Re: [PATCH 08/22] iommu: Make sure a device is always attached to a domain

[Robin Murphy <robin.murphy@arm.com>]

On 28/05/15 17:41, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> Make use of the default domain and re-attach a device to it
> when it is detached from another domain. Also enforce that a
> device has to be in the default domain before it can be
> attached to a different domain.
>
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
>   drivers/iommu/iommu.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++-----
>   1 file changed, 75 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index adeedd2..7bce522 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -52,6 +52,7 @@ struct iommu_group {
>   	char *name;
>   	int id;
>   	struct iommu_domain *default_domain;
> +	struct iommu_domain *domain;
>   };
>
>   struct iommu_device {
> @@ -78,6 +79,12 @@ struct iommu_group_attribute iommu_group_attr_##_name =		\
>
>   static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
>   						 unsigned type);
> +static int __iommu_attach_device(struct iommu_domain *domain,
> +				 struct device *dev);
> +static int __iommu_attach_group(struct iommu_domain *domain,
> +				struct iommu_group *group);
> +static void __iommu_detach_group(struct iommu_domain *domain,
> +				 struct iommu_group *group);
>
>   static ssize_t iommu_group_attr_show(struct kobject *kobj,
>   				     struct attribute *__attr, char *buf)
> @@ -376,6 +383,8 @@ rename:
>
>   	mutex_lock(&group->mutex);
>   	list_add_tail(&device->list, &group->devices);
> +	if (group->domain)
> +		__iommu_attach_device(group->domain, dev);
>   	mutex_unlock(&group->mutex);
>
>   	/* Notify any listeners about change to group. */
> @@ -455,19 +464,30 @@ static int iommu_group_device_count(struct iommu_group *group)
>    * The group->mutex is held across callbacks, which will block calls to
>    * iommu_group_add/remove_device.
>    */
> -int iommu_group_for_each_dev(struct iommu_group *group, void *data,
> -			     int (*fn)(struct device *, void *))
> +static int __iommu_group_for_each_dev(struct iommu_group *group, void *data,
> +				      int (*fn)(struct device *, void *))
>   {
>   	struct iommu_device *device;
>   	int ret = 0;
>
> -	mutex_lock(&group->mutex);
>   	list_for_each_entry(device, &group->devices, list) {

Maybe worth using list_for_each_entry_safe so we can reuse this for 
things like group teardown?

>   		ret = fn(device->dev, data);
>   		if (ret)
>   			break;
>   	}
> +	return ret;
> +}
> +
> +
> +int iommu_group_for_each_dev(struct iommu_group *group, void *data,
> +			     int (*fn)(struct device *, void *))
> +{
> +	int ret;
> +
> +	mutex_lock(&group->mutex);
> +	ret = __iommu_group_for_each_dev(group, data, fn);
>   	mutex_unlock(&group->mutex);
> +
>   	return ret;
>   }
>   EXPORT_SYMBOL_GPL(iommu_group_for_each_dev);
> @@ -1013,7 +1033,7 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
>   	if (iommu_group_device_count(group) != 1)
>   		goto out_unlock;
>
> -	ret = __iommu_attach_device(domain, dev);
> +	ret = __iommu_attach_group(domain, group);
>
>   out_unlock:
>   	mutex_unlock(&group->mutex);
> @@ -1048,7 +1068,7 @@ void iommu_detach_device(struct iommu_domain *domain, struct device *dev)
>   		goto out_unlock;
>   	}
>
> -	__iommu_detach_device(domain, dev);
> +	__iommu_detach_group(domain, group);
>
>   out_unlock:
>   	mutex_unlock(&group->mutex);
> @@ -1073,10 +1093,31 @@ static int iommu_group_do_attach_device(struct device *dev, void *data)
>   	return __iommu_attach_device(domain, dev);
>   }
>
> +static int __iommu_attach_group(struct iommu_domain *domain,
> +				struct iommu_group *group)
> +{
> +	int ret;
> +
> +	if (group->default_domain && group->domain != group->default_domain)
> +		return -EBUSY;
> +
> +	ret = __iommu_group_for_each_dev(group, domain,
> +					 iommu_group_do_attach_device);
> +	if (ret == 0)
> +		group->domain = domain;
> +
> +	return ret;
> +}
> +
>   int iommu_attach_group(struct iommu_domain *domain, struct iommu_group *group)
>   {
> -	return iommu_group_for_each_dev(group, domain,
> -					iommu_group_do_attach_device);
> +	int ret;
> +
> +	mutex_lock(&group->mutex);
> +	ret = __iommu_attach_group(domain, group);
> +	mutex_unlock(&group->mutex);
> +
> +	return ret;
>   }
>   EXPORT_SYMBOL_GPL(iommu_attach_group);
>
> @@ -1089,9 +1130,35 @@ static int iommu_group_do_detach_device(struct device *dev, void *data)
>   	return 0;
>   }
>
> +static void __iommu_detach_group(struct iommu_domain *domain,
> +				 struct iommu_group *group)
> +{
> +	int ret;
> +
> +	if (!group->default_domain) {
> +		__iommu_group_for_each_dev(group, domain,
> +					   iommu_group_do_detach_device);
> +		group->domain = NULL;
> +		return;
> +	}
> +
> +	if (group->domain == group->default_domain)
> +		return;
> +
> +	/* Detach by re-attaching to the default domain */
> +	ret = __iommu_group_for_each_dev(group, group->default_domain,
> +					 iommu_group_do_attach_device);
> +	if (ret != 0)
> +		WARN_ON(1);
> +	else

	if (!(WARN_ON(ret)) ?

Robin.

> +		group->domain = group->default_domain;
> +}
> +
>   void iommu_detach_group(struct iommu_domain *domain, struct iommu_group *group)
>   {
> -	iommu_group_for_each_dev(group, domain, iommu_group_do_detach_device);
> +	mutex_lock(&group->mutex);
> +	__iommu_detach_group(domain, group);
> +	mutex_unlock(&group->mutex);
>   }
>   EXPORT_SYMBOL_GPL(iommu_detach_group);
>
>