coherent_xbar.hh revision 12341 
1/*
2 * Copyright (c) 2011-2015, 2017 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: Ron Dreslinski
41 *          Ali Saidi
42 *          Andreas Hansson
43 *          William Wang
44 */
45
46/**
47 * @file
48 * Declaration of a coherent crossbar.
49 */
50
51#ifndef __MEM_COHERENT_XBAR_HH__
52#define __MEM_COHERENT_XBAR_HH__
53
54#include <unordered_set>
55
56#include "mem/snoop_filter.hh"
57#include "mem/xbar.hh"
58#include "params/CoherentXBar.hh"
59
60/**
61 * A coherent crossbar connects a number of (potentially) snooping
62 * masters and slaves, and routes the request and response packets
63 * based on the address, and also forwards all requests to the
64 * snoopers and deals with the snoop responses.
65 *
66 * The coherent crossbar can be used as a template for modelling QPI,
67 * HyperTransport, ACE and coherent OCP buses, and is typically used
68 * for the L1-to-L2 buses and as the main system interconnect.  @sa
69 * \ref gem5MemorySystem "gem5 Memory System"
70 */
71class CoherentXBar : public BaseXBar
72{
73
74  protected:
75
76    /**
77     * Declare the layers of this crossbar, one vector for requests,
78     * one for responses, and one for snoop responses
79     */
80    std::vector<ReqLayer*> reqLayers;
81    std::vector<RespLayer*> respLayers;
82    std::vector<SnoopRespLayer*> snoopLayers;
83
84    /**
85     * Declaration of the coherent crossbar slave port type, one will
86     * be instantiated for each of the master ports connecting to the
87     * crossbar.
88     */
89    class CoherentXBarSlavePort : public QueuedSlavePort
90    {
91
92      private:
93
94        /** A reference to the crossbar to which this port belongs. */
95        CoherentXBar &xbar;
96
97        /** A normal packet queue used to store responses. */
98        RespPacketQueue queue;
99
100      public:
101
102        CoherentXBarSlavePort(const std::string &_name,
103                             CoherentXBar &_xbar, PortID _id)
104            : QueuedSlavePort(_name, &_xbar, queue, _id), xbar(_xbar),
105              queue(_xbar, *this)
106        { }
107
108      protected:
109
110        /**
111         * When receiving a timing request, pass it to the crossbar.
112         */
113        virtual bool recvTimingReq(PacketPtr pkt)
114        { return xbar.recvTimingReq(pkt, id); }
115
116        /**
117         * When receiving a timing snoop response, pass it to the crossbar.
118         */
119        virtual bool recvTimingSnoopResp(PacketPtr pkt)
120        { return xbar.recvTimingSnoopResp(pkt, id); }
121
122        /**
123         * When receiving an atomic request, pass it to the crossbar.
124         */
125        virtual Tick recvAtomic(PacketPtr pkt)
126        { return xbar.recvAtomic(pkt, id); }
127
128        /**
129         * When receiving a functional request, pass it to the crossbar.
130         */
131        virtual void recvFunctional(PacketPtr pkt)
132        { xbar.recvFunctional(pkt, id); }
133
134        /**
135         * Return the union of all adress ranges seen by this crossbar.
136         */
137        virtual AddrRangeList getAddrRanges() const
138        { return xbar.getAddrRanges(); }
139
140    };
141
142    /**
143     * Declaration of the coherent crossbar master port type, one will be
144     * instantiated for each of the slave interfaces connecting to the
145     * crossbar.
146     */
147    class CoherentXBarMasterPort : public MasterPort
148    {
149      private:
150        /** A reference to the crossbar to which this port belongs. */
151        CoherentXBar &xbar;
152
153      public:
154
155        CoherentXBarMasterPort(const std::string &_name,
156                              CoherentXBar &_xbar, PortID _id)
157            : MasterPort(_name, &_xbar, _id), xbar(_xbar)
158        { }
159
160      protected:
161
162        /**
163         * Determine if this port should be considered a snooper. For
164         * a coherent crossbar master port this is always true.
165         *
166         * @return a boolean that is true if this port is snooping
167         */
168        virtual bool isSnooping() const
169        { return true; }
170
171        /**
172         * When receiving a timing response, pass it to the crossbar.
173         */
174        virtual bool recvTimingResp(PacketPtr pkt)
175        { return xbar.recvTimingResp(pkt, id); }
176
177        /**
178         * When receiving a timing snoop request, pass it to the crossbar.
179         */
180        virtual void recvTimingSnoopReq(PacketPtr pkt)
181        { return xbar.recvTimingSnoopReq(pkt, id); }
182
183        /**
184         * When receiving an atomic snoop request, pass it to the crossbar.
185         */
186        virtual Tick recvAtomicSnoop(PacketPtr pkt)
187        { return xbar.recvAtomicSnoop(pkt, id); }
188
189        /**
190         * When receiving a functional snoop request, pass it to the crossbar.
191         */
192        virtual void recvFunctionalSnoop(PacketPtr pkt)
193        { xbar.recvFunctionalSnoop(pkt, id); }
194
195        /** When reciving a range change from the peer port (at id),
196            pass it to the crossbar. */
197        virtual void recvRangeChange()
198        { xbar.recvRangeChange(id); }
199
200        /** When reciving a retry from the peer port (at id),
201            pass it to the crossbar. */
202        virtual void recvReqRetry()
203        { xbar.recvReqRetry(id); }
204
205    };
206
207    /**
208     * Internal class to bridge between an incoming snoop response
209     * from a slave port and forwarding it through an outgoing slave
210     * port. It is effectively a dangling master port.
211     */
212    class SnoopRespPort : public MasterPort
213    {
214
215      private:
216
217        /** The port which we mirror internally. */
218        QueuedSlavePort& slavePort;
219
220      public:
221
222        /**
223         * Create a snoop response port that mirrors a given slave port.
224         */
225        SnoopRespPort(QueuedSlavePort& slave_port, CoherentXBar& _xbar) :
226            MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
227            slavePort(slave_port) { }
228
229        /**
230         * Override the sending of retries and pass them on through
231         * the mirrored slave port.
232         */
233        void sendRetryResp() {
234            // forward it as a snoop response retry
235            slavePort.sendRetrySnoopResp();
236        }
237
238        /**
239         * Provided as necessary.
240         */
241        void recvReqRetry() { panic("SnoopRespPort should never see retry\n"); }
242
243        /**
244         * Provided as necessary.
245         */
246        bool recvTimingResp(PacketPtr pkt)
247        {
248            panic("SnoopRespPort should never see timing response\n");
249            return false;
250        }
251
252    };
253
254    std::vector<SnoopRespPort*> snoopRespPorts;
255
256    std::vector<QueuedSlavePort*> snoopPorts;
257
258    /**
259     * Store the outstanding requests that we are expecting snoop
260     * responses from so we can determine which snoop responses we
261     * generated and which ones were merely forwarded.
262     */
263    std::unordered_set<RequestPtr> outstandingSnoop;
264
265    /**
266     * Keep a pointer to the system to be allow to querying memory system
267     * properties.
268     */
269    System *system;
270
271    /** A snoop filter that tracks cache line residency and can restrict the
272      * broadcast needed for probes.  NULL denotes an absent filter. */
273    SnoopFilter *snoopFilter;
274
275    /** Cycles of snoop response latency.*/
276    const Cycles snoopResponseLatency;
277
278    /** Is this crossbar the point of coherency? **/
279    const bool pointOfCoherency;
280
281    /** Is this crossbar the point of unification? **/
282    const bool pointOfUnification;
283
284    /**
285     * Upstream caches need this packet until true is returned, so
286     * hold it for deletion until a subsequent call
287     */
288    std::unique_ptr<Packet> pendingDelete;
289
290    /** Function called by the port when the crossbar is recieving a Timing
291      request packet.*/
292    bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
293
294    /** Function called by the port when the crossbar is recieving a Timing
295      response packet.*/
296    bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
297
298    /** Function called by the port when the crossbar is recieving a timing
299        snoop request.*/
300    void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
301
302    /** Function called by the port when the crossbar is recieving a timing
303        snoop response.*/
304    bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
305
306    /** Timing function called by port when it is once again able to process
307     * requests. */
308    void recvReqRetry(PortID master_port_id);
309
310    /**
311     * Forward a timing packet to our snoopers, potentially excluding
312     * one of the connected coherent masters to avoid sending a packet
313     * back to where it came from.
314     *
315     * @param pkt Packet to forward
316     * @param exclude_slave_port_id Id of slave port to exclude
317     */
318    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) {
319        forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
320    }
321
322    /**
323     * Forward a timing packet to a selected list of snoopers, potentially
324     * excluding one of the connected coherent masters to avoid sending a packet
325     * back to where it came from.
326     *
327     * @param pkt Packet to forward
328     * @param exclude_slave_port_id Id of slave port to exclude
329     * @param dests Vector of destination ports for the forwarded pkt
330     */
331    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
332                       const std::vector<QueuedSlavePort*>& dests);
333
334    /** Function called by the port when the crossbar is recieving a Atomic
335      transaction.*/
336    Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
337
338    /** Function called by the port when the crossbar is recieving an
339        atomic snoop transaction.*/
340    Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);
341
342    /**
343     * Forward an atomic packet to our snoopers, potentially excluding
344     * one of the connected coherent masters to avoid sending a packet
345     * back to where it came from.
346     *
347     * @param pkt Packet to forward
348     * @param exclude_slave_port_id Id of slave port to exclude
349     *
350     * @return a pair containing the snoop response and snoop latency
351     */
352    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
353                                          PortID exclude_slave_port_id)
354    {
355        return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID,
356                             snoopPorts);
357    }
358
359    /**
360     * Forward an atomic packet to a selected list of snoopers, potentially
361     * excluding one of the connected coherent masters to avoid sending a packet
362     * back to where it came from.
363     *
364     * @param pkt Packet to forward
365     * @param exclude_slave_port_id Id of slave port to exclude
366     * @param source_master_port_id Id of the master port for snoops from below
367     * @param dests Vector of destination ports for the forwarded pkt
368     *
369     * @return a pair containing the snoop response and snoop latency
370     */
371    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
372                                          PortID exclude_slave_port_id,
373                                          PortID source_master_port_id,
374                                          const std::vector<QueuedSlavePort*>&
375                                          dests);
376
377    /** Function called by the port when the crossbar is recieving a Functional
378        transaction.*/
379    void recvFunctional(PacketPtr pkt, PortID slave_port_id);
380
381    /** Function called by the port when the crossbar is recieving a functional
382        snoop transaction.*/
383    void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
384
385    /**
386     * Forward a functional packet to our snoopers, potentially
387     * excluding one of the connected coherent masters to avoid
388     * sending a packet back to where it came from.
389     *
390     * @param pkt Packet to forward
391     * @param exclude_slave_port_id Id of slave port to exclude
392     */
393    void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
394
395    /**
396     * Determine if the crossbar should sink the packet, as opposed to
397     * forwarding it, or responding.
398     */
399    bool sinkPacket(const PacketPtr pkt) const;
400
401    Stats::Scalar snoops;
402    Stats::Scalar snoopTraffic;
403    Stats::Distribution snoopFanout;
404
405  public:
406
407    virtual void init();
408
409    CoherentXBar(const CoherentXBarParams *p);
410
411    virtual ~CoherentXBar();
412
413    virtual void regStats();
414};
415
416#endif //__MEM_COHERENT_XBAR_HH__
417