Use VZ by default for new instances on macOS >= 13.5

VZ is now the default type for new instances >= 13.5, unless the config
is incompatible with vz (e.g., `firmware.legacyBIOS=true`, `mountType=9p`).

Existing instances will continue to use QEMU by default,
unless `vz-identifier` is present in the instance directory.

Run `limactl start` with `--debug` to see how the vmType is resolved.

Signed-off-by: Akihiro Suda <[email protected]>

.github/workflows/test.yml

@@ -128,6 +128,7 @@ jobs:
 
   integration:
     name: Integration tests
+    # on macOS 12, the default vmType is QEMU
     runs-on: macos-12
     timeout-minutes: 120
     steps:
@@ -397,6 +398,7 @@ jobs:
 
   vz:
     name: "vz"
+    # on macOS 12, the default vmType is VZ
     runs-on: macos-13
     timeout-minutes: 120
     steps:
@@ -411,12 +413,12 @@ jobs:
       with:
         path: ~/Library/Caches/lima/download
         # hashFiles do not seem to support symlinks
-        key: ${{ runner.os }}-${{ hashFiles('examples/experimental/vz.yaml') }}
+        key: ${{ runner.os }}-${{ hashFiles('examples/default.yaml') }}
     - name: Make
       run: make
     - name: Install
       run: make install
     - name: Install test dependencies
       run: brew install qemu bash coreutils
     - name: Test
-      run: ./hack/test-templates.sh templates/experimental/vz.yaml
+      run: ./hack/test-templates.sh templates/default.yaml

examples/default.yaml

@@ -8,7 +8,7 @@
 # VM type: "qemu" or "vz" (on macOS 13 and later).
 # The vmType can be specified only on creating the instance.
 # The vmType of existing instances cannot be changed.
-# 🟢 Builtin default: "qemu"
+# 🟢 Builtin default: "vz" (on macOS 13.5 and later), "qemu" (on others)
 vmType: null
 
 # OS: "Linux".

pkg/limayaml/defaults.go

@@ -3,6 +3,7 @@ package limayaml
 import (
 	"bytes"
 	"crypto/sha256"
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -11,6 +12,7 @@ import (
 	"strconv"
 	"text/template"
 
+	"github.com/coreos/go-semver/semver"
 	"github.com/docker/go-units"
 	"github.com/lima-vm/lima/pkg/networks"
 	"github.com/pbnjay/memory"
@@ -127,13 +129,7 @@ func defaultGuestInstallPrefix() string {
 //   - DNS are picked from the highest priority where DNS is not empty.
 //   - CACertificates Files and Certs are uniquely appended in d, y, o order
 func FillDefault(y, d, o *LimaYAML, filePath string) {
-	if y.VMType == nil {
-		y.VMType = d.VMType
-	}
-	if o.VMType != nil {
-		y.VMType = o.VMType
-	}
-	y.VMType = pointer.String(ResolveVMType(y.VMType))
+	y.VMType = pointer.String(ResolveVMType(y, d, o, filePath))
 	if y.OS == nil {
 		y.OS = d.OS
 	}
@@ -860,11 +856,95 @@ func NewVMType(driver string) VMType {
 	}
 }
 
-func ResolveVMType(s *string) VMType {
-	if s == nil || *s == "" || *s == "default" {
+func isExistingInstanceDir(dir string) bool {
+	// existence of "lima.yaml" does not signify existence of the instance,
+	// because the file is created during the initialization of the instance.
+	for _, f := range []string{filenames.HostAgentStdoutLog, filenames.HostAgentStderrLog,
+		filenames.VzIdentifier, filenames.BaseDisk, filenames.DiffDisk, filenames.CIDataISO} {
+		file := filepath.Join(dir, f)
+		if _, err := os.Lstat(file); !errors.Is(err, os.ErrNotExist) {
+			return true
+		}
+	}
+	return false
+}
+
+func ResolveVMType(y, d, o *LimaYAML, filePath string) VMType {
+	// Check if the VMType is explicitly specified
+	for i, f := range []*LimaYAML{d, y, o} {
+		if f.VMType != nil && *f.VMType != "" && *f.VMType != "default" {
+			logrus.Debugf("ResolveVMType: resolved VMType %q (explicitly specified in []*LimaYAML{d,y,o}[%d])", *f.VMType, i)
+			return NewVMType(*f.VMType)
+		}
+	}
+
+	// If this is an existing instance, guess the VMType from the contents of the instance directory.
+	// Note that the instance directory may be created by a previous version of Lima.
+	if dir, basename := filepath.Split(filePath); dir != "" && basename == filenames.LimaYAML && isExistingInstanceDir(dir) {
+		vzIdentifier := filepath.Join(dir, filenames.VzIdentifier)
+		if _, err := os.Lstat(vzIdentifier); !errors.Is(err, os.ErrNotExist) {
+			logrus.Debugf("ResolveVMType: resolved VMType %q (existing instance, with %q)", VZ, vzIdentifier)
+			return VZ
+		}
+		logrus.Debugf("ResolveVMType: resolved VMType %q (existing instance, without %q)", QEMU, vzIdentifier)
+		return QEMU
+	}
+
+	// Resolve the best type, depending on GOOS
+	switch runtime.GOOS {
+	case "darwin":
+		macOSProductVersion, err := osutil.MacOSProductVersion()
+		if err != nil {
+			logrus.WithError(err).Warn("Failed to get macOS product version")
+			logrus.Debugf("ResolveVMType: resolved VMType %q (default for unknown version of macOS)", QEMU)
+			return QEMU
+		}
+		// Virtualization.framework in macOS prior to 13.5 could not boot Linux kernel v6.2 on Intel
+		// https://github.com/lima-vm/lima/issues/1577
+		if macOSProductVersion.LessThan(*semver.New("13.5.0")) {
+			logrus.Debugf("ResolveVMType: resolved VMType %q (default for macOS prior to 13.5)", QEMU)
+			return QEMU
+		}
+		// Use QEMU if the config depends on QEMU
+		for i, f := range []*LimaYAML{d, y, o} {
+			if f.Arch != nil && !IsNativeArch(*f.Arch) {
+				logrus.Debugf("ResolveVMType: resolved VMType %q (non-native arch=%q is specified in []*LimaYAML{d,y,o}[%d])", *f.Arch, QEMU, i)
+				return QEMU
+			}
+			if f.Firmware.LegacyBIOS != nil && *f.Firmware.LegacyBIOS {
+				logrus.Debugf("ResolveVMType: resolved VMType %q (firmware.legacyBIOS is specified in []*LimaYAML{d,y,o}[%d])", QEMU, i)
+				return QEMU
+			}
+			if f.MountType != nil && *f.MountType == NINEP {
+				logrus.Debugf("ResolveVMType: resolved VMType %q (mountType=%q is specified in []*LimaYAML{d,y,o}[%d])", NINEP, QEMU, i)
+				return QEMU
+			}
+			if f.Audio.Device != nil {
+				switch *f.Audio.Device {
+				case "", "none", "default", "vz":
+					// NOP
+				default:
+					logrus.Debugf("ResolveVMType: resolved VMType %q (audio.device=%q is specified in []*LimaYAML{d,y,o}[%d])", *f.Audio.Device, QEMU, i)
+					return QEMU
+				}
+			}
+			if f.Video.Display != nil {
+				switch *f.Video.Display {
+				case "", "none", "default", "vz":
+					// NOP
+				default:
+					logrus.Debugf("ResolveVMType: resolved VMType %q (video.display=%q is specified in []*LimaYAML{d,y,o}[%d])", *f.Video.Display, QEMU, i)
+					return QEMU
+				}
+			}
+		}
+		// Use VZ if the config is compatible with VZ
+		logrus.Debugf("ResolveVMType: resolved VMType %q (default for macOS 13.5 and later)", VZ)
+		return VZ
+	default:
+		logrus.Debugf("ResolveVMType: resolved VMType %q (default for GOOS=%q)", QEMU, runtime.GOOS)
 		return QEMU
 	}
-	return NewVMType(*s)
 }
 
 func ResolveOS(s *string) OS {

website/content/en/docs/Config/VMType/_index.md

@@ -22,9 +22,12 @@ flowchart
   intel_on_arm --  "No" --> vz["VZ"]
 ```
 
+The default vmType is QEMU in Lima prior to v1.0.
+Starting with Lima v1.0, Lima will use VZ by default on macOS (>= 13.5) for new instances,
+unless the config is incompatible with VZ.
+
 ## QEMU
 "qemu" option makes use of QEMU to run guest operating system. 
-This option is used by default if "vmType" is not set.
 
 ## VZ
 > **Warning**