qemu: agent: handle agent connection errors in one place

qemuConnectAgent return -1 or -2 in case of different errors.
A. -1 is a case of unsuccessuful connection to guest agent.
B. -2 is a case of destoyed domain during connection attempt.

All qemuConnectAgent callers handle the first error the same way
so let's move this logic into qemuConnectAgent itself. Patched
function returns 0 in case A and -1 in case B.

src/qemu/qemu_driver.c

@@ -4409,7 +4409,6 @@ processSerialChangedEvent(virQEMUDriverPtr driver,
     virObjectEventPtr event = NULL;
     virDomainDeviceDef dev;
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    int rc;
 
     if (connected)
         newstate = VIR_DOMAIN_CHR_DEVICE_STATE_CONNECTED;
@@ -4462,13 +4461,8 @@ processSerialChangedEvent(virQEMUDriverPtr driver,
 
     if (STREQ_NULLABLE(dev.data.chr->target.name, "org.qemu.guest_agent.0")) {
         if (newstate == VIR_DOMAIN_CHR_DEVICE_STATE_CONNECTED) {
-            if (!priv->agent) {
-                if ((rc = qemuConnectAgent(driver, vm)) == -2)
-                    goto endjob;
-
-                if (rc < 0)
-                    priv->agentError = true;
-            }
+            if (!priv->agent && qemuConnectAgent(driver, vm) < 0)
+                goto endjob;
         } else {
             if (priv->agent) {
                 qemuAgentClose(priv->agent);

src/qemu/qemu_migration.c

@@ -6183,7 +6183,6 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
     unsigned short port;
     unsigned long long timeReceived = 0;
     virObjectEventPtr event;
-    int rc;
     qemuDomainJobInfoPtr jobInfo = NULL;
     bool inPostCopy = false;
     bool doKill = true;
@@ -6256,16 +6255,8 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
                                       QEMU_ASYNC_JOB_MIGRATION_IN) < 0)
         goto endjob;
 
-    if ((rc = qemuConnectAgent(driver, vm)) < 0) {
-        if (rc == -2)
-            goto endjob;
-
-        VIR_WARN("Cannot connect to QEMU guest agent for %s",
-                 vm->def->name);
-        virResetLastError();
-        priv->agentError = true;
-    }
-
+    if (qemuConnectAgent(driver, vm) < 0)
+        goto endjob;
 
     if (flags & VIR_MIGRATE_PERSIST_DEST) {
         if (qemuMigrationPersist(driver, vm, mig, !v3proto) < 0) {

src/qemu/qemu_process.c

@@ -204,7 +204,6 @@ int
 qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    int ret = -1;
     qemuAgentPtr agent = NULL;
     virDomainChrDefPtr config = qemuFindAgentConfig(vm->def);
 
@@ -248,8 +247,7 @@ qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
         qemuAgentClose(agent);
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("guest crashed while connecting to the guest agent"));
-        ret = -2;
-        goto cleanup;
+        return -1;
     }
 
     if (virSecurityManagerClearSocketLabel(driver->securityManager,
@@ -260,18 +258,18 @@ qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
         goto cleanup;
     }
 
-
     priv->agent = agent;
-
-    if (priv->agent == NULL) {
+    if (!priv->agent)
         VIR_INFO("Failed to connect agent for %s", vm->def->name);
-        goto cleanup;
-    }
-
-    ret = 0;
 
  cleanup:
-    return ret;
+    if (!priv->agent) {
+        VIR_WARN("Cannot connect to QEMU guest agent for %s", vm->def->name);
+        priv->agentError = true;
+        virResetLastError();
+    }
+
+    return 0;
 }
 
 
@@ -3268,7 +3266,6 @@ qemuProcessReconnect(void *opaque)
     int reason;
     virQEMUDriverConfigPtr cfg;
     size_t i;
-    int ret;
     unsigned int stopFlags = 0;
     bool jobStarted = false;
     virCapsPtr caps = NULL;
@@ -3414,16 +3411,8 @@ qemuProcessReconnect(void *opaque)
 
     qemuProcessReconnectCheckMemAliasOrderMismatch(obj);
 
-    /* Failure to connect to agent shouldn't be fatal */
-    if ((ret = qemuConnectAgent(driver, obj)) < 0) {
-        if (ret == -2)
-            goto error;
-
-        VIR_WARN("Cannot connect to QEMU guest agent for %s",
-                 obj->def->name);
-        virResetLastError();
-        priv->agentError = true;
-    }
+    if (qemuConnectAgent(driver, obj) < 0)
+        goto error;
 
     /* update domain state XML with possibly updated state in virDomainObj */
     if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, obj, driver->caps) < 0)
@@ -5565,16 +5554,8 @@ qemuProcessLaunch(virConnectPtr conn,
     if (qemuProcessWaitForMonitor(driver, vm, asyncJob, priv->qemuCaps, logCtxt) < 0)
         goto cleanup;
 
-    /* Failure to connect to agent shouldn't be fatal */
-    if ((rv = qemuConnectAgent(driver, vm)) < 0) {
-        if (rv == -2)
-            goto cleanup;
-
-        VIR_WARN("Cannot connect to QEMU guest agent for %s",
-                 vm->def->name);
-        virResetLastError();
-        priv->agentError = true;
-    }
+    if (qemuConnectAgent(driver, vm) < 0)
+        goto cleanup;
 
     VIR_DEBUG("Detecting if required emulator features are present");
     if (!qemuProcessVerifyGuestCPU(driver, vm, asyncJob))
@@ -6264,7 +6245,6 @@ int qemuProcessAttach(virConnectPtr conn ATTRIBUTE_UNUSED,
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
     virCapsPtr caps = NULL;
     bool active = false;
-    int ret;
 
     VIR_DEBUG("Beginning VM attach process");
 
@@ -6391,16 +6371,8 @@ int qemuProcessAttach(virConnectPtr conn ATTRIBUTE_UNUSED,
     if (qemuProcessWaitForMonitor(driver, vm, QEMU_ASYNC_JOB_NONE, priv->qemuCaps, NULL) < 0)
         goto error;
 
-    /* Failure to connect to agent shouldn't be fatal */
-    if ((ret = qemuConnectAgent(driver, vm)) < 0) {
-        if (ret == -2)
-            goto error;
-
-        VIR_WARN("Cannot connect to QEMU guest agent for %s",
-                 vm->def->name);
-        virResetLastError();
-        priv->agentError = true;
-    }
+    if (qemuConnectAgent(driver, vm) < 0)
+        goto error;
 
     VIR_DEBUG("Detecting VCPU PIDs");
     if (qemuDomainRefreshVcpuInfo(driver, vm, QEMU_ASYNC_JOB_NONE, false) < 0)