--- a/hotspot/src/share/vm/runtime/arguments.cpp	Mon Oct 17 19:18:08 2016 -0400
+++ b/hotspot/src/share/vm/runtime/arguments.cpp	Tue Oct 18 01:47:24 2016 +0000
@@ -351,14 +351,6 @@
  *         Deprecated options should be tested in VMDeprecatedOptions.java.
  */
 
-// Obsolete or deprecated -XX flag.
-typedef struct {
-  const char* name;
-  JDK_Version deprecated_in; // When the deprecation warning started (or "undefined").
-  JDK_Version obsolete_in;   // When the obsolete warning started (or "undefined").
-  JDK_Version expired_in;    // When the option expires (or "undefined").
-} SpecialFlag;
-
 // The special_jvm_flags table declares options that are being deprecated and/or obsoleted. The
 // "deprecated_in" or "obsolete_in" fields may be set to "undefined", but not both.
 // When the JDK version reaches 'deprecated_in' limit, the JVM will process this flag on
@@ -498,7 +490,14 @@
   }
 }
 
+extern bool lookup_special_flag_ext(const char *flag_name, SpecialFlag& flag);
+
 static bool lookup_special_flag(const char *flag_name, SpecialFlag& flag) {
+  // Allow extensions to have priority
+  if (lookup_special_flag_ext(flag_name, flag)) {
+    return true;
+  }
+
   for (size_t i = 0; special_jvm_flags[i].name != NULL; i++) {
     if ((strcmp(special_jvm_flags[i].name, flag_name) == 0)) {
       flag = special_jvm_flags[i];
@@ -1804,6 +1803,7 @@
   if (os::is_server_class_machine()) {
     if (should_auto_select_low_pause_collector()) {
       FLAG_SET_ERGO_IF_DEFAULT(bool, UseConcMarkSweepGC, true);
+      FLAG_SET_ERGO_IF_DEFAULT(bool, UseParNewGC, true);
     } else {
       FLAG_SET_ERGO_IF_DEFAULT(bool, UseG1GC, true);
     }
@@ -2870,11 +2870,13 @@
       if (FLAG_SET_CMDLINE(bool, UseConcMarkSweepGC, true) != Flag::SUCCESS) {
         return JNI_EINVAL;
       }
+      handle_extra_cms_flags("-Xconcgc uses UseConcMarkSweepGC");
     // -Xnoconcgc
     } else if (match_option(option, "-Xnoconcgc")) {
       if (FLAG_SET_CMDLINE(bool, UseConcMarkSweepGC, false) != Flag::SUCCESS) {
         return JNI_EINVAL;
       }
+      handle_extra_cms_flags("-Xnoconcgc uses UseConcMarkSweepGC");
     // -Xbatch
     } else if (match_option(option, "-Xbatch")) {
       if (FLAG_SET_CMDLINE(bool, BackgroundCompilation, false) != Flag::SUCCESS) {
@@ -4157,6 +4159,15 @@
   return true;
 }
 
+void Arguments::handle_extra_cms_flags(const char* msg) {
+  SpecialFlag flag;
+  const char *flag_name = "UseConcMarkSweepGC";
+  if (lookup_special_flag(flag_name, flag)) {
+    handle_aliases_and_deprecation(flag_name, /* print warning */ true);
+    warning("%s", msg);
+  }
+}
+
 // Parse entry point called from JNI_CreateJavaVM
 
 jint Arguments::parse(const JavaVMInitArgs* initial_cmd_args) {

--- a/hotspot/src/share/vm/runtime/arguments.hpp	Mon Oct 17 19:18:08 2016 -0400
+++ b/hotspot/src/share/vm/runtime/arguments.hpp	Tue Oct 18 01:47:24 2016 +0000
@@ -41,6 +41,14 @@
   typedef jint (JNICALL *vfprintf_hook_t)(FILE *fp, const char *format, va_list args)  ATTRIBUTE_PRINTF(2, 0);
 }
 
+// Obsolete or deprecated -XX flag.
+struct SpecialFlag {
+  const char* name;
+  JDK_Version deprecated_in; // When the deprecation warning started (or "undefined").
+  JDK_Version obsolete_in;   // When the obsolete warning started (or "undefined").
+  JDK_Version expired_in;    // When the option expires (or "undefined").
+};
+
 // PathString is used as:
 //  - the underlying value for a SystemProperty
 //  - the path portion of an --patch-module module/path pair
@@ -519,6 +527,8 @@
 
   static bool handle_deprecated_print_gc_flags();
 
+  static void handle_extra_cms_flags(const char* msg);
+
   static jint parse_vm_init_args(const JavaVMInitArgs *java_tool_options_args,
                                  const JavaVMInitArgs *java_options_args,
                                  const JavaVMInitArgs *cmd_line_args);

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/runtime/arguments_ext.cpp	Tue Oct 18 01:47:24 2016 +0000
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "runtime/arguments.hpp"
+
+bool lookup_special_flag_ext(const char *flag_name, SpecialFlag& flag) {
+  return false;
+}

--- a/hotspot/test/gc/startup_warnings/TestCMS.java	Mon Oct 17 19:18:08 2016 -0400
+++ b/hotspot/test/gc/startup_warnings/TestCMS.java	Tue Oct 18 01:47:24 2016 +0000
@@ -24,8 +24,8 @@
 /*
 * @test TestCMS
 * @key gc
-* @bug 8006398
-* @summary Test that CMS does not print a warning message
+* @bug 8006398 8155948
+* @summary Test that CMS prints a warning message only for a commercial build
 * @library /test/lib
 * @modules java.base/jdk.internal.misc
 *          java.management
@@ -33,16 +33,27 @@
 
 import jdk.test.lib.process.ProcessTools;
 import jdk.test.lib.process.OutputAnalyzer;
-
+import jdk.test.lib.BuildHelper;
 
 public class TestCMS {
 
-  public static void main(String args[]) throws Exception {
-    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-XX:+UseConcMarkSweepGC", "-version");
+  public static void runTest(String[] args) throws Exception {
+    boolean isCommercial = BuildHelper.isCommercialBuild();
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(args);
     OutputAnalyzer output = new OutputAnalyzer(pb.start());
-    output.shouldNotContain("deprecated");
+    if (isCommercial) {
+      output.shouldContain("deprecated");
+    } else {
+      output.shouldNotContain("deprecated");
+    }
     output.shouldNotContain("error");
     output.shouldHaveExitValue(0);
   }
 
+  public static void main(String args[]) throws Exception {
+    runTest(new String[] {"-XX:+UseConcMarkSweepGC", "-version"});
+    runTest(new String[] {"-Xconcgc", "-version"});
+    runTest(new String[] {"-Xnoconcgc", "-version"});
+  }
+
 }