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 means that system_wakeup is silently failing, which can be
considered a bug. Adding error handling isn't an API break in this
case - applications that didn't check the result will remain broken,
the ones that check it will have a chance to deal with it.
Adding to that, recent changes in query-target added a new flag called
wakeup-suspend-support that indicates if the guest has the capability
of waking up from suspended state. Although such guest will never
reach SUSPENDED state and erroring it out in this scenario would
suffice, it is more informative for the user to differentiate between a
failure because the guest isn't suspended versus a failure because the
guest does not have support for wake up at all.
All this considered, this patch changes qmp_system_wakeup to:
- check if the guest has the capability to wake-up from suspend. If
not, error out informing about the lack of support;
- 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.
After this patch, this is the output of system_wakeup in a guest that
does not have wake-up from suspend support (ppc64):
(qemu) system_wakeup
wake-up from suspend is not supported by this guest
(qemu)
And this is the output of system_wakeup in a x86 guest that has the
support but isn't suspended:
(qemu) system_wakeup
Unable to wake up: guest is not in suspended state
(qemu)
Reported-by: Balamuruhan S <bal...@linux.vnet.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danie...@linux.ibm.com>
---
hmp.c | 4 +++-
qapi/misc.json | 3 ++-
qmp.c | 10 ++++++++++
3 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/hmp.c b/hmp.c
index ef93f4878b..d177d14cc9 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/qapi/misc.json b/qapi/misc.json
index efba0449a6..73bfc3e436 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -1247,7 +1247,8 @@
#
# If the guest has wake-up from suspend support enabled
# (wakeup-suspend-support flag from query-target), wakeup guest from
-# suspend. Does nothing otherwise.
+# suspend if the guest is in SUSPENDED state. Returns an error
+# otherwise.
#
# Since: 1.1
#
diff --git a/qmp.c b/qmp.c
index 25fdc9a5b2..5366e963ad 100644
--- a/qmp.c
+++ b/qmp.c
@@ -205,6 +205,16 @@ void qmp_cont(Error **errp)
void qmp_system_wakeup(Error **errp)
{
+ if (!qemu_wakeup_suspend_support()) {
+ error_setg(errp,
+ "wake-up from suspend is not supported by this guest");
+ return;
+ }
+ 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
