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Mon, 9 Jan 2023 17:43:58 GMT Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 100357805E; Mon, 9 Jan 2023 19:20:30 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1840C7805C; Mon, 9 Jan 2023 19:20:28 +0000 (GMT) Received: from lingrow.int.hansenpartnership.com (unknown [9.163.48.220]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 9 Jan 2023 19:20:28 +0000 (GMT) Message-ID: <5c07f6ab6adfe53f7e7fbeeda67f2eb62afccdfa.camel@linux.ibm.com> Subject: Re: [PATCH 2/2] tpm: add backend for mssim From: James Bottomley To: "Dr. David Alan Gilbert" , "Daniel P." =?ISO-8859-1?Q?Berrang=E9?= Cc: Stefan Berger , qemu-devel@nongnu.org, Markus Armbruster Date: Mon, 09 Jan 2023 12:43:54 -0500 In-Reply-To: References: <10fbda0f-7c8a-3819-fb22-34a9249ac138@linux.ibm.com> <9fac7d95-d891-413f-93f1-18324c7943ea@linux.ibm.com> <29e99f54-d5e8-b18d-08a6-d24435032272@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: -c4wj0ZIstS03W5W_90TZ4dTWJo2SrDE X-Proofpoint-ORIG-GUID: -aC_PeAbtbXQx2lbs7z1FQyLrWGLuVZF X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2023-01-09_10,2023-01-09_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 phishscore=0 lowpriorityscore=0 mlxlogscore=913 spamscore=0 priorityscore=1501 adultscore=0 mlxscore=0 impostorscore=0 malwarescore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2301090125 Received-SPF: pass client-ip=148.163.158.5; envelope-from=jejb@linux.ibm.com; helo=mx0b-001b2d01.pphosted.com X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: jejb@linux.ibm.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, 2023-01-09 at 16:59 +0000, Dr. David Alan Gilbert wrote: > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > On Fri, Dec 16, 2022 at 08:32:44AM -0500, Stefan Berger wrote: [...] > > > I do see it because the *volatile state* cannot be extracted from > > > this device. The state of the PCRs is going to be lost. > > > > All the objections you're raising are related to the current > > specifics of the implementation of the mssim remote server. > > While valid, this is of no concern to QEMU when deciding whether > > to require a migration blocker on the client side. This is 3rd > > party remote service that should be considered a black box from > > QEMU's POV. It is possible to write a remote server that supports > > the mssim network protocol, and has the ability to serialize > > its state. Whether such an impl exists today or not is separate. > > We would normally want an example of a working implementation though > wouldn't we? > > So I think it's fair to at least want some documentation; if it can > be documented and works, fine; if it doesn't work, then it needs a > blocker. It works under limited circumstances ... in fact similar circumstances passthrough migration works under, which is also not documented. The external MSSIM TPM emulator has to be kept running to preserve the state. If you restart it, the migration will fail. James