The SEV-SNP attestation approach is very similar to what Andi described
for the TDX. However, in the case of legacy SEV and ES, the attestation
verification is performed before the guest is booted. In this case, the
hyervisor puts the secret provided by the guest owner (after the
attestation) at a fixed location. Dov's driver is simply reading that
fixed location and making it available through the simple text file.
That's the same as our SVKL model.
The (not yet posted) driver is here:
https://github.com/intel/tdx/commit/62c2d9fae275d5bf50f869e8cfb71d2ca1f71363
We opted to use ioctls, with the idea that it should be just read and
cleared once to not let the secret lying around. Typically you would
just use it to set up dmcrypt or similar once. I think read-and-clear
with explicit operations is a better model than some virtual file
because of the security properties.
-Andi
