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Date:   Thu, 26 Nov 2020 16:50:13 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     baolu.lu@...ux.intel.com, 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()

Hi Yi,

On 2020/11/26 15:21, Liu, Yi L wrote:
> 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

Will fix this typo. Thanks!

> 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.

This is just a sample code. The callers are free to decide when to get
and release the vfio_group.

> 
> Regards,
> Yi Liu

Best regards,
baolu

> 
>> 	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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