d6208dde97621166195726b55fd32ab5f9b3c19c
2 * Copyright (c) 2012-2013, 2015-2018 ARM Limited
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.
14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010 Advanced Micro Devices, Inc.
16 * All rights reserved.
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.
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.
41 * Authors: Erik Hallnor
47 * Miss Status and Handling Register (MSHR) definitions.
50 #include "mem/cache/mshr.hh"
55 #include "base/logging.hh"
56 #include "base/trace.hh"
57 #include "base/types.hh"
58 #include "debug/Cache.hh"
59 #include "mem/cache/base.hh"
60 #include "mem/request.hh"
61 #include "sim/core.hh"
63 MSHR::MSHR() : downstreamPending(false),
64 pendingModified(false),
65 postInvalidate(false), postDowngrade(false),
70 MSHR::TargetList::TargetList()
71 : needsWritable(false), hasUpgrade(false), allocOnFill(false),
77 MSHR::TargetList::updateFlags(PacketPtr pkt
, Target::Source source
,
80 if (source
!= Target::FromSnoop
) {
81 if (pkt
->needsWritable()) {
85 // StoreCondReq is effectively an upgrade if it's in an MSHR
86 // since it would have been failed already if we didn't have a
88 if (pkt
->isUpgrade() || pkt
->cmd
== MemCmd::StoreCondReq
) {
92 // potentially re-evaluate whether we should allocate on a fill or
94 allocOnFill
= allocOnFill
|| alloc_on_fill
;
96 if (source
!= Target::FromPrefetcher
) {
97 hasFromCache
= hasFromCache
|| pkt
->fromCache();
103 MSHR::TargetList::populateFlags()
106 for (auto& t
: *this) {
107 updateFlags(t
.pkt
, t
.source
, t
.allocOnFill
);
112 MSHR::TargetList::add(PacketPtr pkt
, Tick readyTime
,
113 Counter order
, Target::Source source
, bool markPending
,
116 updateFlags(pkt
, source
, alloc_on_fill
);
118 // Iterate over the SenderState stack and see if we find
119 // an MSHR entry. If we do, set the downstreamPending
120 // flag. Otherwise, do nothing.
121 MSHR
*mshr
= pkt
->findNextSenderState
<MSHR
>();
122 if (mshr
!= nullptr) {
123 assert(!mshr
->downstreamPending
);
124 mshr
->downstreamPending
= true;
126 // No need to clear downstreamPending later
131 emplace_back(pkt
, readyTime
, order
, source
, markPending
, alloc_on_fill
);
136 replaceUpgrade(PacketPtr pkt
)
138 // remember if the current packet has data allocated
139 bool has_data
= pkt
->hasData() || pkt
->hasRespData();
141 if (pkt
->cmd
== MemCmd::UpgradeReq
) {
142 pkt
->cmd
= MemCmd::ReadExReq
;
143 DPRINTF(Cache
, "Replacing UpgradeReq with ReadExReq\n");
144 } else if (pkt
->cmd
== MemCmd::SCUpgradeReq
) {
145 pkt
->cmd
= MemCmd::SCUpgradeFailReq
;
146 DPRINTF(Cache
, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
147 } else if (pkt
->cmd
== MemCmd::StoreCondReq
) {
148 pkt
->cmd
= MemCmd::StoreCondFailReq
;
149 DPRINTF(Cache
, "Replacing StoreCondReq with StoreCondFailReq\n");
153 // there is no sensible way of setting the data field if the
154 // new command actually would carry data
155 assert(!pkt
->hasData());
157 if (pkt
->hasRespData()) {
158 // we went from a packet that had no data (neither request,
159 // nor response), to one that does, and therefore we need to
160 // actually allocate space for the data payload
168 MSHR::TargetList::replaceUpgrades()
173 for (auto& t
: *this) {
174 replaceUpgrade(t
.pkt
);
182 MSHR::TargetList::clearDownstreamPending(MSHR::TargetList::iterator begin
,
183 MSHR::TargetList::iterator end
)
185 for (auto t
= begin
; t
!= end
; t
++) {
186 if (t
->markedPending
) {
187 // Iterate over the SenderState stack and see if we find
188 // an MSHR entry. If we find one, clear the
189 // downstreamPending flag by calling
190 // clearDownstreamPending(). This recursively clears the
191 // downstreamPending flag in all caches this packet has
193 MSHR
*mshr
= t
->pkt
->findNextSenderState
<MSHR
>();
194 if (mshr
!= nullptr) {
195 mshr
->clearDownstreamPending();
197 t
->markedPending
= false;
203 MSHR::TargetList::clearDownstreamPending()
205 clearDownstreamPending(begin(), end());
210 MSHR::TargetList::checkFunctional(PacketPtr pkt
)
212 for (auto& t
: *this) {
213 if (pkt
->checkFunctional(t
.pkt
)) {
223 MSHR::TargetList::print(std::ostream
&os
, int verbosity
,
224 const std::string
&prefix
) const
226 for (auto& t
: *this) {
229 case Target::FromCPU
:
232 case Target::FromSnoop
:
235 case Target::FromPrefetcher
:
236 s
= "FromPrefetcher";
242 ccprintf(os
, "%s%s: ", prefix
, s
);
243 t
.pkt
->print(os
, verbosity
, "");
250 MSHR::allocate(Addr blk_addr
, unsigned blk_size
, PacketPtr target
,
251 Tick when_ready
, Counter _order
, bool alloc_on_fill
)
255 isSecure
= target
->isSecure();
256 readyTime
= when_ready
;
260 _isUncacheable
= target
->req
->isUncacheable();
262 downstreamPending
= false;
263 assert(targets
.isReset());
264 // Don't know of a case where we would allocate a new MSHR for a
265 // snoop (mem-side request), so set source according to request here
266 Target::Source source
= (target
->cmd
== MemCmd::HardPFReq
) ?
267 Target::FromPrefetcher
: Target::FromCPU
;
268 targets
.add(target
, when_ready
, _order
, source
, true, alloc_on_fill
);
269 assert(deferredTargets
.isReset());
274 MSHR::clearDownstreamPending()
276 assert(downstreamPending
);
277 downstreamPending
= false;
278 // recursively clear flag on any MSHRs we will be forwarding
280 targets
.clearDownstreamPending();
284 MSHR::markInService(bool pending_modified_resp
)
289 pendingModified
= targets
.needsWritable
|| pending_modified_resp
;
290 postInvalidate
= postDowngrade
= false;
292 if (!downstreamPending
) {
293 // let upstream caches know that the request has made it to a
294 // level where it's going to get a response
295 targets
.clearDownstreamPending();
303 assert(targets
.empty());
304 targets
.resetFlags();
305 assert(deferredTargets
.isReset());
310 * Adds a target to an MSHR
313 MSHR::allocateTarget(PacketPtr pkt
, Tick whenReady
, Counter _order
,
316 // assume we'd never issue a prefetch when we've got an
318 assert(pkt
->cmd
!= MemCmd::HardPFReq
);
320 // if there's a request already in service for this MSHR, we will
321 // have to defer the new target until after the response if any of
322 // the following are true:
323 // - there are other targets already deferred
324 // - there's a pending invalidate to be applied after the response
325 // comes back (but before this target is processed)
326 // - the MSHR's first (and only) non-deferred target is a cache
327 // maintenance packet
328 // - the new target is a cache maintenance packet (this is probably
329 // overly conservative but certainly safe)
330 // - this target requires a writable block and either we're not
331 // getting a writable block back or we have already snooped
332 // another read request that will downgrade our writable block
333 // to non-writable (Shared or Owned)
334 PacketPtr tgt_pkt
= targets
.front().pkt
;
335 if (pkt
->req
->isCacheMaintenance() ||
336 tgt_pkt
->req
->isCacheMaintenance() ||
337 !deferredTargets
.empty() ||
339 (hasPostInvalidate() ||
340 (pkt
->needsWritable() &&
341 (!isPendingModified() || hasPostDowngrade() || isForward
))))) {
342 // need to put on deferred list
343 if (inService
&& hasPostInvalidate())
345 deferredTargets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, true,
348 // No request outstanding, or still OK to append to
349 // outstanding request: append to regular target list. Only
350 // mark pending if current request hasn't been issued yet
351 // (isn't in service).
352 targets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, !inService
,
358 MSHR::handleSnoop(PacketPtr pkt
, Counter _order
)
360 DPRINTF(Cache
, "%s for %s\n", __func__
, pkt
->print());
362 // when we snoop packets the needsWritable and isInvalidate flags
363 // should always be the same, however, this assumes that we never
364 // snoop writes as they are currently not marked as invalidations
365 panic_if((pkt
->needsWritable() != pkt
->isInvalidate()) &&
366 !pkt
->req
->isCacheMaintenance(),
367 "%s got snoop %s where needsWritable, "
368 "does not match isInvalidate", name(), pkt
->print());
370 if (!inService
|| (pkt
->isExpressSnoop() && downstreamPending
)) {
371 // Request has not been issued yet, or it's been issued
372 // locally but is buffered unissued at some downstream cache
373 // which is forwarding us this snoop. Either way, the packet
374 // we're snooping logically precedes this MSHR's request, so
375 // the snoop has no impact on the MSHR, but must be processed
376 // in the standard way by the cache. The only exception is
377 // that if we're an L2+ cache buffering an UpgradeReq from a
378 // higher-level cache, and the snoop is invalidating, then our
379 // buffered upgrades must be converted to read exclusives,
380 // since the upper-level cache no longer has a valid copy.
381 // That is, even though the upper-level cache got out on its
382 // local bus first, some other invalidating transaction
383 // reached the global bus before the upgrade did.
384 if (pkt
->needsWritable() || pkt
->req
->isCacheInvalidate()) {
385 targets
.replaceUpgrades();
386 deferredTargets
.replaceUpgrades();
392 // From here on down, the request issued by this MSHR logically
393 // precedes the request we're snooping.
394 if (pkt
->needsWritable() || pkt
->req
->isCacheInvalidate()) {
395 // snooped request still precedes the re-request we'll have to
396 // issue for deferred targets, if any...
397 deferredTargets
.replaceUpgrades();
400 PacketPtr tgt_pkt
= targets
.front().pkt
;
401 if (hasPostInvalidate() || tgt_pkt
->req
->isCacheInvalidate()) {
402 // a prior snoop has already appended an invalidation or a
403 // cache invalidation operation is in progress, so logically
404 // we don't have the block anymore; no need for further
409 if (isPendingModified() || pkt
->isInvalidate()) {
410 // We need to save and replay the packet in two cases:
411 // 1. We're awaiting a writable copy (Modified or Exclusive),
412 // so this MSHR is the orgering point, and we need to respond
413 // after we receive data.
414 // 2. It's an invalidation (e.g., UpgradeReq), and we need
415 // to forward the snoop up the hierarchy after the current
416 // transaction completes.
418 // Start by determining if we will eventually respond or not,
419 // matching the conditions checked in Cache::handleSnoop
420 bool will_respond
= isPendingModified() && pkt
->needsResponse() &&
423 // The packet we are snooping may be deleted by the time we
424 // actually process the target, and we consequently need to
425 // save a copy here. Clear flags and also allocate new data as
426 // the original packet data storage may have been deleted by
427 // the time we get to process this packet. In the cases where
428 // we are not responding after handling the snoop we also need
429 // to create a copy of the request to be on the safe side. In
430 // the latter case the cache is responsible for deleting both
431 // the packet and the request as part of handling the deferred
433 PacketPtr cp_pkt
= will_respond
? new Packet(pkt
, true, true) :
434 new Packet(std::make_shared
<Request
>(*pkt
->req
), pkt
->cmd
,
438 // we are the ordering point, and will consequently
439 // respond, and depending on whether the packet
440 // needsWritable or not we either pass a Shared line or a
442 pkt
->setCacheResponding();
444 // inform the cache hierarchy that this cache had the line
445 // in the Modified state, even if the response is passed
446 // as Shared (and thus non-writable)
447 pkt
->setResponderHadWritable();
449 // in the case of an uncacheable request there is no need
450 // to set the responderHadWritable flag, but since the
451 // recipient does not care there is no harm in doing so
453 targets
.add(cp_pkt
, curTick(), _order
, Target::FromSnoop
,
454 downstreamPending
&& targets
.needsWritable
, false);
456 if (pkt
->needsWritable() || pkt
->isInvalidate()) {
457 // This transaction will take away our pending copy
458 postInvalidate
= true;
461 if (isPendingModified() && pkt
->isClean()) {
466 if (!pkt
->needsWritable() && !pkt
->req
->isUncacheable()) {
467 // This transaction will get a read-shared copy, downgrading
468 // our copy if we had a writable one
469 postDowngrade
= true;
470 // make sure that any downstream cache does not respond with a
471 // writable (and dirty) copy even if it has one, unless it was
472 // explicitly asked for one
473 pkt
->setHasSharers();
480 MSHR::extractServiceableTargets(PacketPtr pkt
)
482 TargetList ready_targets
;
483 // If the downstream MSHR got an invalidation request then we only
484 // service the first of the FromCPU targets and any other
485 // non-FromCPU target. This way the remaining FromCPU targets
486 // issue a new request and get a fresh copy of the block and we
487 // avoid memory consistency violations.
488 if (pkt
->cmd
== MemCmd::ReadRespWithInvalidate
) {
489 auto it
= targets
.begin();
490 assert((it
->source
== Target::FromCPU
) ||
491 (it
->source
== Target::FromPrefetcher
));
492 ready_targets
.push_back(*it
);
493 it
= targets
.erase(it
);
494 while (it
!= targets
.end()) {
495 if (it
->source
== Target::FromCPU
) {
498 assert(it
->source
== Target::FromSnoop
);
499 ready_targets
.push_back(*it
);
500 it
= targets
.erase(it
);
503 ready_targets
.populateFlags();
505 std::swap(ready_targets
, targets
);
507 targets
.populateFlags();
509 return ready_targets
;
513 MSHR::promoteDeferredTargets()
515 if (targets
.empty() && deferredTargets
.empty()) {
516 // nothing to promote
520 // the deferred targets can be generally promoted unless they
521 // contain a cache maintenance request
523 // find the first target that is a cache maintenance request
524 auto it
= std::find_if(deferredTargets
.begin(), deferredTargets
.end(),
525 [](MSHR::Target
&t
) {
526 return t
.pkt
->req
->isCacheMaintenance();
528 if (it
== deferredTargets
.begin()) {
529 // if the first deferred target is a cache maintenance packet
530 // then we can promote provided the targets list is empty and
531 // we can service it on its own
532 if (targets
.empty()) {
533 targets
.splice(targets
.end(), deferredTargets
, it
);
536 // if a cache maintenance operation exists, we promote all the
537 // deferred targets that precede it, or all deferred targets
539 targets
.splice(targets
.end(), deferredTargets
,
540 deferredTargets
.begin(), it
);
543 deferredTargets
.populateFlags();
544 targets
.populateFlags();
545 order
= targets
.front().order
;
546 readyTime
= std::max(curTick(), targets
.front().readyTime
);
553 MSHR::promoteWritable()
555 if (deferredTargets
.needsWritable
&&
556 !(hasPostInvalidate() || hasPostDowngrade())) {
557 // We got a writable response, but we have deferred targets
558 // which are waiting to request a writable copy (not because
559 // of a pending invalidate). This can happen if the original
560 // request was for a read-only block, but we got a writable
561 // response anyway. Since we got the writable copy there's no
562 // need to defer the targets, so move them up to the regular
564 assert(!targets
.needsWritable
);
565 targets
.needsWritable
= true;
566 // if any of the deferred targets were upper-level cache
567 // requests marked downstreamPending, need to clear that
568 assert(!downstreamPending
); // not pending here anymore
569 deferredTargets
.clearDownstreamPending();
570 // this clears out deferredTargets too
571 targets
.splice(targets
.end(), deferredTargets
);
572 deferredTargets
.resetFlags();
578 MSHR::checkFunctional(PacketPtr pkt
)
580 // For printing, we treat the MSHR as a whole as single entity.
581 // For other requests, we iterate over the individual targets
582 // since that's where the actual data lies.
583 if (pkt
->isPrint()) {
584 pkt
->checkFunctional(this, blkAddr
, isSecure
, blkSize
, nullptr);
587 return (targets
.checkFunctional(pkt
) ||
588 deferredTargets
.checkFunctional(pkt
));
593 MSHR::sendPacket(BaseCache
&cache
)
595 return cache
.sendMSHRQueuePacket(this);
599 MSHR::print(std::ostream
&os
, int verbosity
, const std::string
&prefix
) const
601 ccprintf(os
, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s %s\n",
602 prefix
, blkAddr
, blkAddr
+ blkSize
- 1,
603 isSecure
? "s" : "ns",
604 isForward
? "Forward" : "",
605 allocOnFill() ? "AllocOnFill" : "",
606 needsWritable() ? "Wrtbl" : "",
607 _isUncacheable
? "Unc" : "",
608 inService
? "InSvc" : "",
609 downstreamPending
? "DwnPend" : "",
610 postInvalidate
? "PostInv" : "",
611 postDowngrade
? "PostDowngr" : "",
612 hasFromCache() ? "HasFromCache" : "");
614 if (!targets
.empty()) {
615 ccprintf(os
, "%s Targets:\n", prefix
);
616 targets
.print(os
, verbosity
, prefix
+ " ");
618 if (!deferredTargets
.empty()) {
619 ccprintf(os
, "%s Deferred Targets:\n", prefix
);
620 deferredTargets
.print(os
, verbosity
, prefix
+ " ");
627 std::ostringstream str
;