linux-kernel - Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu

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Message-ID: <CALCETrWTCB9xLVdKCODghpeQpJ_3Rz3OwE8FB+5hjYXMYwYPLg@mail.gmail.com>
Date:   Thu, 2 May 2019 09:29:01 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Rik van Riel <riel@...riel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Nicolai Stange <nstange@...e.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu_begin/end() export

On Thu, May 2, 2019 at 8:41 AM Sebastian Andrzej Siewior
<bigeasy@...utronix.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@...utronix.de>
> > Cc:: Borislav Petkov <bp@...e.de>
> > Cc: Rik van Riel <riel@...riel.com>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: "Jason A. Donenfeld" <Jason@...c4.com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Nicolai Stange <nstange@...e.de>
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Radim Krčmář <rkrcmar@...hat.com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: x86@...nel.org
> > Cc: stable@...r.kernel.org
> > Fixes: 12209993e98c ("x86/fpu: Don't export __kernel_fpu_{begin,end}()")
> > Signed-off-by: Andy Lutomirski <luto@...nel.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