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@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Signed-off-by: Pengyu Zhang <zpenya1314@gmail.com>
---
 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
-- 
2.25.1

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@kernel.org>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
> Signed-off-by: Pengyu Zhang <zpenya1314@gmail.com>
Reviewed-by: Yanteng Si <si.yanteng@linux.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