linux-kernel - Re: [PATCH 1/3] x86/mm: Simplify memory mapping PFN calculation

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Date:	Sat, 14 Jul 2012 13:34:22 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 1/3] x86/mm: Simplify memory mapping PFN calculation

On Sat, Jul 14, 2012 at 6:41 AM, Pekka Enberg <penberg@...nel.org> wrote:
> Introduce two new helper functions, addr_to_pmd_pfn() and
> addr_to_pud_pfn(), to simplify init_memory_mapping() code flow.
>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Yinghai Lu <yinghai@...nel.org>
> Signed-off-by: Pekka Enberg <penberg@...nel.org>

Acked-by: Yinghai Lu <yinghai@...nel.org>

> ---
>  arch/x86/mm/init.c |   38 +++++++++++++++++++++-----------------
>  1 files changed, 21 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index bc4e9d8..9eb53c2 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -117,6 +117,16 @@ static int __meminit save_mr(struct map_range *mr, int nr_range,
>         return nr_range;
>  }
>
> +static unsigned long addr_to_pmd_pfn(unsigned long addr)
> +{
> +       return (addr >> PMD_SHIFT) << (PMD_SHIFT - PAGE_SHIFT);
> +}
> +
> +static unsigned long addr_to_pud_pfn(unsigned long addr)
> +{
> +       return (addr >> PUD_SHIFT) << (PUD_SHIFT - PAGE_SHIFT);
> +}
> +
>  /*
>   * Setup the direct mapping of the physical memory at PAGE_OFFSET.
>   * This runs before bootmem is initialized and gets pages directly from
> @@ -180,11 +190,9 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>         if (pos == 0)
>                 end_pfn = 1<<(PMD_SHIFT - PAGE_SHIFT);
>         else
> -               end_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
> -                                << (PMD_SHIFT - PAGE_SHIFT);
> +               end_pfn = addr_to_pmd_pfn(pos + (PMD_SIZE - 1));
>  #else /* CONFIG_X86_64 */
> -       end_pfn = ((pos + (PMD_SIZE - 1)) >> PMD_SHIFT)
> -                       << (PMD_SHIFT - PAGE_SHIFT);
> +       end_pfn = addr_to_pmd_pfn(pos + (PMD_SIZE - 1));
>  #endif
>         if (end_pfn > (end >> PAGE_SHIFT))
>                 end_pfn = end >> PAGE_SHIFT;
> @@ -194,15 +202,13 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>         }
>
>         /* big page (2M) range */
> -       start_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
> -                        << (PMD_SHIFT - PAGE_SHIFT);
> +       start_pfn = addr_to_pmd_pfn(pos + (PMD_SIZE - 1));
>  #ifdef CONFIG_X86_32
> -       end_pfn = (end>>PMD_SHIFT) << (PMD_SHIFT - PAGE_SHIFT);
> +       end_pfn = addr_to_pmd_pfn(end);
>  #else /* CONFIG_X86_64 */
> -       end_pfn = ((pos + (PUD_SIZE - 1))>>PUD_SHIFT)
> -                        << (PUD_SHIFT - PAGE_SHIFT);
> -       if (end_pfn > ((end>>PMD_SHIFT)<<(PMD_SHIFT - PAGE_SHIFT)))
> -               end_pfn = ((end>>PMD_SHIFT)<<(PMD_SHIFT - PAGE_SHIFT));
> +       end_pfn = addr_to_pud_pfn(pos + (PUD_SIZE - 1));
> +       if (end_pfn > addr_to_pmd_pfn(end))
> +               end_pfn = addr_to_pmd_pfn(end);
>  #endif
>
>         if (start_pfn < end_pfn) {
> @@ -213,9 +219,8 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>
>  #ifdef CONFIG_X86_64
>         /* big page (1G) range */
> -       start_pfn = ((pos + (PUD_SIZE - 1))>>PUD_SHIFT)
> -                        << (PUD_SHIFT - PAGE_SHIFT);
> -       end_pfn = (end >> PUD_SHIFT) << (PUD_SHIFT - PAGE_SHIFT);
> +       start_pfn = addr_to_pud_pfn(pos + (PUD_SIZE - 1));
> +       end_pfn = addr_to_pud_pfn(end);
>         if (start_pfn < end_pfn) {
>                 nr_range = save_mr(mr, nr_range, start_pfn, end_pfn,
>                                 page_size_mask &
> @@ -224,9 +229,8 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
>         }
>
>         /* tail is not big page (1G) alignment */
> -       start_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
> -                        << (PMD_SHIFT - PAGE_SHIFT);
> -       end_pfn = (end >> PMD_SHIFT) << (PMD_SHIFT - PAGE_SHIFT);
> +       start_pfn = addr_to_pmd_pfn(pos + (PMD_SIZE - 1));
> +       end_pfn = addr_to_pmd_pfn(end);
>         if (start_pfn < end_pfn) {
>                 nr_range = save_mr(mr, nr_range, start_pfn, end_pfn,
>                                 page_size_mask & (1<<PG_LEVEL_2M));
> --
> 1.7.7.6
>
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