qemu: make sure agent returns error when required data are missing

Commit 5b3492fa aimed to fix this and caught one error but exposed
another one.  When agent command is being executed and the thread
waiting for the reply is woken up by an event (e.g. EOF in case of
shutdown), the command finishes with no data (rxObject == NULL), but
no error is reported, since this might be desired by the caller
(e.g. suspend through agent).  However, in other situations, when the
data are required (e.g. getting vCPUs), we proceed to getting desired
data out of the reply, but none of the virJSON*() functions works well
with NULLs.  I chose the way of a new parameter for qemuAgentCommand()
function that specifies whether reply is required and behaves
according to that.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1058149Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>
(cherry picked from commit 736e017e)

src/qemu/qemu_agent.c

@@ -1076,6 +1076,7 @@ static int
 qemuAgentCommand(qemuAgentPtr mon,
                  virJSONValuePtr cmd,
                  virJSONValuePtr *reply,
+                 bool needReply,
                  int seconds)
 {
     int ret = -1;
@@ -1107,7 +1108,7 @@ qemuAgentCommand(qemuAgentPtr mon,
         /* If we haven't obtained any reply but we wait for an
          * event, then don't report this as error */
         if (!msg.rxObject) {
-            if (await_event) {
+            if (await_event && !needReply) {
                 VIR_DEBUG("Woken up by event %d", await_event);
             } else {
                 virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -1271,7 +1272,7 @@ int qemuAgentShutdown(qemuAgentPtr mon,
         mon->await_event = QEMU_AGENT_EVENT_RESET;
     else
         mon->await_event = QEMU_AGENT_EVENT_SHUTDOWN;
-    ret = qemuAgentCommand(mon, cmd, &reply,
+    ret = qemuAgentCommand(mon, cmd, &reply, false,
                            VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK);
 
     virJSONValueFree(cmd);
@@ -1301,7 +1302,7 @@ int qemuAgentFSFreeze(qemuAgentPtr mon)
     if (!cmd)
         return -1;
 
-    if (qemuAgentCommand(mon, cmd, &reply,
+    if (qemuAgentCommand(mon, cmd, &reply, true,
                          VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK) < 0)
         goto cleanup;
 
@@ -1338,7 +1339,7 @@ int qemuAgentFSThaw(qemuAgentPtr mon)
     if (!cmd)
         return -1;
 
-    if (qemuAgentCommand(mon, cmd, &reply,
+    if (qemuAgentCommand(mon, cmd, &reply, true,
                          VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK) < 0)
         goto cleanup;
 
@@ -1375,7 +1376,7 @@ qemuAgentSuspend(qemuAgentPtr mon,
         return -1;
 
     mon->await_event = QEMU_AGENT_EVENT_SUSPEND;
-    ret = qemuAgentCommand(mon, cmd, &reply,
+    ret = qemuAgentCommand(mon, cmd, &reply, false,
                            VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK);
 
     virJSONValueFree(cmd);
@@ -1405,7 +1406,7 @@ qemuAgentArbitraryCommand(qemuAgentPtr mon,
     if (!(cmd = virJSONValueFromString(cmd_str)))
         goto cleanup;
 
-    if ((ret = qemuAgentCommand(mon, cmd, &reply, timeout)) < 0)
+    if ((ret = qemuAgentCommand(mon, cmd, &reply, true, timeout)) < 0)
         goto cleanup;
 
     if (!(*result = virJSONValueToString(reply, false)))
@@ -1432,7 +1433,7 @@ qemuAgentFSTrim(qemuAgentPtr mon,
     if (!cmd)
         return ret;
 
-    ret = qemuAgentCommand(mon, cmd, &reply,
+    ret = qemuAgentCommand(mon, cmd, &reply, false,
                            VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK);
 
     virJSONValueFree(cmd);
@@ -1454,7 +1455,7 @@ qemuAgentGetVCPUs(qemuAgentPtr mon,
     if (!(cmd = qemuAgentMakeCommand("guest-get-vcpus", NULL)))
         return -1;
 
-    if (qemuAgentCommand(mon, cmd, &reply,
+    if (qemuAgentCommand(mon, cmd, &reply, true,
                          VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK) < 0)
         goto cleanup;
 
@@ -1562,7 +1563,7 @@ qemuAgentSetVCPUs(qemuAgentPtr mon,
 
     cpus = NULL;
 
-    if (qemuAgentCommand(mon, cmd, &reply,
+    if (qemuAgentCommand(mon, cmd, &reply, true,
                          VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK) < 0)
         goto cleanup;