Since asserting dma ownership now causes the group to have its DMA blocked
the iommu layer requires a working iommu. This means the dma_owner APIs
cannot be used on the fake groups that VFIO creates. Test for this and
avoid calling them.

Otherwise asserting dma ownership will fail for VFIO mdev devices as a
BLOCKING iommu_domain cannot be allocated due to the NULL iommu ops.

Fixes: 0286300e6045 ("iommu: iommu_group_claim_dma_owner() must always assign a 
domain")
Reported-by: Eric Farman <far...@linux.ibm.com>
Tested-by: Eric Farman <far...@linux.ibm.com>
Signed-off-by: Jason Gunthorpe <j...@nvidia.com>
---
 drivers/vfio/vfio.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

Sort of a v2 from here:

https://lore.kernel.org/all/20220518191446.gu1343...@nvidia.com/

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index cfcff7764403fc..f5ed03897210c3 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -927,7 +927,8 @@ static void __vfio_group_unset_container(struct vfio_group 
*group)
                driver->ops->detach_group(container->iommu_data,
                                          group->iommu_group);
 
-       iommu_group_release_dma_owner(group->iommu_group);
+       if (group->type == VFIO_IOMMU)
+               iommu_group_release_dma_owner(group->iommu_group);
 
        group->container = NULL;
        group->container_users = 0;
@@ -1001,9 +1002,11 @@ static int vfio_group_set_container(struct vfio_group 
*group, int container_fd)
                goto unlock_out;
        }
 
-       ret = iommu_group_claim_dma_owner(group->iommu_group, f.file);
-       if (ret)
-               goto unlock_out;
+       if (group->type == VFIO_IOMMU) {
+               ret = iommu_group_claim_dma_owner(group->iommu_group, f.file);
+               if (ret)
+                       goto unlock_out;
+       }
 
        driver = container->iommu_driver;
        if (driver) {
@@ -1011,7 +1014,9 @@ static int vfio_group_set_container(struct vfio_group 
*group, int container_fd)
                                                group->iommu_group,
                                                group->type);
                if (ret) {
-                       iommu_group_release_dma_owner(group->iommu_group);
+                       if (group->type == VFIO_IOMMU)
+                               iommu_group_release_dma_owner(
+                                       group->iommu_group);
                        goto unlock_out;
                }
        }

base-commit: 7ab5e10eda02da1d9562ffde562c51055d368e9c
-- 
2.36.0

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