mshr.hh revision 10503:94d58056729f 
1/*
2 * Copyright (c) 2012-2013 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) 2002-2005 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 */
42
43/**
44 * @file
45 * Miss Status and Handling Register (MSHR) declaration.
46 */
47
48#ifndef __MSHR_HH__
49#define __MSHR_HH__
50
51#include <list>
52
53#include "base/printable.hh"
54#include "mem/packet.hh"
55
56class CacheBlk;
57class MSHRQueue;
58
59/**
60 * Miss Status and handling Register. This class keeps all the information
61 * needed to handle a cache miss including a list of target requests.
62 * @sa  \ref gem5MemorySystem "gem5 Memory System"
63 */
64class MSHR : public Packet::SenderState, public Printable
65{
66
67    /**
68     * Consider the MSHRQueue a friend to avoid making everything public
69     */
70    friend class MSHRQueue;
71
72  private:
73
74    /** Cycle when ready to issue */
75    Tick readyTime;
76
77    /** True if the request is uncacheable */
78    bool _isUncacheable;
79
80    /** Flag set by downstream caches */
81    bool downstreamPending;
82
83    /** Will we have a dirty copy after this request? */
84    bool pendingDirty;
85
86    /** Will we have a clean copy after this request?  (i.e. is writeback) */
87    bool pendingClean;
88
89    /** Did we snoop an invalidate while waiting for data? */
90    bool postInvalidate;
91
92    /** Did we snoop a read while waiting for data? */
93    bool postDowngrade;
94
95    /** Did we get WriteInvalidate'd (and therefore obsoleted)? */
96    bool _isObsolete;
97
98  public:
99
100    class Target {
101      public:
102
103        enum Source {
104            FromCPU,
105            FromSnoop,
106            FromPrefetcher
107        };
108
109        Tick recvTime;  //!< Time when request was received (for stats)
110        Tick readyTime; //!< Time when request is ready to be serviced
111        Counter order;  //!< Global order (for memory consistency mgmt)
112        PacketPtr pkt;  //!< Pending request packet.
113        Source source;  //!< Did request come from cpu, memory, or prefetcher?
114        bool markedPending; //!< Did we mark upstream MSHR
115                            //!<  as downstreamPending?
116
117        Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
118               Source _source, bool _markedPending)
119            : recvTime(curTick()), readyTime(_readyTime), order(_order),
120              pkt(_pkt), source(_source), markedPending(_markedPending)
121        {}
122    };
123
124    class TargetList : public std::list<Target> {
125        /** Target list iterator. */
126        typedef std::list<Target>::iterator Iterator;
127        typedef std::list<Target>::const_iterator ConstIterator;
128
129      public:
130        bool needsExclusive;
131        bool hasUpgrade;
132
133        TargetList();
134        void resetFlags() { needsExclusive = hasUpgrade = false; }
135        bool isReset()    { return !needsExclusive && !hasUpgrade; }
136        void add(PacketPtr pkt, Tick readyTime, Counter order,
137                 Target::Source source, bool markPending);
138        void replaceUpgrades();
139        void clearDownstreamPending();
140        bool checkFunctional(PacketPtr pkt);
141        void print(std::ostream &os, int verbosity,
142                   const std::string &prefix) const;
143    };
144
145    /** A list of MSHRs. */
146    typedef std::list<MSHR *> List;
147    /** MSHR list iterator. */
148    typedef List::iterator Iterator;
149    /** MSHR list const_iterator. */
150    typedef List::const_iterator ConstIterator;
151
152    /** Pointer to queue containing this MSHR. */
153    MSHRQueue *queue;
154
155    /** Order number assigned by the miss queue. */
156    Counter order;
157
158    /** Address of the request. */
159    Addr addr;
160
161    /** Size of the request. */
162    int size;
163
164    /** True if the request targets the secure memory space. */
165    bool isSecure;
166
167    /** True if the request has been sent to the bus. */
168    bool inService;
169
170    /** True if the request is just a simple forward from an upper level */
171    bool isForward;
172
173    /** The pending* and post* flags are only valid if inService is
174     *  true.  Using the accessor functions lets us detect if these
175     *  flags are accessed improperly.
176     */
177
178    /** True if we need to get an exclusive copy of the block. */
179    bool needsExclusive() const { return targets.needsExclusive; }
180
181    bool isPendingDirty() const {
182        assert(inService); return pendingDirty;
183    }
184
185    bool isPendingClean() const {
186        return pendingClean;
187    }
188
189    bool hasPostInvalidate() const {
190        assert(inService); return postInvalidate;
191    }
192
193    bool hasPostDowngrade() const {
194        assert(inService); return postDowngrade;
195    }
196
197    /** Thread number of the miss. */
198    ThreadID threadNum;
199
200  private:
201
202    /** Data buffer (if needed).  Currently used only for pending
203     * upgrade handling. */
204    uint8_t *data;
205
206    /**
207     * Pointer to this MSHR on the ready list.
208     * @sa MissQueue, MSHRQueue::readyList
209     */
210    Iterator readyIter;
211
212    /**
213     * Pointer to this MSHR on the allocated list.
214     * @sa MissQueue, MSHRQueue::allocatedList
215     */
216    Iterator allocIter;
217
218    /** List of all requests that match the address */
219    TargetList targets;
220
221    TargetList deferredTargets;
222
223  public:
224
225    bool isUncacheable() const { return _isUncacheable; }
226
227    bool isObsolete() const { return _isObsolete; }
228
229    /**
230     * Allocate a miss to this MSHR.
231     * @param cmd The requesting command.
232     * @param addr The address of the miss.
233     * @param asid The address space id of the miss.
234     * @param size The number of bytes to request.
235     * @param pkt  The original miss.
236     */
237    void allocate(Addr addr, int size, PacketPtr pkt,
238                  Tick when, Counter _order);
239
240    bool markInService(PacketPtr pkt);
241
242    void clearDownstreamPending();
243
244    /**
245     * Mark this MSHR as free.
246     */
247    void deallocate();
248
249    /**
250     * Add a request to the list of targets.
251     * @param target The target.
252     */
253    void allocateTarget(PacketPtr target, Tick when, Counter order);
254    bool handleSnoop(PacketPtr target, Counter order);
255
256    /** A simple constructor. */
257    MSHR();
258
259    /**
260     * Returns the current number of allocated targets.
261     * @return The current number of allocated targets.
262     */
263    int getNumTargets() const
264    { return targets.size() + deferredTargets.size(); }
265
266    /**
267     * Returns true if there are targets left.
268     * @return true if there are targets
269     */
270    bool hasTargets() const { return !targets.empty(); }
271
272    /**
273     * Returns a reference to the first target.
274     * @return A pointer to the first target.
275     */
276    Target *getTarget()
277    {
278        assert(hasTargets());
279        return &targets.front();
280    }
281
282    /**
283     * Pop first target.
284     */
285    void popTarget()
286    {
287        targets.pop_front();
288    }
289
290    bool isForwardNoResponse() const
291    {
292        if (getNumTargets() != 1)
293            return false;
294        const Target *tgt = &targets.front();
295        return tgt->source == Target::FromCPU && !tgt->pkt->needsResponse();
296    }
297
298    bool promoteDeferredTargets();
299
300    void handleFill(Packet *pkt, CacheBlk *blk);
301
302    bool checkFunctional(PacketPtr pkt);
303
304    /** Mark this MSHR as tracking a transaction with obsoleted data. It still
305      * needs to complete its lifecycle, but should not modify the cache. */
306    void markObsolete() {
307        _isObsolete = true;
308    }
309
310    /**
311     * Prints the contents of this MSHR for debugging.
312     */
313    void print(std::ostream &os,
314               int verbosity = 0,
315               const std::string &prefix = "") const;
316    /**
317     * A no-args wrapper of print(std::ostream...)  meant to be
318     * invoked from DPRINTFs avoiding string overheads in fast mode
319     *
320     * @return string with mshr fields + [deferred]targets
321     */
322    std::string print() const;
323};
324
325#endif //__MSHR_HH__
326