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/*
* Copyright (c) 2011-2015, 2017, 2019 ARM Limited
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*
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* property including but not limited to intellectual property relating
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* modified or unmodified, in source code or in binary form.
*
* Copyright (c) 2002-2005 The Regents of The University of Michigan
* All rights reserved.
*
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/**
* @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"
namespace gem5
{
/**
* A coherent crossbar connects a number of (potentially) snooping
* requestors and responders, 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 CPU-side port type, one will
* be instantiated for each of the mem_side_ports connecting to the
* crossbar.
*/
class CoherentXBarResponsePort : public QueuedResponsePort
{
private:
/** A reference to the crossbar to which this port belongs. */
CoherentXBar &xbar;
/** A normal packet queue used to store responses. */
RespPacketQueue queue;
public:
CoherentXBarResponsePort(const std::string &_name,
CoherentXBar &_xbar, PortID _id)
: QueuedResponsePort(_name, 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);
}
void
recvMemBackdoorReq(const MemBackdoorReq &req,
MemBackdoorPtr &backdoor) override
{
xbar.recvMemBackdoorReq(req, backdoor);
}
AddrRangeList
getAddrRanges() const override
{
return xbar.getAddrRanges();
}
};
/**
* Declaration of the coherent crossbar memory-side port type, one will be
* instantiated for each of the CPU-side-port interfaces connecting to the
* crossbar.
*/
class CoherentXBarRequestPort : public RequestPort
{
private:
/** A reference to the crossbar to which this port belongs. */
CoherentXBar &xbar;
public:
CoherentXBarRequestPort(const std::string &_name,
CoherentXBar &_xbar, PortID _id)
: RequestPort(_name, _id), xbar(_xbar)
{ }
protected:
/**
* Determine if this port should be considered a snooper. For
* a coherent crossbar memory-side 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 CPU-side port and forwarding it through an outgoing
* CPU-side port. It is effectively a dangling memory-side port.
*/
class SnoopRespPort : public RequestPort
{
private:
/** The port which we mirror internally. */
QueuedResponsePort& cpuSidePort;
public:
/**
* Create a snoop response port that mirrors a given CPU-side port.
*/
SnoopRespPort(QueuedResponsePort& cpu_side_port,
CoherentXBar& _xbar) :
RequestPort(cpu_side_port.name() + ".snoopRespPort"),
cpuSidePort(cpu_side_port) { }
/**
* Override the sending of retries and pass them on through
* the mirrored CPU-side port.
*/
void
sendRetryResp() override
{
// forward it as a snoop response retry
cpuSidePort.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<QueuedResponsePort*> 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 cpu_side_port_id);
bool recvTimingResp(PacketPtr pkt, PortID mem_side_port_id);
void recvTimingSnoopReq(PacketPtr pkt, PortID mem_side_port_id);
bool recvTimingSnoopResp(PacketPtr pkt, PortID cpu_side_port_id);
void recvReqRetry(PortID mem_side_port_id);
/**
* Forward a timing packet to our snoopers, potentially excluding
* one of the connected coherent requestors to avoid sending a packet
* back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_cpu_side_port_id Id of CPU-side port to exclude
*/
void
forwardTiming(PacketPtr pkt, PortID exclude_cpu_side_port_id)
{
forwardTiming(pkt, exclude_cpu_side_port_id, snoopPorts);
}
/**
* Forward a timing packet to a selected list of snoopers, potentially
* excluding one of the connected coherent requestors to avoid sending
* a packet back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_cpu_side_port_id Id of CPU-side port to exclude
* @param dests Vector of destination ports for the forwarded pkt
*/
void forwardTiming(PacketPtr pkt, PortID exclude_cpu_side_port_id,
const std::vector<QueuedResponsePort*>& dests);
Tick recvAtomicBackdoor(PacketPtr pkt, PortID cpu_side_port_id,
MemBackdoorPtr *backdoor=nullptr);
Tick recvAtomicSnoop(PacketPtr pkt, PortID mem_side_port_id);
/**
* Forward an atomic packet to our snoopers, potentially excluding
* one of the connected coherent requestors to avoid sending a packet
* back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_cpu_side_port_id Id of CPU-side port to exclude
*
* @return a pair containing the snoop response and snoop latency
*/
std::pair<MemCmd, Tick>
forwardAtomic(PacketPtr pkt, PortID exclude_cpu_side_port_id)
{
return forwardAtomic(pkt, exclude_cpu_side_port_id, InvalidPortID,
snoopPorts);
}
/**
* Forward an atomic packet to a selected list of snoopers, potentially
* excluding one of the connected coherent requestors to avoid sending a
* packet back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_cpu_side_port_id Id of CPU-side port to exclude
* @param source_mem_side_port_id Id of the memory-side 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_cpu_side_port_id,
PortID source_mem_side_port_id,
const std::vector<QueuedResponsePort*>&
dests);
/** Function called by the port when the crossbar is receiving a Functional
transaction.*/
void recvFunctional(PacketPtr pkt, PortID cpu_side_port_id);
/** Function called by the port when the crossbar receives a request for
a memory backdoor.*/
void recvMemBackdoorReq(const MemBackdoorReq &req,
MemBackdoorPtr &backdoor);
/** Function called by the port when the crossbar is receiving a functional
snoop transaction.*/
void recvFunctionalSnoop(PacketPtr pkt, PortID mem_side_port_id);
/**
* Forward a functional packet to our snoopers, potentially
* excluding one of the connected coherent requestors to avoid
* sending a packet back to where it came from.
*
* @param pkt Packet to forward
* @param exclude_cpu_side_port_id Id of CPU-side port to exclude
*/
void forwardFunctional(PacketPtr pkt, PortID exclude_cpu_side_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);
}
statistics::Scalar snoops;
statistics::Scalar snoopTraffic;
statistics::Distribution snoopFanout;
public:
virtual void init();
CoherentXBar(const CoherentXBarParams &p);
virtual ~CoherentXBar();
virtual void regStats();
};
} // namespace gem5
#endif //__MEM_COHERENT_XBAR_HH__