linux-kernel - Re: [PATCH v3 1/2] mm: introduce ARCH_HAS_PTE

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Message-ID: <20180411083419.GB23400@dhcp22.suse.cz>
Date:   Wed, 11 Apr 2018 10:34:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Laurent Dufour <ldufour@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        Jerome Glisse <jglisse@...hat.com>,
        aneesh.kumar@...ux.vnet.ibm.com, akpm@...ux-foundation.org,
        mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <albert@...ive.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v3 1/2] mm: introduce ARCH_HAS_PTE_SPECIAL

On Wed 11-04-18 10:03:35, Laurent Dufour wrote:
> Currently the PTE special supports is turned on in per architecture header
> files. Most of the time, it is defined in arch/*/include/asm/pgtable.h
> depending or not on some other per architecture static definition.
> 
> This patch introduce a new configuration variable to manage this directly
> in the Kconfig files. It would later replace __HAVE_ARCH_PTE_SPECIAL.
> 
> Here notes for some architecture where the definition of
> __HAVE_ARCH_PTE_SPECIAL is not obvious:
> 
> arm
>  __HAVE_ARCH_PTE_SPECIAL which is currently defined in
> arch/arm/include/asm/pgtable-3level.h which is included by
> arch/arm/include/asm/pgtable.h when CONFIG_ARM_LPAE is set.
> So select ARCH_HAS_PTE_SPECIAL if ARM_LPAE.
> 
> powerpc
> __HAVE_ARCH_PTE_SPECIAL is defined in 2 files:
>  - arch/powerpc/include/asm/book3s/64/pgtable.h
>  - arch/powerpc/include/asm/pte-common.h
> The first one is included if (PPC_BOOK3S & PPC64) while the second is
> included in all the other cases.
> So select ARCH_HAS_PTE_SPECIAL all the time.
> 
> sparc:
> __HAVE_ARCH_PTE_SPECIAL is defined if defined(__sparc__) &&
> defined(__arch64__) which are defined through the compiler in
> sparc/Makefile if !SPARC32 which I assume to be if SPARC64.
> So select ARCH_HAS_PTE_SPECIAL if SPARC64
> 
> There is no functional change introduced by this patch.
> 
> Suggested-by: Jerome Glisse <jglisse@...hat>
> Reviewed-by: Jerome Glisse <jglisse@...hat>
> Acked-by: David Rientjes <rientjes@...gle.com>
> Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>

Looks good to me. I have checked x86 and the generic code and it looks
good to me. Anyway arch maintainers really have to double check this.
-- 
Michal Hocko
SUSE Labs