[PATCH v4 3/6] iommu: Allow iommu_change_dev_def_domain() realloc default domain for same type

[John Garry <john.garry@huawei.com>]

Allow iommu_change_dev_def_domain() to create a new default domain, keeping
the same as current when type is unset.

Also remove comment about function purpose, which will become stale.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 drivers/iommu/iommu.c | 54 ++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 26 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 8a815ac261f0..d8198a9aff4e 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3036,6 +3036,7 @@ u32 iommu_sva_get_pasid(struct iommu_sva *handle)
 }
 EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
 
+
 /*
  * Changes the default domain of an iommu group that has *only* one device
  *
@@ -3043,16 +3044,13 @@ EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
  * @prev_dev: The device in the group (this is used to make sure that the device
  *	 hasn't changed after the caller has called this function)
  * @type: The type of the new default domain that gets associated with the group
+ * @new: Allocate new default domain, keeping same type when no type passed
  *
  * Returns 0 on success and error code on failure
  *
- * Note:
- * 1. Presently, this function is called only when user requests to change the
- *    group's default domain type through /sys/kernel/iommu_groups/<grp_id>/type
- *    Please take a closer look if intended to use for other purposes.
  */
 static int iommu_change_dev_def_domain(struct iommu_group *group,
-				       struct device *prev_dev, int type)
+				       struct device *prev_dev, int type, bool new)
 {
 	struct iommu_domain *prev_dom;
 	struct group_device *grp_dev;
@@ -3102,28 +3100,32 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
 		goto out;
 	}
 
-	dev_def_dom = iommu_get_def_domain_type(dev);
-	if (!type) {
+	if (new && !type) {
+		type = prev_dom->type;
+	} else {
+		dev_def_dom = iommu_get_def_domain_type(dev);
+		if (!type) {
+			/*
+			 * If the user hasn't requested any specific type of domain and
+			 * if the device supports both the domains, then default to the
+			 * domain the device was booted with
+			 */
+			type = dev_def_dom ? : iommu_def_domain_type;
+		} else if (dev_def_dom && type != dev_def_dom) {
+			dev_err_ratelimited(prev_dev, "Device cannot be in %s domain\n",
+					    iommu_domain_type_str(type));
+			ret = -EINVAL;
+			goto out;
+		}
+
 		/*
-		 * If the user hasn't requested any specific type of domain and
-		 * if the device supports both the domains, then default to the
-		 * domain the device was booted with
+		 * Switch to a new domain only if the requested domain type is different
+		 * from the existing default domain type
 		 */
-		type = dev_def_dom ? : iommu_def_domain_type;
-	} else if (dev_def_dom && type != dev_def_dom) {
-		dev_err_ratelimited(prev_dev, "Device cannot be in %s domain\n",
-				    iommu_domain_type_str(type));
-		ret = -EINVAL;
-		goto out;
-	}
-
-	/*
-	 * Switch to a new domain only if the requested domain type is different
-	 * from the existing default domain type
-	 */
-	if (prev_dom->type == type) {
-		ret = 0;
-		goto out;
+		if (prev_dom->type == type) {
+			ret = 0;
+			goto out;
+		}
 	}
 
 	/* Sets group->default_domain to the newly allocated domain */
@@ -3267,7 +3269,7 @@ static int iommu_group_store_type_cb(const char *buf,
 	else
 		return -EINVAL;
 
-	return iommu_change_dev_def_domain(group, dev, type);
+	return iommu_change_dev_def_domain(group, dev, type, false);
 }
 
 static ssize_t iommu_group_store_type(struct iommu_group *group,
-- 
2.26.2

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