Re: [PATCH drm-next 03/14] drm: manager to keep track of GPUs VA mappings

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Jan 18, 2023 at 07:12:45AM +0100, Danilo Krummrich wrote:
> This adds the infrastructure for a manager implementation to keep track
> of GPU virtual address (VA) mappings.
> 
> 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 a dedicated range allocator to track GPU VA allocations and
>    mappings, making use of the drm_mm range allocator.
> 
> 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.
> 
> Idea-suggested-by: Dave Airlie <airlied@redhat.com>
> Signed-off-by: Danilo Krummrich <dakr@redhat.com>

<snip>

> +++ b/drivers/gpu/drm/drm_gpuva_mgr.c

<snip>

> +struct drm_gpuva *
> +drm_gpuva_find(struct drm_gpuva_manager *mgr,
> +	       u64 addr, u64 range)
> +{
> +	struct drm_gpuva *va;
> +
> +	drm_gpuva_for_each_va_in_range(va, mgr, addr, range) {

Last argument should be: range + addr, right?

> +		if (va->node.start == addr &&
> +		    va->node.size == range)
> +			return va;
> +	}
> +
> +	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)
> +{
> +	struct drm_mm_node *node;
> +
> +	if (start <= mgr->mm_start ||
> +	    start > (mgr->mm_start + mgr->mm_range))
> +		return NULL;
> +
> +	node = __drm_mm_interval_first(&mgr->va_mm, start - 1, start);
> +	if (node == &mgr->va_mm.head_node)
> +		return NULL;
> +
> +	return (struct drm_gpuva *)node;
> +}
> +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)
> +{
> +	struct drm_mm_node *node;
> +
> +	if (end < mgr->mm_start ||
> +	    end >= (mgr->mm_start + mgr->mm_range))
> +		return NULL;
> +
> +	node = __drm_mm_interval_first(&mgr->va_mm, end, end + 1);
> +	if (node == &mgr->va_mm.head_node)
> +		return NULL;
> +
> +	return (struct drm_gpuva *)node;
> +}
> +EXPORT_SYMBOL(drm_gpuva_find_next);
> +
> +/**
> + * drm_gpuva_region_insert - insert a &drm_gpuva_region
> + * @mgr: the &drm_gpuva_manager to insert the &drm_gpuva in
> + * @reg: the &drm_gpuva_region to insert
> + * @addr: the start address of the GPU VA
> + * @range: the range of the GPU VA
> + *
> + * Insert a &drm_gpuva_region with a given address and range into a
> + * &drm_gpuva_manager.
> + *
> + * Returns: 0 on success, negative error code on failure.
> + */
> +int
> +drm_gpuva_region_insert(struct drm_gpuva_manager *mgr,
> +			struct drm_gpuva_region *reg,
> +			u64 addr, u64 range)
> +{
> +	int ret;
> +
> +	ret = drm_mm_insert_node_in_range(&mgr->region_mm, &reg->node,
> +					  range, 0,
> +					  0, addr,
> +					  addr + range,
> +					  DRM_MM_INSERT_LOW|
> +					  DRM_MM_INSERT_ONCE);
> +	if (ret)
> +		return ret;
> +
> +	reg->mgr = mgr;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_gpuva_region_insert);
> +
> +/**
> + * drm_gpuva_region_destroy - destroy a &drm_gpuva_region
> + * @mgr: the &drm_gpuva_manager holding the region
> + * @reg: the &drm_gpuva to destroy
> + *
> + * This removes the given &reg from the underlaying range allocator.
> + */
> +void
> +drm_gpuva_region_destroy(struct drm_gpuva_manager *mgr,
> +			 struct drm_gpuva_region *reg)
> +{
> +	struct drm_gpuva *va;
> +
> +	drm_gpuva_for_each_va_in_range(va, mgr,
> +				       reg->node.start,
> +				       reg->node.size) {

Last argument should be: reg->node.start + reg->node.size, right?

Matt

> +		WARN(1, "GPU VA region must be empty on destroy.\n");
> +		return;
> +	}
> +
> +	if (&reg->node == &mgr->kernel_alloc_node) {
> +		WARN(1, "Can't destroy kernel reserved region.\n");
> +		return;
> +	}
> +
> +	drm_mm_remove_node(&reg->node);
> +}
> +EXPORT_SYMBOL(drm_gpuva_region_destroy);