From: Timothy Hayes <timothy.hayes@arm.com>
Date: Tue, 21 Apr 2020 09:26:02 +0000 (+0100)
Subject: mem-ruby: fix MESI_Three_Level erroneous transition
X-Git-Tag: v20.0.0.0~65
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=af1f3b35b0259d705830cc624a43e7936e137d1c;p=gem5.git

mem-ruby: fix MESI_Three_Level erroneous transition

The MESI_Three_Level protocol includes a transition in its L1
definition to invalidate an SM state but this transition does
not notify the L0 cache. The unintended side effect of this
allows stale values to be read by the L0 cache. This can cause
incorrect behaviour when executing LL/SC based mutexes. This
patch ensures that all invalidates to SM states are exposed to
the L0 cache.

Change-Id: I7fefabdaa8027fdfa4c9c362abd7e467493196aa
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28047
Reviewed-by: John Alsop <johnathan.alsop@amd.com>
Reviewed-by: Pouya Fotouhi <pfotouhi@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
---

diff --git a/src/mem/ruby/protocol/MESI_Three_Level-L1cache.sm b/src/mem/ruby/protocol/MESI_Three_Level-L1cache.sm
index 00d897a81..1890bcc57 100644
--- a/src/mem/ruby/protocol/MESI_Three_Level-L1cache.sm
+++ b/src/mem/ruby/protocol/MESI_Three_Level-L1cache.sm
@@ -262,7 +262,8 @@ machine(MachineType:L1Cache, "MESI Directory L1 Cache CMP")
   }
 
   bool inL0Cache(State state) {
-    if (state == State:S || state == State:E || state == State:M ||
+    if (state == State:S || state == State:E ||
+        state == State:M || state == State:SM ||
         state == State:S_IL0 || state == State:E_IL0 ||
         state == State:M_IL0 || state == State:SM_IL0) {
         return true;
@@ -996,7 +997,7 @@ machine(MachineType:L1Cache, "MESI Directory L1 Cache CMP")
   }
 
   // Transitions from IM
-  transition({IM,SM}, Inv, IM) {
+  transition(IM, Inv, IM) {
     fi_sendInvAck;
     l_popL2RequestQueue;
   }