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Date:   Wed, 20 Apr 2022 15:27:49 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     Anshuman Khandual <anshuman.khandual@arm.com>,
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Subject: Re: [PATCH v2 7/9] mm: Calc the right pfn if page size is not 4K
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On Tue, 19 Apr 2022 20:29:27 +0200 Ard Biesheuvel <ardb@kernel.org> wrote:

> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> > >
> > >                       usable_startpfn = memblock_region_memory_base_pfn(r);
> > >
> > > -                     if (usable_startpfn < 0x100000) {
> > > +                     if (usable_startpfn < PHYS_PFN(SZ_4G)) {
> > >                               mem_below_4gb_not_mirrored = true;
> > >                               continue;
> > >                       }
> >
> > Regardless PFN value should never be encoded directly.
> >
> > Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> 
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> 
> Andrew, can you please take this one through the -mm tree? The rest of
> the series needs a bit more work, but is an obvious fix and there is
> no point in holding it up.

Sure.

I'm not seeing any description of the runtime effects of this
shortcoming.  I tentatively queued the fix for 5.18, without a
cc:stable for backporting.  But that might not be the best decision?