[PATCH v4 15/15] vfio/common: Block migration with vIOMMUs without address width limits

[Joao Martins]

Only block the case when the underlying vIOMMU model does not report any
address space limits, in addition to DMA translation being off or no
vIOMMU present. The limits are needed such that can define the IOVA limits
that arm the device dirty tracker.

Additionally, reword the migration blocker error message to clarify that
we the configured vIOMMU does not support migration, as opposed to
implying that just being there blocks migration.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 hw/vfio/common.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 62f91e8e102d..c3cc0dd47044 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -449,15 +449,18 @@ static int vfio_viommu_get_max_iova(hwaddr *max_iova)
 
 int vfio_block_giommu_migration(Error **errp)
 {
+    hwaddr max;
     int ret;
 
     if (giommu_migration_blocker ||
-        !vfio_viommu_preset()) {
+        !vfio_viommu_preset() ||
+        (vfio_viommu_preset() && !vfio_viommu_get_max_iova(&max))) {
         return 0;
     }
 
     error_setg(&giommu_migration_blocker,
-               "Migration is currently not supported with vIOMMU enabled");
+               "Migration with vIOMMU is currently not supported "
+               "without vIOMMU address space boundaries");
     ret = migrate_add_blocker(giommu_migration_blocker, errp);
     if (ret < 0) {
         error_free(giommu_migration_blocker);
-- 
2.17.2