Re: [PATCH v8 1/3] x86/cpu: Clear feature bits disabled at compile-time

[Sohil Mehta]

On 3/2/2026 7:25 AM, Maciej Wieczor-Retman wrote:

>  /* Aligned to unsigned long to avoid split lock in atomic bitmap ops */
> -__u32 cpu_caps_cleared[NCAPINTS + NBUGINTS] __aligned(sizeof(unsigned long));
> +__u32 cpu_caps_cleared[NCAPINTS + NBUGINTS] __aligned(sizeof(unsigned long)) =
> +	DISABLED_MASK_INITIALIZER;

IIUC, DISABLED_MASK_INITIALIZER only contains the X86_FEATURE_* bits.
So, the NBUGINTS bits in cpu_caps_cleared[] are implicitly set to 0.

Should that be mentioned in the comment above? It wasn't obvious to me
when I first looked at it.

>  __u32 cpu_caps_set[NCAPINTS + NBUGINTS] __aligned(sizeof(unsigned long));
>  
>  #ifdef CONFIG_X86_32
> diff --git a/arch/x86/tools/cpufeaturemasks.awk b/arch/x86/tools/cpufeaturemasks.awk
> index 173d5bf2d999..b7f4e775a365 100755
> --- a/arch/x86/tools/cpufeaturemasks.awk
> +++ b/arch/x86/tools/cpufeaturemasks.awk
> @@ -82,6 +82,12 @@ END {
>  		}
>  		printf " 0\t\\\n";
>  		printf "\t) & (1U << ((x) & 31)))\n\n";
> +
> +		printf "\n#define %s_MASK_INITIALIZER\t\t\t\\", s;
> +		printf "\n\t{\t\t\t\t\t\t\\";
> +		for (i = 0; i < ncapints; i++)
> +			printf "\n\t\t%s_MASK%d,\t\t\t\\", s, i;
> +		printf "\n\t}\n\n";
>  	}
>  
>  	printf "#endif /* _ASM_X86_CPUFEATUREMASKS_H */\n";