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SubjectRe: [PATCH] arm64: mm: fix max_mapnr is assigned the wrong value
On Sat, Mar 30, 2019 at 09:13:46PM +0800, Muchun Song wrote:
> When we not use flat memory, the mem_map will be NULL and
> pfn_to_page(max_pfn) is a pointer which is located in kernel space. So
> max_mapnr is assigned a very large number(e.g., 0xffffxxxx_xxxxxxxx) - fix
> it.
>
> Signed-off-by: Muchun Song <smuchun@gmail.com>
> ---
> arch/arm64/mm/init.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index bc02818fa48b..e86c21a44c88 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -535,7 +535,7 @@ void __init mem_init(void)
> else
> swiotlb_force = SWIOTLB_NO_FORCE;
>
> - set_max_mapnr(pfn_to_page(max_pfn) - mem_map);
> + set_max_mapnr(max_pfn - PHYS_PFN_OFFSET);
>
> #ifndef CONFIG_SPARSEMEM_VMEMMAP
> free_unused_memmap();

The patch looks fine but did you actually hit any problem? max_mapnr
seems to only be used in the generic pfn_valid() which we do not use on
arm64 (just wondering if it needs a cc stable; it doesn't look like as
it's not a regression).

--
Catalin

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