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Message-ID: <86b8d81d760ac1f6e622f1c873a5f9aad7862734.camel@surriel.com>
Subject: Re: [PATCH] x86/fpu: Remove the _GPL from the
 kernel_fpu_begin/end() export
From:   Rik van Riel <riel@surriel.com>
To:     Sebastian Gottschall <s.gottschall@newmedia-net.de>,
        Ingo Molnar <mingo@kernel.org>, Jiri Kosina <jikos@kernel.org>
Cc:     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>,
        Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        stable@vger.kernel.org, Jiri Kosina <jikos@jikos.cz>
Date:   Sun, 05 May 2019 12:05:32 -0400
In-Reply-To: <2238f6ed-9338-903c-760c-6200e73b1599@newmedia-net.de>
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         <2238f6ed-9338-903c-760c-6200e73b1599@newmedia-net.de>
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On Sat, 2019-05-04 at 04:28 +0200, Sebastian Gottschall wrote:

> Using fpu code in kernel space in a kernel module is a derived work
> of=20
> the kernel itself?
> dont get me wrong, but this is absurd. i mean you limit the use of
> cpu=20
> instructions. the use
> of cpu instructions should be free of any licensing issue. i would
> even=20
> argument you are violating
> the license of the cpu ower given to the kernel by executing it, by=20
> 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.

However, using kernel_fpu_begin/end() does get that
module some nice optimizations that are specific to
Linux.

--=20
All Rights Reversed.

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