1/*
2 * Copyright (c) 2010-2018 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) 2010,2015 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 * Nathan Binkert
44 * Steve Reinhardt
45 * Ron Dreslinski
46 * Andreas Sandberg
47 * Nikos Nikoleris
48 */
49
50/**
51 * @file
52 * Cache definitions.
53 */
54
55#include "mem/cache/cache.hh"
56
57#include <cassert>
58
59#include "base/compiler.hh"
60#include "base/logging.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CacheTags.hh"
65#include "debug/CacheVerbose.hh"
66#include "enums/Clusivity.hh"
67#include "mem/cache/cache_blk.hh"
68#include "mem/cache/mshr.hh"
69#include "mem/cache/tags/base.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/request.hh"
72#include "params/Cache.hh"
73
74Cache::Cache(const CacheParams *p)
75 : BaseCache(p, p->system->cacheLineSize()),
76 doFastWrites(true)
77{
78}
79
80void
81Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
82 bool deferred_response, bool pending_downgrade)
83{
84 BaseCache::satisfyRequest(pkt, blk);
85
86 if (pkt->isRead()) {
87 // determine if this read is from a (coherent) cache or not
88 if (pkt->fromCache()) {
89 assert(pkt->getSize() == blkSize);
90 // special handling for coherent block requests from
91 // upper-level caches
92 if (pkt->needsWritable()) {
93 // sanity check
94 assert(pkt->cmd == MemCmd::ReadExReq ||
95 pkt->cmd == MemCmd::SCUpgradeFailReq);
96 assert(!pkt->hasSharers());
97
98 // if we have a dirty copy, make sure the recipient
99 // keeps it marked dirty (in the modified state)
100 if (blk->isDirty()) {
101 pkt->setCacheResponding();
102 blk->status &= ~BlkDirty;
103 }
104 } else if (blk->isWritable() && !pending_downgrade &&
105 !pkt->hasSharers() &&
106 pkt->cmd != MemCmd::ReadCleanReq) {
107 // we can give the requester a writable copy on a read
108 // request if:
109 // - we have a writable copy at this level (& below)
110 // - we don't have a pending snoop from below
111 // signaling another read request
112 // - no other cache above has a copy (otherwise it
113 // would have set hasSharers flag when
114 // snooping the packet)
115 // - the read has explicitly asked for a clean
116 // copy of the line
117 if (blk->isDirty()) {
118 // special considerations if we're owner:
119 if (!deferred_response) {
120 // respond with the line in Modified state
121 // (cacheResponding set, hasSharers not set)
122 pkt->setCacheResponding();
123
124 // if this cache is mostly inclusive, we
125 // keep the block in the Exclusive state,
126 // and pass it upwards as Modified
127 // (writable and dirty), hence we have
128 // multiple caches, all on the same path
129 // towards memory, all considering the
130 // same block writable, but only one
131 // considering it Modified
132
133 // we get away with multiple caches (on
134 // the same path to memory) considering
135 // the block writeable as we always enter
136 // the cache hierarchy through a cache,
137 // and first snoop upwards in all other
138 // branches
139 blk->status &= ~BlkDirty;
140 } else {
141 // if we're responding after our own miss,
142 // there's a window where the recipient didn't
143 // know it was getting ownership and may not
144 // have responded to snoops correctly, so we
145 // have to respond with a shared line
146 pkt->setHasSharers();
147 }
148 }
149 } else {
150 // otherwise only respond with a shared copy
151 pkt->setHasSharers();
152 }
153 }
154 }
155}
156
157/////////////////////////////////////////////////////
158//
159// Access path: requests coming in from the CPU side
160//
161/////////////////////////////////////////////////////
162
163bool
164Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
165 PacketList &writebacks)
166{
167
168 if (pkt->req->isUncacheable()) {
169 assert(pkt->isRequest());
170
171 chatty_assert(!(isReadOnly && pkt->isWrite()),
172 "Should never see a write in a read-only cache %s\n",
173 name());
174
175 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
176
177 // flush and invalidate any existing block
178 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
179 if (old_blk && old_blk->isValid()) {
180 evictBlock(old_blk, writebacks);
181 }
182
183 blk = nullptr;
184 // lookupLatency is the latency in case the request is uncacheable.
185 lat = lookupLatency;
186 return false;
187 }
188
189 return BaseCache::access(pkt, blk, lat, writebacks);
190}
191
192void
193Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
194{
195 while (!writebacks.empty()) {
196 PacketPtr wbPkt = writebacks.front();
197 // We use forwardLatency here because we are copying writebacks to
198 // write buffer.
199
200 // Call isCachedAbove for Writebacks, CleanEvicts and
201 // WriteCleans to discover if the block is cached above.
202 if (isCachedAbove(wbPkt)) {
203 if (wbPkt->cmd == MemCmd::CleanEvict) {
204 // Delete CleanEvict because cached copies exist above. The
205 // packet destructor will delete the request object because
206 // this is a non-snoop request packet which does not require a
207 // response.
208 delete wbPkt;
209 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
210 // clean writeback, do not send since the block is
211 // still cached above
212 assert(writebackClean);
213 delete wbPkt;
214 } else {
215 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
216 wbPkt->cmd == MemCmd::WriteClean);
217 // Set BLOCK_CACHED flag in Writeback and send below, so that
218 // the Writeback does not reset the bit corresponding to this
219 // address in the snoop filter below.
220 wbPkt->setBlockCached();
221 allocateWriteBuffer(wbPkt, forward_time);
222 }
223 } else {
224 // If the block is not cached above, send packet below. Both
225 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
226 // reset the bit corresponding to this address in the snoop filter
227 // below.
228 allocateWriteBuffer(wbPkt, forward_time);
229 }
230 writebacks.pop_front();
231 }
232}
233
234void
235Cache::doWritebacksAtomic(PacketList& writebacks)
236{
237 while (!writebacks.empty()) {
238 PacketPtr wbPkt = writebacks.front();
239 // Call isCachedAbove for both Writebacks and CleanEvicts. If
240 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
241 // and discard CleanEvicts.
242 if (isCachedAbove(wbPkt, false)) {
243 if (wbPkt->cmd == MemCmd::WritebackDirty ||
244 wbPkt->cmd == MemCmd::WriteClean) {
245 // Set BLOCK_CACHED flag in Writeback and send below,
246 // so that the Writeback does not reset the bit
247 // corresponding to this address in the snoop filter
248 // below. We can discard CleanEvicts because cached
249 // copies exist above. Atomic mode isCachedAbove
250 // modifies packet to set BLOCK_CACHED flag
251 memSidePort.sendAtomic(wbPkt);
252 }
253 } else {
254 // If the block is not cached above, send packet below. Both
255 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
256 // reset the bit corresponding to this address in the snoop filter
257 // below.
258 memSidePort.sendAtomic(wbPkt);
259 }
260 writebacks.pop_front();
261 // In case of CleanEvicts, the packet destructor will delete the
262 // request object because this is a non-snoop request packet which
263 // does not require a response.
264 delete wbPkt;
265 }
266}
267
268
269void
270Cache::recvTimingSnoopResp(PacketPtr pkt)
271{
272 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
273
274 // determine if the response is from a snoop request we created
275 // (in which case it should be in the outstandingSnoop), or if we
276 // merely forwarded someone else's snoop request
277 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
278 outstandingSnoop.end();
279
280 if (!forwardAsSnoop) {
281 // the packet came from this cache, so sink it here and do not
282 // forward it
283 assert(pkt->cmd == MemCmd::HardPFResp);
284
285 outstandingSnoop.erase(pkt->req);
286
287 DPRINTF(Cache, "Got prefetch response from above for addr "
288 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
289 recvTimingResp(pkt);
290 return;
291 }
292
293 // forwardLatency is set here because there is a response from an
294 // upper level cache.
295 // To pay the delay that occurs if the packet comes from the bus,
296 // we charge also headerDelay.
297 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
298 // Reset the timing of the packet.
299 pkt->headerDelay = pkt->payloadDelay = 0;
300 memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time);
301}
302
303void
304Cache::promoteWholeLineWrites(PacketPtr pkt)
305{
306 // Cache line clearing instructions
307 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
308 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
309 pkt->cmd = MemCmd::WriteLineReq;
310 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
311 }
312}
313
314void
315Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
316{
317 // should never be satisfying an uncacheable access as we
318 // flush and invalidate any existing block as part of the
319 // lookup
320 assert(!pkt->req->isUncacheable());
321
322 BaseCache::handleTimingReqHit(pkt, blk, request_time);
323}
324
325void
326Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
327 Tick request_time)
328{
329 if (pkt->req->isUncacheable()) {
330 // ignore any existing MSHR if we are dealing with an
331 // uncacheable request
332
333 // should have flushed and have no valid block
334 assert(!blk || !blk->isValid());
335
336 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
337
338 if (pkt->isWrite()) {
339 allocateWriteBuffer(pkt, forward_time);
340 } else {
341 assert(pkt->isRead());
342
343 // uncacheable accesses always allocate a new MSHR
344
345 // Here we are using forward_time, modelling the latency of
346 // a miss (outbound) just as forwardLatency, neglecting the
347 // lookupLatency component.
348 allocateMissBuffer(pkt, forward_time);
349 }
350
351 return;
352 }
353
354 Addr blk_addr = pkt->getBlockAddr(blkSize);
355
356 MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
357
358 // Software prefetch handling:
359 // To keep the core from waiting on data it won't look at
360 // anyway, send back a response with dummy data. Miss handling
361 // will continue asynchronously. Unfortunately, the core will
362 // insist upon freeing original Packet/Request, so we have to
363 // create a new pair with a different lifecycle. Note that this
364 // processing happens before any MSHR munging on the behalf of
365 // this request because this new Request will be the one stored
366 // into the MSHRs, not the original.
367 if (pkt->cmd.isSWPrefetch()) {
368 assert(pkt->needsResponse());
369 assert(pkt->req->hasPaddr());
370 assert(!pkt->req->isUncacheable());
371
372 // There's no reason to add a prefetch as an additional target
373 // to an existing MSHR. If an outstanding request is already
374 // in progress, there is nothing for the prefetch to do.
375 // If this is the case, we don't even create a request at all.
376 PacketPtr pf = nullptr;
377
378 if (!mshr) {
379 // copy the request and create a new SoftPFReq packet
380 RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(),
381 pkt->req->getSize(),
382 pkt->req->getFlags(),
383 pkt->req->masterId());
384 pf = new Packet(req, pkt->cmd);
385 pf->allocate();
386 assert(pf->getAddr() == pkt->getAddr());
387 assert(pf->getSize() == pkt->getSize());
388 }
389
390 pkt->makeTimingResponse();
391
392 // request_time is used here, taking into account lat and the delay
393 // charged if the packet comes from the xbar.
394 cpuSidePort.schedTimingResp(pkt, request_time, true);
395
396 // If an outstanding request is in progress (we found an
397 // MSHR) this is set to null
398 pkt = pf;
399 }
400
401 BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time);
402}
403
404void
405Cache::recvTimingReq(PacketPtr pkt)
406{
407 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
408
409 promoteWholeLineWrites(pkt);
410
411 if (pkt->cacheResponding()) {
412 // a cache above us (but not where the packet came from) is
413 // responding to the request, in other words it has the line
414 // in Modified or Owned state
415 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
416 pkt->print());
417
418 // if the packet needs the block to be writable, and the cache
419 // that has promised to respond (setting the cache responding
420 // flag) is not providing writable (it is in Owned rather than
421 // the Modified state), we know that there may be other Shared
422 // copies in the system; go out and invalidate them all
423 assert(pkt->needsWritable() && !pkt->responderHadWritable());
424
425 // an upstream cache that had the line in Owned state
426 // (dirty, but not writable), is responding and thus
427 // transferring the dirty line from one branch of the
428 // cache hierarchy to another
429
430 // send out an express snoop and invalidate all other
431 // copies (snooping a packet that needs writable is the
432 // same as an invalidation), thus turning the Owned line
433 // into a Modified line, note that we don't invalidate the
434 // block in the current cache or any other cache on the
435 // path to memory
436
437 // create a downstream express snoop with cleared packet
438 // flags, there is no need to allocate any data as the
439 // packet is merely used to co-ordinate state transitions
440 Packet *snoop_pkt = new Packet(pkt, true, false);
441
442 // also reset the bus time that the original packet has
443 // not yet paid for
444 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
445
446 // make this an instantaneous express snoop, and let the
447 // other caches in the system know that the another cache
448 // is responding, because we have found the authorative
449 // copy (Modified or Owned) that will supply the right
450 // data
451 snoop_pkt->setExpressSnoop();
452 snoop_pkt->setCacheResponding();
453
454 // this express snoop travels towards the memory, and at
455 // every crossbar it is snooped upwards thus reaching
456 // every cache in the system
457 bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt);
458 // express snoops always succeed
459 assert(success);
460
461 // main memory will delete the snoop packet
462
463 // queue for deletion, as opposed to immediate deletion, as
464 // the sending cache is still relying on the packet
465 pendingDelete.reset(pkt);
466
467 // no need to take any further action in this particular cache
468 // as an upstram cache has already committed to responding,
469 // and we have already sent out any express snoops in the
470 // section above to ensure all other copies in the system are
471 // invalidated
472 return;
473 }
474
475 BaseCache::recvTimingReq(pkt);
476}
477
478PacketPtr
479Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
| 1/*
2 * Copyright (c) 2010-2018 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) 2010,2015 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 * Nathan Binkert
44 * Steve Reinhardt
45 * Ron Dreslinski
46 * Andreas Sandberg
47 * Nikos Nikoleris
48 */
49
50/**
51 * @file
52 * Cache definitions.
53 */
54
55#include "mem/cache/cache.hh"
56
57#include <cassert>
58
59#include "base/compiler.hh"
60#include "base/logging.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CacheTags.hh"
65#include "debug/CacheVerbose.hh"
66#include "enums/Clusivity.hh"
67#include "mem/cache/cache_blk.hh"
68#include "mem/cache/mshr.hh"
69#include "mem/cache/tags/base.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/request.hh"
72#include "params/Cache.hh"
73
74Cache::Cache(const CacheParams *p)
75 : BaseCache(p, p->system->cacheLineSize()),
76 doFastWrites(true)
77{
78}
79
80void
81Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
82 bool deferred_response, bool pending_downgrade)
83{
84 BaseCache::satisfyRequest(pkt, blk);
85
86 if (pkt->isRead()) {
87 // determine if this read is from a (coherent) cache or not
88 if (pkt->fromCache()) {
89 assert(pkt->getSize() == blkSize);
90 // special handling for coherent block requests from
91 // upper-level caches
92 if (pkt->needsWritable()) {
93 // sanity check
94 assert(pkt->cmd == MemCmd::ReadExReq ||
95 pkt->cmd == MemCmd::SCUpgradeFailReq);
96 assert(!pkt->hasSharers());
97
98 // if we have a dirty copy, make sure the recipient
99 // keeps it marked dirty (in the modified state)
100 if (blk->isDirty()) {
101 pkt->setCacheResponding();
102 blk->status &= ~BlkDirty;
103 }
104 } else if (blk->isWritable() && !pending_downgrade &&
105 !pkt->hasSharers() &&
106 pkt->cmd != MemCmd::ReadCleanReq) {
107 // we can give the requester a writable copy on a read
108 // request if:
109 // - we have a writable copy at this level (& below)
110 // - we don't have a pending snoop from below
111 // signaling another read request
112 // - no other cache above has a copy (otherwise it
113 // would have set hasSharers flag when
114 // snooping the packet)
115 // - the read has explicitly asked for a clean
116 // copy of the line
117 if (blk->isDirty()) {
118 // special considerations if we're owner:
119 if (!deferred_response) {
120 // respond with the line in Modified state
121 // (cacheResponding set, hasSharers not set)
122 pkt->setCacheResponding();
123
124 // if this cache is mostly inclusive, we
125 // keep the block in the Exclusive state,
126 // and pass it upwards as Modified
127 // (writable and dirty), hence we have
128 // multiple caches, all on the same path
129 // towards memory, all considering the
130 // same block writable, but only one
131 // considering it Modified
132
133 // we get away with multiple caches (on
134 // the same path to memory) considering
135 // the block writeable as we always enter
136 // the cache hierarchy through a cache,
137 // and first snoop upwards in all other
138 // branches
139 blk->status &= ~BlkDirty;
140 } else {
141 // if we're responding after our own miss,
142 // there's a window where the recipient didn't
143 // know it was getting ownership and may not
144 // have responded to snoops correctly, so we
145 // have to respond with a shared line
146 pkt->setHasSharers();
147 }
148 }
149 } else {
150 // otherwise only respond with a shared copy
151 pkt->setHasSharers();
152 }
153 }
154 }
155}
156
157/////////////////////////////////////////////////////
158//
159// Access path: requests coming in from the CPU side
160//
161/////////////////////////////////////////////////////
162
163bool
164Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
165 PacketList &writebacks)
166{
167
168 if (pkt->req->isUncacheable()) {
169 assert(pkt->isRequest());
170
171 chatty_assert(!(isReadOnly && pkt->isWrite()),
172 "Should never see a write in a read-only cache %s\n",
173 name());
174
175 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
176
177 // flush and invalidate any existing block
178 CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
179 if (old_blk && old_blk->isValid()) {
180 evictBlock(old_blk, writebacks);
181 }
182
183 blk = nullptr;
184 // lookupLatency is the latency in case the request is uncacheable.
185 lat = lookupLatency;
186 return false;
187 }
188
189 return BaseCache::access(pkt, blk, lat, writebacks);
190}
191
192void
193Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
194{
195 while (!writebacks.empty()) {
196 PacketPtr wbPkt = writebacks.front();
197 // We use forwardLatency here because we are copying writebacks to
198 // write buffer.
199
200 // Call isCachedAbove for Writebacks, CleanEvicts and
201 // WriteCleans to discover if the block is cached above.
202 if (isCachedAbove(wbPkt)) {
203 if (wbPkt->cmd == MemCmd::CleanEvict) {
204 // Delete CleanEvict because cached copies exist above. The
205 // packet destructor will delete the request object because
206 // this is a non-snoop request packet which does not require a
207 // response.
208 delete wbPkt;
209 } else if (wbPkt->cmd == MemCmd::WritebackClean) {
210 // clean writeback, do not send since the block is
211 // still cached above
212 assert(writebackClean);
213 delete wbPkt;
214 } else {
215 assert(wbPkt->cmd == MemCmd::WritebackDirty ||
216 wbPkt->cmd == MemCmd::WriteClean);
217 // Set BLOCK_CACHED flag in Writeback and send below, so that
218 // the Writeback does not reset the bit corresponding to this
219 // address in the snoop filter below.
220 wbPkt->setBlockCached();
221 allocateWriteBuffer(wbPkt, forward_time);
222 }
223 } else {
224 // If the block is not cached above, send packet below. Both
225 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
226 // reset the bit corresponding to this address in the snoop filter
227 // below.
228 allocateWriteBuffer(wbPkt, forward_time);
229 }
230 writebacks.pop_front();
231 }
232}
233
234void
235Cache::doWritebacksAtomic(PacketList& writebacks)
236{
237 while (!writebacks.empty()) {
238 PacketPtr wbPkt = writebacks.front();
239 // Call isCachedAbove for both Writebacks and CleanEvicts. If
240 // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
241 // and discard CleanEvicts.
242 if (isCachedAbove(wbPkt, false)) {
243 if (wbPkt->cmd == MemCmd::WritebackDirty ||
244 wbPkt->cmd == MemCmd::WriteClean) {
245 // Set BLOCK_CACHED flag in Writeback and send below,
246 // so that the Writeback does not reset the bit
247 // corresponding to this address in the snoop filter
248 // below. We can discard CleanEvicts because cached
249 // copies exist above. Atomic mode isCachedAbove
250 // modifies packet to set BLOCK_CACHED flag
251 memSidePort.sendAtomic(wbPkt);
252 }
253 } else {
254 // If the block is not cached above, send packet below. Both
255 // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
256 // reset the bit corresponding to this address in the snoop filter
257 // below.
258 memSidePort.sendAtomic(wbPkt);
259 }
260 writebacks.pop_front();
261 // In case of CleanEvicts, the packet destructor will delete the
262 // request object because this is a non-snoop request packet which
263 // does not require a response.
264 delete wbPkt;
265 }
266}
267
268
269void
270Cache::recvTimingSnoopResp(PacketPtr pkt)
271{
272 DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
273
274 // determine if the response is from a snoop request we created
275 // (in which case it should be in the outstandingSnoop), or if we
276 // merely forwarded someone else's snoop request
277 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
278 outstandingSnoop.end();
279
280 if (!forwardAsSnoop) {
281 // the packet came from this cache, so sink it here and do not
282 // forward it
283 assert(pkt->cmd == MemCmd::HardPFResp);
284
285 outstandingSnoop.erase(pkt->req);
286
287 DPRINTF(Cache, "Got prefetch response from above for addr "
288 "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
289 recvTimingResp(pkt);
290 return;
291 }
292
293 // forwardLatency is set here because there is a response from an
294 // upper level cache.
295 // To pay the delay that occurs if the packet comes from the bus,
296 // we charge also headerDelay.
297 Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
298 // Reset the timing of the packet.
299 pkt->headerDelay = pkt->payloadDelay = 0;
300 memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time);
301}
302
303void
304Cache::promoteWholeLineWrites(PacketPtr pkt)
305{
306 // Cache line clearing instructions
307 if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
308 (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
309 pkt->cmd = MemCmd::WriteLineReq;
310 DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
311 }
312}
313
314void
315Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
316{
317 // should never be satisfying an uncacheable access as we
318 // flush and invalidate any existing block as part of the
319 // lookup
320 assert(!pkt->req->isUncacheable());
321
322 BaseCache::handleTimingReqHit(pkt, blk, request_time);
323}
324
325void
326Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
327 Tick request_time)
328{
329 if (pkt->req->isUncacheable()) {
330 // ignore any existing MSHR if we are dealing with an
331 // uncacheable request
332
333 // should have flushed and have no valid block
334 assert(!blk || !blk->isValid());
335
336 mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
337
338 if (pkt->isWrite()) {
339 allocateWriteBuffer(pkt, forward_time);
340 } else {
341 assert(pkt->isRead());
342
343 // uncacheable accesses always allocate a new MSHR
344
345 // Here we are using forward_time, modelling the latency of
346 // a miss (outbound) just as forwardLatency, neglecting the
347 // lookupLatency component.
348 allocateMissBuffer(pkt, forward_time);
349 }
350
351 return;
352 }
353
354 Addr blk_addr = pkt->getBlockAddr(blkSize);
355
356 MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
357
358 // Software prefetch handling:
359 // To keep the core from waiting on data it won't look at
360 // anyway, send back a response with dummy data. Miss handling
361 // will continue asynchronously. Unfortunately, the core will
362 // insist upon freeing original Packet/Request, so we have to
363 // create a new pair with a different lifecycle. Note that this
364 // processing happens before any MSHR munging on the behalf of
365 // this request because this new Request will be the one stored
366 // into the MSHRs, not the original.
367 if (pkt->cmd.isSWPrefetch()) {
368 assert(pkt->needsResponse());
369 assert(pkt->req->hasPaddr());
370 assert(!pkt->req->isUncacheable());
371
372 // There's no reason to add a prefetch as an additional target
373 // to an existing MSHR. If an outstanding request is already
374 // in progress, there is nothing for the prefetch to do.
375 // If this is the case, we don't even create a request at all.
376 PacketPtr pf = nullptr;
377
378 if (!mshr) {
379 // copy the request and create a new SoftPFReq packet
380 RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(),
381 pkt->req->getSize(),
382 pkt->req->getFlags(),
383 pkt->req->masterId());
384 pf = new Packet(req, pkt->cmd);
385 pf->allocate();
386 assert(pf->getAddr() == pkt->getAddr());
387 assert(pf->getSize() == pkt->getSize());
388 }
389
390 pkt->makeTimingResponse();
391
392 // request_time is used here, taking into account lat and the delay
393 // charged if the packet comes from the xbar.
394 cpuSidePort.schedTimingResp(pkt, request_time, true);
395
396 // If an outstanding request is in progress (we found an
397 // MSHR) this is set to null
398 pkt = pf;
399 }
400
401 BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time);
402}
403
404void
405Cache::recvTimingReq(PacketPtr pkt)
406{
407 DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
408
409 promoteWholeLineWrites(pkt);
410
411 if (pkt->cacheResponding()) {
412 // a cache above us (but not where the packet came from) is
413 // responding to the request, in other words it has the line
414 // in Modified or Owned state
415 DPRINTF(Cache, "Cache above responding to %s: not responding\n",
416 pkt->print());
417
418 // if the packet needs the block to be writable, and the cache
419 // that has promised to respond (setting the cache responding
420 // flag) is not providing writable (it is in Owned rather than
421 // the Modified state), we know that there may be other Shared
422 // copies in the system; go out and invalidate them all
423 assert(pkt->needsWritable() && !pkt->responderHadWritable());
424
425 // an upstream cache that had the line in Owned state
426 // (dirty, but not writable), is responding and thus
427 // transferring the dirty line from one branch of the
428 // cache hierarchy to another
429
430 // send out an express snoop and invalidate all other
431 // copies (snooping a packet that needs writable is the
432 // same as an invalidation), thus turning the Owned line
433 // into a Modified line, note that we don't invalidate the
434 // block in the current cache or any other cache on the
435 // path to memory
436
437 // create a downstream express snoop with cleared packet
438 // flags, there is no need to allocate any data as the
439 // packet is merely used to co-ordinate state transitions
440 Packet *snoop_pkt = new Packet(pkt, true, false);
441
442 // also reset the bus time that the original packet has
443 // not yet paid for
444 snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
445
446 // make this an instantaneous express snoop, and let the
447 // other caches in the system know that the another cache
448 // is responding, because we have found the authorative
449 // copy (Modified or Owned) that will supply the right
450 // data
451 snoop_pkt->setExpressSnoop();
452 snoop_pkt->setCacheResponding();
453
454 // this express snoop travels towards the memory, and at
455 // every crossbar it is snooped upwards thus reaching
456 // every cache in the system
457 bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt);
458 // express snoops always succeed
459 assert(success);
460
461 // main memory will delete the snoop packet
462
463 // queue for deletion, as opposed to immediate deletion, as
464 // the sending cache is still relying on the packet
465 pendingDelete.reset(pkt);
466
467 // no need to take any further action in this particular cache
468 // as an upstram cache has already committed to responding,
469 // and we have already sent out any express snoops in the
470 // section above to ensure all other copies in the system are
471 // invalidated
472 return;
473 }
474
475 BaseCache::recvTimingReq(pkt);
476}
477
478PacketPtr
479Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
|
480 bool needsWritable) const
| 480 bool needsWritable,
481 bool is_whole_line_write) const
|
481{
482 // should never see evictions here
483 assert(!cpu_pkt->isEviction());
484
485 bool blkValid = blk && blk->isValid();
486
487 if (cpu_pkt->req->isUncacheable() ||
488 (!blkValid && cpu_pkt->isUpgrade()) ||
489 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
490 // uncacheable requests and upgrades from upper-level caches
491 // that missed completely just go through as is
492 return nullptr;
493 }
494
495 assert(cpu_pkt->needsResponse());
496
497 MemCmd cmd;
498 // @TODO make useUpgrades a parameter.
499 // Note that ownership protocols require upgrade, otherwise a
500 // write miss on a shared owned block will generate a ReadExcl,
501 // which will clobber the owned copy.
502 const bool useUpgrades = true;
| 482{
483 // should never see evictions here
484 assert(!cpu_pkt->isEviction());
485
486 bool blkValid = blk && blk->isValid();
487
488 if (cpu_pkt->req->isUncacheable() ||
489 (!blkValid && cpu_pkt->isUpgrade()) ||
490 cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
491 // uncacheable requests and upgrades from upper-level caches
492 // that missed completely just go through as is
493 return nullptr;
494 }
495
496 assert(cpu_pkt->needsResponse());
497
498 MemCmd cmd;
499 // @TODO make useUpgrades a parameter.
500 // Note that ownership protocols require upgrade, otherwise a
501 // write miss on a shared owned block will generate a ReadExcl,
502 // which will clobber the owned copy.
503 const bool useUpgrades = true;
|
503 if (cpu_pkt->cmd == MemCmd::WriteLineReq) {
| 504 assert(cpu_pkt->cmd != MemCmd::WriteLineReq || is_whole_line_write);
505 if (is_whole_line_write) {
|
504 assert(!blkValid || !blk->isWritable());
505 // forward as invalidate to all other caches, this gives us
506 // the line in Exclusive state, and invalidates all other
507 // copies
508 cmd = MemCmd::InvalidateReq;
509 } else if (blkValid && useUpgrades) {
510 // only reason to be here is that blk is read only and we need
511 // it to be writable
512 assert(needsWritable);
513 assert(!blk->isWritable());
514 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
515 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
516 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
517 // Even though this SC will fail, we still need to send out the
518 // request and get the data to supply it to other snoopers in the case
519 // where the determination the StoreCond fails is delayed due to
520 // all caches not being on the same local bus.
521 cmd = MemCmd::SCUpgradeFailReq;
522 } else {
523 // block is invalid
524
525 // If the request does not need a writable there are two cases
526 // where we need to ensure the response will not fetch the
527 // block in dirty state:
528 // * this cache is read only and it does not perform
529 // writebacks,
530 // * this cache is mostly exclusive and will not fill (since
531 // it does not fill it will have to writeback the dirty data
532 // immediately which generates uneccesary writebacks).
533 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
534 cmd = needsWritable ? MemCmd::ReadExReq :
535 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
536 }
537 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
538
539 // if there are upstream caches that have already marked the
540 // packet as having sharers (not passing writable), pass that info
541 // downstream
542 if (cpu_pkt->hasSharers() && !needsWritable) {
543 // note that cpu_pkt may have spent a considerable time in the
544 // MSHR queue and that the information could possibly be out
545 // of date, however, there is no harm in conservatively
546 // assuming the block has sharers
547 pkt->setHasSharers();
548 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
549 __func__, cpu_pkt->print(), pkt->print());
550 }
551
552 // the packet should be block aligned
553 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
554
555 pkt->allocate();
556 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
557 cpu_pkt->print());
558 return pkt;
559}
560
561
562Cycles
563Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
564 PacketList &writebacks)
565{
566 // deal with the packets that go through the write path of
567 // the cache, i.e. any evictions and writes
568 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
569 (pkt->req->isUncacheable() && pkt->isWrite())) {
570 Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt));
571
572 // at this point, if the request was an uncacheable write
573 // request, it has been satisfied by a memory below and the
574 // packet carries the response back
575 assert(!(pkt->req->isUncacheable() && pkt->isWrite()) ||
576 pkt->isResponse());
577
578 return latency;
579 }
580
581 // only misses left
582
| 506 assert(!blkValid || !blk->isWritable());
507 // forward as invalidate to all other caches, this gives us
508 // the line in Exclusive state, and invalidates all other
509 // copies
510 cmd = MemCmd::InvalidateReq;
511 } else if (blkValid && useUpgrades) {
512 // only reason to be here is that blk is read only and we need
513 // it to be writable
514 assert(needsWritable);
515 assert(!blk->isWritable());
516 cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
517 } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
518 cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
519 // Even though this SC will fail, we still need to send out the
520 // request and get the data to supply it to other snoopers in the case
521 // where the determination the StoreCond fails is delayed due to
522 // all caches not being on the same local bus.
523 cmd = MemCmd::SCUpgradeFailReq;
524 } else {
525 // block is invalid
526
527 // If the request does not need a writable there are two cases
528 // where we need to ensure the response will not fetch the
529 // block in dirty state:
530 // * this cache is read only and it does not perform
531 // writebacks,
532 // * this cache is mostly exclusive and will not fill (since
533 // it does not fill it will have to writeback the dirty data
534 // immediately which generates uneccesary writebacks).
535 bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
536 cmd = needsWritable ? MemCmd::ReadExReq :
537 (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
538 }
539 PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
540
541 // if there are upstream caches that have already marked the
542 // packet as having sharers (not passing writable), pass that info
543 // downstream
544 if (cpu_pkt->hasSharers() && !needsWritable) {
545 // note that cpu_pkt may have spent a considerable time in the
546 // MSHR queue and that the information could possibly be out
547 // of date, however, there is no harm in conservatively
548 // assuming the block has sharers
549 pkt->setHasSharers();
550 DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
551 __func__, cpu_pkt->print(), pkt->print());
552 }
553
554 // the packet should be block aligned
555 assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
556
557 pkt->allocate();
558 DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
559 cpu_pkt->print());
560 return pkt;
561}
562
563
564Cycles
565Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
566 PacketList &writebacks)
567{
568 // deal with the packets that go through the write path of
569 // the cache, i.e. any evictions and writes
570 if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
571 (pkt->req->isUncacheable() && pkt->isWrite())) {
572 Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt));
573
574 // at this point, if the request was an uncacheable write
575 // request, it has been satisfied by a memory below and the
576 // packet carries the response back
577 assert(!(pkt->req->isUncacheable() && pkt->isWrite()) ||
578 pkt->isResponse());
579
580 return latency;
581 }
582
583 // only misses left
584
|
583 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable());
| 585 PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable(),
586 pkt->isWholeLineWrite(blkSize));
|
584
585 bool is_forward = (bus_pkt == nullptr);
586
587 if (is_forward) {
588 // just forwarding the same request to the next level
589 // no local cache operation involved
590 bus_pkt = pkt;
591 }
592
593 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
594 bus_pkt->print());
595
596#if TRACING_ON
597 CacheBlk::State old_state = blk ? blk->status : 0;
598#endif
599
600 Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt));
601
602 bool is_invalidate = bus_pkt->isInvalidate();
603
604 // We are now dealing with the response handling
605 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
606 bus_pkt->print(), old_state);
607
608 // If packet was a forward, the response (if any) is already
609 // in place in the bus_pkt == pkt structure, so we don't need
610 // to do anything. Otherwise, use the separate bus_pkt to
611 // generate response to pkt and then delete it.
612 if (!is_forward) {
613 if (pkt->needsResponse()) {
614 assert(bus_pkt->isResponse());
615 if (bus_pkt->isError()) {
616 pkt->makeAtomicResponse();
617 pkt->copyError(bus_pkt);
| 587
588 bool is_forward = (bus_pkt == nullptr);
589
590 if (is_forward) {
591 // just forwarding the same request to the next level
592 // no local cache operation involved
593 bus_pkt = pkt;
594 }
595
596 DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
597 bus_pkt->print());
598
599#if TRACING_ON
600 CacheBlk::State old_state = blk ? blk->status : 0;
601#endif
602
603 Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt));
604
605 bool is_invalidate = bus_pkt->isInvalidate();
606
607 // We are now dealing with the response handling
608 DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
609 bus_pkt->print(), old_state);
610
611 // If packet was a forward, the response (if any) is already
612 // in place in the bus_pkt == pkt structure, so we don't need
613 // to do anything. Otherwise, use the separate bus_pkt to
614 // generate response to pkt and then delete it.
615 if (!is_forward) {
616 if (pkt->needsResponse()) {
617 assert(bus_pkt->isResponse());
618 if (bus_pkt->isError()) {
619 pkt->makeAtomicResponse();
620 pkt->copyError(bus_pkt);
|
618 } else if (pkt->cmd == MemCmd::WriteLineReq) {
| 621 } else if (pkt->isWholeLineWrite(blkSize)) {
|
619 // note the use of pkt, not bus_pkt here.
620
621 // write-line request to the cache that promoted
622 // the write to a whole line
| 622 // note the use of pkt, not bus_pkt here.
623
624 // write-line request to the cache that promoted
625 // the write to a whole line
|
623 blk = handleFill(pkt, blk, writebacks,
| 626 blk = handleFill(bus_pkt, blk, writebacks,
|
624 allocOnFill(pkt->cmd));
625 assert(blk != NULL);
626 is_invalidate = false;
627 satisfyRequest(pkt, blk);
628 } else if (bus_pkt->isRead() ||
629 bus_pkt->cmd == MemCmd::UpgradeResp) {
630 // we're updating cache state to allow us to
631 // satisfy the upstream request from the cache
632 blk = handleFill(bus_pkt, blk, writebacks,
633 allocOnFill(pkt->cmd));
634 satisfyRequest(pkt, blk);
635 maintainClusivity(pkt->fromCache(), blk);
636 } else {
637 // we're satisfying the upstream request without
638 // modifying cache state, e.g., a write-through
639 pkt->makeAtomicResponse();
640 }
641 }
642 delete bus_pkt;
643 }
644
645 if (is_invalidate && blk && blk->isValid()) {
646 invalidateBlock(blk);
647 }
648
649 return latency;
650}
651
652Tick
653Cache::recvAtomic(PacketPtr pkt)
654{
655 promoteWholeLineWrites(pkt);
656
657 return BaseCache::recvAtomic(pkt);
658}
659
660
661/////////////////////////////////////////////////////
662//
663// Response handling: responses from the memory side
664//
665/////////////////////////////////////////////////////
666
667
668void
669Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk,
670 PacketList &writebacks)
671{
672 MSHR::Target *initial_tgt = mshr->getTarget();
673 // First offset for critical word first calculations
674 const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
675
676 const bool is_error = pkt->isError();
677 // allow invalidation responses originating from write-line
678 // requests to be discarded
| 627 allocOnFill(pkt->cmd));
628 assert(blk != NULL);
629 is_invalidate = false;
630 satisfyRequest(pkt, blk);
631 } else if (bus_pkt->isRead() ||
632 bus_pkt->cmd == MemCmd::UpgradeResp) {
633 // we're updating cache state to allow us to
634 // satisfy the upstream request from the cache
635 blk = handleFill(bus_pkt, blk, writebacks,
636 allocOnFill(pkt->cmd));
637 satisfyRequest(pkt, blk);
638 maintainClusivity(pkt->fromCache(), blk);
639 } else {
640 // we're satisfying the upstream request without
641 // modifying cache state, e.g., a write-through
642 pkt->makeAtomicResponse();
643 }
644 }
645 delete bus_pkt;
646 }
647
648 if (is_invalidate && blk && blk->isValid()) {
649 invalidateBlock(blk);
650 }
651
652 return latency;
653}
654
655Tick
656Cache::recvAtomic(PacketPtr pkt)
657{
658 promoteWholeLineWrites(pkt);
659
660 return BaseCache::recvAtomic(pkt);
661}
662
663
664/////////////////////////////////////////////////////
665//
666// Response handling: responses from the memory side
667//
668/////////////////////////////////////////////////////
669
670
671void
672Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk,
673 PacketList &writebacks)
674{
675 MSHR::Target *initial_tgt = mshr->getTarget();
676 // First offset for critical word first calculations
677 const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
678
679 const bool is_error = pkt->isError();
680 // allow invalidation responses originating from write-line
681 // requests to be discarded
|
679 bool is_invalidate = pkt->isInvalidate();
| 682 bool is_invalidate = pkt->isInvalidate() &&
683 !mshr->wasWholeLineWrite;
|
680
681 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
682 for (auto &target: targets) {
683 Packet *tgt_pkt = target.pkt;
684 switch (target.source) {
685 case MSHR::Target::FromCPU:
686 Tick completion_time;
687 // Here we charge on completion_time the delay of the xbar if the
688 // packet comes from it, charged on headerDelay.
689 completion_time = pkt->headerDelay;
690
691 // Software prefetch handling for cache closest to core
692 if (tgt_pkt->cmd.isSWPrefetch()) {
693 // a software prefetch would have already been ack'd
694 // immediately with dummy data so the core would be able to
695 // retire it. This request completes right here, so we
696 // deallocate it.
697 delete tgt_pkt;
698 break; // skip response
699 }
700
701 // unlike the other packet flows, where data is found in other
702 // caches or memory and brought back, write-line requests always
703 // have the data right away, so the above check for "is fill?"
704 // cannot actually be determined until examining the stored MSHR
705 // state. We "catch up" with that logic here, which is duplicated
706 // from above.
707 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
708 assert(!is_error);
| 684
685 MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
686 for (auto &target: targets) {
687 Packet *tgt_pkt = target.pkt;
688 switch (target.source) {
689 case MSHR::Target::FromCPU:
690 Tick completion_time;
691 // Here we charge on completion_time the delay of the xbar if the
692 // packet comes from it, charged on headerDelay.
693 completion_time = pkt->headerDelay;
694
695 // Software prefetch handling for cache closest to core
696 if (tgt_pkt->cmd.isSWPrefetch()) {
697 // a software prefetch would have already been ack'd
698 // immediately with dummy data so the core would be able to
699 // retire it. This request completes right here, so we
700 // deallocate it.
701 delete tgt_pkt;
702 break; // skip response
703 }
704
705 // unlike the other packet flows, where data is found in other
706 // caches or memory and brought back, write-line requests always
707 // have the data right away, so the above check for "is fill?"
708 // cannot actually be determined until examining the stored MSHR
709 // state. We "catch up" with that logic here, which is duplicated
710 // from above.
711 if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
712 assert(!is_error);
|
709 // we got the block in a writable state, so promote
710 // any deferred targets if possible
711 mshr->promoteWritable();
712 // NB: we use the original packet here and not the response!
713 blk = handleFill(tgt_pkt, blk, writebacks,
714 targets.allocOnFill);
| |
715 assert(blk);
| 713 assert(blk);
|
716
717 // discard the invalidation response
718 is_invalidate = false;
| 714 assert(blk->isWritable());
|
719 }
720
721 if (blk && blk->isValid() && !mshr->isForward) {
722 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
723
724 // How many bytes past the first request is this one
725 int transfer_offset =
726 tgt_pkt->getOffset(blkSize) - initial_offset;
727 if (transfer_offset < 0) {
728 transfer_offset += blkSize;
729 }
730
731 // If not critical word (offset) return payloadDelay.
732 // responseLatency is the latency of the return path
733 // from lower level caches/memory to an upper level cache or
734 // the core.
735 completion_time += clockEdge(responseLatency) +
736 (transfer_offset ? pkt->payloadDelay : 0);
737
738 assert(!tgt_pkt->req->isUncacheable());
739
740 assert(tgt_pkt->req->masterId() < system->maxMasters());
741 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
742 completion_time - target.recvTime;
743 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
744 // failed StoreCond upgrade
745 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
746 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
747 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
748 // responseLatency is the latency of the return path
749 // from lower level caches/memory to an upper level cache or
750 // the core.
751 completion_time += clockEdge(responseLatency) +
752 pkt->payloadDelay;
753 tgt_pkt->req->setExtraData(0);
754 } else {
755 // We are about to send a response to a cache above
756 // that asked for an invalidation; we need to
757 // invalidate our copy immediately as the most
758 // up-to-date copy of the block will now be in the
759 // cache above. It will also prevent this cache from
760 // responding (if the block was previously dirty) to
761 // snoops as they should snoop the caches above where
762 // they will get the response from.
763 if (is_invalidate && blk && blk->isValid()) {
764 invalidateBlock(blk);
765 }
766 // not a cache fill, just forwarding response
767 // responseLatency is the latency of the return path
768 // from lower level cahces/memory to the core.
769 completion_time += clockEdge(responseLatency) +
770 pkt->payloadDelay;
771 if (pkt->isRead() && !is_error) {
772 // sanity check
773 assert(pkt->getAddr() == tgt_pkt->getAddr());
774 assert(pkt->getSize() >= tgt_pkt->getSize());
775
776 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
777 }
778 }
779 tgt_pkt->makeTimingResponse();
780 // if this packet is an error copy that to the new packet
781 if (is_error)
782 tgt_pkt->copyError(pkt);
783 if (tgt_pkt->cmd == MemCmd::ReadResp &&
784 (is_invalidate || mshr->hasPostInvalidate())) {
785 // If intermediate cache got ReadRespWithInvalidate,
786 // propagate that. Response should not have
787 // isInvalidate() set otherwise.
788 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
789 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
790 tgt_pkt->print());
791 }
792 // Reset the bus additional time as it is now accounted for
793 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
794 cpuSidePort.schedTimingResp(tgt_pkt, completion_time, true);
795 break;
796
797 case MSHR::Target::FromPrefetcher:
798 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
799 if (blk)
800 blk->status |= BlkHWPrefetched;
801 delete tgt_pkt;
802 break;
803
804 case MSHR::Target::FromSnoop:
805 // I don't believe that a snoop can be in an error state
806 assert(!is_error);
807 // response to snoop request
808 DPRINTF(Cache, "processing deferred snoop...\n");
809 // If the response is invalidating, a snooping target can
810 // be satisfied if it is also invalidating. If the reponse is, not
811 // only invalidating, but more specifically an InvalidateResp and
812 // the MSHR was created due to an InvalidateReq then a cache above
813 // is waiting to satisfy a WriteLineReq. In this case even an
814 // non-invalidating snoop is added as a target here since this is
815 // the ordering point. When the InvalidateResp reaches this cache,
816 // the snooping target will snoop further the cache above with the
817 // WriteLineReq.
818 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
819 pkt->req->isCacheMaintenance() ||
820 mshr->hasPostInvalidate());
821 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
822 break;
823
824 default:
825 panic("Illegal target->source enum %d\n", target.source);
826 }
827 }
828
829 maintainClusivity(targets.hasFromCache, blk);
830
831 if (blk && blk->isValid()) {
832 // an invalidate response stemming from a write line request
833 // should not invalidate the block, so check if the
834 // invalidation should be discarded
835 if (is_invalidate || mshr->hasPostInvalidate()) {
836 invalidateBlock(blk);
837 } else if (mshr->hasPostDowngrade()) {
838 blk->status &= ~BlkWritable;
839 }
840 }
841}
842
843PacketPtr
844Cache::evictBlock(CacheBlk *blk)
845{
846 PacketPtr pkt = (blk->isDirty() || writebackClean) ?
847 writebackBlk(blk) : cleanEvictBlk(blk);
848
849 invalidateBlock(blk);
850
851 return pkt;
852}
853
854void
855Cache::evictBlock(CacheBlk *blk, PacketList &writebacks)
856{
857 PacketPtr pkt = evictBlock(blk);
858 if (pkt) {
859 writebacks.push_back(pkt);
860 }
861}
862
863PacketPtr
864Cache::cleanEvictBlk(CacheBlk *blk)
865{
866 assert(!writebackClean);
867 assert(blk && blk->isValid() && !blk->isDirty());
868
869 // Creating a zero sized write, a message to the snoop filter
870 RequestPtr req = std::make_shared<Request>(
871 regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId);
872
873 if (blk->isSecure())
874 req->setFlags(Request::SECURE);
875
876 req->taskId(blk->task_id);
877
878 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
879 pkt->allocate();
880 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
881
882 return pkt;
883}
884
885/////////////////////////////////////////////////////
886//
887// Snoop path: requests coming in from the memory side
888//
889/////////////////////////////////////////////////////
890
891void
892Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
893 bool already_copied, bool pending_inval)
894{
895 // sanity check
896 assert(req_pkt->isRequest());
897 assert(req_pkt->needsResponse());
898
899 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
900 // timing-mode snoop responses require a new packet, unless we
901 // already made a copy...
902 PacketPtr pkt = req_pkt;
903 if (!already_copied)
904 // do not clear flags, and allocate space for data if the
905 // packet needs it (the only packets that carry data are read
906 // responses)
907 pkt = new Packet(req_pkt, false, req_pkt->isRead());
908
909 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
910 pkt->hasSharers());
911 pkt->makeTimingResponse();
912 if (pkt->isRead()) {
913 pkt->setDataFromBlock(blk_data, blkSize);
914 }
915 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
916 // Assume we defer a response to a read from a far-away cache
917 // A, then later defer a ReadExcl from a cache B on the same
918 // bus as us. We'll assert cacheResponding in both cases, but
919 // in the latter case cacheResponding will keep the
920 // invalidation from reaching cache A. This special response
921 // tells cache A that it gets the block to satisfy its read,
922 // but must immediately invalidate it.
923 pkt->cmd = MemCmd::ReadRespWithInvalidate;
924 }
925 // Here we consider forward_time, paying for just forward latency and
926 // also charging the delay provided by the xbar.
927 // forward_time is used as send_time in next allocateWriteBuffer().
928 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
929 // Here we reset the timing of the packet.
930 pkt->headerDelay = pkt->payloadDelay = 0;
931 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
932 pkt->print(), forward_time);
933 memSidePort.schedTimingSnoopResp(pkt, forward_time, true);
934}
935
936uint32_t
937Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
938 bool is_deferred, bool pending_inval)
939{
940 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
941 // deferred snoops can only happen in timing mode
942 assert(!(is_deferred && !is_timing));
943 // pending_inval only makes sense on deferred snoops
944 assert(!(pending_inval && !is_deferred));
945 assert(pkt->isRequest());
946
947 // the packet may get modified if we or a forwarded snooper
948 // responds in atomic mode, so remember a few things about the
949 // original packet up front
950 bool invalidate = pkt->isInvalidate();
951 bool M5_VAR_USED needs_writable = pkt->needsWritable();
952
953 // at the moment we could get an uncacheable write which does not
954 // have the invalidate flag, and we need a suitable way of dealing
955 // with this case
956 panic_if(invalidate && pkt->req->isUncacheable(),
957 "%s got an invalidating uncacheable snoop request %s",
958 name(), pkt->print());
959
960 uint32_t snoop_delay = 0;
961
962 if (forwardSnoops) {
963 // first propagate snoop upward to see if anyone above us wants to
964 // handle it. save & restore packet src since it will get
965 // rewritten to be relative to cpu-side bus (if any)
966 bool alreadyResponded = pkt->cacheResponding();
967 if (is_timing) {
968 // copy the packet so that we can clear any flags before
969 // forwarding it upwards, we also allocate data (passing
970 // the pointer along in case of static data), in case
971 // there is a snoop hit in upper levels
972 Packet snoopPkt(pkt, true, true);
973 snoopPkt.setExpressSnoop();
974 // the snoop packet does not need to wait any additional
975 // time
976 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
977 cpuSidePort.sendTimingSnoopReq(&snoopPkt);
978
979 // add the header delay (including crossbar and snoop
980 // delays) of the upward snoop to the snoop delay for this
981 // cache
982 snoop_delay += snoopPkt.headerDelay;
983
984 if (snoopPkt.cacheResponding()) {
985 // cache-to-cache response from some upper cache
986 assert(!alreadyResponded);
987 pkt->setCacheResponding();
988 }
989 // upstream cache has the block, or has an outstanding
990 // MSHR, pass the flag on
991 if (snoopPkt.hasSharers()) {
992 pkt->setHasSharers();
993 }
994 // If this request is a prefetch or clean evict and an upper level
995 // signals block present, make sure to propagate the block
996 // presence to the requester.
997 if (snoopPkt.isBlockCached()) {
998 pkt->setBlockCached();
999 }
1000 // If the request was satisfied by snooping the cache
1001 // above, mark the original packet as satisfied too.
1002 if (snoopPkt.satisfied()) {
1003 pkt->setSatisfied();
1004 }
1005 } else {
1006 cpuSidePort.sendAtomicSnoop(pkt);
1007 if (!alreadyResponded && pkt->cacheResponding()) {
1008 // cache-to-cache response from some upper cache:
1009 // forward response to original requester
1010 assert(pkt->isResponse());
1011 }
1012 }
1013 }
1014
1015 bool respond = false;
1016 bool blk_valid = blk && blk->isValid();
1017 if (pkt->isClean()) {
1018 if (blk_valid && blk->isDirty()) {
1019 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
1020 __func__, pkt->print(), blk->print());
1021 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1022 PacketList writebacks;
1023 writebacks.push_back(wb_pkt);
1024
1025 if (is_timing) {
1026 // anything that is merely forwarded pays for the forward
1027 // latency and the delay provided by the crossbar
1028 Tick forward_time = clockEdge(forwardLatency) +
1029 pkt->headerDelay;
1030 doWritebacks(writebacks, forward_time);
1031 } else {
1032 doWritebacksAtomic(writebacks);
1033 }
1034 pkt->setSatisfied();
1035 }
1036 } else if (!blk_valid) {
1037 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
1038 pkt->print());
1039 if (is_deferred) {
1040 // we no longer have the block, and will not respond, but a
1041 // packet was allocated in MSHR::handleSnoop and we have
1042 // to delete it
1043 assert(pkt->needsResponse());
1044
1045 // we have passed the block to a cache upstream, that
1046 // cache should be responding
1047 assert(pkt->cacheResponding());
1048
1049 delete pkt;
1050 }
1051 return snoop_delay;
1052 } else {
1053 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
1054 pkt->print(), blk->print());
1055
1056 // We may end up modifying both the block state and the packet (if
1057 // we respond in atomic mode), so just figure out what to do now
1058 // and then do it later. We respond to all snoops that need
1059 // responses provided we have the block in dirty state. The
1060 // invalidation itself is taken care of below. We don't respond to
1061 // cache maintenance operations as this is done by the destination
1062 // xbar.
1063 respond = blk->isDirty() && pkt->needsResponse();
1064
1065 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
1066 "a dirty block in a read-only cache %s\n", name());
1067 }
1068
1069 // Invalidate any prefetch's from below that would strip write permissions
1070 // MemCmd::HardPFReq is only observed by upstream caches. After missing
1071 // above and in it's own cache, a new MemCmd::ReadReq is created that
1072 // downstream caches observe.
1073 if (pkt->mustCheckAbove()) {
1074 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
1075 "from lower cache\n", pkt->getAddr(), pkt->print());
1076 pkt->setBlockCached();
1077 return snoop_delay;
1078 }
1079
1080 if (pkt->isRead() && !invalidate) {
1081 // reading without requiring the line in a writable state
1082 assert(!needs_writable);
1083 pkt->setHasSharers();
1084
1085 // if the requesting packet is uncacheable, retain the line in
1086 // the current state, otherwhise unset the writable flag,
1087 // which means we go from Modified to Owned (and will respond
1088 // below), remain in Owned (and will respond below), from
1089 // Exclusive to Shared, or remain in Shared
1090 if (!pkt->req->isUncacheable())
1091 blk->status &= ~BlkWritable;
1092 DPRINTF(Cache, "new state is %s\n", blk->print());
1093 }
1094
1095 if (respond) {
1096 // prevent anyone else from responding, cache as well as
1097 // memory, and also prevent any memory from even seeing the
1098 // request
1099 pkt->setCacheResponding();
1100 if (!pkt->isClean() && blk->isWritable()) {
1101 // inform the cache hierarchy that this cache had the line
1102 // in the Modified state so that we avoid unnecessary
1103 // invalidations (see Packet::setResponderHadWritable)
1104 pkt->setResponderHadWritable();
1105
1106 // in the case of an uncacheable request there is no point
1107 // in setting the responderHadWritable flag, but since the
1108 // recipient does not care there is no harm in doing so
1109 } else {
1110 // if the packet has needsWritable set we invalidate our
1111 // copy below and all other copies will be invalidates
1112 // through express snoops, and if needsWritable is not set
1113 // we already called setHasSharers above
1114 }
1115
1116 // if we are returning a writable and dirty (Modified) line,
1117 // we should be invalidating the line
1118 panic_if(!invalidate && !pkt->hasSharers(),
1119 "%s is passing a Modified line through %s, "
1120 "but keeping the block", name(), pkt->print());
1121
1122 if (is_timing) {
1123 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
1124 } else {
1125 pkt->makeAtomicResponse();
1126 // packets such as upgrades do not actually have any data
1127 // payload
1128 if (pkt->hasData())
1129 pkt->setDataFromBlock(blk->data, blkSize);
1130 }
1131 }
1132
1133 if (!respond && is_deferred) {
1134 assert(pkt->needsResponse());
1135 delete pkt;
1136 }
1137
1138 // Do this last in case it deallocates block data or something
1139 // like that
1140 if (blk_valid && invalidate) {
1141 invalidateBlock(blk);
1142 DPRINTF(Cache, "new state is %s\n", blk->print());
1143 }
1144
1145 return snoop_delay;
1146}
1147
1148
1149void
1150Cache::recvTimingSnoopReq(PacketPtr pkt)
1151{
1152 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
1153
1154 // no need to snoop requests that are not in range
1155 if (!inRange(pkt->getAddr())) {
1156 return;
1157 }
1158
1159 bool is_secure = pkt->isSecure();
1160 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1161
1162 Addr blk_addr = pkt->getBlockAddr(blkSize);
1163 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1164
1165 // Update the latency cost of the snoop so that the crossbar can
1166 // account for it. Do not overwrite what other neighbouring caches
1167 // have already done, rather take the maximum. The update is
1168 // tentative, for cases where we return before an upward snoop
1169 // happens below.
1170 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
1171 lookupLatency * clockPeriod());
1172
1173 // Inform request(Prefetch, CleanEvict or Writeback) from below of
1174 // MSHR hit, set setBlockCached.
1175 if (mshr && pkt->mustCheckAbove()) {
1176 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
1177 "mshr hit\n", pkt->print());
1178 pkt->setBlockCached();
1179 return;
1180 }
1181
1182 // Bypass any existing cache maintenance requests if the request
1183 // has been satisfied already (i.e., the dirty block has been
1184 // found).
1185 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
1186 return;
1187 }
1188
1189 // Let the MSHR itself track the snoop and decide whether we want
1190 // to go ahead and do the regular cache snoop
1191 if (mshr && mshr->handleSnoop(pkt, order++)) {
1192 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
1193 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
1194 mshr->print());
1195
1196 if (mshr->getNumTargets() > numTarget)
1197 warn("allocating bonus target for snoop"); //handle later
1198 return;
1199 }
1200
1201 //We also need to check the writeback buffers and handle those
1202 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
1203 if (wb_entry) {
1204 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
1205 pkt->getAddr(), is_secure ? "s" : "ns");
1206 // Expect to see only Writebacks and/or CleanEvicts here, both of
1207 // which should not be generated for uncacheable data.
1208 assert(!wb_entry->isUncacheable());
1209 // There should only be a single request responsible for generating
1210 // Writebacks/CleanEvicts.
1211 assert(wb_entry->getNumTargets() == 1);
1212 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
1213 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
1214
1215 if (pkt->isEviction()) {
1216 // if the block is found in the write queue, set the BLOCK_CACHED
1217 // flag for Writeback/CleanEvict snoop. On return the snoop will
1218 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
1219 // any CleanEvicts from travelling down the memory hierarchy.
1220 pkt->setBlockCached();
1221 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
1222 "hit\n", __func__, pkt->print());
1223 return;
1224 }
1225
1226 // conceptually writebacks are no different to other blocks in
1227 // this cache, so the behaviour is modelled after handleSnoop,
1228 // the difference being that instead of querying the block
1229 // state to determine if it is dirty and writable, we use the
1230 // command and fields of the writeback packet
1231 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
1232 pkt->needsResponse();
1233 bool have_writable = !wb_pkt->hasSharers();
1234 bool invalidate = pkt->isInvalidate();
1235
1236 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
1237 assert(!pkt->needsWritable());
1238 pkt->setHasSharers();
1239 wb_pkt->setHasSharers();
1240 }
1241
1242 if (respond) {
1243 pkt->setCacheResponding();
1244
1245 if (have_writable) {
1246 pkt->setResponderHadWritable();
1247 }
1248
1249 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
1250 false, false);
1251 }
1252
1253 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
1254 // Invalidation trumps our writeback... discard here
1255 // Note: markInService will remove entry from writeback buffer.
1256 markInService(wb_entry);
1257 delete wb_pkt;
1258 }
1259 }
1260
1261 // If this was a shared writeback, there may still be
1262 // other shared copies above that require invalidation.
1263 // We could be more selective and return here if the
1264 // request is non-exclusive or if the writeback is
1265 // exclusive.
1266 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
1267
1268 // Override what we did when we first saw the snoop, as we now
1269 // also have the cost of the upwards snoops to account for
1270 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
1271 lookupLatency * clockPeriod());
1272}
1273
1274Tick
1275Cache::recvAtomicSnoop(PacketPtr pkt)
1276{
1277 // no need to snoop requests that are not in range.
1278 if (!inRange(pkt->getAddr())) {
1279 return 0;
1280 }
1281
1282 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1283 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
1284 return snoop_delay + lookupLatency * clockPeriod();
1285}
1286
1287bool
1288Cache::isCachedAbove(PacketPtr pkt, bool is_timing)
1289{
1290 if (!forwardSnoops)
1291 return false;
1292 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
1293 // Writeback snoops into upper level caches to check for copies of the
1294 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
1295 // packet, the cache can inform the crossbar below of presence or absence
1296 // of the block.
1297 if (is_timing) {
1298 Packet snoop_pkt(pkt, true, false);
1299 snoop_pkt.setExpressSnoop();
1300 // Assert that packet is either Writeback or CleanEvict and not a
1301 // prefetch request because prefetch requests need an MSHR and may
1302 // generate a snoop response.
1303 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
1304 snoop_pkt.senderState = nullptr;
1305 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1306 // Writeback/CleanEvict snoops do not generate a snoop response.
1307 assert(!(snoop_pkt.cacheResponding()));
1308 return snoop_pkt.isBlockCached();
1309 } else {
1310 cpuSidePort.sendAtomicSnoop(pkt);
1311 return pkt->isBlockCached();
1312 }
1313}
1314
1315bool
1316Cache::sendMSHRQueuePacket(MSHR* mshr)
1317{
1318 assert(mshr);
1319
1320 // use request from 1st target
1321 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
1322
1323 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
1324 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
1325
1326 // we should never have hardware prefetches to allocated
1327 // blocks
1328 assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure));
1329
1330 // We need to check the caches above us to verify that
1331 // they don't have a copy of this block in the dirty state
1332 // at the moment. Without this check we could get a stale
1333 // copy from memory that might get used in place of the
1334 // dirty one.
1335 Packet snoop_pkt(tgt_pkt, true, false);
1336 snoop_pkt.setExpressSnoop();
1337 // We are sending this packet upwards, but if it hits we will
1338 // get a snoop response that we end up treating just like a
1339 // normal response, hence it needs the MSHR as its sender
1340 // state
1341 snoop_pkt.senderState = mshr;
1342 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1343
1344 // Check to see if the prefetch was squashed by an upper cache (to
1345 // prevent us from grabbing the line) or if a Check to see if a
1346 // writeback arrived between the time the prefetch was placed in
1347 // the MSHRs and when it was selected to be sent or if the
1348 // prefetch was squashed by an upper cache.
1349
1350 // It is important to check cacheResponding before
1351 // prefetchSquashed. If another cache has committed to
1352 // responding, it will be sending a dirty response which will
1353 // arrive at the MSHR allocated for this request. Checking the
1354 // prefetchSquash first may result in the MSHR being
1355 // prematurely deallocated.
1356 if (snoop_pkt.cacheResponding()) {
1357 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
1358 assert(r.second);
1359
1360 // if we are getting a snoop response with no sharers it
1361 // will be allocated as Modified
1362 bool pending_modified_resp = !snoop_pkt.hasSharers();
1363 markInService(mshr, pending_modified_resp);
1364
1365 DPRINTF(Cache, "Upward snoop of prefetch for addr"
1366 " %#x (%s) hit\n",
1367 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
1368 return false;
1369 }
1370
1371 if (snoop_pkt.isBlockCached()) {
1372 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
1373 "Deallocating mshr target %#x.\n",
1374 mshr->blkAddr);
1375
1376 // Deallocate the mshr target
1377 if (mshrQueue.forceDeallocateTarget(mshr)) {
1378 // Clear block if this deallocation resulted freed an
1379 // mshr when all had previously been utilized
1380 clearBlocked(Blocked_NoMSHRs);
1381 }
1382
1383 // given that no response is expected, delete Request and Packet
1384 delete tgt_pkt;
1385
1386 return false;
1387 }
1388 }
1389
1390 return BaseCache::sendMSHRQueuePacket(mshr);
1391}
1392
1393Cache*
1394CacheParams::create()
1395{
1396 assert(tags);
1397 assert(replacement_policy);
1398
1399 return new Cache(this);
1400}
| 715 }
716
717 if (blk && blk->isValid() && !mshr->isForward) {
718 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
719
720 // How many bytes past the first request is this one
721 int transfer_offset =
722 tgt_pkt->getOffset(blkSize) - initial_offset;
723 if (transfer_offset < 0) {
724 transfer_offset += blkSize;
725 }
726
727 // If not critical word (offset) return payloadDelay.
728 // responseLatency is the latency of the return path
729 // from lower level caches/memory to an upper level cache or
730 // the core.
731 completion_time += clockEdge(responseLatency) +
732 (transfer_offset ? pkt->payloadDelay : 0);
733
734 assert(!tgt_pkt->req->isUncacheable());
735
736 assert(tgt_pkt->req->masterId() < system->maxMasters());
737 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
738 completion_time - target.recvTime;
739 } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
740 // failed StoreCond upgrade
741 assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
742 tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
743 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
744 // responseLatency is the latency of the return path
745 // from lower level caches/memory to an upper level cache or
746 // the core.
747 completion_time += clockEdge(responseLatency) +
748 pkt->payloadDelay;
749 tgt_pkt->req->setExtraData(0);
750 } else {
751 // We are about to send a response to a cache above
752 // that asked for an invalidation; we need to
753 // invalidate our copy immediately as the most
754 // up-to-date copy of the block will now be in the
755 // cache above. It will also prevent this cache from
756 // responding (if the block was previously dirty) to
757 // snoops as they should snoop the caches above where
758 // they will get the response from.
759 if (is_invalidate && blk && blk->isValid()) {
760 invalidateBlock(blk);
761 }
762 // not a cache fill, just forwarding response
763 // responseLatency is the latency of the return path
764 // from lower level cahces/memory to the core.
765 completion_time += clockEdge(responseLatency) +
766 pkt->payloadDelay;
767 if (pkt->isRead() && !is_error) {
768 // sanity check
769 assert(pkt->getAddr() == tgt_pkt->getAddr());
770 assert(pkt->getSize() >= tgt_pkt->getSize());
771
772 tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
773 }
774 }
775 tgt_pkt->makeTimingResponse();
776 // if this packet is an error copy that to the new packet
777 if (is_error)
778 tgt_pkt->copyError(pkt);
779 if (tgt_pkt->cmd == MemCmd::ReadResp &&
780 (is_invalidate || mshr->hasPostInvalidate())) {
781 // If intermediate cache got ReadRespWithInvalidate,
782 // propagate that. Response should not have
783 // isInvalidate() set otherwise.
784 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
785 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
786 tgt_pkt->print());
787 }
788 // Reset the bus additional time as it is now accounted for
789 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
790 cpuSidePort.schedTimingResp(tgt_pkt, completion_time, true);
791 break;
792
793 case MSHR::Target::FromPrefetcher:
794 assert(tgt_pkt->cmd == MemCmd::HardPFReq);
795 if (blk)
796 blk->status |= BlkHWPrefetched;
797 delete tgt_pkt;
798 break;
799
800 case MSHR::Target::FromSnoop:
801 // I don't believe that a snoop can be in an error state
802 assert(!is_error);
803 // response to snoop request
804 DPRINTF(Cache, "processing deferred snoop...\n");
805 // If the response is invalidating, a snooping target can
806 // be satisfied if it is also invalidating. If the reponse is, not
807 // only invalidating, but more specifically an InvalidateResp and
808 // the MSHR was created due to an InvalidateReq then a cache above
809 // is waiting to satisfy a WriteLineReq. In this case even an
810 // non-invalidating snoop is added as a target here since this is
811 // the ordering point. When the InvalidateResp reaches this cache,
812 // the snooping target will snoop further the cache above with the
813 // WriteLineReq.
814 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
815 pkt->req->isCacheMaintenance() ||
816 mshr->hasPostInvalidate());
817 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
818 break;
819
820 default:
821 panic("Illegal target->source enum %d\n", target.source);
822 }
823 }
824
825 maintainClusivity(targets.hasFromCache, blk);
826
827 if (blk && blk->isValid()) {
828 // an invalidate response stemming from a write line request
829 // should not invalidate the block, so check if the
830 // invalidation should be discarded
831 if (is_invalidate || mshr->hasPostInvalidate()) {
832 invalidateBlock(blk);
833 } else if (mshr->hasPostDowngrade()) {
834 blk->status &= ~BlkWritable;
835 }
836 }
837}
838
839PacketPtr
840Cache::evictBlock(CacheBlk *blk)
841{
842 PacketPtr pkt = (blk->isDirty() || writebackClean) ?
843 writebackBlk(blk) : cleanEvictBlk(blk);
844
845 invalidateBlock(blk);
846
847 return pkt;
848}
849
850void
851Cache::evictBlock(CacheBlk *blk, PacketList &writebacks)
852{
853 PacketPtr pkt = evictBlock(blk);
854 if (pkt) {
855 writebacks.push_back(pkt);
856 }
857}
858
859PacketPtr
860Cache::cleanEvictBlk(CacheBlk *blk)
861{
862 assert(!writebackClean);
863 assert(blk && blk->isValid() && !blk->isDirty());
864
865 // Creating a zero sized write, a message to the snoop filter
866 RequestPtr req = std::make_shared<Request>(
867 regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId);
868
869 if (blk->isSecure())
870 req->setFlags(Request::SECURE);
871
872 req->taskId(blk->task_id);
873
874 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
875 pkt->allocate();
876 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
877
878 return pkt;
879}
880
881/////////////////////////////////////////////////////
882//
883// Snoop path: requests coming in from the memory side
884//
885/////////////////////////////////////////////////////
886
887void
888Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
889 bool already_copied, bool pending_inval)
890{
891 // sanity check
892 assert(req_pkt->isRequest());
893 assert(req_pkt->needsResponse());
894
895 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
896 // timing-mode snoop responses require a new packet, unless we
897 // already made a copy...
898 PacketPtr pkt = req_pkt;
899 if (!already_copied)
900 // do not clear flags, and allocate space for data if the
901 // packet needs it (the only packets that carry data are read
902 // responses)
903 pkt = new Packet(req_pkt, false, req_pkt->isRead());
904
905 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
906 pkt->hasSharers());
907 pkt->makeTimingResponse();
908 if (pkt->isRead()) {
909 pkt->setDataFromBlock(blk_data, blkSize);
910 }
911 if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
912 // Assume we defer a response to a read from a far-away cache
913 // A, then later defer a ReadExcl from a cache B on the same
914 // bus as us. We'll assert cacheResponding in both cases, but
915 // in the latter case cacheResponding will keep the
916 // invalidation from reaching cache A. This special response
917 // tells cache A that it gets the block to satisfy its read,
918 // but must immediately invalidate it.
919 pkt->cmd = MemCmd::ReadRespWithInvalidate;
920 }
921 // Here we consider forward_time, paying for just forward latency and
922 // also charging the delay provided by the xbar.
923 // forward_time is used as send_time in next allocateWriteBuffer().
924 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
925 // Here we reset the timing of the packet.
926 pkt->headerDelay = pkt->payloadDelay = 0;
927 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
928 pkt->print(), forward_time);
929 memSidePort.schedTimingSnoopResp(pkt, forward_time, true);
930}
931
932uint32_t
933Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
934 bool is_deferred, bool pending_inval)
935{
936 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
937 // deferred snoops can only happen in timing mode
938 assert(!(is_deferred && !is_timing));
939 // pending_inval only makes sense on deferred snoops
940 assert(!(pending_inval && !is_deferred));
941 assert(pkt->isRequest());
942
943 // the packet may get modified if we or a forwarded snooper
944 // responds in atomic mode, so remember a few things about the
945 // original packet up front
946 bool invalidate = pkt->isInvalidate();
947 bool M5_VAR_USED needs_writable = pkt->needsWritable();
948
949 // at the moment we could get an uncacheable write which does not
950 // have the invalidate flag, and we need a suitable way of dealing
951 // with this case
952 panic_if(invalidate && pkt->req->isUncacheable(),
953 "%s got an invalidating uncacheable snoop request %s",
954 name(), pkt->print());
955
956 uint32_t snoop_delay = 0;
957
958 if (forwardSnoops) {
959 // first propagate snoop upward to see if anyone above us wants to
960 // handle it. save & restore packet src since it will get
961 // rewritten to be relative to cpu-side bus (if any)
962 bool alreadyResponded = pkt->cacheResponding();
963 if (is_timing) {
964 // copy the packet so that we can clear any flags before
965 // forwarding it upwards, we also allocate data (passing
966 // the pointer along in case of static data), in case
967 // there is a snoop hit in upper levels
968 Packet snoopPkt(pkt, true, true);
969 snoopPkt.setExpressSnoop();
970 // the snoop packet does not need to wait any additional
971 // time
972 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
973 cpuSidePort.sendTimingSnoopReq(&snoopPkt);
974
975 // add the header delay (including crossbar and snoop
976 // delays) of the upward snoop to the snoop delay for this
977 // cache
978 snoop_delay += snoopPkt.headerDelay;
979
980 if (snoopPkt.cacheResponding()) {
981 // cache-to-cache response from some upper cache
982 assert(!alreadyResponded);
983 pkt->setCacheResponding();
984 }
985 // upstream cache has the block, or has an outstanding
986 // MSHR, pass the flag on
987 if (snoopPkt.hasSharers()) {
988 pkt->setHasSharers();
989 }
990 // If this request is a prefetch or clean evict and an upper level
991 // signals block present, make sure to propagate the block
992 // presence to the requester.
993 if (snoopPkt.isBlockCached()) {
994 pkt->setBlockCached();
995 }
996 // If the request was satisfied by snooping the cache
997 // above, mark the original packet as satisfied too.
998 if (snoopPkt.satisfied()) {
999 pkt->setSatisfied();
1000 }
1001 } else {
1002 cpuSidePort.sendAtomicSnoop(pkt);
1003 if (!alreadyResponded && pkt->cacheResponding()) {
1004 // cache-to-cache response from some upper cache:
1005 // forward response to original requester
1006 assert(pkt->isResponse());
1007 }
1008 }
1009 }
1010
1011 bool respond = false;
1012 bool blk_valid = blk && blk->isValid();
1013 if (pkt->isClean()) {
1014 if (blk_valid && blk->isDirty()) {
1015 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
1016 __func__, pkt->print(), blk->print());
1017 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1018 PacketList writebacks;
1019 writebacks.push_back(wb_pkt);
1020
1021 if (is_timing) {
1022 // anything that is merely forwarded pays for the forward
1023 // latency and the delay provided by the crossbar
1024 Tick forward_time = clockEdge(forwardLatency) +
1025 pkt->headerDelay;
1026 doWritebacks(writebacks, forward_time);
1027 } else {
1028 doWritebacksAtomic(writebacks);
1029 }
1030 pkt->setSatisfied();
1031 }
1032 } else if (!blk_valid) {
1033 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
1034 pkt->print());
1035 if (is_deferred) {
1036 // we no longer have the block, and will not respond, but a
1037 // packet was allocated in MSHR::handleSnoop and we have
1038 // to delete it
1039 assert(pkt->needsResponse());
1040
1041 // we have passed the block to a cache upstream, that
1042 // cache should be responding
1043 assert(pkt->cacheResponding());
1044
1045 delete pkt;
1046 }
1047 return snoop_delay;
1048 } else {
1049 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
1050 pkt->print(), blk->print());
1051
1052 // We may end up modifying both the block state and the packet (if
1053 // we respond in atomic mode), so just figure out what to do now
1054 // and then do it later. We respond to all snoops that need
1055 // responses provided we have the block in dirty state. The
1056 // invalidation itself is taken care of below. We don't respond to
1057 // cache maintenance operations as this is done by the destination
1058 // xbar.
1059 respond = blk->isDirty() && pkt->needsResponse();
1060
1061 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
1062 "a dirty block in a read-only cache %s\n", name());
1063 }
1064
1065 // Invalidate any prefetch's from below that would strip write permissions
1066 // MemCmd::HardPFReq is only observed by upstream caches. After missing
1067 // above and in it's own cache, a new MemCmd::ReadReq is created that
1068 // downstream caches observe.
1069 if (pkt->mustCheckAbove()) {
1070 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
1071 "from lower cache\n", pkt->getAddr(), pkt->print());
1072 pkt->setBlockCached();
1073 return snoop_delay;
1074 }
1075
1076 if (pkt->isRead() && !invalidate) {
1077 // reading without requiring the line in a writable state
1078 assert(!needs_writable);
1079 pkt->setHasSharers();
1080
1081 // if the requesting packet is uncacheable, retain the line in
1082 // the current state, otherwhise unset the writable flag,
1083 // which means we go from Modified to Owned (and will respond
1084 // below), remain in Owned (and will respond below), from
1085 // Exclusive to Shared, or remain in Shared
1086 if (!pkt->req->isUncacheable())
1087 blk->status &= ~BlkWritable;
1088 DPRINTF(Cache, "new state is %s\n", blk->print());
1089 }
1090
1091 if (respond) {
1092 // prevent anyone else from responding, cache as well as
1093 // memory, and also prevent any memory from even seeing the
1094 // request
1095 pkt->setCacheResponding();
1096 if (!pkt->isClean() && blk->isWritable()) {
1097 // inform the cache hierarchy that this cache had the line
1098 // in the Modified state so that we avoid unnecessary
1099 // invalidations (see Packet::setResponderHadWritable)
1100 pkt->setResponderHadWritable();
1101
1102 // in the case of an uncacheable request there is no point
1103 // in setting the responderHadWritable flag, but since the
1104 // recipient does not care there is no harm in doing so
1105 } else {
1106 // if the packet has needsWritable set we invalidate our
1107 // copy below and all other copies will be invalidates
1108 // through express snoops, and if needsWritable is not set
1109 // we already called setHasSharers above
1110 }
1111
1112 // if we are returning a writable and dirty (Modified) line,
1113 // we should be invalidating the line
1114 panic_if(!invalidate && !pkt->hasSharers(),
1115 "%s is passing a Modified line through %s, "
1116 "but keeping the block", name(), pkt->print());
1117
1118 if (is_timing) {
1119 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
1120 } else {
1121 pkt->makeAtomicResponse();
1122 // packets such as upgrades do not actually have any data
1123 // payload
1124 if (pkt->hasData())
1125 pkt->setDataFromBlock(blk->data, blkSize);
1126 }
1127 }
1128
1129 if (!respond && is_deferred) {
1130 assert(pkt->needsResponse());
1131 delete pkt;
1132 }
1133
1134 // Do this last in case it deallocates block data or something
1135 // like that
1136 if (blk_valid && invalidate) {
1137 invalidateBlock(blk);
1138 DPRINTF(Cache, "new state is %s\n", blk->print());
1139 }
1140
1141 return snoop_delay;
1142}
1143
1144
1145void
1146Cache::recvTimingSnoopReq(PacketPtr pkt)
1147{
1148 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
1149
1150 // no need to snoop requests that are not in range
1151 if (!inRange(pkt->getAddr())) {
1152 return;
1153 }
1154
1155 bool is_secure = pkt->isSecure();
1156 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1157
1158 Addr blk_addr = pkt->getBlockAddr(blkSize);
1159 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1160
1161 // Update the latency cost of the snoop so that the crossbar can
1162 // account for it. Do not overwrite what other neighbouring caches
1163 // have already done, rather take the maximum. The update is
1164 // tentative, for cases where we return before an upward snoop
1165 // happens below.
1166 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
1167 lookupLatency * clockPeriod());
1168
1169 // Inform request(Prefetch, CleanEvict or Writeback) from below of
1170 // MSHR hit, set setBlockCached.
1171 if (mshr && pkt->mustCheckAbove()) {
1172 DPRINTF(Cache, "Setting block cached for %s from lower cache on "
1173 "mshr hit\n", pkt->print());
1174 pkt->setBlockCached();
1175 return;
1176 }
1177
1178 // Bypass any existing cache maintenance requests if the request
1179 // has been satisfied already (i.e., the dirty block has been
1180 // found).
1181 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
1182 return;
1183 }
1184
1185 // Let the MSHR itself track the snoop and decide whether we want
1186 // to go ahead and do the regular cache snoop
1187 if (mshr && mshr->handleSnoop(pkt, order++)) {
1188 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
1189 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
1190 mshr->print());
1191
1192 if (mshr->getNumTargets() > numTarget)
1193 warn("allocating bonus target for snoop"); //handle later
1194 return;
1195 }
1196
1197 //We also need to check the writeback buffers and handle those
1198 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
1199 if (wb_entry) {
1200 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
1201 pkt->getAddr(), is_secure ? "s" : "ns");
1202 // Expect to see only Writebacks and/or CleanEvicts here, both of
1203 // which should not be generated for uncacheable data.
1204 assert(!wb_entry->isUncacheable());
1205 // There should only be a single request responsible for generating
1206 // Writebacks/CleanEvicts.
1207 assert(wb_entry->getNumTargets() == 1);
1208 PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
1209 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
1210
1211 if (pkt->isEviction()) {
1212 // if the block is found in the write queue, set the BLOCK_CACHED
1213 // flag for Writeback/CleanEvict snoop. On return the snoop will
1214 // propagate the BLOCK_CACHED flag in Writeback packets and prevent
1215 // any CleanEvicts from travelling down the memory hierarchy.
1216 pkt->setBlockCached();
1217 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
1218 "hit\n", __func__, pkt->print());
1219 return;
1220 }
1221
1222 // conceptually writebacks are no different to other blocks in
1223 // this cache, so the behaviour is modelled after handleSnoop,
1224 // the difference being that instead of querying the block
1225 // state to determine if it is dirty and writable, we use the
1226 // command and fields of the writeback packet
1227 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
1228 pkt->needsResponse();
1229 bool have_writable = !wb_pkt->hasSharers();
1230 bool invalidate = pkt->isInvalidate();
1231
1232 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
1233 assert(!pkt->needsWritable());
1234 pkt->setHasSharers();
1235 wb_pkt->setHasSharers();
1236 }
1237
1238 if (respond) {
1239 pkt->setCacheResponding();
1240
1241 if (have_writable) {
1242 pkt->setResponderHadWritable();
1243 }
1244
1245 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
1246 false, false);
1247 }
1248
1249 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
1250 // Invalidation trumps our writeback... discard here
1251 // Note: markInService will remove entry from writeback buffer.
1252 markInService(wb_entry);
1253 delete wb_pkt;
1254 }
1255 }
1256
1257 // If this was a shared writeback, there may still be
1258 // other shared copies above that require invalidation.
1259 // We could be more selective and return here if the
1260 // request is non-exclusive or if the writeback is
1261 // exclusive.
1262 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
1263
1264 // Override what we did when we first saw the snoop, as we now
1265 // also have the cost of the upwards snoops to account for
1266 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
1267 lookupLatency * clockPeriod());
1268}
1269
1270Tick
1271Cache::recvAtomicSnoop(PacketPtr pkt)
1272{
1273 // no need to snoop requests that are not in range.
1274 if (!inRange(pkt->getAddr())) {
1275 return 0;
1276 }
1277
1278 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1279 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
1280 return snoop_delay + lookupLatency * clockPeriod();
1281}
1282
1283bool
1284Cache::isCachedAbove(PacketPtr pkt, bool is_timing)
1285{
1286 if (!forwardSnoops)
1287 return false;
1288 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
1289 // Writeback snoops into upper level caches to check for copies of the
1290 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
1291 // packet, the cache can inform the crossbar below of presence or absence
1292 // of the block.
1293 if (is_timing) {
1294 Packet snoop_pkt(pkt, true, false);
1295 snoop_pkt.setExpressSnoop();
1296 // Assert that packet is either Writeback or CleanEvict and not a
1297 // prefetch request because prefetch requests need an MSHR and may
1298 // generate a snoop response.
1299 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
1300 snoop_pkt.senderState = nullptr;
1301 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1302 // Writeback/CleanEvict snoops do not generate a snoop response.
1303 assert(!(snoop_pkt.cacheResponding()));
1304 return snoop_pkt.isBlockCached();
1305 } else {
1306 cpuSidePort.sendAtomicSnoop(pkt);
1307 return pkt->isBlockCached();
1308 }
1309}
1310
1311bool
1312Cache::sendMSHRQueuePacket(MSHR* mshr)
1313{
1314 assert(mshr);
1315
1316 // use request from 1st target
1317 PacketPtr tgt_pkt = mshr->getTarget()->pkt;
1318
1319 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
1320 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
1321
1322 // we should never have hardware prefetches to allocated
1323 // blocks
1324 assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure));
1325
1326 // We need to check the caches above us to verify that
1327 // they don't have a copy of this block in the dirty state
1328 // at the moment. Without this check we could get a stale
1329 // copy from memory that might get used in place of the
1330 // dirty one.
1331 Packet snoop_pkt(tgt_pkt, true, false);
1332 snoop_pkt.setExpressSnoop();
1333 // We are sending this packet upwards, but if it hits we will
1334 // get a snoop response that we end up treating just like a
1335 // normal response, hence it needs the MSHR as its sender
1336 // state
1337 snoop_pkt.senderState = mshr;
1338 cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1339
1340 // Check to see if the prefetch was squashed by an upper cache (to
1341 // prevent us from grabbing the line) or if a Check to see if a
1342 // writeback arrived between the time the prefetch was placed in
1343 // the MSHRs and when it was selected to be sent or if the
1344 // prefetch was squashed by an upper cache.
1345
1346 // It is important to check cacheResponding before
1347 // prefetchSquashed. If another cache has committed to
1348 // responding, it will be sending a dirty response which will
1349 // arrive at the MSHR allocated for this request. Checking the
1350 // prefetchSquash first may result in the MSHR being
1351 // prematurely deallocated.
1352 if (snoop_pkt.cacheResponding()) {
1353 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
1354 assert(r.second);
1355
1356 // if we are getting a snoop response with no sharers it
1357 // will be allocated as Modified
1358 bool pending_modified_resp = !snoop_pkt.hasSharers();
1359 markInService(mshr, pending_modified_resp);
1360
1361 DPRINTF(Cache, "Upward snoop of prefetch for addr"
1362 " %#x (%s) hit\n",
1363 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
1364 return false;
1365 }
1366
1367 if (snoop_pkt.isBlockCached()) {
1368 DPRINTF(Cache, "Block present, prefetch squashed by cache. "
1369 "Deallocating mshr target %#x.\n",
1370 mshr->blkAddr);
1371
1372 // Deallocate the mshr target
1373 if (mshrQueue.forceDeallocateTarget(mshr)) {
1374 // Clear block if this deallocation resulted freed an
1375 // mshr when all had previously been utilized
1376 clearBlocked(Blocked_NoMSHRs);
1377 }
1378
1379 // given that no response is expected, delete Request and Packet
1380 delete tgt_pkt;
1381
1382 return false;
1383 }
1384 }
1385
1386 return BaseCache::sendMSHRQueuePacket(mshr);
1387}
1388
1389Cache*
1390CacheParams::create()
1391{
1392 assert(tags);
1393 assert(replacement_policy);
1394
1395 return new Cache(this);
1396}
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