--- a/arch/x86/realmode/rm/wakeup_asm.S	2013-05-02 17:20:25.266667541 +0200
+++ b/arch/x86/realmode/rm/wakeup_asm.S	2013-05-02 18:54:49.176667541 +0200
@@ -112,13 +112,17 @@
 
 	btl	$WAKEUP_BEHAVIOR_RESTORE_CR4, %edi
 	jnc	1f
-	movl	pmode_cr4, %eax
-	movl	%eax, %cr4
+	movl	pmode_cr4, %ecx
+	jecxz	1f
+	movl	%ecx, %cr4
 1:
 	btl	$WAKEUP_BEHAVIOR_RESTORE_EFER, %edi
 	jnc	1f
 	movl	pmode_efer, %eax
 	movl	pmode_efer + 4, %edx
+	movl	%eax, %ecx
+	orl	%edx, %ecx
+	jz	1f
 	movl	$MSR_EFER, %ecx
 	wrmsr
 1: