linux-kernel - Re: [PATCH v7 5/5] x86/xsave: Using generic CPUID clearing when disabling XSAVE

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Message-ID: <alpine.DEB.2.20.1710051531580.2083@nanos>
Date:   Thu, 5 Oct 2017 15:44:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <andi@...stfloor.org>
cc:     x86@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v7 5/5] x86/xsave: Using generic CPUID clearing when
 disabling XSAVE

On Wed, 4 Oct 2017, Andi Kleen wrote:

> From: Andi Kleen <ak@...ux.intel.com>
> 
> Now that the generic CPUID clearing understands dependencies,
> it's enough to clear the XSAVE CPUID bit to clear all depending
> features when XSAVE gets disabled.
> 
> So we don't need this hard to maintain explicit list
> of features depending on XSAVE anymore. Just call the generic
> clear_cpu_cap() function for XSAVE.

This changelog is hard to read and uses terms like 'CPUID clearing'. I know
what you want to say, but this is far from being precise and
understandable.

Aside of that the changelog violates as usual the changelog guidelines in
Documentation/....

Something like this would be clear and precise:

  Clearing a CPU feature with setup_clear_cpu_cap() clears all features
  which depend on it. Expressing feature dependencies in one place is
  easier to maintain than keeping functions like
  fpu__xstate_clear_all_cpu_caps() up to date.

  The features which depend on XSAVE have their dependency expressed in the
  dependency table, so its sufficient to clear X86_FEATURE_XSAVE.

  Remove the explicit clearing of XSAVE dependend features. 

Hmm?

For the code patch itself:

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

Thanks,

	tglx