Implement feature toggle for GA forwarding mode in QEMU

Current code supports 2 modes:
- forwarding via SSH forwarding
- forwarding by QEMU via serialport

In GA they are exclusive modes - it either talks to device or exposes
Unix socket inside VM.

At some point the GA part was switched to Unix socket only, but QEMU
start command line was not updated. SSH forwarder takes care
of it by removing Unix socket before starting its own, but there is no
point in having it, when it can't be used.

This code introduces feature toggle allowing to use either mode. Keeping
the "unstable" option could be beneficial for environments, where Unix
socket forwarding is tricky (Windows hosts).

Signed-off-by: Arthur Sengileyev <[email protected]>

Author: arixmkii

pkg/hostagent/hostagent.go

@@ -134,8 +134,9 @@ func New(instName string, stdout io.Writer, signalCh chan os.Signal, opts ...Opt
 		}
 		vSockPort = port
 	} else if *inst.Config.VMType == limayaml.QEMU {
-		// virtserialport doesn't seem to work reliably: https://github.com/lima-vm/lima/issues/2064
-		virtioPort = "" // filenames.VirtioPort
+		if *inst.Config.VMOpts.QEMU.VirtioGA {
+			virtioPort = filenames.VirtioPort
+		}
 	}
 
 	if err := cidata.GenerateCloudConfig(inst.Dir, instName, inst.Config); err != nil {

pkg/limayaml/defaults.go

@@ -888,6 +888,17 @@ func FillDefault(y, d, o *LimaYAML, filePath string, warn bool) {
 	y.CACertificates.Files = unique(slices.Concat(d.CACertificates.Files, y.CACertificates.Files, o.CACertificates.Files))
 	y.CACertificates.Certs = unique(slices.Concat(d.CACertificates.Certs, y.CACertificates.Certs, o.CACertificates.Certs))
 
+	if y.VMOpts.QEMU.VirtioGA == nil {
+		y.VMOpts.QEMU.VirtioGA = d.VMOpts.QEMU.VirtioGA
+	}
+	if o.VMOpts.QEMU.VirtioGA != nil {
+		y.VMOpts.QEMU.VirtioGA = o.VMOpts.QEMU.VirtioGA
+	}
+	if y.VMOpts.QEMU.VirtioGA == nil {
+		// virtserialport doesn't seem to work reliably, so, default to false: https://github.com/lima-vm/lima/issues/2064
+		y.VMOpts.QEMU.VirtioGA = ptr.Of(runtime.GOOS == "windows")
+	}
+
 	if runtime.GOOS == "darwin" && IsNativeArch(AARCH64) {
 		if y.Rosetta.Enabled == nil {
 			y.Rosetta.Enabled = d.Rosetta.Enabled

pkg/limayaml/limayaml.go

@@ -110,6 +110,7 @@ type VMOpts struct {
 
 type QEMUOpts struct {
 	MinimumVersion *string `yaml:"minimumVersion,omitempty" json:"minimumVersion,omitempty" jsonschema:"nullable"`
+	VirtioGA       *bool   `yaml:"virtioGA,omitempty" json:"virtioGA,omitempty" jsonschema:"nullable"`
 }
 
 type Rosetta struct {

pkg/qemu/qemu.go

@@ -45,6 +45,7 @@ type Config struct {
 	LimaYAML     *limayaml.LimaYAML
 	SSHLocalPort int
 	SSHAddress   string
+	VirtioGA     bool
 }
 
 // MinimumQemuVersion is the minimum supported QEMU version.
@@ -987,11 +988,13 @@ func Cmdline(ctx context.Context, cfg Config) (exe string, args []string, err er
 	args = append(args, "-chardev", fmt.Sprintf("socket,id=%s,path=%s,server=on,wait=off", qmpChardev, qmpSock))
 	args = append(args, "-qmp", "chardev:"+qmpChardev)
 
-	// Guest agent via serialport
-	guestSock := filepath.Join(cfg.InstanceDir, filenames.GuestAgentSock)
-	args = append(args, "-chardev", fmt.Sprintf("socket,path=%s,server=on,wait=off,id=qga0", guestSock))
-	args = append(args, "-device", "virtio-serial")
-	args = append(args, "-device", "virtserialport,chardev=qga0,name="+filenames.VirtioPort)
+	if cfg.VirtioGA {
+		// Guest agent via serialport
+		guestSock := filepath.Join(cfg.InstanceDir, filenames.GuestAgentSock)
+		args = append(args, "-chardev", fmt.Sprintf("socket,path=%s,server=on,wait=off,id=qga0", guestSock))
+		args = append(args, "-device", "virtio-serial")
+		args = append(args, "-device", "virtserialport,chardev=qga0,name="+filenames.VirtioPort)
+	}
 
 	// QEMU process
 	args = append(args, "-name", "lima-"+cfg.Name)

pkg/qemu/qemu_driver.go

@@ -77,6 +77,7 @@ func (l *LimaQemuDriver) Start(ctx context.Context) (chan error, error) {
 		LimaYAML:     l.Instance.Config,
 		SSHLocalPort: l.SSHLocalPort,
 		SSHAddress:   l.Instance.SSHAddress,
+		VirtioGA:     *l.Instance.Config.VMOpts.QEMU.VirtioGA,
 	}
 	qExe, qArgs, err := Cmdline(ctx, qCfg)
 	if err != nil {

templates/default.yaml

@@ -343,6 +343,10 @@ vmOpts:
     # Will be ignored if the vmType is not "qemu"
     # 🟢 Builtin default: not set
     minimumVersion: null
+    # Enable virtio port for GA. If disabled then will forward GA via SSH.
+    # Will be ignored if the vmType is not "qemu"
+    # 🟢 Builtin default: true on Windows and false otherwise
+    virtioGA: null
 
 # OS: "Linux".
 # 🟢 Builtin default: "Linux"