ACPI tables from untrusted host input are not reconstructed or measured for CVMs #4533

Usually, we would expect ACPI tables being measured into TDX RTMR0 / vTPM PCR1 as they are untrusted host input. On OpenHCL TDX VMs, they are not measured into RTMR0/PCR1. Instead, the ACPI tables supplied by the untrusted host are partially dropped (e.g., the if(!isolated) gate in openhcl/underhill_core/src/loader/mod.rs:476) and generated within OpenHCL/UEFI firmware, i.e., within the TCB, which should be fine.

However, some ACPI tables do not have the isolated gate, e.g. SLIT (openhcl/underhill_core/src/loader/mod.rs:571). According to my understanding, these tables are supplied by the untrusted host and not covered by any measurement. There also seem to be no signature checks, it looks like the host could place arbitrary AML code.

However, considering that there have already been AML Attacks on CVMs in the past, I therefore wanted to ask, if there are plans to either construct these table instead of getting them from the untrusted host, or measure them? We require this for establishing trust in Azure CVMs during remote attestation.