From 9ce80f5fdea428be58e7f1cbb81950a968a5a40c Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 17 Apr 2008 17:40:45 +0200
Subject: [PATCH] --- yaml --- r: 88579 b: refs/heads/master c:
 00d1c5e05736f947687be27706bda01cec104e57 h: refs/heads/master i:   88577:
 2c1cc4398fb03022aa2c8831f51fe632742bceb0   88575:
 31b55bb28847f0b8de9f1d58e93870aa107f8db4 v: v3

---
 [refs]                                      |  2 +-
 trunk/Documentation/x86_64/boot-options.txt |  5 +++++
 trunk/arch/x86/Kconfig.debug                | 12 ++++++++++++
 trunk/arch/x86/mm/init_64.c                 | 20 ++++++++++++++++++++
 trunk/include/asm-x86/pgtable_64.h          |  2 ++
 5 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 10bae12cf0e8..d014d7f8172e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: fe770bf0310d90b3b033c19044d45b7de5f2041c
+refs/heads/master: 00d1c5e05736f947687be27706bda01cec104e57
diff --git a/trunk/Documentation/x86_64/boot-options.txt b/trunk/Documentation/x86_64/boot-options.txt
index 34abae4e9442..b0c7b6c4abda 100644
--- a/trunk/Documentation/x86_64/boot-options.txt
+++ b/trunk/Documentation/x86_64/boot-options.txt
@@ -307,3 +307,8 @@ Debugging
 			stuck (default)
 
 Miscellaneous
+
+	nogbpages
+		Do not use GB pages for kernel direct mappings.
+	gbpages
+		Use GB pages for kernel direct mappings.
diff --git a/trunk/arch/x86/Kconfig.debug b/trunk/arch/x86/Kconfig.debug
index 7ce8e7025661..f4413c04e687 100644
--- a/trunk/arch/x86/Kconfig.debug
+++ b/trunk/arch/x86/Kconfig.debug
@@ -76,6 +76,18 @@ config DEBUG_RODATA
 	  data. This is recommended so that we can catch kernel bugs sooner.
 	  If in doubt, say "Y".
 
+config DIRECT_GBPAGES
+	bool "Enable gbpages-mapped kernel pagetables"
+	depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
+	help
+	  Enable gigabyte pages support (if the CPU supports it). This can
+	  improve the kernel's performance a tiny bit by reducing TLB
+	  pressure.
+
+	  This is experimental code.
+
+	  If in doubt, say "N".
+
 config DEBUG_RODATA_TEST
 	bool "Testcase for the DEBUG_RODATA feature"
 	depends on DEBUG_RODATA
diff --git a/trunk/arch/x86/mm/init_64.c b/trunk/arch/x86/mm/init_64.c
index a02a14f0f324..6e7d5a42a09a 100644
--- a/trunk/arch/x86/mm/init_64.c
+++ b/trunk/arch/x86/mm/init_64.c
@@ -54,6 +54,26 @@ static unsigned long dma_reserve __initdata;
 
 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
 
+int direct_gbpages __meminitdata
+#ifdef CONFIG_DIRECT_GBPAGES
+				= 1
+#endif
+;
+
+static int __init parse_direct_gbpages_off(char *arg)
+{
+	direct_gbpages = 0;
+	return 0;
+}
+early_param("nogbpages", parse_direct_gbpages_off);
+
+static int __init parse_direct_gbpages_on(char *arg)
+{
+	direct_gbpages = 1;
+	return 0;
+}
+early_param("gbpages", parse_direct_gbpages_on);
+
 /*
  * NOTE: pagetable_init alloc all the fixmap pagetables contiguous on the
  * physical space so we can cache the place of the first one and move
diff --git a/trunk/include/asm-x86/pgtable_64.h b/trunk/include/asm-x86/pgtable_64.h
index 01d2359e7a34..6ef09914acbe 100644
--- a/trunk/include/asm-x86/pgtable_64.h
+++ b/trunk/include/asm-x86/pgtable_64.h
@@ -239,6 +239,8 @@ static inline int pud_large(pud_t pte)
 
 #define update_mmu_cache(vma,address,pte) do { } while (0)
 
+extern int direct_gbpages;
+
 /* Encode and de-code a swap entry */
 #define __swp_type(x)			(((x).val >> 1) & 0x3f)
 #define __swp_offset(x)			((x).val >> 8)