On 3/18/26 11:06 AM, Pierrick Bouvier wrote:
Using iommufd requires two different kernel config:
CONFIG_IOMMUFD and CONFIG_VFIO_DEVICE_CDEV
https://docs.kernel.org/driver-api/vfio.html#vfio-device-cdev

It can be complex to identify what is missing when trying to use it. This series
gives hints to user about it.

Suggested on:
https://lore.kernel.org/qemu-devel/[email protected]/

Tested using a cross compiled QEMU and a custom kernel + debian rootfs [1].

[1] https://github.com/p-b-o/qemu-linux-stack/tree/device_passthrough

v2
--

- Move /dev/iommu to iommufd_backend_complete, so we can report the error
   instead of aborting.

Pierrick Bouvier (2):
   backends/iommufd.c: report error when /dev/iommu is not available
   hw/vfio/iommufd.c: report hint to user when vfio-dev/vfio*/dev is
     missing

  backends/iommufd.c | 6 ++++++
  hw/vfio/iommufd.c  | 5 ++++-
  2 files changed, 10 insertions(+), 1 deletion(-)


sent v3:
https://lore.kernel.org/qemu-devel/[email protected]/T/#t

Regards,
Pierrick

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