Add documentation about using IOMMUFD backed VFIO device with intel_iommu with x-flts=on.
Suggested-by: Yi Liu <yi.l....@intel.com> Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com> --- docs/devel/vfio-iommufd.rst | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/docs/devel/vfio-iommufd.rst b/docs/devel/vfio-iommufd.rst index 3d1c11f175..d9cb9e7f5e 100644 --- a/docs/devel/vfio-iommufd.rst +++ b/docs/devel/vfio-iommufd.rst @@ -164,3 +164,27 @@ RAM discarding for mdev. ``vfio-ap`` and ``vfio-ccw`` devices don't have same issue as their backend devices are always mdev and RAM discarding is force enabled. + +Usage with intel_iommu with x-flts=on +------------------------------------- + +Only IOMMUFD backed VFIO device is supported when intel_iommu is configured +with x-flts=on, for legacy container backed VFIO device, below error shows: + +.. code-block:: none + + qemu-system-x86_64: -device vfio-pci,host=0000:02:00.0: vfio 0000:02:00.0: Failed to set vIOMMU: Need IOMMUFD backend when x-flts=on + +VFIO device under PCI bridge is unsupported, use PCIE bridge if necessary, +or else below error shows: + +.. code-block:: none + + qemu-system-x86_64: -device vfio-pci,host=0000:02:00.0,bus=bridge1,iommufd=iommufd0: vfio 0000:02:00.0: Failed to set vIOMMU: Host device under PCI bridge is unsupported when x-flts=on + +If host IOMMU has ERRATA_772415_SPR17, kexec or reboot from "intel_iommu=on,sm_on" +to "intel_iommu=on,sm_off" in guest is also unsupported. Configure scalable mode +off as below if it's not needed by guest. + +.. code-block:: bash + -device intel-iommu,x-scalable-mode=off -- 2.47.1
