vfio/migration: Change vIOMMU blocker from global to per device

Contrary to multiple device blocker which needs to consider already-attached
devices to unblock/block dynamically, the vIOMMU migration blocker is a device
specific config. Meaning it only needs to know whether the device is bypassing
or not the vIOMMU (via machine property, or per pxb-pcie::bypass_iommu), and
does not need the state of currently present devices. For this reason, the
vIOMMU global migration blocker can be consolidated into the per-device
migration blocker, allowing us to remove some unnecessary code.

This change also makes vfio_mig_active() more accurate as it doesn't check for
global blocker.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/common.c

@@ -362,7 +362,6 @@ bool vfio_mig_active(void)
 }
 
 static Error *multiple_devices_migration_blocker;
-static Error *giommu_migration_blocker;
 
 static unsigned int vfio_migratable_device_num(void)
 {
@@ -420,55 +419,9 @@ void vfio_unblock_multiple_devices_migration(void)
     multiple_devices_migration_blocker = NULL;
 }
 
-static bool vfio_viommu_preset(void)
+bool vfio_viommu_preset(VFIODevice *vbasedev)
 {
-    VFIOAddressSpace *space;
+    return vbasedev->group->container->space->as != &address_space_memory;
-
-    QLIST_FOREACH(space, &vfio_address_spaces, list) {
-        if (space->as != &address_space_memory) {
-            return true;
-        }
-    }
-
-    return false;
-}
-
-int vfio_block_giommu_migration(VFIODevice *vbasedev, Error **errp)
-{
-    int ret;
-
-    if (giommu_migration_blocker ||
-        !vfio_viommu_preset()) {
-        return 0;
-    }
-
-    if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
-        error_setg(errp,
-                   "Migration is currently not supported with vIOMMU enabled");
-        return -EINVAL;
-    }
-
-    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_migration_finalize(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)

hw/vfio/migration.c

@@ -878,9 +878,10 @@ int vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
         return ret;
     }
 
-    ret = vfio_block_giommu_migration(vbasedev, errp);
+    if (vfio_viommu_preset(vbasedev)) {
-    if (ret) {
+        error_setg(&err, "%s: Migration is currently not supported "
-        return ret;
+                   "with vIOMMU enabled", vbasedev->name);
+        return vfio_block_migration(vbasedev, err, errp);
     }
 
     trace_vfio_migration_realize(vbasedev->name);

hw/vfio/pci.c

@@ -3255,7 +3255,6 @@ static void vfio_instance_finalize(Object *obj)
      */
     vfio_put_device(vdev);
     vfio_put_group(group);
-    vfio_migration_finalize();
 }
 
 static void vfio_exitfn(PCIDevice *pdev)

include/hw/vfio/vfio-common.h

@@ -227,7 +227,7 @@ extern VFIOGroupList vfio_group_list;
 bool vfio_mig_active(void);
 int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp);
 void vfio_unblock_multiple_devices_migration(void);
-int vfio_block_giommu_migration(VFIODevice *vbasedev, Error **errp);
+bool vfio_viommu_preset(VFIODevice *vbasedev);
 int64_t vfio_mig_bytes_transferred(void);
 void vfio_reset_bytes_transferred(void);
 
@@ -254,6 +254,5 @@ int vfio_spapr_remove_window(VFIOContainer *container,
 
 int vfio_migration_realize(VFIODevice *vbasedev, Error **errp);
 void vfio_migration_exit(VFIODevice *vbasedev);
-void vfio_migration_finalize(void);
 
 #endif /* HW_VFIO_VFIO_COMMON_H */