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Date:   Mon, 27 Sep 2021 20:22:46 +0300
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Subject: Re: [RFC] arm64: mm: update max_pfn after memory hotplug
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To:     Chris Goldsworthy <quic_cgoldswo@quicinc.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
CC:     David Hildenbrand <david@redhat.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
References: <cover.1632437225.git.quic_cgoldswo@quicinc.com>
 <595d09279824faf1f54961cef52b745609b05d97.1632437225.git.quic_cgoldswo@quicinc.com>
From:   Georgi Djakov <quic_c_gdjako@quicinc.com>
In-Reply-To: <595d09279824faf1f54961cef52b745609b05d97.1632437225.git.quic_cgoldswo@quicinc.com>
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On 9/24/2021 1:54 AM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <quic_sudaraja@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@quicinc.com>
> Signed-off-by: Chris Goldsworthy <quic_cgoldswo@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@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;
>   }
>   
>