From 02e7e7d0110785609d41c28760f3fd422bec9125 Mon Sep 17 00:00:00 2001
From: David Harris <david_harris@hmc.edu>
Date: Sun, 19 Mar 2023 05:46:34 -0700
Subject: [PATCH] Added comments about PMP checker fixes when test cases will
 be ready to initialize PMP before entering user mode

---
 src/mmu/pmpchecker.sv | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/mmu/pmpchecker.sv b/src/mmu/pmpchecker.sv
index 9c9c745b..828747e2 100644
--- a/src/mmu/pmpchecker.sv
+++ b/src/mmu/pmpchecker.sv
@@ -50,14 +50,14 @@ module pmpchecker (
 );
 
   // Bit i is high when the address falls in PMP region i
-  logic                    EnforcePMP;
-  logic [`PMP_ENTRIES-1:0] Match; // physical address matches one of the pmp ranges
+  logic                    EnforcePMP; // should PMP be checked in this privilege level
+  logic [`PMP_ENTRIES-1:0] Match;      // physical address matches one of the pmp ranges
   logic [`PMP_ENTRIES-1:0] FirstMatch; // onehot encoding for the first pmpaddr to match the current address.
   logic [`PMP_ENTRIES-1:0] Active;     // PMP register i is non-null
   logic [`PMP_ENTRIES-1:0] L, X, W, R; // PMP matches and has flag set
-  logic [`PMP_ENTRIES-1:0]   PAgePMPAdr;  // for TOR PMP matching, PhysicalAddress > PMPAdr[i]
+  logic [`PMP_ENTRIES-1:0] PAgePMPAdr; // for TOR PMP matching, PhysicalAddress > PMPAdr[i]
 
-  if (`PMP_ENTRIES > 0) 
+  if (`PMP_ENTRIES > 0) // prevent complaints about array of no elements when PMP_ENTRIES = 0
     pmpadrdec pmpadrdecs[`PMP_ENTRIES-1:0](
       .PhysicalAddress, 
       .PMPCfg(PMPCFG_ARRAY_REGW),
@@ -68,8 +68,10 @@ module pmpchecker (
 
   priorityonehot #(`PMP_ENTRIES) pmppriority(.a(Match), .y(FirstMatch)); // combine the match signal from all the adress decoders to find the first one that matches.
 
-  // Only enforce PMP checking for S and U modes when at least one PMP is active or in Machine mode when L bit is set in selected region
+  // Only enforce PMP checking for S and U modes or in Machine mode when L bit is set in selected region
   assign EnforcePMP = (PrivilegeModeW == `M_MODE) ? |(L & FirstMatch) : |Active; 
+//  assign EnforcePMP = (PrivilegeModeW != `M_MODE) | |(L & FirstMatch); // *** switch to this logic when PMP is initialized for non-machine mode
+//  *** remove unused Active lines from pmpadrdecs
 
   assign PMPInstrAccessFaultF     = EnforcePMP & ExecuteAccessF & ~|(X & FirstMatch) ;
   assign PMPStoreAmoAccessFaultM  = EnforcePMP & WriteAccessM   & ~|(W & FirstMatch) ;