qmp: support command 'query-qmp-schema'

The upper hyervisor manager application maybe need to wait some
QMP event to control boot sequence, but the event we wanted maybe
not exist in some older version, so we need query all QMP ABI and
check the event is supported or not.

related: kata-containers/runtime#1918

Signed-off-by: Ning Bo <ning.bo9@zte.com.cn>

qemu/qmp.go

@@ -84,6 +84,9 @@ type QMPConfig struct {
 	// logger is used by the qmpStart function and all the go routines
 	// it spawns to log information.
 	Logger QMPLog
+
+	// specify the capacity of buffer used by receive QMP response.
+	MaxCapacity int
 }
 
 type qmpEventFilter struct {
@@ -242,8 +245,19 @@ type MigrationStatus struct {
 	XbzrleCache  MigrationXbzrleCache     `json:"xbzrle-cache,omitempty"`
 }
 
+// SchemaInfo represents all QMP wire ABI
+type SchemaInfo struct {
+	MetaType string `json:"meta-type"`
+	Name     string `json:"name"`
+}
+
 func (q *QMP) readLoop(fromVMCh chan<- []byte) {
 	scanner := bufio.NewScanner(q.conn)
+	if q.cfg.MaxCapacity > 0 {
+		buffer := make([]byte, q.cfg.MaxCapacity)
+		scanner.Buffer(buffer, q.cfg.MaxCapacity)
+	}
+
 	for scanner.Scan() {
 		line := scanner.Bytes()
 		if q.cfg.Logger.V(1) {
@@ -260,6 +274,7 @@ func (q *QMP) readLoop(fromVMCh chan<- []byte) {
 
 		fromVMCh <- sendLine
 	}
+	q.cfg.Logger.Infof("sanner return error: %v", scanner.Err())
 	close(fromVMCh)
 }
 
@@ -1509,3 +1524,24 @@ func (q *QMP) ExecuteMigrationIncoming(ctx context.Context, uri string) error {
 	}
 	return q.executeCommand(ctx, "migrate-incoming", args, nil)
 }
+
+// ExecQueryQmpSchema query all QMP wire ABI and returns a slice
+func (q *QMP) ExecQueryQmpSchema(ctx context.Context) ([]SchemaInfo, error) {
+	response, err := q.executeCommandWithResponse(ctx, "query-qmp-schema", nil, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// convert response to json
+	data, err := json.Marshal(response)
+	if err != nil {
+		return nil, fmt.Errorf("unable to extract memory devices information: %v", err)
+	}
+
+	var schemaInfo []SchemaInfo
+	if err = json.Unmarshal(data, &schemaInfo); err != nil {
+		return nil, fmt.Errorf("unable to convert json to schemaInfo: %v", err)
+	}
+
+	return schemaInfo, nil
+}

qemu/qmp_test.go

@@ -1588,3 +1588,38 @@ func TestMainLoopEventBeforeGreeting(t *testing.T) {
 	q.Shutdown()
 	<-disconnectedCh
 }
+
+func TestQMPExecQueryQmpSchema(t *testing.T) {
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	schemaInfo := []SchemaInfo{
+		{
+			MetaType: "command",
+			Name:     "object-add",
+		},
+		{
+			MetaType: "event",
+			Name:     "VSOCK_RUNNING",
+		},
+	}
+	buf.AddCommand("query-qmp-schema", nil, "return", schemaInfo)
+	cfg := QMPConfig{
+		Logger:      qmpTestLogger{},
+		MaxCapacity: 1024,
+	}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+	info, err := q.ExecQueryQmpSchema(context.Background())
+	if err != nil {
+		t.Fatalf("Unexpected error: %v\n", err)
+	}
+	if len(schemaInfo) != 2 {
+		t.Fatalf("Expected schema infos length equals to 2\n")
+	}
+	if reflect.DeepEqual(info, schemaInfo) == false {
+		t.Fatalf("Expected %v equals to %v\n", info, schemaInfo)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}