This only checks the DEVICE stage, which is a very special stage, and only
checked together with ACTIVE+POSTCOPY_ACTIVE.

It's debatable why this needs a separate helper just to be exported.
Theoretically speaking, DEVICE stage is also part of ACTIVE stage, where
we're reaching the switchover phase but waiting for some external
operation, during which VM stopped but migration is definitely active.

Report DEVICE as active too, then we can drop migration_is_device().

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/migration/misc.h |  1 -
 hw/vfio/common.c         |  2 +-
 migration/migration.c    | 19 +++++++++----------
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/include/migration/misc.h b/include/migration/misc.h
index 804eb23c06..ad1e25826a 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -54,7 +54,6 @@ void migration_object_init(void);
 void migration_shutdown(void);
 
 bool migration_is_active(void);
-bool migration_is_device(void);
 bool migration_is_running(void);
 bool migration_thread_is_self(void);
 
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index dcef44fe55..cc72282c71 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -174,7 +174,7 @@ static bool vfio_devices_all_dirty_tracking(VFIOContainerBase *bcontainer)
 {
     VFIODevice *vbasedev;
 
-    if (!migration_is_active() && !migration_is_device()) {
+    if (!migration_is_active()) {
         return false;
     }
 
diff --git a/migration/migration.c b/migration/migration.c
index f86c709699..127b01734d 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1638,17 +1638,16 @@ bool migration_in_bg_snapshot(void)
 
 bool migration_is_active(void)
 {
-    MigrationState *s = current_migration;
-
-    return (s->state == MIGRATION_STATUS_ACTIVE ||
-            s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
-}
+    MigrationStatus state = current_migration->state;
 
-bool migration_is_device(void)
-{
-    MigrationState *s = current_migration;
-
-    return s->state == MIGRATION_STATUS_DEVICE;
+    switch (state) {
+    case MIGRATION_STATUS_ACTIVE:
+    case MIGRATION_STATUS_POSTCOPY_ACTIVE:
+    case MIGRATION_STATUS_DEVICE:
+        return true;
+    default:
+        return false;
+    }
 }
 
 bool migration_thread_is_self(void)
-- 
2.45.0