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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 DFE76C432C0 for ; Thu, 21 Nov 2019 19:47:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B15A72063A for ; Thu, 21 Nov 2019 19:47:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="pRKiYlpF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726976AbfKUTrE (ORCPT ); Thu, 21 Nov 2019 14:47:04 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:37274 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726563AbfKUTrE (ORCPT ); Thu, 21 Nov 2019 14:47:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=uDnrPO1tl5vXSE/f3VQxCFB1olb1bF+zShCGCQYuB7o=; b=pRKiYlpFirip+dnTqEjeOQm+M u30mv3OXCjhLway7hxFFdcyw2HVKihH24n6UqZmV5TWf03EzMhmveRcv2ZRitUsyJKH+NybaRRwu9 eGlS5Tugqv0arzXWxuhdb3yAp9TZxODC+398uh93/vIf/2D/abx2ZbquPwxx6vvVe968QL10dfd+6 lHj1zNAVzoER5LNCmeNYb+eeY/uBIclmpiv3Vo0WL+ePxy8n1/zcKOvJWCcqOFJNPd3Cp/Fpn5ZiA L4L3RasJNBEhQhlD8Mbs6rnSH0wFRVnfCVze86eKvO/tcEdq6Lw6hSRZHHG1q5OBZC5VRAOoMeVWP 0zzCvmMEQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iXsPl-0005mg-GO; Thu, 21 Nov 2019 19:46:53 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BD1EE300606; Thu, 21 Nov 2019 20:45:39 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B75F22022FCFB; Thu, 21 Nov 2019 20:46:50 +0100 (CET) Date: Thu, 21 Nov 2019 20:46:50 +0100 From: Peter Zijlstra To: Fenghua Yu Cc: Andy Lutomirski , David Laight , Ingo Molnar , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Tony Luck , Ashok Raj , Ravi V Shankar , linux-kernel , x86 Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Message-ID: <20191121194650.GU4097@hirez.programming.kicks-ass.net> References: <1574297603-198156-1-git-send-email-fenghua.yu@intel.com> <1574297603-198156-7-git-send-email-fenghua.yu@intel.com> <20191121060444.GA55272@gmail.com> <20191121130153.GS4097@hirez.programming.kicks-ass.net> <20191121171214.GD12042@gmail.com> <3481175cbe14457a947f934343946d52@AcuMS.aculab.com> <20191121185303.GB199273@romley-ivt3.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191121185303.GB199273@romley-ivt3.sc.intel.com> 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 Thu, Nov 21, 2019 at 10:53:03AM -0800, Fenghua Yu wrote: > We are working on a separate patch set to fix all split lock issues > in atomic bitops. Per Peter Anvin and Tony Luck suggestions: > 1. Still keep the byte optimization if nr is constant. No split lock. > 2. If type of *addr is unsigned long, do quadword atomic instruction > on addr. No split lock. > 3. If type of *addr is unsigned int, do word atomic instruction > on addr. No split lock. > 4. Otherwise, re-calculate addr to point the 32-bit address which contains > the bit and operate on the bit. No split lock. Yeah, let's not do that. That sounds overly complicated for no real purpose.