v0.9.4-scalar

This release contains all updates relating to feedback from our architectural review. The original feedback can be found on the Scalar Cryptography extension status page here under "Architecture & Opcode consistency review".

Decisions Taken:

• Stop overlapping the aes32* and aes64* opcodes.

Changes:

• The aes32* opcodes have changed.

• All scalar crypto specific instructions which produce 32-bit results now sign-extend them to XLEN bits where relevant. Previously they were zero extended.

• The misa.K bit is no longer used to identify the scalar cryptography extension. Feature detection of scalar cryptography extensions will be done using the work-in-progress discovery mechanisms for RISC-V.

• The Entropy source section has been re-organised to move all non-normative text to an appendix. Functional changes to the normative part of the spec include:

  • The encodings for ES16 and WAIT states have changed.

  • How BIST is reported due to a non-fatal statistical alarm has been changed to allow software to record the events, without them happening silently. This was always a recommendation, but was made more explicit and moved to the normative part of the spec.

• Various misc changes to make the specification clearer / easier to read etc.

Additions:

• None

Removals:

• The mnoise CSR is now only provided as an example mechanism to vendors in the appendix, it is not required by the specification.

Open Issues:

See the status of the open issues in the project board.