1 files changed, 25 insertions, 3 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3b67144dead2..770ba7e7ef4d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -36,6 +36,7 @@
 
 static struct kset *iommu_group_kset;
 static DEFINE_IDA(iommu_group_ida);
+static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;
 
 struct iommu_callback_data {
         const struct iommu_ops *ops;
@@ -112,6 +113,18 @@ static int __iommu_attach_group(struct iommu_domain *domain,
 static void __iommu_detach_group(struct iommu_domain *domain,
                                  struct iommu_group *group);
 
+static int __init iommu_set_def_domain_type(char *str)
+{
+        bool pt;
+
+        if (!str || strtobool(str, &pt))
+                return -EINVAL;
+
+        iommu_def_domain_type = pt ? IOMMU_DOMAIN_IDENTITY : IOMMU_DOMAIN_DMA;
+        return 0;
+}
+early_param("iommu.passthrough", iommu_set_def_domain_type);
+
 static ssize_t iommu_group_attr_show(struct kobject *kobj,
                                      struct attribute *__attr, char *buf)
 {
@@ -1015,10 +1028,19 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev)
          * IOMMU driver.
          */
         if (!group->default_domain) {
-                group->default_domain = __iommu_domain_alloc(dev->bus,
-                                                             IOMMU_DOMAIN_DMA);
+                struct iommu_domain *dom;
+
+                dom = __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
+                if (!dom && iommu_def_domain_type != IOMMU_DOMAIN_DMA) {
+                        dev_warn(dev,
+                                 "failed to allocate default IOMMU domain of type %u; falling back to IOMMU_DOMAIN_DMA",
+                                 iommu_def_domain_type);
+                        dom = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_DMA);
+                }
+
+                group->default_domain = dom;
                 if (!group->domain)
-                        group->domain = group->default_domain;
+                        group->domain = dom;
         }
 
         ret = iommu_group_add_device(group, dev);