Re: [PATCH v4 2/4] memblock: update initialization of reserved pages

[Ard Biesheuvel]

On Tue, 11 May 2021 at 12:06, Mike Rapoport <rppt@xxxxxxxxxx> wrote:
>
> From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
>
> The struct pages representing a reserved memory region are initialized
> using reserve_bootmem_range() function. This function is called for each
> reserved region just before the memory is freed from memblock to the buddy
> page allocator.
>
> The struct pages for MEMBLOCK_NOMAP regions are kept with the default
> values set by the memory map initialization which makes it necessary to
> have a special treatment for such pages in pfn_valid() and
> pfn_valid_within().
>
> Split out initialization of the reserved pages to a function with a
> meaningful name and treat the MEMBLOCK_NOMAP regions the same way as the
> reserved regions and mark struct pages for the NOMAP regions as
> PageReserved.
>
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

> ---
>  include/linux/memblock.h |  4 +++-
>  mm/memblock.c            | 28 ++++++++++++++++++++++++++--
>  2 files changed, 29 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 5984fff3f175..1b4c97c151ae 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -30,7 +30,9 @@ extern unsigned long long max_possible_pfn;
>   * @MEMBLOCK_NONE: no special request
>   * @MEMBLOCK_HOTPLUG: hotpluggable region
>   * @MEMBLOCK_MIRROR: mirrored region
> - * @MEMBLOCK_NOMAP: don't add to kernel direct mapping
> + * @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as
> + * reserved in the memory map; refer to memblock_mark_nomap() description
> + * for further details
>   */
>  enum memblock_flags {
>         MEMBLOCK_NONE           = 0x0,  /* No special request */
> diff --git a/mm/memblock.c b/mm/memblock.c
> index afaefa8fc6ab..3abf2c3fea7f 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -906,6 +906,11 @@ int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
>   * @base: the base phys addr of the region
>   * @size: the size of the region
>   *
> + * The memory regions marked with %MEMBLOCK_NOMAP will not be added to the
> + * direct mapping of the physical memory. These regions will still be
> + * covered by the memory map. The struct page representing NOMAP memory
> + * frames in the memory map will be PageReserved()
> + *
>   * Return: 0 on success, -errno on failure.
>   */
>  int __init_memblock memblock_mark_nomap(phys_addr_t base, phys_addr_t size)
> @@ -2002,6 +2007,26 @@ static unsigned long __init __free_memory_core(phys_addr_t start,
>         return end_pfn - start_pfn;
>  }
>
> +static void __init memmap_init_reserved_pages(void)
> +{
> +       struct memblock_region *region;
> +       phys_addr_t start, end;
> +       u64 i;
> +
> +       /* initialize struct pages for the reserved regions */
> +       for_each_reserved_mem_range(i, &start, &end)
> +               reserve_bootmem_region(start, end);
> +
> +       /* and also treat struct pages for the NOMAP regions as PageReserved */
> +       for_each_mem_region(region) {
> +               if (memblock_is_nomap(region)) {
> +                       start = region->base;
> +                       end = start + region->size;
> +                       reserve_bootmem_region(start, end);
> +               }
> +       }
> +}
> +
>  static unsigned long __init free_low_memory_core_early(void)
>  {
>         unsigned long count = 0;
> @@ -2010,8 +2035,7 @@ static unsigned long __init free_low_memory_core_early(void)
>
>         memblock_clear_hotplug(0, -1);
>
> -       for_each_reserved_mem_range(i, &start, &end)
> -               reserve_bootmem_region(start, end);
> +       memmap_init_reserved_pages();
>
>         /*
>          * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id
> --
> 2.28.0
>