linux-kernel - Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages

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Message-ID: <YHl4mqgh5CtNk1l7@kernel.org>
Date:   Fri, 16 Apr 2021 14:44:26 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved
 pages

On Thu, Apr 15, 2021 at 11:30:12AM +0200, David Hildenbrand wrote:
> > Not sure we really need a new pagetype here, PG_Reserved seems to be quite
> > enough to say "don't touch this".  I generally agree that we could make
> > PG_Reserved a PageType and then have several sub-types for reserved memory.
> > This definitely will add clarity but I'm not sure that this justifies
> > amount of churn and effort required to audit uses of PageResrved().
> > > Then, we could mostly avoid having to query memblock at runtime to figure
> > > out that this is special memory. This would obviously be an extension to
> > > this series. Just a thought.
> > 
> > Stop pushing memblock out of kernel! ;-)
> 
> Can't stop. Won't stop. :D
> 
> It's lovely for booting up a kernel until we have other data-structures in
> place ;)

A bit more seriously, we don't have any data structure that reliably
represents physical memory layout and arch-independent fashion. 
memblock is probably the best starting point for eventually having one.

-- 
Sincerely yours,
Mike.