linux-kernel - Re: [PATCH V4] LoongArch: Provide kernel fpu functions

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Date:   Fri, 10 Mar 2023 14:33:16 +0800
From:   WANG Xuerui <kernel@...0n.name>
To:     Huacai Chen <chenhuacai@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>,
        Huacai Chen <chenhuacai@...nel.org>
Cc:     loongarch@...ts.linux.dev, linux-arch@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH V4] LoongArch: Provide kernel fpu functions

On 2023/3/10 10:51, Huacai Chen wrote:
> Provide kernel_fpu_begin()/kernel_fpu_end() to allow the kernel itself
> to use fpu. They can be used by some other kernel components, e.g., the
> AMDGPU graphic driver for DCN.

Actually, as Christoph suggested earlier, you should probably send this 
together with the amdgpu modifications so that "actual usage" of the 
interface is established.

> 
> Reported-by: WANG Xuerui <kernel@...0n.name>
> Tested-by: WANG Xuerui <kernel@...0n.name>
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
> V2: Use non-GPL exports and update commit messages.
> V3: Add spaces for coding style.
> V4: WARN_ON unexpected requests and use GPL exports again.

We should probably provide more archaeology or legal evidence as to why 
the in-kernel FPU ops must be GPL-only. After all the status quo is that 
among all arches that provide such ops, only the x86 ones are exported 
GPL, so if loongarch should go GPL for this interface then probably 
everyone else should too. It's not only affecting loongarch IMO.

> 
>   arch/loongarch/include/asm/fpu.h |  3 +++
>   arch/loongarch/kernel/Makefile   |  2 +-
>   arch/loongarch/kernel/kfpu.c     | 43 ++++++++++++++++++++++++++++++++
>   3 files changed, 47 insertions(+), 1 deletion(-)
>   create mode 100644 arch/loongarch/kernel/kfpu.c
> 

-- 
WANG "xen0n" Xuerui

Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/