Re: [PATCH v2] xen/config.h: Move BITS_PER_* definitions from asm/config.h to xen/config.h

[Jan Beulich <jbeulich@suse.com>]

On 27.03.2025 18:33, Oleksii Kurochko wrote:
> BITS_PER_* values can be defined in a common way using compiler-provided macros.
> Thus, these definitions are moved to xen/config.h to reduce duplication across
> architectures.
> 
> Additionally, *_BYTEORDER macros are removed, as BITS_PER_* values now come
> directly from the compiler environment.
> 
> The arch_fls() implementation for Arm and PPC is updated to use BITS_PER_INT
> instead of a hardcoded value of 32.
> 
> Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>
albeit ...

> --- a/xen/include/xen/config.h
> +++ b/xen/include/xen/config.h
> @@ -98,4 +98,14 @@
>  #define ZERO_BLOCK_PTR ((void *)-1L)
>  #endif
>  
> +#define BYTES_PER_LONG  __SIZEOF_LONG__

... I remain unconvinced that we actually need this (yet then not its sibling
for int). All uses I can spot could be replaced by sizeof(long). This (and its
sibling) would be needed only for #if uses, and there I would then wonder why
we couldn't use __SIZEOF_LONG__ directly, now that we assume its universally
available.

Jan