2 * Copyright (c) 2012-2013, 2015 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.
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),
70 threadNum(InvalidThreadID
), data(NULL
)
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;
220 assert(targets
.isReset());
221 // Don't know of a case where we would allocate a new MSHR for a
222 // snoop (mem-side request), so set source according to request here
223 Target::Source source
= (target
->cmd
== MemCmd::HardPFReq
) ?
224 Target::FromPrefetcher
: Target::FromCPU
;
225 targets
.add(target
, when_ready
, _order
, source
, true);
226 assert(deferredTargets
.isReset());
232 MSHR::clearDownstreamPending()
234 assert(downstreamPending
);
235 downstreamPending
= false;
236 // recursively clear flag on any MSHRs we will be forwarding
238 targets
.clearDownstreamPending();
242 MSHR::markInService(bool pending_dirty_resp
)
245 if (isForwardNoResponse()) {
246 // we just forwarded the request packet & don't expect a
247 // response, so get rid of it
248 assert(getNumTargets() == 1);
254 pendingDirty
= targets
.needsExclusive
|| pending_dirty_resp
;
255 postInvalidate
= postDowngrade
= false;
257 if (!downstreamPending
) {
258 // let upstream caches know that the request has made it to a
259 // level where it's going to get a response
260 targets
.clearDownstreamPending();
269 assert(targets
.empty());
270 targets
.resetFlags();
271 assert(deferredTargets
.isReset());
276 * Adds a target to an MSHR
279 MSHR::allocateTarget(PacketPtr pkt
, Tick whenReady
, Counter _order
,
282 // assume we'd never issue a prefetch when we've got an
284 assert(pkt
->cmd
!= MemCmd::HardPFReq
);
286 // uncacheable accesses always allocate a new MSHR, and cacheable
287 // accesses ignore any uncacheable MSHRs, thus we should never
288 // have targets addded if originally allocated uncacheable
289 assert(!_isUncacheable
);
291 // potentially re-evaluate whether we should allocate on a fill or
293 allocOnFill
= allocOnFill
|| alloc_on_fill
;
295 // if there's a request already in service for this MSHR, we will
296 // have to defer the new target until after the response if any of
297 // the following are true:
298 // - there are other targets already deferred
299 // - there's a pending invalidate to be applied after the response
300 // comes back (but before this target is processed)
301 // - this target requires an exclusive block and either we're not
302 // getting an exclusive block back or we have already snooped
303 // another read request that will downgrade our exclusive block
306 (!deferredTargets
.empty() || hasPostInvalidate() ||
307 (pkt
->needsExclusive() &&
308 (!isPendingDirty() || hasPostDowngrade() || isForward
)))) {
309 // need to put on deferred list
310 if (hasPostInvalidate())
312 deferredTargets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, true);
314 // No request outstanding, or still OK to append to
315 // outstanding request: append to regular target list. Only
316 // mark pending if current request hasn't been issued yet
317 // (isn't in service).
318 targets
.add(pkt
, whenReady
, _order
, Target::FromCPU
, !inService
);
323 MSHR::handleSnoop(PacketPtr pkt
, Counter _order
)
325 DPRINTF(Cache
, "%s for %s addr %#llx size %d\n", __func__
,
326 pkt
->cmdString(), pkt
->getAddr(), pkt
->getSize());
327 if (!inService
|| (pkt
->isExpressSnoop() && downstreamPending
)) {
328 // Request has not been issued yet, or it's been issued
329 // locally but is buffered unissued at some downstream cache
330 // which is forwarding us this snoop. Either way, the packet
331 // we're snooping logically precedes this MSHR's request, so
332 // the snoop has no impact on the MSHR, but must be processed
333 // in the standard way by the cache. The only exception is
334 // that if we're an L2+ cache buffering an UpgradeReq from a
335 // higher-level cache, and the snoop is invalidating, then our
336 // buffered upgrades must be converted to read exclusives,
337 // since the upper-level cache no longer has a valid copy.
338 // That is, even though the upper-level cache got out on its
339 // local bus first, some other invalidating transaction
340 // reached the global bus before the upgrade did.
341 if (pkt
->needsExclusive()) {
342 targets
.replaceUpgrades();
343 deferredTargets
.replaceUpgrades();
349 // From here on down, the request issued by this MSHR logically
350 // precedes the request we're snooping.
351 if (pkt
->needsExclusive()) {
352 // snooped request still precedes the re-request we'll have to
353 // issue for deferred targets, if any...
354 deferredTargets
.replaceUpgrades();
357 if (hasPostInvalidate()) {
358 // a prior snoop has already appended an invalidation, so
359 // logically we don't have the block anymore; no need for
364 if (isPendingDirty() || pkt
->isInvalidate()) {
365 // We need to save and replay the packet in two cases:
366 // 1. We're awaiting an exclusive copy, so ownership is pending,
367 // and we need to deal with the snoop after we receive data.
368 // 2. It's an invalidation (e.g., UpgradeReq), and we need
369 // to forward the snoop up the hierarchy after the current
370 // transaction completes.
372 // Start by determining if we will eventually respond or not,
373 // matching the conditions checked in Cache::handleSnoop
374 bool will_respond
= isPendingDirty() && pkt
->needsResponse() &&
375 pkt
->cmd
!= MemCmd::InvalidateReq
;
377 // The packet we are snooping may be deleted by the time we
378 // actually process the target, and we consequently need to
379 // save a copy here. Clear flags and also allocate new data as
380 // the original packet data storage may have been deleted by
381 // the time we get to process this packet. In the cases where
382 // we are not responding after handling the snoop we also need
383 // to create a copy of the request to be on the safe side. In
384 // the latter case the cache is responsible for deleting both
385 // the packet and the request as part of handling the deferred
387 PacketPtr cp_pkt
= will_respond
? new Packet(pkt
, true, true) :
388 new Packet(new Request(*pkt
->req
), pkt
->cmd
);
390 if (isPendingDirty()) {
391 // The new packet will need to get the response from the
392 // MSHR already queued up here
393 pkt
->assertMemInhibit();
394 // in the case of an uncacheable request there is no need
395 // to set the exclusive flag, but since the recipient does
396 // not care there is no harm in doing so
397 pkt
->setSupplyExclusive();
399 targets
.add(cp_pkt
, curTick(), _order
, Target::FromSnoop
,
400 downstreamPending
&& targets
.needsExclusive
);
402 if (pkt
->needsExclusive()) {
403 // This transaction will take away our pending copy
404 postInvalidate
= true;
408 if (!pkt
->needsExclusive() && !pkt
->req
->isUncacheable()) {
409 // This transaction will get a read-shared copy, downgrading
410 // our copy if we had an exclusive one
411 postDowngrade
= true;
420 MSHR::promoteDeferredTargets()
422 assert(targets
.empty());
423 if (deferredTargets
.empty()) {
427 // swap targets & deferredTargets lists
428 std::swap(targets
, deferredTargets
);
430 // clear deferredTargets flags
431 deferredTargets
.resetFlags();
433 order
= targets
.front().order
;
434 readyTime
= std::max(curTick(), targets
.front().readyTime
);
441 MSHR::promoteExclusive()
443 if (deferredTargets
.needsExclusive
&&
444 !(hasPostInvalidate() || hasPostDowngrade())) {
445 // We got an exclusive response, but we have deferred targets
446 // which are waiting to request an exclusive copy (not because
447 // of a pending invalidate). This can happen if the original
448 // request was for a read-only (non-exclusive) block, but we
449 // got an exclusive copy anyway because of the E part of the
450 // MOESI/MESI protocol. Since we got the exclusive copy
451 // there's no need to defer the targets, so move them up to
452 // the regular target list.
453 assert(!targets
.needsExclusive
);
454 targets
.needsExclusive
= true;
455 // if any of the deferred targets were upper-level cache
456 // requests marked downstreamPending, need to clear that
457 assert(!downstreamPending
); // not pending here anymore
458 deferredTargets
.clearDownstreamPending();
459 // this clears out deferredTargets too
460 targets
.splice(targets
.end(), deferredTargets
);
461 deferredTargets
.resetFlags();
467 MSHR::checkFunctional(PacketPtr pkt
)
469 // For printing, we treat the MSHR as a whole as single entity.
470 // For other requests, we iterate over the individual targets
471 // since that's where the actual data lies.
472 if (pkt
->isPrint()) {
473 pkt
->checkFunctional(this, blkAddr
, isSecure
, blkSize
, NULL
);
476 return (targets
.checkFunctional(pkt
) ||
477 deferredTargets
.checkFunctional(pkt
));
483 MSHR::print(std::ostream
&os
, int verbosity
, const std::string
&prefix
) const
485 ccprintf(os
, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
486 prefix
, blkAddr
, blkAddr
+ blkSize
- 1,
487 isSecure
? "s" : "ns",
488 isForward
? "Forward" : "",
489 allocOnFill
? "AllocOnFill" : "",
490 isForwardNoResponse() ? "ForwNoResp" : "",
491 needsExclusive() ? "Excl" : "",
492 _isUncacheable
? "Unc" : "",
493 inService
? "InSvc" : "",
494 downstreamPending
? "DwnPend" : "",
495 hasPostInvalidate() ? "PostInv" : "",
496 hasPostDowngrade() ? "PostDowngr" : "");
498 ccprintf(os
, "%s Targets:\n", prefix
);
499 targets
.print(os
, verbosity
, prefix
+ " ");
500 if (!deferredTargets
.empty()) {
501 ccprintf(os
, "%s Deferred Targets:\n", prefix
);
502 deferredTargets
.print(os
, verbosity
, prefix
+ " ");