[PATCH v2 1/2] iommu: iommu_aux_at(de)tach_device() extension

Lu Baolu
2020-07-07T01:44:42Z

The hardware assistant vfio mediated device is a use case of iommu
aux-domain. The interactions between vfio/mdev and iommu during mdev
creation and passthr are:

- Create a group for mdev with iommu_group_alloc();
- Add the device to the group with
group = iommu_group_alloc();
if (IS_ERR(group))
return PTR_ERR(group);

ret = iommu_group_add_device(group, &mdev->dev);
if (!ret)
dev_info(&mdev->dev, "MDEV: group_id = %d\n",
iommu_group_id(group));
- Allocate an aux-domain
iommu_domain_alloc()
- Attach the aux-domain to the physical device from which the mdev is
created.
iommu_aux_attach_device()

In the whole process, an iommu group was allocated for the mdev and an
iommu domain was attached to the group, but the group->domain leaves
NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore.

The iommu_get_domain_for_dev() is a necessary interface for device
drivers that want to support aux-domain. For example,

struct iommu_domain *domain;
struct device *dev = mdev_dev(mdev);
unsigned long pasid;

domain = iommu_get_domain_for_dev(dev);
if (!domain)
return -ENODEV;

pasid = iommu_aux_get_pasid(domain, dev->parent);
if (pasid == IOASID_INVALID)
return -EINVAL;

/* Program the device context with the PASID value */
....

This extends iommu_aux_at(de)tach_device() so that the users could pass
in an optional device pointer (struct device for vfio/mdev for example),
and the necessary check and data link could be done.

Fixes: a3a195929d40b ("iommu: Add APIs for multiple domains per device")
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
drivers/iommu/iommu.c | 86 +++++++++++++++++++++++++++++----
drivers/vfio/vfio_iommu_type1.c | 5 +-
include/linux/iommu.h | 12 +++--
3 files changed, 87 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 1ed1e14a1f0c..435835058209 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2723,26 +2723,92 @@ EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
* This should make us safe against a device being attached to a guest as a
* whole while there are still pasid users on it (aux and sva).
*/
-int iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev)
+int iommu_aux_attach_device(struct iommu_domain *domain,
+ struct device *phys_dev, struct device *dev)
{
- int ret = -ENODEV;
+ struct iommu_group *group;
+ int ret;

- if (domain->ops->aux_attach_dev)
- ret = domain->ops->aux_attach_dev(domain, dev);
+ if (!domain->ops->aux_attach_dev ||
+ !iommu_dev_feature_enabled(phys_dev, IOMMU_DEV_FEAT_AUX))
+ return -ENODEV;

- if (!ret)
- trace_attach_device_to_domain(dev);
+ /* Bare use only. */
+ if (!dev) {
+ ret = domain->ops->aux_attach_dev(domain, phys_dev);
+ if (!ret)
+ trace_attach_device_to_domain(phys_dev);
+
+ return ret;
+ }
+
+ /*
+ * The caller has created a made-up device (for example, vfio/mdev)
+ * and allocated an iommu_group for user level direct assignment.
+ * Make sure that the group has only single device and hasn't been
+ * attached by any other domain.
+ */
+ group = iommu_group_get(dev);
+ if (!group)
+ return -ENODEV;
+
+ /*
+ * Lock the group to make sure the device-count doesn't change while
+ * we are attaching.
+ */
+ mutex_lock(&group->mutex);
+ ret = -EINVAL;
+ if ((iommu_group_device_count(group) != 1) || group->domain)
+ goto out_unlock;
+
+ ret = -EBUSY;
+ if (group->default_domain && group->domain != group->default_domain)
+ goto out_unlock;
+
+ ret = domain->ops->aux_attach_dev(domain, phys_dev);
+ if (!ret) {
+ trace_attach_device_to_domain(phys_dev);
+ group->domain = domain;
+ }
+
+out_unlock:
+ mutex_unlock(&group->mutex);
+ iommu_group_put(group);

return ret;
}
EXPORT_SYMBOL_GPL(iommu_aux_attach_device);

-void iommu_aux_detach_device(struct iommu_domain *domain, struct device *dev)
+void iommu_aux_detach_device(struct iommu_domain *domain,
+ struct device *phys_dev, struct device *dev)
{
- if (domain->ops->aux_detach_dev) {
- domain->ops->aux_detach_dev(domain, dev);
- trace_detach_device_from_domain(dev);
+ struct iommu_group *group;
+
+ if (WARN_ON_ONCE(!domain->ops->aux_detach_dev))
+ return;
+
+ if (!dev) {
+ domain->ops->aux_detach_dev(domain, phys_dev);
+ trace_detach_device_from_domain(phys_dev);
+
+ return;
}
+
+ group = iommu_group_get(dev);
+ if (!group)
+ return;
+
+ mutex_lock(&group->mutex);
+ if (WARN_ON(iommu_group_device_count(group) != 1))
+ goto out_unlock;
+
+ domain->ops->aux_detach_dev(domain, phys_dev);
+ group->domain = NULL;
+ trace_detach_device_from_domain(phys_dev);
+
+out_unlock:
+ mutex_unlock(&group->mutex);
+ iommu_group_put(group);
}
EXPORT_SYMBOL_GPL(iommu_aux_detach_device);

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 5e556ac9102a..d3be45dfa58e 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -1635,7 +1635,8 @@ static int vfio_mdev_attach_domain(struct device *dev, void *data)
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);
+ return iommu_aux_attach_device(domain,
+ iommu_device, dev);
else
return iommu_attach_device(domain, iommu_device);
}
@@ -1651,7 +1652,7 @@ static int vfio_mdev_detach_domain(struct device *dev, void *data)
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);
+ iommu_aux_detach_device(domain, iommu_device, dev);
else
iommu_detach_device(domain, iommu_device);
}
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 5657d4fef9f2..7da5e67bf7dc 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -632,8 +632,10 @@ bool iommu_dev_has_feature(struct device *dev, enum iommu_dev_features f);
int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features f);
int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features f);
-int iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev);
-void iommu_aux_detach_device(struct iommu_domain *domain, struct device *dev);
+int iommu_aux_attach_device(struct iommu_domain *domain,
+ struct device *phys_dev, struct device *dev);
+void iommu_aux_detach_device(struct iommu_domain *domain,
+ struct device *phys_dev, struct device *dev);
int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev);

struct iommu_sva *iommu_sva_bind_device(struct device *dev,
@@ -1007,13 +1009,15 @@ iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features feat)
}

static inline int
-iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev)
+iommu_aux_attach_device(struct iommu_domain *domain,
+ struct device *phys_dev, struct device *dev)
{
return -ENODEV;
}

static inline void
-iommu_aux_detach_device(struct iommu_domain *domain, struct device *dev)
+iommu_aux_detach_device(struct iommu_domain *domain,
+ struct device *phys_dev, struct device *dev)
{
}

--
2.17.1