Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <761345df6285930339aced868ebf8ec459091383.1556807897.git.luto@kernel.org>
 <20190502154043.gfv4iplcvzjz3mc6@linutronix.de>
In-Reply-To: <20190502154043.gfv4iplcvzjz3mc6@linutronix.de>
From:   Andy Lutomirski <luto@kernel.org>
Date:   Thu, 2 May 2019 09:29:01 -0700
Message-ID: <CALCETrWTCB9xLVdKCODghpeQpJ_3Rz3OwE8FB+5hjYXMYwYPLg@mail.gmail.com>
Subject: Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu_begin/end() export
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Rik van Riel <riel@surriel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        Nicolai Stange <nstange@suse.de>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>,
        stable <stable@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, May 2, 2019 at 8:41 AM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> On 2019-05-02 07:42:14 [-0700], Andy Lutomirski wrote:
> > The FPU is not a super-Linuxy internal detail, so remove the _GPL
> > from its export.  Without something like this patch, it's impossible
> > for even highly license-respecting non-GPL modules to use the FPU,
> > which seems silly to me.  After all, the FPU is a CPU feature, not
> > really a kernel feature at all.
> >
> > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> > Cc:: Borislav Petkov <bp@suse.de>
> > Cc: Rik van Riel <riel@surriel.com>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Nicolai Stange <nstange@suse.de>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Radim Kr=C4=8Dm=C3=A1=C5=99 <rkrcmar@redhat.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: x86@kernel.org
> > Cc: stable@vger.kernel.org
> > Fixes: 12209993e98c ("x86/fpu: Don't export __kernel_fpu_{begin,end}()"=
)
> > Signed-off-by: Andy Lutomirski <luto@kernel.org>
> > ---
> >
> > This fixes a genuine annoyance for ZFS on Linux.  Regardless of what
> > one may think about the people who distribute ZFS on Linux
> > *binaries*, as far as I know, the source and the users who build it
> > themselves are entirely respectful of everyone's license.  I have no
> > problem with EXPORT_SYMBOL_GPL() in general, but let's please avoid
> > using it for things that aren't fundamentally Linux internals.
>
> Please don't start this. We have everything _GPL that is used for FPU
> related code and only a few functions are exported because KVM needs it.
> Also with the recent FPU rework it is much easier to get this wrong so I
> would not want for any OOT code to mess with it.
>

I'm not saying that we should export things for ZFS's benefit.  But,
as far as I know, _GPL means "this interface is sufficiently specific
to Linux details that we think that any user must be a derived work".
I don't think that kernel_fpu_begin() is an example of that.

--Andy