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SubjectRe: [PATCH] ARC: Use max_high_pfn as a HIGHMEM zone border
Hi,

On Mon, Apr 26, 2021 at 01:10:04PM +0300, Vladimir Isaev wrote:
> Commit 4af22ded0ecf ("arc: fix memory initialization for systems with two
> memory banks") fixed highmem, but not for PAE case when highmem is
> actually bigger than lowmem.
>
> Signed-off-by: Vladimir Isaev <isaev@synopsys.com>
> Cc: Mike Rapoport <rppt@linux.ibm.com>
> ---
> arch/arc/mm/init.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
> index ce07e697916c..59bad6f94105 100644
> --- a/arch/arc/mm/init.c
> +++ b/arch/arc/mm/init.c
> @@ -157,7 +157,7 @@ void __init setup_arch_memory(void)
> min_high_pfn = PFN_DOWN(high_mem_start);
> max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz);
>
> - max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn;
> + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn;

This is correct with PAE40, but it will break !PAE40 when "highmem" has
lower addresses than lowmem.

It rather should be something like:

if (IS_ENABLED(CONFIG_ARC_HAS_PAE40))
max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn;
else
max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn;


>
> high_memory = (void *)(min_high_pfn << PAGE_SHIFT);
>
> --
> 2.16.2
>

--
Sincerely yours,
Mike.

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