Added Ssstrict option.

rva23-profile.adoc

@@ -320,8 +320,8 @@ NOTE: The following extensions were required when the hypervisor was implemented
 ==== RVA23S64 Optional Extensions
 
 RVA23S64 has ten unprivileged options (Zvkng, Zvksg, Zacas, Zvbc, Zfh,
-Zbc, Zvfh, Zfbfmin, Zvfbfmin, Zvfbfwma) from RVA23U64, and five
-privileged options (Sv48, Sv57, Svadu, Zkr, Sdext).
+Zbc, Zvfh, Zfbfmin, Zvfbfmin, Zvfbfwma) from RVA23U64, and six
+privileged options (Sv48, Sv57, Svadu, Zkr, Sdext, Ssstrict).
 
 ===== Localized Options
 
@@ -347,14 +347,24 @@ The following are new privileged expansion options in RVA23S64
 
 - *Sdext* Debug triggers
 
+- *Ssstrict* No non-conforming extensions are present. Attempts to
+ execute unimplemented opcodes or access unimplemented CSRs in the
+ standard or reserved encoding spaces raises an illegal instruction
+ exception that results in a contained trap to the supervisor-mode
+ trap handler.
+
+NOTE: Ssstrict does not prescribe behavior for the custom encoding
+spaces or CSRs.
+
 ===== Transitory Options
 
 There are no privileged transitory options in RVA23S64.
 
 ==== RVA23S64 Recommendations
 
-- Implementations are strongly recommended to raise illegal-instruction
- exceptions when attempting to execute unimplemented opcodes.
+- Implementations are strongly recommended to raise
+ illegal-instruction exceptions when attempting to execute
+ unimplemented opcodes or access unimplemented CSRs.
 
 == Glossary of ISA Extensions