[RFC] arm64: mm: update max_pfn after memory hotplug

[Georgi Djakov]

On 9/24/2021 1:54 AM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <quic_sudaraja at quicinc.com>
> 
> After new memory blocks have been hotplugged, max_pfn and max_low_pfn
> needs updating to reflect on new PFNs being hot added to system.
> 
> Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja at quicinc.com>
> Signed-off-by: Chris Goldsworthy <quic_cgoldswo at quicinc.com>

Thanks for the patch, Chris!

With this patch, the data in /proc/kpageflags appears to be correct and
memory tools like procrank work again on arm64 platforms.

Tested-by: Georgi Djakov <quic_c_gdjako at quicinc.com>

Maybe we should add fixes tag, as it has been broken since the following
commit:
Fixes: abec749facff ("fs/proc/page.c: allow inspection of last section 
and fix end detection")

Thanks,
Georgi

> ---
>   arch/arm64/mm/mmu.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index cfd9deb..fd85b51 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
>   	if (ret)
>   		__remove_pgd_mapping(swapper_pg_dir,
>   				     __phys_to_virt(start), size);
> +	else {
> +		max_pfn = PFN_UP(start + size);
> +		max_low_pfn = max_pfn;
> +	}
> +
>   	return ret;
>   }
>   
>