Re: [PATCH for-9.0 v2 00/10] vfio: Introduce a VFIOIOMMUClass

["Cédric Le Goater" <clg@redhat.com>]

On 12/19/23 07:58, Cédric Le Goater wrote:
> Hello,
> 
> The VFIO object hierarchy has some constraints because each VFIO type
> has a dual nature: a VFIO nature for passthrough support and a bus
> nature (PCI, AP, CCW, Platform) for its initial presentation. It
> seemed the best approach made because multi-inheritance is not
> feasible with QOM and both aspect of the VFIO object, passthrough and
> bus, require state. A QOM interface in that case is not sufficient.
> 
> One aspect of passthrough is interaction with the IOMMU. IOMMUFD
> support was recently added and for this purpose, we introduced an
> IOMMU backend framework simply based on a VFIOIOMMUOps struct. We
> didn't want to use QOM again because it would have exposed the various
> lowlevel backend objects to the QEMU machine and human interface which
> felt unnecessary at the time.
> 
> The changes of this series introduce a VFIO_IOMMU QOM interface and
> its VFIOIOMMUClass to replace the current VFIOIOMMUOps. This provides
> better code abstraction for the type1 and sPAPR IOMMU backends and
> allows us to improve the vfio_connect_container() implementation.
> Also, QOM interfaces are not exposed at the QEMU interface level. Most
> important, we can now avoid compiling the sPAPR IOMMU support on
> targets not needing it. This saves some text in QEMU.


Applied to vfio-next.

Thanks,

C.