From: Alexey Kardashevskiy <aik@ozlabs.ru>

The vfio_iommu_spapr_tce driver advertises kernel's support for
v1 and v2 IOMMU support, however it is not always possible to use
the requested IOMMU type. For example, a pseries host platform does not
support dynamic DMA windows so v2 cannot initialize and QEMU fails to
start.

This adds a fallback to the v1 IOMMU if v2 cannot be used.

Fixes: 318f67ce1371 ("vfio: spapr: Add DMA memory preregistering (SPAPR IOMMU v2)")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 hw/vfio/common.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 216eec68ef68..b77be3a8b36b 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1043,6 +1043,11 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
             v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU;
         ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
         if (ret) {
+            container->iommu_type = VFIO_SPAPR_TCE_IOMMU;
+            v2 = false;
+            ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
+        }
+        if (ret) {
             error_setg_errno(errp, errno, "failed to set iommu for container");
             ret = -errno;
             goto free_container_exit;