1/*
2 * Copyright (c) 2010-2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
16 * All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions are
20 * met: redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer;
22 * redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution;
25 * neither the name of the copyright holders nor the names of its
26 * contributors may be used to endorse or promote products derived from
27 * this software without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Authors: Erik Hallnor
42 * Dave Greene
43 * Nathan Binkert
44 * Steve Reinhardt
45 * Ron Dreslinski
46 * Andreas Sandberg
47 * Nikos Nikoleris
48 */
49
50/**
51 * @file
52 * Cache definitions.
53 */
54
55#include "mem/cache/cache.hh"
56
57#include <cassert>
58
59#include "base/compiler.hh"
60#include "base/logging.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CacheTags.hh"
65#include "debug/CacheVerbose.hh"
66#include "enums/Clusivity.hh"
67#include "mem/cache/cache_blk.hh"
68#include "mem/cache/mshr.hh"
69#include "mem/cache/tags/base.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/request.hh"
72#include "params/Cache.hh"
73
74Cache::Cache(const CacheParams *p)
75 : BaseCache(p, p->system->cacheLineSize()),
76 doFastWrites(true)
77{
78}
79
80void
81Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
82 bool deferred_response, bool pending_downgrade)
83{
84 BaseCache::satisfyRequest(pkt, blk);
85
86 if (pkt->isRead()) {
87 // determine if this read is from a (coherent) cache or not
88 if (pkt->fromCache()) {
89 assert(pkt->getSize() == blkSize);
90 // special handling for coherent block requests from
91 // upper-level caches
92 if (pkt->needsWritable()) {
93 // sanity check
94 assert(pkt->cmd == MemCmd::ReadExReq ||
95 pkt->cmd == MemCmd::SCUpgradeFailReq);
96 assert(!pkt->hasSharers());
97
98 // if we have a dirty copy, make sure the recipient
99 // keeps it marked dirty (in the modified state)
100 if (blk->isDirty()) {
101 pkt->setCacheResponding();
102 blk->status &= ~BlkDirty;
103 }
104 } else if (blk->isWritable() && !pending_downgrade &&
105 !pkt->hasSharers() &&
106 pkt->cmd != MemCmd::ReadCleanReq) {
107 // we can give the requester a writable copy on a read
108 // request if:
109 // - we have a writable copy at this level (& below)
110 // - we don't have a pending snoop from below
111 // signaling another read request
112 // - no other cache above has a copy (otherwise it
113 // would have set hasSharers flag when
114 // snooping the packet)
115 // - the read has explicitly asked for a clean
116 // copy of the line
117 if (blk->isDirty()) {
118 // special considerations if we're owner:
119 if (!deferred_response) {
120 // respond with the line in Modified state
121 // (cacheResponding set, hasSharers not set)
122 pkt->setCacheResponding();
123
124 // if this cache is mostly inclusive, we
125 // keep the block in the Exclusive state,
126 // and pass it upwards as Modified
127 // (writable and dirty), hence we have
128 // multiple caches, all on the same path
129 // towards memory, all considering the
130 // same block writable, but only one
131 // considering it Modified
132
133 // we get away with multiple caches (on
134 // the same path to memory) considering
135 // the block writeable as we always enter
136 // the cache hierarchy through a cache,
137 // and first snoop upwards in all other
138 // branches
139 blk->status &= ~BlkDirty;
140 } else {
141 // if we're responding after our own miss,
142 // there's a window where the recipient didn't
143 // know it was getting ownership and may not
144 // have responded to snoops correctly, so we
145 // have to respond with a shared line
146 pkt->setHasSharers();
147 }
148 }
149 } else {
150 // otherwise only respond with a shared copy
151 pkt->setHasSharers();
152 }
153 }
154 }
155}
156
157/////////////////////////////////////////////////////
158//
159// Access path: requests coming in from the CPU side
160//
161/////////////////////////////////////////////////////
162
163bool
164Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
165 PacketList &writebacks)
166{
167
168 if (pkt->req->isUncacheable()) {
169 assert(pkt->isRequest());
170
171 chatty_assert(!(isReadOnly && pkt->isWrite()),
172 "Should never see a write in a read-only cache %s\n",
173 name());
174
175 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
176
177 // flush and invalidate any existing block
178 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
179 if (old_blk && old_blk->isValid()) {
180 BaseCache::evictBlock(old_blk, writebacks);
181 }
182
183 blk = nullptr;
184 // lookupLatency is the latency in case the request is uncacheable.
185 lat = lookupLatency;
186 return false;
187 }
188
189 return BaseCache::access(pkt, blk, lat, writebacks);
190}
191
192void
193Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
194{
195 while (!writebacks.empty()) {
196 PacketPtr wbPkt = writebacks.front();
197 // We use forwardLatency here because we are copying writebacks to
198 // write buffer.
199
200 // Call isCachedAbove for Writebacks, CleanEvicts and
201 // WriteCleans to discover if the block is cached above.
202 if (isCachedAbove(wbPkt)) {
203 if (wbPkt->cmd == MemCmd::CleanEvict) {
204 // Delete CleanEvict because cached copies exist above. The
205 // packet destructor will delete the request object because
206 // this is a non-snoop request packet which does not require a
207 // response.
208 delete wbPkt;
209 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
210 // clean writeback, do not send since the block is
211 // still cached above
212 assert(writebackClean);
213 delete wbPkt;
214 } else {
215 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
216 wbPkt->cmd == MemCmd::WriteClean);
217 // Set BLOCK_CACHED flag in Writeback and send below, so that
218 // the Writeback does not reset the bit corresponding to this
219 // address in the snoop filter below.
220 wbPkt->setBlockCached();
221 allocateWriteBuffer(wbPkt, forward_time);
222 }
223 } else {
224 // If the block is not cached above, send packet below. Both
225 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
226 // reset the bit corresponding to this address in the snoop filter
227 // below.
228 allocateWriteBuffer(wbPkt, forward_time);
229 }
230 writebacks.pop_front();
231 }
232}
233
234void
235Cache::doWritebacksAtomic(PacketList& writebacks)
236{
237 while (!writebacks.empty()) {
238 PacketPtr wbPkt = writebacks.front();
239 // Call isCachedAbove for both Writebacks and CleanEvicts. If
240 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
241 // and discard CleanEvicts.
242 if (isCachedAbove(wbPkt, false)) {
243 if (wbPkt->cmd == MemCmd::WritebackDirty ||
244 wbPkt->cmd == MemCmd::WriteClean) {
245 // Set BLOCK_CACHED flag in Writeback and send below,
246 // so that the Writeback does not reset the bit
247 // corresponding to this address in the snoop filter
248 // below. We can discard CleanEvicts because cached
249 // copies exist above. Atomic mode isCachedAbove
250 // modifies packet to set BLOCK_CACHED flag
251 memSidePort.sendAtomic(wbPkt);
252 }
253 } else {
254 // If the block is not cached above, send packet below. Both
255 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
256 // reset the bit corresponding to this address in the snoop filter
257 // below.
258 memSidePort.sendAtomic(wbPkt);
259 }
260 writebacks.pop_front();
261 // In case of CleanEvicts, the packet destructor will delete the
262 // request object because this is a non-snoop request packet which
263 // does not require a response.
264 delete wbPkt;
265 }
266}
267
268
269void
270Cache::recvTimingSnoopResp(PacketPtr pkt)
271{
272 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
273
274 // determine if the response is from a snoop request we created
275 // (in which case it should be in the outstandingSnoop), or if we
276 // merely forwarded someone else's snoop request
277 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
278 outstandingSnoop.end();
279
280 if (!forwardAsSnoop) {
281 // the packet came from this cache, so sink it here and do not
282 // forward it
283 assert(pkt->cmd == MemCmd::HardPFResp);
284
285 outstandingSnoop.erase(pkt->req);
286
287 DPRINTF(Cache, "Got prefetch response from above for addr "
288 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
289 recvTimingResp(pkt);
290 return;
291 }
292
293 // forwardLatency is set here because there is a response from an
294 // upper level cache.
295 // To pay the delay that occurs if the packet comes from the bus,
296 // we charge also headerDelay.
297 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
298 // Reset the timing of the packet.
299 pkt->headerDelay = pkt->payloadDelay = 0;
300 memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time);
301}
302
303void
304Cache::promoteWholeLineWrites(PacketPtr pkt)
305{
306 // Cache line clearing instructions
307 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
308 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
309 pkt->cmd = MemCmd::WriteLineReq;
310 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
311 }
312}
313
314void
315Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
316{
317 // should never be satisfying an uncacheable access as we
318 // flush and invalidate any existing block as part of the
319 // lookup
320 assert(!pkt->req->isUncacheable());
321
322 BaseCache::handleTimingReqHit(pkt, blk, request_time);
323}
324
325void
326Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
327 Tick request_time)
328{
329 if (pkt->req->isUncacheable()) {
330 // ignore any existing MSHR if we are dealing with an
331 // uncacheable request
332
333 // should have flushed and have no valid block
334 assert(!blk || !blk->isValid());
335
336 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
337
338 if (pkt->isWrite()) {
339 allocateWriteBuffer(pkt, forward_time);
340 } else {
341 assert(pkt->isRead());
342
343 // uncacheable accesses always allocate a new MSHR
344
345 // Here we are using forward_time, modelling the latency of
346 // a miss (outbound) just as forwardLatency, neglecting the
347 // lookupLatency component.
348 allocateMissBuffer(pkt, forward_time);
349 }
350
351 return;
352 }
353
354 Addr blk_addr = pkt->getBlockAddr(blkSize);
355
356 MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
357
358 // Software prefetch handling:
359 // To keep the core from waiting on data it won't look at
360 // anyway, send back a response with dummy data. Miss handling
361 // will continue asynchronously. Unfortunately, the core will
362 // insist upon freeing original Packet/Request, so we have to
363 // create a new pair with a different lifecycle. Note that this
364 // processing happens before any MSHR munging on the behalf of
365 // this request because this new Request will be the one stored
366 // into the MSHRs, not the original.
367 if (pkt->cmd.isSWPrefetch()) {
368 assert(pkt->needsResponse());
369 assert(pkt->req->hasPaddr());
370 assert(!pkt->req->isUncacheable());
371
372 // There's no reason to add a prefetch as an additional target
373 // to an existing MSHR. If an outstanding request is already
374 // in progress, there is nothing for the prefetch to do.
375 // If this is the case, we don't even create a request at all.
376 PacketPtr pf = nullptr;
377
378 if (!mshr) {
379 // copy the request and create a new SoftPFReq packet
380 RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(),
381 pkt->req->getSize(),
382 pkt->req->getFlags(),
383 pkt->req->masterId());
384 pf = new Packet(req, pkt->cmd);
385 pf->allocate();
386 assert(pf->getAddr() == pkt->getAddr());
387 assert(pf->getSize() == pkt->getSize());
388 }
389
390 pkt->makeTimingResponse();
391
392 // request_time is used here, taking into account lat and the delay
393 // charged if the packet comes from the xbar.
394 cpuSidePort.schedTimingResp(pkt, request_time, true);
395
396 // If an outstanding request is in progress (we found an
397 // MSHR) this is set to null
398 pkt = pf;
399 }
400
401 BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time);
402}
403
404void
405Cache::recvTimingReq(PacketPtr pkt)
406{
407 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
408
409 promoteWholeLineWrites(pkt);
410
411 if (pkt->cacheResponding()) {
412 // a cache above us (but not where the packet came from) is
413 // responding to the request, in other words it has the line
414 // in Modified or Owned state
415 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
416 pkt->print());
417
418 // if the packet needs the block to be writable, and the cache
419 // that has promised to respond (setting the cache responding
420 // flag) is not providing writable (it is in Owned rather than
421 // the Modified state), we know that there may be other Shared
422 // copies in the system; go out and invalidate them all
423 assert(pkt->needsWritable() && !pkt->responderHadWritable());
424
425 // an upstream cache that had the line in Owned state
426 // (dirty, but not writable), is responding and thus
427 // transferring the dirty line from one branch of the
428 // cache hierarchy to another
429
430 // send out an express snoop and invalidate all other
431 // copies (snooping a packet that needs writable is the
432 // same as an invalidation), thus turning the Owned line
433 // into a Modified line, note that we don't invalidate the
434 // block in the current cache or any other cache on the
435 // path to memory
436
437 // create a downstream express snoop with cleared packet
438 // flags, there is no need to allocate any data as the
439 // packet is merely used to co-ordinate state transitions
440 Packet *snoop_pkt = new Packet(pkt, true, false);
441
442 // also reset the bus time that the original packet has
443 // not yet paid for
444 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
445
446 // make this an instantaneous express snoop, and let the
447 // other caches in the system know that the another cache
448 // is responding, because we have found the authorative
449 // copy (Modified or Owned) that will supply the right
450 // data
451 snoop_pkt->setExpressSnoop();
452 snoop_pkt->setCacheResponding();
453
454 // this express snoop travels towards the memory, and at
455 // every crossbar it is snooped upwards thus reaching
456 // every cache in the system
457 bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt);
458 // express snoops always succeed
459 assert(success);
460
461 // main memory will delete the snoop packet
462
463 // queue for deletion, as opposed to immediate deletion, as
464 // the sending cache is still relying on the packet
465 pendingDelete.reset(pkt);
466
467 // no need to take any further action in this particular cache
468 // as an upstram cache has already committed to responding,
469 // and we have already sent out any express snoops in the
470 // section above to ensure all other copies in the system are
471 // invalidated
472 return;
473 }
474
475 BaseCache::recvTimingReq(pkt);
476}
477
478PacketPtr
479Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
480 bool needsWritable,
481 bool is_whole_line_write) const
482{
483 // should never see evictions here
484 assert(!cpu_pkt->isEviction());
485
486 bool blkValid = blk && blk->isValid();
487
488 if (cpu_pkt->req->isUncacheable() ||
489 (!blkValid && cpu_pkt->isUpgrade()) ||
490 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
491 // uncacheable requests and upgrades from upper-level caches
492 // that missed completely just go through as is
493 return nullptr;
494 }
495
496 assert(cpu_pkt->needsResponse());
497
498 MemCmd cmd;
499 // @TODO make useUpgrades a parameter.
500 // Note that ownership protocols require upgrade, otherwise a
501 // write miss on a shared owned block will generate a ReadExcl,
502 // which will clobber the owned copy.
503 const bool useUpgrades = true;
504 assert(cpu_pkt->cmd != MemCmd::WriteLineReq || is_whole_line_write);
505 if (is_whole_line_write) {
506 assert(!blkValid || !blk->isWritable());
507 // forward as invalidate to all other caches, this gives us
508 // the line in Exclusive state, and invalidates all other
509 // copies
510 cmd = MemCmd::InvalidateReq;
511 } else if (blkValid && useUpgrades) {
512 // only reason to be here is that blk is read only and we need
513 // it to be writable
514 assert(needsWritable);
515 assert(!blk->isWritable());
516 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
517 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
518 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
519 // Even though this SC will fail, we still need to send out the
520 // request and get the data to supply it to other snoopers in the case
521 // where the determination the StoreCond fails is delayed due to
522 // all caches not being on the same local bus.
523 cmd = MemCmd::SCUpgradeFailReq;
524 } else {
525 // block is invalid
526
527 // If the request does not need a writable there are two cases
528 // where we need to ensure the response will not fetch the
529 // block in dirty state:
530 // * this cache is read only and it does not perform
531 // writebacks,
532 // * this cache is mostly exclusive and will not fill (since
533 // it does not fill it will have to writeback the dirty data
534 // immediately which generates uneccesary writebacks).
535 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
536 cmd = needsWritable ? MemCmd::ReadExReq :
537 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
538 }
539 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
540
541 // if there are upstream caches that have already marked the
542 // packet as having sharers (not passing writable), pass that info
543 // downstream
544 if (cpu_pkt->hasSharers() && !needsWritable) {
545 // note that cpu_pkt may have spent a considerable time in the
546 // MSHR queue and that the information could possibly be out
547 // of date, however, there is no harm in conservatively
548 // assuming the block has sharers
549 pkt->setHasSharers();
550 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
551 __func__, cpu_pkt->print(), pkt->print());
552 }
553
554 // the packet should be block aligned
555 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
556
557 pkt->allocate();
558 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
559 cpu_pkt->print());
560 return pkt;
561}
562
563
564Cycles
565Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
566 PacketList &writebacks)
567{
568 // deal with the packets that go through the write path of
569 // the cache, i.e. any evictions and writes
570 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
571 (pkt->req->isUncacheable() && pkt->isWrite())) {
572 Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt));
573
574 // at this point, if the request was an uncacheable write
575 // request, it has been satisfied by a memory below and the
576 // packet carries the response back
577 assert(!(pkt->req->isUncacheable() && pkt->isWrite()) ||
578 pkt->isResponse());
579
580 return latency;
581 }
582
583 // only misses left
584
585 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable(),
586 pkt->isWholeLineWrite(blkSize));
587
588 bool is_forward = (bus_pkt == nullptr);
589
590 if (is_forward) {
591 // just forwarding the same request to the next level
592 // no local cache operation involved
593 bus_pkt = pkt;
594 }
595
596 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
597 bus_pkt->print());
598
599#if TRACING_ON
600 CacheBlk::State old_state = blk ? blk->status : 0;
601#endif
602
603 Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt));
604
605 bool is_invalidate = bus_pkt->isInvalidate();
606
607 // We are now dealing with the response handling
608 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
609 bus_pkt->print(), old_state);
610
611 // If packet was a forward, the response (if any) is already
612 // in place in the bus_pkt == pkt structure, so we don't need
613 // to do anything. Otherwise, use the separate bus_pkt to
614 // generate response to pkt and then delete it.
615 if (!is_forward) {
616 if (pkt->needsResponse()) {
617 assert(bus_pkt->isResponse());
618 if (bus_pkt->isError()) {
619 pkt->makeAtomicResponse();
620 pkt->copyError(bus_pkt);
621 } else if (pkt->isWholeLineWrite(blkSize)) {
622 // note the use of pkt, not bus_pkt here.
623
624 // write-line request to the cache that promoted
625 // the write to a whole line
626 const bool allocate = allocOnFill(pkt->cmd) &&
627 (!writeAllocator || writeAllocator->allocate());
628 blk = handleFill(bus_pkt, blk, writebacks, allocate);
629 assert(blk != NULL);
630 is_invalidate = false;
631 satisfyRequest(pkt, blk);
632 } else if (bus_pkt->isRead() ||
633 bus_pkt->cmd == MemCmd::UpgradeResp) {
634 // we're updating cache state to allow us to
635 // satisfy the upstream request from the cache
636 blk = handleFill(bus_pkt, blk, writebacks,
637 allocOnFill(pkt->cmd));
638 satisfyRequest(pkt, blk);
639 maintainClusivity(pkt->fromCache(), blk);
640 } else {
641 // we're satisfying the upstream request without
642 // modifying cache state, e.g., a write-through
643 pkt->makeAtomicResponse();
644 }
645 }
646 delete bus_pkt;
647 }
648
649 if (is_invalidate && blk && blk->isValid()) {
650 invalidateBlock(blk);
651 }
652
653 return latency;
654}
655
656Tick
657Cache::recvAtomic(PacketPtr pkt)
658{
659 promoteWholeLineWrites(pkt);
660
661 // follow the same flow as in recvTimingReq, and check if a cache
662 // above us is responding
663 if (pkt->cacheResponding()) {
664 assert(!pkt->req->isCacheInvalidate());
665 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
666 pkt->print());
667
668 // if a cache is responding, and it had the line in Owned
669 // rather than Modified state, we need to invalidate any
670 // copies that are not on the same path to memory
671 assert(pkt->needsWritable() && !pkt->responderHadWritable());
672
673 return memSidePort.sendAtomic(pkt);
674 }
675
676 return BaseCache::recvAtomic(pkt);
677}
678
679
680/////////////////////////////////////////////////////
681//
682// Response handling: responses from the memory side
683//
684/////////////////////////////////////////////////////
685
686
687void
| 1/*
2 * Copyright (c) 2010-2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
16 * All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions are
20 * met: redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer;
22 * redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution;
25 * neither the name of the copyright holders nor the names of its
26 * contributors may be used to endorse or promote products derived from
27 * this software without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Authors: Erik Hallnor
42 * Dave Greene
43 * Nathan Binkert
44 * Steve Reinhardt
45 * Ron Dreslinski
46 * Andreas Sandberg
47 * Nikos Nikoleris
48 */
49
50/**
51 * @file
52 * Cache definitions.
53 */
54
55#include "mem/cache/cache.hh"
56
57#include <cassert>
58
59#include "base/compiler.hh"
60#include "base/logging.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CacheTags.hh"
65#include "debug/CacheVerbose.hh"
66#include "enums/Clusivity.hh"
67#include "mem/cache/cache_blk.hh"
68#include "mem/cache/mshr.hh"
69#include "mem/cache/tags/base.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/request.hh"
72#include "params/Cache.hh"
73
74Cache::Cache(const CacheParams *p)
75 : BaseCache(p, p->system->cacheLineSize()),
76 doFastWrites(true)
77{
78}
79
80void
81Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
82 bool deferred_response, bool pending_downgrade)
83{
84 BaseCache::satisfyRequest(pkt, blk);
85
86 if (pkt->isRead()) {
87 // determine if this read is from a (coherent) cache or not
88 if (pkt->fromCache()) {
89 assert(pkt->getSize() == blkSize);
90 // special handling for coherent block requests from
91 // upper-level caches
92 if (pkt->needsWritable()) {
93 // sanity check
94 assert(pkt->cmd == MemCmd::ReadExReq ||
95 pkt->cmd == MemCmd::SCUpgradeFailReq);
96 assert(!pkt->hasSharers());
97
98 // if we have a dirty copy, make sure the recipient
99 // keeps it marked dirty (in the modified state)
100 if (blk->isDirty()) {
101 pkt->setCacheResponding();
102 blk->status &= ~BlkDirty;
103 }
104 } else if (blk->isWritable() && !pending_downgrade &&
105 !pkt->hasSharers() &&
106 pkt->cmd != MemCmd::ReadCleanReq) {
107 // we can give the requester a writable copy on a read
108 // request if:
109 // - we have a writable copy at this level (& below)
110 // - we don't have a pending snoop from below
111 // signaling another read request
112 // - no other cache above has a copy (otherwise it
113 // would have set hasSharers flag when
114 // snooping the packet)
115 // - the read has explicitly asked for a clean
116 // copy of the line
117 if (blk->isDirty()) {
118 // special considerations if we're owner:
119 if (!deferred_response) {
120 // respond with the line in Modified state
121 // (cacheResponding set, hasSharers not set)
122 pkt->setCacheResponding();
123
124 // if this cache is mostly inclusive, we
125 // keep the block in the Exclusive state,
126 // and pass it upwards as Modified
127 // (writable and dirty), hence we have
128 // multiple caches, all on the same path
129 // towards memory, all considering the
130 // same block writable, but only one
131 // considering it Modified
132
133 // we get away with multiple caches (on
134 // the same path to memory) considering
135 // the block writeable as we always enter
136 // the cache hierarchy through a cache,
137 // and first snoop upwards in all other
138 // branches
139 blk->status &= ~BlkDirty;
140 } else {
141 // if we're responding after our own miss,
142 // there's a window where the recipient didn't
143 // know it was getting ownership and may not
144 // have responded to snoops correctly, so we
145 // have to respond with a shared line
146 pkt->setHasSharers();
147 }
148 }
149 } else {
150 // otherwise only respond with a shared copy
151 pkt->setHasSharers();
152 }
153 }
154 }
155}
156
157/////////////////////////////////////////////////////
158//
159// Access path: requests coming in from the CPU side
160//
161/////////////////////////////////////////////////////
162
163bool
164Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
165 PacketList &writebacks)
166{
167
168 if (pkt->req->isUncacheable()) {
169 assert(pkt->isRequest());
170
171 chatty_assert(!(isReadOnly && pkt->isWrite()),
172 "Should never see a write in a read-only cache %s\n",
173 name());
174
175 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
176
177 // flush and invalidate any existing block
178 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
179 if (old_blk && old_blk->isValid()) {
180 BaseCache::evictBlock(old_blk, writebacks);
181 }
182
183 blk = nullptr;
184 // lookupLatency is the latency in case the request is uncacheable.
185 lat = lookupLatency;
186 return false;
187 }
188
189 return BaseCache::access(pkt, blk, lat, writebacks);
190}
191
192void
193Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
194{
195 while (!writebacks.empty()) {
196 PacketPtr wbPkt = writebacks.front();
197 // We use forwardLatency here because we are copying writebacks to
198 // write buffer.
199
200 // Call isCachedAbove for Writebacks, CleanEvicts and
201 // WriteCleans to discover if the block is cached above.
202 if (isCachedAbove(wbPkt)) {
203 if (wbPkt->cmd == MemCmd::CleanEvict) {
204 // Delete CleanEvict because cached copies exist above. The
205 // packet destructor will delete the request object because
206 // this is a non-snoop request packet which does not require a
207 // response.
208 delete wbPkt;
209 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
210 // clean writeback, do not send since the block is
211 // still cached above
212 assert(writebackClean);
213 delete wbPkt;
214 } else {
215 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
216 wbPkt->cmd == MemCmd::WriteClean);
217 // Set BLOCK_CACHED flag in Writeback and send below, so that
218 // the Writeback does not reset the bit corresponding to this
219 // address in the snoop filter below.
220 wbPkt->setBlockCached();
221 allocateWriteBuffer(wbPkt, forward_time);
222 }
223 } else {
224 // If the block is not cached above, send packet below. Both
225 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
226 // reset the bit corresponding to this address in the snoop filter
227 // below.
228 allocateWriteBuffer(wbPkt, forward_time);
229 }
230 writebacks.pop_front();
231 }
232}
233
234void
235Cache::doWritebacksAtomic(PacketList& writebacks)
236{
237 while (!writebacks.empty()) {
238 PacketPtr wbPkt = writebacks.front();
239 // Call isCachedAbove for both Writebacks and CleanEvicts. If
240 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
241 // and discard CleanEvicts.
242 if (isCachedAbove(wbPkt, false)) {
243 if (wbPkt->cmd == MemCmd::WritebackDirty ||
244 wbPkt->cmd == MemCmd::WriteClean) {
245 // Set BLOCK_CACHED flag in Writeback and send below,
246 // so that the Writeback does not reset the bit
247 // corresponding to this address in the snoop filter
248 // below. We can discard CleanEvicts because cached
249 // copies exist above. Atomic mode isCachedAbove
250 // modifies packet to set BLOCK_CACHED flag
251 memSidePort.sendAtomic(wbPkt);
252 }
253 } else {
254 // If the block is not cached above, send packet below. Both
255 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
256 // reset the bit corresponding to this address in the snoop filter
257 // below.
258 memSidePort.sendAtomic(wbPkt);
259 }
260 writebacks.pop_front();
261 // In case of CleanEvicts, the packet destructor will delete the
262 // request object because this is a non-snoop request packet which
263 // does not require a response.
264 delete wbPkt;
265 }
266}
267
268
269void
270Cache::recvTimingSnoopResp(PacketPtr pkt)
271{
272 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
273
274 // determine if the response is from a snoop request we created
275 // (in which case it should be in the outstandingSnoop), or if we
276 // merely forwarded someone else's snoop request
277 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
278 outstandingSnoop.end();
279
280 if (!forwardAsSnoop) {
281 // the packet came from this cache, so sink it here and do not
282 // forward it
283 assert(pkt->cmd == MemCmd::HardPFResp);
284
285 outstandingSnoop.erase(pkt->req);
286
287 DPRINTF(Cache, "Got prefetch response from above for addr "
288 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
289 recvTimingResp(pkt);
290 return;
291 }
292
293 // forwardLatency is set here because there is a response from an
294 // upper level cache.
295 // To pay the delay that occurs if the packet comes from the bus,
296 // we charge also headerDelay.
297 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
298 // Reset the timing of the packet.
299 pkt->headerDelay = pkt->payloadDelay = 0;
300 memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time);
301}
302
303void
304Cache::promoteWholeLineWrites(PacketPtr pkt)
305{
306 // Cache line clearing instructions
307 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
308 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
309 pkt->cmd = MemCmd::WriteLineReq;
310 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
311 }
312}
313
314void
315Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
316{
317 // should never be satisfying an uncacheable access as we
318 // flush and invalidate any existing block as part of the
319 // lookup
320 assert(!pkt->req->isUncacheable());
321
322 BaseCache::handleTimingReqHit(pkt, blk, request_time);
323}
324
325void
326Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
327 Tick request_time)
328{
329 if (pkt->req->isUncacheable()) {
330 // ignore any existing MSHR if we are dealing with an
331 // uncacheable request
332
333 // should have flushed and have no valid block
334 assert(!blk || !blk->isValid());
335
336 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
337
338 if (pkt->isWrite()) {
339 allocateWriteBuffer(pkt, forward_time);
340 } else {
341 assert(pkt->isRead());
342
343 // uncacheable accesses always allocate a new MSHR
344
345 // Here we are using forward_time, modelling the latency of
346 // a miss (outbound) just as forwardLatency, neglecting the
347 // lookupLatency component.
348 allocateMissBuffer(pkt, forward_time);
349 }
350
351 return;
352 }
353
354 Addr blk_addr = pkt->getBlockAddr(blkSize);
355
356 MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
357
358 // Software prefetch handling:
359 // To keep the core from waiting on data it won't look at
360 // anyway, send back a response with dummy data. Miss handling
361 // will continue asynchronously. Unfortunately, the core will
362 // insist upon freeing original Packet/Request, so we have to
363 // create a new pair with a different lifecycle. Note that this
364 // processing happens before any MSHR munging on the behalf of
365 // this request because this new Request will be the one stored
366 // into the MSHRs, not the original.
367 if (pkt->cmd.isSWPrefetch()) {
368 assert(pkt->needsResponse());
369 assert(pkt->req->hasPaddr());
370 assert(!pkt->req->isUncacheable());
371
372 // There's no reason to add a prefetch as an additional target
373 // to an existing MSHR. If an outstanding request is already
374 // in progress, there is nothing for the prefetch to do.
375 // If this is the case, we don't even create a request at all.
376 PacketPtr pf = nullptr;
377
378 if (!mshr) {
379 // copy the request and create a new SoftPFReq packet
380 RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(),
381 pkt->req->getSize(),
382 pkt->req->getFlags(),
383 pkt->req->masterId());
384 pf = new Packet(req, pkt->cmd);
385 pf->allocate();
386 assert(pf->getAddr() == pkt->getAddr());
387 assert(pf->getSize() == pkt->getSize());
388 }
389
390 pkt->makeTimingResponse();
391
392 // request_time is used here, taking into account lat and the delay
393 // charged if the packet comes from the xbar.
394 cpuSidePort.schedTimingResp(pkt, request_time, true);
395
396 // If an outstanding request is in progress (we found an
397 // MSHR) this is set to null
398 pkt = pf;
399 }
400
401 BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time);
402}
403
404void
405Cache::recvTimingReq(PacketPtr pkt)
406{
407 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
408
409 promoteWholeLineWrites(pkt);
410
411 if (pkt->cacheResponding()) {
412 // a cache above us (but not where the packet came from) is
413 // responding to the request, in other words it has the line
414 // in Modified or Owned state
415 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
416 pkt->print());
417
418 // if the packet needs the block to be writable, and the cache
419 // that has promised to respond (setting the cache responding
420 // flag) is not providing writable (it is in Owned rather than
421 // the Modified state), we know that there may be other Shared
422 // copies in the system; go out and invalidate them all
423 assert(pkt->needsWritable() && !pkt->responderHadWritable());
424
425 // an upstream cache that had the line in Owned state
426 // (dirty, but not writable), is responding and thus
427 // transferring the dirty line from one branch of the
428 // cache hierarchy to another
429
430 // send out an express snoop and invalidate all other
431 // copies (snooping a packet that needs writable is the
432 // same as an invalidation), thus turning the Owned line
433 // into a Modified line, note that we don't invalidate the
434 // block in the current cache or any other cache on the
435 // path to memory
436
437 // create a downstream express snoop with cleared packet
438 // flags, there is no need to allocate any data as the
439 // packet is merely used to co-ordinate state transitions
440 Packet *snoop_pkt = new Packet(pkt, true, false);
441
442 // also reset the bus time that the original packet has
443 // not yet paid for
444 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
445
446 // make this an instantaneous express snoop, and let the
447 // other caches in the system know that the another cache
448 // is responding, because we have found the authorative
449 // copy (Modified or Owned) that will supply the right
450 // data
451 snoop_pkt->setExpressSnoop();
452 snoop_pkt->setCacheResponding();
453
454 // this express snoop travels towards the memory, and at
455 // every crossbar it is snooped upwards thus reaching
456 // every cache in the system
457 bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt);
458 // express snoops always succeed
459 assert(success);
460
461 // main memory will delete the snoop packet
462
463 // queue for deletion, as opposed to immediate deletion, as
464 // the sending cache is still relying on the packet
465 pendingDelete.reset(pkt);
466
467 // no need to take any further action in this particular cache
468 // as an upstram cache has already committed to responding,
469 // and we have already sent out any express snoops in the
470 // section above to ensure all other copies in the system are
471 // invalidated
472 return;
473 }
474
475 BaseCache::recvTimingReq(pkt);
476}
477
478PacketPtr
479Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
480 bool needsWritable,
481 bool is_whole_line_write) const
482{
483 // should never see evictions here
484 assert(!cpu_pkt->isEviction());
485
486 bool blkValid = blk && blk->isValid();
487
488 if (cpu_pkt->req->isUncacheable() ||
489 (!blkValid && cpu_pkt->isUpgrade()) ||
490 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
491 // uncacheable requests and upgrades from upper-level caches
492 // that missed completely just go through as is
493 return nullptr;
494 }
495
496 assert(cpu_pkt->needsResponse());
497
498 MemCmd cmd;
499 // @TODO make useUpgrades a parameter.
500 // Note that ownership protocols require upgrade, otherwise a
501 // write miss on a shared owned block will generate a ReadExcl,
502 // which will clobber the owned copy.
503 const bool useUpgrades = true;
504 assert(cpu_pkt->cmd != MemCmd::WriteLineReq || is_whole_line_write);
505 if (is_whole_line_write) {
506 assert(!blkValid || !blk->isWritable());
507 // forward as invalidate to all other caches, this gives us
508 // the line in Exclusive state, and invalidates all other
509 // copies
510 cmd = MemCmd::InvalidateReq;
511 } else if (blkValid && useUpgrades) {
512 // only reason to be here is that blk is read only and we need
513 // it to be writable
514 assert(needsWritable);
515 assert(!blk->isWritable());
516 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
517 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
518 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
519 // Even though this SC will fail, we still need to send out the
520 // request and get the data to supply it to other snoopers in the case
521 // where the determination the StoreCond fails is delayed due to
522 // all caches not being on the same local bus.
523 cmd = MemCmd::SCUpgradeFailReq;
524 } else {
525 // block is invalid
526
527 // If the request does not need a writable there are two cases
528 // where we need to ensure the response will not fetch the
529 // block in dirty state:
530 // * this cache is read only and it does not perform
531 // writebacks,
532 // * this cache is mostly exclusive and will not fill (since
533 // it does not fill it will have to writeback the dirty data
534 // immediately which generates uneccesary writebacks).
535 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
536 cmd = needsWritable ? MemCmd::ReadExReq :
537 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
538 }
539 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
540
541 // if there are upstream caches that have already marked the
542 // packet as having sharers (not passing writable), pass that info
543 // downstream
544 if (cpu_pkt->hasSharers() && !needsWritable) {
545 // note that cpu_pkt may have spent a considerable time in the
546 // MSHR queue and that the information could possibly be out
547 // of date, however, there is no harm in conservatively
548 // assuming the block has sharers
549 pkt->setHasSharers();
550 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
551 __func__, cpu_pkt->print(), pkt->print());
552 }
553
554 // the packet should be block aligned
555 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
556
557 pkt->allocate();
558 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
559 cpu_pkt->print());
560 return pkt;
561}
562
563
564Cycles
565Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
566 PacketList &writebacks)
567{
568 // deal with the packets that go through the write path of
569 // the cache, i.e. any evictions and writes
570 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
571 (pkt->req->isUncacheable() && pkt->isWrite())) {
572 Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt));
573
574 // at this point, if the request was an uncacheable write
575 // request, it has been satisfied by a memory below and the
576 // packet carries the response back
577 assert(!(pkt->req->isUncacheable() && pkt->isWrite()) ||
578 pkt->isResponse());
579
580 return latency;
581 }
582
583 // only misses left
584
585 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable(),
586 pkt->isWholeLineWrite(blkSize));
587
588 bool is_forward = (bus_pkt == nullptr);
589
590 if (is_forward) {
591 // just forwarding the same request to the next level
592 // no local cache operation involved
593 bus_pkt = pkt;
594 }
595
596 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
597 bus_pkt->print());
598
599#if TRACING_ON
600 CacheBlk::State old_state = blk ? blk->status : 0;
601#endif
602
603 Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt));
604
605 bool is_invalidate = bus_pkt->isInvalidate();
606
607 // We are now dealing with the response handling
608 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
609 bus_pkt->print(), old_state);
610
611 // If packet was a forward, the response (if any) is already
612 // in place in the bus_pkt == pkt structure, so we don't need
613 // to do anything. Otherwise, use the separate bus_pkt to
614 // generate response to pkt and then delete it.
615 if (!is_forward) {
616 if (pkt->needsResponse()) {
617 assert(bus_pkt->isResponse());
618 if (bus_pkt->isError()) {
619 pkt->makeAtomicResponse();
620 pkt->copyError(bus_pkt);
621 } else if (pkt->isWholeLineWrite(blkSize)) {
622 // note the use of pkt, not bus_pkt here.
623
624 // write-line request to the cache that promoted
625 // the write to a whole line
626 const bool allocate = allocOnFill(pkt->cmd) &&
627 (!writeAllocator || writeAllocator->allocate());
628 blk = handleFill(bus_pkt, blk, writebacks, allocate);
629 assert(blk != NULL);
630 is_invalidate = false;
631 satisfyRequest(pkt, blk);
632 } else if (bus_pkt->isRead() ||
633 bus_pkt->cmd == MemCmd::UpgradeResp) {
634 // we're updating cache state to allow us to
635 // satisfy the upstream request from the cache
636 blk = handleFill(bus_pkt, blk, writebacks,
637 allocOnFill(pkt->cmd));
638 satisfyRequest(pkt, blk);
639 maintainClusivity(pkt->fromCache(), blk);
640 } else {
641 // we're satisfying the upstream request without
642 // modifying cache state, e.g., a write-through
643 pkt->makeAtomicResponse();
644 }
645 }
646 delete bus_pkt;
647 }
648
649 if (is_invalidate && blk && blk->isValid()) {
650 invalidateBlock(blk);
651 }
652
653 return latency;
654}
655
656Tick
657Cache::recvAtomic(PacketPtr pkt)
658{
659 promoteWholeLineWrites(pkt);
660
661 // follow the same flow as in recvTimingReq, and check if a cache
662 // above us is responding
663 if (pkt->cacheResponding()) {
664 assert(!pkt->req->isCacheInvalidate());
665 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
666 pkt->print());
667
668 // if a cache is responding, and it had the line in Owned
669 // rather than Modified state, we need to invalidate any
670 // copies that are not on the same path to memory
671 assert(pkt->needsWritable() && !pkt->responderHadWritable());
672
673 return memSidePort.sendAtomic(pkt);
674 }
675
676 return BaseCache::recvAtomic(pkt);
677}
678
679
680/////////////////////////////////////////////////////
681//
682// Response handling: responses from the memory side
683//
684/////////////////////////////////////////////////////
685
686
687void
|
690{
691 MSHR::Target *initial_tgt = mshr->getTarget();
692 // First offset for critical word first calculations
693 const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
694
695 const bool is_error = pkt->isError();
696 // allow invalidation responses originating from write-line
697 // requests to be discarded
698 bool is_invalidate = pkt->isInvalidate() &&
699 !mshr->wasWholeLineWrite;
700
701 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
702 for (auto &target: targets) {
703 Packet *tgt_pkt = target.pkt;
704 switch (target.source) {
705 case MSHR::Target::FromCPU:
706 Tick completion_time;
707 // Here we charge on completion_time the delay of the xbar if the
708 // packet comes from it, charged on headerDelay.
709 completion_time = pkt->headerDelay;
710
711 // Software prefetch handling for cache closest to core
712 if (tgt_pkt->cmd.isSWPrefetch()) {
713 // a software prefetch would have already been ack'd
714 // immediately with dummy data so the core would be able to
715 // retire it. This request completes right here, so we
716 // deallocate it.
717 delete tgt_pkt;
718 break; // skip response
719 }
720
721 // unlike the other packet flows, where data is found in other
722 // caches or memory and brought back, write-line requests always
723 // have the data right away, so the above check for "is fill?"
724 // cannot actually be determined until examining the stored MSHR
725 // state. We "catch up" with that logic here, which is duplicated
726 // from above.
727 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
728 assert(!is_error);
729 assert(blk);
730 assert(blk->isWritable());
731 }
732
733 if (blk && blk->isValid() && !mshr->isForward) {
734 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
735
736 // How many bytes past the first request is this one
737 int transfer_offset =
738 tgt_pkt->getOffset(blkSize) - initial_offset;
739 if (transfer_offset < 0) {
740 transfer_offset += blkSize;
741 }
742
743 // If not critical word (offset) return payloadDelay.
744 // responseLatency is the latency of the return path
745 // from lower level caches/memory to an upper level cache or
746 // the core.
747 completion_time += clockEdge(responseLatency) +
748 (transfer_offset ? pkt->payloadDelay : 0);
749
750 assert(!tgt_pkt->req->isUncacheable());
751
752 assert(tgt_pkt->req->masterId() < system->maxMasters());
753 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
754 completion_time - target.recvTime;
755 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
756 // failed StoreCond upgrade
757 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
758 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
759 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
760 // responseLatency is the latency of the return path
761 // from lower level caches/memory to an upper level cache or
762 // the core.
763 completion_time += clockEdge(responseLatency) +
764 pkt->payloadDelay;
765 tgt_pkt->req->setExtraData(0);
766 } else {
767 // We are about to send a response to a cache above
768 // that asked for an invalidation; we need to
769 // invalidate our copy immediately as the most
770 // up-to-date copy of the block will now be in the
771 // cache above. It will also prevent this cache from
772 // responding (if the block was previously dirty) to
773 // snoops as they should snoop the caches above where
774 // they will get the response from.
775 if (is_invalidate && blk && blk->isValid()) {
776 invalidateBlock(blk);
777 }
778 // not a cache fill, just forwarding response
779 // responseLatency is the latency of the return path
780 // from lower level cahces/memory to the core.
781 completion_time += clockEdge(responseLatency) +
782 pkt->payloadDelay;
783 if (pkt->isRead() && !is_error) {
784 // sanity check
785 assert(pkt->getAddr() == tgt_pkt->getAddr());
786 assert(pkt->getSize() >= tgt_pkt->getSize());
787
788 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
789 }
790 }
791 tgt_pkt->makeTimingResponse();
792 // if this packet is an error copy that to the new packet
793 if (is_error)
794 tgt_pkt->copyError(pkt);
795 if (tgt_pkt->cmd == MemCmd::ReadResp &&
796 (is_invalidate || mshr->hasPostInvalidate())) {
797 // If intermediate cache got ReadRespWithInvalidate,
798 // propagate that. Response should not have
799 // isInvalidate() set otherwise.
800 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
801 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
802 tgt_pkt->print());
803 }
804 // Reset the bus additional time as it is now accounted for
805 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
806 cpuSidePort.schedTimingResp(tgt_pkt, completion_time, true);
807 break;
808
809 case MSHR::Target::FromPrefetcher:
810 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
811 if (blk)
812 blk->status |= BlkHWPrefetched;
813 delete tgt_pkt;
814 break;
815
816 case MSHR::Target::FromSnoop:
817 // I don't believe that a snoop can be in an error state
818 assert(!is_error);
819 // response to snoop request
820 DPRINTF(Cache, "processing deferred snoop...\n");
821 // If the response is invalidating, a snooping target can
822 // be satisfied if it is also invalidating. If the reponse is, not
823 // only invalidating, but more specifically an InvalidateResp and
824 // the MSHR was created due to an InvalidateReq then a cache above
825 // is waiting to satisfy a WriteLineReq. In this case even an
826 // non-invalidating snoop is added as a target here since this is
827 // the ordering point. When the InvalidateResp reaches this cache,
828 // the snooping target will snoop further the cache above with the
829 // WriteLineReq.
830 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
831 pkt->req->isCacheMaintenance() ||
832 mshr->hasPostInvalidate());
833 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
834 break;
835
836 default:
837 panic("Illegal target->source enum %d\n", target.source);
838 }
839 }
840
841 maintainClusivity(targets.hasFromCache, blk);
842
843 if (blk && blk->isValid()) {
844 // an invalidate response stemming from a write line request
845 // should not invalidate the block, so check if the
846 // invalidation should be discarded
847 if (is_invalidate || mshr->hasPostInvalidate()) {
848 invalidateBlock(blk);
849 } else if (mshr->hasPostDowngrade()) {
850 blk->status &= ~BlkWritable;
851 }
852 }
853}
854
855PacketPtr
856Cache::evictBlock(CacheBlk *blk)
857{
858 PacketPtr pkt = (blk->isDirty() || writebackClean) ?
859 writebackBlk(blk) : cleanEvictBlk(blk);
860
861 invalidateBlock(blk);
862
863 return pkt;
864}
865
866PacketPtr
867Cache::cleanEvictBlk(CacheBlk *blk)
868{
869 assert(!writebackClean);
870 assert(blk && blk->isValid() && !blk->isDirty());
871
872 // Creating a zero sized write, a message to the snoop filter
873 RequestPtr req = std::make_shared<Request>(
874 regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId);
875
876 if (blk->isSecure())
877 req->setFlags(Request::SECURE);
878
879 req->taskId(blk->task_id);
880
881 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
882 pkt->allocate();
883 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
884
885 return pkt;
886}
887
888/////////////////////////////////////////////////////
889//
890// Snoop path: requests coming in from the memory side
891//
892/////////////////////////////////////////////////////
893
894void
895Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
896 bool already_copied, bool pending_inval)
897{
898 // sanity check
899 assert(req_pkt->isRequest());
900 assert(req_pkt->needsResponse());
901
902 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
903 // timing-mode snoop responses require a new packet, unless we
904 // already made a copy...
905 PacketPtr pkt = req_pkt;
906 if (!already_copied)
907 // do not clear flags, and allocate space for data if the
908 // packet needs it (the only packets that carry data are read
909 // responses)
910 pkt = new Packet(req_pkt, false, req_pkt->isRead());
911
912 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
913 pkt->hasSharers());
914 pkt->makeTimingResponse();
915 if (pkt->isRead()) {
916 pkt->setDataFromBlock(blk_data, blkSize);
917 }
918 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
919 // Assume we defer a response to a read from a far-away cache
920 // A, then later defer a ReadExcl from a cache B on the same
921 // bus as us. We'll assert cacheResponding in both cases, but
922 // in the latter case cacheResponding will keep the
923 // invalidation from reaching cache A. This special response
924 // tells cache A that it gets the block to satisfy its read,
925 // but must immediately invalidate it.
926 pkt->cmd = MemCmd::ReadRespWithInvalidate;
927 }
928 // Here we consider forward_time, paying for just forward latency and
929 // also charging the delay provided by the xbar.
930 // forward_time is used as send_time in next allocateWriteBuffer().
931 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
932 // Here we reset the timing of the packet.
933 pkt->headerDelay = pkt->payloadDelay = 0;
934 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
935 pkt->print(), forward_time);
936 memSidePort.schedTimingSnoopResp(pkt, forward_time, true);
937}
938
939uint32_t
940Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
941 bool is_deferred, bool pending_inval)
942{
943 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
944 // deferred snoops can only happen in timing mode
945 assert(!(is_deferred && !is_timing));
946 // pending_inval only makes sense on deferred snoops
947 assert(!(pending_inval && !is_deferred));
948 assert(pkt->isRequest());
949
950 // the packet may get modified if we or a forwarded snooper
951 // responds in atomic mode, so remember a few things about the
952 // original packet up front
953 bool invalidate = pkt->isInvalidate();
954 bool M5_VAR_USED needs_writable = pkt->needsWritable();
955
956 // at the moment we could get an uncacheable write which does not
957 // have the invalidate flag, and we need a suitable way of dealing
958 // with this case
959 panic_if(invalidate && pkt->req->isUncacheable(),
960 "%s got an invalidating uncacheable snoop request %s",
961 name(), pkt->print());
962
963 uint32_t snoop_delay = 0;
964
965 if (forwardSnoops) {
966 // first propagate snoop upward to see if anyone above us wants to
967 // handle it. save & restore packet src since it will get
968 // rewritten to be relative to cpu-side bus (if any)
969 bool alreadyResponded = pkt->cacheResponding();
970 if (is_timing) {
971 // copy the packet so that we can clear any flags before
972 // forwarding it upwards, we also allocate data (passing
973 // the pointer along in case of static data), in case
974 // there is a snoop hit in upper levels
975 Packet snoopPkt(pkt, true, true);
976 snoopPkt.setExpressSnoop();
977 // the snoop packet does not need to wait any additional
978 // time
979 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
980 cpuSidePort.sendTimingSnoopReq(&snoopPkt);
981
982 // add the header delay (including crossbar and snoop
983 // delays) of the upward snoop to the snoop delay for this
984 // cache
985 snoop_delay += snoopPkt.headerDelay;
986
987 if (snoopPkt.cacheResponding()) {
988 // cache-to-cache response from some upper cache
989 assert(!alreadyResponded);
990 pkt->setCacheResponding();
991 }
992 // upstream cache has the block, or has an outstanding
993 // MSHR, pass the flag on
994 if (snoopPkt.hasSharers()) {
995 pkt->setHasSharers();
996 }
997 // If this request is a prefetch or clean evict and an upper level
998 // signals block present, make sure to propagate the block
999 // presence to the requester.
1000 if (snoopPkt.isBlockCached()) {
1001 pkt->setBlockCached();
1002 }
1003 // If the request was satisfied by snooping the cache
1004 // above, mark the original packet as satisfied too.
1005 if (snoopPkt.satisfied()) {
1006 pkt->setSatisfied();
1007 }
1008 } else {
1009 cpuSidePort.sendAtomicSnoop(pkt);
1010 if (!alreadyResponded && pkt->cacheResponding()) {
1011 // cache-to-cache response from some upper cache:
1012 // forward response to original requester
1013 assert(pkt->isResponse());
1014 }
1015 }
1016 }
1017
1018 bool respond = false;
1019 bool blk_valid = blk && blk->isValid();
1020 if (pkt->isClean()) {
1021 if (blk_valid && blk->isDirty()) {
1022 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
1023 __func__, pkt->print(), blk->print());
1024 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1025 PacketList writebacks;
1026 writebacks.push_back(wb_pkt);
1027
1028 if (is_timing) {
1029 // anything that is merely forwarded pays for the forward
1030 // latency and the delay provided by the crossbar
1031 Tick forward_time = clockEdge(forwardLatency) +
1032 pkt->headerDelay;
1033 doWritebacks(writebacks, forward_time);
1034 } else {
1035 doWritebacksAtomic(writebacks);
1036 }
1037 pkt->setSatisfied();
1038 }
1039 } else if (!blk_valid) {
1040 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
1041 pkt->print());
1042 if (is_deferred) {
1043 // we no longer have the block, and will not respond, but a
1044 // packet was allocated in MSHR::handleSnoop and we have
1045 // to delete it
1046 assert(pkt->needsResponse());
1047
1048 // we have passed the block to a cache upstream, that
1049 // cache should be responding
1050 assert(pkt->cacheResponding());
1051
1052 delete pkt;
1053 }
1054 return snoop_delay;
1055 } else {
1056 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
1057 pkt->print(), blk->print());
1058
1059 // We may end up modifying both the block state and the packet (if
1060 // we respond in atomic mode), so just figure out what to do now
1061 // and then do it later. We respond to all snoops that need
1062 // responses provided we have the block in dirty state. The
1063 // invalidation itself is taken care of below. We don't respond to
1064 // cache maintenance operations as this is done by the destination
1065 // xbar.
1066 respond = blk->isDirty() && pkt->needsResponse();
1067
1068 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
1069 "a dirty block in a read-only cache %s\n", name());
1070 }
1071
1072 // Invalidate any prefetch's from below that would strip write permissions
1073 // MemCmd::HardPFReq is only observed by upstream caches. After missing
1074 // above and in it's own cache, a new MemCmd::ReadReq is created that
1075 // downstream caches observe.
1076 if (pkt->mustCheckAbove()) {
1077 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
1078 "from lower cache\n", pkt->getAddr(), pkt->print());
1079 pkt->setBlockCached();
1080 return snoop_delay;
1081 }
1082
1083 if (pkt->isRead() && !invalidate) {
1084 // reading without requiring the line in a writable state
1085 assert(!needs_writable);
1086 pkt->setHasSharers();
1087
1088 // if the requesting packet is uncacheable, retain the line in
1089 // the current state, otherwhise unset the writable flag,
1090 // which means we go from Modified to Owned (and will respond
1091 // below), remain in Owned (and will respond below), from
1092 // Exclusive to Shared, or remain in Shared
1093 if (!pkt->req->isUncacheable())
1094 blk->status &= ~BlkWritable;
1095 DPRINTF(Cache, "new state is %s\n", blk->print());
1096 }
1097
1098 if (respond) {
1099 // prevent anyone else from responding, cache as well as
1100 // memory, and also prevent any memory from even seeing the
1101 // request
1102 pkt->setCacheResponding();
1103 if (!pkt->isClean() && blk->isWritable()) {
1104 // inform the cache hierarchy that this cache had the line
1105 // in the Modified state so that we avoid unnecessary
1106 // invalidations (see Packet::setResponderHadWritable)
1107 pkt->setResponderHadWritable();
1108
1109 // in the case of an uncacheable request there is no point
1110 // in setting the responderHadWritable flag, but since the
1111 // recipient does not care there is no harm in doing so
1112 } else {
1113 // if the packet has needsWritable set we invalidate our
1114 // copy below and all other copies will be invalidates
1115 // through express snoops, and if needsWritable is not set
1116 // we already called setHasSharers above
1117 }
1118
1119 // if we are returning a writable and dirty (Modified) line,
1120 // we should be invalidating the line
1121 panic_if(!invalidate && !pkt->hasSharers(),
1122 "%s is passing a Modified line through %s, "
1123 "but keeping the block", name(), pkt->print());
1124
1125 if (is_timing) {
1126 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
1127 } else {
1128 pkt->makeAtomicResponse();
1129 // packets such as upgrades do not actually have any data
1130 // payload
1131 if (pkt->hasData())
1132 pkt->setDataFromBlock(blk->data, blkSize);
1133 }
1134 }
1135
1136 if (!respond && is_deferred) {
1137 assert(pkt->needsResponse());
1138 delete pkt;
1139 }
1140
1141 // Do this last in case it deallocates block data or something
1142 // like that
1143 if (blk_valid && invalidate) {
1144 invalidateBlock(blk);
1145 DPRINTF(Cache, "new state is %s\n", blk->print());
1146 }
1147
1148 return snoop_delay;
1149}
1150
1151
1152void
1153Cache::recvTimingSnoopReq(PacketPtr pkt)
1154{
1155 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
1156
1157 // no need to snoop requests that are not in range
1158 if (!inRange(pkt->getAddr())) {
1159 return;
1160 }
1161
1162 bool is_secure = pkt->isSecure();
1163 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1164
1165 Addr blk_addr = pkt->getBlockAddr(blkSize);
1166 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1167
1168 // Update the latency cost of the snoop so that the crossbar can
1169 // account for it. Do not overwrite what other neighbouring caches
1170 // have already done, rather take the maximum. The update is
1171 // tentative, for cases where we return before an upward snoop
1172 // happens below.
1173 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
1174 lookupLatency * clockPeriod());
1175
1176 // Inform request(Prefetch, CleanEvict or Writeback) from below of
1177 // MSHR hit, set setBlockCached.
1178 if (mshr && pkt->mustCheckAbove()) {
1179 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
1180 "mshr hit\n", pkt->print());
1181 pkt->setBlockCached();
1182 return;
1183 }
1184
1185 // Bypass any existing cache maintenance requests if the request
1186 // has been satisfied already (i.e., the dirty block has been
1187 // found).
1188 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
1189 return;
1190 }
1191
1192 // Let the MSHR itself track the snoop and decide whether we want
1193 // to go ahead and do the regular cache snoop
1194 if (mshr && mshr->handleSnoop(pkt, order++)) {
1195 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
1196 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
1197 mshr->print());
1198
1199 if (mshr->getNumTargets() > numTarget)
1200 warn("allocating bonus target for snoop"); //handle later
1201 return;
1202 }
1203
1204 //We also need to check the writeback buffers and handle those
1205 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
1206 if (wb_entry) {
1207 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
1208 pkt->getAddr(), is_secure ? "s" : "ns");
1209 // Expect to see only Writebacks and/or CleanEvicts here, both of
1210 // which should not be generated for uncacheable data.
1211 assert(!wb_entry->isUncacheable());
1212 // There should only be a single request responsible for generating
1213 // Writebacks/CleanEvicts.
1214 assert(wb_entry->getNumTargets() == 1);
1215 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
1216 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
1217
1218 if (pkt->isEviction()) {
1219 // if the block is found in the write queue, set the BLOCK_CACHED
1220 // flag for Writeback/CleanEvict snoop. On return the snoop will
1221 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
1222 // any CleanEvicts from travelling down the memory hierarchy.
1223 pkt->setBlockCached();
1224 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
1225 "hit\n", __func__, pkt->print());
1226 return;
1227 }
1228
1229 // conceptually writebacks are no different to other blocks in
1230 // this cache, so the behaviour is modelled after handleSnoop,
1231 // the difference being that instead of querying the block
1232 // state to determine if it is dirty and writable, we use the
1233 // command and fields of the writeback packet
1234 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
1235 pkt->needsResponse();
1236 bool have_writable = !wb_pkt->hasSharers();
1237 bool invalidate = pkt->isInvalidate();
1238
1239 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
1240 assert(!pkt->needsWritable());
1241 pkt->setHasSharers();
1242 wb_pkt->setHasSharers();
1243 }
1244
1245 if (respond) {
1246 pkt->setCacheResponding();
1247
1248 if (have_writable) {
1249 pkt->setResponderHadWritable();
1250 }
1251
1252 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
1253 false, false);
1254 }
1255
1256 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
1257 // Invalidation trumps our writeback... discard here
1258 // Note: markInService will remove entry from writeback buffer.
1259 markInService(wb_entry);
1260 delete wb_pkt;
1261 }
1262 }
1263
1264 // If this was a shared writeback, there may still be
1265 // other shared copies above that require invalidation.
1266 // We could be more selective and return here if the
1267 // request is non-exclusive or if the writeback is
1268 // exclusive.
1269 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
1270
1271 // Override what we did when we first saw the snoop, as we now
1272 // also have the cost of the upwards snoops to account for
1273 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
1274 lookupLatency * clockPeriod());
1275}
1276
1277Tick
1278Cache::recvAtomicSnoop(PacketPtr pkt)
1279{
1280 // no need to snoop requests that are not in range.
1281 if (!inRange(pkt->getAddr())) {
1282 return 0;
1283 }
1284
1285 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1286 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
1287 return snoop_delay + lookupLatency * clockPeriod();
1288}
1289
1290bool
1291Cache::isCachedAbove(PacketPtr pkt, bool is_timing)
1292{
1293 if (!forwardSnoops)
1294 return false;
1295 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
1296 // Writeback snoops into upper level caches to check for copies of the
1297 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
1298 // packet, the cache can inform the crossbar below of presence or absence
1299 // of the block.
1300 if (is_timing) {
1301 Packet snoop_pkt(pkt, true, false);
1302 snoop_pkt.setExpressSnoop();
1303 // Assert that packet is either Writeback or CleanEvict and not a
1304 // prefetch request because prefetch requests need an MSHR and may
1305 // generate a snoop response.
1306 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
1307 snoop_pkt.senderState = nullptr;
1308 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1309 // Writeback/CleanEvict snoops do not generate a snoop response.
1310 assert(!(snoop_pkt.cacheResponding()));
1311 return snoop_pkt.isBlockCached();
1312 } else {
1313 cpuSidePort.sendAtomicSnoop(pkt);
1314 return pkt->isBlockCached();
1315 }
1316}
1317
1318bool
1319Cache::sendMSHRQueuePacket(MSHR* mshr)
1320{
1321 assert(mshr);
1322
1323 // use request from 1st target
1324 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
1325
1326 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
1327 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
1328
1329 // we should never have hardware prefetches to allocated
1330 // blocks
1331 assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure));
1332
1333 // We need to check the caches above us to verify that
1334 // they don't have a copy of this block in the dirty state
1335 // at the moment. Without this check we could get a stale
1336 // copy from memory that might get used in place of the
1337 // dirty one.
1338 Packet snoop_pkt(tgt_pkt, true, false);
1339 snoop_pkt.setExpressSnoop();
1340 // We are sending this packet upwards, but if it hits we will
1341 // get a snoop response that we end up treating just like a
1342 // normal response, hence it needs the MSHR as its sender
1343 // state
1344 snoop_pkt.senderState = mshr;
1345 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1346
1347 // Check to see if the prefetch was squashed by an upper cache (to
1348 // prevent us from grabbing the line) or if a Check to see if a
1349 // writeback arrived between the time the prefetch was placed in
1350 // the MSHRs and when it was selected to be sent or if the
1351 // prefetch was squashed by an upper cache.
1352
1353 // It is important to check cacheResponding before
1354 // prefetchSquashed. If another cache has committed to
1355 // responding, it will be sending a dirty response which will
1356 // arrive at the MSHR allocated for this request. Checking the
1357 // prefetchSquash first may result in the MSHR being
1358 // prematurely deallocated.
1359 if (snoop_pkt.cacheResponding()) {
1360 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
1361 assert(r.second);
1362
1363 // if we are getting a snoop response with no sharers it
1364 // will be allocated as Modified
1365 bool pending_modified_resp = !snoop_pkt.hasSharers();
1366 markInService(mshr, pending_modified_resp);
1367
1368 DPRINTF(Cache, "Upward snoop of prefetch for addr"
1369 " %#x (%s) hit\n",
1370 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
1371 return false;
1372 }
1373
1374 if (snoop_pkt.isBlockCached()) {
1375 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
1376 "Deallocating mshr target %#x.\n",
1377 mshr->blkAddr);
1378
1379 // Deallocate the mshr target
1380 if (mshrQueue.forceDeallocateTarget(mshr)) {
1381 // Clear block if this deallocation resulted freed an
1382 // mshr when all had previously been utilized
1383 clearBlocked(Blocked_NoMSHRs);
1384 }
1385
1386 // given that no response is expected, delete Request and Packet
1387 delete tgt_pkt;
1388
1389 return false;
1390 }
1391 }
1392
1393 return BaseCache::sendMSHRQueuePacket(mshr);
1394}
1395
1396Cache*
1397CacheParams::create()
1398{
1399 assert(tags);
1400 assert(replacement_policy);
1401
1402 return new Cache(this);
1403}
| 689{
690 MSHR::Target *initial_tgt = mshr->getTarget();
691 // First offset for critical word first calculations
692 const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
693
694 const bool is_error = pkt->isError();
695 // allow invalidation responses originating from write-line
696 // requests to be discarded
697 bool is_invalidate = pkt->isInvalidate() &&
698 !mshr->wasWholeLineWrite;
699
700 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
701 for (auto &target: targets) {
702 Packet *tgt_pkt = target.pkt;
703 switch (target.source) {
704 case MSHR::Target::FromCPU:
705 Tick completion_time;
706 // Here we charge on completion_time the delay of the xbar if the
707 // packet comes from it, charged on headerDelay.
708 completion_time = pkt->headerDelay;
709
710 // Software prefetch handling for cache closest to core
711 if (tgt_pkt->cmd.isSWPrefetch()) {
712 // a software prefetch would have already been ack'd
713 // immediately with dummy data so the core would be able to
714 // retire it. This request completes right here, so we
715 // deallocate it.
716 delete tgt_pkt;
717 break; // skip response
718 }
719
720 // unlike the other packet flows, where data is found in other
721 // caches or memory and brought back, write-line requests always
722 // have the data right away, so the above check for "is fill?"
723 // cannot actually be determined until examining the stored MSHR
724 // state. We "catch up" with that logic here, which is duplicated
725 // from above.
726 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
727 assert(!is_error);
728 assert(blk);
729 assert(blk->isWritable());
730 }
731
732 if (blk && blk->isValid() && !mshr->isForward) {
733 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
734
735 // How many bytes past the first request is this one
736 int transfer_offset =
737 tgt_pkt->getOffset(blkSize) - initial_offset;
738 if (transfer_offset < 0) {
739 transfer_offset += blkSize;
740 }
741
742 // If not critical word (offset) return payloadDelay.
743 // responseLatency is the latency of the return path
744 // from lower level caches/memory to an upper level cache or
745 // the core.
746 completion_time += clockEdge(responseLatency) +
747 (transfer_offset ? pkt->payloadDelay : 0);
748
749 assert(!tgt_pkt->req->isUncacheable());
750
751 assert(tgt_pkt->req->masterId() < system->maxMasters());
752 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
753 completion_time - target.recvTime;
754 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
755 // failed StoreCond upgrade
756 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
757 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
758 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
759 // responseLatency is the latency of the return path
760 // from lower level caches/memory to an upper level cache or
761 // the core.
762 completion_time += clockEdge(responseLatency) +
763 pkt->payloadDelay;
764 tgt_pkt->req->setExtraData(0);
765 } else {
766 // We are about to send a response to a cache above
767 // that asked for an invalidation; we need to
768 // invalidate our copy immediately as the most
769 // up-to-date copy of the block will now be in the
770 // cache above. It will also prevent this cache from
771 // responding (if the block was previously dirty) to
772 // snoops as they should snoop the caches above where
773 // they will get the response from.
774 if (is_invalidate && blk && blk->isValid()) {
775 invalidateBlock(blk);
776 }
777 // not a cache fill, just forwarding response
778 // responseLatency is the latency of the return path
779 // from lower level cahces/memory to the core.
780 completion_time += clockEdge(responseLatency) +
781 pkt->payloadDelay;
782 if (pkt->isRead() && !is_error) {
783 // sanity check
784 assert(pkt->getAddr() == tgt_pkt->getAddr());
785 assert(pkt->getSize() >= tgt_pkt->getSize());
786
787 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
788 }
789 }
790 tgt_pkt->makeTimingResponse();
791 // if this packet is an error copy that to the new packet
792 if (is_error)
793 tgt_pkt->copyError(pkt);
794 if (tgt_pkt->cmd == MemCmd::ReadResp &&
795 (is_invalidate || mshr->hasPostInvalidate())) {
796 // If intermediate cache got ReadRespWithInvalidate,
797 // propagate that. Response should not have
798 // isInvalidate() set otherwise.
799 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
800 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
801 tgt_pkt->print());
802 }
803 // Reset the bus additional time as it is now accounted for
804 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
805 cpuSidePort.schedTimingResp(tgt_pkt, completion_time, true);
806 break;
807
808 case MSHR::Target::FromPrefetcher:
809 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
810 if (blk)
811 blk->status |= BlkHWPrefetched;
812 delete tgt_pkt;
813 break;
814
815 case MSHR::Target::FromSnoop:
816 // I don't believe that a snoop can be in an error state
817 assert(!is_error);
818 // response to snoop request
819 DPRINTF(Cache, "processing deferred snoop...\n");
820 // If the response is invalidating, a snooping target can
821 // be satisfied if it is also invalidating. If the reponse is, not
822 // only invalidating, but more specifically an InvalidateResp and
823 // the MSHR was created due to an InvalidateReq then a cache above
824 // is waiting to satisfy a WriteLineReq. In this case even an
825 // non-invalidating snoop is added as a target here since this is
826 // the ordering point. When the InvalidateResp reaches this cache,
827 // the snooping target will snoop further the cache above with the
828 // WriteLineReq.
829 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
830 pkt->req->isCacheMaintenance() ||
831 mshr->hasPostInvalidate());
832 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
833 break;
834
835 default:
836 panic("Illegal target->source enum %d\n", target.source);
837 }
838 }
839
840 maintainClusivity(targets.hasFromCache, blk);
841
842 if (blk && blk->isValid()) {
843 // an invalidate response stemming from a write line request
844 // should not invalidate the block, so check if the
845 // invalidation should be discarded
846 if (is_invalidate || mshr->hasPostInvalidate()) {
847 invalidateBlock(blk);
848 } else if (mshr->hasPostDowngrade()) {
849 blk->status &= ~BlkWritable;
850 }
851 }
852}
853
854PacketPtr
855Cache::evictBlock(CacheBlk *blk)
856{
857 PacketPtr pkt = (blk->isDirty() || writebackClean) ?
858 writebackBlk(blk) : cleanEvictBlk(blk);
859
860 invalidateBlock(blk);
861
862 return pkt;
863}
864
865PacketPtr
866Cache::cleanEvictBlk(CacheBlk *blk)
867{
868 assert(!writebackClean);
869 assert(blk && blk->isValid() && !blk->isDirty());
870
871 // Creating a zero sized write, a message to the snoop filter
872 RequestPtr req = std::make_shared<Request>(
873 regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId);
874
875 if (blk->isSecure())
876 req->setFlags(Request::SECURE);
877
878 req->taskId(blk->task_id);
879
880 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
881 pkt->allocate();
882 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
883
884 return pkt;
885}
886
887/////////////////////////////////////////////////////
888//
889// Snoop path: requests coming in from the memory side
890//
891/////////////////////////////////////////////////////
892
893void
894Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
895 bool already_copied, bool pending_inval)
896{
897 // sanity check
898 assert(req_pkt->isRequest());
899 assert(req_pkt->needsResponse());
900
901 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
902 // timing-mode snoop responses require a new packet, unless we
903 // already made a copy...
904 PacketPtr pkt = req_pkt;
905 if (!already_copied)
906 // do not clear flags, and allocate space for data if the
907 // packet needs it (the only packets that carry data are read
908 // responses)
909 pkt = new Packet(req_pkt, false, req_pkt->isRead());
910
911 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
912 pkt->hasSharers());
913 pkt->makeTimingResponse();
914 if (pkt->isRead()) {
915 pkt->setDataFromBlock(blk_data, blkSize);
916 }
917 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
918 // Assume we defer a response to a read from a far-away cache
919 // A, then later defer a ReadExcl from a cache B on the same
920 // bus as us. We'll assert cacheResponding in both cases, but
921 // in the latter case cacheResponding will keep the
922 // invalidation from reaching cache A. This special response
923 // tells cache A that it gets the block to satisfy its read,
924 // but must immediately invalidate it.
925 pkt->cmd = MemCmd::ReadRespWithInvalidate;
926 }
927 // Here we consider forward_time, paying for just forward latency and
928 // also charging the delay provided by the xbar.
929 // forward_time is used as send_time in next allocateWriteBuffer().
930 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
931 // Here we reset the timing of the packet.
932 pkt->headerDelay = pkt->payloadDelay = 0;
933 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
934 pkt->print(), forward_time);
935 memSidePort.schedTimingSnoopResp(pkt, forward_time, true);
936}
937
938uint32_t
939Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
940 bool is_deferred, bool pending_inval)
941{
942 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
943 // deferred snoops can only happen in timing mode
944 assert(!(is_deferred && !is_timing));
945 // pending_inval only makes sense on deferred snoops
946 assert(!(pending_inval && !is_deferred));
947 assert(pkt->isRequest());
948
949 // the packet may get modified if we or a forwarded snooper
950 // responds in atomic mode, so remember a few things about the
951 // original packet up front
952 bool invalidate = pkt->isInvalidate();
953 bool M5_VAR_USED needs_writable = pkt->needsWritable();
954
955 // at the moment we could get an uncacheable write which does not
956 // have the invalidate flag, and we need a suitable way of dealing
957 // with this case
958 panic_if(invalidate && pkt->req->isUncacheable(),
959 "%s got an invalidating uncacheable snoop request %s",
960 name(), pkt->print());
961
962 uint32_t snoop_delay = 0;
963
964 if (forwardSnoops) {
965 // first propagate snoop upward to see if anyone above us wants to
966 // handle it. save & restore packet src since it will get
967 // rewritten to be relative to cpu-side bus (if any)
968 bool alreadyResponded = pkt->cacheResponding();
969 if (is_timing) {
970 // copy the packet so that we can clear any flags before
971 // forwarding it upwards, we also allocate data (passing
972 // the pointer along in case of static data), in case
973 // there is a snoop hit in upper levels
974 Packet snoopPkt(pkt, true, true);
975 snoopPkt.setExpressSnoop();
976 // the snoop packet does not need to wait any additional
977 // time
978 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
979 cpuSidePort.sendTimingSnoopReq(&snoopPkt);
980
981 // add the header delay (including crossbar and snoop
982 // delays) of the upward snoop to the snoop delay for this
983 // cache
984 snoop_delay += snoopPkt.headerDelay;
985
986 if (snoopPkt.cacheResponding()) {
987 // cache-to-cache response from some upper cache
988 assert(!alreadyResponded);
989 pkt->setCacheResponding();
990 }
991 // upstream cache has the block, or has an outstanding
992 // MSHR, pass the flag on
993 if (snoopPkt.hasSharers()) {
994 pkt->setHasSharers();
995 }
996 // If this request is a prefetch or clean evict and an upper level
997 // signals block present, make sure to propagate the block
998 // presence to the requester.
999 if (snoopPkt.isBlockCached()) {
1000 pkt->setBlockCached();
1001 }
1002 // If the request was satisfied by snooping the cache
1003 // above, mark the original packet as satisfied too.
1004 if (snoopPkt.satisfied()) {
1005 pkt->setSatisfied();
1006 }
1007 } else {
1008 cpuSidePort.sendAtomicSnoop(pkt);
1009 if (!alreadyResponded && pkt->cacheResponding()) {
1010 // cache-to-cache response from some upper cache:
1011 // forward response to original requester
1012 assert(pkt->isResponse());
1013 }
1014 }
1015 }
1016
1017 bool respond = false;
1018 bool blk_valid = blk && blk->isValid();
1019 if (pkt->isClean()) {
1020 if (blk_valid && blk->isDirty()) {
1021 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
1022 __func__, pkt->print(), blk->print());
1023 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1024 PacketList writebacks;
1025 writebacks.push_back(wb_pkt);
1026
1027 if (is_timing) {
1028 // anything that is merely forwarded pays for the forward
1029 // latency and the delay provided by the crossbar
1030 Tick forward_time = clockEdge(forwardLatency) +
1031 pkt->headerDelay;
1032 doWritebacks(writebacks, forward_time);
1033 } else {
1034 doWritebacksAtomic(writebacks);
1035 }
1036 pkt->setSatisfied();
1037 }
1038 } else if (!blk_valid) {
1039 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
1040 pkt->print());
1041 if (is_deferred) {
1042 // we no longer have the block, and will not respond, but a
1043 // packet was allocated in MSHR::handleSnoop and we have
1044 // to delete it
1045 assert(pkt->needsResponse());
1046
1047 // we have passed the block to a cache upstream, that
1048 // cache should be responding
1049 assert(pkt->cacheResponding());
1050
1051 delete pkt;
1052 }
1053 return snoop_delay;
1054 } else {
1055 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
1056 pkt->print(), blk->print());
1057
1058 // We may end up modifying both the block state and the packet (if
1059 // we respond in atomic mode), so just figure out what to do now
1060 // and then do it later. We respond to all snoops that need
1061 // responses provided we have the block in dirty state. The
1062 // invalidation itself is taken care of below. We don't respond to
1063 // cache maintenance operations as this is done by the destination
1064 // xbar.
1065 respond = blk->isDirty() && pkt->needsResponse();
1066
1067 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
1068 "a dirty block in a read-only cache %s\n", name());
1069 }
1070
1071 // Invalidate any prefetch's from below that would strip write permissions
1072 // MemCmd::HardPFReq is only observed by upstream caches. After missing
1073 // above and in it's own cache, a new MemCmd::ReadReq is created that
1074 // downstream caches observe.
1075 if (pkt->mustCheckAbove()) {
1076 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
1077 "from lower cache\n", pkt->getAddr(), pkt->print());
1078 pkt->setBlockCached();
1079 return snoop_delay;
1080 }
1081
1082 if (pkt->isRead() && !invalidate) {
1083 // reading without requiring the line in a writable state
1084 assert(!needs_writable);
1085 pkt->setHasSharers();
1086
1087 // if the requesting packet is uncacheable, retain the line in
1088 // the current state, otherwhise unset the writable flag,
1089 // which means we go from Modified to Owned (and will respond
1090 // below), remain in Owned (and will respond below), from
1091 // Exclusive to Shared, or remain in Shared
1092 if (!pkt->req->isUncacheable())
1093 blk->status &= ~BlkWritable;
1094 DPRINTF(Cache, "new state is %s\n", blk->print());
1095 }
1096
1097 if (respond) {
1098 // prevent anyone else from responding, cache as well as
1099 // memory, and also prevent any memory from even seeing the
1100 // request
1101 pkt->setCacheResponding();
1102 if (!pkt->isClean() && blk->isWritable()) {
1103 // inform the cache hierarchy that this cache had the line
1104 // in the Modified state so that we avoid unnecessary
1105 // invalidations (see Packet::setResponderHadWritable)
1106 pkt->setResponderHadWritable();
1107
1108 // in the case of an uncacheable request there is no point
1109 // in setting the responderHadWritable flag, but since the
1110 // recipient does not care there is no harm in doing so
1111 } else {
1112 // if the packet has needsWritable set we invalidate our
1113 // copy below and all other copies will be invalidates
1114 // through express snoops, and if needsWritable is not set
1115 // we already called setHasSharers above
1116 }
1117
1118 // if we are returning a writable and dirty (Modified) line,
1119 // we should be invalidating the line
1120 panic_if(!invalidate && !pkt->hasSharers(),
1121 "%s is passing a Modified line through %s, "
1122 "but keeping the block", name(), pkt->print());
1123
1124 if (is_timing) {
1125 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
1126 } else {
1127 pkt->makeAtomicResponse();
1128 // packets such as upgrades do not actually have any data
1129 // payload
1130 if (pkt->hasData())
1131 pkt->setDataFromBlock(blk->data, blkSize);
1132 }
1133 }
1134
1135 if (!respond && is_deferred) {
1136 assert(pkt->needsResponse());
1137 delete pkt;
1138 }
1139
1140 // Do this last in case it deallocates block data or something
1141 // like that
1142 if (blk_valid && invalidate) {
1143 invalidateBlock(blk);
1144 DPRINTF(Cache, "new state is %s\n", blk->print());
1145 }
1146
1147 return snoop_delay;
1148}
1149
1150
1151void
1152Cache::recvTimingSnoopReq(PacketPtr pkt)
1153{
1154 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
1155
1156 // no need to snoop requests that are not in range
1157 if (!inRange(pkt->getAddr())) {
1158 return;
1159 }
1160
1161 bool is_secure = pkt->isSecure();
1162 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1163
1164 Addr blk_addr = pkt->getBlockAddr(blkSize);
1165 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1166
1167 // Update the latency cost of the snoop so that the crossbar can
1168 // account for it. Do not overwrite what other neighbouring caches
1169 // have already done, rather take the maximum. The update is
1170 // tentative, for cases where we return before an upward snoop
1171 // happens below.
1172 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
1173 lookupLatency * clockPeriod());
1174
1175 // Inform request(Prefetch, CleanEvict or Writeback) from below of
1176 // MSHR hit, set setBlockCached.
1177 if (mshr && pkt->mustCheckAbove()) {
1178 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
1179 "mshr hit\n", pkt->print());
1180 pkt->setBlockCached();
1181 return;
1182 }
1183
1184 // Bypass any existing cache maintenance requests if the request
1185 // has been satisfied already (i.e., the dirty block has been
1186 // found).
1187 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
1188 return;
1189 }
1190
1191 // Let the MSHR itself track the snoop and decide whether we want
1192 // to go ahead and do the regular cache snoop
1193 if (mshr && mshr->handleSnoop(pkt, order++)) {
1194 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
1195 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
1196 mshr->print());
1197
1198 if (mshr->getNumTargets() > numTarget)
1199 warn("allocating bonus target for snoop"); //handle later
1200 return;
1201 }
1202
1203 //We also need to check the writeback buffers and handle those
1204 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
1205 if (wb_entry) {
1206 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
1207 pkt->getAddr(), is_secure ? "s" : "ns");
1208 // Expect to see only Writebacks and/or CleanEvicts here, both of
1209 // which should not be generated for uncacheable data.
1210 assert(!wb_entry->isUncacheable());
1211 // There should only be a single request responsible for generating
1212 // Writebacks/CleanEvicts.
1213 assert(wb_entry->getNumTargets() == 1);
1214 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
1215 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
1216
1217 if (pkt->isEviction()) {
1218 // if the block is found in the write queue, set the BLOCK_CACHED
1219 // flag for Writeback/CleanEvict snoop. On return the snoop will
1220 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
1221 // any CleanEvicts from travelling down the memory hierarchy.
1222 pkt->setBlockCached();
1223 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
1224 "hit\n", __func__, pkt->print());
1225 return;
1226 }
1227
1228 // conceptually writebacks are no different to other blocks in
1229 // this cache, so the behaviour is modelled after handleSnoop,
1230 // the difference being that instead of querying the block
1231 // state to determine if it is dirty and writable, we use the
1232 // command and fields of the writeback packet
1233 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
1234 pkt->needsResponse();
1235 bool have_writable = !wb_pkt->hasSharers();
1236 bool invalidate = pkt->isInvalidate();
1237
1238 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
1239 assert(!pkt->needsWritable());
1240 pkt->setHasSharers();
1241 wb_pkt->setHasSharers();
1242 }
1243
1244 if (respond) {
1245 pkt->setCacheResponding();
1246
1247 if (have_writable) {
1248 pkt->setResponderHadWritable();
1249 }
1250
1251 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
1252 false, false);
1253 }
1254
1255 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
1256 // Invalidation trumps our writeback... discard here
1257 // Note: markInService will remove entry from writeback buffer.
1258 markInService(wb_entry);
1259 delete wb_pkt;
1260 }
1261 }
1262
1263 // If this was a shared writeback, there may still be
1264 // other shared copies above that require invalidation.
1265 // We could be more selective and return here if the
1266 // request is non-exclusive or if the writeback is
1267 // exclusive.
1268 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
1269
1270 // Override what we did when we first saw the snoop, as we now
1271 // also have the cost of the upwards snoops to account for
1272 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
1273 lookupLatency * clockPeriod());
1274}
1275
1276Tick
1277Cache::recvAtomicSnoop(PacketPtr pkt)
1278{
1279 // no need to snoop requests that are not in range.
1280 if (!inRange(pkt->getAddr())) {
1281 return 0;
1282 }
1283
1284 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1285 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
1286 return snoop_delay + lookupLatency * clockPeriod();
1287}
1288
1289bool
1290Cache::isCachedAbove(PacketPtr pkt, bool is_timing)
1291{
1292 if (!forwardSnoops)
1293 return false;
1294 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
1295 // Writeback snoops into upper level caches to check for copies of the
1296 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
1297 // packet, the cache can inform the crossbar below of presence or absence
1298 // of the block.
1299 if (is_timing) {
1300 Packet snoop_pkt(pkt, true, false);
1301 snoop_pkt.setExpressSnoop();
1302 // Assert that packet is either Writeback or CleanEvict and not a
1303 // prefetch request because prefetch requests need an MSHR and may
1304 // generate a snoop response.
1305 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
1306 snoop_pkt.senderState = nullptr;
1307 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1308 // Writeback/CleanEvict snoops do not generate a snoop response.
1309 assert(!(snoop_pkt.cacheResponding()));
1310 return snoop_pkt.isBlockCached();
1311 } else {
1312 cpuSidePort.sendAtomicSnoop(pkt);
1313 return pkt->isBlockCached();
1314 }
1315}
1316
1317bool
1318Cache::sendMSHRQueuePacket(MSHR* mshr)
1319{
1320 assert(mshr);
1321
1322 // use request from 1st target
1323 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
1324
1325 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
1326 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
1327
1328 // we should never have hardware prefetches to allocated
1329 // blocks
1330 assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure));
1331
1332 // We need to check the caches above us to verify that
1333 // they don't have a copy of this block in the dirty state
1334 // at the moment. Without this check we could get a stale
1335 // copy from memory that might get used in place of the
1336 // dirty one.
1337 Packet snoop_pkt(tgt_pkt, true, false);
1338 snoop_pkt.setExpressSnoop();
1339 // We are sending this packet upwards, but if it hits we will
1340 // get a snoop response that we end up treating just like a
1341 // normal response, hence it needs the MSHR as its sender
1342 // state
1343 snoop_pkt.senderState = mshr;
1344 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1345
1346 // Check to see if the prefetch was squashed by an upper cache (to
1347 // prevent us from grabbing the line) or if a Check to see if a
1348 // writeback arrived between the time the prefetch was placed in
1349 // the MSHRs and when it was selected to be sent or if the
1350 // prefetch was squashed by an upper cache.
1351
1352 // It is important to check cacheResponding before
1353 // prefetchSquashed. If another cache has committed to
1354 // responding, it will be sending a dirty response which will
1355 // arrive at the MSHR allocated for this request. Checking the
1356 // prefetchSquash first may result in the MSHR being
1357 // prematurely deallocated.
1358 if (snoop_pkt.cacheResponding()) {
1359 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
1360 assert(r.second);
1361
1362 // if we are getting a snoop response with no sharers it
1363 // will be allocated as Modified
1364 bool pending_modified_resp = !snoop_pkt.hasSharers();
1365 markInService(mshr, pending_modified_resp);
1366
1367 DPRINTF(Cache, "Upward snoop of prefetch for addr"
1368 " %#x (%s) hit\n",
1369 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
1370 return false;
1371 }
1372
1373 if (snoop_pkt.isBlockCached()) {
1374 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
1375 "Deallocating mshr target %#x.\n",
1376 mshr->blkAddr);
1377
1378 // Deallocate the mshr target
1379 if (mshrQueue.forceDeallocateTarget(mshr)) {
1380 // Clear block if this deallocation resulted freed an
1381 // mshr when all had previously been utilized
1382 clearBlocked(Blocked_NoMSHRs);
1383 }
1384
1385 // given that no response is expected, delete Request and Packet
1386 delete tgt_pkt;
1387
1388 return false;
1389 }
1390 }
1391
1392 return BaseCache::sendMSHRQueuePacket(mshr);
1393}
1394
1395Cache*
1396CacheParams::create()
1397{
1398 assert(tags);
1399 assert(replacement_policy);
1400
1401 return new Cache(this);
1402}
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