Re: [PATCH V2] mm: Standardize printing for pgtable entries

[David Hildenbrand (Arm)]

On 7/8/26 05:28, Anshuman Khandual wrote:
> From: "David Hildenbrand (Arm)" <david@xxxxxxxxxx>
> 
> Bad page map reporting currently stores page table entry values in an
> unsigned long long and prints them with fixed 64-bit-oriented format
> strings. This is inconsistent across call sites and does not work well for
> architectures where page table entry values are not naturally represented
> as 64-bit values, such as 32-bit or 128-bit entries.
> 
> Introduce a common helper to convert raw page table entry values into a
> fixed-width hexadecimal string based on the actual entry size. Use it for
> bad page map reporting and for dumping the page table walk in
> __print_bad_page_map_pgtable().
> 
> Pass page table entry values to the reporting path as raw bytes together
> with their size, instead of forcing them through an unsigned long long.
> It keeps the printed output consistent and avoids truncation or misleading
> formatting for non-64-bit page table entries.
> 
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

I still think you should add your

Co-developed-by :)

> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> This patch applies on v7.2-rc2
> 
> Changes in V2:
> 
> - Dropped space after ":" during print per Matthew
> - Dropped CONFIG_CPU_BIG_ENDIAN per David
> 
> Changes in V1:
> 
> https://lore.kernel.org/all/20260707041703.658021-1-anshuman.khandual@xxxxxxx/
> 
>  mm/memory.c | 98 ++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 75 insertions(+), 23 deletions(-)
> 

In general, LGTM (I wrote of it, lol)

> diff --git a/mm/memory.c b/mm/memory.c
> index ff338c2abe92..a2b63af82792 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -519,9 +519,48 @@ static bool is_bad_page_map_ratelimited(void)
>  	return false;
>  }
>  
> +#define PTVAL_STR_MAX	(32 + 1) /* Max 128-bit value in hex + NUL */

We could reduce the stack space for !__SIZEOF_INT128__, but not sure if worth it.

__print_bad_page_map_pgtable() will currently consume 132 bytes for strings,
guess that's still tolerable.

-- 
Cheers,

David