From patchwork Wed Jan 9 11:47:25 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 10753943 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6D6B4746 for ; Wed, 9 Jan 2019 11:51:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5D8EC28F77 for ; Wed, 9 Jan 2019 11:51:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5120328F81; Wed, 9 Jan 2019 11:51:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EC4BF28F77 for ; Wed, 9 Jan 2019 11:51:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730391AbfAILvP (ORCPT ); Wed, 9 Jan 2019 06:51:15 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:56127 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730871AbfAILsb (ORCPT ); Wed, 9 Jan 2019 06:48:31 -0500 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1ghCLR-0007Al-GS; Wed, 09 Jan 2019 12:48:25 +0100 From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Andy Lutomirski , Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen , Sebastian Andrzej Siewior Subject: [PATCH 03/22] x86/fpu: Remove preempt_disable() in fpu__clear() Date: Wed, 9 Jan 2019 12:47:25 +0100 Message-Id: <20190109114744.10936-4-bigeasy@linutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190109114744.10936-1-bigeasy@linutronix.de> References: <20190109114744.10936-1-bigeasy@linutronix.de> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The preempt_disable() section was introduced in commit a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic") 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 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 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 Reviewed-by: Borislav Petkov --- 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(); } }