qemu: Update blockdev-add qmp command to support newer qemu versions

With qemu 2.9, the qmp block-dev command was updated  from:
{ "execute": "blockdev-add", "arguments": { "options": { ... } } }

to:
{ "execute": "blockdev-add", "arguments": { ... } }

Also, instead of id, blockdev-add now requires a node-name for the
root node(https://wiki.qemu.org/index.php/ChangeLog/2.9)

Store the version information with QMPStart and use that to issue
qmp command for adding block devices in the correct format.

Signed-off-by: Archana Shinde <archana.m.shinde@intel.com>

qmp.go

@@ -127,6 +127,7 @@ type QMP struct {
 	cfg            QMPConfig
 	connectedCh    chan<- *QMPVersion
 	disconnectedCh chan struct{}
+	version        *QMPVersion
 }
 
 // QMPVersion contains the version number and the capabailities of a QEMU
@@ -533,7 +534,6 @@ func QMPStart(ctx context.Context, socket string, cfg QMPConfig, disconnectedCh
 
 	connectedCh := make(chan *QMPVersion)
 
-	var version *QMPVersion
 	q := startQMPLoop(conn, cfg, connectedCh, disconnectedCh)
 	select {
 	case <-ctx.Done():
@@ -542,13 +542,13 @@ func QMPStart(ctx context.Context, socket string, cfg QMPConfig, disconnectedCh
 		return nil, nil, fmt.Errorf("Canceled by caller")
 	case <-disconnectedCh:
 		return nil, nil, fmt.Errorf("Lost connection to VM")
-	case version = <-connectedCh:
-		if version == nil {
+	case q.version = <-connectedCh:
+		if q.version == nil {
 			return nil, nil, fmt.Errorf("Failed to find QMP version information")
 		}
 	}
 
-	return q, version, nil
+	return q, q.version, nil
 }
 
 // Shutdown closes the domain socket used to monitor a QEMU instance and
@@ -602,16 +602,26 @@ func (q *QMP) ExecuteQuit(ctx context.Context) error {
 // used to name the device.  As this identifier will be passed directly to QMP,
 // it must obey QMP's naming rules, e,g., it must start with a letter.
 func (q *QMP) ExecuteBlockdevAdd(ctx context.Context, device, blockdevID string) error {
-	args := map[string]interface{}{
-		"options": map[string]interface{}{
-			"driver": "raw",
-			"file": map[string]interface{}{
-				"driver":   "file",
-				"filename": device,
-			},
-			"id": blockdevID,
+	var args map[string]interface{}
+
+	blockdevArgs := map[string]interface{}{
+		"driver": "raw",
+		"file": map[string]interface{}{
+			"driver":   "file",
+			"filename": device,
 		},
 	}
+
+	if q.version.Major > 2 || (q.version.Major == 2 && q.version.Minor >= 9) {
+		blockdevArgs["node-name"] = blockdevID
+		args = blockdevArgs
+	} else {
+		blockdevArgs["id"] = blockdevID
+		args = map[string]interface{}{
+			"options": blockdevArgs,
+		}
+	}
+
 	return q.executeCommand(ctx, "blockdev-add", args, nil)
 }
 

qmp_test.go

@@ -212,7 +212,7 @@ func (b *qmpTestCommandBuffer) Write(p []byte) (int, error) {
 	return len(p), nil
 }
 
-func checkVersion(t *testing.T, connectedCh <-chan *QMPVersion) {
+func checkVersion(t *testing.T, connectedCh <-chan *QMPVersion) *QMPVersion {
 	var version *QMPVersion
 	select {
 	case <-time.After(time.Second):
@@ -233,6 +233,8 @@ func checkVersion(t *testing.T, connectedCh <-chan *QMPVersion) {
 			t.Fatal("Invalid capabilities")
 		}
 	}
+
+	return version
 }
 
 // Checks that a QMP Loop can be started and shutdown.
@@ -356,7 +358,7 @@ func TestQMPBlockdevAdd(t *testing.T) {
 	buf.AddCommand("blockdev-add", nil, "return", nil)
 	cfg := QMPConfig{Logger: qmpTestLogger{}}
 	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
-	checkVersion(t, connectedCh)
+	q.version = checkVersion(t, connectedCh)
 	err := q.ExecuteBlockdevAdd(context.Background(), "/dev/rbd0",
 		fmt.Sprintf("drive_%s", testutil.VolumeUUID))
 	if err != nil {