[PATCH v1 1/8] iommu: Add iommu_group_replace_domain()

From: Lu Baolu
Date: Wed Jan 05 2022 - 21:22:03 EST


Expose an interface to replace the domain of an iommu group for frameworks
like vfio which claims the ownership of the whole iommu group.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
include/linux/iommu.h | 10 ++++++++++
drivers/iommu/iommu.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 408a6d2b3034..66ebce3d1e11 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -677,6 +677,9 @@ void iommu_device_unuse_dma_api(struct device *dev);
int iommu_group_set_dma_owner(struct iommu_group *group, void *owner);
void iommu_group_release_dma_owner(struct iommu_group *group);
bool iommu_group_dma_owner_claimed(struct iommu_group *group);
+int iommu_group_replace_domain(struct iommu_group *group,
+ struct iommu_domain *old,
+ struct iommu_domain *new);

#else /* CONFIG_IOMMU_API */

@@ -1090,6 +1093,13 @@ static inline bool iommu_group_dma_owner_claimed(struct iommu_group *group)
{
return false;
}
+
+static inline int
+iommu_group_replace_domain(struct iommu_group *group, struct iommu_domain *old,
+ struct iommu_domain *new)
+{
+ return -ENODEV;
+}
#endif /* CONFIG_IOMMU_API */

/**
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 72a95dea688e..ab8ab95969f5 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3431,3 +3431,40 @@ bool iommu_group_dma_owner_claimed(struct iommu_group *group)
return user;
}
EXPORT_SYMBOL_GPL(iommu_group_dma_owner_claimed);
+
+/**
+ * iommu_group_replace_domain() - Replace group's domain
+ * @group: The group.
+ * @old: The previous attached domain. NULL for none.
+ * @new: The new domain about to be attached.
+ *
+ * This is to support backward compatibility for vfio which manages the dma
+ * ownership in iommu_group level.
+ */
+int iommu_group_replace_domain(struct iommu_group *group,
+ struct iommu_domain *old,
+ struct iommu_domain *new)
+{
+ int ret = 0;
+
+ mutex_lock(&group->mutex);
+ if (!group->owner || group->domain != old) {
+ ret = -EPERM;
+ goto unlock_out;
+ }
+
+ if (old)
+ __iommu_detach_group(old, group);
+
+ if (new) {
+ ret = __iommu_attach_group(new, group);
+ if (ret && old)
+ __iommu_attach_group(old, group);
+ }
+
+unlock_out:
+ mutex_unlock(&group->mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_group_replace_domain);
--
2.25.1