migration: Add blocker information

Modify query-migrate so that it has a flag indicating if outbound
migration is blocked, and if it is a list of reasons.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20210202135522.127380-2-dgilbert@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

3 files changed, 37 insertions, 2 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 38efaee..a5ddf43 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -174,6 +174,8 @@ INITIALIZE_MIGRATE_CAPS_SET(check_caps_background_snapshot,
 static MigrationState *current_migration;
 static MigrationIncomingState *current_incoming;
 
+static GSList *migration_blockers;
+
 static bool migration_object_check(MigrationState *ms, Error **errp);
 static int migration_maybe_pause(MigrationState *s,
                                  int *current_active_state,
@@ -1074,6 +1076,27 @@ static void fill_source_migration_info(MigrationInfo *info)
 {
     MigrationState *s = migrate_get_current();
 
+    info->blocked = migration_is_blocked(NULL);
+    info->has_blocked_reasons = info->blocked;
+    info->blocked_reasons = NULL;
+    if (info->blocked) {
+        GSList *cur_blocker = migration_blockers;
+
+        /*
+         * There are two types of reasons a migration might be blocked;
+         * a) devices marked in VMState as non-migratable, and
+         * b) Explicit migration blockers
+         * We need to add both of them here.
+         */
+        qemu_savevm_non_migratable_list(&info->blocked_reasons);
+
+        while (cur_blocker) {
+            QAPI_LIST_PREPEND(info->blocked_reasons,
+                              g_strdup(error_get_pretty(cur_blocker->data)));
+            cur_blocker = g_slist_next(cur_blocker);
+        }
+    }
+
     switch (s->state) {
     case MIGRATION_STATUS_NONE:
         /* no migration has happened ever */
@@ -2025,8 +2048,6 @@ void migrate_init(MigrationState *s)
     s->threshold_size = 0;
 }
 
-static GSList *migration_blockers;
-
 int migrate_add_blocker(Error *reason, Error **errp)
 {
     if (only_migratable) {
diff --git a/migration/savevm.c b/migration/savevm.c
index d5bf533..1178c6c 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1154,6 +1154,19 @@ bool qemu_savevm_state_blocked(Error **errp)
     return false;
 }
 
+void qemu_savevm_non_migratable_list(strList **reasons)
+{
+    SaveStateEntry *se;
+
+    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+        if (se->vmsd && se->vmsd->unmigratable) {
+            QAPI_LIST_PREPEND(*reasons,
+                              g_strdup_printf("non-migratable device: %s",
+                                              se->idstr));
+        }
+    }
+}
+
 void qemu_savevm_state_header(QEMUFile *f)
 {
     trace_savevm_state_header();
diff --git a/migration/savevm.h b/migration/savevm.h
index aaee252..6461342 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -30,6 +30,7 @@
 #define QEMU_VM_SECTION_FOOTER       0x7e
 
 bool qemu_savevm_state_blocked(Error **errp);
+void qemu_savevm_non_migratable_list(strList **reasons);
 void qemu_savevm_state_setup(QEMUFile *f);
 bool qemu_savevm_state_guest_unplug_pending(void);
 int qemu_savevm_state_resume_prepare(MigrationState *s);