[PATCH v4 2/5] iommu: Add iommu_at(de)tach_subdev_group()

From: Lu Baolu
Date: Mon Aug 31 2020 - 23:40:20 EST


This adds two new APIs for the use cases like vfio/mdev where subdevices
derived from physical devices are created and put in an iommu_group. The
new IOMMU API interfaces mimic the vfio_mdev_at(de)tach_domain() directly,
testing whether the resulting device supports IOMMU_DEV_FEAT_AUX and using
an aux vs non-aux at(de)tach.

By doing this we could

- Set the iommu_group.domain. The iommu_group.domain is private to iommu
core (therefore vfio code cannot set it), but we need it set in order
for iommu_get_domain_for_dev() to work with a group attached to an aux
domain.

- Prefer to use the _attach_group() interfaces while the _attach_device()
interfaces are relegated to special cases.

Link: https://lore.kernel.org/linux-iommu/20200730134658.44c57a67@xxxxxxx/
Link: https://lore.kernel.org/linux-iommu/20200730151703.5daf8ad4@xxxxxxx/
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/iommu/iommu.c | 136 ++++++++++++++++++++++++++++++++++++++++++
include/linux/iommu.h | 20 +++++++
2 files changed, 156 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 38cdfeb887e1..fb21c2ff4861 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2757,6 +2757,142 @@ int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
}
EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);

+static int __iommu_aux_attach_device(struct iommu_domain *domain,
+ struct device *phys_dev,
+ struct device *sub_dev)
+{
+ int ret;
+
+ if (unlikely(!domain->ops->aux_attach_dev))
+ return -ENODEV;
+
+ ret = domain->ops->aux_attach_dev(domain, phys_dev, sub_dev);
+ if (!ret)
+ trace_attach_device_to_domain(sub_dev);
+
+ return ret;
+}
+
+static void __iommu_aux_detach_device(struct iommu_domain *domain,
+ struct device *phys_dev,
+ struct device *sub_dev)
+{
+ if (unlikely(!domain->ops->aux_detach_dev))
+ return;
+
+ domain->ops->aux_detach_dev(domain, phys_dev, sub_dev);
+ trace_detach_device_from_domain(sub_dev);
+}
+
+static int __iommu_attach_subdev_group(struct iommu_domain *domain,
+ struct iommu_group *group,
+ iommu_device_lookup_t fn)
+{
+ struct group_device *device;
+ struct device *phys_dev;
+ int ret = -ENODEV;
+
+ list_for_each_entry(device, &group->devices, list) {
+ phys_dev = fn(device->dev);
+ if (!phys_dev) {
+ ret = -ENODEV;
+ break;
+ }
+
+ if (iommu_dev_feature_enabled(phys_dev, IOMMU_DEV_FEAT_AUX))
+ ret = __iommu_aux_attach_device(domain, phys_dev,
+ device->dev);
+ else
+ ret = __iommu_attach_device(domain, phys_dev);
+
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static void __iommu_detach_subdev_group(struct iommu_domain *domain,
+ struct iommu_group *group,
+ iommu_device_lookup_t fn)
+{
+ struct group_device *device;
+ struct device *phys_dev;
+
+ list_for_each_entry(device, &group->devices, list) {
+ phys_dev = fn(device->dev);
+ if (!phys_dev)
+ break;
+
+ if (iommu_dev_feature_enabled(phys_dev, IOMMU_DEV_FEAT_AUX))
+ __iommu_aux_detach_device(domain, phys_dev, device->dev);
+ else
+ __iommu_detach_device(domain, phys_dev);
+ }
+}
+
+/**
+ * iommu_attach_subdev_group - attach domain to an iommu_group which
+ * contains subdevices.
+ *
+ * @domain: domain
+ * @group: iommu_group which contains subdevices
+ * @fn: callback for each subdevice in the @iommu_group to retrieve the
+ * physical device where the subdevice was created from.
+ *
+ * Returns 0 on success, or an error value.
+ */
+int iommu_attach_subdev_group(struct iommu_domain *domain,
+ struct iommu_group *group,
+ iommu_device_lookup_t fn)
+{
+ int ret = -ENODEV;
+
+ mutex_lock(&group->mutex);
+ if (group->domain) {
+ ret = -EBUSY;
+ goto unlock_out;
+ }
+
+ ret = __iommu_attach_subdev_group(domain, group, fn);
+ if (ret)
+ __iommu_detach_subdev_group(domain, group, fn);
+ else
+ group->domain = domain;
+
+unlock_out:
+ mutex_unlock(&group->mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_attach_subdev_group);
+
+/**
+ * iommu_detach_subdev_group - detach domain from an iommu_group which
+ * contains subdevices
+ *
+ * @domain: domain
+ * @group: iommu_group which contains subdevices
+ * @fn: callback for each subdevice in the @iommu_group to retrieve the
+ * physical device where the subdevice was created from.
+ *
+ * The domain must have been attached to @group via iommu_attach_subdev_group().
+ */
+void iommu_detach_subdev_group(struct iommu_domain *domain,
+ struct iommu_group *group,
+ iommu_device_lookup_t fn)
+{
+ mutex_lock(&group->mutex);
+ if (!group->domain)
+ goto unlock_out;
+
+ __iommu_detach_subdev_group(domain, group, fn);
+ group->domain = NULL;
+
+unlock_out:
+ mutex_unlock(&group->mutex);
+}
+EXPORT_SYMBOL_GPL(iommu_detach_subdev_group);
+
/**
* iommu_sva_bind_device() - Bind a process address space to a device
* @dev: the device
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 871267104915..b9df8b510d4f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -48,6 +48,7 @@ struct iommu_fault_event;
typedef int (*iommu_fault_handler_t)(struct iommu_domain *,
struct device *, unsigned long, int, void *);
typedef int (*iommu_dev_fault_handler_t)(struct iommu_fault *, void *);
+typedef struct device *(*iommu_device_lookup_t)(struct device *);

struct iommu_domain_geometry {
dma_addr_t aperture_start; /* First address that can be mapped */
@@ -631,6 +632,12 @@ 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_get_pasid(struct iommu_domain *domain, struct device *dev);
+int iommu_attach_subdev_group(struct iommu_domain *domain,
+ struct iommu_group *group,
+ iommu_device_lookup_t fn);
+void iommu_detach_subdev_group(struct iommu_domain *domain,
+ struct iommu_group *group,
+ iommu_device_lookup_t fn);

struct iommu_sva *iommu_sva_bind_device(struct device *dev,
struct mm_struct *mm,
@@ -1019,6 +1026,19 @@ iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
return -ENODEV;
}

+static inline int
+iommu_attach_subdev_group(struct iommu_domain *domain, struct iommu_group *group,
+ iommu_device_lookup_t fn)
+{
+ return -ENODEV;
+}
+
+static inline void
+iommu_detach_subdev_group(struct iommu_domain *domain, struct iommu_group *group,
+ iommu_device_lookup_t fn)
+{
+}
+
static inline struct iommu_sva *
iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
{
--
2.17.1