linux-kernel - Re: [PATCH 23/27] x86/fpu: Defer FPU state load until return to userspace

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Message-ID: <20190412162213.GF19808@zn.tnic>
Date:   Fri, 12 Apr 2019 18:22:13 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, 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>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 23/27] x86/fpu: Defer FPU state load until return to
 userspace

On Fri, Apr 12, 2019 at 05:24:37PM +0200, Sebastian Andrzej Siewior wrote:
> Isn't it called from fpu__clear()?

$ git grep trace_x86_fpu_activate_state
$

all 23 patches applied. Grepping the later patches doesn't give
trace_x86_fpu_activate_state() either.

> > Shouldn't it be called below, before fpregs_activate() because
> > fpregs_activate() does trace_x86_fpu_regs_activated()?
> 
> Why? fpu__initialize() wipes the FPU state and starts from zero.
> fpregs_mark_activate() on the other hand marks this FPU context is
> currently active.

Well, then the naming still needs adjusting.

"trace_x86_fpu_activate_state" reads to me like the state is being
activated here, at the call site. And fpregs_mark_activate() marks which
*fpu is the active one.

Hmm.

-- 
Regards/Gruss,
    Boris.

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