SEV guest attestation

[Tyler Fanelli]

Hi,

We recently discussed a way for remote SEV guest attestation through 
QEMU. My initial approach was to get data needed for attestation through 
different QMP commands (all of which are already available, so no 
changes required there), deriving hashes and certificate data; and 
collecting all of this into a new QMP struct (SevLaunchStart, which 
would include the VM's policy, secret, and GPA) which would need to be 
upstreamed into QEMU. Once this is provided, QEMU would then need to 
have support for attestation before a VM is started. Upon speaking to 
Dave about this proposal, he mentioned that this may not be the best 
approach, as some situations would render the attestation unavailable, 
such as the instance where a VM is running in a cloud, and a guest owner 
would like to perform attestation via QMP (a likely scenario), yet a 
cloud provider cannot simply let anyone pass arbitrary QMP commands, as 
this could be an issue.

So I ask, does anyone involved in QEMU's SEV implementation have any 
input on a quality way to perform guest attestation? If so, I'd be 
interested. Thanks.


Tyler.

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Tyler Fanelli (tfanelli)