1/*
2 * Copyright (c) 2012-2013, 2015 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 <algorithm>
51#include <cassert>
52#include <string>
53#include <vector>
54
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"
61
62using namespace std;
63
64MSHR::MSHR() : readyTime(0), _isUncacheable(false), downstreamPending(false),
65 pendingDirty(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)
71{
72}
73
74
75MSHR::TargetList::TargetList()
76 : needsExclusive(false), hasUpgrade(false)
77{}
78
79
80inline void
81MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
82 Counter order, Target::Source source, bool markPending)
83{
84 if (source != Target::FromSnoop) {
85 if (pkt->needsExclusive()) {
86 needsExclusive = true;
87 }
88
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
91 // read-only copy
92 if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) {
93 hasUpgrade = true;
94 }
95 }
96
97 if (markPending) {
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>();
102 if (mshr != NULL) {
103 assert(!mshr->downstreamPending);
104 mshr->downstreamPending = true;
105 } else {
106 // No need to clear downstreamPending later
107 markPending = false;
108 }
109 }
110
111 emplace_back(pkt, readyTime, order, source, markPending);
112}
113
114
115static void
116replaceUpgrade(PacketPtr pkt)
117{
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");
127 }
128}
129
130
131void
132MSHR::TargetList::replaceUpgrades()
133{
134 if (!hasUpgrade)
135 return;
136
137 for (auto& t : *this) {
138 replaceUpgrade(t.pkt);
139 }
140
141 hasUpgrade = false;
142}
143
144
145void
146MSHR::TargetList::clearDownstreamPending()
147{
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
155 // passed through.
156 MSHR *mshr = t.pkt->findNextSenderState<MSHR>();
157 if (mshr != NULL) {
158 mshr->clearDownstreamPending();
159 }
160 }
161 }
162}
163
164
165bool
166MSHR::TargetList::checkFunctional(PacketPtr pkt)
167{
168 for (auto& t : *this) {
169 if (pkt->checkFunctional(t.pkt)) {
170 return true;
171 }
172 }
173
174 return false;
175}
176
177
178void
179MSHR::TargetList::print(std::ostream &os, int verbosity,
180 const std::string &prefix) const
181{
182 for (auto& t : *this) {
183 const char *s;
184 switch (t.source) {
185 case Target::FromCPU:
186 s = "FromCPU";
187 break;
188 case Target::FromSnoop:
189 s = "FromSnoop";
190 break;
191 case Target::FromPrefetcher:
192 s = "FromPrefetcher";
193 break;
194 default:
195 s = "";
196 break;
197 }
198 ccprintf(os, "%s%s: ", prefix, s);
199 t.pkt->print(os, verbosity, "");
200 }
201}
202
203
204void
205MSHR::allocate(Addr blk_addr, unsigned blk_size, PacketPtr target,
206 Tick when_ready, Counter _order, bool alloc_on_fill)
207{
208 blkAddr = blk_addr;
209 blkSize = blk_size;
210 isSecure = target->isSecure();
211 readyTime = when_ready;
212 order = _order;
213 assert(target);
214 isForward = false;
215 allocOnFill = alloc_on_fill;
216 _isUncacheable = target->req->isUncacheable();
217 inService = false;
218 downstreamPending = false;
219 threadNum = 0;
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());
227 data = NULL;
228}
229
230
231void
232MSHR::clearDownstreamPending()
233{
234 assert(downstreamPending);
235 downstreamPending = false;
236 // recursively clear flag on any MSHRs we will be forwarding
237 // responses to
238 targets.clearDownstreamPending();
239}
240
241bool
242MSHR::markInService(bool pending_dirty_resp)
243{
244 assert(!inService);
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);
249 popTarget();
250 return true;
251 }
252
253 inService = true;
254 pendingDirty = targets.needsExclusive || pending_dirty_resp;
255 postInvalidate = postDowngrade = false;
256
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();
261 }
262 return false;
263}
264
265
266void
267MSHR::deallocate()
268{
269 assert(targets.empty());
270 targets.resetFlags();
271 assert(deferredTargets.isReset());
272 inService = false;
273}
274
275/*
276 * Adds a target to an MSHR
277 */
278void
279MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order,
280 bool alloc_on_fill)
281{
282 // assume we'd never issue a prefetch when we've got an
283 // outstanding miss
284 assert(pkt->cmd != MemCmd::HardPFReq);
285
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);
290
291 // potentially re-evaluate whether we should allocate on a fill or
292 // not
293 allocOnFill = allocOnFill || alloc_on_fill;
294
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
304 // to shared
305 if (inService &&
306 (!deferredTargets.empty() || hasPostInvalidate() ||
307 (pkt->needsExclusive() &&
308 (!isPendingDirty() || hasPostDowngrade() || isForward)))) {
309 // need to put on deferred list
310 if (hasPostInvalidate())
311 replaceUpgrade(pkt);
312 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true);
313 } else {
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);
319 }
320}
321
322bool
323MSHR::handleSnoop(PacketPtr pkt, Counter _order)
324{
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();
344 }
345
346 return false;
347 }
348
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();
355 }
356
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
360 // further snooping.
361 return true;
362 }
363
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 respond 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.
371
372 // Actual target device (typ. a memory) will delete the
373 // packet on reception, so we need to save a copy here.
374
375 // Clear flags and also allocate new data as the original
376 // packet data storage may have been deleted by the time we
377 // get to send this packet.
378 PacketPtr cp_pkt = nullptr;
379
380 if (isPendingDirty()) {
381 // Case 1: The new packet will need to get the response from the
382 // MSHR already queued up here
383 cp_pkt = new Packet(pkt, true, true);
384 pkt->assertMemInhibit();
385 // in the case of an uncacheable request there is no need
386 // to set the exclusive flag, but since the recipient does
387 // not care there is no harm in doing so
388 pkt->setSupplyExclusive();
389 } else {
390 // Case 2: We only need to buffer the packet for information
391 // purposes; the original request can proceed without waiting
392 // => Create a copy of the request, as that may get deallocated as
393 // well
394 cp_pkt = new Packet(new Request(*pkt->req), pkt->cmd);
395 DPRINTF(Cache, "Copying packet %p -> %p and request %p -> %p\n",
396 pkt, cp_pkt, pkt->req, cp_pkt->req);
397 }
398 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop,
399 downstreamPending && targets.needsExclusive);
400
401 if (pkt->needsExclusive()) {
402 // This transaction will take away our pending copy
403 postInvalidate = true;
404 }
405 }
406
407 if (!pkt->needsExclusive() && !pkt->req->isUncacheable()) {
408 // This transaction will get a read-shared copy, downgrading
409 // our copy if we had an exclusive one
410 postDowngrade = true;
411 pkt->assertShared();
412 }
413
414 return true;
415}
416
417
418bool
419MSHR::promoteDeferredTargets()
420{
421 assert(targets.empty());
422 if (deferredTargets.empty()) {
423 return false;
424 }
425
426 // swap targets & deferredTargets lists
427 std::swap(targets, deferredTargets);
428
429 // clear deferredTargets flags
430 deferredTargets.resetFlags();
431
432 order = targets.front().order;
433 readyTime = std::max(curTick(), targets.front().readyTime);
434
435 return true;
436}
437
438
439void
440MSHR::promoteExclusive()
441{
442 if (deferredTargets.needsExclusive &&
443 !(hasPostInvalidate() || hasPostDowngrade())) {
444 // We got an exclusive response, but we have deferred targets
445 // which are waiting to request an exclusive copy (not because
446 // of a pending invalidate). This can happen if the original
447 // request was for a read-only (non-exclusive) block, but we
448 // got an exclusive copy anyway because of the E part of the
449 // MOESI/MESI protocol. Since we got the exclusive copy
450 // there's no need to defer the targets, so move them up to
451 // the regular target list.
452 assert(!targets.needsExclusive);
453 targets.needsExclusive = true;
454 // if any of the deferred targets were upper-level cache
455 // requests marked downstreamPending, need to clear that
456 assert(!downstreamPending); // not pending here anymore
457 deferredTargets.clearDownstreamPending();
458 // this clears out deferredTargets too
459 targets.splice(targets.end(), deferredTargets);
460 deferredTargets.resetFlags();
461 }
462}
463
464
465bool
466MSHR::checkFunctional(PacketPtr pkt)
467{
468 // For printing, we treat the MSHR as a whole as single entity.
469 // For other requests, we iterate over the individual targets
470 // since that's where the actual data lies.
471 if (pkt->isPrint()) {
472 pkt->checkFunctional(this, blkAddr, isSecure, blkSize, NULL);
473 return false;
474 } else {
475 return (targets.checkFunctional(pkt) ||
476 deferredTargets.checkFunctional(pkt));
477 }
478}
479
480
481void
482MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const
483{
484 ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
485 prefix, blkAddr, blkAddr + blkSize - 1,
486 isSecure ? "s" : "ns",
487 isForward ? "Forward" : "",
488 allocOnFill ? "AllocOnFill" : "",
489 isForwardNoResponse() ? "ForwNoResp" : "",
490 needsExclusive() ? "Excl" : "",
491 _isUncacheable ? "Unc" : "",
492 inService ? "InSvc" : "",
493 downstreamPending ? "DwnPend" : "",
494 hasPostInvalidate() ? "PostInv" : "",
495 hasPostDowngrade() ? "PostDowngr" : "");
496
497 ccprintf(os, "%s Targets:\n", prefix);
498 targets.print(os, verbosity, prefix + " ");
499 if (!deferredTargets.empty()) {
500 ccprintf(os, "%s Deferred Targets:\n", prefix);
501 deferredTargets.print(os, verbosity, prefix + " ");
502 }
503}
504
505std::string
506MSHR::print() const
507{
508 ostringstream str;
509 print(str);
510 return str.str();
511}