On Tue, Sep 24, 2013 at 06:06:41PM +0800, Zhang Yanfei wrote:
> +/**
> + * memory_map_top_down - Map [map_start, map_end) top down
> + * @map_start: start address of the target memory range
> + * @map_end: end address of the target memory range
> + *
> + * This function will setup direct mapping for memory range [map_start,
> map_end)
> + * in a heuristic way. In the beginning, step_size is small. The more memory
> we
> + * map memory in the next loop.
> + */
The comment reads a bit weird to me. The step size is increased
gradually but that really isn't really a heuristic and it doesn't
mention mapping direction.
...
> @@ -430,19 +430,13 @@ void __init init_mem_mapping(void)
> min_pfn_mapped = real_end >> PAGE_SHIFT;
> last_start = start = real_end;
>
> - /*
> - * We start from the top (end of memory) and go to the bottom.
> - * The memblock_find_in_range() gets us a block of RAM from the
> - * end of RAM in [min_pfn_mapped, max_pfn_mapped) used as new pages
> - * for page table.
> - */
I think this comment should stay here with the variable names
updated.
> - while (last_start > ISA_END_ADDRESS) {
> + while (last_start > map_start) {
> if (last_start > step_size) {
> start = round_down(last_start - 1, step_size);
> - if (start < ISA_END_ADDRESS)
> - start = ISA_END_ADDRESS;
> + if (start < map_start)
> + start = map_start;
> } else
> - start = ISA_END_ADDRESS;
> + start = map_start;
> new_mapped_ram_size = init_range_memory_mapping(start,
> last_start);
> last_start = start;
> @@ -453,8 +447,32 @@ void __init init_mem_mapping(void)
> mapped_ram_size += new_mapped_ram_size;
> }
>
> - if (real_end < end)
> - init_range_memory_mapping(real_end, end);
> + if (real_end < map_end)
> + init_range_memory_mapping(real_end, map_end);
> +}
> +
> +void __init init_mem_mapping(void)
> +{
> + unsigned long end;
> +
> + probe_page_size_mask();
> +
> +#ifdef CONFIG_X86_64
> + end = max_pfn << PAGE_SHIFT;
> +#else
> + end = max_low_pfn << PAGE_SHIFT;
> +#endif
> +
> + /* the ISA range is always mapped regardless of memory holes */
> + init_memory_mapping(0, ISA_END_ADDRESS);
> +
> + /*
> + * We start from the top (end of memory) and go to the bottom.
> + * The memblock_find_in_range() gets us a block of RAM from the
> + * end of RAM in [min_pfn_mapped, max_pfn_mapped) used as new pages
> + * for page table.
> + */
And just mention the range and direction in the comment here?
> + memory_map_top_down(ISA_END_ADDRESS, end);
Thanks.
--
tejun
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