powerpc: Hugetlb for BookE

Enable hugepages on Freescale BookE processors.  This allows the kernel to
use huge TLB entries to map pages, which can greatly reduce the number of
TLB misses and the amount of TLB thrashing experienced by applications with
large memory footprints.  Care should be taken when using this on FSL
processors, as the number of large TLB entries supported by the core is low
(16-64) on current processors.

The supported set of hugepage sizes include 4m, 16m, 64m, 256m, and 1g.
Page sizes larger than the max zone size are called "gigantic" pages and
must be allocated on the command line (and cannot be deallocated).

This is currently only fully implemented for Freescale 32-bit BookE
processors, but there is some infrastructure in the code for
64-bit BooKE.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/init_32.c

@@ -32,6 +32,8 @@
 #include <linux/pagemap.h>
 #include <linux/memblock.h>
 #include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/hugetlb.h>
 
 #include <asm/pgalloc.h>
 #include <asm/prom.h>
@@ -44,6 +46,7 @@
 #include <asm/tlb.h>
 #include <asm/sections.h>
 #include <asm/system.h>
+#include <asm/hugetlb.h>
 
 #include "mmu_decl.h"
 
@@ -123,6 +126,12 @@ void __init MMU_init(void)
 	/* parse args from command line */
 	MMU_setup();
 
+	/*
+	 * Reserve gigantic pages for hugetlb.  This MUST occur before
+	 * lowmem_end_addr is initialized below.
+	 */
+	reserve_hugetlb_gpages();
+
 	if (memblock.memory.cnt > 1) {
 #ifndef CONFIG_WII
 		memblock.memory.cnt = 1;