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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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