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Subject: Re: [PATCH 1/6] arm64/mm: Enable sysfs based memory hot add interface
To:     Robin Murphy <robin.murphy@arm.com>,
        David Hildenbrand <david@redhat.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, akpm@linux-foundation.org, will.deacon@arm.com,
        catalin.marinas@arm.com
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        mark.rutland@arm.com, cpandya@codeaurora.org,
        arunks@codeaurora.org, dan.j.williams@intel.com, osalvador@suse.de,
        logang@deltatee.com, cai@lca.pw
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 <e5665673-60ab-eee8-bc05-53dafb941039@arm.com>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <514d246d-2619-08a9-bd1d-92d6b70b5a01@arm.com>
Date:   Thu, 4 Apr 2019 10:51:03 +0530
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On 04/03/2019 06:42 PM, Robin Murphy wrote:
> On 03/04/2019 09:20, David Hildenbrand wrote:
>> On 03.04.19 06:30, Anshuman Khandual wrote:
>>> Sysfs memory probe interface (/sys/devices/system/memory/probe) can accept
>>> starting physical address of an entire memory block to be hot added into
>>> the kernel. This is in addition to the existing ACPI based interface. This
>>> just enables it with the required config CONFIG_ARCH_MEMORY_PROBE.
>>>
>>
>> We recently discussed that the similar interface for removal should
>> rather be moved to a debug/test module
>>
>> I wonder if we should try to do the same for the sysfs probing
>> interface. Rather try to get rid of it than open the doors for more users.
> 
> Agreed - if this option even exists in a released kernel, there's a risk that distros will turn it on for the sake of it, and at that point arm64 is stuck carrying the same ABI baggage as well.

True. Only if we really dont like that interface.

> 
> If users turn up in future with a desperate and unavoidable need for the legacy half-an-API on arm64, we can always reconsider adding it at that point. It was very much deliberate that my original hot-add support did not include a patch like this one.

Sure. Will drop this one next time around.