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/*
* Copyright (c) 2002-2005 The Regents of The University of Michigan
* 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.
*
* Authors: Erik Hallnor
* Ron Dreslinski
* Steve Reinhardt
*/
/**
* @file
* Declaration of CoherenceProcotol a basic coherence policy.
*/
#ifndef __COHERENCE_PROTOCOL_HH__
#define __COHERENCE_PROTOCOL_HH__
#include <string>
#include "sim/sim_object.hh"
#include "mem/packet.hh"
#include "mem/cache/cache_blk.hh"
#include "base/statistics.hh"
class BaseCache;
class MSHR;
/**
* A simple coherence policy for the memory hierarchy. Currently implements
* MSI, MESI, and MOESI protocols.
*/
class CoherenceProtocol : public SimObject
{
public:
/**
* Contruct and initialize this policy.
* @param name The name of this policy.
* @param protocol The string representation of the protocol to use.
* @param doUpgrades True if bus upgrades should be used.
*/
CoherenceProtocol(const std::string &name, const std::string &protocol,
const bool doUpgrades);
/**
* Destructor.
*/
virtual ~CoherenceProtocol() {};
/**
* Register statistics
*/
virtual void regStats();
/**
* Get the proper bus command for the given command and status.
* @param cmd The request's command.
* @param status The current state of the cache block.
* @param mshr The MSHR matching the request.
* @return The proper bus command, as determined by the protocol.
*/
Packet::Command getBusCmd(Packet::Command cmd, CacheBlk::State status,
MSHR *mshr = NULL);
/**
* Return the proper state given the current state and the bus response.
* @param pkt The bus response.
* @param oldState The current block state.
* @return The new state.
*/
CacheBlk::State getNewState(Packet * &pkt,
CacheBlk::State oldState);
/**
* Handle snooped bus requests.
* @param cache The cache that snooped the request.
* @param pkt The snooped bus request.
* @param blk The cache block corresponding to the request, if any.
* @param mshr The MSHR corresponding to the request, if any.
* @param new_state The new coherence state of the block.
* @return True if the request should be satisfied locally.
*/
bool handleBusRequest(BaseCache *cache, Packet * &pkt, CacheBlk *blk,
MSHR *mshr, CacheBlk::State &new_state);
protected:
/** Snoop function type. */
typedef bool (*SnoopFuncType)(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
//
// Standard snoop transition functions
//
/**
* Do nothing transition.
*/
static bool nullTransition(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Invalid transition, basically panic.
*/
static bool invalidTransition(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Invalidate block, move to Invalid state.
*/
static bool invalidateTrans(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Supply data, no state transition.
*/
static bool supplyTrans(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Supply data and go to Shared state.
*/
static bool supplyAndGotoSharedTrans(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Supply data and go to Owned state.
*/
static bool supplyAndGotoOwnedTrans(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Invalidate block, supply data, and go to Invalid state.
*/
static bool supplyAndInvalidateTrans(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Assert the shared line for a block that is shared/exclusive.
*/
static bool assertShared(BaseCache *, Packet *&, CacheBlk *,
MSHR *, CacheBlk::State&);
/**
* Definition of protocol state transitions.
*/
class StateTransition
{
friend class CoherenceProtocol;
/** The bus command of this transition. */
Packet::Command busCmd;
/** The state to transition to. */
int newState;
/** The snoop function for this transition. */
SnoopFuncType snoopFunc;
/**
* Constructor, defaults to invalid transition.
*/
StateTransition();
/**
* Initialize bus command.
* @param cmd The bus command to use.
*/
void onRequest(Packet::Command cmd)
{
busCmd = cmd;
}
/**
* Set the transition state.
* @param s The new state.
*/
void onResponse(CacheBlk::State s)
{
newState = s;
}
/**
* Initialize the snoop function.
* @param f The new snoop function.
*/
void onSnoop(SnoopFuncType f)
{
snoopFunc = f;
}
};
friend class CoherenceProtocol::StateTransition;
/** Mask to select status bits relevant to coherence protocol. */
const static CacheBlk::State
stateMask = BlkValid | BlkWritable | BlkDirty;
/** The Modified (M) state. */
const static CacheBlk::State
Modified = BlkValid | BlkWritable | BlkDirty;
/** The Owned (O) state. */
const static CacheBlk::State
Owned = BlkValid | BlkDirty;
/** The Exclusive (E) state. */
const static CacheBlk::State
Exclusive = BlkValid | BlkWritable;
/** The Shared (S) state. */
const static CacheBlk::State
Shared = BlkValid;
/** The Invalid (I) state. */
const static CacheBlk::State
Invalid = 0;
/**
* Maximum state encoding value (used to size transition lookup
* table). Could be more than number of states, depends on
* encoding of status bits.
*/
const static int stateMax = stateMask;
/**
* The table of all possible transitions, organized by starting state and
* request command.
*/
StateTransition transitionTable[stateMax+1][NUM_MEM_CMDS];
/**
* @addtogroup CoherenceStatistics
* @{
*/
/**
* State accesses from parent cache.
*/
Stats::Scalar<> requestCount[stateMax+1][NUM_MEM_CMDS];
/**
* State accesses from snooped requests.
*/
Stats::Scalar<> snoopCount[stateMax+1][NUM_MEM_CMDS];
/**
* @}
*/
};
#endif // __COHERENCE_PROTOCOL_HH__
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