linux-kernel - Re: [PATCH 5/7] x86/fpu: Change fpu->fpregs_active users to fpu->fpstate

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Date:   Thu, 26 Jan 2017 16:53:07 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Rik van Riel <riel@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: Re: [PATCH 5/7] x86/fpu: Change fpu->fpregs_active users to
 fpu->fpstate_active

* Rik van Riel <riel@...hat.com> wrote:

> Let me go totally reimplement this whole project in a different way...

Note that I can still be convinced about complicating the FPU state machine as 
well if that ends up being the best approach for KVM - but it appears to me (from 
a very superficial look) that turning vCPU threads into no-FPU kthreads or 
representing the guest FPU state directly with the host FPU context would be even 
more beneficial, from the simplicity and KVM performance POV?

> At least I found some good FPU bugs and cleanups along the way.

Absolutely, and your efforts are much appreciated! This ptrace state handling 
madness that bit you on SkyLake was something I missed entirely.

Thanks,

	Ingo