start filling in

diff --git a/isa_conflict_resolution.mdwn b/isa_conflict_resolution.mdwn
index b2b3b212458f5b661e286270f5aeaef5619b628a..d72c0a54e1e3dee92d795640b90bcb7bc3836a8d 100644 (file)
--- a/isa_conflict_resolution.mdwn
+++ b/isa_conflict_resolution.mdwn
@@ -158,6 +158,15 @@ be hardest hit by the resultant chaos, and that will just be the more
 TBD (basically, may not be RV Foundation's "scope", still results in
 problem, so not an option)
 
 TBD (basically, may not be RV Foundation's "scope", still results in
 problem, so not an option)
 

+The summary here was that Compliance testing of Custom Extensions is
+not just out-of-scope, but even if it was taken into account that
+binary-encoding meanings could change, it would still be out-of-scope.
+
+However at the time that this argument was made, it had not yet been
+appreciated fully the impact that revisions to the Standard would have,
+when billions of dollars worth of (older, legacy) RISC-V hardware had
+already been deployed.
+

 Two interestingly diametrically-opposed equally valid arguments exist here:
 
 * Whilst Compliance testing of Custom Extensions is definitely legitimately
 Two interestingly diametrically-opposed equally valid arguments exist here:
 
 * Whilst Compliance testing of Custom Extensions is definitely legitimately


@@ -197,6 +206,31 @@ a hundred percent unsuitable for solving the problem.
 TBD, basically same as mvend/march WARL except needs an extra CSR where
 mv/ma doesn't.
 
 TBD, basically same as mvend/march WARL except needs an extra CSR where
 mv/ma doesn't.
 

+Out of the MISA discussion came a "MISA-like" proposal, which would
+take into account the flaws pointed out by trying to use "MISA":
+
+* The MISA-like CSR's meaning would be identified by compilers using the
+  mvendor-id/march-id tuple as a compiler target
+* Each custom-defined bit of the MISA-like CSR would (mutually-exclusively)
+  redirect binary encoding(s) to specific encodings
+* No Extension would *actually* be disabled: its internal state would
+  be left on (permanently) so that switching could be done inside
+  inner loops.
+
+Whilst it was the first "workable" solution it was also noted that the
+scheme is quite invasive: it requires an entirely new CSR to be added
+to the privileged spec.  This does not completely fulfil the "minimum
+impact" requirement.
+
+Also interesting around the same time an additional discussion was
+raised that covered the *compiler* side of the same equation.  This
+revolved around using mvendorid-marchid tuples at the compiler level,
+to be put into assembly output (by gcc), preserving the required
+*globally* unique identifying information for binutils to successfully
+turn the custom instruction into an actual binary-encoding (plus
+binary-encoding of the context-switching information).  (**TBD, Jacob,
+separate page?  review this para?**)
+

 # mvendorid/marchid WARL
 
 TBD paraphrase and clarify
 # mvendorid/marchid WARL
 
 TBD paraphrase and clarify