1/*
2 * Copyright (c) 2012-2013, 2015-2016 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 __MEM_CACHE_MSHR_HH__
49#define __MEM_CACHE_MSHR_HH__
50
51#include <list>
52
53#include "base/printable.hh"
54#include "mem/cache/queue_entry.hh"
55
56class Cache;
57
58/**
59 * Miss Status and handling Register. This class keeps all the information
60 * needed to handle a cache miss including a list of target requests.
61 * @sa \ref gem5MemorySystem "gem5 Memory System"
62 */
63class MSHR : public QueueEntry, public Printable
64{
65
66 /**
67 * Consider the queues friends to avoid making everything public.
68 */
69 template<typename Entry>
70 friend class Queue;
71 friend class MSHRQueue;
72
73 private:
74
75 /** Flag set by downstream caches */
76 bool downstreamPending;
77
78 /**
79 * Here we use one flag to track both if:
80 *
81 * 1. We are going to become owner or not, i.e., we will get the
82 * block in an ownership state (Owned or Modified) with BlkDirty
83 * set. This determines whether or not we are going to become the
84 * responder and ordering point for future requests that we snoop.
85 *
86 * 2. We know that we are going to get a writable block, i.e. we
87 * will get the block in writable state (Exclusive or Modified
88 * state) with BlkWritable set. That determines whether additional
89 * targets with needsWritable set will be able to be satisfied, or
90 * if not should be put on the deferred list to possibly wait for
91 * another request that does give us writable access.
92 *
93 * Condition 2 is actually just a shortcut that saves us from
94 * possibly building a deferred target list and calling
95 * promoteWritable() every time we get a writable block. Condition
96 * 1, tracking ownership, is what is important. However, we never
97 * receive ownership without marking the block dirty, and
98 * consequently use pendingModified to track both ownership and
99 * writability rather than having separate pendingDirty and
100 * pendingWritable flags.
101 */
102 bool pendingModified;
103
104 /** Did we snoop an invalidate while waiting for data? */
105 bool postInvalidate;
106
107 /** Did we snoop a read while waiting for data? */
108 bool postDowngrade;
109
110 public:
111
112 /** True if the entry is just a simple forward from an upper level */
113 bool isForward;
114
115 class Target {
116 public:
117
118 enum Source {
119 FromCPU,
120 FromSnoop,
121 FromPrefetcher
122 };
123
124 const Tick recvTime; //!< Time when request was received (for stats)
125 const Tick readyTime; //!< Time when request is ready to be serviced
126 const Counter order; //!< Global order (for memory consistency mgmt)
127 const PacketPtr pkt; //!< Pending request packet.
128 const Source source; //!< Request from cpu, memory, or prefetcher?
129 const bool markedPending; //!< Did we mark upstream MSHR
130 //!< as downstreamPending?
131
132 Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
133 Source _source, bool _markedPending)
134 : recvTime(curTick()), readyTime(_readyTime), order(_order),
135 pkt(_pkt), source(_source), markedPending(_markedPending)
136 {}
137 };
138
139 class TargetList : public std::list<Target> {
140
141 public:
142 bool needsWritable;
143 bool hasUpgrade;
144
145 TargetList();
146
147 /**
148 * Use the provided packet and the source to update the
149 * flags of this TargetList.
150 *
151 * @param pkt Packet considered for the flag update
152 * @param source Indicates the source of the packet
153 */
154 void updateFlags(PacketPtr pkt, Target::Source source);
155
156 void resetFlags() { needsWritable = hasUpgrade = false; }
157
158 /**
159 * Goes through the list of targets and uses them to populate
160 * the flags of this TargetList. When the function returns the
161 * flags are consistent with the properties of packets in the
162 * list.
163 */
164 void populateFlags();
165
166 bool isReset() const { return !needsWritable && !hasUpgrade; }
167 void add(PacketPtr pkt, Tick readyTime, Counter order,
168 Target::Source source, bool markPending);
169
170 /**
171 * Convert upgrades to the equivalent request if the cache line they
172 * refer to would have been invalid (Upgrade -> ReadEx, SC* -> Fail).
173 * Used to rejig ordering between targets waiting on an MSHR. */
174 void replaceUpgrades();
175
176 void clearDownstreamPending();
177 bool checkFunctional(PacketPtr pkt);
178 void print(std::ostream &os, int verbosity,
179 const std::string &prefix) const;
180 };
181
182 /** A list of MSHRs. */
183 typedef std::list<MSHR *> List;
184 /** MSHR list iterator. */
185 typedef List::iterator Iterator;
186
187 /** Keep track of whether we should allocate on fill or not */
188 bool allocOnFill;
189
190 /** The pending* and post* flags are only valid if inService is
191 * true. Using the accessor functions lets us detect if these
192 * flags are accessed improperly.
193 */
194
195 /** True if we need to get a writable copy of the block. */
196 bool needsWritable() const { return targets.needsWritable; }
197
198 bool isPendingModified() const {
199 assert(inService); return pendingModified;
200 }
201
202 bool hasPostInvalidate() const {
203 assert(inService); return postInvalidate;
204 }
205
206 bool hasPostDowngrade() const {
207 assert(inService); return postDowngrade;
208 }
209
210 bool sendPacket(Cache &cache);
211
212 private:
213
214 /**
215 * Pointer to this MSHR on the ready list.
216 * @sa MissQueue, MSHRQueue::readyList
217 */
218 Iterator readyIter;
219
220 /**
221 * Pointer to this MSHR on the allocated list.
222 * @sa MissQueue, MSHRQueue::allocatedList
223 */
224 Iterator allocIter;
225
226 /** List of all requests that match the address */
227 TargetList targets;
228
229 TargetList deferredTargets;
230
231 public:
232
233 /**
234 * Allocate a miss to this MSHR.
235 * @param blk_addr The address of the block.
236 * @param blk_size The number of bytes to request.
237 * @param pkt The original miss.
238 * @param when_ready When should the MSHR be ready to act upon.
239 * @param _order The logical order of this MSHR
240 * @param alloc_on_fill Should the cache allocate a block on fill
241 */
242 void allocate(Addr blk_addr, unsigned blk_size, PacketPtr pkt,
243 Tick when_ready, Counter _order, bool alloc_on_fill);
244
245 void markInService(bool pending_modified_resp);
246
247 void clearDownstreamPending();
248
249 /**
250 * Mark this MSHR as free.
251 */
252 void deallocate();
253
254 /**
255 * Add a request to the list of targets.
256 * @param target The target.
257 */
258 void allocateTarget(PacketPtr target, Tick when, Counter order,
259 bool alloc_on_fill);
260 bool handleSnoop(PacketPtr target, Counter order);
261
262 /** A simple constructor. */
263 MSHR();
264
265 /**
266 * Returns the current number of allocated targets.
267 * @return The current number of allocated targets.
268 */
269 int getNumTargets() const
270 { return targets.size() + deferredTargets.size(); }
271
272 /**
273 * Returns true if there are targets left.
274 * @return true if there are targets
275 */
276 bool hasTargets() const { return !targets.empty(); }
277
278 /**
279 * Returns a reference to the first target.
280 * @return A pointer to the first target.
281 */
282 Target *getTarget()
283 {
284 assert(hasTargets());
285 return &targets.front();
286 }
287
288 /**
289 * Pop first target.
290 */
291 void popTarget()
292 {
293 targets.pop_front();
294 }
295
296 bool promoteDeferredTargets();
297
298 void promoteWritable();
299
300 bool checkFunctional(PacketPtr pkt);
301
302 /**
303 * Prints the contents of this MSHR for debugging.
304 */
305 void print(std::ostream &os,
306 int verbosity = 0,
307 const std::string &prefix = "") const;
308 /**
309 * A no-args wrapper of print(std::ostream...) meant to be
310 * invoked from DPRINTFs avoiding string overheads in fast mode
311 *
312 * @return string with mshr fields + [deferred]targets
313 */
314 std::string print() const;
315};
316
317#endif // __MEM_CACHE_MSHR_HH__