linux-kernel - Re: [PATCH 07/11] x86/pkeys: Drop the preempt-disable section

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Date:   Fri, 12 Oct 2018 10:58:42 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 07/11] x86/pkeys: Drop the preempt-disable section

On 10/04/2018 07:05 AM, Sebastian Andrzej Siewior wrote:
> The fpu->initialized flag should not be changed underneath us. This might be a
> fallout during the removal of the LazyFPU support. The FPU is marked
> initialized as soon as the state has been set to an initial value. It does not
> signal if the CPU's FPU registers are loaded.

If this is true, then the check for fpu->initialized should also go away.

If we were paranoid, we might also add a WARN_ON_ONCE() to make sure our
assumption holds true.