linux-kernel - Re: [PATCH 1/2] mm/memory_hotplug: allow marking of memory sections as hotpluggable

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Message-ID: <20201021095428.GB392079@kernel.org>
Date:   Wed, 21 Oct 2020 12:54:28 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Sudarshan Rajagopalan <sudaraja@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mark Rutland <mark.rutland@....com>,
        Steven Price <steven.price@....com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH 1/2] mm/memory_hotplug: allow marking of memory sections
 as hotpluggable

On Sat, Oct 17, 2020 at 11:36:39AM +0200, David Hildenbrand wrote:
> On 17.10.20 10:26, Mike Rapoport wrote:
> > On Fri, Oct 16, 2020 at 07:02:23PM -0700, Sudarshan Rajagopalan wrote:
> >> Certain architectures such as arm64 doesn't allow boot memory to be
> >> offlined and removed. Distinguish certain memory sections as
> >> "hotpluggable" which can be marked by module drivers stating to memory
> >> hotplug layer that these sections can be offlined and then removed.
> > 
> > I don't quite follow why marking sections as hotpluggable or not should
> > be done by a device driver. Can you describe in more details your
> > use-case and why there is a need to add a flag to the memory map?
> > 
> 
> This seems to be related to
> 
> https://lkml.kernel.org/r/de8388df2fbc5a6a33aab95831ba7db4@codeaurora.org

Thanks for the pointer.

> After reading how the driver is trying to abuse memory hot(un)plug
> infrastructure, my tentative
> 
> Nacked-by: David Hildenbrand <david@...hat.com>

I also don't think we would want to let drivers play with the memory
map.

> -- 
> Thanks,
> 
> David / dhildenb
> 

-- 
Sincerely yours,
Mike.