From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Subject: Re: [PATCH V2] mm/special: Create generic fallbacks for
 pte_special() and pte_mkspecial()
Date: Tue, 10 Mar 2020 14:27:47 +0100
Message-ID: <20200310132747.GA12601@alpha.franken.de>
References: <1583802551-15406-1-git-send-email-anshuman.khandual@arm.com>
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To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-mm@kvack.org, Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, Russell King <linux@armlinux.org.uk>, Guo Ren <guoren@kernel.org>, Brian Cain <bcain@codeaurora.org>, Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Sam Creasey <sammy@sammy.net>, Michal Simek <monstr@monstr.eu>, Ralf Baechle <ralf@linux-mips.org>, Paul Burton <paulburton@kernel.org>, Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>, Vincent Chen <deanbo422@gmail.com>, Ley Foon Tan <ley.foon.tan@intel.com>, Jonas Bonn <jonas@southpole.se>, Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>, Stafford Horne <shorne@gmail.com>

On Tue, Mar 10, 2020 at 06:39:11AM +0530, Anshuman Khandual wrote:
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index aef5378f909c..8e4e4be1ca00 100644
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -269,6 +269,36 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
>   */
>  extern pgd_t swapper_pg_dir[];
>  
> +/*
> + * Platform specific pte_special() and pte_mkspecial() definitions
> + * are required only when ARCH_HAS_PTE_SPECIAL is enabled.
> + */
> +#if !defined(CONFIG_32BIT) && !defined(CONFIG_CPU_HAS_RIXI)

this looks wrong.

current Kconfig statement is

select ARCH_HAS_PTE_SPECIAL if !(32BIT && CPU_HAS_RIXI)

so we can't use PTE_SPECIAL on 32bit _and_ CPUs with RIXI support.

Why can't we use

#if defined(CONFIG_ARCH_HAS_PTE_SPECIAL)

here as the comment already suggests ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]