libvirt: add cpuset support for CPU pinning

Add --cpuset flag and LIBVIRT_CPUSET env var to pin vCPUs to specific
physical CPUs. Useful for AI inferencing where cores from different
sockets improve performance.

Changes:
- Add CPUSet field to Config and vmConfig structures
- Add --cpuset CLI flag and LIBVIRT_CPUSET environment variable
- Embed CPUSet attribute in Domain XML for all architectures
- Expose LIBVIRT_CPUSET in kustomization.yaml for deployment
- Add unit tests for CPUSet functionality

Fixes: #2397
Signed-off-by: tak-ka3 <[email protected]>

Author: tak-ka3

src/cloud-api-adaptor/install/overlays/libvirt/kustomization.yaml

@@ -30,6 +30,7 @@ configMapGenerator:
   #- LIBVIRT_VOL_NAME="" # Uncomment and set if you want to use a specific volume name. Defaults to podvm-base.qcow2
   #- LIBVIRT_CPU="2"
   #- LIBVIRT_MEMORY="8192"
+  #- LIBVIRT_CPUSET="" # Uncomment and set to pin vCPUs to physical CPUs (e.g., "0,2,4,6" or "0-3")
   #- PAUSE_IMAGE="" # Uncomment and set if you want to use a specific pause image
   #- TUNNEL_TYPE="" # Uncomment and set if you want to use a specific tunnel type. Defaults to vxlan
   #- VXLAN_PORT="" # Uncomment and set if you want to use a specific vxlan port. Defaults to 4789

src/cloud-providers/libvirt/libvirt.go

@@ -250,7 +250,8 @@ func createDomainXMLs390x(client *libvirtClient, cfg *domainConfig, vm *vmConfig
 			Value: cfg.mem, Unit: "MiB",
 		},
 		VCPU: &libvirtxml.DomainVCPU{
-			Value: cfg.cpu,
+			Value:  cfg.cpu,
+			CPUSet: vm.cpuset,
 		},
 		Clock: &libvirtxml.DomainClock{
 			Offset: "utc",
@@ -309,7 +310,7 @@ func createDomainXMLx86_64(client *libvirtClient, cfg *domainConfig, vm *vmConfi
 		Name:        cfg.name,
 		Description: "This Virtual Machine is the peer-pod VM",
 		Memory:      &libvirtxml.DomainMemory{Value: cfg.mem, Unit: "MiB", DumpCore: "on"},
-		VCPU:        &libvirtxml.DomainVCPU{Value: cfg.cpu},
+		VCPU:        &libvirtxml.DomainVCPU{Value: cfg.cpu, CPUSet: vm.cpuset},
 		OS: &libvirtxml.DomainOS{
 			Type: &libvirtxml.DomainOSType{Arch: "x86_64", Type: typeHardwareVirtualMachine},
 		},
@@ -459,7 +460,7 @@ func createDomainXMLaarch64(client *libvirtClient, cfg *domainConfig, vm *vmConf
 			Firmware: "efi",
 		},
 		Memory: &libvirtxml.DomainMemory{Value: cfg.mem, Unit: "MiB"},
-		VCPU:   &libvirtxml.DomainVCPU{Value: cfg.cpu},
+		VCPU:   &libvirtxml.DomainVCPU{Value: cfg.cpu, CPUSet: vm.cpuset},
 		CPU:    &libvirtxml.DomainCPU{Mode: "host-passthrough"},
 		Devices: &libvirtxml.DomainDeviceList{
 			Disks: []libvirtxml.DomainDisk{

src/cloud-providers/libvirt/libvirt_test.go

@@ -152,3 +152,108 @@ func TestCreateDomainXMLaarch64(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func TestCPUSetInDomainXML(t *testing.T) {
+	checkConfig(t)
+
+	client, err := NewLibvirtClient(testCfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.connection.Close()
+
+	testCases := []struct {
+		name           string
+		cpuset         string
+		expectedCPUSet string
+	}{
+		{
+			name:           "with cpuset specified",
+			cpuset:         "0,2,4,6",
+			expectedCPUSet: "0,2,4,6",
+		},
+		{
+			name:           "with cpuset range",
+			cpuset:         "0-3",
+			expectedCPUSet: "0-3",
+		},
+		{
+			name:           "with empty cpuset",
+			cpuset:         "",
+			expectedCPUSet: "",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			vm := vmConfig{
+				cpuset: tc.cpuset,
+			}
+
+			domainCfg := domainConfig{
+				name:        "TestCPUSet",
+				cpu:         4,
+				mem:         4096,
+				networkName: client.networkName,
+				bootDisk:    "/var/lib/libvirt/images/root.qcow2",
+				cidataDisk:  "/var/lib/libvirt/images/cidata.iso",
+			}
+
+			domCfg, err := createDomainXML(client, &domainCfg, &vm)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+
+			assert.Equal(t, tc.expectedCPUSet, domCfg.VCPU.CPUSet,
+				"CPUSet should be set correctly in domain XML")
+		})
+	}
+}
+
+func TestCPUSetXMLMarshaling(t *testing.T) {
+	// Test that CPUSet is correctly marshaled to XML without requiring libvirt connection
+	testCases := []struct {
+		name           string
+		cpuset         string
+		expectedSubstr string
+	}{
+		{
+			name:           "cpuset with comma-separated values",
+			cpuset:         "0,2,4,6",
+			expectedSubstr: `cpuset="0,2,4,6"`,
+		},
+		{
+			name:           "cpuset with range",
+			cpuset:         "0-7",
+			expectedSubstr: `cpuset="0-7"`,
+		},
+		{
+			name:           "cpuset with mixed format",
+			cpuset:         "0,2,4-7,10",
+			expectedSubstr: `cpuset="0,2,4-7,10"`,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			domain := &libvirtxml.Domain{
+				Type: "kvm",
+				Name: "test-vm",
+				VCPU: &libvirtxml.DomainVCPU{
+					Value:  4,
+					CPUSet: tc.cpuset,
+				},
+			}
+
+			xmlStr, err := domain.Marshal()
+			if err != nil {
+				t.Errorf("Failed to marshal domain XML: %v", err)
+				return
+			}
+
+			assert.Contains(t, xmlStr, tc.expectedSubstr,
+				"Marshaled XML should contain cpuset attribute")
+		})
+	}
+}

src/cloud-providers/libvirt/manager.go

@@ -43,6 +43,7 @@ func (_ *Manager) ParseCmd(flags *flag.FlagSet) {
 	reg.StringWithEnv(&libvirtcfg.Firmware, "firmware", defaultFirmware, "LIBVIRT_EFI_FIRMWARE", "Path to OVMF")
 	reg.UintWithEnv(&libvirtcfg.CPU, "cpu", 2, "LIBVIRT_CPU", "Number of processors allocated")
 	reg.UintWithEnv(&libvirtcfg.Memory, "memory", 8192, "LIBVIRT_MEMORY", "Amount of memory in MiB")
+	reg.StringWithEnv(&libvirtcfg.CPUSet, "cpuset", "", "LIBVIRT_CPUSET", "CPU set for pinning vCPUs to physical CPUs (e.g., \"0,2,4,6\" or \"0-3\")")
 
 	// Flags without environment variable support (pass empty string for envVarName)
 	reg.StringWithEnv(&libvirtcfg.DataDir, "data-dir", defaultDataDir, "", "libvirt storage dir")

src/cloud-providers/libvirt/provider.go

@@ -71,7 +71,7 @@ func (p *libvirtProvider) CreateInstance(ctx context.Context, podName, sandboxID
 	}
 
 	// TODO: Specify the maximum instance name length in Libvirt
-	vm := &vmConfig{name: instanceName, cpu: instanceVCPUs, mem: instanceMemory, userData: userData, firmware: p.serviceConfig.Firmware}
+	vm := &vmConfig{name: instanceName, cpu: instanceVCPUs, mem: instanceMemory, userData: userData, firmware: p.serviceConfig.Firmware, cpuset: p.serviceConfig.CPUSet}
 
 	if p.serviceConfig.DisableCVM {
 		vm.launchSecurityType = NoLaunchSecurity

src/cloud-providers/libvirt/types.go

@@ -22,7 +22,8 @@ type Config struct {
 	LaunchSecurity string
 	Firmware       string
 	CPU            uint
-	Memory         uint // It stores the value in MiB
+	Memory         uint   // It stores the value in MiB
+	CPUSet         string // CPU set for pinning vCPUs (e.g., "0,2,4,6" or "0-3")
 }
 
 type vmConfig struct {
@@ -35,6 +36,7 @@ type vmConfig struct {
 	instanceId         string //keeping it consistent with sandbox.vsi
 	launchSecurityType LaunchSecurityType
 	firmware           string
+	cpuset             string // CPU set for pinning vCPUs (e.g., "0,2,4,6" or "0-3")
 }
 
 type createDomainOutput struct {