Re: [RFC PATCH 33/34] iommu: Remove add_device()/remove_device() code-paths

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Joerg

On 07.04.2020 20:37, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> All drivers are converted to use the probe/release_device()
> call-backs, so the add_device/remove_device() pointers are unused and
> the code using them can be removed.
>
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
>   drivers/iommu/iommu.c | 145 ++++++++----------------------------------
>   include/linux/iommu.h |   4 --
>   2 files changed, 27 insertions(+), 122 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index cf25c1e48830..d9032f9d597c 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -220,7 +220,7 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
>   	return ret;
>   }
>   
> -static int __iommu_probe_device_helper(struct device *dev)
> +int iommu_probe_device(struct device *dev)
>   {
>   	const struct iommu_ops *ops = dev->bus->iommu_ops;
>   	struct iommu_group *group;
> @@ -264,70 +264,17 @@ static int __iommu_probe_device_helper(struct device *dev)
>   
>   }
>   
> -int iommu_probe_device(struct device *dev)
> +void iommu_release_device(struct device *dev)
>   {
>   	const struct iommu_ops *ops = dev->bus->iommu_ops;
> -	struct iommu_group *group;
> -	int ret;
> -
> -	WARN_ON(dev->iommu_group);
> -
> -	if (!ops)
> -		return -EINVAL;
> -
> -	if (!dev_iommu_get(dev))
> -		return -ENOMEM;
> -
> -	if (!try_module_get(ops->owner)) {
> -		ret = -EINVAL;
> -		goto err_free_dev_param;
> -	}
> -
> -	if (ops->probe_device)
> -		return __iommu_probe_device_helper(dev);
> -
> -	ret = ops->add_device(dev);
> -	if (ret)
> -		goto err_module_put;
>   
> -	group = iommu_group_get(dev);
> -	iommu_create_device_direct_mappings(group, dev);
> -	iommu_group_put(group);
> -
> -	if (ops->probe_finalize)
> -		ops->probe_finalize(dev);
> -
> -	return 0;
> -
> -err_module_put:
> -	module_put(ops->owner);
> -err_free_dev_param:
> -	dev_iommu_free(dev);
> -	return ret;
> -}
> -
> -static void __iommu_release_device(struct device *dev)
> -{
> -	const struct iommu_ops *ops = dev->bus->iommu_ops;
> +	if (!dev->iommu)
> +		return;
>   
>   	iommu_device_unlink(dev->iommu->iommu_dev, dev);
> -
>   	iommu_group_remove_device(dev);
>   
>   	ops->release_device(dev);
> -}
> -
> -void iommu_release_device(struct device *dev)
> -{
> -	const struct iommu_ops *ops = dev->bus->iommu_ops;
> -
> -	if (!dev->iommu)
> -		return;
> -
> -	if (ops->release_device)
> -		__iommu_release_device(dev);
> -	else if (dev->iommu_group)
> -		ops->remove_device(dev);
>   
>   	module_put(ops->owner);
>   	dev_iommu_free(dev);
> @@ -1560,23 +1507,6 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev)
>   	if (ret)
>   		goto out_put_group;
>   
> -	/*
> -	 * Try to allocate a default domain - needs support from the
> -	 * IOMMU driver. There are still some drivers which don't support
> -	 * default domains, so the return value is not yet checked. Only
> -	 * allocate the domain here when the driver still has the
> -	 * add_device/remove_device call-backs implemented.
> -	 */
> -	if (!ops->probe_device) {
> -		iommu_alloc_default_domain(dev);
> -
> -		if (group->default_domain)
> -			ret = __iommu_attach_device(group->default_domain, dev);
> -
> -		if (ret)
> -			goto out_put_group;
> -	}
> -
>   	return group;
>   
>   out_put_group:
> @@ -1591,21 +1521,6 @@ struct iommu_domain *iommu_group_default_domain(struct iommu_group *group)
>   	return group->default_domain;
>   }
>   
> -static int add_iommu_group(struct device *dev, void *data)
> -{
> -	int ret = iommu_probe_device(dev);
> -
> -	/*
> -	 * We ignore -ENODEV errors for now, as they just mean that the
> -	 * device is not translated by an IOMMU. We still care about
> -	 * other errors and fail to initialize when they happen.
> -	 */
> -	if (ret == -ENODEV)
> -		ret = 0;
> -
> -	return ret;
> -}
> -
>   static int probe_iommu_group(struct device *dev, void *data)
>   {
>   	const struct iommu_ops *ops = dev->bus->iommu_ops;
> @@ -1789,45 +1704,39 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group)
>   
>   int bus_iommu_probe(struct bus_type *bus)
>   {
> -	const struct iommu_ops *ops = bus->iommu_ops;
> +	struct iommu_group *group, *next;
> +	LIST_HEAD(group_list);
>   	int ret;
>   
> -	if (ops->probe_device) {
> -		struct iommu_group *group, *next;
> -		LIST_HEAD(group_list);
> -
> -		/*
> -		 * This code-path does not allocate the default domain when
> -		 * creating the iommu group, so do it after the groups are
> -		 * created.
> -		 */
> -		ret = bus_for_each_dev(bus, NULL, &group_list, probe_iommu_group);
> -		if (ret)
> -			return ret;
> +	/*
> +	 * This code-path does not allocate the default domain when
> +	 * creating the iommu group, so do it after the groups are
> +	 * created.
> +	 */
> +	ret = bus_for_each_dev(bus, NULL, &group_list, probe_iommu_group);
> +	if (ret)
> +		return ret;
>   
> -		list_for_each_entry_safe(group, next, &group_list, entry) {
> -			/* Remove item from the list */
> -			list_del_init(&group->entry);
> +	list_for_each_entry_safe(group, next, &group_list, entry) {
> +		/* Remove item from the list */
> +		list_del_init(&group->entry);
>   
> -			mutex_lock(&group->mutex);
> +		mutex_lock(&group->mutex);
>   
> -			/* Try to allocate default domain */
> -			probe_alloc_default_domain(bus, group);
> +		/* Try to allocate default domain */
> +		probe_alloc_default_domain(bus, group);
>   
> -			if (!group->default_domain)
> -				continue;
> +		if (!group->default_domain)
> +			continue;

It doesn't look straight from the above diff, but this continue leaks 
group->lock taken.

>   
> -			iommu_group_create_direct_mappings(group);
> +		iommu_group_create_direct_mappings(group);
>   
> -			ret = __iommu_group_dma_attach(group);
> +		ret = __iommu_group_dma_attach(group);
>   
> -			mutex_unlock(&group->mutex);
> +		mutex_unlock(&group->mutex);
>   
> -			if (ret)
> -				break;
> -		}
> -	} else {
> -		ret = bus_for_each_dev(bus, NULL, NULL, add_iommu_group);
> +		if (ret)
> +			break;
>   	}
>   
>   	return ret;
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index fea1622408ad..dd076366383f 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -223,8 +223,6 @@ struct iommu_iotlb_gather {
>    * @iotlb_sync: Flush all queued ranges from the hardware TLBs and empty flush
>    *            queue
>    * @iova_to_phys: translate iova to physical address
> - * @add_device: add device to iommu grouping
> - * @remove_device: remove device from iommu grouping
>    * @probe_device: Add device to iommu driver handling
>    * @release_device: Remove device from iommu driver handling
>    * @probe_finalize: Do final setup work after the device is added to an IOMMU
> @@ -277,8 +275,6 @@ struct iommu_ops {
>   	void (*iotlb_sync)(struct iommu_domain *domain,
>   			   struct iommu_iotlb_gather *iotlb_gather);
>   	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain, dma_addr_t iova);
> -	int (*add_device)(struct device *dev);
> -	void (*remove_device)(struct device *dev);
>   	struct iommu_device *(*probe_device)(struct device *dev);
>   	void (*release_device)(struct device *dev);
>   	void (*probe_finalize)(struct device *dev);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland