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Date:   Thu, 26 Nov 2020 07:21:50 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>
CC:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        "Robin Murphy" <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Zeng, Xin" <xin.zeng@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: RE: [PATCH v2 1/1] vfio/type1: Add vfio_group_domain()

On Thurs, Nov 26, 2020, at 9:27 AM, Lu Baolu 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);(dev);

duplicate (dev); 😊other parts looks good to me. perhaps, you can also
describe that the release function of a sub-device fd should also call
vfio_group_put_external_user() to release its reference on the vfio_group.

Regards,
Yi Liu 

> 	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@...ux.intel.com>
> ---
>  drivers/vfio/vfio.c             | 18 ++++++++++++++++++
>  drivers/vfio/vfio_iommu_type1.c | 23 +++++++++++++++++++++++
>  include/linux/vfio.h            |  3 +++
>  3 files changed, 44 insertions(+)
> 
> Change log:
>  - v1: https://lore.kernel.org/linux-iommu/20201112022407.2063896-1-baolu.lu@linux.intel.com/
>  - Changed according to comments @ https://lore.kernel.org/linux-iommu/20201116125631.2d043fcd@w520.home/
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 2151bc7f87ab..62c652111c88 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)
> +{
> +	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);
> +	else
> +		return ERR_PTR(-ENOTTY);
> +}
> +EXPORT_SYMBOL(vfio_group_domain);
> +
>  /**
>   * Module/class support
>   */
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 67e827638995..783f18f21b95 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 void *vfio_iommu_type1_group_domain(void *iommu_data,
> +					   struct iommu_group *iommu_group)
> +{
> +	struct vfio_iommu *iommu = iommu_data;
> +	struct iommu_domain *domain = NULL;
> +	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..a0613a6f21cc 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);
> +	void		*(*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,
> --
> 2.25.1

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