qmp: add ExecutePCIVhostUserDevAdd API

Caller can hotplug vhost-user device via qmp.
The Qemu vhost-user device, like vhost-user-blk-pci and
vhost-user-scsi-pci can be hotplugged by qmp API:
ExecuteCharDevUnixSocketAdd() together with
ExecutePCIVhostUserDevAdd()

Signed-off-by: Liu Xiaodong <xiaodong.liu@intel.com>

qemu/qmp.go

@@ -1135,6 +1135,27 @@ func (q *QMP) ExecutePCIDeviceAdd(ctx context.Context, blockdevID, devID, driver
 	return q.executeCommand(ctx, "device_add", args, nil)
 }
 
+// ExecutePCIVhostUserDevAdd adds a vhost-user device to a QEMU instance using the device_add command.
+// This function can be used to hot plug vhost-user devices on PCI(E) bridges.
+// It receives the bus and the device address on its parent bus. bus is optional.
+// devID is the id of the device to add.Must be valid QMP identifier. chardevID
+// is the QMP identifier of character device using a unix socket as backend.
+// driver is the name of vhost-user driver, like vhost-user-blk-pci.
+func (q *QMP) ExecutePCIVhostUserDevAdd(ctx context.Context, driver, devID, chardevID, addr, bus string) error {
+	args := map[string]interface{}{
+		"driver":  driver,
+		"id":      devID,
+		"chardev": chardevID,
+		"addr":    addr,
+	}
+
+	if bus != "" {
+		args["bus"] = bus
+	}
+
+	return q.executeCommand(ctx, "device_add", args, nil)
+}
+
 // ExecuteVFIODeviceAdd adds a VFIO device to a QEMU instance
 // using the device_add command. devID is the id of the device to add.
 // Must be valid QMP identifier. bdf is the PCI bus-device-function

qemu/qmp_test.go

@@ -1329,6 +1329,26 @@ func TestExecutePCIVSockAdd(t *testing.T) {
 	<-disconnectedCh
 }
 
+// Checks vhost-user-pci hotplug
+func TestExecutePCIVhostUserDevAdd(t *testing.T) {
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	buf.AddCommand("device_add", nil, "return", nil)
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+	driver := "vhost-user-blk-pci"
+	devID := "vhost-user-blk0"
+	chardevID := "vhost-user-blk-char0"
+	err := q.ExecutePCIVhostUserDevAdd(context.Background(), driver, devID, chardevID, "1", "1")
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}
+
 // Checks getfd
 func TestExecuteGetFdD(t *testing.T) {
 	connectedCh := make(chan *QMPVersion)