iommu: Allocate a default domain for iommu groups

The default domain will be used (if supported by the iommu
driver) when the devices in the iommu group are not attached
to any other domain.
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -51,6 +51,7 @@ struct iommu_group {
 	void (*iommu_data_release)(void *iommu_data);
 	char *name;
 	int id;
+	struct iommu_domain *default_domain;
 };
 
 struct iommu_device {
@@ -75,6 +76,9 @@ struct iommu_group_attribute iommu_group_attr_##_name =		\
 #define to_iommu_group(_kobj)		\
 	container_of(_kobj, struct iommu_group, kobj)
 
+static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+						 unsigned type);
+
 static ssize_t iommu_group_attr_show(struct kobject *kobj,
 				     struct attribute *__attr, char *buf)
 {
@@ -137,6 +141,9 @@ static void iommu_group_release(struct kobject *kobj)
 	ida_remove(&iommu_group_ida, group->id);
 	mutex_unlock(&iommu_group_mutex);
 
+	if (group->default_domain)
+		iommu_domain_free(group->default_domain);
+
 	kfree(group->name);
 	kfree(group);
 }
@@ -701,7 +708,17 @@ static struct iommu_group *iommu_group_get_for_pci_dev(struct pci_dev *pdev)
 		return group;
 
 	/* No shared group found, allocate new */
-	return iommu_group_alloc();
+	group = iommu_group_alloc();
+	if (group) {
+		/*
+		 * Try to allocate a default domain - needs support from the
+		 * IOMMU driver.
+		 */
+		group->default_domain = __iommu_domain_alloc(pdev->dev.bus,
+							     IOMMU_DOMAIN_DMA);
+	}
+
+	return group;
 }
 
 /**
@@ -922,22 +939,28 @@ void iommu_set_fault_handler(struct iommu_domain *domain,
 }
 EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
 
-struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
+static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+						 unsigned type)
 {
 	struct iommu_domain *domain;
 
 	if (bus == NULL || bus->iommu_ops == NULL)
 		return NULL;
 
-	domain = bus->iommu_ops->domain_alloc(IOMMU_DOMAIN_UNMANAGED);
+	domain = bus->iommu_ops->domain_alloc(type);
 	if (!domain)
 		return NULL;
 
 	domain->ops  = bus->iommu_ops;
-	domain->type = IOMMU_DOMAIN_UNMANAGED;
+	domain->type = type;
 
 	return domain;
 }
+
+struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
+{
+	return __iommu_domain_alloc(bus, IOMMU_DOMAIN_UNMANAGED);
+}
 EXPORT_SYMBOL_GPL(iommu_domain_alloc);
 
 void iommu_domain_free(struct iommu_domain *domain)