mshr.hh revision 10502:f2f1dbfd505e 
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    /** Did we snoop an invalidate while waiting for data? */
87    bool postInvalidate;
88
89    /** Did we snoop a read while waiting for data? */
90    bool postDowngrade;
91
92    /** Did we get WriteInvalidate'd (and therefore obsoleted)? */
93    bool _isObsolete;
94
95  public:
96
97    class Target {
98      public:
99
100        enum Source {
101            FromCPU,
102            FromSnoop,
103            FromPrefetcher
104        };
105
106        Tick recvTime;  //!< Time when request was received (for stats)
107        Tick readyTime; //!< Time when request is ready to be serviced
108        Counter order;  //!< Global order (for memory consistency mgmt)
109        PacketPtr pkt;  //!< Pending request packet.
110        Source source;  //!< Did request come from cpu, memory, or prefetcher?
111        bool markedPending; //!< Did we mark upstream MSHR
112                            //!<  as downstreamPending?
113
114        Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
115               Source _source, bool _markedPending)
116            : recvTime(curTick()), readyTime(_readyTime), order(_order),
117              pkt(_pkt), source(_source), markedPending(_markedPending)
118        {}
119    };
120
121    class TargetList : public std::list<Target> {
122        /** Target list iterator. */
123        typedef std::list<Target>::iterator Iterator;
124        typedef std::list<Target>::const_iterator ConstIterator;
125
126      public:
127        bool needsExclusive;
128        bool hasUpgrade;
129
130        TargetList();
131        void resetFlags() { needsExclusive = hasUpgrade = false; }
132        bool isReset()    { return !needsExclusive && !hasUpgrade; }
133        void add(PacketPtr pkt, Tick readyTime, Counter order,
134                 Target::Source source, bool markPending);
135        void replaceUpgrades();
136        void clearDownstreamPending();
137        bool checkFunctional(PacketPtr pkt);
138        void print(std::ostream &os, int verbosity,
139                   const std::string &prefix) const;
140    };
141
142    /** A list of MSHRs. */
143    typedef std::list<MSHR *> List;
144    /** MSHR list iterator. */
145    typedef List::iterator Iterator;
146    /** MSHR list const_iterator. */
147    typedef List::const_iterator ConstIterator;
148
149    /** Pointer to queue containing this MSHR. */
150    MSHRQueue *queue;
151
152    /** Order number assigned by the miss queue. */
153    Counter order;
154
155    /** Address of the request. */
156    Addr addr;
157
158    /** Size of the request. */
159    int size;
160
161    /** True if the request targets the secure memory space. */
162    bool isSecure;
163
164    /** True if the request has been sent to the bus. */
165    bool inService;
166
167    /** True if the request is just a simple forward from an upper level */
168    bool isForward;
169
170    /** The pending* and post* flags are only valid if inService is
171     *  true.  Using the accessor functions lets us detect if these
172     *  flags are accessed improperly.
173     */
174
175    /** True if we need to get an exclusive copy of the block. */
176    bool needsExclusive() const { return targets.needsExclusive; }
177
178    bool isPendingDirty() const {
179        assert(inService); return pendingDirty;
180    }
181
182    bool hasPostInvalidate() const {
183        assert(inService); return postInvalidate;
184    }
185
186    bool hasPostDowngrade() const {
187        assert(inService); return postDowngrade;
188    }
189
190    /** Thread number of the miss. */
191    ThreadID threadNum;
192
193  private:
194
195    /** Data buffer (if needed).  Currently used only for pending
196     * upgrade handling. */
197    uint8_t *data;
198
199    /**
200     * Pointer to this MSHR on the ready list.
201     * @sa MissQueue, MSHRQueue::readyList
202     */
203    Iterator readyIter;
204
205    /**
206     * Pointer to this MSHR on the allocated list.
207     * @sa MissQueue, MSHRQueue::allocatedList
208     */
209    Iterator allocIter;
210
211    /** List of all requests that match the address */
212    TargetList targets;
213
214    TargetList deferredTargets;
215
216  public:
217
218    bool isUncacheable() const { return _isUncacheable; }
219
220    bool isObsolete() const { return _isObsolete; }
221
222    /**
223     * Allocate a miss to this MSHR.
224     * @param cmd The requesting command.
225     * @param addr The address of the miss.
226     * @param asid The address space id of the miss.
227     * @param size The number of bytes to request.
228     * @param pkt  The original miss.
229     */
230    void allocate(Addr addr, int size, PacketPtr pkt,
231                  Tick when, Counter _order);
232
233    bool markInService(PacketPtr pkt);
234
235    void clearDownstreamPending();
236
237    /**
238     * Mark this MSHR as free.
239     */
240    void deallocate();
241
242    /**
243     * Add a request to the list of targets.
244     * @param target The target.
245     */
246    void allocateTarget(PacketPtr target, Tick when, Counter order);
247    bool handleSnoop(PacketPtr target, Counter order);
248
249    /** A simple constructor. */
250    MSHR();
251
252    /**
253     * Returns the current number of allocated targets.
254     * @return The current number of allocated targets.
255     */
256    int getNumTargets() const
257    { return targets.size() + deferredTargets.size(); }
258
259    /**
260     * Returns true if there are targets left.
261     * @return true if there are targets
262     */
263    bool hasTargets() const { return !targets.empty(); }
264
265    /**
266     * Returns a reference to the first target.
267     * @return A pointer to the first target.
268     */
269    Target *getTarget()
270    {
271        assert(hasTargets());
272        return &targets.front();
273    }
274
275    /**
276     * Pop first target.
277     */
278    void popTarget()
279    {
280        targets.pop_front();
281    }
282
283    bool isForwardNoResponse() const
284    {
285        if (getNumTargets() != 1)
286            return false;
287        const Target *tgt = &targets.front();
288        return tgt->source == Target::FromCPU && !tgt->pkt->needsResponse();
289    }
290
291    bool promoteDeferredTargets();
292
293    void handleFill(Packet *pkt, CacheBlk *blk);
294
295    bool checkFunctional(PacketPtr pkt);
296
297    /** Mark this MSHR as tracking a transaction with obsoleted data. It still
298      * needs to complete its lifecycle, but should not modify the cache. */
299    void markObsolete() {
300        _isObsolete = true;
301    }
302
303    /**
304     * Prints the contents of this MSHR for debugging.
305     */
306    void print(std::ostream &os,
307               int verbosity = 0,
308               const std::string &prefix = "") const;
309    /**
310     * A no-args wrapper of print(std::ostream...)  meant to be
311     * invoked from DPRINTFs avoiding string overheads in fast mode
312     *
313     * @return string with mshr fields + [deferred]targets
314     */
315    std::string print() const;
316};
317
318#endif //__MSHR_HH__
319