Re: [PATCH v3 4/4] vfio/type1: Use iommu_aux_at(de)tach_group() APIs

From: Alex Williamson <alex.williamson@redhat.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Kevin Tian <kevin.tian@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	kvm@vger.kernel.org, Cornelia Huck <cohuck@redhat.com>,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v3 4/4] vfio/type1: Use iommu_aux_at(de)tach_group() APIs
Date: Wed, 29 Jul 2020 14:32:58 -0600
Message-ID: <20200729143258.22533170@x1.home> (raw)
In-Reply-To: <20200714055703.5510-5-baolu.lu@linux.intel.com>

On Tue, 14 Jul 2020 13:57:03 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:

> Replace iommu_aux_at(de)tach_device() with iommu_aux_at(de)tach_group().
> It also saves the IOMMU_DEV_FEAT_AUX-capable physcail device in the
> vfio_group data structure so that it could be reused in other places.
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 44 ++++++---------------------------
>  1 file changed, 7 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 5e556ac9102a..f8812e68de77 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -100,6 +100,7 @@ struct vfio_dma {
>  struct vfio_group {
>  	struct iommu_group	*iommu_group;
>  	struct list_head	next;
> +	struct device		*iommu_device;
>  	bool			mdev_group;	/* An mdev group */
>  	bool			pinned_page_dirty_scope;
>  };
> @@ -1627,45 +1628,13 @@ static struct device *vfio_mdev_get_iommu_device(struct device *dev)
>  	return NULL;
>  }
>  
> -static int vfio_mdev_attach_domain(struct device *dev, void *data)
> -{
> -	struct iommu_domain *domain = data;
> -	struct device *iommu_device;
> -
> -	iommu_device = vfio_mdev_get_iommu_device(dev);
> -	if (iommu_device) {
> -		if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
> -			return iommu_aux_attach_device(domain, iommu_device);
> -		else
> -			return iommu_attach_device(domain, iommu_device);
> -	}
> -
> -	return -EINVAL;
> -}
> -
> -static int vfio_mdev_detach_domain(struct device *dev, void *data)
> -{
> -	struct iommu_domain *domain = data;
> -	struct device *iommu_device;
> -
> -	iommu_device = vfio_mdev_get_iommu_device(dev);
> -	if (iommu_device) {
> -		if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
> -			iommu_aux_detach_device(domain, iommu_device);
> -		else
> -			iommu_detach_device(domain, iommu_device);
> -	}
> -
> -	return 0;
> -}
> -
>  static int vfio_iommu_attach_group(struct vfio_domain *domain,
>  				   struct vfio_group *group)
>  {
>  	if (group->mdev_group)
> -		return iommu_group_for_each_dev(group->iommu_group,
> -						domain->domain,
> -						vfio_mdev_attach_domain);
> +		return iommu_aux_attach_group(domain->domain,
> +					      group->iommu_group,
> +					      group->iommu_device);

No, we previously iterated all devices in the group and used the aux
interface only when we have an iommu_device supporting aux.  If we
simply assume an mdev group only uses an aux domain we break existing
users, ex. SR-IOV VF backed mdevs.  Thanks,

Alex

>  	else
>  		return iommu_attach_group(domain->domain, group->iommu_group);
>  }
> @@ -1674,8 +1643,8 @@ static void vfio_iommu_detach_group(struct vfio_domain *domain,
>  				    struct vfio_group *group)
>  {
>  	if (group->mdev_group)
> -		iommu_group_for_each_dev(group->iommu_group, domain->domain,
> -					 vfio_mdev_detach_domain);
> +		iommu_aux_detach_group(domain->domain, group->iommu_group,
> +				       group->iommu_device);
>  	else
>  		iommu_detach_group(domain->domain, group->iommu_group);
>  }
> @@ -2007,6 +1976,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  			return 0;
>  		}
>  
> +		group->iommu_device = iommu_device;
>  		bus = iommu_device->bus;
>  	}
>  

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