Re: x86/fpu: Don't export __kernel_fpu_{begin,end}()

From: Lukas Wunner <lukas@wunner.de>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	"Hutter, Tony" <hutter2@llnl.gov>,
	Marc Dionne <marc.c.dionne@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	Kash Pande <kash@tripleback.net>, Ingo Molnar <mingo@kernel.org>
Subject: Re: x86/fpu: Don't export __kernel_fpu_{begin,end}()
Date: Fri, 11 Jan 2019 19:06:17 +0100	[thread overview]
Message-ID: <20190111180617.2k5uundov6hf4m7h@wunner.de> (raw)
In-Reply-To: <20190111054058.GA27966@kroah.com>

[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