gem5/src/cpu/simple/atomic.hh

/*
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 *
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 * property including but not limited to intellectual property relating
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 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
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 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2002-2005 The Regents of The University of Michigan
 * All rights reserved.
 *
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 * 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;
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#ifndef __CPU_SIMPLE_ATOMIC_HH__
#define __CPU_SIMPLE_ATOMIC_HH__

#include "cpu/simple/base.hh"
#include "cpu/simple/exec_context.hh"
#include "mem/request.hh"
#include "params/AtomicSimpleCPU.hh"
#include "sim/probe/probe.hh"

namespace gem5
{

class AtomicSimpleCPU : public BaseSimpleCPU
{
  public:

    AtomicSimpleCPU(const AtomicSimpleCPUParams &params);
    virtual ~AtomicSimpleCPU();

    void init() override;

  protected:
    EventFunctionWrapper tickEvent;

    const int width;
    bool locked;
    const bool simulate_data_stalls;
    const bool simulate_inst_stalls;

    // main simulation loop (one cycle)
    void tick();

    /**
     * Check if a system is in a drained state.
     *
     * We need to drain if:
     * <ul>
     * <li>We are in the middle of a microcode sequence as some CPUs
     *     (e.g., HW accelerated CPUs) can't be started in the middle
     *     of a gem5 microcode sequence.
     *
     * <li>The CPU is in a LLSC region. This shouldn't normally happen
     *     as these are executed atomically within a single tick()
     *     call. The only way this can happen at the moment is if
     *     there is an event in the PC event queue that affects the
     *     CPU state while it is in an LLSC region.
     *
     * <li>Stay at PC is true.
     * </ul>
     */
    bool
    isCpuDrained() const
    {
        SimpleExecContext &t_info = *threadInfo[curThread];
        return t_info.thread->microPC() == 0 &&
            !locked && !t_info.stayAtPC;
    }

    /**
     * Try to complete a drain request.
     *
     * @returns true if the CPU is drained, false otherwise.
     */
    bool tryCompleteDrain();

    virtual Tick sendPacket(RequestPort &port, const PacketPtr &pkt);
    virtual Tick fetchInstMem();

    /**
     * An AtomicCPUPort overrides the default behaviour of the
     * recvAtomicSnoop and ignores the packet instead of panicking. It
     * also provides an implementation for the purely virtual timing
     * functions and panics on either of these.
     */
    class AtomicCPUPort : public RequestPort
    {

      public:

        AtomicCPUPort(const std::string &_name, BaseSimpleCPU* _cpu)
            : RequestPort(_name, _cpu)
        { }

      protected:

        bool
        recvTimingResp(PacketPtr pkt)
        {
            panic("Atomic CPU doesn't expect recvTimingResp!\n");
        }

        void
        recvReqRetry()
        {
            panic("Atomic CPU doesn't expect recvRetry!\n");
        }

    };

    class AtomicCPUDPort : public AtomicCPUPort
    {

      public:
        AtomicCPUDPort(const std::string &_name, BaseSimpleCPU *_cpu)
            : AtomicCPUPort(_name, _cpu), cpu(_cpu)
        {
            cacheBlockMask = ~(cpu->cacheLineSize() - 1);
        }

        bool isSnooping() const { return true; }

        Addr cacheBlockMask;
      protected:
        BaseSimpleCPU *cpu;

        virtual Tick recvAtomicSnoop(PacketPtr pkt);
        virtual void recvFunctionalSnoop(PacketPtr pkt);
    };


    AtomicCPUPort icachePort;
    AtomicCPUDPort dcachePort;


    RequestPtr ifetch_req;
    RequestPtr data_read_req;
    RequestPtr data_write_req;
    RequestPtr data_amo_req;

    bool dcache_access;
    Tick dcache_latency;

    /** Probe Points. */
    ProbePointArg<std::pair<SimpleThread *, const StaticInstPtr>> *ppCommit;

  protected:

    /** Return a reference to the data port. */
    Port &getDataPort() override { return dcachePort; }

    /** Return a reference to the instruction port. */
    Port &getInstPort() override { return icachePort; }

    /** Perform snoop for other cpu-local thread contexts. */
    void threadSnoop(PacketPtr pkt, ThreadID sender);

  public:

    DrainState drain() override;
    void drainResume() override;

    void switchOut() override;
    void takeOverFrom(BaseCPU *old_cpu) override;

    void verifyMemoryMode() const override;

    void activateContext(ThreadID thread_num) override;
    void suspendContext(ThreadID thread_num) override;

    /**
     * Helper function used to set up the request for a single fragment of a
     * memory access.
     *
     * Takes care of setting up the appropriate byte-enable mask for the
     * fragment, given the mask for the entire memory access.
     *
     * @param req Pointer to the Request object to populate.
     * @param frag_addr Start address of the fragment.
     * @param size Total size of the memory access in bytes.
     * @param flags Request flags.
     * @param byte_enable Byte-enable mask for the entire memory access.
     * @param[out] frag_size Fragment size.
     * @param[in,out] size_left Size left to be processed in the memory access.
     * @return True if the byte-enable mask for the fragment is not all-false.
     */
    bool genMemFragmentRequest(const RequestPtr &req, Addr frag_addr,
                               int size, Request::Flags flags,
                               const std::vector<bool> &byte_enable,
                               int &frag_size, int &size_left) const;

    Fault readMem(Addr addr, uint8_t *data, unsigned size,
                  Request::Flags flags,
                  const std::vector<bool> &byte_enable=std::vector<bool>())
        override;

    Fault
    initiateHtmCmd(Request::Flags flags) override
    {
        panic("initiateHtmCmd() is for timing accesses, and should "
              "never be called on AtomicSimpleCPU.\n");
    }

    void
    htmSendAbortSignal(ThreadID tid, uint64_t htm_uid,
                       HtmFailureFaultCause cause) override
    {
        panic("htmSendAbortSignal() is for timing accesses, and should "
              "never be called on AtomicSimpleCPU.");
    }

    Fault writeMem(uint8_t *data, unsigned size,
                   Addr addr, Request::Flags flags, uint64_t *res,
                   const std::vector<bool> &byte_enable=std::vector<bool>())
        override;

    Fault amoMem(Addr addr, uint8_t *data, unsigned size,
                 Request::Flags flags, AtomicOpFunctorPtr amo_op) override;

    void regProbePoints() override;

    /**
     * Print state of address in memory system via PrintReq (for
     * debugging).
     */
    void printAddr(Addr a);
};

} // namespace gem5

#endif // __CPU_SIMPLE_ATOMIC_HH__