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 }
402 // only mark the block dirty if we got a writeback command,
403 // and leave it as is for a clean writeback
404 if (pkt->cmd == MemCmd::WritebackDirty) {
405 assert(!blk->isDirty());
406 blk->status |= BlkDirty;
407 }
408 // if the packet does not have sharers, it is passing
409 // writable, and we got the writeback in Modified or Exclusive
410 // state, if not we are in the Owned or Shared state
411 if (!pkt->hasSharers()) {
412 blk->status |= BlkWritable;
413 }
414 // nothing else to do; writeback doesn't expect response
415 assert(!pkt->needsResponse());
416 pkt->writeDataToBlock(blk->data, blkSize);
417 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
418 incHitCount(pkt);
419 // populate the time when the block will be ready to access.
420 blk->whenReady = clockEdge(fillLatency) + pkt->headerDelay +
421 pkt->payloadDelay;
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 }
462 }
463
464 // at this point either this is a writeback or a write-through
465 // write clean operation and the block is already in this
466 // cache, we need to update the data and the block flags
467 assert(blk);
468 assert(!blk->isDirty());
469 if (!pkt->writeThrough()) {
470 blk->status |= BlkDirty;
471 }
472 // nothing else to do; writeback doesn't expect response
473 assert(!pkt->needsResponse());
474 pkt->writeDataToBlock(blk->data, blkSize);
475 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
476
477 incHitCount(pkt);
478 // populate the time when the block will be ready to access.
479 blk->whenReady = clockEdge(fillLatency) + pkt->headerDelay +
480 pkt->payloadDelay;
481 // if this a write-through packet it will be sent to cache
482 // below
483 return !pkt->writeThrough();
484 } else if (blk && (pkt->needsWritable() ? blk->isWritable() :
485 blk->isReadable())) {
486 // OK to satisfy access
487 incHitCount(pkt);
488 satisfyRequest(pkt, blk);
489 maintainClusivity(pkt->fromCache(), blk);
490
491 return true;
492 }
493
494 // Can't satisfy access normally... either no block (blk == nullptr)
495 // or have block but need writable
496
497 incMissCount(pkt);
498
499 if (blk == nullptr && pkt->isLLSC() && pkt->isWrite()) {
500 // complete miss on store conditional... just give up now
501 pkt->req->setExtraData(0);
502 return true;
503 }
504
505 return false;
506}
507
508void
509Cache::maintainClusivity(bool from_cache, CacheBlk *blk)
510{
511 if (from_cache && blk && blk->isValid() && !blk->isDirty() &&
512 clusivity == Enums::mostly_excl) {
513 // if we have responded to a cache, and our block is still
514 // valid, but not dirty, and this cache is mostly exclusive
515 // with respect to the cache above, drop the block
516 invalidateBlock(blk);
517 }
518}
519
520void
521Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
522{
523 while (!writebacks.empty()) {
524 PacketPtr wbPkt = writebacks.front();
525 // We use forwardLatency here because we are copying writebacks to
526 // write buffer.
527
528 // Call isCachedAbove for Writebacks, CleanEvicts and
529 // WriteCleans to discover if the block is cached above.
530 if (isCachedAbove(wbPkt)) {
531 if (wbPkt->cmd == MemCmd::CleanEvict) {
532 // Delete CleanEvict because cached copies exist above. The
533 // packet destructor will delete the request object because
534 // this is a non-snoop request packet which does not require a
535 // response.
536 delete wbPkt;
537 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
538 // clean writeback, do not send since the block is
539 // still cached above
540 assert(writebackClean);
541 delete wbPkt;
542 } else {
543 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
544 wbPkt->cmd == MemCmd::WriteClean);
545 // Set BLOCK_CACHED flag in Writeback and send below, so that
546 // the Writeback does not reset the bit corresponding to this
547 // address in the snoop filter below.
548 wbPkt->setBlockCached();
549 allocateWriteBuffer(wbPkt, forward_time);
550 }
551 } else {
552 // If the block is not cached above, send packet below. Both
553 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
554 // reset the bit corresponding to this address in the snoop filter
555 // below.
556 allocateWriteBuffer(wbPkt, forward_time);
557 }
558 writebacks.pop_front();
559 }
560}
561
562void
563Cache::doWritebacksAtomic(PacketList& writebacks)
564{
565 while (!writebacks.empty()) {
566 PacketPtr wbPkt = writebacks.front();
567 // Call isCachedAbove for both Writebacks and CleanEvicts. If
568 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
569 // and discard CleanEvicts.
570 if (isCachedAbove(wbPkt, false)) {
571 if (wbPkt->cmd == MemCmd::WritebackDirty ||
572 wbPkt->cmd == MemCmd::WriteClean) {
573 // Set BLOCK_CACHED flag in Writeback and send below,
574 // so that the Writeback does not reset the bit
575 // corresponding to this address in the snoop filter
576 // below. We can discard CleanEvicts because cached
577 // copies exist above. Atomic mode isCachedAbove
578 // modifies packet to set BLOCK_CACHED flag
579 memSidePort->sendAtomic(wbPkt);
580 }
581 } else {
582 // If the block is not cached above, send packet below. Both
583 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
584 // reset the bit corresponding to this address in the snoop filter
585 // below.
586 memSidePort->sendAtomic(wbPkt);
587 }
588 writebacks.pop_front();
589 // In case of CleanEvicts, the packet destructor will delete the
590 // request object because this is a non-snoop request packet which
591 // does not require a response.
592 delete wbPkt;
593 }
594}
595
596
597void
598Cache::recvTimingSnoopResp(PacketPtr pkt)
599{
600 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
601
602 assert(pkt->isResponse());
603 assert(!system->bypassCaches());
604
605 // determine if the response is from a snoop request we created
606 // (in which case it should be in the outstandingSnoop), or if we
607 // merely forwarded someone else's snoop request
608 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
609 outstandingSnoop.end();
610
611 if (!forwardAsSnoop) {
612 // the packet came from this cache, so sink it here and do not
613 // forward it
614 assert(pkt->cmd == MemCmd::HardPFResp);
615
616 outstandingSnoop.erase(pkt->req);
617
618 DPRINTF(Cache, "Got prefetch response from above for addr "
619 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
620 recvTimingResp(pkt);
621 return;
622 }
623
624 // forwardLatency is set here because there is a response from an
625 // upper level cache.
626 // To pay the delay that occurs if the packet comes from the bus,
627 // we charge also headerDelay.
628 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
629 // Reset the timing of the packet.
630 pkt->headerDelay = pkt->payloadDelay = 0;
631 memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time);
632}
633
634void
635Cache::promoteWholeLineWrites(PacketPtr pkt)
636{
637 // Cache line clearing instructions
638 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
639 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
640 pkt->cmd = MemCmd::WriteLineReq;
641 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
642 }
643}
644
645void
646Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
647{
648 // should never be satisfying an uncacheable access as we
649 // flush and invalidate any existing block as part of the
650 // lookup
651 assert(!pkt->req->isUncacheable());
652
653 if (pkt->needsResponse()) {
654 pkt->makeTimingResponse();
655 // @todo: Make someone pay for this
656 pkt->headerDelay = pkt->payloadDelay = 0;
657
658 // In this case we are considering request_time that takes
659 // into account the delay of the xbar, if any, and just
660 // lat, neglecting responseLatency, modelling hit latency
661 // just as lookupLatency or or the value of lat overriden
662 // by access(), that calls accessBlock() function.
663 cpuSidePort->schedTimingResp(pkt, request_time, true);
664 } else {
665 DPRINTF(Cache, "%s satisfied %s, no response needed\n", __func__,
666 pkt->print());
667
668 // queue the packet for deletion, as the sending cache is
669 // still relying on it; if the block is found in access(),
670 // CleanEvict and Writeback messages will be deleted
671 // here as well
672 pendingDelete.reset(pkt);
673 }
674}
675
676void
677Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
678 Tick request_time)
679{
680 Addr blk_addr = pkt->getBlockAddr(blkSize);
681
682 // ignore any existing MSHR if we are dealing with an
683 // uncacheable request
684 MSHR *mshr = pkt->req->isUncacheable() ? nullptr :
685 mshrQueue.findMatch(blk_addr, pkt->isSecure());
686
687 // Software prefetch handling:
688 // To keep the core from waiting on data it won't look at
689 // anyway, send back a response with dummy data. Miss handling
690 // will continue asynchronously. Unfortunately, the core will
691 // insist upon freeing original Packet/Request, so we have to
692 // create a new pair with a different lifecycle. Note that this
693 // processing happens before any MSHR munging on the behalf of
694 // this request because this new Request will be the one stored
695 // into the MSHRs, not the original.
696 if (pkt->cmd.isSWPrefetch()) {
697 assert(pkt->needsResponse());
698 assert(pkt->req->hasPaddr());
699 assert(!pkt->req->isUncacheable());
700
701 // There's no reason to add a prefetch as an additional target
702 // to an existing MSHR. If an outstanding request is already
703 // in progress, there is nothing for the prefetch to do.
704 // If this is the case, we don't even create a request at all.
705 PacketPtr pf = nullptr;
706
707 if (!mshr) {
708 // copy the request and create a new SoftPFReq packet
709 RequestPtr req = new Request(pkt->req->getPaddr(),
710 pkt->req->getSize(),
711 pkt->req->getFlags(),
712 pkt->req->masterId());
713 pf = new Packet(req, pkt->cmd);
714 pf->allocate();
715 assert(pf->getAddr() == pkt->getAddr());
716 assert(pf->getSize() == pkt->getSize());
717 }
718
719 pkt->makeTimingResponse();
720
721 // request_time is used here, taking into account lat and the delay
722 // charged if the packet comes from the xbar.
723 cpuSidePort->schedTimingResp(pkt, request_time, true);
724
725 // If an outstanding request is in progress (we found an
726 // MSHR) this is set to null
727 pkt = pf;
728 }
729
730 if (mshr) {
731 /// MSHR hit
732 /// @note writebacks will be checked in getNextMSHR()
733 /// for any conflicting requests to the same block
734
735 //@todo remove hw_pf here
736
737 // Coalesce unless it was a software prefetch (see above).
738 if (pkt) {
739 assert(!pkt->isWriteback());
740 // CleanEvicts corresponding to blocks which have
741 // outstanding requests in MSHRs are simply sunk here
742 if (pkt->cmd == MemCmd::CleanEvict) {
743 pendingDelete.reset(pkt);
744 } else if (pkt->cmd == MemCmd::WriteClean) {
745 // A WriteClean should never coalesce with any
746 // outstanding cache maintenance requests.
747
748 // We use forward_time here because there is an
749 // uncached memory write, forwarded to WriteBuffer.
750 allocateWriteBuffer(pkt, forward_time);
751 } else {
752 DPRINTF(Cache, "%s coalescing MSHR for %s\n", __func__,
753 pkt->print());
754
755 assert(pkt->req->masterId() < system->maxMasters());
756 mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
757
758 // uncacheable accesses always allocate a new
759 // MSHR, and cacheable accesses ignore any
760 // uncacheable MSHRs, thus we should never have
761 // targets addded if originally allocated
762 // uncacheable
763 assert(!mshr->isUncacheable());
764
765 // We use forward_time here because it is the same
766 // considering new targets. We have multiple
767 // requests for the same address here. It
768 // specifies the latency to allocate an internal
769 // buffer and to schedule an event to the queued
770 // port and also takes into account the additional
771 // delay of the xbar.
772 mshr->allocateTarget(pkt, forward_time, order++,
773 allocOnFill(pkt->cmd));
774 if (mshr->getNumTargets() == numTarget) {
775 noTargetMSHR = mshr;
776 setBlocked(Blocked_NoTargets);
777 // need to be careful with this... if this mshr isn't
778 // ready yet (i.e. time > curTick()), we don't want to
779 // move it ahead of mshrs that are ready
780 // mshrQueue.moveToFront(mshr);
781 }
782 }
783 }
784 } else {
785 // no MSHR
786 assert(pkt->req->masterId() < system->maxMasters());
787 if (pkt->req->isUncacheable()) {
788 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
789 } else {
790 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
791 }
792
793 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
794 (pkt->req->isUncacheable() && pkt->isWrite())) {
795 // We use forward_time here because there is an
796 // uncached memory write, forwarded to WriteBuffer.
797 allocateWriteBuffer(pkt, forward_time);
798 } else {
799 if (blk && blk->isValid()) {
800 // should have flushed and have no valid block
801 assert(!pkt->req->isUncacheable());
802
803 // If we have a write miss to a valid block, we
804 // need to mark the block non-readable. Otherwise
805 // if we allow reads while there's an outstanding
806 // write miss, the read could return stale data
807 // out of the cache block... a more aggressive
808 // system could detect the overlap (if any) and
809 // forward data out of the MSHRs, but we don't do
810 // that yet. Note that we do need to leave the
811 // block valid so that it stays in the cache, in
812 // case we get an upgrade response (and hence no
813 // new data) when the write miss completes.
814 // As long as CPUs do proper store/load forwarding
815 // internally, and have a sufficiently weak memory
816 // model, this is probably unnecessary, but at some
817 // point it must have seemed like we needed it...
818 assert((pkt->needsWritable() && !blk->isWritable()) ||
819 pkt->req->isCacheMaintenance());
820 blk->status &= ~BlkReadable;
821 }
822 // Here we are using forward_time, modelling the latency of
823 // a miss (outbound) just as forwardLatency, neglecting the
824 // lookupLatency component.
825 allocateMissBuffer(pkt, forward_time);
826 }
827 }
828}
829
830void
831Cache::recvTimingReq(PacketPtr pkt)
832{
833 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
834
835 assert(pkt->isRequest());
836
837 // Just forward the packet if caches are disabled.
838 if (system->bypassCaches()) {
839 // @todo This should really enqueue the packet rather
840 bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt);
841 assert(success);
842 return;
843 }
844
845 promoteWholeLineWrites(pkt);
846
847 // Cache maintenance operations have to visit all the caches down
848 // to the specified xbar (PoC, PoU, etc.). Even if a cache above
849 // is responding we forward the packet to the memory below rather
850 // than creating an express snoop.
851 if (pkt->cacheResponding()) {
852 // a cache above us (but not where the packet came from) is
853 // responding to the request, in other words it has the line
854 // in Modified or Owned state
855 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
856 pkt->print());
857
858 // if the packet needs the block to be writable, and the cache
859 // that has promised to respond (setting the cache responding
860 // flag) is not providing writable (it is in Owned rather than
861 // the Modified state), we know that there may be other Shared
862 // copies in the system; go out and invalidate them all
863 assert(pkt->needsWritable() && !pkt->responderHadWritable());
864
865 // an upstream cache that had the line in Owned state
866 // (dirty, but not writable), is responding and thus
867 // transferring the dirty line from one branch of the
868 // cache hierarchy to another
869
870 // send out an express snoop and invalidate all other
871 // copies (snooping a packet that needs writable is the
872 // same as an invalidation), thus turning the Owned line
873 // into a Modified line, note that we don't invalidate the
874 // block in the current cache or any other cache on the
875 // path to memory
876
877 // create a downstream express snoop with cleared packet
878 // flags, there is no need to allocate any data as the
879 // packet is merely used to co-ordinate state transitions
880 Packet *snoop_pkt = new Packet(pkt, true, false);
881
882 // also reset the bus time that the original packet has
883 // not yet paid for
884 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
885
886 // make this an instantaneous express snoop, and let the
887 // other caches in the system know that the another cache
888 // is responding, because we have found the authorative
889 // copy (Modified or Owned) that will supply the right
890 // data
891 snoop_pkt->setExpressSnoop();
892 snoop_pkt->setCacheResponding();
893
894 // this express snoop travels towards the memory, and at
895 // every crossbar it is snooped upwards thus reaching
896 // every cache in the system
897 bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt);
898 // express snoops always succeed
899 assert(success);
900
901 // main memory will delete the snoop packet
902
903 // queue for deletion, as opposed to immediate deletion, as
904 // the sending cache is still relying on the packet
905 pendingDelete.reset(pkt);
906
907 // no need to take any further action in this particular cache
908 // as an upstram cache has already committed to responding,
909 // and we have already sent out any express snoops in the
910 // section above to ensure all other copies in the system are
911 // invalidated
912 return;
913 }
914
915 // anything that is merely forwarded pays for the forward latency and
916 // the delay provided by the crossbar
917 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
918
919 // We use lookupLatency here because it is used to specify the latency
920 // to access.
921 Cycles lat = lookupLatency;
922 CacheBlk *blk = nullptr;
923 bool satisfied = false;
924 {
925 PacketList writebacks;
926 // Note that lat is passed by reference here. The function
927 // access() calls accessBlock() which can modify lat value.
928 satisfied = access(pkt, blk, lat, writebacks);
929
930 // copy writebacks to write buffer here to ensure they logically
931 // proceed anything happening below
932 doWritebacks(writebacks, forward_time);
933 }
934
935 // Here we charge the headerDelay that takes into account the latencies
936 // of the bus, if the packet comes from it.
937 // The latency charged it is just lat that is the value of lookupLatency
938 // modified by access() function, or if not just lookupLatency.
939 // In case of a hit we are neglecting response latency.
940 // In case of a miss we are neglecting forward latency.
941 Tick request_time = clockEdge(lat) + pkt->headerDelay;
942 // Here we reset the timing of the packet.
943 pkt->headerDelay = pkt->payloadDelay = 0;
944
945 // track time of availability of next prefetch, if any
946 Tick next_pf_time = MaxTick;
947
948 if (satisfied) {
949 // if need to notify the prefetcher we need to do it anything
950 // else, handleTimingReqHit might turn the packet into a
951 // response
952 if (prefetcher &&
953 (prefetchOnAccess || (blk && blk->wasPrefetched()))) {
954 if (blk)
955 blk->status &= ~BlkHWPrefetched;
956
957 // Don't notify on SWPrefetch
958 if (!pkt->cmd.isSWPrefetch()) {
959 assert(!pkt->req->isCacheMaintenance());
960 next_pf_time = prefetcher->notify(pkt);
961 }
962 }
963
964 handleTimingReqHit(pkt, blk, request_time);
965 } else {
966 handleTimingReqMiss(pkt, blk, forward_time, request_time);
967
968 // We should call the prefetcher reguardless if the request is
969 // satisfied or not, reguardless if the request is in the MSHR
970 // or not. The request could be a ReadReq hit, but still not
971 // satisfied (potentially because of a prior write to the same
972 // cache line. So, even when not satisfied, there is an MSHR
973 // already allocated for this, we need to let the prefetcher
974 // know about the request
975 if (prefetcher && pkt &&
976 !pkt->cmd.isSWPrefetch() &&
977 !pkt->req->isCacheMaintenance()) {
978 next_pf_time = prefetcher->notify(pkt);
979 }
980 }
981
982 if (next_pf_time != MaxTick)
983 schedMemSideSendEvent(next_pf_time);
984}
985
986PacketPtr
987Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
988 bool needsWritable) const
989{
990 // should never see evictions here
991 assert(!cpu_pkt->isEviction());
992
993 bool blkValid = blk && blk->isValid();
994
995 if (cpu_pkt->req->isUncacheable() ||
996 (!blkValid && cpu_pkt->isUpgrade()) ||
997 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
998 // uncacheable requests and upgrades from upper-level caches
999 // that missed completely just go through as is
1000 return nullptr;
1001 }
1002
1003 assert(cpu_pkt->needsResponse());
1004
1005 MemCmd cmd;
1006 // @TODO make useUpgrades a parameter.
1007 // Note that ownership protocols require upgrade, otherwise a
1008 // write miss on a shared owned block will generate a ReadExcl,
1009 // which will clobber the owned copy.
1010 const bool useUpgrades = true;
1011 if (cpu_pkt->cmd == MemCmd::WriteLineReq) {
1012 assert(!blkValid || !blk->isWritable());
1013 // forward as invalidate to all other caches, this gives us
1014 // the line in Exclusive state, and invalidates all other
1015 // copies
1016 cmd = MemCmd::InvalidateReq;
1017 } else if (blkValid && useUpgrades) {
1018 // only reason to be here is that blk is read only and we need
1019 // it to be writable
1020 assert(needsWritable);
1021 assert(!blk->isWritable());
1022 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
1023 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
1024 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
1025 // Even though this SC will fail, we still need to send out the
1026 // request and get the data to supply it to other snoopers in the case
1027 // where the determination the StoreCond fails is delayed due to
1028 // all caches not being on the same local bus.
1029 cmd = MemCmd::SCUpgradeFailReq;
1030 } else {
1031 // block is invalid
1032
1033 // If the request does not need a writable there are two cases
1034 // where we need to ensure the response will not fetch the
1035 // block in dirty state:
1036 // * this cache is read only and it does not perform
1037 // writebacks,
1038 // * this cache is mostly exclusive and will not fill (since
1039 // it does not fill it will have to writeback the dirty data
1040 // immediately which generates uneccesary writebacks).
1041 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
1042 cmd = needsWritable ? MemCmd::ReadExReq :
1043 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
1044 }
1045 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
1046
1047 // if there are upstream caches that have already marked the
1048 // packet as having sharers (not passing writable), pass that info
1049 // downstream
1050 if (cpu_pkt->hasSharers() && !needsWritable) {
1051 // note that cpu_pkt may have spent a considerable time in the
1052 // MSHR queue and that the information could possibly be out
1053 // of date, however, there is no harm in conservatively
1054 // assuming the block has sharers
1055 pkt->setHasSharers();
1056 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
1057 __func__, cpu_pkt->print(), pkt->print());
1058 }
1059
1060 // the packet should be block aligned
1061 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
1062
1063 pkt->allocate();
1064 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
1065 cpu_pkt->print());
1066 return pkt;
1067}
1068
1069
| 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 }
402 // only mark the block dirty if we got a writeback command,
403 // and leave it as is for a clean writeback
404 if (pkt->cmd == MemCmd::WritebackDirty) {
405 assert(!blk->isDirty());
406 blk->status |= BlkDirty;
407 }
408 // if the packet does not have sharers, it is passing
409 // writable, and we got the writeback in Modified or Exclusive
410 // state, if not we are in the Owned or Shared state
411 if (!pkt->hasSharers()) {
412 blk->status |= BlkWritable;
413 }
414 // nothing else to do; writeback doesn't expect response
415 assert(!pkt->needsResponse());
416 pkt->writeDataToBlock(blk->data, blkSize);
417 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
418 incHitCount(pkt);
419 // populate the time when the block will be ready to access.
420 blk->whenReady = clockEdge(fillLatency) + pkt->headerDelay +
421 pkt->payloadDelay;
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 }
462 }
463
464 // at this point either this is a writeback or a write-through
465 // write clean operation and the block is already in this
466 // cache, we need to update the data and the block flags
467 assert(blk);
468 assert(!blk->isDirty());
469 if (!pkt->writeThrough()) {
470 blk->status |= BlkDirty;
471 }
472 // nothing else to do; writeback doesn't expect response
473 assert(!pkt->needsResponse());
474 pkt->writeDataToBlock(blk->data, blkSize);
475 DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
476
477 incHitCount(pkt);
478 // populate the time when the block will be ready to access.
479 blk->whenReady = clockEdge(fillLatency) + pkt->headerDelay +
480 pkt->payloadDelay;
481 // if this a write-through packet it will be sent to cache
482 // below
483 return !pkt->writeThrough();
484 } else if (blk && (pkt->needsWritable() ? blk->isWritable() :
485 blk->isReadable())) {
486 // OK to satisfy access
487 incHitCount(pkt);
488 satisfyRequest(pkt, blk);
489 maintainClusivity(pkt->fromCache(), blk);
490
491 return true;
492 }
493
494 // Can't satisfy access normally... either no block (blk == nullptr)
495 // or have block but need writable
496
497 incMissCount(pkt);
498
499 if (blk == nullptr && pkt->isLLSC() && pkt->isWrite()) {
500 // complete miss on store conditional... just give up now
501 pkt->req->setExtraData(0);
502 return true;
503 }
504
505 return false;
506}
507
508void
509Cache::maintainClusivity(bool from_cache, CacheBlk *blk)
510{
511 if (from_cache && blk && blk->isValid() && !blk->isDirty() &&
512 clusivity == Enums::mostly_excl) {
513 // if we have responded to a cache, and our block is still
514 // valid, but not dirty, and this cache is mostly exclusive
515 // with respect to the cache above, drop the block
516 invalidateBlock(blk);
517 }
518}
519
520void
521Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
522{
523 while (!writebacks.empty()) {
524 PacketPtr wbPkt = writebacks.front();
525 // We use forwardLatency here because we are copying writebacks to
526 // write buffer.
527
528 // Call isCachedAbove for Writebacks, CleanEvicts and
529 // WriteCleans to discover if the block is cached above.
530 if (isCachedAbove(wbPkt)) {
531 if (wbPkt->cmd == MemCmd::CleanEvict) {
532 // Delete CleanEvict because cached copies exist above. The
533 // packet destructor will delete the request object because
534 // this is a non-snoop request packet which does not require a
535 // response.
536 delete wbPkt;
537 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
538 // clean writeback, do not send since the block is
539 // still cached above
540 assert(writebackClean);
541 delete wbPkt;
542 } else {
543 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
544 wbPkt->cmd == MemCmd::WriteClean);
545 // Set BLOCK_CACHED flag in Writeback and send below, so that
546 // the Writeback does not reset the bit corresponding to this
547 // address in the snoop filter below.
548 wbPkt->setBlockCached();
549 allocateWriteBuffer(wbPkt, forward_time);
550 }
551 } else {
552 // If the block is not cached above, send packet below. Both
553 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
554 // reset the bit corresponding to this address in the snoop filter
555 // below.
556 allocateWriteBuffer(wbPkt, forward_time);
557 }
558 writebacks.pop_front();
559 }
560}
561
562void
563Cache::doWritebacksAtomic(PacketList& writebacks)
564{
565 while (!writebacks.empty()) {
566 PacketPtr wbPkt = writebacks.front();
567 // Call isCachedAbove for both Writebacks and CleanEvicts. If
568 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
569 // and discard CleanEvicts.
570 if (isCachedAbove(wbPkt, false)) {
571 if (wbPkt->cmd == MemCmd::WritebackDirty ||
572 wbPkt->cmd == MemCmd::WriteClean) {
573 // Set BLOCK_CACHED flag in Writeback and send below,
574 // so that the Writeback does not reset the bit
575 // corresponding to this address in the snoop filter
576 // below. We can discard CleanEvicts because cached
577 // copies exist above. Atomic mode isCachedAbove
578 // modifies packet to set BLOCK_CACHED flag
579 memSidePort->sendAtomic(wbPkt);
580 }
581 } else {
582 // If the block is not cached above, send packet below. Both
583 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
584 // reset the bit corresponding to this address in the snoop filter
585 // below.
586 memSidePort->sendAtomic(wbPkt);
587 }
588 writebacks.pop_front();
589 // In case of CleanEvicts, the packet destructor will delete the
590 // request object because this is a non-snoop request packet which
591 // does not require a response.
592 delete wbPkt;
593 }
594}
595
596
597void
598Cache::recvTimingSnoopResp(PacketPtr pkt)
599{
600 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
601
602 assert(pkt->isResponse());
603 assert(!system->bypassCaches());
604
605 // determine if the response is from a snoop request we created
606 // (in which case it should be in the outstandingSnoop), or if we
607 // merely forwarded someone else's snoop request
608 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
609 outstandingSnoop.end();
610
611 if (!forwardAsSnoop) {
612 // the packet came from this cache, so sink it here and do not
613 // forward it
614 assert(pkt->cmd == MemCmd::HardPFResp);
615
616 outstandingSnoop.erase(pkt->req);
617
618 DPRINTF(Cache, "Got prefetch response from above for addr "
619 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
620 recvTimingResp(pkt);
621 return;
622 }
623
624 // forwardLatency is set here because there is a response from an
625 // upper level cache.
626 // To pay the delay that occurs if the packet comes from the bus,
627 // we charge also headerDelay.
628 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
629 // Reset the timing of the packet.
630 pkt->headerDelay = pkt->payloadDelay = 0;
631 memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time);
632}
633
634void
635Cache::promoteWholeLineWrites(PacketPtr pkt)
636{
637 // Cache line clearing instructions
638 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
639 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
640 pkt->cmd = MemCmd::WriteLineReq;
641 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
642 }
643}
644
645void
646Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
647{
648 // should never be satisfying an uncacheable access as we
649 // flush and invalidate any existing block as part of the
650 // lookup
651 assert(!pkt->req->isUncacheable());
652
653 if (pkt->needsResponse()) {
654 pkt->makeTimingResponse();
655 // @todo: Make someone pay for this
656 pkt->headerDelay = pkt->payloadDelay = 0;
657
658 // In this case we are considering request_time that takes
659 // into account the delay of the xbar, if any, and just
660 // lat, neglecting responseLatency, modelling hit latency
661 // just as lookupLatency or or the value of lat overriden
662 // by access(), that calls accessBlock() function.
663 cpuSidePort->schedTimingResp(pkt, request_time, true);
664 } else {
665 DPRINTF(Cache, "%s satisfied %s, no response needed\n", __func__,
666 pkt->print());
667
668 // queue the packet for deletion, as the sending cache is
669 // still relying on it; if the block is found in access(),
670 // CleanEvict and Writeback messages will be deleted
671 // here as well
672 pendingDelete.reset(pkt);
673 }
674}
675
676void
677Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
678 Tick request_time)
679{
680 Addr blk_addr = pkt->getBlockAddr(blkSize);
681
682 // ignore any existing MSHR if we are dealing with an
683 // uncacheable request
684 MSHR *mshr = pkt->req->isUncacheable() ? nullptr :
685 mshrQueue.findMatch(blk_addr, pkt->isSecure());
686
687 // Software prefetch handling:
688 // To keep the core from waiting on data it won't look at
689 // anyway, send back a response with dummy data. Miss handling
690 // will continue asynchronously. Unfortunately, the core will
691 // insist upon freeing original Packet/Request, so we have to
692 // create a new pair with a different lifecycle. Note that this
693 // processing happens before any MSHR munging on the behalf of
694 // this request because this new Request will be the one stored
695 // into the MSHRs, not the original.
696 if (pkt->cmd.isSWPrefetch()) {
697 assert(pkt->needsResponse());
698 assert(pkt->req->hasPaddr());
699 assert(!pkt->req->isUncacheable());
700
701 // There's no reason to add a prefetch as an additional target
702 // to an existing MSHR. If an outstanding request is already
703 // in progress, there is nothing for the prefetch to do.
704 // If this is the case, we don't even create a request at all.
705 PacketPtr pf = nullptr;
706
707 if (!mshr) {
708 // copy the request and create a new SoftPFReq packet
709 RequestPtr req = new Request(pkt->req->getPaddr(),
710 pkt->req->getSize(),
711 pkt->req->getFlags(),
712 pkt->req->masterId());
713 pf = new Packet(req, pkt->cmd);
714 pf->allocate();
715 assert(pf->getAddr() == pkt->getAddr());
716 assert(pf->getSize() == pkt->getSize());
717 }
718
719 pkt->makeTimingResponse();
720
721 // request_time is used here, taking into account lat and the delay
722 // charged if the packet comes from the xbar.
723 cpuSidePort->schedTimingResp(pkt, request_time, true);
724
725 // If an outstanding request is in progress (we found an
726 // MSHR) this is set to null
727 pkt = pf;
728 }
729
730 if (mshr) {
731 /// MSHR hit
732 /// @note writebacks will be checked in getNextMSHR()
733 /// for any conflicting requests to the same block
734
735 //@todo remove hw_pf here
736
737 // Coalesce unless it was a software prefetch (see above).
738 if (pkt) {
739 assert(!pkt->isWriteback());
740 // CleanEvicts corresponding to blocks which have
741 // outstanding requests in MSHRs are simply sunk here
742 if (pkt->cmd == MemCmd::CleanEvict) {
743 pendingDelete.reset(pkt);
744 } else if (pkt->cmd == MemCmd::WriteClean) {
745 // A WriteClean should never coalesce with any
746 // outstanding cache maintenance requests.
747
748 // We use forward_time here because there is an
749 // uncached memory write, forwarded to WriteBuffer.
750 allocateWriteBuffer(pkt, forward_time);
751 } else {
752 DPRINTF(Cache, "%s coalescing MSHR for %s\n", __func__,
753 pkt->print());
754
755 assert(pkt->req->masterId() < system->maxMasters());
756 mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
757
758 // uncacheable accesses always allocate a new
759 // MSHR, and cacheable accesses ignore any
760 // uncacheable MSHRs, thus we should never have
761 // targets addded if originally allocated
762 // uncacheable
763 assert(!mshr->isUncacheable());
764
765 // We use forward_time here because it is the same
766 // considering new targets. We have multiple
767 // requests for the same address here. It
768 // specifies the latency to allocate an internal
769 // buffer and to schedule an event to the queued
770 // port and also takes into account the additional
771 // delay of the xbar.
772 mshr->allocateTarget(pkt, forward_time, order++,
773 allocOnFill(pkt->cmd));
774 if (mshr->getNumTargets() == numTarget) {
775 noTargetMSHR = mshr;
776 setBlocked(Blocked_NoTargets);
777 // need to be careful with this... if this mshr isn't
778 // ready yet (i.e. time > curTick()), we don't want to
779 // move it ahead of mshrs that are ready
780 // mshrQueue.moveToFront(mshr);
781 }
782 }
783 }
784 } else {
785 // no MSHR
786 assert(pkt->req->masterId() < system->maxMasters());
787 if (pkt->req->isUncacheable()) {
788 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
789 } else {
790 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
791 }
792
793 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
794 (pkt->req->isUncacheable() && pkt->isWrite())) {
795 // We use forward_time here because there is an
796 // uncached memory write, forwarded to WriteBuffer.
797 allocateWriteBuffer(pkt, forward_time);
798 } else {
799 if (blk && blk->isValid()) {
800 // should have flushed and have no valid block
801 assert(!pkt->req->isUncacheable());
802
803 // If we have a write miss to a valid block, we
804 // need to mark the block non-readable. Otherwise
805 // if we allow reads while there's an outstanding
806 // write miss, the read could return stale data
807 // out of the cache block... a more aggressive
808 // system could detect the overlap (if any) and
809 // forward data out of the MSHRs, but we don't do
810 // that yet. Note that we do need to leave the
811 // block valid so that it stays in the cache, in
812 // case we get an upgrade response (and hence no
813 // new data) when the write miss completes.
814 // As long as CPUs do proper store/load forwarding
815 // internally, and have a sufficiently weak memory
816 // model, this is probably unnecessary, but at some
817 // point it must have seemed like we needed it...
818 assert((pkt->needsWritable() && !blk->isWritable()) ||
819 pkt->req->isCacheMaintenance());
820 blk->status &= ~BlkReadable;
821 }
822 // Here we are using forward_time, modelling the latency of
823 // a miss (outbound) just as forwardLatency, neglecting the
824 // lookupLatency component.
825 allocateMissBuffer(pkt, forward_time);
826 }
827 }
828}
829
830void
831Cache::recvTimingReq(PacketPtr pkt)
832{
833 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
834
835 assert(pkt->isRequest());
836
837 // Just forward the packet if caches are disabled.
838 if (system->bypassCaches()) {
839 // @todo This should really enqueue the packet rather
840 bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt);
841 assert(success);
842 return;
843 }
844
845 promoteWholeLineWrites(pkt);
846
847 // Cache maintenance operations have to visit all the caches down
848 // to the specified xbar (PoC, PoU, etc.). Even if a cache above
849 // is responding we forward the packet to the memory below rather
850 // than creating an express snoop.
851 if (pkt->cacheResponding()) {
852 // a cache above us (but not where the packet came from) is
853 // responding to the request, in other words it has the line
854 // in Modified or Owned state
855 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
856 pkt->print());
857
858 // if the packet needs the block to be writable, and the cache
859 // that has promised to respond (setting the cache responding
860 // flag) is not providing writable (it is in Owned rather than
861 // the Modified state), we know that there may be other Shared
862 // copies in the system; go out and invalidate them all
863 assert(pkt->needsWritable() && !pkt->responderHadWritable());
864
865 // an upstream cache that had the line in Owned state
866 // (dirty, but not writable), is responding and thus
867 // transferring the dirty line from one branch of the
868 // cache hierarchy to another
869
870 // send out an express snoop and invalidate all other
871 // copies (snooping a packet that needs writable is the
872 // same as an invalidation), thus turning the Owned line
873 // into a Modified line, note that we don't invalidate the
874 // block in the current cache or any other cache on the
875 // path to memory
876
877 // create a downstream express snoop with cleared packet
878 // flags, there is no need to allocate any data as the
879 // packet is merely used to co-ordinate state transitions
880 Packet *snoop_pkt = new Packet(pkt, true, false);
881
882 // also reset the bus time that the original packet has
883 // not yet paid for
884 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
885
886 // make this an instantaneous express snoop, and let the
887 // other caches in the system know that the another cache
888 // is responding, because we have found the authorative
889 // copy (Modified or Owned) that will supply the right
890 // data
891 snoop_pkt->setExpressSnoop();
892 snoop_pkt->setCacheResponding();
893
894 // this express snoop travels towards the memory, and at
895 // every crossbar it is snooped upwards thus reaching
896 // every cache in the system
897 bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt);
898 // express snoops always succeed
899 assert(success);
900
901 // main memory will delete the snoop packet
902
903 // queue for deletion, as opposed to immediate deletion, as
904 // the sending cache is still relying on the packet
905 pendingDelete.reset(pkt);
906
907 // no need to take any further action in this particular cache
908 // as an upstram cache has already committed to responding,
909 // and we have already sent out any express snoops in the
910 // section above to ensure all other copies in the system are
911 // invalidated
912 return;
913 }
914
915 // anything that is merely forwarded pays for the forward latency and
916 // the delay provided by the crossbar
917 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
918
919 // We use lookupLatency here because it is used to specify the latency
920 // to access.
921 Cycles lat = lookupLatency;
922 CacheBlk *blk = nullptr;
923 bool satisfied = false;
924 {
925 PacketList writebacks;
926 // Note that lat is passed by reference here. The function
927 // access() calls accessBlock() which can modify lat value.
928 satisfied = access(pkt, blk, lat, writebacks);
929
930 // copy writebacks to write buffer here to ensure they logically
931 // proceed anything happening below
932 doWritebacks(writebacks, forward_time);
933 }
934
935 // Here we charge the headerDelay that takes into account the latencies
936 // of the bus, if the packet comes from it.
937 // The latency charged it is just lat that is the value of lookupLatency
938 // modified by access() function, or if not just lookupLatency.
939 // In case of a hit we are neglecting response latency.
940 // In case of a miss we are neglecting forward latency.
941 Tick request_time = clockEdge(lat) + pkt->headerDelay;
942 // Here we reset the timing of the packet.
943 pkt->headerDelay = pkt->payloadDelay = 0;
944
945 // track time of availability of next prefetch, if any
946 Tick next_pf_time = MaxTick;
947
948 if (satisfied) {
949 // if need to notify the prefetcher we need to do it anything
950 // else, handleTimingReqHit might turn the packet into a
951 // response
952 if (prefetcher &&
953 (prefetchOnAccess || (blk && blk->wasPrefetched()))) {
954 if (blk)
955 blk->status &= ~BlkHWPrefetched;
956
957 // Don't notify on SWPrefetch
958 if (!pkt->cmd.isSWPrefetch()) {
959 assert(!pkt->req->isCacheMaintenance());
960 next_pf_time = prefetcher->notify(pkt);
961 }
962 }
963
964 handleTimingReqHit(pkt, blk, request_time);
965 } else {
966 handleTimingReqMiss(pkt, blk, forward_time, request_time);
967
968 // We should call the prefetcher reguardless if the request is
969 // satisfied or not, reguardless if the request is in the MSHR
970 // or not. The request could be a ReadReq hit, but still not
971 // satisfied (potentially because of a prior write to the same
972 // cache line. So, even when not satisfied, there is an MSHR
973 // already allocated for this, we need to let the prefetcher
974 // know about the request
975 if (prefetcher && pkt &&
976 !pkt->cmd.isSWPrefetch() &&
977 !pkt->req->isCacheMaintenance()) {
978 next_pf_time = prefetcher->notify(pkt);
979 }
980 }
981
982 if (next_pf_time != MaxTick)
983 schedMemSideSendEvent(next_pf_time);
984}
985
986PacketPtr
987Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
988 bool needsWritable) const
989{
990 // should never see evictions here
991 assert(!cpu_pkt->isEviction());
992
993 bool blkValid = blk && blk->isValid();
994
995 if (cpu_pkt->req->isUncacheable() ||
996 (!blkValid && cpu_pkt->isUpgrade()) ||
997 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
998 // uncacheable requests and upgrades from upper-level caches
999 // that missed completely just go through as is
1000 return nullptr;
1001 }
1002
1003 assert(cpu_pkt->needsResponse());
1004
1005 MemCmd cmd;
1006 // @TODO make useUpgrades a parameter.
1007 // Note that ownership protocols require upgrade, otherwise a
1008 // write miss on a shared owned block will generate a ReadExcl,
1009 // which will clobber the owned copy.
1010 const bool useUpgrades = true;
1011 if (cpu_pkt->cmd == MemCmd::WriteLineReq) {
1012 assert(!blkValid || !blk->isWritable());
1013 // forward as invalidate to all other caches, this gives us
1014 // the line in Exclusive state, and invalidates all other
1015 // copies
1016 cmd = MemCmd::InvalidateReq;
1017 } else if (blkValid && useUpgrades) {
1018 // only reason to be here is that blk is read only and we need
1019 // it to be writable
1020 assert(needsWritable);
1021 assert(!blk->isWritable());
1022 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
1023 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
1024 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
1025 // Even though this SC will fail, we still need to send out the
1026 // request and get the data to supply it to other snoopers in the case
1027 // where the determination the StoreCond fails is delayed due to
1028 // all caches not being on the same local bus.
1029 cmd = MemCmd::SCUpgradeFailReq;
1030 } else {
1031 // block is invalid
1032
1033 // If the request does not need a writable there are two cases
1034 // where we need to ensure the response will not fetch the
1035 // block in dirty state:
1036 // * this cache is read only and it does not perform
1037 // writebacks,
1038 // * this cache is mostly exclusive and will not fill (since
1039 // it does not fill it will have to writeback the dirty data
1040 // immediately which generates uneccesary writebacks).
1041 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
1042 cmd = needsWritable ? MemCmd::ReadExReq :
1043 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
1044 }
1045 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
1046
1047 // if there are upstream caches that have already marked the
1048 // packet as having sharers (not passing writable), pass that info
1049 // downstream
1050 if (cpu_pkt->hasSharers() && !needsWritable) {
1051 // note that cpu_pkt may have spent a considerable time in the
1052 // MSHR queue and that the information could possibly be out
1053 // of date, however, there is no harm in conservatively
1054 // assuming the block has sharers
1055 pkt->setHasSharers();
1056 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
1057 __func__, cpu_pkt->print(), pkt->print());
1058 }
1059
1060 // the packet should be block aligned
1061 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
1062
1063 pkt->allocate();
1064 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
1065 cpu_pkt->print());
1066 return pkt;
1067}
1068
1069
|
1199 }
1200
1201 // Note that we don't invoke the prefetcher at all in atomic mode.
1202 // It's not clear how to do it properly, particularly for
1203 // prefetchers that aggressively generate prefetch candidates and
1204 // rely on bandwidth contention to throttle them; these will tend
1205 // to pollute the cache in atomic mode since there is no bandwidth
1206 // contention. If we ever do want to enable prefetching in atomic
1207 // mode, though, this is the place to do it... see timingAccess()
1208 // for an example (though we'd want to issue the prefetch(es)
1209 // immediately rather than calling requestMemSideBus() as we do
1210 // there).
1211
1212 // do any writebacks resulting from the response handling
1213 doWritebacksAtomic(writebacks);
1214
1215 // if we used temp block, check to see if its valid and if so
1216 // clear it out, but only do so after the call to recvAtomic is
1217 // finished so that any downstream observers (such as a snoop
1218 // filter), first see the fill, and only then see the eviction
1219 if (blk == tempBlock && tempBlock->isValid()) {
1220 // the atomic CPU calls recvAtomic for fetch and load/store
1221 // sequentuially, and we may already have a tempBlock
1222 // writeback from the fetch that we have not yet sent
1223 if (tempBlockWriteback) {
1224 // if that is the case, write the prevoius one back, and
1225 // do not schedule any new event
1226 writebackTempBlockAtomic();
1227 } else {
1228 // the writeback/clean eviction happens after the call to
1229 // recvAtomic has finished (but before any successive
1230 // calls), so that the response handling from the fill is
1231 // allowed to happen first
1232 schedule(writebackTempBlockAtomicEvent, curTick());
1233 }
1234
1235 tempBlockWriteback = (blk->isDirty() || writebackClean) ?
1236 writebackBlk(blk) : cleanEvictBlk(blk);
1237 invalidateBlock(blk);
1238 }
1239
1240 if (pkt->needsResponse()) {
1241 pkt->makeAtomicResponse();
1242 }
1243
1244 return lat * clockPeriod();
1245}
1246
1247
1248void
1249Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide)
1250{
1251 if (system->bypassCaches()) {
1252 // Packets from the memory side are snoop request and
1253 // shouldn't happen in bypass mode.
1254 assert(fromCpuSide);
1255
1256 // The cache should be flushed if we are in cache bypass mode,
1257 // so we don't need to check if we need to update anything.
1258 memSidePort->sendFunctional(pkt);
1259 return;
1260 }
1261
1262 Addr blk_addr = pkt->getBlockAddr(blkSize);
1263 bool is_secure = pkt->isSecure();
1264 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1265 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1266
1267 pkt->pushLabel(name());
1268
1269 CacheBlkPrintWrapper cbpw(blk);
1270
1271 // Note that just because an L2/L3 has valid data doesn't mean an
1272 // L1 doesn't have a more up-to-date modified copy that still
1273 // needs to be found. As a result we always update the request if
1274 // we have it, but only declare it satisfied if we are the owner.
1275
1276 // see if we have data at all (owned or otherwise)
1277 bool have_data = blk && blk->isValid()
1278 && pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize,
1279 blk->data);
1280
1281 // data we have is dirty if marked as such or if we have an
1282 // in-service MSHR that is pending a modified line
1283 bool have_dirty =
1284 have_data && (blk->isDirty() ||
1285 (mshr && mshr->inService && mshr->isPendingModified()));
1286
1287 bool done = have_dirty
1288 || cpuSidePort->checkFunctional(pkt)
1289 || mshrQueue.checkFunctional(pkt, blk_addr)
1290 || writeBuffer.checkFunctional(pkt, blk_addr)
1291 || memSidePort->checkFunctional(pkt);
1292
1293 DPRINTF(CacheVerbose, "%s: %s %s%s%s\n", __func__, pkt->print(),
1294 (blk && blk->isValid()) ? "valid " : "",
1295 have_data ? "data " : "", done ? "done " : "");
1296
1297 // We're leaving the cache, so pop cache->name() label
1298 pkt->popLabel();
1299
1300 if (done) {
1301 pkt->makeResponse();
1302 } else {
1303 // if it came as a request from the CPU side then make sure it
1304 // continues towards the memory side
1305 if (fromCpuSide) {
1306 memSidePort->sendFunctional(pkt);
1307 } else if (cpuSidePort->isSnooping()) {
1308 // if it came from the memory side, it must be a snoop request
1309 // and we should only forward it if we are forwarding snoops
1310 cpuSidePort->sendFunctionalSnoop(pkt);
1311 }
1312 }
1313}
1314
1315
1316/////////////////////////////////////////////////////
1317//
1318// Response handling: responses from the memory side
1319//
1320/////////////////////////////////////////////////////
1321
1322
1323void
1324Cache::handleUncacheableWriteResp(PacketPtr pkt)
1325{
1326 Tick completion_time = clockEdge(responseLatency) +
1327 pkt->headerDelay + pkt->payloadDelay;
1328
1329 // Reset the bus additional time as it is now accounted for
1330 pkt->headerDelay = pkt->payloadDelay = 0;
1331
1332 cpuSidePort->schedTimingResp(pkt, completion_time, true);
1333}
1334
1335void
1336Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk,
1337 PacketList &writebacks)
1338{
1339 MSHR::Target *initial_tgt = mshr->getTarget();
1340 // First offset for critical word first calculations
1341 const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
1342
1343 const bool is_error = pkt->isError();
1344 bool is_fill = !mshr->isForward &&
1345 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
1346 // allow invalidation responses originating from write-line
1347 // requests to be discarded
1348 bool is_invalidate = pkt->isInvalidate();
1349
1350 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
1351 for (auto &target: targets) {
1352 Packet *tgt_pkt = target.pkt;
1353 switch (target.source) {
1354 case MSHR::Target::FromCPU:
1355 Tick completion_time;
1356 // Here we charge on completion_time the delay of the xbar if the
1357 // packet comes from it, charged on headerDelay.
1358 completion_time = pkt->headerDelay;
1359
1360 // Software prefetch handling for cache closest to core
1361 if (tgt_pkt->cmd.isSWPrefetch()) {
1362 // a software prefetch would have already been ack'd
1363 // immediately with dummy data so the core would be able to
1364 // retire it. This request completes right here, so we
1365 // deallocate it.
1366 delete tgt_pkt->req;
1367 delete tgt_pkt;
1368 break; // skip response
1369 }
1370
1371 // unlike the other packet flows, where data is found in other
1372 // caches or memory and brought back, write-line requests always
1373 // have the data right away, so the above check for "is fill?"
1374 // cannot actually be determined until examining the stored MSHR
1375 // state. We "catch up" with that logic here, which is duplicated
1376 // from above.
1377 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
1378 assert(!is_error);
1379 // we got the block in a writable state, so promote
1380 // any deferred targets if possible
1381 mshr->promoteWritable();
1382 // NB: we use the original packet here and not the response!
1383 blk = handleFill(tgt_pkt, blk, writebacks,
1384 targets.allocOnFill);
1385 assert(blk);
1386
1387 // treat as a fill, and discard the invalidation
1388 // response
1389 is_fill = true;
1390 is_invalidate = false;
1391 }
1392
1393 if (is_fill) {
1394 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
1395
1396 // How many bytes past the first request is this one
1397 int transfer_offset =
1398 tgt_pkt->getOffset(blkSize) - initial_offset;
1399 if (transfer_offset < 0) {
1400 transfer_offset += blkSize;
1401 }
1402
1403 // If not critical word (offset) return payloadDelay.
1404 // responseLatency is the latency of the return path
1405 // from lower level caches/memory to an upper level cache or
1406 // the core.
1407 completion_time += clockEdge(responseLatency) +
1408 (transfer_offset ? pkt->payloadDelay : 0);
1409
1410 assert(!tgt_pkt->req->isUncacheable());
1411
1412 assert(tgt_pkt->req->masterId() < system->maxMasters());
1413 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
1414 completion_time - target.recvTime;
1415 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
1416 // failed StoreCond upgrade
1417 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
1418 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
1419 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
1420 // responseLatency is the latency of the return path
1421 // from lower level caches/memory to an upper level cache or
1422 // the core.
1423 completion_time += clockEdge(responseLatency) +
1424 pkt->payloadDelay;
1425 tgt_pkt->req->setExtraData(0);
1426 } else {
1427 // We are about to send a response to a cache above
1428 // that asked for an invalidation; we need to
1429 // invalidate our copy immediately as the most
1430 // up-to-date copy of the block will now be in the
1431 // cache above. It will also prevent this cache from
1432 // responding (if the block was previously dirty) to
1433 // snoops as they should snoop the caches above where
1434 // they will get the response from.
1435 if (is_invalidate && blk && blk->isValid()) {
1436 invalidateBlock(blk);
1437 }
1438 // not a cache fill, just forwarding response
1439 // responseLatency is the latency of the return path
1440 // from lower level cahces/memory to the core.
1441 completion_time += clockEdge(responseLatency) +
1442 pkt->payloadDelay;
1443 if (pkt->isRead() && !is_error) {
1444 // sanity check
1445 assert(pkt->getAddr() == tgt_pkt->getAddr());
1446 assert(pkt->getSize() >= tgt_pkt->getSize());
1447
1448 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
1449 }
1450 }
1451 tgt_pkt->makeTimingResponse();
1452 // if this packet is an error copy that to the new packet
1453 if (is_error)
1454 tgt_pkt->copyError(pkt);
1455 if (tgt_pkt->cmd == MemCmd::ReadResp &&
1456 (is_invalidate || mshr->hasPostInvalidate())) {
1457 // If intermediate cache got ReadRespWithInvalidate,
1458 // propagate that. Response should not have
1459 // isInvalidate() set otherwise.
1460 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
1461 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
1462 tgt_pkt->print());
1463 }
1464 // Reset the bus additional time as it is now accounted for
1465 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
1466 cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true);
1467 break;
1468
1469 case MSHR::Target::FromPrefetcher:
1470 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
1471 if (blk)
1472 blk->status |= BlkHWPrefetched;
1473 delete tgt_pkt->req;
1474 delete tgt_pkt;
1475 break;
1476
1477 case MSHR::Target::FromSnoop:
1478 // I don't believe that a snoop can be in an error state
1479 assert(!is_error);
1480 // response to snoop request
1481 DPRINTF(Cache, "processing deferred snoop...\n");
1482 // If the response is invalidating, a snooping target can
1483 // be satisfied if it is also invalidating. If the reponse is, not
1484 // only invalidating, but more specifically an InvalidateResp and
1485 // the MSHR was created due to an InvalidateReq then a cache above
1486 // is waiting to satisfy a WriteLineReq. In this case even an
1487 // non-invalidating snoop is added as a target here since this is
1488 // the ordering point. When the InvalidateResp reaches this cache,
1489 // the snooping target will snoop further the cache above with the
1490 // WriteLineReq.
1491 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
1492 pkt->req->isCacheMaintenance() ||
1493 mshr->hasPostInvalidate());
1494 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
1495 break;
1496
1497 default:
1498 panic("Illegal target->source enum %d\n", target.source);
1499 }
1500 }
1501
1502 maintainClusivity(targets.hasFromCache, blk);
1503
1504 if (blk && blk->isValid()) {
1505 // an invalidate response stemming from a write line request
1506 // should not invalidate the block, so check if the
1507 // invalidation should be discarded
1508 if (is_invalidate || mshr->hasPostInvalidate()) {
1509 invalidateBlock(blk);
1510 } else if (mshr->hasPostDowngrade()) {
1511 blk->status &= ~BlkWritable;
1512 }
1513 }
1514}
1515
1516void
1517Cache::recvTimingResp(PacketPtr pkt)
1518{
1519 assert(pkt->isResponse());
1520
1521 // all header delay should be paid for by the crossbar, unless
1522 // this is a prefetch response from above
1523 panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp,
1524 "%s saw a non-zero packet delay\n", name());
1525
1526 const bool is_error = pkt->isError();
1527
1528 if (is_error) {
1529 DPRINTF(Cache, "%s: Cache received %s with error\n", __func__,
1530 pkt->print());
1531 }
1532
1533 DPRINTF(Cache, "%s: Handling response %s\n", __func__,
1534 pkt->print());
1535
1536 // if this is a write, we should be looking at an uncacheable
1537 // write
1538 if (pkt->isWrite()) {
1539 assert(pkt->req->isUncacheable());
1540 handleUncacheableWriteResp(pkt);
1541 return;
1542 }
1543
1544 // we have dealt with any (uncacheable) writes above, from here on
1545 // we know we are dealing with an MSHR due to a miss or a prefetch
1546 MSHR *mshr = dynamic_cast<MSHR*>(pkt->popSenderState());
1547 assert(mshr);
1548
1549 if (mshr == noTargetMSHR) {
1550 // we always clear at least one target
1551 clearBlocked(Blocked_NoTargets);
1552 noTargetMSHR = nullptr;
1553 }
1554
1555 // Initial target is used just for stats
1556 MSHR::Target *initial_tgt = mshr->getTarget();
1557 int stats_cmd_idx = initial_tgt->pkt->cmdToIndex();
1558 Tick miss_latency = curTick() - initial_tgt->recvTime;
1559
1560 if (pkt->req->isUncacheable()) {
1561 assert(pkt->req->masterId() < system->maxMasters());
1562 mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] +=
1563 miss_latency;
1564 } else {
1565 assert(pkt->req->masterId() < system->maxMasters());
1566 mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] +=
1567 miss_latency;
1568 }
1569
1570 PacketList writebacks;
1571
1572 bool is_fill = !mshr->isForward &&
1573 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
1574
1575 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1576
1577 if (is_fill && !is_error) {
1578 DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n",
1579 pkt->getAddr());
1580
1581 blk = handleFill(pkt, blk, writebacks, mshr->allocOnFill());
1582 assert(blk != nullptr);
1583 }
1584
1585 if (blk && blk->isValid() && pkt->isClean() && !pkt->isInvalidate()) {
1586 // The block was marked not readable while there was a pending
1587 // cache maintenance operation, restore its flag.
1588 blk->status |= BlkReadable;
1589 }
1590
1591 if (blk && blk->isWritable() && !pkt->req->isCacheInvalidate()) {
1592 // If at this point the referenced block is writable and the
1593 // response is not a cache invalidate, we promote targets that
1594 // were deferred as we couldn't guarrantee a writable copy
1595 mshr->promoteWritable();
1596 }
1597
1598 serviceMSHRTargets(mshr, pkt, blk, writebacks);
1599
1600 if (mshr->promoteDeferredTargets()) {
1601 // avoid later read getting stale data while write miss is
1602 // outstanding.. see comment in timingAccess()
1603 if (blk) {
1604 blk->status &= ~BlkReadable;
1605 }
1606 mshrQueue.markPending(mshr);
1607 schedMemSideSendEvent(clockEdge() + pkt->payloadDelay);
1608 } else {
1609 // while we deallocate an mshr from the queue we still have to
1610 // check the isFull condition before and after as we might
1611 // have been using the reserved entries already
1612 const bool was_full = mshrQueue.isFull();
1613 mshrQueue.deallocate(mshr);
1614 if (was_full && !mshrQueue.isFull()) {
1615 clearBlocked(Blocked_NoMSHRs);
1616 }
1617
1618 // Request the bus for a prefetch if this deallocation freed enough
1619 // MSHRs for a prefetch to take place
1620 if (prefetcher && mshrQueue.canPrefetch()) {
1621 Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(),
1622 clockEdge());
1623 if (next_pf_time != MaxTick)
1624 schedMemSideSendEvent(next_pf_time);
1625 }
1626 }
1627
1628 // if we used temp block, check to see if its valid and then clear it out
1629 if (blk == tempBlock && tempBlock->isValid()) {
1630 PacketPtr wb_pkt = tempBlock->isDirty() || writebackClean ?
1631 writebackBlk(blk) : cleanEvictBlk(blk);
1632 writebacks.push_back(wb_pkt);
1633 invalidateBlock(tempBlock);
1634 }
1635
1636 const Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
1637 // copy writebacks to write buffer
1638 doWritebacks(writebacks, forward_time);
1639
1640 DPRINTF(CacheVerbose, "%s: Leaving with %s\n", __func__, pkt->print());
1641 delete pkt;
1642}
1643
1644PacketPtr
1645Cache::writebackBlk(CacheBlk *blk)
1646{
1647 chatty_assert(!isReadOnly || writebackClean,
1648 "Writeback from read-only cache");
1649 assert(blk && blk->isValid() && (blk->isDirty() || writebackClean));
1650
1651 writebacks[Request::wbMasterId]++;
1652
1653 Request *req = new Request(tags->regenerateBlkAddr(blk), blkSize, 0,
1654 Request::wbMasterId);
1655 if (blk->isSecure())
1656 req->setFlags(Request::SECURE);
1657
1658 req->taskId(blk->task_id);
1659
1660 PacketPtr pkt =
1661 new Packet(req, blk->isDirty() ?
1662 MemCmd::WritebackDirty : MemCmd::WritebackClean);
1663
1664 DPRINTF(Cache, "Create Writeback %s writable: %d, dirty: %d\n",
1665 pkt->print(), blk->isWritable(), blk->isDirty());
1666
1667 if (blk->isWritable()) {
1668 // not asserting shared means we pass the block in modified
1669 // state, mark our own block non-writeable
1670 blk->status &= ~BlkWritable;
1671 } else {
1672 // we are in the Owned state, tell the receiver
1673 pkt->setHasSharers();
1674 }
1675
1676 // make sure the block is not marked dirty
1677 blk->status &= ~BlkDirty;
1678
1679 pkt->allocate();
1680 pkt->setDataFromBlock(blk->data, blkSize);
1681
1682 return pkt;
1683}
1684
1685PacketPtr
1686Cache::writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id)
1687{
1688 Request *req = new Request(tags->regenerateBlkAddr(blk), blkSize, 0,
1689 Request::wbMasterId);
1690 if (blk->isSecure()) {
1691 req->setFlags(Request::SECURE);
1692 }
1693 req->taskId(blk->task_id);
1694
1695 PacketPtr pkt = new Packet(req, MemCmd::WriteClean, blkSize, id);
1696
1697 if (dest) {
1698 req->setFlags(dest);
1699 pkt->setWriteThrough();
1700 }
1701
1702 DPRINTF(Cache, "Create %s writable: %d, dirty: %d\n", pkt->print(),
1703 blk->isWritable(), blk->isDirty());
1704
1705 if (blk->isWritable()) {
1706 // not asserting shared means we pass the block in modified
1707 // state, mark our own block non-writeable
1708 blk->status &= ~BlkWritable;
1709 } else {
1710 // we are in the Owned state, tell the receiver
1711 pkt->setHasSharers();
1712 }
1713
1714 // make sure the block is not marked dirty
1715 blk->status &= ~BlkDirty;
1716
1717 pkt->allocate();
1718 pkt->setDataFromBlock(blk->data, blkSize);
1719
1720 return pkt;
1721}
1722
1723
1724PacketPtr
1725Cache::cleanEvictBlk(CacheBlk *blk)
1726{
1727 assert(!writebackClean);
1728 assert(blk && blk->isValid() && !blk->isDirty());
1729 // Creating a zero sized write, a message to the snoop filter
1730 Request *req =
1731 new Request(tags->regenerateBlkAddr(blk), blkSize, 0,
1732 Request::wbMasterId);
1733 if (blk->isSecure())
1734 req->setFlags(Request::SECURE);
1735
1736 req->taskId(blk->task_id);
1737
1738 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
1739 pkt->allocate();
1740 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
1741
1742 return pkt;
1743}
1744
1745void
1746Cache::memWriteback()
1747{
1748 CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor);
1749 tags->forEachBlk(visitor);
1750}
1751
1752void
1753Cache::memInvalidate()
1754{
1755 CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor);
1756 tags->forEachBlk(visitor);
1757}
1758
1759bool
1760Cache::isDirty() const
1761{
1762 CacheBlkIsDirtyVisitor visitor;
1763 tags->forEachBlk(visitor);
1764
1765 return visitor.isDirty();
1766}
1767
1768bool
1769Cache::writebackVisitor(CacheBlk &blk)
1770{
1771 if (blk.isDirty()) {
1772 assert(blk.isValid());
1773
1774 Request request(tags->regenerateBlkAddr(&blk), blkSize, 0,
1775 Request::funcMasterId);
1776 request.taskId(blk.task_id);
1777 if (blk.isSecure()) {
1778 request.setFlags(Request::SECURE);
1779 }
1780
1781 Packet packet(&request, MemCmd::WriteReq);
1782 packet.dataStatic(blk.data);
1783
1784 memSidePort->sendFunctional(&packet);
1785
1786 blk.status &= ~BlkDirty;
1787 }
1788
1789 return true;
1790}
1791
1792bool
1793Cache::invalidateVisitor(CacheBlk &blk)
1794{
1795
1796 if (blk.isDirty())
1797 warn_once("Invalidating dirty cache lines. Expect things to break.\n");
1798
1799 if (blk.isValid()) {
1800 assert(!blk.isDirty());
1801 invalidateBlock(&blk);
1802 }
1803
1804 return true;
1805}
1806
1807CacheBlk*
1808Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks)
1809{
1810 // Find replacement victim
1811 CacheBlk *blk = tags->findVictim(addr);
1812
1813 // It is valid to return nullptr if there is no victim
1814 if (!blk)
1815 return nullptr;
1816
1817 if (blk->isValid()) {
1818 Addr repl_addr = tags->regenerateBlkAddr(blk);
1819 MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
1820 if (repl_mshr) {
1821 // must be an outstanding upgrade or clean request
1822 // on a block we're about to replace...
1823 assert((!blk->isWritable() && repl_mshr->needsWritable()) ||
1824 repl_mshr->isCleaning());
1825 // too hard to replace block with transient state
1826 // allocation failed, block not inserted
1827 return nullptr;
1828 } else {
1829 DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx "
1830 "(%s): %s\n", repl_addr, blk->isSecure() ? "s" : "ns",
1831 addr, is_secure ? "s" : "ns",
1832 blk->isDirty() ? "writeback" : "clean");
1833
1834 if (blk->wasPrefetched()) {
1835 unusedPrefetches++;
1836 }
1837 // Will send up Writeback/CleanEvict snoops via isCachedAbove
1838 // when pushing this writeback list into the write buffer.
1839 if (blk->isDirty() || writebackClean) {
1840 // Save writeback packet for handling by caller
1841 writebacks.push_back(writebackBlk(blk));
1842 } else {
1843 writebacks.push_back(cleanEvictBlk(blk));
1844 }
1845 replacements++;
1846 }
1847 }
1848
1849 return blk;
1850}
1851
1852void
1853Cache::invalidateBlock(CacheBlk *blk)
1854{
1855 if (blk != tempBlock)
1856 tags->invalidate(blk);
1857 blk->invalidate();
1858}
1859
1860// Note that the reason we return a list of writebacks rather than
1861// inserting them directly in the write buffer is that this function
1862// is called by both atomic and timing-mode accesses, and in atomic
1863// mode we don't mess with the write buffer (we just perform the
1864// writebacks atomically once the original request is complete).
1865CacheBlk*
1866Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks,
1867 bool allocate)
1868{
1869 assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq);
1870 Addr addr = pkt->getAddr();
1871 bool is_secure = pkt->isSecure();
1872#if TRACING_ON
1873 CacheBlk::State old_state = blk ? blk->status : 0;
1874#endif
1875
1876 // When handling a fill, we should have no writes to this line.
1877 assert(addr == pkt->getBlockAddr(blkSize));
1878 assert(!writeBuffer.findMatch(addr, is_secure));
1879
1880 if (blk == nullptr) {
1881 // better have read new data...
1882 assert(pkt->hasData());
1883
1884 // only read responses and write-line requests have data;
1885 // note that we don't write the data here for write-line - that
1886 // happens in the subsequent call to satisfyRequest
1887 assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq);
1888
1889 // need to do a replacement if allocating, otherwise we stick
1890 // with the temporary storage
1891 blk = allocate ? allocateBlock(addr, is_secure, writebacks) : nullptr;
1892
1893 if (blk == nullptr) {
1894 // No replaceable block or a mostly exclusive
1895 // cache... just use temporary storage to complete the
1896 // current request and then get rid of it
1897 assert(!tempBlock->isValid());
1898 blk = tempBlock;
1899 tempBlock->set = tags->extractSet(addr);
1900 tempBlock->tag = tags->extractTag(addr);
1901 if (is_secure) {
1902 tempBlock->status |= BlkSecure;
1903 }
1904 DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr,
1905 is_secure ? "s" : "ns");
1906 } else {
1907 tags->insertBlock(pkt, blk);
1908 }
1909
1910 // we should never be overwriting a valid block
1911 assert(!blk->isValid());
1912 } else {
1913 // existing block... probably an upgrade
1914 assert(blk->tag == tags->extractTag(addr));
1915 // either we're getting new data or the block should already be valid
1916 assert(pkt->hasData() || blk->isValid());
1917 // don't clear block status... if block is already dirty we
1918 // don't want to lose that
1919 }
1920
1921 if (is_secure)
1922 blk->status |= BlkSecure;
1923 blk->status |= BlkValid | BlkReadable;
1924
1925 // sanity check for whole-line writes, which should always be
1926 // marked as writable as part of the fill, and then later marked
1927 // dirty as part of satisfyRequest
1928 if (pkt->cmd == MemCmd::WriteLineReq) {
1929 assert(!pkt->hasSharers());
1930 }
1931
1932 // here we deal with setting the appropriate state of the line,
1933 // and we start by looking at the hasSharers flag, and ignore the
1934 // cacheResponding flag (normally signalling dirty data) if the
1935 // packet has sharers, thus the line is never allocated as Owned
1936 // (dirty but not writable), and always ends up being either
1937 // Shared, Exclusive or Modified, see Packet::setCacheResponding
1938 // for more details
1939 if (!pkt->hasSharers()) {
1940 // we could get a writable line from memory (rather than a
1941 // cache) even in a read-only cache, note that we set this bit
1942 // even for a read-only cache, possibly revisit this decision
1943 blk->status |= BlkWritable;
1944
1945 // check if we got this via cache-to-cache transfer (i.e., from a
1946 // cache that had the block in Modified or Owned state)
1947 if (pkt->cacheResponding()) {
1948 // we got the block in Modified state, and invalidated the
1949 // owners copy
1950 blk->status |= BlkDirty;
1951
1952 chatty_assert(!isReadOnly, "Should never see dirty snoop response "
1953 "in read-only cache %s\n", name());
1954 }
1955 }
1956
1957 DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n",
1958 addr, is_secure ? "s" : "ns", old_state, blk->print());
1959
1960 // if we got new data, copy it in (checking for a read response
1961 // and a response that has data is the same in the end)
1962 if (pkt->isRead()) {
1963 // sanity checks
1964 assert(pkt->hasData());
1965 assert(pkt->getSize() == blkSize);
1966
1967 pkt->writeDataToBlock(blk->data, blkSize);
1968 }
1969 // We pay for fillLatency here.
1970 blk->whenReady = clockEdge() + fillLatency * clockPeriod() +
1971 pkt->payloadDelay;
1972
1973 return blk;
1974}
1975
1976
1977/////////////////////////////////////////////////////
1978//
1979// Snoop path: requests coming in from the memory side
1980//
1981/////////////////////////////////////////////////////
1982
1983void
1984Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
1985 bool already_copied, bool pending_inval)
1986{
1987 // sanity check
1988 assert(req_pkt->isRequest());
1989 assert(req_pkt->needsResponse());
1990
1991 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
1992 // timing-mode snoop responses require a new packet, unless we
1993 // already made a copy...
1994 PacketPtr pkt = req_pkt;
1995 if (!already_copied)
1996 // do not clear flags, and allocate space for data if the
1997 // packet needs it (the only packets that carry data are read
1998 // responses)
1999 pkt = new Packet(req_pkt, false, req_pkt->isRead());
2000
2001 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
2002 pkt->hasSharers());
2003 pkt->makeTimingResponse();
2004 if (pkt->isRead()) {
2005 pkt->setDataFromBlock(blk_data, blkSize);
2006 }
2007 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
2008 // Assume we defer a response to a read from a far-away cache
2009 // A, then later defer a ReadExcl from a cache B on the same
2010 // bus as us. We'll assert cacheResponding in both cases, but
2011 // in the latter case cacheResponding will keep the
2012 // invalidation from reaching cache A. This special response
2013 // tells cache A that it gets the block to satisfy its read,
2014 // but must immediately invalidate it.
2015 pkt->cmd = MemCmd::ReadRespWithInvalidate;
2016 }
2017 // Here we consider forward_time, paying for just forward latency and
2018 // also charging the delay provided by the xbar.
2019 // forward_time is used as send_time in next allocateWriteBuffer().
2020 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
2021 // Here we reset the timing of the packet.
2022 pkt->headerDelay = pkt->payloadDelay = 0;
2023 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
2024 pkt->print(), forward_time);
2025 memSidePort->schedTimingSnoopResp(pkt, forward_time, true);
2026}
2027
2028uint32_t
2029Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
2030 bool is_deferred, bool pending_inval)
2031{
2032 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2033 // deferred snoops can only happen in timing mode
2034 assert(!(is_deferred && !is_timing));
2035 // pending_inval only makes sense on deferred snoops
2036 assert(!(pending_inval && !is_deferred));
2037 assert(pkt->isRequest());
2038
2039 // the packet may get modified if we or a forwarded snooper
2040 // responds in atomic mode, so remember a few things about the
2041 // original packet up front
2042 bool invalidate = pkt->isInvalidate();
2043 bool M5_VAR_USED needs_writable = pkt->needsWritable();
2044
2045 // at the moment we could get an uncacheable write which does not
2046 // have the invalidate flag, and we need a suitable way of dealing
2047 // with this case
2048 panic_if(invalidate && pkt->req->isUncacheable(),
2049 "%s got an invalidating uncacheable snoop request %s",
2050 name(), pkt->print());
2051
2052 uint32_t snoop_delay = 0;
2053
2054 if (forwardSnoops) {
2055 // first propagate snoop upward to see if anyone above us wants to
2056 // handle it. save & restore packet src since it will get
2057 // rewritten to be relative to cpu-side bus (if any)
2058 bool alreadyResponded = pkt->cacheResponding();
2059 if (is_timing) {
2060 // copy the packet so that we can clear any flags before
2061 // forwarding it upwards, we also allocate data (passing
2062 // the pointer along in case of static data), in case
2063 // there is a snoop hit in upper levels
2064 Packet snoopPkt(pkt, true, true);
2065 snoopPkt.setExpressSnoop();
2066 // the snoop packet does not need to wait any additional
2067 // time
2068 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
2069 cpuSidePort->sendTimingSnoopReq(&snoopPkt);
2070
2071 // add the header delay (including crossbar and snoop
2072 // delays) of the upward snoop to the snoop delay for this
2073 // cache
2074 snoop_delay += snoopPkt.headerDelay;
2075
2076 if (snoopPkt.cacheResponding()) {
2077 // cache-to-cache response from some upper cache
2078 assert(!alreadyResponded);
2079 pkt->setCacheResponding();
2080 }
2081 // upstream cache has the block, or has an outstanding
2082 // MSHR, pass the flag on
2083 if (snoopPkt.hasSharers()) {
2084 pkt->setHasSharers();
2085 }
2086 // If this request is a prefetch or clean evict and an upper level
2087 // signals block present, make sure to propagate the block
2088 // presence to the requester.
2089 if (snoopPkt.isBlockCached()) {
2090 pkt->setBlockCached();
2091 }
2092 // If the request was satisfied by snooping the cache
2093 // above, mark the original packet as satisfied too.
2094 if (snoopPkt.satisfied()) {
2095 pkt->setSatisfied();
2096 }
2097 } else {
2098 cpuSidePort->sendAtomicSnoop(pkt);
2099 if (!alreadyResponded && pkt->cacheResponding()) {
2100 // cache-to-cache response from some upper cache:
2101 // forward response to original requester
2102 assert(pkt->isResponse());
2103 }
2104 }
2105 }
2106
2107 bool respond = false;
2108 bool blk_valid = blk && blk->isValid();
2109 if (pkt->isClean()) {
2110 if (blk_valid && blk->isDirty()) {
2111 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
2112 __func__, pkt->print(), blk->print());
2113 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
2114 PacketList writebacks;
2115 writebacks.push_back(wb_pkt);
2116
2117 if (is_timing) {
2118 // anything that is merely forwarded pays for the forward
2119 // latency and the delay provided by the crossbar
2120 Tick forward_time = clockEdge(forwardLatency) +
2121 pkt->headerDelay;
2122 doWritebacks(writebacks, forward_time);
2123 } else {
2124 doWritebacksAtomic(writebacks);
2125 }
2126 pkt->setSatisfied();
2127 }
2128 } else if (!blk_valid) {
2129 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
2130 pkt->print());
2131 if (is_deferred) {
2132 // we no longer have the block, and will not respond, but a
2133 // packet was allocated in MSHR::handleSnoop and we have
2134 // to delete it
2135 assert(pkt->needsResponse());
2136
2137 // we have passed the block to a cache upstream, that
2138 // cache should be responding
2139 assert(pkt->cacheResponding());
2140
2141 delete pkt;
2142 }
2143 return snoop_delay;
2144 } else {
2145 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
2146 pkt->print(), blk->print());
2147
2148 // We may end up modifying both the block state and the packet (if
2149 // we respond in atomic mode), so just figure out what to do now
2150 // and then do it later. We respond to all snoops that need
2151 // responses provided we have the block in dirty state. The
2152 // invalidation itself is taken care of below. We don't respond to
2153 // cache maintenance operations as this is done by the destination
2154 // xbar.
2155 respond = blk->isDirty() && pkt->needsResponse();
2156
2157 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
2158 "a dirty block in a read-only cache %s\n", name());
2159 }
2160
2161 // Invalidate any prefetch's from below that would strip write permissions
2162 // MemCmd::HardPFReq is only observed by upstream caches. After missing
2163 // above and in it's own cache, a new MemCmd::ReadReq is created that
2164 // downstream caches observe.
2165 if (pkt->mustCheckAbove()) {
2166 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
2167 "from lower cache\n", pkt->getAddr(), pkt->print());
2168 pkt->setBlockCached();
2169 return snoop_delay;
2170 }
2171
2172 if (pkt->isRead() && !invalidate) {
2173 // reading without requiring the line in a writable state
2174 assert(!needs_writable);
2175 pkt->setHasSharers();
2176
2177 // if the requesting packet is uncacheable, retain the line in
2178 // the current state, otherwhise unset the writable flag,
2179 // which means we go from Modified to Owned (and will respond
2180 // below), remain in Owned (and will respond below), from
2181 // Exclusive to Shared, or remain in Shared
2182 if (!pkt->req->isUncacheable())
2183 blk->status &= ~BlkWritable;
2184 DPRINTF(Cache, "new state is %s\n", blk->print());
2185 }
2186
2187 if (respond) {
2188 // prevent anyone else from responding, cache as well as
2189 // memory, and also prevent any memory from even seeing the
2190 // request
2191 pkt->setCacheResponding();
2192 if (!pkt->isClean() && blk->isWritable()) {
2193 // inform the cache hierarchy that this cache had the line
2194 // in the Modified state so that we avoid unnecessary
2195 // invalidations (see Packet::setResponderHadWritable)
2196 pkt->setResponderHadWritable();
2197
2198 // in the case of an uncacheable request there is no point
2199 // in setting the responderHadWritable flag, but since the
2200 // recipient does not care there is no harm in doing so
2201 } else {
2202 // if the packet has needsWritable set we invalidate our
2203 // copy below and all other copies will be invalidates
2204 // through express snoops, and if needsWritable is not set
2205 // we already called setHasSharers above
2206 }
2207
2208 // if we are returning a writable and dirty (Modified) line,
2209 // we should be invalidating the line
2210 panic_if(!invalidate && !pkt->hasSharers(),
2211 "%s is passing a Modified line through %s, "
2212 "but keeping the block", name(), pkt->print());
2213
2214 if (is_timing) {
2215 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
2216 } else {
2217 pkt->makeAtomicResponse();
2218 // packets such as upgrades do not actually have any data
2219 // payload
2220 if (pkt->hasData())
2221 pkt->setDataFromBlock(blk->data, blkSize);
2222 }
2223 }
2224
2225 if (!respond && is_deferred) {
2226 assert(pkt->needsResponse());
2227
2228 // if we copied the deferred packet with the intention to
2229 // respond, but are not responding, then a cache above us must
2230 // be, and we can use this as the indication of whether this
2231 // is a packet where we created a copy of the request or not
2232 if (!pkt->cacheResponding()) {
2233 delete pkt->req;
2234 }
2235
2236 delete pkt;
2237 }
2238
2239 // Do this last in case it deallocates block data or something
2240 // like that
2241 if (blk_valid && invalidate) {
2242 invalidateBlock(blk);
2243 DPRINTF(Cache, "new state is %s\n", blk->print());
2244 }
2245
2246 return snoop_delay;
2247}
2248
2249
2250void
2251Cache::recvTimingSnoopReq(PacketPtr pkt)
2252{
2253 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2254
2255 // Snoops shouldn't happen when bypassing caches
2256 assert(!system->bypassCaches());
2257
2258 // no need to snoop requests that are not in range
2259 if (!inRange(pkt->getAddr())) {
2260 return;
2261 }
2262
2263 bool is_secure = pkt->isSecure();
2264 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
2265
2266 Addr blk_addr = pkt->getBlockAddr(blkSize);
2267 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
2268
2269 // Update the latency cost of the snoop so that the crossbar can
2270 // account for it. Do not overwrite what other neighbouring caches
2271 // have already done, rather take the maximum. The update is
2272 // tentative, for cases where we return before an upward snoop
2273 // happens below.
2274 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
2275 lookupLatency * clockPeriod());
2276
2277 // Inform request(Prefetch, CleanEvict or Writeback) from below of
2278 // MSHR hit, set setBlockCached.
2279 if (mshr && pkt->mustCheckAbove()) {
2280 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
2281 "mshr hit\n", pkt->print());
2282 pkt->setBlockCached();
2283 return;
2284 }
2285
2286 // Bypass any existing cache maintenance requests if the request
2287 // has been satisfied already (i.e., the dirty block has been
2288 // found).
2289 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
2290 return;
2291 }
2292
2293 // Let the MSHR itself track the snoop and decide whether we want
2294 // to go ahead and do the regular cache snoop
2295 if (mshr && mshr->handleSnoop(pkt, order++)) {
2296 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
2297 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
2298 mshr->print());
2299
2300 if (mshr->getNumTargets() > numTarget)
2301 warn("allocating bonus target for snoop"); //handle later
2302 return;
2303 }
2304
2305 //We also need to check the writeback buffers and handle those
2306 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
2307 if (wb_entry) {
2308 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
2309 pkt->getAddr(), is_secure ? "s" : "ns");
2310 // Expect to see only Writebacks and/or CleanEvicts here, both of
2311 // which should not be generated for uncacheable data.
2312 assert(!wb_entry->isUncacheable());
2313 // There should only be a single request responsible for generating
2314 // Writebacks/CleanEvicts.
2315 assert(wb_entry->getNumTargets() == 1);
2316 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
2317 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
2318
2319 if (pkt->isEviction()) {
2320 // if the block is found in the write queue, set the BLOCK_CACHED
2321 // flag for Writeback/CleanEvict snoop. On return the snoop will
2322 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
2323 // any CleanEvicts from travelling down the memory hierarchy.
2324 pkt->setBlockCached();
2325 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
2326 "hit\n", __func__, pkt->print());
2327 return;
2328 }
2329
2330 // conceptually writebacks are no different to other blocks in
2331 // this cache, so the behaviour is modelled after handleSnoop,
2332 // the difference being that instead of querying the block
2333 // state to determine if it is dirty and writable, we use the
2334 // command and fields of the writeback packet
2335 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
2336 pkt->needsResponse();
2337 bool have_writable = !wb_pkt->hasSharers();
2338 bool invalidate = pkt->isInvalidate();
2339
2340 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
2341 assert(!pkt->needsWritable());
2342 pkt->setHasSharers();
2343 wb_pkt->setHasSharers();
2344 }
2345
2346 if (respond) {
2347 pkt->setCacheResponding();
2348
2349 if (have_writable) {
2350 pkt->setResponderHadWritable();
2351 }
2352
2353 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
2354 false, false);
2355 }
2356
2357 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
2358 // Invalidation trumps our writeback... discard here
2359 // Note: markInService will remove entry from writeback buffer.
2360 markInService(wb_entry);
2361 delete wb_pkt;
2362 }
2363 }
2364
2365 // If this was a shared writeback, there may still be
2366 // other shared copies above that require invalidation.
2367 // We could be more selective and return here if the
2368 // request is non-exclusive or if the writeback is
2369 // exclusive.
2370 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
2371
2372 // Override what we did when we first saw the snoop, as we now
2373 // also have the cost of the upwards snoops to account for
2374 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
2375 lookupLatency * clockPeriod());
2376}
2377
2378bool
2379Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
2380{
2381 // Express snoop responses from master to slave, e.g., from L1 to L2
2382 cache->recvTimingSnoopResp(pkt);
2383 return true;
2384}
2385
2386Tick
2387Cache::recvAtomicSnoop(PacketPtr pkt)
2388{
2389 // Snoops shouldn't happen when bypassing caches
2390 assert(!system->bypassCaches());
2391
2392 // no need to snoop requests that are not in range.
2393 if (!inRange(pkt->getAddr())) {
2394 return 0;
2395 }
2396
2397 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
2398 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
2399 return snoop_delay + lookupLatency * clockPeriod();
2400}
2401
2402
2403QueueEntry*
2404Cache::getNextQueueEntry()
2405{
2406 // Check both MSHR queue and write buffer for potential requests,
2407 // note that null does not mean there is no request, it could
2408 // simply be that it is not ready
2409 MSHR *miss_mshr = mshrQueue.getNext();
2410 WriteQueueEntry *wq_entry = writeBuffer.getNext();
2411
2412 // If we got a write buffer request ready, first priority is a
2413 // full write buffer, otherwise we favour the miss requests
2414 if (wq_entry && (writeBuffer.isFull() || !miss_mshr)) {
2415 // need to search MSHR queue for conflicting earlier miss.
2416 MSHR *conflict_mshr =
2417 mshrQueue.findPending(wq_entry->blkAddr,
2418 wq_entry->isSecure);
2419
2420 if (conflict_mshr && conflict_mshr->order < wq_entry->order) {
2421 // Service misses in order until conflict is cleared.
2422 return conflict_mshr;
2423
2424 // @todo Note that we ignore the ready time of the conflict here
2425 }
2426
2427 // No conflicts; issue write
2428 return wq_entry;
2429 } else if (miss_mshr) {
2430 // need to check for conflicting earlier writeback
2431 WriteQueueEntry *conflict_mshr =
2432 writeBuffer.findPending(miss_mshr->blkAddr,
2433 miss_mshr->isSecure);
2434 if (conflict_mshr) {
2435 // not sure why we don't check order here... it was in the
2436 // original code but commented out.
2437
2438 // The only way this happens is if we are
2439 // doing a write and we didn't have permissions
2440 // then subsequently saw a writeback (owned got evicted)
2441 // We need to make sure to perform the writeback first
2442 // To preserve the dirty data, then we can issue the write
2443
2444 // should we return wq_entry here instead? I.e. do we
2445 // have to flush writes in order? I don't think so... not
2446 // for Alpha anyway. Maybe for x86?
2447 return conflict_mshr;
2448
2449 // @todo Note that we ignore the ready time of the conflict here
2450 }
2451
2452 // No conflicts; issue read
2453 return miss_mshr;
2454 }
2455
2456 // fall through... no pending requests. Try a prefetch.
2457 assert(!miss_mshr && !wq_entry);
2458 if (prefetcher && mshrQueue.canPrefetch()) {
2459 // If we have a miss queue slot, we can try a prefetch
2460 PacketPtr pkt = prefetcher->getPacket();
2461 if (pkt) {
2462 Addr pf_addr = pkt->getBlockAddr(blkSize);
2463 if (!tags->findBlock(pf_addr, pkt->isSecure()) &&
2464 !mshrQueue.findMatch(pf_addr, pkt->isSecure()) &&
2465 !writeBuffer.findMatch(pf_addr, pkt->isSecure())) {
2466 // Update statistic on number of prefetches issued
2467 // (hwpf_mshr_misses)
2468 assert(pkt->req->masterId() < system->maxMasters());
2469 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
2470
2471 // allocate an MSHR and return it, note
2472 // that we send the packet straight away, so do not
2473 // schedule the send
2474 return allocateMissBuffer(pkt, curTick(), false);
2475 } else {
2476 // free the request and packet
2477 delete pkt->req;
2478 delete pkt;
2479 }
2480 }
2481 }
2482
2483 return nullptr;
2484}
2485
2486bool
2487Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const
2488{
2489 if (!forwardSnoops)
2490 return false;
2491 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
2492 // Writeback snoops into upper level caches to check for copies of the
2493 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
2494 // packet, the cache can inform the crossbar below of presence or absence
2495 // of the block.
2496 if (is_timing) {
2497 Packet snoop_pkt(pkt, true, false);
2498 snoop_pkt.setExpressSnoop();
2499 // Assert that packet is either Writeback or CleanEvict and not a
2500 // prefetch request because prefetch requests need an MSHR and may
2501 // generate a snoop response.
2502 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
2503 snoop_pkt.senderState = nullptr;
2504 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2505 // Writeback/CleanEvict snoops do not generate a snoop response.
2506 assert(!(snoop_pkt.cacheResponding()));
2507 return snoop_pkt.isBlockCached();
2508 } else {
2509 cpuSidePort->sendAtomicSnoop(pkt);
2510 return pkt->isBlockCached();
2511 }
2512}
2513
2514Tick
2515Cache::nextQueueReadyTime() const
2516{
2517 Tick nextReady = std::min(mshrQueue.nextReadyTime(),
2518 writeBuffer.nextReadyTime());
2519
2520 // Don't signal prefetch ready time if no MSHRs available
2521 // Will signal once enoguh MSHRs are deallocated
2522 if (prefetcher && mshrQueue.canPrefetch()) {
2523 nextReady = std::min(nextReady,
2524 prefetcher->nextPrefetchReadyTime());
2525 }
2526
2527 return nextReady;
2528}
2529
2530bool
2531Cache::sendMSHRQueuePacket(MSHR* mshr)
2532{
2533 assert(mshr);
2534
2535 // use request from 1st target
2536 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
2537
2538 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
2539
2540 CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure);
2541
2542 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
2543 // we should never have hardware prefetches to allocated
2544 // blocks
2545 assert(blk == nullptr);
2546
2547 // We need to check the caches above us to verify that
2548 // they don't have a copy of this block in the dirty state
2549 // at the moment. Without this check we could get a stale
2550 // copy from memory that might get used in place of the
2551 // dirty one.
2552 Packet snoop_pkt(tgt_pkt, true, false);
2553 snoop_pkt.setExpressSnoop();
2554 // We are sending this packet upwards, but if it hits we will
2555 // get a snoop response that we end up treating just like a
2556 // normal response, hence it needs the MSHR as its sender
2557 // state
2558 snoop_pkt.senderState = mshr;
2559 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2560
2561 // Check to see if the prefetch was squashed by an upper cache (to
2562 // prevent us from grabbing the line) or if a Check to see if a
2563 // writeback arrived between the time the prefetch was placed in
2564 // the MSHRs and when it was selected to be sent or if the
2565 // prefetch was squashed by an upper cache.
2566
2567 // It is important to check cacheResponding before
2568 // prefetchSquashed. If another cache has committed to
2569 // responding, it will be sending a dirty response which will
2570 // arrive at the MSHR allocated for this request. Checking the
2571 // prefetchSquash first may result in the MSHR being
2572 // prematurely deallocated.
2573 if (snoop_pkt.cacheResponding()) {
2574 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
2575 assert(r.second);
2576
2577 // if we are getting a snoop response with no sharers it
2578 // will be allocated as Modified
2579 bool pending_modified_resp = !snoop_pkt.hasSharers();
2580 markInService(mshr, pending_modified_resp);
2581
2582 DPRINTF(Cache, "Upward snoop of prefetch for addr"
2583 " %#x (%s) hit\n",
2584 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
2585 return false;
2586 }
2587
2588 if (snoop_pkt.isBlockCached()) {
2589 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
2590 "Deallocating mshr target %#x.\n",
2591 mshr->blkAddr);
2592
2593 // Deallocate the mshr target
2594 if (mshrQueue.forceDeallocateTarget(mshr)) {
2595 // Clear block if this deallocation resulted freed an
2596 // mshr when all had previously been utilized
2597 clearBlocked(Blocked_NoMSHRs);
2598 }
2599
2600 // given that no response is expected, delete Request and Packet
2601 delete tgt_pkt->req;
2602 delete tgt_pkt;
2603
2604 return false;
2605 }
2606 }
2607
2608 // either a prefetch that is not present upstream, or a normal
2609 // MSHR request, proceed to get the packet to send downstream
2610 PacketPtr pkt = createMissPacket(tgt_pkt, blk, mshr->needsWritable());
2611
2612 mshr->isForward = (pkt == nullptr);
2613
2614 if (mshr->isForward) {
2615 // not a cache block request, but a response is expected
2616 // make copy of current packet to forward, keep current
2617 // copy for response handling
2618 pkt = new Packet(tgt_pkt, false, true);
2619 assert(!pkt->isWrite());
2620 }
2621
2622 // play it safe and append (rather than set) the sender state,
2623 // as forwarded packets may already have existing state
2624 pkt->pushSenderState(mshr);
2625
2626 if (pkt->isClean() && blk && blk->isDirty()) {
2627 // A cache clean opearation is looking for a dirty block. Mark
2628 // the packet so that the destination xbar can determine that
2629 // there will be a follow-up write packet as well.
2630 pkt->setSatisfied();
2631 }
2632
2633 if (!memSidePort->sendTimingReq(pkt)) {
2634 // we are awaiting a retry, but we
2635 // delete the packet and will be creating a new packet
2636 // when we get the opportunity
2637 delete pkt;
2638
2639 // note that we have now masked any requestBus and
2640 // schedSendEvent (we will wait for a retry before
2641 // doing anything), and this is so even if we do not
2642 // care about this packet and might override it before
2643 // it gets retried
2644 return true;
2645 } else {
2646 // As part of the call to sendTimingReq the packet is
2647 // forwarded to all neighbouring caches (and any caches
2648 // above them) as a snoop. Thus at this point we know if
2649 // any of the neighbouring caches are responding, and if
2650 // so, we know it is dirty, and we can determine if it is
2651 // being passed as Modified, making our MSHR the ordering
2652 // point
2653 bool pending_modified_resp = !pkt->hasSharers() &&
2654 pkt->cacheResponding();
2655 markInService(mshr, pending_modified_resp);
2656 if (pkt->isClean() && blk && blk->isDirty()) {
2657 // A cache clean opearation is looking for a dirty
2658 // block. If a dirty block is encountered a WriteClean
2659 // will update any copies to the path to the memory
2660 // until the point of reference.
2661 DPRINTF(CacheVerbose, "%s: packet %s found block: %s\n",
2662 __func__, pkt->print(), blk->print());
2663 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(),
2664 pkt->id);
2665 PacketList writebacks;
2666 writebacks.push_back(wb_pkt);
2667 doWritebacks(writebacks, 0);
2668 }
2669
2670 return false;
2671 }
2672}
2673
2674bool
2675Cache::sendWriteQueuePacket(WriteQueueEntry* wq_entry)
2676{
2677 assert(wq_entry);
2678
2679 // always a single target for write queue entries
2680 PacketPtr tgt_pkt = wq_entry->getTarget()->pkt;
2681
2682 DPRINTF(Cache, "%s: write %s\n", __func__, tgt_pkt->print());
2683
2684 // forward as is, both for evictions and uncacheable writes
2685 if (!memSidePort->sendTimingReq(tgt_pkt)) {
2686 // note that we have now masked any requestBus and
2687 // schedSendEvent (we will wait for a retry before
2688 // doing anything), and this is so even if we do not
2689 // care about this packet and might override it before
2690 // it gets retried
2691 return true;
2692 } else {
2693 markInService(wq_entry);
2694 return false;
2695 }
2696}
2697
2698void
2699Cache::serialize(CheckpointOut &cp) const
2700{
2701 bool dirty(isDirty());
2702
2703 if (dirty) {
2704 warn("*** The cache still contains dirty data. ***\n");
2705 warn(" Make sure to drain the system using the correct flags.\n");
2706 warn(" This checkpoint will not restore correctly and dirty data "
2707 " in the cache will be lost!\n");
2708 }
2709
2710 // Since we don't checkpoint the data in the cache, any dirty data
2711 // will be lost when restoring from a checkpoint of a system that
2712 // wasn't drained properly. Flag the checkpoint as invalid if the
2713 // cache contains dirty data.
2714 bool bad_checkpoint(dirty);
2715 SERIALIZE_SCALAR(bad_checkpoint);
2716}
2717
2718void
2719Cache::unserialize(CheckpointIn &cp)
2720{
2721 bool bad_checkpoint;
2722 UNSERIALIZE_SCALAR(bad_checkpoint);
2723 if (bad_checkpoint) {
2724 fatal("Restoring from checkpoints with dirty caches is not supported "
2725 "in the classic memory system. Please remove any caches or "
2726 " drain them properly before taking checkpoints.\n");
2727 }
2728}
2729
2730///////////////
2731//
2732// CpuSidePort
2733//
2734///////////////
2735
2736AddrRangeList
2737Cache::CpuSidePort::getAddrRanges() const
2738{
2739 return cache->getAddrRanges();
2740}
2741
2742bool
2743Cache::CpuSidePort::tryTiming(PacketPtr pkt)
2744{
2745 assert(!cache->system->bypassCaches());
2746
2747 // always let express snoop packets through if even if blocked
2748 if (pkt->isExpressSnoop()) {
2749 return true;
2750 } else if (isBlocked() || mustSendRetry) {
2751 // either already committed to send a retry, or blocked
2752 mustSendRetry = true;
2753 return false;
2754 }
2755 mustSendRetry = false;
2756 return true;
2757}
2758
2759bool
2760Cache::CpuSidePort::recvTimingReq(PacketPtr pkt)
2761{
2762 assert(!cache->system->bypassCaches());
2763
2764 // always let express snoop packets through if even if blocked
2765 if (pkt->isExpressSnoop() || tryTiming(pkt)) {
2766 cache->recvTimingReq(pkt);
2767 return true;
2768 }
2769 return false;
2770}
2771
2772Tick
2773Cache::CpuSidePort::recvAtomic(PacketPtr pkt)
2774{
2775 return cache->recvAtomic(pkt);
2776}
2777
2778void
2779Cache::CpuSidePort::recvFunctional(PacketPtr pkt)
2780{
2781 // functional request
2782 cache->functionalAccess(pkt, true);
2783}
2784
2785Cache::
2786CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache,
2787 const std::string &_label)
2788 : BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache)
2789{
2790}
2791
2792Cache*
2793CacheParams::create()
2794{
2795 assert(tags);
2796 assert(replacement_policy);
2797
2798 return new Cache(this);
2799}
2800///////////////
2801//
2802// MemSidePort
2803//
2804///////////////
2805
2806bool
2807Cache::MemSidePort::recvTimingResp(PacketPtr pkt)
2808{
2809 cache->recvTimingResp(pkt);
2810 return true;
2811}
2812
2813// Express snooping requests to memside port
2814void
2815Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt)
2816{
2817 // handle snooping requests
2818 cache->recvTimingSnoopReq(pkt);
2819}
2820
2821Tick
2822Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt)
2823{
2824 return cache->recvAtomicSnoop(pkt);
2825}
2826
2827void
2828Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt)
2829{
2830 // functional snoop (note that in contrast to atomic we don't have
2831 // a specific functionalSnoop method, as they have the same
2832 // behaviour regardless)
2833 cache->functionalAccess(pkt, false);
2834}
2835
2836void
2837Cache::CacheReqPacketQueue::sendDeferredPacket()
2838{
2839 // sanity check
2840 assert(!waitingOnRetry);
2841
2842 // there should never be any deferred request packets in the
2843 // queue, instead we resly on the cache to provide the packets
2844 // from the MSHR queue or write queue
2845 assert(deferredPacketReadyTime() == MaxTick);
2846
2847 // check for request packets (requests & writebacks)
2848 QueueEntry* entry = cache.getNextQueueEntry();
2849
2850 if (!entry) {
2851 // can happen if e.g. we attempt a writeback and fail, but
2852 // before the retry, the writeback is eliminated because
2853 // we snoop another cache's ReadEx.
2854 } else {
2855 // let our snoop responses go first if there are responses to
2856 // the same addresses
2857 if (checkConflictingSnoop(entry->blkAddr)) {
2858 return;
2859 }
2860 waitingOnRetry = entry->sendPacket(cache);
2861 }
2862
2863 // if we succeeded and are not waiting for a retry, schedule the
2864 // next send considering when the next queue is ready, note that
2865 // snoop responses have their own packet queue and thus schedule
2866 // their own events
2867 if (!waitingOnRetry) {
2868 schedSendEvent(cache.nextQueueReadyTime());
2869 }
2870}
2871
2872Cache::
2873MemSidePort::MemSidePort(const std::string &_name, Cache *_cache,
2874 const std::string &_label)
2875 : BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue),
2876 _reqQueue(*_cache, *this, _snoopRespQueue, _label),
2877 _snoopRespQueue(*_cache, *this, _label), cache(_cache)
2878{
2879}
| 1215 }
1216
1217 // Note that we don't invoke the prefetcher at all in atomic mode.
1218 // It's not clear how to do it properly, particularly for
1219 // prefetchers that aggressively generate prefetch candidates and
1220 // rely on bandwidth contention to throttle them; these will tend
1221 // to pollute the cache in atomic mode since there is no bandwidth
1222 // contention. If we ever do want to enable prefetching in atomic
1223 // mode, though, this is the place to do it... see timingAccess()
1224 // for an example (though we'd want to issue the prefetch(es)
1225 // immediately rather than calling requestMemSideBus() as we do
1226 // there).
1227
1228 // do any writebacks resulting from the response handling
1229 doWritebacksAtomic(writebacks);
1230
1231 // if we used temp block, check to see if its valid and if so
1232 // clear it out, but only do so after the call to recvAtomic is
1233 // finished so that any downstream observers (such as a snoop
1234 // filter), first see the fill, and only then see the eviction
1235 if (blk == tempBlock && tempBlock->isValid()) {
1236 // the atomic CPU calls recvAtomic for fetch and load/store
1237 // sequentuially, and we may already have a tempBlock
1238 // writeback from the fetch that we have not yet sent
1239 if (tempBlockWriteback) {
1240 // if that is the case, write the prevoius one back, and
1241 // do not schedule any new event
1242 writebackTempBlockAtomic();
1243 } else {
1244 // the writeback/clean eviction happens after the call to
1245 // recvAtomic has finished (but before any successive
1246 // calls), so that the response handling from the fill is
1247 // allowed to happen first
1248 schedule(writebackTempBlockAtomicEvent, curTick());
1249 }
1250
1251 tempBlockWriteback = (blk->isDirty() || writebackClean) ?
1252 writebackBlk(blk) : cleanEvictBlk(blk);
1253 invalidateBlock(blk);
1254 }
1255
1256 if (pkt->needsResponse()) {
1257 pkt->makeAtomicResponse();
1258 }
1259
1260 return lat * clockPeriod();
1261}
1262
1263
1264void
1265Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide)
1266{
1267 if (system->bypassCaches()) {
1268 // Packets from the memory side are snoop request and
1269 // shouldn't happen in bypass mode.
1270 assert(fromCpuSide);
1271
1272 // The cache should be flushed if we are in cache bypass mode,
1273 // so we don't need to check if we need to update anything.
1274 memSidePort->sendFunctional(pkt);
1275 return;
1276 }
1277
1278 Addr blk_addr = pkt->getBlockAddr(blkSize);
1279 bool is_secure = pkt->isSecure();
1280 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1281 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1282
1283 pkt->pushLabel(name());
1284
1285 CacheBlkPrintWrapper cbpw(blk);
1286
1287 // Note that just because an L2/L3 has valid data doesn't mean an
1288 // L1 doesn't have a more up-to-date modified copy that still
1289 // needs to be found. As a result we always update the request if
1290 // we have it, but only declare it satisfied if we are the owner.
1291
1292 // see if we have data at all (owned or otherwise)
1293 bool have_data = blk && blk->isValid()
1294 && pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize,
1295 blk->data);
1296
1297 // data we have is dirty if marked as such or if we have an
1298 // in-service MSHR that is pending a modified line
1299 bool have_dirty =
1300 have_data && (blk->isDirty() ||
1301 (mshr && mshr->inService && mshr->isPendingModified()));
1302
1303 bool done = have_dirty
1304 || cpuSidePort->checkFunctional(pkt)
1305 || mshrQueue.checkFunctional(pkt, blk_addr)
1306 || writeBuffer.checkFunctional(pkt, blk_addr)
1307 || memSidePort->checkFunctional(pkt);
1308
1309 DPRINTF(CacheVerbose, "%s: %s %s%s%s\n", __func__, pkt->print(),
1310 (blk && blk->isValid()) ? "valid " : "",
1311 have_data ? "data " : "", done ? "done " : "");
1312
1313 // We're leaving the cache, so pop cache->name() label
1314 pkt->popLabel();
1315
1316 if (done) {
1317 pkt->makeResponse();
1318 } else {
1319 // if it came as a request from the CPU side then make sure it
1320 // continues towards the memory side
1321 if (fromCpuSide) {
1322 memSidePort->sendFunctional(pkt);
1323 } else if (cpuSidePort->isSnooping()) {
1324 // if it came from the memory side, it must be a snoop request
1325 // and we should only forward it if we are forwarding snoops
1326 cpuSidePort->sendFunctionalSnoop(pkt);
1327 }
1328 }
1329}
1330
1331
1332/////////////////////////////////////////////////////
1333//
1334// Response handling: responses from the memory side
1335//
1336/////////////////////////////////////////////////////
1337
1338
1339void
1340Cache::handleUncacheableWriteResp(PacketPtr pkt)
1341{
1342 Tick completion_time = clockEdge(responseLatency) +
1343 pkt->headerDelay + pkt->payloadDelay;
1344
1345 // Reset the bus additional time as it is now accounted for
1346 pkt->headerDelay = pkt->payloadDelay = 0;
1347
1348 cpuSidePort->schedTimingResp(pkt, completion_time, true);
1349}
1350
1351void
1352Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk,
1353 PacketList &writebacks)
1354{
1355 MSHR::Target *initial_tgt = mshr->getTarget();
1356 // First offset for critical word first calculations
1357 const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
1358
1359 const bool is_error = pkt->isError();
1360 bool is_fill = !mshr->isForward &&
1361 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
1362 // allow invalidation responses originating from write-line
1363 // requests to be discarded
1364 bool is_invalidate = pkt->isInvalidate();
1365
1366 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
1367 for (auto &target: targets) {
1368 Packet *tgt_pkt = target.pkt;
1369 switch (target.source) {
1370 case MSHR::Target::FromCPU:
1371 Tick completion_time;
1372 // Here we charge on completion_time the delay of the xbar if the
1373 // packet comes from it, charged on headerDelay.
1374 completion_time = pkt->headerDelay;
1375
1376 // Software prefetch handling for cache closest to core
1377 if (tgt_pkt->cmd.isSWPrefetch()) {
1378 // a software prefetch would have already been ack'd
1379 // immediately with dummy data so the core would be able to
1380 // retire it. This request completes right here, so we
1381 // deallocate it.
1382 delete tgt_pkt->req;
1383 delete tgt_pkt;
1384 break; // skip response
1385 }
1386
1387 // unlike the other packet flows, where data is found in other
1388 // caches or memory and brought back, write-line requests always
1389 // have the data right away, so the above check for "is fill?"
1390 // cannot actually be determined until examining the stored MSHR
1391 // state. We "catch up" with that logic here, which is duplicated
1392 // from above.
1393 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
1394 assert(!is_error);
1395 // we got the block in a writable state, so promote
1396 // any deferred targets if possible
1397 mshr->promoteWritable();
1398 // NB: we use the original packet here and not the response!
1399 blk = handleFill(tgt_pkt, blk, writebacks,
1400 targets.allocOnFill);
1401 assert(blk);
1402
1403 // treat as a fill, and discard the invalidation
1404 // response
1405 is_fill = true;
1406 is_invalidate = false;
1407 }
1408
1409 if (is_fill) {
1410 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
1411
1412 // How many bytes past the first request is this one
1413 int transfer_offset =
1414 tgt_pkt->getOffset(blkSize) - initial_offset;
1415 if (transfer_offset < 0) {
1416 transfer_offset += blkSize;
1417 }
1418
1419 // If not critical word (offset) return payloadDelay.
1420 // responseLatency is the latency of the return path
1421 // from lower level caches/memory to an upper level cache or
1422 // the core.
1423 completion_time += clockEdge(responseLatency) +
1424 (transfer_offset ? pkt->payloadDelay : 0);
1425
1426 assert(!tgt_pkt->req->isUncacheable());
1427
1428 assert(tgt_pkt->req->masterId() < system->maxMasters());
1429 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
1430 completion_time - target.recvTime;
1431 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
1432 // failed StoreCond upgrade
1433 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
1434 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
1435 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
1436 // responseLatency is the latency of the return path
1437 // from lower level caches/memory to an upper level cache or
1438 // the core.
1439 completion_time += clockEdge(responseLatency) +
1440 pkt->payloadDelay;
1441 tgt_pkt->req->setExtraData(0);
1442 } else {
1443 // We are about to send a response to a cache above
1444 // that asked for an invalidation; we need to
1445 // invalidate our copy immediately as the most
1446 // up-to-date copy of the block will now be in the
1447 // cache above. It will also prevent this cache from
1448 // responding (if the block was previously dirty) to
1449 // snoops as they should snoop the caches above where
1450 // they will get the response from.
1451 if (is_invalidate && blk && blk->isValid()) {
1452 invalidateBlock(blk);
1453 }
1454 // not a cache fill, just forwarding response
1455 // responseLatency is the latency of the return path
1456 // from lower level cahces/memory to the core.
1457 completion_time += clockEdge(responseLatency) +
1458 pkt->payloadDelay;
1459 if (pkt->isRead() && !is_error) {
1460 // sanity check
1461 assert(pkt->getAddr() == tgt_pkt->getAddr());
1462 assert(pkt->getSize() >= tgt_pkt->getSize());
1463
1464 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
1465 }
1466 }
1467 tgt_pkt->makeTimingResponse();
1468 // if this packet is an error copy that to the new packet
1469 if (is_error)
1470 tgt_pkt->copyError(pkt);
1471 if (tgt_pkt->cmd == MemCmd::ReadResp &&
1472 (is_invalidate || mshr->hasPostInvalidate())) {
1473 // If intermediate cache got ReadRespWithInvalidate,
1474 // propagate that. Response should not have
1475 // isInvalidate() set otherwise.
1476 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
1477 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
1478 tgt_pkt->print());
1479 }
1480 // Reset the bus additional time as it is now accounted for
1481 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
1482 cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true);
1483 break;
1484
1485 case MSHR::Target::FromPrefetcher:
1486 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
1487 if (blk)
1488 blk->status |= BlkHWPrefetched;
1489 delete tgt_pkt->req;
1490 delete tgt_pkt;
1491 break;
1492
1493 case MSHR::Target::FromSnoop:
1494 // I don't believe that a snoop can be in an error state
1495 assert(!is_error);
1496 // response to snoop request
1497 DPRINTF(Cache, "processing deferred snoop...\n");
1498 // If the response is invalidating, a snooping target can
1499 // be satisfied if it is also invalidating. If the reponse is, not
1500 // only invalidating, but more specifically an InvalidateResp and
1501 // the MSHR was created due to an InvalidateReq then a cache above
1502 // is waiting to satisfy a WriteLineReq. In this case even an
1503 // non-invalidating snoop is added as a target here since this is
1504 // the ordering point. When the InvalidateResp reaches this cache,
1505 // the snooping target will snoop further the cache above with the
1506 // WriteLineReq.
1507 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
1508 pkt->req->isCacheMaintenance() ||
1509 mshr->hasPostInvalidate());
1510 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
1511 break;
1512
1513 default:
1514 panic("Illegal target->source enum %d\n", target.source);
1515 }
1516 }
1517
1518 maintainClusivity(targets.hasFromCache, blk);
1519
1520 if (blk && blk->isValid()) {
1521 // an invalidate response stemming from a write line request
1522 // should not invalidate the block, so check if the
1523 // invalidation should be discarded
1524 if (is_invalidate || mshr->hasPostInvalidate()) {
1525 invalidateBlock(blk);
1526 } else if (mshr->hasPostDowngrade()) {
1527 blk->status &= ~BlkWritable;
1528 }
1529 }
1530}
1531
1532void
1533Cache::recvTimingResp(PacketPtr pkt)
1534{
1535 assert(pkt->isResponse());
1536
1537 // all header delay should be paid for by the crossbar, unless
1538 // this is a prefetch response from above
1539 panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp,
1540 "%s saw a non-zero packet delay\n", name());
1541
1542 const bool is_error = pkt->isError();
1543
1544 if (is_error) {
1545 DPRINTF(Cache, "%s: Cache received %s with error\n", __func__,
1546 pkt->print());
1547 }
1548
1549 DPRINTF(Cache, "%s: Handling response %s\n", __func__,
1550 pkt->print());
1551
1552 // if this is a write, we should be looking at an uncacheable
1553 // write
1554 if (pkt->isWrite()) {
1555 assert(pkt->req->isUncacheable());
1556 handleUncacheableWriteResp(pkt);
1557 return;
1558 }
1559
1560 // we have dealt with any (uncacheable) writes above, from here on
1561 // we know we are dealing with an MSHR due to a miss or a prefetch
1562 MSHR *mshr = dynamic_cast<MSHR*>(pkt->popSenderState());
1563 assert(mshr);
1564
1565 if (mshr == noTargetMSHR) {
1566 // we always clear at least one target
1567 clearBlocked(Blocked_NoTargets);
1568 noTargetMSHR = nullptr;
1569 }
1570
1571 // Initial target is used just for stats
1572 MSHR::Target *initial_tgt = mshr->getTarget();
1573 int stats_cmd_idx = initial_tgt->pkt->cmdToIndex();
1574 Tick miss_latency = curTick() - initial_tgt->recvTime;
1575
1576 if (pkt->req->isUncacheable()) {
1577 assert(pkt->req->masterId() < system->maxMasters());
1578 mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] +=
1579 miss_latency;
1580 } else {
1581 assert(pkt->req->masterId() < system->maxMasters());
1582 mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] +=
1583 miss_latency;
1584 }
1585
1586 PacketList writebacks;
1587
1588 bool is_fill = !mshr->isForward &&
1589 (pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
1590
1591 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1592
1593 if (is_fill && !is_error) {
1594 DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n",
1595 pkt->getAddr());
1596
1597 blk = handleFill(pkt, blk, writebacks, mshr->allocOnFill());
1598 assert(blk != nullptr);
1599 }
1600
1601 if (blk && blk->isValid() && pkt->isClean() && !pkt->isInvalidate()) {
1602 // The block was marked not readable while there was a pending
1603 // cache maintenance operation, restore its flag.
1604 blk->status |= BlkReadable;
1605 }
1606
1607 if (blk && blk->isWritable() && !pkt->req->isCacheInvalidate()) {
1608 // If at this point the referenced block is writable and the
1609 // response is not a cache invalidate, we promote targets that
1610 // were deferred as we couldn't guarrantee a writable copy
1611 mshr->promoteWritable();
1612 }
1613
1614 serviceMSHRTargets(mshr, pkt, blk, writebacks);
1615
1616 if (mshr->promoteDeferredTargets()) {
1617 // avoid later read getting stale data while write miss is
1618 // outstanding.. see comment in timingAccess()
1619 if (blk) {
1620 blk->status &= ~BlkReadable;
1621 }
1622 mshrQueue.markPending(mshr);
1623 schedMemSideSendEvent(clockEdge() + pkt->payloadDelay);
1624 } else {
1625 // while we deallocate an mshr from the queue we still have to
1626 // check the isFull condition before and after as we might
1627 // have been using the reserved entries already
1628 const bool was_full = mshrQueue.isFull();
1629 mshrQueue.deallocate(mshr);
1630 if (was_full && !mshrQueue.isFull()) {
1631 clearBlocked(Blocked_NoMSHRs);
1632 }
1633
1634 // Request the bus for a prefetch if this deallocation freed enough
1635 // MSHRs for a prefetch to take place
1636 if (prefetcher && mshrQueue.canPrefetch()) {
1637 Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(),
1638 clockEdge());
1639 if (next_pf_time != MaxTick)
1640 schedMemSideSendEvent(next_pf_time);
1641 }
1642 }
1643
1644 // if we used temp block, check to see if its valid and then clear it out
1645 if (blk == tempBlock && tempBlock->isValid()) {
1646 PacketPtr wb_pkt = tempBlock->isDirty() || writebackClean ?
1647 writebackBlk(blk) : cleanEvictBlk(blk);
1648 writebacks.push_back(wb_pkt);
1649 invalidateBlock(tempBlock);
1650 }
1651
1652 const Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
1653 // copy writebacks to write buffer
1654 doWritebacks(writebacks, forward_time);
1655
1656 DPRINTF(CacheVerbose, "%s: Leaving with %s\n", __func__, pkt->print());
1657 delete pkt;
1658}
1659
1660PacketPtr
1661Cache::writebackBlk(CacheBlk *blk)
1662{
1663 chatty_assert(!isReadOnly || writebackClean,
1664 "Writeback from read-only cache");
1665 assert(blk && blk->isValid() && (blk->isDirty() || writebackClean));
1666
1667 writebacks[Request::wbMasterId]++;
1668
1669 Request *req = new Request(tags->regenerateBlkAddr(blk), blkSize, 0,
1670 Request::wbMasterId);
1671 if (blk->isSecure())
1672 req->setFlags(Request::SECURE);
1673
1674 req->taskId(blk->task_id);
1675
1676 PacketPtr pkt =
1677 new Packet(req, blk->isDirty() ?
1678 MemCmd::WritebackDirty : MemCmd::WritebackClean);
1679
1680 DPRINTF(Cache, "Create Writeback %s writable: %d, dirty: %d\n",
1681 pkt->print(), blk->isWritable(), blk->isDirty());
1682
1683 if (blk->isWritable()) {
1684 // not asserting shared means we pass the block in modified
1685 // state, mark our own block non-writeable
1686 blk->status &= ~BlkWritable;
1687 } else {
1688 // we are in the Owned state, tell the receiver
1689 pkt->setHasSharers();
1690 }
1691
1692 // make sure the block is not marked dirty
1693 blk->status &= ~BlkDirty;
1694
1695 pkt->allocate();
1696 pkt->setDataFromBlock(blk->data, blkSize);
1697
1698 return pkt;
1699}
1700
1701PacketPtr
1702Cache::writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id)
1703{
1704 Request *req = new Request(tags->regenerateBlkAddr(blk), blkSize, 0,
1705 Request::wbMasterId);
1706 if (blk->isSecure()) {
1707 req->setFlags(Request::SECURE);
1708 }
1709 req->taskId(blk->task_id);
1710
1711 PacketPtr pkt = new Packet(req, MemCmd::WriteClean, blkSize, id);
1712
1713 if (dest) {
1714 req->setFlags(dest);
1715 pkt->setWriteThrough();
1716 }
1717
1718 DPRINTF(Cache, "Create %s writable: %d, dirty: %d\n", pkt->print(),
1719 blk->isWritable(), blk->isDirty());
1720
1721 if (blk->isWritable()) {
1722 // not asserting shared means we pass the block in modified
1723 // state, mark our own block non-writeable
1724 blk->status &= ~BlkWritable;
1725 } else {
1726 // we are in the Owned state, tell the receiver
1727 pkt->setHasSharers();
1728 }
1729
1730 // make sure the block is not marked dirty
1731 blk->status &= ~BlkDirty;
1732
1733 pkt->allocate();
1734 pkt->setDataFromBlock(blk->data, blkSize);
1735
1736 return pkt;
1737}
1738
1739
1740PacketPtr
1741Cache::cleanEvictBlk(CacheBlk *blk)
1742{
1743 assert(!writebackClean);
1744 assert(blk && blk->isValid() && !blk->isDirty());
1745 // Creating a zero sized write, a message to the snoop filter
1746 Request *req =
1747 new Request(tags->regenerateBlkAddr(blk), blkSize, 0,
1748 Request::wbMasterId);
1749 if (blk->isSecure())
1750 req->setFlags(Request::SECURE);
1751
1752 req->taskId(blk->task_id);
1753
1754 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
1755 pkt->allocate();
1756 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
1757
1758 return pkt;
1759}
1760
1761void
1762Cache::memWriteback()
1763{
1764 CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor);
1765 tags->forEachBlk(visitor);
1766}
1767
1768void
1769Cache::memInvalidate()
1770{
1771 CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor);
1772 tags->forEachBlk(visitor);
1773}
1774
1775bool
1776Cache::isDirty() const
1777{
1778 CacheBlkIsDirtyVisitor visitor;
1779 tags->forEachBlk(visitor);
1780
1781 return visitor.isDirty();
1782}
1783
1784bool
1785Cache::writebackVisitor(CacheBlk &blk)
1786{
1787 if (blk.isDirty()) {
1788 assert(blk.isValid());
1789
1790 Request request(tags->regenerateBlkAddr(&blk), blkSize, 0,
1791 Request::funcMasterId);
1792 request.taskId(blk.task_id);
1793 if (blk.isSecure()) {
1794 request.setFlags(Request::SECURE);
1795 }
1796
1797 Packet packet(&request, MemCmd::WriteReq);
1798 packet.dataStatic(blk.data);
1799
1800 memSidePort->sendFunctional(&packet);
1801
1802 blk.status &= ~BlkDirty;
1803 }
1804
1805 return true;
1806}
1807
1808bool
1809Cache::invalidateVisitor(CacheBlk &blk)
1810{
1811
1812 if (blk.isDirty())
1813 warn_once("Invalidating dirty cache lines. Expect things to break.\n");
1814
1815 if (blk.isValid()) {
1816 assert(!blk.isDirty());
1817 invalidateBlock(&blk);
1818 }
1819
1820 return true;
1821}
1822
1823CacheBlk*
1824Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks)
1825{
1826 // Find replacement victim
1827 CacheBlk *blk = tags->findVictim(addr);
1828
1829 // It is valid to return nullptr if there is no victim
1830 if (!blk)
1831 return nullptr;
1832
1833 if (blk->isValid()) {
1834 Addr repl_addr = tags->regenerateBlkAddr(blk);
1835 MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
1836 if (repl_mshr) {
1837 // must be an outstanding upgrade or clean request
1838 // on a block we're about to replace...
1839 assert((!blk->isWritable() && repl_mshr->needsWritable()) ||
1840 repl_mshr->isCleaning());
1841 // too hard to replace block with transient state
1842 // allocation failed, block not inserted
1843 return nullptr;
1844 } else {
1845 DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx "
1846 "(%s): %s\n", repl_addr, blk->isSecure() ? "s" : "ns",
1847 addr, is_secure ? "s" : "ns",
1848 blk->isDirty() ? "writeback" : "clean");
1849
1850 if (blk->wasPrefetched()) {
1851 unusedPrefetches++;
1852 }
1853 // Will send up Writeback/CleanEvict snoops via isCachedAbove
1854 // when pushing this writeback list into the write buffer.
1855 if (blk->isDirty() || writebackClean) {
1856 // Save writeback packet for handling by caller
1857 writebacks.push_back(writebackBlk(blk));
1858 } else {
1859 writebacks.push_back(cleanEvictBlk(blk));
1860 }
1861 replacements++;
1862 }
1863 }
1864
1865 return blk;
1866}
1867
1868void
1869Cache::invalidateBlock(CacheBlk *blk)
1870{
1871 if (blk != tempBlock)
1872 tags->invalidate(blk);
1873 blk->invalidate();
1874}
1875
1876// Note that the reason we return a list of writebacks rather than
1877// inserting them directly in the write buffer is that this function
1878// is called by both atomic and timing-mode accesses, and in atomic
1879// mode we don't mess with the write buffer (we just perform the
1880// writebacks atomically once the original request is complete).
1881CacheBlk*
1882Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks,
1883 bool allocate)
1884{
1885 assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq);
1886 Addr addr = pkt->getAddr();
1887 bool is_secure = pkt->isSecure();
1888#if TRACING_ON
1889 CacheBlk::State old_state = blk ? blk->status : 0;
1890#endif
1891
1892 // When handling a fill, we should have no writes to this line.
1893 assert(addr == pkt->getBlockAddr(blkSize));
1894 assert(!writeBuffer.findMatch(addr, is_secure));
1895
1896 if (blk == nullptr) {
1897 // better have read new data...
1898 assert(pkt->hasData());
1899
1900 // only read responses and write-line requests have data;
1901 // note that we don't write the data here for write-line - that
1902 // happens in the subsequent call to satisfyRequest
1903 assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq);
1904
1905 // need to do a replacement if allocating, otherwise we stick
1906 // with the temporary storage
1907 blk = allocate ? allocateBlock(addr, is_secure, writebacks) : nullptr;
1908
1909 if (blk == nullptr) {
1910 // No replaceable block or a mostly exclusive
1911 // cache... just use temporary storage to complete the
1912 // current request and then get rid of it
1913 assert(!tempBlock->isValid());
1914 blk = tempBlock;
1915 tempBlock->set = tags->extractSet(addr);
1916 tempBlock->tag = tags->extractTag(addr);
1917 if (is_secure) {
1918 tempBlock->status |= BlkSecure;
1919 }
1920 DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr,
1921 is_secure ? "s" : "ns");
1922 } else {
1923 tags->insertBlock(pkt, blk);
1924 }
1925
1926 // we should never be overwriting a valid block
1927 assert(!blk->isValid());
1928 } else {
1929 // existing block... probably an upgrade
1930 assert(blk->tag == tags->extractTag(addr));
1931 // either we're getting new data or the block should already be valid
1932 assert(pkt->hasData() || blk->isValid());
1933 // don't clear block status... if block is already dirty we
1934 // don't want to lose that
1935 }
1936
1937 if (is_secure)
1938 blk->status |= BlkSecure;
1939 blk->status |= BlkValid | BlkReadable;
1940
1941 // sanity check for whole-line writes, which should always be
1942 // marked as writable as part of the fill, and then later marked
1943 // dirty as part of satisfyRequest
1944 if (pkt->cmd == MemCmd::WriteLineReq) {
1945 assert(!pkt->hasSharers());
1946 }
1947
1948 // here we deal with setting the appropriate state of the line,
1949 // and we start by looking at the hasSharers flag, and ignore the
1950 // cacheResponding flag (normally signalling dirty data) if the
1951 // packet has sharers, thus the line is never allocated as Owned
1952 // (dirty but not writable), and always ends up being either
1953 // Shared, Exclusive or Modified, see Packet::setCacheResponding
1954 // for more details
1955 if (!pkt->hasSharers()) {
1956 // we could get a writable line from memory (rather than a
1957 // cache) even in a read-only cache, note that we set this bit
1958 // even for a read-only cache, possibly revisit this decision
1959 blk->status |= BlkWritable;
1960
1961 // check if we got this via cache-to-cache transfer (i.e., from a
1962 // cache that had the block in Modified or Owned state)
1963 if (pkt->cacheResponding()) {
1964 // we got the block in Modified state, and invalidated the
1965 // owners copy
1966 blk->status |= BlkDirty;
1967
1968 chatty_assert(!isReadOnly, "Should never see dirty snoop response "
1969 "in read-only cache %s\n", name());
1970 }
1971 }
1972
1973 DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n",
1974 addr, is_secure ? "s" : "ns", old_state, blk->print());
1975
1976 // if we got new data, copy it in (checking for a read response
1977 // and a response that has data is the same in the end)
1978 if (pkt->isRead()) {
1979 // sanity checks
1980 assert(pkt->hasData());
1981 assert(pkt->getSize() == blkSize);
1982
1983 pkt->writeDataToBlock(blk->data, blkSize);
1984 }
1985 // We pay for fillLatency here.
1986 blk->whenReady = clockEdge() + fillLatency * clockPeriod() +
1987 pkt->payloadDelay;
1988
1989 return blk;
1990}
1991
1992
1993/////////////////////////////////////////////////////
1994//
1995// Snoop path: requests coming in from the memory side
1996//
1997/////////////////////////////////////////////////////
1998
1999void
2000Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
2001 bool already_copied, bool pending_inval)
2002{
2003 // sanity check
2004 assert(req_pkt->isRequest());
2005 assert(req_pkt->needsResponse());
2006
2007 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
2008 // timing-mode snoop responses require a new packet, unless we
2009 // already made a copy...
2010 PacketPtr pkt = req_pkt;
2011 if (!already_copied)
2012 // do not clear flags, and allocate space for data if the
2013 // packet needs it (the only packets that carry data are read
2014 // responses)
2015 pkt = new Packet(req_pkt, false, req_pkt->isRead());
2016
2017 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
2018 pkt->hasSharers());
2019 pkt->makeTimingResponse();
2020 if (pkt->isRead()) {
2021 pkt->setDataFromBlock(blk_data, blkSize);
2022 }
2023 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
2024 // Assume we defer a response to a read from a far-away cache
2025 // A, then later defer a ReadExcl from a cache B on the same
2026 // bus as us. We'll assert cacheResponding in both cases, but
2027 // in the latter case cacheResponding will keep the
2028 // invalidation from reaching cache A. This special response
2029 // tells cache A that it gets the block to satisfy its read,
2030 // but must immediately invalidate it.
2031 pkt->cmd = MemCmd::ReadRespWithInvalidate;
2032 }
2033 // Here we consider forward_time, paying for just forward latency and
2034 // also charging the delay provided by the xbar.
2035 // forward_time is used as send_time in next allocateWriteBuffer().
2036 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
2037 // Here we reset the timing of the packet.
2038 pkt->headerDelay = pkt->payloadDelay = 0;
2039 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
2040 pkt->print(), forward_time);
2041 memSidePort->schedTimingSnoopResp(pkt, forward_time, true);
2042}
2043
2044uint32_t
2045Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
2046 bool is_deferred, bool pending_inval)
2047{
2048 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2049 // deferred snoops can only happen in timing mode
2050 assert(!(is_deferred && !is_timing));
2051 // pending_inval only makes sense on deferred snoops
2052 assert(!(pending_inval && !is_deferred));
2053 assert(pkt->isRequest());
2054
2055 // the packet may get modified if we or a forwarded snooper
2056 // responds in atomic mode, so remember a few things about the
2057 // original packet up front
2058 bool invalidate = pkt->isInvalidate();
2059 bool M5_VAR_USED needs_writable = pkt->needsWritable();
2060
2061 // at the moment we could get an uncacheable write which does not
2062 // have the invalidate flag, and we need a suitable way of dealing
2063 // with this case
2064 panic_if(invalidate && pkt->req->isUncacheable(),
2065 "%s got an invalidating uncacheable snoop request %s",
2066 name(), pkt->print());
2067
2068 uint32_t snoop_delay = 0;
2069
2070 if (forwardSnoops) {
2071 // first propagate snoop upward to see if anyone above us wants to
2072 // handle it. save & restore packet src since it will get
2073 // rewritten to be relative to cpu-side bus (if any)
2074 bool alreadyResponded = pkt->cacheResponding();
2075 if (is_timing) {
2076 // copy the packet so that we can clear any flags before
2077 // forwarding it upwards, we also allocate data (passing
2078 // the pointer along in case of static data), in case
2079 // there is a snoop hit in upper levels
2080 Packet snoopPkt(pkt, true, true);
2081 snoopPkt.setExpressSnoop();
2082 // the snoop packet does not need to wait any additional
2083 // time
2084 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
2085 cpuSidePort->sendTimingSnoopReq(&snoopPkt);
2086
2087 // add the header delay (including crossbar and snoop
2088 // delays) of the upward snoop to the snoop delay for this
2089 // cache
2090 snoop_delay += snoopPkt.headerDelay;
2091
2092 if (snoopPkt.cacheResponding()) {
2093 // cache-to-cache response from some upper cache
2094 assert(!alreadyResponded);
2095 pkt->setCacheResponding();
2096 }
2097 // upstream cache has the block, or has an outstanding
2098 // MSHR, pass the flag on
2099 if (snoopPkt.hasSharers()) {
2100 pkt->setHasSharers();
2101 }
2102 // If this request is a prefetch or clean evict and an upper level
2103 // signals block present, make sure to propagate the block
2104 // presence to the requester.
2105 if (snoopPkt.isBlockCached()) {
2106 pkt->setBlockCached();
2107 }
2108 // If the request was satisfied by snooping the cache
2109 // above, mark the original packet as satisfied too.
2110 if (snoopPkt.satisfied()) {
2111 pkt->setSatisfied();
2112 }
2113 } else {
2114 cpuSidePort->sendAtomicSnoop(pkt);
2115 if (!alreadyResponded && pkt->cacheResponding()) {
2116 // cache-to-cache response from some upper cache:
2117 // forward response to original requester
2118 assert(pkt->isResponse());
2119 }
2120 }
2121 }
2122
2123 bool respond = false;
2124 bool blk_valid = blk && blk->isValid();
2125 if (pkt->isClean()) {
2126 if (blk_valid && blk->isDirty()) {
2127 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
2128 __func__, pkt->print(), blk->print());
2129 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
2130 PacketList writebacks;
2131 writebacks.push_back(wb_pkt);
2132
2133 if (is_timing) {
2134 // anything that is merely forwarded pays for the forward
2135 // latency and the delay provided by the crossbar
2136 Tick forward_time = clockEdge(forwardLatency) +
2137 pkt->headerDelay;
2138 doWritebacks(writebacks, forward_time);
2139 } else {
2140 doWritebacksAtomic(writebacks);
2141 }
2142 pkt->setSatisfied();
2143 }
2144 } else if (!blk_valid) {
2145 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
2146 pkt->print());
2147 if (is_deferred) {
2148 // we no longer have the block, and will not respond, but a
2149 // packet was allocated in MSHR::handleSnoop and we have
2150 // to delete it
2151 assert(pkt->needsResponse());
2152
2153 // we have passed the block to a cache upstream, that
2154 // cache should be responding
2155 assert(pkt->cacheResponding());
2156
2157 delete pkt;
2158 }
2159 return snoop_delay;
2160 } else {
2161 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
2162 pkt->print(), blk->print());
2163
2164 // We may end up modifying both the block state and the packet (if
2165 // we respond in atomic mode), so just figure out what to do now
2166 // and then do it later. We respond to all snoops that need
2167 // responses provided we have the block in dirty state. The
2168 // invalidation itself is taken care of below. We don't respond to
2169 // cache maintenance operations as this is done by the destination
2170 // xbar.
2171 respond = blk->isDirty() && pkt->needsResponse();
2172
2173 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
2174 "a dirty block in a read-only cache %s\n", name());
2175 }
2176
2177 // Invalidate any prefetch's from below that would strip write permissions
2178 // MemCmd::HardPFReq is only observed by upstream caches. After missing
2179 // above and in it's own cache, a new MemCmd::ReadReq is created that
2180 // downstream caches observe.
2181 if (pkt->mustCheckAbove()) {
2182 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
2183 "from lower cache\n", pkt->getAddr(), pkt->print());
2184 pkt->setBlockCached();
2185 return snoop_delay;
2186 }
2187
2188 if (pkt->isRead() && !invalidate) {
2189 // reading without requiring the line in a writable state
2190 assert(!needs_writable);
2191 pkt->setHasSharers();
2192
2193 // if the requesting packet is uncacheable, retain the line in
2194 // the current state, otherwhise unset the writable flag,
2195 // which means we go from Modified to Owned (and will respond
2196 // below), remain in Owned (and will respond below), from
2197 // Exclusive to Shared, or remain in Shared
2198 if (!pkt->req->isUncacheable())
2199 blk->status &= ~BlkWritable;
2200 DPRINTF(Cache, "new state is %s\n", blk->print());
2201 }
2202
2203 if (respond) {
2204 // prevent anyone else from responding, cache as well as
2205 // memory, and also prevent any memory from even seeing the
2206 // request
2207 pkt->setCacheResponding();
2208 if (!pkt->isClean() && blk->isWritable()) {
2209 // inform the cache hierarchy that this cache had the line
2210 // in the Modified state so that we avoid unnecessary
2211 // invalidations (see Packet::setResponderHadWritable)
2212 pkt->setResponderHadWritable();
2213
2214 // in the case of an uncacheable request there is no point
2215 // in setting the responderHadWritable flag, but since the
2216 // recipient does not care there is no harm in doing so
2217 } else {
2218 // if the packet has needsWritable set we invalidate our
2219 // copy below and all other copies will be invalidates
2220 // through express snoops, and if needsWritable is not set
2221 // we already called setHasSharers above
2222 }
2223
2224 // if we are returning a writable and dirty (Modified) line,
2225 // we should be invalidating the line
2226 panic_if(!invalidate && !pkt->hasSharers(),
2227 "%s is passing a Modified line through %s, "
2228 "but keeping the block", name(), pkt->print());
2229
2230 if (is_timing) {
2231 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
2232 } else {
2233 pkt->makeAtomicResponse();
2234 // packets such as upgrades do not actually have any data
2235 // payload
2236 if (pkt->hasData())
2237 pkt->setDataFromBlock(blk->data, blkSize);
2238 }
2239 }
2240
2241 if (!respond && is_deferred) {
2242 assert(pkt->needsResponse());
2243
2244 // if we copied the deferred packet with the intention to
2245 // respond, but are not responding, then a cache above us must
2246 // be, and we can use this as the indication of whether this
2247 // is a packet where we created a copy of the request or not
2248 if (!pkt->cacheResponding()) {
2249 delete pkt->req;
2250 }
2251
2252 delete pkt;
2253 }
2254
2255 // Do this last in case it deallocates block data or something
2256 // like that
2257 if (blk_valid && invalidate) {
2258 invalidateBlock(blk);
2259 DPRINTF(Cache, "new state is %s\n", blk->print());
2260 }
2261
2262 return snoop_delay;
2263}
2264
2265
2266void
2267Cache::recvTimingSnoopReq(PacketPtr pkt)
2268{
2269 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
2270
2271 // Snoops shouldn't happen when bypassing caches
2272 assert(!system->bypassCaches());
2273
2274 // no need to snoop requests that are not in range
2275 if (!inRange(pkt->getAddr())) {
2276 return;
2277 }
2278
2279 bool is_secure = pkt->isSecure();
2280 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
2281
2282 Addr blk_addr = pkt->getBlockAddr(blkSize);
2283 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
2284
2285 // Update the latency cost of the snoop so that the crossbar can
2286 // account for it. Do not overwrite what other neighbouring caches
2287 // have already done, rather take the maximum. The update is
2288 // tentative, for cases where we return before an upward snoop
2289 // happens below.
2290 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
2291 lookupLatency * clockPeriod());
2292
2293 // Inform request(Prefetch, CleanEvict or Writeback) from below of
2294 // MSHR hit, set setBlockCached.
2295 if (mshr && pkt->mustCheckAbove()) {
2296 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
2297 "mshr hit\n", pkt->print());
2298 pkt->setBlockCached();
2299 return;
2300 }
2301
2302 // Bypass any existing cache maintenance requests if the request
2303 // has been satisfied already (i.e., the dirty block has been
2304 // found).
2305 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
2306 return;
2307 }
2308
2309 // Let the MSHR itself track the snoop and decide whether we want
2310 // to go ahead and do the regular cache snoop
2311 if (mshr && mshr->handleSnoop(pkt, order++)) {
2312 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
2313 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
2314 mshr->print());
2315
2316 if (mshr->getNumTargets() > numTarget)
2317 warn("allocating bonus target for snoop"); //handle later
2318 return;
2319 }
2320
2321 //We also need to check the writeback buffers and handle those
2322 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
2323 if (wb_entry) {
2324 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
2325 pkt->getAddr(), is_secure ? "s" : "ns");
2326 // Expect to see only Writebacks and/or CleanEvicts here, both of
2327 // which should not be generated for uncacheable data.
2328 assert(!wb_entry->isUncacheable());
2329 // There should only be a single request responsible for generating
2330 // Writebacks/CleanEvicts.
2331 assert(wb_entry->getNumTargets() == 1);
2332 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
2333 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
2334
2335 if (pkt->isEviction()) {
2336 // if the block is found in the write queue, set the BLOCK_CACHED
2337 // flag for Writeback/CleanEvict snoop. On return the snoop will
2338 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
2339 // any CleanEvicts from travelling down the memory hierarchy.
2340 pkt->setBlockCached();
2341 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
2342 "hit\n", __func__, pkt->print());
2343 return;
2344 }
2345
2346 // conceptually writebacks are no different to other blocks in
2347 // this cache, so the behaviour is modelled after handleSnoop,
2348 // the difference being that instead of querying the block
2349 // state to determine if it is dirty and writable, we use the
2350 // command and fields of the writeback packet
2351 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
2352 pkt->needsResponse();
2353 bool have_writable = !wb_pkt->hasSharers();
2354 bool invalidate = pkt->isInvalidate();
2355
2356 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
2357 assert(!pkt->needsWritable());
2358 pkt->setHasSharers();
2359 wb_pkt->setHasSharers();
2360 }
2361
2362 if (respond) {
2363 pkt->setCacheResponding();
2364
2365 if (have_writable) {
2366 pkt->setResponderHadWritable();
2367 }
2368
2369 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
2370 false, false);
2371 }
2372
2373 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
2374 // Invalidation trumps our writeback... discard here
2375 // Note: markInService will remove entry from writeback buffer.
2376 markInService(wb_entry);
2377 delete wb_pkt;
2378 }
2379 }
2380
2381 // If this was a shared writeback, there may still be
2382 // other shared copies above that require invalidation.
2383 // We could be more selective and return here if the
2384 // request is non-exclusive or if the writeback is
2385 // exclusive.
2386 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
2387
2388 // Override what we did when we first saw the snoop, as we now
2389 // also have the cost of the upwards snoops to account for
2390 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
2391 lookupLatency * clockPeriod());
2392}
2393
2394bool
2395Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
2396{
2397 // Express snoop responses from master to slave, e.g., from L1 to L2
2398 cache->recvTimingSnoopResp(pkt);
2399 return true;
2400}
2401
2402Tick
2403Cache::recvAtomicSnoop(PacketPtr pkt)
2404{
2405 // Snoops shouldn't happen when bypassing caches
2406 assert(!system->bypassCaches());
2407
2408 // no need to snoop requests that are not in range.
2409 if (!inRange(pkt->getAddr())) {
2410 return 0;
2411 }
2412
2413 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
2414 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
2415 return snoop_delay + lookupLatency * clockPeriod();
2416}
2417
2418
2419QueueEntry*
2420Cache::getNextQueueEntry()
2421{
2422 // Check both MSHR queue and write buffer for potential requests,
2423 // note that null does not mean there is no request, it could
2424 // simply be that it is not ready
2425 MSHR *miss_mshr = mshrQueue.getNext();
2426 WriteQueueEntry *wq_entry = writeBuffer.getNext();
2427
2428 // If we got a write buffer request ready, first priority is a
2429 // full write buffer, otherwise we favour the miss requests
2430 if (wq_entry && (writeBuffer.isFull() || !miss_mshr)) {
2431 // need to search MSHR queue for conflicting earlier miss.
2432 MSHR *conflict_mshr =
2433 mshrQueue.findPending(wq_entry->blkAddr,
2434 wq_entry->isSecure);
2435
2436 if (conflict_mshr && conflict_mshr->order < wq_entry->order) {
2437 // Service misses in order until conflict is cleared.
2438 return conflict_mshr;
2439
2440 // @todo Note that we ignore the ready time of the conflict here
2441 }
2442
2443 // No conflicts; issue write
2444 return wq_entry;
2445 } else if (miss_mshr) {
2446 // need to check for conflicting earlier writeback
2447 WriteQueueEntry *conflict_mshr =
2448 writeBuffer.findPending(miss_mshr->blkAddr,
2449 miss_mshr->isSecure);
2450 if (conflict_mshr) {
2451 // not sure why we don't check order here... it was in the
2452 // original code but commented out.
2453
2454 // The only way this happens is if we are
2455 // doing a write and we didn't have permissions
2456 // then subsequently saw a writeback (owned got evicted)
2457 // We need to make sure to perform the writeback first
2458 // To preserve the dirty data, then we can issue the write
2459
2460 // should we return wq_entry here instead? I.e. do we
2461 // have to flush writes in order? I don't think so... not
2462 // for Alpha anyway. Maybe for x86?
2463 return conflict_mshr;
2464
2465 // @todo Note that we ignore the ready time of the conflict here
2466 }
2467
2468 // No conflicts; issue read
2469 return miss_mshr;
2470 }
2471
2472 // fall through... no pending requests. Try a prefetch.
2473 assert(!miss_mshr && !wq_entry);
2474 if (prefetcher && mshrQueue.canPrefetch()) {
2475 // If we have a miss queue slot, we can try a prefetch
2476 PacketPtr pkt = prefetcher->getPacket();
2477 if (pkt) {
2478 Addr pf_addr = pkt->getBlockAddr(blkSize);
2479 if (!tags->findBlock(pf_addr, pkt->isSecure()) &&
2480 !mshrQueue.findMatch(pf_addr, pkt->isSecure()) &&
2481 !writeBuffer.findMatch(pf_addr, pkt->isSecure())) {
2482 // Update statistic on number of prefetches issued
2483 // (hwpf_mshr_misses)
2484 assert(pkt->req->masterId() < system->maxMasters());
2485 mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
2486
2487 // allocate an MSHR and return it, note
2488 // that we send the packet straight away, so do not
2489 // schedule the send
2490 return allocateMissBuffer(pkt, curTick(), false);
2491 } else {
2492 // free the request and packet
2493 delete pkt->req;
2494 delete pkt;
2495 }
2496 }
2497 }
2498
2499 return nullptr;
2500}
2501
2502bool
2503Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const
2504{
2505 if (!forwardSnoops)
2506 return false;
2507 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
2508 // Writeback snoops into upper level caches to check for copies of the
2509 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
2510 // packet, the cache can inform the crossbar below of presence or absence
2511 // of the block.
2512 if (is_timing) {
2513 Packet snoop_pkt(pkt, true, false);
2514 snoop_pkt.setExpressSnoop();
2515 // Assert that packet is either Writeback or CleanEvict and not a
2516 // prefetch request because prefetch requests need an MSHR and may
2517 // generate a snoop response.
2518 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
2519 snoop_pkt.senderState = nullptr;
2520 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2521 // Writeback/CleanEvict snoops do not generate a snoop response.
2522 assert(!(snoop_pkt.cacheResponding()));
2523 return snoop_pkt.isBlockCached();
2524 } else {
2525 cpuSidePort->sendAtomicSnoop(pkt);
2526 return pkt->isBlockCached();
2527 }
2528}
2529
2530Tick
2531Cache::nextQueueReadyTime() const
2532{
2533 Tick nextReady = std::min(mshrQueue.nextReadyTime(),
2534 writeBuffer.nextReadyTime());
2535
2536 // Don't signal prefetch ready time if no MSHRs available
2537 // Will signal once enoguh MSHRs are deallocated
2538 if (prefetcher && mshrQueue.canPrefetch()) {
2539 nextReady = std::min(nextReady,
2540 prefetcher->nextPrefetchReadyTime());
2541 }
2542
2543 return nextReady;
2544}
2545
2546bool
2547Cache::sendMSHRQueuePacket(MSHR* mshr)
2548{
2549 assert(mshr);
2550
2551 // use request from 1st target
2552 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
2553
2554 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
2555
2556 CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure);
2557
2558 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
2559 // we should never have hardware prefetches to allocated
2560 // blocks
2561 assert(blk == nullptr);
2562
2563 // We need to check the caches above us to verify that
2564 // they don't have a copy of this block in the dirty state
2565 // at the moment. Without this check we could get a stale
2566 // copy from memory that might get used in place of the
2567 // dirty one.
2568 Packet snoop_pkt(tgt_pkt, true, false);
2569 snoop_pkt.setExpressSnoop();
2570 // We are sending this packet upwards, but if it hits we will
2571 // get a snoop response that we end up treating just like a
2572 // normal response, hence it needs the MSHR as its sender
2573 // state
2574 snoop_pkt.senderState = mshr;
2575 cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
2576
2577 // Check to see if the prefetch was squashed by an upper cache (to
2578 // prevent us from grabbing the line) or if a Check to see if a
2579 // writeback arrived between the time the prefetch was placed in
2580 // the MSHRs and when it was selected to be sent or if the
2581 // prefetch was squashed by an upper cache.
2582
2583 // It is important to check cacheResponding before
2584 // prefetchSquashed. If another cache has committed to
2585 // responding, it will be sending a dirty response which will
2586 // arrive at the MSHR allocated for this request. Checking the
2587 // prefetchSquash first may result in the MSHR being
2588 // prematurely deallocated.
2589 if (snoop_pkt.cacheResponding()) {
2590 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
2591 assert(r.second);
2592
2593 // if we are getting a snoop response with no sharers it
2594 // will be allocated as Modified
2595 bool pending_modified_resp = !snoop_pkt.hasSharers();
2596 markInService(mshr, pending_modified_resp);
2597
2598 DPRINTF(Cache, "Upward snoop of prefetch for addr"
2599 " %#x (%s) hit\n",
2600 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
2601 return false;
2602 }
2603
2604 if (snoop_pkt.isBlockCached()) {
2605 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
2606 "Deallocating mshr target %#x.\n",
2607 mshr->blkAddr);
2608
2609 // Deallocate the mshr target
2610 if (mshrQueue.forceDeallocateTarget(mshr)) {
2611 // Clear block if this deallocation resulted freed an
2612 // mshr when all had previously been utilized
2613 clearBlocked(Blocked_NoMSHRs);
2614 }
2615
2616 // given that no response is expected, delete Request and Packet
2617 delete tgt_pkt->req;
2618 delete tgt_pkt;
2619
2620 return false;
2621 }
2622 }
2623
2624 // either a prefetch that is not present upstream, or a normal
2625 // MSHR request, proceed to get the packet to send downstream
2626 PacketPtr pkt = createMissPacket(tgt_pkt, blk, mshr->needsWritable());
2627
2628 mshr->isForward = (pkt == nullptr);
2629
2630 if (mshr->isForward) {
2631 // not a cache block request, but a response is expected
2632 // make copy of current packet to forward, keep current
2633 // copy for response handling
2634 pkt = new Packet(tgt_pkt, false, true);
2635 assert(!pkt->isWrite());
2636 }
2637
2638 // play it safe and append (rather than set) the sender state,
2639 // as forwarded packets may already have existing state
2640 pkt->pushSenderState(mshr);
2641
2642 if (pkt->isClean() && blk && blk->isDirty()) {
2643 // A cache clean opearation is looking for a dirty block. Mark
2644 // the packet so that the destination xbar can determine that
2645 // there will be a follow-up write packet as well.
2646 pkt->setSatisfied();
2647 }
2648
2649 if (!memSidePort->sendTimingReq(pkt)) {
2650 // we are awaiting a retry, but we
2651 // delete the packet and will be creating a new packet
2652 // when we get the opportunity
2653 delete pkt;
2654
2655 // note that we have now masked any requestBus and
2656 // schedSendEvent (we will wait for a retry before
2657 // doing anything), and this is so even if we do not
2658 // care about this packet and might override it before
2659 // it gets retried
2660 return true;
2661 } else {
2662 // As part of the call to sendTimingReq the packet is
2663 // forwarded to all neighbouring caches (and any caches
2664 // above them) as a snoop. Thus at this point we know if
2665 // any of the neighbouring caches are responding, and if
2666 // so, we know it is dirty, and we can determine if it is
2667 // being passed as Modified, making our MSHR the ordering
2668 // point
2669 bool pending_modified_resp = !pkt->hasSharers() &&
2670 pkt->cacheResponding();
2671 markInService(mshr, pending_modified_resp);
2672 if (pkt->isClean() && blk && blk->isDirty()) {
2673 // A cache clean opearation is looking for a dirty
2674 // block. If a dirty block is encountered a WriteClean
2675 // will update any copies to the path to the memory
2676 // until the point of reference.
2677 DPRINTF(CacheVerbose, "%s: packet %s found block: %s\n",
2678 __func__, pkt->print(), blk->print());
2679 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(),
2680 pkt->id);
2681 PacketList writebacks;
2682 writebacks.push_back(wb_pkt);
2683 doWritebacks(writebacks, 0);
2684 }
2685
2686 return false;
2687 }
2688}
2689
2690bool
2691Cache::sendWriteQueuePacket(WriteQueueEntry* wq_entry)
2692{
2693 assert(wq_entry);
2694
2695 // always a single target for write queue entries
2696 PacketPtr tgt_pkt = wq_entry->getTarget()->pkt;
2697
2698 DPRINTF(Cache, "%s: write %s\n", __func__, tgt_pkt->print());
2699
2700 // forward as is, both for evictions and uncacheable writes
2701 if (!memSidePort->sendTimingReq(tgt_pkt)) {
2702 // note that we have now masked any requestBus and
2703 // schedSendEvent (we will wait for a retry before
2704 // doing anything), and this is so even if we do not
2705 // care about this packet and might override it before
2706 // it gets retried
2707 return true;
2708 } else {
2709 markInService(wq_entry);
2710 return false;
2711 }
2712}
2713
2714void
2715Cache::serialize(CheckpointOut &cp) const
2716{
2717 bool dirty(isDirty());
2718
2719 if (dirty) {
2720 warn("*** The cache still contains dirty data. ***\n");
2721 warn(" Make sure to drain the system using the correct flags.\n");
2722 warn(" This checkpoint will not restore correctly and dirty data "
2723 " in the cache will be lost!\n");
2724 }
2725
2726 // Since we don't checkpoint the data in the cache, any dirty data
2727 // will be lost when restoring from a checkpoint of a system that
2728 // wasn't drained properly. Flag the checkpoint as invalid if the
2729 // cache contains dirty data.
2730 bool bad_checkpoint(dirty);
2731 SERIALIZE_SCALAR(bad_checkpoint);
2732}
2733
2734void
2735Cache::unserialize(CheckpointIn &cp)
2736{
2737 bool bad_checkpoint;
2738 UNSERIALIZE_SCALAR(bad_checkpoint);
2739 if (bad_checkpoint) {
2740 fatal("Restoring from checkpoints with dirty caches is not supported "
2741 "in the classic memory system. Please remove any caches or "
2742 " drain them properly before taking checkpoints.\n");
2743 }
2744}
2745
2746///////////////
2747//
2748// CpuSidePort
2749//
2750///////////////
2751
2752AddrRangeList
2753Cache::CpuSidePort::getAddrRanges() const
2754{
2755 return cache->getAddrRanges();
2756}
2757
2758bool
2759Cache::CpuSidePort::tryTiming(PacketPtr pkt)
2760{
2761 assert(!cache->system->bypassCaches());
2762
2763 // always let express snoop packets through if even if blocked
2764 if (pkt->isExpressSnoop()) {
2765 return true;
2766 } else if (isBlocked() || mustSendRetry) {
2767 // either already committed to send a retry, or blocked
2768 mustSendRetry = true;
2769 return false;
2770 }
2771 mustSendRetry = false;
2772 return true;
2773}
2774
2775bool
2776Cache::CpuSidePort::recvTimingReq(PacketPtr pkt)
2777{
2778 assert(!cache->system->bypassCaches());
2779
2780 // always let express snoop packets through if even if blocked
2781 if (pkt->isExpressSnoop() || tryTiming(pkt)) {
2782 cache->recvTimingReq(pkt);
2783 return true;
2784 }
2785 return false;
2786}
2787
2788Tick
2789Cache::CpuSidePort::recvAtomic(PacketPtr pkt)
2790{
2791 return cache->recvAtomic(pkt);
2792}
2793
2794void
2795Cache::CpuSidePort::recvFunctional(PacketPtr pkt)
2796{
2797 // functional request
2798 cache->functionalAccess(pkt, true);
2799}
2800
2801Cache::
2802CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache,
2803 const std::string &_label)
2804 : BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache)
2805{
2806}
2807
2808Cache*
2809CacheParams::create()
2810{
2811 assert(tags);
2812 assert(replacement_policy);
2813
2814 return new Cache(this);
2815}
2816///////////////
2817//
2818// MemSidePort
2819//
2820///////////////
2821
2822bool
2823Cache::MemSidePort::recvTimingResp(PacketPtr pkt)
2824{
2825 cache->recvTimingResp(pkt);
2826 return true;
2827}
2828
2829// Express snooping requests to memside port
2830void
2831Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt)
2832{
2833 // handle snooping requests
2834 cache->recvTimingSnoopReq(pkt);
2835}
2836
2837Tick
2838Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt)
2839{
2840 return cache->recvAtomicSnoop(pkt);
2841}
2842
2843void
2844Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt)
2845{
2846 // functional snoop (note that in contrast to atomic we don't have
2847 // a specific functionalSnoop method, as they have the same
2848 // behaviour regardless)
2849 cache->functionalAccess(pkt, false);
2850}
2851
2852void
2853Cache::CacheReqPacketQueue::sendDeferredPacket()
2854{
2855 // sanity check
2856 assert(!waitingOnRetry);
2857
2858 // there should never be any deferred request packets in the
2859 // queue, instead we resly on the cache to provide the packets
2860 // from the MSHR queue or write queue
2861 assert(deferredPacketReadyTime() == MaxTick);
2862
2863 // check for request packets (requests & writebacks)
2864 QueueEntry* entry = cache.getNextQueueEntry();
2865
2866 if (!entry) {
2867 // can happen if e.g. we attempt a writeback and fail, but
2868 // before the retry, the writeback is eliminated because
2869 // we snoop another cache's ReadEx.
2870 } else {
2871 // let our snoop responses go first if there are responses to
2872 // the same addresses
2873 if (checkConflictingSnoop(entry->blkAddr)) {
2874 return;
2875 }
2876 waitingOnRetry = entry->sendPacket(cache);
2877 }
2878
2879 // if we succeeded and are not waiting for a retry, schedule the
2880 // next send considering when the next queue is ready, note that
2881 // snoop responses have their own packet queue and thus schedule
2882 // their own events
2883 if (!waitingOnRetry) {
2884 schedSendEvent(cache.nextQueueReadyTime());
2885 }
2886}
2887
2888Cache::
2889MemSidePort::MemSidePort(const std::string &_name, Cache *_cache,
2890 const std::string &_label)
2891 : BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue),
2892 _reqQueue(*_cache, *this, _snoopRespQueue, _label),
2893 _snoopRespQueue(*_cache, *this, _label), cache(_cache)
2894{
2895}
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