linux-kernel - Re: [PATCH v2] x86/fpu: Disable BH while while loading FPU registers in __fpu__restore

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Message-ID: <20181119173135.sqxemqwfpuzszyfb@linutronix.de>
Date:   Mon, 19 Nov 2018 18:31:36 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.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 v2] x86/fpu: Disable BH while while loading FPU registers
 in __fpu__restore_sig()

On 2018-11-19 18:27:43 [+0100], Borislav Petkov wrote:
> On Mon, Nov 19, 2018 at 06:11:29PM +0100, Sebastian Andrzej Siewior wrote:
> > On 2018-11-19 09:02:45 [-0800], Dave Hansen wrote:
> > > On 11/19/18 8:04 AM, Sebastian Andrzej Siewior wrote:
> > > > v1…v2: A more verbose commit as message.
> > > 
> > > I was really hoping for code comments. :)
> > 
> > I though we agreed to make those in the larger series because those
> > comments in __fpu__restore_sig() would be removed anyway (as part of the
> > series).
> 
> Also, over local_bh_disable() does not really fit as this is generic
> code and Sebastian said ARM does the whole thing a bit differently, for
> one.
> 
> We probably should put that comment somewhere prominent in
> arch/x86/kernel/fpu/core.c or similar - somewhere people poking at FPU
> stuff will see it.

I though about __fpregs_changes_begin() in the last patch of the commit:
 https://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/staging.git/commit/?h=x86_fpu_rtu_v4

Sebastian