vfio/migration: Block migration with vIOMMU

Migrating with vIOMMU will require either tracking maximum
IOMMU supported address space (e.g. 39/48 address width on Intel)
or range-track current mappings and dirty track the new ones
post starting dirty tracking. This will be done as a separate
series, so add a live migration blocker until that is fixed.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20230307125450.62409-14-joao.m.martins@oracle.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

hw/vfio/common.c

@@ -362,6 +362,7 @@ bool vfio_mig_active(void)
 }
 
 static Error *multiple_devices_migration_blocker;
+static Error *giommu_migration_blocker;
 
 static unsigned int vfio_migratable_device_num(void)
 {
@@ -413,6 +414,51 @@ void vfio_unblock_multiple_devices_migration(void)
     multiple_devices_migration_blocker = NULL;
 }
 
+static bool vfio_viommu_preset(void)
+{
+    VFIOAddressSpace *space;
+
+    QLIST_FOREACH(space, &vfio_address_spaces, list) {
+        if (space->as != &address_space_memory) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+int vfio_block_giommu_migration(Error **errp)
+{
+    int ret;
+
+    if (giommu_migration_blocker ||
+        !vfio_viommu_preset()) {
+        return 0;
+    }
+
+    error_setg(&giommu_migration_blocker,
+               "Migration is currently not supported with vIOMMU enabled");
+    ret = migrate_add_blocker(giommu_migration_blocker, errp);
+    if (ret < 0) {
+        error_free(giommu_migration_blocker);
+        giommu_migration_blocker = NULL;
+    }
+
+    return ret;
+}
+
+void vfio_unblock_giommu_migration(void)
+{
+    if (!giommu_migration_blocker ||
+        vfio_viommu_preset()) {
+        return;
+    }
+
+    migrate_del_blocker(giommu_migration_blocker);
+    error_free(giommu_migration_blocker);
+    giommu_migration_blocker = NULL;
+}
+
 static void vfio_set_migration_error(int err)
 {
     MigrationState *ms = migrate_get_current();

hw/vfio/migration.c

@@ -634,6 +634,11 @@ int vfio_migration_probe(VFIODevice *vbasedev, Error **errp)
         return ret;
     }
 
+    ret = vfio_block_giommu_migration(errp);
+    if (ret) {
+        return ret;
+    }
+
     trace_vfio_migration_probe(vbasedev->name);
     return 0;
 

hw/vfio/pci.c

@@ -3185,6 +3185,7 @@ static void vfio_instance_finalize(Object *obj)
      */
     vfio_put_device(vdev);
     vfio_put_group(group);
+    vfio_unblock_giommu_migration();
 }
 
 static void vfio_exitfn(PCIDevice *pdev)

include/hw/vfio/vfio-common.h

@@ -222,6 +222,8 @@ extern VFIOGroupList vfio_group_list;
 bool vfio_mig_active(void);
 int vfio_block_multiple_devices_migration(Error **errp);
 void vfio_unblock_multiple_devices_migration(void);
+int vfio_block_giommu_migration(Error **errp);
+void vfio_unblock_giommu_migration(void);
 int64_t vfio_mig_bytes_transferred(void);
 
 #ifdef CONFIG_LINUX