* Daniel P. Berrangé (berra...@redhat.com) wrote: > On Thu, Nov 25, 2021 at 03:40:36PM +0000, Dr. David Alan Gilbert wrote: > > * Sergio Lopez (s...@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 / dgilb...@redhat.com / Manchester, UK
