base.hh revision 13749:b2486662285d
1/*
2 * Copyright (c) 2012-2013, 2015-2016, 2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Erik Hallnor
41 *          Steve Reinhardt
42 *          Ron Dreslinski
43 *          Andreas Hansson
44 *          Nikos Nikoleris
45 */
46
47/**
48 * @file
49 * Declares a basic cache interface BaseCache.
50 */
51
52#ifndef __MEM_CACHE_BASE_HH__
53#define __MEM_CACHE_BASE_HH__
54
55#include <cassert>
56#include <cstdint>
57#include <string>
58
59#include "base/addr_range.hh"
60#include "base/statistics.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CachePort.hh"
65#include "enums/Clusivity.hh"
66#include "mem/cache/cache_blk.hh"
67#include "mem/cache/mshr_queue.hh"
68#include "mem/cache/tags/base.hh"
69#include "mem/cache/write_queue.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/mem_object.hh"
72#include "mem/packet.hh"
73#include "mem/packet_queue.hh"
74#include "mem/qport.hh"
75#include "mem/request.hh"
76#include "params/WriteAllocator.hh"
77#include "sim/eventq.hh"
78#include "sim/probe/probe.hh"
79#include "sim/serialize.hh"
80#include "sim/sim_exit.hh"
81#include "sim/system.hh"
82
83class BaseMasterPort;
84class BasePrefetcher;
85class BaseSlavePort;
86class MSHR;
87class MasterPort;
88class QueueEntry;
89struct BaseCacheParams;
90
91/**
92 * A basic cache interface. Implements some common functions for speed.
93 */
94class BaseCache : public MemObject
95{
96  protected:
97    /**
98     * Indexes to enumerate the MSHR queues.
99     */
100    enum MSHRQueueIndex {
101        MSHRQueue_MSHRs,
102        MSHRQueue_WriteBuffer
103    };
104
105  public:
106    /**
107     * Reasons for caches to be blocked.
108     */
109    enum BlockedCause {
110        Blocked_NoMSHRs = MSHRQueue_MSHRs,
111        Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
112        Blocked_NoTargets,
113        NUM_BLOCKED_CAUSES
114    };
115
116  protected:
117
118    /**
119     * A cache master port is used for the memory-side port of the
120     * cache, and in addition to the basic timing port that only sends
121     * response packets through a transmit list, it also offers the
122     * ability to schedule and send request packets (requests &
123     * writebacks). The send event is scheduled through schedSendEvent,
124     * and the sendDeferredPacket of the timing port is modified to
125     * consider both the transmit list and the requests from the MSHR.
126     */
127    class CacheMasterPort : public QueuedMasterPort
128    {
129
130      public:
131
132        /**
133         * Schedule a send of a request packet (from the MSHR). Note
134         * that we could already have a retry outstanding.
135         */
136        void schedSendEvent(Tick time)
137        {
138            DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
139            reqQueue.schedSendEvent(time);
140        }
141
142      protected:
143
144        CacheMasterPort(const std::string &_name, BaseCache *_cache,
145                        ReqPacketQueue &_reqQueue,
146                        SnoopRespPacketQueue &_snoopRespQueue) :
147            QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
148        { }
149
150        /**
151         * Memory-side port always snoops.
152         *
153         * @return always true
154         */
155        virtual bool isSnooping() const { return true; }
156    };
157
158    /**
159     * Override the default behaviour of sendDeferredPacket to enable
160     * the memory-side cache port to also send requests based on the
161     * current MSHR status. This queue has a pointer to our specific
162     * cache implementation and is used by the MemSidePort.
163     */
164    class CacheReqPacketQueue : public ReqPacketQueue
165    {
166
167      protected:
168
169        BaseCache &cache;
170        SnoopRespPacketQueue &snoopRespQueue;
171
172      public:
173
174        CacheReqPacketQueue(BaseCache &cache, MasterPort &port,
175                            SnoopRespPacketQueue &snoop_resp_queue,
176                            const std::string &label) :
177            ReqPacketQueue(cache, port, label), cache(cache),
178            snoopRespQueue(snoop_resp_queue) { }
179
180        /**
181         * Override the normal sendDeferredPacket and do not only
182         * consider the transmit list (used for responses), but also
183         * requests.
184         */
185        virtual void sendDeferredPacket();
186
187        /**
188         * Check if there is a conflicting snoop response about to be
189         * send out, and if so simply stall any requests, and schedule
190         * a send event at the same time as the next snoop response is
191         * being sent out.
192         */
193        bool checkConflictingSnoop(Addr addr)
194        {
195            if (snoopRespQueue.hasAddr(addr)) {
196                DPRINTF(CachePort, "Waiting for snoop response to be "
197                        "sent\n");
198                Tick when = snoopRespQueue.deferredPacketReadyTime();
199                schedSendEvent(when);
200                return true;
201            }
202            return false;
203        }
204    };
205
206
207    /**
208     * The memory-side port extends the base cache master port with
209     * access functions for functional, atomic and timing snoops.
210     */
211    class MemSidePort : public CacheMasterPort
212    {
213      private:
214
215        /** The cache-specific queue. */
216        CacheReqPacketQueue _reqQueue;
217
218        SnoopRespPacketQueue _snoopRespQueue;
219
220        // a pointer to our specific cache implementation
221        BaseCache *cache;
222
223      protected:
224
225        virtual void recvTimingSnoopReq(PacketPtr pkt);
226
227        virtual bool recvTimingResp(PacketPtr pkt);
228
229        virtual Tick recvAtomicSnoop(PacketPtr pkt);
230
231        virtual void recvFunctionalSnoop(PacketPtr pkt);
232
233      public:
234
235        MemSidePort(const std::string &_name, BaseCache *_cache,
236                    const std::string &_label);
237    };
238
239    /**
240     * A cache slave port is used for the CPU-side port of the cache,
241     * and it is basically a simple timing port that uses a transmit
242     * list for responses to the CPU (or connected master). In
243     * addition, it has the functionality to block the port for
244     * incoming requests. If blocked, the port will issue a retry once
245     * unblocked.
246     */
247    class CacheSlavePort : public QueuedSlavePort
248    {
249
250      public:
251
252        /** Do not accept any new requests. */
253        void setBlocked();
254
255        /** Return to normal operation and accept new requests. */
256        void clearBlocked();
257
258        bool isBlocked() const { return blocked; }
259
260      protected:
261
262        CacheSlavePort(const std::string &_name, BaseCache *_cache,
263                       const std::string &_label);
264
265        /** A normal packet queue used to store responses. */
266        RespPacketQueue queue;
267
268        bool blocked;
269
270        bool mustSendRetry;
271
272      private:
273
274        void processSendRetry();
275
276        EventFunctionWrapper sendRetryEvent;
277
278    };
279
280    /**
281     * The CPU-side port extends the base cache slave port with access
282     * functions for functional, atomic and timing requests.
283     */
284    class CpuSidePort : public CacheSlavePort
285    {
286      private:
287
288        // a pointer to our specific cache implementation
289        BaseCache *cache;
290
291      protected:
292        virtual bool recvTimingSnoopResp(PacketPtr pkt) override;
293
294        virtual bool tryTiming(PacketPtr pkt) override;
295
296        virtual bool recvTimingReq(PacketPtr pkt) override;
297
298        virtual Tick recvAtomic(PacketPtr pkt) override;
299
300        virtual void recvFunctional(PacketPtr pkt) override;
301
302        virtual AddrRangeList getAddrRanges() const override;
303
304      public:
305
306        CpuSidePort(const std::string &_name, BaseCache *_cache,
307                    const std::string &_label);
308
309    };
310
311    CpuSidePort cpuSidePort;
312    MemSidePort memSidePort;
313
314  protected:
315
316    /** Miss status registers */
317    MSHRQueue mshrQueue;
318
319    /** Write/writeback buffer */
320    WriteQueue writeBuffer;
321
322    /** Tag and data Storage */
323    BaseTags *tags;
324
325    /** Prefetcher */
326    BasePrefetcher *prefetcher;
327
328    /** To probe when a cache hit occurs */
329    ProbePointArg<PacketPtr> *ppHit;
330
331    /** To probe when a cache miss occurs */
332    ProbePointArg<PacketPtr> *ppMiss;
333
334    /** To probe when a cache fill occurs */
335    ProbePointArg<PacketPtr> *ppFill;
336
337    /**
338     * The writeAllocator drive optimizations for streaming writes.
339     * It first determines whether a WriteReq MSHR should be delayed,
340     * thus ensuring that we wait longer in cases when we are write
341     * coalescing and allowing all the bytes of the line to be written
342     * before the MSHR packet is sent downstream. This works in unison
343     * with the tracking in the MSHR to check if the entire line is
344     * written. The write mode also affects the behaviour on filling
345     * any whole-line writes. Normally the cache allocates the line
346     * when receiving the InvalidateResp, but after seeing enough
347     * consecutive lines we switch to using the tempBlock, and thus
348     * end up not allocating the line, and instead turning the
349     * whole-line write into a writeback straight away.
350     */
351    WriteAllocator * const writeAllocator;
352
353    /**
354     * Temporary cache block for occasional transitory use.  We use
355     * the tempBlock to fill when allocation fails (e.g., when there
356     * is an outstanding request that accesses the victim block) or
357     * when we want to avoid allocation (e.g., exclusive caches)
358     */
359    TempCacheBlk *tempBlock;
360
361    /**
362     * Upstream caches need this packet until true is returned, so
363     * hold it for deletion until a subsequent call
364     */
365    std::unique_ptr<Packet> pendingDelete;
366
367    /**
368     * Mark a request as in service (sent downstream in the memory
369     * system), effectively making this MSHR the ordering point.
370     */
371    void markInService(MSHR *mshr, bool pending_modified_resp)
372    {
373        bool wasFull = mshrQueue.isFull();
374        mshrQueue.markInService(mshr, pending_modified_resp);
375
376        if (wasFull && !mshrQueue.isFull()) {
377            clearBlocked(Blocked_NoMSHRs);
378        }
379    }
380
381    void markInService(WriteQueueEntry *entry)
382    {
383        bool wasFull = writeBuffer.isFull();
384        writeBuffer.markInService(entry);
385
386        if (wasFull && !writeBuffer.isFull()) {
387            clearBlocked(Blocked_NoWBBuffers);
388        }
389    }
390
391    /**
392     * Determine whether we should allocate on a fill or not. If this
393     * cache is mostly inclusive with regards to the upstream cache(s)
394     * we always allocate (for any non-forwarded and cacheable
395     * requests). In the case of a mostly exclusive cache, we allocate
396     * on fill if the packet did not come from a cache, thus if we:
397     * are dealing with a whole-line write (the latter behaves much
398     * like a writeback), the original target packet came from a
399     * non-caching source, or if we are performing a prefetch or LLSC.
400     *
401     * @param cmd Command of the incoming requesting packet
402     * @return Whether we should allocate on the fill
403     */
404    inline bool allocOnFill(MemCmd cmd) const
405    {
406        return clusivity == Enums::mostly_incl ||
407            cmd == MemCmd::WriteLineReq ||
408            cmd == MemCmd::ReadReq ||
409            cmd == MemCmd::WriteReq ||
410            cmd.isPrefetch() ||
411            cmd.isLLSC();
412    }
413
414    /**
415     * Regenerate block address using tags.
416     * Block address regeneration depends on whether we're using a temporary
417     * block or not.
418     *
419     * @param blk The block to regenerate address.
420     * @return The block's address.
421     */
422    Addr regenerateBlkAddr(CacheBlk* blk);
423
424    /**
425     * Calculate latency of accesses that only touch the tag array.
426     * @sa calculateAccessLatency
427     *
428     * @param delay The delay until the packet's metadata is present.
429     * @param lookup_lat Latency of the respective tag lookup.
430     * @return The number of ticks that pass due to a tag-only access.
431     */
432    Cycles calculateTagOnlyLatency(const uint32_t delay,
433                                   const Cycles lookup_lat) const;
434    /**
435     * Calculate access latency in ticks given a tag lookup latency, and
436     * whether access was a hit or miss.
437     *
438     * @param blk The cache block that was accessed.
439     * @param delay The delay until the packet's metadata is present.
440     * @param lookup_lat Latency of the respective tag lookup.
441     * @return The number of ticks that pass due to a block access.
442     */
443    Cycles calculateAccessLatency(const CacheBlk* blk, const uint32_t delay,
444                                  const Cycles lookup_lat) const;
445
446    /**
447     * Does all the processing necessary to perform the provided request.
448     * @param pkt The memory request to perform.
449     * @param blk The cache block to be updated.
450     * @param lat The latency of the access.
451     * @param writebacks List for any writebacks that need to be performed.
452     * @return Boolean indicating whether the request was satisfied.
453     */
454    virtual bool access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
455                        PacketList &writebacks);
456
457    /*
458     * Handle a timing request that hit in the cache
459     *
460     * @param ptk The request packet
461     * @param blk The referenced block
462     * @param request_time The tick at which the block lookup is compete
463     */
464    virtual void handleTimingReqHit(PacketPtr pkt, CacheBlk *blk,
465                                    Tick request_time);
466
467    /*
468     * Handle a timing request that missed in the cache
469     *
470     * Implementation specific handling for different cache
471     * implementations
472     *
473     * @param ptk The request packet
474     * @param blk The referenced block
475     * @param forward_time The tick at which we can process dependent requests
476     * @param request_time The tick at which the block lookup is compete
477     */
478    virtual void handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk,
479                                     Tick forward_time,
480                                     Tick request_time) = 0;
481
482    /*
483     * Handle a timing request that missed in the cache
484     *
485     * Common functionality across different cache implementations
486     *
487     * @param ptk The request packet
488     * @param blk The referenced block
489     * @param mshr Any existing mshr for the referenced cache block
490     * @param forward_time The tick at which we can process dependent requests
491     * @param request_time The tick at which the block lookup is compete
492     */
493    void handleTimingReqMiss(PacketPtr pkt, MSHR *mshr, CacheBlk *blk,
494                             Tick forward_time, Tick request_time);
495
496    /**
497     * Performs the access specified by the request.
498     * @param pkt The request to perform.
499     */
500    virtual void recvTimingReq(PacketPtr pkt);
501
502    /**
503     * Handling the special case of uncacheable write responses to
504     * make recvTimingResp less cluttered.
505     */
506    void handleUncacheableWriteResp(PacketPtr pkt);
507
508    /**
509     * Service non-deferred MSHR targets using the received response
510     *
511     * Iterates through the list of targets that can be serviced with
512     * the current response.
513     *
514     * @param mshr The MSHR that corresponds to the reponse
515     * @param pkt The response packet
516     * @param blk The reference block
517     */
518    virtual void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt,
519                                    CacheBlk *blk) = 0;
520
521    /**
522     * Handles a response (cache line fill/write ack) from the bus.
523     * @param pkt The response packet
524     */
525    virtual void recvTimingResp(PacketPtr pkt);
526
527    /**
528     * Snoops bus transactions to maintain coherence.
529     * @param pkt The current bus transaction.
530     */
531    virtual void recvTimingSnoopReq(PacketPtr pkt) = 0;
532
533    /**
534     * Handle a snoop response.
535     * @param pkt Snoop response packet
536     */
537    virtual void recvTimingSnoopResp(PacketPtr pkt) = 0;
538
539    /**
540     * Handle a request in atomic mode that missed in this cache
541     *
542     * Creates a downstream request, sends it to the memory below and
543     * handles the response. As we are in atomic mode all operations
544     * are performed immediately.
545     *
546     * @param pkt The packet with the requests
547     * @param blk The referenced block
548     * @param writebacks A list with packets for any performed writebacks
549     * @return Cycles for handling the request
550     */
551    virtual Cycles handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
552                                       PacketList &writebacks) = 0;
553
554    /**
555     * Performs the access specified by the request.
556     * @param pkt The request to perform.
557     * @return The number of ticks required for the access.
558     */
559    virtual Tick recvAtomic(PacketPtr pkt);
560
561    /**
562     * Snoop for the provided request in the cache and return the estimated
563     * time taken.
564     * @param pkt The memory request to snoop
565     * @return The number of ticks required for the snoop.
566     */
567    virtual Tick recvAtomicSnoop(PacketPtr pkt) = 0;
568
569    /**
570     * Performs the access specified by the request.
571     *
572     * @param pkt The request to perform.
573     * @param fromCpuSide from the CPU side port or the memory side port
574     */
575    virtual void functionalAccess(PacketPtr pkt, bool from_cpu_side);
576
577    /**
578     * Handle doing the Compare and Swap function for SPARC.
579     */
580    void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
581
582    /**
583     * Return the next queue entry to service, either a pending miss
584     * from the MSHR queue, a buffered write from the write buffer, or
585     * something from the prefetcher. This function is responsible
586     * for prioritizing among those sources on the fly.
587     */
588    QueueEntry* getNextQueueEntry();
589
590    /**
591     * Insert writebacks into the write buffer
592     */
593    virtual void doWritebacks(PacketList& writebacks, Tick forward_time) = 0;
594
595    /**
596     * Send writebacks down the memory hierarchy in atomic mode
597     */
598    virtual void doWritebacksAtomic(PacketList& writebacks) = 0;
599
600    /**
601     * Create an appropriate downstream bus request packet.
602     *
603     * Creates a new packet with the request to be send to the memory
604     * below, or nullptr if the current request in cpu_pkt should just
605     * be forwarded on.
606     *
607     * @param cpu_pkt The miss packet that needs to be satisfied.
608     * @param blk The referenced block, can be nullptr.
609     * @param needs_writable Indicates that the block must be writable
610     * even if the request in cpu_pkt doesn't indicate that.
611     * @param is_whole_line_write True if there are writes for the
612     * whole line
613     * @return A packet send to the memory below
614     */
615    virtual PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
616                                       bool needs_writable,
617                                       bool is_whole_line_write) const = 0;
618
619    /**
620     * Determine if clean lines should be written back or not. In
621     * cases where a downstream cache is mostly inclusive we likely
622     * want it to act as a victim cache also for lines that have not
623     * been modified. Hence, we cannot simply drop the line (or send a
624     * clean evict), but rather need to send the actual data.
625     */
626    const bool writebackClean;
627
628    /**
629     * Writebacks from the tempBlock, resulting on the response path
630     * in atomic mode, must happen after the call to recvAtomic has
631     * finished (for the right ordering of the packets). We therefore
632     * need to hold on to the packets, and have a method and an event
633     * to send them.
634     */
635    PacketPtr tempBlockWriteback;
636
637    /**
638     * Send the outstanding tempBlock writeback. To be called after
639     * recvAtomic finishes in cases where the block we filled is in
640     * fact the tempBlock, and now needs to be written back.
641     */
642    void writebackTempBlockAtomic() {
643        assert(tempBlockWriteback != nullptr);
644        PacketList writebacks{tempBlockWriteback};
645        doWritebacksAtomic(writebacks);
646        tempBlockWriteback = nullptr;
647    }
648
649    /**
650     * An event to writeback the tempBlock after recvAtomic
651     * finishes. To avoid other calls to recvAtomic getting in
652     * between, we create this event with a higher priority.
653     */
654    EventFunctionWrapper writebackTempBlockAtomicEvent;
655
656    /**
657     * Perform any necessary updates to the block and perform any data
658     * exchange between the packet and the block. The flags of the
659     * packet are also set accordingly.
660     *
661     * @param pkt Request packet from upstream that hit a block
662     * @param blk Cache block that the packet hit
663     * @param deferred_response Whether this request originally missed
664     * @param pending_downgrade Whether the writable flag is to be removed
665     */
666    virtual void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
667                                bool deferred_response = false,
668                                bool pending_downgrade = false);
669
670    /**
671     * Maintain the clusivity of this cache by potentially
672     * invalidating a block. This method works in conjunction with
673     * satisfyRequest, but is separate to allow us to handle all MSHR
674     * targets before potentially dropping a block.
675     *
676     * @param from_cache Whether we have dealt with a packet from a cache
677     * @param blk The block that should potentially be dropped
678     */
679    void maintainClusivity(bool from_cache, CacheBlk *blk);
680
681    /**
682     * Handle a fill operation caused by a received packet.
683     *
684     * Populates a cache block and handles all outstanding requests for the
685     * satisfied fill request. This version takes two memory requests. One
686     * contains the fill data, the other is an optional target to satisfy.
687     * Note that the reason we return a list of writebacks rather than
688     * inserting them directly in the write buffer is that this function
689     * is called by both atomic and timing-mode accesses, and in atomic
690     * mode we don't mess with the write buffer (we just perform the
691     * writebacks atomically once the original request is complete).
692     *
693     * @param pkt The memory request with the fill data.
694     * @param blk The cache block if it already exists.
695     * @param writebacks List for any writebacks that need to be performed.
696     * @param allocate Whether to allocate a block or use the temp block
697     * @return Pointer to the new cache block.
698     */
699    CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
700                         PacketList &writebacks, bool allocate);
701
702    /**
703     * Allocate a new block and perform any necessary writebacks
704     *
705     * Find a victim block and if necessary prepare writebacks for any
706     * existing data. May return nullptr if there are no replaceable
707     * blocks. If a replaceable block is found, it inserts the new block in
708     * its place. The new block, however, is not set as valid yet.
709     *
710     * @param pkt Packet holding the address to update
711     * @param writebacks A list of writeback packets for the evicted blocks
712     * @return the allocated block
713     */
714    CacheBlk *allocateBlock(const PacketPtr pkt, PacketList &writebacks);
715    /**
716     * Evict a cache block.
717     *
718     * Performs a writeback if necesssary and invalidates the block
719     *
720     * @param blk Block to invalidate
721     * @return A packet with the writeback, can be nullptr
722     */
723    M5_NODISCARD virtual PacketPtr evictBlock(CacheBlk *blk) = 0;
724
725    /**
726     * Evict a cache block.
727     *
728     * Performs a writeback if necesssary and invalidates the block
729     *
730     * @param blk Block to invalidate
731     * @param writebacks Return a list of packets with writebacks
732     */
733    void evictBlock(CacheBlk *blk, PacketList &writebacks);
734
735    /**
736     * Invalidate a cache block.
737     *
738     * @param blk Block to invalidate
739     */
740    void invalidateBlock(CacheBlk *blk);
741
742    /**
743     * Create a writeback request for the given block.
744     *
745     * @param blk The block to writeback.
746     * @return The writeback request for the block.
747     */
748    PacketPtr writebackBlk(CacheBlk *blk);
749
750    /**
751     * Create a writeclean request for the given block.
752     *
753     * Creates a request that writes the block to the cache below
754     * without evicting the block from the current cache.
755     *
756     * @param blk The block to write clean.
757     * @param dest The destination of the write clean operation.
758     * @param id Use the given packet id for the write clean operation.
759     * @return The generated write clean packet.
760     */
761    PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id);
762
763    /**
764     * Write back dirty blocks in the cache using functional accesses.
765     */
766    virtual void memWriteback() override;
767
768    /**
769     * Invalidates all blocks in the cache.
770     *
771     * @warn Dirty cache lines will not be written back to
772     * memory. Make sure to call functionalWriteback() first if you
773     * want the to write them to memory.
774     */
775    virtual void memInvalidate() override;
776
777    /**
778     * Determine if there are any dirty blocks in the cache.
779     *
780     * @return true if at least one block is dirty, false otherwise.
781     */
782    bool isDirty() const;
783
784    /**
785     * Determine if an address is in the ranges covered by this
786     * cache. This is useful to filter snoops.
787     *
788     * @param addr Address to check against
789     *
790     * @return If the address in question is in range
791     */
792    bool inRange(Addr addr) const;
793
794    /**
795     * Find next request ready time from among possible sources.
796     */
797    Tick nextQueueReadyTime() const;
798
799    /** Block size of this cache */
800    const unsigned blkSize;
801
802    /**
803     * The latency of tag lookup of a cache. It occurs when there is
804     * an access to the cache.
805     */
806    const Cycles lookupLatency;
807
808    /**
809     * The latency of data access of a cache. It occurs when there is
810     * an access to the cache.
811     */
812    const Cycles dataLatency;
813
814    /**
815     * This is the forward latency of the cache. It occurs when there
816     * is a cache miss and a request is forwarded downstream, in
817     * particular an outbound miss.
818     */
819    const Cycles forwardLatency;
820
821    /** The latency to fill a cache block */
822    const Cycles fillLatency;
823
824    /**
825     * The latency of sending reponse to its upper level cache/core on
826     * a linefill. The responseLatency parameter captures this
827     * latency.
828     */
829    const Cycles responseLatency;
830
831    /**
832     * Whether tags and data are accessed sequentially.
833     */
834    const bool sequentialAccess;
835
836    /** The number of targets for each MSHR. */
837    const int numTarget;
838
839    /** Do we forward snoops from mem side port through to cpu side port? */
840    bool forwardSnoops;
841
842    /**
843     * Clusivity with respect to the upstream cache, determining if we
844     * fill into both this cache and the cache above on a miss. Note
845     * that we currently do not support strict clusivity policies.
846     */
847    const Enums::Clusivity clusivity;
848
849    /**
850     * Is this cache read only, for example the instruction cache, or
851     * table-walker cache. A cache that is read only should never see
852     * any writes, and should never get any dirty data (and hence
853     * never have to do any writebacks).
854     */
855    const bool isReadOnly;
856
857    /**
858     * Bit vector of the blocking reasons for the access path.
859     * @sa #BlockedCause
860     */
861    uint8_t blocked;
862
863    /** Increasing order number assigned to each incoming request. */
864    uint64_t order;
865
866    /** Stores time the cache blocked for statistics. */
867    Cycles blockedCycle;
868
869    /** Pointer to the MSHR that has no targets. */
870    MSHR *noTargetMSHR;
871
872    /** The number of misses to trigger an exit event. */
873    Counter missCount;
874
875    /**
876     * The address range to which the cache responds on the CPU side.
877     * Normally this is all possible memory addresses. */
878    const AddrRangeList addrRanges;
879
880  public:
881    /** System we are currently operating in. */
882    System *system;
883
884    // Statistics
885    /**
886     * @addtogroup CacheStatistics
887     * @{
888     */
889
890    /** Number of hits per thread for each type of command.
891        @sa Packet::Command */
892    Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
893    /** Number of hits for demand accesses. */
894    Stats::Formula demandHits;
895    /** Number of hit for all accesses. */
896    Stats::Formula overallHits;
897
898    /** Number of misses per thread for each type of command.
899        @sa Packet::Command */
900    Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
901    /** Number of misses for demand accesses. */
902    Stats::Formula demandMisses;
903    /** Number of misses for all accesses. */
904    Stats::Formula overallMisses;
905
906    /**
907     * Total number of cycles per thread/command spent waiting for a miss.
908     * Used to calculate the average miss latency.
909     */
910    Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
911    /** Total number of cycles spent waiting for demand misses. */
912    Stats::Formula demandMissLatency;
913    /** Total number of cycles spent waiting for all misses. */
914    Stats::Formula overallMissLatency;
915
916    /** The number of accesses per command and thread. */
917    Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
918    /** The number of demand accesses. */
919    Stats::Formula demandAccesses;
920    /** The number of overall accesses. */
921    Stats::Formula overallAccesses;
922
923    /** The miss rate per command and thread. */
924    Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
925    /** The miss rate of all demand accesses. */
926    Stats::Formula demandMissRate;
927    /** The miss rate for all accesses. */
928    Stats::Formula overallMissRate;
929
930    /** The average miss latency per command and thread. */
931    Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
932    /** The average miss latency for demand misses. */
933    Stats::Formula demandAvgMissLatency;
934    /** The average miss latency for all misses. */
935    Stats::Formula overallAvgMissLatency;
936
937    /** The total number of cycles blocked for each blocked cause. */
938    Stats::Vector blocked_cycles;
939    /** The number of times this cache blocked for each blocked cause. */
940    Stats::Vector blocked_causes;
941
942    /** The average number of cycles blocked for each blocked cause. */
943    Stats::Formula avg_blocked;
944
945    /** The number of times a HW-prefetched block is evicted w/o reference. */
946    Stats::Scalar unusedPrefetches;
947
948    /** Number of blocks written back per thread. */
949    Stats::Vector writebacks;
950
951    /** Number of misses that hit in the MSHRs per command and thread. */
952    Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
953    /** Demand misses that hit in the MSHRs. */
954    Stats::Formula demandMshrHits;
955    /** Total number of misses that hit in the MSHRs. */
956    Stats::Formula overallMshrHits;
957
958    /** Number of misses that miss in the MSHRs, per command and thread. */
959    Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
960    /** Demand misses that miss in the MSHRs. */
961    Stats::Formula demandMshrMisses;
962    /** Total number of misses that miss in the MSHRs. */
963    Stats::Formula overallMshrMisses;
964
965    /** Number of misses that miss in the MSHRs, per command and thread. */
966    Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
967    /** Total number of misses that miss in the MSHRs. */
968    Stats::Formula overallMshrUncacheable;
969
970    /** Total cycle latency of each MSHR miss, per command and thread. */
971    Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
972    /** Total cycle latency of demand MSHR misses. */
973    Stats::Formula demandMshrMissLatency;
974    /** Total cycle latency of overall MSHR misses. */
975    Stats::Formula overallMshrMissLatency;
976
977    /** Total cycle latency of each MSHR miss, per command and thread. */
978    Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
979    /** Total cycle latency of overall MSHR misses. */
980    Stats::Formula overallMshrUncacheableLatency;
981
982#if 0
983    /** The total number of MSHR accesses per command and thread. */
984    Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
985    /** The total number of demand MSHR accesses. */
986    Stats::Formula demandMshrAccesses;
987    /** The total number of MSHR accesses. */
988    Stats::Formula overallMshrAccesses;
989#endif
990
991    /** The miss rate in the MSHRs pre command and thread. */
992    Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
993    /** The demand miss rate in the MSHRs. */
994    Stats::Formula demandMshrMissRate;
995    /** The overall miss rate in the MSHRs. */
996    Stats::Formula overallMshrMissRate;
997
998    /** The average latency of an MSHR miss, per command and thread. */
999    Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
1000    /** The average latency of a demand MSHR miss. */
1001    Stats::Formula demandAvgMshrMissLatency;
1002    /** The average overall latency of an MSHR miss. */
1003    Stats::Formula overallAvgMshrMissLatency;
1004
1005    /** The average latency of an MSHR miss, per command and thread. */
1006    Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
1007    /** The average overall latency of an MSHR miss. */
1008    Stats::Formula overallAvgMshrUncacheableLatency;
1009
1010    /** Number of replacements of valid blocks. */
1011    Stats::Scalar replacements;
1012
1013    /**
1014     * @}
1015     */
1016
1017    /**
1018     * Register stats for this object.
1019     */
1020    void regStats() override;
1021
1022    /** Registers probes. */
1023    void regProbePoints() override;
1024
1025  public:
1026    BaseCache(const BaseCacheParams *p, unsigned blk_size);
1027    ~BaseCache();
1028
1029    void init() override;
1030
1031    BaseMasterPort &getMasterPort(const std::string &if_name,
1032                                  PortID idx = InvalidPortID) override;
1033    BaseSlavePort &getSlavePort(const std::string &if_name,
1034                                PortID idx = InvalidPortID) override;
1035
1036    /**
1037     * Query block size of a cache.
1038     * @return  The block size
1039     */
1040    unsigned
1041    getBlockSize() const
1042    {
1043        return blkSize;
1044    }
1045
1046    const AddrRangeList &getAddrRanges() const { return addrRanges; }
1047
1048    MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
1049    {
1050        MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
1051                                        pkt, time, order++,
1052                                        allocOnFill(pkt->cmd));
1053
1054        if (mshrQueue.isFull()) {
1055            setBlocked((BlockedCause)MSHRQueue_MSHRs);
1056        }
1057
1058        if (sched_send) {
1059            // schedule the send
1060            schedMemSideSendEvent(time);
1061        }
1062
1063        return mshr;
1064    }
1065
1066    void allocateWriteBuffer(PacketPtr pkt, Tick time)
1067    {
1068        // should only see writes or clean evicts here
1069        assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);
1070
1071        Addr blk_addr = pkt->getBlockAddr(blkSize);
1072
1073        WriteQueueEntry *wq_entry =
1074            writeBuffer.findMatch(blk_addr, pkt->isSecure());
1075        if (wq_entry && !wq_entry->inService) {
1076            DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
1077        }
1078
1079        writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);
1080
1081        if (writeBuffer.isFull()) {
1082            setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
1083        }
1084
1085        // schedule the send
1086        schedMemSideSendEvent(time);
1087    }
1088
1089    /**
1090     * Returns true if the cache is blocked for accesses.
1091     */
1092    bool isBlocked() const
1093    {
1094        return blocked != 0;
1095    }
1096
1097    /**
1098     * Marks the access path of the cache as blocked for the given cause. This
1099     * also sets the blocked flag in the slave interface.
1100     * @param cause The reason for the cache blocking.
1101     */
1102    void setBlocked(BlockedCause cause)
1103    {
1104        uint8_t flag = 1 << cause;
1105        if (blocked == 0) {
1106            blocked_causes[cause]++;
1107            blockedCycle = curCycle();
1108            cpuSidePort.setBlocked();
1109        }
1110        blocked |= flag;
1111        DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
1112    }
1113
1114    /**
1115     * Marks the cache as unblocked for the given cause. This also clears the
1116     * blocked flags in the appropriate interfaces.
1117     * @param cause The newly unblocked cause.
1118     * @warning Calling this function can cause a blocked request on the bus to
1119     * access the cache. The cache must be in a state to handle that request.
1120     */
1121    void clearBlocked(BlockedCause cause)
1122    {
1123        uint8_t flag = 1 << cause;
1124        blocked &= ~flag;
1125        DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
1126        if (blocked == 0) {
1127            blocked_cycles[cause] += curCycle() - blockedCycle;
1128            cpuSidePort.clearBlocked();
1129        }
1130    }
1131
1132    /**
1133     * Schedule a send event for the memory-side port. If already
1134     * scheduled, this may reschedule the event at an earlier
1135     * time. When the specified time is reached, the port is free to
1136     * send either a response, a request, or a prefetch request.
1137     *
1138     * @param time The time when to attempt sending a packet.
1139     */
1140    void schedMemSideSendEvent(Tick time)
1141    {
1142        memSidePort.schedSendEvent(time);
1143    }
1144
1145    bool inCache(Addr addr, bool is_secure) const {
1146        return tags->findBlock(addr, is_secure);
1147    }
1148
1149    bool hasBeenPrefetched(Addr addr, bool is_secure) const {
1150        CacheBlk *block = tags->findBlock(addr, is_secure);
1151        if (block) {
1152            return block->wasPrefetched();
1153        } else {
1154            return false;
1155        }
1156    }
1157
1158    bool inMissQueue(Addr addr, bool is_secure) const {
1159        return mshrQueue.findMatch(addr, is_secure);
1160    }
1161
1162    void incMissCount(PacketPtr pkt)
1163    {
1164        assert(pkt->req->masterId() < system->maxMasters());
1165        misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
1166        pkt->req->incAccessDepth();
1167        if (missCount) {
1168            --missCount;
1169            if (missCount == 0)
1170                exitSimLoop("A cache reached the maximum miss count");
1171        }
1172    }
1173    void incHitCount(PacketPtr pkt)
1174    {
1175        assert(pkt->req->masterId() < system->maxMasters());
1176        hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
1177
1178    }
1179
1180    /**
1181     * Checks if the cache is coalescing writes
1182     *
1183     * @return True if the cache is coalescing writes
1184     */
1185    bool coalesce() const;
1186
1187
1188    /**
1189     * Cache block visitor that writes back dirty cache blocks using
1190     * functional writes.
1191     */
1192    void writebackVisitor(CacheBlk &blk);
1193
1194    /**
1195     * Cache block visitor that invalidates all blocks in the cache.
1196     *
1197     * @warn Dirty cache lines will not be written back to memory.
1198     */
1199    void invalidateVisitor(CacheBlk &blk);
1200
1201    /**
1202     * Take an MSHR, turn it into a suitable downstream packet, and
1203     * send it out. This construct allows a queue entry to choose a suitable
1204     * approach based on its type.
1205     *
1206     * @param mshr The MSHR to turn into a packet and send
1207     * @return True if the port is waiting for a retry
1208     */
1209    virtual bool sendMSHRQueuePacket(MSHR* mshr);
1210
1211    /**
1212     * Similar to sendMSHR, but for a write-queue entry
1213     * instead. Create the packet, and send it, and if successful also
1214     * mark the entry in service.
1215     *
1216     * @param wq_entry The write-queue entry to turn into a packet and send
1217     * @return True if the port is waiting for a retry
1218     */
1219    bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
1220
1221    /**
1222     * Serialize the state of the caches
1223     *
1224     * We currently don't support checkpointing cache state, so this panics.
1225     */
1226    void serialize(CheckpointOut &cp) const override;
1227    void unserialize(CheckpointIn &cp) override;
1228};
1229
1230/**
1231 * The write allocator inspects write packets and detects streaming
1232 * patterns. The write allocator supports a single stream where writes
1233 * are expected to access consecutive locations and keeps track of
1234 * size of the area covered by the concecutive writes in byteCount.
1235 *
1236 * 1) When byteCount has surpassed the coallesceLimit the mode
1237 * switches from ALLOCATE to COALESCE where writes should be delayed
1238 * until the whole block is written at which point a single packet
1239 * (whole line write) can service them.
1240 *
1241 * 2) When byteCount has also exceeded the noAllocateLimit (whole
1242 * line) we switch to NO_ALLOCATE when writes should not allocate in
1243 * the cache but rather send a whole line write to the memory below.
1244 */
1245class WriteAllocator : public SimObject {
1246  public:
1247    WriteAllocator(const WriteAllocatorParams *p) :
1248        SimObject(p),
1249        coalesceLimit(p->coalesce_limit * p->block_size),
1250        noAllocateLimit(p->no_allocate_limit * p->block_size),
1251        delayThreshold(p->delay_threshold)
1252    {
1253        reset();
1254    }
1255
1256    /**
1257     * Should writes be coalesced? This is true if the mode is set to
1258     * NO_ALLOCATE.
1259     *
1260     * @return return true if the cache should coalesce writes.
1261     */
1262    bool coalesce() const {
1263        return mode != WriteMode::ALLOCATE;
1264    }
1265
1266    /**
1267     * Should writes allocate?
1268     *
1269     * @return return true if the cache should not allocate for writes.
1270     */
1271    bool allocate() const {
1272        return mode != WriteMode::NO_ALLOCATE;
1273    }
1274
1275    /**
1276     * Reset the write allocator state, meaning that it allocates for
1277     * writes and has not recorded any information about qualifying
1278     * writes that might trigger a switch to coalescing and later no
1279     * allocation.
1280     */
1281    void reset() {
1282        mode = WriteMode::ALLOCATE;
1283        byteCount = 0;
1284        nextAddr = 0;
1285    }
1286
1287    /**
1288     * Access whether we need to delay the current write.
1289     *
1290     * @param blk_addr The block address the packet writes to
1291     * @return true if the current packet should be delayed
1292     */
1293    bool delay(Addr blk_addr) {
1294        if (delayCtr[blk_addr] > 0) {
1295            --delayCtr[blk_addr];
1296            return true;
1297        } else {
1298            return false;
1299        }
1300    }
1301
1302    /**
1303     * Clear delay counter for the input block
1304     *
1305     * @param blk_addr The accessed cache block
1306     */
1307    void resetDelay(Addr blk_addr) {
1308        delayCtr.erase(blk_addr);
1309    }
1310
1311    /**
1312     * Update the write mode based on the current write
1313     * packet. This method compares the packet's address with any
1314     * current stream, and updates the tracking and the mode
1315     * accordingly.
1316     *
1317     * @param write_addr Start address of the write request
1318     * @param write_size Size of the write request
1319     * @param blk_addr The block address that this packet writes to
1320     */
1321    void updateMode(Addr write_addr, unsigned write_size, Addr blk_addr);
1322
1323  private:
1324    /**
1325     * The current mode for write coalescing and allocation, either
1326     * normal operation (ALLOCATE), write coalescing (COALESCE), or
1327     * write coalescing without allocation (NO_ALLOCATE).
1328     */
1329    enum class WriteMode : char {
1330        ALLOCATE,
1331        COALESCE,
1332        NO_ALLOCATE,
1333    };
1334    WriteMode mode;
1335
1336    /** Address to match writes against to detect streams. */
1337    Addr nextAddr;
1338
1339    /**
1340     * Bytes written contiguously. Saturating once we no longer
1341     * allocate.
1342     */
1343    uint32_t byteCount;
1344
1345    /**
1346     * Limits for when to switch between the different write modes.
1347     */
1348    const uint32_t coalesceLimit;
1349    const uint32_t noAllocateLimit;
1350    /**
1351     * The number of times the allocator will delay an WriteReq MSHR.
1352     */
1353    const uint32_t delayThreshold;
1354
1355    /**
1356     * Keep track of the number of times the allocator has delayed an
1357     * WriteReq MSHR.
1358     */
1359    std::unordered_map<Addr, Counter> delayCtr;
1360};
1361
1362#endif //__MEM_CACHE_BASE_HH__
1363