qemu: Add function to hotplug CPUs

ExecuteCPUDeviceAdd hot-adds a CPU to a running VM

Signed-off-by: Julio Montes <julio.montes@intel.com>

qmp.go

@@ -736,3 +736,18 @@ func (q *QMP) ExecutePCIVFIODeviceAdd(ctx context.Context, devID, bdf, addr, bus
 	}
 	return q.executeCommand(ctx, "device_add", args, nil)
 }
+
+// ExecuteCPUDeviceAdd adds a CPU to a QEMU instance using the device_add command.
+// driver is the CPU model, cpuID must be a unique ID to identify the CPU, socketID is the socket number within
+// node/board the CPU belongs to, coreID is the core number within socket the CPU belongs to, threadID is the
+// thread number within core the CPU belongs to.
+func (q *QMP) ExecuteCPUDeviceAdd(ctx context.Context, driver, cpuID, socketID, coreID, threadID string) error {
+	args := map[string]interface{}{
+		"driver":    driver,
+		"id":        cpuID,
+		"socket-id": socketID,
+		"core-id":   coreID,
+		"thread-id": threadID,
+	}
+	return q.executeCommand(ctx, "device_add", args, nil)
+}

qmp_test.go

@@ -810,3 +810,25 @@ func TestQMPPCIDeviceAdd(t *testing.T) {
 	q.Shutdown()
 	<-disconnectedCh
 }
+
+// Checks that CPU are correctly added using device_add
+func TestQMPCPUDeviceAdd(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 := "qemu64-x86_64-cpu"
+	cpuID := "cpu-0"
+	socketID := "0"
+	coreID := "1"
+	threadID := "0"
+	err := q.ExecuteCPUDeviceAdd(context.Background(), driver, cpuID, socketID, coreID, threadID)
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}