ARC Minutes 2025-02-25

Minutes

Content:

1. The SBI 3.0 spec, updated with prior feedback, was reviewed [1] and is now ARC approved. ARC
   is concerned about ratifying SBI 3.0 with the MPXY extension before RPMI completes AR. ARC suggests the TG may either delay public review until RPMI AR is done or move MPXY to a later
   SBI version.

2. ARC discussed a request for input [2] on xcause stacking from the fast interrupts TG. ARC suggests the TG continue development. Whether xcause stacking can be a sub-extension independent of CLIC can be decided during CLIC AR or later.

3. ARC was asked about the cadence for regular official releases and publication of the Unpriv. and Priv. ISA Manuals on the RISC-V website. The plan is for ratification of new extensions by the Board to trigger a release (once merging of them into the manuals has been completed). In addition, when a significant number of clarifications have accumulated, or when a major clarification is added, and there has not been a recent release, the Unpriv and Priv IC chairs will trigger a new release.

4. ARC discussed the Cheri TG’s request to use bits 60:59 for the Svucrg Cheri extension. These bits were also proposed for Svrsw60t59b [3]. Expanding PA width by a future virtual memory system extension should be a consideration in resolving this, as the PPN field in the PTE should remain contiguous. ARC will suggest two options to Cheri TG to help resolve this.

5. ARC reviewed a request for input on utilizing the state enable extension to optimize context switching of the Ssctr state. Using *stateen to detect access to an extension's state and leveraging the resulting virtual-instruction or illegal-instruction trap to infer the first attempted use of the extension is considered an acceptable use of the *stateen extension.