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    Subject[PATCH 1/3] x86: calculate precisely the memory needed by init_memory_mapping
    Date
    From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

    - take into account the size of the initial pagetable;

    - remove the extra PMD_SIZE added when use_pse, because the previously
    allocated PMDs are always 2M aligned;

    - remove the extra page added on x86_32 for the fixmap because is not
    needed: the PMD entry is already allocated and contiguous for the whole
    range (a PMD page covers 4G of virtual addresses) and the pte entry is
    already allocated by early_ioremap_init.

    Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    ---
    arch/x86/mm/init.c | 62 ++++++++++++++++++++++++++++++++++++++-------------
    1 files changed, 46 insertions(+), 16 deletions(-)

    diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
    index 3032644..0cfe8d4 100644
    --- a/arch/x86/mm/init.c
    +++ b/arch/x86/mm/init.c
    @@ -28,22 +28,52 @@ int direct_gbpages
    #endif
    ;

    -static void __init find_early_table_space(unsigned long end, int use_pse,
    - int use_gbpages)
    +static void __init find_early_table_space(unsigned long start,
    + unsigned long end, int use_pse, int use_gbpages)
    {
    - unsigned long puds, pmds, ptes, tables, start = 0, good_end = end;
    + unsigned long pmds = 0, ptes = 0, tables = 0, good_end = end,
    + pud_mapped = 0, pmd_mapped = 0, size = end - start;
    phys_addr_t base;

    - puds = (end + PUD_SIZE - 1) >> PUD_SHIFT;
    - tables = roundup(puds * sizeof(pud_t), PAGE_SIZE);
    + pud_mapped = DIV_ROUND_UP(PFN_PHYS(max_pfn_mapped),
    + (PUD_SIZE * PTRS_PER_PUD));
    + pud_mapped *= (PUD_SIZE * PTRS_PER_PUD);
    + pmd_mapped = DIV_ROUND_UP(PFN_PHYS(max_pfn_mapped),
    + (PMD_SIZE * PTRS_PER_PMD));
    + pmd_mapped *= (PMD_SIZE * PTRS_PER_PMD);
    +
    + if (start < PFN_PHYS(max_pfn_mapped)) {
    + if (PFN_PHYS(max_pfn_mapped) < end)
    + size -= PFN_PHYS(max_pfn_mapped) - start;
    + else
    + size = 0;
    + }
    +
    +#ifndef __PAGETABLE_PUD_FOLDED
    + if (end > pud_mapped) {
    + unsigned long puds;
    + if (start < pud_mapped)
    + puds = (end - pud_mapped + PUD_SIZE - 1) >> PUD_SHIFT;
    + else
    + puds = (end - start + PUD_SIZE - 1) >> PUD_SHIFT;
    + tables += roundup(puds * sizeof(pud_t), PAGE_SIZE);
    + }
    +#endif

    if (use_gbpages) {
    unsigned long extra;

    extra = end - ((end>>PUD_SHIFT) << PUD_SHIFT);
    pmds = (extra + PMD_SIZE - 1) >> PMD_SHIFT;
    - } else
    - pmds = (end + PMD_SIZE - 1) >> PMD_SHIFT;
    + }
    +#ifndef __PAGETABLE_PMD_FOLDED
    + else if (end > pmd_mapped) {
    + if (start < pmd_mapped)
    + pmds = (end - pmd_mapped + PMD_SIZE - 1) >> PMD_SHIFT;
    + else
    + pmds = (end - start + PMD_SIZE - 1) >> PMD_SHIFT;
    + }
    +#endif

    tables += roundup(pmds * sizeof(pmd_t), PAGE_SIZE);

    @@ -51,23 +81,20 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
    unsigned long extra;

    extra = end - ((end>>PMD_SHIFT) << PMD_SHIFT);
    -#ifdef CONFIG_X86_32
    - extra += PMD_SIZE;
    -#endif
    ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
    } else
    - ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
    + ptes = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;

    tables += roundup(ptes * sizeof(pte_t), PAGE_SIZE);

    -#ifdef CONFIG_X86_32
    - /* for fixmap */
    - tables += roundup(__end_of_fixed_addresses * sizeof(pte_t), PAGE_SIZE);
    + if (!tables)
    + return;

    +#ifdef CONFIG_X86_32
    good_end = max_pfn_mapped << PAGE_SHIFT;
    #endif

    - base = memblock_find_in_range(start, good_end, tables, PAGE_SIZE);
    + base = memblock_find_in_range(0x00, good_end, tables, PAGE_SIZE);
    if (base == MEMBLOCK_ERROR)
    panic("Cannot find space for the kernel page tables");

    @@ -261,7 +288,7 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
    * nodes are discovered.
    */
    if (!after_bootmem)
    - find_early_table_space(end, use_pse, use_gbpages);
    + find_early_table_space(start, end, use_pse, use_gbpages);

    for (i = 0; i < nr_range; i++)
    ret = kernel_physical_mapping_init(mr[i].start, mr[i].end,
    @@ -275,6 +302,9 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,

    __flush_tlb_all();

    + if (pgt_buf_end != pgt_buf_top)
    + printk(KERN_DEBUG "initial kernel pagetable allocation wasted %lx"
    + " pages\n", pgt_buf_top - pgt_buf_end);
    /*
    * Reserve the kernel pagetable pages we used (pgt_buf_start -
    * pgt_buf_end) and free the other ones (pgt_buf_end - pgt_buf_top)
    --
    1.7.2.3


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