Merge tag 'pull-vfio-20231219' of https://github.com/legoater/qemu into staging

vfio queue:

* Introduce an IOMMU interface backend for VFIO devices
* Convert IOMMU type1 and sPAPR IOMMU to respective backends
* Introduce a new IOMMUFD backend for ARM, x86_64 and s390x platforms

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* tag 'pull-vfio-20231219' of https://github.com/legoater/qemu: (47 commits)
  hw/ppc/Kconfig: Imply VFIO_PCI
  docs/devel: Add VFIO iommufd backend documentation
  vfio: Introduce a helper function to initialize VFIODevice
  vfio/ccw: Move VFIODevice initializations in vfio_ccw_instance_init
  vfio/ap: Move VFIODevice initializations in vfio_ap_instance_init
  vfio/platform: Move VFIODevice initializations in vfio_platform_instance_init
  vfio/pci: Move VFIODevice initializations in vfio_instance_init
  hw/i386: Activate IOMMUFD for q35 machines
  kconfig: Activate IOMMUFD for s390x machines
  hw/arm: Activate IOMMUFD for virt machines
  vfio: Make VFIOContainerBase poiner parameter const in VFIOIOMMUOps callbacks
  vfio/ccw: Make vfio cdev pre-openable by passing a file handle
  vfio/ccw: Allow the selection of a given iommu backend
  vfio/ap: Make vfio cdev pre-openable by passing a file handle
  vfio/ap: Allow the selection of a given iommu backend
  vfio/platform: Make vfio cdev pre-openable by passing a file handle
  vfio/platform: Allow the selection of a given iommu backend
  vfio/pci: Make vfio cdev pre-openable by passing a file handle
  vfio/pci: Allow the selection of a given iommu backend
  vfio/iommufd: Enable pci hot reset through iommufd cdev interface
  ...

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/qemu-options.hx b/qemu-options.hx
index 42fd09e4de..5fe8ea57d2 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -5224,6 +5224,18 @@ SRST
 
         The ``share`` boolean option is on by default with memfd.
 
+    ``-object iommufd,id=id[,fd=fd]``
+        Creates an iommufd backend which allows control of DMA mapping
+        through the ``/dev/iommu`` device.
+
+        The ``id`` parameter is a unique ID which frontends (such as
+        vfio-pci of vdpa) will use to connect with the iommufd backend.
+
+        The ``fd`` parameter is an optional pre-opened file descriptor
+        resulting from ``/dev/iommu`` opening. Usually the iommufd is shared
+        across all subsystems, bringing the benefit of centralized
+        reference counting.
+
     ``-object rng-builtin,id=id``
         Creates a random number generator backend which obtains entropy
         from QEMU builtin functions. The ``id`` parameter is a unique ID