qemu/qmp: Implement function to hot plug PCI devices

ExecutePCIDeviceAdd is a function that can be used to hot plug
devices directly on pci(e).0 or pci(e) bridges. ExecutePCIDeviceAdd
is PCI specific because unlike ExecuteDeviceAdd, it includes an
extra parameter to specify the device address on its parent bus.

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

qmp.go

@@ -675,3 +675,19 @@ func (q *QMP) ExecuteDeviceDel(ctx context.Context, devID string) error {
 	}
 	return q.executeCommand(ctx, "device_del", args, filter)
 }
+
+// ExecutePCIDeviceAdd is the PCI version of ExecuteDeviceAdd. This function can be used
+// to hot plug PCI devices on PCI(E) bridges, unlike ExecuteDeviceAdd this function receive the
+// device address on its parent bus. bus is optional.
+func (q *QMP) ExecutePCIDeviceAdd(ctx context.Context, blockdevID, devID, driver, addr, bus string) error {
+	args := map[string]interface{}{
+		"id":     devID,
+		"driver": driver,
+		"drive":  blockdevID,
+		"addr":   addr,
+	}
+	if bus != "" {
+		args["bus"] = bus
+	}
+	return q.executeCommand(ctx, "device_add", args, nil)
+}

qmp_test.go

@@ -785,3 +785,28 @@ func TestQMPLostLoop(t *testing.T) {
 		t.Error("Expected executeQMPCapabilities to fail")
 	}
 }
+
+// Checks that PCI devices are correctly added using device_add.
+//
+// We start a QMPLoop, send the device_add command and stop the loop.
+//
+// The device_add command should be correctly sent and the QMP loop should
+// exit gracefully.
+func TestQMPPCIDeviceAdd(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)
+	blockdevID := fmt.Sprintf("drive_%s", testutil.VolumeUUID)
+	devID := fmt.Sprintf("device_%s", testutil.VolumeUUID)
+	err := q.ExecutePCIDeviceAdd(context.Background(), blockdevID, devID,
+		"virtio-blk-pci", "0x1", "")
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}