Re: [PATCH v3 1/1] vfio/type1: Add vfio_group_domain()

[Alex Williamson]

On Tue,  1 Dec 2020 09:23:28 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:

> Add the API for getting the domain from a vfio group. This could be used
> by the physical device drivers which rely on the vfio/mdev framework for
> mediated device user level access. The typical use case like below:
> 
> 	unsigned int pasid;
> 	struct vfio_group *vfio_group;
> 	struct iommu_domain *iommu_domain;
> 	struct device *dev = mdev_dev(mdev);
> 	struct device *iommu_device = mdev_get_iommu_device(dev);
> 
> 	if (!iommu_device ||
> 	    !iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
> 		return -EINVAL;
> 
> 	vfio_group = vfio_group_get_external_user_from_dev(dev);
> 	if (IS_ERR_OR_NULL(vfio_group))
> 		return -EFAULT;
> 
> 	iommu_domain = vfio_group_domain(vfio_group);
> 	if (IS_ERR_OR_NULL(iommu_domain)) {
> 		vfio_group_put_external_user(vfio_group);
> 		return -EFAULT;
> 	}
> 
> 	pasid = iommu_aux_get_pasid(iommu_domain, iommu_device);
> 	if (pasid < 0) {
> 		vfio_group_put_external_user(vfio_group);
> 		return -EFAULT;
> 	}
> 
> 	/* Program device context with pasid value. */
> 	...
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> ---
>  drivers/vfio/vfio.c             | 18 ++++++++++++++++++
>  drivers/vfio/vfio_iommu_type1.c | 23 +++++++++++++++++++++++
>  include/linux/vfio.h            |  3 +++
>  3 files changed, 44 insertions(+)
> 
> Change log:
>  - v2: https://lore.kernel.org/linux-iommu/20201126012726.1185171-1-baolu.lu@xxxxxxxxxxxxxxx/
>  - Changed according to comments @ https://lore.kernel.org/linux-iommu/20201130135725.70fdf17f@xxxxxxxxx/
>  - Fix a typo https://lore.kernel.org/linux-iommu/DM5PR11MB143560E51C84BAF83AE54AC0C3F90@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 2151bc7f87ab..588e8026d94b 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -2331,6 +2331,24 @@ int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
>  }
>  EXPORT_SYMBOL(vfio_unregister_notifier);
>  
> +struct iommu_domain *vfio_group_domain(struct vfio_group *group)

Could we make this vfio_group_iommu_domain()?  We're making a callback
specific to a vfio IOMMU backend participating in the IOMMU API, so we
might as well make this callback explicitly tied to it.

> +{
> +	struct vfio_container *container;
> +	struct vfio_iommu_driver *driver;
> +
> +	if (!group)
> +		return ERR_PTR(-EINVAL);
> +
> +	container = group->container;
> +	driver = container->iommu_driver;
> +	if (likely(driver && driver->ops->group_domain))
> +		return driver->ops->group_domain(container->iommu_data,
> +						 group->iommu_group);

Likewise group_iommu_domain()?


> +	else
> +		return ERR_PTR(-ENOTTY);

Nit, we don't need 'else' here, the first branch always returns.

Otherwise I think it looks good.  Thanks,

Alex

> +}
> +EXPORT_SYMBOL_GPL(vfio_group_domain);
> +
>  /**
>   * Module/class support
>   */
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 67e827638995..d7b5acb3056a 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2980,6 +2980,28 @@ static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t user_iova,
>  	return ret;
>  }
>  
> +static struct iommu_domain *
> +vfio_iommu_type1_group_domain(void *iommu_data, struct iommu_group *iommu_group)
> +{
> +	struct iommu_domain *domain = ERR_PTR(-ENODEV);
> +	struct vfio_iommu *iommu = iommu_data;
> +	struct vfio_domain *d;
> +
> +	if (!iommu || !iommu_group)
> +		return ERR_PTR(-EINVAL);
> +
> +	mutex_lock(&iommu->lock);
> +	list_for_each_entry(d, &iommu->domain_list, next) {
> +		if (find_iommu_group(d, iommu_group)) {
> +			domain = d->domain;
> +			break;
> +		}
> +	}
> +	mutex_unlock(&iommu->lock);
> +
> +	return domain;
> +}
> +
>  static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
>  	.name			= "vfio-iommu-type1",
>  	.owner			= THIS_MODULE,
> @@ -2993,6 +3015,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
>  	.register_notifier	= vfio_iommu_type1_register_notifier,
>  	.unregister_notifier	= vfio_iommu_type1_unregister_notifier,
>  	.dma_rw			= vfio_iommu_type1_dma_rw,
> +	.group_domain		= vfio_iommu_type1_group_domain,
>  };
>  
>  static int __init vfio_iommu_type1_init(void)
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 38d3c6a8dc7e..6cd0de2764cb 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -90,6 +90,7 @@ struct vfio_iommu_driver_ops {
>  					       struct notifier_block *nb);
>  	int		(*dma_rw)(void *iommu_data, dma_addr_t user_iova,
>  				  void *data, size_t count, bool write);
> +	struct iommu_domain *(*group_domain)(void *iommu_data, struct iommu_group *group);
>  };
>  
>  extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
> @@ -126,6 +127,8 @@ extern int vfio_group_unpin_pages(struct vfio_group *group,
>  extern int vfio_dma_rw(struct vfio_group *group, dma_addr_t user_iova,
>  		       void *data, size_t len, bool write);
>  
> +extern struct iommu_domain *vfio_group_domain(struct vfio_group *group);
> +
>  /* each type has independent events */
>  enum vfio_notify_type {
>  	VFIO_IOMMU_NOTIFY = 0,