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Date:   Thu, 23 Mar 2023 10:15:33 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
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        Geert Uytterhoeven <geert@linux-m68k.org>,
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        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
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Subject: Re: [PATCH 02/14] arm64: drop ranges in definition of
 ARCH_FORCE_MAX_ORDER
Message-ID: <ZBwmxbRJrF8RxZEp@arm.com>
References: <20230323092156.2545741-1-rppt@kernel.org>
 <20230323092156.2545741-3-rppt@kernel.org>
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On Thu, Mar 23, 2023 at 11:21:44AM +0200, Mike Rapoport wrote:
> From: "Mike Rapoport (IBM)" <rppt@kernel.org>
> 
> It is not a good idea to change fundamental parameters of core memory
> management. Having predefined ranges suggests that the values within
> those ranges are sensible, but one has to *really* understand
> implications of changing MAX_ORDER before actually amending it and
> ranges don't help here.
> 
> Drop ranges in definition of ARCH_FORCE_MAX_ORDER
> 
> Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
> ---
>  arch/arm64/Kconfig | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index e60baf7859d1..bab6483e4317 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1489,9 +1489,7 @@ config XEN
>  config ARCH_FORCE_MAX_ORDER
>  	int "Maximum zone order" if ARM64_4K_PAGES || ARM64_16K_PAGES
>  	default "13" if ARM64_64K_PAGES
> -	range 11 13 if ARM64_16K_PAGES
>  	default "11" if ARM64_16K_PAGES
> -	range 10 15 if ARM64_4K_PAGES
>  	default "10"

I don't mind rewriting the help text as in the subsequent patch but I'd
keep the ranges as a safety measure. It's less wasted time explaining to
people why some random max order doesn't work. Alternatively, we can
drop the ranges but make this option configurable only if EXPERT.

-- 
Catalin