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

 /*
  * Copyright (c) 2012, 2014, 2018 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 __SYSTEM_HH__
 #define __SYSTEM_HH__

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

 #include "arch/page_size.hh"
 #include "base/loader/memory_image.hh"
 #include "base/loader/symtab.hh"
 #include "base/statistics.hh"
 #include "config/the_isa.hh"
 #include "cpu/pc_event.hh"
 #include "enums/MemoryMode.hh"
 #include "mem/mem_requestor.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/mem_pool.hh"
 #include "sim/redirect_path.hh"
 #include "sim/se_signal.hh"
 #include "sim/sim_object.hh"
 #include "sim/workload.hh"

 namespace gem5
 {

 class BaseRemoteGDB;
 class KvmVM;
 class ThreadContext;

 class System : public SimObject, public PCEventScope
 {
   private:

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

         /**
          * Create a system port with a name and an owner.
          */
         SystemPort(const std::string &_name, SimObject *_owner)
             : RequestPort(_name, _owner)
         { }

         bool
         recvTimingResp(PacketPtr pkt) override
         {
             panic("SystemPort does not receive timing!");
         }

         void
         recvReqRetry() override
         {
             panic("SystemPort does not expect retry!");
         }
     };

     std::list<PCEvent *> liveEvents;
     SystemPort _systemPort;

     // Map of memory address ranges for devices with their own backing stores
     std::unordered_map<RequestorID, std::vector<memory::AbstractMemory *>>
         deviceMemMap;

   public:

     class Threads
     {
       private:
         struct Thread
         {
             ThreadContext *context = nullptr;
             bool active = false;
             Event *resumeEvent = nullptr;

             void resume();
             std::string name() const;
             void quiesce() const;
         };

         std::vector<Thread> threads;

         Thread &
         thread(ContextID id)
         {
             assert(id < size());
             return threads[id];
         }

         const Thread &
         thread(ContextID id) const
         {
             assert(id < size());
             return threads[id];
         }

         void insert(ThreadContext *tc, ContextID id=InvalidContextID);
         void replace(ThreadContext *tc, ContextID id);

         friend class System;

       public:
         class const_iterator
         {
           private:
             const Threads &threads;
             int pos;

             friend class Threads;

             const_iterator(const Threads &_threads, int _pos) :
                 threads(_threads), pos(_pos)
             {}

           public:
             const_iterator(const const_iterator &) = default;
             const_iterator &operator = (const const_iterator &) = default;

             using iterator_category = std::forward_iterator_tag;
             using value_type = ThreadContext *;
             using difference_type = int;
             using pointer = const value_type *;
             using reference = const value_type &;

             const_iterator &
             operator ++ ()
             {
                 pos++;
                 return *this;
             }

             const_iterator
             operator ++ (int)
             {
                 return const_iterator(threads, pos++);
             }

             reference operator * () { return threads.thread(pos).context; }
             pointer operator -> () { return &threads.thread(pos).context; }

             bool
             operator == (const const_iterator &other) const
             {
                 return &threads == &other.threads && pos == other.pos;
             }

             bool
             operator != (const const_iterator &other) const
             {
                 return !(*this == other);
             }
         };

         ThreadContext *findFree();

         ThreadContext *
         operator [](ContextID id) const
         {
             return thread(id).context;
         }

         void markActive(ContextID id) { thread(id).active = true; }

         int size() const { return threads.size(); }
         bool empty() const { return threads.empty(); }
         int numRunning() const;
         int
         numActive() const
         {
             int count = 0;
             for (auto &thread: threads) {
                 if (thread.active)
                     count++;
             }
             return count;
         }

         void quiesce(ContextID id);
         void quiesceTick(ContextID id, Tick when);

         const_iterator begin() const { return const_iterator(*this, 0); }
         const_iterator end() const { return const_iterator(*this, size()); }
     };

     /**
      * 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
      */
     RequestPort& getSystemPort() { return _systemPort; }

     /**
      * Additional function to return the Port of a memory object.
      */
     Port &getPort(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; }

     Threads threads;

     const bool multiThread;

     using SimObject::schedule;

     bool schedule(PCEvent *event) override;
     bool remove(PCEvent *event) override;

     /** Memory allocation objects for all physical memories in the system. */
     std::vector<MemPool> memPools;

     uint64_t init_param;

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

     /** OS kernel */
     Workload *workload = nullptr;

   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 */
     memory::PhysicalMemory& getPhysMem() { return physmem; }

     /** Amount of physical memory that is still free */
     Addr freeMemSize(int poolID = 0) const;

     /** Amount of physical memory that exists */
     Addr memSize(int poolID = 0) 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;

     /**
      * Add a physical memory range for a device. The ranges added here will
      * be considered a non-PIO memory address if the requestorId of the packet
      * and range match something in the device memory map.
      */
     void addDeviceMemory(RequestorID requestorId,
         memory::AbstractMemory *deviceMemory);

     /**
      * Similar to isMemAddr but for devices. Checks if a physical address
      * of the packet match an address range of a device corresponding to the
      * RequestorId of the request.
      */
     bool isDeviceMemAddr(const PacketPtr& pkt) const;

     /**
      * Return a pointer to the device memory.
      */
     memory::AbstractMemory *getDeviceMemory(const PacketPtr& pkt) const;

     /*
      * Return the list of address ranges backed by a shadowed ROM.
      *
      * @return List of address ranges backed by a shadowed ROM
      */
     AddrRangeList getShadowRomRanges() const { return ShadowRomRanges; }

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

     /**
      * Get the guest byte order.
      */
     ByteOrder
     getGuestByteOrder() const
     {
         return params().byte_order;
     }

      /**
      * 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 = nullptr;

     memory::PhysicalMemory physmem;

     AddrRangeList ShadowRomRanges;

     enums::MemoryMode memoryMode;

     const unsigned int _cacheLineSize;

     uint64_t workItemsBegin = 0;
     uint64_t workItemsEnd = 0;
     uint32_t numWorkIds;

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

     ThermalModel * thermalModel;

   protected:
     /**
      * Strips off the system name from a requestor name
      */
     std::string stripSystemName(const std::string& requestor_name) const;

   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 requestor ids must be fixed by the
      * regStats() phase that immediately precedes it. This allows objects in
      * the memory system to understand how many requestors may exist and
      * appropriately name the bins of their per-requestor stats before the
      * stats are finalized.
      *
      * Registers a RequestorID:
      * This method takes two parameters, one of which is optional.
      * The first one is the requestor object, and it is compulsory; in case
      * a object has multiple (sub)requestors, a second parameter must be
      * provided and it contains the name of the subrequestor. The method will
      * create a requestor's name by concatenating the SimObject name with the
      * eventual subrequestor string, separated by a dot.
      *
      * As an example:
      * For a cpu having two requestors: a data requestor and an
      * instruction requestor,
      * the method must be called twice:
      *
      * instRequestorId = getRequestorId(cpu, "inst");
      * dataRequestorId = getRequestorId(cpu, "data");
      *
      * and the requestors' names will be:
      * - "cpu.inst"
      * - "cpu.data"
      *
      * @param requestor SimObject related to the requestor
      * @param subrequestor String containing the subrequestor's name
      * @return the requestor's ID.
      */
     RequestorID getRequestorId(const SimObject* requestor,
                          std::string subrequestor={});

     /**
      * Registers a GLOBAL RequestorID, which is a RequestorID not related
      * to any particular SimObject; since no SimObject is passed,
      * the requestor gets registered by providing the full requestor name.
      *
      * @param requestorName full name of the requestor
      * @return the requestor's ID.
      */
     RequestorID getGlobalRequestorId(const std::string& requestor_name);

     /**
      * Get the name of an object for a given request id.
      */
     std::string getRequestorName(RequestorID requestor_id);

     /**
      * Looks up the RequestorID for a given SimObject
      * returns an invalid RequestorID (invldRequestorId) if not found.
      */
     RequestorID lookupRequestorId(const SimObject* obj) const;

     /**
      * Looks up the RequestorID for a given object name string
      * returns an invalid RequestorID (invldRequestorId) if not found.
      */
     RequestorID lookupRequestorId(const std::string& name) const;

     /** Get the number of requestors registered in the system */
     RequestorID maxRequestors() { return requestors.size(); }

   protected:
     /** helper function for getRequestorId */
     RequestorID _getRequestorId(const SimObject* requestor,
                           const std::string& requestor_name);

     /**
      * Helper function for constructing the full (sub)requestor name
      * by providing the root requestor and the relative subrequestor name.
      */
     std::string leafRequestorName(const SimObject* requestor,
                                const std::string& subrequestor);

   public:

     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)
     {
         threads.markActive(index);
         return threads.numActive();
     }

     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);

     /* Returns whether we successfully trapped into GDB. */
     bool trapToGdb(int signal, ContextID ctx_id) const;

   protected:
     /**
      * Range for memory-mapped m5 pseudo ops. The range will be
      * invalid/empty if disabled.
      */
     const AddrRange _m5opRange;

   public:
     PARAMS(System);

     System(const Params &p);
     ~System();

     /**
      * Range used by memory-mapped m5 pseudo-ops if enabled. Returns
      * an invalid/empty range if disabled.
      */
     const AddrRange &m5opRange() const { return _m5opRange; }

   public:

     /// Allocate npages contiguous unused physical pages
     /// @return Starting address of first page
     Addr allocPhysPages(int npages, int poolID = 0);

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

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

   public:
     std::map<std::pair<uint32_t, uint32_t>, Tick>  lastWorkItemStarted;
     std::map<uint32_t, statistics::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;

     // Used by syscall-emulation mode. This member contains paths which need
     // to be redirected to the faux-filesystem (a duplicate filesystem
     // intended to replace certain files on the host filesystem).
     std::vector<RedirectPath*> redirectPaths;
 };

 void printSystems();

 } // namespace gem5

 #endif // __SYSTEM_HH__
	/*
	* Copyright (c) 2012, 2014, 2018 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 __SYSTEM_HH__
	#define __SYSTEM_HH__

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

	#include "arch/page_size.hh"
	#include "base/loader/memory_image.hh"
	#include "base/loader/symtab.hh"
	#include "base/statistics.hh"
	#include "config/the_isa.hh"
	#include "cpu/pc_event.hh"
	#include "enums/MemoryMode.hh"
	#include "mem/mem_requestor.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/mem_pool.hh"
	#include "sim/redirect_path.hh"
	#include "sim/se_signal.hh"
	#include "sim/sim_object.hh"
	#include "sim/workload.hh"

	namespace gem5
	{

	class BaseRemoteGDB;
	class KvmVM;
	class ThreadContext;

	class System : public SimObject, public PCEventScope
	{
	private:

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

	/**
	* Create a system port with a name and an owner.
	*/
	SystemPort(const std::string &_name, SimObject *_owner)
	: RequestPort(_name, _owner)
	{ }

	bool
	recvTimingResp(PacketPtr pkt) override
	{
	panic("SystemPort does not receive timing!");
	}

	void
	recvReqRetry() override
	{
	panic("SystemPort does not expect retry!");
	}
	};

	std::list<PCEvent *> liveEvents;
	SystemPort _systemPort;

	// Map of memory address ranges for devices with their own backing stores
	std::unordered_map<RequestorID, std::vector<memory::AbstractMemory *>>
	deviceMemMap;

	public:

	class Threads
	{
	private:
	struct Thread
	{
	ThreadContext *context = nullptr;
	bool active = false;
	Event *resumeEvent = nullptr;

	void resume();
	std::string name() const;
	void quiesce() const;
	};

	std::vector<Thread> threads;

	Thread &
	thread(ContextID id)
	{
	assert(id < size());
	return threads[id];
	}

	const Thread &
	thread(ContextID id) const
	{
	assert(id < size());
	return threads[id];
	}

	void insert(ThreadContext *tc, ContextID id=InvalidContextID);
	void replace(ThreadContext *tc, ContextID id);

	friend class System;

	public:
	class const_iterator
	{
	private:
	const Threads &threads;
	int pos;

	friend class Threads;

	const_iterator(const Threads &_threads, int _pos) :
	threads(_threads), pos(_pos)
	{}

	public:
	const_iterator(const const_iterator &) = default;
	const_iterator &operator = (const const_iterator &) = default;

	using iterator_category = std::forward_iterator_tag;
	using value_type = ThreadContext *;
	using difference_type = int;
	using pointer = const value_type *;
	using reference = const value_type &;

	const_iterator &
	operator ++ ()
	{
	pos++;
	return *this;
	}

	const_iterator
	operator ++ (int)
	{
	return const_iterator(threads, pos++);
	}

	reference operator * () { return threads.thread(pos).context; }
	pointer operator -> () { return &threads.thread(pos).context; }

	bool
	operator == (const const_iterator &other) const
	{
	return &threads == &other.threads && pos == other.pos;
	}

	bool
	operator != (const const_iterator &other) const
	{
	return !(*this == other);
	}
	};

	ThreadContext *findFree();

	ThreadContext *
	operator [](ContextID id) const
	{
	return thread(id).context;
	}

	void markActive(ContextID id) { thread(id).active = true; }

	int size() const { return threads.size(); }
	bool empty() const { return threads.empty(); }
	int numRunning() const;
	int
	numActive() const
	{
	int count = 0;
	for (auto &thread: threads) {
	if (thread.active)
	count++;
	}
	return count;
	}

	void quiesce(ContextID id);
	void quiesceTick(ContextID id, Tick when);

	const_iterator begin() const { return const_iterator(*this, 0); }
	const_iterator end() const { return const_iterator(*this, size()); }
	};

	/**
	* 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
	*/
	RequestPort& getSystemPort() { return _systemPort; }

	/**
	* Additional function to return the Port of a memory object.
	*/
	Port &getPort(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; }

	Threads threads;

	const bool multiThread;

	using SimObject::schedule;

	bool schedule(PCEvent *event) override;
	bool remove(PCEvent *event) override;

	/** Memory allocation objects for all physical memories in the system. */
	std::vector<MemPool> memPools;

	uint64_t init_param;

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

	/** OS kernel */
	Workload *workload = nullptr;

	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 */
	memory::PhysicalMemory& getPhysMem() { return physmem; }

	/** Amount of physical memory that is still free */
	Addr freeMemSize(int poolID = 0) const;

	/** Amount of physical memory that exists */
	Addr memSize(int poolID = 0) 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;

	/**
	* Add a physical memory range for a device. The ranges added here will
	* be considered a non-PIO memory address if the requestorId of the packet
	* and range match something in the device memory map.
	*/
	void addDeviceMemory(RequestorID requestorId,
	memory::AbstractMemory *deviceMemory);

	/**
	* Similar to isMemAddr but for devices. Checks if a physical address
	* of the packet match an address range of a device corresponding to the
	* RequestorId of the request.
	*/
	bool isDeviceMemAddr(const PacketPtr& pkt) const;

	/**
	* Return a pointer to the device memory.
	*/
	memory::AbstractMemory *getDeviceMemory(const PacketPtr& pkt) const;

	/*
	* Return the list of address ranges backed by a shadowed ROM.
	*
	* @return List of address ranges backed by a shadowed ROM
	*/
	AddrRangeList getShadowRomRanges() const { return ShadowRomRanges; }

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

	/**
	* Get the guest byte order.
	*/
	ByteOrder
	getGuestByteOrder() const
	{
	return params().byte_order;
	}

	/**
	* 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 = nullptr;

	memory::PhysicalMemory physmem;

	AddrRangeList ShadowRomRanges;

	enums::MemoryMode memoryMode;

	const unsigned int _cacheLineSize;

	uint64_t workItemsBegin = 0;
	uint64_t workItemsEnd = 0;
	uint32_t numWorkIds;

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

	ThermalModel * thermalModel;

	protected:
	/**
	* Strips off the system name from a requestor name
	*/
	std::string stripSystemName(const std::string& requestor_name) const;

	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 requestor ids must be fixed by the
	* regStats() phase that immediately precedes it. This allows objects in
	* the memory system to understand how many requestors may exist and
	* appropriately name the bins of their per-requestor stats before the
	* stats are finalized.
	*
	* Registers a RequestorID:
	* This method takes two parameters, one of which is optional.
	* The first one is the requestor object, and it is compulsory; in case
	* a object has multiple (sub)requestors, a second parameter must be
	* provided and it contains the name of the subrequestor. The method will
	* create a requestor's name by concatenating the SimObject name with the
	* eventual subrequestor string, separated by a dot.
	*
	* As an example:
	* For a cpu having two requestors: a data requestor and an
	* instruction requestor,
	* the method must be called twice:
	*
	* instRequestorId = getRequestorId(cpu, "inst");
	* dataRequestorId = getRequestorId(cpu, "data");
	*
	* and the requestors' names will be:
	* - "cpu.inst"
	* - "cpu.data"
	*
	* @param requestor SimObject related to the requestor
	* @param subrequestor String containing the subrequestor's name
	* @return the requestor's ID.
	*/
	RequestorID getRequestorId(const SimObject* requestor,
	std::string subrequestor={});

	/**
	* Registers a GLOBAL RequestorID, which is a RequestorID not related
	* to any particular SimObject; since no SimObject is passed,
	* the requestor gets registered by providing the full requestor name.
	*
	* @param requestorName full name of the requestor
	* @return the requestor's ID.
	*/
	RequestorID getGlobalRequestorId(const std::string& requestor_name);

	/**
	* Get the name of an object for a given request id.
	*/
	std::string getRequestorName(RequestorID requestor_id);

	/**
	* Looks up the RequestorID for a given SimObject
	* returns an invalid RequestorID (invldRequestorId) if not found.
	*/
	RequestorID lookupRequestorId(const SimObject* obj) const;

	/**
	* Looks up the RequestorID for a given object name string
	* returns an invalid RequestorID (invldRequestorId) if not found.
	*/
	RequestorID lookupRequestorId(const std::string& name) const;

	/** Get the number of requestors registered in the system */
	RequestorID maxRequestors() { return requestors.size(); }

	protected:
	/** helper function for getRequestorId */
	RequestorID _getRequestorId(const SimObject* requestor,
	const std::string& requestor_name);

	/**
	* Helper function for constructing the full (sub)requestor name
	* by providing the root requestor and the relative subrequestor name.
	*/
	std::string leafRequestorName(const SimObject* requestor,
	const std::string& subrequestor);

	public:

	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)
	{
	threads.markActive(index);
	return threads.numActive();
	}

	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);

	/* Returns whether we successfully trapped into GDB. */
	bool trapToGdb(int signal, ContextID ctx_id) const;

	protected:
	/**
	* Range for memory-mapped m5 pseudo ops. The range will be
	* invalid/empty if disabled.
	*/
	const AddrRange _m5opRange;

	public:
	PARAMS(System);

	System(const Params &p);
	~System();

	/**
	* Range used by memory-mapped m5 pseudo-ops if enabled. Returns
	* an invalid/empty range if disabled.
	*/
	const AddrRange &m5opRange() const { return _m5opRange; }

	public:

	/// Allocate npages contiguous unused physical pages
	/// @return Starting address of first page
	Addr allocPhysPages(int npages, int poolID = 0);

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

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

	public:
	std::map<std::pair<uint32_t, uint32_t>, Tick> lastWorkItemStarted;
	std::map<uint32_t, statistics::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;

	// Used by syscall-emulation mode. This member contains paths which need
	// to be redirected to the faux-filesystem (a duplicate filesystem
	// intended to replace certain files on the host filesystem).
	std::vector<RedirectPath*> redirectPaths;
	};

	void printSystems();

	} // namespace gem5

	#endif // __SYSTEM_HH__