[PATCH v4 08/25] iommu: Reorganize iommu_get_default_domain_type() to respect def_domain_type()

[Jason Gunthorpe]

Except for dart every driver returns 0 or IDENTITY from def_domain_type().

The drivers that return IDENTITY have some kind of good reason, typically
that quirky hardware really can't support anything other than IDENTITY.

Arrange things so that if the driver says it needs IDENTITY then
iommu_get_default_domain_type() either fails or returns IDENTITY.  It will
never reject the driver's override to IDENTITY.

The only real functional difference is that the PCI untrusted flag is now
ignored for quirky HW instead of overriding the IOMMU driver.

This makes the next patch cleaner that wants to force IDENTITY always for
ARM_IOMMU because there is no support for DMA.

Tested-by: Steven Price <steven.price at arm.com>
Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
Tested-by: Nicolin Chen <nicolinc at nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
---
 drivers/iommu/iommu.c | 66 +++++++++++++++++++++----------------------
 1 file changed, 33 insertions(+), 33 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index c8f6664767152d..0c4fc46c210366 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1608,19 +1608,6 @@ struct iommu_group *fsl_mc_device_group(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(fsl_mc_device_group);
 
-static int iommu_get_def_domain_type(struct device *dev)
-{
-	const struct iommu_ops *ops = dev_iommu_ops(dev);
-
-	if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted)
-		return IOMMU_DOMAIN_DMA;
-
-	if (ops->def_domain_type)
-		return ops->def_domain_type(dev);
-
-	return 0;
-}
-
 static struct iommu_domain *
 __iommu_group_alloc_default_domain(const struct bus_type *bus,
 				   struct iommu_group *group, int req_type)
@@ -1761,36 +1748,49 @@ static int iommu_bus_notifier(struct notifier_block *nb,
 static int iommu_get_default_domain_type(struct iommu_group *group,
 					 int target_type)
 {
+	const struct iommu_ops *ops = dev_iommu_ops(
+		list_first_entry(&group->devices, struct group_device, list)
+			->dev);
 	int best_type = target_type;
 	struct group_device *gdev;
 	struct device *last_dev;
+	int type;
 
 	lockdep_assert_held(&group->mutex);
-
 	for_each_group_device(group, gdev) {
-		unsigned int type = iommu_get_def_domain_type(gdev->dev);
-
-		if (best_type && type && best_type != type) {
-			if (target_type) {
-				dev_err_ratelimited(
-					gdev->dev,
-					"Device cannot be in %s domain\n",
-					iommu_domain_type_str(target_type));
-				return -1;
-			}
-
-			dev_warn(
-				gdev->dev,
-				"Device needs domain type %s, but device %s in the same iommu group requires type %s - using default\n",
-				iommu_domain_type_str(type), dev_name(last_dev),
-				iommu_domain_type_str(best_type));
-			return 0;
+		type = best_type;
+		if (ops->def_domain_type) {
+			type = ops->def_domain_type(gdev->dev);
+			if (best_type && type && best_type != type)
+				goto err;
 		}
-		if (!best_type)
-			best_type = type;
+
+		if (dev_is_pci(gdev->dev) && to_pci_dev(gdev->dev)->untrusted) {
+			type = IOMMU_DOMAIN_DMA;
+			if (best_type && type && best_type != type)
+				goto err;
+		}
+		best_type = type;
 		last_dev = gdev->dev;
 	}
 	return best_type;
+
+err:
+	if (target_type) {
+		dev_err_ratelimited(
+			gdev->dev,
+			"Device cannot be in %s domain - it is forcing %s\n",
+			iommu_domain_type_str(target_type),
+			iommu_domain_type_str(type));
+		return -1;
+	}
+
+	dev_warn(
+		gdev->dev,
+		"Device needs domain type %s, but device %s in the same iommu group requires type %s - using default\n",
+		iommu_domain_type_str(type), dev_name(last_dev),
+		iommu_domain_type_str(best_type));
+	return 0;
 }
 
 static void iommu_group_do_probe_finalize(struct device *dev)
-- 
2.40.1