Re: [Intel-gfx] [PATCH v2 1/5] drm/i915/gem: Implement object migration

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On 6/28/21 11:09 AM, Thomas Hellström wrote:
> Introduce an interface to migrate objects between regions.
> This is primarily intended to migrate objects to LMEM for display and
> to SYSTEM for dma-buf, but might be reused in one form or another for
> performande-based migration.
>
> v2:
> - Verify that the memory region given as an id really exists.
>    (Reported by Matthew Auld)
> - Call i915_gem_object_{init,release}_memory_region() when switching region
>    to handle also switching region lists. (Reported by Matthew Auld)
>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_object.c    | 96 +++++++++++++++++++
>   drivers/gpu/drm/i915/gem/i915_gem_object.h    | 12 +++
>   .../gpu/drm/i915/gem/i915_gem_object_types.h  |  9 ++
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c       | 69 +++++++++----
>   drivers/gpu/drm/i915/gem/i915_gem_wait.c      | 19 ++++
>   5 files changed, 188 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> index 07e8ff9a8aae..52a37619054d 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> @@ -513,6 +513,102 @@ bool i915_gem_object_has_iomem(const struct drm_i915_gem_object *obj)
>   	return obj->mem_flags & I915_BO_FLAG_IOMEM;
>   }
>   
> +/**
> + * i915_gem_object_can_migrate - Whether an object likely can be migrated
> + *
> + * @obj: The object to migrate
> + * @id: The region intended to migrate to
> + *
> + * Check whether the object backend supports migration to the
> + * given region. Note that pinning may affect the ability to migrate.
> + *
> + * Return: true if migration is possible, false otherwise.
> + */
> +bool i915_gem_object_can_migrate(struct drm_i915_gem_object *obj,
> +				 enum intel_region_id id)
> +{
> +	struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +	unsigned int num_allowed = obj->mm.n_placements;
> +	struct intel_memory_region *mr;
> +	unsigned int i;
> +
> +	GEM_BUG_ON(id >= INTEL_REGION_UNKNOWN);
> +	GEM_BUG_ON(obj->mm.madv != I915_MADV_WILLNEED);
> +
> +	if (!obj->ops->migrate)
> +		return false;
> +
> +	mr = i915->mm.regions[id];
> +	if (!mr)
> +		return false;


Hmm. Should probably switch order between these two, otherwise 
can_migrate will always return false on !TTM

/Thomas


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