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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 A502AC31E5D for ; Tue, 18 Jun 2019 20:05:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 86E5920679 for ; Tue, 18 Jun 2019 20:05:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730579AbfFRUFq (ORCPT ); Tue, 18 Jun 2019 16:05:46 -0400 Received: from mga07.intel.com ([134.134.136.100]:41618 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729331AbfFRUFq (ORCPT ); Tue, 18 Jun 2019 16:05:46 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Jun 2019 13:05:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,390,1557212400"; d="scan'208";a="160156703" Received: from schen9-desk.jf.intel.com (HELO [10.54.74.162]) ([10.54.74.162]) by fmsmga008.fm.intel.com with ESMTP; 18 Jun 2019 13:05:44 -0700 To: Jon Masters , Thomas Gleixner Cc: Alexei Starovoitov , Jonathan Corbet , Greg Kroah-Hartman , Ben Greear , stable@vger.kernel.org, Andi Kleen , Dave Hansen , Jun Nakajima , Jiri Kosina , Linus Torvalds , Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Asit Mallick , Arjan van de Ven , Waiman Long , Borislav Petkov , Mark Gross , LKML , x86@kernel.org References: <5ff842bb-e0b8-c4aa-134d-32c9d838a162@redhat.com> <526833c7-b9b4-1847-9f9b-52dd248548ad@redhat.com> From: Tim Chen Openpgp: preference=signencrypt Autocrypt: addr=tim.c.chen@linux.intel.com; prefer-encrypt=mutual; keydata= mQINBE6ONugBEAC1c8laQ2QrezbYFetwrzD0v8rOqanj5X1jkySQr3hm/rqVcDJudcfdSMv0 BNCCjt2dofFxVfRL0G8eQR4qoSgzDGDzoFva3NjTJ/34TlK9MMouLY7X5x3sXdZtrV4zhKGv 3Rt2osfARdH3QDoTUHujhQxlcPk7cwjTXe4o3aHIFbcIBUmxhqPaz3AMfdCqbhd7uWe9MAZX 7M9vk6PboyO4PgZRAs5lWRoD4ZfROtSViX49KEkO7BDClacVsODITpiaWtZVDxkYUX/D9OxG AkxmqrCxZxxZHDQos1SnS08aKD0QITm/LWQtwx1y0P4GGMXRlIAQE4rK69BDvzSaLB45ppOw AO7kw8aR3eu/sW8p016dx34bUFFTwbILJFvazpvRImdjmZGcTcvRd8QgmhNV5INyGwtfA8sn L4V13aZNZA9eWd+iuB8qZfoFiyAeHNWzLX/Moi8hB7LxFuEGnvbxYByRS83jsxjH2Bd49bTi XOsAY/YyGj6gl8KkjSbKOkj0IRy28nLisFdGBvgeQrvaLaA06VexptmrLjp1Qtyesw6zIJeP oHUImJltjPjFvyfkuIPfVIB87kukpB78bhSRA5mC365LsLRl+nrX7SauEo8b7MX0qbW9pg0f wsiyCCK0ioTTm4IWL2wiDB7PeiJSsViBORNKoxA093B42BWFJQARAQABtDRUaW0gQ2hlbiAo d29yayByZWxhdGVkKSA8dGltLmMuY2hlbkBsaW51eC5pbnRlbC5jb20+iQI+BBMBAgAoAhsD BgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAUCXFIuxAUJEYZe0wAKCRCiZ7WKota4STH3EACW 1jBRzdzEd5QeTQWrTtB0Dxs5cC8/P7gEYlYQCr3Dod8fG7UcPbY7wlZXc3vr7+A47/bSTVc0 DhUAUwJT+VBMIpKdYUbvfjmgicL9mOYW73/PHTO38BsMyoeOtuZlyoUl3yoxWmIqD4S1xV04 q5qKyTakghFa+1ZlGTAIqjIzixY0E6309spVTHoImJTkXNdDQSF0AxjW0YNejt52rkGXXSoi IgYLRb3mLJE/k1KziYtXbkgQRYssty3n731prN5XrupcS4AiZIQl6+uG7nN2DGn9ozy2dgTi smPAOFH7PKJwj8UU8HUYtX24mQA6LKRNmOgB290PvrIy89FsBot/xKT2kpSlk20Ftmke7KCa 65br/ExDzfaBKLynztcF8o72DXuJ4nS2IxfT/Zmkekvvx/s9R4kyPyebJ5IA/CH2Ez6kXIP+ q0QVS25WF21vOtK52buUgt4SeRbqSpTZc8bpBBpWQcmeJqleo19WzITojpt0JvdVNC/1H7mF 4l7og76MYSTCqIKcLzvKFeJSie50PM3IOPp4U2czSrmZURlTO0o1TRAa7Z5v/j8KxtSJKTgD lYKhR0MTIaNw3z5LPWCCYCmYfcwCsIa2vd3aZr3/Ao31ZnBuF4K2LCkZR7RQgLu+y5Tr8P7c e82t/AhTZrzQowzP0Vl6NQo8N6C2fcwjSrkCDQROjjboARAAx+LxKhznLH0RFvuBEGTcntrC 3S0tpYmVsuWbdWr2ZL9VqZmXh6UWb0K7w7OpPNW1FiaWtVLnG1nuMmBJhE5jpYsi+yU8sbMA 5BEiQn2hUo0k5eww5/oiyNI9H7vql9h628JhYd9T1CcDMghTNOKfCPNGzQ8Js33cFnszqL4I N9jh+qdg5FnMHs/+oBNtlvNjD1dQdM6gm8WLhFttXNPn7nRUPuLQxTqbuoPgoTmxUxR3/M5A KDjntKEdYZziBYfQJkvfLJdnRZnuHvXhO2EU1/7bAhdz7nULZktw9j1Sp9zRYfKRnQdIvXXa jHkOn3N41n0zjoKV1J1KpAH3UcVfOmnTj+u6iVMW5dkxLo07CddJDaayXtCBSmmd90OG0Odx cq9VaIu/DOQJ8OZU3JORiuuq40jlFsF1fy7nZSvQFsJlSmHkb+cDMZDc1yk0ko65girmNjMF hsAdVYfVsqS1TJrnengBgbPgesYO5eY0Tm3+0pa07EkONsxnzyWJDn4fh/eA6IEUo2JrOrex O6cRBNv9dwrUfJbMgzFeKdoyq/Zwe9QmdStkFpoh9036iWsj6Nt58NhXP8WDHOfBg9o86z9O VMZMC2Q0r6pGm7L0yHmPiixrxWdW0dGKvTHu/DH/ORUrjBYYeMsCc4jWoUt4Xq49LX98KDGN dhkZDGwKnAUAEQEAAYkCJQQYAQIADwIbDAUCXFIulQUJEYZenwAKCRCiZ7WKota4SYqUEACj P/GMnWbaG6s4TPM5Dg6lkiSjFLWWJi74m34I19vaX2CAJDxPXoTU6ya8KwNgXU4yhVq7TMId keQGTIw/fnCv3RLNRcTAapLarxwDPRzzq2snkZKIeNh+WcwilFjTpTRASRMRy9ehKYMq6Zh7 PXXULzxblhF60dsvi7CuRsyiYprJg0h2iZVJbCIjhumCrsLnZ531SbZpnWz6OJM9Y16+HILp iZ77miSE87+xNa5Ye1W1ASRNnTd9ftWoTgLezi0/MeZVQ4Qz2Shk0MIOu56UxBb0asIaOgRj B5RGfDpbHfjy3Ja5WBDWgUQGgLd2b5B6MVruiFjpYK5WwDGPsj0nAOoENByJ+Oa6vvP2Olkl gQzSV2zm9vjgWeWx9H+X0eq40U+ounxTLJYNoJLK3jSkguwdXOfL2/Bvj2IyU35EOC5sgO6h VRt3kA/JPvZK+6MDxXmm6R8OyohR8uM/9NCb9aDw/DnLEWcFPHfzzFFn0idp7zD5SNgAXHzV PFY6UGIm86OuPZuSG31R0AU5zvcmWCeIvhxl5ZNfmZtv5h8TgmfGAgF4PSD0x/Bq4qobcfaL ugWG5FwiybPzu2H9ZLGoaRwRmCnzblJG0pRzNaC/F+0hNf63F1iSXzIlncHZ3By15bnt5QDk l50q2K/r651xphs7CGEdKi1nU0YJVbQxJQ== Subject: Re: [PATCH v3] Documentation: Add section about CPU vulnerabilities for Spectre Message-ID: <95881c0e-5849-9062-a0c5-eb55081a06aa@linux.intel.com> Date: Tue, 18 Jun 2019 13:05:43 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <526833c7-b9b4-1847-9f9b-52dd248548ad@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/17/19 1:30 PM, Jon Masters wrote: > On 6/17/19 4:22 PM, Jon Masters wrote: > >>> + For kernel code that has been identified where data pointers could >>> + potentially be influenced for Spectre attacks, new "nospec" accessor >>> + macros are used to prevent speculative loading of data. >> >> Maybe explain that nospec (speculative clamping) relies on the absence >> of value prediction in the masking (in current hardware). It may NOT >> always be a safe approach in future hardware, where Spectre-v1 attacks >> are likely to persist but hardware may speculate about the mask value. > > Something like the Arm CSDB barrier would seem to be potentially useful > for $FUTURE_X86 as a fence with lighter-weight semantics than an *fence. > Is it necessary to go into such level of implementation details on nospec? These seem to be appropriate as code comments in nospec for kernel developer. But for an admin-guide doc, it may confuse sys admin to think that nospec could not be ineffective. When new hardware appears that need new implementations of nospec, we should tweak nospec and not need the admin to worry about such implementation details. Tim