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 91562C282D7 for ; Wed, 30 Jan 2019 11:56:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64BE320855 for ; Wed, 30 Jan 2019 11:56:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="c5DFRKoN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730822AbfA3L4V (ORCPT ); Wed, 30 Jan 2019 06:56:21 -0500 Received: from mail.skyhub.de ([5.9.137.197]:34140 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730308AbfA3L4U (ORCPT ); Wed, 30 Jan 2019 06:56:20 -0500 Received: from zn.tnic (p200300EC2BCAED00D014CE199A91CB87.dip0.t-ipconnect.de [IPv6:2003:ec:2bca:ed00:d014:ce19:9a91:cb87]) (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 138871EC04F3; Wed, 30 Jan 2019 12:56:18 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1548849378; 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=wwFVobSeJGnSQkzACO0nPrAoWxqdCnm8PIo8GBGCqn4=; b=c5DFRKoN8hJxWmPYPhp6rT2NPQghZPzIAz5NRAyk4RwbJnmaV2OfnXAXtvScobXMBnXn31 UwTGllnLqJF5LtBMMQyNKNwNggjL9jMH9KJR1FlU0koA7m5Hl5PmSxci6Q1CImlyL3F7eS Jw50tGXfStC8+BIL2G6s1c83Hz0udMI= Date: Wed, 30 Jan 2019 12:56:14 +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 17/22] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD Message-ID: <20190130115614.GF18383@zn.tnic> References: <20190109114744.10936-1-bigeasy@linutronix.de> <20190109114744.10936-18-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190109114744.10936-18-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 12:47:39PM +0100, Sebastian Andrzej Siewior wrote: > From: Rik van Riel > > The FPU registers need only to be saved if TIF_NEED_FPU_LOAD is not set. > Otherwise this has been already done and can be skipped. > > Signed-off-by: Rik van Riel > Signed-off-by: Sebastian Andrzej Siewior > --- > arch/x86/kernel/fpu/signal.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > index bf4e6caad305e..a25be217f9a2c 100644 > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -156,7 +156,16 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) > sizeof(struct user_i387_ia32_struct), NULL, > (struct _fpstate_32 __user *) buf) ? -1 : 1; > > - copy_fpregs_to_fpstate(fpu); > + __fpregs_changes_begin(); > + /* > + * If we do not need to load the FPU registers at return to userspace > + * then the CPU has the current state and we need to save it. Otherwise > + * it is already done and we can skip it. > + */ > + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) > + copy_fpregs_to_fpstate(fpu); I wonder if this flag would make the code more easy to follow by calling it TIF_FPU_REGS_VALID instead, to denote that the FPU registers in the CPU have a valid content. Then the test becomes: if (test_thread_flag(TIF_FPU_REGS_VALID)) copy_fpregs_to_fpstate(fpu); -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.