[PATCH 4/5] qdev: Make qdev_get_machine() not use container_get()

[Peter Xu <peterx@redhat.com>]

Currently, qdev_get_machine() has a slightly misuse of container_get(), as
the helper says "get a container" but in reality the goal is to get the
machine object.

Note that it _may_ get a container (at "/machine") in our current unit test
of test-qdev-global-props.c, but it's probably unexpected and worked by
accident..

Switch to an explicit object_resolve_path_component(), with a side benefit
that qdev_get_machine() can happen a lot, and we don't need to split the
string ("/machine") every time.  This also paves way for making the helper
container_get() never try to return a non-container at all.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 hw/core/qdev.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index eff297e584..e828088c58 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -825,7 +825,13 @@ Object *qdev_get_machine(void)
     static Object *dev;
 
     if (dev == NULL) {
-        dev = container_get(object_get_root(), "/machine");
+        /*
+         * NOTE: when the machine is not yet created, this helper will
+         * also keep the cached object untouched and return NULL.  The next
+         * invoke of the helper will try to look for the machine again.
+         * It'll only cache the pointer when it's found the first time.
+         */
+        dev = object_resolve_path_component(object_get_root(), "machine");
     }
 
     return dev;
-- 
2.45.0