[Qemu-devel] [PATCH v2 1/1] qmp.c: system_wakeup: adding RUN_STATE_SUSPENDED check before proceeding

[Daniel Henrique Barboza]

The qmp/hmp command 'system_wakeup' is simply a direct call to
'qemu_system_wakeup_request' from vl.c. This function verifies if
runstate is SUSPENDED and if the wake up reason is valid before
proceeding.

However, no error or warning is thrown if any of those
pre-requirements isn't met. There is no way for the caller to
differentiate between a successful wakeup or an error state caused
when trying to wake up a guest that wasn't suspended.

This patch changes qmp_system_wakeup to make the runstate verification
before proceeding to call qemu_system_wakeup_request, firing up
an error message if the user tries to wake up a machine that
isn't in SUSPENDED state. The change isn't made inside
qemu_system_wakeup_request because it is used in migration,
ACPI and others where this usage might be valid.

Signed-off-by: Daniel Henrique Barboza <address@hidden>
CC: Markus Armbruster <address@hidden>
CC: Dr. David Alan Gilbert <address@hidden>
CC: Eric Blake <address@hidden>
---

This is a v2 of a patch that got buried:

http://lists.gnu.org/archive/html/qemu-devel/2018-01/msg00092.html

The changes in this version was all in the wording of the commit,
reflecting the understanding reached in that discusssion: silent
failure should be interpreted as a bug and there is no API break
in fixing this behavior - applications that didn't check the result
will remain broken, the ones that check will have a chance to deal
with it.


 hmp.c | 4 +++-
 qmp.c | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/hmp.c b/hmp.c
index 898e25f3e1..2c4c867cab 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1156,7 +1156,9 @@ void hmp_cont(Monitor *mon, const QDict *qdict)
 
 void hmp_system_wakeup(Monitor *mon, const QDict *qdict)
 {
-    qmp_system_wakeup(NULL);
+    Error *err = NULL;
+    qmp_system_wakeup(&err);
+    hmp_handle_error(mon, &err);
 }
 
 void hmp_nmi(Monitor *mon, const QDict *qdict)
diff --git a/qmp.c b/qmp.c
index 25fdc9a5b2..9c1d0df1ab 100644
--- a/qmp.c
+++ b/qmp.c
@@ -205,6 +205,11 @@ void qmp_cont(Error **errp)
 
 void qmp_system_wakeup(Error **errp)
 {
+    if (!runstate_check(RUN_STATE_SUSPENDED)) {
+        error_setg(errp,
+                   "Unable to wake up: guest is not in suspended state");
+        return;
+    }
     qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
 }
 
-- 
2.14.3