Re: [PATCH 1/1] vfio/type1: Add subdev_ioasid callback to vfio_iommu_driver_ops

[Alex Williamson]

On Thu, 12 Nov 2020 10:24:07 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:

> Add API for getting the ioasid of a subdevice (vfio/mdev). This calls
> into the backend IOMMU module to get the actual value or error number
> if ioasid for subdevice is not supported. The physical device driver
> implementations which rely on the vfio/mdev framework for mediated
> device user level access could typically consume this interface like
> below:
> 
> 	struct device *dev = mdev_dev(mdev);
> 	unsigned int pasid;
> 	int ret;
> 
> 	ret = vfio_subdev_ioasid(dev, &pasid);
> 	if (ret < 0)
> 		return ret;
> 
>          /* Program device context with pasid value. */
>          ....


Seems like an overly specific callback.  We already export means for
you to get a vfio_group, test that a device is an mdev, and get the
iommu device from an mdev.  So you can already test whether a given
device is an mdev with an iommu backing device that supports aux
domains.  The only missing piece seems to be that you can't get the
domain for a group in order to retrieve the pasid.  So why aren't we
exporting a callback that given a vfio_group provides the iommu domain?
Thanks,

Alex

> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> ---
>  drivers/vfio/vfio.c             | 34 ++++++++++++++++++++
>  drivers/vfio/vfio_iommu_type1.c | 57 +++++++++++++++++++++++++++++++++
>  include/linux/vfio.h            |  4 +++
>  3 files changed, 95 insertions(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 2151bc7f87ab..4931e1492921 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -2331,6 +2331,40 @@ int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
>  }
>  EXPORT_SYMBOL(vfio_unregister_notifier);
>  
> +int vfio_subdev_ioasid(struct device *dev, unsigned int *id)
> +{
> +	struct vfio_container *container;
> +	struct vfio_iommu_driver *driver;
> +	struct vfio_group *group;
> +	int ret;
> +
> +	if (!dev || !id)
> +		return -EINVAL;
> +
> +	group = vfio_group_get_from_dev(dev);
> +	if (!group)
> +		return -ENODEV;
> +
> +	ret = vfio_group_add_container_user(group);
> +	if (ret)
> +		goto out;
> +
> +	container = group->container;
> +	driver = container->iommu_driver;
> +	if (likely(driver && driver->ops->subdev_ioasid))
> +		ret = driver->ops->subdev_ioasid(container->iommu_data,
> +						 group->iommu_group, id);
> +	else
> +		ret = -ENOTTY;
> +
> +	vfio_group_try_dissolve_container(group);
> +
> +out:
> +	vfio_group_put(group);
> +	return ret;
> +}
> +EXPORT_SYMBOL(vfio_subdev_ioasid);
> +
>  /**
>   * Module/class support
>   */
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 67e827638995..f94cc7707d7e 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2980,6 +2980,62 @@ static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t user_iova,
>  	return ret;
>  }
>  
> +static int vfio_iommu_type1_subdev_ioasid(void *iommu_data,
> +					  struct iommu_group *iommu_group,
> +					  unsigned int *id)
> +{
> +	struct vfio_iommu *iommu = iommu_data;
> +	struct vfio_domain *domain = NULL, *d;
> +	struct device *iommu_device = NULL;
> +	struct bus_type *bus = NULL;
> +	int ret;
> +
> +	if (!iommu || !iommu_group || !id)
> +		return -EINVAL;
> +
> +	mutex_lock(&iommu->lock);
> +	ret = iommu_group_for_each_dev(iommu_group, &bus, vfio_bus_type);
> +	if (ret)
> +		goto out;
> +
> +	if (!vfio_bus_is_mdev(bus)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = iommu_group_for_each_dev(iommu_group, &iommu_device,
> +				       vfio_mdev_iommu_device);
> +	if (ret || !iommu_device ||
> +	    !iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX)) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	list_for_each_entry(d, &iommu->domain_list, next) {
> +		if (find_iommu_group(d, iommu_group)) {
> +			domain = d;
> +			break;
> +		}
> +	}
> +
> +	if (!domain) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	ret = iommu_aux_get_pasid(domain->domain, iommu_device);
> +	if (ret > 0) {
> +		*id = ret;
> +		ret = 0;
> +	} else {
> +		ret = -ENOSPC;
> +	}
> +
> +out:
> +	mutex_unlock(&iommu->lock);
> +	return ret;
> +}
> +
>  static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
>  	.name			= "vfio-iommu-type1",
>  	.owner			= THIS_MODULE,
> @@ -2993,6 +3049,7 @@ 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,
> +	.subdev_ioasid		= vfio_iommu_type1_subdev_ioasid,
>  };
>  
>  static int __init vfio_iommu_type1_init(void)
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 38d3c6a8dc7e..6dcf09a2796d 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -90,6 +90,9 @@ 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);
> +	int		(*subdev_ioasid)(void *iommu_data,
> +					 struct iommu_group *group,
> +					 unsigned int *id);
>  };
>  
>  extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
> @@ -125,6 +128,7 @@ 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 int vfio_subdev_ioasid(struct device *dev, unsigned int *id);
>  
>  /* each type has independent events */
>  enum vfio_notify_type {