linux-kernel - Support generic disabling of all XSAVE features

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Message-Id: <20171004234930.5685-1-andi@firstfloor.org>
Date:   Wed,  4 Oct 2017 16:49:25 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     x86@...nel.org
Cc:     hpa@...or.com, linux-kernel@...r.kernel.org
Subject: Support generic disabling of all XSAVE features

For performance testing and debugging it can be useful to disable XSAVE
features individually. 

This patchkit hooks up XSAVE with the generic clearcpuid=... option,
so that disabling a CPUID feature automatically disables the respective
XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.
v5:
Fix dependency algorithm. Clean dups in table. Rebase.
v6: 
Rebase. No changes to code.
v7:
Rebase. No changes to code.