iommu: Put domain allocation in __iommu_group_alloc_blocking_domain()

There is no longer a reason to call __iommu_domain_alloc() to allocate
the blocking domain. All drivers that support a native blocking domain
provide it via the ops, for other drivers we should call
iommu_paging_domain_alloc().

__iommu_group_alloc_blocking_domain() is the only place that allocates
an BLOCKED domain, so move the ops->blocked_domain logic there.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20241028093810.5901-12-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: jgunthorpe

drivers/iommu/iommu.c

@@ -1956,8 +1956,6 @@ static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
 
 	if (alloc_type == IOMMU_DOMAIN_IDENTITY && ops->identity_domain)
 		return ops->identity_domain;
-	else if (alloc_type == IOMMU_DOMAIN_BLOCKED && ops->blocked_domain)
-		return ops->blocked_domain;
 	else if (type & __IOMMU_DOMAIN_PAGING && ops->domain_alloc_paging)
 		domain = ops->domain_alloc_paging(dev);
 	else if (ops->domain_alloc)
@@ -3147,22 +3145,25 @@ void iommu_device_unuse_default_domain(struct device *dev)
 
 static int __iommu_group_alloc_blocking_domain(struct iommu_group *group)
 {
+	struct device *dev = iommu_group_first_dev(group);
+	const struct iommu_ops *ops = dev_iommu_ops(dev);
 	struct iommu_domain *domain;
 
 	if (group->blocking_domain)
 		return 0;
 
-	domain = __iommu_group_domain_alloc(group, IOMMU_DOMAIN_BLOCKED);
-	if (IS_ERR(domain)) {
-		/*
-		 * For drivers that do not yet understand IOMMU_DOMAIN_BLOCKED
-		 * create an empty domain instead.
-		 */
-		domain = __iommu_group_domain_alloc(group,
-						    IOMMU_DOMAIN_UNMANAGED);
-		if (IS_ERR(domain))
-			return PTR_ERR(domain);
+	if (ops->blocked_domain) {
+		group->blocking_domain = ops->blocked_domain;
+		return 0;
 	}
+
+	/*
+	 * For drivers that do not yet understand IOMMU_DOMAIN_BLOCKED create an
+	 * empty PAGING domain instead.
+	 */
+	domain = iommu_paging_domain_alloc(dev);
+	if (IS_ERR(domain))
+		return PTR_ERR(domain);
 	group->blocking_domain = domain;
 	return 0;
 }