linux-kernel - Re: [PATCH] x86/fpu: allow kernel_fpu_{begin,end} to be used by non-GPL modules

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Message-ID: <20190522100959.GA15390@kroah.com>
Date:   Wed, 22 May 2019 12:09:59 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Aleksa Sarai <cyphar@...har.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>,
        Nicolai Stange <nstange@...e.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        zfs-devel@...t.zfsonlinux.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/fpu: allow kernel_fpu_{begin,end} to be used by
 non-GPL modules

On Wed, May 22, 2019 at 02:42:04PM +1000, Aleksa Sarai wrote:
> Prior to [1], all non-GPL modules were able to make use of SIMD on x86
> by making use of the __kernel_fpu_* API. Given that __kernel_fpu_* were
> both EXPORT_SYMBOL'd and kernel_fpu_* are such trivial wrappers around
> the now-static __kernel_fpu_*, it seems to me that there is no reason to
> have different licensing rules for them.
> 
> In the case of OpenZFS, the lack of SIMD on newer Linux kernels has
> caused significant performance problems (since ZFS uses SIMD for
> calculation of blkptr checksums as well as raidz calculations).
> 
> [1]: commit 12209993e98c ("x86/fpu: Don't export __kernel_fpu_{begin,end}()")
> 
> Cc: "Jason A. Donenfeld" <Jason@...c4.com>
> Signed-off-by: Aleksa Sarai <cyphar@...har.com>
> ---
>  arch/x86/kernel/fpu/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index 2e5003fef51a..8de5687a470d 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -127,14 +127,14 @@ void kernel_fpu_begin(void)
>  	preempt_disable();
>  	__kernel_fpu_begin();
>  }
> -EXPORT_SYMBOL_GPL(kernel_fpu_begin);
> +EXPORT_SYMBOL(kernel_fpu_begin);
>  
>  void kernel_fpu_end(void)
>  {
>  	__kernel_fpu_end();
>  	preempt_enable();
>  }
> -EXPORT_SYMBOL_GPL(kernel_fpu_end);
> +EXPORT_SYMBOL(kernel_fpu_end);

No, please, we have gone over this before, we do not care at all about
external kernel modules, ESPECIALLY ones that are not GPL compatible.

greg k-h