x86: make sure initmem is writable on 64-bit

Impact: unification

This patch ports commit 3c1df68b848b39270752ff8d4b956cc4a4dce0f6 ("x86: make
sure initmem is writable") to the 64-bit version to unify implementations of
free_init_pages().

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <1236078904.2675.17.camel@penberg-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/init_64.c

@@ -962,6 +962,13 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
 		begin, PAGE_ALIGN(end));
 	set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
 #else
+	/*
+	 * We just marked the kernel text read only above, now that
+	 * we are going to free part of that, we need to make that
+	 * writeable first.
+	 */
+	set_memory_rw(begin, (end - begin) >> PAGE_SHIFT);
+
 	printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
 
 	for (; addr < end; addr += PAGE_SIZE) {