qmp: add "query-cpus" support

Add "query-cpus" and "query-cpus-fast" to query CPU information from qemu

Signed-off-by: Wei Zhang <zhangwei555@huawei.com>

qemu/qmp.go

@@ -144,7 +144,7 @@ type QMPVersion struct {
 	Capabilities []string
 }
 
-// CPUProperties contains the properties to be used for hotplugging a CPU instance
+// CPUProperties contains the properties of a CPU instance
 type CPUProperties struct {
 	Node   int `json:"node-id"`
 	Socket int `json:"socket-id"`
@@ -178,6 +178,28 @@ type MemoryDevices struct {
 	Type string            `json:"type"`
 }
 
+// CPUInfo represents information about each virtual CPU
+type CPUInfo struct {
+	CPU      int           `json:"CPU"`
+	Current  bool          `json:"current"`
+	Halted   bool          `json:"halted"`
+	QomPath  string        `json:"qom_path"`
+	Arch     string        `json:"arch"`
+	Pc       int           `json:"pc"`
+	ThreadID int           `json:"thread_id"`
+	Props    CPUProperties `json:"props"`
+}
+
+// CPUInfoFast represents information about each virtual CPU
+type CPUInfoFast struct {
+	CPUIndex int           `json:"cpu-index"`
+	QomPath  string        `json:"qom-path"`
+	Arch     string        `json:"arch"`
+	ThreadID int           `json:"thread-id"`
+	Target   string        `json:"target"`
+	Props    CPUProperties `json:"props"`
+}
+
 func (q *QMP) readLoop(fromVMCh chan<- []byte) {
 	scanner := bufio.NewScanner(q.conn)
 	for scanner.Scan() {
@@ -1033,6 +1055,54 @@ func (q *QMP) ExecQueryMemoryDevices(ctx context.Context) ([]MemoryDevices, erro
 	return memoryDevices, nil
 }
 
+// ExecQueryCpus returns a slice with the list of `CpuInfo`
+// Since qemu 2.12, we have `query-cpus-fast` as a better choice in production
+// we can still choose `ExecQueryCpus` for compatibility though not recommended.
+func (q *QMP) ExecQueryCpus(ctx context.Context) ([]CPUInfo, error) {
+	response, err := q.executeCommandWithResponse(ctx, "query-cpus", nil, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// convert response to json
+	data, err := json.Marshal(response)
+	if err != nil {
+		return nil, fmt.Errorf("Unable to extract memory devices information: %v", err)
+	}
+
+	var cpuInfo []CPUInfo
+	// convert json to []CPUInfo
+	if err = json.Unmarshal(data, &cpuInfo); err != nil {
+		return nil, fmt.Errorf("unable to convert json to CPUInfo: %v", err)
+	}
+
+	return cpuInfo, nil
+}
+
+// ExecQueryCpusFast returns a slice with the list of `CpuInfoFast`
+// This is introduced since 2.12, it does not incur a performance penalty and
+// should be used in production instead of query-cpus.
+func (q *QMP) ExecQueryCpusFast(ctx context.Context) ([]CPUInfoFast, error) {
+	response, err := q.executeCommandWithResponse(ctx, "query-cpus-fast", nil, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// convert response to json
+	data, err := json.Marshal(response)
+	if err != nil {
+		return nil, fmt.Errorf("Unable to extract memory devices information: %v", err)
+	}
+
+	var cpuInfoFast []CPUInfoFast
+	// convert json to []CPUInfoFast
+	if err = json.Unmarshal(data, &cpuInfoFast); err != nil {
+		return nil, fmt.Errorf("unable to convert json to CPUInfoFast: %v", err)
+	}
+
+	return cpuInfoFast, nil
+}
+
 // ExecHotplugMemory adds size of MiB memory to the guest
 func (q *QMP) ExecHotplugMemory(ctx context.Context, qomtype, id, mempath string, size int) error {
 	args := map[string]interface{}{

qemu/qmp_test.go

@@ -1096,6 +1096,80 @@ func TestQMPExecuteQueryMemoryDevices(t *testing.T) {
 	<-disconnectedCh
 }
 
+// Checks that cpus are listed correctly
+func TestQMPExecuteQueryCpus(t *testing.T) {
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	cpuInfo := CPUInfo{
+		CPU:      1,
+		Current:  false,
+		Halted:   false,
+		Arch:     "x86_64",
+		QomPath:  "/tmp/testQom",
+		Pc:       123456,
+		ThreadID: 123457,
+		Props: CPUProperties{
+			Node:   0,
+			Socket: 1,
+			Core:   1,
+			Thread: 1966,
+		},
+	}
+	buf.AddCommand("query-cpus", nil, "return", []interface{}{cpuInfo})
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+	cpus, err := q.ExecQueryCpus(context.Background())
+	if err != nil {
+		t.Fatalf("Unexpected error: %v\n", err)
+	}
+	if len(cpus) != 1 {
+		t.Fatalf("Expected memory devices length equals to 1\n")
+	}
+	if reflect.DeepEqual(cpus[0], cpuInfo) == false {
+		t.Fatalf("Expected %v equals to %v\n", cpus[0], cpuInfo)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}
+
+// Checks that cpus are listed correctly
+func TestQMPExecuteQueryCpusFast(t *testing.T) {
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	cpuInfoFast := CPUInfoFast{
+		CPUIndex: 1,
+		Arch:     "x86",
+		Target:   "x86_64",
+		QomPath:  "/tmp/testQom",
+		ThreadID: 123457,
+		Props: CPUProperties{
+			Node:   0,
+			Socket: 1,
+			Core:   1,
+			Thread: 1966,
+		},
+	}
+	buf.AddCommand("query-cpus-fast", nil, "return", []interface{}{cpuInfoFast})
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+	cpus, err := q.ExecQueryCpusFast(context.Background())
+	if err != nil {
+		t.Fatalf("Unexpected error: %v\n", err)
+	}
+	if len(cpus) != 1 {
+		t.Fatalf("Expected memory devices length equals to 1\n")
+	}
+	if reflect.DeepEqual(cpus[0], cpuInfoFast) == false {
+		t.Fatalf("Expected %v equals to %v\n", cpus[0], cpuInfoFast)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}
+
 // Checks that migrate capabilities can be set
 func TestExecSetMigrationCaps(t *testing.T) {
 	connectedCh := make(chan *QMPVersion)