iommu: Create __iommu_alloc_identity_domain()

Consolidate all the code to create an IDENTITY domain into one
function. This removes the legacy __iommu_domain_alloc() path from all
paths, and preps it for final removal.

BLOCKED/IDENTITY/PAGING are now always allocated via a type specific
function.

[Joerg: Actually remove __iommu_domain_alloc()]

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/20241028093810.5901-13-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: jgunthorpe

drivers/iommu/iommu.c

@@ -94,8 +94,6 @@ static const char * const iommu_group_resv_type_string[] = {
 static int iommu_bus_notifier(struct notifier_block *nb,
 			      unsigned long action, void *data);
 static void iommu_release_device(struct device *dev);
-static struct iommu_domain *
-__iommu_group_domain_alloc(struct iommu_group *group, unsigned int type);
 static int __iommu_attach_device(struct iommu_domain *domain,
 				 struct device *dev);
 static int __iommu_attach_group(struct iommu_domain *domain,
@@ -137,6 +135,8 @@ static struct group_device *iommu_group_alloc_device(struct iommu_group *group,
 						     struct device *dev);
 static void __iommu_group_free_device(struct iommu_group *group,
 				      struct group_device *grp_dev);
+static void iommu_domain_init(struct iommu_domain *domain, unsigned int type,
+			      const struct iommu_ops *ops);
 
 #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store)		\
 struct iommu_group_attribute iommu_group_attr_##_name =		\
@@ -1586,6 +1586,28 @@ struct iommu_group *fsl_mc_device_group(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(fsl_mc_device_group);
 
+static struct iommu_domain *__iommu_alloc_identity_domain(struct device *dev)
+{
+	const struct iommu_ops *ops = dev_iommu_ops(dev);
+	struct iommu_domain *domain;
+
+	if (ops->identity_domain)
+		return ops->identity_domain;
+
+	/* Older drivers create the identity domain via ops->domain_alloc() */
+	if (!ops->domain_alloc)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	domain = ops->domain_alloc(IOMMU_DOMAIN_IDENTITY);
+	if (IS_ERR(domain))
+		return domain;
+	if (!domain)
+		return ERR_PTR(-ENOMEM);
+
+	iommu_domain_init(domain, IOMMU_DOMAIN_IDENTITY, ops);
+	return domain;
+}
+
 static struct iommu_domain *
 __iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 {
@@ -1613,7 +1635,10 @@ __iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 		return dom;
 	}
 
-	return __iommu_group_domain_alloc(group, req_type);
+	if (req_type == IOMMU_DOMAIN_IDENTITY)
+		return __iommu_alloc_identity_domain(dev);
+
+	return ERR_PTR(-EINVAL);
 }
 
 /*
@@ -1947,44 +1972,6 @@ static void iommu_domain_init(struct iommu_domain *domain, unsigned int type,
 		domain->pgsize_bitmap = ops->pgsize_bitmap;
 }
 
-static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
-						 struct device *dev,
-						 unsigned int type)
-{
-	struct iommu_domain *domain;
-	unsigned int alloc_type = type & IOMMU_DOMAIN_ALLOC_FLAGS;
-
-	if (alloc_type == IOMMU_DOMAIN_IDENTITY && ops->identity_domain)
-		return ops->identity_domain;
-	else if (type & __IOMMU_DOMAIN_PAGING && ops->domain_alloc_paging)
-		domain = ops->domain_alloc_paging(dev);
-	else if (ops->domain_alloc)
-		domain = ops->domain_alloc(alloc_type);
-	else
-		return ERR_PTR(-EOPNOTSUPP);
-
-	/*
-	 * Many domain_alloc ops now return ERR_PTR, make things easier for the
-	 * driver by accepting ERR_PTR from all domain_alloc ops instead of
-	 * having two rules.
-	 */
-	if (IS_ERR(domain))
-		return domain;
-	if (!domain)
-		return ERR_PTR(-ENOMEM);
-
-	iommu_domain_init(domain, type, ops);
-	return domain;
-}
-
-static struct iommu_domain *
-__iommu_group_domain_alloc(struct iommu_group *group, unsigned int type)
-{
-	struct device *dev = iommu_group_first_dev(group);
-
-	return __iommu_domain_alloc(dev_iommu_ops(dev), dev, type);
-}
-
 static struct iommu_domain *
 __iommu_paging_domain_alloc_flags(struct device *dev, unsigned int type,
 				  unsigned int flags)