ruby: add a three level MESI protocol.

The first two levels (L0, L1) are private to the core, the third level (L2)is
possibly shared. The protocol supports clustered designs.  For example, one
can have two sets of two cores. Each core has an L0 and L1 cache. There are
two L2 controllers where each set accesses only one of the L2 controllers.

1 files changed, 81 insertions, 0 deletions

diff --git a/src/mem/protocol/MESI_Three_Level-msg.sm b/src/mem/protocol/MESI_Three_Level-msg.sm
new file mode 100644
index 000000000..eb29975f9
--- /dev/null
+++ b/src/mem/protocol/MESI_Three_Level-msg.sm
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2013 Mark D. Hill and David A. Wood
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// Various class of messages that can be exchanged between the L0 and the L1
+// controllers.
+enumeration(CoherenceClass, desc="...") {
+  GETX,      desc="Get eXclusive";
+  UPGRADE,   desc="UPGRADE to exclusive";
+  GETS,      desc="Get Shared";
+  GET_INSTR, desc="Get Instruction";
+  INV,       desc="INValidate";
+  PUTX,      desc="Replacement message";
+
+  WB_ACK,    desc="Writeback ack";
+
+  // Request types for sending data and acks from L0 to L1 cache
+  // when an invalidation message is received.
+  INV_DATA;
+  INV_ACK;
+
+  DATA, desc="Data block for L1 cache in S state";
+  DATA_EXCLUSIVE, desc="Data block for L1 cache in M/E state";
+  ACK, desc="Generic invalidate ack";
+
+  // This is a special case in which the L1 cache lost permissions to the
+  // shared block before it got the data. So the L0 cache can use the data
+  // but not store it.
+  STALE_DATA;
+}
+
+// Class for messages sent between the L0 and the L1 controllers.
+structure(CoherenceMsg, desc="...", interface="Message") {
+  Address Addr,              desc="Physical address of the cache block";
+  CoherenceClass Class,         desc="Type of message (GetS, GetX, PutX, etc)";
+  RubyAccessMode AccessMode,    desc="user/supervisor access type";
+  MachineID Sender,             desc="What component sent this message";
+  MachineID Destination,        desc="What machine receives this message";
+  MessageSizeType MessageSize,  desc="size category of the message";
+  DataBlock DataBlk,            desc="Data for the cache line (if PUTX)";
+  bool Dirty, default="false",  desc="Dirty bit";
+
+  bool functionalRead(Packet *pkt) {
+    // Only PUTX messages contains the data block
+    if (Class == CoherenceClass:PUTX) {
+        return testAndRead(Addr, DataBlk, pkt);
+    }
+
+    return false;
+  }
+
+  bool functionalWrite(Packet *pkt) {
+    // No check on message type required since the protocol should
+    // read data from those messages that contain the block
+    return testAndWrite(Addr, DataBlk, pkt);
+  }
+}