linux-kernel - Re: [PATCH] arch : arm : add a criteria for pfn

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Message-ID: <20190817183240.GM13294@shell.armlinux.org.uk>
Date:   Sat, 17 Aug 2019 19:32:40 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Zhaoyang Huang <huangzhaoyang@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Doug Berger <opendmb@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch : arm : add a criteria for pfn_valid

On Sat, Aug 17, 2019 at 11:00:13AM +0800, Zhaoyang Huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> pfn_valid can be wrong while the MSB of physical address be trimed as pfn
> larger than the max_pfn.

What scenario are you addressing here?  At a guess, you're addressing
the non-LPAE case with PFNs that correspond with >= 4GiB of memory?

> 
> Signed-off-by: Zhaoyang Huang <huangzhaoyang@...il.com>
> ---
>  arch/arm/mm/init.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index c2daabb..9c4d938 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -177,7 +177,8 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
>  #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>  int pfn_valid(unsigned long pfn)
>  {
> -	return memblock_is_map_memory(__pfn_to_phys(pfn));
> +	return (pfn > max_pfn) ?
> +		false : memblock_is_map_memory(__pfn_to_phys(pfn));
>  }
>  EXPORT_SYMBOL(pfn_valid);
>  #endif
> -- 
> 1.9.1
> 
> 

-- 
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