but is it possible to verify that the cloud provider has applied the update?
Yes, it is. You do have to have some infrastructure you trust somewhere to validate an attestation report from the confidential VM.
The SEV-SNP attestation includes the microcode version. https://www.amd.com/content/dam/amd/en/documents/developer/l...
/proc/cpuinfo shows the current microcode version
Yes, it is. You do have to have some infrastructure you trust somewhere to validate an attestation report from the confidential VM.