add note about exception handler

Author: tariqkurd-repo

src/cheri-pte-ext.adoc

@@ -162,7 +162,8 @@ bit value of the capability read. This will introduce additional traps during re
 
 ^2^ The choice here follows the pattern of whether to implement the _Svade_ extension
  to take page-fault exceptions for A and D PTE bit state changes, or whether to implement
- a hardware updating mechanism.
+ a hardware updating mechanism. Software should implement support for a page fault in these cases
+ which will not be used if the hardware mechanism is implemented.
 
 [#xstatus_pte]
 === Extending the Supervisor (sstatus) and Virtual Supervisor (vsstatus) Status Registers