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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 17808C433E1 for ; Mon, 6 Jul 2020 18:39:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EDE09207CD for ; Mon, 6 Jul 2020 18:39:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594060778; bh=C73gOuGPht9dIixGPBoEUXES1WGxsODtcKpLKnFrDqc=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=im0hxU4mtkTzcaFFF7asQR3YwesyiETAJOi1yywrUzXZveUQmBxOm0Tree4bxH86N iLk6hNZCM+3YrcUwFG6plDWVU2oZKGIdXYbQC+/1L5wphk2Etza9bYF+9K9wTHojcM Hiqxhv7QAYxtZNQBNayspYQA0vvsq+W/v9twepIY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730063AbgGFSje (ORCPT ); Mon, 6 Jul 2020 14:39:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:39754 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730051AbgGFSje (ORCPT ); Mon, 6 Jul 2020 14:39:34 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-111-31.bvtn.or.frontiernet.net [50.39.111.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DC023207BB; Mon, 6 Jul 2020 18:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594060773; bh=C73gOuGPht9dIixGPBoEUXES1WGxsODtcKpLKnFrDqc=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=DxcjcPLXo5KKl20GXi3gR8saz6u7T52XB2h7KY4zD+cFOdG6eQqu/eTW1KOIHVTH1 wju8yVd1Y7IK4dLVkNpXeViYSln0h7JZ5Y1n9IdBD6jdjIrKMxJo0PG6DWDkUmV68w 2PZAalihX+WlZ2m6xkVYthoCCWtQgQAL3RpYBP7s= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id C7CAE3522637; Mon, 6 Jul 2020 11:39:33 -0700 (PDT) Date: Mon, 6 Jul 2020 11:39:33 -0700 From: "Paul E. McKenney" To: Peter Zijlstra 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: <20200706183933.GE9247@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org 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> <20200706182926.GH4800@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706182926.GH4800@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote: > 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 :-) Many of them really do not care at all. In fact, some would consider Linux failing to run as an added bonus. > > 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/ Just make sure you continually check to make sure that compilers don't break it, along with the others you have added. ;-) Thanx, Paul