src/arch/riscv/pagetable_walker.hh

/*
 * Copyright (c) 2007 The Hewlett-Packard Development Company
 * Copyright (c) 2020 Barkhausen Institut
 * 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
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 *
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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;
 * redistributions in binary form must reproduce the above copyright
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 * this software without specific prior written permission.
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#ifndef __ARCH_RISCV_TABLE_WALKER_HH__
#define __ARCH_RISCV_TABLE_WALKER_HH__

#include <vector>

#include "arch/generic/mmu.hh"
#include "arch/riscv/pagetable.hh"
#include "arch/riscv/pma_checker.hh"
#include "arch/riscv/pmp.hh"
#include "arch/riscv/tlb.hh"
#include "base/types.hh"
#include "mem/packet.hh"
#include "params/RiscvPagetableWalker.hh"
#include "sim/clocked_object.hh"
#include "sim/faults.hh"
#include "sim/system.hh"

namespace gem5
{

class ThreadContext;

namespace RiscvISA
{
    class Walker : public ClockedObject
    {
      protected:
        // Port for accessing memory
        class WalkerPort : public RequestPort
        {
          public:
            WalkerPort(const std::string &_name, Walker * _walker) :
                  RequestPort(_name), walker(_walker)
            {}

          protected:
            Walker *walker;

            bool recvTimingResp(PacketPtr pkt);
            void recvReqRetry();
        };

        friend class WalkerPort;
        WalkerPort port;

        // State to track each walk of the page table
        class WalkerState
        {
          friend class Walker;
          private:
            enum State
            {
                Ready,
                Waiting,
                Translate,
            };

          protected:
            Walker *walker;
            ThreadContext *tc;
            RequestPtr req;
            State state;
            State nextState;
            int level;
            unsigned inflight;
            TlbEntry entry;
            PacketPtr read;
            std::vector<PacketPtr> writes;
            Fault timingFault;
            BaseMMU::Translation * translation;
            BaseMMU::Mode mode;
            SATP satp;
            STATUS status;
            PrivilegeMode pmode;
            bool functional;
            bool timing;
            bool retrying;
            bool started;
            bool squashed;
          public:
            WalkerState(Walker * _walker, BaseMMU::Translation *_translation,
                        const RequestPtr &_req, bool _isFunctional = false) :
                walker(_walker), req(_req), state(Ready),
                nextState(Ready), level(0), inflight(0),
                translation(_translation),
                functional(_isFunctional), timing(false),
                retrying(false), started(false), squashed(false)
            {
            }
            void initState(ThreadContext * _tc, BaseMMU::Mode _mode,
                           bool _isTiming = false);
            Fault startWalk();
            Fault startFunctional(Addr &addr, unsigned &logBytes);
            bool recvPacket(PacketPtr pkt);
            unsigned numInflight() const;
            bool isRetrying();
            bool wasStarted();
            bool isTiming();
            void retry();
            void squash();
            std::string name() const {return walker->name();}

          private:
            void setupWalk(Addr vaddr);
            Fault stepWalk(PacketPtr &write);
            void sendPackets();
            void endWalk();
            Fault pageFault(bool present);
        };

        friend class WalkerState;
        // State for timing and atomic accesses (need multiple per walker in
        // the case of multiple outstanding requests in timing mode)
        std::list<WalkerState *> currStates;
        // State for functional accesses (only need one of these per walker)
        WalkerState funcState;

        struct WalkerSenderState : public Packet::SenderState
        {
            WalkerState * senderWalk;
            WalkerSenderState(WalkerState * _senderWalk) :
                senderWalk(_senderWalk) {}
        };

      public:
        // Kick off the state machine.
        Fault start(ThreadContext * _tc, BaseMMU::Translation *translation,
                const RequestPtr &req, BaseMMU::Mode mode);
        Fault startFunctional(ThreadContext * _tc, Addr &addr,
                unsigned &logBytes, BaseMMU::Mode mode);
        Port &getPort(const std::string &if_name,
                      PortID idx=InvalidPortID) override;

      protected:
        // The TLB we're supposed to load.
        TLB * tlb;
        System * sys;
        PMAChecker * pma;
        PMP * pmp;
        RequestorID requestorId;

        // The number of outstanding walks that can be squashed per cycle.
        unsigned numSquashable;

        // Wrapper for checking for squashes before starting a translation.
        void startWalkWrapper();

        /**
         * Event used to call startWalkWrapper.
         **/
        EventFunctionWrapper startWalkWrapperEvent;

        // Functions for dealing with packets.
        bool recvTimingResp(PacketPtr pkt);
        void recvReqRetry();
        bool sendTiming(WalkerState * sendingState, PacketPtr pkt);

      public:

        void setTLB(TLB * _tlb)
        {
            tlb = _tlb;
        }

        using Params = RiscvPagetableWalkerParams;

        Walker(const Params &params) :
            ClockedObject(params), port(name() + ".port", this),
            funcState(this, NULL, NULL, true), tlb(NULL), sys(params.system),
            pma(params.pma_checker),
            pmp(params.pmp),
            requestorId(sys->getRequestorId(this)),
            numSquashable(params.num_squash_per_cycle),
            startWalkWrapperEvent([this]{ startWalkWrapper(); }, name())
        {
        }
    };

} // namespace RiscvISA
} // namespace gem5

#endif // __ARCH_RISCV_PAGE_TABLE_WALKER_HH__