From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 53A197D91A for ; Sat, 24 Aug 2019 21:37:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728289AbfHXVge (ORCPT ); Sat, 24 Aug 2019 17:36:34 -0400 Received: from terminus.zytor.com ([198.137.202.136]:39725 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727708AbfHXVgd (ORCPT ); Sat, 24 Aug 2019 17:36:33 -0400 Received: from carbon-x1.hos.anvin.org ([IPv6:2601:646:8600:3281:e7ea:4585:74bd:2ff0]) (authenticated bits=0) by mail.zytor.com (8.15.2/8.15.2) with ESMTPSA id x7OLZlZI1693806 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sat, 24 Aug 2019 14:35:47 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com x7OLZlZI1693806 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2019081901; t=1566682550; bh=2gQzKPo4WrQnlvDY26oni/RH8wMNjOHmljo2FnAYqSQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=jfa8ujf6Bo1t5AdTUjdpXdAFm8XuC39+BjMNqj+VUJ3I53oJo8pLL8aqGEuCFFlpF mwuiVt5W4twlgKdrwazMwd/61MKfTF4NAY11XuCMz/Ej1knheH/Kqod+N3MIPMcnIK cktpL1xZjdX5eoOtI9MknxvSwHVr1fI8qBSoNC3LNQYeNSnmeD84o3whZzxDwNPfwG gh/3M8807qmCeoj0hhRip3VMQkcUT2k058MR72yR9RAETn0/4FIKzK3WhJgnwoAar5 HnEPzDPWJwws1MytshNO8EJOiF+QUagVUh1dO3bzXlhf83JKnsGzcKS+aVx/usQ/fp EvEO265n3vcaQ== Subject: Re: [tip: x86/urgent] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h To: Pavel Machek , linux-kernel@vger.kernel.org Cc: linux-tip-commits@vger.kernel.org, "x86@kernel.org" , Thomas Gleixner , stable@vger.kernel.org, "Rafael J. Wysocki" , Paolo Bonzini , Nathan Chancellor , "linux-pm@vger.kernel.org" , "linux-doc@vger.kernel.org" , Kees Cook , Juergen Gross , Josh Poimboeuf , Jonathan Corbet , Ingo Molnar , Chen Yu , Andrew Morton , Andrew Cooper , Borislav Petkov , Tom Lendacky References: <7543af91666f491547bd86cebb1e17c66824ab9f.1566229943.git.thomas.lendacky@amd.com> <156652264945.9541.4969272027980914591.tip-bot2@tip-bot2> <20190824181929.GA18551@amd> From: "H. Peter Anvin" Message-ID: <409703ae-6d70-3f6a-d6fc-b7dada3c2797@zytor.com> Date: Sat, 24 Aug 2019 14:35:40 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190824181929.GA18551@amd> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 8/24/19 11:19 AM, Pavel Machek wrote: > On Fri 2019-08-23 01:10:49, tip-bot2 for Tom Lendacky wrote: >> The following commit has been merged into the x86/urgent branch of tip: >> >> Commit-ID: c49a0a80137c7ca7d6ced4c812c9e07a949f6f24 >> Gitweb: https://git.kernel.org/tip/c49a0a80137c7ca7d6ced4c812c9e07a949f6f24 >> Author: Tom Lendacky >> AuthorDate: Mon, 19 Aug 2019 15:52:35 >> Committer: Borislav Petkov >> CommitterDate: Mon, 19 Aug 2019 19:42:52 +02:00 >> >> x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h >> >> There have been reports of RDRAND issues after resuming from suspend on >> some AMD family 15h and family 16h systems. This issue stems from a BIOS >> not performing the proper steps during resume to ensure RDRAND continues >> to function properly. > > There are quite a few unanswered questions here. > > a) Is there/should there be CVE for this? > > b) Can we perform proper steps in kernel, thus making RDRAND usable > even when BIOS is buggy? > The kernel should at least be able to set its internal "CPUID" bit, visible through /proc/cpuinfo. -hpa