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-rw-r--r--Documentation/x86_64/boot-options.txt5
-rw-r--r--arch/x86/Kconfig.debug12
-rw-r--r--arch/x86/mm/init_64.c20
-rw-r--r--include/asm-x86/pgtable_64.h2
4 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 34abae4e944..b0c7b6c4abd 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/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/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 7ce8e702566..f4413c04e68 100644
--- a/arch/x86/Kconfig.debug
+++ b/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/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a02a14f0f32..6e7d5a42a09 100644
--- a/arch/x86/mm/init_64.c
+++ b/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/include/asm-x86/pgtable_64.h b/include/asm-x86/pgtable_64.h
index 01d2359e7a3..6ef09914acb 100644
--- a/include/asm-x86/pgtable_64.h
+++ b/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)