qemu: allow using legacy serial device for the console

This allows to get guest early boot logs which are usually
missed when virtconsole is used.
- It utilizes previous work on the govmm side:
https://github.com/kata-containers/govmm/pull/203
- unit test added

Fixes: #4237
Signed-off-by: Snir Sheriber <ssheribe@redhat.com>

src/runtime/virtcontainers/qemu_arch_base_test.go

@@ -263,6 +263,34 @@ func TestQemuArchBaseAppendConsoles(t *testing.T) {
 	assert.Contains(qemuArchBase.kernelParams, Param{"console", "hvc1"})
 }
 
+func TestQemuArchBaseAppendConsolesLegacy(t *testing.T) {
+	var devices []govmmQemu.Device
+	var err error
+	assert := assert.New(t)
+	qemuArchBase := newQemuArchBase()
+	qemuArchBase.legacySerial = true
+
+	path := filepath.Join(filepath.Join(fs.MockRunStoragePath(), "test"), consoleSocket)
+
+	expectedOut := []govmmQemu.Device{
+		govmmQemu.LegacySerialDevice{
+			Chardev: "charconsole0",
+		},
+		govmmQemu.CharDevice{
+			Driver:   govmmQemu.LegacySerial,
+			Backend:  govmmQemu.Socket,
+			DeviceID: "console0",
+			ID:       "charconsole0",
+			Path:     path,
+		},
+	}
+
+	devices, err = qemuArchBase.appendConsole(context.Background(), devices, path)
+	assert.NoError(err)
+	assert.Equal(expectedOut, devices)
+	assert.Contains(qemuArchBase.kernelParams, Param{"console", "ttyS0"})
+}
+
 func TestQemuArchBaseAppendImage(t *testing.T) {
 	var devices []govmmQemu.Device
 	assert := assert.New(t)