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Subject[PATCH 2/5] pagetable level size/shift/mask helpers
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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>
---

linux-2.6.git-dave/arch/x86/include/asm/pgtable.h | 14 ++++++++++++++
linux-2.6.git-dave/arch/x86/include/asm/pgtable_types.h | 2 +-
2 files changed, 15 insertions(+), 1 deletion(-)

diff -puN arch/x86/include/asm/pgtable.h~pagetable-level-size-helpers arch/x86/include/asm/pgtable.h
--- linux-2.6.git/arch/x86/include/asm/pgtable.h~pagetable-level-size-helpers 2013-01-22 13:17:15.464309478 -0800
+++ linux-2.6.git-dave/arch/x86/include/asm/pgtable.h 2013-01-22 13:17:15.472309544 -0800
@@ -390,6 +390,7 @@ pte_t *populate_extra_pte(unsigned long

#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
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 -puN arch/x86/include/asm/pgtable_types.h~pagetable-level-size-helpers arch/x86/include/asm/pgtable_types.h
--- linux-2.6.git/arch/x86/include/asm/pgtable_types.h~pagetable-level-size-helpers 2013-01-22 13:17:15.468309511 -0800
+++ linux-2.6.git-dave/arch/x86/include/asm/pgtable_types.h 2013-01-22 13:17:15.472309544 -0800
@@ -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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