Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu_begin/end() export

[Andy Lutomirski]

On Thu, May 2, 2019 at 8:41 AM Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > Cc:: Borislav Petkov <bp@xxxxxxx>
> > Cc: Rik van Riel <riel@xxxxxxxxxxx>
> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > Cc: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Nicolai Stange <nstange@xxxxxxx>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 12209993e98c ("x86/fpu: Don't export __kernel_fpu_{begin,end}()")
> > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> > ---
> >
> > 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