linux-kernel - Re: [PATCH V8 06/44] mm/pkeys: Add Kconfig options for PKS

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Date:   Fri, 4 Feb 2022 11:08:51 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 06/44] mm/pkeys: Add Kconfig options for PKS

On Fri, Jan 28, 2022 at 03:51:56PM -0800, Dave Hansen wrote:
> On 1/28/22 15:10, Ira Weiny wrote:
> > This issue is that because PKS users are in kernel only and are not part of the
> > architecture specific code there needs to be 2 mechanisms within the Kconfig
> > structure.  One to communicate an architectures support PKS such that the user
> > who needs it can depend on that config as well as a second to allow that user
> > to communicate back to the architecture to enable PKS.
> 
> I *think* the point here is to ensure that PKS isn't compiled in unless
> it is supported *AND* needed.

Yes.

> You have to have architecture support
> (ARCH_HAS_SUPERVISOR_PKEYS) to permit features that depend on PKS to be
> enabled.  Then, once one ore more of *THOSE* is enabled,
> ARCH_ENABLE_SUPERVISOR_PKEYS comes into play and actually compiles the
> feature in.
> 
> In other words, there are two things that must happen before the code
> gets compiled in:
> 
> 1. Arch support
> 2. One or more features to use the arch support

Yes.  I really think we are both say the same thing with different words.

Ira