quoted

this to set the VIRTIO_F_IOMMU_PLATFORM flag. But for example
QEMU has the use of iommu_platform attribute disabled for virtio-gpu
device.  So would also like to move towards not having to specify
the VIRTIO_F_IOMMU_PLATFORM flag.

Specifying VIRTIO_F_IOMMU_PLATFORM is the right thing for your 
platform given that you can't directly use physical addresses.
Please fix qemu so that virtio-gpu works with VIRTIO_F_IOMMU_PLATFORM.

This needs both host and guest side changes btw.

Guest side patch is in drm-misc (a3b815f09bb8) and should land in the
next merge window.

Host side patches are here:
  https://git.kraxel.org/cgit/qemu/log/?h=sirius/virtio-gpu-iommu

Should also land in the next qemu version.

cheers,
  Gerd