[PATCH v4 06/13] iommu: Expose group variants of dma ownership interfaces

[Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>]

The vfio needs to set DMA_OWNER_PRIVATE_DOMAIN_USER for the entire group
when attaching it to a vfio container. Expose group variants of setting/
releasing dma ownership for this purpose.

This also exposes the helper iommu_group_dma_owner_unclaimed() for vfio
to report to userspace if the group is viable to user assignment for
compatibility with VFIO_GROUP_FLAGS_VIABLE.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/iommu.h | 21 +++++++++++++++++++
 drivers/iommu/iommu.c | 47 ++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 63 insertions(+), 5 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 53a023ee1ac0..5ad4cf13370d 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -699,6 +699,10 @@ u32 iommu_sva_get_pasid(struct iommu_sva *handle);
 int iommu_device_set_dma_owner(struct device *dev, enum iommu_dma_owner owner,
 			       void *owner_cookie);
 void iommu_device_release_dma_owner(struct device *dev, enum iommu_dma_owner owner);
+int iommu_group_set_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner,
+			      void *owner_cookie);
+void iommu_group_release_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner);
+bool iommu_group_dma_owner_unclaimed(struct iommu_group *group);
 
 #else /* CONFIG_IOMMU_API */
 
@@ -1115,6 +1119,23 @@ static inline void iommu_device_release_dma_owner(struct device *dev,
 						  enum iommu_dma_owner owner)
 {
 }
+
+static inline int iommu_group_set_dma_owner(struct iommu_group *group,
+					    enum iommu_dma_owner owner,
+					    void *owner_cookie)
+{
+	return -EINVAL;
+}
+
+static inline void iommu_group_release_dma_owner(struct iommu_group *group,
+						 enum iommu_dma_owner owner)
+{
+}
+
+static inline bool iommu_group_dma_owner_unclaimed(struct iommu_group *group)
+{
+	return false;
+}
 #endif /* CONFIG_IOMMU_API */
 
 /**
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 573e253bad51..8bec71b1cc18 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3365,9 +3365,19 @@ static ssize_t iommu_group_store_type(struct iommu_group *group,
 	return ret;
 }
 
-static int iommu_group_set_dma_owner(struct iommu_group *group,
-				     enum iommu_dma_owner owner,
-				     void *owner_cookie)
+/**
+ * iommu_group_set_dma_owner() - Set DMA ownership of a group
+ * @group: The group.
+ * @owner: DMA owner type.
+ * @owner_cookie: Caller specified pointer. Could be used for exclusive
+ *                declaration. Could be NULL.
+ *
+ * This is to support backward compatibility for legacy vfio which manages
+ * dma ownership in group level. New invocations on this interface should be
+ * prohibited. Instead, please turn to iommu_device_set_dma_owner().
+ */
+int iommu_group_set_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner,
+			      void *owner_cookie)
 {
 	int ret = 0;
 
@@ -3398,9 +3408,16 @@ static int iommu_group_set_dma_owner(struct iommu_group *group,
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(iommu_group_set_dma_owner);
 
-static void iommu_group_release_dma_owner(struct iommu_group *group,
-					  enum iommu_dma_owner owner)
+/**
+ * iommu_group_release_dma_owner() - Release DMA ownership of a group
+ * @group: The group.
+ * @owner: DMA owner type.
+ *
+ * Release the DMA ownership claimed by iommu_group_set_dma_owner().
+ */
+void iommu_group_release_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner)
 {
 	mutex_lock(&group->mutex);
 	if (WARN_ON(!group->owner_cnt || group->dma_owner != owner))
@@ -3423,6 +3440,26 @@ static void iommu_group_release_dma_owner(struct iommu_group *group,
 unlock_out:
 	mutex_unlock(&group->mutex);
 }
+EXPORT_SYMBOL_GPL(iommu_group_release_dma_owner);
+
+/**
+ * iommu_group_dma_owner_unclaimed() - Is group dma ownership claimed
+ * @group: The group.
+ *
+ * This provides status check on a given group. It is racey and only for
+ * non-binding status reporting.
+ */
+bool iommu_group_dma_owner_unclaimed(struct iommu_group *group)
+{
+	unsigned int user;
+
+	mutex_lock(&group->mutex);
+	user = group->owner_cnt;
+	mutex_unlock(&group->mutex);
+
+	return !user;
+}
+EXPORT_SYMBOL_GPL(iommu_group_dma_owner_unclaimed);
 
 /**
  * iommu_device_set_dma_owner() - Set DMA ownership of a device
-- 
2.25.1