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Docs/mm: Fix a mistake for pfn in page_tables.rst

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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.

Signed-off-by: Pengyu Zhang <zpenya1314@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241009144135.12453-1-zpenya1314@gmail.com
This commit is contained in:
Pengyu Zhang 2024-10-09 22:41:35 +08:00 committed by Jonathan Corbet
parent 443165227d
commit 6a32c8dfec
1 changed files with 1 additions and 1 deletions
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Documentation/mm/page_tables.rst
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@ -29,7 +29,7 @@ address.
With a page granularity of 4KB and a address range of 32 bits, pfn 0 is at 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 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 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 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 address, and this is why `PAGE_SHIFT` in this case is defined as 12 and