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15 * Copyright (c) 2010 Advanced Micro Devices, Inc.
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35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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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), blkAddr(0),
68 blkSize(0), isSecure(false), inService(false),
69 isForward(false), allocOnFill(false),
75 MSHR::TargetList::TargetList()
76 : needsExclusive(false), hasUpgrade(false)
81 MSHR::TargetList::add(PacketPtr pkt
, Tick readyTime
,
82 Counter order
, Target::Source source
, bool markPending
)
84 if (source
!= Target::FromSnoop
) {
85 if (pkt
->needsExclusive()) {
86 needsExclusive
= true;
89 // StoreCondReq is effectively an upgrade if it's in an MSHR
90 // since it would have been failed already if we didn't have a
92 if (pkt
->isUpgrade() || pkt
->cmd
== MemCmd::StoreCondReq
) {
98 // Iterate over the SenderState stack and see if we find
99 // an MSHR entry. If we do, set the downstreamPending
100 // flag. Otherwise, do nothing.
101 MSHR
*mshr
= pkt
->findNextSenderState
<MSHR
>();
103 assert(!mshr
->downstreamPending
);
104 mshr
->downstreamPending
= true;
106 // No need to clear downstreamPending later
111 emplace_back(pkt
, readyTime
, order
, source
, markPending
);
116 replaceUpgrade(PacketPtr pkt
)
118 if (pkt
->cmd
== MemCmd::UpgradeReq
) {
119 pkt
->cmd
= MemCmd::ReadExReq
;
120 DPRINTF(Cache
, "Replacing UpgradeReq with ReadExReq\n");
121 } else if (pkt
->cmd
== MemCmd::SCUpgradeReq
) {
122 pkt
->cmd
= MemCmd::SCUpgradeFailReq
;
123 DPRINTF(Cache
, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
124 } else if (pkt
->cmd
== MemCmd::StoreCondReq
) {
125 pkt
->cmd
= MemCmd::StoreCondFailReq
;
126 DPRINTF(Cache
, "Replacing StoreCondReq with StoreCondFailReq\n");
132 MSHR::TargetList::replaceUpgrades()
137 for (auto& t
: *this) {
138 replaceUpgrade(t
.pkt
);
146 MSHR::TargetList::clearDownstreamPending()
148 for (auto& t
: *this) {
149 if (t
.markedPending
) {
150 // Iterate over the SenderState stack and see if we find
151 // an MSHR entry. If we find one, clear the
152 // downstreamPending flag by calling
153 // clearDownstreamPending(). This recursively clears the
154 // downstreamPending flag in all caches this packet has
156 MSHR
*mshr
= t
.pkt
->findNextSenderState
<MSHR
>();
158 mshr
->clearDownstreamPending();
166 MSHR::TargetList::checkFunctional(PacketPtr pkt
)
168 for (auto& t
: *this) {
169 if (pkt
->checkFunctional(t
.pkt
)) {
179 MSHR::TargetList::print(std::ostream
&os
, int verbosity
,
180 const std::string
&prefix
) const
182 for (auto& t
: *this) {
185 case Target::FromCPU
:
188 case Target::FromSnoop
:
191 case Target::FromPrefetcher
:
192 s
= "FromPrefetcher";
198 ccprintf(os
, "%s%s: ", prefix
, s
);
199 t
.pkt
->print(os
, verbosity
, "");
205 MSHR::allocate(Addr blk_addr
, unsigned blk_size
, PacketPtr target
,
206 Tick when_ready
, Counter _order
, bool alloc_on_fill
)
210 isSecure
= target
->isSecure();
211 readyTime
= when_ready
;
215 allocOnFill
= alloc_on_fill
;
216 _isUncacheable
= target
->req
->isUncacheable();
218 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
, when_ready
, _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
,
281 // assume we'd never issue a prefetch when we've got an
283 assert(pkt
->cmd
!= MemCmd::HardPFReq
);
285 // uncacheable accesses always allocate a new MSHR, and cacheable
286 // accesses ignore any uncacheable MSHRs, thus we should never
287 // have targets addded if originally allocated uncacheable
288 assert(!_isUncacheable
);
290 // potentially re-evaluate whether we should allocate on a fill or
292 allocOnFill
= allocOnFill
|| alloc_on_fill
;
294 // if there's a request already in service for this MSHR, we will
295 // have to defer the new target until after the response if any of
296 // the following are true:
297 // - there are other targets already deferred
298 // - there's a pending invalidate to be applied after the response
299 // comes back (but before this target is processed)
300 // - this target requires an exclusive block and either we're not
301 // getting an exclusive block back or we have already snooped
302 // another read request that will downgrade our exclusive block
305 (!deferredTargets
.empty() || hasPostInvalidate() ||
306 (pkt
->needsExclusive() &&
307 (!isPendingDirty() || hasPostDowngrade() || isForward
)))) {
308 // need to put on deferred list
309 if (hasPostInvalidate())
311 deferredTargets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, true);
313 // No request outstanding, or still OK to append to
314 // outstanding request: append to regular target list. Only
315 // mark pending if current request hasn't been issued yet
316 // (isn't in service).
317 targets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, !inService
);
322 MSHR::handleSnoop(PacketPtr pkt
, Counter _order
)
324 DPRINTF(Cache
, "%s for %s addr %#llx size %d\n", __func__
,
325 pkt
->cmdString(), pkt
->getAddr(), pkt
->getSize());
327 // when we snoop packets the needsExclusive and isInvalidate flags
328 // should always be the same, however, this assumes that we never
329 // snoop writes as they are currently not marked as invalidations
330 panic_if(pkt
->needsExclusive() != pkt
->isInvalidate(),
331 "%s got snoop %s to addr %#llx where needsExclusive, "
332 "does not match isInvalidate", name(), pkt
->cmdString(),
335 if (!inService
|| (pkt
->isExpressSnoop() && downstreamPending
)) {
336 // Request has not been issued yet, or it's been issued
337 // locally but is buffered unissued at some downstream cache
338 // which is forwarding us this snoop. Either way, the packet
339 // we're snooping logically precedes this MSHR's request, so
340 // the snoop has no impact on the MSHR, but must be processed
341 // in the standard way by the cache. The only exception is
342 // that if we're an L2+ cache buffering an UpgradeReq from a
343 // higher-level cache, and the snoop is invalidating, then our
344 // buffered upgrades must be converted to read exclusives,
345 // since the upper-level cache no longer has a valid copy.
346 // That is, even though the upper-level cache got out on its
347 // local bus first, some other invalidating transaction
348 // reached the global bus before the upgrade did.
349 if (pkt
->needsExclusive()) {
350 targets
.replaceUpgrades();
351 deferredTargets
.replaceUpgrades();
357 // From here on down, the request issued by this MSHR logically
358 // precedes the request we're snooping.
359 if (pkt
->needsExclusive()) {
360 // snooped request still precedes the re-request we'll have to
361 // issue for deferred targets, if any...
362 deferredTargets
.replaceUpgrades();
365 if (hasPostInvalidate()) {
366 // a prior snoop has already appended an invalidation, so
367 // logically we don't have the block anymore; no need for
372 if (isPendingDirty() || pkt
->isInvalidate()) {
373 // We need to save and replay the packet in two cases:
374 // 1. We're awaiting an exclusive copy, so ownership is pending,
375 // and we need to deal with the snoop after we receive data.
376 // 2. It's an invalidation (e.g., UpgradeReq), and we need
377 // to forward the snoop up the hierarchy after the current
378 // transaction completes.
380 // Start by determining if we will eventually respond or not,
381 // matching the conditions checked in Cache::handleSnoop
382 bool will_respond
= isPendingDirty() && pkt
->needsResponse() &&
383 pkt
->cmd
!= MemCmd::InvalidateReq
;
385 // The packet we are snooping may be deleted by the time we
386 // actually process the target, and we consequently need to
387 // save a copy here. Clear flags and also allocate new data as
388 // the original packet data storage may have been deleted by
389 // the time we get to process this packet. In the cases where
390 // we are not responding after handling the snoop we also need
391 // to create a copy of the request to be on the safe side. In
392 // the latter case the cache is responsible for deleting both
393 // the packet and the request as part of handling the deferred
395 PacketPtr cp_pkt
= will_respond
? new Packet(pkt
, true, true) :
396 new Packet(new Request(*pkt
->req
), pkt
->cmd
);
398 if (isPendingDirty()) {
399 // The new packet will need to get the response from the
400 // MSHR already queued up here
401 pkt
->assertMemInhibit();
402 // in the case of an uncacheable request there is no need
403 // to set the exclusive flag, but since the recipient does
404 // not care there is no harm in doing so
405 pkt
->setSupplyExclusive();
407 targets
.add(cp_pkt
, curTick(), _order
, Target::FromSnoop
,
408 downstreamPending
&& targets
.needsExclusive
);
410 if (pkt
->needsExclusive()) {
411 // This transaction will take away our pending copy
412 postInvalidate
= true;
416 if (!pkt
->needsExclusive() && !pkt
->req
->isUncacheable()) {
417 // This transaction will get a read-shared copy, downgrading
418 // our copy if we had an exclusive one
419 postDowngrade
= true;
428 MSHR::promoteDeferredTargets()
430 assert(targets
.empty());
431 if (deferredTargets
.empty()) {
435 // swap targets & deferredTargets lists
436 std::swap(targets
, deferredTargets
);
438 // clear deferredTargets flags
439 deferredTargets
.resetFlags();
441 order
= targets
.front().order
;
442 readyTime
= std::max(curTick(), targets
.front().readyTime
);
449 MSHR::promoteExclusive()
451 if (deferredTargets
.needsExclusive
&&
452 !(hasPostInvalidate() || hasPostDowngrade())) {
453 // We got an exclusive response, but we have deferred targets
454 // which are waiting to request an exclusive copy (not because
455 // of a pending invalidate). This can happen if the original
456 // request was for a read-only (non-exclusive) block, but we
457 // got an exclusive copy anyway because of the E part of the
458 // MOESI/MESI protocol. Since we got the exclusive copy
459 // there's no need to defer the targets, so move them up to
460 // the regular target list.
461 assert(!targets
.needsExclusive
);
462 targets
.needsExclusive
= true;
463 // if any of the deferred targets were upper-level cache
464 // requests marked downstreamPending, need to clear that
465 assert(!downstreamPending
); // not pending here anymore
466 deferredTargets
.clearDownstreamPending();
467 // this clears out deferredTargets too
468 targets
.splice(targets
.end(), deferredTargets
);
469 deferredTargets
.resetFlags();
475 MSHR::checkFunctional(PacketPtr pkt
)
477 // For printing, we treat the MSHR as a whole as single entity.
478 // For other requests, we iterate over the individual targets
479 // since that's where the actual data lies.
480 if (pkt
->isPrint()) {
481 pkt
->checkFunctional(this, blkAddr
, isSecure
, blkSize
, NULL
);
484 return (targets
.checkFunctional(pkt
) ||
485 deferredTargets
.checkFunctional(pkt
));
491 MSHR::print(std::ostream
&os
, int verbosity
, const std::string
&prefix
) const
493 ccprintf(os
, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
494 prefix
, blkAddr
, blkAddr
+ blkSize
- 1,
495 isSecure
? "s" : "ns",
496 isForward
? "Forward" : "",
497 allocOnFill
? "AllocOnFill" : "",
498 isForwardNoResponse() ? "ForwNoResp" : "",
499 needsExclusive() ? "Excl" : "",
500 _isUncacheable
? "Unc" : "",
501 inService
? "InSvc" : "",
502 downstreamPending
? "DwnPend" : "",
503 hasPostInvalidate() ? "PostInv" : "",
504 hasPostDowngrade() ? "PostDowngr" : "");
506 ccprintf(os
, "%s Targets:\n", prefix
);
507 targets
.print(os
, verbosity
, prefix
+ " ");
508 if (!deferredTargets
.empty()) {
509 ccprintf(os
, "%s Deferred Targets:\n", prefix
);
510 deferredTargets
.print(os
, verbosity
, prefix
+ " ");