qemu: use x-ignore-shared to implement vm template

qemu upstream has x-ignore-shared that works similar
to our private bypass-shared-memory. We can use it to
implement the vm template feature.

Fixes: kata-containers#1798
Depends-on: github.com/kata-containers/packaging#641
Signed-off-by: Peng Tao <[email protected]>

virtcontainers/qemu.go

@@ -421,8 +421,7 @@ func (q *qemu) setupTemplate(knobs *govmmQemu.Knobs, memory *govmmQemu.Memory) g
 		}
 
 		if q.config.BootFromTemplate {
-			incoming.MigrationType = govmmQemu.MigrationExec
-			incoming.Exec = "cat " + q.config.DevicesStatePath
+			incoming.MigrationType = govmmQemu.MigrationDefer
 		}
 	}
 
@@ -585,6 +584,98 @@ func (q *qemu) vhostFSSocketPath(id string) (string, error) {
 	return utils.BuildSocketPath(store.RunVMStoragePath, id, vhostFSSocket)
 }
 
+func (q *qemu) virtiofsdArgs(sockPath string) []string {
+	// The daemon will terminate when the vhost-user socket
+	// connection with QEMU closes.  Therefore we do not keep track
+	// of this child process after returning from this function.
+	sourcePath := filepath.Join(kataHostSharedDir, q.id)
+	args := []string{
+		"-o", "vhost_user_socket=" + sockPath,
+		"-o", "source=" + sourcePath,
+		"-o", "cache=" + q.config.VirtioFSCache}
+	if q.config.Debug {
+		args = append(args, "-d")
+	} else {
+		args = append(args, "-f")
+	}
+
+	return args
+}
+
+func (q *qemu) setupVirtiofsd(timeout int) (remain int, err error) {
+	sockPath, err := q.vhostFSSocketPath(q.id)
+	if err != nil {
+		return 0, err
+	}
+
+	cmd := exec.Command(q.config.VirtioFSDaemon, q.virtiofsdArgs(sockPath)...)
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return 0, err
+	}
+
+	if err = cmd.Start(); err != nil {
+		return 0, err
+	}
+	defer func() {
+		if err != nil {
+			cmd.Process.Kill()
+		}
+	}()
+
+	// Wait for socket to become available
+	sockReady := make(chan error, 1)
+	timeStart := time.Now()
+	go func() {
+		scanner := bufio.NewScanner(stderr)
+		var sent bool
+		for scanner.Scan() {
+			if q.config.Debug {
+				q.Logger().WithField("source", "virtiofsd").Debug(scanner.Text())
+			}
+			if !sent && strings.Contains(scanner.Text(), "Waiting for vhost-user socket connection...") {
+				sockReady <- nil
+				sent = true
+			}
+		}
+		if !sent {
+			if err := scanner.Err(); err != nil {
+				sockReady <- err
+			} else {
+				sockReady <- fmt.Errorf("virtiofsd did not announce socket connection")
+			}
+		}
+		q.Logger().Info("virtiofsd quits")
+		q.stopSandbox()
+	}()
+
+	return q.waitVirtiofsd(timeStart, timeout, sockReady,
+		fmt.Sprintf("virtiofsd (pid=%d) socket %s", cmd.Process.Pid, sockPath))
+}
+
+func (q *qemu) waitVirtiofsd(start time.Time, timeout int, ready chan error, errMsg string) (int, error) {
+	var err error
+
+	timeoutDuration := time.Duration(timeout) * time.Second
+	select {
+	case err = <-ready:
+	case <-time.After(timeoutDuration):
+		err = fmt.Errorf("timed out waiting for %s", errMsg)
+	}
+	if err != nil {
+		return 0, err
+	}
+
+	// Now reduce timeout by the elapsed time
+	elapsed := time.Since(start)
+	if elapsed < timeoutDuration {
+		timeout = timeout - int(elapsed.Seconds())
+	} else {
+		timeout = 0
+	}
+	return timeout, nil
+}
+
 // startSandbox will start the Sandbox's VM.
 func (q *qemu) startSandbox(timeout int) error {
 	span, _ := q.trace("startSandbox")
@@ -625,81 +716,10 @@ func (q *qemu) startSandbox(timeout int) error {
 	}()
 
 	if q.config.SharedFS == config.VirtioFS {
-		sockPath, err := q.vhostFSSocketPath(q.id)
+		timeout, err = q.setupVirtiofsd(timeout)
 		if err != nil {
 			return err
 		}
-
-		// The daemon will terminate when the vhost-user socket
-		// connection with QEMU closes.  Therefore we do not keep track
-		// of this child process after returning from this function.
-		sourcePath := filepath.Join(kataHostSharedDir, q.id)
-		args := []string{
-			"-o", "vhost_user_socket=" + sockPath,
-			"-o", "source=" + sourcePath,
-			"-o", "cache=" + q.config.VirtioFSCache}
-		if q.config.Debug {
-			args = append(args, "-d")
-		} else {
-			args = append(args, "-f")
-		}
-		cmd := exec.Command(q.config.VirtioFSDaemon, args...)
-		stderr, err := cmd.StderrPipe()
-		if err != nil {
-			return err
-		}
-
-		if err = cmd.Start(); err != nil {
-			return err
-		}
-		defer func() {
-			if err != nil {
-				cmd.Process.Kill()
-			}
-		}()
-
-		// Wait for socket to become available
-		sockReady := make(chan error, 1)
-		timeStart := time.Now()
-		go func() {
-			scanner := bufio.NewScanner(stderr)
-			var sent bool
-			for scanner.Scan() {
-				if q.config.Debug {
-					q.Logger().WithField("source", "virtiofsd").Debug(scanner.Text())
-				}
-				if !sent && strings.Contains(scanner.Text(), "Waiting for vhost-user socket connection...") {
-					sockReady <- nil
-					sent = true
-				}
-			}
-			if !sent {
-				if err := scanner.Err(); err != nil {
-					sockReady <- err
-				} else {
-					sockReady <- fmt.Errorf("virtiofsd did not announce socket connection")
-				}
-			}
-			q.Logger().Info("virtiofsd quits")
-			q.stopSandbox()
-		}()
-		timeoutDuration := time.Duration(timeout) * time.Second
-		select {
-		case err = <-sockReady:
-		case <-time.After(timeoutDuration):
-			err = fmt.Errorf("timed out waiting for virtiofsd (pid=%d) socket %s", cmd.Process.Pid, sockPath)
-		}
-		if err != nil {
-			return err
-		}
-
-		// Now reduce timeout by the elapsed time
-		elapsed := time.Since(timeStart)
-		if elapsed < timeoutDuration {
-			timeout = timeout - int(elapsed.Seconds())
-		} else {
-			timeout = 0
-		}
 	}
 
 	var strErr string
@@ -709,9 +729,39 @@ func (q *qemu) startSandbox(timeout int) error {
 	}
 
 	err = q.waitSandbox(timeout) // the virtiofsd deferred checks err's value
+	if err != nil {
+		return err
+	}
+
+	if q.config.BootFromTemplate {
+		if err = q.bootFromTemplate(); err != nil {
+			return err
+		}
+	}
+
 	return err
 }
 
+func (q *qemu) bootFromTemplate() error {
+	err := q.qmpSetup()
+	if err != nil {
+		return err
+	}
+	defer q.qmpShutdown()
+
+	err = q.arch.setIgnoreSharedMemoryMigrationCaps(q.qmpMonitorCh.ctx, q.qmpMonitorCh.qmp)
+	if err != nil {
+		q.Logger().WithError(err).Error("set migration ignore shared memory")
+		return err
+	}
+	uri := fmt.Sprintf("exec:cat %s", q.config.DevicesStatePath)
+	err = q.qmpMonitorCh.qmp.ExecuteMigrationIncoming(q.qmpMonitorCh.ctx, uri)
+	if err != nil {
+		return err
+	}
+	return q.waitMigration()
+}
+
 // waitSandbox will wait for the Sandbox's VM to be up and running.
 func (q *qemu) waitSandbox(timeout int) error {
 	span, _ := q.trace("waitSandbox")
@@ -1498,9 +1548,9 @@ func (q *qemu) saveSandbox() error {
 	// BootToBeTemplate sets the VM to be a template that other VMs can clone from. We would want to
 	// bypass shared memory when saving the VM to a local file through migration exec.
 	if q.config.BootToBeTemplate {
-		err := q.arch.setBypassSharedMemoryMigrationCaps(q.qmpMonitorCh.ctx, q.qmpMonitorCh.qmp)
+		err := q.arch.setIgnoreSharedMemoryMigrationCaps(q.qmpMonitorCh.ctx, q.qmpMonitorCh.qmp)
 		if err != nil {
-			q.Logger().WithError(err).Error("set migration bypass shared memory")
+			q.Logger().WithError(err).Error("set migration ignore shared memory")
 			return err
 		}
 	}
@@ -1511,6 +1561,10 @@ func (q *qemu) saveSandbox() error {
 		return err
 	}
 
+	return q.waitMigration()
+}
+
+func (q *qemu) waitMigration() error {
 	t := time.NewTimer(qmpMigrationWaitTimeout)
 	defer t.Stop()
 	for {

virtcontainers/qemu_amd64.go

@@ -27,8 +27,6 @@ const defaultQemuMachineType = QemuPC
 
 const defaultQemuMachineOptions = "accel=kvm,kernel_irqchip,nvdimm"
 
-const qmpCapMigrationBypassSharedMemory = "bypass-shared-memory"
-
 const qmpMigrationWaitTimeout = 5 * time.Second
 
 var qemuPaths = map[string]string{

virtcontainers/qemu_arch_base.go

@@ -102,8 +102,8 @@ type qemuArch interface {
 	// supportGuestMemoryHotplug returns if the guest supports memory hotplug
 	supportGuestMemoryHotplug() bool
 
-	// setBypassSharedMemoryMigrationCaps set bypass-shared-memory capability for migration
-	setBypassSharedMemoryMigrationCaps(context.Context, *govmmQemu.QMP) error
+	// setIgnoreSharedMemoryMigrationCaps set bypass-shared-memory capability for migration
+	setIgnoreSharedMemoryMigrationCaps(context.Context, *govmmQemu.QMP) error
 }
 
 type qemuArchBase struct {
@@ -153,6 +153,8 @@ const (
 
 	// QemuCCWVirtio is a QEMU virt machine type for for s390x
 	QemuCCWVirtio = "s390-ccw-virtio"
+
+	qmpCapMigrationIgnoreShared = "x-ignore-shared"
 )
 
 // kernelParamsNonDebug is a list of the default kernel
@@ -579,10 +581,10 @@ func (q *qemuArchBase) supportGuestMemoryHotplug() bool {
 	return true
 }
 
-func (q *qemuArchBase) setBypassSharedMemoryMigrationCaps(ctx context.Context, qmp *govmmQemu.QMP) error {
+func (q *qemuArchBase) setIgnoreSharedMemoryMigrationCaps(ctx context.Context, qmp *govmmQemu.QMP) error {
 	err := qmp.ExecSetMigrationCaps(ctx, []map[string]interface{}{
 		{
-			"capability": qmpCapMigrationBypassSharedMemory,
+			"capability": qmpCapMigrationIgnoreShared,
 			"state":      true,
 		},
 	})

virtcontainers/qemu_arm64.go

@@ -29,8 +29,6 @@ const defaultQemuMachineType = QemuVirt
 
 const qmpMigrationWaitTimeout = 10 * time.Second
 
-const qmpCapMigrationBypassSharedMemory = "bypass-shared-memory"
-
 var defaultQemuMachineOptions = "usb=off,accel=kvm,nvdimm,gic-version=" + getGuestGICVersion()
 
 var qemuPaths = map[string]string{
@@ -199,7 +197,7 @@ func (q *qemuArm64) appendImage(devices []govmmQemu.Device, path string) ([]govm
 	return devices, nil
 }
 
-func (q *qemuArm64) setBypassSharedMemoryMigrationCaps(_ context.Context, _ *govmmQemu.QMP) error {
-	// bypass-shared-memory not support in arm64 for now
+func (q *qemuArm64) setIgnoreSharedMemoryMigrationCaps(_ context.Context, _ *govmmQemu.QMP) error {
+	// x-ignore-shared not support in arm64 for now
 	return nil
 }

virtcontainers/qemu_ppc64le.go

@@ -30,8 +30,6 @@ const defaultQemuMachineOptions = "accel=kvm,usb=off,cap-cfpc=broken,cap-sbbc=br
 
 const defaultMemMaxPPC64le = 32256 // Restrict MemMax to 32Gb on PPC64le
 
-const qmpCapMigrationBypassSharedMemory = "bypass-shared-memory"
-
 const qmpMigrationWaitTimeout = 5 * time.Second
 
 var qemuPaths = map[string]string{

virtcontainers/qemu_s390x.go

@@ -7,10 +7,11 @@ package virtcontainers
 
 import (
 	"fmt"
+	"time"
+
 	govmmQemu "github.com/intel/govmm/qemu"
 	"github.com/kata-containers/runtime/virtcontainers/device/config"
 	"github.com/kata-containers/runtime/virtcontainers/types"
-	"time"
 )
 
 type qemuS390x struct {
@@ -26,8 +27,6 @@ const defaultQemuMachineOptions = "accel=kvm"
 
 const virtioSerialCCW = "virtio-serial-ccw"
 
-const qmpCapMigrationBypassSharedMemory = "bypass-shared-memory"
-
 const qmpMigrationWaitTimeout = 5 * time.Second
 
 var qemuPaths = map[string]string{