diff --git a/[refs] b/[refs]
index 3d4150247e22..ebc8d6f3d01a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6e32d479db6079dd5d4309aa66aecbcf2664a5fe
+refs/heads/master: 42e78e9719aa0c76711e2731b19c90fe5ae05278
diff --git a/trunk/arch/x86/kernel/head_64.S b/trunk/arch/x86/kernel/head_64.S
index 94bf9cc2c7ee..980053c4b9cc 100644
--- a/trunk/arch/x86/kernel/head_64.S
+++ b/trunk/arch/x86/kernel/head_64.S
@@ -252,6 +252,22 @@ ENTRY(secondary_startup_64)
 	pushq	%rax		# target address in negative space
 	lretq
 
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
+ * up already except stack. We just set up stack here. Then call
+ * start_secondary().
+ */
+ENTRY(start_cpu0)
+	movq stack_start(%rip),%rsp
+	movq	initial_code(%rip),%rax
+	pushq	$0		# fake return address to stop unwinder
+	pushq	$__KERNEL_CS	# set correct cs
+	pushq	%rax		# target address in negative space
+	lretq
+ENDPROC(start_cpu0)
+#endif
+
 	/* SMP bootup changes these two */
 	__REFDATA
 	.align	8