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>

arch/i386/kernel/setup.c

@@ -601,6 +601,8 @@ void __init setup_arch(char **cmdline_p)
 	 * NOTE: at this point the bootmem allocator is fully available.
 	 */
 
+	paravirt_post_allocator_init();
+
 	dmi_scan_machine();
 
 #ifdef CONFIG_X86_GENERICARCH

include/asm-i386/paravirt.h

@@ -52,6 +52,8 @@ struct paravirt_ops
 	/* Basic arch-specific setup */
 	void (*arch_setup)(void);
 	char *(*memory_setup)(void);
+	void (*post_allocator_init)(void);
+
 	void (*init_IRQ)(void);
 	void (*time_init)(void);
 
@@ -669,6 +671,12 @@ static inline void setup_secondary_clock(void)
 }
 #endif
 
+static inline void paravirt_post_allocator_init(void)
+{
+	if (paravirt_ops.post_allocator_init)
+		(*paravirt_ops.post_allocator_init)();
+}
+
 static inline void paravirt_pagetable_setup_start(pgd_t *base)
 {
 	if (paravirt_ops.pagetable_setup_start)

include/asm-i386/setup.h

@@ -81,6 +81,10 @@ void __init add_memory_region(unsigned long long start,
 
 extern unsigned long init_pg_tables_end;
 
+#ifndef CONFIG_PARAVIRT
+#define paravirt_post_allocator_init()	do {} while (0)
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif  /*  __KERNEL__  */