[PATCH v6 3/5] vfio/iommu_type1: Remove the domain->ops comparison

Nicolin Chen
2022-08-15T18:17:15Z

The domain->ops validation was added, as a precaution, for mixed-driver
systems.

Per Robin's remarks,
* While bus_set_iommu() still exists, the core code prevents multiple
drivers from registering, so we can't really run into a situation of
having a mixed-driver system:
https://lore.kernel.org/kvm/6e1280c5-4b22-ebb3-3912-6c72bc169982@arm.com/

* And there's plenty more significant problems than this to fix; in future
when many can be permitted, we will rely on the IOMMU core code to check
the domain->ops:
https://lore.kernel.org/kvm/6575de6d-94ba-c427-5b1e-967750ddff23@arm.com/

So remove the check in VFIO for simplicity.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@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 88ee6aaf1c88..523927d61aac 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2288,29 +2288,19 @@ 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