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    Subject[PATCHv6 14/19] x86/mm: Fold p4d page table layer at runtime
    Date
    This patch changes page table helpers to fold p4d at runtime.
    The logic is the same as in <asm-generic/pgtable-nop4d.h>.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    arch/x86/include/asm/paravirt.h | 10 ++++++----
    arch/x86/include/asm/pgalloc.h | 5 ++++-
    arch/x86/include/asm/pgtable.h | 10 +++++++++-
    3 files changed, 19 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
    index 9ccac1926587..be729bcac1c2 100644
    --- a/arch/x86/include/asm/paravirt.h
    +++ b/arch/x86/include/asm/paravirt.h
    @@ -606,14 +606,16 @@ static inline p4dval_t p4d_val(p4d_t p4d)

    static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)
    {
    - pgdval_t val = native_pgd_val(pgd);
    -
    - PVOP_VCALL2(pv_mmu_ops.set_pgd, pgdp, val);
    + if (pgtable_l5_enabled)
    + PVOP_VCALL2(pv_mmu_ops.set_pgd, pgdp, native_pgd_val(pgd));
    + else
    + set_p4d((p4d_t *)(pgdp), (p4d_t) { pgd.pgd });
    }

    static inline void pgd_clear(pgd_t *pgdp)
    {
    - set_pgd(pgdp, __pgd(0));
    + if (pgtable_l5_enabled)
    + set_pgd(pgdp, __pgd(0));
    }

    #endif /* CONFIG_PGTABLE_LEVELS == 5 */
    diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h
    index b2d0cd8288aa..1ce12afcfb04 100644
    --- a/arch/x86/include/asm/pgalloc.h
    +++ b/arch/x86/include/asm/pgalloc.h
    @@ -155,6 +155,8 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
    #if CONFIG_PGTABLE_LEVELS > 4
    static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, p4d_t *p4d)
    {
    + if (!pgtable_l5_enabled)
    + return;
    paravirt_alloc_p4d(mm, __pa(p4d) >> PAGE_SHIFT);
    set_pgd(pgd, __pgd(_PAGE_TABLE | __pa(p4d)));
    }
    @@ -179,7 +181,8 @@ extern void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d);
    static inline void __p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d,
    unsigned long address)
    {
    - ___p4d_free_tlb(tlb, p4d);
    + if (pgtable_l5_enabled)
    + ___p4d_free_tlb(tlb, p4d);
    }

    #endif /* CONFIG_PGTABLE_LEVELS > 4 */
    diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
    index bbeae4a2bd01..9a157b98080f 100644
    --- a/arch/x86/include/asm/pgtable.h
    +++ b/arch/x86/include/asm/pgtable.h
    @@ -65,7 +65,7 @@ extern pmdval_t early_pmd_flags;

    #ifndef __PAGETABLE_P4D_FOLDED
    #define set_pgd(pgdp, pgd) native_set_pgd(pgdp, pgd)
    -#define pgd_clear(pgd) native_pgd_clear(pgd)
    +#define pgd_clear(pgd) (pgtable_l5_enabled ? native_pgd_clear(pgd) : 0)
    #endif

    #ifndef set_p4d
    @@ -861,6 +861,8 @@ static inline unsigned long p4d_index(unsigned long address)
    #if CONFIG_PGTABLE_LEVELS > 4
    static inline int pgd_present(pgd_t pgd)
    {
    + if (!pgtable_l5_enabled)
    + return 1;
    return pgd_flags(pgd) & _PAGE_PRESENT;
    }

    @@ -878,16 +880,22 @@ static inline unsigned long pgd_page_vaddr(pgd_t pgd)
    /* to find an entry in a page-table-directory. */
    static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)
    {
    + if (!pgtable_l5_enabled)
    + return (p4d_t *)pgd;
    return (p4d_t *)pgd_page_vaddr(*pgd) + p4d_index(address);
    }

    static inline int pgd_bad(pgd_t pgd)
    {
    + if (!pgtable_l5_enabled)
    + return 0;
    return (pgd_flags(pgd) & ~_PAGE_USER) != _KERNPG_TABLE;
    }

    static inline int pgd_none(pgd_t pgd)
    {
    + if (!pgtable_l5_enabled)
    + return 0;
    /*
    * There is no need to do a workaround for the KNL stray
    * A/D bit erratum here. PGDs only point to page tables
    --
    2.14.1
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