Re: [PATCH v2 1/1] vfio/type1: Add vfio_group_domain()

[Lu Baolu]

Hi Alex,

Thanks a lot for your review comments.

On 12/1/20 4:57 AM, Alex Williamson wrote:
> On Thu, 26 Nov 2020 09:27:26 +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);(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:
> >   - v1: https://lore.kernel.org/linux-iommu/20201112022407.2063896-1-baolu.lu@xxxxxxxxxxxxxxx/
> >   - Changed according to comments @ https://lore.kernel.org/linux-iommu/20201116125631.2d043fcd@xxxxxxxxx/
> >
> > 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);
>
>
> _GPL?  I don't see that there's a way for a driver to get the
> vfio_group pointer that's not already _GPL.

It should be _GPL. Will fix it.

> > +
> >   /**
> >    * 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;
> > +}
>
>
> Why does this return void* rather than struct iommu_domain*, and why
> does the error case return an ERR_PTR but the not-found case returns
> NULL?

I will change it to return iommu_domain* and return an error number for
the not-found case.

Best regards,
baolu

>  Thanks,
>
> Alex
>
>
> > +
> >   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,