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From: Mike Rapoport <rppt@kernel.org>
To: Stefan Agner <stefan@agner.ch>
Cc: minchan@kernel.org, ngupta@vflare.org,
	sergey.senozhatsky.work@gmail.com, akpm@linux-foundation.org,
	sjenning@linux.vnet.ibm.com, gregkh@linuxfoundation.org,
	arnd@arndb.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/zsmalloc: include sparsemem.h for MAX_PHYSMEM_BITS
Date: Tue, 10 Nov 2020 11:58:06 +0200	[thread overview]
Message-ID: <20201110095806.GH301837@kernel.org> (raw)
In-Reply-To: <7782fb694a6b0c500e8f32ecf895b2bf@agner.ch>

On Tue, Nov 10, 2020 at 10:29:54AM +0100, Stefan Agner wrote:
> On 2020-11-08 07:46, Mike Rapoport wrote:
> > On Sat, Nov 07, 2020 at 04:22:06PM +0100, Stefan Agner wrote:
> >> Most architectures define MAX_PHYSMEM_BITS in asm/sparsemem.h and don't
> >> include it in asm/pgtable.h. Include asm/sparsemem.h directly to get
> >> the MAX_PHYSMEM_BITS define on all architectures.

...

> >> Fixes: 61989a80fb3a ("staging: zsmalloc: zsmalloc memory allocation library")
> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
> >> ---
> >>  mm/zsmalloc.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> >> index c36fdff9a371..260bd48aacd0 100644
> >> --- a/mm/zsmalloc.c
> >> +++ b/mm/zsmalloc.c
> >> @@ -40,6 +40,7 @@
> >>  #include <linux/string.h>
> >>  #include <linux/slab.h>
> >>  #include <linux/pgtable.h>
> >> +#include <asm/sparsemem.h>
> > 
> > asm/sparsemem.h is not available on some architectures.
> > It's better to use linux/mmzone.h instead.
> > 
> 
> Hm, linux/mmzone.h only includes asm/sparsemem.h when CONFIG_SPARSEMEM
> is enabled. However, on ARM at least I can have configurations without
> CONFIG_SPARSEMEM and physical address extension on (e.g.
> multi_v7_defconfig + CONFIG_LPAE + CONFIG_ZSMALLOC).
> 
> While sparsemem seems to be a good idea with LPAE it really seems not
> required (see also https://lore.kernel.org/patchwork/patch/567589/).
> 
> There seem to be also other architectures which define MAX_PHYSMEM_BITS
> only when SPARSEMEM is enabled, e.g.
> arch/riscv/include/asm/sparsemem.h...
> 
> Not sure how to get out of this.. Maybe make ZSMALLOC dependent on
> SPARSEMEM? It feels a bit silly restricting ZSMALLOC selection only due
> to a compile time define...

I think we can define MAX_POSSIBLE_PHYSMEM_BITS in one of 
arch/arm/inclide/asm/pgtable-{2,3}level-*.h headers to values supported
by !LPAE and LPAE.

That's what x86 does: 

$ git grep -w MAX_POSSIBLE_PHYSMEM_BITS arch/
arch/x86/include/asm/pgtable-3level_types.h:#define MAX_POSSIBLE_PHYSMEM_BITS   36
arch/x86/include/asm/pgtable_64_types.h:#define MAX_POSSIBLE_PHYSMEM_BITS       52

It seems that actual numbers would be 36 for !LPAE and 40 for LPAE, but
I'm not sure about that.

> --
> Stefan
> 
> >>  #include <asm/tlbflush.h>
> >>  #include <linux/cpumask.h>
> >>  #include <linux/cpu.h>
> >> --
> >> 2.29.1
> >>
> >>

-- 
Sincerely yours,
Mike.


  reply	other threads:[~2020-11-10  9:58 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-07 15:22 Stefan Agner
2020-11-08  0:56 ` Andrew Morton
2020-11-08  1:16   ` Stefan Agner
2020-11-08  4:54     ` Florian Fainelli
2020-11-09 17:04     ` Minchan Kim
2020-11-08  6:46 ` Mike Rapoport
2020-11-10  9:29   ` Stefan Agner
2020-11-10  9:58     ` Mike Rapoport [this message]
2020-11-10 11:21       ` Arnd Bergmann
2020-11-10 12:22         ` Stefan Agner
2020-11-10 15:19           ` Arnd Bergmann
2020-11-10 16:21         ` Mike Rapoport
2020-11-10 23:36           ` Minchan Kim
2020-11-11  6:52             ` Mike Rapoport
2020-11-12 19:49               ` Minchan Kim
2020-11-11  9:33           ` Arnd Bergmann
2020-11-11 10:26             ` Mike Rapoport
2020-11-11 10:57               ` Arnd Bergmann
2020-11-11 11:04                 ` Mike Rapoport
2020-11-11 13:39                 ` Thomas Bogendoerfer
2020-11-11 14:33                   ` Arnd Bergmann
2020-11-12 19:50                     ` Minchan Kim
2020-11-12 23:46 ` Florian Fainelli

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