coherent_xbar.hh revision 13808:0a44fbc3a853
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_map> 55#include <unordered_set> 56 57#include "mem/snoop_filter.hh" 58#include "mem/xbar.hh" 59#include "params/CoherentXBar.hh" 60 61/** 62 * A coherent crossbar connects a number of (potentially) snooping 63 * masters and slaves, and routes the request and response packets 64 * based on the address, and also forwards all requests to the 65 * snoopers and deals with the snoop responses. 66 * 67 * The coherent crossbar can be used as a template for modelling QPI, 68 * HyperTransport, ACE and coherent OCP buses, and is typically used 69 * for the L1-to-L2 buses and as the main system interconnect. @sa 70 * \ref gem5MemorySystem "gem5 Memory System" 71 */ 72class CoherentXBar : public BaseXBar 73{ 74 75 protected: 76 77 /** 78 * Declare the layers of this crossbar, one vector for requests, 79 * one for responses, and one for snoop responses 80 */ 81 std::vector<ReqLayer*> reqLayers; 82 std::vector<RespLayer*> respLayers; 83 std::vector<SnoopRespLayer*> snoopLayers; 84 85 /** 86 * Declaration of the coherent crossbar slave port type, one will 87 * be instantiated for each of the master ports connecting to the 88 * crossbar. 89 */ 90 class CoherentXBarSlavePort : public QueuedSlavePort 91 { 92 93 private: 94 95 /** A reference to the crossbar to which this port belongs. */ 96 CoherentXBar &xbar; 97 98 /** A normal packet queue used to store responses. */ 99 RespPacketQueue queue; 100 101 public: 102 103 CoherentXBarSlavePort(const std::string &_name, 104 CoherentXBar &_xbar, PortID _id) 105 : QueuedSlavePort(_name, &_xbar, queue, _id), xbar(_xbar), 106 queue(_xbar, *this) 107 { } 108 109 protected: 110 111 bool 112 recvTimingReq(PacketPtr pkt) override 113 { 114 return xbar.recvTimingReq(pkt, id); 115 } 116 117 bool 118 recvTimingSnoopResp(PacketPtr pkt) override 119 { 120 return xbar.recvTimingSnoopResp(pkt, id); 121 } 122 123 Tick 124 recvAtomic(PacketPtr pkt) override 125 { 126 return xbar.recvAtomic(pkt, id); 127 } 128 129 void 130 recvFunctional(PacketPtr pkt) override 131 { 132 xbar.recvFunctional(pkt, id); 133 } 134 135 AddrRangeList 136 getAddrRanges() const override 137 { 138 return xbar.getAddrRanges(); 139 } 140 141 }; 142 143 /** 144 * Declaration of the coherent crossbar master port type, one will be 145 * instantiated for each of the slave interfaces connecting to the 146 * crossbar. 147 */ 148 class CoherentXBarMasterPort : public MasterPort 149 { 150 private: 151 /** A reference to the crossbar to which this port belongs. */ 152 CoherentXBar &xbar; 153 154 public: 155 156 CoherentXBarMasterPort(const std::string &_name, 157 CoherentXBar &_xbar, PortID _id) 158 : MasterPort(_name, &_xbar, _id), xbar(_xbar) 159 { } 160 161 protected: 162 163 /** 164 * Determine if this port should be considered a snooper. For 165 * a coherent crossbar master port this is always true. 166 * 167 * @return a boolean that is true if this port is snooping 168 */ 169 bool isSnooping() const override { return true; } 170 171 bool 172 recvTimingResp(PacketPtr pkt) override 173 { 174 return xbar.recvTimingResp(pkt, id); 175 } 176 177 void 178 recvTimingSnoopReq(PacketPtr pkt) override 179 { 180 return xbar.recvTimingSnoopReq(pkt, id); 181 } 182 183 Tick 184 recvAtomicSnoop(PacketPtr pkt) override 185 { 186 return xbar.recvAtomicSnoop(pkt, id); 187 } 188 189 void 190 recvFunctionalSnoop(PacketPtr pkt) override 191 { 192 xbar.recvFunctionalSnoop(pkt, id); 193 } 194 195 void recvRangeChange() override { xbar.recvRangeChange(id); } 196 void recvReqRetry() override { xbar.recvReqRetry(id); } 197 198 }; 199 200 /** 201 * Internal class to bridge between an incoming snoop response 202 * from a slave port and forwarding it through an outgoing slave 203 * port. It is effectively a dangling master port. 204 */ 205 class SnoopRespPort : public MasterPort 206 { 207 208 private: 209 210 /** The port which we mirror internally. */ 211 QueuedSlavePort& slavePort; 212 213 public: 214 215 /** 216 * Create a snoop response port that mirrors a given slave port. 217 */ 218 SnoopRespPort(QueuedSlavePort& slave_port, CoherentXBar& _xbar) : 219 MasterPort(slave_port.name() + ".snoopRespPort", &_xbar), 220 slavePort(slave_port) { } 221 222 /** 223 * Override the sending of retries and pass them on through 224 * the mirrored slave port. 225 */ 226 void 227 sendRetryResp() override 228 { 229 // forward it as a snoop response retry 230 slavePort.sendRetrySnoopResp(); 231 } 232 233 void 234 recvReqRetry() override 235 { 236 panic("SnoopRespPort should never see retry"); 237 } 238 239 bool 240 recvTimingResp(PacketPtr pkt) override 241 { 242 panic("SnoopRespPort should never see timing response"); 243 } 244 245 }; 246 247 std::vector<SnoopRespPort*> snoopRespPorts; 248 249 std::vector<QueuedSlavePort*> snoopPorts; 250 251 /** 252 * Store the outstanding requests that we are expecting snoop 253 * responses from so we can determine which snoop responses we 254 * generated and which ones were merely forwarded. 255 */ 256 std::unordered_set<RequestPtr> outstandingSnoop; 257 258 /** 259 * Store the outstanding cache maintenance that we are expecting 260 * snoop responses from so we can determine when we received all 261 * snoop responses and if any of the agents satisfied the request. 262 */ 263 std::unordered_map<PacketId, PacketPtr> outstandingCMO; 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 const Cycles snoopResponseLatency; 276 const bool pointOfCoherency; 277 const bool pointOfUnification; 278 279 /** 280 * Upstream caches need this packet until true is returned, so 281 * hold it for deletion until a subsequent call 282 */ 283 std::unique_ptr<Packet> pendingDelete; 284 285 bool recvTimingReq(PacketPtr pkt, PortID slave_port_id); 286 bool recvTimingResp(PacketPtr pkt, PortID master_port_id); 287 void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id); 288 bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id); 289 void recvReqRetry(PortID master_port_id); 290 291 /** 292 * Forward a timing packet to our snoopers, potentially excluding 293 * one of the connected coherent masters to avoid sending a packet 294 * back to where it came from. 295 * 296 * @param pkt Packet to forward 297 * @param exclude_slave_port_id Id of slave port to exclude 298 */ 299 void 300 forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) 301 { 302 forwardTiming(pkt, exclude_slave_port_id, snoopPorts); 303 } 304 305 /** 306 * Forward a timing packet to a selected list of snoopers, potentially 307 * excluding one of the connected coherent masters to avoid sending a packet 308 * back to where it came from. 309 * 310 * @param pkt Packet to forward 311 * @param exclude_slave_port_id Id of slave port to exclude 312 * @param dests Vector of destination ports for the forwarded pkt 313 */ 314 void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id, 315 const std::vector<QueuedSlavePort*>& dests); 316 317 Tick recvAtomic(PacketPtr pkt, PortID slave_port_id); 318 Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id); 319 320 /** 321 * Forward an atomic packet to our snoopers, potentially excluding 322 * one of the connected coherent masters to avoid sending a packet 323 * back to where it came from. 324 * 325 * @param pkt Packet to forward 326 * @param exclude_slave_port_id Id of slave port to exclude 327 * 328 * @return a pair containing the snoop response and snoop latency 329 */ 330 std::pair<MemCmd, Tick> 331 forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id) 332 { 333 return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID, 334 snoopPorts); 335 } 336 337 /** 338 * Forward an atomic packet to a selected list of snoopers, potentially 339 * excluding one of the connected coherent masters to avoid sending a packet 340 * back to where it came from. 341 * 342 * @param pkt Packet to forward 343 * @param exclude_slave_port_id Id of slave port to exclude 344 * @param source_master_port_id Id of the master port for snoops from below 345 * @param dests Vector of destination ports for the forwarded pkt 346 * 347 * @return a pair containing the snoop response and snoop latency 348 */ 349 std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt, 350 PortID exclude_slave_port_id, 351 PortID source_master_port_id, 352 const std::vector<QueuedSlavePort*>& 353 dests); 354 355 /** Function called by the port when the crossbar is recieving a Functional 356 transaction.*/ 357 void recvFunctional(PacketPtr pkt, PortID slave_port_id); 358 359 /** Function called by the port when the crossbar is recieving a functional 360 snoop transaction.*/ 361 void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id); 362 363 /** 364 * Forward a functional packet to our snoopers, potentially 365 * excluding one of the connected coherent masters to avoid 366 * sending a packet back to where it came from. 367 * 368 * @param pkt Packet to forward 369 * @param exclude_slave_port_id Id of slave port to exclude 370 */ 371 void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id); 372 373 /** 374 * Determine if the crossbar should sink the packet, as opposed to 375 * forwarding it, or responding. 376 */ 377 bool sinkPacket(const PacketPtr pkt) const; 378 379 /** 380 * Determine if the crossbar should forward the packet, as opposed to 381 * responding to it. 382 */ 383 bool forwardPacket(const PacketPtr pkt); 384 385 /** 386 * Determine if the packet's destination is the memory below 387 * 388 * The memory below is the destination for a cache mainteance 389 * operation to the Point of Coherence/Unification if this is the 390 * Point of Coherence/Unification. 391 * 392 * @param pkt The processed packet 393 * 394 * @return Whether the memory below is the destination for the packet 395 */ 396 bool 397 isDestination(const PacketPtr pkt) const 398 { 399 return (pkt->req->isToPOC() && pointOfCoherency) || 400 (pkt->req->isToPOU() && pointOfUnification); 401 } 402 403 Stats::Scalar snoops; 404 Stats::Scalar snoopTraffic; 405 Stats::Distribution snoopFanout; 406 407 public: 408 409 virtual void init(); 410 411 CoherentXBar(const CoherentXBarParams *p); 412 413 virtual ~CoherentXBar(); 414 415 virtual void regStats(); 416}; 417 418#endif //__MEM_COHERENT_XBAR_HH__ 419