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14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010 Advanced Micro Devices, Inc.
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19 * modification, are permitted provided that the following conditions are
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22 * redistributions in binary form must reproduce the above copyright
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27 * this software without specific prior written permission.
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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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
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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.
55 #include "base/misc.hh"
56 #include "base/types.hh"
57 #include "debug/Cache.hh"
58 #include "mem/cache/cache.hh"
59 #include "mem/cache/mshr.hh"
60 #include "sim/core.hh"
64 MSHR::MSHR() : readyTime(0), _isUncacheable(false), downstreamPending(false),
66 postInvalidate(false), postDowngrade(false),
67 queue(NULL
), order(0), addr(0),
68 size(0), isSecure(false), inService(false),
69 isForward(false), threadNum(InvalidThreadID
), data(NULL
)
74 MSHR::TargetList::TargetList()
75 : needsExclusive(false), hasUpgrade(false)
80 MSHR::TargetList::add(PacketPtr pkt
, Tick readyTime
,
81 Counter order
, Target::Source source
, bool markPending
)
83 if (source
!= Target::FromSnoop
) {
84 if (pkt
->needsExclusive()) {
85 needsExclusive
= true;
88 // StoreCondReq is effectively an upgrade if it's in an MSHR
89 // since it would have been failed already if we didn't have a
91 if (pkt
->isUpgrade() || pkt
->cmd
== MemCmd::StoreCondReq
) {
97 // Iterate over the SenderState stack and see if we find
98 // an MSHR entry. If we do, set the downstreamPending
99 // flag. Otherwise, do nothing.
100 MSHR
*mshr
= pkt
->findNextSenderState
<MSHR
>();
102 assert(!mshr
->downstreamPending
);
103 mshr
->downstreamPending
= true;
107 push_back(Target(pkt
, readyTime
, order
, source
, markPending
));
112 replaceUpgrade(PacketPtr pkt
)
114 if (pkt
->cmd
== MemCmd::UpgradeReq
) {
115 pkt
->cmd
= MemCmd::ReadExReq
;
116 DPRINTF(Cache
, "Replacing UpgradeReq with ReadExReq\n");
117 } else if (pkt
->cmd
== MemCmd::SCUpgradeReq
) {
118 pkt
->cmd
= MemCmd::SCUpgradeFailReq
;
119 DPRINTF(Cache
, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
120 } else if (pkt
->cmd
== MemCmd::StoreCondReq
) {
121 pkt
->cmd
= MemCmd::StoreCondFailReq
;
122 DPRINTF(Cache
, "Replacing StoreCondReq with StoreCondFailReq\n");
128 MSHR::TargetList::replaceUpgrades()
133 Iterator end_i
= end();
134 for (Iterator i
= begin(); i
!= end_i
; ++i
) {
135 replaceUpgrade(i
->pkt
);
143 MSHR::TargetList::clearDownstreamPending()
145 Iterator end_i
= end();
146 for (Iterator i
= begin(); i
!= end_i
; ++i
) {
147 if (i
->markedPending
) {
148 // Iterate over the SenderState stack and see if we find
149 // an MSHR entry. If we find one, clear the
150 // downstreamPending flag by calling
151 // clearDownstreamPending(). This recursively clears the
152 // downstreamPending flag in all caches this packet has
154 MSHR
*mshr
= i
->pkt
->findNextSenderState
<MSHR
>();
156 mshr
->clearDownstreamPending();
164 MSHR::TargetList::checkFunctional(PacketPtr pkt
)
166 Iterator end_i
= end();
167 for (Iterator i
= begin(); i
!= end_i
; ++i
) {
168 if (pkt
->checkFunctional(i
->pkt
)) {
179 print(std::ostream
&os
, int verbosity
, const std::string
&prefix
) const
181 ConstIterator end_i
= end();
182 for (ConstIterator i
= begin(); i
!= end_i
; ++i
) {
185 case Target::FromCPU
:
188 case Target::FromSnoop
:
191 case Target::FromPrefetcher
:
192 s
= "FromPrefetcher";
198 ccprintf(os
, "%s%s: ", prefix
, s
);
199 i
->pkt
->print(os
, verbosity
, "");
205 MSHR::allocate(Addr _addr
, int _size
, PacketPtr target
, Tick whenReady
,
210 isSecure
= target
->isSecure();
211 readyTime
= whenReady
;
215 _isUncacheable
= target
->req
->isUncacheable();
217 downstreamPending
= false;
219 assert(targets
.isReset());
220 // Don't know of a case where we would allocate a new MSHR for a
221 // snoop (mem-side request), so set source according to request here
222 Target::Source source
= (target
->cmd
== MemCmd::HardPFReq
) ?
223 Target::FromPrefetcher
: Target::FromCPU
;
224 targets
.add(target
, whenReady
, _order
, source
, true);
225 assert(deferredTargets
.isReset());
231 MSHR::clearDownstreamPending()
233 assert(downstreamPending
);
234 downstreamPending
= false;
235 // recursively clear flag on any MSHRs we will be forwarding
237 targets
.clearDownstreamPending();
241 MSHR::markInService(bool pending_dirty_resp
)
244 if (isForwardNoResponse()) {
245 // we just forwarded the request packet & don't expect a
246 // response, so get rid of it
247 assert(getNumTargets() == 1);
253 pendingDirty
= targets
.needsExclusive
|| pending_dirty_resp
;
254 postInvalidate
= postDowngrade
= false;
256 if (!downstreamPending
) {
257 // let upstream caches know that the request has made it to a
258 // level where it's going to get a response
259 targets
.clearDownstreamPending();
268 assert(targets
.empty());
269 targets
.resetFlags();
270 assert(deferredTargets
.isReset());
275 * Adds a target to an MSHR
278 MSHR::allocateTarget(PacketPtr pkt
, Tick whenReady
, Counter _order
)
280 // if there's a request already in service for this MSHR, we will
281 // have to defer the new target until after the response if any of
282 // the following are true:
283 // - there are other targets already deferred
284 // - there's a pending invalidate to be applied after the response
285 // comes back (but before this target is processed)
286 // - this target requires an exclusive block and either we're not
287 // getting an exclusive block back or we have already snooped
288 // another read request that will downgrade our exclusive block
291 // assume we'd never issue a prefetch when we've got an
293 assert(pkt
->cmd
!= MemCmd::HardPFReq
);
296 (!deferredTargets
.empty() || hasPostInvalidate() ||
297 (pkt
->needsExclusive() &&
298 (!isPendingDirty() || hasPostDowngrade() || isForward
)))) {
299 // need to put on deferred list
300 if (hasPostInvalidate())
302 deferredTargets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, true);
304 // No request outstanding, or still OK to append to
305 // outstanding request: append to regular target list. Only
306 // mark pending if current request hasn't been issued yet
307 // (isn't in service).
308 targets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, !inService
);
313 MSHR::handleSnoop(PacketPtr pkt
, Counter _order
)
315 DPRINTF(Cache
, "%s for %s addr %#llx size %d\n", __func__
,
316 pkt
->cmdString(), pkt
->getAddr(), pkt
->getSize());
317 if (!inService
|| (pkt
->isExpressSnoop() && downstreamPending
)) {
318 // Request has not been issued yet, or it's been issued
319 // locally but is buffered unissued at some downstream cache
320 // which is forwarding us this snoop. Either way, the packet
321 // we're snooping logically precedes this MSHR's request, so
322 // the snoop has no impact on the MSHR, but must be processed
323 // in the standard way by the cache. The only exception is
324 // that if we're an L2+ cache buffering an UpgradeReq from a
325 // higher-level cache, and the snoop is invalidating, then our
326 // buffered upgrades must be converted to read exclusives,
327 // since the upper-level cache no longer has a valid copy.
328 // That is, even though the upper-level cache got out on its
329 // local bus first, some other invalidating transaction
330 // reached the global bus before the upgrade did.
331 if (pkt
->needsExclusive()) {
332 targets
.replaceUpgrades();
333 deferredTargets
.replaceUpgrades();
339 // From here on down, the request issued by this MSHR logically
340 // precedes the request we're snooping.
341 if (pkt
->needsExclusive()) {
342 // snooped request still precedes the re-request we'll have to
343 // issue for deferred targets, if any...
344 deferredTargets
.replaceUpgrades();
347 if (hasPostInvalidate()) {
348 // a prior snoop has already appended an invalidation, so
349 // logically we don't have the block anymore; no need for
354 if (isPendingDirty() || pkt
->isInvalidate()) {
355 // We need to save and replay the packet in two cases:
356 // 1. We're awaiting an exclusive copy, so ownership is pending,
357 // and we need to respond after we receive data.
358 // 2. It's an invalidation (e.g., UpgradeReq), and we need
359 // to forward the snoop up the hierarchy after the current
360 // transaction completes.
362 // Actual target device (typ. a memory) will delete the
363 // packet on reception, so we need to save a copy here.
365 // Clear flags and also allocate new data as the original
366 // packet data storage may have been deleted by the time we
367 // get to send this packet.
368 PacketPtr cp_pkt
= new Packet(pkt
, true, true);
369 targets
.add(cp_pkt
, curTick(), _order
, Target::FromSnoop
,
370 downstreamPending
&& targets
.needsExclusive
);
372 if (isPendingDirty()) {
373 pkt
->assertMemInhibit();
374 pkt
->setSupplyExclusive();
377 if (pkt
->needsExclusive()) {
378 // This transaction will take away our pending copy
379 postInvalidate
= true;
383 if (!pkt
->needsExclusive()) {
384 // This transaction will get a read-shared copy, downgrading
385 // our copy if we had an exclusive one
386 postDowngrade
= true;
395 MSHR::promoteDeferredTargets()
397 assert(targets
.empty());
398 if (deferredTargets
.empty()) {
402 // swap targets & deferredTargets lists
403 std::swap(targets
, deferredTargets
);
405 // clear deferredTargets flags
406 deferredTargets
.resetFlags();
408 order
= targets
.front().order
;
409 readyTime
= std::max(curTick(), targets
.front().readyTime
);
416 MSHR::handleFill(Packet
*pkt
, CacheBlk
*blk
)
418 if (!pkt
->sharedAsserted()
419 && !(hasPostInvalidate() || hasPostDowngrade())
420 && deferredTargets
.needsExclusive
) {
421 // We got an exclusive response, but we have deferred targets
422 // which are waiting to request an exclusive copy (not because
423 // of a pending invalidate). This can happen if the original
424 // request was for a read-only (non-exclusive) block, but we
425 // got an exclusive copy anyway because of the E part of the
426 // MOESI/MESI protocol. Since we got the exclusive copy
427 // there's no need to defer the targets, so move them up to
428 // the regular target list.
429 assert(!targets
.needsExclusive
);
430 targets
.needsExclusive
= true;
431 // if any of the deferred targets were upper-level cache
432 // requests marked downstreamPending, need to clear that
433 assert(!downstreamPending
); // not pending here anymore
434 deferredTargets
.clearDownstreamPending();
435 // this clears out deferredTargets too
436 targets
.splice(targets
.end(), deferredTargets
);
437 deferredTargets
.resetFlags();
443 MSHR::checkFunctional(PacketPtr pkt
)
445 // For printing, we treat the MSHR as a whole as single entity.
446 // For other requests, we iterate over the individual targets
447 // since that's where the actual data lies.
448 if (pkt
->isPrint()) {
449 pkt
->checkFunctional(this, addr
, isSecure
, size
, NULL
);
452 return (targets
.checkFunctional(pkt
) ||
453 deferredTargets
.checkFunctional(pkt
));
459 MSHR::print(std::ostream
&os
, int verbosity
, const std::string
&prefix
) const
461 ccprintf(os
, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
462 prefix
, addr
, addr
+size
-1,
463 isSecure
? "s" : "ns",
464 isForward
? "Forward" : "",
465 isForwardNoResponse() ? "ForwNoResp" : "",
466 needsExclusive() ? "Excl" : "",
467 _isUncacheable
? "Unc" : "",
468 inService
? "InSvc" : "",
469 downstreamPending
? "DwnPend" : "",
470 hasPostInvalidate() ? "PostInv" : "",
471 hasPostDowngrade() ? "PostDowngr" : "");
473 ccprintf(os
, "%s Targets:\n", prefix
);
474 targets
.print(os
, verbosity
, prefix
+ " ");
475 if (!deferredTargets
.empty()) {
476 ccprintf(os
, "%s Deferred Targets:\n", prefix
);
477 deferredTargets
.print(os
, verbosity
, prefix
+ " ");