src/cpu/base.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2011-2013, 2017, 2020 ARM Limited
  * All rights reserved
  *
  * 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
  * Copyright (c) 2011 Regents of the University of California
  * 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.
  */

 #ifndef __CPU_BASE_HH__
 #define __CPU_BASE_HH__

 #include <vector>

 #include "arch/generic/interrupts.hh"
 #include "base/statistics.hh"
 #include "debug/Mwait.hh"
 #include "mem/htm.hh"
 #include "mem/port_proxy.hh"
 #include "sim/clocked_object.hh"
 #include "sim/eventq.hh"
 #include "sim/full_system.hh"
 #include "sim/insttracer.hh"
 #include "sim/probe/pmu.hh"
 #include "sim/probe/probe.hh"
 #include "sim/signal.hh"
 #include "sim/system.hh"

 namespace gem5
 {

 class BaseCPU;
 struct BaseCPUParams;
 class CheckerCPU;
 class ThreadContext;

 struct AddressMonitor
 {
     AddressMonitor();
     bool doMonitor(PacketPtr pkt);

     bool armed;
     Addr vAddr;
     Addr pAddr;
     uint64_t val;
     bool waiting;   // 0=normal, 1=mwaiting
     bool gotWakeup;
 };

 class CPUProgressEvent : public Event
 {
   protected:
     Tick _interval;
     Counter lastNumInst;
     BaseCPU *cpu;
     bool _repeatEvent;

   public:
     CPUProgressEvent(BaseCPU *_cpu, Tick ival = 0);

     void process();

     void interval(Tick ival) { _interval = ival; }
     Tick interval() { return _interval; }

     void repeatEvent(bool repeat) { _repeatEvent = repeat; }

     virtual const char *description() const;
 };

 class BaseCPU : public ClockedObject
 {
   protected:

     /// Instruction count used for SPARC misc register
     /// @todo unify this with the counters that cpus individually keep
     Tick instCnt;

     // every cpu has an id, put it in the base cpu
     // Set at initialization, only time a cpuId might change is during a
     // takeover (which should be done from within the BaseCPU anyway,
     // therefore no setCpuId() method is provided
     int _cpuId;

     /** Each cpu will have a socket ID that corresponds to its physical location
      * in the system. This is usually used to bucket cpu cores under single DVFS
      * domain. This information may also be required by the OS to identify the
      * cpu core grouping (as in the case of ARM via MPIDR register)
      */
     const uint32_t _socketId;

     /** instruction side request id that must be placed in all requests */
     RequestorID _instRequestorId;

     /** data side request id that must be placed in all requests */
     RequestorID _dataRequestorId;

     /** An intrenal representation of a task identifier within gem5. This is
      * used so the CPU can add which taskId (which is an internal representation
      * of the OS process ID) to each request so components in the memory system
      * can track which process IDs are ultimately interacting with them
      */
     uint32_t _taskId;

     /** The current OS process ID that is executing on this processor. This is
      * used to generate a taskId */
     uint32_t _pid;

     /** Is the CPU switched out or active? */
     bool _switchedOut;

     /** Cache the cache line size that we get from the system */
     const unsigned int _cacheLineSize;

     /** Global CPU statistics that are merged into the Root object. */
     struct GlobalStats : public statistics::Group
     {
         GlobalStats(statistics::Group *parent);

         statistics::Value simInsts;
         statistics::Value simOps;

         statistics::Formula hostInstRate;
         statistics::Formula hostOpRate;
     };

     /**
      * Pointer to the global stat structure. This needs to be
      * constructed from regStats since we merge it into the root
      * group. */
     static std::unique_ptr<GlobalStats> globalStats;

     SignalSinkPort<bool> modelResetPort;

   public:

     /**
      * Purely virtual method that returns a reference to the data
      * port. All subclasses must implement this method.
      *
      * @return a reference to the data port
      */
     virtual Port &getDataPort() = 0;

     /**
      * Purely virtual method that returns a reference to the instruction
      * port. All subclasses must implement this method.
      *
      * @return a reference to the instruction port
      */
     virtual Port &getInstPort() = 0;

     /** Reads this CPU's ID. */
     int cpuId() const { return _cpuId; }

     /** Reads this CPU's Socket ID. */
     uint32_t socketId() const { return _socketId; }

     /** Reads this CPU's unique data requestor ID */
     RequestorID dataRequestorId() const { return _dataRequestorId; }
     /** Reads this CPU's unique instruction requestor ID */
     RequestorID instRequestorId() const { return _instRequestorId; }

     /**
      * Get a port on this CPU. All CPUs have a data and
      * instruction port, and this method uses getDataPort and
      * getInstPort of the subclasses to resolve the two ports.
      *
      * @param if_name the port name
      * @param idx ignored index
      *
      * @return a reference to the port with the given name
      */
     Port &getPort(const std::string &if_name,
                   PortID idx=InvalidPortID) override;

     /** Get cpu task id */
     uint32_t taskId() const { return _taskId; }
     /** Set cpu task id */
     void taskId(uint32_t id) { _taskId = id; }

     uint32_t getPid() const { return _pid; }
     void setPid(uint32_t pid) { _pid = pid; }

     inline void workItemBegin() { baseStats.numWorkItemsStarted++; }
     inline void workItemEnd() { baseStats.numWorkItemsCompleted++; }
     // @todo remove me after debugging with legion done
     Tick instCount() { return instCnt; }

   protected:
     std::vector<BaseInterrupts*> interrupts;

   public:
     BaseInterrupts *
     getInterruptController(ThreadID tid)
     {
         if (interrupts.empty())
             return NULL;

         assert(interrupts.size() > tid);
         return interrupts[tid];
     }

     virtual void wakeup(ThreadID tid) = 0;

     void postInterrupt(ThreadID tid, int int_num, int index);

     void
     clearInterrupt(ThreadID tid, int int_num, int index)
     {
         interrupts[tid]->clear(int_num, index);
     }

     void
     clearInterrupts(ThreadID tid)
     {
         interrupts[tid]->clearAll();
     }

     bool
     checkInterrupts(ThreadID tid) const
     {
         return FullSystem && interrupts[tid]->checkInterrupts();
     }

   protected:
     std::vector<ThreadContext *> threadContexts;

     trace::InstTracer * tracer;

   public:


     /** Invalid or unknown Pid. Possible when operating system is not present
      *  or has not assigned a pid yet */
     static const uint32_t invldPid = std::numeric_limits<uint32_t>::max();

     /// Provide access to the tracer pointer
     trace::InstTracer * getTracer() { return tracer; }

     /// Notify the CPU that the indicated context is now active.
     virtual void activateContext(ThreadID thread_num);

     /// Notify the CPU that the indicated context is now suspended.
     /// Check if possible to enter a lower power state
     virtual void suspendContext(ThreadID thread_num);

     /// Notify the CPU that the indicated context is now halted.
     virtual void haltContext(ThreadID thread_num);

     /// Given a Thread Context pointer return the thread num
     int findContext(ThreadContext *tc);

     /// Given a thread num get tho thread context for it
     virtual ThreadContext *getContext(int tn) { return threadContexts[tn]; }

     /// Get the number of thread contexts available
     unsigned
     numContexts()
     {
         return static_cast<unsigned>(threadContexts.size());
     }

     /// Convert ContextID to threadID
     ThreadID
     contextToThread(ContextID cid)
     {
         return static_cast<ThreadID>(cid - threadContexts[0]->contextId());
     }

   public:
     PARAMS(BaseCPU);
     BaseCPU(const Params &params, bool is_checker = false);
     virtual ~BaseCPU();

     void init() override;
     void startup() override;
     void regStats() override;

     void regProbePoints() override;

     void registerThreadContexts();

     // Functions to deschedule and reschedule the events to enter the
     // power gating sleep before and after checkpoiting respectively.
     void deschedulePowerGatingEvent();
     void schedulePowerGatingEvent();

     /**
      * Prepare for another CPU to take over execution.
      *
      * When this method exits, all internal state should have been
      * flushed. After the method returns, the simulator calls
      * takeOverFrom() on the new CPU with this CPU as its parameter.
      */
     virtual void switchOut();

     /**
      * Load the state of a CPU from the previous CPU object, invoked
      * on all new CPUs that are about to be switched in.
      *
      * A CPU model implementing this method is expected to initialize
      * its state from the old CPU and connect its memory (unless they
      * are already connected) to the memories connected to the old
      * CPU.
      *
      * @param cpu CPU to initialize read state from.
      */
     virtual void takeOverFrom(BaseCPU *cpu);

     /**
      * Set the reset of the CPU to be either asserted or deasserted.
      *
      * When asserted, the CPU should be stopped and waiting. When deasserted,
      * the CPU should start running again, unless some other condition would
      * also prevent it. At the point the reset is deasserted, it should be
      * reinitialized as defined by the ISA it's running and any other relevant
      * part of its configuration (reset address, etc).
      *
      * @param state The new state of the reset signal to this CPU.
      */
     virtual void setReset(bool state);

     /**
      * Flush all TLBs in the CPU.
      *
      * This method is mainly used to flush stale translations when
      * switching CPUs. It is also exported to the Python world to
      * allow it to request a TLB flush after draining the CPU to make
      * it easier to compare traces when debugging
      * handover/checkpointing.
      */
     void flushTLBs();

     /**
      * Determine if the CPU is switched out.
      *
      * @return True if the CPU is switched out, false otherwise.
      */
     bool switchedOut() const { return _switchedOut; }

     /**
      * Verify that the system is in a memory mode supported by the
      * CPU.
      *
      * Implementations are expected to query the system for the
      * current memory mode and ensure that it is what the CPU model
      * expects. If the check fails, the implementation should
      * terminate the simulation using fatal().
      */
     virtual void verifyMemoryMode() const { };

     /**
      *  Number of threads we're actually simulating (<= SMT_MAX_THREADS).
      * This is a constant for the duration of the simulation.
      */
     ThreadID numThreads;

     System *system;

     /**
      * Get the cache line size of the system.
      */
     inline unsigned int cacheLineSize() const { return _cacheLineSize; }

     /**
      * Serialize this object to the given output stream.
      *
      * @note CPU models should normally overload the serializeThread()
      * method instead of the serialize() method as this provides a
      * uniform data format for all CPU models and promotes better code
      * reuse.
      *
      * @param cp The stream to serialize to.
      */
     void serialize(CheckpointOut &cp) const override;

     /**
      * Reconstruct the state of this object from a checkpoint.
      *
      * @note CPU models should normally overload the
      * unserializeThread() method instead of the unserialize() method
      * as this provides a uniform data format for all CPU models and
      * promotes better code reuse.

      * @param cp The checkpoint use.
      */
     void unserialize(CheckpointIn &cp) override;

     /**
      * Serialize a single thread.
      *
      * @param cp The stream to serialize to.
      * @param tid ID of the current thread.
      */
     virtual void serializeThread(CheckpointOut &cp, ThreadID tid) const {};

     /**
      * Unserialize one thread.
      *
      * @param cp The checkpoint use.
      * @param tid ID of the current thread.
      */
     virtual void unserializeThread(CheckpointIn &cp, ThreadID tid) {};

     virtual Counter totalInsts() const = 0;

     virtual Counter totalOps() const = 0;

     /**
      * Schedule an event that exits the simulation loops after a
      * predefined number of instructions.
      *
      * This method is usually called from the configuration script to
      * get an exit event some time in the future. It is typically used
      * when the script wants to simulate for a specific number of
      * instructions rather than ticks.
      *
      * @param tid Thread monitor.
      * @param insts Number of instructions into the future.
      * @param cause Cause to signal in the exit event.
      */
     void scheduleInstStop(ThreadID tid, Counter insts, std::string cause);

     /**
      * Schedule simpoint events using the scheduleInstStop function.
      *
      * This is used to raise a SIMPOINT_BEGIN exit event in the gem5 standard
      * library.
      *
      * @param inst_starts A vector of number of instructions to start simpoints
      */

     void scheduleSimpointsInstStop(std::vector<Counter> inst_starts);

     /**
      * Schedule an exit event when any threads in the core reach the max_insts
      * instructions using the scheduleInstStop function.
      *
      * This is used to raise a MAX_INSTS exit event in thegem5 standard library
      *
      * @param max_insts Number of instructions into the future.
      */
     void scheduleInstStopAnyThread(Counter max_insts);

     /**
      * Get the number of instructions executed by the specified thread
      * on this CPU. Used by Python to control simulation.
      *
      * @param tid Thread monitor
      * @return Number of instructions executed
      */
     uint64_t getCurrentInstCount(ThreadID tid);

   public:
     /**
      * @{
      * @name PMU Probe points.
      */

     /**
      * Helper method to trigger PMU probes for a committed
      * instruction.
      *
      * @param inst Instruction that just committed
      * @param pc PC of the instruction that just committed
      */
     virtual void probeInstCommit(const StaticInstPtr &inst, Addr pc);

    protected:
     /**
      * Helper method to instantiate probe points belonging to this
      * object.
      *
      * @param name Name of the probe point.
      * @return A unique_ptr to the new probe point.
      */
     probing::PMUUPtr pmuProbePoint(const char *name);

     /**
      * Instruction commit probe point.
      *
      * This probe point is triggered whenever one or more instructions
      * are committed. It is normally triggered once for every
      * instruction. However, CPU models committing bundles of
      * instructions may call notify once for the entire bundle.
      */
     probing::PMUUPtr ppRetiredInsts;
     probing::PMUUPtr ppRetiredInstsPC;

     /** Retired load instructions */
     probing::PMUUPtr ppRetiredLoads;
     /** Retired store instructions */
     probing::PMUUPtr ppRetiredStores;

     /** Retired branches (any type) */
     probing::PMUUPtr ppRetiredBranches;

     /** CPU cycle counter even if any thread Context is suspended*/
     probing::PMUUPtr ppAllCycles;

     /** CPU cycle counter, only counts if any thread contexts is active **/
     probing::PMUUPtr ppActiveCycles;

     /**
      * ProbePoint that signals transitions of threadContexts sets.
      * The ProbePoint reports information through it bool parameter.
      * - If the parameter is true then the last enabled threadContext of the
      * CPU object was disabled.
      * - If the parameter is false then a threadContext was enabled, all the
      * remaining threadContexts are disabled.
      */
     ProbePointArg<bool> *ppSleeping;
     /** @} */

     enum CPUState
     {
         CPU_STATE_ON,
         CPU_STATE_SLEEP,
         CPU_STATE_WAKEUP
     };

     Cycles previousCycle;
     CPUState previousState;

     /** base method keeping track of cycle progression **/
     inline void
     updateCycleCounters(CPUState state)
     {
         uint32_t delta = curCycle() - previousCycle;

         if (previousState == CPU_STATE_ON) {
             ppActiveCycles->notify(delta);
         }

         switch (state) {
           case CPU_STATE_WAKEUP:
             ppSleeping->notify(false);
             break;
           case CPU_STATE_SLEEP:
             ppSleeping->notify(true);
             break;
           default:
             break;
         }

         ppAllCycles->notify(delta);

         previousCycle = curCycle();
         previousState = state;
     }

     // Function tracing
   private:
     bool functionTracingEnabled;
     std::ostream *functionTraceStream;
     Addr currentFunctionStart;
     Addr currentFunctionEnd;
     Tick functionEntryTick;
     void enableFunctionTrace();
     void traceFunctionsInternal(Addr pc);

   private:
     static std::vector<BaseCPU *> cpuList;   //!< Static global cpu list

   public:
     void
     traceFunctions(Addr pc)
     {
         if (functionTracingEnabled)
             traceFunctionsInternal(pc);
     }

     static int numSimulatedCPUs() { return cpuList.size(); }
     static Counter
     numSimulatedInsts()
     {
         Counter total = 0;

         int size = cpuList.size();
         for (int i = 0; i < size; ++i)
             total += cpuList[i]->totalInsts();

         return total;
     }

     static Counter
     numSimulatedOps()
     {
         Counter total = 0;

         int size = cpuList.size();
         for (int i = 0; i < size; ++i)
             total += cpuList[i]->totalOps();

         return total;
     }

   public:
     struct BaseCPUStats : public statistics::Group
     {
         BaseCPUStats(statistics::Group *parent);
         // Number of CPU cycles simulated
         statistics::Scalar numCycles;
         statistics::Scalar numWorkItemsStarted;
         statistics::Scalar numWorkItemsCompleted;
     } baseStats;

   private:
     std::vector<AddressMonitor> addressMonitor;

   public:
     void armMonitor(ThreadID tid, Addr address);
     bool mwait(ThreadID tid, PacketPtr pkt);
     void mwaitAtomic(ThreadID tid, ThreadContext *tc, BaseMMU *mmu);
     AddressMonitor *
     getCpuAddrMonitor(ThreadID tid)
     {
         assert(tid < numThreads);
         return &addressMonitor[tid];
     }

     Cycles syscallRetryLatency;

     /** This function is used to instruct the memory subsystem that a
      * transaction should be aborted and the speculative state should be
      * thrown away.  This is called in the transaction's very last breath in
      * the core.  Afterwards, the core throws away its speculative state and
      * resumes execution at the point the transaction started, i.e. reverses
      * time.  When instruction execution resumes, the core expects the
      * memory subsystem to be in a stable, i.e. pre-speculative, state as
      * well. */
     virtual void
     htmSendAbortSignal(ThreadID tid, uint64_t htm_uid,
                        HtmFailureFaultCause cause)
     {
         panic("htmSendAbortSignal not implemented");
     }

   // Enables CPU to enter power gating on a configurable cycle count
   protected:
     void enterPwrGating();

     const Cycles pwrGatingLatency;
     const bool powerGatingOnIdle;
     EventFunctionWrapper enterPwrGatingEvent;
 };

 } // namespace gem5

 #endif // __CPU_BASE_HH__
	/*
	* Copyright (c) 2011-2013, 2017, 2020 ARM Limited
	* All rights reserved
	*
	* 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
	* Copyright (c) 2011 Regents of the University of California
	* 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.
	*/

	#ifndef __CPU_BASE_HH__
	#define __CPU_BASE_HH__

	#include <vector>

	#include "arch/generic/interrupts.hh"
	#include "base/statistics.hh"
	#include "debug/Mwait.hh"
	#include "mem/htm.hh"
	#include "mem/port_proxy.hh"
	#include "sim/clocked_object.hh"
	#include "sim/eventq.hh"
	#include "sim/full_system.hh"
	#include "sim/insttracer.hh"
	#include "sim/probe/pmu.hh"
	#include "sim/probe/probe.hh"
	#include "sim/signal.hh"
	#include "sim/system.hh"

	namespace gem5
	{

	class BaseCPU;
	struct BaseCPUParams;
	class CheckerCPU;
	class ThreadContext;

	struct AddressMonitor
	{
	AddressMonitor();
	bool doMonitor(PacketPtr pkt);

	bool armed;
	Addr vAddr;
	Addr pAddr;
	uint64_t val;
	bool waiting; // 0=normal, 1=mwaiting
	bool gotWakeup;
	};

	class CPUProgressEvent : public Event
	{
	protected:
	Tick _interval;
	Counter lastNumInst;
	BaseCPU *cpu;
	bool _repeatEvent;

	public:
	CPUProgressEvent(BaseCPU *_cpu, Tick ival = 0);

	void process();

	void interval(Tick ival) { _interval = ival; }
	Tick interval() { return _interval; }

	void repeatEvent(bool repeat) { _repeatEvent = repeat; }

	virtual const char *description() const;
	};

	class BaseCPU : public ClockedObject
	{
	protected:

	/// Instruction count used for SPARC misc register
	/// @todo unify this with the counters that cpus individually keep
	Tick instCnt;

	// every cpu has an id, put it in the base cpu
	// Set at initialization, only time a cpuId might change is during a
	// takeover (which should be done from within the BaseCPU anyway,
	// therefore no setCpuId() method is provided
	int _cpuId;

	/** Each cpu will have a socket ID that corresponds to its physical location
	* in the system. This is usually used to bucket cpu cores under single DVFS
	* domain. This information may also be required by the OS to identify the
	* cpu core grouping (as in the case of ARM via MPIDR register)
	*/
	const uint32_t _socketId;

	/** instruction side request id that must be placed in all requests */
	RequestorID _instRequestorId;

	/** data side request id that must be placed in all requests */
	RequestorID _dataRequestorId;

	/** An intrenal representation of a task identifier within gem5. This is
	* used so the CPU can add which taskId (which is an internal representation
	* of the OS process ID) to each request so components in the memory system
	* can track which process IDs are ultimately interacting with them
	*/
	uint32_t _taskId;

	/** The current OS process ID that is executing on this processor. This is
	* used to generate a taskId */
	uint32_t _pid;

	/** Is the CPU switched out or active? */
	bool _switchedOut;

	/** Cache the cache line size that we get from the system */
	const unsigned int _cacheLineSize;

	/** Global CPU statistics that are merged into the Root object. */
	struct GlobalStats : public statistics::Group
	{
	GlobalStats(statistics::Group *parent);

	statistics::Value simInsts;
	statistics::Value simOps;

	statistics::Formula hostInstRate;
	statistics::Formula hostOpRate;
	};

	/**
	* Pointer to the global stat structure. This needs to be
	* constructed from regStats since we merge it into the root
	* group. */
	static std::unique_ptr<GlobalStats> globalStats;

	SignalSinkPort<bool> modelResetPort;

	public:

	/**
	* Purely virtual method that returns a reference to the data
	* port. All subclasses must implement this method.
	*
	* @return a reference to the data port
	*/
	virtual Port &getDataPort() = 0;

	/**
	* Purely virtual method that returns a reference to the instruction
	* port. All subclasses must implement this method.
	*
	* @return a reference to the instruction port
	*/
	virtual Port &getInstPort() = 0;

	/** Reads this CPU's ID. */
	int cpuId() const { return _cpuId; }

	/** Reads this CPU's Socket ID. */
	uint32_t socketId() const { return _socketId; }

	/** Reads this CPU's unique data requestor ID */
	RequestorID dataRequestorId() const { return _dataRequestorId; }
	/** Reads this CPU's unique instruction requestor ID */
	RequestorID instRequestorId() const { return _instRequestorId; }

	/**
	* Get a port on this CPU. All CPUs have a data and
	* instruction port, and this method uses getDataPort and
	* getInstPort of the subclasses to resolve the two ports.
	*
	* @param if_name the port name
	* @param idx ignored index
	*
	* @return a reference to the port with the given name
	*/
	Port &getPort(const std::string &if_name,
	PortID idx=InvalidPortID) override;

	/** Get cpu task id */
	uint32_t taskId() const { return _taskId; }
	/** Set cpu task id */
	void taskId(uint32_t id) { _taskId = id; }

	uint32_t getPid() const { return _pid; }
	void setPid(uint32_t pid) { _pid = pid; }

	inline void workItemBegin() { baseStats.numWorkItemsStarted++; }
	inline void workItemEnd() { baseStats.numWorkItemsCompleted++; }
	// @todo remove me after debugging with legion done
	Tick instCount() { return instCnt; }

	protected:
	std::vector<BaseInterrupts*> interrupts;

	public:
	BaseInterrupts *
	getInterruptController(ThreadID tid)
	{
	if (interrupts.empty())
	return NULL;

	assert(interrupts.size() > tid);
	return interrupts[tid];
	}

	virtual void wakeup(ThreadID tid) = 0;

	void postInterrupt(ThreadID tid, int int_num, int index);

	void
	clearInterrupt(ThreadID tid, int int_num, int index)
	{
	interrupts[tid]->clear(int_num, index);
	}

	void
	clearInterrupts(ThreadID tid)
	{
	interrupts[tid]->clearAll();
	}

	bool
	checkInterrupts(ThreadID tid) const
	{
	return FullSystem && interrupts[tid]->checkInterrupts();
	}

	protected:
	std::vector<ThreadContext *> threadContexts;

	trace::InstTracer * tracer;

	public:


	/** Invalid or unknown Pid. Possible when operating system is not present
	* or has not assigned a pid yet */
	static const uint32_t invldPid = std::numeric_limits<uint32_t>::max();

	/// Provide access to the tracer pointer
	trace::InstTracer * getTracer() { return tracer; }

	/// Notify the CPU that the indicated context is now active.
	virtual void activateContext(ThreadID thread_num);

	/// Notify the CPU that the indicated context is now suspended.
	/// Check if possible to enter a lower power state
	virtual void suspendContext(ThreadID thread_num);

	/// Notify the CPU that the indicated context is now halted.
	virtual void haltContext(ThreadID thread_num);

	/// Given a Thread Context pointer return the thread num
	int findContext(ThreadContext *tc);

	/// Given a thread num get tho thread context for it
	virtual ThreadContext *getContext(int tn) { return threadContexts[tn]; }

	/// Get the number of thread contexts available
	unsigned
	numContexts()
	{
	return static_cast<unsigned>(threadContexts.size());
	}

	/// Convert ContextID to threadID
	ThreadID
	contextToThread(ContextID cid)
	{
	return static_cast<ThreadID>(cid - threadContexts[0]->contextId());
	}

	public:
	PARAMS(BaseCPU);
	BaseCPU(const Params &params, bool is_checker = false);
	virtual ~BaseCPU();

	void init() override;
	void startup() override;
	void regStats() override;

	void regProbePoints() override;

	void registerThreadContexts();

	// Functions to deschedule and reschedule the events to enter the
	// power gating sleep before and after checkpoiting respectively.
	void deschedulePowerGatingEvent();
	void schedulePowerGatingEvent();

	/**
	* Prepare for another CPU to take over execution.
	*
	* When this method exits, all internal state should have been
	* flushed. After the method returns, the simulator calls
	* takeOverFrom() on the new CPU with this CPU as its parameter.
	*/
	virtual void switchOut();

	/**
	* Load the state of a CPU from the previous CPU object, invoked
	* on all new CPUs that are about to be switched in.
	*
	* A CPU model implementing this method is expected to initialize
	* its state from the old CPU and connect its memory (unless they
	* are already connected) to the memories connected to the old
	* CPU.
	*
	* @param cpu CPU to initialize read state from.
	*/
	virtual void takeOverFrom(BaseCPU *cpu);

	/**
	* Set the reset of the CPU to be either asserted or deasserted.
	*
	* When asserted, the CPU should be stopped and waiting. When deasserted,
	* the CPU should start running again, unless some other condition would
	* also prevent it. At the point the reset is deasserted, it should be
	* reinitialized as defined by the ISA it's running and any other relevant
	* part of its configuration (reset address, etc).
	*
	* @param state The new state of the reset signal to this CPU.
	*/
	virtual void setReset(bool state);

	/**
	* Flush all TLBs in the CPU.
	*
	* This method is mainly used to flush stale translations when
	* switching CPUs. It is also exported to the Python world to
	* allow it to request a TLB flush after draining the CPU to make
	* it easier to compare traces when debugging
	* handover/checkpointing.
	*/
	void flushTLBs();

	/**
	* Determine if the CPU is switched out.
	*
	* @return True if the CPU is switched out, false otherwise.
	*/
	bool switchedOut() const { return _switchedOut; }

	/**
	* Verify that the system is in a memory mode supported by the
	* CPU.
	*
	* Implementations are expected to query the system for the
	* current memory mode and ensure that it is what the CPU model
	* expects. If the check fails, the implementation should
	* terminate the simulation using fatal().
	*/
	virtual void verifyMemoryMode() const { };

	/**
	* Number of threads we're actually simulating (<= SMT_MAX_THREADS).
	* This is a constant for the duration of the simulation.
	*/
	ThreadID numThreads;

	System *system;

	/**
	* Get the cache line size of the system.
	*/
	inline unsigned int cacheLineSize() const { return _cacheLineSize; }

	/**
	* Serialize this object to the given output stream.
	*
	* @note CPU models should normally overload the serializeThread()
	* method instead of the serialize() method as this provides a
	* uniform data format for all CPU models and promotes better code
	* reuse.
	*
	* @param cp The stream to serialize to.
	*/
	void serialize(CheckpointOut &cp) const override;

	/**
	* Reconstruct the state of this object from a checkpoint.
	*
	* @note CPU models should normally overload the
	* unserializeThread() method instead of the unserialize() method
	* as this provides a uniform data format for all CPU models and
	* promotes better code reuse.

	* @param cp The checkpoint use.
	*/
	void unserialize(CheckpointIn &cp) override;

	/**
	* Serialize a single thread.
	*
	* @param cp The stream to serialize to.
	* @param tid ID of the current thread.
	*/
	virtual void serializeThread(CheckpointOut &cp, ThreadID tid) const {};

	/**
	* Unserialize one thread.
	*
	* @param cp The checkpoint use.
	* @param tid ID of the current thread.
	*/
	virtual void unserializeThread(CheckpointIn &cp, ThreadID tid) {};

	virtual Counter totalInsts() const = 0;

	virtual Counter totalOps() const = 0;

	/**
	* Schedule an event that exits the simulation loops after a
	* predefined number of instructions.
	*
	* This method is usually called from the configuration script to
	* get an exit event some time in the future. It is typically used
	* when the script wants to simulate for a specific number of
	* instructions rather than ticks.
	*
	* @param tid Thread monitor.
	* @param insts Number of instructions into the future.
	* @param cause Cause to signal in the exit event.
	*/
	void scheduleInstStop(ThreadID tid, Counter insts, std::string cause);

	/**
	* Schedule simpoint events using the scheduleInstStop function.
	*
	* This is used to raise a SIMPOINT_BEGIN exit event in the gem5 standard
	* library.
	*
	* @param inst_starts A vector of number of instructions to start simpoints
	*/

	void scheduleSimpointsInstStop(std::vector<Counter> inst_starts);

	/**
	* Schedule an exit event when any threads in the core reach the max_insts
	* instructions using the scheduleInstStop function.
	*
	* This is used to raise a MAX_INSTS exit event in thegem5 standard library
	*
	* @param max_insts Number of instructions into the future.
	*/
	void scheduleInstStopAnyThread(Counter max_insts);

	/**
	* Get the number of instructions executed by the specified thread
	* on this CPU. Used by Python to control simulation.
	*
	* @param tid Thread monitor
	* @return Number of instructions executed
	*/
	uint64_t getCurrentInstCount(ThreadID tid);

	public:
	/**
	* @{
	* @name PMU Probe points.
	*/

	/**
	* Helper method to trigger PMU probes for a committed
	* instruction.
	*
	* @param inst Instruction that just committed
	* @param pc PC of the instruction that just committed
	*/
	virtual void probeInstCommit(const StaticInstPtr &inst, Addr pc);

	protected:
	/**
	* Helper method to instantiate probe points belonging to this
	* object.
	*
	* @param name Name of the probe point.
	* @return A unique_ptr to the new probe point.
	*/
	probing::PMUUPtr pmuProbePoint(const char *name);

	/**
	* Instruction commit probe point.
	*
	* This probe point is triggered whenever one or more instructions
	* are committed. It is normally triggered once for every
	* instruction. However, CPU models committing bundles of
	* instructions may call notify once for the entire bundle.
	*/
	probing::PMUUPtr ppRetiredInsts;
	probing::PMUUPtr ppRetiredInstsPC;

	/** Retired load instructions */
	probing::PMUUPtr ppRetiredLoads;
	/** Retired store instructions */
	probing::PMUUPtr ppRetiredStores;

	/** Retired branches (any type) */
	probing::PMUUPtr ppRetiredBranches;

	/** CPU cycle counter even if any thread Context is suspended*/
	probing::PMUUPtr ppAllCycles;

	/ CPU cycle counter, only counts if any thread contexts is active /
	probing::PMUUPtr ppActiveCycles;

	/**
	* ProbePoint that signals transitions of threadContexts sets.
	* The ProbePoint reports information through it bool parameter.
	* - If the parameter is true then the last enabled threadContext of the
	* CPU object was disabled.
	* - If the parameter is false then a threadContext was enabled, all the
	* remaining threadContexts are disabled.
	*/
	ProbePointArg<bool> *ppSleeping;
	/** @} */

	enum CPUState
	{
	CPU_STATE_ON,
	CPU_STATE_SLEEP,
	CPU_STATE_WAKEUP
	};

	Cycles previousCycle;
	CPUState previousState;

	/ base method keeping track of cycle progression /
	inline void
	updateCycleCounters(CPUState state)
	{
	uint32_t delta = curCycle() - previousCycle;

	if (previousState == CPU_STATE_ON) {
	ppActiveCycles->notify(delta);
	}

	switch (state) {
	case CPU_STATE_WAKEUP:
	ppSleeping->notify(false);
	break;
	case CPU_STATE_SLEEP:
	ppSleeping->notify(true);
	break;
	default:
	break;
	}

	ppAllCycles->notify(delta);

	previousCycle = curCycle();
	previousState = state;
	}

	// Function tracing
	private:
	bool functionTracingEnabled;
	std::ostream *functionTraceStream;
	Addr currentFunctionStart;
	Addr currentFunctionEnd;
	Tick functionEntryTick;
	void enableFunctionTrace();
	void traceFunctionsInternal(Addr pc);

	private:
	static std::vector<BaseCPU *> cpuList; //!< Static global cpu list

	public:
	void
	traceFunctions(Addr pc)
	{
	if (functionTracingEnabled)
	traceFunctionsInternal(pc);
	}

	static int numSimulatedCPUs() { return cpuList.size(); }
	static Counter
	numSimulatedInsts()
	{
	Counter total = 0;

	int size = cpuList.size();
	for (int i = 0; i < size; ++i)
	total += cpuList[i]->totalInsts();

	return total;
	}

	static Counter
	numSimulatedOps()
	{
	Counter total = 0;

	int size = cpuList.size();
	for (int i = 0; i < size; ++i)
	total += cpuList[i]->totalOps();

	return total;
	}

	public:
	struct BaseCPUStats : public statistics::Group
	{
	BaseCPUStats(statistics::Group *parent);
	// Number of CPU cycles simulated
	statistics::Scalar numCycles;
	statistics::Scalar numWorkItemsStarted;
	statistics::Scalar numWorkItemsCompleted;
	} baseStats;

	private:
	std::vector<AddressMonitor> addressMonitor;

	public:
	void armMonitor(ThreadID tid, Addr address);
	bool mwait(ThreadID tid, PacketPtr pkt);
	void mwaitAtomic(ThreadID tid, ThreadContext tc, BaseMMU mmu);
	AddressMonitor *
	getCpuAddrMonitor(ThreadID tid)
	{
	assert(tid < numThreads);
	return &addressMonitor[tid];
	}

	Cycles syscallRetryLatency;

	/** This function is used to instruct the memory subsystem that a
	* transaction should be aborted and the speculative state should be
	* thrown away. This is called in the transaction's very last breath in
	* the core. Afterwards, the core throws away its speculative state and
	* resumes execution at the point the transaction started, i.e. reverses
	* time. When instruction execution resumes, the core expects the
	* memory subsystem to be in a stable, i.e. pre-speculative, state as
	* well. */
	virtual void
	htmSendAbortSignal(ThreadID tid, uint64_t htm_uid,
	HtmFailureFaultCause cause)
	{
	panic("htmSendAbortSignal not implemented");
	}

	// Enables CPU to enter power gating on a configurable cycle count
	protected:
	void enterPwrGating();

	const Cycles pwrGatingLatency;
	const bool powerGatingOnIdle;
	EventFunctionWrapper enterPwrGatingEvent;
	};

	} // namespace gem5

	#endif // __CPU_BASE_HH__