qemu: Remember incoming migration errors

If QEMU fails during incoming migration, the domain disappears including
a possibly useful error message read from QEMU log file. Let's remember
the error in virQEMUDriver so that Finish can report more than just "no
such domain".

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_conf.h

@@ -252,6 +252,9 @@ struct _virQEMUDriver {
 
     /* Immutable pointer, self-clocking APIs */
     virCloseCallbacksPtr closeCallbacks;
+
+    /* Immutable pointer, self-locking APIs */
+    virHashAtomicPtr migrationErrors;
 };
 
 typedef struct _qemuDomainCmdlineDef qemuDomainCmdlineDef;

src/qemu/qemu_driver.c

@@ -775,6 +775,9 @@ qemuStateInitialize(bool privileged,
     if (!(qemu_driver->sharedDevices = virHashCreate(30, qemuSharedDeviceEntryFree)))
         goto error;
 
+    if (qemuMigrationErrorInit(qemu_driver) < 0)
+        goto error;
+
     if (privileged) {
         char *channeldir;
 
@@ -1091,6 +1094,7 @@ qemuStateCleanup(void)
     virObjectUnref(qemu_driver->remotePorts);
     virObjectUnref(qemu_driver->webSocketPorts);
     virObjectUnref(qemu_driver->migrationPorts);
+    virObjectUnref(qemu_driver->migrationErrors);
 
     virObjectUnref(qemu_driver->xmlopt);
 
@@ -12117,6 +12121,7 @@ qemuDomainMigrateFinish2(virConnectPtr dconn,
     if (!vm) {
         virReportError(VIR_ERR_NO_DOMAIN,
                        _("no domain with matching name '%s'"), dname);
+        qemuMigrationErrorReport(driver, dname);
         goto cleanup;
     }
 
@@ -12566,11 +12571,16 @@ qemuDomainMigrateFinish3(virConnectPtr dconn,
 
     virCheckFlags(QEMU_MIGRATION_FLAGS, NULL);
 
-    if (!dname ||
-        !(vm = virDomainObjListFindByName(driver->domains, dname))) {
+    if (!dname) {
+        virReportError(VIR_ERR_NO_DOMAIN, "%s", _("missing domain name"));
+        return NULL;
+    }
+
+    vm = virDomainObjListFindByName(driver->domains, dname);
+    if (!vm) {
         virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching name '%s'"),
-                       NULLSTR(dname));
+                       _("no domain with matching name '%s'"), dname);
+        qemuMigrationErrorReport(driver, dname);
         return NULL;
     }
 
@@ -12609,11 +12619,16 @@ qemuDomainMigrateFinish3Params(virConnectPtr dconn,
                                 &dname) < 0)
         return NULL;
 
-    if (!dname ||
-        !(vm = virDomainObjListFindByName(driver->domains, dname))) {
+    if (!dname) {
+        virReportError(VIR_ERR_NO_DOMAIN, "%s", _("missing domain name"));
+        return NULL;
+    }
+
+    vm = virDomainObjListFindByName(driver->domains, dname);
+    if (!vm) {
         virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching name '%s'"),
-                       NULLSTR(dname));
+                       _("no domain with matching name '%s'"), dname);
+        qemuMigrationErrorReport(driver, dname);
         return NULL;
     }
 

src/qemu/qemu_migration.c

@@ -5543,8 +5543,10 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
     if (!(caps = virQEMUDriverGetCapabilities(driver, false)))
         goto cleanup;
 
-    if (!qemuMigrationJobIsActive(vm, QEMU_ASYNC_JOB_MIGRATION_IN))
+    if (!qemuMigrationJobIsActive(vm, QEMU_ASYNC_JOB_MIGRATION_IN)) {
+        qemuMigrationErrorReport(driver, vm->def->name);
         goto cleanup;
+    }
 
     qemuMigrationJobStartPhase(driver, vm,
                                v3proto ? QEMU_MIGRATION_PHASE_FINISH3
@@ -5570,6 +5572,7 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
         if (!virDomainObjIsActive(vm) && !(flags & VIR_MIGRATE_OFFLINE)) {
             virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                            _("guest unexpectedly quit"));
+            qemuMigrationErrorReport(driver, vm->def->name);
             goto endjob;
         }
 
@@ -6094,3 +6097,57 @@ qemuMigrationJobFinish(virQEMUDriverPtr driver, virDomainObjPtr vm)
 {
     qemuDomainObjEndAsyncJob(driver, vm);
 }
+
+
+static void
+qemuMigrationErrorFree(void *data,
+                       const void *name ATTRIBUTE_UNUSED)
+{
+    virErrorPtr err = data;
+    virFreeError(err);
+}
+
+int
+qemuMigrationErrorInit(virQEMUDriverPtr driver)
+{
+    driver->migrationErrors = virHashAtomicNew(64, qemuMigrationErrorFree);
+    if (driver->migrationErrors)
+        return 0;
+    else
+        return -1;
+}
+
+/**
+ * This function consumes @err; the caller should consider the @err pointer
+ * invalid after calling this function.
+ */
+void
+qemuMigrationErrorSave(virQEMUDriverPtr driver,
+                       const char *name,
+                       virErrorPtr err)
+{
+    if (!err)
+        return;
+
+    VIR_DEBUG("Saving incoming migration error for domain %s: %s",
+              name, err->message);
+    if (virHashAtomicUpdate(driver->migrationErrors, name, err) < 0) {
+        VIR_WARN("Failed to save migration error for domain '%s'", name);
+        virFreeError(err);
+    }
+}
+
+void
+qemuMigrationErrorReport(virQEMUDriverPtr driver,
+                         const char *name)
+{
+    virErrorPtr err;
+
+    if (!(err = virHashAtomicSteal(driver->migrationErrors, name)))
+        return;
+
+    VIR_DEBUG("Restoring saved incoming migration error for domain %s: %s",
+              name, err->message);
+    virSetError(err);
+    virFreeError(err);
+}

src/qemu/qemu_migration.h

@@ -193,4 +193,11 @@ int qemuMigrationFetchJobStatus(virQEMUDriverPtr driver,
                                 qemuDomainAsyncJob asyncJob,
                                 qemuDomainJobInfoPtr jobInfo);
 
+int qemuMigrationErrorInit(virQEMUDriverPtr driver);
+void qemuMigrationErrorSave(virQEMUDriverPtr driver,
+                            const char *name,
+                            virErrorPtr err);
+void qemuMigrationErrorReport(virQEMUDriverPtr driver,
+                              const char *name);
+
 #endif /* __QEMU_MIGRATION_H__ */

src/qemu/qemu_monitor.c

@@ -1057,6 +1057,20 @@ qemuMonitorSend(qemuMonitorPtr mon,
 }
 
 
+/**
+ * This function returns a new virError object; the caller is responsible
+ * for freeing it.
+ */
+virErrorPtr
+qemuMonitorLastError(qemuMonitorPtr mon)
+{
+    if (mon->lastError.code == VIR_ERR_OK)
+        return NULL;
+
+    return virErrorCopyNew(&mon->lastError);
+}
+
+
 virJSONValuePtr
 qemuMonitorGetOptions(qemuMonitorPtr mon)
 {

src/qemu/qemu_monitor.h

@@ -240,6 +240,8 @@ qemuMonitorPtr qemuMonitorOpenFD(virDomainObjPtr vm,
 
 void qemuMonitorClose(qemuMonitorPtr mon);
 
+virErrorPtr qemuMonitorLastError(qemuMonitorPtr mon);
+
 int qemuMonitorSetCapabilities(qemuMonitorPtr mon);
 
 int qemuMonitorSetLink(qemuMonitorPtr mon,

src/qemu/qemu_process.c

@@ -310,6 +310,10 @@ qemuProcessHandleMonitorEOF(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
         auditReason = "failed";
     }
 
+    if (qemuMigrationJobIsActive(vm, QEMU_ASYNC_JOB_MIGRATION_IN))
+        qemuMigrationErrorSave(driver, vm->def->name,
+                               qemuMonitorLastError(priv->mon));
+
     event = virDomainEventLifecycleNewFromObj(vm,
                                      VIR_DOMAIN_EVENT_STOPPED,
                                      eventReason);