hypervisor/qemu: add memory hotplug support

So that we can add more memory to an existing guest.

Fixes: #469

Signed-off-by: Peng Tao <bergwolf@gmail.com>

virtcontainers/hypervisor.go

@@ -76,8 +76,16 @@ const (
 
 	// CPUDevice is CPU device type
 	cpuDev
+
+	// memoryDevice is memory device type
+	memoryDev
 )
 
+type memoryDevice struct {
+	slot   uint32
+	sizeMB int
+}
+
 // Set sets an hypervisor type based on the input string.
 func (hType *HypervisorType) Set(value string) error {
 	switch value {

virtcontainers/qemu.go

@@ -7,6 +7,7 @@ package virtcontainers
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -39,12 +40,15 @@ type CPUDevice struct {
 type QemuState struct {
 	Bridges []Bridge
 	// HotpluggedCPUs is the list of CPUs that were hot-added
-	HotpluggedVCPUs []CPUDevice
-	UUID            string
+	HotpluggedVCPUs  []CPUDevice
+	HotpluggedMemory int
+	UUID             string
 }
 
 // qemu is an Hypervisor interface implementation for the Linux qemu hypervisor.
 type qemu struct {
+	vmConfig Resources
+
 	config HypervisorConfig
 
 	qmpMonitorCh qmpChannel
@@ -169,6 +173,7 @@ func (q *qemu) init(sandbox *Sandbox) error {
 		return err
 	}
 
+	q.vmConfig = sandbox.config.VMConfig
 	q.config = sandbox.config.HypervisorConfig
 	q.sandbox = sandbox
 	q.arch = newQemuArch(q.config)
@@ -204,20 +209,27 @@ func (q *qemu) cpuTopology() govmmQemu.SMP {
 	return q.arch.cpuTopology(q.config.DefaultVCPUs, q.config.DefaultMaxVCPUs)
 }
 
-func (q *qemu) memoryTopology(sandboxConfig SandboxConfig) (govmmQemu.Memory, error) {
+func (q *qemu) hostMemMB() (uint64, error) {
 	hostMemKb, err := getHostMemorySizeKb(procMemInfo)
 	if err != nil {
-		return govmmQemu.Memory{}, fmt.Errorf("Unable to read memory info: %s", err)
+		return 0, fmt.Errorf("Unable to read memory info: %s", err)
 	}
 	if hostMemKb == 0 {
-		return govmmQemu.Memory{}, fmt.Errorf("Error host memory size 0")
+		return 0, fmt.Errorf("Error host memory size 0")
 	}
 
-	hostMemMb := uint64(float64(hostMemKb / 1024))
+	return uint64(float64(hostMemKb / 1024)), nil
+}
+
+func (q *qemu) memoryTopology() (govmmQemu.Memory, error) {
+	hostMemMb, err := q.hostMemMB()
+	if err != nil {
+		return govmmQemu.Memory{}, err
+	}
 
 	memMb := uint64(q.config.DefaultMemSz)
-	if sandboxConfig.VMConfig.Memory > 0 {
-		memMb = uint64(sandboxConfig.VMConfig.Memory)
+	if q.vmConfig.Memory > 0 {
+		memMb = uint64(q.vmConfig.Memory)
 	}
 
 	return q.arch.memoryTopology(memMb, hostMemMb), nil
@@ -271,7 +283,7 @@ func (q *qemu) createSandbox(sandboxConfig SandboxConfig) error {
 
 	smp := q.cpuTopology()
 
-	memory, err := q.memoryTopology(sandboxConfig)
+	memory, err := q.memoryTopology()
 	if err != nil {
 		return err
 	}
@@ -705,6 +717,9 @@ func (q *qemu) hotplugDevice(devInfo interface{}, devType deviceType, op operati
 		// TODO: find a way to remove dependency of deviceDrivers lib @weizhang555
 		device := devInfo.(deviceDrivers.VFIODevice)
 		return nil, q.hotplugVFIODevice(device, op)
+	case memoryDev:
+		memdev := devInfo.(*memoryDevice)
+		return nil, q.hotplugMemory(memdev.slot, memdev.sizeMB, op)
 	default:
 		return nil, fmt.Errorf("cannot hotplug device: unsupported device type '%v'", devType)
 	}
@@ -837,6 +852,61 @@ func (q *qemu) hotplugRemoveCPUs(amount uint32) (uint32, error) {
 	return amount, q.sandbox.storage.storeHypervisorState(q.sandbox.id, q.state)
 }
 
+func (q *qemu) hotplugMemory(slot uint32, memMB int, op operation) error {
+	if memMB <= 0 {
+		return errors.New("cannot hotplug zero or negative MB memory")
+	}
+
+	// We do not support memory hot unplug.
+	if op == removeDevice {
+		return errors.New("cannot hot unplug memory device")
+	}
+
+	defer func(qemu *qemu) {
+		if q.qmpMonitorCh.qmp != nil {
+			q.qmpMonitorCh.qmp.Shutdown()
+		}
+	}(q)
+
+	qmp, err := q.qmpSetup()
+	if err != nil {
+		return err
+	}
+
+	q.qmpMonitorCh.qmp = qmp
+
+	return q.hotplugAddMemory(slot, memMB)
+}
+
+func (q *qemu) hotplugAddMemory(slot uint32, amount int) error {
+	maxMem, err := q.hostMemMB()
+	if err != nil {
+		return err
+	}
+
+	// calculate current memory
+	currentMemory := int(q.config.DefaultMemSz)
+	if q.vmConfig.Memory > 0 {
+		currentMemory = int(q.vmConfig.Memory)
+	}
+	currentMemory += q.state.HotpluggedMemory
+
+	// Don't exceed the maximum amount of memory
+	if currentMemory+amount > int(maxMem) {
+		return fmt.Errorf("Unable to hotplug %d MB memory, currently this SB has %d memory and the maximum amount is %d",
+			amount, currentMemory, q.config.DefaultMemSz)
+	}
+
+	err = q.qmpMonitorCh.qmp.ExecHotplugMemory(q.qmpMonitorCh.ctx, "memory-backend-ram", "mem"+strconv.Itoa(int(slot)), "", amount)
+	if err != nil {
+		q.Logger().WithError(err).Error("hotplug memory")
+		return err
+	}
+
+	q.state.HotpluggedMemory += amount
+	return q.sandbox.storage.storeHypervisorState(q.sandbox.id, q.state)
+}
+
 func (q *qemu) pauseSandbox() error {
 	return q.togglePauseSandbox(true)
 }

virtcontainers/qemu_test.go

@@ -167,15 +167,11 @@ func TestQemuMemoryTopology(t *testing.T) {
 		MaxMem: memMax,
 	}
 
-	vmConfig := Resources{
+	q.vmConfig = Resources{
 		Memory: uint(mem),
 	}
 
-	sandboxConfig := SandboxConfig{
-		VMConfig: vmConfig,
-	}
-
-	memory, err := q.memoryTopology(sandboxConfig)
+	memory, err := q.memoryTopology()
 	if err != nil {
 		t.Fatal(err)
 	}