cache.cc revision 11332
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 "debug/CacheVerbose.hh" 62#include "mem/cache/blk.hh" 63#include "mem/cache/mshr.hh" 64#include "mem/cache/prefetch/base.hh" 65#include "sim/sim_exit.hh" 66 67Cache::Cache(const CacheParams *p) 68 : BaseCache(p, p->system->cacheLineSize()), 69 tags(p->tags), 70 prefetcher(p->prefetcher), 71 doFastWrites(true), 72 prefetchOnAccess(p->prefetch_on_access), 73 clusivity(p->clusivity), 74 writebackClean(p->writeback_clean), 75 tempBlockWriteback(nullptr), 76 writebackTempBlockAtomicEvent(this, false, 77 EventBase::Delayed_Writeback_Pri) 78{ 79 tempBlock = new CacheBlk(); 80 tempBlock->data = new uint8_t[blkSize]; 81 82 cpuSidePort = new CpuSidePort(p->name + ".cpu_side", this, 83 "CpuSidePort"); 84 memSidePort = new MemSidePort(p->name + ".mem_side", this, 85 "MemSidePort"); 86 87 tags->setCache(this); 88 if (prefetcher) 89 prefetcher->setCache(this); 90} 91 92Cache::~Cache() 93{ 94 delete [] tempBlock->data; 95 delete tempBlock; 96 97 delete cpuSidePort; 98 delete memSidePort; 99} 100 101void 102Cache::regStats() 103{ 104 BaseCache::regStats(); 105} 106 107void 108Cache::cmpAndSwap(CacheBlk *blk, PacketPtr pkt) 109{ 110 assert(pkt->isRequest()); 111 112 uint64_t overwrite_val; 113 bool overwrite_mem; 114 uint64_t condition_val64; 115 uint32_t condition_val32; 116 117 int offset = tags->extractBlkOffset(pkt->getAddr()); 118 uint8_t *blk_data = blk->data + offset; 119 120 assert(sizeof(uint64_t) >= pkt->getSize()); 121 122 overwrite_mem = true; 123 // keep a copy of our possible write value, and copy what is at the 124 // memory address into the packet 125 pkt->writeData((uint8_t *)&overwrite_val); 126 pkt->setData(blk_data); 127 128 if (pkt->req->isCondSwap()) { 129 if (pkt->getSize() == sizeof(uint64_t)) { 130 condition_val64 = pkt->req->getExtraData(); 131 overwrite_mem = !std::memcmp(&condition_val64, blk_data, 132 sizeof(uint64_t)); 133 } else if (pkt->getSize() == sizeof(uint32_t)) { 134 condition_val32 = (uint32_t)pkt->req->getExtraData(); 135 overwrite_mem = !std::memcmp(&condition_val32, blk_data, 136 sizeof(uint32_t)); 137 } else 138 panic("Invalid size for conditional read/write\n"); 139 } 140 141 if (overwrite_mem) { 142 std::memcpy(blk_data, &overwrite_val, pkt->getSize()); 143 blk->status |= BlkDirty; 144 } 145} 146 147 148void 149Cache::satisfyCpuSideRequest(PacketPtr pkt, CacheBlk *blk, 150 bool deferred_response, bool pending_downgrade) 151{ 152 assert(pkt->isRequest()); 153 154 assert(blk && blk->isValid()); 155 // Occasionally this is not true... if we are a lower-level cache 156 // satisfying a string of Read and ReadEx requests from 157 // upper-level caches, a Read will mark the block as shared but we 158 // can satisfy a following ReadEx anyway since we can rely on the 159 // Read requester(s) to have buffered the ReadEx snoop and to 160 // invalidate their blocks after receiving them. 161 // assert(!pkt->needsWritable() || blk->isWritable()); 162 assert(pkt->getOffset(blkSize) + pkt->getSize() <= blkSize); 163 164 // Check RMW operations first since both isRead() and 165 // isWrite() will be true for them 166 if (pkt->cmd == MemCmd::SwapReq) { 167 cmpAndSwap(blk, pkt); 168 } else if (pkt->isWrite()) { 169 // we have the block in a writable state and can go ahead, 170 // note that the line may be also be considered writable in 171 // downstream caches along the path to memory, but always 172 // Exclusive, and never Modified 173 assert(blk->isWritable()); 174 // Write or WriteLine at the first cache with block in writable state 175 if (blk->checkWrite(pkt)) { 176 pkt->writeDataToBlock(blk->data, blkSize); 177 } 178 // Always mark the line as dirty (and thus transition to the 179 // Modified state) even if we are a failed StoreCond so we 180 // supply data to any snoops that have appended themselves to 181 // this cache before knowing the store will fail. 182 blk->status |= BlkDirty; 183 DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d (write)\n", 184 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 185 } else if (pkt->isRead()) { 186 if (pkt->isLLSC()) { 187 blk->trackLoadLocked(pkt); 188 } 189 190 // all read responses have a data payload 191 assert(pkt->hasRespData()); 192 pkt->setDataFromBlock(blk->data, blkSize); 193 194 // determine if this read is from a (coherent) cache, or not 195 // by looking at the command type; we could potentially add a 196 // packet attribute such as 'FromCache' to make this check a 197 // bit cleaner 198 if (pkt->cmd == MemCmd::ReadExReq || 199 pkt->cmd == MemCmd::ReadSharedReq || 200 pkt->cmd == MemCmd::ReadCleanReq || 201 pkt->cmd == MemCmd::SCUpgradeFailReq) { 202 assert(pkt->getSize() == blkSize); 203 // special handling for coherent block requests from 204 // upper-level caches 205 if (pkt->needsWritable()) { 206 // sanity check 207 assert(pkt->cmd == MemCmd::ReadExReq || 208 pkt->cmd == MemCmd::SCUpgradeFailReq); 209 210 // if we have a dirty copy, make sure the recipient 211 // keeps it marked dirty (in the modified state) 212 if (blk->isDirty()) { 213 pkt->setCacheResponding(); 214 } 215 // on ReadExReq we give up our copy unconditionally, 216 // even if this cache is mostly inclusive, we may want 217 // to revisit this 218 invalidateBlock(blk); 219 } else if (blk->isWritable() && !pending_downgrade && 220 !pkt->hasSharers() && 221 pkt->cmd != MemCmd::ReadCleanReq) { 222 // we can give the requester a writable copy on a read 223 // request if: 224 // - we have a writable copy at this level (& below) 225 // - we don't have a pending snoop from below 226 // signaling another read request 227 // - no other cache above has a copy (otherwise it 228 // would have set hasSharers flag when 229 // snooping the packet) 230 // - the read has explicitly asked for a clean 231 // copy of the line 232 if (blk->isDirty()) { 233 // special considerations if we're owner: 234 if (!deferred_response) { 235 // respond with the line in Modified state 236 // (cacheResponding set, hasSharers not set) 237 pkt->setCacheResponding(); 238 239 if (clusivity == Enums::mostly_excl) { 240 // if this cache is mostly exclusive with 241 // respect to the cache above, drop the 242 // block, no need to first unset the dirty 243 // bit 244 invalidateBlock(blk); 245 } else { 246 // if this cache is mostly inclusive, we 247 // keep the block in the Exclusive state, 248 // and pass it upwards as Modified 249 // (writable and dirty), hence we have 250 // multiple caches, all on the same path 251 // towards memory, all considering the 252 // same block writable, but only one 253 // considering it Modified 254 255 // we get away with multiple caches (on 256 // the same path to memory) considering 257 // the block writeable as we always enter 258 // the cache hierarchy through a cache, 259 // and first snoop upwards in all other 260 // branches 261 blk->status &= ~BlkDirty; 262 } 263 } else { 264 // if we're responding after our own miss, 265 // there's a window where the recipient didn't 266 // know it was getting ownership and may not 267 // have responded to snoops correctly, so we 268 // have to respond with a shared line 269 pkt->setHasSharers(); 270 } 271 } 272 } else { 273 // otherwise only respond with a shared copy 274 pkt->setHasSharers(); 275 } 276 } 277 } else { 278 // Upgrade or Invalidate 279 assert(pkt->isUpgrade() || pkt->isInvalidate()); 280 281 // for invalidations we could be looking at the temp block 282 // (for upgrades we always allocate) 283 invalidateBlock(blk); 284 DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d (invalidation)\n", 285 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 286 } 287} 288 289 290///////////////////////////////////////////////////// 291// 292// MSHR helper functions 293// 294///////////////////////////////////////////////////// 295 296 297void 298Cache::markInService(MSHR *mshr, bool pending_modified_resp) 299{ 300 markInServiceInternal(mshr, pending_modified_resp); 301} 302 303///////////////////////////////////////////////////// 304// 305// Access path: requests coming in from the CPU side 306// 307///////////////////////////////////////////////////// 308 309bool 310Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat, 311 PacketList &writebacks) 312{ 313 // sanity check 314 assert(pkt->isRequest()); 315 316 chatty_assert(!(isReadOnly && pkt->isWrite()), 317 "Should never see a write in a read-only cache %s\n", 318 name()); 319 320 DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d\n", __func__, 321 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 322 323 if (pkt->req->isUncacheable()) { 324 DPRINTF(Cache, "%s%s addr %#llx uncacheable\n", pkt->cmdString(), 325 pkt->req->isInstFetch() ? " (ifetch)" : "", 326 pkt->getAddr()); 327 328 // flush and invalidate any existing block 329 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure())); 330 if (old_blk && old_blk->isValid()) { 331 if (old_blk->isDirty() || writebackClean) 332 writebacks.push_back(writebackBlk(old_blk)); 333 else 334 writebacks.push_back(cleanEvictBlk(old_blk)); 335 tags->invalidate(old_blk); 336 old_blk->invalidate(); 337 } 338 339 blk = NULL; 340 // lookupLatency is the latency in case the request is uncacheable. 341 lat = lookupLatency; 342 return false; 343 } 344 345 ContextID id = pkt->req->hasContextId() ? 346 pkt->req->contextId() : InvalidContextID; 347 // Here lat is the value passed as parameter to accessBlock() function 348 // that can modify its value. 349 blk = tags->accessBlock(pkt->getAddr(), pkt->isSecure(), lat, id); 350 351 DPRINTF(Cache, "%s%s addr %#llx size %d (%s) %s\n", pkt->cmdString(), 352 pkt->req->isInstFetch() ? " (ifetch)" : "", 353 pkt->getAddr(), pkt->getSize(), pkt->isSecure() ? "s" : "ns", 354 blk ? "hit " + blk->print() : "miss"); 355 356 357 if (pkt->isEviction()) { 358 // We check for presence of block in above caches before issuing 359 // Writeback or CleanEvict to write buffer. Therefore the only 360 // possible cases can be of a CleanEvict packet coming from above 361 // encountering a Writeback generated in this cache peer cache and 362 // waiting in the write buffer. Cases of upper level peer caches 363 // generating CleanEvict and Writeback or simply CleanEvict and 364 // CleanEvict almost simultaneously will be caught by snoops sent out 365 // by crossbar. 366 std::vector<MSHR *> outgoing; 367 if (writeBuffer.findMatches(pkt->getAddr(), pkt->isSecure(), 368 outgoing)) { 369 assert(outgoing.size() == 1); 370 MSHR *wb_entry = outgoing[0]; 371 assert(wb_entry->getNumTargets() == 1); 372 PacketPtr wbPkt = wb_entry->getTarget()->pkt; 373 assert(wbPkt->isWriteback()); 374 375 if (pkt->isCleanEviction()) { 376 // The CleanEvict and WritebackClean snoops into other 377 // peer caches of the same level while traversing the 378 // crossbar. If a copy of the block is found, the 379 // packet is deleted in the crossbar. Hence, none of 380 // the other upper level caches connected to this 381 // cache have the block, so we can clear the 382 // BLOCK_CACHED flag in the Writeback if set and 383 // discard the CleanEvict by returning true. 384 wbPkt->clearBlockCached(); 385 return true; 386 } else { 387 assert(pkt->cmd == MemCmd::WritebackDirty); 388 // Dirty writeback from above trumps our clean 389 // writeback... discard here 390 // Note: markInService will remove entry from writeback buffer. 391 markInService(wb_entry, false); 392 delete wbPkt; 393 } 394 } 395 } 396 397 // Writeback handling is special case. We can write the block into 398 // the cache without having a writeable copy (or any copy at all). 399 if (pkt->isWriteback()) { 400 assert(blkSize == pkt->getSize()); 401 402 // we could get a clean writeback while we are having 403 // outstanding accesses to a block, do the simple thing for 404 // now and drop the clean writeback so that we do not upset 405 // any ordering/decisions about ownership already taken 406 if (pkt->cmd == MemCmd::WritebackClean && 407 mshrQueue.findMatch(pkt->getAddr(), pkt->isSecure())) { 408 DPRINTF(Cache, "Clean writeback %#llx to block with MSHR, " 409 "dropping\n", pkt->getAddr()); 410 return true; 411 } 412 413 if (blk == NULL) { 414 // need to do a replacement 415 blk = allocateBlock(pkt->getAddr(), pkt->isSecure(), writebacks); 416 if (blk == NULL) { 417 // no replaceable block available: give up, fwd to next level. 418 incMissCount(pkt); 419 return false; 420 } 421 tags->insertBlock(pkt, blk); 422 423 blk->status = (BlkValid | BlkReadable); 424 if (pkt->isSecure()) { 425 blk->status |= BlkSecure; 426 } 427 } 428 // only mark the block dirty if we got a writeback command, 429 // and leave it as is for a clean writeback 430 if (pkt->cmd == MemCmd::WritebackDirty) { 431 blk->status |= BlkDirty; 432 } 433 // if the packet does not have sharers, it is passing 434 // writable, and we got the writeback in Modified or Exclusive 435 // state, if not we are in the Owned or Shared state 436 if (!pkt->hasSharers()) { 437 blk->status |= BlkWritable; 438 } 439 // nothing else to do; writeback doesn't expect response 440 assert(!pkt->needsResponse()); 441 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize); 442 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print()); 443 incHitCount(pkt); 444 return true; 445 } else if (pkt->cmd == MemCmd::CleanEvict) { 446 if (blk != NULL) { 447 // Found the block in the tags, need to stop CleanEvict from 448 // propagating further down the hierarchy. Returning true will 449 // treat the CleanEvict like a satisfied write request and delete 450 // it. 451 return true; 452 } 453 // We didn't find the block here, propagate the CleanEvict further 454 // down the memory hierarchy. Returning false will treat the CleanEvict 455 // like a Writeback which could not find a replaceable block so has to 456 // go to next level. 457 return false; 458 } else if ((blk != NULL) && 459 (pkt->needsWritable() ? blk->isWritable() : blk->isReadable())) { 460 // OK to satisfy access 461 incHitCount(pkt); 462 satisfyCpuSideRequest(pkt, blk); 463 return true; 464 } 465 466 // Can't satisfy access normally... either no block (blk == NULL) 467 // or have block but need writable 468 469 incMissCount(pkt); 470 471 if (blk == NULL && pkt->isLLSC() && pkt->isWrite()) { 472 // complete miss on store conditional... just give up now 473 pkt->req->setExtraData(0); 474 return true; 475 } 476 477 return false; 478} 479 480void 481Cache::doWritebacks(PacketList& writebacks, Tick forward_time) 482{ 483 while (!writebacks.empty()) { 484 PacketPtr wbPkt = writebacks.front(); 485 // We use forwardLatency here because we are copying writebacks to 486 // write buffer. Call isCachedAbove for both Writebacks and 487 // CleanEvicts. If isCachedAbove returns true we set BLOCK_CACHED flag 488 // in Writebacks and discard CleanEvicts. 489 if (isCachedAbove(wbPkt)) { 490 if (wbPkt->cmd == MemCmd::CleanEvict) { 491 // Delete CleanEvict because cached copies exist above. The 492 // packet destructor will delete the request object because 493 // this is a non-snoop request packet which does not require a 494 // response. 495 delete wbPkt; 496 } else if (wbPkt->cmd == MemCmd::WritebackClean) { 497 // clean writeback, do not send since the block is 498 // still cached above 499 assert(writebackClean); 500 delete wbPkt; 501 } else { 502 assert(wbPkt->cmd == MemCmd::WritebackDirty); 503 // Set BLOCK_CACHED flag in Writeback and send below, so that 504 // the Writeback does not reset the bit corresponding to this 505 // address in the snoop filter below. 506 wbPkt->setBlockCached(); 507 allocateWriteBuffer(wbPkt, forward_time); 508 } 509 } else { 510 // If the block is not cached above, send packet below. Both 511 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 512 // reset the bit corresponding to this address in the snoop filter 513 // below. 514 allocateWriteBuffer(wbPkt, forward_time); 515 } 516 writebacks.pop_front(); 517 } 518} 519 520void 521Cache::doWritebacksAtomic(PacketList& writebacks) 522{ 523 while (!writebacks.empty()) { 524 PacketPtr wbPkt = writebacks.front(); 525 // Call isCachedAbove for both Writebacks and CleanEvicts. If 526 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks 527 // and discard CleanEvicts. 528 if (isCachedAbove(wbPkt, false)) { 529 if (wbPkt->cmd == MemCmd::WritebackDirty) { 530 // Set BLOCK_CACHED flag in Writeback and send below, 531 // so that the Writeback does not reset the bit 532 // corresponding to this address in the snoop filter 533 // below. We can discard CleanEvicts because cached 534 // copies exist above. Atomic mode isCachedAbove 535 // modifies packet to set BLOCK_CACHED flag 536 memSidePort->sendAtomic(wbPkt); 537 } 538 } else { 539 // If the block is not cached above, send packet below. Both 540 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 541 // reset the bit corresponding to this address in the snoop filter 542 // below. 543 memSidePort->sendAtomic(wbPkt); 544 } 545 writebacks.pop_front(); 546 // In case of CleanEvicts, the packet destructor will delete the 547 // request object because this is a non-snoop request packet which 548 // does not require a response. 549 delete wbPkt; 550 } 551} 552 553 554void 555Cache::recvTimingSnoopResp(PacketPtr pkt) 556{ 557 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 558 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 559 560 assert(pkt->isResponse()); 561 assert(!system->bypassCaches()); 562 563 // determine if the response is from a snoop request we created 564 // (in which case it should be in the outstandingSnoop), or if we 565 // merely forwarded someone else's snoop request 566 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) == 567 outstandingSnoop.end(); 568 569 if (!forwardAsSnoop) { 570 // the packet came from this cache, so sink it here and do not 571 // forward it 572 assert(pkt->cmd == MemCmd::HardPFResp); 573 574 outstandingSnoop.erase(pkt->req); 575 576 DPRINTF(Cache, "Got prefetch response from above for addr " 577 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns"); 578 recvTimingResp(pkt); 579 return; 580 } 581 582 // forwardLatency is set here because there is a response from an 583 // upper level cache. 584 // To pay the delay that occurs if the packet comes from the bus, 585 // we charge also headerDelay. 586 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay; 587 // Reset the timing of the packet. 588 pkt->headerDelay = pkt->payloadDelay = 0; 589 memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time); 590} 591 592void 593Cache::promoteWholeLineWrites(PacketPtr pkt) 594{ 595 // Cache line clearing instructions 596 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) && 597 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) { 598 pkt->cmd = MemCmd::WriteLineReq; 599 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n"); 600 } 601} 602 603bool 604Cache::recvTimingReq(PacketPtr pkt) 605{ 606 DPRINTF(CacheTags, "%s tags: %s\n", __func__, tags->print()); 607 608 assert(pkt->isRequest()); 609 610 // Just forward the packet if caches are disabled. 611 if (system->bypassCaches()) { 612 // @todo This should really enqueue the packet rather 613 bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt); 614 assert(success); 615 return true; 616 } 617 618 promoteWholeLineWrites(pkt); 619 620 if (pkt->cacheResponding()) { 621 // a cache above us (but not where the packet came from) is 622 // responding to the request, in other words it has the line 623 // in Modified or Owned state 624 DPRINTF(Cache, "Cache above responding to %#llx (%s): " 625 "not responding\n", 626 pkt->getAddr(), pkt->isSecure() ? "s" : "ns"); 627 628 // if the packet needs the block to be writable, and the cache 629 // that has promised to respond (setting the cache responding 630 // flag) is not providing writable (it is in Owned rather than 631 // the Modified state), we know that there may be other Shared 632 // copies in the system; go out and invalidate them all 633 if (pkt->needsWritable() && !pkt->responderHadWritable()) { 634 // an upstream cache that had the line in Owned state 635 // (dirty, but not writable), is responding and thus 636 // transferring the dirty line from one branch of the 637 // cache hierarchy to another 638 639 // send out an express snoop and invalidate all other 640 // copies (snooping a packet that needs writable is the 641 // same as an invalidation), thus turning the Owned line 642 // into a Modified line, note that we don't invalidate the 643 // block in the current cache or any other cache on the 644 // path to memory 645 646 // create a downstream express snoop with cleared packet 647 // flags, there is no need to allocate any data as the 648 // packet is merely used to co-ordinate state transitions 649 Packet *snoop_pkt = new Packet(pkt, true, false); 650 651 // also reset the bus time that the original packet has 652 // not yet paid for 653 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0; 654 655 // make this an instantaneous express snoop, and let the 656 // other caches in the system know that the another cache 657 // is responding, because we have found the authorative 658 // copy (Modified or Owned) that will supply the right 659 // data 660 snoop_pkt->setExpressSnoop(); 661 snoop_pkt->setCacheResponding(); 662 663 // this express snoop travels towards the memory, and at 664 // every crossbar it is snooped upwards thus reaching 665 // every cache in the system 666 bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt); 667 // express snoops always succeed 668 assert(success); 669 670 // main memory will delete the snoop packet 671 } 672 673 // queue for deletion, as opposed to immediate deletion, as 674 // the sending cache is still relying on the packet 675 pendingDelete.reset(pkt); 676 677 // no need to take any action in this particular cache as an 678 // upstream cache has already committed to responding, and 679 // either the packet does not need writable (and we can let 680 // the cache that set the cache responding flag pass on the 681 // line without any need for intervention), or if the packet 682 // needs writable it is provided, or we have already sent out 683 // any express snoops in the section above 684 return true; 685 } 686 687 // anything that is merely forwarded pays for the forward latency and 688 // the delay provided by the crossbar 689 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 690 691 // We use lookupLatency here because it is used to specify the latency 692 // to access. 693 Cycles lat = lookupLatency; 694 CacheBlk *blk = NULL; 695 bool satisfied = false; 696 { 697 PacketList writebacks; 698 // Note that lat is passed by reference here. The function 699 // access() calls accessBlock() which can modify lat value. 700 satisfied = access(pkt, blk, lat, writebacks); 701 702 // copy writebacks to write buffer here to ensure they logically 703 // proceed anything happening below 704 doWritebacks(writebacks, forward_time); 705 } 706 707 // Here we charge the headerDelay that takes into account the latencies 708 // of the bus, if the packet comes from it. 709 // The latency charged it is just lat that is the value of lookupLatency 710 // modified by access() function, or if not just lookupLatency. 711 // In case of a hit we are neglecting response latency. 712 // In case of a miss we are neglecting forward latency. 713 Tick request_time = clockEdge(lat) + pkt->headerDelay; 714 // Here we reset the timing of the packet. 715 pkt->headerDelay = pkt->payloadDelay = 0; 716 717 // track time of availability of next prefetch, if any 718 Tick next_pf_time = MaxTick; 719 720 bool needsResponse = pkt->needsResponse(); 721 722 if (satisfied) { 723 // should never be satisfying an uncacheable access as we 724 // flush and invalidate any existing block as part of the 725 // lookup 726 assert(!pkt->req->isUncacheable()); 727 728 // hit (for all other request types) 729 730 if (prefetcher && (prefetchOnAccess || (blk && blk->wasPrefetched()))) { 731 if (blk) 732 blk->status &= ~BlkHWPrefetched; 733 734 // Don't notify on SWPrefetch 735 if (!pkt->cmd.isSWPrefetch()) 736 next_pf_time = prefetcher->notify(pkt); 737 } 738 739 if (needsResponse) { 740 pkt->makeTimingResponse(); 741 // @todo: Make someone pay for this 742 pkt->headerDelay = pkt->payloadDelay = 0; 743 744 // In this case we are considering request_time that takes 745 // into account the delay of the xbar, if any, and just 746 // lat, neglecting responseLatency, modelling hit latency 747 // just as lookupLatency or or the value of lat overriden 748 // by access(), that calls accessBlock() function. 749 cpuSidePort->schedTimingResp(pkt, request_time, true); 750 } else { 751 DPRINTF(Cache, "%s satisfied %s addr %#llx, no response needed\n", 752 __func__, pkt->cmdString(), pkt->getAddr(), 753 pkt->getSize()); 754 755 // queue the packet for deletion, as the sending cache is 756 // still relying on it; if the block is found in access(), 757 // CleanEvict and Writeback messages will be deleted 758 // here as well 759 pendingDelete.reset(pkt); 760 } 761 } else { 762 // miss 763 764 Addr blk_addr = blockAlign(pkt->getAddr()); 765 766 // ignore any existing MSHR if we are dealing with an 767 // uncacheable request 768 MSHR *mshr = pkt->req->isUncacheable() ? nullptr : 769 mshrQueue.findMatch(blk_addr, pkt->isSecure()); 770 771 // Software prefetch handling: 772 // To keep the core from waiting on data it won't look at 773 // anyway, send back a response with dummy data. Miss handling 774 // will continue asynchronously. Unfortunately, the core will 775 // insist upon freeing original Packet/Request, so we have to 776 // create a new pair with a different lifecycle. Note that this 777 // processing happens before any MSHR munging on the behalf of 778 // this request because this new Request will be the one stored 779 // into the MSHRs, not the original. 780 if (pkt->cmd.isSWPrefetch()) { 781 assert(needsResponse); 782 assert(pkt->req->hasPaddr()); 783 assert(!pkt->req->isUncacheable()); 784 785 // There's no reason to add a prefetch as an additional target 786 // to an existing MSHR. If an outstanding request is already 787 // in progress, there is nothing for the prefetch to do. 788 // If this is the case, we don't even create a request at all. 789 PacketPtr pf = nullptr; 790 791 if (!mshr) { 792 // copy the request and create a new SoftPFReq packet 793 RequestPtr req = new Request(pkt->req->getPaddr(), 794 pkt->req->getSize(), 795 pkt->req->getFlags(), 796 pkt->req->masterId()); 797 pf = new Packet(req, pkt->cmd); 798 pf->allocate(); 799 assert(pf->getAddr() == pkt->getAddr()); 800 assert(pf->getSize() == pkt->getSize()); 801 } 802 803 pkt->makeTimingResponse(); 804 805 // request_time is used here, taking into account lat and the delay 806 // charged if the packet comes from the xbar. 807 cpuSidePort->schedTimingResp(pkt, request_time, true); 808 809 // If an outstanding request is in progress (we found an 810 // MSHR) this is set to null 811 pkt = pf; 812 } 813 814 if (mshr) { 815 /// MSHR hit 816 /// @note writebacks will be checked in getNextMSHR() 817 /// for any conflicting requests to the same block 818 819 //@todo remove hw_pf here 820 821 // Coalesce unless it was a software prefetch (see above). 822 if (pkt) { 823 assert(!pkt->isWriteback()); 824 // CleanEvicts corresponding to blocks which have 825 // outstanding requests in MSHRs are simply sunk here 826 if (pkt->cmd == MemCmd::CleanEvict) { 827 pendingDelete.reset(pkt); 828 } else { 829 DPRINTF(Cache, "%s coalescing MSHR for %s addr %#llx size %d\n", 830 __func__, pkt->cmdString(), pkt->getAddr(), 831 pkt->getSize()); 832 833 assert(pkt->req->masterId() < system->maxMasters()); 834 mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++; 835 // We use forward_time here because it is the same 836 // considering new targets. We have multiple 837 // requests for the same address here. It 838 // specifies the latency to allocate an internal 839 // buffer and to schedule an event to the queued 840 // port and also takes into account the additional 841 // delay of the xbar. 842 mshr->allocateTarget(pkt, forward_time, order++, 843 allocOnFill(pkt->cmd)); 844 if (mshr->getNumTargets() == numTarget) { 845 noTargetMSHR = mshr; 846 setBlocked(Blocked_NoTargets); 847 // need to be careful with this... if this mshr isn't 848 // ready yet (i.e. time > curTick()), we don't want to 849 // move it ahead of mshrs that are ready 850 // mshrQueue.moveToFront(mshr); 851 } 852 } 853 // We should call the prefetcher reguardless if the request is 854 // satisfied or not, reguardless if the request is in the MSHR or 855 // not. The request could be a ReadReq hit, but still not 856 // satisfied (potentially because of a prior write to the same 857 // cache line. So, even when not satisfied, tehre is an MSHR 858 // already allocated for this, we need to let the prefetcher know 859 // about the request 860 if (prefetcher) { 861 // Don't notify on SWPrefetch 862 if (!pkt->cmd.isSWPrefetch()) 863 next_pf_time = prefetcher->notify(pkt); 864 } 865 } 866 } else { 867 // no MSHR 868 assert(pkt->req->masterId() < system->maxMasters()); 869 if (pkt->req->isUncacheable()) { 870 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++; 871 } else { 872 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++; 873 } 874 875 if (pkt->isEviction() || 876 (pkt->req->isUncacheable() && pkt->isWrite())) { 877 // We use forward_time here because there is an 878 // uncached memory write, forwarded to WriteBuffer. 879 allocateWriteBuffer(pkt, forward_time); 880 } else { 881 if (blk && blk->isValid()) { 882 // should have flushed and have no valid block 883 assert(!pkt->req->isUncacheable()); 884 885 // If we have a write miss to a valid block, we 886 // need to mark the block non-readable. Otherwise 887 // if we allow reads while there's an outstanding 888 // write miss, the read could return stale data 889 // out of the cache block... a more aggressive 890 // system could detect the overlap (if any) and 891 // forward data out of the MSHRs, but we don't do 892 // that yet. Note that we do need to leave the 893 // block valid so that it stays in the cache, in 894 // case we get an upgrade response (and hence no 895 // new data) when the write miss completes. 896 // As long as CPUs do proper store/load forwarding 897 // internally, and have a sufficiently weak memory 898 // model, this is probably unnecessary, but at some 899 // point it must have seemed like we needed it... 900 assert(pkt->needsWritable()); 901 assert(!blk->isWritable()); 902 blk->status &= ~BlkReadable; 903 } 904 // Here we are using forward_time, modelling the latency of 905 // a miss (outbound) just as forwardLatency, neglecting the 906 // lookupLatency component. 907 allocateMissBuffer(pkt, forward_time); 908 } 909 910 if (prefetcher) { 911 // Don't notify on SWPrefetch 912 if (!pkt->cmd.isSWPrefetch()) 913 next_pf_time = prefetcher->notify(pkt); 914 } 915 } 916 } 917 918 if (next_pf_time != MaxTick) 919 schedMemSideSendEvent(next_pf_time); 920 921 return true; 922} 923 924 925// See comment in cache.hh. 926PacketPtr 927Cache::getBusPacket(PacketPtr cpu_pkt, CacheBlk *blk, 928 bool needsWritable) const 929{ 930 bool blkValid = blk && blk->isValid(); 931 932 if (cpu_pkt->req->isUncacheable()) { 933 // note that at the point we see the uncacheable request we 934 // flush any block, but there could be an outstanding MSHR, 935 // and the cache could have filled again before we actually 936 // send out the forwarded uncacheable request (blk could thus 937 // be non-null) 938 return NULL; 939 } 940 941 if (!blkValid && 942 (cpu_pkt->isUpgrade() || 943 cpu_pkt->isEviction())) { 944 // Writebacks that weren't allocated in access() and upgrades 945 // from upper-level caches that missed completely just go 946 // through. 947 return NULL; 948 } 949 950 assert(cpu_pkt->needsResponse()); 951 952 MemCmd cmd; 953 // @TODO make useUpgrades a parameter. 954 // Note that ownership protocols require upgrade, otherwise a 955 // write miss on a shared owned block will generate a ReadExcl, 956 // which will clobber the owned copy. 957 const bool useUpgrades = true; 958 if (blkValid && useUpgrades) { 959 // only reason to be here is that blk is read only and we need 960 // it to be writable 961 assert(needsWritable); 962 assert(!blk->isWritable()); 963 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq; 964 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq || 965 cpu_pkt->cmd == MemCmd::StoreCondFailReq) { 966 // Even though this SC will fail, we still need to send out the 967 // request and get the data to supply it to other snoopers in the case 968 // where the determination the StoreCond fails is delayed due to 969 // all caches not being on the same local bus. 970 cmd = MemCmd::SCUpgradeFailReq; 971 } else if (cpu_pkt->cmd == MemCmd::WriteLineReq) { 972 // forward as invalidate to all other caches, this gives us 973 // the line in Exclusive state, and invalidates all other 974 // copies 975 cmd = MemCmd::InvalidateReq; 976 } else { 977 // block is invalid 978 cmd = needsWritable ? MemCmd::ReadExReq : 979 (isReadOnly ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq); 980 } 981 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize); 982 983 // if there are upstream caches that have already marked the 984 // packet as having sharers (not passing writable), pass that info 985 // downstream 986 if (cpu_pkt->hasSharers()) { 987 // note that cpu_pkt may have spent a considerable time in the 988 // MSHR queue and that the information could possibly be out 989 // of date, however, there is no harm in conservatively 990 // assuming the block has sharers 991 pkt->setHasSharers(); 992 DPRINTF(Cache, "%s passing hasSharers from %s to %s addr %#llx " 993 "size %d\n", 994 __func__, cpu_pkt->cmdString(), pkt->cmdString(), 995 pkt->getAddr(), pkt->getSize()); 996 } 997 998 // the packet should be block aligned 999 assert(pkt->getAddr() == blockAlign(pkt->getAddr())); 1000 1001 pkt->allocate(); 1002 DPRINTF(Cache, "%s created %s from %s for addr %#llx size %d\n", 1003 __func__, pkt->cmdString(), cpu_pkt->cmdString(), pkt->getAddr(), 1004 pkt->getSize()); 1005 return pkt; 1006} 1007 1008 1009Tick 1010Cache::recvAtomic(PacketPtr pkt) 1011{ 1012 // We are in atomic mode so we pay just for lookupLatency here. 1013 Cycles lat = lookupLatency; 1014 // @TODO: make this a parameter 1015 bool last_level_cache = false; 1016 1017 // Forward the request if the system is in cache bypass mode. 1018 if (system->bypassCaches()) 1019 return ticksToCycles(memSidePort->sendAtomic(pkt)); 1020 1021 promoteWholeLineWrites(pkt); 1022 1023 if (pkt->cacheResponding()) { 1024 // have to invalidate ourselves and any lower caches even if 1025 // upper cache will be responding 1026 if (pkt->isInvalidate()) { 1027 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 1028 if (blk && blk->isValid()) { 1029 tags->invalidate(blk); 1030 blk->invalidate(); 1031 DPRINTF(Cache, "Other cache responding to %s on %#llx (%s):" 1032 " invalidating\n", 1033 pkt->cmdString(), pkt->getAddr(), 1034 pkt->isSecure() ? "s" : "ns"); 1035 } 1036 if (!last_level_cache) { 1037 DPRINTF(Cache, "Other cache responding to %s on %#llx (%s):" 1038 " forwarding\n", 1039 pkt->cmdString(), pkt->getAddr(), 1040 pkt->isSecure() ? "s" : "ns"); 1041 lat += ticksToCycles(memSidePort->sendAtomic(pkt)); 1042 } 1043 } else { 1044 DPRINTF(Cache, "Other cache responding to %s on %#llx: " 1045 "not responding\n", 1046 pkt->cmdString(), pkt->getAddr()); 1047 } 1048 1049 return lat * clockPeriod(); 1050 } 1051 1052 // should assert here that there are no outstanding MSHRs or 1053 // writebacks... that would mean that someone used an atomic 1054 // access in timing mode 1055 1056 CacheBlk *blk = NULL; 1057 PacketList writebacks; 1058 bool satisfied = access(pkt, blk, lat, writebacks); 1059 1060 // handle writebacks resulting from the access here to ensure they 1061 // logically proceed anything happening below 1062 doWritebacksAtomic(writebacks); 1063 1064 if (!satisfied) { 1065 // MISS 1066 1067 PacketPtr bus_pkt = getBusPacket(pkt, blk, pkt->needsWritable()); 1068 1069 bool is_forward = (bus_pkt == NULL); 1070 1071 if (is_forward) { 1072 // just forwarding the same request to the next level 1073 // no local cache operation involved 1074 bus_pkt = pkt; 1075 } 1076 1077 DPRINTF(Cache, "Sending an atomic %s for %#llx (%s)\n", 1078 bus_pkt->cmdString(), bus_pkt->getAddr(), 1079 bus_pkt->isSecure() ? "s" : "ns"); 1080 1081#if TRACING_ON 1082 CacheBlk::State old_state = blk ? blk->status : 0; 1083#endif 1084 1085 lat += ticksToCycles(memSidePort->sendAtomic(bus_pkt)); 1086 1087 // We are now dealing with the response handling 1088 DPRINTF(Cache, "Receive response: %s for addr %#llx (%s) in state %i\n", 1089 bus_pkt->cmdString(), bus_pkt->getAddr(), 1090 bus_pkt->isSecure() ? "s" : "ns", 1091 old_state); 1092 1093 // If packet was a forward, the response (if any) is already 1094 // in place in the bus_pkt == pkt structure, so we don't need 1095 // to do anything. Otherwise, use the separate bus_pkt to 1096 // generate response to pkt and then delete it. 1097 if (!is_forward) { 1098 if (pkt->needsResponse()) { 1099 assert(bus_pkt->isResponse()); 1100 if (bus_pkt->isError()) { 1101 pkt->makeAtomicResponse(); 1102 pkt->copyError(bus_pkt); 1103 } else if (pkt->cmd == MemCmd::InvalidateReq) { 1104 if (blk) { 1105 // invalidate response to a cache that received 1106 // an invalidate request 1107 satisfyCpuSideRequest(pkt, blk); 1108 } 1109 } else if (pkt->cmd == MemCmd::WriteLineReq) { 1110 // note the use of pkt, not bus_pkt here. 1111 1112 // write-line request to the cache that promoted 1113 // the write to a whole line 1114 blk = handleFill(pkt, blk, writebacks, 1115 allocOnFill(pkt->cmd)); 1116 satisfyCpuSideRequest(pkt, blk); 1117 } else if (bus_pkt->isRead() || 1118 bus_pkt->cmd == MemCmd::UpgradeResp) { 1119 // we're updating cache state to allow us to 1120 // satisfy the upstream request from the cache 1121 blk = handleFill(bus_pkt, blk, writebacks, 1122 allocOnFill(pkt->cmd)); 1123 satisfyCpuSideRequest(pkt, blk); 1124 } else { 1125 // we're satisfying the upstream request without 1126 // modifying cache state, e.g., a write-through 1127 pkt->makeAtomicResponse(); 1128 } 1129 } 1130 delete bus_pkt; 1131 } 1132 } 1133 1134 // Note that we don't invoke the prefetcher at all in atomic mode. 1135 // It's not clear how to do it properly, particularly for 1136 // prefetchers that aggressively generate prefetch candidates and 1137 // rely on bandwidth contention to throttle them; these will tend 1138 // to pollute the cache in atomic mode since there is no bandwidth 1139 // contention. If we ever do want to enable prefetching in atomic 1140 // mode, though, this is the place to do it... see timingAccess() 1141 // for an example (though we'd want to issue the prefetch(es) 1142 // immediately rather than calling requestMemSideBus() as we do 1143 // there). 1144 1145 // do any writebacks resulting from the response handling 1146 doWritebacksAtomic(writebacks); 1147 1148 // if we used temp block, check to see if its valid and if so 1149 // clear it out, but only do so after the call to recvAtomic is 1150 // finished so that any downstream observers (such as a snoop 1151 // filter), first see the fill, and only then see the eviction 1152 if (blk == tempBlock && tempBlock->isValid()) { 1153 // the atomic CPU calls recvAtomic for fetch and load/store 1154 // sequentuially, and we may already have a tempBlock 1155 // writeback from the fetch that we have not yet sent 1156 if (tempBlockWriteback) { 1157 // if that is the case, write the prevoius one back, and 1158 // do not schedule any new event 1159 writebackTempBlockAtomic(); 1160 } else { 1161 // the writeback/clean eviction happens after the call to 1162 // recvAtomic has finished (but before any successive 1163 // calls), so that the response handling from the fill is 1164 // allowed to happen first 1165 schedule(writebackTempBlockAtomicEvent, curTick()); 1166 } 1167 1168 tempBlockWriteback = (blk->isDirty() || writebackClean) ? 1169 writebackBlk(blk) : cleanEvictBlk(blk); 1170 blk->invalidate(); 1171 } 1172 1173 if (pkt->needsResponse()) { 1174 pkt->makeAtomicResponse(); 1175 } 1176 1177 return lat * clockPeriod(); 1178} 1179 1180 1181void 1182Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide) 1183{ 1184 if (system->bypassCaches()) { 1185 // Packets from the memory side are snoop request and 1186 // shouldn't happen in bypass mode. 1187 assert(fromCpuSide); 1188 1189 // The cache should be flushed if we are in cache bypass mode, 1190 // so we don't need to check if we need to update anything. 1191 memSidePort->sendFunctional(pkt); 1192 return; 1193 } 1194 1195 Addr blk_addr = blockAlign(pkt->getAddr()); 1196 bool is_secure = pkt->isSecure(); 1197 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure); 1198 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure); 1199 1200 pkt->pushLabel(name()); 1201 1202 CacheBlkPrintWrapper cbpw(blk); 1203 1204 // Note that just because an L2/L3 has valid data doesn't mean an 1205 // L1 doesn't have a more up-to-date modified copy that still 1206 // needs to be found. As a result we always update the request if 1207 // we have it, but only declare it satisfied if we are the owner. 1208 1209 // see if we have data at all (owned or otherwise) 1210 bool have_data = blk && blk->isValid() 1211 && pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize, 1212 blk->data); 1213 1214 // data we have is dirty if marked as such or if we have an 1215 // in-service MSHR that is pending a modified line 1216 bool have_dirty = 1217 have_data && (blk->isDirty() || 1218 (mshr && mshr->inService && mshr->isPendingModified())); 1219 1220 bool done = have_dirty 1221 || cpuSidePort->checkFunctional(pkt) 1222 || mshrQueue.checkFunctional(pkt, blk_addr) 1223 || writeBuffer.checkFunctional(pkt, blk_addr) 1224 || memSidePort->checkFunctional(pkt); 1225 1226 DPRINTF(CacheVerbose, "functional %s %#llx (%s) %s%s%s\n", 1227 pkt->cmdString(), pkt->getAddr(), is_secure ? "s" : "ns", 1228 (blk && blk->isValid()) ? "valid " : "", 1229 have_data ? "data " : "", done ? "done " : ""); 1230 1231 // We're leaving the cache, so pop cache->name() label 1232 pkt->popLabel(); 1233 1234 if (done) { 1235 pkt->makeResponse(); 1236 } else { 1237 // if it came as a request from the CPU side then make sure it 1238 // continues towards the memory side 1239 if (fromCpuSide) { 1240 memSidePort->sendFunctional(pkt); 1241 } else if (forwardSnoops && cpuSidePort->isSnooping()) { 1242 // if it came from the memory side, it must be a snoop request 1243 // and we should only forward it if we are forwarding snoops 1244 cpuSidePort->sendFunctionalSnoop(pkt); 1245 } 1246 } 1247} 1248 1249 1250///////////////////////////////////////////////////// 1251// 1252// Response handling: responses from the memory side 1253// 1254///////////////////////////////////////////////////// 1255 1256 1257void 1258Cache::recvTimingResp(PacketPtr pkt) 1259{ 1260 assert(pkt->isResponse()); 1261 1262 // all header delay should be paid for by the crossbar, unless 1263 // this is a prefetch response from above 1264 panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp, 1265 "%s saw a non-zero packet delay\n", name()); 1266 1267 MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState); 1268 bool is_error = pkt->isError(); 1269 1270 assert(mshr); 1271 1272 if (is_error) { 1273 DPRINTF(Cache, "Cache received packet with error for addr %#llx (%s), " 1274 "cmd: %s\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns", 1275 pkt->cmdString()); 1276 } 1277 1278 DPRINTF(Cache, "Handling response %s for addr %#llx size %d (%s)\n", 1279 pkt->cmdString(), pkt->getAddr(), pkt->getSize(), 1280 pkt->isSecure() ? "s" : "ns"); 1281 1282 MSHRQueue *mq = mshr->queue; 1283 bool wasFull = mq->isFull(); 1284 1285 if (mshr == noTargetMSHR) { 1286 // we always clear at least one target 1287 clearBlocked(Blocked_NoTargets); 1288 noTargetMSHR = NULL; 1289 } 1290 1291 // Initial target is used just for stats 1292 MSHR::Target *initial_tgt = mshr->getTarget(); 1293 int stats_cmd_idx = initial_tgt->pkt->cmdToIndex(); 1294 Tick miss_latency = curTick() - initial_tgt->recvTime; 1295 PacketList writebacks; 1296 // We need forward_time here because we have a call of 1297 // allocateWriteBuffer() that need this parameter to specify the 1298 // time to request the bus. In this case we use forward latency 1299 // because there is a writeback. We pay also here for headerDelay 1300 // that is charged of bus latencies if the packet comes from the 1301 // bus. 1302 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 1303 1304 if (pkt->req->isUncacheable()) { 1305 assert(pkt->req->masterId() < system->maxMasters()); 1306 mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] += 1307 miss_latency; 1308 } else { 1309 assert(pkt->req->masterId() < system->maxMasters()); 1310 mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] += 1311 miss_latency; 1312 } 1313 1314 // upgrade deferred targets if the response has no sharers, and is 1315 // thus passing writable 1316 if (!pkt->hasSharers()) { 1317 mshr->promoteWritable(); 1318 } 1319 1320 bool is_fill = !mshr->isForward && 1321 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp); 1322 1323 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 1324 1325 if (is_fill && !is_error) { 1326 DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n", 1327 pkt->getAddr()); 1328 1329 blk = handleFill(pkt, blk, writebacks, mshr->allocOnFill); 1330 assert(blk != NULL); 1331 } 1332 1333 // allow invalidation responses originating from write-line 1334 // requests to be discarded 1335 bool is_invalidate = pkt->isInvalidate(); 1336 1337 // First offset for critical word first calculations 1338 int initial_offset = initial_tgt->pkt->getOffset(blkSize); 1339 1340 while (mshr->hasTargets()) { 1341 MSHR::Target *target = mshr->getTarget(); 1342 Packet *tgt_pkt = target->pkt; 1343 1344 switch (target->source) { 1345 case MSHR::Target::FromCPU: 1346 Tick completion_time; 1347 // Here we charge on completion_time the delay of the xbar if the 1348 // packet comes from it, charged on headerDelay. 1349 completion_time = pkt->headerDelay; 1350 1351 // Software prefetch handling for cache closest to core 1352 if (tgt_pkt->cmd.isSWPrefetch()) { 1353 // a software prefetch would have already been ack'd immediately 1354 // with dummy data so the core would be able to retire it. 1355 // this request completes right here, so we deallocate it. 1356 delete tgt_pkt->req; 1357 delete tgt_pkt; 1358 break; // skip response 1359 } 1360 1361 // unlike the other packet flows, where data is found in other 1362 // caches or memory and brought back, write-line requests always 1363 // have the data right away, so the above check for "is fill?" 1364 // cannot actually be determined until examining the stored MSHR 1365 // state. We "catch up" with that logic here, which is duplicated 1366 // from above. 1367 if (tgt_pkt->cmd == MemCmd::WriteLineReq) { 1368 assert(!is_error); 1369 // we got the block in a writable state, so promote 1370 // any deferred targets if possible 1371 mshr->promoteWritable(); 1372 // NB: we use the original packet here and not the response! 1373 blk = handleFill(tgt_pkt, blk, writebacks, mshr->allocOnFill); 1374 assert(blk != NULL); 1375 1376 // treat as a fill, and discard the invalidation 1377 // response 1378 is_fill = true; 1379 is_invalidate = false; 1380 } 1381 1382 if (is_fill) { 1383 satisfyCpuSideRequest(tgt_pkt, blk, 1384 true, mshr->hasPostDowngrade()); 1385 1386 // How many bytes past the first request is this one 1387 int transfer_offset = 1388 tgt_pkt->getOffset(blkSize) - initial_offset; 1389 if (transfer_offset < 0) { 1390 transfer_offset += blkSize; 1391 } 1392 1393 // If not critical word (offset) return payloadDelay. 1394 // responseLatency is the latency of the return path 1395 // from lower level caches/memory to an upper level cache or 1396 // the core. 1397 completion_time += clockEdge(responseLatency) + 1398 (transfer_offset ? pkt->payloadDelay : 0); 1399 1400 assert(!tgt_pkt->req->isUncacheable()); 1401 1402 assert(tgt_pkt->req->masterId() < system->maxMasters()); 1403 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] += 1404 completion_time - target->recvTime; 1405 } else if (pkt->cmd == MemCmd::UpgradeFailResp) { 1406 // failed StoreCond upgrade 1407 assert(tgt_pkt->cmd == MemCmd::StoreCondReq || 1408 tgt_pkt->cmd == MemCmd::StoreCondFailReq || 1409 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq); 1410 // responseLatency is the latency of the return path 1411 // from lower level caches/memory to an upper level cache or 1412 // the core. 1413 completion_time += clockEdge(responseLatency) + 1414 pkt->payloadDelay; 1415 tgt_pkt->req->setExtraData(0); 1416 } else { 1417 // not a cache fill, just forwarding response 1418 // responseLatency is the latency of the return path 1419 // from lower level cahces/memory to the core. 1420 completion_time += clockEdge(responseLatency) + 1421 pkt->payloadDelay; 1422 if (pkt->isRead() && !is_error) { 1423 // sanity check 1424 assert(pkt->getAddr() == tgt_pkt->getAddr()); 1425 assert(pkt->getSize() >= tgt_pkt->getSize()); 1426 1427 tgt_pkt->setData(pkt->getConstPtr<uint8_t>()); 1428 } 1429 } 1430 tgt_pkt->makeTimingResponse(); 1431 // if this packet is an error copy that to the new packet 1432 if (is_error) 1433 tgt_pkt->copyError(pkt); 1434 if (tgt_pkt->cmd == MemCmd::ReadResp && 1435 (is_invalidate || mshr->hasPostInvalidate())) { 1436 // If intermediate cache got ReadRespWithInvalidate, 1437 // propagate that. Response should not have 1438 // isInvalidate() set otherwise. 1439 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate; 1440 DPRINTF(Cache, "%s updated cmd to %s for addr %#llx\n", 1441 __func__, tgt_pkt->cmdString(), tgt_pkt->getAddr()); 1442 } 1443 // Reset the bus additional time as it is now accounted for 1444 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0; 1445 cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true); 1446 break; 1447 1448 case MSHR::Target::FromPrefetcher: 1449 assert(tgt_pkt->cmd == MemCmd::HardPFReq); 1450 if (blk) 1451 blk->status |= BlkHWPrefetched; 1452 delete tgt_pkt->req; 1453 delete tgt_pkt; 1454 break; 1455 1456 case MSHR::Target::FromSnoop: 1457 // I don't believe that a snoop can be in an error state 1458 assert(!is_error); 1459 // response to snoop request 1460 DPRINTF(Cache, "processing deferred snoop...\n"); 1461 assert(!(is_invalidate && !mshr->hasPostInvalidate())); 1462 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate()); 1463 break; 1464 1465 default: 1466 panic("Illegal target->source enum %d\n", target->source); 1467 } 1468 1469 mshr->popTarget(); 1470 } 1471 1472 if (blk && blk->isValid()) { 1473 // an invalidate response stemming from a write line request 1474 // should not invalidate the block, so check if the 1475 // invalidation should be discarded 1476 if (is_invalidate || mshr->hasPostInvalidate()) { 1477 invalidateBlock(blk); 1478 } else if (mshr->hasPostDowngrade()) { 1479 blk->status &= ~BlkWritable; 1480 } 1481 } 1482 1483 if (mshr->promoteDeferredTargets()) { 1484 // avoid later read getting stale data while write miss is 1485 // outstanding.. see comment in timingAccess() 1486 if (blk) { 1487 blk->status &= ~BlkReadable; 1488 } 1489 mq = mshr->queue; 1490 mq->markPending(mshr); 1491 schedMemSideSendEvent(clockEdge() + pkt->payloadDelay); 1492 } else { 1493 mq->deallocate(mshr); 1494 if (wasFull && !mq->isFull()) { 1495 clearBlocked((BlockedCause)mq->index); 1496 } 1497 1498 // Request the bus for a prefetch if this deallocation freed enough 1499 // MSHRs for a prefetch to take place 1500 if (prefetcher && mq == &mshrQueue && mshrQueue.canPrefetch()) { 1501 Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(), 1502 clockEdge()); 1503 if (next_pf_time != MaxTick) 1504 schedMemSideSendEvent(next_pf_time); 1505 } 1506 } 1507 // reset the xbar additional timinig as it is now accounted for 1508 pkt->headerDelay = pkt->payloadDelay = 0; 1509 1510 // copy writebacks to write buffer 1511 doWritebacks(writebacks, forward_time); 1512 1513 // if we used temp block, check to see if its valid and then clear it out 1514 if (blk == tempBlock && tempBlock->isValid()) { 1515 // We use forwardLatency here because we are copying 1516 // Writebacks/CleanEvicts to write buffer. It specifies the latency to 1517 // allocate an internal buffer and to schedule an event to the 1518 // queued port. 1519 if (blk->isDirty() || writebackClean) { 1520 PacketPtr wbPkt = writebackBlk(blk); 1521 allocateWriteBuffer(wbPkt, forward_time); 1522 // Set BLOCK_CACHED flag if cached above. 1523 if (isCachedAbove(wbPkt)) 1524 wbPkt->setBlockCached(); 1525 } else { 1526 PacketPtr wcPkt = cleanEvictBlk(blk); 1527 // Check to see if block is cached above. If not allocate 1528 // write buffer 1529 if (isCachedAbove(wcPkt)) 1530 delete wcPkt; 1531 else 1532 allocateWriteBuffer(wcPkt, forward_time); 1533 } 1534 blk->invalidate(); 1535 } 1536 1537 DPRINTF(CacheVerbose, "Leaving %s with %s for addr %#llx\n", __func__, 1538 pkt->cmdString(), pkt->getAddr()); 1539 delete pkt; 1540} 1541 1542PacketPtr 1543Cache::writebackBlk(CacheBlk *blk) 1544{ 1545 chatty_assert(!isReadOnly || writebackClean, 1546 "Writeback from read-only cache"); 1547 assert(blk && blk->isValid() && (blk->isDirty() || writebackClean)); 1548 1549 writebacks[Request::wbMasterId]++; 1550 1551 Request *req = new Request(tags->regenerateBlkAddr(blk->tag, blk->set), 1552 blkSize, 0, Request::wbMasterId); 1553 if (blk->isSecure()) 1554 req->setFlags(Request::SECURE); 1555 1556 req->taskId(blk->task_id); 1557 blk->task_id= ContextSwitchTaskId::Unknown; 1558 blk->tickInserted = curTick(); 1559 1560 PacketPtr pkt = 1561 new Packet(req, blk->isDirty() ? 1562 MemCmd::WritebackDirty : MemCmd::WritebackClean); 1563 1564 DPRINTF(Cache, "Create Writeback %#llx writable: %d, dirty: %d\n", 1565 pkt->getAddr(), blk->isWritable(), blk->isDirty()); 1566 1567 if (blk->isWritable()) { 1568 // not asserting shared means we pass the block in modified 1569 // state, mark our own block non-writeable 1570 blk->status &= ~BlkWritable; 1571 } else { 1572 // we are in the Owned state, tell the receiver 1573 pkt->setHasSharers(); 1574 } 1575 1576 // make sure the block is not marked dirty 1577 blk->status &= ~BlkDirty; 1578 1579 pkt->allocate(); 1580 std::memcpy(pkt->getPtr<uint8_t>(), blk->data, blkSize); 1581 1582 return pkt; 1583} 1584 1585PacketPtr 1586Cache::cleanEvictBlk(CacheBlk *blk) 1587{ 1588 assert(!writebackClean); 1589 assert(blk && blk->isValid() && !blk->isDirty()); 1590 // Creating a zero sized write, a message to the snoop filter 1591 Request *req = 1592 new Request(tags->regenerateBlkAddr(blk->tag, blk->set), blkSize, 0, 1593 Request::wbMasterId); 1594 if (blk->isSecure()) 1595 req->setFlags(Request::SECURE); 1596 1597 req->taskId(blk->task_id); 1598 blk->task_id = ContextSwitchTaskId::Unknown; 1599 blk->tickInserted = curTick(); 1600 1601 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict); 1602 pkt->allocate(); 1603 DPRINTF(Cache, "%s%s %x Create CleanEvict\n", pkt->cmdString(), 1604 pkt->req->isInstFetch() ? " (ifetch)" : "", 1605 pkt->getAddr()); 1606 1607 return pkt; 1608} 1609 1610void 1611Cache::memWriteback() 1612{ 1613 CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor); 1614 tags->forEachBlk(visitor); 1615} 1616 1617void 1618Cache::memInvalidate() 1619{ 1620 CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor); 1621 tags->forEachBlk(visitor); 1622} 1623 1624bool 1625Cache::isDirty() const 1626{ 1627 CacheBlkIsDirtyVisitor visitor; 1628 tags->forEachBlk(visitor); 1629 1630 return visitor.isDirty(); 1631} 1632 1633bool 1634Cache::writebackVisitor(CacheBlk &blk) 1635{ 1636 if (blk.isDirty()) { 1637 assert(blk.isValid()); 1638 1639 Request request(tags->regenerateBlkAddr(blk.tag, blk.set), 1640 blkSize, 0, Request::funcMasterId); 1641 request.taskId(blk.task_id); 1642 1643 Packet packet(&request, MemCmd::WriteReq); 1644 packet.dataStatic(blk.data); 1645 1646 memSidePort->sendFunctional(&packet); 1647 1648 blk.status &= ~BlkDirty; 1649 } 1650 1651 return true; 1652} 1653 1654bool 1655Cache::invalidateVisitor(CacheBlk &blk) 1656{ 1657 1658 if (blk.isDirty()) 1659 warn_once("Invalidating dirty cache lines. Expect things to break.\n"); 1660 1661 if (blk.isValid()) { 1662 assert(!blk.isDirty()); 1663 tags->invalidate(&blk); 1664 blk.invalidate(); 1665 } 1666 1667 return true; 1668} 1669 1670CacheBlk* 1671Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks) 1672{ 1673 CacheBlk *blk = tags->findVictim(addr); 1674 1675 // It is valid to return NULL if there is no victim 1676 if (!blk) 1677 return nullptr; 1678 1679 if (blk->isValid()) { 1680 Addr repl_addr = tags->regenerateBlkAddr(blk->tag, blk->set); 1681 MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure()); 1682 if (repl_mshr) { 1683 // must be an outstanding upgrade request 1684 // on a block we're about to replace... 1685 assert(!blk->isWritable() || blk->isDirty()); 1686 assert(repl_mshr->needsWritable()); 1687 // too hard to replace block with transient state 1688 // allocation failed, block not inserted 1689 return NULL; 1690 } else { 1691 DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx (%s): %s\n", 1692 repl_addr, blk->isSecure() ? "s" : "ns", 1693 addr, is_secure ? "s" : "ns", 1694 blk->isDirty() ? "writeback" : "clean"); 1695 1696 // Will send up Writeback/CleanEvict snoops via isCachedAbove 1697 // when pushing this writeback list into the write buffer. 1698 if (blk->isDirty() || writebackClean) { 1699 // Save writeback packet for handling by caller 1700 writebacks.push_back(writebackBlk(blk)); 1701 } else { 1702 writebacks.push_back(cleanEvictBlk(blk)); 1703 } 1704 } 1705 } 1706 1707 return blk; 1708} 1709 1710void 1711Cache::invalidateBlock(CacheBlk *blk) 1712{ 1713 if (blk != tempBlock) 1714 tags->invalidate(blk); 1715 blk->invalidate(); 1716} 1717 1718// Note that the reason we return a list of writebacks rather than 1719// inserting them directly in the write buffer is that this function 1720// is called by both atomic and timing-mode accesses, and in atomic 1721// mode we don't mess with the write buffer (we just perform the 1722// writebacks atomically once the original request is complete). 1723CacheBlk* 1724Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks, 1725 bool allocate) 1726{ 1727 assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq); 1728 Addr addr = pkt->getAddr(); 1729 bool is_secure = pkt->isSecure(); 1730#if TRACING_ON 1731 CacheBlk::State old_state = blk ? blk->status : 0; 1732#endif 1733 1734 // When handling a fill, discard any CleanEvicts for the 1735 // same address in write buffer. 1736 Addr M5_VAR_USED blk_addr = blockAlign(pkt->getAddr()); 1737 std::vector<MSHR *> M5_VAR_USED wbs; 1738 assert (!writeBuffer.findMatches(blk_addr, is_secure, wbs)); 1739 1740 if (blk == NULL) { 1741 // better have read new data... 1742 assert(pkt->hasData()); 1743 1744 // only read responses and write-line requests have data; 1745 // note that we don't write the data here for write-line - that 1746 // happens in the subsequent satisfyCpuSideRequest. 1747 assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq); 1748 1749 // need to do a replacement if allocating, otherwise we stick 1750 // with the temporary storage 1751 blk = allocate ? allocateBlock(addr, is_secure, writebacks) : NULL; 1752 1753 if (blk == NULL) { 1754 // No replaceable block or a mostly exclusive 1755 // cache... just use temporary storage to complete the 1756 // current request and then get rid of it 1757 assert(!tempBlock->isValid()); 1758 blk = tempBlock; 1759 tempBlock->set = tags->extractSet(addr); 1760 tempBlock->tag = tags->extractTag(addr); 1761 // @todo: set security state as well... 1762 DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr, 1763 is_secure ? "s" : "ns"); 1764 } else { 1765 tags->insertBlock(pkt, blk); 1766 } 1767 1768 // we should never be overwriting a valid block 1769 assert(!blk->isValid()); 1770 } else { 1771 // existing block... probably an upgrade 1772 assert(blk->tag == tags->extractTag(addr)); 1773 // either we're getting new data or the block should already be valid 1774 assert(pkt->hasData() || blk->isValid()); 1775 // don't clear block status... if block is already dirty we 1776 // don't want to lose that 1777 } 1778 1779 if (is_secure) 1780 blk->status |= BlkSecure; 1781 blk->status |= BlkValid | BlkReadable; 1782 1783 // sanity check for whole-line writes, which should always be 1784 // marked as writable as part of the fill, and then later marked 1785 // dirty as part of satisfyCpuSideRequest 1786 if (pkt->cmd == MemCmd::WriteLineReq) { 1787 assert(!pkt->hasSharers()); 1788 // at the moment other caches do not respond to the 1789 // invalidation requests corresponding to a whole-line write 1790 assert(!pkt->cacheResponding()); 1791 } 1792 1793 // here we deal with setting the appropriate state of the line, 1794 // and we start by looking at the hasSharers flag, and ignore the 1795 // cacheResponding flag (normally signalling dirty data) if the 1796 // packet has sharers, thus the line is never allocated as Owned 1797 // (dirty but not writable), and always ends up being either 1798 // Shared, Exclusive or Modified, see Packet::setCacheResponding 1799 // for more details 1800 if (!pkt->hasSharers()) { 1801 // we could get a writable line from memory (rather than a 1802 // cache) even in a read-only cache, note that we set this bit 1803 // even for a read-only cache, possibly revisit this decision 1804 blk->status |= BlkWritable; 1805 1806 // check if we got this via cache-to-cache transfer (i.e., from a 1807 // cache that had the block in Modified or Owned state) 1808 if (pkt->cacheResponding()) { 1809 // we got the block in Modified state, and invalidated the 1810 // owners copy 1811 blk->status |= BlkDirty; 1812 1813 chatty_assert(!isReadOnly, "Should never see dirty snoop response " 1814 "in read-only cache %s\n", name()); 1815 } 1816 } 1817 1818 DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n", 1819 addr, is_secure ? "s" : "ns", old_state, blk->print()); 1820 1821 // if we got new data, copy it in (checking for a read response 1822 // and a response that has data is the same in the end) 1823 if (pkt->isRead()) { 1824 // sanity checks 1825 assert(pkt->hasData()); 1826 assert(pkt->getSize() == blkSize); 1827 1828 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize); 1829 } 1830 // We pay for fillLatency here. 1831 blk->whenReady = clockEdge() + fillLatency * clockPeriod() + 1832 pkt->payloadDelay; 1833 1834 return blk; 1835} 1836 1837 1838///////////////////////////////////////////////////// 1839// 1840// Snoop path: requests coming in from the memory side 1841// 1842///////////////////////////////////////////////////// 1843 1844void 1845Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data, 1846 bool already_copied, bool pending_inval) 1847{ 1848 // sanity check 1849 assert(req_pkt->isRequest()); 1850 assert(req_pkt->needsResponse()); 1851 1852 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 1853 req_pkt->cmdString(), req_pkt->getAddr(), req_pkt->getSize()); 1854 // timing-mode snoop responses require a new packet, unless we 1855 // already made a copy... 1856 PacketPtr pkt = req_pkt; 1857 if (!already_copied) 1858 // do not clear flags, and allocate space for data if the 1859 // packet needs it (the only packets that carry data are read 1860 // responses) 1861 pkt = new Packet(req_pkt, false, req_pkt->isRead()); 1862 1863 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() || 1864 pkt->hasSharers()); 1865 pkt->makeTimingResponse(); 1866 if (pkt->isRead()) { 1867 pkt->setDataFromBlock(blk_data, blkSize); 1868 } 1869 if (pkt->cmd == MemCmd::ReadResp && pending_inval) { 1870 // Assume we defer a response to a read from a far-away cache 1871 // A, then later defer a ReadExcl from a cache B on the same 1872 // bus as us. We'll assert cacheResponding in both cases, but 1873 // in the latter case cacheResponding will keep the 1874 // invalidation from reaching cache A. This special response 1875 // tells cache A that it gets the block to satisfy its read, 1876 // but must immediately invalidate it. 1877 pkt->cmd = MemCmd::ReadRespWithInvalidate; 1878 } 1879 // Here we consider forward_time, paying for just forward latency and 1880 // also charging the delay provided by the xbar. 1881 // forward_time is used as send_time in next allocateWriteBuffer(). 1882 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 1883 // Here we reset the timing of the packet. 1884 pkt->headerDelay = pkt->payloadDelay = 0; 1885 DPRINTF(CacheVerbose, 1886 "%s created response: %s addr %#llx size %d tick: %lu\n", 1887 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize(), 1888 forward_time); 1889 memSidePort->schedTimingSnoopResp(pkt, forward_time, true); 1890} 1891 1892uint32_t 1893Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing, 1894 bool is_deferred, bool pending_inval) 1895{ 1896 DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d\n", __func__, 1897 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 1898 // deferred snoops can only happen in timing mode 1899 assert(!(is_deferred && !is_timing)); 1900 // pending_inval only makes sense on deferred snoops 1901 assert(!(pending_inval && !is_deferred)); 1902 assert(pkt->isRequest()); 1903 1904 // the packet may get modified if we or a forwarded snooper 1905 // responds in atomic mode, so remember a few things about the 1906 // original packet up front 1907 bool invalidate = pkt->isInvalidate(); 1908 bool M5_VAR_USED needs_writable = pkt->needsWritable(); 1909 1910 // at the moment we could get an uncacheable write which does not 1911 // have the invalidate flag, and we need a suitable way of dealing 1912 // with this case 1913 panic_if(invalidate && pkt->req->isUncacheable(), 1914 "%s got an invalidating uncacheable snoop request %s to %#llx", 1915 name(), pkt->cmdString(), pkt->getAddr()); 1916 1917 uint32_t snoop_delay = 0; 1918 1919 if (forwardSnoops) { 1920 // first propagate snoop upward to see if anyone above us wants to 1921 // handle it. save & restore packet src since it will get 1922 // rewritten to be relative to cpu-side bus (if any) 1923 bool alreadyResponded = pkt->cacheResponding(); 1924 if (is_timing) { 1925 // copy the packet so that we can clear any flags before 1926 // forwarding it upwards, we also allocate data (passing 1927 // the pointer along in case of static data), in case 1928 // there is a snoop hit in upper levels 1929 Packet snoopPkt(pkt, true, true); 1930 snoopPkt.setExpressSnoop(); 1931 // the snoop packet does not need to wait any additional 1932 // time 1933 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0; 1934 cpuSidePort->sendTimingSnoopReq(&snoopPkt); 1935 1936 // add the header delay (including crossbar and snoop 1937 // delays) of the upward snoop to the snoop delay for this 1938 // cache 1939 snoop_delay += snoopPkt.headerDelay; 1940 1941 if (snoopPkt.cacheResponding()) { 1942 // cache-to-cache response from some upper cache 1943 assert(!alreadyResponded); 1944 pkt->setCacheResponding(); 1945 } 1946 // upstream cache has the block, or has an outstanding 1947 // MSHR, pass the flag on 1948 if (snoopPkt.hasSharers()) { 1949 pkt->setHasSharers(); 1950 } 1951 // If this request is a prefetch or clean evict and an upper level 1952 // signals block present, make sure to propagate the block 1953 // presence to the requester. 1954 if (snoopPkt.isBlockCached()) { 1955 pkt->setBlockCached(); 1956 } 1957 } else { 1958 cpuSidePort->sendAtomicSnoop(pkt); 1959 if (!alreadyResponded && pkt->cacheResponding()) { 1960 // cache-to-cache response from some upper cache: 1961 // forward response to original requester 1962 assert(pkt->isResponse()); 1963 } 1964 } 1965 } 1966 1967 if (!blk || !blk->isValid()) { 1968 DPRINTF(CacheVerbose, "%s snoop miss for %s addr %#llx size %d\n", 1969 __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 1970 return snoop_delay; 1971 } else { 1972 DPRINTF(Cache, "%s snoop hit for %s addr %#llx size %d, " 1973 "old state is %s\n", __func__, pkt->cmdString(), 1974 pkt->getAddr(), pkt->getSize(), blk->print()); 1975 } 1976 1977 chatty_assert(!(isReadOnly && blk->isDirty()), 1978 "Should never have a dirty block in a read-only cache %s\n", 1979 name()); 1980 1981 // We may end up modifying both the block state and the packet (if 1982 // we respond in atomic mode), so just figure out what to do now 1983 // and then do it later. If we find dirty data while snooping for 1984 // an invalidate, we don't need to send a response. The 1985 // invalidation itself is taken care of below. 1986 bool respond = blk->isDirty() && pkt->needsResponse() && 1987 pkt->cmd != MemCmd::InvalidateReq; 1988 bool have_writable = blk->isWritable(); 1989 1990 // Invalidate any prefetch's from below that would strip write permissions 1991 // MemCmd::HardPFReq is only observed by upstream caches. After missing 1992 // above and in it's own cache, a new MemCmd::ReadReq is created that 1993 // downstream caches observe. 1994 if (pkt->mustCheckAbove()) { 1995 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s from" 1996 " lower cache\n", pkt->getAddr(), pkt->cmdString()); 1997 pkt->setBlockCached(); 1998 return snoop_delay; 1999 } 2000 2001 if (pkt->isRead() && !invalidate) { 2002 // reading without requiring the line in a writable state 2003 assert(!needs_writable); 2004 pkt->setHasSharers(); 2005 2006 // if the requesting packet is uncacheable, retain the line in 2007 // the current state, otherwhise unset the writable flag, 2008 // which means we go from Modified to Owned (and will respond 2009 // below), remain in Owned (and will respond below), from 2010 // Exclusive to Shared, or remain in Shared 2011 if (!pkt->req->isUncacheable()) 2012 blk->status &= ~BlkWritable; 2013 } 2014 2015 if (respond) { 2016 // prevent anyone else from responding, cache as well as 2017 // memory, and also prevent any memory from even seeing the 2018 // request 2019 pkt->setCacheResponding(); 2020 if (have_writable) { 2021 // inform the cache hierarchy that this cache had the line 2022 // in the Modified state so that we avoid unnecessary 2023 // invalidations (see Packet::setResponderHadWritable) 2024 pkt->setResponderHadWritable(); 2025 2026 // in the case of an uncacheable request there is no point 2027 // in setting the responderHadWritable flag, but since the 2028 // recipient does not care there is no harm in doing so 2029 } else { 2030 // if the packet has needsWritable set we invalidate our 2031 // copy below and all other copies will be invalidates 2032 // through express snoops, and if needsWritable is not set 2033 // we already called setHasSharers above 2034 } 2035 2036 // if we are returning a writable and dirty (Modified) line, 2037 // we should be invalidating the line 2038 panic_if(!invalidate && !pkt->hasSharers(), 2039 "%s is passing a Modified line through %s to %#llx, " 2040 "but keeping the block", 2041 name(), pkt->cmdString(), pkt->getAddr()); 2042 2043 if (is_timing) { 2044 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval); 2045 } else { 2046 pkt->makeAtomicResponse(); 2047 // packets such as upgrades do not actually have any data 2048 // payload 2049 if (pkt->hasData()) 2050 pkt->setDataFromBlock(blk->data, blkSize); 2051 } 2052 } 2053 2054 if (!respond && is_timing && is_deferred) { 2055 // if it's a deferred timing snoop to which we are not 2056 // responding, then we've made a copy of both the request and 2057 // the packet, delete them here 2058 assert(pkt->needsResponse()); 2059 delete pkt->req; 2060 delete pkt; 2061 } 2062 2063 // Do this last in case it deallocates block data or something 2064 // like that 2065 if (invalidate) { 2066 invalidateBlock(blk); 2067 } 2068 2069 DPRINTF(Cache, "new state is %s\n", blk->print()); 2070 2071 return snoop_delay; 2072} 2073 2074 2075void 2076Cache::recvTimingSnoopReq(PacketPtr pkt) 2077{ 2078 DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d\n", __func__, 2079 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 2080 2081 // Snoops shouldn't happen when bypassing caches 2082 assert(!system->bypassCaches()); 2083 2084 // no need to snoop requests that are not in range 2085 if (!inRange(pkt->getAddr())) { 2086 return; 2087 } 2088 2089 bool is_secure = pkt->isSecure(); 2090 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure); 2091 2092 Addr blk_addr = blockAlign(pkt->getAddr()); 2093 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure); 2094 2095 // Update the latency cost of the snoop so that the crossbar can 2096 // account for it. Do not overwrite what other neighbouring caches 2097 // have already done, rather take the maximum. The update is 2098 // tentative, for cases where we return before an upward snoop 2099 // happens below. 2100 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, 2101 lookupLatency * clockPeriod()); 2102 2103 // Inform request(Prefetch, CleanEvict or Writeback) from below of 2104 // MSHR hit, set setBlockCached. 2105 if (mshr && pkt->mustCheckAbove()) { 2106 DPRINTF(Cache, "Setting block cached for %s from" 2107 "lower cache on mshr hit %#x\n", 2108 pkt->cmdString(), pkt->getAddr()); 2109 pkt->setBlockCached(); 2110 return; 2111 } 2112 2113 // Let the MSHR itself track the snoop and decide whether we want 2114 // to go ahead and do the regular cache snoop 2115 if (mshr && mshr->handleSnoop(pkt, order++)) { 2116 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)." 2117 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns", 2118 mshr->print()); 2119 2120 if (mshr->getNumTargets() > numTarget) 2121 warn("allocating bonus target for snoop"); //handle later 2122 return; 2123 } 2124 2125 //We also need to check the writeback buffers and handle those 2126 std::vector<MSHR *> writebacks; 2127 if (writeBuffer.findMatches(blk_addr, is_secure, writebacks)) { 2128 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n", 2129 pkt->getAddr(), is_secure ? "s" : "ns"); 2130 2131 // Look through writebacks for any cachable writes. 2132 // We should only ever find a single match 2133 assert(writebacks.size() == 1); 2134 MSHR *wb_entry = writebacks[0]; 2135 // Expect to see only Writebacks and/or CleanEvicts here, both of 2136 // which should not be generated for uncacheable data. 2137 assert(!wb_entry->isUncacheable()); 2138 // There should only be a single request responsible for generating 2139 // Writebacks/CleanEvicts. 2140 assert(wb_entry->getNumTargets() == 1); 2141 PacketPtr wb_pkt = wb_entry->getTarget()->pkt; 2142 assert(wb_pkt->isEviction()); 2143 2144 if (pkt->isEviction()) { 2145 // if the block is found in the write queue, set the BLOCK_CACHED 2146 // flag for Writeback/CleanEvict snoop. On return the snoop will 2147 // propagate the BLOCK_CACHED flag in Writeback packets and prevent 2148 // any CleanEvicts from travelling down the memory hierarchy. 2149 pkt->setBlockCached(); 2150 DPRINTF(Cache, "Squashing %s from lower cache on writequeue hit" 2151 " %#x\n", pkt->cmdString(), pkt->getAddr()); 2152 return; 2153 } 2154 2155 // conceptually writebacks are no different to other blocks in 2156 // this cache, so the behaviour is modelled after handleSnoop, 2157 // the difference being that instead of querying the block 2158 // state to determine if it is dirty and writable, we use the 2159 // command and fields of the writeback packet 2160 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty && 2161 pkt->needsResponse() && pkt->cmd != MemCmd::InvalidateReq; 2162 bool have_writable = !wb_pkt->hasSharers(); 2163 bool invalidate = pkt->isInvalidate(); 2164 2165 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) { 2166 assert(!pkt->needsWritable()); 2167 pkt->setHasSharers(); 2168 wb_pkt->setHasSharers(); 2169 } 2170 2171 if (respond) { 2172 pkt->setCacheResponding(); 2173 2174 if (have_writable) { 2175 pkt->setResponderHadWritable(); 2176 } 2177 2178 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(), 2179 false, false); 2180 } 2181 2182 if (invalidate) { 2183 // Invalidation trumps our writeback... discard here 2184 // Note: markInService will remove entry from writeback buffer. 2185 markInService(wb_entry, false); 2186 delete wb_pkt; 2187 } 2188 } 2189 2190 // If this was a shared writeback, there may still be 2191 // other shared copies above that require invalidation. 2192 // We could be more selective and return here if the 2193 // request is non-exclusive or if the writeback is 2194 // exclusive. 2195 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false); 2196 2197 // Override what we did when we first saw the snoop, as we now 2198 // also have the cost of the upwards snoops to account for 2199 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay + 2200 lookupLatency * clockPeriod()); 2201} 2202 2203bool 2204Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt) 2205{ 2206 // Express snoop responses from master to slave, e.g., from L1 to L2 2207 cache->recvTimingSnoopResp(pkt); 2208 return true; 2209} 2210 2211Tick 2212Cache::recvAtomicSnoop(PacketPtr pkt) 2213{ 2214 // Snoops shouldn't happen when bypassing caches 2215 assert(!system->bypassCaches()); 2216 2217 // no need to snoop requests that are not in range. 2218 if (!inRange(pkt->getAddr())) { 2219 return 0; 2220 } 2221 2222 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 2223 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false); 2224 return snoop_delay + lookupLatency * clockPeriod(); 2225} 2226 2227 2228MSHR * 2229Cache::getNextMSHR() 2230{ 2231 // Check both MSHR queue and write buffer for potential requests, 2232 // note that null does not mean there is no request, it could 2233 // simply be that it is not ready 2234 MSHR *miss_mshr = mshrQueue.getNextMSHR(); 2235 MSHR *write_mshr = writeBuffer.getNextMSHR(); 2236 2237 // If we got a write buffer request ready, first priority is a 2238 // full write buffer, otherwhise we favour the miss requests 2239 if (write_mshr && 2240 ((writeBuffer.isFull() && writeBuffer.inServiceEntries == 0) || 2241 !miss_mshr)) { 2242 // need to search MSHR queue for conflicting earlier miss. 2243 MSHR *conflict_mshr = 2244 mshrQueue.findPending(write_mshr->blkAddr, 2245 write_mshr->isSecure); 2246 2247 if (conflict_mshr && conflict_mshr->order < write_mshr->order) { 2248 // Service misses in order until conflict is cleared. 2249 return conflict_mshr; 2250 2251 // @todo Note that we ignore the ready time of the conflict here 2252 } 2253 2254 // No conflicts; issue write 2255 return write_mshr; 2256 } else if (miss_mshr) { 2257 // need to check for conflicting earlier writeback 2258 MSHR *conflict_mshr = 2259 writeBuffer.findPending(miss_mshr->blkAddr, 2260 miss_mshr->isSecure); 2261 if (conflict_mshr) { 2262 // not sure why we don't check order here... it was in the 2263 // original code but commented out. 2264 2265 // The only way this happens is if we are 2266 // doing a write and we didn't have permissions 2267 // then subsequently saw a writeback (owned got evicted) 2268 // We need to make sure to perform the writeback first 2269 // To preserve the dirty data, then we can issue the write 2270 2271 // should we return write_mshr here instead? I.e. do we 2272 // have to flush writes in order? I don't think so... not 2273 // for Alpha anyway. Maybe for x86? 2274 return conflict_mshr; 2275 2276 // @todo Note that we ignore the ready time of the conflict here 2277 } 2278 2279 // No conflicts; issue read 2280 return miss_mshr; 2281 } 2282 2283 // fall through... no pending requests. Try a prefetch. 2284 assert(!miss_mshr && !write_mshr); 2285 if (prefetcher && mshrQueue.canPrefetch()) { 2286 // If we have a miss queue slot, we can try a prefetch 2287 PacketPtr pkt = prefetcher->getPacket(); 2288 if (pkt) { 2289 Addr pf_addr = blockAlign(pkt->getAddr()); 2290 if (!tags->findBlock(pf_addr, pkt->isSecure()) && 2291 !mshrQueue.findMatch(pf_addr, pkt->isSecure()) && 2292 !writeBuffer.findMatch(pf_addr, pkt->isSecure())) { 2293 // Update statistic on number of prefetches issued 2294 // (hwpf_mshr_misses) 2295 assert(pkt->req->masterId() < system->maxMasters()); 2296 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++; 2297 2298 // allocate an MSHR and return it, note 2299 // that we send the packet straight away, so do not 2300 // schedule the send 2301 return allocateMissBuffer(pkt, curTick(), false); 2302 } else { 2303 // free the request and packet 2304 delete pkt->req; 2305 delete pkt; 2306 } 2307 } 2308 } 2309 2310 return NULL; 2311} 2312 2313bool 2314Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const 2315{ 2316 if (!forwardSnoops) 2317 return false; 2318 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and 2319 // Writeback snoops into upper level caches to check for copies of the 2320 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict 2321 // packet, the cache can inform the crossbar below of presence or absence 2322 // of the block. 2323 if (is_timing) { 2324 Packet snoop_pkt(pkt, true, false); 2325 snoop_pkt.setExpressSnoop(); 2326 // Assert that packet is either Writeback or CleanEvict and not a 2327 // prefetch request because prefetch requests need an MSHR and may 2328 // generate a snoop response. 2329 assert(pkt->isEviction()); 2330 snoop_pkt.senderState = NULL; 2331 cpuSidePort->sendTimingSnoopReq(&snoop_pkt); 2332 // Writeback/CleanEvict snoops do not generate a snoop response. 2333 assert(!(snoop_pkt.cacheResponding())); 2334 return snoop_pkt.isBlockCached(); 2335 } else { 2336 cpuSidePort->sendAtomicSnoop(pkt); 2337 return pkt->isBlockCached(); 2338 } 2339} 2340 2341PacketPtr 2342Cache::getTimingPacket() 2343{ 2344 MSHR *mshr = getNextMSHR(); 2345 2346 if (mshr == NULL) { 2347 return NULL; 2348 } 2349 2350 // use request from 1st target 2351 PacketPtr tgt_pkt = mshr->getTarget()->pkt; 2352 PacketPtr pkt = NULL; 2353 2354 DPRINTF(CachePort, "%s %s for addr %#llx size %d\n", __func__, 2355 tgt_pkt->cmdString(), tgt_pkt->getAddr(), tgt_pkt->getSize()); 2356 2357 CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure); 2358 2359 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) { 2360 // We need to check the caches above us to verify that 2361 // they don't have a copy of this block in the dirty state 2362 // at the moment. Without this check we could get a stale 2363 // copy from memory that might get used in place of the 2364 // dirty one. 2365 Packet snoop_pkt(tgt_pkt, true, false); 2366 snoop_pkt.setExpressSnoop(); 2367 // We are sending this packet upwards, but if it hits we will 2368 // get a snoop response that we end up treating just like a 2369 // normal response, hence it needs the MSHR as its sender 2370 // state 2371 snoop_pkt.senderState = mshr; 2372 cpuSidePort->sendTimingSnoopReq(&snoop_pkt); 2373 2374 // Check to see if the prefetch was squashed by an upper cache (to 2375 // prevent us from grabbing the line) or if a Check to see if a 2376 // writeback arrived between the time the prefetch was placed in 2377 // the MSHRs and when it was selected to be sent or if the 2378 // prefetch was squashed by an upper cache. 2379 2380 // It is important to check cacheResponding before 2381 // prefetchSquashed. If another cache has committed to 2382 // responding, it will be sending a dirty response which will 2383 // arrive at the MSHR allocated for this request. Checking the 2384 // prefetchSquash first may result in the MSHR being 2385 // prematurely deallocated. 2386 if (snoop_pkt.cacheResponding()) { 2387 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req); 2388 assert(r.second); 2389 2390 // if we are getting a snoop response with no sharers it 2391 // will be allocated as Modified 2392 bool pending_modified_resp = !snoop_pkt.hasSharers(); 2393 markInService(mshr, pending_modified_resp); 2394 2395 DPRINTF(Cache, "Upward snoop of prefetch for addr" 2396 " %#x (%s) hit\n", 2397 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns"); 2398 return NULL; 2399 } 2400 2401 if (snoop_pkt.isBlockCached() || blk != NULL) { 2402 DPRINTF(Cache, "Block present, prefetch squashed by cache. " 2403 "Deallocating mshr target %#x.\n", 2404 mshr->blkAddr); 2405 // Deallocate the mshr target 2406 if (mshr->queue->forceDeallocateTarget(mshr)) { 2407 // Clear block if this deallocation resulted freed an 2408 // mshr when all had previously been utilized 2409 clearBlocked((BlockedCause)(mshr->queue->index)); 2410 } 2411 return NULL; 2412 } 2413 } 2414 2415 if (mshr->isForwardNoResponse()) { 2416 // no response expected, just forward packet as it is 2417 assert(tags->findBlock(mshr->blkAddr, mshr->isSecure) == NULL); 2418 pkt = tgt_pkt; 2419 } else { 2420 pkt = getBusPacket(tgt_pkt, blk, mshr->needsWritable()); 2421 2422 mshr->isForward = (pkt == NULL); 2423 2424 if (mshr->isForward) { 2425 // not a cache block request, but a response is expected 2426 // make copy of current packet to forward, keep current 2427 // copy for response handling 2428 pkt = new Packet(tgt_pkt, false, true); 2429 if (pkt->isWrite()) { 2430 pkt->setData(tgt_pkt->getConstPtr<uint8_t>()); 2431 } 2432 } 2433 } 2434 2435 assert(pkt != NULL); 2436 // play it safe and append (rather than set) the sender state, as 2437 // forwarded packets may already have existing state 2438 pkt->pushSenderState(mshr); 2439 return pkt; 2440} 2441 2442 2443Tick 2444Cache::nextMSHRReadyTime() const 2445{ 2446 Tick nextReady = std::min(mshrQueue.nextMSHRReadyTime(), 2447 writeBuffer.nextMSHRReadyTime()); 2448 2449 // Don't signal prefetch ready time if no MSHRs available 2450 // Will signal once enoguh MSHRs are deallocated 2451 if (prefetcher && mshrQueue.canPrefetch()) { 2452 nextReady = std::min(nextReady, 2453 prefetcher->nextPrefetchReadyTime()); 2454 } 2455 2456 return nextReady; 2457} 2458 2459void 2460Cache::serialize(CheckpointOut &cp) const 2461{ 2462 bool dirty(isDirty()); 2463 2464 if (dirty) { 2465 warn("*** The cache still contains dirty data. ***\n"); 2466 warn(" Make sure to drain the system using the correct flags.\n"); 2467 warn(" This checkpoint will not restore correctly and dirty data in " 2468 "the cache will be lost!\n"); 2469 } 2470 2471 // Since we don't checkpoint the data in the cache, any dirty data 2472 // will be lost when restoring from a checkpoint of a system that 2473 // wasn't drained properly. Flag the checkpoint as invalid if the 2474 // cache contains dirty data. 2475 bool bad_checkpoint(dirty); 2476 SERIALIZE_SCALAR(bad_checkpoint); 2477} 2478 2479void 2480Cache::unserialize(CheckpointIn &cp) 2481{ 2482 bool bad_checkpoint; 2483 UNSERIALIZE_SCALAR(bad_checkpoint); 2484 if (bad_checkpoint) { 2485 fatal("Restoring from checkpoints with dirty caches is not supported " 2486 "in the classic memory system. Please remove any caches or " 2487 " drain them properly before taking checkpoints.\n"); 2488 } 2489} 2490 2491/////////////// 2492// 2493// CpuSidePort 2494// 2495/////////////// 2496 2497AddrRangeList 2498Cache::CpuSidePort::getAddrRanges() const 2499{ 2500 return cache->getAddrRanges(); 2501} 2502 2503bool 2504Cache::CpuSidePort::recvTimingReq(PacketPtr pkt) 2505{ 2506 assert(!cache->system->bypassCaches()); 2507 2508 bool success = false; 2509 2510 // always let packets through if an upstream cache has committed 2511 // to responding, even if blocked (we should technically look at 2512 // the isExpressSnoop flag, but it is set by the cache itself, and 2513 // consequently we have to rely on the cacheResponding flag) 2514 if (pkt->cacheResponding()) { 2515 // do not change the current retry state 2516 bool M5_VAR_USED bypass_success = cache->recvTimingReq(pkt); 2517 assert(bypass_success); 2518 return true; 2519 } else if (blocked || mustSendRetry) { 2520 // either already committed to send a retry, or blocked 2521 success = false; 2522 } else { 2523 // pass it on to the cache, and let the cache decide if we 2524 // have to retry or not 2525 success = cache->recvTimingReq(pkt); 2526 } 2527 2528 // remember if we have to retry 2529 mustSendRetry = !success; 2530 return success; 2531} 2532 2533Tick 2534Cache::CpuSidePort::recvAtomic(PacketPtr pkt) 2535{ 2536 return cache->recvAtomic(pkt); 2537} 2538 2539void 2540Cache::CpuSidePort::recvFunctional(PacketPtr pkt) 2541{ 2542 // functional request 2543 cache->functionalAccess(pkt, true); 2544} 2545 2546Cache:: 2547CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache, 2548 const std::string &_label) 2549 : BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache) 2550{ 2551} 2552 2553Cache* 2554CacheParams::create() 2555{ 2556 assert(tags); 2557 2558 return new Cache(this); 2559} 2560/////////////// 2561// 2562// MemSidePort 2563// 2564/////////////// 2565 2566bool 2567Cache::MemSidePort::recvTimingResp(PacketPtr pkt) 2568{ 2569 cache->recvTimingResp(pkt); 2570 return true; 2571} 2572 2573// Express snooping requests to memside port 2574void 2575Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt) 2576{ 2577 // handle snooping requests 2578 cache->recvTimingSnoopReq(pkt); 2579} 2580 2581Tick 2582Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt) 2583{ 2584 return cache->recvAtomicSnoop(pkt); 2585} 2586 2587void 2588Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt) 2589{ 2590 // functional snoop (note that in contrast to atomic we don't have 2591 // a specific functionalSnoop method, as they have the same 2592 // behaviour regardless) 2593 cache->functionalAccess(pkt, false); 2594} 2595 2596void 2597Cache::CacheReqPacketQueue::sendDeferredPacket() 2598{ 2599 // sanity check 2600 assert(!waitingOnRetry); 2601 2602 // there should never be any deferred request packets in the 2603 // queue, instead we resly on the cache to provide the packets 2604 // from the MSHR queue or write queue 2605 assert(deferredPacketReadyTime() == MaxTick); 2606 2607 // check for request packets (requests & writebacks) 2608 PacketPtr pkt = cache.getTimingPacket(); 2609 if (pkt == NULL) { 2610 // can happen if e.g. we attempt a writeback and fail, but 2611 // before the retry, the writeback is eliminated because 2612 // we snoop another cache's ReadEx. 2613 } else { 2614 MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState); 2615 // in most cases getTimingPacket allocates a new packet, and 2616 // we must delete it unless it is successfully sent 2617 bool delete_pkt = !mshr->isForwardNoResponse(); 2618 2619 // let our snoop responses go first if there are responses to 2620 // the same addresses we are about to writeback, note that 2621 // this creates a dependency between requests and snoop 2622 // responses, but that should not be a problem since there is 2623 // a chain already and the key is that the snoop responses can 2624 // sink unconditionally 2625 if (snoopRespQueue.hasAddr(pkt->getAddr())) { 2626 DPRINTF(CachePort, "Waiting for snoop response to be sent\n"); 2627 Tick when = snoopRespQueue.deferredPacketReadyTime(); 2628 schedSendEvent(when); 2629 2630 if (delete_pkt) 2631 delete pkt; 2632 2633 return; 2634 } 2635 2636 2637 waitingOnRetry = !masterPort.sendTimingReq(pkt); 2638 2639 if (waitingOnRetry) { 2640 DPRINTF(CachePort, "now waiting on a retry\n"); 2641 if (delete_pkt) { 2642 // we are awaiting a retry, but we 2643 // delete the packet and will be creating a new packet 2644 // when we get the opportunity 2645 delete pkt; 2646 } 2647 // note that we have now masked any requestBus and 2648 // schedSendEvent (we will wait for a retry before 2649 // doing anything), and this is so even if we do not 2650 // care about this packet and might override it before 2651 // it gets retried 2652 } else { 2653 // As part of the call to sendTimingReq the packet is 2654 // forwarded to all neighbouring caches (and any caches 2655 // above them) as a snoop. Thus at this point we know if 2656 // any of the neighbouring caches are responding, and if 2657 // so, we know it is dirty, and we can determine if it is 2658 // being passed as Modified, making our MSHR the ordering 2659 // point 2660 bool pending_modified_resp = !pkt->hasSharers() && 2661 pkt->cacheResponding(); 2662 2663 cache.markInService(mshr, pending_modified_resp); 2664 } 2665 } 2666 2667 // if we succeeded and are not waiting for a retry, schedule the 2668 // next send considering when the next MSHR is ready, note that 2669 // snoop responses have their own packet queue and thus schedule 2670 // their own events 2671 if (!waitingOnRetry) { 2672 schedSendEvent(cache.nextMSHRReadyTime()); 2673 } 2674} 2675 2676Cache:: 2677MemSidePort::MemSidePort(const std::string &_name, Cache *_cache, 2678 const std::string &_label) 2679 : BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue), 2680 _reqQueue(*_cache, *this, _snoopRespQueue, _label), 2681 _snoopRespQueue(*_cache, *this, _label), cache(_cache) 2682{ 2683} 2684