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Subject[tip:x86/mm] x86, mm: Pagetable level size/shift/mask helpers
Commit-ID:  4cbeb51b860c57ba8b2ae50c4016ee7a41f5fbd5
Gitweb: http://git.kernel.org/tip/4cbeb51b860c57ba8b2ae50c4016ee7a41f5fbd5
Author: Dave Hansen <dave@linux.vnet.ibm.com>
AuthorDate: Tue, 22 Jan 2013 13:24:31 -0800
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Fri, 25 Jan 2013 16:33:22 -0800

x86, mm: Pagetable level size/shift/mask helpers

I plan to use lookup_address() to walk the kernel pagetables
in a later patch. It returns a "pte" and the level in the
pagetables where the "pte" was found. The level is just an
enum and needs to be converted to a useful value in order to
do address calculations with it. These helpers will be used
in at least two places.

This also gives the anonymous enum a real name so that no one
gets confused about what they should be passing in to these
helpers.

"PTE_SHIFT" was chosen for naming consistency with the other
pagetable levels (PGD/PUD/PMD_SHIFT).

Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20130122212431.405D3A8C@kernel.stglabs.ibm.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
arch/x86/include/asm/pgtable.h | 14 ++++++++++++++
arch/x86/include/asm/pgtable_types.h | 2 +-
2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 5199db2..bc28e6f 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -390,6 +390,7 @@ pte_t *populate_extra_pte(unsigned long vaddr);

#ifndef __ASSEMBLY__
#include <linux/mm_types.h>
+#include <linux/log2.h>

static inline int pte_none(pte_t pte)
{
@@ -781,6 +782,19 @@ static inline void clone_pgd_range(pgd_t *dst, pgd_t *src, int count)
memcpy(dst, src, count * sizeof(pgd_t));
}

+#define PTE_SHIFT ilog2(PTRS_PER_PTE)
+static inline int page_level_shift(enum pg_level level)
+{
+ return (PAGE_SHIFT - PTE_SHIFT) + level * PTE_SHIFT;
+}
+static inline unsigned long page_level_size(enum pg_level level)
+{
+ return 1UL << page_level_shift(level);
+}
+static inline unsigned long page_level_mask(enum pg_level level)
+{
+ return ~(page_level_size(level) - 1);
+}

#include <asm-generic/pgtable.h>
#endif /* __ASSEMBLY__ */
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 3c32db8..6c297e7 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -331,7 +331,7 @@ extern void native_pagetable_init(void);
struct seq_file;
extern void arch_report_meminfo(struct seq_file *m);

-enum {
+enum pg_level {
PG_LEVEL_NONE,
PG_LEVEL_4K,
PG_LEVEL_2M,

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