src/mem/protocol/MESI_Three_Level-msg.sm

/*
 * 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") {
  Addr 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 Dest,        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);
  }
}