linux-kernel - Re: [PATCH] arm64: fpsimd: Added API to manage fpsimd state inside kernel

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Date:   Fri, 5 Jun 2020 11:37:05 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Wooyeon Kim <wooy88.kim@...sung.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, hk92.kim@...sung.com,
        Wooki Min <wooki.min@...sung.com>,
        Bhupesh Sharma <bhsharma@...hat.com>, yb.song@...sung.com,
        yj.yim@...sung.com, Julien Grall <julien.grall@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Sanghoon Lee <shoon114.lee@...sung.com>,
        jinsoo37.kim@...sung.com, hyewon.ryu@...sung.com,
        yhwan.joo@...sung.com, Anisse Astier <aastier@...ebox.fr>,
        Marc Zyngier <maz@...nel.org>, dongww.kim@...sung.com,
        linux-arm-kernel@...ts.infradead.org, jihun.kim@...sung.com,
        Dave Martin <Dave.Martin@....com>,
        Kees Cook <keescook@...omium.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Kristina Martsenko <kristina.martsenko@....com>,
        junik.lee@...sung.com, sgun.bae@...sung.com,
        Jeongtae Park <jtp.park@...sung.com>, kgene.kim@...sung.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Allison Randal <allison@...utok.net>,
        Steve Capper <steve.capper@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
        hyeyeon5.shim@...sung.com, dh.han@...sung.com
Subject: Re: [PATCH] arm64: fpsimd: Added API to manage fpsimd state inside
 kernel

Hi Wooyeon,

There are a *lot* of people Cc' here, many of whomo will find this
irrelevant. Please try to keep the Cc list constrained to a reasonable
number of interested parties.

On Fri, Jun 05, 2020 at 04:30:52PM +0900, Wooyeon Kim wrote:
> From: Wooki Min <wooki.min@...sung.com>
> 
>      This is an patch to use FPSIMD register in Kernel space.
>      It need to manage to use FPSIMD register without damaging it
>      of the user task.
>      Following items have been implemented and added.

Please introduce the problem you are trying to solve in more detail. We
already have kernel_neon_{begin,end}() for kernel-mode NEON; why is that
not sufficient for your needs? Please answer this before considering
other details.

What do you want to use this for?

> 
>      1. Using FPSIMD in ISR (in_interrupt)
> 	It can used __efi_fpsimd_begin/__efi_fpsimd_end
> 	which is already implemented.
> 	Save fpsimd state before entering ISR,
> 	and restore fpsimd state after ISR ends.
> 	For use in external kernel module,
> 	it is declared as EXPORT_SYMBOL.

This patch adds no in-tree modular users of this, so per the usual
conventions, NAK to EXPORT_SYMBOL().

Thanks,
Mark.