1/*
2 * Copyright (c) 2010-2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
16 * All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions are
20 * met: redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer;
22 * redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution;
25 * neither the name of the copyright holders nor the names of its
26 * contributors may be used to endorse or promote products derived from
27 * this software without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Authors: Erik Hallnor
42 * Dave Greene
43 * Nathan Binkert
44 * Steve Reinhardt
45 * Ron Dreslinski
46 * Andreas Sandberg
47 * Nikos Nikoleris
48 */
49
50/**
51 * @file
52 * Cache definitions.
53 */
54
55#include "mem/cache/cache.hh"
56
57#include "base/logging.hh"
58#include "base/types.hh"
59#include "debug/Cache.hh"
60#include "debug/CachePort.hh"
61#include "debug/CacheTags.hh"
62#include "debug/CacheVerbose.hh"
63#include "mem/cache/blk.hh"
64#include "mem/cache/mshr.hh"
65#include "mem/cache/prefetch/base.hh"
66#include "sim/sim_exit.hh"
67
68Cache::Cache(const CacheParams *p)
69 : BaseCache(p, p->system->cacheLineSize()),
70 tags(p->tags),
71 prefetcher(p->prefetcher),
72 doFastWrites(true),
73 prefetchOnAccess(p->prefetch_on_access),
74 clusivity(p->clusivity),
75 writebackClean(p->writeback_clean),
76 tempBlockWriteback(nullptr),
77 writebackTempBlockAtomicEvent([this]{ writebackTempBlockAtomic(); },
78 name(), false,
79 EventBase::Delayed_Writeback_Pri)
80{
81 tempBlock = new CacheBlk();
82 tempBlock->data = new uint8_t[blkSize];
83
84 cpuSidePort = new CpuSidePort(p->name + ".cpu_side", this,
85 "CpuSidePort");
86 memSidePort = new MemSidePort(p->name + ".mem_side", this,
87 "MemSidePort");
88
89 tags->setCache(this);
90 if (prefetcher)
91 prefetcher->setCache(this);
92}
93
94Cache::~Cache()
95{
96 delete [] tempBlock->data;
97 delete tempBlock;
98
99 delete cpuSidePort;
100 delete memSidePort;
101}
102
103void
104Cache::regStats()
105{
106 BaseCache::regStats();
107}
108
109void
110Cache::cmpAndSwap(CacheBlk *blk, PacketPtr pkt)
111{
112 assert(pkt->isRequest());
113
114 uint64_t overwrite_val;
115 bool overwrite_mem;
116 uint64_t condition_val64;
117 uint32_t condition_val32;
118
119 int offset = tags->extractBlkOffset(pkt->getAddr());
120 uint8_t *blk_data = blk->data + offset;
121
122 assert(sizeof(uint64_t) >= pkt->getSize());
123
124 overwrite_mem = true;
125 // keep a copy of our possible write value, and copy what is at the
126 // memory address into the packet
127 pkt->writeData((uint8_t *)&overwrite_val);
128 pkt->setData(blk_data);
129
130 if (pkt->req->isCondSwap()) {
131 if (pkt->getSize() == sizeof(uint64_t)) {
132 condition_val64 = pkt->req->getExtraData();
133 overwrite_mem = !std::memcmp(&condition_val64, blk_data,
134 sizeof(uint64_t));
135 } else if (pkt->getSize() == sizeof(uint32_t)) {
136 condition_val32 = (uint32_t)pkt->req->getExtraData();
137 overwrite_mem = !std::memcmp(&condition_val32, blk_data,
138 sizeof(uint32_t));
139 } else
140 panic("Invalid size for conditional read/write\n");
141 }
142
143 if (overwrite_mem) {
144 std::memcpy(blk_data, &overwrite_val, pkt->getSize());
145 blk->status |= BlkDirty;
146 }
147}
148
149
150void
151Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
152 bool deferred_response, bool pending_downgrade)
153{
154 assert(pkt->isRequest());
155
156 assert(blk && blk->isValid());
157 // Occasionally this is not true... if we are a lower-level cache
158 // satisfying a string of Read and ReadEx requests from
159 // upper-level caches, a Read will mark the block as shared but we
160 // can satisfy a following ReadEx anyway since we can rely on the
161 // Read requester(s) to have buffered the ReadEx snoop and to
162 // invalidate their blocks after receiving them.
163 // assert(!pkt->needsWritable() || blk->isWritable());
164 assert(pkt->getOffset(blkSize) + pkt->getSize() <= blkSize);
165
166 // Check RMW operations first since both isRead() and
167 // isWrite() will be true for them
168 if (pkt->cmd == MemCmd::SwapReq) {
169 cmpAndSwap(blk, pkt);
170 } else if (pkt->isWrite()) {
171 // we have the block in a writable state and can go ahead,
172 // note that the line may be also be considered writable in
173 // downstream caches along the path to memory, but always
174 // Exclusive, and never Modified
175 assert(blk->isWritable());
176 // Write or WriteLine at the first cache with block in writable state
177 if (blk->checkWrite(pkt)) {
178 pkt->writeDataToBlock(blk->data, blkSize);
179 }
180 // Always mark the line as dirty (and thus transition to the
181 // Modified state) even if we are a failed StoreCond so we
182 // supply data to any snoops that have appended themselves to
183 // this cache before knowing the store will fail.
184 blk->status |= BlkDirty;
185 DPRINTF(CacheVerbose, "%s for %s (write)\n", __func__, pkt->print());
186 } else if (pkt->isRead()) {
187 if (pkt->isLLSC()) {
188 blk->trackLoadLocked(pkt);
189 }
190
191 // all read responses have a data payload
192 assert(pkt->hasRespData());
193 pkt->setDataFromBlock(blk->data, blkSize);
194
195 // determine if this read is from a (coherent) cache or not
196 if (pkt->fromCache()) {
197 assert(pkt->getSize() == blkSize);
198 // special handling for coherent block requests from
199 // upper-level caches
200 if (pkt->needsWritable()) {
201 // sanity check
202 assert(pkt->cmd == MemCmd::ReadExReq ||
203 pkt->cmd == MemCmd::SCUpgradeFailReq);
204 assert(!pkt->hasSharers());
205
206 // if we have a dirty copy, make sure the recipient
207 // keeps it marked dirty (in the modified state)
208 if (blk->isDirty()) {
209 pkt->setCacheResponding();
210 blk->status &= ~BlkDirty;
211 }
212 } else if (blk->isWritable() && !pending_downgrade &&
213 !pkt->hasSharers() &&
214 pkt->cmd != MemCmd::ReadCleanReq) {
215 // we can give the requester a writable copy on a read
216 // request if:
217 // - we have a writable copy at this level (& below)
218 // - we don't have a pending snoop from below
219 // signaling another read request
220 // - no other cache above has a copy (otherwise it
221 // would have set hasSharers flag when
222 // snooping the packet)
223 // - the read has explicitly asked for a clean
224 // copy of the line
225 if (blk->isDirty()) {
226 // special considerations if we're owner:
227 if (!deferred_response) {
228 // respond with the line in Modified state
229 // (cacheResponding set, hasSharers not set)
230 pkt->setCacheResponding();
231
232 // if this cache is mostly inclusive, we
233 // keep the block in the Exclusive state,
234 // and pass it upwards as Modified
235 // (writable and dirty), hence we have
236 // multiple caches, all on the same path
237 // towards memory, all considering the
238 // same block writable, but only one
239 // considering it Modified
240
241 // we get away with multiple caches (on
242 // the same path to memory) considering
243 // the block writeable as we always enter
244 // the cache hierarchy through a cache,
245 // and first snoop upwards in all other
246 // branches
247 blk->status &= ~BlkDirty;
248 } else {
249 // if we're responding after our own miss,
250 // there's a window where the recipient didn't
251 // know it was getting ownership and may not
252 // have responded to snoops correctly, so we
253 // have to respond with a shared line
254 pkt->setHasSharers();
255 }
256 }
257 } else {
258 // otherwise only respond with a shared copy
259 pkt->setHasSharers();
260 }
261 }
262 } else if (pkt->isUpgrade()) {
263 // sanity check
264 assert(!pkt->hasSharers());
265
266 if (blk->isDirty()) {
267 // we were in the Owned state, and a cache above us that
268 // has the line in Shared state needs to be made aware
269 // that the data it already has is in fact dirty
270 pkt->setCacheResponding();
271 blk->status &= ~BlkDirty;
272 }
273 } else {
274 assert(pkt->isInvalidate());
275 invalidateBlock(blk);
276 DPRINTF(CacheVerbose, "%s for %s (invalidation)\n", __func__,
277 pkt->print());
278 }
279}
280
281/////////////////////////////////////////////////////
282//
283// Access path: requests coming in from the CPU side
284//
285/////////////////////////////////////////////////////
286
287bool
288Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
289 PacketList &writebacks)
290{
291 // sanity check
292 assert(pkt->isRequest());
293
294 chatty_assert(!(isReadOnly && pkt->isWrite()),
295 "Should never see a write in a read-only cache %s\n",
296 name());
297
298 DPRINTF(CacheVerbose, "%s for %s\n", __func__, pkt->print());
299
300 if (pkt->req->isUncacheable()) {
301 DPRINTF(Cache, "uncacheable: %s\n", pkt->print());
302
303 // flush and invalidate any existing block
304 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
305 if (old_blk && old_blk->isValid()) {
306 if (old_blk->isDirty() || writebackClean)
307 writebacks.push_back(writebackBlk(old_blk));
308 else
309 writebacks.push_back(cleanEvictBlk(old_blk));
310 invalidateBlock(old_blk);
311 }
312
313 blk = nullptr;
314 // lookupLatency is the latency in case the request is uncacheable.
315 lat = lookupLatency;
316 return false;
317 }
318
319 // Here lat is the value passed as parameter to accessBlock() function
320 // that can modify its value.
321 blk = tags->accessBlock(pkt->getAddr(), pkt->isSecure(), lat);
322
323 DPRINTF(Cache, "%s %s\n", pkt->print(),
324 blk ? "hit " + blk->print() : "miss");
325
326 if (pkt->req->isCacheMaintenance()) {
327 // A cache maintenance operation is always forwarded to the
328 // memory below even if the block is found in dirty state.
329
330 // We defer any changes to the state of the block until we
331 // create and mark as in service the mshr for the downstream
332 // packet.
333 return false;
334 }
335
336 if (pkt->isEviction()) {
337 // We check for presence of block in above caches before issuing
338 // Writeback or CleanEvict to write buffer. Therefore the only
339 // possible cases can be of a CleanEvict packet coming from above
340 // encountering a Writeback generated in this cache peer cache and
341 // waiting in the write buffer. Cases of upper level peer caches
342 // generating CleanEvict and Writeback or simply CleanEvict and
343 // CleanEvict almost simultaneously will be caught by snoops sent out
344 // by crossbar.
345 WriteQueueEntry *wb_entry = writeBuffer.findMatch(pkt->getAddr(),
346 pkt->isSecure());
347 if (wb_entry) {
348 assert(wb_entry->getNumTargets() == 1);
349 PacketPtr wbPkt = wb_entry->getTarget()->pkt;
350 assert(wbPkt->isWriteback());
351
352 if (pkt->isCleanEviction()) {
353 // The CleanEvict and WritebackClean snoops into other
354 // peer caches of the same level while traversing the
355 // crossbar. If a copy of the block is found, the
356 // packet is deleted in the crossbar. Hence, none of
357 // the other upper level caches connected to this
358 // cache have the block, so we can clear the
359 // BLOCK_CACHED flag in the Writeback if set and
360 // discard the CleanEvict by returning true.
361 wbPkt->clearBlockCached();
362 return true;
363 } else {
364 assert(pkt->cmd == MemCmd::WritebackDirty);
365 // Dirty writeback from above trumps our clean
366 // writeback... discard here
367 // Note: markInService will remove entry from writeback buffer.
368 markInService(wb_entry);
369 delete wbPkt;
370 }
371 }
372 }
373
374 // Writeback handling is special case. We can write the block into
375 // the cache without having a writeable copy (or any copy at all).
376 if (pkt->isWriteback()) {
377 assert(blkSize == pkt->getSize());
378
379 // we could get a clean writeback while we are having
380 // outstanding accesses to a block, do the simple thing for
381 // now and drop the clean writeback so that we do not upset
382 // any ordering/decisions about ownership already taken
383 if (pkt->cmd == MemCmd::WritebackClean &&
384 mshrQueue.findMatch(pkt->getAddr(), pkt->isSecure())) {
385 DPRINTF(Cache, "Clean writeback %#llx to block with MSHR, "
386 "dropping\n", pkt->getAddr());
387 return true;
388 }
389
390 if (blk == nullptr) {
391 // need to do a replacement
392 blk = allocateBlock(pkt->getAddr(), pkt->isSecure(), writebacks);
393 if (blk == nullptr) {
394 // no replaceable block available: give up, fwd to next level.
395 incMissCount(pkt);
396 return false;
397 }
398 tags->insertBlock(pkt, blk);
399
400 blk->status = (BlkValid | BlkReadable);
401 if (pkt->isSecure()) {
402 blk->status |= BlkSecure;
403 }
404 }
405 // only mark the block dirty if we got a writeback command,
406 // and leave it as is for a clean writeback
407 if (pkt->cmd == MemCmd::WritebackDirty) {
408 assert(!blk->isDirty());
409 blk->status |= BlkDirty;
410 }
411 // if the packet does not have sharers, it is passing
412 // writable, and we got the writeback in Modified or Exclusive
413 // state, if not we are in the Owned or Shared state
414 if (!pkt->hasSharers()) {
415 blk->status |= BlkWritable;
416 }
417 // nothing else to do; writeback doesn't expect response
418 assert(!pkt->needsResponse());
419 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
420 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
421 incHitCount(pkt);
422 return true;
423 } else if (pkt->cmd == MemCmd::CleanEvict) {
424 if (blk != nullptr) {
425 // Found the block in the tags, need to stop CleanEvict from
426 // propagating further down the hierarchy. Returning true will
427 // treat the CleanEvict like a satisfied write request and delete
428 // it.
429 return true;
430 }
431 // We didn't find the block here, propagate the CleanEvict further
432 // down the memory hierarchy. Returning false will treat the CleanEvict
433 // like a Writeback which could not find a replaceable block so has to
434 // go to next level.
435 return false;
436 } else if (pkt->cmd == MemCmd::WriteClean) {
437 // WriteClean handling is a special case. We can allocate a
438 // block directly if it doesn't exist and we can update the
439 // block immediately. The WriteClean transfers the ownership
440 // of the block as well.
441 assert(blkSize == pkt->getSize());
442
443 if (!blk) {
444 if (pkt->writeThrough()) {
445 // if this is a write through packet, we don't try to
446 // allocate if the block is not present
447 return false;
448 } else {
449 // a writeback that misses needs to allocate a new block
450 blk = allocateBlock(pkt->getAddr(), pkt->isSecure(),
451 writebacks);
452 if (!blk) {
453 // no replaceable block available: give up, fwd to
454 // next level.
455 incMissCount(pkt);
456 return false;
457 }
458 tags->insertBlock(pkt, blk);
459
460 blk->status = (BlkValid | BlkReadable);
461 if (pkt->isSecure()) {
462 blk->status |= BlkSecure;
463 }
464 }
465 }
466
467 // at this point either this is a writeback or a write-through
468 // write clean operation and the block is already in this
469 // cache, we need to update the data and the block flags
470 assert(blk);
471 assert(!blk->isDirty());
472 if (!pkt->writeThrough()) {
473 blk->status |= BlkDirty;
474 }
475 // nothing else to do; writeback doesn't expect response
476 assert(!pkt->needsResponse());
477 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
478 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
479
480 incHitCount(pkt);
481 // populate the time when the block will be ready to access.
482 blk->whenReady = clockEdge(fillLatency) + pkt->headerDelay +
483 pkt->payloadDelay;
484 // if this a write-through packet it will be sent to cache
485 // below
486 return !pkt->writeThrough();
487 } else if (blk && (pkt->needsWritable() ? blk->isWritable() :
488 blk->isReadable())) {
489 // OK to satisfy access
490 incHitCount(pkt);
491 satisfyRequest(pkt, blk);
492 maintainClusivity(pkt->fromCache(), blk);
493
494 return true;
495 }
496
497 // Can't satisfy access normally... either no block (blk == nullptr)
498 // or have block but need writable
499
500 incMissCount(pkt);
501
502 if (blk == nullptr && pkt->isLLSC() && pkt->isWrite()) {
503 // complete miss on store conditional... just give up now
504 pkt->req->setExtraData(0);
505 return true;
506 }
507
508 return false;
509}
510
511void
512Cache::maintainClusivity(bool from_cache, CacheBlk *blk)
513{
514 if (from_cache && blk && blk->isValid() && !blk->isDirty() &&
515 clusivity == Enums::mostly_excl) {
516 // if we have responded to a cache, and our block is still
517 // valid, but not dirty, and this cache is mostly exclusive
518 // with respect to the cache above, drop the block
519 invalidateBlock(blk);
520 }
521}
522
523void
524Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
525{
526 while (!writebacks.empty()) {
527 PacketPtr wbPkt = writebacks.front();
528 // We use forwardLatency here because we are copying writebacks to
529 // write buffer.
530
531 // Call isCachedAbove for Writebacks, CleanEvicts and
532 // WriteCleans to discover if the block is cached above.
533 if (isCachedAbove(wbPkt)) {
534 if (wbPkt->cmd == MemCmd::CleanEvict) {
535 // Delete CleanEvict because cached copies exist above. The
536 // packet destructor will delete the request object because
537 // this is a non-snoop request packet which does not require a
538 // response.
539 delete wbPkt;
540 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
541 // clean writeback, do not send since the block is
542 // still cached above
543 assert(writebackClean);
544 delete wbPkt;
545 } else {
546 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
547 wbPkt->cmd == MemCmd::WriteClean);
548 // Set BLOCK_CACHED flag in Writeback and send below, so that
549 // the Writeback does not reset the bit corresponding to this
550 // address in the snoop filter below.
551 wbPkt->setBlockCached();
552 allocateWriteBuffer(wbPkt, forward_time);
553 }
554 } else {
555 // If the block is not cached above, send packet below. Both
556 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
557 // reset the bit corresponding to this address in the snoop filter
558 // below.
559 allocateWriteBuffer(wbPkt, forward_time);
560 }
561 writebacks.pop_front();
562 }
563}
564
565void
566Cache::doWritebacksAtomic(PacketList& writebacks)
567{
568 while (!writebacks.empty()) {
569 PacketPtr wbPkt = writebacks.front();
570 // Call isCachedAbove for both Writebacks and CleanEvicts. If
571 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
572 // and discard CleanEvicts.
573 if (isCachedAbove(wbPkt, false)) {
574 if (wbPkt->cmd == MemCmd::WritebackDirty ||
575 wbPkt->cmd == MemCmd::WriteClean) {
576 // Set BLOCK_CACHED flag in Writeback and send below,
577 // so that the Writeback does not reset the bit
578 // corresponding to this address in the snoop filter
579 // below. We can discard CleanEvicts because cached
580 // copies exist above. Atomic mode isCachedAbove
581 // modifies packet to set BLOCK_CACHED flag
582 memSidePort->sendAtomic(wbPkt);
583 }
584 } else {
585 // If the block is not cached above, send packet below. Both
586 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
587 // reset the bit corresponding to this address in the snoop filter
588 // below.
589 memSidePort->sendAtomic(wbPkt);
590 }
591 writebacks.pop_front();
592 // In case of CleanEvicts, the packet destructor will delete the
593 // request object because this is a non-snoop request packet which
594 // does not require a response.
595 delete wbPkt;
596 }
597}
598
599
600void
601Cache::recvTimingSnoopResp(PacketPtr pkt)
602{
603 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
604
605 assert(pkt->isResponse());
606 assert(!system->bypassCaches());
607
608 // determine if the response is from a snoop request we created
609 // (in which case it should be in the outstandingSnoop), or if we
610 // merely forwarded someone else's snoop request
611 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
612 outstandingSnoop.end();
613
614 if (!forwardAsSnoop) {
615 // the packet came from this cache, so sink it here and do not
616 // forward it
617 assert(pkt->cmd == MemCmd::HardPFResp);
618
619 outstandingSnoop.erase(pkt->req);
620
621 DPRINTF(Cache, "Got prefetch response from above for addr "
622 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
623 recvTimingResp(pkt);
624 return;
625 }
626
627 // forwardLatency is set here because there is a response from an
628 // upper level cache.
629 // To pay the delay that occurs if the packet comes from the bus,
630 // we charge also headerDelay.
631 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
632 // Reset the timing of the packet.
633 pkt->headerDelay = pkt->payloadDelay = 0;
634 memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time);
635}
636
637void
638Cache::promoteWholeLineWrites(PacketPtr pkt)
639{
640 // Cache line clearing instructions
641 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
642 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
643 pkt->cmd = MemCmd::WriteLineReq;
644 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
645 }
646}
647
648bool
649Cache::recvTimingReq(PacketPtr pkt)
650{
651 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
652
653 assert(pkt->isRequest());
654
655 // Just forward the packet if caches are disabled.
656 if (system->bypassCaches()) {
657 // @todo This should really enqueue the packet rather
658 bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt);
659 assert(success);
660 return true;
661 }
662
663 promoteWholeLineWrites(pkt);
664
665 // Cache maintenance operations have to visit all the caches down
666 // to the specified xbar (PoC, PoU, etc.). Even if a cache above
667 // is responding we forward the packet to the memory below rather
668 // than creating an express snoop.
669 if (pkt->cacheResponding()) {
670 // a cache above us (but not where the packet came from) is
671 // responding to the request, in other words it has the line
672 // in Modified or Owned state
673 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
674 pkt->print());
675
676 // if the packet needs the block to be writable, and the cache
677 // that has promised to respond (setting the cache responding
678 // flag) is not providing writable (it is in Owned rather than
679 // the Modified state), we know that there may be other Shared
680 // copies in the system; go out and invalidate them all
681 assert(pkt->needsWritable() && !pkt->responderHadWritable());
682
683 // an upstream cache that had the line in Owned state
684 // (dirty, but not writable), is responding and thus
685 // transferring the dirty line from one branch of the
686 // cache hierarchy to another
687
688 // send out an express snoop and invalidate all other
689 // copies (snooping a packet that needs writable is the
690 // same as an invalidation), thus turning the Owned line
691 // into a Modified line, note that we don't invalidate the
692 // block in the current cache or any other cache on the
693 // path to memory
694
695 // create a downstream express snoop with cleared packet
696 // flags, there is no need to allocate any data as the
697 // packet is merely used to co-ordinate state transitions
698 Packet *snoop_pkt = new Packet(pkt, true, false);
699
700 // also reset the bus time that the original packet has
701 // not yet paid for
702 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
703
704 // make this an instantaneous express snoop, and let the
705 // other caches in the system know that the another cache
706 // is responding, because we have found the authorative
707 // copy (Modified or Owned) that will supply the right
708 // data
709 snoop_pkt->setExpressSnoop();
710 snoop_pkt->setCacheResponding();
711
712 // this express snoop travels towards the memory, and at
713 // every crossbar it is snooped upwards thus reaching
714 // every cache in the system
715 bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt);
716 // express snoops always succeed
717 assert(success);
718
719 // main memory will delete the snoop packet
720
721 // queue for deletion, as opposed to immediate deletion, as
722 // the sending cache is still relying on the packet
723 pendingDelete.reset(pkt);
724
725 // no need to take any further action in this particular cache
726 // as an upstram cache has already committed to responding,
727 // and we have already sent out any express snoops in the
728 // section above to ensure all other copies in the system are
729 // invalidated
730 return true;
731 }
732
733 // anything that is merely forwarded pays for the forward latency and
734 // the delay provided by the crossbar
735 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
736
737 // We use lookupLatency here because it is used to specify the latency
738 // to access.
739 Cycles lat = lookupLatency;
740 CacheBlk *blk = nullptr;
741 bool satisfied = false;
742 {
743 PacketList writebacks;
744 // Note that lat is passed by reference here. The function
745 // access() calls accessBlock() which can modify lat value.
746 satisfied = access(pkt, blk, lat, writebacks);
747
748 // copy writebacks to write buffer here to ensure they logically
749 // proceed anything happening below
750 doWritebacks(writebacks, forward_time);
751 }
752
753 // Here we charge the headerDelay that takes into account the latencies
754 // of the bus, if the packet comes from it.
755 // The latency charged it is just lat that is the value of lookupLatency
756 // modified by access() function, or if not just lookupLatency.
757 // In case of a hit we are neglecting response latency.
758 // In case of a miss we are neglecting forward latency.
759 Tick request_time = clockEdge(lat) + pkt->headerDelay;
760 // Here we reset the timing of the packet.
761 pkt->headerDelay = pkt->payloadDelay = 0;
762
763 // track time of availability of next prefetch, if any
764 Tick next_pf_time = MaxTick;
765
766 bool needsResponse = pkt->needsResponse();
767
768 if (satisfied) {
769 // should never be satisfying an uncacheable access as we
770 // flush and invalidate any existing block as part of the
771 // lookup
772 assert(!pkt->req->isUncacheable());
773
774 // hit (for all other request types)
775
776 if (prefetcher && (prefetchOnAccess ||
777 (blk && blk->wasPrefetched()))) {
778 if (blk)
779 blk->status &= ~BlkHWPrefetched;
780
781 // Don't notify on SWPrefetch
782 if (!pkt->cmd.isSWPrefetch()) {
783 assert(!pkt->req->isCacheMaintenance());
784 next_pf_time = prefetcher->notify(pkt);
785 }
786 }
787
788 if (needsResponse) {
789 pkt->makeTimingResponse();
790 // @todo: Make someone pay for this
791 pkt->headerDelay = pkt->payloadDelay = 0;
792
793 // In this case we are considering request_time that takes
794 // into account the delay of the xbar, if any, and just
795 // lat, neglecting responseLatency, modelling hit latency
796 // just as lookupLatency or or the value of lat overriden
797 // by access(), that calls accessBlock() function.
798 cpuSidePort->schedTimingResp(pkt, request_time, true);
799 } else {
800 DPRINTF(Cache, "%s satisfied %s, no response needed\n", __func__,
801 pkt->print());
802
803 // queue the packet for deletion, as the sending cache is
804 // still relying on it; if the block is found in access(),
805 // CleanEvict and Writeback messages will be deleted
806 // here as well
807 pendingDelete.reset(pkt);
808 }
809 } else {
810 // miss
811
812 Addr blk_addr = pkt->getBlockAddr(blkSize);
813
814 // ignore any existing MSHR if we are dealing with an
815 // uncacheable request
816 MSHR *mshr = pkt->req->isUncacheable() ? nullptr :
817 mshrQueue.findMatch(blk_addr, pkt->isSecure());
818
819 // Software prefetch handling:
820 // To keep the core from waiting on data it won't look at
821 // anyway, send back a response with dummy data. Miss handling
822 // will continue asynchronously. Unfortunately, the core will
823 // insist upon freeing original Packet/Request, so we have to
824 // create a new pair with a different lifecycle. Note that this
825 // processing happens before any MSHR munging on the behalf of
826 // this request because this new Request will be the one stored
827 // into the MSHRs, not the original.
828 if (pkt->cmd.isSWPrefetch()) {
829 assert(needsResponse);
830 assert(pkt->req->hasPaddr());
831 assert(!pkt->req->isUncacheable());
832
833 // There's no reason to add a prefetch as an additional target
834 // to an existing MSHR. If an outstanding request is already
835 // in progress, there is nothing for the prefetch to do.
836 // If this is the case, we don't even create a request at all.
837 PacketPtr pf = nullptr;
838
839 if (!mshr) {
840 // copy the request and create a new SoftPFReq packet
841 RequestPtr req = new Request(pkt->req->getPaddr(),
842 pkt->req->getSize(),
843 pkt->req->getFlags(),
844 pkt->req->masterId());
845 pf = new Packet(req, pkt->cmd);
846 pf->allocate();
847 assert(pf->getAddr() == pkt->getAddr());
848 assert(pf->getSize() == pkt->getSize());
849 }
850
851 pkt->makeTimingResponse();
852
853 // request_time is used here, taking into account lat and the delay
854 // charged if the packet comes from the xbar.
855 cpuSidePort->schedTimingResp(pkt, request_time, true);
856
857 // If an outstanding request is in progress (we found an
858 // MSHR) this is set to null
859 pkt = pf;
860 }
861
862 if (mshr) {
863 /// MSHR hit
864 /// @note writebacks will be checked in getNextMSHR()
865 /// for any conflicting requests to the same block
866
867 //@todo remove hw_pf here
868
869 // Coalesce unless it was a software prefetch (see above).
870 if (pkt) {
871 assert(!pkt->isWriteback());
872 // CleanEvicts corresponding to blocks which have
873 // outstanding requests in MSHRs are simply sunk here
874 if (pkt->cmd == MemCmd::CleanEvict) {
875 pendingDelete.reset(pkt);
876 } else if (pkt->cmd == MemCmd::WriteClean) {
877 // A WriteClean should never coalesce with any
878 // outstanding cache maintenance requests.
879
880 // We use forward_time here because there is an
881 // uncached memory write, forwarded to WriteBuffer.
882 allocateWriteBuffer(pkt, forward_time);
883 } else {
884 DPRINTF(Cache, "%s coalescing MSHR for %s\n", __func__,
885 pkt->print());
886
887 assert(pkt->req->masterId() < system->maxMasters());
888 mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
889 // We use forward_time here because it is the same
890 // considering new targets. We have multiple
891 // requests for the same address here. It
892 // specifies the latency to allocate an internal
893 // buffer and to schedule an event to the queued
894 // port and also takes into account the additional
895 // delay of the xbar.
896 mshr->allocateTarget(pkt, forward_time, order++,
897 allocOnFill(pkt->cmd));
898 if (mshr->getNumTargets() == numTarget) {
899 noTargetMSHR = mshr;
900 setBlocked(Blocked_NoTargets);
901 // need to be careful with this... if this mshr isn't
902 // ready yet (i.e. time > curTick()), we don't want to
903 // move it ahead of mshrs that are ready
904 // mshrQueue.moveToFront(mshr);
905 }
906 }
907 // We should call the prefetcher reguardless if the request is
908 // satisfied or not, reguardless if the request is in the MSHR
909 // or not. The request could be a ReadReq hit, but still not
910 // satisfied (potentially because of a prior write to the same
911 // cache line. So, even when not satisfied, tehre is an MSHR
912 // already allocated for this, we need to let the prefetcher
913 // know about the request
914 if (prefetcher) {
915 // Don't notify on SWPrefetch
916 if (!pkt->cmd.isSWPrefetch() &&
917 !pkt->req->isCacheMaintenance())
918 next_pf_time = prefetcher->notify(pkt);
919 }
920 }
921 } else {
922 // no MSHR
923 assert(pkt->req->masterId() < system->maxMasters());
924 if (pkt->req->isUncacheable()) {
925 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
926 } else {
927 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
928 }
929
930 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
931 (pkt->req->isUncacheable() && pkt->isWrite())) {
932 // We use forward_time here because there is an
933 // uncached memory write, forwarded to WriteBuffer.
934 allocateWriteBuffer(pkt, forward_time);
935 } else {
936 if (blk && blk->isValid()) {
937 // should have flushed and have no valid block
938 assert(!pkt->req->isUncacheable());
939
940 // If we have a write miss to a valid block, we
941 // need to mark the block non-readable. Otherwise
942 // if we allow reads while there's an outstanding
943 // write miss, the read could return stale data
944 // out of the cache block... a more aggressive
945 // system could detect the overlap (if any) and
946 // forward data out of the MSHRs, but we don't do
947 // that yet. Note that we do need to leave the
948 // block valid so that it stays in the cache, in
949 // case we get an upgrade response (and hence no
950 // new data) when the write miss completes.
951 // As long as CPUs do proper store/load forwarding
952 // internally, and have a sufficiently weak memory
953 // model, this is probably unnecessary, but at some
954 // point it must have seemed like we needed it...
955 assert((pkt->needsWritable() && !blk->isWritable()) ||
956 pkt->req->isCacheMaintenance());
957 blk->status &= ~BlkReadable;
958 }
959 // Here we are using forward_time, modelling the latency of
960 // a miss (outbound) just as forwardLatency, neglecting the
961 // lookupLatency component.
962 allocateMissBuffer(pkt, forward_time);
963 }
964
965 if (prefetcher) {
966 // Don't notify on SWPrefetch
967 if (!pkt->cmd.isSWPrefetch() &&
968 !pkt->req->isCacheMaintenance())
969 next_pf_time = prefetcher->notify(pkt);
970 }
971 }
972 }
973
974 if (next_pf_time != MaxTick)
975 schedMemSideSendEvent(next_pf_time);
976
977 return true;
978}
979
980PacketPtr
981Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
982 bool needsWritable) const
983{
984 // should never see evictions here
985 assert(!cpu_pkt->isEviction());
986
987 bool blkValid = blk && blk->isValid();
988
989 if (cpu_pkt->req->isUncacheable() ||
990 (!blkValid && cpu_pkt->isUpgrade()) ||
991 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
992 // uncacheable requests and upgrades from upper-level caches
993 // that missed completely just go through as is
994 return nullptr;
995 }
996
997 assert(cpu_pkt->needsResponse());
998
999 MemCmd cmd;
1000 // @TODO make useUpgrades a parameter.
1001 // Note that ownership protocols require upgrade, otherwise a
1002 // write miss on a shared owned block will generate a ReadExcl,
1003 // which will clobber the owned copy.
1004 const bool useUpgrades = true;
1005 if (cpu_pkt->cmd == MemCmd::WriteLineReq) {
1006 assert(!blkValid || !blk->isWritable());
1007 // forward as invalidate to all other caches, this gives us
1008 // the line in Exclusive state, and invalidates all other
1009 // copies
1010 cmd = MemCmd::InvalidateReq;
1011 } else if (blkValid && useUpgrades) {
1012 // only reason to be here is that blk is read only and we need
1013 // it to be writable
1014 assert(needsWritable);
1015 assert(!blk->isWritable());
1016 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
1017 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
1018 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
1019 // Even though this SC will fail, we still need to send out the
1020 // request and get the data to supply it to other snoopers in the case
1021 // where the determination the StoreCond fails is delayed due to
1022 // all caches not being on the same local bus.
1023 cmd = MemCmd::SCUpgradeFailReq;
1024 } else {
1025 // block is invalid
1026
1027 // If the request does not need a writable there are two cases
1028 // where we need to ensure the response will not fetch the
1029 // block in dirty state:
1030 // * this cache is read only and it does not perform
1031 // writebacks,
1032 // * this cache is mostly exclusive and will not fill (since
1033 // it does not fill it will have to writeback the dirty data
1034 // immediately which generates uneccesary writebacks).
1035 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
1036 cmd = needsWritable ? MemCmd::ReadExReq :
1037 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
1038 }
1039 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
1040
1041 // if there are upstream caches that have already marked the
1042 // packet as having sharers (not passing writable), pass that info
1043 // downstream
1044 if (cpu_pkt->hasSharers() && !needsWritable) {
1045 // note that cpu_pkt may have spent a considerable time in the
1046 // MSHR queue and that the information could possibly be out
1047 // of date, however, there is no harm in conservatively
1048 // assuming the block has sharers
1049 pkt->setHasSharers();
1050 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
1051 __func__, cpu_pkt->print(), pkt->print());
1052 }
1053
1054 // the packet should be block aligned
1055 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
1056
1057 pkt->allocate();
1058 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
1059 cpu_pkt->print());
1060 return pkt;
1061}
1062
1063
1064Tick
1065Cache::recvAtomic(PacketPtr pkt)
1066{
1067 // We are in atomic mode so we pay just for lookupLatency here.
1068 Cycles lat = lookupLatency;
1069
1070 // Forward the request if the system is in cache bypass mode.
1071 if (system->bypassCaches())
1072 return ticksToCycles(memSidePort->sendAtomic(pkt));
1073
1074 promoteWholeLineWrites(pkt);
1075
1076 // follow the same flow as in recvTimingReq, and check if a cache
1077 // above us is responding
1078 if (pkt->cacheResponding() && !pkt->isClean()) {
1079 assert(!pkt->req->isCacheInvalidate());
1080 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
1081 pkt->print());
1082
1083 // if a cache is responding, and it had the line in Owned
1084 // rather than Modified state, we need to invalidate any
1085 // copies that are not on the same path to memory
1086 assert(pkt->needsWritable() && !pkt->responderHadWritable());
1087 lat += ticksToCycles(memSidePort->sendAtomic(pkt));
1088
1089 return lat * clockPeriod();
1090 }
1091
1092 // should assert here that there are no outstanding MSHRs or
1093 // writebacks... that would mean that someone used an atomic
1094 // access in timing mode
1095
1096 CacheBlk *blk = nullptr;
1097 PacketList writebacks;
1098 bool satisfied = access(pkt, blk, lat, writebacks);
1099
1100 if (pkt->isClean() && blk && blk->isDirty()) {
1101 // A cache clean opearation is looking for a dirty
1102 // block. If a dirty block is encountered a WriteClean
1103 // will update any copies to the path to the memory
1104 // until the point of reference.
1105 DPRINTF(CacheVerbose, "%s: packet %s found block: %s\n",
1106 __func__, pkt->print(), blk->print());
1107 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1108 writebacks.push_back(wb_pkt);
1109 pkt->setSatisfied();
1110 }
1111
1112 // handle writebacks resulting from the access here to ensure they
1113 // logically proceed anything happening below
1114 doWritebacksAtomic(writebacks);
1115
1116 if (!satisfied) {
1117 // MISS
1118
1119 // deal with the packets that go through the write path of
1120 // the cache, i.e. any evictions and writes
1121 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
1122 (pkt->req->isUncacheable() && pkt->isWrite())) {
1123 lat += ticksToCycles(memSidePort->sendAtomic(pkt));
1124 return lat * clockPeriod();
1125 }
1126 // only misses left
1127
1128 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable());
1129
1130 bool is_forward = (bus_pkt == nullptr);
1131
1132 if (is_forward) {
1133 // just forwarding the same request to the next level
1134 // no local cache operation involved
1135 bus_pkt = pkt;
1136 }
1137
1138 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
1139 bus_pkt->print());
1140
1141#if TRACING_ON
1142 CacheBlk::State old_state = blk ? blk->status : 0;
1143#endif
1144
1145 lat += ticksToCycles(memSidePort->sendAtomic(bus_pkt));
1146
1147 bool is_invalidate = bus_pkt->isInvalidate();
1148
1149 // We are now dealing with the response handling
1150 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
1151 bus_pkt->print(), old_state);
1152
1153 // If packet was a forward, the response (if any) is already
1154 // in place in the bus_pkt == pkt structure, so we don't need
1155 // to do anything. Otherwise, use the separate bus_pkt to
1156 // generate response to pkt and then delete it.
1157 if (!is_forward) {
1158 if (pkt->needsResponse()) {
1159 assert(bus_pkt->isResponse());
1160 if (bus_pkt->isError()) {
1161 pkt->makeAtomicResponse();
1162 pkt->copyError(bus_pkt);
1163 } else if (pkt->cmd == MemCmd::WriteLineReq) {
1164 // note the use of pkt, not bus_pkt here.
1165
1166 // write-line request to the cache that promoted
1167 // the write to a whole line
1168 blk = handleFill(pkt, blk, writebacks,
1169 allocOnFill(pkt->cmd));
1170 assert(blk != NULL);
1171 is_invalidate = false;
1172 satisfyRequest(pkt, blk);
1173 } else if (bus_pkt->isRead() ||
1174 bus_pkt->cmd == MemCmd::UpgradeResp) {
1175 // we're updating cache state to allow us to
1176 // satisfy the upstream request from the cache
1177 blk = handleFill(bus_pkt, blk, writebacks,
1178 allocOnFill(pkt->cmd));
1179 satisfyRequest(pkt, blk);
1180 maintainClusivity(pkt->fromCache(), blk);
1181 } else {
1182 // we're satisfying the upstream request without
1183 // modifying cache state, e.g., a write-through
1184 pkt->makeAtomicResponse();
1185 }
1186 }
1187 delete bus_pkt;
1188 }
1189
1190 if (is_invalidate && blk && blk->isValid()) {
1191 invalidateBlock(blk);
1192 }
1193 }
1194
1195 // Note that we don't invoke the prefetcher at all in atomic mode.
1196 // It's not clear how to do it properly, particularly for
1197 // prefetchers that aggressively generate prefetch candidates and
1198 // rely on bandwidth contention to throttle them; these will tend
1199 // to pollute the cache in atomic mode since there is no bandwidth
1200 // contention. If we ever do want to enable prefetching in atomic
1201 // mode, though, this is the place to do it... see timingAccess()
1202 // for an example (though we'd want to issue the prefetch(es)
1203 // immediately rather than calling requestMemSideBus() as we do
1204 // there).
1205
1206 // do any writebacks resulting from the response handling
1207 doWritebacksAtomic(writebacks);
1208
1209 // if we used temp block, check to see if its valid and if so
1210 // clear it out, but only do so after the call to recvAtomic is
1211 // finished so that any downstream observers (such as a snoop
1212 // filter), first see the fill, and only then see the eviction
1213 if (blk == tempBlock && tempBlock->isValid()) {
1214 // the atomic CPU calls recvAtomic for fetch and load/store
1215 // sequentuially, and we may already have a tempBlock
1216 // writeback from the fetch that we have not yet sent
1217 if (tempBlockWriteback) {
1218 // if that is the case, write the prevoius one back, and
1219 // do not schedule any new event
1220 writebackTempBlockAtomic();
1221 } else {
1222 // the writeback/clean eviction happens after the call to
1223 // recvAtomic has finished (but before any successive
1224 // calls), so that the response handling from the fill is
1225 // allowed to happen first
1226 schedule(writebackTempBlockAtomicEvent, curTick());
1227 }
1228
1229 tempBlockWriteback = (blk->isDirty() || writebackClean) ?
1230 writebackBlk(blk) : cleanEvictBlk(blk);
1231 invalidateBlock(blk);
1232 }
1233
1234 if (pkt->needsResponse()) {
1235 pkt->makeAtomicResponse();
1236 }
1237
1238 return lat * clockPeriod();
1239}
1240
1241
1242void
1243Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide)
1244{
1245 if (system->bypassCaches()) {
1246 // Packets from the memory side are snoop request and
1247 // shouldn't happen in bypass mode.
1248 assert(fromCpuSide);
1249
1250 // The cache should be flushed if we are in cache bypass mode,
1251 // so we don't need to check if we need to update anything.
1252 memSidePort->sendFunctional(pkt);
1253 return;
1254 }
1255
1256 Addr blk_addr = pkt->getBlockAddr(blkSize);
1257 bool is_secure = pkt->isSecure();
1258 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1259 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1260
1261 pkt->pushLabel(name());
1262
1263 CacheBlkPrintWrapper cbpw(blk);
1264
1265 // Note that just because an L2/L3 has valid data doesn't mean an
1266 // L1 doesn't have a more up-to-date modified copy that still
1267 // needs to be found. As a result we always update the request if
1268 // we have it, but only declare it satisfied if we are the owner.
1269
1270 // see if we have data at all (owned or otherwise)
1271 bool have_data = blk && blk->isValid()
1272 && pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize,
1273 blk->data);
1274
1275 // data we have is dirty if marked as such or if we have an
1276 // in-service MSHR that is pending a modified line
1277 bool have_dirty =
1278 have_data && (blk->isDirty() ||
1279 (mshr && mshr->inService && mshr->isPendingModified()));
1280
1281 bool done = have_dirty
1282 || cpuSidePort->checkFunctional(pkt)
1283 || mshrQueue.checkFunctional(pkt, blk_addr)
1284 || writeBuffer.checkFunctional(pkt, blk_addr)
1285 || memSidePort->checkFunctional(pkt);
1286
1287 DPRINTF(CacheVerbose, "%s: %s %s%s%s\n", __func__, pkt->print(),
1288 (blk && blk->isValid()) ? "valid " : "",
1289 have_data ? "data " : "", done ? "done " : "");
1290
1291 // We're leaving the cache, so pop cache->name() label
1292 pkt->popLabel();
1293
1294 if (done) {
1295 pkt->makeResponse();
1296 } else {
1297 // if it came as a request from the CPU side then make sure it
1298 // continues towards the memory side
1299 if (fromCpuSide) {
1300 memSidePort->sendFunctional(pkt);
1301 } else if (cpuSidePort->isSnooping()) {
1302 // if it came from the memory side, it must be a snoop request
1303 // and we should only forward it if we are forwarding snoops
1304 cpuSidePort->sendFunctionalSnoop(pkt);
1305 }
1306 }
1307}
1308
1309
1310/////////////////////////////////////////////////////
1311//
1312// Response handling: responses from the memory side
1313//
1314/////////////////////////////////////////////////////
1315
1316
1317void
1318Cache::handleUncacheableWriteResp(PacketPtr pkt)
1319{
1320 Tick completion_time = clockEdge(responseLatency) +
1321 pkt->headerDelay + pkt->payloadDelay;
1322
1323 // Reset the bus additional time as it is now accounted for
1324 pkt->headerDelay = pkt->payloadDelay = 0;
1325
1326 cpuSidePort->schedTimingResp(pkt, completion_time, true);
1327}
1328
1329void
1330Cache::recvTimingResp(PacketPtr pkt)
1331{
1332 assert(pkt->isResponse());
1333
1334 // all header delay should be paid for by the crossbar, unless
1335 // this is a prefetch response from above
1336 panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp,
1337 "%s saw a non-zero packet delay\n", name());
1338
1339 bool is_error = pkt->isError();
1340
1341 if (is_error) {
1342 DPRINTF(Cache, "%s: Cache received %s with error\n", __func__,
1343 pkt->print());
1344 }
1345
1346 DPRINTF(Cache, "%s: Handling response %s\n", __func__,
1347 pkt->print());
1348
1349 // if this is a write, we should be looking at an uncacheable
1350 // write
1351 if (pkt->isWrite()) {
1352 assert(pkt->req->isUncacheable());
1353 handleUncacheableWriteResp(pkt);
1354 return;
1355 }
1356
1357 // we have dealt with any (uncacheable) writes above, from here on
1358 // we know we are dealing with an MSHR due to a miss or a prefetch
1359 MSHR *mshr = dynamic_cast<MSHR*>(pkt->popSenderState());
1360 assert(mshr);
1361
1362 if (mshr == noTargetMSHR) {
1363 // we always clear at least one target
1364 clearBlocked(Blocked_NoTargets);
1365 noTargetMSHR = nullptr;
1366 }
1367
1368 // Initial target is used just for stats
1369 MSHR::Target *initial_tgt = mshr->getTarget();
1370 int stats_cmd_idx = initial_tgt->pkt->cmdToIndex();
1371 Tick miss_latency = curTick() - initial_tgt->recvTime;
1372
1373 if (pkt->req->isUncacheable()) {
1374 assert(pkt->req->masterId() < system->maxMasters());
1375 mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] +=
1376 miss_latency;
1377 } else {
1378 assert(pkt->req->masterId() < system->maxMasters());
1379 mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] +=
1380 miss_latency;
1381 }
1382
1383 bool wasFull = mshrQueue.isFull();
1384
1385 PacketList writebacks;
1386
1387 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
1388
1389 bool is_fill = !mshr->isForward &&
1390 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
1391
1392 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1393 const bool valid_blk = blk && blk->isValid();
1394 // If the response indicates that there are no sharers and we
1395 // either had the block already or the response is filling we can
1396 // promote our copy to writable
1397 if (!pkt->hasSharers() &&
1398 (is_fill || (valid_blk && !pkt->req->isCacheInvalidate()))) {
1399 mshr->promoteWritable();
1400 }
1401
1402 if (is_fill && !is_error) {
1403 DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n",
1404 pkt->getAddr());
1405
1406 blk = handleFill(pkt, blk, writebacks, mshr->allocOnFill());
1407 assert(blk != nullptr);
1408 }
1409
1410 // allow invalidation responses originating from write-line
1411 // requests to be discarded
1412 bool is_invalidate = pkt->isInvalidate();
1413
1414 // The block was marked as not readable while there was a pending
1415 // cache maintenance operation, restore its flag.
1416 if (pkt->isClean() && !is_invalidate && valid_blk) {
1417 blk->status |= BlkReadable;
1418 }
1419
1420 // First offset for critical word first calculations
1421 int initial_offset = initial_tgt->pkt->getOffset(blkSize);
1422
1423 bool from_cache = false;
1424 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
1425 for (auto &target: targets) {
1426 Packet *tgt_pkt = target.pkt;
1427 switch (target.source) {
1428 case MSHR::Target::FromCPU:
1429 Tick completion_time;
1430 // Here we charge on completion_time the delay of the xbar if the
1431 // packet comes from it, charged on headerDelay.
1432 completion_time = pkt->headerDelay;
1433
1434 // Software prefetch handling for cache closest to core
1435 if (tgt_pkt->cmd.isSWPrefetch()) {
1436 // a software prefetch would have already been ack'd
1437 // immediately with dummy data so the core would be able to
1438 // retire it. This request completes right here, so we
1439 // deallocate it.
1440 delete tgt_pkt->req;
1441 delete tgt_pkt;
1442 break; // skip response
1443 }
1444
1445 // keep track of whether we have responded to another
1446 // cache
1447 from_cache = from_cache || tgt_pkt->fromCache();
1448
1449 // unlike the other packet flows, where data is found in other
1450 // caches or memory and brought back, write-line requests always
1451 // have the data right away, so the above check for "is fill?"
1452 // cannot actually be determined until examining the stored MSHR
1453 // state. We "catch up" with that logic here, which is duplicated
1454 // from above.
1455 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
1456 assert(!is_error);
1457 // we got the block in a writable state, so promote
1458 // any deferred targets if possible
1459 mshr->promoteWritable();
1460 // NB: we use the original packet here and not the response!
1461 blk = handleFill(tgt_pkt, blk, writebacks,
1462 targets.allocOnFill);
1463 assert(blk != nullptr);
1464
1465 // treat as a fill, and discard the invalidation
1466 // response
1467 is_fill = true;
1468 is_invalidate = false;
1469 }
1470
1471 if (is_fill) {
1472 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
1473
1474 // How many bytes past the first request is this one
1475 int transfer_offset =
1476 tgt_pkt->getOffset(blkSize) - initial_offset;
1477 if (transfer_offset < 0) {
1478 transfer_offset += blkSize;
1479 }
1480
1481 // If not critical word (offset) return payloadDelay.
1482 // responseLatency is the latency of the return path
1483 // from lower level caches/memory to an upper level cache or
1484 // the core.
1485 completion_time += clockEdge(responseLatency) +
1486 (transfer_offset ? pkt->payloadDelay : 0);
1487
1488 assert(!tgt_pkt->req->isUncacheable());
1489
1490 assert(tgt_pkt->req->masterId() < system->maxMasters());
1491 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
1492 completion_time - target.recvTime;
1493 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
1494 // failed StoreCond upgrade
1495 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
1496 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
1497 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
1498 // responseLatency is the latency of the return path
1499 // from lower level caches/memory to an upper level cache or
1500 // the core.
1501 completion_time += clockEdge(responseLatency) +
1502 pkt->payloadDelay;
1503 tgt_pkt->req->setExtraData(0);
1504 } else {
1505 // We are about to send a response to a cache above
1506 // that asked for an invalidation; we need to
1507 // invalidate our copy immediately as the most
1508 // up-to-date copy of the block will now be in the
1509 // cache above. It will also prevent this cache from
1510 // responding (if the block was previously dirty) to
1511 // snoops as they should snoop the caches above where
1512 // they will get the response from.
1513 if (is_invalidate && blk && blk->isValid()) {
1514 invalidateBlock(blk);
1515 }
1516 // not a cache fill, just forwarding response
1517 // responseLatency is the latency of the return path
1518 // from lower level cahces/memory to the core.
1519 completion_time += clockEdge(responseLatency) +
1520 pkt->payloadDelay;
1521 if (pkt->isRead() && !is_error) {
1522 // sanity check
1523 assert(pkt->getAddr() == tgt_pkt->getAddr());
1524 assert(pkt->getSize() >= tgt_pkt->getSize());
1525
1526 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
1527 }
1528 }
1529 tgt_pkt->makeTimingResponse();
1530 // if this packet is an error copy that to the new packet
1531 if (is_error)
1532 tgt_pkt->copyError(pkt);
1533 if (tgt_pkt->cmd == MemCmd::ReadResp &&
1534 (is_invalidate || mshr->hasPostInvalidate())) {
1535 // If intermediate cache got ReadRespWithInvalidate,
1536 // propagate that. Response should not have
1537 // isInvalidate() set otherwise.
1538 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
1539 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
1540 tgt_pkt->print());
1541 }
1542 // Reset the bus additional time as it is now accounted for
1543 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
1544 cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true);
1545 break;
1546
1547 case MSHR::Target::FromPrefetcher:
1548 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
1549 if (blk)
1550 blk->status |= BlkHWPrefetched;
1551 delete tgt_pkt->req;
1552 delete tgt_pkt;
1553 break;
1554
1555 case MSHR::Target::FromSnoop:
1556 // I don't believe that a snoop can be in an error state
1557 assert(!is_error);
1558 // response to snoop request
1559 DPRINTF(Cache, "processing deferred snoop...\n");
1560 // If the response is invalidating, a snooping target can
1561 // be satisfied if it is also invalidating. If the reponse is, not
1562 // only invalidating, but more specifically an InvalidateResp and
1563 // the MSHR was created due to an InvalidateReq then a cache above
1564 // is waiting to satisfy a WriteLineReq. In this case even an
1565 // non-invalidating snoop is added as a target here since this is
1566 // the ordering point. When the InvalidateResp reaches this cache,
1567 // the snooping target will snoop further the cache above with the
1568 // WriteLineReq.
1569 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
1570 pkt->req->isCacheMaintenance() ||
1571 mshr->hasPostInvalidate());
1572 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
1573 break;
1574
1575 default:
1576 panic("Illegal target->source enum %d\n", target.source);
1577 }
1578 }
1579
1580 maintainClusivity(from_cache, blk);
1581
1582 if (blk && blk->isValid()) {
1583 // an invalidate response stemming from a write line request
1584 // should not invalidate the block, so check if the
1585 // invalidation should be discarded
1586 if (is_invalidate || mshr->hasPostInvalidate()) {
1587 invalidateBlock(blk);
1588 } else if (mshr->hasPostDowngrade()) {
1589 blk->status &= ~BlkWritable;
1590 }
1591 }
1592
1593 if (mshr->promoteDeferredTargets()) {
1594 // avoid later read getting stale data while write miss is
1595 // outstanding.. see comment in timingAccess()
1596 if (blk) {
1597 blk->status &= ~BlkReadable;
1598 }
1599 mshrQueue.markPending(mshr);
1600 schedMemSideSendEvent(clockEdge() + pkt->payloadDelay);
1601 } else {
1602 mshrQueue.deallocate(mshr);
1603 if (wasFull && !mshrQueue.isFull()) {
1604 clearBlocked(Blocked_NoMSHRs);
1605 }
1606
1607 // Request the bus for a prefetch if this deallocation freed enough
1608 // MSHRs for a prefetch to take place
1609 if (prefetcher && mshrQueue.canPrefetch()) {
1610 Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(),
1611 clockEdge());
1612 if (next_pf_time != MaxTick)
1613 schedMemSideSendEvent(next_pf_time);
1614 }
1615 }
1616 // reset the xbar additional timinig as it is now accounted for
1617 pkt->headerDelay = pkt->payloadDelay = 0;
1618
1619 // copy writebacks to write buffer
1620 doWritebacks(writebacks, forward_time);
1621
1622 // if we used temp block, check to see if its valid and then clear it out
1623 if (blk == tempBlock && tempBlock->isValid()) {
1624 // We use forwardLatency here because we are copying
1625 // Writebacks/CleanEvicts to write buffer. It specifies the latency to
1626 // allocate an internal buffer and to schedule an event to the
1627 // queued port.
1628 if (blk->isDirty() || writebackClean) {
1629 PacketPtr wbPkt = writebackBlk(blk);
1630 allocateWriteBuffer(wbPkt, forward_time);
1631 // Set BLOCK_CACHED flag if cached above.
1632 if (isCachedAbove(wbPkt))
1633 wbPkt->setBlockCached();
1634 } else {
1635 PacketPtr wcPkt = cleanEvictBlk(blk);
1636 // Check to see if block is cached above. If not allocate
1637 // write buffer
1638 if (isCachedAbove(wcPkt))
1639 delete wcPkt;
1640 else
1641 allocateWriteBuffer(wcPkt, forward_time);
1642 }
1643 invalidateBlock(blk);
1644 }
1645
1646 DPRINTF(CacheVerbose, "%s: Leaving with %s\n", __func__, pkt->print());
1647 delete pkt;
1648}
1649
1650PacketPtr
1651Cache::writebackBlk(CacheBlk *blk)
1652{
1653 chatty_assert(!isReadOnly || writebackClean,
1654 "Writeback from read-only cache");
1655 assert(blk && blk->isValid() && (blk->isDirty() || writebackClean));
1656
1657 writebacks[Request::wbMasterId]++;
1658
1659 Request *req = new Request(tags->regenerateBlkAddr(blk->tag, blk->set),
1660 blkSize, 0, Request::wbMasterId);
1661 if (blk->isSecure())
1662 req->setFlags(Request::SECURE);
1663
1664 req->taskId(blk->task_id);
1665
1666 PacketPtr pkt =
1667 new Packet(req, blk->isDirty() ?
1668 MemCmd::WritebackDirty : MemCmd::WritebackClean);
1669
1670 DPRINTF(Cache, "Create Writeback %s writable: %d, dirty: %d\n",
1671 pkt->print(), blk->isWritable(), blk->isDirty());
1672
1673 if (blk->isWritable()) {
1674 // not asserting shared means we pass the block in modified
1675 // state, mark our own block non-writeable
1676 blk->status &= ~BlkWritable;
1677 } else {
1678 // we are in the Owned state, tell the receiver
1679 pkt->setHasSharers();
1680 }
1681
1682 // make sure the block is not marked dirty
1683 blk->status &= ~BlkDirty;
1684
1685 pkt->allocate();
1686 std::memcpy(pkt->getPtr<uint8_t>(), blk->data, blkSize);
1687
1688 return pkt;
1689}
1690
1691PacketPtr
1692Cache::writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id)
1693{
1694 Request *req = new Request(tags->regenerateBlkAddr(blk->tag, blk->set),
1695 blkSize, 0, Request::wbMasterId);
1696 if (blk->isSecure()) {
1697 req->setFlags(Request::SECURE);
1698 }
1699 req->taskId(blk->task_id);
1700
1701 PacketPtr pkt = new Packet(req, MemCmd::WriteClean, blkSize, id);
1702
1703 if (dest) {
1704 req->setFlags(dest);
1705 pkt->setWriteThrough();
1706 }
1707
1708 DPRINTF(Cache, "Create %s writable: %d, dirty: %d\n", pkt->print(),
1709 blk->isWritable(), blk->isDirty());
1710
1711 if (blk->isWritable()) {
1712 // not asserting shared means we pass the block in modified
1713 // state, mark our own block non-writeable
1714 blk->status &= ~BlkWritable;
1715 } else {
1716 // we are in the Owned state, tell the receiver
1717 pkt->setHasSharers();
1718 }
1719
1720 // make sure the block is not marked dirty
1721 blk->status &= ~BlkDirty;
1722
1723 pkt->allocate();
1724 std::memcpy(pkt->getPtr<uint8_t>(), blk->data, blkSize);
1725
1726 return pkt;
1727}
1728
1729
1730PacketPtr
1731Cache::cleanEvictBlk(CacheBlk *blk)
1732{
1733 assert(!writebackClean);
1734 assert(blk && blk->isValid() && !blk->isDirty());
1735 // Creating a zero sized write, a message to the snoop filter
1736 Request *req =
1737 new Request(tags->regenerateBlkAddr(blk->tag, blk->set), blkSize, 0,
1738 Request::wbMasterId);
1739 if (blk->isSecure())
1740 req->setFlags(Request::SECURE);
1741
1742 req->taskId(blk->task_id);
1743
1744 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
1745 pkt->allocate();
1746 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
1747
1748 return pkt;
1749}
1750
1751void
1752Cache::memWriteback()
1753{
1754 CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor);
1755 tags->forEachBlk(visitor);
1756}
1757
1758void
1759Cache::memInvalidate()
1760{
1761 CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor);
1762 tags->forEachBlk(visitor);
1763}
1764
1765bool
1766Cache::isDirty() const
1767{
1768 CacheBlkIsDirtyVisitor visitor;
1769 tags->forEachBlk(visitor);
1770
1771 return visitor.isDirty();
1772}
1773
1774bool
1775Cache::writebackVisitor(CacheBlk &blk)
1776{
1777 if (blk.isDirty()) {
1778 assert(blk.isValid());
1779
1780 Request request(tags->regenerateBlkAddr(blk.tag, blk.set),
1781 blkSize, 0, Request::funcMasterId);
1782 request.taskId(blk.task_id);
1783 if (blk.isSecure()) {
1784 request.setFlags(Request::SECURE);
1785 }
1786
1787 Packet packet(&request, MemCmd::WriteReq);
1788 packet.dataStatic(blk.data);
1789
1790 memSidePort->sendFunctional(&packet);
1791
1792 blk.status &= ~BlkDirty;
1793 }
1794
1795 return true;
1796}
1797
1798bool
1799Cache::invalidateVisitor(CacheBlk &blk)
1800{
1801
1802 if (blk.isDirty())
1803 warn_once("Invalidating dirty cache lines. Expect things to break.\n");
1804
1805 if (blk.isValid()) {
1806 assert(!blk.isDirty());
1807 invalidateBlock(&blk);
1808 }
1809
1810 return true;
1811}
1812
1813CacheBlk*
1814Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks)
1815{
1816 CacheBlk *blk = tags->findVictim(addr);
1817
1818 // It is valid to return nullptr if there is no victim
1819 if (!blk)
1820 return nullptr;
1821
1822 if (blk->isValid()) {
1823 Addr repl_addr = tags->regenerateBlkAddr(blk->tag, blk->set);
1824 MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
1825 if (repl_mshr) {
1826 // must be an outstanding upgrade request
1827 // on a block we're about to replace...
1828 assert(!blk->isWritable() || blk->isDirty());
1829 assert(repl_mshr->needsWritable());
1830 // too hard to replace block with transient state
1831 // allocation failed, block not inserted
1832 return nullptr;
1833 } else {
1834 DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx "
1835 "(%s): %s\n", repl_addr, blk->isSecure() ? "s" : "ns",
1836 addr, is_secure ? "s" : "ns",
1837 blk->isDirty() ? "writeback" : "clean");
1838
1839 if (blk->wasPrefetched()) {
1840 unusedPrefetches++;
1841 }
1842 // Will send up Writeback/CleanEvict snoops via isCachedAbove
1843 // when pushing this writeback list into the write buffer.
1844 if (blk->isDirty() || writebackClean) {
1845 // Save writeback packet for handling by caller
1846 writebacks.push_back(writebackBlk(blk));
1847 } else {
1848 writebacks.push_back(cleanEvictBlk(blk));
1849 }
1850 }
1851 }
1852
1853 return blk;
1854}
1855
1856void
1857Cache::invalidateBlock(CacheBlk *blk)
1858{
1859 if (blk != tempBlock)
1860 tags->invalidate(blk);
1861 blk->invalidate();
1862}
1863
1864// Note that the reason we return a list of writebacks rather than
1865// inserting them directly in the write buffer is that this function
1866// is called by both atomic and timing-mode accesses, and in atomic
1867// mode we don't mess with the write buffer (we just perform the
1868// writebacks atomically once the original request is complete).
1869CacheBlk*
1870Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks,
1871 bool allocate)
1872{
1873 assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq);
1874 Addr addr = pkt->getAddr();
1875 bool is_secure = pkt->isSecure();
1876#if TRACING_ON
1877 CacheBlk::State old_state = blk ? blk->status : 0;
1878#endif
1879
1880 // When handling a fill, we should have no writes to this line.
1881 assert(addr == pkt->getBlockAddr(blkSize));
1882 assert(!writeBuffer.findMatch(addr, is_secure));
1883
1884 if (blk == nullptr) {
1885 // better have read new data...
1886 assert(pkt->hasData());
1887
1888 // only read responses and write-line requests have data;
1889 // note that we don't write the data here for write-line - that
1890 // happens in the subsequent call to satisfyRequest
1891 assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq);
1892
1893 // need to do a replacement if allocating, otherwise we stick
1894 // with the temporary storage
1895 blk = allocate ? allocateBlock(addr, is_secure, writebacks) : nullptr;
1896
1897 if (blk == nullptr) {
1898 // No replaceable block or a mostly exclusive
1899 // cache... just use temporary storage to complete the
1900 // current request and then get rid of it
1901 assert(!tempBlock->isValid());
1902 blk = tempBlock;
1903 tempBlock->set = tags->extractSet(addr);
1904 tempBlock->tag = tags->extractTag(addr);
| 1/*
2 * Copyright (c) 2010-2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
16 * All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions are
20 * met: redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer;
22 * redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution;
25 * neither the name of the copyright holders nor the names of its
26 * contributors may be used to endorse or promote products derived from
27 * this software without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Authors: Erik Hallnor
42 * Dave Greene
43 * Nathan Binkert
44 * Steve Reinhardt
45 * Ron Dreslinski
46 * Andreas Sandberg
47 * Nikos Nikoleris
48 */
49
50/**
51 * @file
52 * Cache definitions.
53 */
54
55#include "mem/cache/cache.hh"
56
57#include "base/logging.hh"
58#include "base/types.hh"
59#include "debug/Cache.hh"
60#include "debug/CachePort.hh"
61#include "debug/CacheTags.hh"
62#include "debug/CacheVerbose.hh"
63#include "mem/cache/blk.hh"
64#include "mem/cache/mshr.hh"
65#include "mem/cache/prefetch/base.hh"
66#include "sim/sim_exit.hh"
67
68Cache::Cache(const CacheParams *p)
69 : BaseCache(p, p->system->cacheLineSize()),
70 tags(p->tags),
71 prefetcher(p->prefetcher),
72 doFastWrites(true),
73 prefetchOnAccess(p->prefetch_on_access),
74 clusivity(p->clusivity),
75 writebackClean(p->writeback_clean),
76 tempBlockWriteback(nullptr),
77 writebackTempBlockAtomicEvent([this]{ writebackTempBlockAtomic(); },
78 name(), false,
79 EventBase::Delayed_Writeback_Pri)
80{
81 tempBlock = new CacheBlk();
82 tempBlock->data = new uint8_t[blkSize];
83
84 cpuSidePort = new CpuSidePort(p->name + ".cpu_side", this,
85 "CpuSidePort");
86 memSidePort = new MemSidePort(p->name + ".mem_side", this,
87 "MemSidePort");
88
89 tags->setCache(this);
90 if (prefetcher)
91 prefetcher->setCache(this);
92}
93
94Cache::~Cache()
95{
96 delete [] tempBlock->data;
97 delete tempBlock;
98
99 delete cpuSidePort;
100 delete memSidePort;
101}
102
103void
104Cache::regStats()
105{
106 BaseCache::regStats();
107}
108
109void
110Cache::cmpAndSwap(CacheBlk *blk, PacketPtr pkt)
111{
112 assert(pkt->isRequest());
113
114 uint64_t overwrite_val;
115 bool overwrite_mem;
116 uint64_t condition_val64;
117 uint32_t condition_val32;
118
119 int offset = tags->extractBlkOffset(pkt->getAddr());
120 uint8_t *blk_data = blk->data + offset;
121
122 assert(sizeof(uint64_t) >= pkt->getSize());
123
124 overwrite_mem = true;
125 // keep a copy of our possible write value, and copy what is at the
126 // memory address into the packet
127 pkt->writeData((uint8_t *)&overwrite_val);
128 pkt->setData(blk_data);
129
130 if (pkt->req->isCondSwap()) {
131 if (pkt->getSize() == sizeof(uint64_t)) {
132 condition_val64 = pkt->req->getExtraData();
133 overwrite_mem = !std::memcmp(&condition_val64, blk_data,
134 sizeof(uint64_t));
135 } else if (pkt->getSize() == sizeof(uint32_t)) {
136 condition_val32 = (uint32_t)pkt->req->getExtraData();
137 overwrite_mem = !std::memcmp(&condition_val32, blk_data,
138 sizeof(uint32_t));
139 } else
140 panic("Invalid size for conditional read/write\n");
141 }
142
143 if (overwrite_mem) {
144 std::memcpy(blk_data, &overwrite_val, pkt->getSize());
145 blk->status |= BlkDirty;
146 }
147}
148
149
150void
151Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
152 bool deferred_response, bool pending_downgrade)
153{
154 assert(pkt->isRequest());
155
156 assert(blk && blk->isValid());
157 // Occasionally this is not true... if we are a lower-level cache
158 // satisfying a string of Read and ReadEx requests from
159 // upper-level caches, a Read will mark the block as shared but we
160 // can satisfy a following ReadEx anyway since we can rely on the
161 // Read requester(s) to have buffered the ReadEx snoop and to
162 // invalidate their blocks after receiving them.
163 // assert(!pkt->needsWritable() || blk->isWritable());
164 assert(pkt->getOffset(blkSize) + pkt->getSize() <= blkSize);
165
166 // Check RMW operations first since both isRead() and
167 // isWrite() will be true for them
168 if (pkt->cmd == MemCmd::SwapReq) {
169 cmpAndSwap(blk, pkt);
170 } else if (pkt->isWrite()) {
171 // we have the block in a writable state and can go ahead,
172 // note that the line may be also be considered writable in
173 // downstream caches along the path to memory, but always
174 // Exclusive, and never Modified
175 assert(blk->isWritable());
176 // Write or WriteLine at the first cache with block in writable state
177 if (blk->checkWrite(pkt)) {
178 pkt->writeDataToBlock(blk->data, blkSize);
179 }
180 // Always mark the line as dirty (and thus transition to the
181 // Modified state) even if we are a failed StoreCond so we
182 // supply data to any snoops that have appended themselves to
183 // this cache before knowing the store will fail.
184 blk->status |= BlkDirty;
185 DPRINTF(CacheVerbose, "%s for %s (write)\n", __func__, pkt->print());
186 } else if (pkt->isRead()) {
187 if (pkt->isLLSC()) {
188 blk->trackLoadLocked(pkt);
189 }
190
191 // all read responses have a data payload
192 assert(pkt->hasRespData());
193 pkt->setDataFromBlock(blk->data, blkSize);
194
195 // determine if this read is from a (coherent) cache or not
196 if (pkt->fromCache()) {
197 assert(pkt->getSize() == blkSize);
198 // special handling for coherent block requests from
199 // upper-level caches
200 if (pkt->needsWritable()) {
201 // sanity check
202 assert(pkt->cmd == MemCmd::ReadExReq ||
203 pkt->cmd == MemCmd::SCUpgradeFailReq);
204 assert(!pkt->hasSharers());
205
206 // if we have a dirty copy, make sure the recipient
207 // keeps it marked dirty (in the modified state)
208 if (blk->isDirty()) {
209 pkt->setCacheResponding();
210 blk->status &= ~BlkDirty;
211 }
212 } else if (blk->isWritable() && !pending_downgrade &&
213 !pkt->hasSharers() &&
214 pkt->cmd != MemCmd::ReadCleanReq) {
215 // we can give the requester a writable copy on a read
216 // request if:
217 // - we have a writable copy at this level (& below)
218 // - we don't have a pending snoop from below
219 // signaling another read request
220 // - no other cache above has a copy (otherwise it
221 // would have set hasSharers flag when
222 // snooping the packet)
223 // - the read has explicitly asked for a clean
224 // copy of the line
225 if (blk->isDirty()) {
226 // special considerations if we're owner:
227 if (!deferred_response) {
228 // respond with the line in Modified state
229 // (cacheResponding set, hasSharers not set)
230 pkt->setCacheResponding();
231
232 // if this cache is mostly inclusive, we
233 // keep the block in the Exclusive state,
234 // and pass it upwards as Modified
235 // (writable and dirty), hence we have
236 // multiple caches, all on the same path
237 // towards memory, all considering the
238 // same block writable, but only one
239 // considering it Modified
240
241 // we get away with multiple caches (on
242 // the same path to memory) considering
243 // the block writeable as we always enter
244 // the cache hierarchy through a cache,
245 // and first snoop upwards in all other
246 // branches
247 blk->status &= ~BlkDirty;
248 } else {
249 // if we're responding after our own miss,
250 // there's a window where the recipient didn't
251 // know it was getting ownership and may not
252 // have responded to snoops correctly, so we
253 // have to respond with a shared line
254 pkt->setHasSharers();
255 }
256 }
257 } else {
258 // otherwise only respond with a shared copy
259 pkt->setHasSharers();
260 }
261 }
262 } else if (pkt->isUpgrade()) {
263 // sanity check
264 assert(!pkt->hasSharers());
265
266 if (blk->isDirty()) {
267 // we were in the Owned state, and a cache above us that
268 // has the line in Shared state needs to be made aware
269 // that the data it already has is in fact dirty
270 pkt->setCacheResponding();
271 blk->status &= ~BlkDirty;
272 }
273 } else {
274 assert(pkt->isInvalidate());
275 invalidateBlock(blk);
276 DPRINTF(CacheVerbose, "%s for %s (invalidation)\n", __func__,
277 pkt->print());
278 }
279}
280
281/////////////////////////////////////////////////////
282//
283// Access path: requests coming in from the CPU side
284//
285/////////////////////////////////////////////////////
286
287bool
288Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
289 PacketList &writebacks)
290{
291 // sanity check
292 assert(pkt->isRequest());
293
294 chatty_assert(!(isReadOnly && pkt->isWrite()),
295 "Should never see a write in a read-only cache %s\n",
296 name());
297
298 DPRINTF(CacheVerbose, "%s for %s\n", __func__, pkt->print());
299
300 if (pkt->req->isUncacheable()) {
301 DPRINTF(Cache, "uncacheable: %s\n", pkt->print());
302
303 // flush and invalidate any existing block
304 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
305 if (old_blk && old_blk->isValid()) {
306 if (old_blk->isDirty() || writebackClean)
307 writebacks.push_back(writebackBlk(old_blk));
308 else
309 writebacks.push_back(cleanEvictBlk(old_blk));
310 invalidateBlock(old_blk);
311 }
312
313 blk = nullptr;
314 // lookupLatency is the latency in case the request is uncacheable.
315 lat = lookupLatency;
316 return false;
317 }
318
319 // Here lat is the value passed as parameter to accessBlock() function
320 // that can modify its value.
321 blk = tags->accessBlock(pkt->getAddr(), pkt->isSecure(), lat);
322
323 DPRINTF(Cache, "%s %s\n", pkt->print(),
324 blk ? "hit " + blk->print() : "miss");
325
326 if (pkt->req->isCacheMaintenance()) {
327 // A cache maintenance operation is always forwarded to the
328 // memory below even if the block is found in dirty state.
329
330 // We defer any changes to the state of the block until we
331 // create and mark as in service the mshr for the downstream
332 // packet.
333 return false;
334 }
335
336 if (pkt->isEviction()) {
337 // We check for presence of block in above caches before issuing
338 // Writeback or CleanEvict to write buffer. Therefore the only
339 // possible cases can be of a CleanEvict packet coming from above
340 // encountering a Writeback generated in this cache peer cache and
341 // waiting in the write buffer. Cases of upper level peer caches
342 // generating CleanEvict and Writeback or simply CleanEvict and
343 // CleanEvict almost simultaneously will be caught by snoops sent out
344 // by crossbar.
345 WriteQueueEntry *wb_entry = writeBuffer.findMatch(pkt->getAddr(),
346 pkt->isSecure());
347 if (wb_entry) {
348 assert(wb_entry->getNumTargets() == 1);
349 PacketPtr wbPkt = wb_entry->getTarget()->pkt;
350 assert(wbPkt->isWriteback());
351
352 if (pkt->isCleanEviction()) {
353 // The CleanEvict and WritebackClean snoops into other
354 // peer caches of the same level while traversing the
355 // crossbar. If a copy of the block is found, the
356 // packet is deleted in the crossbar. Hence, none of
357 // the other upper level caches connected to this
358 // cache have the block, so we can clear the
359 // BLOCK_CACHED flag in the Writeback if set and
360 // discard the CleanEvict by returning true.
361 wbPkt->clearBlockCached();
362 return true;
363 } else {
364 assert(pkt->cmd == MemCmd::WritebackDirty);
365 // Dirty writeback from above trumps our clean
366 // writeback... discard here
367 // Note: markInService will remove entry from writeback buffer.
368 markInService(wb_entry);
369 delete wbPkt;
370 }
371 }
372 }
373
374 // Writeback handling is special case. We can write the block into
375 // the cache without having a writeable copy (or any copy at all).
376 if (pkt->isWriteback()) {
377 assert(blkSize == pkt->getSize());
378
379 // we could get a clean writeback while we are having
380 // outstanding accesses to a block, do the simple thing for
381 // now and drop the clean writeback so that we do not upset
382 // any ordering/decisions about ownership already taken
383 if (pkt->cmd == MemCmd::WritebackClean &&
384 mshrQueue.findMatch(pkt->getAddr(), pkt->isSecure())) {
385 DPRINTF(Cache, "Clean writeback %#llx to block with MSHR, "
386 "dropping\n", pkt->getAddr());
387 return true;
388 }
389
390 if (blk == nullptr) {
391 // need to do a replacement
392 blk = allocateBlock(pkt->getAddr(), pkt->isSecure(), writebacks);
393 if (blk == nullptr) {
394 // no replaceable block available: give up, fwd to next level.
395 incMissCount(pkt);
396 return false;
397 }
398 tags->insertBlock(pkt, blk);
399
400 blk->status = (BlkValid | BlkReadable);
401 if (pkt->isSecure()) {
402 blk->status |= BlkSecure;
403 }
404 }
405 // only mark the block dirty if we got a writeback command,
406 // and leave it as is for a clean writeback
407 if (pkt->cmd == MemCmd::WritebackDirty) {
408 assert(!blk->isDirty());
409 blk->status |= BlkDirty;
410 }
411 // if the packet does not have sharers, it is passing
412 // writable, and we got the writeback in Modified or Exclusive
413 // state, if not we are in the Owned or Shared state
414 if (!pkt->hasSharers()) {
415 blk->status |= BlkWritable;
416 }
417 // nothing else to do; writeback doesn't expect response
418 assert(!pkt->needsResponse());
419 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
420 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
421 incHitCount(pkt);
422 return true;
423 } else if (pkt->cmd == MemCmd::CleanEvict) {
424 if (blk != nullptr) {
425 // Found the block in the tags, need to stop CleanEvict from
426 // propagating further down the hierarchy. Returning true will
427 // treat the CleanEvict like a satisfied write request and delete
428 // it.
429 return true;
430 }
431 // We didn't find the block here, propagate the CleanEvict further
432 // down the memory hierarchy. Returning false will treat the CleanEvict
433 // like a Writeback which could not find a replaceable block so has to
434 // go to next level.
435 return false;
436 } else if (pkt->cmd == MemCmd::WriteClean) {
437 // WriteClean handling is a special case. We can allocate a
438 // block directly if it doesn't exist and we can update the
439 // block immediately. The WriteClean transfers the ownership
440 // of the block as well.
441 assert(blkSize == pkt->getSize());
442
443 if (!blk) {
444 if (pkt->writeThrough()) {
445 // if this is a write through packet, we don't try to
446 // allocate if the block is not present
447 return false;
448 } else {
449 // a writeback that misses needs to allocate a new block
450 blk = allocateBlock(pkt->getAddr(), pkt->isSecure(),
451 writebacks);
452 if (!blk) {
453 // no replaceable block available: give up, fwd to
454 // next level.
455 incMissCount(pkt);
456 return false;
457 }
458 tags->insertBlock(pkt, blk);
459
460 blk->status = (BlkValid | BlkReadable);
461 if (pkt->isSecure()) {
462 blk->status |= BlkSecure;
463 }
464 }
465 }
466
467 // at this point either this is a writeback or a write-through
468 // write clean operation and the block is already in this
469 // cache, we need to update the data and the block flags
470 assert(blk);
471 assert(!blk->isDirty());
472 if (!pkt->writeThrough()) {
473 blk->status |= BlkDirty;
474 }
475 // nothing else to do; writeback doesn't expect response
476 assert(!pkt->needsResponse());
477 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
478 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
479
480 incHitCount(pkt);
481 // populate the time when the block will be ready to access.
482 blk->whenReady = clockEdge(fillLatency) + pkt->headerDelay +
483 pkt->payloadDelay;
484 // if this a write-through packet it will be sent to cache
485 // below
486 return !pkt->writeThrough();
487 } else if (blk && (pkt->needsWritable() ? blk->isWritable() :
488 blk->isReadable())) {
489 // OK to satisfy access
490 incHitCount(pkt);
491 satisfyRequest(pkt, blk);
492 maintainClusivity(pkt->fromCache(), blk);
493
494 return true;
495 }
496
497 // Can't satisfy access normally... either no block (blk == nullptr)
498 // or have block but need writable
499
500 incMissCount(pkt);
501
502 if (blk == nullptr && pkt->isLLSC() && pkt->isWrite()) {
503 // complete miss on store conditional... just give up now
504 pkt->req->setExtraData(0);
505 return true;
506 }
507
508 return false;
509}
510
511void
512Cache::maintainClusivity(bool from_cache, CacheBlk *blk)
513{
514 if (from_cache && blk && blk->isValid() && !blk->isDirty() &&
515 clusivity == Enums::mostly_excl) {
516 // if we have responded to a cache, and our block is still
517 // valid, but not dirty, and this cache is mostly exclusive
518 // with respect to the cache above, drop the block
519 invalidateBlock(blk);
520 }
521}
522
523void
524Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
525{
526 while (!writebacks.empty()) {
527 PacketPtr wbPkt = writebacks.front();
528 // We use forwardLatency here because we are copying writebacks to
529 // write buffer.
530
531 // Call isCachedAbove for Writebacks, CleanEvicts and
532 // WriteCleans to discover if the block is cached above.
533 if (isCachedAbove(wbPkt)) {
534 if (wbPkt->cmd == MemCmd::CleanEvict) {
535 // Delete CleanEvict because cached copies exist above. The
536 // packet destructor will delete the request object because
537 // this is a non-snoop request packet which does not require a
538 // response.
539 delete wbPkt;
540 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
541 // clean writeback, do not send since the block is
542 // still cached above
543 assert(writebackClean);
544 delete wbPkt;
545 } else {
546 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
547 wbPkt->cmd == MemCmd::WriteClean);
548 // Set BLOCK_CACHED flag in Writeback and send below, so that
549 // the Writeback does not reset the bit corresponding to this
550 // address in the snoop filter below.
551 wbPkt->setBlockCached();
552 allocateWriteBuffer(wbPkt, forward_time);
553 }
554 } else {
555 // If the block is not cached above, send packet below. Both
556 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
557 // reset the bit corresponding to this address in the snoop filter
558 // below.
559 allocateWriteBuffer(wbPkt, forward_time);
560 }
561 writebacks.pop_front();
562 }
563}
564
565void
566Cache::doWritebacksAtomic(PacketList& writebacks)
567{
568 while (!writebacks.empty()) {
569 PacketPtr wbPkt = writebacks.front();
570 // Call isCachedAbove for both Writebacks and CleanEvicts. If
571 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
572 // and discard CleanEvicts.
573 if (isCachedAbove(wbPkt, false)) {
574 if (wbPkt->cmd == MemCmd::WritebackDirty ||
575 wbPkt->cmd == MemCmd::WriteClean) {
576 // Set BLOCK_CACHED flag in Writeback and send below,
577 // so that the Writeback does not reset the bit
578 // corresponding to this address in the snoop filter
579 // below. We can discard CleanEvicts because cached
580 // copies exist above. Atomic mode isCachedAbove
581 // modifies packet to set BLOCK_CACHED flag
582 memSidePort->sendAtomic(wbPkt);
583 }
584 } else {
585 // If the block is not cached above, send packet below. Both
586 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
587 // reset the bit corresponding to this address in the snoop filter
588 // below.
589 memSidePort->sendAtomic(wbPkt);
590 }
591 writebacks.pop_front();
592 // In case of CleanEvicts, the packet destructor will delete the
593 // request object because this is a non-snoop request packet which
594 // does not require a response.
595 delete wbPkt;
596 }
597}
598
599
600void
601Cache::recvTimingSnoopResp(PacketPtr pkt)
602{
603 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
604
605 assert(pkt->isResponse());
606 assert(!system->bypassCaches());
607
608 // determine if the response is from a snoop request we created
609 // (in which case it should be in the outstandingSnoop), or if we
610 // merely forwarded someone else's snoop request
611 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
612 outstandingSnoop.end();
613
614 if (!forwardAsSnoop) {
615 // the packet came from this cache, so sink it here and do not
616 // forward it
617 assert(pkt->cmd == MemCmd::HardPFResp);
618
619 outstandingSnoop.erase(pkt->req);
620
621 DPRINTF(Cache, "Got prefetch response from above for addr "
622 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
623 recvTimingResp(pkt);
624 return;
625 }
626
627 // forwardLatency is set here because there is a response from an
628 // upper level cache.
629 // To pay the delay that occurs if the packet comes from the bus,
630 // we charge also headerDelay.
631 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
632 // Reset the timing of the packet.
633 pkt->headerDelay = pkt->payloadDelay = 0;
634 memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time);
635}
636
637void
638Cache::promoteWholeLineWrites(PacketPtr pkt)
639{
640 // Cache line clearing instructions
641 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
642 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
643 pkt->cmd = MemCmd::WriteLineReq;
644 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
645 }
646}
647
648bool
649Cache::recvTimingReq(PacketPtr pkt)
650{
651 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
652
653 assert(pkt->isRequest());
654
655 // Just forward the packet if caches are disabled.
656 if (system->bypassCaches()) {
657 // @todo This should really enqueue the packet rather
658 bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt);
659 assert(success);
660 return true;
661 }
662
663 promoteWholeLineWrites(pkt);
664
665 // Cache maintenance operations have to visit all the caches down
666 // to the specified xbar (PoC, PoU, etc.). Even if a cache above
667 // is responding we forward the packet to the memory below rather
668 // than creating an express snoop.
669 if (pkt->cacheResponding()) {
670 // a cache above us (but not where the packet came from) is
671 // responding to the request, in other words it has the line
672 // in Modified or Owned state
673 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
674 pkt->print());
675
676 // if the packet needs the block to be writable, and the cache
677 // that has promised to respond (setting the cache responding
678 // flag) is not providing writable (it is in Owned rather than
679 // the Modified state), we know that there may be other Shared
680 // copies in the system; go out and invalidate them all
681 assert(pkt->needsWritable() && !pkt->responderHadWritable());
682
683 // an upstream cache that had the line in Owned state
684 // (dirty, but not writable), is responding and thus
685 // transferring the dirty line from one branch of the
686 // cache hierarchy to another
687
688 // send out an express snoop and invalidate all other
689 // copies (snooping a packet that needs writable is the
690 // same as an invalidation), thus turning the Owned line
691 // into a Modified line, note that we don't invalidate the
692 // block in the current cache or any other cache on the
693 // path to memory
694
695 // create a downstream express snoop with cleared packet
696 // flags, there is no need to allocate any data as the
697 // packet is merely used to co-ordinate state transitions
698 Packet *snoop_pkt = new Packet(pkt, true, false);
699
700 // also reset the bus time that the original packet has
701 // not yet paid for
702 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
703
704 // make this an instantaneous express snoop, and let the
705 // other caches in the system know that the another cache
706 // is responding, because we have found the authorative
707 // copy (Modified or Owned) that will supply the right
708 // data
709 snoop_pkt->setExpressSnoop();
710 snoop_pkt->setCacheResponding();
711
712 // this express snoop travels towards the memory, and at
713 // every crossbar it is snooped upwards thus reaching
714 // every cache in the system
715 bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt);
716 // express snoops always succeed
717 assert(success);
718
719 // main memory will delete the snoop packet
720
721 // queue for deletion, as opposed to immediate deletion, as
722 // the sending cache is still relying on the packet
723 pendingDelete.reset(pkt);
724
725 // no need to take any further action in this particular cache
726 // as an upstram cache has already committed to responding,
727 // and we have already sent out any express snoops in the
728 // section above to ensure all other copies in the system are
729 // invalidated
730 return true;
731 }
732
733 // anything that is merely forwarded pays for the forward latency and
734 // the delay provided by the crossbar
735 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
736
737 // We use lookupLatency here because it is used to specify the latency
738 // to access.
739 Cycles lat = lookupLatency;
740 CacheBlk *blk = nullptr;
741 bool satisfied = false;
742 {
743 PacketList writebacks;
744 // Note that lat is passed by reference here. The function
745 // access() calls accessBlock() which can modify lat value.
746 satisfied = access(pkt, blk, lat, writebacks);
747
748 // copy writebacks to write buffer here to ensure they logically
749 // proceed anything happening below
750 doWritebacks(writebacks, forward_time);
751 }
752
753 // Here we charge the headerDelay that takes into account the latencies
754 // of the bus, if the packet comes from it.
755 // The latency charged it is just lat that is the value of lookupLatency
756 // modified by access() function, or if not just lookupLatency.
757 // In case of a hit we are neglecting response latency.
758 // In case of a miss we are neglecting forward latency.
759 Tick request_time = clockEdge(lat) + pkt->headerDelay;
760 // Here we reset the timing of the packet.
761 pkt->headerDelay = pkt->payloadDelay = 0;
762
763 // track time of availability of next prefetch, if any
764 Tick next_pf_time = MaxTick;
765
766 bool needsResponse = pkt->needsResponse();
767
768 if (satisfied) {
769 // should never be satisfying an uncacheable access as we
770 // flush and invalidate any existing block as part of the
771 // lookup
772 assert(!pkt->req->isUncacheable());
773
774 // hit (for all other request types)
775
776 if (prefetcher && (prefetchOnAccess ||
777 (blk && blk->wasPrefetched()))) {
778 if (blk)
779 blk->status &= ~BlkHWPrefetched;
780
781 // Don't notify on SWPrefetch
782 if (!pkt->cmd.isSWPrefetch()) {
783 assert(!pkt->req->isCacheMaintenance());
784 next_pf_time = prefetcher->notify(pkt);
785 }
786 }
787
788 if (needsResponse) {
789 pkt->makeTimingResponse();
790 // @todo: Make someone pay for this
791 pkt->headerDelay = pkt->payloadDelay = 0;
792
793 // In this case we are considering request_time that takes
794 // into account the delay of the xbar, if any, and just
795 // lat, neglecting responseLatency, modelling hit latency
796 // just as lookupLatency or or the value of lat overriden
797 // by access(), that calls accessBlock() function.
798 cpuSidePort->schedTimingResp(pkt, request_time, true);
799 } else {
800 DPRINTF(Cache, "%s satisfied %s, no response needed\n", __func__,
801 pkt->print());
802
803 // queue the packet for deletion, as the sending cache is
804 // still relying on it; if the block is found in access(),
805 // CleanEvict and Writeback messages will be deleted
806 // here as well
807 pendingDelete.reset(pkt);
808 }
809 } else {
810 // miss
811
812 Addr blk_addr = pkt->getBlockAddr(blkSize);
813
814 // ignore any existing MSHR if we are dealing with an
815 // uncacheable request
816 MSHR *mshr = pkt->req->isUncacheable() ? nullptr :
817 mshrQueue.findMatch(blk_addr, pkt->isSecure());
818
819 // Software prefetch handling:
820 // To keep the core from waiting on data it won't look at
821 // anyway, send back a response with dummy data. Miss handling
822 // will continue asynchronously. Unfortunately, the core will
823 // insist upon freeing original Packet/Request, so we have to
824 // create a new pair with a different lifecycle. Note that this
825 // processing happens before any MSHR munging on the behalf of
826 // this request because this new Request will be the one stored
827 // into the MSHRs, not the original.
828 if (pkt->cmd.isSWPrefetch()) {
829 assert(needsResponse);
830 assert(pkt->req->hasPaddr());
831 assert(!pkt->req->isUncacheable());
832
833 // There's no reason to add a prefetch as an additional target
834 // to an existing MSHR. If an outstanding request is already
835 // in progress, there is nothing for the prefetch to do.
836 // If this is the case, we don't even create a request at all.
837 PacketPtr pf = nullptr;
838
839 if (!mshr) {
840 // copy the request and create a new SoftPFReq packet
841 RequestPtr req = new Request(pkt->req->getPaddr(),
842 pkt->req->getSize(),
843 pkt->req->getFlags(),
844 pkt->req->masterId());
845 pf = new Packet(req, pkt->cmd);
846 pf->allocate();
847 assert(pf->getAddr() == pkt->getAddr());
848 assert(pf->getSize() == pkt->getSize());
849 }
850
851 pkt->makeTimingResponse();
852
853 // request_time is used here, taking into account lat and the delay
854 // charged if the packet comes from the xbar.
855 cpuSidePort->schedTimingResp(pkt, request_time, true);
856
857 // If an outstanding request is in progress (we found an
858 // MSHR) this is set to null
859 pkt = pf;
860 }
861
862 if (mshr) {
863 /// MSHR hit
864 /// @note writebacks will be checked in getNextMSHR()
865 /// for any conflicting requests to the same block
866
867 //@todo remove hw_pf here
868
869 // Coalesce unless it was a software prefetch (see above).
870 if (pkt) {
871 assert(!pkt->isWriteback());
872 // CleanEvicts corresponding to blocks which have
873 // outstanding requests in MSHRs are simply sunk here
874 if (pkt->cmd == MemCmd::CleanEvict) {
875 pendingDelete.reset(pkt);
876 } else if (pkt->cmd == MemCmd::WriteClean) {
877 // A WriteClean should never coalesce with any
878 // outstanding cache maintenance requests.
879
880 // We use forward_time here because there is an
881 // uncached memory write, forwarded to WriteBuffer.
882 allocateWriteBuffer(pkt, forward_time);
883 } else {
884 DPRINTF(Cache, "%s coalescing MSHR for %s\n", __func__,
885 pkt->print());
886
887 assert(pkt->req->masterId() < system->maxMasters());
888 mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
889 // We use forward_time here because it is the same
890 // considering new targets. We have multiple
891 // requests for the same address here. It
892 // specifies the latency to allocate an internal
893 // buffer and to schedule an event to the queued
894 // port and also takes into account the additional
895 // delay of the xbar.
896 mshr->allocateTarget(pkt, forward_time, order++,
897 allocOnFill(pkt->cmd));
898 if (mshr->getNumTargets() == numTarget) {
899 noTargetMSHR = mshr;
900 setBlocked(Blocked_NoTargets);
901 // need to be careful with this... if this mshr isn't
902 // ready yet (i.e. time > curTick()), we don't want to
903 // move it ahead of mshrs that are ready
904 // mshrQueue.moveToFront(mshr);
905 }
906 }
907 // We should call the prefetcher reguardless if the request is
908 // satisfied or not, reguardless if the request is in the MSHR
909 // or not. The request could be a ReadReq hit, but still not
910 // satisfied (potentially because of a prior write to the same
911 // cache line. So, even when not satisfied, tehre is an MSHR
912 // already allocated for this, we need to let the prefetcher
913 // know about the request
914 if (prefetcher) {
915 // Don't notify on SWPrefetch
916 if (!pkt->cmd.isSWPrefetch() &&
917 !pkt->req->isCacheMaintenance())
918 next_pf_time = prefetcher->notify(pkt);
919 }
920 }
921 } else {
922 // no MSHR
923 assert(pkt->req->masterId() < system->maxMasters());
924 if (pkt->req->isUncacheable()) {
925 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
926 } else {
927 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
928 }
929
930 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
931 (pkt->req->isUncacheable() && pkt->isWrite())) {
932 // We use forward_time here because there is an
933 // uncached memory write, forwarded to WriteBuffer.
934 allocateWriteBuffer(pkt, forward_time);
935 } else {
936 if (blk && blk->isValid()) {
937 // should have flushed and have no valid block
938 assert(!pkt->req->isUncacheable());
939
940 // If we have a write miss to a valid block, we
941 // need to mark the block non-readable. Otherwise
942 // if we allow reads while there's an outstanding
943 // write miss, the read could return stale data
944 // out of the cache block... a more aggressive
945 // system could detect the overlap (if any) and
946 // forward data out of the MSHRs, but we don't do
947 // that yet. Note that we do need to leave the
948 // block valid so that it stays in the cache, in
949 // case we get an upgrade response (and hence no
950 // new data) when the write miss completes.
951 // As long as CPUs do proper store/load forwarding
952 // internally, and have a sufficiently weak memory
953 // model, this is probably unnecessary, but at some
954 // point it must have seemed like we needed it...
955 assert((pkt->needsWritable() && !blk->isWritable()) ||
956 pkt->req->isCacheMaintenance());
957 blk->status &= ~BlkReadable;
958 }
959 // Here we are using forward_time, modelling the latency of
960 // a miss (outbound) just as forwardLatency, neglecting the
961 // lookupLatency component.
962 allocateMissBuffer(pkt, forward_time);
963 }
964
965 if (prefetcher) {
966 // Don't notify on SWPrefetch
967 if (!pkt->cmd.isSWPrefetch() &&
968 !pkt->req->isCacheMaintenance())
969 next_pf_time = prefetcher->notify(pkt);
970 }
971 }
972 }
973
974 if (next_pf_time != MaxTick)
975 schedMemSideSendEvent(next_pf_time);
976
977 return true;
978}
979
980PacketPtr
981Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
982 bool needsWritable) const
983{
984 // should never see evictions here
985 assert(!cpu_pkt->isEviction());
986
987 bool blkValid = blk && blk->isValid();
988
989 if (cpu_pkt->req->isUncacheable() ||
990 (!blkValid && cpu_pkt->isUpgrade()) ||
991 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
992 // uncacheable requests and upgrades from upper-level caches
993 // that missed completely just go through as is
994 return nullptr;
995 }
996
997 assert(cpu_pkt->needsResponse());
998
999 MemCmd cmd;
1000 // @TODO make useUpgrades a parameter.
1001 // Note that ownership protocols require upgrade, otherwise a
1002 // write miss on a shared owned block will generate a ReadExcl,
1003 // which will clobber the owned copy.
1004 const bool useUpgrades = true;
1005 if (cpu_pkt->cmd == MemCmd::WriteLineReq) {
1006 assert(!blkValid || !blk->isWritable());
1007 // forward as invalidate to all other caches, this gives us
1008 // the line in Exclusive state, and invalidates all other
1009 // copies
1010 cmd = MemCmd::InvalidateReq;
1011 } else if (blkValid && useUpgrades) {
1012 // only reason to be here is that blk is read only and we need
1013 // it to be writable
1014 assert(needsWritable);
1015 assert(!blk->isWritable());
1016 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
1017 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
1018 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
1019 // Even though this SC will fail, we still need to send out the
1020 // request and get the data to supply it to other snoopers in the case
1021 // where the determination the StoreCond fails is delayed due to
1022 // all caches not being on the same local bus.
1023 cmd = MemCmd::SCUpgradeFailReq;
1024 } else {
1025 // block is invalid
1026
1027 // If the request does not need a writable there are two cases
1028 // where we need to ensure the response will not fetch the
1029 // block in dirty state:
1030 // * this cache is read only and it does not perform
1031 // writebacks,
1032 // * this cache is mostly exclusive and will not fill (since
1033 // it does not fill it will have to writeback the dirty data
1034 // immediately which generates uneccesary writebacks).
1035 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
1036 cmd = needsWritable ? MemCmd::ReadExReq :
1037 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
1038 }
1039 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
1040
1041 // if there are upstream caches that have already marked the
1042 // packet as having sharers (not passing writable), pass that info
1043 // downstream
1044 if (cpu_pkt->hasSharers() && !needsWritable) {
1045 // note that cpu_pkt may have spent a considerable time in the
1046 // MSHR queue and that the information could possibly be out
1047 // of date, however, there is no harm in conservatively
1048 // assuming the block has sharers
1049 pkt->setHasSharers();
1050 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
1051 __func__, cpu_pkt->print(), pkt->print());
1052 }
1053
1054 // the packet should be block aligned
1055 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
1056
1057 pkt->allocate();
1058 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
1059 cpu_pkt->print());
1060 return pkt;
1061}
1062
1063
1064Tick
1065Cache::recvAtomic(PacketPtr pkt)
1066{
1067 // We are in atomic mode so we pay just for lookupLatency here.
1068 Cycles lat = lookupLatency;
1069
1070 // Forward the request if the system is in cache bypass mode.
1071 if (system->bypassCaches())
1072 return ticksToCycles(memSidePort->sendAtomic(pkt));
1073
1074 promoteWholeLineWrites(pkt);
1075
1076 // follow the same flow as in recvTimingReq, and check if a cache
1077 // above us is responding
1078 if (pkt->cacheResponding() && !pkt->isClean()) {
1079 assert(!pkt->req->isCacheInvalidate());
1080 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
1081 pkt->print());
1082
1083 // if a cache is responding, and it had the line in Owned
1084 // rather than Modified state, we need to invalidate any
1085 // copies that are not on the same path to memory
1086 assert(pkt->needsWritable() && !pkt->responderHadWritable());
1087 lat += ticksToCycles(memSidePort->sendAtomic(pkt));
1088
1089 return lat * clockPeriod();
1090 }
1091
1092 // should assert here that there are no outstanding MSHRs or
1093 // writebacks... that would mean that someone used an atomic
1094 // access in timing mode
1095
1096 CacheBlk *blk = nullptr;
1097 PacketList writebacks;
1098 bool satisfied = access(pkt, blk, lat, writebacks);
1099
1100 if (pkt->isClean() && blk && blk->isDirty()) {
1101 // A cache clean opearation is looking for a dirty
1102 // block. If a dirty block is encountered a WriteClean
1103 // will update any copies to the path to the memory
1104 // until the point of reference.
1105 DPRINTF(CacheVerbose, "%s: packet %s found block: %s\n",
1106 __func__, pkt->print(), blk->print());
1107 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1108 writebacks.push_back(wb_pkt);
1109 pkt->setSatisfied();
1110 }
1111
1112 // handle writebacks resulting from the access here to ensure they
1113 // logically proceed anything happening below
1114 doWritebacksAtomic(writebacks);
1115
1116 if (!satisfied) {
1117 // MISS
1118
1119 // deal with the packets that go through the write path of
1120 // the cache, i.e. any evictions and writes
1121 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
1122 (pkt->req->isUncacheable() && pkt->isWrite())) {
1123 lat += ticksToCycles(memSidePort->sendAtomic(pkt));
1124 return lat * clockPeriod();
1125 }
1126 // only misses left
1127
1128 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable());
1129
1130 bool is_forward = (bus_pkt == nullptr);
1131
1132 if (is_forward) {
1133 // just forwarding the same request to the next level
1134 // no local cache operation involved
1135 bus_pkt = pkt;
1136 }
1137
1138 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
1139 bus_pkt->print());
1140
1141#if TRACING_ON
1142 CacheBlk::State old_state = blk ? blk->status : 0;
1143#endif
1144
1145 lat += ticksToCycles(memSidePort->sendAtomic(bus_pkt));
1146
1147 bool is_invalidate = bus_pkt->isInvalidate();
1148
1149 // We are now dealing with the response handling
1150 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
1151 bus_pkt->print(), old_state);
1152
1153 // If packet was a forward, the response (if any) is already
1154 // in place in the bus_pkt == pkt structure, so we don't need
1155 // to do anything. Otherwise, use the separate bus_pkt to
1156 // generate response to pkt and then delete it.
1157 if (!is_forward) {
1158 if (pkt->needsResponse()) {
1159 assert(bus_pkt->isResponse());
1160 if (bus_pkt->isError()) {
1161 pkt->makeAtomicResponse();
1162 pkt->copyError(bus_pkt);
1163 } else if (pkt->cmd == MemCmd::WriteLineReq) {
1164 // note the use of pkt, not bus_pkt here.
1165
1166 // write-line request to the cache that promoted
1167 // the write to a whole line
1168 blk = handleFill(pkt, blk, writebacks,
1169 allocOnFill(pkt->cmd));
1170 assert(blk != NULL);
1171 is_invalidate = false;
1172 satisfyRequest(pkt, blk);
1173 } else if (bus_pkt->isRead() ||
1174 bus_pkt->cmd == MemCmd::UpgradeResp) {
1175 // we're updating cache state to allow us to
1176 // satisfy the upstream request from the cache
1177 blk = handleFill(bus_pkt, blk, writebacks,
1178 allocOnFill(pkt->cmd));
1179 satisfyRequest(pkt, blk);
1180 maintainClusivity(pkt->fromCache(), blk);
1181 } else {
1182 // we're satisfying the upstream request without
1183 // modifying cache state, e.g., a write-through
1184 pkt->makeAtomicResponse();
1185 }
1186 }
1187 delete bus_pkt;
1188 }
1189
1190 if (is_invalidate && blk && blk->isValid()) {
1191 invalidateBlock(blk);
1192 }
1193 }
1194
1195 // Note that we don't invoke the prefetcher at all in atomic mode.
1196 // It's not clear how to do it properly, particularly for
1197 // prefetchers that aggressively generate prefetch candidates and
1198 // rely on bandwidth contention to throttle them; these will tend
1199 // to pollute the cache in atomic mode since there is no bandwidth
1200 // contention. If we ever do want to enable prefetching in atomic
1201 // mode, though, this is the place to do it... see timingAccess()
1202 // for an example (though we'd want to issue the prefetch(es)
1203 // immediately rather than calling requestMemSideBus() as we do
1204 // there).
1205
1206 // do any writebacks resulting from the response handling
1207 doWritebacksAtomic(writebacks);
1208
1209 // if we used temp block, check to see if its valid and if so
1210 // clear it out, but only do so after the call to recvAtomic is
1211 // finished so that any downstream observers (such as a snoop
1212 // filter), first see the fill, and only then see the eviction
1213 if (blk == tempBlock && tempBlock->isValid()) {
1214 // the atomic CPU calls recvAtomic for fetch and load/store
1215 // sequentuially, and we may already have a tempBlock
1216 // writeback from the fetch that we have not yet sent
1217 if (tempBlockWriteback) {
1218 // if that is the case, write the prevoius one back, and
1219 // do not schedule any new event
1220 writebackTempBlockAtomic();
1221 } else {
1222 // the writeback/clean eviction happens after the call to
1223 // recvAtomic has finished (but before any successive
1224 // calls), so that the response handling from the fill is
1225 // allowed to happen first
1226 schedule(writebackTempBlockAtomicEvent, curTick());
1227 }
1228
1229 tempBlockWriteback = (blk->isDirty() || writebackClean) ?
1230 writebackBlk(blk) : cleanEvictBlk(blk);
1231 invalidateBlock(blk);
1232 }
1233
1234 if (pkt->needsResponse()) {
1235 pkt->makeAtomicResponse();
1236 }
1237
1238 return lat * clockPeriod();
1239}
1240
1241
1242void
1243Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide)
1244{
1245 if (system->bypassCaches()) {
1246 // Packets from the memory side are snoop request and
1247 // shouldn't happen in bypass mode.
1248 assert(fromCpuSide);
1249
1250 // The cache should be flushed if we are in cache bypass mode,
1251 // so we don't need to check if we need to update anything.
1252 memSidePort->sendFunctional(pkt);
1253 return;
1254 }
1255
1256 Addr blk_addr = pkt->getBlockAddr(blkSize);
1257 bool is_secure = pkt->isSecure();
1258 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1259 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1260
1261 pkt->pushLabel(name());
1262
1263 CacheBlkPrintWrapper cbpw(blk);
1264
1265 // Note that just because an L2/L3 has valid data doesn't mean an
1266 // L1 doesn't have a more up-to-date modified copy that still
1267 // needs to be found. As a result we always update the request if
1268 // we have it, but only declare it satisfied if we are the owner.
1269
1270 // see if we have data at all (owned or otherwise)
1271 bool have_data = blk && blk->isValid()
1272 && pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize,
1273 blk->data);
1274
1275 // data we have is dirty if marked as such or if we have an
1276 // in-service MSHR that is pending a modified line
1277 bool have_dirty =
1278 have_data && (blk->isDirty() ||
1279 (mshr && mshr->inService && mshr->isPendingModified()));
1280
1281 bool done = have_dirty
1282 || cpuSidePort->checkFunctional(pkt)
1283 || mshrQueue.checkFunctional(pkt, blk_addr)
1284 || writeBuffer.checkFunctional(pkt, blk_addr)
1285 || memSidePort->checkFunctional(pkt);
1286
1287 DPRINTF(CacheVerbose, "%s: %s %s%s%s\n", __func__, pkt->print(),
1288 (blk && blk->isValid()) ? "valid " : "",
1289 have_data ? "data " : "", done ? "done " : "");
1290
1291 // We're leaving the cache, so pop cache->name() label
1292 pkt->popLabel();
1293
1294 if (done) {
1295 pkt->makeResponse();
1296 } else {
1297 // if it came as a request from the CPU side then make sure it
1298 // continues towards the memory side
1299 if (fromCpuSide) {
1300 memSidePort->sendFunctional(pkt);
1301 } else if (cpuSidePort->isSnooping()) {
1302 // if it came from the memory side, it must be a snoop request
1303 // and we should only forward it if we are forwarding snoops
1304 cpuSidePort->sendFunctionalSnoop(pkt);
1305 }
1306 }
1307}
1308
1309
1310/////////////////////////////////////////////////////
1311//
1312// Response handling: responses from the memory side
1313//
1314/////////////////////////////////////////////////////
1315
1316
1317void
1318Cache::handleUncacheableWriteResp(PacketPtr pkt)
1319{
1320 Tick completion_time = clockEdge(responseLatency) +
1321 pkt->headerDelay + pkt->payloadDelay;
1322
1323 // Reset the bus additional time as it is now accounted for
1324 pkt->headerDelay = pkt->payloadDelay = 0;
1325
1326 cpuSidePort->schedTimingResp(pkt, completion_time, true);
1327}
1328
1329void
1330Cache::recvTimingResp(PacketPtr pkt)
1331{
1332 assert(pkt->isResponse());
1333
1334 // all header delay should be paid for by the crossbar, unless
1335 // this is a prefetch response from above
1336 panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp,
1337 "%s saw a non-zero packet delay\n", name());
1338
1339 bool is_error = pkt->isError();
1340
1341 if (is_error) {
1342 DPRINTF(Cache, "%s: Cache received %s with error\n", __func__,
1343 pkt->print());
1344 }
1345
1346 DPRINTF(Cache, "%s: Handling response %s\n", __func__,
1347 pkt->print());
1348
1349 // if this is a write, we should be looking at an uncacheable
1350 // write
1351 if (pkt->isWrite()) {
1352 assert(pkt->req->isUncacheable());
1353 handleUncacheableWriteResp(pkt);
1354 return;
1355 }
1356
1357 // we have dealt with any (uncacheable) writes above, from here on
1358 // we know we are dealing with an MSHR due to a miss or a prefetch
1359 MSHR *mshr = dynamic_cast<MSHR*>(pkt->popSenderState());
1360 assert(mshr);
1361
1362 if (mshr == noTargetMSHR) {
1363 // we always clear at least one target
1364 clearBlocked(Blocked_NoTargets);
1365 noTargetMSHR = nullptr;
1366 }
1367
1368 // Initial target is used just for stats
1369 MSHR::Target *initial_tgt = mshr->getTarget();
1370 int stats_cmd_idx = initial_tgt->pkt->cmdToIndex();
1371 Tick miss_latency = curTick() - initial_tgt->recvTime;
1372
1373 if (pkt->req->isUncacheable()) {
1374 assert(pkt->req->masterId() < system->maxMasters());
1375 mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] +=
1376 miss_latency;
1377 } else {
1378 assert(pkt->req->masterId() < system->maxMasters());
1379 mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] +=
1380 miss_latency;
1381 }
1382
1383 bool wasFull = mshrQueue.isFull();
1384
1385 PacketList writebacks;
1386
1387 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
1388
1389 bool is_fill = !mshr->isForward &&
1390 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
1391
1392 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1393 const bool valid_blk = blk && blk->isValid();
1394 // If the response indicates that there are no sharers and we
1395 // either had the block already or the response is filling we can
1396 // promote our copy to writable
1397 if (!pkt->hasSharers() &&
1398 (is_fill || (valid_blk && !pkt->req->isCacheInvalidate()))) {
1399 mshr->promoteWritable();
1400 }
1401
1402 if (is_fill && !is_error) {
1403 DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n",
1404 pkt->getAddr());
1405
1406 blk = handleFill(pkt, blk, writebacks, mshr->allocOnFill());
1407 assert(blk != nullptr);
1408 }
1409
1410 // allow invalidation responses originating from write-line
1411 // requests to be discarded
1412 bool is_invalidate = pkt->isInvalidate();
1413
1414 // The block was marked as not readable while there was a pending
1415 // cache maintenance operation, restore its flag.
1416 if (pkt->isClean() && !is_invalidate && valid_blk) {
1417 blk->status |= BlkReadable;
1418 }
1419
1420 // First offset for critical word first calculations
1421 int initial_offset = initial_tgt->pkt->getOffset(blkSize);
1422
1423 bool from_cache = false;
1424 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
1425 for (auto &target: targets) {
1426 Packet *tgt_pkt = target.pkt;
1427 switch (target.source) {
1428 case MSHR::Target::FromCPU:
1429 Tick completion_time;
1430 // Here we charge on completion_time the delay of the xbar if the
1431 // packet comes from it, charged on headerDelay.
1432 completion_time = pkt->headerDelay;
1433
1434 // Software prefetch handling for cache closest to core
1435 if (tgt_pkt->cmd.isSWPrefetch()) {
1436 // a software prefetch would have already been ack'd
1437 // immediately with dummy data so the core would be able to
1438 // retire it. This request completes right here, so we
1439 // deallocate it.
1440 delete tgt_pkt->req;
1441 delete tgt_pkt;
1442 break; // skip response
1443 }
1444
1445 // keep track of whether we have responded to another
1446 // cache
1447 from_cache = from_cache || tgt_pkt->fromCache();
1448
1449 // unlike the other packet flows, where data is found in other
1450 // caches or memory and brought back, write-line requests always
1451 // have the data right away, so the above check for "is fill?"
1452 // cannot actually be determined until examining the stored MSHR
1453 // state. We "catch up" with that logic here, which is duplicated
1454 // from above.
1455 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
1456 assert(!is_error);
1457 // we got the block in a writable state, so promote
1458 // any deferred targets if possible
1459 mshr->promoteWritable();
1460 // NB: we use the original packet here and not the response!
1461 blk = handleFill(tgt_pkt, blk, writebacks,
1462 targets.allocOnFill);
1463 assert(blk != nullptr);
1464
1465 // treat as a fill, and discard the invalidation
1466 // response
1467 is_fill = true;
1468 is_invalidate = false;
1469 }
1470
1471 if (is_fill) {
1472 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
1473
1474 // How many bytes past the first request is this one
1475 int transfer_offset =
1476 tgt_pkt->getOffset(blkSize) - initial_offset;
1477 if (transfer_offset < 0) {
1478 transfer_offset += blkSize;
1479 }
1480
1481 // If not critical word (offset) return payloadDelay.
1482 // responseLatency is the latency of the return path
1483 // from lower level caches/memory to an upper level cache or
1484 // the core.
1485 completion_time += clockEdge(responseLatency) +
1486 (transfer_offset ? pkt->payloadDelay : 0);
1487
1488 assert(!tgt_pkt->req->isUncacheable());
1489
1490 assert(tgt_pkt->req->masterId() < system->maxMasters());
1491 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
1492 completion_time - target.recvTime;
1493 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
1494 // failed StoreCond upgrade
1495 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
1496 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
1497 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
1498 // responseLatency is the latency of the return path
1499 // from lower level caches/memory to an upper level cache or
1500 // the core.
1501 completion_time += clockEdge(responseLatency) +
1502 pkt->payloadDelay;
1503 tgt_pkt->req->setExtraData(0);
1504 } else {
1505 // We are about to send a response to a cache above
1506 // that asked for an invalidation; we need to
1507 // invalidate our copy immediately as the most
1508 // up-to-date copy of the block will now be in the
1509 // cache above. It will also prevent this cache from
1510 // responding (if the block was previously dirty) to
1511 // snoops as they should snoop the caches above where
1512 // they will get the response from.
1513 if (is_invalidate && blk && blk->isValid()) {
1514 invalidateBlock(blk);
1515 }
1516 // not a cache fill, just forwarding response
1517 // responseLatency is the latency of the return path
1518 // from lower level cahces/memory to the core.
1519 completion_time += clockEdge(responseLatency) +
1520 pkt->payloadDelay;
1521 if (pkt->isRead() && !is_error) {
1522 // sanity check
1523 assert(pkt->getAddr() == tgt_pkt->getAddr());
1524 assert(pkt->getSize() >= tgt_pkt->getSize());
1525
1526 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
1527 }
1528 }
1529 tgt_pkt->makeTimingResponse();
1530 // if this packet is an error copy that to the new packet
1531 if (is_error)
1532 tgt_pkt->copyError(pkt);
1533 if (tgt_pkt->cmd == MemCmd::ReadResp &&
1534 (is_invalidate || mshr->hasPostInvalidate())) {
1535 // If intermediate cache got ReadRespWithInvalidate,
1536 // propagate that. Response should not have
1537 // isInvalidate() set otherwise.
1538 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
1539 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
1540 tgt_pkt->print());
1541 }
1542 // Reset the bus additional time as it is now accounted for
1543 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
1544 cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true);
1545 break;
1546
1547 case MSHR::Target::FromPrefetcher:
1548 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
1549 if (blk)
1550 blk->status |= BlkHWPrefetched;
1551 delete tgt_pkt->req;
1552 delete tgt_pkt;
1553 break;
1554
1555 case MSHR::Target::FromSnoop:
1556 // I don't believe that a snoop can be in an error state
1557 assert(!is_error);
1558 // response to snoop request
1559 DPRINTF(Cache, "processing deferred snoop...\n");
1560 // If the response is invalidating, a snooping target can
1561 // be satisfied if it is also invalidating. If the reponse is, not
1562 // only invalidating, but more specifically an InvalidateResp and
1563 // the MSHR was created due to an InvalidateReq then a cache above
1564 // is waiting to satisfy a WriteLineReq. In this case even an
1565 // non-invalidating snoop is added as a target here since this is
1566 // the ordering point. When the InvalidateResp reaches this cache,
1567 // the snooping target will snoop further the cache above with the
1568 // WriteLineReq.
1569 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
1570 pkt->req->isCacheMaintenance() ||
1571 mshr->hasPostInvalidate());
1572 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
1573 break;
1574
1575 default:
1576 panic("Illegal target->source enum %d\n", target.source);
1577 }
1578 }
1579
1580 maintainClusivity(from_cache, blk);
1581
1582 if (blk && blk->isValid()) {
1583 // an invalidate response stemming from a write line request
1584 // should not invalidate the block, so check if the
1585 // invalidation should be discarded
1586 if (is_invalidate || mshr->hasPostInvalidate()) {
1587 invalidateBlock(blk);
1588 } else if (mshr->hasPostDowngrade()) {
1589 blk->status &= ~BlkWritable;
1590 }
1591 }
1592
1593 if (mshr->promoteDeferredTargets()) {
1594 // avoid later read getting stale data while write miss is
1595 // outstanding.. see comment in timingAccess()
1596 if (blk) {
1597 blk->status &= ~BlkReadable;
1598 }
1599 mshrQueue.markPending(mshr);
1600 schedMemSideSendEvent(clockEdge() + pkt->payloadDelay);
1601 } else {
1602 mshrQueue.deallocate(mshr);
1603 if (wasFull && !mshrQueue.isFull()) {
1604 clearBlocked(Blocked_NoMSHRs);
1605 }
1606
1607 // Request the bus for a prefetch if this deallocation freed enough
1608 // MSHRs for a prefetch to take place
1609 if (prefetcher && mshrQueue.canPrefetch()) {
1610 Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(),
1611 clockEdge());
1612 if (next_pf_time != MaxTick)
1613 schedMemSideSendEvent(next_pf_time);
1614 }
1615 }
1616 // reset the xbar additional timinig as it is now accounted for
1617 pkt->headerDelay = pkt->payloadDelay = 0;
1618
1619 // copy writebacks to write buffer
1620 doWritebacks(writebacks, forward_time);
1621
1622 // if we used temp block, check to see if its valid and then clear it out
1623 if (blk == tempBlock && tempBlock->isValid()) {
1624 // We use forwardLatency here because we are copying
1625 // Writebacks/CleanEvicts to write buffer. It specifies the latency to
1626 // allocate an internal buffer and to schedule an event to the
1627 // queued port.
1628 if (blk->isDirty() || writebackClean) {
1629 PacketPtr wbPkt = writebackBlk(blk);
1630 allocateWriteBuffer(wbPkt, forward_time);
1631 // Set BLOCK_CACHED flag if cached above.
1632 if (isCachedAbove(wbPkt))
1633 wbPkt->setBlockCached();
1634 } else {
1635 PacketPtr wcPkt = cleanEvictBlk(blk);
1636 // Check to see if block is cached above. If not allocate
1637 // write buffer
1638 if (isCachedAbove(wcPkt))
1639 delete wcPkt;
1640 else
1641 allocateWriteBuffer(wcPkt, forward_time);
1642 }
1643 invalidateBlock(blk);
1644 }
1645
1646 DPRINTF(CacheVerbose, "%s: Leaving with %s\n", __func__, pkt->print());
1647 delete pkt;
1648}
1649
1650PacketPtr
1651Cache::writebackBlk(CacheBlk *blk)
1652{
1653 chatty_assert(!isReadOnly || writebackClean,
1654 "Writeback from read-only cache");
1655 assert(blk && blk->isValid() && (blk->isDirty() || writebackClean));
1656
1657 writebacks[Request::wbMasterId]++;
1658
1659 Request *req = new Request(tags->regenerateBlkAddr(blk->tag, blk->set),
1660 blkSize, 0, Request::wbMasterId);
1661 if (blk->isSecure())
1662 req->setFlags(Request::SECURE);
1663
1664 req->taskId(blk->task_id);
1665
1666 PacketPtr pkt =
1667 new Packet(req, blk->isDirty() ?
1668 MemCmd::WritebackDirty : MemCmd::WritebackClean);
1669
1670 DPRINTF(Cache, "Create Writeback %s writable: %d, dirty: %d\n",
1671 pkt->print(), blk->isWritable(), blk->isDirty());
1672
1673 if (blk->isWritable()) {
1674 // not asserting shared means we pass the block in modified
1675 // state, mark our own block non-writeable
1676 blk->status &= ~BlkWritable;
1677 } else {
1678 // we are in the Owned state, tell the receiver
1679 pkt->setHasSharers();
1680 }
1681
1682 // make sure the block is not marked dirty
1683 blk->status &= ~BlkDirty;
1684
1685 pkt->allocate();
1686 std::memcpy(pkt->getPtr<uint8_t>(), blk->data, blkSize);
1687
1688 return pkt;
1689}
1690
1691PacketPtr
1692Cache::writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id)
1693{
1694 Request *req = new Request(tags->regenerateBlkAddr(blk->tag, blk->set),
1695 blkSize, 0, Request::wbMasterId);
1696 if (blk->isSecure()) {
1697 req->setFlags(Request::SECURE);
1698 }
1699 req->taskId(blk->task_id);
1700
1701 PacketPtr pkt = new Packet(req, MemCmd::WriteClean, blkSize, id);
1702
1703 if (dest) {
1704 req->setFlags(dest);
1705 pkt->setWriteThrough();
1706 }
1707
1708 DPRINTF(Cache, "Create %s writable: %d, dirty: %d\n", pkt->print(),
1709 blk->isWritable(), blk->isDirty());
1710
1711 if (blk->isWritable()) {
1712 // not asserting shared means we pass the block in modified
1713 // state, mark our own block non-writeable
1714 blk->status &= ~BlkWritable;
1715 } else {
1716 // we are in the Owned state, tell the receiver
1717 pkt->setHasSharers();
1718 }
1719
1720 // make sure the block is not marked dirty
1721 blk->status &= ~BlkDirty;
1722
1723 pkt->allocate();
1724 std::memcpy(pkt->getPtr<uint8_t>(), blk->data, blkSize);
1725
1726 return pkt;
1727}
1728
1729
1730PacketPtr
1731Cache::cleanEvictBlk(CacheBlk *blk)
1732{
1733 assert(!writebackClean);
1734 assert(blk && blk->isValid() && !blk->isDirty());
1735 // Creating a zero sized write, a message to the snoop filter
1736 Request *req =
1737 new Request(tags->regenerateBlkAddr(blk->tag, blk->set), blkSize, 0,
1738 Request::wbMasterId);
1739 if (blk->isSecure())
1740 req->setFlags(Request::SECURE);
1741
1742 req->taskId(blk->task_id);
1743
1744 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
1745 pkt->allocate();
1746 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
1747
1748 return pkt;
1749}
1750
1751void
1752Cache::memWriteback()
1753{
1754 CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor);
1755 tags->forEachBlk(visitor);
1756}
1757
1758void
1759Cache::memInvalidate()
1760{
1761 CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor);
1762 tags->forEachBlk(visitor);
1763}
1764
1765bool
1766Cache::isDirty() const
1767{
1768 CacheBlkIsDirtyVisitor visitor;
1769 tags->forEachBlk(visitor);
1770
1771 return visitor.isDirty();
1772}
1773
1774bool
1775Cache::writebackVisitor(CacheBlk &blk)
1776{
1777 if (blk.isDirty()) {
1778 assert(blk.isValid());
1779
1780 Request request(tags->regenerateBlkAddr(blk.tag, blk.set),
1781 blkSize, 0, Request::funcMasterId);
1782 request.taskId(blk.task_id);
1783 if (blk.isSecure()) {
1784 request.setFlags(Request::SECURE);
1785 }
1786
1787 Packet packet(&request, MemCmd::WriteReq);
1788 packet.dataStatic(blk.data);
1789
1790 memSidePort->sendFunctional(&packet);
1791
1792 blk.status &= ~BlkDirty;
1793 }
1794
1795 return true;
1796}
1797
1798bool
1799Cache::invalidateVisitor(CacheBlk &blk)
1800{
1801
1802 if (blk.isDirty())
1803 warn_once("Invalidating dirty cache lines. Expect things to break.\n");
1804
1805 if (blk.isValid()) {
1806 assert(!blk.isDirty());
1807 invalidateBlock(&blk);
1808 }
1809
1810 return true;
1811}
1812
1813CacheBlk*
1814Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks)
1815{
1816 CacheBlk *blk = tags->findVictim(addr);
1817
1818 // It is valid to return nullptr if there is no victim
1819 if (!blk)
1820 return nullptr;
1821
1822 if (blk->isValid()) {
1823 Addr repl_addr = tags->regenerateBlkAddr(blk->tag, blk->set);
1824 MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
1825 if (repl_mshr) {
1826 // must be an outstanding upgrade request
1827 // on a block we're about to replace...
1828 assert(!blk->isWritable() || blk->isDirty());
1829 assert(repl_mshr->needsWritable());
1830 // too hard to replace block with transient state
1831 // allocation failed, block not inserted
1832 return nullptr;
1833 } else {
1834 DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx "
1835 "(%s): %s\n", repl_addr, blk->isSecure() ? "s" : "ns",
1836 addr, is_secure ? "s" : "ns",
1837 blk->isDirty() ? "writeback" : "clean");
1838
1839 if (blk->wasPrefetched()) {
1840 unusedPrefetches++;
1841 }
1842 // Will send up Writeback/CleanEvict snoops via isCachedAbove
1843 // when pushing this writeback list into the write buffer.
1844 if (blk->isDirty() || writebackClean) {
1845 // Save writeback packet for handling by caller
1846 writebacks.push_back(writebackBlk(blk));
1847 } else {
1848 writebacks.push_back(cleanEvictBlk(blk));
1849 }
1850 }
1851 }
1852
1853 return blk;
1854}
1855
1856void
1857Cache::invalidateBlock(CacheBlk *blk)
1858{
1859 if (blk != tempBlock)
1860 tags->invalidate(blk);
1861 blk->invalidate();
1862}
1863
1864// Note that the reason we return a list of writebacks rather than
1865// inserting them directly in the write buffer is that this function
1866// is called by both atomic and timing-mode accesses, and in atomic
1867// mode we don't mess with the write buffer (we just perform the
1868// writebacks atomically once the original request is complete).
1869CacheBlk*
1870Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks,
1871 bool allocate)
1872{
1873 assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq);
1874 Addr addr = pkt->getAddr();
1875 bool is_secure = pkt->isSecure();
1876#if TRACING_ON
1877 CacheBlk::State old_state = blk ? blk->status : 0;
1878#endif
1879
1880 // When handling a fill, we should have no writes to this line.
1881 assert(addr == pkt->getBlockAddr(blkSize));
1882 assert(!writeBuffer.findMatch(addr, is_secure));
1883
1884 if (blk == nullptr) {
1885 // better have read new data...
1886 assert(pkt->hasData());
1887
1888 // only read responses and write-line requests have data;
1889 // note that we don't write the data here for write-line - that
1890 // happens in the subsequent call to satisfyRequest
1891 assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq);
1892
1893 // need to do a replacement if allocating, otherwise we stick
1894 // with the temporary storage
1895 blk = allocate ? allocateBlock(addr, is_secure, writebacks) : nullptr;
1896
1897 if (blk == nullptr) {
1898 // No replaceable block or a mostly exclusive
1899 // cache... just use temporary storage to complete the
1900 // current request and then get rid of it
1901 assert(!tempBlock->isValid());
1902 blk = tempBlock;
1903 tempBlock->set = tags->extractSet(addr);
1904 tempBlock->tag = tags->extractTag(addr);
|
1906 DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr,
1907 is_secure ? "s" : "ns");
1908 } else {
1909 tags->insertBlock(pkt, blk);
1910 }
1911
1912 // we should never be overwriting a valid block
1913 assert(!blk->isValid());
1914 } else {
1915 // existing block... probably an upgrade
1916 assert(blk->tag == tags->extractTag(addr));
1917 // either we're getting new data or the block should already be valid
1918 assert(pkt->hasData() || blk->isValid());
1919 // don't clear block status... if block is already dirty we
1920 // don't want to lose that
1921 }
1922
1923 if (is_secure)
1924 blk->status |= BlkSecure;
1925 blk->status |= BlkValid | BlkReadable;
1926
1927 // sanity check for whole-line writes, which should always be
1928 // marked as writable as part of the fill, and then later marked
1929 // dirty as part of satisfyRequest
1930 if (pkt->cmd == MemCmd::WriteLineReq) {
1931 assert(!pkt->hasSharers());
1932 }
1933
1934 // here we deal with setting the appropriate state of the line,
1935 // and we start by looking at the hasSharers flag, and ignore the
1936 // cacheResponding flag (normally signalling dirty data) if the
1937 // packet has sharers, thus the line is never allocated as Owned
1938 // (dirty but not writable), and always ends up being either
1939 // Shared, Exclusive or Modified, see Packet::setCacheResponding
1940 // for more details
1941 if (!pkt->hasSharers()) {
1942 // we could get a writable line from memory (rather than a
1943 // cache) even in a read-only cache, note that we set this bit
1944 // even for a read-only cache, possibly revisit this decision
1945 blk->status |= BlkWritable;
1946
1947 // check if we got this via cache-to-cache transfer (i.e., from a
1948 // cache that had the block in Modified or Owned state)
1949 if (pkt->cacheResponding()) {
1950 // we got the block in Modified state, and invalidated the
1951 // owners copy
1952 blk->status |= BlkDirty;
1953
1954 chatty_assert(!isReadOnly, "Should never see dirty snoop response "
1955 "in read-only cache %s\n", name());
1956 }
1957 }
1958
1959 DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n",
1960 addr, is_secure ? "s" : "ns", old_state, blk->print());
1961
1962 // if we got new data, copy it in (checking for a read response
1963 // and a response that has data is the same in the end)
1964 if (pkt->isRead()) {
1965 // sanity checks
1966 assert(pkt->hasData());
1967 assert(pkt->getSize() == blkSize);
1968
1969 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
1970 }
1971 // We pay for fillLatency here.
1972 blk->whenReady = clockEdge() + fillLatency * clockPeriod() +
1973 pkt->payloadDelay;
1974
1975 return blk;
1976}
1977
1978
1979/////////////////////////////////////////////////////
1980//
1981// Snoop path: requests coming in from the memory side
1982//
1983/////////////////////////////////////////////////////
1984
1985void
1986Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
1987 bool already_copied, bool pending_inval)
1988{
1989 // sanity check
1990 assert(req_pkt->isRequest());
1991 assert(req_pkt->needsResponse());
1992
1993 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
1994 // timing-mode snoop responses require a new packet, unless we
1995 // already made a copy...
1996 PacketPtr pkt = req_pkt;
1997 if (!already_copied)
1998 // do not clear flags, and allocate space for data if the
1999 // packet needs it (the only packets that carry data are read
2000 // responses)
2001 pkt = new Packet(req_pkt, false, req_pkt->isRead());
2002
2003 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
2004 pkt->hasSharers());
2005 pkt->makeTimingResponse();
2006 if (pkt->isRead()) {
2007 pkt->setDataFromBlock(blk_data, blkSize);
2008 }
2009 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
2010 // Assume we defer a response to a read from a far-away cache
2011 // A, then later defer a ReadExcl from a cache B on the same
2012 // bus as us. We'll assert cacheResponding in both cases, but
2013 // in the latter case cacheResponding will keep the
2014 // invalidation from reaching cache A. This special response
2015 // tells cache A that it gets the block to satisfy its read,
2016 // but must immediately invalidate it.
2017 pkt->cmd = MemCmd::ReadRespWithInvalidate;
2018 }
2019 // Here we consider forward_time, paying for just forward latency and
2020 // also charging the delay provided by the xbar.
2021 // forward_time is used as send_time in next allocateWriteBuffer().
2022 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
2023 // Here we reset the timing of the packet.
2024 pkt->headerDelay = pkt->payloadDelay = 0;
2025 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
2026 pkt->print(), forward_time);
2027 memSidePort->schedTimingSnoopResp(pkt, forward_time, true);
2028}
2029
2030uint32_t
2031Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
2032 bool is_deferred, bool pending_inval)
2033{
2034 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2035 // deferred snoops can only happen in timing mode
2036 assert(!(is_deferred && !is_timing));
2037 // pending_inval only makes sense on deferred snoops
2038 assert(!(pending_inval && !is_deferred));
2039 assert(pkt->isRequest());
2040
2041 // the packet may get modified if we or a forwarded snooper
2042 // responds in atomic mode, so remember a few things about the
2043 // original packet up front
2044 bool invalidate = pkt->isInvalidate();
2045 bool M5_VAR_USED needs_writable = pkt->needsWritable();
2046
2047 // at the moment we could get an uncacheable write which does not
2048 // have the invalidate flag, and we need a suitable way of dealing
2049 // with this case
2050 panic_if(invalidate && pkt->req->isUncacheable(),
2051 "%s got an invalidating uncacheable snoop request %s",
2052 name(), pkt->print());
2053
2054 uint32_t snoop_delay = 0;
2055
2056 if (forwardSnoops) {
2057 // first propagate snoop upward to see if anyone above us wants to
2058 // handle it. save & restore packet src since it will get
2059 // rewritten to be relative to cpu-side bus (if any)
2060 bool alreadyResponded = pkt->cacheResponding();
2061 if (is_timing) {
2062 // copy the packet so that we can clear any flags before
2063 // forwarding it upwards, we also allocate data (passing
2064 // the pointer along in case of static data), in case
2065 // there is a snoop hit in upper levels
2066 Packet snoopPkt(pkt, true, true);
2067 snoopPkt.setExpressSnoop();
2068 // the snoop packet does not need to wait any additional
2069 // time
2070 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
2071 cpuSidePort->sendTimingSnoopReq(&snoopPkt);
2072
2073 // add the header delay (including crossbar and snoop
2074 // delays) of the upward snoop to the snoop delay for this
2075 // cache
2076 snoop_delay += snoopPkt.headerDelay;
2077
2078 if (snoopPkt.cacheResponding()) {
2079 // cache-to-cache response from some upper cache
2080 assert(!alreadyResponded);
2081 pkt->setCacheResponding();
2082 }
2083 // upstream cache has the block, or has an outstanding
2084 // MSHR, pass the flag on
2085 if (snoopPkt.hasSharers()) {
2086 pkt->setHasSharers();
2087 }
2088 // If this request is a prefetch or clean evict and an upper level
2089 // signals block present, make sure to propagate the block
2090 // presence to the requester.
2091 if (snoopPkt.isBlockCached()) {
2092 pkt->setBlockCached();
2093 }
2094 // If the request was satisfied by snooping the cache
2095 // above, mark the original packet as satisfied too.
2096 if (snoopPkt.satisfied()) {
2097 pkt->setSatisfied();
2098 }
2099 } else {
2100 cpuSidePort->sendAtomicSnoop(pkt);
2101 if (!alreadyResponded && pkt->cacheResponding()) {
2102 // cache-to-cache response from some upper cache:
2103 // forward response to original requester
2104 assert(pkt->isResponse());
2105 }
2106 }
2107 }
2108
2109 bool respond = false;
2110 bool blk_valid = blk && blk->isValid();
2111 if (pkt->isClean()) {
2112 if (blk_valid && blk->isDirty()) {
2113 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
2114 __func__, pkt->print(), blk->print());
2115 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
2116 PacketList writebacks;
2117 writebacks.push_back(wb_pkt);
2118
2119 if (is_timing) {
2120 // anything that is merely forwarded pays for the forward
2121 // latency and the delay provided by the crossbar
2122 Tick forward_time = clockEdge(forwardLatency) +
2123 pkt->headerDelay;
2124 doWritebacks(writebacks, forward_time);
2125 } else {
2126 doWritebacksAtomic(writebacks);
2127 }
2128 pkt->setSatisfied();
2129 }
2130 } else if (!blk_valid) {
2131 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
2132 pkt->print());
2133 if (is_deferred) {
2134 // we no longer have the block, and will not respond, but a
2135 // packet was allocated in MSHR::handleSnoop and we have
2136 // to delete it
2137 assert(pkt->needsResponse());
2138
2139 // we have passed the block to a cache upstream, that
2140 // cache should be responding
2141 assert(pkt->cacheResponding());
2142
2143 delete pkt;
2144 }
2145 return snoop_delay;
2146 } else {
2147 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
2148 pkt->print(), blk->print());
2149
2150 // We may end up modifying both the block state and the packet (if
2151 // we respond in atomic mode), so just figure out what to do now
2152 // and then do it later. We respond to all snoops that need
2153 // responses provided we have the block in dirty state. The
2154 // invalidation itself is taken care of below. We don't respond to
2155 // cache maintenance operations as this is done by the destination
2156 // xbar.
2157 respond = blk->isDirty() && pkt->needsResponse();
2158
2159 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
2160 "a dirty block in a read-only cache %s\n", name());
2161 }
2162
2163 // Invalidate any prefetch's from below that would strip write permissions
2164 // MemCmd::HardPFReq is only observed by upstream caches. After missing
2165 // above and in it's own cache, a new MemCmd::ReadReq is created that
2166 // downstream caches observe.
2167 if (pkt->mustCheckAbove()) {
2168 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
2169 "from lower cache\n", pkt->getAddr(), pkt->print());
2170 pkt->setBlockCached();
2171 return snoop_delay;
2172 }
2173
2174 if (pkt->isRead() && !invalidate) {
2175 // reading without requiring the line in a writable state
2176 assert(!needs_writable);
2177 pkt->setHasSharers();
2178
2179 // if the requesting packet is uncacheable, retain the line in
2180 // the current state, otherwhise unset the writable flag,
2181 // which means we go from Modified to Owned (and will respond
2182 // below), remain in Owned (and will respond below), from
2183 // Exclusive to Shared, or remain in Shared
2184 if (!pkt->req->isUncacheable())
2185 blk->status &= ~BlkWritable;
2186 DPRINTF(Cache, "new state is %s\n", blk->print());
2187 }
2188
2189 if (respond) {
2190 // prevent anyone else from responding, cache as well as
2191 // memory, and also prevent any memory from even seeing the
2192 // request
2193 pkt->setCacheResponding();
2194 if (!pkt->isClean() && blk->isWritable()) {
2195 // inform the cache hierarchy that this cache had the line
2196 // in the Modified state so that we avoid unnecessary
2197 // invalidations (see Packet::setResponderHadWritable)
2198 pkt->setResponderHadWritable();
2199
2200 // in the case of an uncacheable request there is no point
2201 // in setting the responderHadWritable flag, but since the
2202 // recipient does not care there is no harm in doing so
2203 } else {
2204 // if the packet has needsWritable set we invalidate our
2205 // copy below and all other copies will be invalidates
2206 // through express snoops, and if needsWritable is not set
2207 // we already called setHasSharers above
2208 }
2209
2210 // if we are returning a writable and dirty (Modified) line,
2211 // we should be invalidating the line
2212 panic_if(!invalidate && !pkt->hasSharers(),
2213 "%s is passing a Modified line through %s, "
2214 "but keeping the block", name(), pkt->print());
2215
2216 if (is_timing) {
2217 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
2218 } else {
2219 pkt->makeAtomicResponse();
2220 // packets such as upgrades do not actually have any data
2221 // payload
2222 if (pkt->hasData())
2223 pkt->setDataFromBlock(blk->data, blkSize);
2224 }
2225 }
2226
2227 if (!respond && is_deferred) {
2228 assert(pkt->needsResponse());
2229
2230 // if we copied the deferred packet with the intention to
2231 // respond, but are not responding, then a cache above us must
2232 // be, and we can use this as the indication of whether this
2233 // is a packet where we created a copy of the request or not
2234 if (!pkt->cacheResponding()) {
2235 delete pkt->req;
2236 }
2237
2238 delete pkt;
2239 }
2240
2241 // Do this last in case it deallocates block data or something
2242 // like that
2243 if (blk_valid && invalidate) {
2244 invalidateBlock(blk);
2245 DPRINTF(Cache, "new state is %s\n", blk->print());
2246 }
2247
2248 return snoop_delay;
2249}
2250
2251
2252void
2253Cache::recvTimingSnoopReq(PacketPtr pkt)
2254{
2255 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2256
2257 // Snoops shouldn't happen when bypassing caches
2258 assert(!system->bypassCaches());
2259
2260 // no need to snoop requests that are not in range
2261 if (!inRange(pkt->getAddr())) {
2262 return;
2263 }
2264
2265 bool is_secure = pkt->isSecure();
2266 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
2267
2268 Addr blk_addr = pkt->getBlockAddr(blkSize);
2269 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
2270
2271 // Update the latency cost of the snoop so that the crossbar can
2272 // account for it. Do not overwrite what other neighbouring caches
2273 // have already done, rather take the maximum. The update is
2274 // tentative, for cases where we return before an upward snoop
2275 // happens below.
2276 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
2277 lookupLatency * clockPeriod());
2278
2279 // Inform request(Prefetch, CleanEvict or Writeback) from below of
2280 // MSHR hit, set setBlockCached.
2281 if (mshr && pkt->mustCheckAbove()) {
2282 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
2283 "mshr hit\n", pkt->print());
2284 pkt->setBlockCached();
2285 return;
2286 }
2287
2288 // Bypass any existing cache maintenance requests if the request
2289 // has been satisfied already (i.e., the dirty block has been
2290 // found).
2291 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
2292 return;
2293 }
2294
2295 // Let the MSHR itself track the snoop and decide whether we want
2296 // to go ahead and do the regular cache snoop
2297 if (mshr && mshr->handleSnoop(pkt, order++)) {
2298 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
2299 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
2300 mshr->print());
2301
2302 if (mshr->getNumTargets() > numTarget)
2303 warn("allocating bonus target for snoop"); //handle later
2304 return;
2305 }
2306
2307 //We also need to check the writeback buffers and handle those
2308 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
2309 if (wb_entry) {
2310 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
2311 pkt->getAddr(), is_secure ? "s" : "ns");
2312 // Expect to see only Writebacks and/or CleanEvicts here, both of
2313 // which should not be generated for uncacheable data.
2314 assert(!wb_entry->isUncacheable());
2315 // There should only be a single request responsible for generating
2316 // Writebacks/CleanEvicts.
2317 assert(wb_entry->getNumTargets() == 1);
2318 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
2319 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
2320
2321 if (pkt->isEviction()) {
2322 // if the block is found in the write queue, set the BLOCK_CACHED
2323 // flag for Writeback/CleanEvict snoop. On return the snoop will
2324 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
2325 // any CleanEvicts from travelling down the memory hierarchy.
2326 pkt->setBlockCached();
2327 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
2328 "hit\n", __func__, pkt->print());
2329 return;
2330 }
2331
2332 // conceptually writebacks are no different to other blocks in
2333 // this cache, so the behaviour is modelled after handleSnoop,
2334 // the difference being that instead of querying the block
2335 // state to determine if it is dirty and writable, we use the
2336 // command and fields of the writeback packet
2337 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
2338 pkt->needsResponse();
2339 bool have_writable = !wb_pkt->hasSharers();
2340 bool invalidate = pkt->isInvalidate();
2341
2342 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
2343 assert(!pkt->needsWritable());
2344 pkt->setHasSharers();
2345 wb_pkt->setHasSharers();
2346 }
2347
2348 if (respond) {
2349 pkt->setCacheResponding();
2350
2351 if (have_writable) {
2352 pkt->setResponderHadWritable();
2353 }
2354
2355 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
2356 false, false);
2357 }
2358
2359 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
2360 // Invalidation trumps our writeback... discard here
2361 // Note: markInService will remove entry from writeback buffer.
2362 markInService(wb_entry);
2363 delete wb_pkt;
2364 }
2365 }
2366
2367 // If this was a shared writeback, there may still be
2368 // other shared copies above that require invalidation.
2369 // We could be more selective and return here if the
2370 // request is non-exclusive or if the writeback is
2371 // exclusive.
2372 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
2373
2374 // Override what we did when we first saw the snoop, as we now
2375 // also have the cost of the upwards snoops to account for
2376 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
2377 lookupLatency * clockPeriod());
2378}
2379
2380bool
2381Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
2382{
2383 // Express snoop responses from master to slave, e.g., from L1 to L2
2384 cache->recvTimingSnoopResp(pkt);
2385 return true;
2386}
2387
2388Tick
2389Cache::recvAtomicSnoop(PacketPtr pkt)
2390{
2391 // Snoops shouldn't happen when bypassing caches
2392 assert(!system->bypassCaches());
2393
2394 // no need to snoop requests that are not in range.
2395 if (!inRange(pkt->getAddr())) {
2396 return 0;
2397 }
2398
2399 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
2400 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
2401 return snoop_delay + lookupLatency * clockPeriod();
2402}
2403
2404
2405QueueEntry*
2406Cache::getNextQueueEntry()
2407{
2408 // Check both MSHR queue and write buffer for potential requests,
2409 // note that null does not mean there is no request, it could
2410 // simply be that it is not ready
2411 MSHR *miss_mshr = mshrQueue.getNext();
2412 WriteQueueEntry *wq_entry = writeBuffer.getNext();
2413
2414 // If we got a write buffer request ready, first priority is a
2415 // full write buffer, otherwise we favour the miss requests
2416 if (wq_entry && (writeBuffer.isFull() || !miss_mshr)) {
2417 // need to search MSHR queue for conflicting earlier miss.
2418 MSHR *conflict_mshr =
2419 mshrQueue.findPending(wq_entry->blkAddr,
2420 wq_entry->isSecure);
2421
2422 if (conflict_mshr && conflict_mshr->order < wq_entry->order) {
2423 // Service misses in order until conflict is cleared.
2424 return conflict_mshr;
2425
2426 // @todo Note that we ignore the ready time of the conflict here
2427 }
2428
2429 // No conflicts; issue write
2430 return wq_entry;
2431 } else if (miss_mshr) {
2432 // need to check for conflicting earlier writeback
2433 WriteQueueEntry *conflict_mshr =
2434 writeBuffer.findPending(miss_mshr->blkAddr,
2435 miss_mshr->isSecure);
2436 if (conflict_mshr) {
2437 // not sure why we don't check order here... it was in the
2438 // original code but commented out.
2439
2440 // The only way this happens is if we are
2441 // doing a write and we didn't have permissions
2442 // then subsequently saw a writeback (owned got evicted)
2443 // We need to make sure to perform the writeback first
2444 // To preserve the dirty data, then we can issue the write
2445
2446 // should we return wq_entry here instead? I.e. do we
2447 // have to flush writes in order? I don't think so... not
2448 // for Alpha anyway. Maybe for x86?
2449 return conflict_mshr;
2450
2451 // @todo Note that we ignore the ready time of the conflict here
2452 }
2453
2454 // No conflicts; issue read
2455 return miss_mshr;
2456 }
2457
2458 // fall through... no pending requests. Try a prefetch.
2459 assert(!miss_mshr && !wq_entry);
2460 if (prefetcher && mshrQueue.canPrefetch()) {
2461 // If we have a miss queue slot, we can try a prefetch
2462 PacketPtr pkt = prefetcher->getPacket();
2463 if (pkt) {
2464 Addr pf_addr = pkt->getBlockAddr(blkSize);
2465 if (!tags->findBlock(pf_addr, pkt->isSecure()) &&
2466 !mshrQueue.findMatch(pf_addr, pkt->isSecure()) &&
2467 !writeBuffer.findMatch(pf_addr, pkt->isSecure())) {
2468 // Update statistic on number of prefetches issued
2469 // (hwpf_mshr_misses)
2470 assert(pkt->req->masterId() < system->maxMasters());
2471 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
2472
2473 // allocate an MSHR and return it, note
2474 // that we send the packet straight away, so do not
2475 // schedule the send
2476 return allocateMissBuffer(pkt, curTick(), false);
2477 } else {
2478 // free the request and packet
2479 delete pkt->req;
2480 delete pkt;
2481 }
2482 }
2483 }
2484
2485 return nullptr;
2486}
2487
2488bool
2489Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const
2490{
2491 if (!forwardSnoops)
2492 return false;
2493 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
2494 // Writeback snoops into upper level caches to check for copies of the
2495 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
2496 // packet, the cache can inform the crossbar below of presence or absence
2497 // of the block.
2498 if (is_timing) {
2499 Packet snoop_pkt(pkt, true, false);
2500 snoop_pkt.setExpressSnoop();
2501 // Assert that packet is either Writeback or CleanEvict and not a
2502 // prefetch request because prefetch requests need an MSHR and may
2503 // generate a snoop response.
2504 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
2505 snoop_pkt.senderState = nullptr;
2506 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2507 // Writeback/CleanEvict snoops do not generate a snoop response.
2508 assert(!(snoop_pkt.cacheResponding()));
2509 return snoop_pkt.isBlockCached();
2510 } else {
2511 cpuSidePort->sendAtomicSnoop(pkt);
2512 return pkt->isBlockCached();
2513 }
2514}
2515
2516Tick
2517Cache::nextQueueReadyTime() const
2518{
2519 Tick nextReady = std::min(mshrQueue.nextReadyTime(),
2520 writeBuffer.nextReadyTime());
2521
2522 // Don't signal prefetch ready time if no MSHRs available
2523 // Will signal once enoguh MSHRs are deallocated
2524 if (prefetcher && mshrQueue.canPrefetch()) {
2525 nextReady = std::min(nextReady,
2526 prefetcher->nextPrefetchReadyTime());
2527 }
2528
2529 return nextReady;
2530}
2531
2532bool
2533Cache::sendMSHRQueuePacket(MSHR* mshr)
2534{
2535 assert(mshr);
2536
2537 // use request from 1st target
2538 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
2539
2540 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
2541
2542 CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure);
2543
2544 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
2545 // we should never have hardware prefetches to allocated
2546 // blocks
2547 assert(blk == nullptr);
2548
2549 // We need to check the caches above us to verify that
2550 // they don't have a copy of this block in the dirty state
2551 // at the moment. Without this check we could get a stale
2552 // copy from memory that might get used in place of the
2553 // dirty one.
2554 Packet snoop_pkt(tgt_pkt, true, false);
2555 snoop_pkt.setExpressSnoop();
2556 // We are sending this packet upwards, but if it hits we will
2557 // get a snoop response that we end up treating just like a
2558 // normal response, hence it needs the MSHR as its sender
2559 // state
2560 snoop_pkt.senderState = mshr;
2561 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2562
2563 // Check to see if the prefetch was squashed by an upper cache (to
2564 // prevent us from grabbing the line) or if a Check to see if a
2565 // writeback arrived between the time the prefetch was placed in
2566 // the MSHRs and when it was selected to be sent or if the
2567 // prefetch was squashed by an upper cache.
2568
2569 // It is important to check cacheResponding before
2570 // prefetchSquashed. If another cache has committed to
2571 // responding, it will be sending a dirty response which will
2572 // arrive at the MSHR allocated for this request. Checking the
2573 // prefetchSquash first may result in the MSHR being
2574 // prematurely deallocated.
2575 if (snoop_pkt.cacheResponding()) {
2576 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
2577 assert(r.second);
2578
2579 // if we are getting a snoop response with no sharers it
2580 // will be allocated as Modified
2581 bool pending_modified_resp = !snoop_pkt.hasSharers();
2582 markInService(mshr, pending_modified_resp);
2583
2584 DPRINTF(Cache, "Upward snoop of prefetch for addr"
2585 " %#x (%s) hit\n",
2586 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
2587 return false;
2588 }
2589
2590 if (snoop_pkt.isBlockCached()) {
2591 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
2592 "Deallocating mshr target %#x.\n",
2593 mshr->blkAddr);
2594
2595 // Deallocate the mshr target
2596 if (mshrQueue.forceDeallocateTarget(mshr)) {
2597 // Clear block if this deallocation resulted freed an
2598 // mshr when all had previously been utilized
2599 clearBlocked(Blocked_NoMSHRs);
2600 }
2601
2602 // given that no response is expected, delete Request and Packet
2603 delete tgt_pkt->req;
2604 delete tgt_pkt;
2605
2606 return false;
2607 }
2608 }
2609
2610 // either a prefetch that is not present upstream, or a normal
2611 // MSHR request, proceed to get the packet to send downstream
2612 PacketPtr pkt = createMissPacket(tgt_pkt, blk, mshr->needsWritable());
2613
2614 mshr->isForward = (pkt == nullptr);
2615
2616 if (mshr->isForward) {
2617 // not a cache block request, but a response is expected
2618 // make copy of current packet to forward, keep current
2619 // copy for response handling
2620 pkt = new Packet(tgt_pkt, false, true);
2621 assert(!pkt->isWrite());
2622 }
2623
2624 // play it safe and append (rather than set) the sender state,
2625 // as forwarded packets may already have existing state
2626 pkt->pushSenderState(mshr);
2627
2628 if (pkt->isClean() && blk && blk->isDirty()) {
2629 // A cache clean opearation is looking for a dirty block. Mark
2630 // the packet so that the destination xbar can determine that
2631 // there will be a follow-up write packet as well.
2632 pkt->setSatisfied();
2633 }
2634
2635 if (!memSidePort->sendTimingReq(pkt)) {
2636 // we are awaiting a retry, but we
2637 // delete the packet and will be creating a new packet
2638 // when we get the opportunity
2639 delete pkt;
2640
2641 // note that we have now masked any requestBus and
2642 // schedSendEvent (we will wait for a retry before
2643 // doing anything), and this is so even if we do not
2644 // care about this packet and might override it before
2645 // it gets retried
2646 return true;
2647 } else {
2648 // As part of the call to sendTimingReq the packet is
2649 // forwarded to all neighbouring caches (and any caches
2650 // above them) as a snoop. Thus at this point we know if
2651 // any of the neighbouring caches are responding, and if
2652 // so, we know it is dirty, and we can determine if it is
2653 // being passed as Modified, making our MSHR the ordering
2654 // point
2655 bool pending_modified_resp = !pkt->hasSharers() &&
2656 pkt->cacheResponding();
2657 markInService(mshr, pending_modified_resp);
2658 if (pkt->isClean() && blk && blk->isDirty()) {
2659 // A cache clean opearation is looking for a dirty
2660 // block. If a dirty block is encountered a WriteClean
2661 // will update any copies to the path to the memory
2662 // until the point of reference.
2663 DPRINTF(CacheVerbose, "%s: packet %s found block: %s\n",
2664 __func__, pkt->print(), blk->print());
2665 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(),
2666 pkt->id);
2667 PacketList writebacks;
2668 writebacks.push_back(wb_pkt);
2669 doWritebacks(writebacks, 0);
2670 }
2671
2672 return false;
2673 }
2674}
2675
2676bool
2677Cache::sendWriteQueuePacket(WriteQueueEntry* wq_entry)
2678{
2679 assert(wq_entry);
2680
2681 // always a single target for write queue entries
2682 PacketPtr tgt_pkt = wq_entry->getTarget()->pkt;
2683
2684 DPRINTF(Cache, "%s: write %s\n", __func__, tgt_pkt->print());
2685
2686 // forward as is, both for evictions and uncacheable writes
2687 if (!memSidePort->sendTimingReq(tgt_pkt)) {
2688 // note that we have now masked any requestBus and
2689 // schedSendEvent (we will wait for a retry before
2690 // doing anything), and this is so even if we do not
2691 // care about this packet and might override it before
2692 // it gets retried
2693 return true;
2694 } else {
2695 markInService(wq_entry);
2696 return false;
2697 }
2698}
2699
2700void
2701Cache::serialize(CheckpointOut &cp) const
2702{
2703 bool dirty(isDirty());
2704
2705 if (dirty) {
2706 warn("*** The cache still contains dirty data. ***\n");
2707 warn(" Make sure to drain the system using the correct flags.\n");
2708 warn(" This checkpoint will not restore correctly and dirty data "
2709 " in the cache will be lost!\n");
2710 }
2711
2712 // Since we don't checkpoint the data in the cache, any dirty data
2713 // will be lost when restoring from a checkpoint of a system that
2714 // wasn't drained properly. Flag the checkpoint as invalid if the
2715 // cache contains dirty data.
2716 bool bad_checkpoint(dirty);
2717 SERIALIZE_SCALAR(bad_checkpoint);
2718}
2719
2720void
2721Cache::unserialize(CheckpointIn &cp)
2722{
2723 bool bad_checkpoint;
2724 UNSERIALIZE_SCALAR(bad_checkpoint);
2725 if (bad_checkpoint) {
2726 fatal("Restoring from checkpoints with dirty caches is not supported "
2727 "in the classic memory system. Please remove any caches or "
2728 " drain them properly before taking checkpoints.\n");
2729 }
2730}
2731
2732///////////////
2733//
2734// CpuSidePort
2735//
2736///////////////
2737
2738AddrRangeList
2739Cache::CpuSidePort::getAddrRanges() const
2740{
2741 return cache->getAddrRanges();
2742}
2743
2744bool
2745Cache::CpuSidePort::tryTiming(PacketPtr pkt)
2746{
2747 assert(!cache->system->bypassCaches());
2748
2749 // always let express snoop packets through if even if blocked
2750 if (pkt->isExpressSnoop()) {
2751 return true;
2752 } else if (isBlocked() || mustSendRetry) {
2753 // either already committed to send a retry, or blocked
2754 mustSendRetry = true;
2755 return false;
2756 }
2757 mustSendRetry = false;
2758 return true;
2759}
2760
2761bool
2762Cache::CpuSidePort::recvTimingReq(PacketPtr pkt)
2763{
2764 assert(!cache->system->bypassCaches());
2765
2766 // always let express snoop packets through if even if blocked
2767 if (pkt->isExpressSnoop()) {
2768 bool M5_VAR_USED bypass_success = cache->recvTimingReq(pkt);
2769 assert(bypass_success);
2770 return true;
2771 }
2772
2773 return tryTiming(pkt) && cache->recvTimingReq(pkt);
2774}
2775
2776Tick
2777Cache::CpuSidePort::recvAtomic(PacketPtr pkt)
2778{
2779 return cache->recvAtomic(pkt);
2780}
2781
2782void
2783Cache::CpuSidePort::recvFunctional(PacketPtr pkt)
2784{
2785 // functional request
2786 cache->functionalAccess(pkt, true);
2787}
2788
2789Cache::
2790CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache,
2791 const std::string &_label)
2792 : BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache)
2793{
2794}
2795
2796Cache*
2797CacheParams::create()
2798{
2799 assert(tags);
2800
2801 return new Cache(this);
2802}
2803///////////////
2804//
2805// MemSidePort
2806//
2807///////////////
2808
2809bool
2810Cache::MemSidePort::recvTimingResp(PacketPtr pkt)
2811{
2812 cache->recvTimingResp(pkt);
2813 return true;
2814}
2815
2816// Express snooping requests to memside port
2817void
2818Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt)
2819{
2820 // handle snooping requests
2821 cache->recvTimingSnoopReq(pkt);
2822}
2823
2824Tick
2825Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt)
2826{
2827 return cache->recvAtomicSnoop(pkt);
2828}
2829
2830void
2831Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt)
2832{
2833 // functional snoop (note that in contrast to atomic we don't have
2834 // a specific functionalSnoop method, as they have the same
2835 // behaviour regardless)
2836 cache->functionalAccess(pkt, false);
2837}
2838
2839void
2840Cache::CacheReqPacketQueue::sendDeferredPacket()
2841{
2842 // sanity check
2843 assert(!waitingOnRetry);
2844
2845 // there should never be any deferred request packets in the
2846 // queue, instead we resly on the cache to provide the packets
2847 // from the MSHR queue or write queue
2848 assert(deferredPacketReadyTime() == MaxTick);
2849
2850 // check for request packets (requests & writebacks)
2851 QueueEntry* entry = cache.getNextQueueEntry();
2852
2853 if (!entry) {
2854 // can happen if e.g. we attempt a writeback and fail, but
2855 // before the retry, the writeback is eliminated because
2856 // we snoop another cache's ReadEx.
2857 } else {
2858 // let our snoop responses go first if there are responses to
2859 // the same addresses
2860 if (checkConflictingSnoop(entry->blkAddr)) {
2861 return;
2862 }
2863 waitingOnRetry = entry->sendPacket(cache);
2864 }
2865
2866 // if we succeeded and are not waiting for a retry, schedule the
2867 // next send considering when the next queue is ready, note that
2868 // snoop responses have their own packet queue and thus schedule
2869 // their own events
2870 if (!waitingOnRetry) {
2871 schedSendEvent(cache.nextQueueReadyTime());
2872 }
2873}
2874
2875Cache::
2876MemSidePort::MemSidePort(const std::string &_name, Cache *_cache,
2877 const std::string &_label)
2878 : BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue),
2879 _reqQueue(*_cache, *this, _snoopRespQueue, _label),
2880 _snoopRespQueue(*_cache, *this, _label), cache(_cache)
2881{
2882}
| 1908 DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr,
1909 is_secure ? "s" : "ns");
1910 } else {
1911 tags->insertBlock(pkt, blk);
1912 }
1913
1914 // we should never be overwriting a valid block
1915 assert(!blk->isValid());
1916 } else {
1917 // existing block... probably an upgrade
1918 assert(blk->tag == tags->extractTag(addr));
1919 // either we're getting new data or the block should already be valid
1920 assert(pkt->hasData() || blk->isValid());
1921 // don't clear block status... if block is already dirty we
1922 // don't want to lose that
1923 }
1924
1925 if (is_secure)
1926 blk->status |= BlkSecure;
1927 blk->status |= BlkValid | BlkReadable;
1928
1929 // sanity check for whole-line writes, which should always be
1930 // marked as writable as part of the fill, and then later marked
1931 // dirty as part of satisfyRequest
1932 if (pkt->cmd == MemCmd::WriteLineReq) {
1933 assert(!pkt->hasSharers());
1934 }
1935
1936 // here we deal with setting the appropriate state of the line,
1937 // and we start by looking at the hasSharers flag, and ignore the
1938 // cacheResponding flag (normally signalling dirty data) if the
1939 // packet has sharers, thus the line is never allocated as Owned
1940 // (dirty but not writable), and always ends up being either
1941 // Shared, Exclusive or Modified, see Packet::setCacheResponding
1942 // for more details
1943 if (!pkt->hasSharers()) {
1944 // we could get a writable line from memory (rather than a
1945 // cache) even in a read-only cache, note that we set this bit
1946 // even for a read-only cache, possibly revisit this decision
1947 blk->status |= BlkWritable;
1948
1949 // check if we got this via cache-to-cache transfer (i.e., from a
1950 // cache that had the block in Modified or Owned state)
1951 if (pkt->cacheResponding()) {
1952 // we got the block in Modified state, and invalidated the
1953 // owners copy
1954 blk->status |= BlkDirty;
1955
1956 chatty_assert(!isReadOnly, "Should never see dirty snoop response "
1957 "in read-only cache %s\n", name());
1958 }
1959 }
1960
1961 DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n",
1962 addr, is_secure ? "s" : "ns", old_state, blk->print());
1963
1964 // if we got new data, copy it in (checking for a read response
1965 // and a response that has data is the same in the end)
1966 if (pkt->isRead()) {
1967 // sanity checks
1968 assert(pkt->hasData());
1969 assert(pkt->getSize() == blkSize);
1970
1971 std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
1972 }
1973 // We pay for fillLatency here.
1974 blk->whenReady = clockEdge() + fillLatency * clockPeriod() +
1975 pkt->payloadDelay;
1976
1977 return blk;
1978}
1979
1980
1981/////////////////////////////////////////////////////
1982//
1983// Snoop path: requests coming in from the memory side
1984//
1985/////////////////////////////////////////////////////
1986
1987void
1988Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
1989 bool already_copied, bool pending_inval)
1990{
1991 // sanity check
1992 assert(req_pkt->isRequest());
1993 assert(req_pkt->needsResponse());
1994
1995 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
1996 // timing-mode snoop responses require a new packet, unless we
1997 // already made a copy...
1998 PacketPtr pkt = req_pkt;
1999 if (!already_copied)
2000 // do not clear flags, and allocate space for data if the
2001 // packet needs it (the only packets that carry data are read
2002 // responses)
2003 pkt = new Packet(req_pkt, false, req_pkt->isRead());
2004
2005 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
2006 pkt->hasSharers());
2007 pkt->makeTimingResponse();
2008 if (pkt->isRead()) {
2009 pkt->setDataFromBlock(blk_data, blkSize);
2010 }
2011 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
2012 // Assume we defer a response to a read from a far-away cache
2013 // A, then later defer a ReadExcl from a cache B on the same
2014 // bus as us. We'll assert cacheResponding in both cases, but
2015 // in the latter case cacheResponding will keep the
2016 // invalidation from reaching cache A. This special response
2017 // tells cache A that it gets the block to satisfy its read,
2018 // but must immediately invalidate it.
2019 pkt->cmd = MemCmd::ReadRespWithInvalidate;
2020 }
2021 // Here we consider forward_time, paying for just forward latency and
2022 // also charging the delay provided by the xbar.
2023 // forward_time is used as send_time in next allocateWriteBuffer().
2024 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
2025 // Here we reset the timing of the packet.
2026 pkt->headerDelay = pkt->payloadDelay = 0;
2027 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
2028 pkt->print(), forward_time);
2029 memSidePort->schedTimingSnoopResp(pkt, forward_time, true);
2030}
2031
2032uint32_t
2033Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
2034 bool is_deferred, bool pending_inval)
2035{
2036 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2037 // deferred snoops can only happen in timing mode
2038 assert(!(is_deferred && !is_timing));
2039 // pending_inval only makes sense on deferred snoops
2040 assert(!(pending_inval && !is_deferred));
2041 assert(pkt->isRequest());
2042
2043 // the packet may get modified if we or a forwarded snooper
2044 // responds in atomic mode, so remember a few things about the
2045 // original packet up front
2046 bool invalidate = pkt->isInvalidate();
2047 bool M5_VAR_USED needs_writable = pkt->needsWritable();
2048
2049 // at the moment we could get an uncacheable write which does not
2050 // have the invalidate flag, and we need a suitable way of dealing
2051 // with this case
2052 panic_if(invalidate && pkt->req->isUncacheable(),
2053 "%s got an invalidating uncacheable snoop request %s",
2054 name(), pkt->print());
2055
2056 uint32_t snoop_delay = 0;
2057
2058 if (forwardSnoops) {
2059 // first propagate snoop upward to see if anyone above us wants to
2060 // handle it. save & restore packet src since it will get
2061 // rewritten to be relative to cpu-side bus (if any)
2062 bool alreadyResponded = pkt->cacheResponding();
2063 if (is_timing) {
2064 // copy the packet so that we can clear any flags before
2065 // forwarding it upwards, we also allocate data (passing
2066 // the pointer along in case of static data), in case
2067 // there is a snoop hit in upper levels
2068 Packet snoopPkt(pkt, true, true);
2069 snoopPkt.setExpressSnoop();
2070 // the snoop packet does not need to wait any additional
2071 // time
2072 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
2073 cpuSidePort->sendTimingSnoopReq(&snoopPkt);
2074
2075 // add the header delay (including crossbar and snoop
2076 // delays) of the upward snoop to the snoop delay for this
2077 // cache
2078 snoop_delay += snoopPkt.headerDelay;
2079
2080 if (snoopPkt.cacheResponding()) {
2081 // cache-to-cache response from some upper cache
2082 assert(!alreadyResponded);
2083 pkt->setCacheResponding();
2084 }
2085 // upstream cache has the block, or has an outstanding
2086 // MSHR, pass the flag on
2087 if (snoopPkt.hasSharers()) {
2088 pkt->setHasSharers();
2089 }
2090 // If this request is a prefetch or clean evict and an upper level
2091 // signals block present, make sure to propagate the block
2092 // presence to the requester.
2093 if (snoopPkt.isBlockCached()) {
2094 pkt->setBlockCached();
2095 }
2096 // If the request was satisfied by snooping the cache
2097 // above, mark the original packet as satisfied too.
2098 if (snoopPkt.satisfied()) {
2099 pkt->setSatisfied();
2100 }
2101 } else {
2102 cpuSidePort->sendAtomicSnoop(pkt);
2103 if (!alreadyResponded && pkt->cacheResponding()) {
2104 // cache-to-cache response from some upper cache:
2105 // forward response to original requester
2106 assert(pkt->isResponse());
2107 }
2108 }
2109 }
2110
2111 bool respond = false;
2112 bool blk_valid = blk && blk->isValid();
2113 if (pkt->isClean()) {
2114 if (blk_valid && blk->isDirty()) {
2115 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
2116 __func__, pkt->print(), blk->print());
2117 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
2118 PacketList writebacks;
2119 writebacks.push_back(wb_pkt);
2120
2121 if (is_timing) {
2122 // anything that is merely forwarded pays for the forward
2123 // latency and the delay provided by the crossbar
2124 Tick forward_time = clockEdge(forwardLatency) +
2125 pkt->headerDelay;
2126 doWritebacks(writebacks, forward_time);
2127 } else {
2128 doWritebacksAtomic(writebacks);
2129 }
2130 pkt->setSatisfied();
2131 }
2132 } else if (!blk_valid) {
2133 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
2134 pkt->print());
2135 if (is_deferred) {
2136 // we no longer have the block, and will not respond, but a
2137 // packet was allocated in MSHR::handleSnoop and we have
2138 // to delete it
2139 assert(pkt->needsResponse());
2140
2141 // we have passed the block to a cache upstream, that
2142 // cache should be responding
2143 assert(pkt->cacheResponding());
2144
2145 delete pkt;
2146 }
2147 return snoop_delay;
2148 } else {
2149 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
2150 pkt->print(), blk->print());
2151
2152 // We may end up modifying both the block state and the packet (if
2153 // we respond in atomic mode), so just figure out what to do now
2154 // and then do it later. We respond to all snoops that need
2155 // responses provided we have the block in dirty state. The
2156 // invalidation itself is taken care of below. We don't respond to
2157 // cache maintenance operations as this is done by the destination
2158 // xbar.
2159 respond = blk->isDirty() && pkt->needsResponse();
2160
2161 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
2162 "a dirty block in a read-only cache %s\n", name());
2163 }
2164
2165 // Invalidate any prefetch's from below that would strip write permissions
2166 // MemCmd::HardPFReq is only observed by upstream caches. After missing
2167 // above and in it's own cache, a new MemCmd::ReadReq is created that
2168 // downstream caches observe.
2169 if (pkt->mustCheckAbove()) {
2170 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
2171 "from lower cache\n", pkt->getAddr(), pkt->print());
2172 pkt->setBlockCached();
2173 return snoop_delay;
2174 }
2175
2176 if (pkt->isRead() && !invalidate) {
2177 // reading without requiring the line in a writable state
2178 assert(!needs_writable);
2179 pkt->setHasSharers();
2180
2181 // if the requesting packet is uncacheable, retain the line in
2182 // the current state, otherwhise unset the writable flag,
2183 // which means we go from Modified to Owned (and will respond
2184 // below), remain in Owned (and will respond below), from
2185 // Exclusive to Shared, or remain in Shared
2186 if (!pkt->req->isUncacheable())
2187 blk->status &= ~BlkWritable;
2188 DPRINTF(Cache, "new state is %s\n", blk->print());
2189 }
2190
2191 if (respond) {
2192 // prevent anyone else from responding, cache as well as
2193 // memory, and also prevent any memory from even seeing the
2194 // request
2195 pkt->setCacheResponding();
2196 if (!pkt->isClean() && blk->isWritable()) {
2197 // inform the cache hierarchy that this cache had the line
2198 // in the Modified state so that we avoid unnecessary
2199 // invalidations (see Packet::setResponderHadWritable)
2200 pkt->setResponderHadWritable();
2201
2202 // in the case of an uncacheable request there is no point
2203 // in setting the responderHadWritable flag, but since the
2204 // recipient does not care there is no harm in doing so
2205 } else {
2206 // if the packet has needsWritable set we invalidate our
2207 // copy below and all other copies will be invalidates
2208 // through express snoops, and if needsWritable is not set
2209 // we already called setHasSharers above
2210 }
2211
2212 // if we are returning a writable and dirty (Modified) line,
2213 // we should be invalidating the line
2214 panic_if(!invalidate && !pkt->hasSharers(),
2215 "%s is passing a Modified line through %s, "
2216 "but keeping the block", name(), pkt->print());
2217
2218 if (is_timing) {
2219 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
2220 } else {
2221 pkt->makeAtomicResponse();
2222 // packets such as upgrades do not actually have any data
2223 // payload
2224 if (pkt->hasData())
2225 pkt->setDataFromBlock(blk->data, blkSize);
2226 }
2227 }
2228
2229 if (!respond && is_deferred) {
2230 assert(pkt->needsResponse());
2231
2232 // if we copied the deferred packet with the intention to
2233 // respond, but are not responding, then a cache above us must
2234 // be, and we can use this as the indication of whether this
2235 // is a packet where we created a copy of the request or not
2236 if (!pkt->cacheResponding()) {
2237 delete pkt->req;
2238 }
2239
2240 delete pkt;
2241 }
2242
2243 // Do this last in case it deallocates block data or something
2244 // like that
2245 if (blk_valid && invalidate) {
2246 invalidateBlock(blk);
2247 DPRINTF(Cache, "new state is %s\n", blk->print());
2248 }
2249
2250 return snoop_delay;
2251}
2252
2253
2254void
2255Cache::recvTimingSnoopReq(PacketPtr pkt)
2256{
2257 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2258
2259 // Snoops shouldn't happen when bypassing caches
2260 assert(!system->bypassCaches());
2261
2262 // no need to snoop requests that are not in range
2263 if (!inRange(pkt->getAddr())) {
2264 return;
2265 }
2266
2267 bool is_secure = pkt->isSecure();
2268 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
2269
2270 Addr blk_addr = pkt->getBlockAddr(blkSize);
2271 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
2272
2273 // Update the latency cost of the snoop so that the crossbar can
2274 // account for it. Do not overwrite what other neighbouring caches
2275 // have already done, rather take the maximum. The update is
2276 // tentative, for cases where we return before an upward snoop
2277 // happens below.
2278 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
2279 lookupLatency * clockPeriod());
2280
2281 // Inform request(Prefetch, CleanEvict or Writeback) from below of
2282 // MSHR hit, set setBlockCached.
2283 if (mshr && pkt->mustCheckAbove()) {
2284 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
2285 "mshr hit\n", pkt->print());
2286 pkt->setBlockCached();
2287 return;
2288 }
2289
2290 // Bypass any existing cache maintenance requests if the request
2291 // has been satisfied already (i.e., the dirty block has been
2292 // found).
2293 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
2294 return;
2295 }
2296
2297 // Let the MSHR itself track the snoop and decide whether we want
2298 // to go ahead and do the regular cache snoop
2299 if (mshr && mshr->handleSnoop(pkt, order++)) {
2300 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
2301 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
2302 mshr->print());
2303
2304 if (mshr->getNumTargets() > numTarget)
2305 warn("allocating bonus target for snoop"); //handle later
2306 return;
2307 }
2308
2309 //We also need to check the writeback buffers and handle those
2310 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
2311 if (wb_entry) {
2312 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
2313 pkt->getAddr(), is_secure ? "s" : "ns");
2314 // Expect to see only Writebacks and/or CleanEvicts here, both of
2315 // which should not be generated for uncacheable data.
2316 assert(!wb_entry->isUncacheable());
2317 // There should only be a single request responsible for generating
2318 // Writebacks/CleanEvicts.
2319 assert(wb_entry->getNumTargets() == 1);
2320 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
2321 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
2322
2323 if (pkt->isEviction()) {
2324 // if the block is found in the write queue, set the BLOCK_CACHED
2325 // flag for Writeback/CleanEvict snoop. On return the snoop will
2326 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
2327 // any CleanEvicts from travelling down the memory hierarchy.
2328 pkt->setBlockCached();
2329 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
2330 "hit\n", __func__, pkt->print());
2331 return;
2332 }
2333
2334 // conceptually writebacks are no different to other blocks in
2335 // this cache, so the behaviour is modelled after handleSnoop,
2336 // the difference being that instead of querying the block
2337 // state to determine if it is dirty and writable, we use the
2338 // command and fields of the writeback packet
2339 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
2340 pkt->needsResponse();
2341 bool have_writable = !wb_pkt->hasSharers();
2342 bool invalidate = pkt->isInvalidate();
2343
2344 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
2345 assert(!pkt->needsWritable());
2346 pkt->setHasSharers();
2347 wb_pkt->setHasSharers();
2348 }
2349
2350 if (respond) {
2351 pkt->setCacheResponding();
2352
2353 if (have_writable) {
2354 pkt->setResponderHadWritable();
2355 }
2356
2357 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
2358 false, false);
2359 }
2360
2361 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
2362 // Invalidation trumps our writeback... discard here
2363 // Note: markInService will remove entry from writeback buffer.
2364 markInService(wb_entry);
2365 delete wb_pkt;
2366 }
2367 }
2368
2369 // If this was a shared writeback, there may still be
2370 // other shared copies above that require invalidation.
2371 // We could be more selective and return here if the
2372 // request is non-exclusive or if the writeback is
2373 // exclusive.
2374 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
2375
2376 // Override what we did when we first saw the snoop, as we now
2377 // also have the cost of the upwards snoops to account for
2378 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
2379 lookupLatency * clockPeriod());
2380}
2381
2382bool
2383Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
2384{
2385 // Express snoop responses from master to slave, e.g., from L1 to L2
2386 cache->recvTimingSnoopResp(pkt);
2387 return true;
2388}
2389
2390Tick
2391Cache::recvAtomicSnoop(PacketPtr pkt)
2392{
2393 // Snoops shouldn't happen when bypassing caches
2394 assert(!system->bypassCaches());
2395
2396 // no need to snoop requests that are not in range.
2397 if (!inRange(pkt->getAddr())) {
2398 return 0;
2399 }
2400
2401 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
2402 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
2403 return snoop_delay + lookupLatency * clockPeriod();
2404}
2405
2406
2407QueueEntry*
2408Cache::getNextQueueEntry()
2409{
2410 // Check both MSHR queue and write buffer for potential requests,
2411 // note that null does not mean there is no request, it could
2412 // simply be that it is not ready
2413 MSHR *miss_mshr = mshrQueue.getNext();
2414 WriteQueueEntry *wq_entry = writeBuffer.getNext();
2415
2416 // If we got a write buffer request ready, first priority is a
2417 // full write buffer, otherwise we favour the miss requests
2418 if (wq_entry && (writeBuffer.isFull() || !miss_mshr)) {
2419 // need to search MSHR queue for conflicting earlier miss.
2420 MSHR *conflict_mshr =
2421 mshrQueue.findPending(wq_entry->blkAddr,
2422 wq_entry->isSecure);
2423
2424 if (conflict_mshr && conflict_mshr->order < wq_entry->order) {
2425 // Service misses in order until conflict is cleared.
2426 return conflict_mshr;
2427
2428 // @todo Note that we ignore the ready time of the conflict here
2429 }
2430
2431 // No conflicts; issue write
2432 return wq_entry;
2433 } else if (miss_mshr) {
2434 // need to check for conflicting earlier writeback
2435 WriteQueueEntry *conflict_mshr =
2436 writeBuffer.findPending(miss_mshr->blkAddr,
2437 miss_mshr->isSecure);
2438 if (conflict_mshr) {
2439 // not sure why we don't check order here... it was in the
2440 // original code but commented out.
2441
2442 // The only way this happens is if we are
2443 // doing a write and we didn't have permissions
2444 // then subsequently saw a writeback (owned got evicted)
2445 // We need to make sure to perform the writeback first
2446 // To preserve the dirty data, then we can issue the write
2447
2448 // should we return wq_entry here instead? I.e. do we
2449 // have to flush writes in order? I don't think so... not
2450 // for Alpha anyway. Maybe for x86?
2451 return conflict_mshr;
2452
2453 // @todo Note that we ignore the ready time of the conflict here
2454 }
2455
2456 // No conflicts; issue read
2457 return miss_mshr;
2458 }
2459
2460 // fall through... no pending requests. Try a prefetch.
2461 assert(!miss_mshr && !wq_entry);
2462 if (prefetcher && mshrQueue.canPrefetch()) {
2463 // If we have a miss queue slot, we can try a prefetch
2464 PacketPtr pkt = prefetcher->getPacket();
2465 if (pkt) {
2466 Addr pf_addr = pkt->getBlockAddr(blkSize);
2467 if (!tags->findBlock(pf_addr, pkt->isSecure()) &&
2468 !mshrQueue.findMatch(pf_addr, pkt->isSecure()) &&
2469 !writeBuffer.findMatch(pf_addr, pkt->isSecure())) {
2470 // Update statistic on number of prefetches issued
2471 // (hwpf_mshr_misses)
2472 assert(pkt->req->masterId() < system->maxMasters());
2473 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
2474
2475 // allocate an MSHR and return it, note
2476 // that we send the packet straight away, so do not
2477 // schedule the send
2478 return allocateMissBuffer(pkt, curTick(), false);
2479 } else {
2480 // free the request and packet
2481 delete pkt->req;
2482 delete pkt;
2483 }
2484 }
2485 }
2486
2487 return nullptr;
2488}
2489
2490bool
2491Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const
2492{
2493 if (!forwardSnoops)
2494 return false;
2495 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
2496 // Writeback snoops into upper level caches to check for copies of the
2497 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
2498 // packet, the cache can inform the crossbar below of presence or absence
2499 // of the block.
2500 if (is_timing) {
2501 Packet snoop_pkt(pkt, true, false);
2502 snoop_pkt.setExpressSnoop();
2503 // Assert that packet is either Writeback or CleanEvict and not a
2504 // prefetch request because prefetch requests need an MSHR and may
2505 // generate a snoop response.
2506 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
2507 snoop_pkt.senderState = nullptr;
2508 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2509 // Writeback/CleanEvict snoops do not generate a snoop response.
2510 assert(!(snoop_pkt.cacheResponding()));
2511 return snoop_pkt.isBlockCached();
2512 } else {
2513 cpuSidePort->sendAtomicSnoop(pkt);
2514 return pkt->isBlockCached();
2515 }
2516}
2517
2518Tick
2519Cache::nextQueueReadyTime() const
2520{
2521 Tick nextReady = std::min(mshrQueue.nextReadyTime(),
2522 writeBuffer.nextReadyTime());
2523
2524 // Don't signal prefetch ready time if no MSHRs available
2525 // Will signal once enoguh MSHRs are deallocated
2526 if (prefetcher && mshrQueue.canPrefetch()) {
2527 nextReady = std::min(nextReady,
2528 prefetcher->nextPrefetchReadyTime());
2529 }
2530
2531 return nextReady;
2532}
2533
2534bool
2535Cache::sendMSHRQueuePacket(MSHR* mshr)
2536{
2537 assert(mshr);
2538
2539 // use request from 1st target
2540 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
2541
2542 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
2543
2544 CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure);
2545
2546 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
2547 // we should never have hardware prefetches to allocated
2548 // blocks
2549 assert(blk == nullptr);
2550
2551 // We need to check the caches above us to verify that
2552 // they don't have a copy of this block in the dirty state
2553 // at the moment. Without this check we could get a stale
2554 // copy from memory that might get used in place of the
2555 // dirty one.
2556 Packet snoop_pkt(tgt_pkt, true, false);
2557 snoop_pkt.setExpressSnoop();
2558 // We are sending this packet upwards, but if it hits we will
2559 // get a snoop response that we end up treating just like a
2560 // normal response, hence it needs the MSHR as its sender
2561 // state
2562 snoop_pkt.senderState = mshr;
2563 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2564
2565 // Check to see if the prefetch was squashed by an upper cache (to
2566 // prevent us from grabbing the line) or if a Check to see if a
2567 // writeback arrived between the time the prefetch was placed in
2568 // the MSHRs and when it was selected to be sent or if the
2569 // prefetch was squashed by an upper cache.
2570
2571 // It is important to check cacheResponding before
2572 // prefetchSquashed. If another cache has committed to
2573 // responding, it will be sending a dirty response which will
2574 // arrive at the MSHR allocated for this request. Checking the
2575 // prefetchSquash first may result in the MSHR being
2576 // prematurely deallocated.
2577 if (snoop_pkt.cacheResponding()) {
2578 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
2579 assert(r.second);
2580
2581 // if we are getting a snoop response with no sharers it
2582 // will be allocated as Modified
2583 bool pending_modified_resp = !snoop_pkt.hasSharers();
2584 markInService(mshr, pending_modified_resp);
2585
2586 DPRINTF(Cache, "Upward snoop of prefetch for addr"
2587 " %#x (%s) hit\n",
2588 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
2589 return false;
2590 }
2591
2592 if (snoop_pkt.isBlockCached()) {
2593 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
2594 "Deallocating mshr target %#x.\n",
2595 mshr->blkAddr);
2596
2597 // Deallocate the mshr target
2598 if (mshrQueue.forceDeallocateTarget(mshr)) {
2599 // Clear block if this deallocation resulted freed an
2600 // mshr when all had previously been utilized
2601 clearBlocked(Blocked_NoMSHRs);
2602 }
2603
2604 // given that no response is expected, delete Request and Packet
2605 delete tgt_pkt->req;
2606 delete tgt_pkt;
2607
2608 return false;
2609 }
2610 }
2611
2612 // either a prefetch that is not present upstream, or a normal
2613 // MSHR request, proceed to get the packet to send downstream
2614 PacketPtr pkt = createMissPacket(tgt_pkt, blk, mshr->needsWritable());
2615
2616 mshr->isForward = (pkt == nullptr);
2617
2618 if (mshr->isForward) {
2619 // not a cache block request, but a response is expected
2620 // make copy of current packet to forward, keep current
2621 // copy for response handling
2622 pkt = new Packet(tgt_pkt, false, true);
2623 assert(!pkt->isWrite());
2624 }
2625
2626 // play it safe and append (rather than set) the sender state,
2627 // as forwarded packets may already have existing state
2628 pkt->pushSenderState(mshr);
2629
2630 if (pkt->isClean() && blk && blk->isDirty()) {
2631 // A cache clean opearation is looking for a dirty block. Mark
2632 // the packet so that the destination xbar can determine that
2633 // there will be a follow-up write packet as well.
2634 pkt->setSatisfied();
2635 }
2636
2637 if (!memSidePort->sendTimingReq(pkt)) {
2638 // we are awaiting a retry, but we
2639 // delete the packet and will be creating a new packet
2640 // when we get the opportunity
2641 delete pkt;
2642
2643 // note that we have now masked any requestBus and
2644 // schedSendEvent (we will wait for a retry before
2645 // doing anything), and this is so even if we do not
2646 // care about this packet and might override it before
2647 // it gets retried
2648 return true;
2649 } else {
2650 // As part of the call to sendTimingReq the packet is
2651 // forwarded to all neighbouring caches (and any caches
2652 // above them) as a snoop. Thus at this point we know if
2653 // any of the neighbouring caches are responding, and if
2654 // so, we know it is dirty, and we can determine if it is
2655 // being passed as Modified, making our MSHR the ordering
2656 // point
2657 bool pending_modified_resp = !pkt->hasSharers() &&
2658 pkt->cacheResponding();
2659 markInService(mshr, pending_modified_resp);
2660 if (pkt->isClean() && blk && blk->isDirty()) {
2661 // A cache clean opearation is looking for a dirty
2662 // block. If a dirty block is encountered a WriteClean
2663 // will update any copies to the path to the memory
2664 // until the point of reference.
2665 DPRINTF(CacheVerbose, "%s: packet %s found block: %s\n",
2666 __func__, pkt->print(), blk->print());
2667 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(),
2668 pkt->id);
2669 PacketList writebacks;
2670 writebacks.push_back(wb_pkt);
2671 doWritebacks(writebacks, 0);
2672 }
2673
2674 return false;
2675 }
2676}
2677
2678bool
2679Cache::sendWriteQueuePacket(WriteQueueEntry* wq_entry)
2680{
2681 assert(wq_entry);
2682
2683 // always a single target for write queue entries
2684 PacketPtr tgt_pkt = wq_entry->getTarget()->pkt;
2685
2686 DPRINTF(Cache, "%s: write %s\n", __func__, tgt_pkt->print());
2687
2688 // forward as is, both for evictions and uncacheable writes
2689 if (!memSidePort->sendTimingReq(tgt_pkt)) {
2690 // note that we have now masked any requestBus and
2691 // schedSendEvent (we will wait for a retry before
2692 // doing anything), and this is so even if we do not
2693 // care about this packet and might override it before
2694 // it gets retried
2695 return true;
2696 } else {
2697 markInService(wq_entry);
2698 return false;
2699 }
2700}
2701
2702void
2703Cache::serialize(CheckpointOut &cp) const
2704{
2705 bool dirty(isDirty());
2706
2707 if (dirty) {
2708 warn("*** The cache still contains dirty data. ***\n");
2709 warn(" Make sure to drain the system using the correct flags.\n");
2710 warn(" This checkpoint will not restore correctly and dirty data "
2711 " in the cache will be lost!\n");
2712 }
2713
2714 // Since we don't checkpoint the data in the cache, any dirty data
2715 // will be lost when restoring from a checkpoint of a system that
2716 // wasn't drained properly. Flag the checkpoint as invalid if the
2717 // cache contains dirty data.
2718 bool bad_checkpoint(dirty);
2719 SERIALIZE_SCALAR(bad_checkpoint);
2720}
2721
2722void
2723Cache::unserialize(CheckpointIn &cp)
2724{
2725 bool bad_checkpoint;
2726 UNSERIALIZE_SCALAR(bad_checkpoint);
2727 if (bad_checkpoint) {
2728 fatal("Restoring from checkpoints with dirty caches is not supported "
2729 "in the classic memory system. Please remove any caches or "
2730 " drain them properly before taking checkpoints.\n");
2731 }
2732}
2733
2734///////////////
2735//
2736// CpuSidePort
2737//
2738///////////////
2739
2740AddrRangeList
2741Cache::CpuSidePort::getAddrRanges() const
2742{
2743 return cache->getAddrRanges();
2744}
2745
2746bool
2747Cache::CpuSidePort::tryTiming(PacketPtr pkt)
2748{
2749 assert(!cache->system->bypassCaches());
2750
2751 // always let express snoop packets through if even if blocked
2752 if (pkt->isExpressSnoop()) {
2753 return true;
2754 } else if (isBlocked() || mustSendRetry) {
2755 // either already committed to send a retry, or blocked
2756 mustSendRetry = true;
2757 return false;
2758 }
2759 mustSendRetry = false;
2760 return true;
2761}
2762
2763bool
2764Cache::CpuSidePort::recvTimingReq(PacketPtr pkt)
2765{
2766 assert(!cache->system->bypassCaches());
2767
2768 // always let express snoop packets through if even if blocked
2769 if (pkt->isExpressSnoop()) {
2770 bool M5_VAR_USED bypass_success = cache->recvTimingReq(pkt);
2771 assert(bypass_success);
2772 return true;
2773 }
2774
2775 return tryTiming(pkt) && cache->recvTimingReq(pkt);
2776}
2777
2778Tick
2779Cache::CpuSidePort::recvAtomic(PacketPtr pkt)
2780{
2781 return cache->recvAtomic(pkt);
2782}
2783
2784void
2785Cache::CpuSidePort::recvFunctional(PacketPtr pkt)
2786{
2787 // functional request
2788 cache->functionalAccess(pkt, true);
2789}
2790
2791Cache::
2792CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache,
2793 const std::string &_label)
2794 : BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache)
2795{
2796}
2797
2798Cache*
2799CacheParams::create()
2800{
2801 assert(tags);
2802
2803 return new Cache(this);
2804}
2805///////////////
2806//
2807// MemSidePort
2808//
2809///////////////
2810
2811bool
2812Cache::MemSidePort::recvTimingResp(PacketPtr pkt)
2813{
2814 cache->recvTimingResp(pkt);
2815 return true;
2816}
2817
2818// Express snooping requests to memside port
2819void
2820Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt)
2821{
2822 // handle snooping requests
2823 cache->recvTimingSnoopReq(pkt);
2824}
2825
2826Tick
2827Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt)
2828{
2829 return cache->recvAtomicSnoop(pkt);
2830}
2831
2832void
2833Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt)
2834{
2835 // functional snoop (note that in contrast to atomic we don't have
2836 // a specific functionalSnoop method, as they have the same
2837 // behaviour regardless)
2838 cache->functionalAccess(pkt, false);
2839}
2840
2841void
2842Cache::CacheReqPacketQueue::sendDeferredPacket()
2843{
2844 // sanity check
2845 assert(!waitingOnRetry);
2846
2847 // there should never be any deferred request packets in the
2848 // queue, instead we resly on the cache to provide the packets
2849 // from the MSHR queue or write queue
2850 assert(deferredPacketReadyTime() == MaxTick);
2851
2852 // check for request packets (requests & writebacks)
2853 QueueEntry* entry = cache.getNextQueueEntry();
2854
2855 if (!entry) {
2856 // can happen if e.g. we attempt a writeback and fail, but
2857 // before the retry, the writeback is eliminated because
2858 // we snoop another cache's ReadEx.
2859 } else {
2860 // let our snoop responses go first if there are responses to
2861 // the same addresses
2862 if (checkConflictingSnoop(entry->blkAddr)) {
2863 return;
2864 }
2865 waitingOnRetry = entry->sendPacket(cache);
2866 }
2867
2868 // if we succeeded and are not waiting for a retry, schedule the
2869 // next send considering when the next queue is ready, note that
2870 // snoop responses have their own packet queue and thus schedule
2871 // their own events
2872 if (!waitingOnRetry) {
2873 schedSendEvent(cache.nextQueueReadyTime());
2874 }
2875}
2876
2877Cache::
2878MemSidePort::MemSidePort(const std::string &_name, Cache *_cache,
2879 const std::string &_label)
2880 : BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue),
2881 _reqQueue(*_cache, *this, _snoopRespQueue, _label),
2882 _snoopRespQueue(*_cache, *this, _label), cache(_cache)
2883{
2884}
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