util/main-loop: Introduce the main loop into QOM

'event-loop-base' provides basic property handling for all 'AioContext'
based event loops. So let's define a new 'MainLoopClass' that inherits
from it. This will permit tweaking the main loop's properties through
qapi as well as through the command line using the '-object' keyword[1].
Only one instance of 'MainLoopClass' might be created at any time.

'EventLoopBaseClass' learns a new callback, 'can_be_deleted()' so as to
mark 'MainLoop' as non-deletable.

[1] For example:
      -object main-loop,id=main-loop,aio-max-batch=<value>

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20220425075723.20019-3-nsaenzju@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index 89bd9ed..5518845 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -26,9 +26,19 @@
 #define QEMU_MAIN_LOOP_H
 
 #include "block/aio.h"
+#include "qom/object.h"
+#include "sysemu/event-loop-base.h"
 
 #define SIG_IPI SIGUSR1
 
+#define TYPE_MAIN_LOOP  "main-loop"
+OBJECT_DECLARE_TYPE(MainLoop, MainLoopClass, MAIN_LOOP)
+
+struct MainLoop {
+    EventLoopBase parent_obj;
+};
+typedef struct MainLoop MainLoop;
+
 /**
  * qemu_init_main_loop: Set up the process so that it can run the main loop.
  *
diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
index 8e77d8b..fced4c9 100644
--- a/include/sysemu/event-loop-base.h
+++ b/include/sysemu/event-loop-base.h
@@ -25,6 +25,7 @@ struct EventLoopBaseClass {
 
     void (*init)(EventLoopBase *base, Error **errp);
     void (*update_params)(EventLoopBase *base, Error **errp);
+    bool (*can_be_deleted)(EventLoopBase *base);
 };
 
 struct EventLoopBase {