cache.cc revision 11177
1/* 2 * Copyright (c) 2010-2015 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 * Copyright (c) 2010,2015 Advanced Micro Devices, Inc. 16 * All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions are 20 * met: redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer; 22 * redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution; 25 * neither the name of the copyright holders nor the names of its 26 * contributors may be used to endorse or promote products derived from 27 * this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * Authors: Erik Hallnor 42 * Dave Greene 43 * Nathan Binkert 44 * Steve Reinhardt 45 * Ron Dreslinski 46 * Andreas Sandberg 47 */ 48 49/** 50 * @file 51 * Cache definitions. 52 */ 53 54#include "mem/cache/cache.hh" 55 56#include "base/misc.hh" 57#include "base/types.hh" 58#include "debug/Cache.hh" 59#include "debug/CachePort.hh" 60#include "debug/CacheTags.hh" 61#include "mem/cache/blk.hh" 62#include "mem/cache/mshr.hh" 63#include "mem/cache/prefetch/base.hh" 64#include "sim/sim_exit.hh" 65 66Cache::Cache(const CacheParams *p) 67 : BaseCache(p, p->system->cacheLineSize()), 68 tags(p->tags), 69 prefetcher(p->prefetcher), 70 doFastWrites(true), 71 prefetchOnAccess(p->prefetch_on_access) 72{ 73 tempBlock = new CacheBlk(); 74 tempBlock->data = new uint8_t[blkSize]; 75 76 cpuSidePort = new CpuSidePort(p->name + ".cpu_side", this, 77 "CpuSidePort"); 78 memSidePort = new MemSidePort(p->name + ".mem_side", this, 79 "MemSidePort"); 80 81 tags->setCache(this); 82 if (prefetcher) 83 prefetcher->setCache(this); 84} 85 86Cache::~Cache() 87{ 88 delete [] tempBlock->data; 89 delete tempBlock; 90 91 delete cpuSidePort; 92 delete memSidePort; 93} 94 95void 96Cache::regStats() 97{ 98 BaseCache::regStats(); 99} 100 101void 102Cache::cmpAndSwap(CacheBlk *blk, PacketPtr pkt) 103{ 104 assert(pkt->isRequest()); 105 106 uint64_t overwrite_val; 107 bool overwrite_mem; 108 uint64_t condition_val64; 109 uint32_t condition_val32; 110 111 int offset = tags->extractBlkOffset(pkt->getAddr()); 112 uint8_t *blk_data = blk->data + offset; 113 114 assert(sizeof(uint64_t) >= pkt->getSize()); 115 116 overwrite_mem = true; 117 // keep a copy of our possible write value, and copy what is at the 118 // memory address into the packet 119 pkt->writeData((uint8_t *)&overwrite_val); 120 pkt->setData(blk_data); 121 122 if (pkt->req->isCondSwap()) { 123 if (pkt->getSize() == sizeof(uint64_t)) { 124 condition_val64 = pkt->req->getExtraData(); 125 overwrite_mem = !std::memcmp(&condition_val64, blk_data, 126 sizeof(uint64_t)); 127 } else if (pkt->getSize() == sizeof(uint32_t)) { 128 condition_val32 = (uint32_t)pkt->req->getExtraData(); 129 overwrite_mem = !std::memcmp(&condition_val32, blk_data, 130 sizeof(uint32_t)); 131 } else 132 panic("Invalid size for conditional read/write\n"); 133 } 134 135 if (overwrite_mem) { 136 std::memcpy(blk_data, &overwrite_val, pkt->getSize()); 137 blk->status |= BlkDirty; 138 } 139} 140 141 142void 143Cache::satisfyCpuSideRequest(PacketPtr pkt, CacheBlk *blk, 144 bool deferred_response, bool pending_downgrade) 145{ 146 assert(pkt->isRequest()); 147 148 assert(blk && blk->isValid()); 149 // Occasionally this is not true... if we are a lower-level cache 150 // satisfying a string of Read and ReadEx requests from 151 // upper-level caches, a Read will mark the block as shared but we 152 // can satisfy a following ReadEx anyway since we can rely on the 153 // Read requester(s) to have buffered the ReadEx snoop and to 154 // invalidate their blocks after receiving them. 155 // assert(!pkt->needsExclusive() || blk->isWritable()); 156 assert(pkt->getOffset(blkSize) + pkt->getSize() <= blkSize); 157 158 // Check RMW operations first since both isRead() and 159 // isWrite() will be true for them 160 if (pkt->cmd == MemCmd::SwapReq) { 161 cmpAndSwap(blk, pkt); 162 } else if (pkt->isWrite()) { 163 assert(blk->isWritable()); 164 // Write or WriteLine at the first cache with block in Exclusive 165 if (blk->checkWrite(pkt)) { 166 pkt->writeDataToBlock(blk->data, blkSize); 167 } 168 // Always mark the line as dirty even if we are a failed 169 // StoreCond so we supply data to any snoops that have 170 // appended themselves to this cache before knowing the store 171 // will fail. 172 blk->status |= BlkDirty; 173 DPRINTF(Cache, "%s for %s addr %#llx size %d (write)\n", __func__, 174 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 175 } else if (pkt->isRead()) { 176 if (pkt->isLLSC()) { 177 blk->trackLoadLocked(pkt); 178 } 179 pkt->setDataFromBlock(blk->data, blkSize); 180 // determine if this read is from a (coherent) cache, or not 181 // by looking at the command type; we could potentially add a 182 // packet attribute such as 'FromCache' to make this check a 183 // bit cleaner 184 if (pkt->cmd == MemCmd::ReadExReq || 185 pkt->cmd == MemCmd::ReadSharedReq || 186 pkt->cmd == MemCmd::ReadCleanReq || 187 pkt->cmd == MemCmd::SCUpgradeFailReq) { 188 assert(pkt->getSize() == blkSize); 189 // special handling for coherent block requests from 190 // upper-level caches 191 if (pkt->needsExclusive()) { 192 // sanity check 193 assert(pkt->cmd == MemCmd::ReadExReq || 194 pkt->cmd == MemCmd::SCUpgradeFailReq); 195 196 // if we have a dirty copy, make sure the recipient 197 // keeps it marked dirty 198 if (blk->isDirty()) { 199 pkt->assertMemInhibit(); 200 } 201 // on ReadExReq we give up our copy unconditionally 202 if (blk != tempBlock) 203 tags->invalidate(blk); 204 blk->invalidate(); 205 } else if (blk->isWritable() && !pending_downgrade && 206 !pkt->sharedAsserted() && 207 pkt->cmd != MemCmd::ReadCleanReq) { 208 // we can give the requester an exclusive copy (by not 209 // asserting shared line) on a read request if: 210 // - we have an exclusive copy at this level (& below) 211 // - we don't have a pending snoop from below 212 // signaling another read request 213 // - no other cache above has a copy (otherwise it 214 // would have asseretd shared line on request) 215 // - we are not satisfying an instruction fetch (this 216 // prevents dirty data in the i-cache) 217 218 if (blk->isDirty()) { 219 // special considerations if we're owner: 220 if (!deferred_response) { 221 // if we are responding immediately and can 222 // signal that we're transferring ownership 223 // along with exclusivity, do so 224 pkt->assertMemInhibit(); 225 blk->status &= ~BlkDirty; 226 } else { 227 // if we're responding after our own miss, 228 // there's a window where the recipient didn't 229 // know it was getting ownership and may not 230 // have responded to snoops correctly, so we 231 // can't pass off ownership *or* exclusivity 232 pkt->assertShared(); 233 } 234 } 235 } else { 236 // otherwise only respond with a shared copy 237 pkt->assertShared(); 238 } 239 } 240 } else { 241 // Upgrade or Invalidate, since we have it Exclusively (E or 242 // M), we ack then invalidate. 243 assert(pkt->isUpgrade() || pkt->isInvalidate()); 244 assert(blk != tempBlock); 245 tags->invalidate(blk); 246 blk->invalidate(); 247 DPRINTF(Cache, "%s for %s addr %#llx size %d (invalidation)\n", 248 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 249 } 250} 251 252 253///////////////////////////////////////////////////// 254// 255// MSHR helper functions 256// 257///////////////////////////////////////////////////// 258 259 260void 261Cache::markInService(MSHR *mshr, bool pending_dirty_resp) 262{ 263 markInServiceInternal(mshr, pending_dirty_resp); 264} 265 266///////////////////////////////////////////////////// 267// 268// Access path: requests coming in from the CPU side 269// 270///////////////////////////////////////////////////// 271 272bool 273Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat, 274 PacketList &writebacks) 275{ 276 // sanity check 277 assert(pkt->isRequest()); 278 279 chatty_assert(!(isReadOnly && pkt->isWrite()), 280 "Should never see a write in a read-only cache %s\n", 281 name()); 282 283 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 284 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 285 286 if (pkt->req->isUncacheable()) { 287 DPRINTF(Cache, "%s%s addr %#llx uncacheable\n", pkt->cmdString(), 288 pkt->req->isInstFetch() ? " (ifetch)" : "", 289 pkt->getAddr()); 290 291 // flush and invalidate any existing block 292 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure())); 293 if (old_blk && old_blk->isValid()) { 294 if (old_blk->isDirty()) 295 writebacks.push_back(writebackBlk(old_blk)); 296 else 297 writebacks.push_back(cleanEvictBlk(old_blk)); 298 tags->invalidate(old_blk); 299 old_blk->invalidate(); 300 } 301 302 blk = NULL; 303 // lookupLatency is the latency in case the request is uncacheable. 304 lat = lookupLatency; 305 return false; 306 } 307 308 ContextID id = pkt->req->hasContextId() ? 309 pkt->req->contextId() : InvalidContextID; 310 // Here lat is the value passed as parameter to accessBlock() function 311 // that can modify its value. 312 blk = tags->accessBlock(pkt->getAddr(), pkt->isSecure(), lat, id); 313 314 DPRINTF(Cache, "%s%s addr %#llx size %d (%s) %s\n", pkt->cmdString(), 315 pkt->req->isInstFetch() ? " (ifetch)" : "", 316 pkt->getAddr(), pkt->getSize(), pkt->isSecure() ? "s" : "ns", 317 blk ? "hit " + blk->print() : "miss"); 318 319 320 if (pkt->evictingBlock()) { 321 // We check for presence of block in above caches before issuing 322 // Writeback or CleanEvict to write buffer. Therefore the only 323 // possible cases can be of a CleanEvict packet coming from above 324 // encountering a Writeback generated in this cache peer cache and 325 // waiting in the write buffer. Cases of upper level peer caches 326 // generating CleanEvict and Writeback or simply CleanEvict and 327 // CleanEvict almost simultaneously will be caught by snoops sent out 328 // by crossbar. 329 std::vector<MSHR *> outgoing; 330 if (writeBuffer.findMatches(pkt->getAddr(), pkt->isSecure(), 331 outgoing)) { 332 assert(outgoing.size() == 1); 333 PacketPtr wbPkt = outgoing[0]->getTarget()->pkt; 334 assert(pkt->cmd == MemCmd::CleanEvict && 335 wbPkt->cmd == MemCmd::Writeback); 336 // As the CleanEvict is coming from above, it would have snooped 337 // into other peer caches of the same level while traversing the 338 // crossbar. If a copy of the block had been found, the CleanEvict 339 // would have been deleted in the crossbar. Now that the 340 // CleanEvict is here we can be sure none of the other upper level 341 // caches connected to this cache have the block, so we can clear 342 // the BLOCK_CACHED flag in the Writeback if set and discard the 343 // CleanEvict by returning true. 344 wbPkt->clearBlockCached(); 345 return true; 346 } 347 } 348 349 // Writeback handling is special case. We can write the block into 350 // the cache without having a writeable copy (or any copy at all). 351 if (pkt->cmd == MemCmd::Writeback) { 352 assert(blkSize == pkt->getSize()); 353 if (blk == NULL) { 354 // need to do a replacement 355 blk = allocateBlock(pkt->getAddr(), pkt->isSecure(), writebacks); 356 if (blk == NULL) { 357 // no replaceable block available: give up, fwd to next level. 358 incMissCount(pkt); 359 return false; 360 } 361 tags->insertBlock(pkt, blk); 362 363 blk->status = (BlkValid | BlkReadable); 364 if (pkt->isSecure()) { 365 blk->status |= BlkSecure; 366 } 367 } 368 blk->status |= BlkDirty; 369 // if shared is not asserted we got the writeback in modified 370 // state, if it is asserted we are in the owned state 371 if (!pkt->sharedAsserted()) { 372 blk->status |= BlkWritable; 373 } 374 // nothing else to do; writeback doesn't expect response 375 assert(!pkt->needsResponse()); 376 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize); 377 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print()); 378 incHitCount(pkt); 379 return true; 380 } else if (pkt->cmd == MemCmd::CleanEvict) { 381 if (blk != NULL) { 382 // Found the block in the tags, need to stop CleanEvict from 383 // propagating further down the hierarchy. Returning true will 384 // treat the CleanEvict like a satisfied write request and delete 385 // it. 386 return true; 387 } 388 // We didn't find the block here, propagate the CleanEvict further 389 // down the memory hierarchy. Returning false will treat the CleanEvict 390 // like a Writeback which could not find a replaceable block so has to 391 // go to next level. 392 return false; 393 } else if ((blk != NULL) && 394 (pkt->needsExclusive() ? blk->isWritable() 395 : blk->isReadable())) { 396 // OK to satisfy access 397 incHitCount(pkt); 398 satisfyCpuSideRequest(pkt, blk); 399 return true; 400 } 401 402 // Can't satisfy access normally... either no block (blk == NULL) 403 // or have block but need exclusive & only have shared. 404 405 incMissCount(pkt); 406 407 if (blk == NULL && pkt->isLLSC() && pkt->isWrite()) { 408 // complete miss on store conditional... just give up now 409 pkt->req->setExtraData(0); 410 return true; 411 } 412 413 return false; 414} 415 416 417class ForwardResponseRecord : public Packet::SenderState 418{ 419 public: 420 421 ForwardResponseRecord() {} 422}; 423 424void 425Cache::doWritebacks(PacketList& writebacks, Tick forward_time) 426{ 427 while (!writebacks.empty()) { 428 PacketPtr wbPkt = writebacks.front(); 429 // We use forwardLatency here because we are copying writebacks to 430 // write buffer. Call isCachedAbove for both Writebacks and 431 // CleanEvicts. If isCachedAbove returns true we set BLOCK_CACHED flag 432 // in Writebacks and discard CleanEvicts. 433 if (isCachedAbove(wbPkt)) { 434 if (wbPkt->cmd == MemCmd::CleanEvict) { 435 // Delete CleanEvict because cached copies exist above. The 436 // packet destructor will delete the request object because 437 // this is a non-snoop request packet which does not require a 438 // response. 439 delete wbPkt; 440 } else { 441 // Set BLOCK_CACHED flag in Writeback and send below, so that 442 // the Writeback does not reset the bit corresponding to this 443 // address in the snoop filter below. 444 wbPkt->setBlockCached(); 445 allocateWriteBuffer(wbPkt, forward_time); 446 } 447 } else { 448 // If the block is not cached above, send packet below. Both 449 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 450 // reset the bit corresponding to this address in the snoop filter 451 // below. 452 allocateWriteBuffer(wbPkt, forward_time); 453 } 454 writebacks.pop_front(); 455 } 456} 457 458void 459Cache::doWritebacksAtomic(PacketList& writebacks) 460{ 461 while (!writebacks.empty()) { 462 PacketPtr wbPkt = writebacks.front(); 463 // Call isCachedAbove for both Writebacks and CleanEvicts. If 464 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks 465 // and discard CleanEvicts. 466 if (isCachedAbove(wbPkt, false)) { 467 if (wbPkt->cmd == MemCmd::Writeback) { 468 // Set BLOCK_CACHED flag in Writeback and send below, 469 // so that the Writeback does not reset the bit 470 // corresponding to this address in the snoop filter 471 // below. We can discard CleanEvicts because cached 472 // copies exist above. Atomic mode isCachedAbove 473 // modifies packet to set BLOCK_CACHED flag 474 memSidePort->sendAtomic(wbPkt); 475 } 476 } else { 477 // If the block is not cached above, send packet below. Both 478 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 479 // reset the bit corresponding to this address in the snoop filter 480 // below. 481 memSidePort->sendAtomic(wbPkt); 482 } 483 writebacks.pop_front(); 484 // In case of CleanEvicts, the packet destructor will delete the 485 // request object because this is a non-snoop request packet which 486 // does not require a response. 487 delete wbPkt; 488 } 489} 490 491 492void 493Cache::recvTimingSnoopResp(PacketPtr pkt) 494{ 495 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 496 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 497 498 assert(pkt->isResponse()); 499 500 // must be cache-to-cache response from upper to lower level 501 ForwardResponseRecord *rec = 502 dynamic_cast<ForwardResponseRecord *>(pkt->senderState); 503 assert(!system->bypassCaches()); 504 505 if (rec == NULL) { 506 // @todo What guarantee do we have that this HardPFResp is 507 // actually for this cache, and not a cache closer to the 508 // memory? 509 assert(pkt->cmd == MemCmd::HardPFResp); 510 // Check if it's a prefetch response and handle it. We shouldn't 511 // get any other kinds of responses without FRRs. 512 DPRINTF(Cache, "Got prefetch response from above for addr %#llx (%s)\n", 513 pkt->getAddr(), pkt->isSecure() ? "s" : "ns"); 514 recvTimingResp(pkt); 515 return; 516 } 517 518 pkt->popSenderState(); 519 delete rec; 520 // forwardLatency is set here because there is a response from an 521 // upper level cache. 522 // To pay the delay that occurs if the packet comes from the bus, 523 // we charge also headerDelay. 524 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay; 525 // Reset the timing of the packet. 526 pkt->headerDelay = pkt->payloadDelay = 0; 527 memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time); 528} 529 530void 531Cache::promoteWholeLineWrites(PacketPtr pkt) 532{ 533 // Cache line clearing instructions 534 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) && 535 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) { 536 pkt->cmd = MemCmd::WriteLineReq; 537 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n"); 538 } 539} 540 541bool 542Cache::recvTimingReq(PacketPtr pkt) 543{ 544 DPRINTF(CacheTags, "%s tags: %s\n", __func__, tags->print()); 545//@todo Add back in MemDebug Calls 546// MemDebug::cacheAccess(pkt); 547 548 549 /// @todo temporary hack to deal with memory corruption issue until 550 /// 4-phase transactions are complete 551 for (int x = 0; x < pendingDelete.size(); x++) 552 delete pendingDelete[x]; 553 pendingDelete.clear(); 554 555 assert(pkt->isRequest()); 556 557 // Just forward the packet if caches are disabled. 558 if (system->bypassCaches()) { 559 // @todo This should really enqueue the packet rather 560 bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt); 561 assert(success); 562 return true; 563 } 564 565 promoteWholeLineWrites(pkt); 566 567 if (pkt->memInhibitAsserted()) { 568 // a cache above us (but not where the packet came from) is 569 // responding to the request 570 DPRINTF(Cache, "mem inhibited on addr %#llx (%s): not responding\n", 571 pkt->getAddr(), pkt->isSecure() ? "s" : "ns"); 572 573 // if the packet needs exclusive, and the cache that has 574 // promised to respond (setting the inhibit flag) is not 575 // providing exclusive (it is in O vs M state), we know that 576 // there may be other shared copies in the system; go out and 577 // invalidate them all 578 if (pkt->needsExclusive() && !pkt->isSupplyExclusive()) { 579 // create a downstream express snoop with cleared packet 580 // flags, there is no need to allocate any data as the 581 // packet is merely used to co-ordinate state transitions 582 Packet *snoop_pkt = new Packet(pkt, true, false); 583 584 // also reset the bus time that the original packet has 585 // not yet paid for 586 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0; 587 588 // make this an instantaneous express snoop, and let the 589 // other caches in the system know that the packet is 590 // inhibited, because we have found the authorative copy 591 // (O) that will supply the right data 592 snoop_pkt->setExpressSnoop(); 593 snoop_pkt->assertMemInhibit(); 594 595 // this express snoop travels towards the memory, and at 596 // every crossbar it is snooped upwards thus reaching 597 // every cache in the system 598 bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt); 599 // express snoops always succeed 600 assert(success); 601 602 // main memory will delete the packet 603 } 604 605 /// @todo nominally we should just delete the packet here, 606 /// however, until 4-phase stuff we can't because sending 607 /// cache is still relying on it. 608 pendingDelete.push_back(pkt); 609 610 // no need to take any action in this particular cache as the 611 // caches along the path to memory are allowed to keep lines 612 // in a shared state, and a cache above us already committed 613 // to responding 614 return true; 615 } 616 617 // anything that is merely forwarded pays for the forward latency and 618 // the delay provided by the crossbar 619 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 620 621 // We use lookupLatency here because it is used to specify the latency 622 // to access. 623 Cycles lat = lookupLatency; 624 CacheBlk *blk = NULL; 625 bool satisfied = false; 626 { 627 PacketList writebacks; 628 // Note that lat is passed by reference here. The function 629 // access() calls accessBlock() which can modify lat value. 630 satisfied = access(pkt, blk, lat, writebacks); 631 632 // copy writebacks to write buffer here to ensure they logically 633 // proceed anything happening below 634 doWritebacks(writebacks, forward_time); 635 } 636 637 // Here we charge the headerDelay that takes into account the latencies 638 // of the bus, if the packet comes from it. 639 // The latency charged it is just lat that is the value of lookupLatency 640 // modified by access() function, or if not just lookupLatency. 641 // In case of a hit we are neglecting response latency. 642 // In case of a miss we are neglecting forward latency. 643 Tick request_time = clockEdge(lat) + pkt->headerDelay; 644 // Here we reset the timing of the packet. 645 pkt->headerDelay = pkt->payloadDelay = 0; 646 647 // track time of availability of next prefetch, if any 648 Tick next_pf_time = MaxTick; 649 650 bool needsResponse = pkt->needsResponse(); 651 652 if (satisfied) { 653 // should never be satisfying an uncacheable access as we 654 // flush and invalidate any existing block as part of the 655 // lookup 656 assert(!pkt->req->isUncacheable()); 657 658 // hit (for all other request types) 659 660 if (prefetcher && (prefetchOnAccess || (blk && blk->wasPrefetched()))) { 661 if (blk) 662 blk->status &= ~BlkHWPrefetched; 663 664 // Don't notify on SWPrefetch 665 if (!pkt->cmd.isSWPrefetch()) 666 next_pf_time = prefetcher->notify(pkt); 667 } 668 669 if (needsResponse) { 670 pkt->makeTimingResponse(); 671 // @todo: Make someone pay for this 672 pkt->headerDelay = pkt->payloadDelay = 0; 673 674 // In this case we are considering request_time that takes 675 // into account the delay of the xbar, if any, and just 676 // lat, neglecting responseLatency, modelling hit latency 677 // just as lookupLatency or or the value of lat overriden 678 // by access(), that calls accessBlock() function. 679 cpuSidePort->schedTimingResp(pkt, request_time); 680 } else { 681 /// @todo nominally we should just delete the packet here, 682 /// however, until 4-phase stuff we can't because sending cache is 683 /// still relying on it. If the block is found in access(), 684 /// CleanEvict and Writeback messages will be deleted here as 685 /// well. 686 pendingDelete.push_back(pkt); 687 } 688 } else { 689 // miss 690 691 Addr blk_addr = blockAlign(pkt->getAddr()); 692 693 // ignore any existing MSHR if we are dealing with an 694 // uncacheable request 695 MSHR *mshr = pkt->req->isUncacheable() ? nullptr : 696 mshrQueue.findMatch(blk_addr, pkt->isSecure()); 697 698 // Software prefetch handling: 699 // To keep the core from waiting on data it won't look at 700 // anyway, send back a response with dummy data. Miss handling 701 // will continue asynchronously. Unfortunately, the core will 702 // insist upon freeing original Packet/Request, so we have to 703 // create a new pair with a different lifecycle. Note that this 704 // processing happens before any MSHR munging on the behalf of 705 // this request because this new Request will be the one stored 706 // into the MSHRs, not the original. 707 if (pkt->cmd.isSWPrefetch()) { 708 assert(needsResponse); 709 assert(pkt->req->hasPaddr()); 710 assert(!pkt->req->isUncacheable()); 711 712 // There's no reason to add a prefetch as an additional target 713 // to an existing MSHR. If an outstanding request is already 714 // in progress, there is nothing for the prefetch to do. 715 // If this is the case, we don't even create a request at all. 716 PacketPtr pf = nullptr; 717 718 if (!mshr) { 719 // copy the request and create a new SoftPFReq packet 720 RequestPtr req = new Request(pkt->req->getPaddr(), 721 pkt->req->getSize(), 722 pkt->req->getFlags(), 723 pkt->req->masterId()); 724 pf = new Packet(req, pkt->cmd); 725 pf->allocate(); 726 assert(pf->getAddr() == pkt->getAddr()); 727 assert(pf->getSize() == pkt->getSize()); 728 } 729 730 pkt->makeTimingResponse(); 731 // for debugging, set all the bits in the response data 732 // (also keeps valgrind from complaining when debugging settings 733 // print out instruction results) 734 std::memset(pkt->getPtr<uint8_t>(), 0xFF, pkt->getSize()); 735 // request_time is used here, taking into account lat and the delay 736 // charged if the packet comes from the xbar. 737 cpuSidePort->schedTimingResp(pkt, request_time); 738 739 // If an outstanding request is in progress (we found an 740 // MSHR) this is set to null 741 pkt = pf; 742 } 743 744 if (mshr) { 745 /// MSHR hit 746 /// @note writebacks will be checked in getNextMSHR() 747 /// for any conflicting requests to the same block 748 749 //@todo remove hw_pf here 750 751 // Coalesce unless it was a software prefetch (see above). 752 if (pkt) { 753 assert(pkt->cmd != MemCmd::Writeback); 754 // CleanEvicts corresponding to blocks which have outstanding 755 // requests in MSHRs can be deleted here. 756 if (pkt->cmd == MemCmd::CleanEvict) { 757 pendingDelete.push_back(pkt); 758 } else { 759 DPRINTF(Cache, "%s coalescing MSHR for %s addr %#llx size %d\n", 760 __func__, pkt->cmdString(), pkt->getAddr(), 761 pkt->getSize()); 762 763 assert(pkt->req->masterId() < system->maxMasters()); 764 mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++; 765 if (mshr->threadNum != 0/*pkt->req->threadId()*/) { 766 mshr->threadNum = -1; 767 } 768 // We use forward_time here because it is the same 769 // considering new targets. We have multiple 770 // requests for the same address here. It 771 // specifies the latency to allocate an internal 772 // buffer and to schedule an event to the queued 773 // port and also takes into account the additional 774 // delay of the xbar. 775 mshr->allocateTarget(pkt, forward_time, order++); 776 if (mshr->getNumTargets() == numTarget) { 777 noTargetMSHR = mshr; 778 setBlocked(Blocked_NoTargets); 779 // need to be careful with this... if this mshr isn't 780 // ready yet (i.e. time > curTick()), we don't want to 781 // move it ahead of mshrs that are ready 782 // mshrQueue.moveToFront(mshr); 783 } 784 } 785 // We should call the prefetcher reguardless if the request is 786 // satisfied or not, reguardless if the request is in the MSHR or 787 // not. The request could be a ReadReq hit, but still not 788 // satisfied (potentially because of a prior write to the same 789 // cache line. So, even when not satisfied, tehre is an MSHR 790 // already allocated for this, we need to let the prefetcher know 791 // about the request 792 if (prefetcher) { 793 // Don't notify on SWPrefetch 794 if (!pkt->cmd.isSWPrefetch()) 795 next_pf_time = prefetcher->notify(pkt); 796 } 797 } 798 } else { 799 // no MSHR 800 assert(pkt->req->masterId() < system->maxMasters()); 801 if (pkt->req->isUncacheable()) { 802 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++; 803 } else { 804 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++; 805 } 806 807 if (pkt->evictingBlock() || 808 (pkt->req->isUncacheable() && pkt->isWrite())) { 809 // We use forward_time here because there is an 810 // uncached memory write, forwarded to WriteBuffer. 811 allocateWriteBuffer(pkt, forward_time); 812 } else { 813 if (blk && blk->isValid()) { 814 // should have flushed and have no valid block 815 assert(!pkt->req->isUncacheable()); 816 817 // If we have a write miss to a valid block, we 818 // need to mark the block non-readable. Otherwise 819 // if we allow reads while there's an outstanding 820 // write miss, the read could return stale data 821 // out of the cache block... a more aggressive 822 // system could detect the overlap (if any) and 823 // forward data out of the MSHRs, but we don't do 824 // that yet. Note that we do need to leave the 825 // block valid so that it stays in the cache, in 826 // case we get an upgrade response (and hence no 827 // new data) when the write miss completes. 828 // As long as CPUs do proper store/load forwarding 829 // internally, and have a sufficiently weak memory 830 // model, this is probably unnecessary, but at some 831 // point it must have seemed like we needed it... 832 assert(pkt->needsExclusive()); 833 assert(!blk->isWritable()); 834 blk->status &= ~BlkReadable; 835 } 836 // Here we are using forward_time, modelling the latency of 837 // a miss (outbound) just as forwardLatency, neglecting the 838 // lookupLatency component. 839 allocateMissBuffer(pkt, forward_time); 840 } 841 842 if (prefetcher) { 843 // Don't notify on SWPrefetch 844 if (!pkt->cmd.isSWPrefetch()) 845 next_pf_time = prefetcher->notify(pkt); 846 } 847 } 848 } 849 850 if (next_pf_time != MaxTick) 851 schedMemSideSendEvent(next_pf_time); 852 853 return true; 854} 855 856 857// See comment in cache.hh. 858PacketPtr 859Cache::getBusPacket(PacketPtr cpu_pkt, CacheBlk *blk, 860 bool needsExclusive) const 861{ 862 bool blkValid = blk && blk->isValid(); 863 864 if (cpu_pkt->req->isUncacheable()) { 865 // note that at the point we see the uncacheable request we 866 // flush any block, but there could be an outstanding MSHR, 867 // and the cache could have filled again before we actually 868 // send out the forwarded uncacheable request (blk could thus 869 // be non-null) 870 return NULL; 871 } 872 873 if (!blkValid && 874 (cpu_pkt->isUpgrade() || 875 cpu_pkt->evictingBlock())) { 876 // Writebacks that weren't allocated in access() and upgrades 877 // from upper-level caches that missed completely just go 878 // through. 879 return NULL; 880 } 881 882 assert(cpu_pkt->needsResponse()); 883 884 MemCmd cmd; 885 // @TODO make useUpgrades a parameter. 886 // Note that ownership protocols require upgrade, otherwise a 887 // write miss on a shared owned block will generate a ReadExcl, 888 // which will clobber the owned copy. 889 const bool useUpgrades = true; 890 if (blkValid && useUpgrades) { 891 // only reason to be here is that blk is shared 892 // (read-only) and we need exclusive 893 assert(needsExclusive); 894 assert(!blk->isWritable()); 895 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq; 896 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq || 897 cpu_pkt->cmd == MemCmd::StoreCondFailReq) { 898 // Even though this SC will fail, we still need to send out the 899 // request and get the data to supply it to other snoopers in the case 900 // where the determination the StoreCond fails is delayed due to 901 // all caches not being on the same local bus. 902 cmd = MemCmd::SCUpgradeFailReq; 903 } else if (cpu_pkt->cmd == MemCmd::WriteLineReq) { 904 // forward as invalidate to all other caches, this gives us 905 // the line in exclusive state, and invalidates all other 906 // copies 907 cmd = MemCmd::InvalidateReq; 908 } else { 909 // block is invalid 910 cmd = needsExclusive ? MemCmd::ReadExReq : 911 (isReadOnly ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq); 912 } 913 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize); 914 915 // if there are sharers in the upper levels, pass that info downstream 916 if (cpu_pkt->sharedAsserted()) { 917 // note that cpu_pkt may have spent a considerable time in the 918 // MSHR queue and that the information could possibly be out 919 // of date, however, there is no harm in conservatively 920 // assuming the block is shared 921 pkt->assertShared(); 922 DPRINTF(Cache, "%s passing shared from %s to %s addr %#llx size %d\n", 923 __func__, cpu_pkt->cmdString(), pkt->cmdString(), 924 pkt->getAddr(), pkt->getSize()); 925 } 926 927 // the packet should be block aligned 928 assert(pkt->getAddr() == blockAlign(pkt->getAddr())); 929 930 pkt->allocate(); 931 DPRINTF(Cache, "%s created %s from %s for addr %#llx size %d\n", 932 __func__, pkt->cmdString(), cpu_pkt->cmdString(), pkt->getAddr(), 933 pkt->getSize()); 934 return pkt; 935} 936 937 938Tick 939Cache::recvAtomic(PacketPtr pkt) 940{ 941 // We are in atomic mode so we pay just for lookupLatency here. 942 Cycles lat = lookupLatency; 943 // @TODO: make this a parameter 944 bool last_level_cache = false; 945 946 // Forward the request if the system is in cache bypass mode. 947 if (system->bypassCaches()) 948 return ticksToCycles(memSidePort->sendAtomic(pkt)); 949 950 promoteWholeLineWrites(pkt); 951 952 if (pkt->memInhibitAsserted()) { 953 // have to invalidate ourselves and any lower caches even if 954 // upper cache will be responding 955 if (pkt->isInvalidate()) { 956 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 957 if (blk && blk->isValid()) { 958 tags->invalidate(blk); 959 blk->invalidate(); 960 DPRINTF(Cache, "rcvd mem-inhibited %s on %#llx (%s):" 961 " invalidating\n", 962 pkt->cmdString(), pkt->getAddr(), 963 pkt->isSecure() ? "s" : "ns"); 964 } 965 if (!last_level_cache) { 966 DPRINTF(Cache, "forwarding mem-inhibited %s on %#llx (%s)\n", 967 pkt->cmdString(), pkt->getAddr(), 968 pkt->isSecure() ? "s" : "ns"); 969 lat += ticksToCycles(memSidePort->sendAtomic(pkt)); 970 } 971 } else { 972 DPRINTF(Cache, "rcvd mem-inhibited %s on %#llx: not responding\n", 973 pkt->cmdString(), pkt->getAddr()); 974 } 975 976 return lat * clockPeriod(); 977 } 978 979 // should assert here that there are no outstanding MSHRs or 980 // writebacks... that would mean that someone used an atomic 981 // access in timing mode 982 983 CacheBlk *blk = NULL; 984 PacketList writebacks; 985 bool satisfied = access(pkt, blk, lat, writebacks); 986 987 // handle writebacks resulting from the access here to ensure they 988 // logically proceed anything happening below 989 doWritebacksAtomic(writebacks); 990 991 if (!satisfied) { 992 // MISS 993 994 PacketPtr bus_pkt = getBusPacket(pkt, blk, pkt->needsExclusive()); 995 996 bool is_forward = (bus_pkt == NULL); 997 998 if (is_forward) { 999 // just forwarding the same request to the next level 1000 // no local cache operation involved 1001 bus_pkt = pkt; 1002 } 1003 1004 DPRINTF(Cache, "Sending an atomic %s for %#llx (%s)\n", 1005 bus_pkt->cmdString(), bus_pkt->getAddr(), 1006 bus_pkt->isSecure() ? "s" : "ns"); 1007 1008#if TRACING_ON 1009 CacheBlk::State old_state = blk ? blk->status : 0; 1010#endif 1011 1012 lat += ticksToCycles(memSidePort->sendAtomic(bus_pkt)); 1013 1014 // We are now dealing with the response handling 1015 DPRINTF(Cache, "Receive response: %s for addr %#llx (%s) in state %i\n", 1016 bus_pkt->cmdString(), bus_pkt->getAddr(), 1017 bus_pkt->isSecure() ? "s" : "ns", 1018 old_state); 1019 1020 // If packet was a forward, the response (if any) is already 1021 // in place in the bus_pkt == pkt structure, so we don't need 1022 // to do anything. Otherwise, use the separate bus_pkt to 1023 // generate response to pkt and then delete it. 1024 if (!is_forward) { 1025 if (pkt->needsResponse()) { 1026 assert(bus_pkt->isResponse()); 1027 if (bus_pkt->isError()) { 1028 pkt->makeAtomicResponse(); 1029 pkt->copyError(bus_pkt); 1030 } else if (pkt->cmd == MemCmd::InvalidateReq) { 1031 if (blk) { 1032 // invalidate response to a cache that received 1033 // an invalidate request 1034 satisfyCpuSideRequest(pkt, blk); 1035 } 1036 } else if (pkt->cmd == MemCmd::WriteLineReq) { 1037 // note the use of pkt, not bus_pkt here. 1038 1039 // write-line request to the cache that promoted 1040 // the write to a whole line 1041 blk = handleFill(pkt, blk, writebacks); 1042 satisfyCpuSideRequest(pkt, blk); 1043 } else if (bus_pkt->isRead() || 1044 bus_pkt->cmd == MemCmd::UpgradeResp) { 1045 // we're updating cache state to allow us to 1046 // satisfy the upstream request from the cache 1047 blk = handleFill(bus_pkt, blk, writebacks); 1048 satisfyCpuSideRequest(pkt, blk); 1049 } else { 1050 // we're satisfying the upstream request without 1051 // modifying cache state, e.g., a write-through 1052 pkt->makeAtomicResponse(); 1053 } 1054 } 1055 delete bus_pkt; 1056 } 1057 } 1058 1059 // Note that we don't invoke the prefetcher at all in atomic mode. 1060 // It's not clear how to do it properly, particularly for 1061 // prefetchers that aggressively generate prefetch candidates and 1062 // rely on bandwidth contention to throttle them; these will tend 1063 // to pollute the cache in atomic mode since there is no bandwidth 1064 // contention. If we ever do want to enable prefetching in atomic 1065 // mode, though, this is the place to do it... see timingAccess() 1066 // for an example (though we'd want to issue the prefetch(es) 1067 // immediately rather than calling requestMemSideBus() as we do 1068 // there). 1069 1070 // Handle writebacks (from the response handling) if needed 1071 doWritebacksAtomic(writebacks); 1072 1073 if (pkt->needsResponse()) { 1074 pkt->makeAtomicResponse(); 1075 } 1076 1077 return lat * clockPeriod(); 1078} 1079 1080 1081void 1082Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide) 1083{ 1084 if (system->bypassCaches()) { 1085 // Packets from the memory side are snoop request and 1086 // shouldn't happen in bypass mode. 1087 assert(fromCpuSide); 1088 1089 // The cache should be flushed if we are in cache bypass mode, 1090 // so we don't need to check if we need to update anything. 1091 memSidePort->sendFunctional(pkt); 1092 return; 1093 } 1094 1095 Addr blk_addr = blockAlign(pkt->getAddr()); 1096 bool is_secure = pkt->isSecure(); 1097 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure); 1098 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure); 1099 1100 pkt->pushLabel(name()); 1101 1102 CacheBlkPrintWrapper cbpw(blk); 1103 1104 // Note that just because an L2/L3 has valid data doesn't mean an 1105 // L1 doesn't have a more up-to-date modified copy that still 1106 // needs to be found. As a result we always update the request if 1107 // we have it, but only declare it satisfied if we are the owner. 1108 1109 // see if we have data at all (owned or otherwise) 1110 bool have_data = blk && blk->isValid() 1111 && pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize, 1112 blk->data); 1113 1114 // data we have is dirty if marked as such or if valid & ownership 1115 // pending due to outstanding UpgradeReq 1116 bool have_dirty = 1117 have_data && (blk->isDirty() || 1118 (mshr && mshr->inService && mshr->isPendingDirty())); 1119 1120 bool done = have_dirty 1121 || cpuSidePort->checkFunctional(pkt) 1122 || mshrQueue.checkFunctional(pkt, blk_addr) 1123 || writeBuffer.checkFunctional(pkt, blk_addr) 1124 || memSidePort->checkFunctional(pkt); 1125 1126 DPRINTF(Cache, "functional %s %#llx (%s) %s%s%s\n", 1127 pkt->cmdString(), pkt->getAddr(), is_secure ? "s" : "ns", 1128 (blk && blk->isValid()) ? "valid " : "", 1129 have_data ? "data " : "", done ? "done " : ""); 1130 1131 // We're leaving the cache, so pop cache->name() label 1132 pkt->popLabel(); 1133 1134 if (done) { 1135 pkt->makeResponse(); 1136 } else { 1137 // if it came as a request from the CPU side then make sure it 1138 // continues towards the memory side 1139 if (fromCpuSide) { 1140 memSidePort->sendFunctional(pkt); 1141 } else if (forwardSnoops && cpuSidePort->isSnooping()) { 1142 // if it came from the memory side, it must be a snoop request 1143 // and we should only forward it if we are forwarding snoops 1144 cpuSidePort->sendFunctionalSnoop(pkt); 1145 } 1146 } 1147} 1148 1149 1150///////////////////////////////////////////////////// 1151// 1152// Response handling: responses from the memory side 1153// 1154///////////////////////////////////////////////////// 1155 1156 1157void 1158Cache::recvTimingResp(PacketPtr pkt) 1159{ 1160 assert(pkt->isResponse()); 1161 1162 // all header delay should be paid for by the crossbar, unless 1163 // this is a prefetch response from above 1164 panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp, 1165 "%s saw a non-zero packet delay\n", name()); 1166 1167 MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState); 1168 bool is_error = pkt->isError(); 1169 1170 assert(mshr); 1171 1172 if (is_error) { 1173 DPRINTF(Cache, "Cache received packet with error for addr %#llx (%s), " 1174 "cmd: %s\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns", 1175 pkt->cmdString()); 1176 } 1177 1178 DPRINTF(Cache, "Handling response %s for addr %#llx size %d (%s)\n", 1179 pkt->cmdString(), pkt->getAddr(), pkt->getSize(), 1180 pkt->isSecure() ? "s" : "ns"); 1181 1182 MSHRQueue *mq = mshr->queue; 1183 bool wasFull = mq->isFull(); 1184 1185 if (mshr == noTargetMSHR) { 1186 // we always clear at least one target 1187 clearBlocked(Blocked_NoTargets); 1188 noTargetMSHR = NULL; 1189 } 1190 1191 // Initial target is used just for stats 1192 MSHR::Target *initial_tgt = mshr->getTarget(); 1193 int stats_cmd_idx = initial_tgt->pkt->cmdToIndex(); 1194 Tick miss_latency = curTick() - initial_tgt->recvTime; 1195 PacketList writebacks; 1196 // We need forward_time here because we have a call of 1197 // allocateWriteBuffer() that need this parameter to specify the 1198 // time to request the bus. In this case we use forward latency 1199 // because there is a writeback. We pay also here for headerDelay 1200 // that is charged of bus latencies if the packet comes from the 1201 // bus. 1202 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 1203 1204 if (pkt->req->isUncacheable()) { 1205 assert(pkt->req->masterId() < system->maxMasters()); 1206 mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] += 1207 miss_latency; 1208 } else { 1209 assert(pkt->req->masterId() < system->maxMasters()); 1210 mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] += 1211 miss_latency; 1212 } 1213 1214 // upgrade deferred targets if we got exclusive 1215 if (!pkt->sharedAsserted()) { 1216 mshr->promoteExclusive(); 1217 } 1218 1219 bool is_fill = !mshr->isForward && 1220 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp); 1221 1222 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 1223 1224 if (is_fill && !is_error) { 1225 DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n", 1226 pkt->getAddr()); 1227 1228 blk = handleFill(pkt, blk, writebacks); 1229 assert(blk != NULL); 1230 } 1231 1232 // allow invalidation responses originating from write-line 1233 // requests to be discarded 1234 bool is_invalidate = pkt->isInvalidate(); 1235 1236 // First offset for critical word first calculations 1237 int initial_offset = initial_tgt->pkt->getOffset(blkSize); 1238 1239 while (mshr->hasTargets()) { 1240 MSHR::Target *target = mshr->getTarget(); 1241 Packet *tgt_pkt = target->pkt; 1242 1243 switch (target->source) { 1244 case MSHR::Target::FromCPU: 1245 Tick completion_time; 1246 // Here we charge on completion_time the delay of the xbar if the 1247 // packet comes from it, charged on headerDelay. 1248 completion_time = pkt->headerDelay; 1249 1250 // Software prefetch handling for cache closest to core 1251 if (tgt_pkt->cmd.isSWPrefetch()) { 1252 // a software prefetch would have already been ack'd immediately 1253 // with dummy data so the core would be able to retire it. 1254 // this request completes right here, so we deallocate it. 1255 delete tgt_pkt->req; 1256 delete tgt_pkt; 1257 break; // skip response 1258 } 1259 1260 // unlike the other packet flows, where data is found in other 1261 // caches or memory and brought back, write-line requests always 1262 // have the data right away, so the above check for "is fill?" 1263 // cannot actually be determined until examining the stored MSHR 1264 // state. We "catch up" with that logic here, which is duplicated 1265 // from above. 1266 if (tgt_pkt->cmd == MemCmd::WriteLineReq) { 1267 assert(!is_error); 1268 // we got the block in exclusive state, so promote any 1269 // deferred targets if possible 1270 mshr->promoteExclusive(); 1271 // NB: we use the original packet here and not the response! 1272 blk = handleFill(tgt_pkt, blk, writebacks); 1273 assert(blk != NULL); 1274 1275 // treat as a fill, and discard the invalidation 1276 // response 1277 is_fill = true; 1278 is_invalidate = false; 1279 } 1280 1281 if (is_fill) { 1282 satisfyCpuSideRequest(tgt_pkt, blk, 1283 true, mshr->hasPostDowngrade()); 1284 1285 // How many bytes past the first request is this one 1286 int transfer_offset = 1287 tgt_pkt->getOffset(blkSize) - initial_offset; 1288 if (transfer_offset < 0) { 1289 transfer_offset += blkSize; 1290 } 1291 1292 // If not critical word (offset) return payloadDelay. 1293 // responseLatency is the latency of the return path 1294 // from lower level caches/memory to an upper level cache or 1295 // the core. 1296 completion_time += clockEdge(responseLatency) + 1297 (transfer_offset ? pkt->payloadDelay : 0); 1298 1299 assert(!tgt_pkt->req->isUncacheable()); 1300 1301 assert(tgt_pkt->req->masterId() < system->maxMasters()); 1302 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] += 1303 completion_time - target->recvTime; 1304 } else if (pkt->cmd == MemCmd::UpgradeFailResp) { 1305 // failed StoreCond upgrade 1306 assert(tgt_pkt->cmd == MemCmd::StoreCondReq || 1307 tgt_pkt->cmd == MemCmd::StoreCondFailReq || 1308 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq); 1309 // responseLatency is the latency of the return path 1310 // from lower level caches/memory to an upper level cache or 1311 // the core. 1312 completion_time += clockEdge(responseLatency) + 1313 pkt->payloadDelay; 1314 tgt_pkt->req->setExtraData(0); 1315 } else { 1316 // not a cache fill, just forwarding response 1317 // responseLatency is the latency of the return path 1318 // from lower level cahces/memory to the core. 1319 completion_time += clockEdge(responseLatency) + 1320 pkt->payloadDelay; 1321 if (pkt->isRead() && !is_error) { 1322 // sanity check 1323 assert(pkt->getAddr() == tgt_pkt->getAddr()); 1324 assert(pkt->getSize() >= tgt_pkt->getSize()); 1325 1326 tgt_pkt->setData(pkt->getConstPtr<uint8_t>()); 1327 } 1328 } 1329 tgt_pkt->makeTimingResponse(); 1330 // if this packet is an error copy that to the new packet 1331 if (is_error) 1332 tgt_pkt->copyError(pkt); 1333 if (tgt_pkt->cmd == MemCmd::ReadResp && 1334 (is_invalidate || mshr->hasPostInvalidate())) { 1335 // If intermediate cache got ReadRespWithInvalidate, 1336 // propagate that. Response should not have 1337 // isInvalidate() set otherwise. 1338 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate; 1339 DPRINTF(Cache, "%s updated cmd to %s for addr %#llx\n", 1340 __func__, tgt_pkt->cmdString(), tgt_pkt->getAddr()); 1341 } 1342 // Reset the bus additional time as it is now accounted for 1343 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0; 1344 cpuSidePort->schedTimingResp(tgt_pkt, completion_time); 1345 break; 1346 1347 case MSHR::Target::FromPrefetcher: 1348 assert(tgt_pkt->cmd == MemCmd::HardPFReq); 1349 if (blk) 1350 blk->status |= BlkHWPrefetched; 1351 delete tgt_pkt->req; 1352 delete tgt_pkt; 1353 break; 1354 1355 case MSHR::Target::FromSnoop: 1356 // I don't believe that a snoop can be in an error state 1357 assert(!is_error); 1358 // response to snoop request 1359 DPRINTF(Cache, "processing deferred snoop...\n"); 1360 assert(!(is_invalidate && !mshr->hasPostInvalidate())); 1361 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate()); 1362 break; 1363 1364 default: 1365 panic("Illegal target->source enum %d\n", target->source); 1366 } 1367 1368 mshr->popTarget(); 1369 } 1370 1371 if (blk && blk->isValid()) { 1372 // an invalidate response stemming from a write line request 1373 // should not invalidate the block, so check if the 1374 // invalidation should be discarded 1375 if (is_invalidate || mshr->hasPostInvalidate()) { 1376 assert(blk != tempBlock); 1377 tags->invalidate(blk); 1378 blk->invalidate(); 1379 } else if (mshr->hasPostDowngrade()) { 1380 blk->status &= ~BlkWritable; 1381 } 1382 } 1383 1384 if (mshr->promoteDeferredTargets()) { 1385 // avoid later read getting stale data while write miss is 1386 // outstanding.. see comment in timingAccess() 1387 if (blk) { 1388 blk->status &= ~BlkReadable; 1389 } 1390 mq = mshr->queue; 1391 mq->markPending(mshr); 1392 schedMemSideSendEvent(clockEdge() + pkt->payloadDelay); 1393 } else { 1394 mq->deallocate(mshr); 1395 if (wasFull && !mq->isFull()) { 1396 clearBlocked((BlockedCause)mq->index); 1397 } 1398 1399 // Request the bus for a prefetch if this deallocation freed enough 1400 // MSHRs for a prefetch to take place 1401 if (prefetcher && mq == &mshrQueue && mshrQueue.canPrefetch()) { 1402 Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(), 1403 clockEdge()); 1404 if (next_pf_time != MaxTick) 1405 schedMemSideSendEvent(next_pf_time); 1406 } 1407 } 1408 // reset the xbar additional timinig as it is now accounted for 1409 pkt->headerDelay = pkt->payloadDelay = 0; 1410 1411 // copy writebacks to write buffer 1412 doWritebacks(writebacks, forward_time); 1413 1414 // if we used temp block, check to see if its valid and then clear it out 1415 if (blk == tempBlock && tempBlock->isValid()) { 1416 // We use forwardLatency here because we are copying 1417 // Writebacks/CleanEvicts to write buffer. It specifies the latency to 1418 // allocate an internal buffer and to schedule an event to the 1419 // queued port. 1420 if (blk->isDirty()) { 1421 PacketPtr wbPkt = writebackBlk(blk); 1422 allocateWriteBuffer(wbPkt, forward_time); 1423 // Set BLOCK_CACHED flag if cached above. 1424 if (isCachedAbove(wbPkt)) 1425 wbPkt->setBlockCached(); 1426 } else { 1427 PacketPtr wcPkt = cleanEvictBlk(blk); 1428 // Check to see if block is cached above. If not allocate 1429 // write buffer 1430 if (isCachedAbove(wcPkt)) 1431 delete wcPkt; 1432 else 1433 allocateWriteBuffer(wcPkt, forward_time); 1434 } 1435 blk->invalidate(); 1436 } 1437 1438 DPRINTF(Cache, "Leaving %s with %s for addr %#llx\n", __func__, 1439 pkt->cmdString(), pkt->getAddr()); 1440 delete pkt; 1441} 1442 1443PacketPtr 1444Cache::writebackBlk(CacheBlk *blk) 1445{ 1446 chatty_assert(!isReadOnly, "Writeback from read-only cache"); 1447 assert(blk && blk->isValid() && blk->isDirty()); 1448 1449 writebacks[Request::wbMasterId]++; 1450 1451 Request *writebackReq = 1452 new Request(tags->regenerateBlkAddr(blk->tag, blk->set), blkSize, 0, 1453 Request::wbMasterId); 1454 if (blk->isSecure()) 1455 writebackReq->setFlags(Request::SECURE); 1456 1457 writebackReq->taskId(blk->task_id); 1458 blk->task_id= ContextSwitchTaskId::Unknown; 1459 blk->tickInserted = curTick(); 1460 1461 PacketPtr writeback = new Packet(writebackReq, MemCmd::Writeback); 1462 if (blk->isWritable()) { 1463 // not asserting shared means we pass the block in modified 1464 // state, mark our own block non-writeable 1465 blk->status &= ~BlkWritable; 1466 } else { 1467 // we are in the owned state, tell the receiver 1468 writeback->assertShared(); 1469 } 1470 1471 writeback->allocate(); 1472 std::memcpy(writeback->getPtr<uint8_t>(), blk->data, blkSize); 1473 1474 blk->status &= ~BlkDirty; 1475 return writeback; 1476} 1477 1478PacketPtr 1479Cache::cleanEvictBlk(CacheBlk *blk) 1480{ 1481 assert(blk && blk->isValid() && !blk->isDirty()); 1482 // Creating a zero sized write, a message to the snoop filter 1483 Request *req = 1484 new Request(tags->regenerateBlkAddr(blk->tag, blk->set), blkSize, 0, 1485 Request::wbMasterId); 1486 if (blk->isSecure()) 1487 req->setFlags(Request::SECURE); 1488 1489 req->taskId(blk->task_id); 1490 blk->task_id = ContextSwitchTaskId::Unknown; 1491 blk->tickInserted = curTick(); 1492 1493 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict); 1494 pkt->allocate(); 1495 DPRINTF(Cache, "%s%s %x Create CleanEvict\n", pkt->cmdString(), 1496 pkt->req->isInstFetch() ? " (ifetch)" : "", 1497 pkt->getAddr()); 1498 1499 return pkt; 1500} 1501 1502void 1503Cache::memWriteback() 1504{ 1505 CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor); 1506 tags->forEachBlk(visitor); 1507} 1508 1509void 1510Cache::memInvalidate() 1511{ 1512 CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor); 1513 tags->forEachBlk(visitor); 1514} 1515 1516bool 1517Cache::isDirty() const 1518{ 1519 CacheBlkIsDirtyVisitor visitor; 1520 tags->forEachBlk(visitor); 1521 1522 return visitor.isDirty(); 1523} 1524 1525bool 1526Cache::writebackVisitor(CacheBlk &blk) 1527{ 1528 if (blk.isDirty()) { 1529 assert(blk.isValid()); 1530 1531 Request request(tags->regenerateBlkAddr(blk.tag, blk.set), 1532 blkSize, 0, Request::funcMasterId); 1533 request.taskId(blk.task_id); 1534 1535 Packet packet(&request, MemCmd::WriteReq); 1536 packet.dataStatic(blk.data); 1537 1538 memSidePort->sendFunctional(&packet); 1539 1540 blk.status &= ~BlkDirty; 1541 } 1542 1543 return true; 1544} 1545 1546bool 1547Cache::invalidateVisitor(CacheBlk &blk) 1548{ 1549 1550 if (blk.isDirty()) 1551 warn_once("Invalidating dirty cache lines. Expect things to break.\n"); 1552 1553 if (blk.isValid()) { 1554 assert(!blk.isDirty()); 1555 tags->invalidate(&blk); 1556 blk.invalidate(); 1557 } 1558 1559 return true; 1560} 1561 1562CacheBlk* 1563Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks) 1564{ 1565 CacheBlk *blk = tags->findVictim(addr); 1566 1567 // It is valid to return NULL if there is no victim 1568 if (!blk) 1569 return nullptr; 1570 1571 if (blk->isValid()) { 1572 Addr repl_addr = tags->regenerateBlkAddr(blk->tag, blk->set); 1573 MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure()); 1574 if (repl_mshr) { 1575 // must be an outstanding upgrade request 1576 // on a block we're about to replace... 1577 assert(!blk->isWritable() || blk->isDirty()); 1578 assert(repl_mshr->needsExclusive()); 1579 // too hard to replace block with transient state 1580 // allocation failed, block not inserted 1581 return NULL; 1582 } else { 1583 DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx (%s): %s\n", 1584 repl_addr, blk->isSecure() ? "s" : "ns", 1585 addr, is_secure ? "s" : "ns", 1586 blk->isDirty() ? "writeback" : "clean"); 1587 1588 // Will send up Writeback/CleanEvict snoops via isCachedAbove 1589 // when pushing this writeback list into the write buffer. 1590 if (blk->isDirty()) { 1591 // Save writeback packet for handling by caller 1592 writebacks.push_back(writebackBlk(blk)); 1593 } else { 1594 writebacks.push_back(cleanEvictBlk(blk)); 1595 } 1596 } 1597 } 1598 1599 return blk; 1600} 1601 1602 1603// Note that the reason we return a list of writebacks rather than 1604// inserting them directly in the write buffer is that this function 1605// is called by both atomic and timing-mode accesses, and in atomic 1606// mode we don't mess with the write buffer (we just perform the 1607// writebacks atomically once the original request is complete). 1608CacheBlk* 1609Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks) 1610{ 1611 assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq); 1612 Addr addr = pkt->getAddr(); 1613 bool is_secure = pkt->isSecure(); 1614#if TRACING_ON 1615 CacheBlk::State old_state = blk ? blk->status : 0; 1616#endif 1617 1618 // When handling a fill, discard any CleanEvicts for the 1619 // same address in write buffer. 1620 Addr M5_VAR_USED blk_addr = blockAlign(pkt->getAddr()); 1621 std::vector<MSHR *> M5_VAR_USED wbs; 1622 assert (!writeBuffer.findMatches(blk_addr, is_secure, wbs)); 1623 1624 if (blk == NULL) { 1625 // better have read new data... 1626 assert(pkt->hasData()); 1627 1628 // only read responses and write-line requests have data; 1629 // note that we don't write the data here for write-line - that 1630 // happens in the subsequent satisfyCpuSideRequest. 1631 assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq); 1632 1633 // need to do a replacement 1634 blk = allocateBlock(addr, is_secure, writebacks); 1635 if (blk == NULL) { 1636 // No replaceable block... just use temporary storage to 1637 // complete the current request and then get rid of it 1638 assert(!tempBlock->isValid()); 1639 blk = tempBlock; 1640 tempBlock->set = tags->extractSet(addr); 1641 tempBlock->tag = tags->extractTag(addr); 1642 // @todo: set security state as well... 1643 DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr, 1644 is_secure ? "s" : "ns"); 1645 } else { 1646 tags->insertBlock(pkt, blk); 1647 } 1648 1649 // we should never be overwriting a valid block 1650 assert(!blk->isValid()); 1651 } else { 1652 // existing block... probably an upgrade 1653 assert(blk->tag == tags->extractTag(addr)); 1654 // either we're getting new data or the block should already be valid 1655 assert(pkt->hasData() || blk->isValid()); 1656 // don't clear block status... if block is already dirty we 1657 // don't want to lose that 1658 } 1659 1660 if (is_secure) 1661 blk->status |= BlkSecure; 1662 blk->status |= BlkValid | BlkReadable; 1663 1664 // sanity check for whole-line writes, which should always be 1665 // marked as writable as part of the fill, and then later marked 1666 // dirty as part of satisfyCpuSideRequest 1667 if (pkt->cmd == MemCmd::WriteLineReq) { 1668 assert(!pkt->sharedAsserted()); 1669 // at the moment other caches do not respond to the 1670 // invalidation requests corresponding to a whole-line write 1671 assert(!pkt->memInhibitAsserted()); 1672 } 1673 1674 if (!pkt->sharedAsserted()) { 1675 // we could get non-shared responses from memory (rather than 1676 // a cache) even in a read-only cache, note that we set this 1677 // bit even for a read-only cache as we use it to represent 1678 // the exclusive state 1679 blk->status |= BlkWritable; 1680 1681 // If we got this via cache-to-cache transfer (i.e., from a 1682 // cache that was an owner) and took away that owner's copy, 1683 // then we need to write it back. Normally this happens 1684 // anyway as a side effect of getting a copy to write it, but 1685 // there are cases (such as failed store conditionals or 1686 // compare-and-swaps) where we'll demand an exclusive copy but 1687 // end up not writing it. 1688 if (pkt->memInhibitAsserted()) { 1689 blk->status |= BlkDirty; 1690 1691 chatty_assert(!isReadOnly, "Should never see dirty snoop response " 1692 "in read-only cache %s\n", name()); 1693 } 1694 } 1695 1696 DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n", 1697 addr, is_secure ? "s" : "ns", old_state, blk->print()); 1698 1699 // if we got new data, copy it in (checking for a read response 1700 // and a response that has data is the same in the end) 1701 if (pkt->isRead()) { 1702 // sanity checks 1703 assert(pkt->hasData()); 1704 assert(pkt->getSize() == blkSize); 1705 1706 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize); 1707 } 1708 // We pay for fillLatency here. 1709 blk->whenReady = clockEdge() + fillLatency * clockPeriod() + 1710 pkt->payloadDelay; 1711 1712 return blk; 1713} 1714 1715 1716///////////////////////////////////////////////////// 1717// 1718// Snoop path: requests coming in from the memory side 1719// 1720///////////////////////////////////////////////////// 1721 1722void 1723Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data, 1724 bool already_copied, bool pending_inval) 1725{ 1726 // sanity check 1727 assert(req_pkt->isRequest()); 1728 assert(req_pkt->needsResponse()); 1729 1730 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 1731 req_pkt->cmdString(), req_pkt->getAddr(), req_pkt->getSize()); 1732 // timing-mode snoop responses require a new packet, unless we 1733 // already made a copy... 1734 PacketPtr pkt = req_pkt; 1735 if (!already_copied) 1736 // do not clear flags, and allocate space for data if the 1737 // packet needs it (the only packets that carry data are read 1738 // responses) 1739 pkt = new Packet(req_pkt, false, req_pkt->isRead()); 1740 1741 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() || 1742 pkt->sharedAsserted()); 1743 pkt->makeTimingResponse(); 1744 if (pkt->isRead()) { 1745 pkt->setDataFromBlock(blk_data, blkSize); 1746 } 1747 if (pkt->cmd == MemCmd::ReadResp && pending_inval) { 1748 // Assume we defer a response to a read from a far-away cache 1749 // A, then later defer a ReadExcl from a cache B on the same 1750 // bus as us. We'll assert MemInhibit in both cases, but in 1751 // the latter case MemInhibit will keep the invalidation from 1752 // reaching cache A. This special response tells cache A that 1753 // it gets the block to satisfy its read, but must immediately 1754 // invalidate it. 1755 pkt->cmd = MemCmd::ReadRespWithInvalidate; 1756 } 1757 // Here we consider forward_time, paying for just forward latency and 1758 // also charging the delay provided by the xbar. 1759 // forward_time is used as send_time in next allocateWriteBuffer(). 1760 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 1761 // Here we reset the timing of the packet. 1762 pkt->headerDelay = pkt->payloadDelay = 0; 1763 DPRINTF(Cache, "%s created response: %s addr %#llx size %d tick: %lu\n", 1764 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize(), 1765 forward_time); 1766 memSidePort->schedTimingSnoopResp(pkt, forward_time, true); 1767} 1768 1769uint32_t 1770Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing, 1771 bool is_deferred, bool pending_inval) 1772{ 1773 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 1774 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 1775 // deferred snoops can only happen in timing mode 1776 assert(!(is_deferred && !is_timing)); 1777 // pending_inval only makes sense on deferred snoops 1778 assert(!(pending_inval && !is_deferred)); 1779 assert(pkt->isRequest()); 1780 1781 // the packet may get modified if we or a forwarded snooper 1782 // responds in atomic mode, so remember a few things about the 1783 // original packet up front 1784 bool invalidate = pkt->isInvalidate(); 1785 bool M5_VAR_USED needs_exclusive = pkt->needsExclusive(); 1786 1787 uint32_t snoop_delay = 0; 1788 1789 if (forwardSnoops) { 1790 // first propagate snoop upward to see if anyone above us wants to 1791 // handle it. save & restore packet src since it will get 1792 // rewritten to be relative to cpu-side bus (if any) 1793 bool alreadyResponded = pkt->memInhibitAsserted(); 1794 if (is_timing) { 1795 // copy the packet so that we can clear any flags before 1796 // forwarding it upwards, we also allocate data (passing 1797 // the pointer along in case of static data), in case 1798 // there is a snoop hit in upper levels 1799 Packet snoopPkt(pkt, true, true); 1800 snoopPkt.setExpressSnoop(); 1801 snoopPkt.pushSenderState(new ForwardResponseRecord()); 1802 // the snoop packet does not need to wait any additional 1803 // time 1804 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0; 1805 cpuSidePort->sendTimingSnoopReq(&snoopPkt); 1806 1807 // add the header delay (including crossbar and snoop 1808 // delays) of the upward snoop to the snoop delay for this 1809 // cache 1810 snoop_delay += snoopPkt.headerDelay; 1811 1812 if (snoopPkt.memInhibitAsserted()) { 1813 // cache-to-cache response from some upper cache 1814 assert(!alreadyResponded); 1815 pkt->assertMemInhibit(); 1816 } else { 1817 // no cache (or anyone else for that matter) will 1818 // respond, so delete the ForwardResponseRecord here 1819 delete snoopPkt.popSenderState(); 1820 } 1821 if (snoopPkt.sharedAsserted()) { 1822 pkt->assertShared(); 1823 } 1824 // If this request is a prefetch or clean evict and an upper level 1825 // signals block present, make sure to propagate the block 1826 // presence to the requester. 1827 if (snoopPkt.isBlockCached()) { 1828 pkt->setBlockCached(); 1829 } 1830 } else { 1831 cpuSidePort->sendAtomicSnoop(pkt); 1832 if (!alreadyResponded && pkt->memInhibitAsserted()) { 1833 // cache-to-cache response from some upper cache: 1834 // forward response to original requester 1835 assert(pkt->isResponse()); 1836 } 1837 } 1838 } 1839 1840 if (!blk || !blk->isValid()) { 1841 DPRINTF(Cache, "%s snoop miss for %s addr %#llx size %d\n", 1842 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 1843 return snoop_delay; 1844 } else { 1845 DPRINTF(Cache, "%s snoop hit for %s for addr %#llx size %d, " 1846 "old state is %s\n", __func__, pkt->cmdString(), 1847 pkt->getAddr(), pkt->getSize(), blk->print()); 1848 } 1849 1850 chatty_assert(!(isReadOnly && blk->isDirty()), 1851 "Should never have a dirty block in a read-only cache %s\n", 1852 name()); 1853 1854 // We may end up modifying both the block state and the packet (if 1855 // we respond in atomic mode), so just figure out what to do now 1856 // and then do it later. If we find dirty data while snooping for 1857 // an invalidate, we don't need to send a response. The 1858 // invalidation itself is taken care of below. 1859 bool respond = blk->isDirty() && pkt->needsResponse() && 1860 pkt->cmd != MemCmd::InvalidateReq; 1861 bool have_exclusive = blk->isWritable(); 1862 1863 // Invalidate any prefetch's from below that would strip write permissions 1864 // MemCmd::HardPFReq is only observed by upstream caches. After missing 1865 // above and in it's own cache, a new MemCmd::ReadReq is created that 1866 // downstream caches observe. 1867 if (pkt->mustCheckAbove()) { 1868 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s from" 1869 " lower cache\n", pkt->getAddr(), pkt->cmdString()); 1870 pkt->setBlockCached(); 1871 return snoop_delay; 1872 } 1873 1874 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) { 1875 // reading non-exclusive shared data, note that we retain 1876 // the block in owned state if it is dirty, with the response 1877 // taken care of below, and otherwhise simply downgrade to 1878 // shared 1879 assert(!needs_exclusive); 1880 pkt->assertShared(); 1881 blk->status &= ~BlkWritable; 1882 } 1883 1884 if (respond) { 1885 // prevent anyone else from responding, cache as well as 1886 // memory, and also prevent any memory from even seeing the 1887 // request (with current inhibited semantics), note that this 1888 // applies both to reads and writes and that for writes it 1889 // works thanks to the fact that we still have dirty data and 1890 // will write it back at a later point 1891 pkt->assertMemInhibit(); 1892 if (have_exclusive) { 1893 // in the case of an uncacheable request there is no point 1894 // in setting the exclusive flag, but since the recipient 1895 // does not care there is no harm in doing so, in any case 1896 // it is just a hint 1897 pkt->setSupplyExclusive(); 1898 } 1899 if (is_timing) { 1900 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval); 1901 } else { 1902 pkt->makeAtomicResponse(); 1903 pkt->setDataFromBlock(blk->data, blkSize); 1904 } 1905 } 1906 1907 if (!respond && is_timing && is_deferred) { 1908 // if it's a deferred timing snoop then we've made a copy of 1909 // both the request and the packet, and so if we're not using 1910 // those copies to respond and delete them here 1911 DPRINTF(Cache, "Deleting pkt %p and request %p for cmd %s addr: %p\n", 1912 pkt, pkt->req, pkt->cmdString(), pkt->getAddr()); 1913 1914 // the packets needs a response (just not from us), so we also 1915 // need to delete the request and not rely on the packet 1916 // destructor 1917 assert(pkt->needsResponse()); 1918 delete pkt->req; 1919 delete pkt; 1920 } 1921 1922 // Do this last in case it deallocates block data or something 1923 // like that 1924 if (invalidate) { 1925 if (blk != tempBlock) 1926 tags->invalidate(blk); 1927 blk->invalidate(); 1928 } 1929 1930 DPRINTF(Cache, "new state is %s\n", blk->print()); 1931 1932 return snoop_delay; 1933} 1934 1935 1936void 1937Cache::recvTimingSnoopReq(PacketPtr pkt) 1938{ 1939 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 1940 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 1941 1942 // Snoops shouldn't happen when bypassing caches 1943 assert(!system->bypassCaches()); 1944 1945 // no need to snoop requests that are not in range 1946 if (!inRange(pkt->getAddr())) { 1947 return; 1948 } 1949 1950 bool is_secure = pkt->isSecure(); 1951 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure); 1952 1953 Addr blk_addr = blockAlign(pkt->getAddr()); 1954 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure); 1955 1956 // Update the latency cost of the snoop so that the crossbar can 1957 // account for it. Do not overwrite what other neighbouring caches 1958 // have already done, rather take the maximum. The update is 1959 // tentative, for cases where we return before an upward snoop 1960 // happens below. 1961 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, 1962 lookupLatency * clockPeriod()); 1963 1964 // Inform request(Prefetch, CleanEvict or Writeback) from below of 1965 // MSHR hit, set setBlockCached. 1966 if (mshr && pkt->mustCheckAbove()) { 1967 DPRINTF(Cache, "Setting block cached for %s from" 1968 "lower cache on mshr hit %#x\n", 1969 pkt->cmdString(), pkt->getAddr()); 1970 pkt->setBlockCached(); 1971 return; 1972 } 1973 1974 // Let the MSHR itself track the snoop and decide whether we want 1975 // to go ahead and do the regular cache snoop 1976 if (mshr && mshr->handleSnoop(pkt, order++)) { 1977 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)." 1978 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns", 1979 mshr->print()); 1980 1981 if (mshr->getNumTargets() > numTarget) 1982 warn("allocating bonus target for snoop"); //handle later 1983 return; 1984 } 1985 1986 //We also need to check the writeback buffers and handle those 1987 std::vector<MSHR *> writebacks; 1988 if (writeBuffer.findMatches(blk_addr, is_secure, writebacks)) { 1989 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n", 1990 pkt->getAddr(), is_secure ? "s" : "ns"); 1991 1992 // Look through writebacks for any cachable writes. 1993 // We should only ever find a single match 1994 assert(writebacks.size() == 1); 1995 MSHR *wb_entry = writebacks[0]; 1996 // Expect to see only Writebacks and/or CleanEvicts here, both of 1997 // which should not be generated for uncacheable data. 1998 assert(!wb_entry->isUncacheable()); 1999 // There should only be a single request responsible for generating 2000 // Writebacks/CleanEvicts. 2001 assert(wb_entry->getNumTargets() == 1); 2002 PacketPtr wb_pkt = wb_entry->getTarget()->pkt; 2003 assert(wb_pkt->evictingBlock()); 2004 2005 if (pkt->evictingBlock()) { 2006 // if the block is found in the write queue, set the BLOCK_CACHED 2007 // flag for Writeback/CleanEvict snoop. On return the snoop will 2008 // propagate the BLOCK_CACHED flag in Writeback packets and prevent 2009 // any CleanEvicts from travelling down the memory hierarchy. 2010 pkt->setBlockCached(); 2011 DPRINTF(Cache, "Squashing %s from lower cache on writequeue hit" 2012 " %#x\n", pkt->cmdString(), pkt->getAddr()); 2013 return; 2014 } 2015 2016 if (wb_pkt->cmd == MemCmd::Writeback) { 2017 assert(!pkt->memInhibitAsserted()); 2018 pkt->assertMemInhibit(); 2019 if (!pkt->needsExclusive()) { 2020 pkt->assertShared(); 2021 // the writeback is no longer passing exclusivity (the 2022 // receiving cache should consider the block owned 2023 // rather than modified) 2024 wb_pkt->assertShared(); 2025 } else { 2026 // if we're not asserting the shared line, we need to 2027 // invalidate our copy. we'll do that below as long as 2028 // the packet's invalidate flag is set... 2029 assert(pkt->isInvalidate()); 2030 } 2031 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(), 2032 false, false); 2033 } else { 2034 assert(wb_pkt->cmd == MemCmd::CleanEvict); 2035 // The cache technically holds the block until the 2036 // corresponding CleanEvict message reaches the crossbar 2037 // below. Therefore when a snoop encounters a CleanEvict 2038 // message we must set assertShared (just like when it 2039 // encounters a Writeback) to avoid the snoop filter 2040 // prematurely clearing the holder bit in the crossbar 2041 // below 2042 if (!pkt->needsExclusive()) 2043 pkt->assertShared(); 2044 else 2045 assert(pkt->isInvalidate()); 2046 } 2047 2048 if (pkt->isInvalidate()) { 2049 // Invalidation trumps our writeback... discard here 2050 // Note: markInService will remove entry from writeback buffer. 2051 markInService(wb_entry, false); 2052 delete wb_pkt; 2053 } 2054 } 2055 2056 // If this was a shared writeback, there may still be 2057 // other shared copies above that require invalidation. 2058 // We could be more selective and return here if the 2059 // request is non-exclusive or if the writeback is 2060 // exclusive. 2061 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false); 2062 2063 // Override what we did when we first saw the snoop, as we now 2064 // also have the cost of the upwards snoops to account for 2065 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay + 2066 lookupLatency * clockPeriod()); 2067} 2068 2069bool 2070Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt) 2071{ 2072 // Express snoop responses from master to slave, e.g., from L1 to L2 2073 cache->recvTimingSnoopResp(pkt); 2074 return true; 2075} 2076 2077Tick 2078Cache::recvAtomicSnoop(PacketPtr pkt) 2079{ 2080 // Snoops shouldn't happen when bypassing caches 2081 assert(!system->bypassCaches()); 2082 2083 // no need to snoop requests that are not in range. 2084 if (!inRange(pkt->getAddr())) { 2085 return 0; 2086 } 2087 2088 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 2089 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false); 2090 return snoop_delay + lookupLatency * clockPeriod(); 2091} 2092 2093 2094MSHR * 2095Cache::getNextMSHR() 2096{ 2097 // Check both MSHR queue and write buffer for potential requests, 2098 // note that null does not mean there is no request, it could 2099 // simply be that it is not ready 2100 MSHR *miss_mshr = mshrQueue.getNextMSHR(); 2101 MSHR *write_mshr = writeBuffer.getNextMSHR(); 2102 2103 // If we got a write buffer request ready, first priority is a 2104 // full write buffer, otherwhise we favour the miss requests 2105 if (write_mshr && 2106 ((writeBuffer.isFull() && writeBuffer.inServiceEntries == 0) || 2107 !miss_mshr)) { 2108 // need to search MSHR queue for conflicting earlier miss. 2109 MSHR *conflict_mshr = 2110 mshrQueue.findPending(write_mshr->blkAddr, 2111 write_mshr->isSecure); 2112 2113 if (conflict_mshr && conflict_mshr->order < write_mshr->order) { 2114 // Service misses in order until conflict is cleared. 2115 return conflict_mshr; 2116 2117 // @todo Note that we ignore the ready time of the conflict here 2118 } 2119 2120 // No conflicts; issue write 2121 return write_mshr; 2122 } else if (miss_mshr) { 2123 // need to check for conflicting earlier writeback 2124 MSHR *conflict_mshr = 2125 writeBuffer.findPending(miss_mshr->blkAddr, 2126 miss_mshr->isSecure); 2127 if (conflict_mshr) { 2128 // not sure why we don't check order here... it was in the 2129 // original code but commented out. 2130 2131 // The only way this happens is if we are 2132 // doing a write and we didn't have permissions 2133 // then subsequently saw a writeback (owned got evicted) 2134 // We need to make sure to perform the writeback first 2135 // To preserve the dirty data, then we can issue the write 2136 2137 // should we return write_mshr here instead? I.e. do we 2138 // have to flush writes in order? I don't think so... not 2139 // for Alpha anyway. Maybe for x86? 2140 return conflict_mshr; 2141 2142 // @todo Note that we ignore the ready time of the conflict here 2143 } 2144 2145 // No conflicts; issue read 2146 return miss_mshr; 2147 } 2148 2149 // fall through... no pending requests. Try a prefetch. 2150 assert(!miss_mshr && !write_mshr); 2151 if (prefetcher && mshrQueue.canPrefetch()) { 2152 // If we have a miss queue slot, we can try a prefetch 2153 PacketPtr pkt = prefetcher->getPacket(); 2154 if (pkt) { 2155 Addr pf_addr = blockAlign(pkt->getAddr()); 2156 if (!tags->findBlock(pf_addr, pkt->isSecure()) && 2157 !mshrQueue.findMatch(pf_addr, pkt->isSecure()) && 2158 !writeBuffer.findMatch(pf_addr, pkt->isSecure())) { 2159 // Update statistic on number of prefetches issued 2160 // (hwpf_mshr_misses) 2161 assert(pkt->req->masterId() < system->maxMasters()); 2162 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++; 2163 2164 // allocate an MSHR and return it, note 2165 // that we send the packet straight away, so do not 2166 // schedule the send 2167 return allocateMissBuffer(pkt, curTick(), false); 2168 } else { 2169 // free the request and packet 2170 delete pkt->req; 2171 delete pkt; 2172 } 2173 } 2174 } 2175 2176 return NULL; 2177} 2178 2179bool 2180Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const 2181{ 2182 if (!forwardSnoops) 2183 return false; 2184 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and 2185 // Writeback snoops into upper level caches to check for copies of the 2186 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict 2187 // packet, the cache can inform the crossbar below of presence or absence 2188 // of the block. 2189 if (is_timing) { 2190 Packet snoop_pkt(pkt, true, false); 2191 snoop_pkt.setExpressSnoop(); 2192 // Assert that packet is either Writeback or CleanEvict and not a 2193 // prefetch request because prefetch requests need an MSHR and may 2194 // generate a snoop response. 2195 assert(pkt->evictingBlock()); 2196 snoop_pkt.senderState = NULL; 2197 cpuSidePort->sendTimingSnoopReq(&snoop_pkt); 2198 // Writeback/CleanEvict snoops do not generate a snoop response. 2199 assert(!(snoop_pkt.memInhibitAsserted())); 2200 return snoop_pkt.isBlockCached(); 2201 } else { 2202 cpuSidePort->sendAtomicSnoop(pkt); 2203 return pkt->isBlockCached(); 2204 } 2205} 2206 2207PacketPtr 2208Cache::getTimingPacket() 2209{ 2210 MSHR *mshr = getNextMSHR(); 2211 2212 if (mshr == NULL) { 2213 return NULL; 2214 } 2215 2216 // use request from 1st target 2217 PacketPtr tgt_pkt = mshr->getTarget()->pkt; 2218 PacketPtr pkt = NULL; 2219 2220 DPRINTF(CachePort, "%s %s for addr %#llx size %d\n", __func__, 2221 tgt_pkt->cmdString(), tgt_pkt->getAddr(), tgt_pkt->getSize()); 2222 2223 CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure); 2224 2225 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) { 2226 // We need to check the caches above us to verify that 2227 // they don't have a copy of this block in the dirty state 2228 // at the moment. Without this check we could get a stale 2229 // copy from memory that might get used in place of the 2230 // dirty one. 2231 Packet snoop_pkt(tgt_pkt, true, false); 2232 snoop_pkt.setExpressSnoop(); 2233 snoop_pkt.senderState = mshr; 2234 cpuSidePort->sendTimingSnoopReq(&snoop_pkt); 2235 2236 // Check to see if the prefetch was squashed by an upper cache (to 2237 // prevent us from grabbing the line) or if a Check to see if a 2238 // writeback arrived between the time the prefetch was placed in 2239 // the MSHRs and when it was selected to be sent or if the 2240 // prefetch was squashed by an upper cache. 2241 2242 // It is important to check memInhibitAsserted before 2243 // prefetchSquashed. If another cache has asserted MEM_INGIBIT, it 2244 // will be sending a response which will arrive at the MSHR 2245 // allocated ofr this request. Checking the prefetchSquash first 2246 // may result in the MSHR being prematurely deallocated. 2247 2248 if (snoop_pkt.memInhibitAsserted()) { 2249 // If we are getting a non-shared response it is dirty 2250 bool pending_dirty_resp = !snoop_pkt.sharedAsserted(); 2251 markInService(mshr, pending_dirty_resp); 2252 DPRINTF(Cache, "Upward snoop of prefetch for addr" 2253 " %#x (%s) hit\n", 2254 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns"); 2255 return NULL; 2256 } 2257 2258 if (snoop_pkt.isBlockCached() || blk != NULL) { 2259 DPRINTF(Cache, "Block present, prefetch squashed by cache. " 2260 "Deallocating mshr target %#x.\n", 2261 mshr->blkAddr); 2262 2263 // Deallocate the mshr target 2264 if (tgt_pkt->cmd != MemCmd::Writeback) { 2265 if (mshr->queue->forceDeallocateTarget(mshr)) { 2266 // Clear block if this deallocation resulted freed an 2267 // mshr when all had previously been utilized 2268 clearBlocked((BlockedCause)(mshr->queue->index)); 2269 } 2270 return NULL; 2271 } else { 2272 // If this is a Writeback, and the snoops indicate that the blk 2273 // is cached above, set the BLOCK_CACHED flag in the Writeback 2274 // packet, so that it does not reset the bits corresponding to 2275 // this block in the snoop filter below. 2276 tgt_pkt->setBlockCached(); 2277 } 2278 } 2279 } 2280 2281 if (mshr->isForwardNoResponse()) { 2282 // no response expected, just forward packet as it is 2283 assert(tags->findBlock(mshr->blkAddr, mshr->isSecure) == NULL); 2284 pkt = tgt_pkt; 2285 } else { 2286 pkt = getBusPacket(tgt_pkt, blk, mshr->needsExclusive()); 2287 2288 mshr->isForward = (pkt == NULL); 2289 2290 if (mshr->isForward) { 2291 // not a cache block request, but a response is expected 2292 // make copy of current packet to forward, keep current 2293 // copy for response handling 2294 pkt = new Packet(tgt_pkt, false, true); 2295 if (pkt->isWrite()) { 2296 pkt->setData(tgt_pkt->getConstPtr<uint8_t>()); 2297 } 2298 } 2299 } 2300 2301 assert(pkt != NULL); 2302 pkt->senderState = mshr; 2303 return pkt; 2304} 2305 2306 2307Tick 2308Cache::nextMSHRReadyTime() const 2309{ 2310 Tick nextReady = std::min(mshrQueue.nextMSHRReadyTime(), 2311 writeBuffer.nextMSHRReadyTime()); 2312 2313 // Don't signal prefetch ready time if no MSHRs available 2314 // Will signal once enoguh MSHRs are deallocated 2315 if (prefetcher && mshrQueue.canPrefetch()) { 2316 nextReady = std::min(nextReady, 2317 prefetcher->nextPrefetchReadyTime()); 2318 } 2319 2320 return nextReady; 2321} 2322 2323void 2324Cache::serialize(CheckpointOut &cp) const 2325{ 2326 bool dirty(isDirty()); 2327 2328 if (dirty) { 2329 warn("*** The cache still contains dirty data. ***\n"); 2330 warn(" Make sure to drain the system using the correct flags.\n"); 2331 warn(" This checkpoint will not restore correctly and dirty data in " 2332 "the cache will be lost!\n"); 2333 } 2334 2335 // Since we don't checkpoint the data in the cache, any dirty data 2336 // will be lost when restoring from a checkpoint of a system that 2337 // wasn't drained properly. Flag the checkpoint as invalid if the 2338 // cache contains dirty data. 2339 bool bad_checkpoint(dirty); 2340 SERIALIZE_SCALAR(bad_checkpoint); 2341} 2342 2343void 2344Cache::unserialize(CheckpointIn &cp) 2345{ 2346 bool bad_checkpoint; 2347 UNSERIALIZE_SCALAR(bad_checkpoint); 2348 if (bad_checkpoint) { 2349 fatal("Restoring from checkpoints with dirty caches is not supported " 2350 "in the classic memory system. Please remove any caches or " 2351 " drain them properly before taking checkpoints.\n"); 2352 } 2353} 2354 2355/////////////// 2356// 2357// CpuSidePort 2358// 2359/////////////// 2360 2361AddrRangeList 2362Cache::CpuSidePort::getAddrRanges() const 2363{ 2364 return cache->getAddrRanges(); 2365} 2366 2367bool 2368Cache::CpuSidePort::recvTimingReq(PacketPtr pkt) 2369{ 2370 assert(!cache->system->bypassCaches()); 2371 2372 bool success = false; 2373 2374 // always let inhibited requests through, even if blocked, 2375 // ultimately we should check if this is an express snoop, but at 2376 // the moment that flag is only set in the cache itself 2377 if (pkt->memInhibitAsserted()) { 2378 // do not change the current retry state 2379 bool M5_VAR_USED bypass_success = cache->recvTimingReq(pkt); 2380 assert(bypass_success); 2381 return true; 2382 } else if (blocked || mustSendRetry) { 2383 // either already committed to send a retry, or blocked 2384 success = false; 2385 } else { 2386 // pass it on to the cache, and let the cache decide if we 2387 // have to retry or not 2388 success = cache->recvTimingReq(pkt); 2389 } 2390 2391 // remember if we have to retry 2392 mustSendRetry = !success; 2393 return success; 2394} 2395 2396Tick 2397Cache::CpuSidePort::recvAtomic(PacketPtr pkt) 2398{ 2399 return cache->recvAtomic(pkt); 2400} 2401 2402void 2403Cache::CpuSidePort::recvFunctional(PacketPtr pkt) 2404{ 2405 // functional request 2406 cache->functionalAccess(pkt, true); 2407} 2408 2409Cache:: 2410CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache, 2411 const std::string &_label) 2412 : BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache) 2413{ 2414} 2415 2416Cache* 2417CacheParams::create() 2418{ 2419 assert(tags); 2420 2421 return new Cache(this); 2422} 2423/////////////// 2424// 2425// MemSidePort 2426// 2427/////////////// 2428 2429bool 2430Cache::MemSidePort::recvTimingResp(PacketPtr pkt) 2431{ 2432 cache->recvTimingResp(pkt); 2433 return true; 2434} 2435 2436// Express snooping requests to memside port 2437void 2438Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt) 2439{ 2440 // handle snooping requests 2441 cache->recvTimingSnoopReq(pkt); 2442} 2443 2444Tick 2445Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt) 2446{ 2447 return cache->recvAtomicSnoop(pkt); 2448} 2449 2450void 2451Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt) 2452{ 2453 // functional snoop (note that in contrast to atomic we don't have 2454 // a specific functionalSnoop method, as they have the same 2455 // behaviour regardless) 2456 cache->functionalAccess(pkt, false); 2457} 2458 2459void 2460Cache::CacheReqPacketQueue::sendDeferredPacket() 2461{ 2462 // sanity check 2463 assert(!waitingOnRetry); 2464 2465 // there should never be any deferred request packets in the 2466 // queue, instead we resly on the cache to provide the packets 2467 // from the MSHR queue or write queue 2468 assert(deferredPacketReadyTime() == MaxTick); 2469 2470 // check for request packets (requests & writebacks) 2471 PacketPtr pkt = cache.getTimingPacket(); 2472 if (pkt == NULL) { 2473 // can happen if e.g. we attempt a writeback and fail, but 2474 // before the retry, the writeback is eliminated because 2475 // we snoop another cache's ReadEx. 2476 } else { 2477 MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState); 2478 // in most cases getTimingPacket allocates a new packet, and 2479 // we must delete it unless it is successfully sent 2480 bool delete_pkt = !mshr->isForwardNoResponse(); 2481 2482 // let our snoop responses go first if there are responses to 2483 // the same addresses we are about to writeback, note that 2484 // this creates a dependency between requests and snoop 2485 // responses, but that should not be a problem since there is 2486 // a chain already and the key is that the snoop responses can 2487 // sink unconditionally 2488 if (snoopRespQueue.hasAddr(pkt->getAddr())) { 2489 DPRINTF(CachePort, "Waiting for snoop response to be sent\n"); 2490 Tick when = snoopRespQueue.deferredPacketReadyTime(); 2491 schedSendEvent(when); 2492 2493 if (delete_pkt) 2494 delete pkt; 2495 2496 return; 2497 } 2498 2499 2500 waitingOnRetry = !masterPort.sendTimingReq(pkt); 2501 2502 if (waitingOnRetry) { 2503 DPRINTF(CachePort, "now waiting on a retry\n"); 2504 if (delete_pkt) { 2505 // we are awaiting a retry, but we 2506 // delete the packet and will be creating a new packet 2507 // when we get the opportunity 2508 delete pkt; 2509 } 2510 // note that we have now masked any requestBus and 2511 // schedSendEvent (we will wait for a retry before 2512 // doing anything), and this is so even if we do not 2513 // care about this packet and might override it before 2514 // it gets retried 2515 } else { 2516 // As part of the call to sendTimingReq the packet is 2517 // forwarded to all neighbouring caches (and any 2518 // caches above them) as a snoop. The packet is also 2519 // sent to any potential cache below as the 2520 // interconnect is not allowed to buffer the 2521 // packet. Thus at this point we know if any of the 2522 // neighbouring, or the downstream cache is 2523 // responding, and if so, if it is with a dirty line 2524 // or not. 2525 bool pending_dirty_resp = !pkt->sharedAsserted() && 2526 pkt->memInhibitAsserted(); 2527 2528 cache.markInService(mshr, pending_dirty_resp); 2529 } 2530 } 2531 2532 // if we succeeded and are not waiting for a retry, schedule the 2533 // next send considering when the next MSHR is ready, note that 2534 // snoop responses have their own packet queue and thus schedule 2535 // their own events 2536 if (!waitingOnRetry) { 2537 schedSendEvent(cache.nextMSHRReadyTime()); 2538 } 2539} 2540 2541Cache:: 2542MemSidePort::MemSidePort(const std::string &_name, Cache *_cache, 2543 const std::string &_label) 2544 : BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue), 2545 _reqQueue(*_cache, *this, _snoopRespQueue, _label), 2546 _snoopRespQueue(*_cache, *this, _label), cache(_cache) 2547{ 2548} 2549