On 28 March 2017 at 07:50, AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> wrote:
> Add memblock_cap_memory_range() which will remove all the memblock regions
> except the memory range specified in the arguments. In addition, rework is
> done on memblock_mem_limit_remove_map() to re-implement it using
> memblock_cap_memory_range().
>
> 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, or 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@xxxxxxxxxx>
> Reviewed-by: Will Deacon <will.deacon@xxxxxxx>
> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Acked-by: Dennis Chen <dennis.chen@xxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> include/linux/memblock.h | 1 +
> mm/memblock.c | 44 +++++++++++++++++++++++++++++---------------
> 2 files changed, 30 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index e82daffcfc44..4ce24a376262 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -336,6 +336,7 @@ phys_addr_t memblock_mem_size(unsigned long limit_pfn);
> 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_cap_memory_range(phys_addr_t base, phys_addr_t size);
> void memblock_mem_limit_remove_map(phys_addr_t limit);
> bool memblock_is_memory(phys_addr_t addr);
> int memblock_is_map_memory(phys_addr_t addr);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 2f4ca8104ea4..b049c9b2dba8 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1543,11 +1543,37 @@ void __init memblock_enforce_memory_limit(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);
> +}
> +
> void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> {
> - struct memblock_type *type = &memblock.memory;
> phys_addr_t max_addr;
> - int i, ret, start_rgn, end_rgn;
>
> if (!limit)
> return;
> @@ -1558,19 +1584,7 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> if (max_addr == (phys_addr_t)ULLONG_MAX)
> return;
>
> - ret = memblock_isolate_range(type, max_addr, (phys_addr_t)ULLONG_MAX,
> - &start_rgn, &end_rgn);
> - if (ret)
> - return;
> -
> - /* remove all the MAP regions above the limit */
> - for (i = end_rgn - 1; i >= start_rgn; i--) {
> - if (!memblock_is_nomap(&type->regions[i]))
> - memblock_remove_region(type, i);
> - }
> - /* truncate the reserved regions */
> - memblock_remove_range(&memblock.reserved, max_addr,
> - (phys_addr_t)ULLONG_MAX);
> + memblock_cap_memory_range(0, max_addr);
> }
>
> static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
> --
> 2.11.1
>
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