linux-kernel - Re: [PATCH v5 2/3] Docs/mm: Fix a mistake for pfn in page

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Message-ID: <db9cd093-ed7b-4c09-a47a-4e45e303242a@linux.dev>
Date: Tue, 15 Oct 2024 10:29:16 +0800
From: Yanteng Si <si.yanteng@...ux.dev>
To: Pengyu Zhang <zpenya1314@...il.com>, alexs@...nel.org,
 siyanteng@...ngson.cn, corbet@....net, seakeel@...il.com
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 yaxin_wang_uestc@....com, zenghui.yu@...ux.dev,
 Mike Rapoport <rppt@...nel.org>, Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v5 2/3] Docs/mm: Fix a mistake for pfn in page_tables.rst




在 2024/10/14 23:55, Pengyu Zhang 写道:
> The documentation incorrectly calculate the pfn value as 0x3fffff,
> which should be 0x3ffff instead. It is obtained by right-shifting
> 0xffffc000 by 14 bits.
>
> This patch corrects the value to prevent any potential confusion
> for developers referencing this document.
>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> Reviewed-by: Zenghui Yu <zenghui.yu@...ux.dev>
> Signed-off-by: Pengyu Zhang <zpenya1314@...il.com>
Reviewed-by: Yanteng Si <si.yanteng@...ux.dev>

Thanks,
Yanteng
> ---
>   Documentation/mm/page_tables.rst | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Documentation/mm/page_tables.rst b/Documentation/mm/page_tables.rst
> index be47b192a596..e7c69cc32493 100644
> --- a/Documentation/mm/page_tables.rst
> +++ b/Documentation/mm/page_tables.rst
> @@ -29,7 +29,7 @@ address.
>   With a page granularity of 4KB and a address range of 32 bits, pfn 0 is at
>   address 0x00000000, pfn 1 is at address 0x00001000, pfn 2 is at 0x00002000
>   and so on until we reach pfn 0xfffff at 0xfffff000. With 16KB pages pfs are
> -at 0x00004000, 0x00008000 ... 0xffffc000 and pfn goes from 0 to 0x3fffff.
> +at 0x00004000, 0x00008000 ... 0xffffc000 and pfn goes from 0 to 0x3ffff.
>   
>   As you can see, with 4KB pages the page base address uses bits 12-31 of the
>   address, and this is why `PAGE_SHIFT` in this case is defined as 12 and