take #2 on envcfg.CBIE WARL (#200)

Author: dhower-qc

arch/csr/menvcfg.yaml

@@ -247,8 +247,8 @@ menvcfg:
       type: RW-R
       sw_write(csr_value): |
         if ((csr_value.CBIE == 0) ||
-            (ALLOW_CBO_INVAL_UPGRADE_TO_FLUSH && (csr_value.CBIE == 1)) ||
-            (csr_value.CBIE == 3)) {
+            (csr_value.CBIE == 1) ||
+            ((!FORCE_UPGRADE_CBO_INVAL_TO_FLUSH) && (csr_value.CBIE == 3))) {
           return csr_value.CBIE;
         } else {
           return CSR[menvcfg].CBIE;

arch/ext/Zicbom.yaml

@@ -15,12 +15,12 @@ Zicbom:
       also_defined_in: [Zicboz, Zicbop]
       schema:
         type: integer
-    ALLOW_CBO_INVAL_UPGRADE_TO_FLUSH:
+    FORCE_UPGRADE_CBO_INVAL_TO_FLUSH:
       description: |
-        When true, an implementation can (when `menvcfg.CBIE` == `01`) upgrade a `cbo.inval`
-        instruction to a `cbo.flush`.
+        When true, an implementation prohibits setting `menvcfg.CBIE` == `11` such that all `cbo.inval`
+        instructions either trap (when `menvcfg.CBIE` == '00') or flush (when `menvcfg.CBIE` == '01').
 
-        When false, an implementation does not support the upgrade, and the value '01' cannot be
-        written to `menvcfg.CBIE`.
+        When false, an implementation allows a true INVAL operation for `cbo.inval`, and thus supports
+        the setting `menvcfg.CBIE` == `11`.
       schema:
         type: boolean

cfgs/generic_rv64/params.yaml

@@ -514,4 +514,4 @@ params:
   MSTATUS_FS_WRITEABLE: true
   MSTATUS_TVM_IMPLEMENTED: true
   HW_MSTATUS_FS_DIRTY_UPDATE: precise
-  ALLOW_CBO_INVAL_UPGRADE_TO_FLUSH: true
+  FORCE_UPGRADE_CBO_INVAL_TO_FLUSH: true