Brett Neumeier schrob:
> 2. patch QEMU to add a signal handler so that it will gracefully
> shutdown when it receives a specific signal (and then tell s6 to use
> that signal to take the service down); or

A patch to do that has been available since 2017 at least, but the qemu
developers apparently can't agree to any signal to use. See
https://patchwork.kernel.org/project/qemu-devel/patch/23d89ab3bd16ebf7a864ab75c300de7b@whitewinterwolf.com/
and https://gitlab.com/qemu-project/qemu/-/issues/148 .

Here's a current version with SIGPWR.

HTH,
    Jan

diff --git a/os-posix.c b/os-posix.c
index 43f9a43f3..55fb3999a 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -64,6 +64,9 @@ void os_setup_signal_handling(void)
     sigaction(SIGINT,  &act, NULL);
     sigaction(SIGHUP,  &act, NULL);
     sigaction(SIGTERM, &act, NULL);
+#ifdef SIGPWR
+    sigaction(SIGPWR, &act, NULL);
+#endif
 }
 
 void os_set_proc_name(const char *s)
diff --git a/system/runstate.c b/system/runstate.c
index c833316f6..a75c10aa6 100644
--- a/system/runstate.c
+++ b/system/runstate.c
@@ -680,8 +680,18 @@ void qemu_system_killed(int signal, pid_t pid)
     /* Cannot call qemu_system_shutdown_request directly because
      * we are in a signal handler.
      */
-    shutdown_requested = SHUTDOWN_CAUSE_HOST_SIGNAL;
-    qemu_notify_event();
+#ifdef SIGPWR
+    if (signal==SIGPWR)
+    {
+       powerdown_requested = 1;
+       qemu_notify_event();
+    }
+    else
+#endif
+    {
+       shutdown_requested = SHUTDOWN_CAUSE_HOST_SIGNAL;
+       qemu_notify_event();
+    }
 }
 
 void qemu_system_shutdown_request_with_code(ShutdownCause reason,