linux-kernel - Re: x86/fpu: Don't export __kernel_fpu

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Date:   Fri, 11 Jan 2019 19:06:17 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "Hutter, Tony" <hutter2@...l.gov>,
        Marc Dionne <marc.c.dionne@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Kash Pande <kash@...pleback.net>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: x86/fpu: Don't export __kernel_fpu_{begin,end}()

[cc += Ingo]

On Fri, Jan 11, 2019 at 06:40:58AM +0100, Greg Kroah-Hartman wrote:
> On Fri, Jan 11, 2019 at 06:04:07AM +0100, Lukas Wunner wrote:
> > On Thu, Jan 10, 2019 at 07:24:13PM +0100, Greg Kroah-Hartman wrote:
> > > My tolerance for ZFS is pretty non-existant.  Sun explicitly did not
> > > want their code to work on Linux, so why would we do extra work to get
> > > their code to work properly?
> > 
> > ZoL facilitates seamless r/w cross-mounting with macOS, something no
> > other filesystem allows, and that feature is critical for me to work
> > on Linux drivers for Mac hardware.  Please don't make life harder than
> > necessary for developers like me.  Your "extra work" argument seems
> > disingenuous to me, Sebastian's patch is causing extra work for
> > ZFS developers, not the kernel community.  The maintenance burden
> > for the kernel community to retain the export is zero.
> 
> Sorry, no, we do not keep symbols exported for no in-kernel users.

AFAICS the only other alternative would be to remove the _GPL from
the export of kernel_fpu_begin()/end().  Those functions were static
inlines until v4.2 when Ingo uninlined them with commit d63e79b114c0
(x86/fpu: Uninline kernel_fpu_begin()/end()).

Ingo, why did you choose _GPL back then, given that the functions
were not restricted to GPL before?  Any objections to making them
available to non-GPL again?

As it stands, v5.0 removes the ability from non-GPL modules to use
the FPU or SIMD instructions and that kills ZFS on Linux.  This isn't
hurting Oracle, they're not using OpenZFS, it's only hurting ZoL users.

Thanks,

Lukas