[PATCH v3 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 being present. The limits are needed such that can define the IOVA
limits to 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 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5b211380306a..b0cf86559032 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -474,15 +474,17 @@ 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 is currently not supported with the configured 
vIOMMU");
     ret = migrate_add_blocker(giommu_migration_blocker, errp);
     if (ret < 0) {
         error_free(giommu_migration_blocker);
-- 
2.39.3