tart run --nested to enable nested virtualization when available (#938)

Only works for Linux VMs under Sequoia hosts.

Fixes #933
Fixes #701

.ci/set-version.sh

@@ -3,3 +3,5 @@
 TMPFILE=$(mktemp)
 envsubst < Sources/tart/CI/CI.swift > $TMPFILE
 mv $TMPFILE Sources/tart/CI/CI.swift
+
+/usr/libexec/PlistBuddy -c "Add :CFBundleShortVersionString string ${CIRRUS_TAG}" Resources/Info.plist

PROFILING.md

@@ -0,0 +1,64 @@
+# Profiling Tart
+
+## Using `time(1)`
+
+Perhaps, the easiest, but not the most comprehensive way to tell what's going on with Tart is to use the [`time(1)`](https://ss64.com/mac/time.html) command.
+
+In the example below, you will run `tart pull` via `time(1)` to gather generalized CPU, I/O and memory usage metrics:
+
+```shell
+/usr/bin/time -l tart pull ghcr.io/cirruslabs/macos-sequoia-base:latest
+```
+
+**Note:** you need to specify a full path to `time(1)` binary, otherwise the shell's built-in `time` command will be invoked, which doesn't have the `-l` command-line argument.
+
+**Note:** The `-l` command-line argument makes `time(1)` return much more useful information, for example, maximum memory usage.
+
+When running the command above, you'll see the `tart pull` output first as it pulls the image, and then the `time(1)` output, which will be printed once the Tart process finishes:
+
+```
+      172.17 real        10.29 user         8.36 sys
+           353796096  maximum resident set size
+                   0  average shared memory size
+                   0  average unshared data size
+                   0  average unshared stack size
+               23838  page reclaims
+                  35  page faults
+                   0  swaps
+                   0  block input operations
+                   0  block output operations
+                   8  messages sent
+                   8  messages received
+                   0  signals received
+                 146  voluntary context switches
+              222950  involuntary context switches
+         39683070975  instructions retired
+         27562035252  cycles elapsed
+           170920448  peak memory footprint
+```
+
+From the output above, you can tell that `tart pull` spent nearly 90% of time off-CPU (`real` > `user` + `sys`), which means that Tart was mostly waiting for the I/O (be it a network or disk), instead of decompressing disk layers or doing other useful computations.
+
+## Using `xctrace(1)`
+
+[`xctrace(1)`](https://keith.github.io/xcode-man-pages/xctrace.1.html) is a `.trace` format recorder for the [Instruments](https://en.wikipedia.org/wiki/Instruments_(software)) app, which yields much more powerful insights compared to `time(1)`. For example, it can tell which Tart functions spent the most time on the CPU, thus allowing the Tart developers to further optimize these functions.
+
+To use it, make sure that [Xcode](https://developer.apple.com/xcode/resources/) is installed. If you're installing Xcode for the first time on the machine, you'll need to launch it once and click the blue "Install" button. There's no need to choose any platforms except for the macOS.
+
+Once done, you can create a CPU profile of `tart pull`:
+
+```shell
+xctrace record --template "CPU Profiler" --target-stdout - --launch -- /opt/homebrew/bin/tart pull ghcr.io/cirruslabs/macos-sequoia-base:latest
+```
+
+Now that `xctrace(1)` is running, you'll see the `tart pull`-related output first, and once finished, the following line will appear:
+
+```
+Output file saved as: Launch_[...].trace
+```
+
+To view this trace in the Instruments app, simply find this directory in Finder and double-click it. Instruments app will appear:
+
+![](Resources/Instruments.png)
+
+To send this trace, right-click its directory in Finder and choose "Compress [...]". This will result in a similarly named file with a `.zip` at the end, which can now be conveniently sent via email or uploaded.

Package.resolved

@@ -1,13 +1,13 @@
 {
-  "originHash" : "2c514a4a1d7e106713db744bee89edb40d75da63e6611990ec2f4b0da53c0455",
+  "originHash" : "6a15657d8cb1d3e2b447f31aff5b47d6a9655d2262e48ca76476ba525435269b",
   "pins" : [
     {
       "identity" : "antlr4",
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/antlr/antlr4",
       "state" : {
-        "branch" : "dev",
-        "revision" : "2703a8516c0fb7fe92db6b9c40e0113f577646d2"
+        "revision" : "cc82115a4e7f53d71d9d905caa2c2dfa4da58899",
+        "version" : "4.13.2"
       }
     },
     {
@@ -24,8 +24,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/groue/Semaphore",
       "state" : {
-        "revision" : "f1c4a0acabeb591068dea6cffdd39660b86dec28",
-        "version" : "0.0.8"
+        "revision" : "2543679282aa6f6c8ecf2138acd613ed20790bc2",
+        "version" : "0.1.0"
       }
     },
     {
@@ -33,8 +33,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/getsentry/sentry-cocoa",
       "state" : {
-        "revision" : "ef4fec9dfb8dd5027b09a4a5c9362feafd118e1a",
-        "version" : "8.24.0"
+        "revision" : "5575af93efb776414f243e93d6af9f6258dc539a",
+        "version" : "8.36.0"
       }
     },
     {
@@ -51,8 +51,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-argument-parser",
       "state" : {
-        "revision" : "46989693916f56d1186bd59ac15124caef896560",
-        "version" : "1.3.1"
+        "revision" : "41982a3656a71c768319979febd796c6fd111d5c",
+        "version" : "1.5.0"
       }
     },
     {
@@ -61,7 +61,7 @@
       "location" : "https://github.com/apple/swift-async-algorithms",
       "state" : {
         "branch" : "main",
-        "revision" : "f05e450f0b909c0e80670a47516c4b9700b9e5da"
+        "revision" : "5c8bd186f48c16af0775972700626f0b74588278"
       }
     },
     {
@@ -78,8 +78,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-collections.git",
       "state" : {
-        "revision" : "f504716c27d2e5d4144fa4794b12129301d17729",
-        "version" : "1.0.3"
+        "revision" : "9bf03ff58ce34478e66aaee630e491823326fd06",
+        "version" : "1.1.3"
       }
     },
     {
@@ -87,8 +87,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-log.git",
       "state" : {
-        "revision" : "e97a6fcb1ab07462881ac165fdbb37f067e205d5",
-        "version" : "1.5.4"
+        "revision" : "9cb486020ebf03bfa5b5df985387a14a98744537",
+        "version" : "1.6.1"
       }
     },
     {
@@ -105,8 +105,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/fumoboy007/swift-retry",
       "state" : {
-        "revision" : "9f133487ffc2ab4539688c29efe57bb1ba31d7b0",
-        "version" : "0.2.3"
+        "revision" : "df9d7b185d2e433147ec0083a73c257e665eea0d",
+        "version" : "0.2.4"
       }
     },
     {
@@ -141,8 +141,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/nicklockwood/SwiftFormat",
       "state" : {
-        "revision" : "9df3b01f477163b33d5e63c5e2e5b9f946a49c56",
-        "version" : "0.53.6"
+        "revision" : "ab6844edb79a7b88dc6320e6cee0a0db7674dac3",
+        "version" : "0.54.5"
       }
     },
     {

Package.swift

@@ -15,10 +15,10 @@ let package = Package(
     .package(url: "https://github.com/apple/swift-algorithms", from: "1.2.0"),
     .package(url: "https://github.com/apple/swift-async-algorithms", branch: "main"),
     .package(url: "https://github.com/malcommac/SwiftDate", from: "7.0.0"),
-    .package(url: "https://github.com/antlr/antlr4", branch: "dev"),
+    .package(url: "https://github.com/antlr/antlr4", exact: "4.13.2"),
     .package(url: "https://github.com/apple/swift-atomics.git", .upToNextMajor(from: "1.2.0")),
     .package(url: "https://github.com/nicklockwood/SwiftFormat", from: "0.53.6"),
-    .package(url: "https://github.com/getsentry/sentry-cocoa", from: "8.24.0"),
+    .package(url: "https://github.com/getsentry/sentry-cocoa", from: "8.36.0"),
     .package(url: "https://github.com/cfilipov/TextTable", branch: "master"),
     .package(url: "https://github.com/sersoft-gmbh/swift-sysctl.git", from: "1.8.0"),
     .package(url: "https://github.com/orchetect/SwiftRadix", from: "1.3.1"),

Resources/Info.plist

@@ -2,22 +2,22 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-    <key>CFBundleName</key>
-    <string>tart</string>
-    <key>CFBundleIdentifier</key>
-    <string>org.cirruslabs.tart</string>
-    <key>CFBundleExecutable</key>
-    <string>tart</string>
-    <key>LSBackgroundOnly</key>
-    <string>1</string>
-    <key>CFBundleIconFiles</key>
-    <array>
-        <string>AppIcon.png</string>
-    </array>
-    <key>NSAppTransportSecurity</key>
-    <dict>
-        <key>NSAllowsArbitraryLoads</key>
-        <true/>
-    </dict>
+	<key>CFBundleName</key>
+	<string>Tart</string>
+	<key>CFBundleDisplayName</key>
+	<string>Tart</string>
+	<key>CFBundleIdentifier</key>
+	<string>org.cirruslabs.tart</string>
+	<key>CFBundleExecutable</key>
+	<string>tart</string>
+	<key>CFBundleIconFiles</key>
+	<array>
+		<string>AppIcon.png</string>
+	</array>
+	<key>NSAppTransportSecurity</key>
+	<dict>
+		<key>NSAllowsArbitraryLoads</key>
+		<true/>
+	</dict>
 </dict>
 </plist>

Sources/tart/Commands/Clone.swift

@@ -9,12 +9,10 @@ struct Clone: AsyncParsableCommand {
     Creates a local virtual machine by cloning either a remote or another local virtual machine.
 
     Due to copy-on-write magic in Apple File System, a cloned VM won't actually claim all the space right away.
-    Only changes to a cloned disk will be written and claim new space. By default, Tart checks available capacity
-    in Tart's home directory and checks if there is enough space for the worst possible scenario: when the whole disk
-    will be modified.
+    Only changes to a cloned disk will be written and claim new space. This also speeds up clones enormously.
 
-    This behaviour can be disabled by setting TART_NO_AUTO_PRUNE environment variable. This might be helpful
-    for use cases when the original image is very big and a workload is known to only modify a fraction of the cloned disk.
+    By default, Tart checks available capacity in Tart's home directory and tries to reclaim minimum possible storage for the cloned image
+    to fit. This behaviour is called "automatic pruning" and can be disabled by setting TART_NO_AUTO_PRUNE environment variable.
     """
   )
 
@@ -30,6 +28,9 @@ struct Clone: AsyncParsableCommand {
   @Option(help: "network concurrency to use when pulling a remote VM from the OCI-compatible registry")
   var concurrency: UInt = 4
 
+  @Flag(help: .hidden)
+  var deduplicate: Bool = false
+
   func validate() throws {
     if newName.contains("/") {
       throw ValidationError("<new-name> should be a local name")
@@ -47,7 +48,7 @@ struct Clone: AsyncParsableCommand {
     if let remoteName = try? RemoteName(sourceName), !ociStorage.exists(remoteName) {
       // Pull the VM in case it's OCI-based and doesn't exist locally yet
       let registry = try Registry(host: remoteName.host, namespace: remoteName.namespace, insecure: insecure)
-      try await ociStorage.pull(remoteName, registry: registry, concurrency: concurrency)
+      try await ociStorage.pull(remoteName, registry: registry, concurrency: concurrency, deduplicate: deduplicate)
     }
 
     let sourceVM = try VMStorageHelper.open(sourceName)

Sources/tart/Commands/Pull.swift

@@ -9,8 +9,8 @@ struct Pull: AsyncParsableCommand {
     Pulls a virtual machine from a remote OCI-compatible registry. Supports authorization via Keychain (see "tart login --help"),
     Docker credential helpers defined in ~/.docker/config.json or via TART_REGISTRY_USERNAME/TART_REGISTRY_PASSWORD environment variables.
 
-    By default, Tart checks available capacity in Tart's home directory and tries to reclaim minimum possible storage for the remote image to fit via "tart prune".
-    This behaviour can be disabled by setting TART_NO_AUTO_PRUNE environment variable.
+    By default, Tart checks available capacity in Tart's home directory and tries to reclaim minimum possible storage for the remote image
+    to fit. This behaviour is called "automatic pruning" and can be disabled by setting TART_NO_AUTO_PRUNE environment variable.
     """
   )
 
@@ -23,6 +23,9 @@ struct Pull: AsyncParsableCommand {
   @Option(help: "network concurrency to use when pulling a remote VM from the OCI-compatible registry")
   var concurrency: UInt = 4
 
+  @Flag(help: .hidden)
+  var deduplicate: Bool = false
+
   func validate() throws {
     if concurrency < 1 {
       throw ValidationError("network concurrency cannot be less than 1")
@@ -43,6 +46,6 @@ struct Pull: AsyncParsableCommand {
 
     defaultLogger.appendNewLine("pulling \(remoteName)...")
 
-    try await VMStorageOCI().pull(remoteName, registry: registry, concurrency: concurrency)
+    try await VMStorageOCI().pull(remoteName, registry: registry, concurrency: concurrency, deduplicate: deduplicate)
   }
 }

Sources/tart/Commands/Run.swift

@@ -156,6 +156,9 @@ struct Run: AsyncParsableCommand {
   """, valueName: "[name:]path[:options]"))
   var dir: [String] = []
 
+  @Flag(help: ArgumentHelp("Enable nested virtualization if possible"))
+  var nested: Bool = false
+
   @Option(help: ArgumentHelp("""
   Use bridged networking instead of the default shared (NAT) networking \n(e.g. --net-bridged=en0 or --net-bridged=\"Wi-Fi\")
   """, discussion: """
@@ -221,6 +224,14 @@ struct Run: AsyncParsableCommand {
       throw ValidationError("--captures-system-keys can only be used with the default VM view")
     }
 
+    if nested {
+      if #unavailable(macOS 15) {
+        throw ValidationError("Nested virtualization is supported on hosts starting with macOS 15 (Sequia), and later.")
+      } else if !VZGenericPlatformConfiguration.isNestedVirtualizationSupported {
+        throw ValidationError("Nested virtualization is available for Mac with the M3 chip, and later.")
+      }
+    }
+
     let localStorage = VMStorageLocal()
     let vmDir = try localStorage.open(name)
     if try vmDir.state() == .Suspended {
@@ -294,6 +305,7 @@ struct Run: AsyncParsableCommand {
       directorySharingDevices: directoryShares() + rosettaDirectoryShare(),
       serialPorts: serialPorts,
       suspendable: suspendable,
+      nested: nested,
       audio: !noAudio,
       clipboard: !noClipboard,
       sync: VZDiskImageSynchronizationMode(diskOptions.syncModeRaw)

Sources/tart/Credentials/DockerConfigCredentialsProvider.swift

@@ -39,9 +39,10 @@ class DockerConfigCredentialsProvider: CredentialsProvider {
     inPipe.fileHandleForWriting.write("\(host)\n".data(using: .utf8)!)
     inPipe.fileHandleForWriting.closeFile()
 
+    let outputData = try outPipe.fileHandleForReading.readToEnd()
+
     process.waitUntilExit()
 
-    let outputData = try outPipe.fileHandleForReading.readToEnd()
     if !(process.terminationReason == .exit && process.terminationStatus == 0) {
       if let outputData = outputData {
         print(String(decoding: outputData, as: UTF8.self))

Sources/tart/MACAddressResolver/ARPCache.swift

@@ -52,6 +52,11 @@ struct ARPCache {
     process.standardInput = FileHandle.nullDevice
 
     try process.run()
+
+    guard let arpCommandOutput = try pipe.fileHandleForReading.readToEnd() else {
+      throw ARPCommandYieldedInvalidOutputError(explanation: "empty output")
+    }
+
     process.waitUntilExit()
 
     if !(process.terminationReason == .exit && process.terminationStatus == 0) {
@@ -60,10 +65,6 @@ struct ARPCache {
         terminationStatus: process.terminationStatus)
     }
 
-    guard let arpCommandOutput = try pipe.fileHandleForReading.readToEnd() else {
-      throw ARPCommandYieldedInvalidOutputError(explanation: "empty output")
-    }
-
     self.arpCommandOutput = arpCommandOutput
   }
 

Sources/tart/OCI/Layerizer/Disk.swift

@@ -2,5 +2,5 @@ import Foundation
 
 protocol Disk {
   static func push(diskURL: URL, registry: Registry, chunkSizeMb: Int, concurrency: UInt, progress: Progress) async throws -> [OCIManifestLayer]
-  static func pull(registry: Registry, diskLayers: [OCIManifestLayer], diskURL: URL, concurrency: UInt, progress: Progress, localLayerCache: LocalLayerCache?) async throws
+  static func pull(registry: Registry, diskLayers: [OCIManifestLayer], diskURL: URL, concurrency: UInt, progress: Progress, localLayerCache: LocalLayerCache?, deduplicate: Bool) async throws
 }

Sources/tart/OCI/Layerizer/DiskV1.swift

@@ -45,7 +45,7 @@ class DiskV1: Disk {
     return pushedLayers
   }
 
-  static func pull(registry: Registry, diskLayers: [OCIManifestLayer], diskURL: URL, concurrency: UInt, progress: Progress, localLayerCache: LocalLayerCache? = nil) async throws {
+  static func pull(registry: Registry, diskLayers: [OCIManifestLayer], diskURL: URL, concurrency: UInt, progress: Progress, localLayerCache: LocalLayerCache? = nil, deduplicate: Bool = false) async throws {
     if !FileManager.default.createFile(atPath: diskURL.path, contents: nil) {
       throw OCIError.FailedToCreateVmFile
     }

Sources/tart/OCI/Layerizer/DiskV2.swift

@@ -69,12 +69,12 @@ class DiskV2: Disk {
     }
   }
 
-  static func pull(registry: Registry, diskLayers: [OCIManifestLayer], diskURL: URL, concurrency: UInt, progress: Progress, localLayerCache: LocalLayerCache? = nil) async throws {
+  static func pull(registry: Registry, diskLayers: [OCIManifestLayer], diskURL: URL, concurrency: UInt, progress: Progress, localLayerCache: LocalLayerCache? = nil, deduplicate: Bool = false) async throws {
     // Support resumable pulls
     let pullResumed = FileManager.default.fileExists(atPath: diskURL.path)
 
     if !pullResumed {
-      if let localLayerCache = localLayerCache {
+      if deduplicate, let localLayerCache = localLayerCache {
         // Clone the local layer cache's disk and use it as a base, potentially
         // reducing the space usage since some blocks won't be written at all
         try FileManager.default.copyItem(at: localLayerCache.diskURL, to: diskURL)
@@ -151,26 +151,31 @@ class DiskV2: Disk {
 
           // Also open the disk file for reading and verifying
           // its contents in case the local layer cache is used
-          let rdisk: FileHandle? = if localLayerCache != nil {
+          let rdisk: FileHandle? = if deduplicate && localLayerCache != nil {
             try FileHandle(forReadingFrom: diskURL)
           } else {
             nil
           }
 
-          // Check if we already have this layer contents in the local layer cache
-          if let localLayerCache = localLayerCache, let localLayerInfo = localLayerCache.findInfo(digest: diskLayer.digest, offsetHint: diskWritingOffset) {
-            // indicates that the locally cloned disk image has the same content at the given offset
-            let localHit = localLayerInfo.uncompressedContentDigest == uncompressedLayerContentDigest
-              && localLayerInfo.range.lowerBound == diskWritingOffset
-            // doesn't seem that localHit can ever be false if the localLayerCache is not nil
-            // but let's just add extra safety here and check it
-            if !localHit {
+          // Check if we already have this layer contents in the local layer cache,
+          // or perhaps even on the cloned disk (when the deduplication is enabled)
+          if let localLayerCache = localLayerCache,
+             let localLayerInfo = localLayerCache.findInfo(digest: diskLayer.digest, offsetHint: diskWritingOffset),
+             localLayerInfo.uncompressedContentDigest == uncompressedLayerContentDigest {
+            if deduplicate && localLayerInfo.range.lowerBound == diskWritingOffset {
+              // Do nothing, because the data is already on the disk that we've inherited from
+            } else {
               // Fulfil the layer contents from the local blob cache
               let data = localLayerCache.subdata(localLayerInfo.range)
               _ = try zeroSkippingWrite(disk, rdisk, fsBlockSize, diskWritingOffset, data)
             }
+
             try disk.close()
 
+            if let rdisk = rdisk {
+              try rdisk.close()
+            }
+
             // Update the progress
             progress.completedUnitCount += Int64(diskLayer.size)
 
@@ -198,6 +203,10 @@ class DiskV2: Disk {
           try filter.finalize()
 
           try disk.close()
+
+          if let rdisk = rdisk {
+            try rdisk.close()
+          }
         }
 
         globalDiskWritingOffset += uncompressedLayerSize

Sources/tart/OCI/Reference/Generated/ReferenceBaseListener.swift

@@ -1,4 +1,4 @@
-// Generated from java-escape by ANTLR 4.11.1
+// Generated from Reference.g4 by ANTLR 4.13.2
 
 import Antlr4
 

Sources/tart/OCI/Reference/Generated/ReferenceLexer.swift

@@ -1,4 +1,4 @@
-// Generated from java-escape by ANTLR 4.11.1
+// Generated from Reference.g4 by ANTLR 4.13.2
 import Antlr4
 
 open class ReferenceLexer: Lexer {
@@ -49,7 +49,7 @@ open class ReferenceLexer: Lexer {
 
 	public
 	required init(_ input: CharStream) {
-	    RuntimeMetaData.checkVersion("4.11.1", RuntimeMetaData.VERSION)
+	    RuntimeMetaData.checkVersion("4.13.2", RuntimeMetaData.VERSION)
 		super.init(input)
 		_interp = LexerATNSimulator(self, ReferenceLexer._ATN, ReferenceLexer._decisionToDFA, ReferenceLexer._sharedContextCache)
 	}

Sources/tart/OCI/Reference/Generated/ReferenceListener.swift

@@ -1,4 +1,4 @@
-// Generated from java-escape by ANTLR 4.11.1
+// Generated from Reference.g4 by ANTLR 4.13.2
 import Antlr4
 
 /**

Sources/tart/OCI/Reference/Generated/ReferenceParser.swift

@@ -1,4 +1,4 @@
-// Generated from java-escape by ANTLR 4.11.1
+// Generated from Reference.g4 by ANTLR 4.13.2
 import Antlr4
 
 open class ReferenceParser: Parser {
@@ -41,7 +41,7 @@ open class ReferenceParser: Parser {
 	static let VOCABULARY = Vocabulary(_LITERAL_NAMES, _SYMBOLIC_NAMES)
 
 	override open
-	func getGrammarFileName() -> String { return "java-escape" }
+	func getGrammarFileName() -> String { return "Reference.g4" }
 
 	override open
 	func getRuleNames() -> [String] { return ReferenceParser.ruleNames }
@@ -60,7 +60,7 @@ open class ReferenceParser: Parser {
 
 	override public
 	init(_ input:TokenStream) throws {
-	    RuntimeMetaData.checkVersion("4.11.1", RuntimeMetaData.VERSION)
+	    RuntimeMetaData.checkVersion("4.13.2", RuntimeMetaData.VERSION)
 		try super.init(input)
 		_interp = ParserATNSimulator(self,ReferenceParser._ATN,ReferenceParser._decisionToDFA, ReferenceParser._sharedContextCache)
 	}
@@ -460,7 +460,7 @@ open class ReferenceParser: Parser {
 		 		setState(63)
 		 		try _errHandler.sync(self)
 		 		_la = try _input.LA(1)
-		 		if ((Int64(_la) & ~0x3f) == 0 && ((Int64(1) << _la) & 88) != 0) {
+		 		if (((Int64(_la) & ~0x3f) == 0 && ((Int64(1) << _la) & 88) != 0)) {
 		 			setState(62)
 		 			try separator()
 
@@ -611,7 +611,7 @@ open class ReferenceParser: Parser {
 		 	setState(84)
 		 	try _errHandler.sync(self)
 		 	_la = try _input.LA(1)
-		 	while ((Int64(_la) & ~0x3f) == 0 && ((Int64(1) << _la) & 88) != 0) {
+		 	while (((Int64(_la) & ~0x3f) == 0 && ((Int64(1) << _la) & 88) != 0)) {
 		 		setState(79)
 		 		try separator()
 		 		setState(80)
@@ -664,7 +664,7 @@ open class ReferenceParser: Parser {
 		 	try enterOuterAlt(_localctx, 1)
 		 	setState(87)
 		 	_la = try _input.LA(1)
-		 	if (!((Int64(_la) & ~0x3f) == 0 && ((Int64(1) << _la) & 88) != 0)) {
+		 	if (!(((Int64(_la) & ~0x3f) == 0 && ((Int64(1) << _la) & 88) != 0))) {
 		 	try _errHandler.recoverInline(self)
 		 	}
 		 	else {

Sources/tart/OCI/Registry.swift

@@ -327,12 +327,12 @@ class Registry {
       request.httpBody = body
     }
 
-    var (channel, response) = try await authAwareRequest(request: request, viaFile: viaFile)
+    var (channel, response) = try await authAwareRequest(request: request, viaFile: viaFile, doAuth: doAuth)
 
     if doAuth && response.statusCode == HTTPCode.Unauthorized.rawValue {
       _ = try await channel.asData()
       try await auth(response: response)
-      (channel, response) = try await authAwareRequest(request: request, viaFile: viaFile)
+      (channel, response) = try await authAwareRequest(request: request, viaFile: viaFile, doAuth: doAuth)
     }
 
     return (channel, response)
@@ -413,11 +413,13 @@ class Registry {
     return nil
   }
 
-  private func authAwareRequest(request: URLRequest, viaFile: Bool = false) async throws -> (AsyncThrowingChannel<Data, Error>, HTTPURLResponse) {
+  private func authAwareRequest(request: URLRequest, viaFile: Bool = false, doAuth: Bool) async throws -> (AsyncThrowingChannel<Data, Error>, HTTPURLResponse) {
     var request = request
 
-    if let (name, value) = await authenticationKeeper.header() {
-      request.addValue(value, forHTTPHeaderField: name)
+    if doAuth {
+      if let (name, value) = await authenticationKeeper.header() {
+        request.addValue(value, forHTTPHeaderField: name)
+      }
     }
 
     request.setValue("Tart/\(CI.version) (\(DeviceInfo.os); \(DeviceInfo.model))",

Sources/tart/PIDLock.swift

@@ -11,7 +11,7 @@ class PIDLock {
     if fd == -1 {
       let details = Errno(rawValue: CInt(errno))
 
-      throw RuntimeError.PIDLockFailed("failed to open lock file \(url): \(details)")
+      throw RuntimeError.PIDLockMissing("failed to open lock file \(url): \(details)")
     }
   }
 

Sources/tart/Platform/Darwin.swift

@@ -58,7 +58,11 @@ struct UnsupportedHostOSError: Error, CustomStringConvertible {
       VZMacOSBootLoader()
     }
 
-    func platform(nvramURL: URL) throws -> VZPlatformConfiguration {
+    func platform(nvramURL: URL, needsNestedVirtualization: Bool) throws -> VZPlatformConfiguration {
+      if needsNestedVirtualization {
+        throw RuntimeError.VMConfigurationError("macOS virtual machines do not support nested virtualization")
+      }
+
       let result = VZMacPlatformConfiguration()
 
       result.machineIdentifier = ecid

Sources/tart/Platform/Linux.swift

@@ -14,8 +14,12 @@ struct Linux: Platform {
     return result
   }
 
-  func platform(nvramURL: URL) throws -> VZPlatformConfiguration {
-    VZGenericPlatformConfiguration()
+  func platform(nvramURL: URL, needsNestedVirtualization: Bool) throws -> VZPlatformConfiguration {
+    let config = VZGenericPlatformConfiguration()
+    if #available(macOS 15, *) {
+      config.isNestedVirtualizationEnabled = needsNestedVirtualization
+    }
+    return config
   }
 
   func graphicsDevice(vmConfig: VMConfig) -> VZGraphicsDeviceConfiguration {

Sources/tart/Platform/Platform.swift

@@ -3,7 +3,7 @@ import Virtualization
 protocol Platform: Codable {
   func os() -> OS
   func bootLoader(nvramURL: URL) throws -> VZBootLoader
-  func platform(nvramURL: URL) throws -> VZPlatformConfiguration
+  func platform(nvramURL: URL, needsNestedVirtualization: Bool) throws -> VZPlatformConfiguration
   func graphicsDevice(vmConfig: VMConfig) -> VZGraphicsDeviceConfiguration
   func keyboards() -> [VZKeyboardConfiguration]
   func pointingDevices() -> [VZPointingDeviceConfiguration]

Sources/tart/URL+AccessDate.swift

@@ -1,4 +1,5 @@
 import Foundation
+import System
 
 extension URL {
   func accessDate() throws -> Date {
@@ -13,7 +14,9 @@ extension URL {
     let times = [accessDate.asTimeval(), modificationDate.asTimeval()]
     let ret = utimes(path, times)
     if ret != 0 {
-      throw RuntimeError.FailedToUpdateAccessDate("utimes(2) failed: \(ret.explanation())")
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.FailedToUpdateAccessDate("utimes(2) failed: \(details)")
     }
   }
 }

Sources/tart/VM.swift

@@ -47,6 +47,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
        directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = [],
        serialPorts: [VZSerialPortConfiguration] = [],
        suspendable: Bool = false,
+       nested: Bool = false,
        audio: Bool = true,
        clipboard: Bool = true,
        sync: VZDiskImageSynchronizationMode = .full
@@ -66,6 +67,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
                                                 directorySharingDevices: directorySharingDevices,
                                                 serialPorts: serialPorts,
                                                 suspendable: suspendable,
+                                                nested: nested,
                                                 audio: audio,
                                                 clipboard: clipboard,
                                                 sync: sync
@@ -295,6 +297,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     directorySharingDevices: [VZDirectorySharingDeviceConfiguration],
     serialPorts: [VZSerialPortConfiguration],
     suspendable: Bool = false,
+    nested: Bool = false,
     audio: Bool = true,
     clipboard: Bool = true,
     sync: VZDiskImageSynchronizationMode = .full
@@ -309,7 +312,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     configuration.memorySize = vmConfig.memorySize
 
     // Platform
-    configuration.platform = try vmConfig.platform.platform(nvramURL: nvramURL)
+    configuration.platform = try vmConfig.platform.platform(nvramURL: nvramURL, needsNestedVirtualization: nested)
 
     // Display
     configuration.graphicsDevices = [vmConfig.platform.graphicsDevice(vmConfig: vmConfig)]
@@ -365,13 +368,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
       try VZDiskImageStorageDeviceAttachment(url: diskURL, readOnly: false, cachingMode: .cached, synchronizationMode: sync) :
       try VZDiskImageStorageDeviceAttachment(url: diskURL, readOnly: false, cachingMode: .automatic, synchronizationMode: sync)
 
-    var device: VZStorageDeviceConfiguration
-    if #available(macOS 14, *), vmConfig.os == .linux {
-      device = VZNVMExpressControllerDeviceConfiguration(attachment: attachment)
-    } else {
-      device = VZVirtioBlockDeviceConfiguration(attachment: attachment)
-    }
-    var devices: [VZStorageDeviceConfiguration] = [device]
+    var devices: [VZStorageDeviceConfiguration] = [VZVirtioBlockDeviceConfiguration(attachment: attachment)]
     devices.append(contentsOf: additionalStorageDevices)
     configuration.storageDevices = devices
 

Sources/tart/VMDirectory+OCI.swift

@@ -11,7 +11,7 @@ enum OCIError: Error {
 }
 
 extension VMDirectory {
-  func pullFromRegistry(registry: Registry, manifest: OCIManifest, concurrency: UInt, localLayerCache: LocalLayerCache?) async throws {
+  func pullFromRegistry(registry: Registry, manifest: OCIManifest, concurrency: UInt, localLayerCache: LocalLayerCache?, deduplicate: Bool) async throws {
     // Pull VM's config file layer and re-serialize it into a config file
     let configLayers = manifest.layers.filter {
       $0.mediaType == configMediaType
@@ -54,12 +54,13 @@ extension VMDirectory {
     do {
       try await diskImplType.pull(registry: registry, diskLayers: layers, diskURL: diskURL,
                                   concurrency: concurrency, progress: progress,
-                                  localLayerCache: localLayerCache)
+                                  localLayerCache: localLayerCache,
+                                  deduplicate: deduplicate)
     } catch let error where error is FilterError {
       throw RuntimeError.PullFailed("failed to decompress disk: \(error.localizedDescription)")
     }
 
-    if let llc = localLayerCache {
+    if deduplicate, let llc = localLayerCache {
       // set custom attribute to remember deduplicated bytes
       diskURL.setDeduplicatedBytes(llc.deduplicatedBytes)
     }

Sources/tart/VMStorageHelper.swift

@@ -24,6 +24,8 @@ class VMStorageHelper {
   private static func missingVMWrap<R: Any>(_ name: String, closure: () throws -> R) throws -> R {
     do {
       return try closure()
+    } catch RuntimeError.PIDLockMissing {
+      throw RuntimeError.VMDoesNotExist(name: name)
     } catch {
       if error.isFileNotFound() {
         throw RuntimeError.VMDoesNotExist(name: name)
@@ -59,6 +61,7 @@ enum RuntimeError : Error {
   case InvalidDiskSize(_ message: String)
   case FailedToUpdateAccessDate(_ message: String)
   case PIDLockFailed(_ message: String)
+  case PIDLockMissing(_ message: String)
   case FailedToParseRemoteName(_ message: String)
   case VMTerminationFailed(_ message: String)
   case ImproperlyFormattedHost(_ host: String, _ hint: String)
@@ -105,6 +108,8 @@ extension RuntimeError : CustomStringConvertible {
       return message
     case .PIDLockFailed(let message):
       return message
+    case .PIDLockMissing(let message):
+      return message
     case .FailedToParseRemoteName(let cause):
       return "failed to parse remote name: \(cause)"
     case .VMTerminationFailed(let message):

Sources/tart/VMStorageOCI.swift

@@ -140,7 +140,7 @@ class VMStorageOCI: PrunableStorage {
     try list().filter { (_, _, isSymlink) in !isSymlink }.map { (_, vmDir, _) in vmDir }
   }
 
-  func pull(_ name: RemoteName, registry: Registry, concurrency: UInt) async throws {
+  func pull(_ name: RemoteName, registry: Registry, concurrency: UInt, deduplicate: Bool) async throws {
     SentrySDK.configureScope { scope in
       scope.setContext(value: ["imageName": name.description], key: "OCI")
     }
@@ -203,10 +203,14 @@ class VMStorageOCI: PrunableStorage {
           if let llc = localLayerCache {
             let deduplicatedHuman = ByteCountFormatter.string(fromByteCount: Int64(llc.deduplicatedBytes), countStyle: .file)
 
-            defaultLogger.appendNewLine("found an image \(llc.name) that will allow us to deduplicate \(deduplicatedHuman), using it as a base...")
+            if deduplicate {
+              defaultLogger.appendNewLine("found an image \(llc.name) that will allow us to deduplicate \(deduplicatedHuman), using it as a base...")
+            } else {
+              defaultLogger.appendNewLine("found an image \(llc.name) that will allow us to avoid fetching \(deduplicatedHuman), will try use it...")
+            }
           }
 
-          try await tmpVMDir.pullFromRegistry(registry: registry, manifest: manifest, concurrency: concurrency, localLayerCache: localLayerCache)
+          try await tmpVMDir.pullFromRegistry(registry: registry, manifest: manifest, concurrency: concurrency, localLayerCache: localLayerCache, deduplicate: deduplicate)
         } recoverFromFailure: { error in
           if error is Retryable {
             print("Error: \(error.localizedDescription)")
@@ -235,6 +239,9 @@ class VMStorageOCI: PrunableStorage {
       // are excluded from garbage collection
       VMDirectory(baseURL: vmURL(name)).markExplicitlyPulled()
     }
+
+    // to explicitly set the image as being accessed so it won't get pruned immediately
+    _ = try VMStorageOCI().open(name)
   }
 
   func linked(from: RemoteName, to: RemoteName) -> Bool {

docs/faq.md

@@ -90,3 +90,21 @@ Instead of Anka Registry, Tart can work with any OCI-compatible container regist
 and scalable experience for distributing virtual machines.
 
 Tart doesn't yet have an analogue of Anka Controller for managing long living VMs but [soon will be](https://github.com/cirruslabs/tart/issues/372).
+
+## Automatic pruning
+
+`tart pull` and `tart clone` commands check the remaining space available on the volume associated with `TART_HOME` directory (defaults to `~/.tart`) before pulling or cloning anything.
+
+In case there's not enough space to fit the newly pulled or cloned VM image, Tart will remove the least recently accessed VMs from OCI cache and `.ipsw` files from IPSW cache until enough free space is available.
+
+To disable this functionality, set the `TART_NO_AUTO_PRUNE` environment variable either globally:
+
+```shell
+export TART_NO_AUTO_PRUNE=
+```
+
+...or per `tart pull` and `tart clone` invocation as follows:
+
+```shell
+TART_NO_AUTO_PRUNE= tart pull ...
+```