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Date:   Sun, 5 May 2019 21:09:09 +0200 (CEST)
From:   Jiri Kosina <jikos@kernel.org>
To:     Rik van Riel <riel@surriel.com>
cc:     Sebastian Gottschall <s.gottschall@newmedia-net.de>,
        Ingo Molnar <mingo@kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        Nicolai Stange <nstange@suse.de>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?ISO-8859-2?Q?Radim_Kr=E8m=E1=F8?= <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        stable@vger.kernel.org, Jiri Kosina <jikos@jikos.cz>
Subject: Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu_begin/end()
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On Sun, 5 May 2019, Rik van Riel wrote:

> > Using fpu code in kernel space in a kernel module is a derived work of 
> > the kernel itself? dont get me wrong, but this is absurd. i mean you 
> > limit the use of cpu instructions. the use of cpu instructions should 
> > be free of any licensing issue. i would even argument you are 
> > violating the license of the cpu ower given to the kernel by executing 
> > it, by restricting its use for no reason
> 
> Using FPU code in kernel space in a kernel module does not require the 
> use of kernel_fpu_begin/end().
> 
> The kernel module could simply disable preemption, save the FPU 
> registers, use the FPU, restore the FPU registers, and reenable 
> preemption.

That means the module basically reimplemented kernel_fpu_begin/end() in 
its whole (not getting the further optimizations implemented by the 
kernel, sure). And therefore I sort of don't see the point of "hiding" it.

Thanks,

-- 
Jiri Kosina
SUSE Labs