/*
* Copyright (c) 2011-2015, 2017, 2019 ARM Limited
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*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* 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: Ron Dreslinski
* Ali Saidi
* Andreas Hansson
* William Wang
*/
/**
* @file
* Declaration of a coherent crossbar.
*/
#ifndef __MEM_COHERENT_XBAR_HH__
#define __MEM_COHERENT_XBAR_HH__
#include <unordered_map>
#include <unordered_set>
#include "mem/snoop_filter.hh"
#include "mem/xbar.hh"
#include "params/CoherentXBar.hh"
/**
* A coherent crossbar connects a number of (potentially) snooping
* masters and slaves, and routes the request and response packets
* based on the address, and also forwards all requests to the
* snoopers and deals with the snoop responses.
*
* The coherent crossbar can be used as a template for modelling QPI,
* HyperTransport, ACE and coherent OCP buses, and is typically used
* for the L1-to-L2 buses and as the main system interconnect. @sa
* \ref gem5MemorySystem "gem5 Memory System"
*/
class CoherentXBar : public BaseXBar
{
protected:
/**
* Declare the layers of this crossbar, one vector for requests,
* one for responses, and one for snoop responses
*/
std::vector<ReqLayer*> reqLayers;
std::vector<RespLayer*> respLayers;
std::vector<SnoopRespLayer*> snoopLayers;
/**
* Declaration of the coherent crossbar slave port type, one will
* be instantiated for each of the master ports connecting to the
* crossbar.
*/
class CoherentXBarSlavePort : public QueuedSlavePort
{
private:
/** A reference to the crossbar to which this port belongs. */
CoherentXBar &xbar;
/** A normal packet queue used to store responses. */
RespPacketQueue queue;
public:
CoherentXBarSlavePort(const std::string &_name,
CoherentXBar &_xbar, PortID _id)
: QueuedSlavePort(_name, &_xbar, queue, _id), xbar(_xbar),
queue(_xbar, *this)
{ }
protected:
bool
recvTimingReq(PacketPtr pkt) override
{
return xbar.recvTimingReq(pkt, id);
}
bool
recvTimingSnoopResp(PacketPtr pkt) override
{
return xbar.recvTimingSnoopResp(pkt, id);
}
Tick
recvAtomic(PacketPtr pkt) override
{
return xbar.recvAtomicBackdoor(pkt, id);
}
Tick
recvAtomicBackdoor(PacketPtr pkt, MemBackdoorPtr &backdoor) override
{
return xbar.recvAtomicBackdoor(pkt, id, &backdoor);
}
void
recvFunctional(PacketPtr pkt) override
{
xbar.recvFunctional(pkt, id);
}
AddrRangeList
getAddrRanges() const override
{
return xbar.getAddrRanges();
}
};
/**
* Declaration of the coherent crossbar master port type, one will be
* instantiated for each of the slave interfaces connecting to the
* crossbar.
*/
class CoherentXBarMasterPort : public MasterPort
{
private:
/** A reference to the crossbar to which this port belongs. */
CoherentXBar &xbar;
public:
CoherentXBarMasterPort(const std::string &_name,
CoherentXBar &_xbar, PortID _id)
: MasterPort(_name, &_xbar, _id), xbar(_xbar)
{ }
protected:
/**
* Determine if this port should be considered a snooper. For
* a coherent crossbar master port this is always true.
*
* @return a boolean that is true if this port is snooping
*/
bool isSnooping() const override { return true; }
bool
recvTimingResp(PacketPtr pkt) override
{
return xbar.recvTimingResp(pkt, id);
}
void
recvTimingSnoopReq(PacketPtr pkt) override
{
return xbar.recvTimingSnoopReq(pkt, id);
}
Tick
recvAtomicSnoop(PacketPtr pkt) override
{
return xbar.recvAtomicSnoop(pkt, id);
}
void
recvFunctionalSnoop(PacketPtr pkt) override
{
xbar.recvFunctionalSnoop(pkt, id);
}
void recvRangeChange() override { xbar.recvRangeChange(id); }
void recvReqRetry() override { xbar.recvReqRetry(id); }
};
/**
* Internal class to bridge between an incoming snoop response
* from a slave port and forwarding it through an outgoing slave
* port. It is effectively a dangling master port.
*/
class SnoopRespPort : public MasterPort
{
private:
/** The port which we mirror internally. */
QueuedSlavePort& slavePort;
public:
/**
* Create a snoop response port that mirrors a given slave port.
*/
SnoopRespPort(QueuedSlavePort& slave_port, CoherentXBar& _xbar) :
MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
slavePort(slave_port) { }
/**
* Override the sending of retries and pass them on through
* the mirrored slave port.
*/
void
sendRetryResp() override
{
// forward it as a snoop response retry
slavePort.sendRetrySnoopResp();
}
void
recvReqRetry() override
{
panic("SnoopRespPort should never see retry");
}
bool
recvTimingResp(PacketPtr pkt) override
{
panic("SnoopRespPort should never see timing response");
}
};
std::vector<SnoopRespPort*> snoopRespPorts;
std::vector<QueuedSlavePort*> snoopPorts;
/**
* Store the outstanding requests that we are expecting snoop
* responses from so we can determine which snoop responses we
* generated and which ones were merely forwarded.
*/
std::unordered_set<RequestPtr> outstandingSnoop;
/**
* Store the outstanding cache maintenance that we are expecting
* snoop responses from so we can determine when we received all
* snoop responses and if any of the agents satisfied the request.
*/
std::unordered_map<PacketId, PacketPtr> outstandingCMO;
/**
* Keep a pointer to the system to be allow to querying memory system
* properties.
*/
System *system;
/** A snoop filter that tracks cache line residency and can restrict the
* broadcast needed for probes. NULL denotes an absent filter. */
SnoopFilter *snoopFilter;
/** Cycles of snoop response latency.*/
const Cycles snoopResponseLatency;
/** Maximum number of outstading snoops sanity check*/
const unsigned int maxOutstandingSnoopCheck;
/** Maximum routing table size sanity check*/
const unsigned int maxRoutingTableSizeCheck;
/** Is this crossbar the point of coherency? **/
const bool pointOfCoherency;
/** Is this crossbar the point of unification? **/
const bool pointOfUnification;
/**
* Upstream caches need this packet until true is returned, so
* hold it for deletion until a subsequent call
*/
std::unique_ptr<Packet> pendingDelete;
bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
void recvReqRetry(PortID master_port_id);
/**
* Forward a timing packet to our snoopers, potentially excluding
* one of the connected coherent masters to avoid sending a packet
* back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_slave_port_id Id of slave port to exclude
*/
void
forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id)
{
forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
}
/**
* Forward a timing packet to a selected list of snoopers, potentially
* excluding one of the connected coherent masters to avoid sending a packet
* back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_slave_port_id Id of slave port to exclude
* @param dests Vector of destination ports for the forwarded pkt
*/
void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
const std::vector<QueuedSlavePort*>& dests);
Tick recvAtomicBackdoor(PacketPtr pkt, PortID slave_port_id,
MemBackdoorPtr *backdoor=nullptr);
Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);
/**
* Forward an atomic packet to our snoopers, potentially excluding
* one of the connected coherent masters to avoid sending a packet
* back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_slave_port_id Id of slave port to exclude
*
* @return a pair containing the snoop response and snoop latency
*/
std::pair<MemCmd, Tick>
forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id)
{
return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID,
snoopPorts);
}
/**
* Forward an atomic packet to a selected list of snoopers, potentially
* excluding one of the connected coherent masters to avoid sending a packet
* back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_slave_port_id Id of slave port to exclude
* @param source_master_port_id Id of the master port for snoops from below
* @param dests Vector of destination ports for the forwarded pkt
*
* @return a pair containing the snoop response and snoop latency
*/
std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
PortID exclude_slave_port_id,
PortID source_master_port_id,
const std::vector<QueuedSlavePort*>&
dests);
/** Function called by the port when the crossbar is recieving a Functional
transaction.*/
void recvFunctional(PacketPtr pkt, PortID slave_port_id);
/** Function called by the port when the crossbar is recieving a functional
snoop transaction.*/
void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
/**
* Forward a functional packet to our snoopers, potentially
* excluding one of the connected coherent masters to avoid
* sending a packet back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_slave_port_id Id of slave port to exclude
*/
void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
/**
* Determine if the crossbar should sink the packet, as opposed to
* forwarding it, or responding.
*/
bool sinkPacket(const PacketPtr pkt) const;
/**
* Determine if the crossbar should forward the packet, as opposed to
* responding to it.
*/
bool forwardPacket(const PacketPtr pkt);
/**
* Determine if the packet's destination is the memory below
*
* The memory below is the destination for a cache mainteance
* operation to the Point of Coherence/Unification if this is the
* Point of Coherence/Unification.
*
* @param pkt The processed packet
*
* @return Whether the memory below is the destination for the packet
*/
bool
isDestination(const PacketPtr pkt) const
{
return (pkt->req->isToPOC() && pointOfCoherency) ||
(pkt->req->isToPOU() && pointOfUnification);
}
Stats::Scalar snoops;
Stats::Scalar snoopTraffic;
Stats::Distribution snoopFanout;
public:
virtual void init();
CoherentXBar(const CoherentXBarParams *p);
virtual ~CoherentXBar();
virtual void regStats();
};
#endif //__MEM_COHERENT_XBAR_HH__