linux-kernel - Re: [PATCH] x86/fpu: Remove the _GPL from the kernel_fpu

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Message-ID: <86b8d81d760ac1f6e622f1c873a5f9aad7862734.camel@surriel.com>
Date:   Sun, 05 May 2019 12:05:32 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Sebastian Gottschall <s.gottschall@...media-net.de>,
        Ingo Molnar <mingo@...nel.org>, Jiri Kosina <jikos@...nel.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Nicolai Stange <nstange@...e.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        stable@...r.kernel.org, Jiri Kosina <jikos@...os.cz>
Subject: Re: [PATCH] x86/fpu: Remove the _GPL from the
 kernel_fpu_begin/end() export

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 
> 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.

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

-- 
All Rights Reversed.

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