Allow invalid virtual addresses not to match at all

Sdtrig.tex

@@ -323,8 +323,15 @@ \subsection{Invalid Virtual Addresses}
 
 For virtual address matches without a mask, \RcsrTdataTwo must be able to hold
 all valid virtual addresses but it need not be capable of holding other values.
-Implementations may convert an invalid virtual address to a different invalid
-virtual address before comparing the address to \RcsrTdataTwo.
+If \RcsrTdataTwo can contain any invalid virtual addresses, then writes of an
+invalid virtual address that can not be represented as-is should be converted to
+a different invalid virtual address that can be represented.
+Note that valid virtual addresses are sign extended, while valid physical
+addresses are zero extended. It must be possible to represent all of them in
+\RcsrTdataTwo.
+
+The compare value for an invalid virtual address may be a different invalid
+virtual address than the effective address.
 
 \begin{commentary}
     A straightforward trigger implementation would compare the effective address
@@ -338,6 +345,15 @@ \subsection{Invalid Virtual Addresses}
     invalid virtual address.
 \end{commentary}
 
+In addition, implementations may decide not to perform trigger matching against
+invalid virtual addresses at all.
+
+\begin{commentary}
+    The behavior of a given hart when matching against invalid virtual addresses
+    is hard to predict. Furthermore, accessing memory at an invalid virtual
+    address is already easy to catch because an exception will be generated.
+\end{commentary}
+
 \section{Multiple State Change Instructions} \label{sec:multistate}
 
 An instruction that performs multiple architectural state changes (e.g.,