[PATCH v2 5/6] qapi: device-sync-config: check runstate

[Vladimir Sementsov-Ogievskiy]

Command result is racy if allow it during migration. Let's allow the
sync only in RUNNING state.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
---
 include/sysemu/runstate.h |  1 +
 system/qdev-monitor.c     | 27 ++++++++++++++++++++++++++-
 system/runstate.c         |  5 +++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
index 0117d243c4..296af52322 100644
--- a/include/sysemu/runstate.h
+++ b/include/sysemu/runstate.h
@@ -5,6 +5,7 @@
 #include "qemu/notify.h"
 
 bool runstate_check(RunState state);
+const char *current_run_state_str(void);
 void runstate_set(RunState new_state);
 RunState runstate_get(void);
 bool runstate_is_running(void);
diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c
index e3107a12d7..b83b5d23c9 100644
--- a/system/qdev-monitor.c
+++ b/system/qdev-monitor.c
@@ -23,6 +23,7 @@
 #include "monitor/monitor.h"
 #include "monitor/qdev.h"
 #include "sysemu/arch_init.h"
+#include "sysemu/runstate.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-qdev.h"
 #include "qapi/qmp/dispatch.h"
@@ -983,7 +984,31 @@ int qdev_sync_config(DeviceState *dev, Error **errp)
 
 void qmp_device_sync_config(const char *id, Error **errp)
 {
-    DeviceState *dev = find_device_state(id, true, errp);
+    MigrationState *s = migrate_get_current();
+    DeviceState *dev;
+
+    /*
+     * During migration there is a race between syncing`config and migrating 
it,
+     * so let's just not allow it.
+     *
+     * Moreover, let's not rely on setting up interrupts in paused state, which
+     * may be a part of migration process.
+     */
+
+    if (migration_is_running(s->state)) {
+        error_setg(errp, "Config synchronization is not allowed "
+                   "during migration.");
+        return;
+    }
+
+    if (!runstate_is_running()) {
+        error_setg(errp, "Config synchronization allowed only in '%s' state, "
+                   "current state is '%s'", RunState_str(RUN_STATE_RUNNING),
+                   current_run_state_str());
+        return;
+    }
+
+    dev = find_device_state(id, true, errp);
     if (!dev) {
         return;
     }
diff --git a/system/runstate.c b/system/runstate.c
index d6ab860eca..8fd89172ae 100644
--- a/system/runstate.c
+++ b/system/runstate.c
@@ -189,6 +189,11 @@ bool runstate_check(RunState state)
     return current_run_state == state;
 }
 
+const char *current_run_state_str(void)
+{
+    return RunState_str(current_run_state);
+}
+
 static void runstate_init(void)
 {
     const RunStateTransition *p;
-- 
2.34.1