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

From: Thomas Gleixner
Date: Thu Oct 05 2017 - 09:44:49 EST

On Wed, 4 Oct 2017, Andi Kleen wrote:

> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 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

Aside of that the changelog violates as usual the changelog guidelines in

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.


For the code patch itself:

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>