linux-kernel - Re: [PATCH] mm/memblock: export max

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Date:   Thu, 4 Jun 2020 11:39:47 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     David Hildenbrand <david@...hat.com>
CC:     Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>
Subject: Re: [PATCH] mm/memblock: export max_pfn for kernel modules

On Wed, 2020-06-03 at 18:16 +0200, David Hildenbrand wrote:
> On 03.06.20 18:11, Miles Chen wrote:
> > max_pfn is uesd to get the highest pfn in the system. Drivers like
> > drivers/iommu/mtk_iommu.c checks max_pfn to see if it should enable
> > its "4GB mode".
> > 
> > This patch exports the max_pfn symbol, so we can build the driver as
> > a kernel module.
> 
> Please add that change to the respective user patch (and cc MM-people
> for that patch), so we have the actual user right along the change and
> can figure out if this is the right thing to do.
> 

Thanks for the comment.

Mike points out another alternative way to do this by totalram_pages().
I will use that approach so we don't have to export max_pfn here.

https://lkml.org/lkml/2020/6/3/771

Miles

> > 
> > Signed-off-by: Miles Chen <miles.chen@...iatek.com>
> > ---
> >  mm/memblock.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/mm/memblock.c b/mm/memblock.c
> > index c79ba6f9920c..3b2b21ecebb6 100644
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -99,6 +99,7 @@ EXPORT_SYMBOL(contig_page_data);
> >  unsigned long max_low_pfn;
> >  unsigned long min_low_pfn;
> >  unsigned long max_pfn;
> > +EXPORT_SYMBOL(max_pfn);
> >  unsigned long long max_possible_pfn;
> >  
> >  static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
> > 
> 
>