cache.cc revision 12748
1/* 2 * Copyright (c) 2010-2018 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 * Nikos Nikoleris 48 */ 49 50/** 51 * @file 52 * Cache definitions. 53 */ 54 55#include "mem/cache/cache.hh" 56 57#include <cassert> 58 59#include "base/compiler.hh" 60#include "base/logging.hh" 61#include "base/trace.hh" 62#include "base/types.hh" 63#include "debug/Cache.hh" 64#include "debug/CacheTags.hh" 65#include "debug/CacheVerbose.hh" 66#include "enums/Clusivity.hh" 67#include "mem/cache/blk.hh" 68#include "mem/cache/mshr.hh" 69#include "mem/cache/tags/base.hh" 70#include "mem/cache/write_queue_entry.hh" 71#include "mem/request.hh" 72#include "params/Cache.hh" 73 74Cache::Cache(const CacheParams *p) 75 : BaseCache(p, p->system->cacheLineSize()), 76 doFastWrites(true) 77{ 78} 79 80void 81Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk, 82 bool deferred_response, bool pending_downgrade) 83{ 84 BaseCache::satisfyRequest(pkt, blk); 85 86 if (pkt->isRead()) { 87 // determine if this read is from a (coherent) cache or not 88 if (pkt->fromCache()) { 89 assert(pkt->getSize() == blkSize); 90 // special handling for coherent block requests from 91 // upper-level caches 92 if (pkt->needsWritable()) { 93 // sanity check 94 assert(pkt->cmd == MemCmd::ReadExReq || 95 pkt->cmd == MemCmd::SCUpgradeFailReq); 96 assert(!pkt->hasSharers()); 97 98 // if we have a dirty copy, make sure the recipient 99 // keeps it marked dirty (in the modified state) 100 if (blk->isDirty()) { 101 pkt->setCacheResponding(); 102 blk->status &= ~BlkDirty; 103 } 104 } else if (blk->isWritable() && !pending_downgrade && 105 !pkt->hasSharers() && 106 pkt->cmd != MemCmd::ReadCleanReq) { 107 // we can give the requester a writable copy on a read 108 // request if: 109 // - we have a writable copy at this level (& below) 110 // - we don't have a pending snoop from below 111 // signaling another read request 112 // - no other cache above has a copy (otherwise it 113 // would have set hasSharers flag when 114 // snooping the packet) 115 // - the read has explicitly asked for a clean 116 // copy of the line 117 if (blk->isDirty()) { 118 // special considerations if we're owner: 119 if (!deferred_response) { 120 // respond with the line in Modified state 121 // (cacheResponding set, hasSharers not set) 122 pkt->setCacheResponding(); 123 124 // if this cache is mostly inclusive, we 125 // keep the block in the Exclusive state, 126 // and pass it upwards as Modified 127 // (writable and dirty), hence we have 128 // multiple caches, all on the same path 129 // towards memory, all considering the 130 // same block writable, but only one 131 // considering it Modified 132 133 // we get away with multiple caches (on 134 // the same path to memory) considering 135 // the block writeable as we always enter 136 // the cache hierarchy through a cache, 137 // and first snoop upwards in all other 138 // branches 139 blk->status &= ~BlkDirty; 140 } else { 141 // if we're responding after our own miss, 142 // there's a window where the recipient didn't 143 // know it was getting ownership and may not 144 // have responded to snoops correctly, so we 145 // have to respond with a shared line 146 pkt->setHasSharers(); 147 } 148 } 149 } else { 150 // otherwise only respond with a shared copy 151 pkt->setHasSharers(); 152 } 153 } 154 } 155} 156 157///////////////////////////////////////////////////// 158// 159// Access path: requests coming in from the CPU side 160// 161///////////////////////////////////////////////////// 162 163bool 164Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat, 165 PacketList &writebacks) 166{ 167 168 if (pkt->req->isUncacheable()) { 169 assert(pkt->isRequest()); 170 171 chatty_assert(!(isReadOnly && pkt->isWrite()), 172 "Should never see a write in a read-only cache %s\n", 173 name()); 174 175 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print()); 176 177 // flush and invalidate any existing block 178 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure())); 179 if (old_blk && old_blk->isValid()) { 180 evictBlock(old_blk, writebacks); 181 } 182 183 blk = nullptr; 184 // lookupLatency is the latency in case the request is uncacheable. 185 lat = lookupLatency; 186 return false; 187 } 188 189 return BaseCache::access(pkt, blk, lat, writebacks); 190} 191 192void 193Cache::doWritebacks(PacketList& writebacks, Tick forward_time) 194{ 195 while (!writebacks.empty()) { 196 PacketPtr wbPkt = writebacks.front(); 197 // We use forwardLatency here because we are copying writebacks to 198 // write buffer. 199 200 // Call isCachedAbove for Writebacks, CleanEvicts and 201 // WriteCleans to discover if the block is cached above. 202 if (isCachedAbove(wbPkt)) { 203 if (wbPkt->cmd == MemCmd::CleanEvict) { 204 // Delete CleanEvict because cached copies exist above. The 205 // packet destructor will delete the request object because 206 // this is a non-snoop request packet which does not require a 207 // response. 208 delete wbPkt; 209 } else if (wbPkt->cmd == MemCmd::WritebackClean) { 210 // clean writeback, do not send since the block is 211 // still cached above 212 assert(writebackClean); 213 delete wbPkt; 214 } else { 215 assert(wbPkt->cmd == MemCmd::WritebackDirty || 216 wbPkt->cmd == MemCmd::WriteClean); 217 // Set BLOCK_CACHED flag in Writeback and send below, so that 218 // the Writeback does not reset the bit corresponding to this 219 // address in the snoop filter below. 220 wbPkt->setBlockCached(); 221 allocateWriteBuffer(wbPkt, forward_time); 222 } 223 } else { 224 // If the block is not cached above, send packet below. Both 225 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 226 // reset the bit corresponding to this address in the snoop filter 227 // below. 228 allocateWriteBuffer(wbPkt, forward_time); 229 } 230 writebacks.pop_front(); 231 } 232} 233 234void 235Cache::doWritebacksAtomic(PacketList& writebacks) 236{ 237 while (!writebacks.empty()) { 238 PacketPtr wbPkt = writebacks.front(); 239 // Call isCachedAbove for both Writebacks and CleanEvicts. If 240 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks 241 // and discard CleanEvicts. 242 if (isCachedAbove(wbPkt, false)) { 243 if (wbPkt->cmd == MemCmd::WritebackDirty || 244 wbPkt->cmd == MemCmd::WriteClean) { 245 // Set BLOCK_CACHED flag in Writeback and send below, 246 // so that the Writeback does not reset the bit 247 // corresponding to this address in the snoop filter 248 // below. We can discard CleanEvicts because cached 249 // copies exist above. Atomic mode isCachedAbove 250 // modifies packet to set BLOCK_CACHED flag 251 memSidePort.sendAtomic(wbPkt); 252 } 253 } else { 254 // If the block is not cached above, send packet below. Both 255 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 256 // reset the bit corresponding to this address in the snoop filter 257 // below. 258 memSidePort.sendAtomic(wbPkt); 259 } 260 writebacks.pop_front(); 261 // In case of CleanEvicts, the packet destructor will delete the 262 // request object because this is a non-snoop request packet which 263 // does not require a response. 264 delete wbPkt; 265 } 266} 267 268 269void 270Cache::recvTimingSnoopResp(PacketPtr pkt) 271{ 272 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print()); 273 274 // determine if the response is from a snoop request we created 275 // (in which case it should be in the outstandingSnoop), or if we 276 // merely forwarded someone else's snoop request 277 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) == 278 outstandingSnoop.end(); 279 280 if (!forwardAsSnoop) { 281 // the packet came from this cache, so sink it here and do not 282 // forward it 283 assert(pkt->cmd == MemCmd::HardPFResp); 284 285 outstandingSnoop.erase(pkt->req); 286 287 DPRINTF(Cache, "Got prefetch response from above for addr " 288 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns"); 289 recvTimingResp(pkt); 290 return; 291 } 292 293 // forwardLatency is set here because there is a response from an 294 // upper level cache. 295 // To pay the delay that occurs if the packet comes from the bus, 296 // we charge also headerDelay. 297 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay; 298 // Reset the timing of the packet. 299 pkt->headerDelay = pkt->payloadDelay = 0; 300 memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time); 301} 302 303void 304Cache::promoteWholeLineWrites(PacketPtr pkt) 305{ 306 // Cache line clearing instructions 307 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) && 308 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) { 309 pkt->cmd = MemCmd::WriteLineReq; 310 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n"); 311 } 312} 313 314void 315Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time) 316{ 317 // should never be satisfying an uncacheable access as we 318 // flush and invalidate any existing block as part of the 319 // lookup 320 assert(!pkt->req->isUncacheable()); 321 322 BaseCache::handleTimingReqHit(pkt, blk, request_time); 323} 324 325void 326Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time, 327 Tick request_time) 328{ 329 if (pkt->req->isUncacheable()) { 330 // ignore any existing MSHR if we are dealing with an 331 // uncacheable request 332 333 // should have flushed and have no valid block 334 assert(!blk || !blk->isValid()); 335 336 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++; 337 338 if (pkt->isWrite()) { 339 allocateWriteBuffer(pkt, forward_time); 340 } else { 341 assert(pkt->isRead()); 342 343 // uncacheable accesses always allocate a new MSHR 344 345 // Here we are using forward_time, modelling the latency of 346 // a miss (outbound) just as forwardLatency, neglecting the 347 // lookupLatency component. 348 allocateMissBuffer(pkt, forward_time); 349 } 350 351 return; 352 } 353 354 Addr blk_addr = pkt->getBlockAddr(blkSize); 355 356 MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure()); 357 358 // Software prefetch handling: 359 // To keep the core from waiting on data it won't look at 360 // anyway, send back a response with dummy data. Miss handling 361 // will continue asynchronously. Unfortunately, the core will 362 // insist upon freeing original Packet/Request, so we have to 363 // create a new pair with a different lifecycle. Note that this 364 // processing happens before any MSHR munging on the behalf of 365 // this request because this new Request will be the one stored 366 // into the MSHRs, not the original. 367 if (pkt->cmd.isSWPrefetch()) { 368 assert(pkt->needsResponse()); 369 assert(pkt->req->hasPaddr()); 370 assert(!pkt->req->isUncacheable()); 371 372 // There's no reason to add a prefetch as an additional target 373 // to an existing MSHR. If an outstanding request is already 374 // in progress, there is nothing for the prefetch to do. 375 // If this is the case, we don't even create a request at all. 376 PacketPtr pf = nullptr; 377 378 if (!mshr) { 379 // copy the request and create a new SoftPFReq packet 380 RequestPtr req = new Request(pkt->req->getPaddr(), 381 pkt->req->getSize(), 382 pkt->req->getFlags(), 383 pkt->req->masterId()); 384 pf = new Packet(req, pkt->cmd); 385 pf->allocate(); 386 assert(pf->getAddr() == pkt->getAddr()); 387 assert(pf->getSize() == pkt->getSize()); 388 } 389 390 pkt->makeTimingResponse(); 391 392 // request_time is used here, taking into account lat and the delay 393 // charged if the packet comes from the xbar. 394 cpuSidePort.schedTimingResp(pkt, request_time, true); 395 396 // If an outstanding request is in progress (we found an 397 // MSHR) this is set to null 398 pkt = pf; 399 } 400 401 BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time); 402} 403 404void 405Cache::recvTimingReq(PacketPtr pkt) 406{ 407 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print()); 408 409 promoteWholeLineWrites(pkt); 410 411 if (pkt->cacheResponding()) { 412 // a cache above us (but not where the packet came from) is 413 // responding to the request, in other words it has the line 414 // in Modified or Owned state 415 DPRINTF(Cache, "Cache above responding to %s: not responding\n", 416 pkt->print()); 417 418 // if the packet needs the block to be writable, and the cache 419 // that has promised to respond (setting the cache responding 420 // flag) is not providing writable (it is in Owned rather than 421 // the Modified state), we know that there may be other Shared 422 // copies in the system; go out and invalidate them all 423 assert(pkt->needsWritable() && !pkt->responderHadWritable()); 424 425 // an upstream cache that had the line in Owned state 426 // (dirty, but not writable), is responding and thus 427 // transferring the dirty line from one branch of the 428 // cache hierarchy to another 429 430 // send out an express snoop and invalidate all other 431 // copies (snooping a packet that needs writable is the 432 // same as an invalidation), thus turning the Owned line 433 // into a Modified line, note that we don't invalidate the 434 // block in the current cache or any other cache on the 435 // path to memory 436 437 // create a downstream express snoop with cleared packet 438 // flags, there is no need to allocate any data as the 439 // packet is merely used to co-ordinate state transitions 440 Packet *snoop_pkt = new Packet(pkt, true, false); 441 442 // also reset the bus time that the original packet has 443 // not yet paid for 444 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0; 445 446 // make this an instantaneous express snoop, and let the 447 // other caches in the system know that the another cache 448 // is responding, because we have found the authorative 449 // copy (Modified or Owned) that will supply the right 450 // data 451 snoop_pkt->setExpressSnoop(); 452 snoop_pkt->setCacheResponding(); 453 454 // this express snoop travels towards the memory, and at 455 // every crossbar it is snooped upwards thus reaching 456 // every cache in the system 457 bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt); 458 // express snoops always succeed 459 assert(success); 460 461 // main memory will delete the snoop packet 462 463 // queue for deletion, as opposed to immediate deletion, as 464 // the sending cache is still relying on the packet 465 pendingDelete.reset(pkt); 466 467 // no need to take any further action in this particular cache 468 // as an upstram cache has already committed to responding, 469 // and we have already sent out any express snoops in the 470 // section above to ensure all other copies in the system are 471 // invalidated 472 return; 473 } 474 475 BaseCache::recvTimingReq(pkt); 476} 477 478PacketPtr 479Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk, 480 bool needsWritable) const 481{ 482 // should never see evictions here 483 assert(!cpu_pkt->isEviction()); 484 485 bool blkValid = blk && blk->isValid(); 486 487 if (cpu_pkt->req->isUncacheable() || 488 (!blkValid && cpu_pkt->isUpgrade()) || 489 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) { 490 // uncacheable requests and upgrades from upper-level caches 491 // that missed completely just go through as is 492 return nullptr; 493 } 494 495 assert(cpu_pkt->needsResponse()); 496 497 MemCmd cmd; 498 // @TODO make useUpgrades a parameter. 499 // Note that ownership protocols require upgrade, otherwise a 500 // write miss on a shared owned block will generate a ReadExcl, 501 // which will clobber the owned copy. 502 const bool useUpgrades = true; 503 if (cpu_pkt->cmd == MemCmd::WriteLineReq) { 504 assert(!blkValid || !blk->isWritable()); 505 // forward as invalidate to all other caches, this gives us 506 // the line in Exclusive state, and invalidates all other 507 // copies 508 cmd = MemCmd::InvalidateReq; 509 } else if (blkValid && useUpgrades) { 510 // only reason to be here is that blk is read only and we need 511 // it to be writable 512 assert(needsWritable); 513 assert(!blk->isWritable()); 514 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq; 515 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq || 516 cpu_pkt->cmd == MemCmd::StoreCondFailReq) { 517 // Even though this SC will fail, we still need to send out the 518 // request and get the data to supply it to other snoopers in the case 519 // where the determination the StoreCond fails is delayed due to 520 // all caches not being on the same local bus. 521 cmd = MemCmd::SCUpgradeFailReq; 522 } else { 523 // block is invalid 524 525 // If the request does not need a writable there are two cases 526 // where we need to ensure the response will not fetch the 527 // block in dirty state: 528 // * this cache is read only and it does not perform 529 // writebacks, 530 // * this cache is mostly exclusive and will not fill (since 531 // it does not fill it will have to writeback the dirty data 532 // immediately which generates uneccesary writebacks). 533 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl; 534 cmd = needsWritable ? MemCmd::ReadExReq : 535 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq); 536 } 537 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize); 538 539 // if there are upstream caches that have already marked the 540 // packet as having sharers (not passing writable), pass that info 541 // downstream 542 if (cpu_pkt->hasSharers() && !needsWritable) { 543 // note that cpu_pkt may have spent a considerable time in the 544 // MSHR queue and that the information could possibly be out 545 // of date, however, there is no harm in conservatively 546 // assuming the block has sharers 547 pkt->setHasSharers(); 548 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n", 549 __func__, cpu_pkt->print(), pkt->print()); 550 } 551 552 // the packet should be block aligned 553 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize)); 554 555 pkt->allocate(); 556 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(), 557 cpu_pkt->print()); 558 return pkt; 559} 560 561 562Cycles 563Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *blk, 564 PacketList &writebacks) 565{ 566 // deal with the packets that go through the write path of 567 // the cache, i.e. any evictions and writes 568 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean || 569 (pkt->req->isUncacheable() && pkt->isWrite())) { 570 Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt)); 571 572 // at this point, if the request was an uncacheable write 573 // request, it has been satisfied by a memory below and the 574 // packet carries the response back 575 assert(!(pkt->req->isUncacheable() && pkt->isWrite()) || 576 pkt->isResponse()); 577 578 return latency; 579 } 580 581 // only misses left 582 583 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable()); 584 585 bool is_forward = (bus_pkt == nullptr); 586 587 if (is_forward) { 588 // just forwarding the same request to the next level 589 // no local cache operation involved 590 bus_pkt = pkt; 591 } 592 593 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__, 594 bus_pkt->print()); 595 596#if TRACING_ON 597 CacheBlk::State old_state = blk ? blk->status : 0; 598#endif 599 600 Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt)); 601 602 bool is_invalidate = bus_pkt->isInvalidate(); 603 604 // We are now dealing with the response handling 605 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__, 606 bus_pkt->print(), old_state); 607 608 // If packet was a forward, the response (if any) is already 609 // in place in the bus_pkt == pkt structure, so we don't need 610 // to do anything. Otherwise, use the separate bus_pkt to 611 // generate response to pkt and then delete it. 612 if (!is_forward) { 613 if (pkt->needsResponse()) { 614 assert(bus_pkt->isResponse()); 615 if (bus_pkt->isError()) { 616 pkt->makeAtomicResponse(); 617 pkt->copyError(bus_pkt); 618 } else if (pkt->cmd == MemCmd::WriteLineReq) { 619 // note the use of pkt, not bus_pkt here. 620 621 // write-line request to the cache that promoted 622 // the write to a whole line 623 blk = handleFill(pkt, blk, writebacks, 624 allocOnFill(pkt->cmd)); 625 assert(blk != NULL); 626 is_invalidate = false; 627 satisfyRequest(pkt, blk); 628 } else if (bus_pkt->isRead() || 629 bus_pkt->cmd == MemCmd::UpgradeResp) { 630 // we're updating cache state to allow us to 631 // satisfy the upstream request from the cache 632 blk = handleFill(bus_pkt, blk, writebacks, 633 allocOnFill(pkt->cmd)); 634 satisfyRequest(pkt, blk); 635 maintainClusivity(pkt->fromCache(), blk); 636 } else { 637 // we're satisfying the upstream request without 638 // modifying cache state, e.g., a write-through 639 pkt->makeAtomicResponse(); 640 } 641 } 642 delete bus_pkt; 643 } 644 645 if (is_invalidate && blk && blk->isValid()) { 646 invalidateBlock(blk); 647 } 648 649 return latency; 650} 651 652Tick 653Cache::recvAtomic(PacketPtr pkt) 654{ 655 promoteWholeLineWrites(pkt); 656 657 return BaseCache::recvAtomic(pkt); 658} 659 660 661///////////////////////////////////////////////////// 662// 663// Response handling: responses from the memory side 664// 665///////////////////////////////////////////////////// 666 667 668void 669Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk, 670 PacketList &writebacks) 671{ 672 MSHR::Target *initial_tgt = mshr->getTarget(); 673 // First offset for critical word first calculations 674 const int initial_offset = initial_tgt->pkt->getOffset(blkSize); 675 676 const bool is_error = pkt->isError(); 677 bool is_fill = !mshr->isForward && 678 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp); 679 // allow invalidation responses originating from write-line 680 // requests to be discarded 681 bool is_invalidate = pkt->isInvalidate(); 682 683 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt); 684 for (auto &target: targets) { 685 Packet *tgt_pkt = target.pkt; 686 switch (target.source) { 687 case MSHR::Target::FromCPU: 688 Tick completion_time; 689 // Here we charge on completion_time the delay of the xbar if the 690 // packet comes from it, charged on headerDelay. 691 completion_time = pkt->headerDelay; 692 693 // Software prefetch handling for cache closest to core 694 if (tgt_pkt->cmd.isSWPrefetch()) { 695 // a software prefetch would have already been ack'd 696 // immediately with dummy data so the core would be able to 697 // retire it. This request completes right here, so we 698 // deallocate it. 699 delete tgt_pkt->req; 700 delete tgt_pkt; 701 break; // skip response 702 } 703 704 // unlike the other packet flows, where data is found in other 705 // caches or memory and brought back, write-line requests always 706 // have the data right away, so the above check for "is fill?" 707 // cannot actually be determined until examining the stored MSHR 708 // state. We "catch up" with that logic here, which is duplicated 709 // from above. 710 if (tgt_pkt->cmd == MemCmd::WriteLineReq) { 711 assert(!is_error); 712 // we got the block in a writable state, so promote 713 // any deferred targets if possible 714 mshr->promoteWritable(); 715 // NB: we use the original packet here and not the response! 716 blk = handleFill(tgt_pkt, blk, writebacks, 717 targets.allocOnFill); 718 assert(blk); 719 720 // treat as a fill, and discard the invalidation 721 // response 722 is_fill = true; 723 is_invalidate = false; 724 } 725 726 if (is_fill) { 727 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade()); 728 729 // How many bytes past the first request is this one 730 int transfer_offset = 731 tgt_pkt->getOffset(blkSize) - initial_offset; 732 if (transfer_offset < 0) { 733 transfer_offset += blkSize; 734 } 735 736 // If not critical word (offset) return payloadDelay. 737 // responseLatency is the latency of the return path 738 // from lower level caches/memory to an upper level cache or 739 // the core. 740 completion_time += clockEdge(responseLatency) + 741 (transfer_offset ? pkt->payloadDelay : 0); 742 743 assert(!tgt_pkt->req->isUncacheable()); 744 745 assert(tgt_pkt->req->masterId() < system->maxMasters()); 746 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] += 747 completion_time - target.recvTime; 748 } else if (pkt->cmd == MemCmd::UpgradeFailResp) { 749 // failed StoreCond upgrade 750 assert(tgt_pkt->cmd == MemCmd::StoreCondReq || 751 tgt_pkt->cmd == MemCmd::StoreCondFailReq || 752 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq); 753 // responseLatency is the latency of the return path 754 // from lower level caches/memory to an upper level cache or 755 // the core. 756 completion_time += clockEdge(responseLatency) + 757 pkt->payloadDelay; 758 tgt_pkt->req->setExtraData(0); 759 } else { 760 // We are about to send a response to a cache above 761 // that asked for an invalidation; we need to 762 // invalidate our copy immediately as the most 763 // up-to-date copy of the block will now be in the 764 // cache above. It will also prevent this cache from 765 // responding (if the block was previously dirty) to 766 // snoops as they should snoop the caches above where 767 // they will get the response from. 768 if (is_invalidate && blk && blk->isValid()) { 769 invalidateBlock(blk); 770 } 771 // not a cache fill, just forwarding response 772 // responseLatency is the latency of the return path 773 // from lower level cahces/memory to the core. 774 completion_time += clockEdge(responseLatency) + 775 pkt->payloadDelay; 776 if (pkt->isRead() && !is_error) { 777 // sanity check 778 assert(pkt->getAddr() == tgt_pkt->getAddr()); 779 assert(pkt->getSize() >= tgt_pkt->getSize()); 780 781 tgt_pkt->setData(pkt->getConstPtr<uint8_t>()); 782 } 783 } 784 tgt_pkt->makeTimingResponse(); 785 // if this packet is an error copy that to the new packet 786 if (is_error) 787 tgt_pkt->copyError(pkt); 788 if (tgt_pkt->cmd == MemCmd::ReadResp && 789 (is_invalidate || mshr->hasPostInvalidate())) { 790 // If intermediate cache got ReadRespWithInvalidate, 791 // propagate that. Response should not have 792 // isInvalidate() set otherwise. 793 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate; 794 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__, 795 tgt_pkt->print()); 796 } 797 // Reset the bus additional time as it is now accounted for 798 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0; 799 cpuSidePort.schedTimingResp(tgt_pkt, completion_time, true); 800 break; 801 802 case MSHR::Target::FromPrefetcher: 803 assert(tgt_pkt->cmd == MemCmd::HardPFReq); 804 if (blk) 805 blk->status |= BlkHWPrefetched; 806 delete tgt_pkt->req; 807 delete tgt_pkt; 808 break; 809 810 case MSHR::Target::FromSnoop: 811 // I don't believe that a snoop can be in an error state 812 assert(!is_error); 813 // response to snoop request 814 DPRINTF(Cache, "processing deferred snoop...\n"); 815 // If the response is invalidating, a snooping target can 816 // be satisfied if it is also invalidating. If the reponse is, not 817 // only invalidating, but more specifically an InvalidateResp and 818 // the MSHR was created due to an InvalidateReq then a cache above 819 // is waiting to satisfy a WriteLineReq. In this case even an 820 // non-invalidating snoop is added as a target here since this is 821 // the ordering point. When the InvalidateResp reaches this cache, 822 // the snooping target will snoop further the cache above with the 823 // WriteLineReq. 824 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp || 825 pkt->req->isCacheMaintenance() || 826 mshr->hasPostInvalidate()); 827 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate()); 828 break; 829 830 default: 831 panic("Illegal target->source enum %d\n", target.source); 832 } 833 } 834 835 maintainClusivity(targets.hasFromCache, blk); 836 837 if (blk && blk->isValid()) { 838 // an invalidate response stemming from a write line request 839 // should not invalidate the block, so check if the 840 // invalidation should be discarded 841 if (is_invalidate || mshr->hasPostInvalidate()) { 842 invalidateBlock(blk); 843 } else if (mshr->hasPostDowngrade()) { 844 blk->status &= ~BlkWritable; 845 } 846 } 847} 848 849PacketPtr 850Cache::evictBlock(CacheBlk *blk) 851{ 852 PacketPtr pkt = (blk->isDirty() || writebackClean) ? 853 writebackBlk(blk) : cleanEvictBlk(blk); 854 855 invalidateBlock(blk); 856 857 return pkt; 858} 859 860void 861Cache::evictBlock(CacheBlk *blk, PacketList &writebacks) 862{ 863 PacketPtr pkt = evictBlock(blk); 864 if (pkt) { 865 writebacks.push_back(pkt); 866 } 867} 868 869PacketPtr 870Cache::cleanEvictBlk(CacheBlk *blk) 871{ 872 assert(!writebackClean); 873 assert(blk && blk->isValid() && !blk->isDirty()); 874 // Creating a zero sized write, a message to the snoop filter 875 876 RequestPtr req = 877 new Request(regenerateBlkAddr(blk), blkSize, 0, 878 Request::wbMasterId); 879 if (blk->isSecure()) 880 req->setFlags(Request::SECURE); 881 882 req->taskId(blk->task_id); 883 884 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict); 885 pkt->allocate(); 886 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print()); 887 888 return pkt; 889} 890 891///////////////////////////////////////////////////// 892// 893// Snoop path: requests coming in from the memory side 894// 895///////////////////////////////////////////////////// 896 897void 898Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data, 899 bool already_copied, bool pending_inval) 900{ 901 // sanity check 902 assert(req_pkt->isRequest()); 903 assert(req_pkt->needsResponse()); 904 905 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print()); 906 // timing-mode snoop responses require a new packet, unless we 907 // already made a copy... 908 PacketPtr pkt = req_pkt; 909 if (!already_copied) 910 // do not clear flags, and allocate space for data if the 911 // packet needs it (the only packets that carry data are read 912 // responses) 913 pkt = new Packet(req_pkt, false, req_pkt->isRead()); 914 915 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() || 916 pkt->hasSharers()); 917 pkt->makeTimingResponse(); 918 if (pkt->isRead()) { 919 pkt->setDataFromBlock(blk_data, blkSize); 920 } 921 if (pkt->cmd == MemCmd::ReadResp && pending_inval) { 922 // Assume we defer a response to a read from a far-away cache 923 // A, then later defer a ReadExcl from a cache B on the same 924 // bus as us. We'll assert cacheResponding in both cases, but 925 // in the latter case cacheResponding will keep the 926 // invalidation from reaching cache A. This special response 927 // tells cache A that it gets the block to satisfy its read, 928 // but must immediately invalidate it. 929 pkt->cmd = MemCmd::ReadRespWithInvalidate; 930 } 931 // Here we consider forward_time, paying for just forward latency and 932 // also charging the delay provided by the xbar. 933 // forward_time is used as send_time in next allocateWriteBuffer(). 934 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 935 // Here we reset the timing of the packet. 936 pkt->headerDelay = pkt->payloadDelay = 0; 937 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__, 938 pkt->print(), forward_time); 939 memSidePort.schedTimingSnoopResp(pkt, forward_time, true); 940} 941 942uint32_t 943Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing, 944 bool is_deferred, bool pending_inval) 945{ 946 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print()); 947 // deferred snoops can only happen in timing mode 948 assert(!(is_deferred && !is_timing)); 949 // pending_inval only makes sense on deferred snoops 950 assert(!(pending_inval && !is_deferred)); 951 assert(pkt->isRequest()); 952 953 // the packet may get modified if we or a forwarded snooper 954 // responds in atomic mode, so remember a few things about the 955 // original packet up front 956 bool invalidate = pkt->isInvalidate(); 957 bool M5_VAR_USED needs_writable = pkt->needsWritable(); 958 959 // at the moment we could get an uncacheable write which does not 960 // have the invalidate flag, and we need a suitable way of dealing 961 // with this case 962 panic_if(invalidate && pkt->req->isUncacheable(), 963 "%s got an invalidating uncacheable snoop request %s", 964 name(), pkt->print()); 965 966 uint32_t snoop_delay = 0; 967 968 if (forwardSnoops) { 969 // first propagate snoop upward to see if anyone above us wants to 970 // handle it. save & restore packet src since it will get 971 // rewritten to be relative to cpu-side bus (if any) 972 bool alreadyResponded = pkt->cacheResponding(); 973 if (is_timing) { 974 // copy the packet so that we can clear any flags before 975 // forwarding it upwards, we also allocate data (passing 976 // the pointer along in case of static data), in case 977 // there is a snoop hit in upper levels 978 Packet snoopPkt(pkt, true, true); 979 snoopPkt.setExpressSnoop(); 980 // the snoop packet does not need to wait any additional 981 // time 982 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0; 983 cpuSidePort.sendTimingSnoopReq(&snoopPkt); 984 985 // add the header delay (including crossbar and snoop 986 // delays) of the upward snoop to the snoop delay for this 987 // cache 988 snoop_delay += snoopPkt.headerDelay; 989 990 if (snoopPkt.cacheResponding()) { 991 // cache-to-cache response from some upper cache 992 assert(!alreadyResponded); 993 pkt->setCacheResponding(); 994 } 995 // upstream cache has the block, or has an outstanding 996 // MSHR, pass the flag on 997 if (snoopPkt.hasSharers()) { 998 pkt->setHasSharers(); 999 } 1000 // If this request is a prefetch or clean evict and an upper level 1001 // signals block present, make sure to propagate the block 1002 // presence to the requester. 1003 if (snoopPkt.isBlockCached()) { 1004 pkt->setBlockCached(); 1005 } 1006 // If the request was satisfied by snooping the cache 1007 // above, mark the original packet as satisfied too. 1008 if (snoopPkt.satisfied()) { 1009 pkt->setSatisfied(); 1010 } 1011 } else { 1012 cpuSidePort.sendAtomicSnoop(pkt); 1013 if (!alreadyResponded && pkt->cacheResponding()) { 1014 // cache-to-cache response from some upper cache: 1015 // forward response to original requester 1016 assert(pkt->isResponse()); 1017 } 1018 } 1019 } 1020 1021 bool respond = false; 1022 bool blk_valid = blk && blk->isValid(); 1023 if (pkt->isClean()) { 1024 if (blk_valid && blk->isDirty()) { 1025 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n", 1026 __func__, pkt->print(), blk->print()); 1027 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id); 1028 PacketList writebacks; 1029 writebacks.push_back(wb_pkt); 1030 1031 if (is_timing) { 1032 // anything that is merely forwarded pays for the forward 1033 // latency and the delay provided by the crossbar 1034 Tick forward_time = clockEdge(forwardLatency) + 1035 pkt->headerDelay; 1036 doWritebacks(writebacks, forward_time); 1037 } else { 1038 doWritebacksAtomic(writebacks); 1039 } 1040 pkt->setSatisfied(); 1041 } 1042 } else if (!blk_valid) { 1043 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__, 1044 pkt->print()); 1045 if (is_deferred) { 1046 // we no longer have the block, and will not respond, but a 1047 // packet was allocated in MSHR::handleSnoop and we have 1048 // to delete it 1049 assert(pkt->needsResponse()); 1050 1051 // we have passed the block to a cache upstream, that 1052 // cache should be responding 1053 assert(pkt->cacheResponding()); 1054 1055 delete pkt; 1056 } 1057 return snoop_delay; 1058 } else { 1059 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__, 1060 pkt->print(), blk->print()); 1061 1062 // We may end up modifying both the block state and the packet (if 1063 // we respond in atomic mode), so just figure out what to do now 1064 // and then do it later. We respond to all snoops that need 1065 // responses provided we have the block in dirty state. The 1066 // invalidation itself is taken care of below. We don't respond to 1067 // cache maintenance operations as this is done by the destination 1068 // xbar. 1069 respond = blk->isDirty() && pkt->needsResponse(); 1070 1071 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have " 1072 "a dirty block in a read-only cache %s\n", name()); 1073 } 1074 1075 // Invalidate any prefetch's from below that would strip write permissions 1076 // MemCmd::HardPFReq is only observed by upstream caches. After missing 1077 // above and in it's own cache, a new MemCmd::ReadReq is created that 1078 // downstream caches observe. 1079 if (pkt->mustCheckAbove()) { 1080 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s " 1081 "from lower cache\n", pkt->getAddr(), pkt->print()); 1082 pkt->setBlockCached(); 1083 return snoop_delay; 1084 } 1085 1086 if (pkt->isRead() && !invalidate) { 1087 // reading without requiring the line in a writable state 1088 assert(!needs_writable); 1089 pkt->setHasSharers(); 1090 1091 // if the requesting packet is uncacheable, retain the line in 1092 // the current state, otherwhise unset the writable flag, 1093 // which means we go from Modified to Owned (and will respond 1094 // below), remain in Owned (and will respond below), from 1095 // Exclusive to Shared, or remain in Shared 1096 if (!pkt->req->isUncacheable()) 1097 blk->status &= ~BlkWritable; 1098 DPRINTF(Cache, "new state is %s\n", blk->print()); 1099 } 1100 1101 if (respond) { 1102 // prevent anyone else from responding, cache as well as 1103 // memory, and also prevent any memory from even seeing the 1104 // request 1105 pkt->setCacheResponding(); 1106 if (!pkt->isClean() && blk->isWritable()) { 1107 // inform the cache hierarchy that this cache had the line 1108 // in the Modified state so that we avoid unnecessary 1109 // invalidations (see Packet::setResponderHadWritable) 1110 pkt->setResponderHadWritable(); 1111 1112 // in the case of an uncacheable request there is no point 1113 // in setting the responderHadWritable flag, but since the 1114 // recipient does not care there is no harm in doing so 1115 } else { 1116 // if the packet has needsWritable set we invalidate our 1117 // copy below and all other copies will be invalidates 1118 // through express snoops, and if needsWritable is not set 1119 // we already called setHasSharers above 1120 } 1121 1122 // if we are returning a writable and dirty (Modified) line, 1123 // we should be invalidating the line 1124 panic_if(!invalidate && !pkt->hasSharers(), 1125 "%s is passing a Modified line through %s, " 1126 "but keeping the block", name(), pkt->print()); 1127 1128 if (is_timing) { 1129 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval); 1130 } else { 1131 pkt->makeAtomicResponse(); 1132 // packets such as upgrades do not actually have any data 1133 // payload 1134 if (pkt->hasData()) 1135 pkt->setDataFromBlock(blk->data, blkSize); 1136 } 1137 } 1138 1139 if (!respond && is_deferred) { 1140 assert(pkt->needsResponse()); 1141 1142 // if we copied the deferred packet with the intention to 1143 // respond, but are not responding, then a cache above us must 1144 // be, and we can use this as the indication of whether this 1145 // is a packet where we created a copy of the request or not 1146 if (!pkt->cacheResponding()) { 1147 delete pkt->req; 1148 } 1149 1150 delete pkt; 1151 } 1152 1153 // Do this last in case it deallocates block data or something 1154 // like that 1155 if (blk_valid && invalidate) { 1156 invalidateBlock(blk); 1157 DPRINTF(Cache, "new state is %s\n", blk->print()); 1158 } 1159 1160 return snoop_delay; 1161} 1162 1163 1164void 1165Cache::recvTimingSnoopReq(PacketPtr pkt) 1166{ 1167 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print()); 1168 1169 // no need to snoop requests that are not in range 1170 if (!inRange(pkt->getAddr())) { 1171 return; 1172 } 1173 1174 bool is_secure = pkt->isSecure(); 1175 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure); 1176 1177 Addr blk_addr = pkt->getBlockAddr(blkSize); 1178 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure); 1179 1180 // Update the latency cost of the snoop so that the crossbar can 1181 // account for it. Do not overwrite what other neighbouring caches 1182 // have already done, rather take the maximum. The update is 1183 // tentative, for cases where we return before an upward snoop 1184 // happens below. 1185 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, 1186 lookupLatency * clockPeriod()); 1187 1188 // Inform request(Prefetch, CleanEvict or Writeback) from below of 1189 // MSHR hit, set setBlockCached. 1190 if (mshr && pkt->mustCheckAbove()) { 1191 DPRINTF(Cache, "Setting block cached for %s from lower cache on " 1192 "mshr hit\n", pkt->print()); 1193 pkt->setBlockCached(); 1194 return; 1195 } 1196 1197 // Bypass any existing cache maintenance requests if the request 1198 // has been satisfied already (i.e., the dirty block has been 1199 // found). 1200 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) { 1201 return; 1202 } 1203 1204 // Let the MSHR itself track the snoop and decide whether we want 1205 // to go ahead and do the regular cache snoop 1206 if (mshr && mshr->handleSnoop(pkt, order++)) { 1207 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)." 1208 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns", 1209 mshr->print()); 1210 1211 if (mshr->getNumTargets() > numTarget) 1212 warn("allocating bonus target for snoop"); //handle later 1213 return; 1214 } 1215 1216 //We also need to check the writeback buffers and handle those 1217 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure); 1218 if (wb_entry) { 1219 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n", 1220 pkt->getAddr(), is_secure ? "s" : "ns"); 1221 // Expect to see only Writebacks and/or CleanEvicts here, both of 1222 // which should not be generated for uncacheable data. 1223 assert(!wb_entry->isUncacheable()); 1224 // There should only be a single request responsible for generating 1225 // Writebacks/CleanEvicts. 1226 assert(wb_entry->getNumTargets() == 1); 1227 PacketPtr wb_pkt = wb_entry->getTarget()->pkt; 1228 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean); 1229 1230 if (pkt->isEviction()) { 1231 // if the block is found in the write queue, set the BLOCK_CACHED 1232 // flag for Writeback/CleanEvict snoop. On return the snoop will 1233 // propagate the BLOCK_CACHED flag in Writeback packets and prevent 1234 // any CleanEvicts from travelling down the memory hierarchy. 1235 pkt->setBlockCached(); 1236 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue " 1237 "hit\n", __func__, pkt->print()); 1238 return; 1239 } 1240 1241 // conceptually writebacks are no different to other blocks in 1242 // this cache, so the behaviour is modelled after handleSnoop, 1243 // the difference being that instead of querying the block 1244 // state to determine if it is dirty and writable, we use the 1245 // command and fields of the writeback packet 1246 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty && 1247 pkt->needsResponse(); 1248 bool have_writable = !wb_pkt->hasSharers(); 1249 bool invalidate = pkt->isInvalidate(); 1250 1251 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) { 1252 assert(!pkt->needsWritable()); 1253 pkt->setHasSharers(); 1254 wb_pkt->setHasSharers(); 1255 } 1256 1257 if (respond) { 1258 pkt->setCacheResponding(); 1259 1260 if (have_writable) { 1261 pkt->setResponderHadWritable(); 1262 } 1263 1264 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(), 1265 false, false); 1266 } 1267 1268 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) { 1269 // Invalidation trumps our writeback... discard here 1270 // Note: markInService will remove entry from writeback buffer. 1271 markInService(wb_entry); 1272 delete wb_pkt; 1273 } 1274 } 1275 1276 // If this was a shared writeback, there may still be 1277 // other shared copies above that require invalidation. 1278 // We could be more selective and return here if the 1279 // request is non-exclusive or if the writeback is 1280 // exclusive. 1281 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false); 1282 1283 // Override what we did when we first saw the snoop, as we now 1284 // also have the cost of the upwards snoops to account for 1285 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay + 1286 lookupLatency * clockPeriod()); 1287} 1288 1289Tick 1290Cache::recvAtomicSnoop(PacketPtr pkt) 1291{ 1292 // no need to snoop requests that are not in range. 1293 if (!inRange(pkt->getAddr())) { 1294 return 0; 1295 } 1296 1297 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 1298 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false); 1299 return snoop_delay + lookupLatency * clockPeriod(); 1300} 1301 1302bool 1303Cache::isCachedAbove(PacketPtr pkt, bool is_timing) 1304{ 1305 if (!forwardSnoops) 1306 return false; 1307 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and 1308 // Writeback snoops into upper level caches to check for copies of the 1309 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict 1310 // packet, the cache can inform the crossbar below of presence or absence 1311 // of the block. 1312 if (is_timing) { 1313 Packet snoop_pkt(pkt, true, false); 1314 snoop_pkt.setExpressSnoop(); 1315 // Assert that packet is either Writeback or CleanEvict and not a 1316 // prefetch request because prefetch requests need an MSHR and may 1317 // generate a snoop response. 1318 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean); 1319 snoop_pkt.senderState = nullptr; 1320 cpuSidePort.sendTimingSnoopReq(&snoop_pkt); 1321 // Writeback/CleanEvict snoops do not generate a snoop response. 1322 assert(!(snoop_pkt.cacheResponding())); 1323 return snoop_pkt.isBlockCached(); 1324 } else { 1325 cpuSidePort.sendAtomicSnoop(pkt); 1326 return pkt->isBlockCached(); 1327 } 1328} 1329 1330bool 1331Cache::sendMSHRQueuePacket(MSHR* mshr) 1332{ 1333 assert(mshr); 1334 1335 // use request from 1st target 1336 PacketPtr tgt_pkt = mshr->getTarget()->pkt; 1337 1338 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) { 1339 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print()); 1340 1341 // we should never have hardware prefetches to allocated 1342 // blocks 1343 assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure)); 1344 1345 // We need to check the caches above us to verify that 1346 // they don't have a copy of this block in the dirty state 1347 // at the moment. Without this check we could get a stale 1348 // copy from memory that might get used in place of the 1349 // dirty one. 1350 Packet snoop_pkt(tgt_pkt, true, false); 1351 snoop_pkt.setExpressSnoop(); 1352 // We are sending this packet upwards, but if it hits we will 1353 // get a snoop response that we end up treating just like a 1354 // normal response, hence it needs the MSHR as its sender 1355 // state 1356 snoop_pkt.senderState = mshr; 1357 cpuSidePort.sendTimingSnoopReq(&snoop_pkt); 1358 1359 // Check to see if the prefetch was squashed by an upper cache (to 1360 // prevent us from grabbing the line) or if a Check to see if a 1361 // writeback arrived between the time the prefetch was placed in 1362 // the MSHRs and when it was selected to be sent or if the 1363 // prefetch was squashed by an upper cache. 1364 1365 // It is important to check cacheResponding before 1366 // prefetchSquashed. If another cache has committed to 1367 // responding, it will be sending a dirty response which will 1368 // arrive at the MSHR allocated for this request. Checking the 1369 // prefetchSquash first may result in the MSHR being 1370 // prematurely deallocated. 1371 if (snoop_pkt.cacheResponding()) { 1372 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req); 1373 assert(r.second); 1374 1375 // if we are getting a snoop response with no sharers it 1376 // will be allocated as Modified 1377 bool pending_modified_resp = !snoop_pkt.hasSharers(); 1378 markInService(mshr, pending_modified_resp); 1379 1380 DPRINTF(Cache, "Upward snoop of prefetch for addr" 1381 " %#x (%s) hit\n", 1382 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns"); 1383 return false; 1384 } 1385 1386 if (snoop_pkt.isBlockCached()) { 1387 DPRINTF(Cache, "Block present, prefetch squashed by cache. " 1388 "Deallocating mshr target %#x.\n", 1389 mshr->blkAddr); 1390 1391 // Deallocate the mshr target 1392 if (mshrQueue.forceDeallocateTarget(mshr)) { 1393 // Clear block if this deallocation resulted freed an 1394 // mshr when all had previously been utilized 1395 clearBlocked(Blocked_NoMSHRs); 1396 } 1397 1398 // given that no response is expected, delete Request and Packet 1399 delete tgt_pkt->req; 1400 delete tgt_pkt; 1401 1402 return false; 1403 } 1404 } 1405 1406 return BaseCache::sendMSHRQueuePacket(mshr); 1407} 1408 1409Cache* 1410CacheParams::create() 1411{ 1412 assert(tags); 1413 assert(replacement_policy); 1414 1415 return new Cache(this); 1416} 1417