From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7C30C43387 for ; Mon, 14 Jan 2019 18:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 839B42064C for ; Mon, 14 Jan 2019 18:55:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="LPptIHJo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726833AbfANSzO (ORCPT ); Mon, 14 Jan 2019 13:55:14 -0500 Received: from mail.skyhub.de ([5.9.137.197]:45200 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726729AbfANSzN (ORCPT ); Mon, 14 Jan 2019 13:55:13 -0500 Received: from zn.tnic (p200300EC2BC4CA000555087DEC7D7788.dip0.t-ipconnect.de [IPv6:2003:ec:2bc4:ca00:555:87d:ec7d:7788]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 2A9E31EC0230; Mon, 14 Jan 2019 19:55:12 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1547492112; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=zQUWLxNfiXTBCJZstDnk5WvniFBosJUqWtd8UKSnxao=; b=LPptIHJoZmj6/pt8T4Lqbe5/tKklmj3SlT80jfAEXWFnDZxT46TrhbLvSfMlVoBbj61Lka QQXnI85VkcXa4yPsK4VEeUTS4ytECIBK0ado/6q00FSjGuiWwc/PpFp4/JLfYJh2gpsehW M9L7s+Juqbq3Hkp4YTBk/jWsYHub3Ow= Date: Mon, 14 Jan 2019 19:55:06 +0100 From: Borislav Petkov To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen Subject: Re: [PATCH 03/22] x86/fpu: Remove preempt_disable() in fpu__clear() Message-ID: <20190114185506.GP2773@zn.tnic> References: <20190109114744.10936-1-bigeasy@linutronix.de> <20190109114744.10936-4-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190109114744.10936-4-bigeasy@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 09, 2019 at 12:47:25PM +0100, Sebastian Andrzej Siewior wrote: > The preempt_disable() section was introduced in commit <---- newline here. > a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic") <---- newline here. > and it was said to be temporary. > > fpu__initialize() initializes the FPU struct to its "init" value and > then sets ->initialized to 1. The last part is the important one. > The content of the `state' does not matter because it gets set via > copy_init_fpstate_to_fpregs(). > A preemption here has little meaning because the register will always be s/register/registers/ > set to the same content after copy_init_fpstate_to_fpregs(). A softirq > with a kernel_fpu_begin() could also force to save FPU's register after ditto. > fpu__initialize() without changing the outcome here. > > Remove the preempt_disable() section in fpu__clear(), preemption here > does not hurt. > > Signed-off-by: Sebastian Andrzej Siewior > --- > arch/x86/kernel/fpu/core.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c > index 1d3ae7988f7f2..1940319268aef 100644 > --- a/arch/x86/kernel/fpu/core.c > +++ b/arch/x86/kernel/fpu/core.c > @@ -366,11 +366,9 @@ void fpu__clear(struct fpu *fpu) > * Make sure fpstate is cleared and initialized. > */ > if (static_cpu_has(X86_FEATURE_FPU)) { > - preempt_disable(); > fpu__initialize(fpu); > user_fpu_begin(); > copy_init_fpstate_to_fpregs(); > - preempt_enable(); > } > } > > -- With the above addressed: Reviewed-by: Borislav Petkov -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.