On Wed, Nov 02, 2016 at 01:51:53PM +0900, AKASHI Takahiro wrote:
> Add memblock_cap_memory_range() which will remove all the memblock regions
> except the range specified in the arguments.
>
> This function, like memblock_mem_limit_remove_map(), will not remove
> memblocks with MEMMAP_NOMAP attribute as they may be mapped and accessed
> later as "device memory."
> See the commit a571d4eb55d8 ("mm/memblock.c: add new infrastructure to
> address the mem limit issue").
>
> This function is used, in a succeeding patch in the series of arm64 kdump
> suuport, to limit the range of usable memory, System RAM, on crash dump
> kernel.
> (Please note that "mem=" parameter is of little use for this purpose.)
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> Cc: linux-mm at kvack.org
> Cc: Andrew Morton <akpm at linux-foundation.org>
> ---
> include/linux/memblock.h | 1 +
> mm/memblock.c | 28 ++++++++++++++++++++++++++++
> 2 files changed, 29 insertions(+)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 5b759c9..0e770af 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -334,6 +334,7 @@ phys_addr_t memblock_start_of_DRAM(void);
> phys_addr_t memblock_end_of_DRAM(void);
> void memblock_enforce_memory_limit(phys_addr_t memory_limit);
> void memblock_mem_limit_remove_map(phys_addr_t limit);
> +void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
> bool memblock_is_memory(phys_addr_t addr);
> int memblock_is_map_memory(phys_addr_t addr);
> int memblock_is_region_memory(phys_addr_t base, phys_addr_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 7608bc3..eb53876 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1544,6 +1544,34 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> (phys_addr_t)ULLONG_MAX);
> }
>
> +void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
> +{
> + int start_rgn, end_rgn;
> + int i, ret;
> +
> + if (!size)
> + return;
> +
> + ret = memblock_isolate_range(&memblock.memory, base, size,
> + &start_rgn, &end_rgn);
> + if (ret)
> + return;
> +
> + /* remove all the MAP regions */
> + for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
> + if (!memblock_is_nomap(&memblock.memory.regions[i]))
> + memblock_remove_region(&memblock.memory, i);
> +
> + for (i = start_rgn - 1; i >= 0; i--)
> + if (!memblock_is_nomap(&memblock.memory.regions[i]))
> + memblock_remove_region(&memblock.memory, i);
> +
> + /* truncate the reserved regions */
> + memblock_remove_range(&memblock.reserved, 0, base);
> + memblock_remove_range(&memblock.reserved,
> + base + size, (phys_addr_t)ULLONG_MAX);
> +}
This duplicates a bunch of the logic in memblock_mem_limit_remove_map. Can
you not implement that in terms of your new, more general, function? e.g.
by passing base == 0, and size == limit?
Will
