Re: [PATCH v2 12/14] iommu: Consolidate the default_domain setup to one function

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Mar 30, 2023 at 11:45:10AM -0300, Jason Gunthorpe wrote:

> IIRC the existing code had both orderings :( I'll add a note about
> this justification

Robin, would this be helpful in the short term for ARM?

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index c31c5d6f913194..39c923e71e625a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1778,6 +1778,7 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 	struct bus_type *bus =
 		list_first_entry(&group->devices, struct group_device, list)
 			->dev->bus;
+	bool direct_failed;
 	int req_type;
 	int ret;
 
@@ -1824,8 +1825,10 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 	 * mapped before their device is attached, in order to guarantee
 	 * continuity with any FW activity
 	 */
+	direct_failed = false;
 	for_each_group_device(group, gdev)
-		iommu_create_device_direct_mappings(dom, gdev->dev);
+		if (iommu_create_device_direct_mappings(dom, gdev->dev))
+			direct_failed = true;
 
 	ret = __iommu_group_set_domain_internal(group, dom,
 						IOMMU_SET_DOMAIN_WITH_DEFERRED);
@@ -1845,6 +1848,16 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 		goto out_set;
 	}
 
+	/*
+	 * Driver's are supposed to allow mappings to be installed in a domain
+	 * before device attachment, but some don't. Hack around this defect by
+	 * trying again after.
+	 */
+	if (direct_failed) {
+		for_each_group_device(group, gdev)
+			iommu_create_device_direct_mappings(dom, gdev->dev);
+	}
+
 out_set:
 	if (group->default_domain)
 		iommu_domain_free(group->default_domain);