drm_gpuva_op_type {
> +	/**
> +	 * @DRM_GPUVA_OP_MAP: the map op type
> +	 */
> +	DRM_GPUVA_OP_MAP,
> +
> +	/**
> +	 * @DRM_GPUVA_OP_REMAP: the remap op type
> +	 */
> +	DRM_GPUVA_OP_REMAP,
> +
> +	/**
> +	 * @DRM_GPUVA_OP_UNMAP: the unmap op type
> +	 */
> +	DRM_GPUVA_OP_UNMAP,
> +
> +	/**
> +	 * @DRM_GPUVA_OP_PREFETCH: the prefetch op type
> +	 */
> +	DRM_GPUVA_OP_PREFETCH,
> +};
> +
> +/**
> + * struct drm_gpuva_op_map - GPU VA map operation
> + *
> + * This structure represents a single map operation generated by the
> + * DRM GPU VA manager.
> + */
> +struct drm_gpuva_op_map {
> +	/**
> +	 * @va: structure containing address and range of a map
> +	 * operation
> +	 */
> +	struct {
> +		/**
> +		 * @addr: the base address of the new mapping
> +		 */
> +		u64 addr;
> +
> +		/**
> +		 * @range: the range of the new mapping
> +		 */
> +		u64 range;
> +	} va;
> +
> +	/**
> +	 * @gem: structure containing the &drm_gem_object and it's offset
> +	 */
> +	struct {
> +		/**
> +		 * @offset: the offset within the &drm_gem_object
> +		 */
> +		u64 offset;
> +
> +		/**
> +		 * @obj: the &drm_gem_object to map
> +		 */
> +		struct drm_gem_object *obj;
> +	} gem;
> +};
> +
> +/**
> + * struct drm_gpuva_op_unmap - GPU VA unmap operation
> + *
> + * This structure represents a single unmap operation generated by the
> + * DRM GPU VA manager.
> + */
> +struct drm_gpuva_op_unmap {
> +	/**
> +	 * @va: the &drm_gpuva to unmap
> +	 */
> +	struct drm_gpuva *va;
> +
> +	/**
> +	 * @keep:
> +	 *
> +	 * Indicates whether this &drm_gpuva is physically contiguous with the
> +	 * original mapping request.
> +	 *
> +	 * Optionally, if &keep is set, drivers may keep the actual page table
> +	 * mappings for this &drm_gpuva, adding the missing page table entries
> +	 * only and update the &drm_gpuva_manager accordingly.
> +	 */
> +	bool keep;
> +};
> +
> +/**
> + * struct drm_gpuva_op_remap - GPU VA remap operation
> + *
> + * This represents a single remap operation generated by the DRM GPU VA manager.
> + *
> + * A remap operation is generated when an existing GPU VA mmapping is split up
> + * by inserting a new GPU VA mapping or by partially unmapping existent
> + * mapping(s), hence it consists of a maximum of two map and one unmap
> + * operation.
> + *
> + * The @unmap operation takes care of removing the original existing mapping.
> + * @prev is used to remap the preceding part, @next the subsequent part.
> + *
> + * If either a new mapping's start address is aligned with the start address
> + * of the old mapping or the new mapping's end address is aligned with the
> + * end address of the old mapping, either @prev or @next is NULL.
> + *
> + * Note, the reason for a dedicated remap operation, rather than arbitrary
> + * unmap and map operations, is to give drivers the chance of extracting driver
> + * specific data for creating the new mappings from the unmap operations's
> + * &drm_gpuva structure which typically is embedded in larger driver specific
> + * structures.
> + */
> +struct drm_gpuva_op_remap {
> +	/**
> +	 * @prev: the preceding part of a split mapping
> +	 */
> +	struct drm_gpuva_op_map *prev;
> +
> +	/**
> +	 * @next: the subsequent part of a split mapping
> +	 */
> +	struct drm_gpuva_op_map *next;
> +
> +	/**
> +	 * @unmap: the unmap operation for the original existing mapping
> +	 */
> +	struct drm_gpuva_op_unmap *unmap;
> +};
> +
> +/**
> + * struct drm_gpuva_op_prefetch - GPU VA prefetch operation
> + *
> + * This structure represents a single prefetch operation generated by the
> + * DRM GPU VA manager.
> + */
> +struct drm_gpuva_op_prefetch {
> +	/**
> +	 * @va: the &drm_gpuva to prefetch
> +	 */
> +	struct drm_gpuva *va;
> +};
> +
> +/**
> + * struct drm_gpuva_op - GPU VA operation
> + *
> + * This structure represents a single generic operation.
> + *
> + * The particular type of the operation is defined by @op.
> + */
> +struct drm_gpuva_op {
> +	/**
> +	 * @entry:
> +	 *
> +	 * The &list_head used to distribute instances of this struct within
> +	 * &drm_gpuva_ops.
> +	 */
> +	struct list_head entry;
> +
> +	/**
> +	 * @op: the type of the operation
> +	 */
> +	enum drm_gpuva_op_type op;
> +
> +	union {
> +		/**
> +		 * @map: the map operation
> +		 */
> +		struct drm_gpuva_op_map map;
> +
> +		/**
> +		 * @remap: the remap operation
> +		 */
> +		struct drm_gpuva_op_remap remap;
> +
> +		/**
> +		 * @unmap: the unmap operation
> +		 */
> +		struct drm_gpuva_op_unmap unmap;
> +
> +		/**
> +		 * @prefetch: the prefetch operation
> +		 */
> +		struct drm_gpuva_op_prefetch prefetch;
> +	};
> +};
> +
> +/**
> + * struct drm_gpuva_ops - wraps a list of &drm_gpuva_op
> + */
> +struct drm_gpuva_ops {
> +	/**
> +	 * @list: the &list_head
> +	 */
> +	struct list_head list;
> +};
> +
> +/**
> + * drm_gpuva_for_each_op - iterator to walk over &drm_gpuva_ops
> + * @op: &drm_gpuva_op to assign in each iteration step
> + * @ops: &drm_gpuva_ops to walk
> + *
> + * This iterator walks over all ops within a given list of operations.
> + */
> +#define drm_gpuva_for_each_op(op, ops) list_for_each_entry(op, &(ops)->list, entry)
> +
> +/**
> + * drm_gpuva_for_each_op_safe - iterator to safely walk over &drm_gpuva_ops
> + * @op: &drm_gpuva_op to assign in each iteration step
> + * @next: &next &drm_gpuva_op to store the next step
> + * @ops: &drm_gpuva_ops to walk
> + *
> + * This iterator walks over all ops within a given list of operations. It is
> + * implemented with list_for_each_safe(), so save against removal of elements.
> + */
> +#define drm_gpuva_for_each_op_safe(op, next, ops) \
> +	list_for_each_entry_safe(op, next, &(ops)->list, entry)
> +
> +/**
> + * drm_gpuva_for_each_op_from_reverse - iterate backwards from the given point
> + * @op: &drm_gpuva_op to assign in each iteration step
> + * @ops: &drm_gpuva_ops to walk
> + *
> + * This iterator walks over all ops within a given list of operations beginning
> + * from the given operation in reverse order.
> + */
> +#define drm_gpuva_for_each_op_from_reverse(op, ops) \
> +	list_for_each_entry_from_reverse(op, &(ops)->list, entry)
> +
> +/**
> + * drm_gpuva_first_op - returns the first &drm_gpuva_op from &drm_gpuva_ops
> + * @ops: the &drm_gpuva_ops to get the fist &drm_gpuva_op from
> + */
> +#define drm_gpuva_first_op(ops) \
> +	list_first_entry(&(ops)->list, struct drm_gpuva_op, entry)
> +
> +/**
> + * drm_gpuva_last_op - returns the last &drm_gpuva_op from &drm_gpuva_ops
> + * @ops: the &drm_gpuva_ops to get the last &drm_gpuva_op from
> + */
> +#define drm_gpuva_last_op(ops) \
> +	list_last_entry(&(ops)->list, struct drm_gpuva_op, entry)
> +
> +/**
> + * drm_gpuva_prev_op - previous &drm_gpuva_op in the list
> + * @op: the current &drm_gpuva_op
> + */
> +#define drm_gpuva_prev_op(op) list_prev_entry(op, entry)
> +
> +/**
> + * drm_gpuva_next_op - next &drm_gpuva_op in the list
> + * @op: the current &drm_gpuva_op
> + */
> +#define drm_gpuva_next_op(op) list_next_entry(op, entry)
> +
> +struct drm_gpuva_ops *
> +drm_gpuva_sm_map_ops_create(struct drm_gpuva_manager *mgr,
> +			    u64 addr, u64 range,
> +			    struct drm_gem_object *obj, u64 offset);
> +struct drm_gpuva_ops *
> +drm_gpuva_sm_unmap_ops_create(struct drm_gpuva_manager *mgr,
> +			      u64 addr, u64 range);
> +
> +struct drm_gpuva_ops *
> +drm_gpuva_prefetch_ops_create(struct drm_gpuva_manager *mgr,
> +				 u64 addr, u64 range);
> +
> +struct drm_gpuva_ops *
> +drm_gpuva_gem_unmap_ops_create(struct drm_gpuva_manager *mgr,
> +			       struct drm_gem_object *obj);
> +
> +void drm_gpuva_ops_free(struct drm_gpuva_manager *mgr,
> +			struct drm_gpuva_ops *ops);
> +
> +static inline void drm_gpuva_init_from_op(struct drm_gpuva *va,
> +					  struct drm_gpuva_op_map *op)
> +{
> +	drm_gpuva_init(va, op->va.addr, op->va.range,
> +		       op->gem.obj, op->gem.offset);
> +}
> +
> +/**
> + * struct drm_gpuva_fn_ops - callbacks for split/merge steps
> + *
> + * This structure defines the callbacks used by &drm_gpuva_sm_map and
> + * &drm_gpuva_sm_unmap to provide the split/merge steps for map and unmap
> + * operations to drivers.
> + */
> +struct drm_gpuva_fn_ops {
> +	/**
> +	 * @op_alloc: called when the &drm_gpuva_manager allocates
> +	 * a struct drm_gpuva_op
> +	 *
> +	 * Some drivers may want to embed struct drm_gpuva_op into driver
> +	 * specific structures. By implementing this callback drivers can
> +	 * allocate memory accordingly.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	struct drm_gpuva_op *(*op_alloc)(void);
> +
> +	/**
> +	 * @op_free: called when the &drm_gpuva_manager frees a
> +	 * struct drm_gpuva_op
> +	 *
> +	 * Some drivers may want to embed struct drm_gpuva_op into driver
> +	 * specific structures. By implementing this callback drivers can
> +	 * free the previously allocated memory accordingly.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void (*op_free)(struct drm_gpuva_op *op);
> +
> +	/**
> +	 * @sm_step_map: called from &drm_gpuva_sm_map to finally insert the
> +	 * mapping once all previous steps were completed
> +	 *
> +	 * The &priv pointer matches the one the driver passed to
> +	 * &drm_gpuva_sm_map or &drm_gpuva_sm_unmap, respectively.
> +	 *
> +	 * Can be NULL if &drm_gpuva_sm_map is used.
> +	 */
> +	int (*sm_step_map)(struct drm_gpuva_op *op, void *priv);
> +
> +	/**
> +	 * @sm_step_remap: called from &drm_gpuva_sm_map and
> +	 * &drm_gpuva_sm_unmap to split up an existent mapping
> +	 *
> +	 * This callback is called when existent mapping needs to be split up.
> +	 * This is the case when either a newly requested mapping overlaps or
> +	 * is enclosed by an existent mapping or a partial unmap of an existent
> +	 * mapping is requested.
> +	 *
> +	 * The &priv pointer matches the one the driver passed to
> +	 * &drm_gpuva_sm_map or &drm_gpuva_sm_unmap, respectively.
> +	 *
> +	 * Can be NULL if neither &drm_gpuva_sm_map nor &drm_gpuva_sm_unmap is
> +	 * used.
> +	 */
> +	int (*sm_step_remap)(struct drm_gpuva_op *op, void *priv);
> +
> +	/**
> +	 * @sm_step_unmap: called from &drm_gpuva_sm_map and
> +	 * &drm_gpuva_sm_unmap to unmap an existent mapping
> +	 *
> +	 * This callback is called when existent mapping needs to be unmapped.
> +	 * This is the case when either a newly requested mapping encloses an
> +	 * existent mapping or an unmap of an existent mapping is requested.
> +	 *
> +	 * The &priv pointer matches the one the driver passed to
> +	 * &drm_gpuva_sm_map or &drm_gpuva_sm_unmap, respectively.
> +	 *
> +	 * Can be NULL if neither &drm_gpuva_sm_map nor &drm_gpuva_sm_unmap is
> +	 * used.
> +	 */
> +	int (*sm_step_unmap)(struct drm_gpuva_op *op, void *priv);
> +};
> +
> +int drm_gpuva_sm_map(struct drm_gpuva_manager *mgr, void *priv,
> +		     u64 addr, u64 range,
> +		     struct drm_gem_object *obj, u64 offset);
> +
> +int drm_gpuva_sm_unmap(struct drm_gpuva_manager *mgr, void *priv,
> +		       u64 addr, u64 range);
> +
> +void drm_gpuva_map(struct drm_gpuva_manager *mgr,
> +		   struct drm_gpuva *va,
> +		   struct drm_gpuva_op_map *op);
Missing newline
> +void drm_gpuva_remap(struct drm_gpuva *prev,
> +		     struct drm_gpuva *next,
> +		     struct drm_gpuva_op_remap *op);
Missing newline
> +void drm_gpuva_unmap(struct drm_gpuva_op_unmap *op);
> +
> +#endif /* __DRM_GPUVA_MGR_H__ */