[PATCH v2 3/5] vfio/iommu_type1: Remove the domain->ops comparison

[Nicolin Chen]

The domain->ops validation was added, as a precaution, for mixed-driver
systems. However, at this moment only one iommu driver is possible. So
remove it.

Per discussion with Robin, in future when many can be permitted we will
rely on the IOMMU core code to check the domain->ops:
https://lore.kernel.org/linux-iommu/6575de6d-94ba-c427-5b1e-967750ddff23@arm.com/

Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index f4e3b423a453..11be5f95580b 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2277,29 +2277,19 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 			domain->domain->ops->enforce_cache_coherency(
 				domain->domain);
 
-	/*
-	 * Try to match an existing compatible domain.  We don't want to
-	 * preclude an IOMMU driver supporting multiple bus_types and being
-	 * able to include different bus_types in the same IOMMU domain, so
-	 * we test whether the domains use the same iommu_ops rather than
-	 * testing if they're on the same bus_type.
-	 */
+	/* Try to match an existing compatible domain */
 	list_for_each_entry(d, &iommu->domain_list, next) {
-		if (d->domain->ops == domain->domain->ops) {
-			iommu_detach_group(domain->domain, group->iommu_group);
-			if (!iommu_attach_group(d->domain,
-						group->iommu_group)) {
-				list_add(&group->next, &d->group_list);
-				iommu_domain_free(domain->domain);
-				kfree(domain);
-				goto done;
-			}
-
-			ret = iommu_attach_group(domain->domain,
-						 group->iommu_group);
-			if (ret)
-				goto out_domain;
+		iommu_detach_group(domain->domain, group->iommu_group);
+		if (!iommu_attach_group(d->domain, group->iommu_group)) {
+			list_add(&group->next, &d->group_list);
+			iommu_domain_free(domain->domain);
+			kfree(domain);
+			goto done;
 		}
+
+		ret = iommu_attach_group(domain->domain,  group->iommu_group);
+		if (ret)
+			goto out_domain;
 	}
 
 	vfio_test_domain_fgsp(domain);
-- 
2.17.1