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

Lu Baolu
2020-07-15T00:52:21Z

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@linux.intel.com> 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@linux.intel.com>
>> ---
>> 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