Re: [RESEND v1 1/3] x86/cpufeatures: Add {required,disabled} feature configs

[Xin Li]

On 6/12/2024 6:33 AM, Borislav Petkov wrote:
> On Thu, May 09, 2024 at 01:53:38PM -0700, Xin Li (Intel) wrote:
> > diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
> > index 2a7279d80460..719302d37053 100644
> > --- a/arch/x86/Kconfig.cpu
> > +++ b/arch/x86/Kconfig.cpu
> > @@ -358,6 +358,10 @@ config X86_P6_NOP
> >   	depends on X86_64
> >   	depends on (MCORE2 || MPENTIUM4 || MPSC)
> >   
> > +config X86_REQUIRED_FEATURE_NOPL
>
> Can we keep the X86_{REQUIRED,DISABLED}_ prefixes solely in
> arch/x86/Kconfig.cpufeatures and not spill them out into the rest of the tree?

Good point, let me try.

> This way there will be no confusion between X86_FEATURE_, X86_REQUIRED_FEATURE_,
> X86_DISABLED_FEATURE_ and so on, and which one I am supposed to use where...

Currently X86_DISABLED_FEATURE_ macros are defined only in:
arch/x86/Kconfig.cpufeatures. But X86_REQUIRED_FEATURE_ macros are not.


> > diff --git a/arch/x86/Kconfig.cpufeatures b/arch/x86/Kconfig.cpufeatures
> > new file mode 100644
> > index 000000000000..326a8410ff06
> > --- /dev/null
> > +++ b/arch/x86/Kconfig.cpufeatures
> > @@ -0,0 +1,153 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# x86 feature bits (see arch/x86/include/asm/cpufeatures.h) that are
> > +# either REQUIRED to be enabled, or DISABLED (always ignored) for this
> > +# particular compile-time configuration.  The tests for these features
> > +# are turned into compile-time constants via the generated
> > +# <asm/featuremasks.h>.
> > +#
> > +# The naming of these variables *must* match asm/cpufeatures.h.
>
> I presume they must match X86_FEATURE_<name>?

Right, let me add this.

> And REQUIRED and DISABLED is manipulated in by the script?
>
> I guess I'll see later.

Yep!

Thanks!
    Xin