[PATCH v4 0/2] Allow memory_region_register_iommu_notifier() to fail

[Eric Auger <eric.auger@redhat.com>]

This series allows the memory_region_register_iommu_notifier()
to fail. As of now, when a MAP notifier is attempted to be
registered along with SMMUv3 or AMD IOMMU, we exit in the IOMMU
MR notify_flag_changed() callback.

In case of VFIO assigned device hotplug, this could be handled
more nicely directly within the VFIO code, simply rejecting
the hotplug without exiting. This is what the series achieves
by handling the memory_region_register_iommu_notifier() returned
value and Error object.

To propagate errors collected during vfio_listener_region_add()
we now store the error handle inside the VFIO container instead
of a returned value.

The message now is:
(QEMU) device_add id=hot0 driver=vfio-pci host=0000:89:00.0 bus=pcie.1
{"error": {"class": "GenericError", "desc": "vfio 0000:89:00.0: failed
to setup container for group 2: memory listener initialization failed:
Region smmuv3-iommu-memory-region-0-6: device 01.00.0 requires iommu MAP
notifier which is not currently supported"}}

Best Regards

Eric

This series can be found at:
https://github.com/eauger/qemu/tree/v4.1.0_register_iommu_notifier_fail_v4

History:

v3 -> v4:
- added Peter's R-b on 2d patch
- 1st patch: restore hw_error, remove useless ret assignment, improve
  DMA host window error message, remove local mr variable

v2 -> v3:
- also pass an Error handle (suggested by Peter)

v1 -> v2:
- Intel IOMMU now handles the problem differently with machine init done
  notifier and machine hotplug allowed hook.
- use assert(!ret)
- message rewording in SMMUv3

Follow-up of "VFIO/SMMUv3: Fail on VFIO/HW nested paging detection"
https://patchew.org/QEMU/20190829090141.21821-1-eric.auger@redhat.com/


Eric Auger (2):
  vfio: Turn the container error into an Error handle
  memory: allow memory_region_register_iommu_notifier() to fail

 exec.c                        | 10 +++++--
 hw/arm/smmuv3.c               | 18 ++++++------
 hw/i386/amd_iommu.c           | 17 +++++++-----
 hw/i386/intel_iommu.c         |  8 ++++--
 hw/ppc/spapr_iommu.c          |  8 ++++--
 hw/vfio/common.c              | 52 +++++++++++++++++++++++------------
 hw/vfio/spapr.c               |  4 ++-
 hw/virtio/vhost.c             |  9 ++++--
 include/exec/memory.h         | 21 ++++++++++----
 include/hw/vfio/vfio-common.h |  2 +-
 memory.c                      | 31 +++++++++++++--------
 11 files changed, 120 insertions(+), 60 deletions(-)

-- 
2.20.1