Re: [PATCH v4 11/15] drm/shmem-helper: Add generic memory shrinker

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Hi

Am 18.04.22 um 00:37 schrieb Dmitry Osipenko:
> Introduce a common DRM SHMEM shrinker. It allows to reduce code
> duplication among DRM drivers that implement theirs own shrinkers.
> This is initial version of the shrinker that covers basic needs of
> GPU drivers, both purging and eviction of shmem objects are supported.
>
> This patch is based on a couple ideas borrowed from Rob's Clark MSM
> shrinker and Thomas' Zimmermann variant of SHMEM shrinker.
>
> In order to start using DRM SHMEM shrinker drivers should:
>
> 1. Implement new purge(), evict() + swap_in() GEM callbacks.
> 2. Register shrinker using drm_gem_shmem_shrinker_register(drm_device).
> 3. Use drm_gem_shmem_set_purgeable_and_evictable(shmem) and alike API
>     functions to activate shrinking of GEMs.
>
> Signed-off-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
>   drivers/gpu/drm/drm_gem_shmem_helper.c | 765 ++++++++++++++++++++++++-
>   include/drm/drm_device.h               |   4 +
>   include/drm/drm_gem.h                  |  35 ++
>   include/drm/drm_gem_shmem_helper.h     | 105 +++-
>   4 files changed, 877 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 3ecef571eff3..3838fb8d6f3a 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -88,6 +88,13 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
>   
>   	INIT_LIST_HEAD(&shmem->madv_list);
>   
> +	/*
> +	 * Eviction and purging are disabled by default, shmem user must enable
> +	 * them explicitly using drm_gem_shmem_set_evictable/purgeable().
> +	 */
> +	shmem->eviction_disable_count = 1;
> +	shmem->purging_disable_count = 1;
> +
>   	if (!private) {
>   		/*
>   		 * Our buffers are kept pinned, so allocating them
> @@ -126,6 +133,107 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
>   }
>   EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
>   
> +static void
> +drm_gem_shmem_add_pages_to_shrinker(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
> +	size_t page_count = obj->size >> PAGE_SHIFT;
> +
> +	if (!shmem->pages_shrinkable) {
> +		WARN_ON(gem_shrinker->shrinkable_count + page_count < page_count);
> +		gem_shrinker->shrinkable_count += page_count;
> +		shmem->pages_shrinkable = true;
> +	}
> +}
> +
> +static void
> +drm_gem_shmem_remove_pages_from_shrinker(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
> +	size_t page_count = obj->size >> PAGE_SHIFT;
> +
> +	if (shmem->pages_shrinkable) {
> +		WARN_ON(gem_shrinker->shrinkable_count < page_count);
> +		gem_shrinker->shrinkable_count -= page_count;
> +		shmem->pages_shrinkable = false;
> +	}
> +}
> +
> +static void
> +drm_gem_shmem_set_pages_state_locked(struct drm_gem_shmem_object *shmem,
> +				     enum drm_gem_shmem_pages_state new_state)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
> +
> +	lockdep_assert_held(&gem_shrinker->lock);
> +	lockdep_assert_held(&obj->resv->lock.base);
> +
> +	if (new_state >= DRM_GEM_SHMEM_PAGES_STATE_PINNED) {
> +		if (drm_gem_shmem_is_evictable(shmem))
> +			new_state = DRM_GEM_SHMEM_PAGES_STATE_EVICTABLE;
> +
> +		if (drm_gem_shmem_is_purgeable(shmem))
> +			new_state = DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE;
> +
> +		if (!shmem->pages)
> +			new_state = DRM_GEM_SHMEM_PAGES_STATE_UNPINNED;
> +
> +		if (shmem->evicted)
> +			new_state = DRM_GEM_SHMEM_PAGES_STATE_EVICTED;
> +	}
> +
> +	if (shmem->pages_state == new_state)
> +		return;
> +
> +	switch (new_state) {
> +	case DRM_GEM_SHMEM_PAGES_STATE_UNPINNED:
> +	case DRM_GEM_SHMEM_PAGES_STATE_PURGED:
> +		drm_gem_shmem_remove_pages_from_shrinker(shmem);
> +		list_del_init(&shmem->madv_list);
> +		break;
> +
> +	case DRM_GEM_SHMEM_PAGES_STATE_PINNED:
> +		drm_gem_shmem_remove_pages_from_shrinker(shmem);
> +		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_active);
> +		break;
> +
> +	case DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE:
> +		drm_gem_shmem_add_pages_to_shrinker(shmem);
> +		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_purgeable);
> +		break;
> +
> +	case DRM_GEM_SHMEM_PAGES_STATE_EVICTABLE:
> +		drm_gem_shmem_add_pages_to_shrinker(shmem);
> +		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_evictable);
> +		break;
> +
> +	case DRM_GEM_SHMEM_PAGES_STATE_EVICTED:
> +		drm_gem_shmem_remove_pages_from_shrinker(shmem);
> +		list_move_tail(&shmem->madv_list, &gem_shrinker->lru_evicted);
> +		break;
> +	}
> +
> +	shmem->pages_state = new_state;
> +}
> +
> +static void
> +drm_gem_shmem_set_pages_state(struct drm_gem_shmem_object *shmem,
> +			      enum drm_gem_shmem_pages_state new_state)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
> +
> +	if (!gem_shrinker)
> +		return;
> +
> +	mutex_lock(&gem_shrinker->lock);
> +	drm_gem_shmem_set_pages_state_locked(shmem, new_state);
> +	mutex_unlock(&gem_shrinker->lock);
> +}
> +
>   /**
>    * drm_gem_shmem_free - Free resources associated with a shmem GEM object
>    * @shmem: shmem GEM object to free
> @@ -137,6 +245,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>   {
>   	struct drm_gem_object *obj = &shmem->base;
>   
> +	/* take out shmem GEM object from the memory shrinker */
> +	drm_gem_shmem_madvise(shmem, -1);
> +
>   	WARN_ON(shmem->vmap_use_count);
>   
>   	if (obj->import_attach) {
> @@ -148,7 +259,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>   			sg_free_table(shmem->sgt);
>   			kfree(shmem->sgt);
>   		}
> -		if (shmem->pages)
> +		if (shmem->pages_use_count)
>   			drm_gem_shmem_put_pages(shmem);
>   	}
>   
> @@ -159,18 +270,226 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
>   }
>   EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
>   
> -static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +static void drm_gem_shmem_update_pages_state_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
> +	enum drm_gem_shmem_pages_state new_state;
> +
> +	if (!gem_shrinker || obj->import_attach)
> +		return;
> +
> +	mutex_lock(&gem_shrinker->lock);
> +
> +	if (!shmem->madv)
> +		new_state = DRM_GEM_SHMEM_PAGES_STATE_PINNED;
> +	else if (shmem->madv > 0)
> +		new_state = DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE;
> +	else
> +		new_state = DRM_GEM_SHMEM_PAGES_STATE_PURGED;
> +
> +	drm_gem_shmem_set_pages_state_locked(shmem, new_state);
> +
> +	mutex_unlock(&gem_shrinker->lock);
> +}
> +
> +static void drm_gem_shmem_update_pages_state(struct drm_gem_shmem_object *shmem)
> +{
> +	dma_resv_lock(shmem->base.resv, NULL);
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +	dma_resv_unlock(shmem->base.resv);
> +}
> +
> +static int
> +drm_gem_shmem_set_evictable_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret = 0;
> +
> +	WARN_ON_ONCE(!shmem->eviction_disable_count--);
> +
> +	if (shmem->madv < 0)
> +		ret = -ENOMEM;
> +
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
> +	return ret;
> +}
> +
> +static int
> +drm_gem_shmem_set_unevictable_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	int err;
> +
> +	if (shmem->madv < 0)
> +		return -ENOMEM;
> +
> +	if (shmem->evicted) {
> +		err = obj->funcs->swap_in(obj);
> +		if (err)
> +			return err;
> +	}
> +
> +	shmem->eviction_disable_count++;
> +
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
> +	return 0;
> +}
> +
> +static int
> +drm_gem_shmem_set_purgeable_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret = 0;
> +
> +	WARN_ON_ONCE(!shmem->purging_disable_count--);
> +
> +	if (shmem->madv < 0)
> +		ret = -ENOMEM;
> +
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
> +	return ret;
> +}
> +
> +/**
> + * drm_gem_shmem_set_purgeable() - Make GEM purgeable by memory shrinker
> + * @shmem: shmem GEM object
> + *
> + * Tell memory shrinker that this GEM can be purged. Initially purging is
> + * disabled for all GEMs. Each set_pureable() call must have corresponding
> + * set_unpureable() call. If GEM was purged, then -ENOMEM is returned.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_set_purgeable(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	dma_resv_lock(shmem->base.resv, NULL);
> +	ret = drm_gem_shmem_set_purgeable_locked(shmem);
> +	dma_resv_unlock(shmem->base.resv);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable);
> +
> +static int
> +drm_gem_shmem_set_unpurgeable_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	if (shmem->madv < 0)
> +		return -ENOMEM;
> +
> +	shmem->purging_disable_count++;
> +
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
> +	return 0;
> +}
> +
> +static int
> +drm_gem_shmem_set_purgeable_and_evictable_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	ret = drm_gem_shmem_set_evictable_locked(shmem);
> +	if (!ret) {
> +		ret = drm_gem_shmem_set_purgeable_locked(shmem);
> +		if (ret)
> +			drm_gem_shmem_set_unevictable_locked(shmem);
> +	}
> +
> +	return ret;
> +}
> +
> +static int
> +drm_gem_shmem_set_unpurgeable_and_unevictable_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	ret = drm_gem_shmem_set_unpurgeable_locked(shmem);
> +	if (!ret) {
> +		ret = drm_gem_shmem_set_unevictable_locked(shmem);
> +		if (ret)
> +			drm_gem_shmem_set_purgeable_locked(shmem);
> +	}
> +
> +	return ret;
> +}
> +
> +/**
> + * drm_gem_shmem_set_purgeable_and_evictable() - Make GEM unpurgeable and
> + * 						 unevictable by memory shrinker
> + * @shmem: shmem GEM object
> + *
> + * Tell memory shrinker that this GEM can't be purged and evicted. Each
> + * set_purgeable_and_evictable() call must have corresponding
> + * unpurgeable_and_unevictable() call. If GEM was purged, then -ENOMEM
> + * is returned.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_set_purgeable_and_evictable(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	dma_resv_lock(shmem->base.resv, NULL);
> +	ret = drm_gem_shmem_set_purgeable_and_evictable_locked(shmem);
> +	dma_resv_unlock(shmem->base.resv);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_purgeable_and_evictable);
> +
> +/**
> + * drm_gem_shmem_set_unpurgeable_and_unevictable() - Make GEM purgeable and
> + * 						     evictable by memory shrinker
> + * @shmem: shmem GEM object
> + *
> + * Tell memory shrinker that this GEM can be purged and evicted. Each
> + * unpurgeable_and_unevictable() call must have corresponding
> + * set_purgeable_and_evictable() call. If GEM was purged, then -ENOMEM
> + * is returned.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_set_unpurgeable_and_unevictable(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
> +	if (ret)
> +		return ret;
> +
> +	ret = drm_gem_shmem_set_unpurgeable_and_unevictable_locked(shmem);
> +	dma_resv_unlock(shmem->base.resv);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_set_unpurgeable_and_unevictable);
> +
> +static int
> +drm_gem_shmem_acquire_pages_locked(struct drm_gem_shmem_object *shmem)
>   {
>   	struct drm_gem_object *obj = &shmem->base;
>   	struct page **pages;
>   
> -	if (shmem->pages_use_count++ > 0)
> +	if (shmem->madv < 0) {
> +		WARN_ON(shmem->pages);
> +		return -ENOMEM;
> +	}
> +
> +	if (shmem->pages) {
> +		WARN_ON(!shmem->evicted);
>   		return 0;
> +	}
>   
>   	pages = drm_gem_get_pages(obj);
>   	if (IS_ERR(pages)) {
>   		DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
> -		shmem->pages_use_count = 0;
>   		return PTR_ERR(pages);
>   	}
>   
> @@ -189,6 +508,25 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
>   	return 0;
>   }
>   
> +static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	int err;
> +
> +	if (shmem->madv < 0)
> +		return -ENOMEM;
> +
> +	if (shmem->pages_use_count++ > 0)
> +		return 0;
> +
> +	err = drm_gem_shmem_acquire_pages_locked(shmem);
> +	if (err) {
> +		shmem->pages_use_count = 0;
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
>   /*
>    * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
>    * @shmem: shmem GEM object
> @@ -209,21 +547,38 @@ int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
>   	if (ret)
>   		return ret;
>   	ret = drm_gem_shmem_get_pages_locked(shmem);
> +
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
>   	dma_resv_unlock(shmem->base.resv);
>   
>   	return ret;
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_get_pages);
>   
> -static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
> +static void drm_gem_shmem_get_pages_no_fail(struct drm_gem_shmem_object *shmem)
>   {
> -	struct drm_gem_object *obj = &shmem->base;
> +	WARN_ON(shmem->base.import_attach);
>   
> -	if (WARN_ON_ONCE(!shmem->pages_use_count))
> -		return;
> +	dma_resv_lock(shmem->base.resv, NULL);
>   
> -	if (--shmem->pages_use_count > 0)
> +	if (drm_gem_shmem_get_pages_locked(shmem))
> +		shmem->pages_use_count++;
> +
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
> +	dma_resv_unlock(shmem->base.resv);
> +}
> +
> +static void
> +drm_gem_shmem_release_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	if (!shmem->pages) {
> +		WARN_ON(!shmem->evicted && shmem->madv >= 0);
>   		return;
> +	}
>   
>   #ifdef CONFIG_X86
>   	if (shmem->map_wc)
> @@ -236,6 +591,21 @@ static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>   	shmem->pages = NULL;
>   }
>   
> +static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	lockdep_assert_held(&obj->resv->lock.base);
> +
> +	if (WARN_ON(!shmem->pages_use_count))
> +		return;
> +
> +	if (--shmem->pages_use_count > 0)
> +		return;
> +
> +	drm_gem_shmem_release_pages_locked(shmem);
> +}
> +
>   /*
>    * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
>    * @shmem: shmem GEM object
> @@ -246,6 +616,7 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
>   {
>   	dma_resv_lock(shmem->base.resv, NULL);
>   	drm_gem_shmem_put_pages_locked(shmem);
> +	drm_gem_shmem_update_pages_state_locked(shmem);
>   	dma_resv_unlock(shmem->base.resv);
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_put_pages);
> @@ -262,9 +633,21 @@ EXPORT_SYMBOL(drm_gem_shmem_put_pages);
>    */
>   int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>   {
> +	int err;
> +
>   	WARN_ON(shmem->base.import_attach);
>   
> -	return drm_gem_shmem_get_pages(shmem);
> +	err = drm_gem_shmem_set_unpurgeable_and_unevictable(shmem);
> +	if (err)
> +		return err;
> +
> +	err = drm_gem_shmem_get_pages(shmem);
> +	if (err) {
> +		drm_gem_shmem_set_purgeable_and_evictable(shmem);
> +		return err;
> +	}
> +
> +	return 0;
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_pin);
>   
> @@ -280,6 +663,7 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
>   	WARN_ON(shmem->base.import_attach);
>   
>   	drm_gem_shmem_put_pages(shmem);
> +	drm_gem_shmem_set_purgeable_and_evictable(shmem);
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_unpin);
>   
> @@ -359,7 +743,18 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
>   	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
>   	if (ret)
>   		return ret;
> +
> +	ret = drm_gem_shmem_set_unpurgeable_and_unevictable_locked(shmem);
> +	if (ret)
> +		goto unlock;
> +
>   	ret = drm_gem_shmem_vmap_locked(shmem, map);
> +	if (ret)
> +		drm_gem_shmem_set_purgeable_and_evictable_locked(shmem);
> +	else
> +		drm_gem_shmem_update_pages_state_locked(shmem);
> +
> +unlock:
>   	dma_resv_unlock(shmem->base.resv);
>   
>   	return ret;
> @@ -404,9 +799,9 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
>   {
>   	dma_resv_lock(shmem->base.resv, NULL);
>   	drm_gem_shmem_vunmap_locked(shmem, map);
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +	drm_gem_shmem_set_purgeable_and_evictable_locked(shmem);
>   	dma_resv_unlock(shmem->base.resv);
> -
> -	drm_gem_shmem_update_purgeable_status(shmem);
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_vunmap);
>   
> @@ -447,29 +842,140 @@ int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
>   
>   	madv = shmem->madv;
>   
> +	drm_gem_shmem_update_pages_state_locked(shmem);
> +
>   	dma_resv_unlock(shmem->base.resv);
>   
>   	return (madv >= 0);
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_madvise);
>   
> -void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> +/**
> + * drm_gem_shmem_swap_in_pages_locked() - Moves shmem pages back to memory
> + * @shmem: shmem GEM object
> + *
> + * This function moves pages back to memory if they were previously evicted
> + * by the memory shrinker.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_swap_in_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct sg_table *sgt;
> +	int ret;
> +
> +	lockdep_assert_held(&obj->resv->lock.base);
> +
> +	if (shmem->evicted) {
> +		ret = drm_gem_shmem_acquire_pages_locked(shmem);
> +		if (ret)
> +			return ret;
> +
> +		sgt = drm_gem_shmem_get_sg_table(shmem);
> +		if (IS_ERR(sgt))
> +			return PTR_ERR(sgt);
> +
> +		ret = dma_map_sgtable(obj->dev->dev, sgt,
> +				      DMA_BIDIRECTIONAL, 0);
> +		if (ret) {
> +			sg_free_table(sgt);
> +			kfree(sgt);
> +			return ret;
> +		}
> +
> +		shmem->sgt = sgt;
> +		shmem->evicted = false;
> +		shmem->pages_state = DRM_GEM_SHMEM_PAGES_STATE_PINNED;
> +
> +		drm_gem_shmem_update_pages_state_locked(shmem);
> +	}
> +
> +	return shmem->pages ? 0 : -ENOMEM;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in_pages_locked);
> +
> +/**
> + * drm_gem_shmem_swap_in_locked() - Moves shmem GEM back to memory
> + * @shmem: shmem GEM object
> + *
> + * This function moves shmem GEM back to memory if it was previously evicted
> + * by the memory shrinker. The GEM is ready to use on success.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_swap_in_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	lockdep_assert_held(&obj->resv->lock.base);
> +
> +	if (shmem->evicted)
> +		return obj->funcs->swap_in(obj);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_swap_in_locked);
> +
> +static void drm_gem_shmem_unpin_pages_locked(struct drm_gem_shmem_object *shmem)
>   {
>   	struct drm_gem_object *obj = &shmem->base;
>   	struct drm_device *dev = obj->dev;
>   
> -	WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
> +	if (shmem->evicted)
> +		return;
>   
>   	dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
> +	drm_gem_shmem_release_pages_locked(shmem);
> +	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
> +
>   	sg_free_table(shmem->sgt);
>   	kfree(shmem->sgt);
>   	shmem->sgt = NULL;
> +}
>   
> -	drm_gem_shmem_put_pages_locked(shmem);
> +/**
> + * drm_gem_shmem_evict_locked - Evict shmem pages
> + * @shmem: shmem GEM object
> + *
> + * This function unpins shmem pages, allowing them to be swapped out from
> + * memory.
> + */
> +void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
>   
> -	shmem->madv = -1;
> +	lockdep_assert_held(&obj->resv->lock.base);
>   
> -	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
> +	WARN_ON(!drm_gem_shmem_is_evictable(shmem));
> +	WARN_ON(shmem->madv < 0);
> +	WARN_ON(shmem->evicted);
> +
> +	drm_gem_shmem_unpin_pages_locked(shmem);
> +
> +	shmem->evicted = true;
> +	drm_gem_shmem_set_pages_state(shmem, DRM_GEM_SHMEM_PAGES_STATE_EVICTED);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_evict_locked);
> +
> +/**
> + * drm_gem_shmem_purge_locked - Purge shmem pages
> + * @shmem: shmem GEM object
> + *
> + * This function permanently releases shmem pages.
> + */
> +void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	lockdep_assert_held(&obj->resv->lock.base);
> +
> +	WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
> +	WARN_ON(shmem->madv < 0);
> +
> +	drm_gem_shmem_unpin_pages_locked(shmem);
>   	drm_gem_free_mmap_offset(obj);
>   
>   	/* Our goal here is to return as much of the memory as
> @@ -480,6 +986,9 @@ void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
>   	shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
>   
>   	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
> +
> +	shmem->madv = -1;
> +	drm_gem_shmem_set_pages_state(shmem, DRM_GEM_SHMEM_PAGES_STATE_PURGED);
>   }
>   EXPORT_SYMBOL(drm_gem_shmem_purge_locked);
>   
> @@ -543,22 +1052,31 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
>   	vm_fault_t ret;
>   	struct page *page;
>   	pgoff_t page_offset;
> +	bool pages_inactive;
> +	int err;
>   
>   	/* We don't use vmf->pgoff since that has the fake offset */
>   	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
>   
>   	dma_resv_lock(shmem->base.resv, NULL);
>   
> -	if (page_offset >= num_pages ||
> -	    WARN_ON_ONCE(!shmem->pages) ||
> -	    shmem->madv < 0) {
> +	pages_inactive = shmem->pages_state < DRM_GEM_SHMEM_PAGES_STATE_PINNED;
> +	WARN_ON_ONCE(!shmem->pages ^ pages_inactive);
> +
> +	if (page_offset >= num_pages || (!shmem->pages && !shmem->evicted)) {
>   		ret = VM_FAULT_SIGBUS;
>   	} else {
> +		err = drm_gem_shmem_swap_in_locked(shmem);
> +		if (err) {
> +			ret = VM_FAULT_OOM;
> +			goto unlock;
> +		}
> +
>   		page = shmem->pages[page_offset];
>   
>   		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
>   	}
> -
> +unlock:
>   	dma_resv_unlock(shmem->base.resv);
>   
>   	return ret;
> @@ -568,13 +1086,8 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>   {
>   	struct drm_gem_object *obj = vma->vm_private_data;
>   	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> -	int ret;
> -
> -	WARN_ON(shmem->base.import_attach);
> -
> -	ret = drm_gem_shmem_get_pages(shmem);
> -	WARN_ON_ONCE(ret != 0);
>   
> +	drm_gem_shmem_get_pages_no_fail(shmem);
>   	drm_gem_vm_open(vma);
>   }
>   
> @@ -716,6 +1229,8 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)
>   
>   	shmem->sgt = sgt;
>   
> +	drm_gem_shmem_update_pages_state(shmem);
> +
>   	return sgt;
>   
>   err_free_sgt:
> @@ -762,6 +1277,202 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
>   }
>   EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
>   
> +static struct drm_gem_shmem_shrinker *
> +to_drm_shrinker(struct shrinker *shrinker)
> +{
> +	return container_of(shrinker, struct drm_gem_shmem_shrinker, base);
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_count_objects(struct shrinker *shrinker,
> +				     struct shrink_control *sc)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker = to_drm_shrinker(shrinker);
> +	u64 count = READ_ONCE(gem_shrinker->shrinkable_count);
> +
> +	if (count >= SHRINK_EMPTY)
> +		return SHRINK_EMPTY - 1;
> +
> +	return count ?: SHRINK_EMPTY;
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_run_objects_scan(struct shrinker *shrinker,
> +					unsigned long nr_to_scan,
> +					bool *lock_contention,
> +					bool evict)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker = to_drm_shrinker(shrinker);
> +	struct drm_gem_shmem_object *shmem;
> +	struct list_head still_in_list;
> +	struct drm_gem_object *obj;
> +	unsigned long freed = 0;
> +	struct list_head *lru;
> +	size_t page_count;
> +
> +	INIT_LIST_HEAD(&still_in_list);
> +
> +	mutex_lock(&gem_shrinker->lock);
> +
> +	if (evict)
> +		lru = &gem_shrinker->lru_evictable;
> +	else
> +		lru = &gem_shrinker->lru_purgeable;
> +
> +	while (freed < nr_to_scan) {
> +		shmem = list_first_entry_or_null(lru, typeof(*shmem), madv_list);
> +		if (!shmem)
> +			break;
> +
> +		obj = &shmem->base;
> +		page_count = obj->size >> PAGE_SHIFT;
> +		list_move_tail(&shmem->madv_list, &still_in_list);
> +
> +		if (evict && get_nr_swap_pages() < page_count)
> +			continue;
> +
> +		/*
> +		 * If it's in the process of being freed, gem_object->free()
> +		 * may be blocked on lock waiting to remove it.  So just
> +		 * skip it.
> +		 */
> +		if (!kref_get_unless_zero(&obj->refcount))
> +			continue;
> +
> +		mutex_unlock(&gem_shrinker->lock);
> +
> +		/* prevent racing with job-submission code paths */
> +		if (!dma_resv_trylock(obj->resv)) {
> +			*lock_contention |= true;
> +			goto shrinker_lock;
> +		}
> +
> +		/* prevent racing with the dma-buf exporting */
> +		if (!mutex_trylock(&gem_shrinker->dev->object_name_lock)) {
> +			*lock_contention |= true;
> +			goto resv_unlock;
> +		}
> +
> +		/* check whether h/w uses this object */
> +		if (!dma_resv_test_signaled(obj->resv, DMA_RESV_USAGE_WRITE))
> +			goto object_name_unlock;
> +
> +		/* GEM may've become unpurgeable while shrinker was unlocked */
> +		if (evict) {
> +			if (!drm_gem_shmem_is_evictable(shmem))
> +				goto object_name_unlock;
> +		} else {
> +			if (!drm_gem_shmem_is_purgeable(shmem))
> +				goto object_name_unlock;
> +		}
> +
> +		if (evict)
> +			freed += obj->funcs->evict(obj);
> +		else
> +			freed += obj->funcs->purge(obj);
> +object_name_unlock:
> +		mutex_unlock(&gem_shrinker->dev->object_name_lock);
> +resv_unlock:
> +		dma_resv_unlock(obj->resv);
> +shrinker_lock:
> +		drm_gem_object_put(&shmem->base);
> +		mutex_lock(&gem_shrinker->lock);
> +	}
> +
> +	list_splice_tail(&still_in_list, lru);
> +
> +	mutex_unlock(&gem_shrinker->lock);
> +
> +	return freed;
> +}
> +
> +static unsigned long
> +drm_gem_shmem_shrinker_scan_objects(struct shrinker *shrinker,
> +				    struct shrink_control *sc)
> +{
> +	unsigned long nr_to_scan = sc->nr_to_scan;
> +	bool lock_contention = false;
> +	unsigned long freed;
> +
> +	/* purge as many objects as we can */
> +	freed = drm_gem_shmem_shrinker_run_objects_scan(shrinker, nr_to_scan,
> +							&lock_contention, false);
> +	nr_to_scan -= freed;
> +
> +	/* evict as many objects as we can */
> +	if (freed < nr_to_scan)
> +		freed += drm_gem_shmem_shrinker_run_objects_scan(shrinker,
> +								 nr_to_scan,
> +								 &lock_contention,
> +								 true);
> +
> +	return (!freed && !lock_contention) ? SHRINK_STOP : freed;
> +}
> +
> +/**
> + * drm_gem_shmem_shrinker_register() - Register shmem shrinker
> + * @dev: DRM device
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_shrinker_register(struct drm_device *dev)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker;
> +	int err;
> +
> +	if (WARN_ON(dev->shmem_shrinker))
> +		return -EBUSY;
> +
> +	gem_shrinker = kzalloc(sizeof(*gem_shrinker), GFP_KERNEL);
> +	if (!gem_shrinker)
> +		return -ENOMEM;
> +
> +	gem_shrinker->base.count_objects = drm_gem_shmem_shrinker_count_objects;
> +	gem_shrinker->base.scan_objects = drm_gem_shmem_shrinker_scan_objects;
> +	gem_shrinker->base.seeks = DEFAULT_SEEKS;
> +	gem_shrinker->dev = dev;
> +
> +	INIT_LIST_HEAD(&gem_shrinker->lru_purgeable);
> +	INIT_LIST_HEAD(&gem_shrinker->lru_evictable);
> +	INIT_LIST_HEAD(&gem_shrinker->lru_evicted);
> +	INIT_LIST_HEAD(&gem_shrinker->lru_active);
> +	mutex_init(&gem_shrinker->lock);
> +
> +	dev->shmem_shrinker = gem_shrinker;
> +
> +	err = register_shrinker(&gem_shrinker->base);
> +	if (err) {
> +		dev->shmem_shrinker = NULL;
> +		kfree(gem_shrinker);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_shrinker_register);
> +
> +/**
> + * drm_gem_shmem_shrinker_unregister() - Unregister shmem shrinker
> + * @dev: DRM device
> + */
> +void drm_gem_shmem_shrinker_unregister(struct drm_device *dev)
> +{
> +	struct drm_gem_shmem_shrinker *gem_shrinker = dev->shmem_shrinker;
> +
> +	if (gem_shrinker) {
> +		unregister_shrinker(&gem_shrinker->base);
> +		WARN_ON(!list_empty(&gem_shrinker->lru_purgeable));
> +		WARN_ON(!list_empty(&gem_shrinker->lru_evictable));
> +		WARN_ON(!list_empty(&gem_shrinker->lru_evicted));
> +		WARN_ON(!list_empty(&gem_shrinker->lru_active));
> +		mutex_destroy(&gem_shrinker->lock);
> +		dev->shmem_shrinker = NULL;
> +		kfree(gem_shrinker);
> +	}
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_shrinker_unregister);
> +
>   MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
>   MODULE_IMPORT_NS(DMA_BUF);
>   MODULE_LICENSE("GPL v2");
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 9923c7a6885e..929546cad894 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -16,6 +16,7 @@ struct drm_vblank_crtc;
>   struct drm_vma_offset_manager;
>   struct drm_vram_mm;
>   struct drm_fb_helper;
> +struct drm_gem_shmem_shrinker;
>   
>   struct inode;
>   
> @@ -277,6 +278,9 @@ struct drm_device {
>   	/** @vram_mm: VRAM MM memory manager */
>   	struct drm_vram_mm *vram_mm;
>   
> +	/** @shmem_shrinker: SHMEM GEM memory shrinker */
> +	struct drm_gem_shmem_shrinker *shmem_shrinker;
> +
>   	/**
>   	 * @switch_power_state:
>   	 *
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 9d7c61a122dc..390d1ce08ed3 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -172,6 +172,41 @@ struct drm_gem_object_funcs {
>   	 * This is optional but necessary for mmap support.
>   	 */
>   	const struct vm_operations_struct *vm_ops;
> +
> +	/**
> +	 * @purge:
> +	 *
> +	 * Releases the GEM object's allocated backing storage to the system.
> +	 *
> +	 * Returns the number of pages that have been freed by purging the GEM object.
> +	 *
> +	 * This callback is used by the GEM shrinker.
> +	 */
> +	unsigned long (*purge)(struct drm_gem_object *obj);
> +
> +	/**
> +	 * @evict:
> +	 *
> +	 * Unpins the GEM object's allocated backing storage, allowing shmem pages
> +	 * to be swapped out.

What's the difference to the existing unpin() callback?

> +	 *
> +	 * Returns the number of pages that have been unpinned.
> +	 *
> +	 * This callback is used by the GEM shrinker.
> +	 */
> +	unsigned long (*evict)(struct drm_gem_object *obj);
> +
> +	/**
> +	 * @swap_in:
> +	 *
> +	 * Pins GEM object's allocated backing storage if it was previously evicted,
> +	 * moving swapped out pages back to memory.
> +	 *
> +	 * Returns 0 on success, or -errno on error.
> +	 *
> +	 * This callback is used by the GEM shrinker.
> +	 */
> +	int (*swap_in)(struct drm_gem_object *obj);

Why do you need swap_in()? This can be done on-demand as part of a pin 
or vmap operation.

>   };
>   
>   /**
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 70889533962a..a65557b446e6 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -6,6 +6,7 @@
>   #include <linux/fs.h>
>   #include <linux/mm.h>
>   #include <linux/mutex.h>
> +#include <linux/shrinker.h>
>   
>   #include <drm/drm_file.h>
>   #include <drm/drm_gem.h>
> @@ -15,8 +16,18 @@
>   struct dma_buf_attachment;
>   struct drm_mode_create_dumb;
>   struct drm_printer;
> +struct drm_device;
>   struct sg_table;
>   
> +enum drm_gem_shmem_pages_state {
> +	DRM_GEM_SHMEM_PAGES_STATE_PURGED = -2,
> +	DRM_GEM_SHMEM_PAGES_STATE_EVICTED = -1,
> +	DRM_GEM_SHMEM_PAGES_STATE_UNPINNED = 0,
> +	DRM_GEM_SHMEM_PAGES_STATE_PINNED = 1,
> +	DRM_GEM_SHMEM_PAGES_STATE_EVICTABLE = 2,
> +	DRM_GEM_SHMEM_PAGES_STATE_PURGEABLE = 3,
> +};

These states can be detected by looking at the vmap and pin refcounts. 
No need to store them explicitly. In your patch, they also come with a 
big zoo of trivial helpers. None of that seems necessary AFAICT.

What's the difference between purge and evict BTW?

> +
>   /**
>    * struct drm_gem_shmem_object - GEM object backed by shmem
>    */
> @@ -43,8 +54,8 @@ struct drm_gem_shmem_object {
>   	 * @madv: State for madvise
>   	 *
>   	 * 0 is active/inuse.
> +	 * 1 is not-needed/can-be-purged
>   	 * A negative value is the object is purged.
> -	 * Positive values are driver specific and not used by the helpers.
>   	 */
>   	int madv;
>   
> @@ -91,6 +102,40 @@ struct drm_gem_shmem_object {
>   	 * @map_wc: map object write-combined (instead of using shmem defaults).
>   	 */
>   	bool map_wc;
> +
> +	/**
> +	 * @eviction_disable_count:
> +	 *
> +	 * The shmem pages are disallowed to be evicted by the memory shrinker
> +	 * while count is non-zero. Used internally by memory shrinker.
> +	 */
> +	unsigned int eviction_disable_count;
> +
> +	/**
> +	 * @purging_disable_count:
> +	 *
> +	 * The shmem pages are disallowed to be purged by the memory shrinker
> +	 * while count is non-zero. Used internally by memory shrinker.
> +	 */
> +	unsigned int purging_disable_count;
> +
> +	/**
> +	 * @pages_state: Current state of shmem pages. Used internally by
> +	 * memory shrinker.
> +	 */
> +	enum drm_gem_shmem_pages_state pages_state;
> +
> +	/**
> +	 * @evicted: True if shmem pages were evicted by the memory shrinker.
> +	 * Used internally by memory shrinker.
> +	 */
> +	bool evicted;
> +
> +	/**
> +	 * @pages_shrinkable: True if shmem pages can be evicted or purged
> +	 * by the memory shrinker. Used internally by memory shrinker.
> +	 */
> +	bool pages_shrinkable;

As commented before, this state can be foundby looking at existing 
fields. No need to store it separately.

Best regards
Thomas

>   };
>   
>   #define to_drm_gem_shmem_obj(obj) \
> @@ -111,15 +156,33 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
>   
>   int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv);
>   
> +int drm_gem_shmem_set_purgeable(struct drm_gem_shmem_object *shmem);
> +int drm_gem_shmem_set_purgeable_and_evictable(struct drm_gem_shmem_object *shmem);
> +int drm_gem_shmem_set_unpurgeable_and_unevictable(struct drm_gem_shmem_object *shmem);
> +
> +static inline bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
> +{
> +	return (shmem->madv >= 0) && !shmem->eviction_disable_count &&
> +		shmem->base.funcs->evict && shmem->base.funcs->swap_in &&
> +		!shmem->vmap_use_count && !shmem->base.dma_buf &&
> +		!shmem->base.import_attach && shmem->sgt;
> +}
> +
>   static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
>   {
> -	return (shmem->madv > 0) &&
> -		!shmem->vmap_use_count && shmem->sgt &&
> -		!shmem->base.dma_buf && !shmem->base.import_attach;
> +	return (shmem->madv > 0) && !shmem->purging_disable_count &&
> +		!shmem->vmap_use_count && shmem->base.funcs->purge &&
> +		!shmem->base.dma_buf && !shmem->base.import_attach &&
> +		shmem->sgt;
>   }
>   
> -void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
> +int drm_gem_shmem_swap_in_pages_locked(struct drm_gem_shmem_object *shmem);
> +int drm_gem_shmem_swap_in_locked(struct drm_gem_shmem_object *shmem);
> +
> +void drm_gem_shmem_evict_locked(struct drm_gem_shmem_object *shmem);
> +
>   bool drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
> +void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
>   
>   struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
>   struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem);
> @@ -262,6 +325,38 @@ static inline int drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct v
>   	return drm_gem_shmem_mmap(shmem, vma);
>   }
>   
> +/**
> + * struct drm_gem_shmem_shrinker - Generic memory shrinker for shmem GEMs
> + */
> +struct drm_gem_shmem_shrinker {
> +	/** @base: Shrinker for purging shmem GEM objects */
> +	struct shrinker base;
> +
> +	/** @lock: Protects @lru_* */
> +	struct mutex lock;
> +
> +	/** @lru_purgeable: List of shmem GEM objects available for purging */
> +	struct list_head lru_purgeable;
> +
> +	/** @lru_active: List of active shmem GEM objects */
> +	struct list_head lru_active;
> +
> +	/** @lru_evictable: List of shmem GEM objects that can be evicted */
> +	struct list_head lru_evictable;
> +
> +	/** @lru_evicted: List of evicted shmem GEM objects */
> +	struct list_head lru_evicted;
> +
> +	/** @dev: DRM device that uses this shrinker */
> +	struct drm_device *dev;
> +
> +	/** @shrinkable_count: Count of shmem GEM pages to be purged and evicted */
> +	u64 shrinkable_count;
> +};
> +
> +int drm_gem_shmem_shrinker_register(struct drm_device *dev);
> +void drm_gem_shmem_shrinker_unregister(struct drm_device *dev);
> +
>   /*
>    * Driver ops
>    */

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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