Hi Eric, All done for suggestions on this patch and patch21.
Thanks Zhenzhong >-----Original Message----- >From: Eric Auger <[email protected]> >Subject: Re: [PATCH v7 23/23] docs/devel: Add IOMMUFD nesting >documentation > >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
