vfio: Do not manipulate iommu dma_owner for fake iommu groups

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 <farman@linux.ibm.com>
Tested-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/0-v1-9cfc47edbcd4+13546-vfio_dma_owner_fix_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index cfcff7764403fc35ac7c721f4c20bbb51028512d..f5ed03897210c3d18f9a0d39d85e16b18c0cbfde 100644 (file)
--- 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;
                }
        }