softmmu/runstate: add a way to detect force shutdowns

This can be useful for devices that might take too long to shut down
gracefully, but may have a way to shutdown quickly otherwise if needed
or explicitly requested by a force shutdown.

For now we only consider SIGTERM or the QMP quit() command a force
shutdown, since those bypass the guest entirely and are equivalent to
pulling the power plug.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Message-Id: <20250609212547.2859224-2-d-tatianin@yandex-team.ru>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/system/runstate.h

@@ -107,6 +107,7 @@ void qemu_system_vmstop_request(RunState reason);
 void qemu_system_vmstop_request_prepare(void);
 bool qemu_vmstop_requested(RunState *r);
 ShutdownCause qemu_shutdown_requested_get(void);
+bool qemu_force_shutdown_requested(void);
 ShutdownCause qemu_reset_requested_get(void);
 void qemu_system_killed(int signal, pid_t pid);
 void qemu_system_reset(ShutdownCause reason);

system/runstate.c

@@ -437,6 +437,7 @@ static ShutdownCause reset_requested;
 static ShutdownCause shutdown_requested;
 static int shutdown_exit_code = EXIT_SUCCESS;
 static int shutdown_signal;
+static bool force_shutdown;
 static pid_t shutdown_pid;
 static int powerdown_requested;
 static int debug_requested;
@@ -457,6 +458,11 @@ ShutdownCause qemu_shutdown_requested_get(void)
     return shutdown_requested;
 }
 
+bool qemu_force_shutdown_requested(void)
+{
+    return force_shutdown;
+}
+
 ShutdownCause qemu_reset_requested_get(void)
 {
     return reset_requested;
@@ -805,6 +811,7 @@ void qemu_system_killed(int signal, pid_t pid)
      * we are in a signal handler.
      */
     shutdown_requested = SHUTDOWN_CAUSE_HOST_SIGNAL;
+    force_shutdown = true;
     qemu_notify_event();
 }
 
@@ -820,6 +827,9 @@ void qemu_system_shutdown_request(ShutdownCause reason)
     trace_qemu_system_shutdown_request(reason);
     replay_shutdown_request(reason);
     shutdown_requested = reason;
+    if (reason == SHUTDOWN_CAUSE_HOST_QMP_QUIT) {
+        force_shutdown = true;
+    }
     qemu_notify_event();
 }