[v1] qmp.c: system_wakeup: adding RUN_STATE_SUSPENDED check before proceeding

Commit Message

Daniel Henrique Barboza Dec. 1, 2017, 5:14 p.m. UTC

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.

This leads to situations such as the one described in
https://github.com/open-power-host-os/qemu/issues/31, where one
can induce the OS to be suspended by using pm-suspend (via
dompmsuspend, for example) but for some reason the machine failed to
go to the SUSPENDED runstate, staying at runstate RUNNING. The user
then tries to wake up the guest using system_wakeup (or dompmwakeup),
no error is thrown but nothing happened either because the wake up
wasn't fired at all. In the end, the user is left with a guest that
is dormant and believing that system_wakeup isn't working.

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. This patch
by no means fixes the situation described above, but it can direct
the user/management closer to the real problem.

Signed-off-by: Daniel Henrique Barboza <[e-mail]>
CC: Markus Armbruster <[e-mail]>
CC: Dr. David Alan Gilbert <[e-mail]>
---
 hmp.c | 4 +++-
 qmp.c | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)

Patch

diff --git a/hmp.c b/hmp.c
index 35a7041824..2c2326a00e 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1158,7 +1158,9 @@  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 e8c303116a..9b8f99f225 100644
--- a/qmp.c
+++ b/qmp.c
@@ -206,6 +206,11 @@  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);
 }