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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id h2sm3073237wrz.23.2021.11.25.08.08.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Nov 2021 08:08:50 -0800 (PST) Date: Thu, 25 Nov 2021 16:08:48 +0000 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: SEV guest attestation Message-ID: References: <20211125071428.dpnavgxd3w4bzktr@mhamilton> <53dc2a76-a6bb-dc8d-1a47-faf7577e59e8@linux.ibm.com> <20211125151107.nhh7jfofk7qhkujd@mhamilton> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.1.3 (2021-09-10) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: , Cc: Hubertus Franke , Sergio Lopez , afrosi@redhat.com, James Bottomley , qemu-devel@nongnu.org, Dov Murik , Tyler Fanelli , Tobin Feldman-Fitzthum , Jim Cadden , dinechin@redhat.com, John Ferlan Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Daniel P. Berrangé (berrange@redhat.com) wrote: > On Thu, Nov 25, 2021 at 03:40:36PM +0000, Dr. David Alan Gilbert wrote: > > * Sergio Lopez (slp@redhat.com) wrote: > > > On Thu, Nov 25, 2021 at 02:44:51PM +0200, Dov Murik wrote: > > > > > > > > SEV-ES has pre-launch measurement and secret injection, just like SEV > > > > (except that the measurement includes the initial states of all vcpus, > > > > that is, their VMSAs. BTW that means that in order to calculate the > > > > measurement the Attestation Server must know exactly how many vcpus are > > > > in the VM). > > > > > > You need the number of vCPUs and an idea of what their initial state > > > is going to be, to be able to reproduce the same VMSA struct in the > > > Attestation Server. > > > > > > This may tie the Attestation Server with a particular version of both > > > QEMU and KVM. I haven't checked if configuration changes in QEMU may > > > also have an impact on it. > > > > That's all OK; I'm expecting the attestation server to be given a whole > > pile of information about the apparent environment to check. > > Generally though we try not to let a VM to tied to a specific > version of software. eg use machine types to ensure that the > guest can run on any QEMU version, and get the same environment. > This lets host admin upgrade the host software for bug/security > fixes without negatively impacting users. It'd be nice not to > loose that feature with SEV if possible. > > IOW, if there are aspects of the vCPU initial state that might > vary over time with different QEMU versions, should we be looking > to tie that variance into the machine type version. It's not tied to a particular version; but you may need to let the attesting server know what version it's using so that it can check everything adds up. Dave > For KVM changes, this might again come back to the idea fo a > "host type version". > > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK