migration: Add 'pause-before-switchover' capability

When 'pause-before-switchover' is enabled, the outgoing migration
will pause before invalidating the block devices and serializing
the device state.
At this point the management layer gets the chance to clean up any
device jobs or other device users before the migration completes.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 3feffb5e26..c041ec7aed 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1511,6 +1511,16 @@ bool migrate_use_multifd(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_X_MULTIFD];
 }
 
+bool migrate_pause_before_switchover(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[
+        MIGRATION_CAPABILITY_PAUSE_BEFORE_SWITCHOVER];
+}
+
 int migrate_multifd_channels(void)
 {
     MigrationState *s;
diff --git a/migration/migration.h b/migration/migration.h
index b83cceadc4..969866303e 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -177,6 +177,7 @@ bool migrate_zero_blocks(void);
 
 bool migrate_auto_converge(void);
 bool migrate_use_multifd(void);
+bool migrate_pause_before_switchover(void);
 int migrate_multifd_channels(void);
 int migrate_multifd_page_count(void);