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=-5.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 5F34FC47082 for ; Thu, 3 Jun 2021 18:02:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 45710613E3 for ; Thu, 3 Jun 2021 18:02:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230098AbhFCSDn (ORCPT ); Thu, 3 Jun 2021 14:03:43 -0400 Received: from mga02.intel.com ([134.134.136.20]:4287 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229973AbhFCSDl (ORCPT ); Thu, 3 Jun 2021 14:03:41 -0400 IronPort-SDR: oL7hzVOXAmKP/jHPbl+YWvyt0sLXGgIT3isq4ZyhOBKxGvoJZAU+uSG1ohEb7I3VnNiLl7MDS2 Ksb/pZkhTfkA== X-IronPort-AV: E=McAfee;i="6200,9189,10004"; a="191216405" X-IronPort-AV: E=Sophos;i="5.83,246,1616482800"; d="scan'208";a="191216405" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2021 11:00:51 -0700 IronPort-SDR: zWl9IAVAqjS/nU7br8N4D0lZd7U38PTrXKOJDam1wiKAadNjauAH+/i6mcx4J0u5MOYtULc7BU orc5GUV+Jo2Q== X-IronPort-AV: E=Sophos;i="5.83,246,1616482800"; d="scan'208";a="550787338" Received: from akleen-mobl1.amr.corp.intel.com (HELO [10.209.7.237]) ([10.209.7.237]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2021 11:00:48 -0700 Subject: Re: [PATCH v1 1/8] virtio: Force only split mode with protected guest To: Andy Lutomirski , mst@redhat.com Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com, iommu@lists.linux-foundation.org, x86@kernel.org, sathyanarayanan.kuppuswamy@linux.intel.com, jpoimboe@redhat.com, linux-kernel@vger.kernel.org References: <20210603004133.4079390-1-ak@linux.intel.com> <20210603004133.4079390-2-ak@linux.intel.com> From: Andi Kleen Message-ID: Date: Thu, 3 Jun 2021 11:00:47 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/3/2021 10:33 AM, Andy Lutomirski wrote: > On 6/2/21 5:41 PM, Andi Kleen wrote: >> Only allow split mode when in a protected guest. Followon >> patches harden the split mode code paths, and we don't want >> an malicious host to force anything else. Also disallow >> indirect mode for similar reasons. > I read this as "the virtio driver is buggy. Let's disable most of the > buggy code in one special case in which we need a driver without bugs. > In all the other cases (e.g. hardware virtio device connected over > USB-C), driver bugs are still allowed." My understanding is most of the other modes (except for split with separate descriptors) are obsolete and just there for compatibility. As long as they're deprecated they won't harm anyone. -Andi