Re: [PATCH V3] mm: Standardize printing for pgtable entries

[Andy Shevchenko]

On Thu, Jul 09, 2026 at 11:12:58AM +0200, David Hildenbrand (Arm) wrote:
> On 7/9/26 09:40, Andy Shevchenko wrote:
> > On Thu, Jul 09, 2026 at 10:13:34AM +0530, Anshuman Khandual wrote:

> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> >> Cc: linux-mm@xxxxxxxxx
> >> Cc: linux-kernel@xxxxxxxxxxxxxxx
> > 
> > FWIW, you may move these to be after...
> 
> We generally don't handle it like that in MM. Maybe one day we'll switch over
> and document it accordingly.
> 
> For now, having selected patches doing this differently is not any helpful.

Can you elaborate "differently"? Except a big noise and churn in the commit message
I do not see any benefit of doing the "old" way. Lately I saw some patch-bot messages
from Andrew, I assume he updates his scripts towards newer tooling, which may be
a good sign that the (good) changes are still possible.

[...]

> >> +static void ptval_bytes_to_hex_str(char *buf, size_t buf_size, const void *entry, size_t entry_size)
> >> +{
> >> +	if (WARN_ON_ONCE(buf_size < entry_size * 2 + 1)) {
> >> +		snprintf(buf, buf_size, "overflow");
> >> +		return;
> >> +	}
> >> +
> >> +	switch (entry_size) {
> >> +	case sizeof(u32):
> >> +		snprintf(buf, buf_size, "%08x", *(const u32 *)entry);
> >> +		break;
> >> +	case sizeof(u64):
> >> +		snprintf(buf, buf_size, "%016llx", *(const u64 *)entry);
> >> +		break;
> >> +#if defined(__SIZEOF_INT128__)
> >> +	case sizeof(u128):
> >> +		snprintf(buf, buf_size, "%016llx%016llx",
> >> +			 (unsigned long long)(*(const u128 *)entry >> 64),
> >> +			 (unsigned long long)*(const u128 *)entry);
> >> +		break;
> >> +#endif
> >> +	default:
> >> +		snprintf(buf, buf_size, "unsupported");
> >> +		break;
> >> +	}
> >> +}
> >> +
> >> +#define ptval_to_str(buf, val)								\
> >> +	do {										\
> >> +		auto __val = (val);							\
> >> +											\
> >> +		ptval_bytes_to_hex_str((buf), sizeof(buf), &__val, sizeof(__val));	\
> >> +	} while (0)
> >> +
> >> +#if defined(__SIZEOF_INT128__)
> >> +#define PTVAL_STR_MAX	(32 + 1) /* Max 128-bit value in hex + NUL */
> >> +#else
> >> +#define PTVAL_STR_MAX	(16 + 1) /* Max 64-bit value in hex + NUL */
> >> +#endif
> > 
> > The above is quite duplicative with what we have in lib/vsprintf.c. Have you considered
> > using something from there instead? (Yes, it might require some functions to be wrapped
> > or dropped from static.)
> 
> Which part in particular do you have in mind?
> 
> num_to_str() does not apply due to the u128.
> 
> We could have u128 variant that we would only provide with __SIZEOF_INT128__
> 
> int num128_to_str(char *buf, int size, u128 num, unsigned int width)
> 
> And then have the code pass the value instead of a pointer to the value. A bit
> tricky to handle this based on conditional __SIZEOF_INT128__ support, but could
> be done.
> 
> Not sure if that is really what we want here, though. ptval_bytes_to_hex_str()
> is pretty ... simple :)
> 
> I didn't immediately spot a replacement for PTVAL_STR_MAX.

I referred mostly to special_hex_number().

> So it would be good if you could clarify what you had in mind, thanks!

-- 
With Best Regards,
Andy Shevchenko