gem5/src/sim/sim_object.hh

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 * Copyright (c) 2010 Advanced Micro Devices, Inc.
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/* @file
 * User Console Definitions
 */

#ifndef __SIM_OBJECT_HH__
#define __SIM_OBJECT_HH__

#include <string>
#include <vector>

#include "base/stats/group.hh"
#include "params/SimObject.hh"
#include "sim/drain.hh"
#include "sim/eventq.hh"
#include "sim/port.hh"
#include "sim/serialize.hh"

class EventManager;
class ProbeManager;

/**
 * Abstract superclass for simulation objects.  Represents things that
 * correspond to physical components and can be specified via the
 * config file (CPUs, caches, etc.).
 *
 * SimObject initialization is controlled by the instantiate method in
 * src/python/m5/simulate.py. There are slightly different
 * initialization paths when starting the simulation afresh and when
 * loading from a checkpoint.  After instantiation and connecting
 * ports, simulate.py initializes the object using the following call
 * sequence:
 *
 * <ol>
 * <li>SimObject::init()
 * <li>SimObject::regStats()
 * <li><ul>
 *     <li>SimObject::initState() if starting afresh.
 *     <li>SimObject::loadState() if restoring from a checkpoint.
 *     </ul>
 * <li>SimObject::resetStats()
 * <li>SimObject::startup()
 * <li>Drainable::drainResume() if resuming from a checkpoint.
 * </ol>
 *
 * @note Whenever a method is called on all objects in the simulator's
 * object tree (e.g., init(), startup(), or loadState()), a pre-order
 * depth-first traversal is performed (see descendants() in
 * SimObject.py). This has the effect of calling the method on the
 * parent node <i>before</i> its children.
 */
class SimObject : public EventManager, public Serializable, public Drainable,
                  public Stats::Group
{
  private:
    typedef std::vector<SimObject *> SimObjectList;

    /** List of all instantiated simulation objects. */
    static SimObjectList simObjectList;

    /** Manager coordinates hooking up probe points with listeners. */
    ProbeManager *probeManager;

  protected:
    /**
     * Cached copy of the object parameters.
     *
     * @ingroup api_simobject
     */
    const SimObjectParams *_params;

  public:
    typedef SimObjectParams Params;
    /**
     * @return This function returns the cached copy of the object parameters.
     *
     * @ingroup api_simobject
     */
    const Params *params() const { return _params; }

    /**
     * @ingroup api_simobject
     */
    SimObject(const Params *_params);

    virtual ~SimObject();

  public:

    /**
     * @ingroup api_simobject
     */
    virtual const std::string name() const { return params()->name; }

    /**
     * init() is called after all C++ SimObjects have been created and
     * all ports are connected.  Initializations that are independent
     * of unserialization but rely on a fully instantiated and
     * connected SimObject graph should be done here.
     *
     * @ingroup api_simobject
     */
    virtual void init();

    /**
     * loadState() is called on each SimObject when restoring from a
     * checkpoint.  The default implementation simply calls
     * unserialize() if there is a corresponding section in the
     * checkpoint.  However, objects can override loadState() to get
     * other behaviors, e.g., doing other programmed initializations
     * after unserialize(), or complaining if no checkpoint section is
     * found.
     *
     * @param cp Checkpoint to restore the state from.
     *
     * @ingroup api_serialize
     */
    virtual void loadState(CheckpointIn &cp);

    /**
     * initState() is called on each SimObject when *not* restoring
     * from a checkpoint.  This provides a hook for state
     * initializations that are only required for a "cold start".
     *
     * @ingroup api_serialize
     */
    virtual void initState();

    /**
     * Register probe points for this object.
     *
     * @ingroup api_simobject
     */
    virtual void regProbePoints();

    /**
     * Register probe listeners for this object.
     *
     * @ingroup api_simobject
     */
    virtual void regProbeListeners();

    /**
     * Get the probe manager for this object.
     *
     * Probes generate traces. A trace is a file that
     * keeps a log of events. For example, we can have a probe
     * listener for an address and the trace will be a file that
     * has time stamps for all the reads and writes to that address.
     *
     * @ingroup api_simobject
     */
    ProbeManager *getProbeManager();

    /**
     * Get a port with a given name and index. This is used at binding time
     * and returns a reference to a protocol-agnostic port.
     *
     * gem5 has a request and response port interface. All memory objects
     * are connected together via ports. These ports provide a rigid
     * interface between these memory objects. These ports implement
     * three different memory system modes: timing, atomic, and
     * functional. The most important mode is the timing mode and here
     * timing mode is used for conducting cycle-level timing
     * experiments. The other modes are only used in special
     * circumstances and should *not* be used to conduct cycle-level
     * timing experiments. The other modes are only used in special
     * circumstances. These ports allow SimObjects to communicate with
     * each other.
     *
     * @param if_name Port name
     * @param idx Index in the case of a VectorPort
     *
     * @return A reference to the given port
     *
     * @ingroup api_simobject
     */
    virtual Port &getPort(const std::string &if_name,
                          PortID idx=InvalidPortID);

    /**
     * startup() is the final initialization call before simulation.
     * All state is initialized (including unserialized state, if any,
     * such as the curTick() value), so this is the appropriate place to
     * schedule initial event(s) for objects that need them.
     *
     * @ingroup api_simobject
     */
    virtual void startup();

    /**
     * Provide a default implementation of the drain interface for
     * objects that don't need draining.
     */
    DrainState drain() override { return DrainState::Drained; }

    /**
     * Write back dirty buffers to memory using functional writes.
     *
     * After returning, an object implementing this method should have
     * written all its dirty data back to memory. This method is
     * typically used to prepare a system with caches for
     * checkpointing.
     *
     * @ingroup api_simobject
     */
    virtual void memWriteback() {};

    /**
     * Invalidate the contents of memory buffers.
     *
     * When the switching to hardware virtualized CPU models, we need
     * to make sure that we don't have any cached state in the system
     * that might become stale when we return. This method is used to
     * flush all such state back to main memory.
     *
     * @warn This does <i>not</i> cause any dirty state to be written
     * back to memory.
     *
     * @ingroup api_simobject
     */
    virtual void memInvalidate() {};

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

    /**
     * Serialize all SimObjects in the system.
     */
    static void serializeAll(CheckpointOut &cp);

#ifdef DEBUG
  public:
    bool doDebugBreak;
    static void debugObjectBreak(const std::string &objs);
#endif

    /**
     * Find the SimObject with the given name and return a pointer to
     * it.  Primarily used for interactive debugging.  Argument is
     * char* rather than std::string to make it callable from gdb.
     *
     * @ingroup api_simobject
     */
    static SimObject *find(const char *name);
};

/**
 * Base class to wrap object resolving functionality.
 *
 * This can be provided to the serialization framework to allow it to
 * map object names onto C++ objects.
 */
class SimObjectResolver
{
  public:
    virtual ~SimObjectResolver() { }

    /**
     * Find a SimObject given a full path name
     *
     * @ingroup api_serialize
     */
    virtual SimObject *resolveSimObject(const std::string &name) = 0;
};

#ifdef DEBUG
void debugObjectBreak(const char *objs);
#endif

#endif // __SIM_OBJECT_HH__