This works with below kernel commit id

    commit f200d9a1de755f3bb98e21535e22b9adf6ba83f7 (HEAD -> iommufd-v5.19-rc5)
    Author: Yi Liu <yi.l.liu@intel.com>
    Date:   Thu Jul 14 01:56:46 2022 -0700

        cover-letter: Add iommufd nesting support

    https://github.com/yiliu1765/iommufd/tree/iommufd-v5.19-rc5

    Tested with Intel scalable mode vIOMMU for PF passthrough

    Example to passthrough a vfio-pci device and expose scalable mode vIOMMU
    to guest:

     -object iommufd,id=iommufd0 \
     -device intel-iommu,caching-mode=on,dma-drain=on,x-scalable-mode="modern",device-iotlb=on,aw-bits=48,iommufd=iommufd0 \
     -device vfio-pci,host=6a:01.0,id=hostdev0,addr=0x6,iommufd=iommufd0 \

Signed-off-by: Yi Liu <yi.l.liu@intel.com>