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>

1 files changed, 30 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 2cd664ef0a5e..dd9c4fd038e0 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -36,6 +36,18 @@
 
 #define PAGE_SIZE		(ASM_CONST(1) << PAGE_SHIFT)
 
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_HUGETLB_PAGE
+extern unsigned int HPAGE_SHIFT;
+#else
+#define HPAGE_SHIFT PAGE_SHIFT
+#endif
+#define HPAGE_SIZE		((1UL) << HPAGE_SHIFT)
+#define HPAGE_MASK		(~(HPAGE_SIZE - 1))
+#define HUGETLB_PAGE_ORDER	(HPAGE_SHIFT - PAGE_SHIFT)
+#define HUGE_MAX_HSTATE		(MMU_PAGE_COUNT-1)
+#endif
+
 /* We do define AT_SYSINFO_EHDR but don't use the gate mechanism */
 #define __HAVE_ARCH_GATE_AREA		1
 
@@ -158,6 +170,24 @@ extern phys_addr_t kernstart_addr;
 #define is_kernel_addr(x)	((x) >= PAGE_OFFSET)
 #endif
 
+/*
+ * Use the top bit of the higher-level page table entries to indicate whether
+ * the entries we point to contain hugepages.  This works because we know that
+ * the page tables live in kernel space.  If we ever decide to support having
+ * page tables at arbitrary addresses, this breaks and will have to change.
+ */
+#ifdef CONFIG_PPC64
+#define PD_HUGE 0x8000000000000000
+#else
+#define PD_HUGE 0x80000000
+#endif
+
+/*
+ * Some number of bits at the level of the page table that points to
+ * a hugepte are used to encode the size.  This masks those bits.
+ */
+#define HUGEPD_SHIFT_MASK     0x3f
+
 #ifndef __ASSEMBLY__
 
 #undef STRICT_MM_TYPECHECKS
@@ -243,7 +273,6 @@ typedef unsigned long pgprot_t;
 #endif
 
 typedef struct { signed long pd; } hugepd_t;
-#define HUGEPD_SHIFT_MASK     0x3f
 
 #ifdef CONFIG_HUGETLB_PAGE
 static inline int hugepd_ok(hugepd_t hpd)