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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), 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;
105 // No need to clear downstreamPending later
110 emplace_back(pkt
, readyTime
, order
, source
, markPending
);
115 replaceUpgrade(PacketPtr pkt
)
117 if (pkt
->cmd
== MemCmd::UpgradeReq
) {
118 pkt
->cmd
= MemCmd::ReadExReq
;
119 DPRINTF(Cache
, "Replacing UpgradeReq with ReadExReq\n");
120 } else if (pkt
->cmd
== MemCmd::SCUpgradeReq
) {
121 pkt
->cmd
= MemCmd::SCUpgradeFailReq
;
122 DPRINTF(Cache
, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
123 } else if (pkt
->cmd
== MemCmd::StoreCondReq
) {
124 pkt
->cmd
= MemCmd::StoreCondFailReq
;
125 DPRINTF(Cache
, "Replacing StoreCondReq with StoreCondFailReq\n");
131 MSHR::TargetList::replaceUpgrades()
136 for (auto& t
: *this) {
137 replaceUpgrade(t
.pkt
);
145 MSHR::TargetList::clearDownstreamPending()
147 for (auto& t
: *this) {
148 if (t
.markedPending
) {
149 // Iterate over the SenderState stack and see if we find
150 // an MSHR entry. If we find one, clear the
151 // downstreamPending flag by calling
152 // clearDownstreamPending(). This recursively clears the
153 // downstreamPending flag in all caches this packet has
155 MSHR
*mshr
= t
.pkt
->findNextSenderState
<MSHR
>();
157 mshr
->clearDownstreamPending();
165 MSHR::TargetList::checkFunctional(PacketPtr pkt
)
167 for (auto& t
: *this) {
168 if (pkt
->checkFunctional(t
.pkt
)) {
178 MSHR::TargetList::print(std::ostream
&os
, int verbosity
,
179 const std::string
&prefix
) const
181 for (auto& t
: *this) {
184 case Target::FromCPU
:
187 case Target::FromSnoop
:
190 case Target::FromPrefetcher
:
191 s
= "FromPrefetcher";
197 ccprintf(os
, "%s%s: ", prefix
, s
);
198 t
.pkt
->print(os
, verbosity
, "");
204 MSHR::allocate(Addr blk_addr
, unsigned blk_size
, PacketPtr target
,
205 Tick when_ready
, Counter _order
)
209 isSecure
= target
->isSecure();
210 readyTime
= when_ready
;
214 _isUncacheable
= target
->req
->isUncacheable();
216 downstreamPending
= false;
218 assert(targets
.isReset());
219 // Don't know of a case where we would allocate a new MSHR for a
220 // snoop (mem-side request), so set source according to request here
221 Target::Source source
= (target
->cmd
== MemCmd::HardPFReq
) ?
222 Target::FromPrefetcher
: Target::FromCPU
;
223 targets
.add(target
, when_ready
, _order
, source
, true);
224 assert(deferredTargets
.isReset());
230 MSHR::clearDownstreamPending()
232 assert(downstreamPending
);
233 downstreamPending
= false;
234 // recursively clear flag on any MSHRs we will be forwarding
236 targets
.clearDownstreamPending();
240 MSHR::markInService(bool pending_dirty_resp
)
243 if (isForwardNoResponse()) {
244 // we just forwarded the request packet & don't expect a
245 // response, so get rid of it
246 assert(getNumTargets() == 1);
252 pendingDirty
= targets
.needsExclusive
|| pending_dirty_resp
;
253 postInvalidate
= postDowngrade
= false;
255 if (!downstreamPending
) {
256 // let upstream caches know that the request has made it to a
257 // level where it's going to get a response
258 targets
.clearDownstreamPending();
267 assert(targets
.empty());
268 targets
.resetFlags();
269 assert(deferredTargets
.isReset());
274 * Adds a target to an MSHR
277 MSHR::allocateTarget(PacketPtr pkt
, Tick whenReady
, Counter _order
)
279 // assume we'd never issue a prefetch when we've got an
281 assert(pkt
->cmd
!= MemCmd::HardPFReq
);
283 // uncacheable accesses always allocate a new MSHR, and cacheable
284 // accesses ignore any uncacheable MSHRs, thus we should never
285 // have targets addded if originally allocated uncacheable
286 assert(!_isUncacheable
);
288 // if there's a request already in service for this MSHR, we will
289 // have to defer the new target until after the response if any of
290 // the following are true:
291 // - there are other targets already deferred
292 // - there's a pending invalidate to be applied after the response
293 // comes back (but before this target is processed)
294 // - this target requires an exclusive block and either we're not
295 // getting an exclusive block back or we have already snooped
296 // another read request that will downgrade our exclusive block
299 (!deferredTargets
.empty() || hasPostInvalidate() ||
300 (pkt
->needsExclusive() &&
301 (!isPendingDirty() || hasPostDowngrade() || isForward
)))) {
302 // need to put on deferred list
303 if (hasPostInvalidate())
305 deferredTargets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, true);
307 // No request outstanding, or still OK to append to
308 // outstanding request: append to regular target list. Only
309 // mark pending if current request hasn't been issued yet
310 // (isn't in service).
311 targets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, !inService
);
316 MSHR::handleSnoop(PacketPtr pkt
, Counter _order
)
318 DPRINTF(Cache
, "%s for %s addr %#llx size %d\n", __func__
,
319 pkt
->cmdString(), pkt
->getAddr(), pkt
->getSize());
320 if (!inService
|| (pkt
->isExpressSnoop() && downstreamPending
)) {
321 // Request has not been issued yet, or it's been issued
322 // locally but is buffered unissued at some downstream cache
323 // which is forwarding us this snoop. Either way, the packet
324 // we're snooping logically precedes this MSHR's request, so
325 // the snoop has no impact on the MSHR, but must be processed
326 // in the standard way by the cache. The only exception is
327 // that if we're an L2+ cache buffering an UpgradeReq from a
328 // higher-level cache, and the snoop is invalidating, then our
329 // buffered upgrades must be converted to read exclusives,
330 // since the upper-level cache no longer has a valid copy.
331 // That is, even though the upper-level cache got out on its
332 // local bus first, some other invalidating transaction
333 // reached the global bus before the upgrade did.
334 if (pkt
->needsExclusive()) {
335 targets
.replaceUpgrades();
336 deferredTargets
.replaceUpgrades();
342 // From here on down, the request issued by this MSHR logically
343 // precedes the request we're snooping.
344 if (pkt
->needsExclusive()) {
345 // snooped request still precedes the re-request we'll have to
346 // issue for deferred targets, if any...
347 deferredTargets
.replaceUpgrades();
350 if (hasPostInvalidate()) {
351 // a prior snoop has already appended an invalidation, so
352 // logically we don't have the block anymore; no need for
357 if (isPendingDirty() || pkt
->isInvalidate()) {
358 // We need to save and replay the packet in two cases:
359 // 1. We're awaiting an exclusive copy, so ownership is pending,
360 // and we need to respond after we receive data.
361 // 2. It's an invalidation (e.g., UpgradeReq), and we need
362 // to forward the snoop up the hierarchy after the current
363 // transaction completes.
365 // Actual target device (typ. a memory) will delete the
366 // packet on reception, so we need to save a copy here.
368 // Clear flags and also allocate new data as the original
369 // packet data storage may have been deleted by the time we
370 // get to send this packet.
371 PacketPtr cp_pkt
= nullptr;
373 if (isPendingDirty()) {
374 // Case 1: The new packet will need to get the response from the
375 // MSHR already queued up here
376 cp_pkt
= new Packet(pkt
, true, true);
377 pkt
->assertMemInhibit();
378 // in the case of an uncacheable request there is no need
379 // to set the exclusive flag, but since the recipient does
380 // not care there is no harm in doing so
381 pkt
->setSupplyExclusive();
383 // Case 2: We only need to buffer the packet for information
384 // purposes; the original request can proceed without waiting
385 // => Create a copy of the request, as that may get deallocated as
387 cp_pkt
= new Packet(new Request(*pkt
->req
), pkt
->cmd
);
388 DPRINTF(Cache
, "Copying packet %p -> %p and request %p -> %p\n",
389 pkt
, cp_pkt
, pkt
->req
, cp_pkt
->req
);
391 targets
.add(cp_pkt
, curTick(), _order
, Target::FromSnoop
,
392 downstreamPending
&& targets
.needsExclusive
);
394 if (pkt
->needsExclusive()) {
395 // This transaction will take away our pending copy
396 postInvalidate
= true;
400 if (!pkt
->needsExclusive() && !pkt
->req
->isUncacheable()) {
401 // This transaction will get a read-shared copy, downgrading
402 // our copy if we had an exclusive one
403 postDowngrade
= true;
412 MSHR::promoteDeferredTargets()
414 assert(targets
.empty());
415 if (deferredTargets
.empty()) {
419 // swap targets & deferredTargets lists
420 std::swap(targets
, deferredTargets
);
422 // clear deferredTargets flags
423 deferredTargets
.resetFlags();
425 order
= targets
.front().order
;
426 readyTime
= std::max(curTick(), targets
.front().readyTime
);
433 MSHR::handleFill(PacketPtr pkt
, CacheBlk
*blk
)
435 if (!pkt
->sharedAsserted()
436 && !(hasPostInvalidate() || hasPostDowngrade())
437 && deferredTargets
.needsExclusive
) {
438 // We got an exclusive response, but we have deferred targets
439 // which are waiting to request an exclusive copy (not because
440 // of a pending invalidate). This can happen if the original
441 // request was for a read-only (non-exclusive) block, but we
442 // got an exclusive copy anyway because of the E part of the
443 // MOESI/MESI protocol. Since we got the exclusive copy
444 // there's no need to defer the targets, so move them up to
445 // the regular target list.
446 assert(!targets
.needsExclusive
);
447 targets
.needsExclusive
= true;
448 // if any of the deferred targets were upper-level cache
449 // requests marked downstreamPending, need to clear that
450 assert(!downstreamPending
); // not pending here anymore
451 deferredTargets
.clearDownstreamPending();
452 // this clears out deferredTargets too
453 targets
.splice(targets
.end(), deferredTargets
);
454 deferredTargets
.resetFlags();
460 MSHR::checkFunctional(PacketPtr pkt
)
462 // For printing, we treat the MSHR as a whole as single entity.
463 // For other requests, we iterate over the individual targets
464 // since that's where the actual data lies.
465 if (pkt
->isPrint()) {
466 pkt
->checkFunctional(this, blkAddr
, isSecure
, blkSize
, NULL
);
469 return (targets
.checkFunctional(pkt
) ||
470 deferredTargets
.checkFunctional(pkt
));
476 MSHR::print(std::ostream
&os
, int verbosity
, const std::string
&prefix
) const
478 ccprintf(os
, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
479 prefix
, blkAddr
, blkAddr
+ blkSize
- 1,
480 isSecure
? "s" : "ns",
481 isForward
? "Forward" : "",
482 isForwardNoResponse() ? "ForwNoResp" : "",
483 needsExclusive() ? "Excl" : "",
484 _isUncacheable
? "Unc" : "",
485 inService
? "InSvc" : "",
486 downstreamPending
? "DwnPend" : "",
487 hasPostInvalidate() ? "PostInv" : "",
488 hasPostDowngrade() ? "PostDowngr" : "");
490 ccprintf(os
, "%s Targets:\n", prefix
);
491 targets
.print(os
, verbosity
, prefix
+ " ");
492 if (!deferredTargets
.empty()) {
493 ccprintf(os
, "%s Deferred Targets:\n", prefix
);
494 deferredTargets
.print(os
, verbosity
, prefix
+ " ");