Zhenzhong, On 10/24/25 10:43 AM, Zhenzhong Duan wrote: > Add documentation about using IOMMUFD backed VFIO device with intel_iommu with > x-flts=on. > > Suggested-by: Yi Liu <[email protected]> > Signed-off-by: Zhenzhong Duan <[email protected]> > --- > docs/devel/vfio-iommufd.rst | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/docs/devel/vfio-iommufd.rst b/docs/devel/vfio-iommufd.rst > index 3d1c11f175..f1e4d940e6 100644 > --- a/docs/devel/vfio-iommufd.rst > +++ b/docs/devel/vfio-iommufd.rst > @@ -164,3 +164,28 @@ 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 s/with/featuring to void repetition? > +------------------------------------- > + > +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: s/or else/otherwise > + > +.. 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 s/under PCI bridge/downstream to a PCI bridge may have been better I think > + > +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 Besides Reviewed-by: Eric Auger <[email protected]>
Eric
