linux-kernel - Re: [patch 17/17] x86/fpu: Move FPU initialization into arch_cpu_finalize

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Message-ID: <87o7li8j75.ffs@tglx>
Date:   Wed, 14 Jun 2023 11:52:14 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>,
        Nikolay Borisov <nik.borisov@...e.com>,
        "Ahmed S. Darwish" <darwi@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k@...ts.linux-m68k.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        linux-sh@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        sparclinux@...r.kernel.org, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org,
        Richard Henderson <richard.henderson@...aro.org>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Chris Zankel <chris@...kel.net>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [patch 17/17] x86/fpu: Move FPU initialization into
 arch_cpu_finalize_init()

On Tue, Jun 13 2023 at 22:03, Chang S. Bae wrote:

> On 6/13/2023 4:39 PM, Thomas Gleixner wrote:
>>   
>> @@ -2396,6 +2393,13 @@ void __init arch_cpu_finalize_init(void)
>>   			'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
>>   	}
>>   
>> +	/*
>> +	 * Must be before alternatives because it might set or clear
>> +	 * feature bits.
>> +	 */
>> +	fpu__init_system();
>> +	fpu__init_cpu();
>
> fpu__init_cpu() appears to be duplicated here because fpu__init_system() 
> invoked this already:
>
> void __init fpu__init_system(void)
> {
> ...
> 	/*
> 	 * The FPU has to be operational for some of the
> 	 * later FPU init activities:
> 	 */
> 	fpu__init_cpu();

Well, that's _before_ xstate initialization and I couldn't convince
myself that it's good enough. All of this is such a horrible mess...