clh: enable CPU hotplug

With the HTTP API 'vm.resize()', the CPU hotplug with CLH is much simpler
comparing with QEMU. This is because we don't need to distinguish adding from
removing CPUs.

Fixes: #2495

Depends-on: github.com/kata-containers/packaging#968
Depends-on: github.com/kata-containers/tests#2364

Signed-off-by: Bo Chen <chen.bo@intel.com>

virtcontainers/clh.go

@@ -76,6 +76,7 @@ type clhClient interface {
 	// No lint: golint suggest to rename to VMInfoGet.
 	VmInfoGet(ctx context.Context) (chclient.VmInfo, *http.Response, error) //nolint:golint
 	BootVM(ctx context.Context) (*http.Response, error)
+	VmResizePut(ctx context.Context, vmResize chclient.VmResize) (*http.Response, error)
 }
 
 type CloudHypervisorVersion struct {
@@ -391,8 +392,47 @@ func (clh *cloudHypervisor) resizeMemory(reqMemMB uint32, memoryBlockSizeMB uint
 }
 
 func (clh *cloudHypervisor) resizeVCPUs(reqVCPUs uint32) (currentVCPUs uint32, newVCPUs uint32, err error) {
-	clh.Logger().WithField("function", "resizeVCPUs").Warn("not supported")
-	return 0, 0, nil
+	cl := clh.client()
+
+	// Retrieve the number of current vCPUs via HTTP API
+	ctx, cancel := context.WithTimeout(context.Background(), clhAPITimeout*time.Second)
+	info, _, err := cl.VmInfoGet(ctx)
+	if err != nil {
+		clh.Logger().WithField("function", "resizeVCPUs").WithError(openAPIClientError(err)).Info("[clh] VmInfoGet failed")
+		return 0, 0, openAPIClientError(err)
+	}
+	// Reset the timer after the first HTTP API call
+	cancel()
+
+	currentVCPUs = uint32(info.Config.Cpus.BootVcpus)
+	newVCPUs = currentVCPUs
+
+	// Sanity check
+	if reqVCPUs == 0 {
+		clh.Logger().WithField("function", "resizeVCPUs").Debugf("Cannot resize vCPU to 0")
+		return currentVCPUs, newVCPUs, fmt.Errorf("Cannot resize vCPU to 0")
+	}
+	if reqVCPUs > clh.config.DefaultMaxVCPUs || reqVCPUs > uint32(info.Config.Cpus.MaxVcpus) {
+		clh.Logger().WithFields(log.Fields{
+			"function":              "resizeVCPUs",
+			"reqVCPUs":              reqVCPUs,
+			"configDefaultMaxVCPUs": clh.config.DefaultMaxVCPUs,
+			"clhMaxVCPUs":           info.Config.Cpus.MaxVcpus,
+		}).Debug("exceeding the maxVCPUs")
+		return currentVCPUs, newVCPUs, fmt.Errorf("Cannot resize vCPU to %d: exceeding the maximum amount of vCPUs (%d or %d)",
+			reqVCPUs, clh.config.DefaultMaxVCPUs, info.Config.Cpus.MaxVcpus)
+	}
+
+	// Resize (hot-plug) vCPUs via HTTP API
+	ctx, cancel = context.WithTimeout(context.Background(), clhAPITimeout*time.Second)
+	defer cancel()
+	if _, err = cl.VmResizePut(ctx, chclient.VmResize{DesiredVcpus: int32(reqVCPUs)}); err != nil {
+		return currentVCPUs, newVCPUs, errors.Wrap(err, "[clh] VmResizePut failed")
+	}
+
+	newVCPUs = reqVCPUs
+
+	return currentVCPUs, newVCPUs, nil
 }
 
 func (clh *cloudHypervisor) cleanup() error {

virtcontainers/clh_test.go

@@ -81,6 +81,11 @@ func (c *clhClientMock) BootVM(ctx context.Context) (*http.Response, error) {
 	return nil, nil
 }
 
+//nolint:golint
+func (c *clhClientMock) VmResizePut(ctx context.Context, vmResize chclient.VmResize) (*http.Response, error) {
+	return nil, nil
+}
+
 func TestCloudHypervisorAddVSock(t *testing.T) {
 	assert := assert.New(t)
 	clh := cloudHypervisor{}