[Feature]: Provide SEV_FEATURES and VINTR_CTRL from user space to stabilize attestation

[jarkkojs]

Is there an existing issue for this?

• I have searched the existing issues

Description

SEV_FEATURES and VINTR_CTRL change in Linux can break any program using SEV-SNP attestation, as the digest calculation might rely on older values. This could cause old binaries break on new kernel versions without warning.

Something like LAUNCH_UPDATE_VMSA_RESET_VECTOR command with SEV_FEATURES and VINTR_CTRL as parameters would work out, which would partially overwrite kernel VMSA.

Potentially they could be capped by kernel, i.e. "further restrict what kernel allows" should work out.

Acceptance Criteria

Suggestions for a technical implementation

[jarkkojs]

https://hackmd.io/@enarx/HJKSlW2Lo