lguest: set max_pfn_mapped, growl loudly at Yinghai Lu

6af61a7614a306fe882a0c2b4ddc63b65aa66efc 'x86: clean up max_pfn_mapped
usage - 32-bit' makes the following comment:

    XEN PV and lguest may need to assign max_pfn_mapped too.

But no CC.  Yinghai, wasting fellow developers' time is a VERY bad
habit.  If you do it again, I will hunt you down and try to extract
the three hours of my life I just lost :)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>

arch/x86/lguest/boot.c

@@ -1014,6 +1014,9 @@ __init void lguest_init(void)
 	init_pg_tables_start = __pa(pg0);
 	init_pg_tables_end = __pa(pg0);
 
+	/* As described in head_32.S, we map the first 128M of memory. */
+	max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
+
 	/* Load the %fs segment register (the per-cpu segment register) with
 	 * the normal data segment to get through booting. */
 	asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");