linux-kernel - Re: [PATCH V2] mm: Define default value for FIRST_USER

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Message-ID: <20210506102736.GB22164@arm.com>
Date:   Thu, 6 May 2021 11:27:36 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        Richard Henderson <rth@...ddle.net>,
        Vineet Gupta <vgupta@...opsys.com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Brian Cain <bcain@...eaurora.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Jeff Dike <jdike@...toit.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Chris Zankel <chris@...kel.net>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mm: Define default value for FIRST_USER_ADDRESS

On Fri, Apr 16, 2021 at 10:47:34AM +0530, Anshuman Khandual wrote:
> Currently most platforms define FIRST_USER_ADDRESS as 0UL duplication the
> same code all over. Instead just define a generic default value (i.e 0UL)
> for FIRST_USER_ADDRESS and let the platforms override when required. This
> makes it much cleaner with reduced code.
> 
> The default FIRST_USER_ADDRESS here would be skipped in <linux/pgtable.h>
> when the given platform overrides its value via <asm/pgtable.h>.
> 
> Cc: Richard Henderson <rth@...ddle.net>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Guo Ren <guoren@...nel.org>
> Cc: Brian Cain <bcain@...eaurora.org>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Michal Simek <monstr@...str.eu>
> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> Cc: Ley Foon Tan <ley.foon.tan@...el.com>
> Cc: Jonas Bonn <jonas@...thpole.se>
> Cc: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
> Cc: Stafford Horne <shorne@...il.com>
> Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Jeff Dike <jdike@...toit.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-arch@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
[...]
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 47027796c2f9..f6ab8b64967e 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -26,8 +26,6 @@
>  
>  #define vmemmap			((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
>  
> -#define FIRST_USER_ADDRESS	0UL
> -
>  #ifndef __ASSEMBLY__
>  
>  #include <asm/cmpxchg.h>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@....com>