1/*
2 * Copyright (c) 2012-2013, 2015-2016 ARM Limited
3 * All rights reserved.
4 *
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.
13 *
14 * Copyright (c) 2002-2005 The Regents of The University of Michigan
15 * Copyright (c) 2010 Advanced Micro Devices, Inc.
16 * All rights reserved.
17 *
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.
28 *
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.
40 *
41 * Authors: Erik Hallnor
42 * Dave Greene
43 */
44
45/**
46 * @file
47 * Miss Status and Handling Register (MSHR) definitions.
48 */
49
50#include "mem/cache/mshr.hh"
51
52#include <algorithm>
53#include <cassert>
54#include <string>
55#include <vector>
56
57#include "base/misc.hh"
58#include "base/types.hh"
59#include "debug/Cache.hh"
60#include "mem/cache/cache.hh"
61#include "sim/core.hh"
62
63using namespace std;
64
65MSHR::MSHR() : downstreamPending(false),
66 pendingModified(false),
67 postInvalidate(false), postDowngrade(false),
68 isForward(false)
69{
70}
71
72MSHR::TargetList::TargetList()
73 : needsWritable(false), hasUpgrade(false), allocOnFill(false)
74{}
75
76
77void
78MSHR::TargetList::updateFlags(PacketPtr pkt, Target::Source source,
79 bool alloc_on_fill)
80{
81 if (source != Target::FromSnoop) {
82 if (pkt->needsWritable()) {
83 needsWritable = true;
84 }
85
86 // StoreCondReq is effectively an upgrade if it's in an MSHR
87 // since it would have been failed already if we didn't have a
88 // read-only copy
89 if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) {
90 hasUpgrade = true;
91 }
92
93 // potentially re-evaluate whether we should allocate on a fill or
94 // not
95 allocOnFill = allocOnFill || alloc_on_fill;
96 }
97}
98
99void
100MSHR::TargetList::populateFlags()
101{
102 resetFlags();
103 for (auto& t: *this) {
104 updateFlags(t.pkt, t.source, t.allocOnFill);
105 }
106}
107
108inline void
109MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
110 Counter order, Target::Source source, bool markPending,
111 bool alloc_on_fill)
112{
113 updateFlags(pkt, source, alloc_on_fill);
114 if (markPending) {
115 // Iterate over the SenderState stack and see if we find
116 // an MSHR entry. If we do, set the downstreamPending
117 // flag. Otherwise, do nothing.
118 MSHR *mshr = pkt->findNextSenderState<MSHR>();
119 if (mshr != nullptr) {
120 assert(!mshr->downstreamPending);
121 mshr->downstreamPending = true;
122 } else {
123 // No need to clear downstreamPending later
124 markPending = false;
125 }
126 }
127
128 emplace_back(pkt, readyTime, order, source, markPending, alloc_on_fill);
129}
130
131
132static void
133replaceUpgrade(PacketPtr pkt)
134{
135 // remember if the current packet has data allocated
136 bool has_data = pkt->hasData() || pkt->hasRespData();
137
138 if (pkt->cmd == MemCmd::UpgradeReq) {
139 pkt->cmd = MemCmd::ReadExReq;
140 DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n");
141 } else if (pkt->cmd == MemCmd::SCUpgradeReq) {
142 pkt->cmd = MemCmd::SCUpgradeFailReq;
143 DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
144 } else if (pkt->cmd == MemCmd::StoreCondReq) {
145 pkt->cmd = MemCmd::StoreCondFailReq;
146 DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n");
147 }
148
149 if (!has_data) {
150 // there is no sensible way of setting the data field if the
151 // new command actually would carry data
152 assert(!pkt->hasData());
153
154 if (pkt->hasRespData()) {
155 // we went from a packet that had no data (neither request,
156 // nor response), to one that does, and therefore we need to
157 // actually allocate space for the data payload
158 pkt->allocate();
159 }
160 }
161}
162
163
164void
165MSHR::TargetList::replaceUpgrades()
166{
167 if (!hasUpgrade)
168 return;
169
170 for (auto& t : *this) {
171 replaceUpgrade(t.pkt);
172 }
173
174 hasUpgrade = false;
175}
176
177
178void
179MSHR::TargetList::clearDownstreamPending()
180{
181 for (auto& t : *this) {
182 if (t.markedPending) {
183 // Iterate over the SenderState stack and see if we find
184 // an MSHR entry. If we find one, clear the
185 // downstreamPending flag by calling
186 // clearDownstreamPending(). This recursively clears the
187 // downstreamPending flag in all caches this packet has
188 // passed through.
189 MSHR *mshr = t.pkt->findNextSenderState<MSHR>();
190 if (mshr != nullptr) {
191 mshr->clearDownstreamPending();
192 }
193 }
194 }
195}
196
197
198bool
199MSHR::TargetList::checkFunctional(PacketPtr pkt)
200{
201 for (auto& t : *this) {
202 if (pkt->checkFunctional(t.pkt)) {
203 return true;
204 }
205 }
206
207 return false;
208}
209
210
211void
212MSHR::TargetList::print(std::ostream &os, int verbosity,
213 const std::string &prefix) const
214{
215 for (auto& t : *this) {
216 const char *s;
217 switch (t.source) {
218 case Target::FromCPU:
219 s = "FromCPU";
220 break;
221 case Target::FromSnoop:
222 s = "FromSnoop";
223 break;
224 case Target::FromPrefetcher:
225 s = "FromPrefetcher";
226 break;
227 default:
228 s = "";
229 break;
230 }
231 ccprintf(os, "%s%s: ", prefix, s);
232 t.pkt->print(os, verbosity, "");
233 }
234}
235
236
237void
238MSHR::allocate(Addr blk_addr, unsigned blk_size, PacketPtr target,
239 Tick when_ready, Counter _order, bool alloc_on_fill)
240{
241 blkAddr = blk_addr;
242 blkSize = blk_size;
243 isSecure = target->isSecure();
244 readyTime = when_ready;
245 order = _order;
246 assert(target);
247 isForward = false;
248 _isUncacheable = target->req->isUncacheable();
249 inService = false;
250 downstreamPending = false;
251 assert(targets.isReset());
252 // Don't know of a case where we would allocate a new MSHR for a
253 // snoop (mem-side request), so set source according to request here
254 Target::Source source = (target->cmd == MemCmd::HardPFReq) ?
255 Target::FromPrefetcher : Target::FromCPU;
256 targets.add(target, when_ready, _order, source, true, alloc_on_fill);
257 assert(deferredTargets.isReset());
258}
259
260
261void
262MSHR::clearDownstreamPending()
263{
264 assert(downstreamPending);
265 downstreamPending = false;
266 // recursively clear flag on any MSHRs we will be forwarding
267 // responses to
268 targets.clearDownstreamPending();
269}
270
271void
272MSHR::markInService(bool pending_modified_resp)
273{
274 assert(!inService);
275
276 inService = true;
277 pendingModified = targets.needsWritable || pending_modified_resp;
278 postInvalidate = postDowngrade = false;
279
280 if (!downstreamPending) {
281 // let upstream caches know that the request has made it to a
282 // level where it's going to get a response
283 targets.clearDownstreamPending();
284 }
285}
286
287
288void
289MSHR::deallocate()
290{
291 assert(targets.empty());
292 targets.resetFlags();
293 assert(deferredTargets.isReset());
294 inService = false;
295}
296
297/*
298 * Adds a target to an MSHR
299 */
300void
301MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order,
302 bool alloc_on_fill)
303{
304 // assume we'd never issue a prefetch when we've got an
305 // outstanding miss
306 assert(pkt->cmd != MemCmd::HardPFReq);
307
308 // uncacheable accesses always allocate a new MSHR, and cacheable
309 // accesses ignore any uncacheable MSHRs, thus we should never
310 // have targets addded if originally allocated uncacheable
311 assert(!_isUncacheable);
312
313 // if there's a request already in service for this MSHR, we will
314 // have to defer the new target until after the response if any of
315 // the following are true:
316 // - there are other targets already deferred
317 // - there's a pending invalidate to be applied after the response
318 // comes back (but before this target is processed)
319 // - this target requires a writable block and either we're not
320 // getting a writable block back or we have already snooped
321 // another read request that will downgrade our writable block
322 // to non-writable (Shared or Owned)
323 if (inService &&
324 (!deferredTargets.empty() || hasPostInvalidate() ||
325 (pkt->needsWritable() &&
326 (!isPendingModified() || hasPostDowngrade() || isForward)))) {
327 // need to put on deferred list
328 if (hasPostInvalidate())
329 replaceUpgrade(pkt);
330 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true,
331 alloc_on_fill);
332 } else {
333 // No request outstanding, or still OK to append to
334 // outstanding request: append to regular target list. Only
335 // mark pending if current request hasn't been issued yet
336 // (isn't in service).
337 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService,
338 alloc_on_fill);
339 }
340}
341
342bool
343MSHR::handleSnoop(PacketPtr pkt, Counter _order)
344{
345 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__,
346 pkt->cmdString(), pkt->getAddr(), pkt->getSize());
347
348 // when we snoop packets the needsWritable and isInvalidate flags
349 // should always be the same, however, this assumes that we never
350 // snoop writes as they are currently not marked as invalidations
351 panic_if(pkt->needsWritable() != pkt->isInvalidate(),
352 "%s got snoop %s to addr %#llx where needsWritable, "
353 "does not match isInvalidate", name(), pkt->cmdString(),
354 pkt->getAddr());
355
356 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) {
357 // Request has not been issued yet, or it's been issued
358 // locally but is buffered unissued at some downstream cache
359 // which is forwarding us this snoop. Either way, the packet
360 // we're snooping logically precedes this MSHR's request, so
361 // the snoop has no impact on the MSHR, but must be processed
362 // in the standard way by the cache. The only exception is
363 // that if we're an L2+ cache buffering an UpgradeReq from a
364 // higher-level cache, and the snoop is invalidating, then our
365 // buffered upgrades must be converted to read exclusives,
366 // since the upper-level cache no longer has a valid copy.
367 // That is, even though the upper-level cache got out on its
368 // local bus first, some other invalidating transaction
369 // reached the global bus before the upgrade did.
370 if (pkt->needsWritable()) {
371 targets.replaceUpgrades();
372 deferredTargets.replaceUpgrades();
373 }
374
375 return false;
376 }
377
378 // From here on down, the request issued by this MSHR logically
379 // precedes the request we're snooping.
380 if (pkt->needsWritable()) {
381 // snooped request still precedes the re-request we'll have to
382 // issue for deferred targets, if any...
383 deferredTargets.replaceUpgrades();
384 }
385
386 if (hasPostInvalidate()) {
387 // a prior snoop has already appended an invalidation, so
388 // logically we don't have the block anymore; no need for
389 // further snooping.
390 return true;
391 }
392
393 if (isPendingModified() || pkt->isInvalidate()) {
394 // We need to save and replay the packet in two cases:
395 // 1. We're awaiting a writable copy (Modified or Exclusive),
396 // so this MSHR is the orgering point, and we need to respond
397 // after we receive data.
398 // 2. It's an invalidation (e.g., UpgradeReq), and we need
399 // to forward the snoop up the hierarchy after the current
400 // transaction completes.
401
402 // Start by determining if we will eventually respond or not,
403 // matching the conditions checked in Cache::handleSnoop
404 bool will_respond = isPendingModified() && pkt->needsResponse() &&
405 pkt->cmd != MemCmd::InvalidateReq;
406
407 // The packet we are snooping may be deleted by the time we
408 // actually process the target, and we consequently need to
409 // save a copy here. Clear flags and also allocate new data as
410 // the original packet data storage may have been deleted by
411 // the time we get to process this packet. In the cases where
412 // we are not responding after handling the snoop we also need
413 // to create a copy of the request to be on the safe side. In
414 // the latter case the cache is responsible for deleting both
415 // the packet and the request as part of handling the deferred
416 // snoop.
417 PacketPtr cp_pkt = will_respond ? new Packet(pkt, true, true) :
418 new Packet(new Request(*pkt->req), pkt->cmd);
419
420 if (will_respond) {
421 // we are the ordering point, and will consequently
422 // respond, and depending on whether the packet
423 // needsWritable or not we either pass a Shared line or a
424 // Modified line
425 pkt->setCacheResponding();
426
427 // inform the cache hierarchy that this cache had the line
428 // in the Modified state, even if the response is passed
429 // as Shared (and thus non-writable)
430 pkt->setResponderHadWritable();
431
432 // in the case of an uncacheable request there is no need
433 // to set the responderHadWritable flag, but since the
434 // recipient does not care there is no harm in doing so
435 }
436 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop,
437 downstreamPending && targets.needsWritable, false);
438
439 if (pkt->needsWritable()) {
440 // This transaction will take away our pending copy
441 postInvalidate = true;
442 }
443 }
444
445 if (!pkt->needsWritable() && !pkt->req->isUncacheable()) {
446 // This transaction will get a read-shared copy, downgrading
447 // our copy if we had a writable one
448 postDowngrade = true;
449 // make sure that any downstream cache does not respond with a
450 // writable (and dirty) copy even if it has one, unless it was
451 // explicitly asked for one
452 pkt->setHasSharers();
453 }
454
455 return true;
456}
457
458
459bool
460MSHR::promoteDeferredTargets()
461{
462 assert(targets.empty());
463 if (deferredTargets.empty()) {
464 return false;
465 }
466
467 // swap targets & deferredTargets lists
468 std::swap(targets, deferredTargets);
469
470 // clear deferredTargets flags
471 deferredTargets.resetFlags();
472
473 order = targets.front().order;
474 readyTime = std::max(curTick(), targets.front().readyTime);
475
476 return true;
477}
478
479
480void
481MSHR::promoteWritable()
482{
483 if (deferredTargets.needsWritable &&
484 !(hasPostInvalidate() || hasPostDowngrade())) {
485 // We got a writable response, but we have deferred targets
486 // which are waiting to request a writable copy (not because
487 // of a pending invalidate). This can happen if the original
488 // request was for a read-only block, but we got a writable
489 // response anyway. Since we got the writable copy there's no
490 // need to defer the targets, so move them up to the regular
491 // target list.
492 assert(!targets.needsWritable);
493 targets.needsWritable = true;
494 // if any of the deferred targets were upper-level cache
495 // requests marked downstreamPending, need to clear that
496 assert(!downstreamPending); // not pending here anymore
497 deferredTargets.clearDownstreamPending();
498 // this clears out deferredTargets too
499 targets.splice(targets.end(), deferredTargets);
500 deferredTargets.resetFlags();
501 }
502}
503
504
505bool
506MSHR::checkFunctional(PacketPtr pkt)
507{
508 // For printing, we treat the MSHR as a whole as single entity.
509 // For other requests, we iterate over the individual targets
510 // since that's where the actual data lies.
511 if (pkt->isPrint()) {
512 pkt->checkFunctional(this, blkAddr, isSecure, blkSize, nullptr);
513 return false;
514 } else {
515 return (targets.checkFunctional(pkt) ||
516 deferredTargets.checkFunctional(pkt));
517 }
518}
519
520bool
521MSHR::sendPacket(Cache &cache)
522{
523 return cache.sendMSHRQueuePacket(this);
524}
525
526void
527MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const
528{
529 ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
530 prefix, blkAddr, blkAddr + blkSize - 1,
531 isSecure ? "s" : "ns",
532 isForward ? "Forward" : "",
533 allocOnFill() ? "AllocOnFill" : "",
534 needsWritable() ? "Wrtbl" : "",
535 _isUncacheable ? "Unc" : "",
536 inService ? "InSvc" : "",
537 downstreamPending ? "DwnPend" : "",
538 postInvalidate ? "PostInv" : "",
539 postDowngrade ? "PostDowngr" : "");
540
541 if (!targets.empty()) {
542 ccprintf(os, "%s Targets:\n", prefix);
543 targets.print(os, verbosity, prefix + " ");
544 }
545 if (!deferredTargets.empty()) {
546 ccprintf(os, "%s Deferred Targets:\n", prefix);
547 deferredTargets.print(os, verbosity, prefix + " ");
548 }
549}
550
551std::string
552MSHR::print() const
553{
554 ostringstream str;
555 print(str);
556 return str.str();
557}