Re: [PATCH 1/4] x86/cpufeature: Add User-Mode Instruction Prevention definitions

[Ricardo Neri]

On Wed, 2016-11-09 at 03:02 -0800, Andy Lutomirski wrote:
> On Tue, Nov 8, 2016 at 8:25 PM, Ricardo Neri
> <ricardo.neri-calderon@xxxxxxxxxxxxxxx> wrote:
> > On Tue, 2016-11-08 at 07:32 -0800, Andy Lutomirski wrote:
> >> > diff --git a/arch/x86/include/asm/disabled-features.h
> >> b/arch/x86/include/asm/disabled-features.h
> >> > index 85599ad..4707445 100644
> >> > --- a/arch/x86/include/asm/disabled-features.h
> >> > +++ b/arch/x86/include/asm/disabled-features.h
> >> > @@ -16,6 +16,12 @@
> >> >  # define DISABLE_MPX   (1<<(X86_FEATURE_MPX & 31))
> >> >  #endif
> >> >
> >> > +#ifdef CONFIG_X86_INTEL_UMIP
> >>
> >> ^^^^^
> >>
> >> What's this?
> >>
> >> Let's try to do this with a minimum of configuration.
> >
> > My intention here is put in this file all the #if build configurations
> > so that I don't have to put them other files by using functions such as
> > cpu_feature_enable. Isn't this the intention of this file?
> 
> What I mean is: why does this need a config option at all?

I intended this feature to be configurable at build time in case someone
wants to build a kernel without it; similar to other features such as
SMAP. Is this not needed? Should Linux be built with this feature always
enabled?

This feature could always be disabled via a kernel parameter, though;
even if Linux is built with it.

Thanks and BR,
Ricardo
> 
> --Andy