Re: [PATCH] x86: Clear LAM and FRED feature bits

[Dave Hansen]

On 7/22/25 02:08, Xin Li wrote:
>> +    /*
>> +     * If a feature is disabled during compile time clear its feature
>> +     * bit to prevent it from showing up in the x86_capability bitmask.
>> +     */
>> +    if (!cpu_feature_enabled(X86_FEATURE_LAM))
>> +        setup_clear_cpu_cap(X86_FEATURE_LAM);
>> +
>> +    if (!cpu_feature_enabled(X86_FEATURE_FRED))
>> +        setup_clear_cpu_cap(X86_FEATURE_FRED);
>> +
> 
> The following code will work as a generic fix:
> 
>     c->x86_capability[i] &= ~DISABLED_MASK(i);
> 
> And DISABLED_MASK(x) needs to be defined like DISABLED_MASK_BIT_SET(x).

Maciej, I would much rather have a generic fix than force everyone to
remember to open-code this for every new feature that gets disabled.