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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, 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 D8260C2D0E4 for ; Tue, 17 Nov 2020 19:01:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D7F421D7E for ; Tue, 17 Nov 2020 19:01:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="KeampoBc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729454AbgKQTBD (ORCPT ); Tue, 17 Nov 2020 14:01:03 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:40994 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726644AbgKQTBC (ORCPT ); Tue, 17 Nov 2020 14:01:02 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0AHIxq70028846; Tue, 17 Nov 2020 19:00:41 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=kFhpvmVlIgv+wqtZAim1r+yLEWpAFdL90ENg0K3Wbp0=; b=KeampoBcYOqID7YX4N/DVLeiW5HCBfFU9MQ5u+yXNBbXoumb+5VzoJxp0Fpn3Lu0t/AK Obn17Ieg0ZTZhyoFnv7rYpCWuHqWuWpfMZrL4abYWhS0twYQjMW2XNatfUMU7/NICaIA RxIgd5kZcSjLkoM63JZh2DFzAHaLsP1NB5eoywX9RBA6nka8Ci1t1rpmWiaKPwJoLFMM iY43rAKoKjDoC+WtrkZ7l+tNVIsCI0mkH7eUyCiodffyKArsAefKHdt92++aIAAjcEwa gF+T8ogJn9Tir/yzfeQjCCARYfzq9yrQnV6MMRQUUUiwedyZlv4pzMKFV2uvJVBzMpEz Qw== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 34t7vn483x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 17 Nov 2020 19:00:41 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0AHItTO1027581; Tue, 17 Nov 2020 19:00:41 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 34ts0ra84x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 17 Nov 2020 19:00:41 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 0AHJ0Wf0011449; Tue, 17 Nov 2020 19:00:37 GMT Received: from linux.home (/92.157.91.83) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 17 Nov 2020 11:00:32 -0800 Subject: Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code To: Borislav Petkov Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, jroedel@suse.de, konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, junaids@google.com, oweisse@google.com, rppt@linux.vnet.ibm.com, graf@amazon.de, mgross@linux.intel.com, kuzuno@gmail.com References: <20201116144757.1920077-1-alexandre.chartre@oracle.com> <20201116201711.GE1131@zn.tnic> <44a88648-738a-4a4b-9c25-6b70000e037c@oracle.com> <20201117165539.GG5719@zn.tnic> <890f6b7e-a268-2257-edcb-5eacc7db3d8e@oracle.com> <20201117182809.GK5719@zn.tnic> From: Alexandre Chartre Message-ID: <33a1c6ee-0122-0b0c-ed2d-1578b29ef7c1@oracle.com> Date: Tue, 17 Nov 2020 20:02:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201117182809.GK5719@zn.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9808 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 adultscore=0 bulkscore=0 suspectscore=0 spamscore=0 malwarescore=0 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011170136 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9808 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 suspectscore=0 malwarescore=0 bulkscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 mlxscore=0 priorityscore=1501 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011170137 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/17/20 7:28 PM, Borislav Petkov wrote: > On Tue, Nov 17, 2020 at 07:12:07PM +0100, Alexandre Chartre wrote: >> Yes. L1TF/MDS allow some inter cpu-thread attacks which are not mitigated at >> the moment. In particular, this allows a guest VM to attack another guest VM >> or the host kernel running on a sibling cpu-thread. Core Scheduling will >> mitigate the guest-to-guest attack but not the guest-to-host attack. > > I see in vmx_vcpu_enter_exit(): > > /* L1D Flush includes CPU buffer clear to mitigate MDS */ > if (static_branch_unlikely(&vmx_l1d_should_flush)) > vmx_l1d_flush(vcpu); > else if (static_branch_unlikely(&mds_user_clear)) > mds_clear_cpu_buffers(); > > Is that not enough? No. This prevents the guest VM from gathering data from the host kernel on the same cpu-thread. But there's no mitigation for a guest VM running on a cpu-thread attacking another cpu-thread (which can be running another guest VM or the host kernel) from the same cpu-core. You cannot use flush/clear barriers because the two cpu-threads are running in parallel. alex.