paravirt: add a hook for once the allocator is ready

Add a hook so that the paravirt backend knows when the allocator is
ready.  This is useful for the obvious reason that the allocator is
available, but the other side-effect of having the bootmem allocator
available is that each page now has an associated "struct page".

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
index 2d61e65..74871d0 100644
--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c
@@ -601,6 +601,8 @@
 	 * NOTE: at this point the bootmem allocator is fully available.
 	 */
 
+	paravirt_post_allocator_init();
+
 	dmi_scan_machine();
 
 #ifdef CONFIG_X86_GENERICARCH