Re: [tip:x86/urgent] x86, mm: Find_early_table_space based on rangesthat are actually being mapped

[Yinghai Lu]

On Wed, Oct 24, 2012 at 2:49 PM, tip-bot for Jacob Shin
<jacob.shin@xxxxxxx> wrote:
> Commit-ID:  844ab6f993b1d32eb40512503d35ff6ad0c57030
> Gitweb:     http://git.kernel.org/tip/844ab6f993b1d32eb40512503d35ff6ad0c57030
> Author:     Jacob Shin <jacob.shin@xxxxxxx>
> AuthorDate: Wed, 24 Oct 2012 14:24:44 -0500
> Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> CommitDate: Wed, 24 Oct 2012 13:37:04 -0700
>
> x86, mm: Find_early_table_space based on ranges that are actually being mapped
>
> Current logic finds enough space for direct mapping page tables from 0
> to end. Instead, we only need to find enough space to cover mr[0].start
> to mr[nr_range].end -- the range that is actually being mapped by
> init_memory_mapping()
>
> This is needed after 1bbbbe779aabe1f0768c2bf8f8c0a5583679b54a, to address
> the panic reported here:
>
>   https://lkml.org/lkml/2012/10/20/160
>   https://lkml.org/lkml/2012/10/21/157
>
> Signed-off-by: Jacob Shin <jacob.shin@xxxxxxx>
> Link: 20121024195311.GB11779@jshin-Toonie">http://lkml.kernel.org/r/20121024195311.GB11779@jshin-Toonie
> Tested-by: Tom Rini <trini@xxxxxx>
> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/mm/init.c |   70 ++++++++++++++++++++++++++++++---------------------
>  1 files changed, 41 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 8653b3a..bc287d6 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -29,36 +29,54 @@ int direct_gbpages
>  #endif
>  ;
>
> -static void __init find_early_table_space(unsigned long end, int use_pse,
> -                                         int use_gbpages)
> +struct map_range {
> +       unsigned long start;
> +       unsigned long end;
> +       unsigned page_size_mask;
> +};
> +
> +/*
> + * First calculate space needed for kernel direct mapping page tables to cover
> + * mr[0].start to mr[nr_range - 1].end, while accounting for possible 2M and 1GB
> + * pages. Then find enough contiguous space for those page tables.
> + */
> +static void __init find_early_table_space(struct map_range *mr, int nr_range)
>  {
> -       unsigned long puds, pmds, ptes, tables, start = 0, good_end = end;
> +       int i;
> +       unsigned long puds = 0, pmds = 0, ptes = 0, tables;
> +       unsigned long start = 0, good_end;
>         phys_addr_t base;
>
> -       puds = (end + PUD_SIZE - 1) >> PUD_SHIFT;
> -       tables = roundup(puds * sizeof(pud_t), PAGE_SIZE);
> +       for (i = 0; i < nr_range; i++) {
> +               unsigned long range, extra;
>
> -       if (use_gbpages) {
> -               unsigned long extra;
> +               range = mr[i].end - mr[i].start;
> +               puds += (range + PUD_SIZE - 1) >> PUD_SHIFT;
>
> -               extra = end - ((end>>PUD_SHIFT) << PUD_SHIFT);
> -               pmds = (extra + PMD_SIZE - 1) >> PMD_SHIFT;
> -       } else
> -               pmds = (end + PMD_SIZE - 1) >> PMD_SHIFT;
> -
> -       tables += roundup(pmds * sizeof(pmd_t), PAGE_SIZE);
> +               if (mr[i].page_size_mask & (1 << PG_LEVEL_1G)) {
> +                       extra = range - ((range >> PUD_SHIFT) << PUD_SHIFT);
> +                       pmds += (extra + PMD_SIZE - 1) >> PMD_SHIFT;
> +               } else {
> +                       pmds += (range + PMD_SIZE - 1) >> PMD_SHIFT;
> +               }
>
> -       if (use_pse) {
> -               unsigned long extra;
> -
> -               extra = end - ((end>>PMD_SHIFT) << PMD_SHIFT);
> +               if (mr[i].page_size_mask & (1 << PG_LEVEL_2M)) {
> +                       extra = range - ((range >> PMD_SHIFT) << PMD_SHIFT);
>  #ifdef CONFIG_X86_32
> -               extra += PMD_SIZE;
> +                       extra += PMD_SIZE;
>  #endif
> -               ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
> -       } else
> -               ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +                       /* The first 2/4M doesn't use large pages. */
> +                       if (mr[i].start < PMD_SIZE)
> +                               extra += range;

those three lines should be added back.

it just get reverted in 7b16bbf9

    Revert "x86/mm: Fix the size calculation of mapping tables"


> +
> +                       ptes += (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +               } else {
> +                       ptes += (range + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +               }
> +       }
>
> +       tables = roundup(puds * sizeof(pud_t), PAGE_SIZE);
> +       tables += roundup(pmds * sizeof(pmd_t), PAGE_SIZE);
>         tables += roundup(ptes * sizeof(pte_t), PAGE_SIZE);
>
>  #ifdef CONFIG_X86_32
> @@ -76,7 +94,7 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
>         pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT);
>
>         printk(KERN_DEBUG "kernel direct mapping tables up to %#lx @ [mem %#010lx-%#010lx]\n",
> -               end - 1, pgt_buf_start << PAGE_SHIFT,
> +               mr[nr_range - 1].end - 1, pgt_buf_start << PAGE_SHIFT,
>                 (pgt_buf_top << PAGE_SHIFT) - 1);
>  }
>
> @@ -85,12 +103,6 @@ void __init native_pagetable_reserve(u64 start, u64 end)
>         memblock_reserve(start, end - start);
>  }
>
> -struct map_range {
> -       unsigned long start;
> -       unsigned long end;
> -       unsigned page_size_mask;
> -};
> -
>  #ifdef CONFIG_X86_32
>  #define NR_RANGE_MR 3
>  #else /* CONFIG_X86_64 */
> @@ -263,7 +275,7 @@ 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(mr, nr_range);
>
>         for (i = 0; i < nr_range; i++)
>                 ret = kernel_physical_mapping_init(mr[i].start, mr[i].end,
> --
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