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

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Message-ID: <20190502154043.gfv4iplcvzjz3mc6@linutronix.de>
Date:   Thu, 2 May 2019 17:40:43 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     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@...nel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu_begin/end()
 export

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.

And again: It does not change whether or not ZFS can be used on Linux
(excluding the license issue). They simply can't use crc32 with their
SSE assembly and this is it.

Sebastian