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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 67BBAC433DF for ; Mon, 6 Jul 2020 18:29:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4724B20663 for ; Mon, 6 Jul 2020 18:29:47 +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="qbfi+0eU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729797AbgGFS3q (ORCPT ); Mon, 6 Jul 2020 14:29:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729713AbgGFS3p (ORCPT ); Mon, 6 Jul 2020 14:29:45 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38180C061755; Mon, 6 Jul 2020 11:29:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=Do5ubF9fSscGPClrokRq/R+dJR1UND+xOUqU52LNcLY=; b=qbfi+0eUNgOUvrS/172K4oJy+c +6cvYoTiN6i7rxY2lKCxArxd7eY83amayJ59D8O1py/4d9s6P4RqhHn1YxV7zVXeTetbIlRbo28Ie gCd9otH5ECaPEhZ8Ge/IBJo3+RpoisW5Ms4DZ89U+kQmjoKqC/4gOLn1rpAjmh910g68gBREeN853 D9OutRrJ3YidRcvHov/mXEAHK/teWgqK5dRcbklwPj7Zu+LAUPsEALJWfBtbZMLbt9OhdAf3SVyqB t12O6B1a3TCkvPr8cZa7kIvTauI0iVcGCIWrMpjaav/KQZRjPDPGe/rm2UlYyWtRnwA22XnbRhDgo CON822NQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jsVrx-0007O5-Sd; Mon, 06 Jul 2020 18:29:34 +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 13EBC3013E5; Mon, 6 Jul 2020 20:29:26 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 06776213912F6; Mon, 6 Jul 2020 20:29:26 +0200 (CEST) Date: Mon, 6 Jul 2020 20:29:26 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Marco Elver , Nick Desaulniers , Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , LKML , linux-pci@vger.kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200706182926.GH4800@hirez.programming.kicks-ass.net> References: <20200701114027.GO4800@hirez.programming.kicks-ass.net> <20200701140654.GL9247@paulmck-ThinkPad-P72> <20200701150512.GH4817@hirez.programming.kicks-ass.net> <20200701160338.GN9247@paulmck-ThinkPad-P72> <20200702082040.GB4781@hirez.programming.kicks-ass.net> <20200702175948.GV9247@paulmck-ThinkPad-P72> <20200703131330.GX4800@hirez.programming.kicks-ass.net> <20200703144228.GF9247@paulmck-ThinkPad-P72> <20200706162633.GA13288@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706162633.GA13288@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote: > And perhaps more constructively, we do need to prioritize address and data > dependencies over control dependencies. For one thing, there are a lot > more address/data dependencies in existing code than there are control > dependencies, and (sadly, perhaps more importantly) there are a lot more > people who are convinced that address/data dependencies are important. If they do not consider their Linux OS running correctly :-) > For another (admittedly more theoretical) thing, the OOTA scenarios > stemming from control dependencies are a lot less annoying than those > from address/data dependencies. > > And address/data dependencies are as far as I know vulnerable to things > like conditional-move instructions that can cause problems for control > dependencies. > > Nevertheless, yes, control dependencies also need attention. Today I added one more \o/