> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Friday, May 20, 2022 1:04 AM
>
> 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@xxxxxxxxxxxxx>
> Tested-by: Eric Farman <farman@xxxxxxxxxxxxx>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> ---
> drivers/vfio/vfio.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> Sort of a v2 from here:
>
> https://lore.kernel.org/all/20220518191446.GU1343366@xxxxxxxxxx/
>
> 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
