Re: [PATCH v3 2/4] iommu: Add iommu_aux_at(de)tach_group()

[Lu Baolu]

Hi Jacob,

On 7/15/20 12:39 AM, Jacob Pan wrote:
> On Tue, 14 Jul 2020 13:57:01 +0800
> Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>  wrote:
>
> > This adds two new aux-domain APIs for a use case like vfio/mdev where
> > sub-devices derived from an aux-domain capable device are created and
> > put in an iommu_group.
> >
> > /**
> >   * iommu_aux_attach_group - attach an aux-domain to an iommu_group
> > which
> >   *                          contains sub-devices (for example mdevs)
> > derived
> >   *                          from @dev.
> >   * @domain: an aux-domain;
> >   * @group:  an iommu_group which contains sub-devices derived from
> > @dev;
> >   * @dev:    the physical device which supports IOMMU_DEV_FEAT_AUX.
> >   *
> >   * Returns 0 on success, or an error value.
> >   */
> > int iommu_aux_attach_group(struct iommu_domain *domain,
> >                             struct iommu_group *group,
> >                             struct device *dev)
> >
> > /**
> >   * iommu_aux_detach_group - detach an aux-domain from an iommu_group
> >   *
> >   * @domain: an aux-domain;
> >   * @group:  an iommu_group which contains sub-devices derived from
> > @dev;
> >   * @dev:    the physical device which supports IOMMU_DEV_FEAT_AUX.
> >   *
> >   * @domain must have been attached to @group via
> > iommu_aux_attach_group(). */
> > void iommu_aux_detach_group(struct iommu_domain *domain,
> >                              struct iommu_group *group,
> >                              struct device *dev)
> >
> > It also adds a flag in the iommu_group data structure to identify
> > an iommu_group with aux-domain attached from those normal ones.
> >
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/iommu.c | 58
> > +++++++++++++++++++++++++++++++++++++++++++ include/linux/iommu.h |
> > 17 +++++++++++++ 2 files changed, 75 insertions(+)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index e1fdd3531d65..cad5a19ebf22 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -45,6 +45,7 @@ struct iommu_group {
> >   	struct iommu_domain *default_domain;
> >   	struct iommu_domain *domain;
> >   	struct list_head entry;
> > +	unsigned int aux_domain_attached:1;
> >   };
> >   
> >   struct group_device {
> > @@ -2759,6 +2760,63 @@ int iommu_aux_get_pasid(struct iommu_domain
> > *domain, struct device *dev) }
> >   EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
> >   
> > +/**
> > + * iommu_aux_attach_group - attach an aux-domain to an iommu_group
> > which
> > + *                          contains sub-devices (for example mdevs)
> > derived
> > + *                          from @dev.
> > + * @domain: an aux-domain;
> > + * @group:  an iommu_group which contains sub-devices derived from
> > @dev;
> > + * @dev:    the physical device which supports IOMMU_DEV_FEAT_AUX.
> > + *
> > + * Returns 0 on success, or an error value.
> > + */
> > +int iommu_aux_attach_group(struct iommu_domain *domain,
> > +			   struct iommu_group *group, struct device
> > *dev) +{
> > +	int ret = -EBUSY;
> > +
> > +	mutex_lock(&group->mutex);
> > +	if (group->domain)
> > +		goto out_unlock;
> > +
> Perhaps I missed something but are we assuming only one mdev per mdev
> group? That seems to change the logic where vfio does:
> iommu_group_for_each_dev()
> 	iommu_aux_attach_device()

It has been changed in PATCH 4/4:

static int vfio_iommu_attach_group(struct vfio_domain *domain,
                                   struct vfio_group *group)
{
        if (group->mdev_group)
                return iommu_aux_attach_group(domain->domain,
                                              group->iommu_group,
                                              group->iommu_device);
        else
                return iommu_attach_group(domain->domain, 
group->iommu_group);
}

So, for both normal domain and aux-domain, we use the same concept:
attach a domain to a group.

Best regards,
baolu