linux-kernel - Re: [PATCH v9 03/11] drm/gem: Add evict() callback to drm_gem_object

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Date:   Wed, 23 Nov 2022 15:58:14 +0000
From:   Steven Price <steven.price@....com>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        David Airlie <airlied@...il.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Daniel Almeida <daniel.almeida@...labora.com>,
        Gustavo Padovan <gustavo.padovan@...labora.com>,
        Daniel Stone <daniel@...ishbar.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Rob Clark <robdclark@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Qiang Yu <yuq825@...il.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Rob Herring <robh@...nel.org>, Sean Paul <sean@...rly.run>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     kernel@...labora.com, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v9 03/11] drm/gem: Add evict() callback to
 drm_gem_object_funcs

On 23/11/2022 02:57, Dmitry Osipenko wrote:
> Add new common evict() callback to drm_gem_object_funcs and corresponding
> drm_gem_object_evict() helper. This is a first step on a way to providing
> common GEM-shrinker API for DRM drivers.
> 
> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> ---
>  drivers/gpu/drm/drm_gem.c | 15 +++++++++++++++
>  include/drm/drm_gem.h     | 12 ++++++++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 299bca1390aa..c0510b8080d2 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -1458,3 +1458,18 @@ drm_gem_lru_scan(struct drm_gem_lru *lru,
>  	return freed;
>  }
>  EXPORT_SYMBOL(drm_gem_lru_scan);
> +
> +/**
> + * drm_gem_object_evict - helper to evict backing pages for a GEM object
> + * @obj: obj in question
> + */
> +bool
> +drm_gem_object_evict(struct drm_gem_object *obj)
> +{
> +	dma_resv_assert_held(obj->resv);
> +
> +	if (obj->funcs->evict)
> +		return obj->funcs->evict(obj);
> +
> +	return false;
> +}

This function needs exporting for the module build to work correctly.

Steve

> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index b46ade812443..add1371453f0 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -172,6 +172,16 @@ struct drm_gem_object_funcs {
>  	 * This is optional but necessary for mmap support.
>  	 */
>  	const struct vm_operations_struct *vm_ops;
> +
> +	/**
> +	 * @evict:
> +	 *
> +	 * Evicts gem object out from memory. Used by the drm_gem_object_evict()
> +	 * helper. Returns true on success, false otherwise.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	bool (*evict)(struct drm_gem_object *obj);
>  };
>  
>  /**
> @@ -480,4 +490,6 @@ unsigned long drm_gem_lru_scan(struct drm_gem_lru *lru,
>  			       unsigned long *remaining,
>  			       bool (*shrink)(struct drm_gem_object *obj));
>  
> +bool drm_gem_object_evict(struct drm_gem_object *obj);
> +
>  #endif /* __DRM_GEM_H__ */