diff --git a/deps/v8/.gitignore b/deps/v8/.gitignore
index d5c64a8e83c0e6..bfc93c7d444980 100644
--- a/deps/v8/.gitignore
+++ b/deps/v8/.gitignore
@@ -86,6 +86,7 @@
 !/third_party/v8
 !/third_party/wasm-api
 /tools/builtins-pgo/profiles/*.profile
+/tools/builtins-pgo/profiles/profiles_version
 /tools/clang
 /tools/gcmole/bootstrap
 /tools/gcmole/gcmole-tools
diff --git a/deps/v8/include/v8-version.h b/deps/v8/include/v8-version.h
index a3c31c5b29cc3c..e665e9b67dfc98 100644
--- a/deps/v8/include/v8-version.h
+++ b/deps/v8/include/v8-version.h
@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 12
 #define V8_MINOR_VERSION 4
 #define V8_BUILD_NUMBER 254
-#define V8_PATCH_LEVEL 20
+#define V8_PATCH_LEVEL 21
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
diff --git a/deps/v8/tools/builtins-pgo/download_profiles.py b/deps/v8/tools/builtins-pgo/download_profiles.py
index 23eb871e8371b3..e5adb339c29254 100755
--- a/deps/v8/tools/builtins-pgo/download_profiles.py
+++ b/deps/v8/tools/builtins-pgo/download_profiles.py
@@ -11,6 +11,7 @@
 """
 
 import argparse
+import contextlib
 import os
 import pathlib
 import re
@@ -79,6 +80,12 @@ def parse_args(cmd_args):
       default=DEPOT_TOOLS_DEFAULT_PATH,
   )
 
+  parser.add_argument(
+      '--force',
+      help=('force download, overwriting existing profiles'),
+      action='store_true',
+  )
+
   return parser.parse_args(cmd_args)
 
 
@@ -109,14 +116,45 @@ def retrieve_version(args):
   return version
 
 
+def download_profiles(version_path, requested_version, args):
+  if args.force:
+    return True
+
+  if not version_path.is_file():
+    return True
+
+  with open(version_path) as version_file:
+    profiles_version = version_file.read()
+
+  if profiles_version != requested_version:
+    return True
+
+  print('Profiles already downloaded, use --force to overwrite.')
+  return False
+
+
+@contextlib.contextmanager
+def ensure_profiles(version, args):
+  version_path = PGO_PROFILE_DIR / 'profiles_version'
+  require_profiles = download_profiles(version_path, version, args)
+  yield require_profiles
+  if require_profiles:
+    with open(version_path, 'w') as version_file:
+      version_file.write(version)
+
+
 def perform_action(version, args):
   path = f'{PGO_PROFILE_BUCKET}/by-version/{version}'
 
   if args.action == 'download':
-    cmd = ['cp', '-R', f'gs://{path}/*.profile', str(PGO_PROFILE_DIR)]
-    failure_hint = f'https://storage.googleapis.com/{path} does not exist.'
-    call_gsutil(cmd, failure_hint)
-    return
+    with ensure_profiles(version, args) as require_profiles:
+      if not require_profiles:
+        return
+
+      cmd = ['cp', '-R', f'gs://{path}/*.profile', str(PGO_PROFILE_DIR)]
+      failure_hint = f'https://storage.googleapis.com/{path} does not exist.'
+      call_gsutil(cmd, failure_hint)
+      return
 
   if args.action == 'validate':
     meta_json = f'{path}/meta.json'
diff --git a/deps/v8/tools/builtins-pgo/download_profiles_test.py b/deps/v8/tools/builtins-pgo/download_profiles_test.py
index a326f5e17f463e..5e0e03fffa3927 100644
--- a/deps/v8/tools/builtins-pgo/download_profiles_test.py
+++ b/deps/v8/tools/builtins-pgo/download_profiles_test.py
@@ -7,6 +7,7 @@
 import contextlib
 import io
 import os
+import pathlib
 import unittest
 
 from tempfile import TemporaryDirectory
@@ -34,12 +35,31 @@ def test_validate_profiles(self):
 
   def test_download_profiles(self):
     with TemporaryDirectory() as td, \
-        patch('download_profiles.PGO_PROFILE_DIR', td):
+        patch('download_profiles.PGO_PROFILE_DIR', pathlib.Path(td)):
       out, err = self._test_cmd(['download', '--version', '11.1.0.0'], 0)
       self.assertEqual(len(out), 0)
       self.assertEqual(len(err), 0)
       self.assertGreater(
           len([f for f in os.listdir(td) if f.endswith('.profile')]), 0)
+      with open(pathlib.Path(td) / 'profiles_version') as f:
+        self.assertEqual(f.read(), '11.1.0.0')
+
+      # A second download should not be started as profiles exist already
+      with patch('download_profiles.call_gsutil') as gsutil:
+        out, err = self._test_cmd(['download', '--version', '11.1.0.0'], 0)
+        self.assertEqual(
+            out,
+            'Profiles already downloaded, use --force to overwrite.\n',
+        )
+        gsutil.assert_not_called()
+
+      # A forced download should always trigger
+      with patch('download_profiles.call_gsutil') as gsutil:
+        cmd = ['download', '--version', '11.1.0.0', '--force']
+        out, err = self._test_cmd(cmd, 0)
+        self.assertEqual(len(out), 0)
+        self.assertEqual(len(err), 0)
+        gsutil.assert_called_once()
 
   def test_invalid_args(self):
     out, err = self._test_cmd(['invalid-action'], 2)
@@ -83,14 +103,18 @@ def test_retrieve_parameter_version(self):
     self.assertEqual(version, '11.1.1.42')
 
   def test_retrieve_untagged_version(self):
+    out = io.StringIO()
     with patch(
         'builtins.open',
         new=mock_open(read_data=self.mock_version_file(11, 4, 0, 0))), \
+        contextlib.redirect_stdout(out), \
         self.assertRaises(SystemExit) as se:
       args = parse_args(['download'])
       version = retrieve_version(args)
 
     self.assertEqual(se.exception.code, 0)
+    self.assertEqual(out.getvalue(),
+        'The version file specifies 11.4.0.0, which has no profiles.\n')
 
 if __name__ == '__main__':
   unittest.main()