Hi Cédric, >-----Original Message----- >From: Cédric Le Goater <c...@redhat.com> >Subject: Re: [PATCH v6 22/22] docs/devel: Add IOMMUFD nesting >documentation > >Hello Zhenzhong > >On 9/18/25 10:58, Zhenzhong Duan wrote: >> 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 > >an new line lacks after code-block.
Thanks for pointing out, will fix, I forgot to make docs once again☹ BRs, Zhenzhong
