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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 D1C80C433B4 for ; Tue, 6 Apr 2021 07:44:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 39800613C4 for ; Tue, 6 Apr 2021 07:44:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 39800613C4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 47DB56B007E; Tue, 6 Apr 2021 03:44:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 456006B0080; Tue, 6 Apr 2021 03:44:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 31C946B0081; Tue, 6 Apr 2021 03:44:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0216.hostedemail.com [216.40.44.216]) by kanga.kvack.org (Postfix) with ESMTP id 16A956B007E for ; Tue, 6 Apr 2021 03:44:20 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C884662FF for ; Tue, 6 Apr 2021 07:44:19 +0000 (UTC) X-FDA: 78001154238.23.AC9364E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf05.hostedemail.com (Postfix) with ESMTP id BD22AE000114 for ; Tue, 6 Apr 2021 07:44:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617695058; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FF1uXJ/ehFZn2D0SiRBmUa38k2IDpVhcvasGXt63J3A=; b=YtmaRP3gkAc4e5P+fscZF15Ayy0LbUCXtcKnzKaM6SBSdthCvgZKkOqvXPe0I5g7x64ncq DchLTckc8MtCyNeLoestE1BF4Z71q7Kf0INf7oR2EhNytH8gGMbxjxW5iYbdudakBnVIyo vrReZLiSiXbhesFRf+Vywf+mWcMd3jo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-330-hwQxCJHxMGKyMmXMnWp8dQ-1; Tue, 06 Apr 2021 03:44:14 -0400 X-MC-Unique: hwQxCJHxMGKyMmXMnWp8dQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EBAB5612A2; Tue, 6 Apr 2021 07:44:12 +0000 (UTC) Received: from [10.36.113.79] (ovpn-113-79.ams2.redhat.com [10.36.113.79]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6FED65D741; Tue, 6 Apr 2021 07:44:08 +0000 (UTC) To: "Kirill A. Shutemov" , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Jim Mattson Cc: David Rientjes , "Edgecombe, Rick P" , "Kleen, Andi" , "Yamahata, Isaku" , x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" References: <20210402152645.26680-1-kirill.shutemov@linux.intel.com> <20210402152645.26680-8-kirill.shutemov@linux.intel.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages Message-ID: Date: Tue, 6 Apr 2021 09:44:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210402152645.26680-8-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Stat-Signature: si956u1ttb4q65k18h5jhdz7z58nxdof X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: BD22AE000114 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617695058-297904 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 02.04.21 17:26, Kirill A. Shutemov wrote: > TDX architecture aims to provide resiliency against confidentiality and > integrity attacks. Towards this goal, the TDX architecture helps enforc= e > the enabling of memory integrity for all TD-private memory. >=20 > The CPU memory controller computes the integrity check value (MAC) for > the data (cache line) during writes, and it stores the MAC with the > memory as meta-data. A 28-bit MAC is stored in the ECC bits. >=20 > Checking of memory integrity is performed during memory reads. If > integrity check fails, CPU poisones cache line. >=20 > On a subsequent consumption (read) of the poisoned data by software, > there are two possible scenarios: >=20 > - Core determines that the execution can continue and it treats > poison with exception semantics signaled as a #MCE >=20 > - Core determines execution cannot continue,and it does an unbreakabl= e > shutdown >=20 > For more details, see Chapter 14 of Intel TDX Module EAS[1] >=20 > As some of integrity check failures may lead to system shutdown host > kernel must not allow any writes to TD-private memory. This requirment > clashes with KVM design: KVM expects the guest memory to be mapped into > host userspace (e.g. QEMU). So what you are saying is that if QEMU would write to such memory, it=20 could crash the kernel? What a broken design. "As some of integrity check failures may lead to system shutdown host"=20 -- usually we expect to recover from an MCE by killing the affected=20 process, which would be the right thing to do here. How can it happen that "Core determines execution cannot continue,and it=20 does an unbreakable shutdown". Who is "Core"? CPU "core", MM "core" ?=20 And why would it decide to do a shutdown instead of just killing the=20 process? --=20 Thanks, David / dhildenb