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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 6BC0AC43441 for ; Mon, 19 Nov 2018 21:33:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FEB72080C for ; Mon, 19 Nov 2018 21:33:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2FEB72080C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731068AbeKTH6n (ORCPT ); Tue, 20 Nov 2018 02:58:43 -0500 Received: from mga12.intel.com ([192.55.52.136]:4551 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725898AbeKTH6n (ORCPT ); Tue, 20 Nov 2018 02:58:43 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Nov 2018 13:33:08 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,254,1539673200"; d="scan'208";a="275270894" Received: from ray.jf.intel.com (HELO [10.7.201.15]) ([10.7.201.15]) by orsmga005.jf.intel.com with ESMTP; 19 Nov 2018 13:33:08 -0800 Subject: Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes To: Andrea Arcangeli , Jiri Kosina Cc: Thomas Gleixner , Tim Chen , Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , David Woodhouse , Andi Kleen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , LKML , x86@kernel.org, Willy Tarreau References: <20181119193253.GE29258@redhat.com> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181119193253.GE29258@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 11/19/18 11:32 AM, Andrea Arcangeli wrote: > The specs don't say if by making it immune from BTB mistraining, it > also could prevent to mistrain the BTB in order to attack what's > outside the SECCOMP jail. Probably it won't and I doubt we can rely on > it even if some implementation could do that. I just talked with Andi and Tim about this. The *current* spec for STIBP[1] states that it bidirectional: setting it on one thread provides mitigation against any threads attacking any other thread on the core. This means that it provides protection for victims being in and out of SECCOMP jail when the attacker is either in or out of SECCOMP jail. However, the current spec[1], differs from the *original* spec PDF that Intel released last year. Both are correct in that they describe all current (Intel) implementations of STIBP. However, the new _description_ of STIBP is stronger than it was originally. Here's the current description: > Setting ... STIBP ... on a logical processor prevents the predicted > targets of indirect branches on any logical processor of that core > from being controlled by software that executes (or executed > previously) on another logical processor of the same core. 1. https://software.intel.com/security-software-guidance/insights/deep-dive-single-thread-indirect-branch-predictors