[PATCH 4/6] vfio/migration: Change vfio_mig_active() semantics

[Avihai Horon]

vfio_mig_active() is used by migration_populate_vfio_info() to populate
VFIO migration info when it is active. Currently, VFIO migration is
considered active if there are VFIO devices and none of them has a
migration blocker.

Change that and consider VFIO migration to be active if there is a VFIO
device that is using VFIO migration, regardless of whether a device has
migration blocker or not.

This is done in preparation for next patches which will block VFIO
migration with postcopy migration or background snapshot, as they are
not compatible together. It will allow adding a migration blocker for
such cases even if the VFIO device already has a blocker.

Note that migration_populate_vfio_info() still behaves correctly, as if
there is a VFIO device with migration blocker, migration can't be
started and thus migration_populate_vfio_info() will never be called.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
---
 hw/vfio/common.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 57a76feab1..373f6e5932 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -342,25 +342,6 @@ static int vfio_bitmap_alloc(VFIOBitmap *vbmap, hwaddr 
size)
 static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
                                  uint64_t size, ram_addr_t ram_addr);
 
-bool vfio_mig_active(void)
-{
-    VFIOGroup *group;
-    VFIODevice *vbasedev;
-
-    if (QLIST_EMPTY(&vfio_group_list)) {
-        return false;
-    }
-
-    QLIST_FOREACH(group, &vfio_group_list, next) {
-        QLIST_FOREACH(vbasedev, &group->device_list, next) {
-            if (vbasedev->migration_blocker) {
-                return false;
-            }
-        }
-    }
-    return true;
-}
-
 static Error *multiple_devices_migration_blocker;
 
 static unsigned int vfio_migratable_devices_num(void)
@@ -446,6 +427,11 @@ void vfio_unblock_multiple_devices_migration(void)
     multiple_devices_migration_blocker = NULL;
 }
 
+bool vfio_mig_active(void)
+{
+    return vfio_migratable_devices_num();
+}
+
 bool vfio_viommu_preset(VFIODevice *vbasedev)
 {
     return vbasedev->group->container->space->as != &address_space_memory;
-- 
2.26.3