[Qemu-ppc] Proper usage of the SPAPR vIOMMU with VFIO?

[Shawn Anastasio]

Hello all,

I'm attempting to write a VFIO driver for QEMU's ivshmem shared memory
device on a ppc64 guest. Unfortunately, without using VFIO's unsafe
No-IOMMU mode, I'm unable to properly interface with the device.

When booting the guest with the iommu=on kernel parameter, the ivshmem
device can be binded to the vfio_pci kernel module and a group at
/dev/vfio/0 appears. When opening the group and checking its flags
with VFIO_GROUP_GET_STATUS, though, VFIO_GROUP_FLAGS_VIABLE is not
set. Ignoring this and attempting to set the VFIO container's IOMMU
mode to VFIO_SPAPR_TCE_v2_IOMMU fails with EPERM, though I'm not
sure if that's related.

Can anybody familiar with the SPAPR vIOMMU chime in here?
I have attached the C99 code I'm using to try to access the device.

Thanks in advance,
Shawn

vfio_spapr_test.c
Description: Text Data