--- old/src/hotspot/cpu/x86/stubGenerator_x86_64.cpp	2018-08-20 11:53:30.720405751 +0100
+++ new/src/hotspot/cpu/x86/stubGenerator_x86_64.cpp	2018-08-20 11:53:30.437404908 +0100
@@ -2785,6 +2785,49 @@
     return start;
   }
 
+  address generate_data_cache_writeback() {
+    bool optimized = VM_Version::supports_clflushopt();
+    bool no_evict = VM_Version::supports_clwb();
+
+    const Register src        = c_rarg0;  // source address
+
+    __ align(CodeEntryAlignment);
+
+    StubCodeMark mark(this, "StubRoutines", "_data_cache_writeback");
+
+    address start = __ pc();
+    __ enter();
+    const Address line(src, 0);
+    __ cache_wb(line);
+    __ leave();
+    __ ret(0);
+
+    return start;    
+  }
+
+  address generate_data_cache_writeback_sync() {
+    const Register is_pre    = c_rarg0;  // pre or post sync
+
+    __ align(CodeEntryAlignment);
+
+    StubCodeMark mark(this, "StubRoutines", "_data_cache_writeback_sync");
+
+    // pre wbsync is a no-op
+    // post wbsync translates to an sfence
+
+    Label skip;
+    address start = __ pc();
+    __ enter();
+    __ cmpl(is_pre, 0);
+    __ jcc(Assembler::notEqual, skip); 
+    __ cache_wbsync(false);
+    __ bind(skip);
+    __ leave();
+    __ ret(0);
+
+    return start;
+  }
+
   void generate_arraycopy_stubs() {
     address entry;
     address entry_jbyte_arraycopy;
@@ -5777,6 +5820,10 @@
     // support for verify_oop (must happen after universe_init)
     StubRoutines::_verify_oop_subroutine_entry = generate_verify_oop();
 
+    // data cache line writeback
+    StubRoutines::_data_cache_writeback = generate_data_cache_writeback();
+    StubRoutines::_data_cache_writeback_sync = generate_data_cache_writeback_sync();
+    
     // arraycopy stubs used by compilers
     generate_arraycopy_stubs();