Commit a3da1ab6 authored May 19, 2022 by Jason Gunthorpe Committed by Alex Williamson May 23, 2022

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: 0286300e ("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>

parent 7ab5e10e

drivers/vfio/vfio.c

+10 −5

Original line number	Diff line number	Diff line
		@@ -927,6 +927,7 @@ static void __vfio_group_unset_container(struct vfio_group *group)
		driver->ops->detach_group(container->iommu_data,
		group->iommu_group);

		if (group->type == VFIO_IOMMU)
		iommu_group_release_dma_owner(group->iommu_group);

		group->container = NULL;
		@@ -1001,9 +1002,11 @@ static int vfio_group_set_container(struct vfio_group *group, int container_fd)
		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;
		}
		}