linux-kernel - Re: [PATCH 2/2] powerpc: rectify selection to ARCH_ENABLE_SPLIT_PMD

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Date:   Thu, 19 Aug 2021 15:26:44 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Neuling <mikey@...ling.org>, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Cc:     stable@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] powerpc: rectify selection to
 ARCH_ENABLE_SPLIT_PMD_PTLOCK



On 8/19/21 3:02 PM, Lukas Bulwahn wrote:
> Commit 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK")
> selects the non-existing config ARCH_ENABLE_PMD_SPLIT_PTLOCK in
> ./arch/powerpc/platforms/Kconfig.cputype, but clearly it intends to select
> ARCH_ENABLE_SPLIT_PMD_PTLOCK here (notice the word swapping!), as this
> commit does select that for all other architectures.

Right, indeed the words here got swapped. They look very similar and also
a cross compile would not even detect the problem because the non-existent
config option would simply evaluate to 0. Thanks for catching this.

> 
> Rectify selection to ARCH_ENABLE_SPLIT_PMD_PTLOCK instead.
> 
> Fixes: 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK")
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> ---
>  arch/powerpc/platforms/Kconfig.cputype | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
> index 6794145603de..a208997ade88 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -98,7 +98,7 @@ config PPC_BOOK3S_64
>  	select PPC_HAVE_PMU_SUPPORT
>  	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
>  	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
> -	select ARCH_ENABLE_PMD_SPLIT_PTLOCK
> +	select ARCH_ENABLE_SPLIT_PMD_PTLOCK
>  	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
>  	select ARCH_SUPPORTS_HUGETLBFS
>  	select ARCH_SUPPORTS_NUMA_BALANCING
>