Re: [PATCH v6 00/90] x86: Introduce a centralized CPUID data model

[Ahmed S. Darwish]

Hi!

On Tue, 31 Mar 2026, Borislav Petkov wrote:
>
> Well, since the goal is to have *all* CPUID leaves available to the kernel,
> then we *technically* don't need the synthetic ones anymore with the exception
> of a handful ones which we defined for ourselves, like X86_FEATURE_ALWAYS, for
> example.
>
> But *all* synthetic bits which have correspondence to real CPUID leaves - and
> they're synthetic because we wanted to save space... i.e., all those bits in
> arch/x86/kernel/cpu/scattered.c, they don't need synthetic flags anymore
> because the corresponding full leafs (damn spelling of Blätter eh!) are there.
>
> Then, I'm thinking, we can reorder all the remaining really-synthetic ones
> into the unique 4-byte entries and then not even expose them in any db and not
> make them available in anything because we will have to cast them in stone
> then.
>

I guess that's a very sensible plan.

The X86_FEATURE integration and synthetic bits work is covered by the late
part of the queue (patches #77 => #90), so I'll rework 'em to do the above.

Can I get some review feedback for the patches on top (patches #04 => #76)?
They shouldn't be affected by the requested X86_FEATURE changes.

Thanks,
Ahmed