src/sim/system.hh - arm/gem5 - Git at Google

 /*
  * Copyright (c) 2012, 2014 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.
  *
  * Authors: Steve Reinhardt
  *          Lisa Hsu
  *          Nathan Binkert
  *          Rick Strong
  */

 #ifndef __SYSTEM_HH__
 #define __SYSTEM_HH__

 #include <string>
 #include <unordered_map>
 #include <utility>
 #include <vector>

 #include "arch/isa_traits.hh"
 #include "base/loader/symtab.hh"
 #include "base/statistics.hh"
 #include "config/the_isa.hh"
 #include "enums/MemoryMode.hh"
 #include "mem/mem_object.hh"
 #include "mem/physical.hh"
 #include "mem/port.hh"
 #include "mem/port_proxy.hh"
 #include "params/System.hh"
 #include "sim/futex_map.hh"
 #include "sim/se_signal.hh"

 /**
  * To avoid linking errors with LTO, only include the header if we
  * actually have the definition.
  */
 #if THE_ISA != NULL_ISA
 #include "cpu/pc_event.hh"

 #endif

 class BaseRemoteGDB;
 class KvmVM;
 class ObjectFile;
 class ThreadContext;

 class System : public MemObject
 {
   private:

     /**
      * Private class for the system port which is only used as a
      * master for debug access and for non-structural entities that do
      * not have a port of their own.
      */
     class SystemPort : public MasterPort
     {
       public:

         /**
          * Create a system port with a name and an owner.
          */
         SystemPort(const std::string &_name, MemObject *_owner)
             : MasterPort(_name, _owner)
         { }
         bool recvTimingResp(PacketPtr pkt) override
         { panic("SystemPort does not receive timing!\n"); return false; }
         void recvReqRetry() override
         { panic("SystemPort does not expect retry!\n"); }
     };

     SystemPort _systemPort;

   public:

     /**
      * After all objects have been created and all ports are
      * connected, check that the system port is connected.
      */
     void init() override;

     /**
      * Get a reference to the system port that can be used by
      * non-structural simulation objects like processes or threads, or
      * external entities like loaders and debuggers, etc, to access
      * the memory system.
      *
      * @return a reference to the system port we own
      */
     MasterPort& getSystemPort() { return _systemPort; }

     /**
      * Additional function to return the Port of a memory object.
      */
     BaseMasterPort& getMasterPort(const std::string &if_name,
                                   PortID idx = InvalidPortID) override;

     /** @{ */
     /**
      * Is the system in atomic mode?
      *
      * There are currently two different atomic memory modes:
      * 'atomic', which supports caches; and 'atomic_noncaching', which
      * bypasses caches. The latter is used by hardware virtualized
      * CPUs. SimObjects are expected to use Port::sendAtomic() and
      * Port::recvAtomic() when accessing memory in this mode.
      */
     bool isAtomicMode() const {
         return memoryMode == Enums::atomic ||
             memoryMode == Enums::atomic_noncaching;
     }

     /**
      * Is the system in timing mode?
      *
      * SimObjects are expected to use Port::sendTiming() and
      * Port::recvTiming() when accessing memory in this mode.
      */
     bool isTimingMode() const {
         return memoryMode == Enums::timing;
     }

     /**
      * Should caches be bypassed?
      *
      * Some CPUs need to bypass caches to allow direct memory
      * accesses, which is required for hardware virtualization.
      */
     bool bypassCaches() const {
         return memoryMode == Enums::atomic_noncaching;
     }
     /** @} */

     /** @{ */
     /**
      * Get the memory mode of the system.
      *
      * \warn This should only be used by the Python world. The C++
      * world should use one of the query functions above
      * (isAtomicMode(), isTimingMode(), bypassCaches()).
      */
     Enums::MemoryMode getMemoryMode() const { return memoryMode; }

     /**
      * Change the memory mode of the system.
      *
      * \warn This should only be called by the Python!
      *
      * @param mode Mode to change to (atomic/timing/...)
      */
     void setMemoryMode(Enums::MemoryMode mode);
     /** @} */

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

 #if THE_ISA != NULL_ISA
     PCEventQueue pcEventQueue;
 #endif

     std::vector<ThreadContext *> threadContexts;
     int _numContexts;
     const bool multiThread;

     ThreadContext *getThreadContext(ContextID tid)
     {
         return threadContexts[tid];
     }

     int numContexts()
     {
         assert(_numContexts == (int)threadContexts.size());
         return _numContexts;
     }

     /** Return number of running (non-halted) thread contexts in
      * system.  These threads could be Active or Suspended. */
     int numRunningContexts();

     Addr pagePtr;

     uint64_t init_param;

     /** Port to physical memory used for writing object files into ram at
      * boot.*/
     PortProxy physProxy;

     /** kernel symbol table */
     SymbolTable *kernelSymtab;

     /** Object pointer for the kernel code */
     ObjectFile *kernel;

     /** Additional object files */
     std::vector<ObjectFile *> kernelExtras;

     /** Beginning of kernel code */
     Addr kernelStart;

     /** End of kernel code */
     Addr kernelEnd;

     /** Entry point in the kernel to start at */
     Addr kernelEntry;

     /** Mask that should be anded for binary/symbol loading.
      * This allows one two different OS requirements for the same ISA to be
      * handled.  Some OSes are compiled for a virtual address and need to be
      * loaded into physical memory that starts at address 0, while other
      * bare metal tools generate images that start at address 0.
      */
     Addr loadAddrMask;

     /** Offset that should be used for binary/symbol loading.
      * This further allows more flexibility than the loadAddrMask allows alone
      * in loading kernels and similar. The loadAddrOffset is applied after the
      * loadAddrMask.
      */
     Addr loadAddrOffset;

   public:
     /**
      * Get a pointer to the Kernel Virtual Machine (KVM) SimObject,
      * if present.
      */
     KvmVM* getKvmVM() {
         return kvmVM;
     }

     /** Verify gem5 configuration will support KVM emulation */
     bool validKvmEnvironment() const;

     /** Get a pointer to access the physical memory of the system */
     PhysicalMemory& getPhysMem() { return physmem; }

     /** Amount of physical memory that is still free */
     Addr freeMemSize() const;

     /** Amount of physical memory that exists */
     Addr memSize() const;

     /**
      * Check if a physical address is within a range of a memory that
      * is part of the global address map.
      *
      * @param addr A physical address
      * @return Whether the address corresponds to a memory
      */
     bool isMemAddr(Addr addr) const;

     /**
      * Get the architecture.
      */
     Arch getArch() const { return Arch::TheISA; }

      /**
      * Get the page bytes for the ISA.
      */
     Addr getPageBytes() const { return TheISA::PageBytes; }

     /**
      * Get the number of bits worth of in-page address for the ISA.
      */
     Addr getPageShift() const { return TheISA::PageShift; }

     /**
      * The thermal model used for this system (if any).
      */
     ThermalModel * getThermalModel() const { return thermalModel; }

   protected:

     KvmVM *const kvmVM;

     PhysicalMemory physmem;

     Enums::MemoryMode memoryMode;

     const unsigned int _cacheLineSize;

     uint64_t workItemsBegin;
     uint64_t workItemsEnd;
     uint32_t numWorkIds;
     std::vector<bool> activeCpus;

     /** This array is a per-system list of all devices capable of issuing a
      * memory system request and an associated string for each master id.
      * It's used to uniquely id any master in the system by name for things
      * like cache statistics.
      */
     std::vector<std::string> masterIds;

     ThermalModel * thermalModel;

   public:

     /** Request an id used to create a request object in the system. All objects
      * that intend to issues requests into the memory system must request an id
      * in the init() phase of startup. All master ids must be fixed by the
      * regStats() phase that immediately precedes it. This allows objects in
      * the memory system to understand how many masters may exist and
      * appropriately name the bins of their per-master stats before the stats
      * are finalized
      */
     MasterID getMasterId(std::string req_name);

     /** Get the name of an object for a given request id.
      */
     std::string getMasterName(MasterID master_id);

     /** Get the number of masters registered in the system */
     MasterID maxMasters()
     {
         return masterIds.size();
     }

     void regStats() override;
     /**
      * Called by pseudo_inst to track the number of work items started by this
      * system.
      */
     uint64_t
     incWorkItemsBegin()
     {
         return ++workItemsBegin;
     }

     /**
      * Called by pseudo_inst to track the number of work items completed by
      * this system.
      */
     uint64_t
     incWorkItemsEnd()
     {
         return ++workItemsEnd;
     }

     /**
      * Called by pseudo_inst to mark the cpus actively executing work items.
      * Returns the total number of cpus that have executed work item begin or
      * ends.
      */
     int
     markWorkItem(int index)
     {
         int count = 0;
         assert(index < activeCpus.size());
         activeCpus[index] = true;
         for (std::vector<bool>::iterator i = activeCpus.begin();
              i < activeCpus.end(); i++) {
             if (*i) count++;
         }
         return count;
     }

     inline void workItemBegin(uint32_t tid, uint32_t workid)
     {
         std::pair<uint32_t,uint32_t> p(tid, workid);
         lastWorkItemStarted[p] = curTick();
     }

     void workItemEnd(uint32_t tid, uint32_t workid);

     /**
      * Fix up an address used to match PCs for hooking simulator
      * events on to target function executions.  See comment in
      * system.cc for details.
      */
     virtual Addr fixFuncEventAddr(Addr addr)
     {
         panic("Base fixFuncEventAddr not implemented.\n");
     }

     /** @{ */
     /**
      * Add a function-based event to the given function, to be looked
      * up in the specified symbol table.
      *
      * The ...OrPanic flavor of the method causes the simulator to
      * panic if the symbol can't be found.
      *
      * @param symtab Symbol table to use for look up.
      * @param lbl Function to hook the event to.
      * @param desc Description to be passed to the event.
      * @param args Arguments to be forwarded to the event constructor.
      */
     template <class T, typename... Args>
     T *addFuncEvent(const SymbolTable *symtab, const char *lbl,
                     const std::string &desc, Args... args)
     {
         Addr addr M5_VAR_USED = 0; // initialize only to avoid compiler warning

 #if THE_ISA != NULL_ISA
         if (symtab->findAddress(lbl, addr)) {
             T *ev = new T(&pcEventQueue, desc, fixFuncEventAddr(addr),
                           std::forward<Args>(args)...);
             return ev;
         }
 #endif

         return NULL;
     }

     template <class T>
     T *addFuncEvent(const SymbolTable *symtab, const char *lbl)
     {
         return addFuncEvent<T>(symtab, lbl, lbl);
     }

     template <class T, typename... Args>
     T *addFuncEventOrPanic(const SymbolTable *symtab, const char *lbl,
                            Args... args)
     {
         T *e(addFuncEvent<T>(symtab, lbl, std::forward<Args>(args)...));
         if (!e)
             panic("Failed to find symbol '%s'", lbl);
         return e;
     }
     /** @} */

     /** @{ */
     /**
      * Add a function-based event to a kernel symbol.
      *
      * These functions work like their addFuncEvent() and
      * addFuncEventOrPanic() counterparts. The only difference is that
      * they automatically use the kernel symbol table. All arguments
      * are forwarded to the underlying method.
      *
      * @see addFuncEvent()
      * @see addFuncEventOrPanic()
      *
      * @param lbl Function to hook the event to.
      * @param args Arguments to be passed to addFuncEvent
      */
     template <class T, typename... Args>
     T *addKernelFuncEvent(const char *lbl, Args... args)
     {
         return addFuncEvent<T>(kernelSymtab, lbl,
                                std::forward<Args>(args)...);
     }

     template <class T, typename... Args>
     T *addKernelFuncEventOrPanic(const char *lbl, Args... args)
     {
         T *e(addFuncEvent<T>(kernelSymtab, lbl,
                              std::forward<Args>(args)...));
         if (!e)
             panic("Failed to find kernel symbol '%s'", lbl);
         return e;
     }
     /** @} */

   public:
     std::vector<BaseRemoteGDB *> remoteGDB;
     bool breakpoint();

   public:
     typedef SystemParams Params;

   protected:
     Params *_params;

   public:
     System(Params *p);
     ~System();

     void initState() override;

     const Params *params() const { return (const Params *)_params; }

   public:

     /**
      * Returns the address the kernel starts at.
      * @return address the kernel starts at
      */
     Addr getKernelStart() const { return kernelStart; }

     /**
      * Returns the address the kernel ends at.
      * @return address the kernel ends at
      */
     Addr getKernelEnd() const { return kernelEnd; }

     /**
      * Returns the address the entry point to the kernel code.
      * @return entry point of the kernel code
      */
     Addr getKernelEntry() const { return kernelEntry; }

     /// Allocate npages contiguous unused physical pages
     /// @return Starting address of first page
     Addr allocPhysPages(int npages);

     ContextID registerThreadContext(ThreadContext *tc,
                                     ContextID assigned = InvalidContextID);
     void replaceThreadContext(ThreadContext *tc, ContextID context_id);

     void serialize(CheckpointOut &cp) const override;
     void unserialize(CheckpointIn &cp) override;

     void drainResume() override;

   public:
     Counter totalNumInsts;
     EventQueue instEventQueue;
     std::map<std::pair<uint32_t,uint32_t>, Tick>  lastWorkItemStarted;
     std::map<uint32_t, Stats::Histogram*> workItemStats;

     ////////////////////////////////////////////
     //
     // STATIC GLOBAL SYSTEM LIST
     //
     ////////////////////////////////////////////

     static std::vector<System *> systemList;
     static int numSystemsRunning;

     static void printSystems();

     FutexMap futexMap;

     static const int maxPID = 32768;

     /** Process set to track which PIDs have already been allocated */
     std::set<int> PIDs;

     // By convention, all signals are owned by the receiving process. The
     // receiver will delete the signal upon reception.
     std::list<BasicSignal> signalList;

   protected:

     /**
      * If needed, serialize additional symbol table entries for a
      * specific subclass of this system. Currently this is used by
      * Alpha and MIPS.
      *
      * @param os stream to serialize to
      */
     virtual void serializeSymtab(CheckpointOut &os) const {}

     /**
      * If needed, unserialize additional symbol table entries for a
      * specific subclass of this system.
      *
      * @param cp checkpoint to unserialize from
      * @param section relevant section in the checkpoint
      */
     virtual void unserializeSymtab(CheckpointIn &cp) {}

 };

 void printSystems();

 #endif // __SYSTEM_HH__
	/*
	* Copyright (c) 2012, 2014 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.
	*
	* Authors: Steve Reinhardt
	* Lisa Hsu
	* Nathan Binkert
	* Rick Strong
	*/

	#ifndef __SYSTEM_HH__
	#define __SYSTEM_HH__

	#include <string>
	#include <unordered_map>
	#include <utility>
	#include <vector>

	#include "arch/isa_traits.hh"
	#include "base/loader/symtab.hh"
	#include "base/statistics.hh"
	#include "config/the_isa.hh"
	#include "enums/MemoryMode.hh"
	#include "mem/mem_object.hh"
	#include "mem/physical.hh"
	#include "mem/port.hh"
	#include "mem/port_proxy.hh"
	#include "params/System.hh"
	#include "sim/futex_map.hh"
	#include "sim/se_signal.hh"

	/**
	* To avoid linking errors with LTO, only include the header if we
	* actually have the definition.
	*/
	#if THE_ISA != NULL_ISA
	#include "cpu/pc_event.hh"

	#endif

	class BaseRemoteGDB;
	class KvmVM;
	class ObjectFile;
	class ThreadContext;

	class System : public MemObject
	{
	private:

	/**
	* Private class for the system port which is only used as a
	* master for debug access and for non-structural entities that do
	* not have a port of their own.
	*/
	class SystemPort : public MasterPort
	{
	public:

	/**
	* Create a system port with a name and an owner.
	*/
	SystemPort(const std::string &_name, MemObject *_owner)
	: MasterPort(_name, _owner)
	{ }
	bool recvTimingResp(PacketPtr pkt) override
	{ panic("SystemPort does not receive timing!\n"); return false; }
	void recvReqRetry() override
	{ panic("SystemPort does not expect retry!\n"); }
	};

	SystemPort _systemPort;

	public:

	/**
	* After all objects have been created and all ports are
	* connected, check that the system port is connected.
	*/
	void init() override;

	/**
	* Get a reference to the system port that can be used by
	* non-structural simulation objects like processes or threads, or
	* external entities like loaders and debuggers, etc, to access
	* the memory system.
	*
	* @return a reference to the system port we own
	*/
	MasterPort& getSystemPort() { return _systemPort; }

	/**
	* Additional function to return the Port of a memory object.
	*/
	BaseMasterPort& getMasterPort(const std::string &if_name,
	PortID idx = InvalidPortID) override;

	/** @{ */
	/**
	* Is the system in atomic mode?
	*
	* There are currently two different atomic memory modes:
	* 'atomic', which supports caches; and 'atomic_noncaching', which
	* bypasses caches. The latter is used by hardware virtualized
	* CPUs. SimObjects are expected to use Port::sendAtomic() and
	* Port::recvAtomic() when accessing memory in this mode.
	*/
	bool isAtomicMode() const {
	return memoryMode == Enums::atomic \|\|
	memoryMode == Enums::atomic_noncaching;
	}

	/**
	* Is the system in timing mode?
	*
	* SimObjects are expected to use Port::sendTiming() and
	* Port::recvTiming() when accessing memory in this mode.
	*/
	bool isTimingMode() const {
	return memoryMode == Enums::timing;
	}

	/**
	* Should caches be bypassed?
	*
	* Some CPUs need to bypass caches to allow direct memory
	* accesses, which is required for hardware virtualization.
	*/
	bool bypassCaches() const {
	return memoryMode == Enums::atomic_noncaching;
	}
	/** @} */

	/** @{ */
	/**
	* Get the memory mode of the system.
	*
	* \warn This should only be used by the Python world. The C++
	* world should use one of the query functions above
	* (isAtomicMode(), isTimingMode(), bypassCaches()).
	*/
	Enums::MemoryMode getMemoryMode() const { return memoryMode; }

	/**
	* Change the memory mode of the system.
	*
	* \warn This should only be called by the Python!
	*
	* @param mode Mode to change to (atomic/timing/...)
	*/
	void setMemoryMode(Enums::MemoryMode mode);
	/** @} */

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

	#if THE_ISA != NULL_ISA
	PCEventQueue pcEventQueue;
	#endif

	std::vector<ThreadContext *> threadContexts;
	int _numContexts;
	const bool multiThread;

	ThreadContext *getThreadContext(ContextID tid)
	{
	return threadContexts[tid];
	}

	int numContexts()
	{
	assert(_numContexts == (int)threadContexts.size());
	return _numContexts;
	}

	/** Return number of running (non-halted) thread contexts in
	* system. These threads could be Active or Suspended. */
	int numRunningContexts();

	Addr pagePtr;

	uint64_t init_param;

	/** Port to physical memory used for writing object files into ram at
	* boot.*/
	PortProxy physProxy;

	/** kernel symbol table */
	SymbolTable *kernelSymtab;

	/** Object pointer for the kernel code */
	ObjectFile *kernel;

	/** Additional object files */
	std::vector<ObjectFile *> kernelExtras;

	/** Beginning of kernel code */
	Addr kernelStart;

	/** End of kernel code */
	Addr kernelEnd;

	/** Entry point in the kernel to start at */
	Addr kernelEntry;

	/** Mask that should be anded for binary/symbol loading.
	* This allows one two different OS requirements for the same ISA to be
	* handled. Some OSes are compiled for a virtual address and need to be
	* loaded into physical memory that starts at address 0, while other
	* bare metal tools generate images that start at address 0.
	*/
	Addr loadAddrMask;

	/** Offset that should be used for binary/symbol loading.
	* This further allows more flexibility than the loadAddrMask allows alone
	* in loading kernels and similar. The loadAddrOffset is applied after the
	* loadAddrMask.
	*/
	Addr loadAddrOffset;

	public:
	/**
	* Get a pointer to the Kernel Virtual Machine (KVM) SimObject,
	* if present.
	*/
	KvmVM* getKvmVM() {
	return kvmVM;
	}

	/** Verify gem5 configuration will support KVM emulation */
	bool validKvmEnvironment() const;

	/** Get a pointer to access the physical memory of the system */
	PhysicalMemory& getPhysMem() { return physmem; }

	/** Amount of physical memory that is still free */
	Addr freeMemSize() const;

	/** Amount of physical memory that exists */
	Addr memSize() const;

	/**
	* Check if a physical address is within a range of a memory that
	* is part of the global address map.
	*
	* @param addr A physical address
	* @return Whether the address corresponds to a memory
	*/
	bool isMemAddr(Addr addr) const;

	/**
	* Get the architecture.
	*/
	Arch getArch() const { return Arch::TheISA; }

	/**
	* Get the page bytes for the ISA.
	*/
	Addr getPageBytes() const { return TheISA::PageBytes; }

	/**
	* Get the number of bits worth of in-page address for the ISA.
	*/
	Addr getPageShift() const { return TheISA::PageShift; }

	/**
	* The thermal model used for this system (if any).
	*/
	ThermalModel * getThermalModel() const { return thermalModel; }

	protected:

	KvmVM *const kvmVM;

	PhysicalMemory physmem;

	Enums::MemoryMode memoryMode;

	const unsigned int _cacheLineSize;

	uint64_t workItemsBegin;
	uint64_t workItemsEnd;
	uint32_t numWorkIds;
	std::vector<bool> activeCpus;

	/** This array is a per-system list of all devices capable of issuing a
	* memory system request and an associated string for each master id.
	* It's used to uniquely id any master in the system by name for things
	* like cache statistics.
	*/
	std::vector<std::string> masterIds;

	ThermalModel * thermalModel;

	public:

	/** Request an id used to create a request object in the system. All objects
	* that intend to issues requests into the memory system must request an id
	* in the init() phase of startup. All master ids must be fixed by the
	* regStats() phase that immediately precedes it. This allows objects in
	* the memory system to understand how many masters may exist and
	* appropriately name the bins of their per-master stats before the stats
	* are finalized
	*/
	MasterID getMasterId(std::string req_name);

	/** Get the name of an object for a given request id.
	*/
	std::string getMasterName(MasterID master_id);

	/** Get the number of masters registered in the system */
	MasterID maxMasters()
	{
	return masterIds.size();
	}

	void regStats() override;
	/**
	* Called by pseudo_inst to track the number of work items started by this
	* system.
	*/
	uint64_t
	incWorkItemsBegin()
	{
	return ++workItemsBegin;
	}

	/**
	* Called by pseudo_inst to track the number of work items completed by
	* this system.
	*/
	uint64_t
	incWorkItemsEnd()
	{
	return ++workItemsEnd;
	}

	/**
	* Called by pseudo_inst to mark the cpus actively executing work items.
	* Returns the total number of cpus that have executed work item begin or
	* ends.
	*/
	int
	markWorkItem(int index)
	{
	int count = 0;
	assert(index < activeCpus.size());
	activeCpus[index] = true;
	for (std::vector<bool>::iterator i = activeCpus.begin();
	i < activeCpus.end(); i++) {
	if (*i) count++;
	}
	return count;
	}

	inline void workItemBegin(uint32_t tid, uint32_t workid)
	{
	std::pair<uint32_t,uint32_t> p(tid, workid);
	lastWorkItemStarted[p] = curTick();
	}

	void workItemEnd(uint32_t tid, uint32_t workid);

	/**
	* Fix up an address used to match PCs for hooking simulator
	* events on to target function executions. See comment in
	* system.cc for details.
	*/
	virtual Addr fixFuncEventAddr(Addr addr)
	{
	panic("Base fixFuncEventAddr not implemented.\n");
	}

	/** @{ */
	/**
	* Add a function-based event to the given function, to be looked
	* up in the specified symbol table.
	*
	* The ...OrPanic flavor of the method causes the simulator to
	* panic if the symbol can't be found.
	*
	* @param symtab Symbol table to use for look up.
	* @param lbl Function to hook the event to.
	* @param desc Description to be passed to the event.
	* @param args Arguments to be forwarded to the event constructor.
	*/
	template <class T, typename... Args>
	T addFuncEvent(const SymbolTable symtab, const char *lbl,
	const std::string &desc, Args... args)
	{
	Addr addr M5_VAR_USED = 0; // initialize only to avoid compiler warning

	#if THE_ISA != NULL_ISA
	if (symtab->findAddress(lbl, addr)) {
	T *ev = new T(&pcEventQueue, desc, fixFuncEventAddr(addr),
	std::forward<Args>(args)...);
	return ev;
	}
	#endif

	return NULL;
	}

	template <class T>
	T addFuncEvent(const SymbolTable symtab, const char *lbl)
	{
	return addFuncEvent<T>(symtab, lbl, lbl);
	}

	template <class T, typename... Args>
	T addFuncEventOrPanic(const SymbolTable symtab, const char *lbl,
	Args... args)
	{
	T *e(addFuncEvent<T>(symtab, lbl, std::forward<Args>(args)...));
	if (!e)
	panic("Failed to find symbol '%s'", lbl);
	return e;
	}
	/** @} */

	/** @{ */
	/**
	* Add a function-based event to a kernel symbol.
	*
	* These functions work like their addFuncEvent() and
	* addFuncEventOrPanic() counterparts. The only difference is that
	* they automatically use the kernel symbol table. All arguments
	* are forwarded to the underlying method.
	*
	* @see addFuncEvent()
	* @see addFuncEventOrPanic()
	*
	* @param lbl Function to hook the event to.
	* @param args Arguments to be passed to addFuncEvent
	*/
	template <class T, typename... Args>
	T addKernelFuncEvent(const char lbl, Args... args)
	{
	return addFuncEvent<T>(kernelSymtab, lbl,
	std::forward<Args>(args)...);
	}

	template <class T, typename... Args>
	T addKernelFuncEventOrPanic(const char lbl, Args... args)
	{
	T *e(addFuncEvent<T>(kernelSymtab, lbl,
	std::forward<Args>(args)...));
	if (!e)
	panic("Failed to find kernel symbol '%s'", lbl);
	return e;
	}
	/** @} */

	public:
	std::vector<BaseRemoteGDB *> remoteGDB;
	bool breakpoint();

	public:
	typedef SystemParams Params;

	protected:
	Params *_params;

	public:
	System(Params *p);
	~System();

	void initState() override;

	const Params params() const { return (const Params )_params; }

	public:

	/**
	* Returns the address the kernel starts at.
	* @return address the kernel starts at
	*/
	Addr getKernelStart() const { return kernelStart; }

	/**
	* Returns the address the kernel ends at.
	* @return address the kernel ends at
	*/
	Addr getKernelEnd() const { return kernelEnd; }

	/**
	* Returns the address the entry point to the kernel code.
	* @return entry point of the kernel code
	*/
	Addr getKernelEntry() const { return kernelEntry; }

	/// Allocate npages contiguous unused physical pages
	/// @return Starting address of first page
	Addr allocPhysPages(int npages);

	ContextID registerThreadContext(ThreadContext *tc,
	ContextID assigned = InvalidContextID);
	void replaceThreadContext(ThreadContext *tc, ContextID context_id);

	void serialize(CheckpointOut &cp) const override;
	void unserialize(CheckpointIn &cp) override;

	void drainResume() override;

	public:
	Counter totalNumInsts;
	EventQueue instEventQueue;
	std::map<std::pair<uint32_t,uint32_t>, Tick> lastWorkItemStarted;
	std::map<uint32_t, Stats::Histogram*> workItemStats;

	////////////////////////////////////////////
	//
	// STATIC GLOBAL SYSTEM LIST
	//
	////////////////////////////////////////////

	static std::vector<System *> systemList;
	static int numSystemsRunning;

	static void printSystems();

	FutexMap futexMap;

	static const int maxPID = 32768;

	/** Process set to track which PIDs have already been allocated */
	std::set<int> PIDs;

	// By convention, all signals are owned by the receiving process. The
	// receiver will delete the signal upon reception.
	std::list<BasicSignal> signalList;

	protected:

	/**
	* If needed, serialize additional symbol table entries for a
	* specific subclass of this system. Currently this is used by
	* Alpha and MIPS.
	*
	* @param os stream to serialize to
	*/
	virtual void serializeSymtab(CheckpointOut &os) const {}

	/**
	* If needed, unserialize additional symbol table entries for a
	* specific subclass of this system.
	*
	* @param cp checkpoint to unserialize from
	* @param section relevant section in the checkpoint
	*/
	virtual void unserializeSymtab(CheckpointIn &cp) {}

	};

	void printSystems();

	#endif // __SYSTEM_HH__