[PATCH v6 02/10] iommu: Remove sva handle list

[Lu Baolu]

The struct sva_iommu represents an association between an SVA domain and
a PASID of a device. It's stored in the iommu group's pasid array and also
tracked by a list in the per-mm data structure. Removes duplicate tracking
of sva_iommu by eliminating the list.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/iommu.h      |  2 --
 drivers/iommu/iommu-priv.h |  3 +++
 drivers/iommu/iommu-sva.c  | 21 ++++++++++++---------
 drivers/iommu/iommu.c      | 31 +++++++++++++++++++++++++++++++
 4 files changed, 46 insertions(+), 11 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index b89404acacd6..823fa3bcc2c6 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1005,14 +1005,12 @@ struct iommu_attach_handle {
 struct iommu_sva {
 	struct iommu_attach_handle	handle;
 	struct device			*dev;
-	struct list_head		handle_item;
 	refcount_t			users;
 };
 
 struct iommu_mm_data {
 	u32			pasid;
 	struct list_head	sva_domains;
-	struct list_head	sva_handles;
 };
 
 int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
diff --git a/drivers/iommu/iommu-priv.h b/drivers/iommu/iommu-priv.h
index 5f731d994803..f1536a5ebb0d 100644
--- a/drivers/iommu/iommu-priv.h
+++ b/drivers/iommu/iommu-priv.h
@@ -28,4 +28,7 @@ void iommu_device_unregister_bus(struct iommu_device *iommu,
 				 const struct bus_type *bus,
 				 struct notifier_block *nb);
 
+struct iommu_attach_handle *iommu_attach_handle_get(struct iommu_group *group,
+						    ioasid_t pasid,
+						    unsigned int type);
 #endif /* __LINUX_IOMMU_PRIV_H */
diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 0fb923254062..e85f4ccc9dcc 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -41,7 +41,6 @@ static struct iommu_mm_data *iommu_alloc_mm_data(struct mm_struct *mm, struct de
 	}
 	iommu_mm->pasid = pasid;
 	INIT_LIST_HEAD(&iommu_mm->sva_domains);
-	INIT_LIST_HEAD(&iommu_mm->sva_handles);
 	/*
 	 * Make sure the write to mm->iommu_mm is not reordered in front of
 	 * initialization to iommu_mm fields. If it does, readers may see a
@@ -69,11 +68,16 @@ static struct iommu_mm_data *iommu_alloc_mm_data(struct mm_struct *mm, struct de
  */
 struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
 {
+	struct iommu_group *group = dev->iommu_group;
+	struct iommu_attach_handle *attach_handle;
 	struct iommu_mm_data *iommu_mm;
 	struct iommu_domain *domain;
 	struct iommu_sva *handle;
 	int ret;
 
+	if (!group)
+		return ERR_PTR(-ENODEV);
+
 	mutex_lock(&iommu_sva_lock);
 
 	/* Allocate mm->pasid if necessary. */
@@ -83,12 +87,13 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
 		goto out_unlock;
 	}
 
-	list_for_each_entry(handle, &mm->iommu_mm->sva_handles, handle_item) {
-		if (handle->dev == dev) {
-			refcount_inc(&handle->users);
-			mutex_unlock(&iommu_sva_lock);
-			return handle;
-		}
+	/* A bond already exists, just take a reference`. */
+	attach_handle = iommu_attach_handle_get(group, iommu_mm->pasid, IOMMU_DOMAIN_SVA);
+	if (!IS_ERR(attach_handle)) {
+		handle = container_of(attach_handle, struct iommu_sva, handle);
+		refcount_inc(&handle->users);
+		mutex_unlock(&iommu_sva_lock);
+		return handle;
 	}
 
 	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
@@ -125,7 +130,6 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
 
 out:
 	refcount_set(&handle->users, 1);
-	list_add(&handle->handle_item, &mm->iommu_mm->sva_handles);
 	mutex_unlock(&iommu_sva_lock);
 	handle->dev = dev;
 	return handle;
@@ -159,7 +163,6 @@ void iommu_sva_unbind_device(struct iommu_sva *handle)
 		mutex_unlock(&iommu_sva_lock);
 		return;
 	}
-	list_del(&handle->handle_item);
 
 	iommu_detach_device_pasid(domain, dev, iommu_mm->pasid);
 	if (--domain->users == 0) {
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index efd281ddfa63..0263814cba6b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3483,3 +3483,34 @@ void iommu_free_global_pasid(ioasid_t pasid)
 	ida_free(&iommu_global_pasid_ida, pasid);
 }
 EXPORT_SYMBOL_GPL(iommu_free_global_pasid);
+
+/**
+ * iommu_attach_handle_get - Return the attach handle
+ * @group: the iommu group that domain was attached to
+ * @pasid: the pasid within the group
+ * @type: matched domain type, 0 for any match
+ *
+ * Return handle or ERR_PTR(-ENOENT) on none, ERR_PTR(-EBUSY) on mismatch.
+ *
+ * Return the attach handle to the caller. The life cycle of an iommu attach
+ * handle is from the time when the domain is attached to the time when the
+ * domain is detached. Callers are required to synchronize the call of
+ * iommu_attach_handle_get() with domain attachment and detachment. The attach
+ * handle can only be used during its life cycle.
+ */
+struct iommu_attach_handle *
+iommu_attach_handle_get(struct iommu_group *group, ioasid_t pasid, unsigned int type)
+{
+	struct iommu_attach_handle *handle;
+
+	xa_lock(&group->pasid_array);
+	handle = xa_load(&group->pasid_array, pasid);
+	if (!handle)
+		handle = ERR_PTR(-ENOENT);
+	else if (type && handle->domain->type != type)
+		handle = ERR_PTR(-EBUSY);
+	xa_unlock(&group->pasid_array);
+
+	return handle;
+}
+EXPORT_SYMBOL_NS_GPL(iommu_attach_handle_get, IOMMUFD_INTERNAL);
-- 
2.34.1