cache.cc revision 13564:9bbd53a77887
112855Sgabeblack@google.com/* 212855Sgabeblack@google.com * Copyright (c) 2010-2018 ARM Limited 312855Sgabeblack@google.com * All rights reserved. 412855Sgabeblack@google.com * 512855Sgabeblack@google.com * The license below extends only to copyright in the software and shall 612855Sgabeblack@google.com * not be construed as granting a license to any other intellectual 712855Sgabeblack@google.com * property including but not limited to intellectual property relating 812855Sgabeblack@google.com * to a hardware implementation of the functionality of the software 912855Sgabeblack@google.com * licensed hereunder. You may use the software subject to the license 1012855Sgabeblack@google.com * terms below provided that you ensure that this notice is replicated 1112855Sgabeblack@google.com * unmodified and in its entirety in all distributions of the software, 1212855Sgabeblack@google.com * modified or unmodified, in source code or in binary form. 1312855Sgabeblack@google.com * 1412855Sgabeblack@google.com * Copyright (c) 2002-2005 The Regents of The University of Michigan 1512855Sgabeblack@google.com * Copyright (c) 2010,2015 Advanced Micro Devices, Inc. 1612855Sgabeblack@google.com * All rights reserved. 1712855Sgabeblack@google.com * 1812855Sgabeblack@google.com * Redistribution and use in source and binary forms, with or without 1912855Sgabeblack@google.com * modification, are permitted provided that the following conditions are 2012855Sgabeblack@google.com * met: redistributions of source code must retain the above copyright 2112855Sgabeblack@google.com * notice, this list of conditions and the following disclaimer; 2212855Sgabeblack@google.com * redistributions in binary form must reproduce the above copyright 2312855Sgabeblack@google.com * notice, this list of conditions and the following disclaimer in the 2412855Sgabeblack@google.com * documentation and/or other materials provided with the distribution; 2512855Sgabeblack@google.com * neither the name of the copyright holders nor the names of its 2612855Sgabeblack@google.com * contributors may be used to endorse or promote products derived from 2712855Sgabeblack@google.com * this software without specific prior written permission. 2812855Sgabeblack@google.com * 2912855Sgabeblack@google.com * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 3012855Sgabeblack@google.com * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 3112855Sgabeblack@google.com * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 3212855Sgabeblack@google.com * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 3312855Sgabeblack@google.com * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 3412855Sgabeblack@google.com * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 3512855Sgabeblack@google.com * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 3612855Sgabeblack@google.com * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 3712855Sgabeblack@google.com * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 3812855Sgabeblack@google.com * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 3912855Sgabeblack@google.com * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 4012855Sgabeblack@google.com * 4112855Sgabeblack@google.com * Authors: Erik Hallnor 4212855Sgabeblack@google.com * Dave Greene 4312855Sgabeblack@google.com * Nathan Binkert 4412855Sgabeblack@google.com * Steve Reinhardt 4512855Sgabeblack@google.com * Ron Dreslinski 4612855Sgabeblack@google.com * Andreas Sandberg 4712855Sgabeblack@google.com * Nikos Nikoleris 4812855Sgabeblack@google.com */ 4912855Sgabeblack@google.com 5012855Sgabeblack@google.com/** 5112855Sgabeblack@google.com * @file 5212855Sgabeblack@google.com * Cache definitions. 5312855Sgabeblack@google.com */ 5412855Sgabeblack@google.com 5512855Sgabeblack@google.com#include "mem/cache/cache.hh" 5612855Sgabeblack@google.com 5712855Sgabeblack@google.com#include <cassert> 5812855Sgabeblack@google.com 5912855Sgabeblack@google.com#include "base/compiler.hh" 6012855Sgabeblack@google.com#include "base/logging.hh" 6112855Sgabeblack@google.com#include "base/trace.hh" 6212855Sgabeblack@google.com#include "base/types.hh" 6312855Sgabeblack@google.com#include "debug/Cache.hh" 6412855Sgabeblack@google.com#include "debug/CacheTags.hh" 6512855Sgabeblack@google.com#include "debug/CacheVerbose.hh" 6612855Sgabeblack@google.com#include "enums/Clusivity.hh" 6712855Sgabeblack@google.com#include "mem/cache/cache_blk.hh" 6812855Sgabeblack@google.com#include "mem/cache/mshr.hh" 6912855Sgabeblack@google.com#include "mem/cache/tags/base.hh" 7012855Sgabeblack@google.com#include "mem/cache/write_queue_entry.hh" 7112855Sgabeblack@google.com#include "mem/request.hh" 7212855Sgabeblack@google.com#include "params/Cache.hh" 7312855Sgabeblack@google.com 7412855Sgabeblack@google.comCache::Cache(const CacheParams *p) 7512855Sgabeblack@google.com : BaseCache(p, p->system->cacheLineSize()), 7612855Sgabeblack@google.com doFastWrites(true) 7712855Sgabeblack@google.com{ 7812855Sgabeblack@google.com} 7912855Sgabeblack@google.com 8012855Sgabeblack@google.comvoid 8112855Sgabeblack@google.comCache::satisfyRequest(PacketPtr pkt, CacheBlk *blk, 8212855Sgabeblack@google.com bool deferred_response, bool pending_downgrade) 8312855Sgabeblack@google.com{ 8412855Sgabeblack@google.com BaseCache::satisfyRequest(pkt, blk); 8512855Sgabeblack@google.com 8612855Sgabeblack@google.com if (pkt->isRead()) { 8712855Sgabeblack@google.com // determine if this read is from a (coherent) cache or not 8812855Sgabeblack@google.com if (pkt->fromCache()) { 8912855Sgabeblack@google.com assert(pkt->getSize() == blkSize); 9012855Sgabeblack@google.com // special handling for coherent block requests from 9112855Sgabeblack@google.com // upper-level caches 9212855Sgabeblack@google.com if (pkt->needsWritable()) { 9312855Sgabeblack@google.com // sanity check 9412855Sgabeblack@google.com assert(pkt->cmd == MemCmd::ReadExReq || 9512855Sgabeblack@google.com pkt->cmd == MemCmd::SCUpgradeFailReq); 9612855Sgabeblack@google.com assert(!pkt->hasSharers()); 9712855Sgabeblack@google.com 9812855Sgabeblack@google.com // if we have a dirty copy, make sure the recipient 9912855Sgabeblack@google.com // keeps it marked dirty (in the modified state) 10012855Sgabeblack@google.com if (blk->isDirty()) { 10112855Sgabeblack@google.com pkt->setCacheResponding(); 10212855Sgabeblack@google.com blk->status &= ~BlkDirty; 10312855Sgabeblack@google.com } 10412855Sgabeblack@google.com } else if (blk->isWritable() && !pending_downgrade && 10512855Sgabeblack@google.com !pkt->hasSharers() && 10612855Sgabeblack@google.com pkt->cmd != MemCmd::ReadCleanReq) { 10712855Sgabeblack@google.com // we can give the requester a writable copy on a read 10812855Sgabeblack@google.com // request if: 10912855Sgabeblack@google.com // - we have a writable copy at this level (& below) 11012855Sgabeblack@google.com // - we don't have a pending snoop from below 11112855Sgabeblack@google.com // signaling another read request 11212855Sgabeblack@google.com // - no other cache above has a copy (otherwise it 11312855Sgabeblack@google.com // would have set hasSharers flag when 11412855Sgabeblack@google.com // snooping the packet) 11512855Sgabeblack@google.com // - the read has explicitly asked for a clean 11612855Sgabeblack@google.com // copy of the line 11712855Sgabeblack@google.com if (blk->isDirty()) { 11812855Sgabeblack@google.com // special considerations if we're owner: 11912855Sgabeblack@google.com if (!deferred_response) { 12012855Sgabeblack@google.com // respond with the line in Modified state 12112855Sgabeblack@google.com // (cacheResponding set, hasSharers not set) 12212855Sgabeblack@google.com pkt->setCacheResponding(); 12312855Sgabeblack@google.com 12412855Sgabeblack@google.com // if this cache is mostly inclusive, we 12512855Sgabeblack@google.com // keep the block in the Exclusive state, 12612855Sgabeblack@google.com // and pass it upwards as Modified 12712855Sgabeblack@google.com // (writable and dirty), hence we have 12812855Sgabeblack@google.com // multiple caches, all on the same path 12912855Sgabeblack@google.com // towards memory, all considering the 13012855Sgabeblack@google.com // same block writable, but only one 13112855Sgabeblack@google.com // considering it Modified 13212855Sgabeblack@google.com 13312855Sgabeblack@google.com // we get away with multiple caches (on 13412855Sgabeblack@google.com // the same path to memory) considering 13512855Sgabeblack@google.com // the block writeable as we always enter 13612855Sgabeblack@google.com // the cache hierarchy through a cache, 13712855Sgabeblack@google.com // and first snoop upwards in all other 13812855Sgabeblack@google.com // branches 13912855Sgabeblack@google.com blk->status &= ~BlkDirty; 14012855Sgabeblack@google.com } else { 14112855Sgabeblack@google.com // if we're responding after our own miss, 14212855Sgabeblack@google.com // there's a window where the recipient didn't 14312855Sgabeblack@google.com // know it was getting ownership and may not 14412855Sgabeblack@google.com // have responded to snoops correctly, so we 14512855Sgabeblack@google.com // have to respond with a shared line 14612855Sgabeblack@google.com pkt->setHasSharers(); 14712855Sgabeblack@google.com } 14812855Sgabeblack@google.com } 14912855Sgabeblack@google.com } else { 15012855Sgabeblack@google.com // otherwise only respond with a shared copy 15112855Sgabeblack@google.com pkt->setHasSharers(); 15212855Sgabeblack@google.com } 15312855Sgabeblack@google.com } 15412855Sgabeblack@google.com } 15512855Sgabeblack@google.com} 15612855Sgabeblack@google.com 15712855Sgabeblack@google.com///////////////////////////////////////////////////// 15812855Sgabeblack@google.com// 15912855Sgabeblack@google.com// Access path: requests coming in from the CPU side 16012855Sgabeblack@google.com// 16112855Sgabeblack@google.com///////////////////////////////////////////////////// 16212855Sgabeblack@google.com 16312855Sgabeblack@google.combool 16412855Sgabeblack@google.comCache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat, 16512855Sgabeblack@google.com PacketList &writebacks) 16612855Sgabeblack@google.com{ 16712855Sgabeblack@google.com 16812855Sgabeblack@google.com if (pkt->req->isUncacheable()) { 16912855Sgabeblack@google.com assert(pkt->isRequest()); 17012855Sgabeblack@google.com 17112855Sgabeblack@google.com chatty_assert(!(isReadOnly && pkt->isWrite()), 17212855Sgabeblack@google.com "Should never see a write in a read-only cache %s\n", 17312855Sgabeblack@google.com name()); 17412855Sgabeblack@google.com 17512855Sgabeblack@google.com DPRINTF(Cache, "%s for %s\n", __func__, pkt->print()); 17612855Sgabeblack@google.com 17712855Sgabeblack@google.com // flush and invalidate any existing block 17812855Sgabeblack@google.com CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure())); 17912855Sgabeblack@google.com if (old_blk && old_blk->isValid()) { 18012855Sgabeblack@google.com BaseCache::evictBlock(old_blk, writebacks); 18112855Sgabeblack@google.com } 18212855Sgabeblack@google.com 18312855Sgabeblack@google.com blk = nullptr; 18412855Sgabeblack@google.com // lookupLatency is the latency in case the request is uncacheable. 18512855Sgabeblack@google.com lat = lookupLatency; 18612855Sgabeblack@google.com return false; 18712855Sgabeblack@google.com } 18812855Sgabeblack@google.com 18912855Sgabeblack@google.com return BaseCache::access(pkt, blk, lat, writebacks); 19012855Sgabeblack@google.com} 19112855Sgabeblack@google.com 19212855Sgabeblack@google.comvoid 19312855Sgabeblack@google.comCache::doWritebacks(PacketList& writebacks, Tick forward_time) 19412855Sgabeblack@google.com{ 19512855Sgabeblack@google.com while (!writebacks.empty()) { 19612855Sgabeblack@google.com PacketPtr wbPkt = writebacks.front(); 19712855Sgabeblack@google.com // We use forwardLatency here because we are copying writebacks to 19812855Sgabeblack@google.com // write buffer. 19912855Sgabeblack@google.com 20012855Sgabeblack@google.com // Call isCachedAbove for Writebacks, CleanEvicts and 20112855Sgabeblack@google.com // WriteCleans to discover if the block is cached above. 20212855Sgabeblack@google.com if (isCachedAbove(wbPkt)) { 20312855Sgabeblack@google.com if (wbPkt->cmd == MemCmd::CleanEvict) { 20412855Sgabeblack@google.com // Delete CleanEvict because cached copies exist above. The 20512855Sgabeblack@google.com // packet destructor will delete the request object because 20612855Sgabeblack@google.com // this is a non-snoop request packet which does not require a 20712855Sgabeblack@google.com // response. 20812855Sgabeblack@google.com delete wbPkt; 20912855Sgabeblack@google.com } else if (wbPkt->cmd == MemCmd::WritebackClean) { 21012855Sgabeblack@google.com // clean writeback, do not send since the block is 21112855Sgabeblack@google.com // still cached above 21212855Sgabeblack@google.com assert(writebackClean); 21312855Sgabeblack@google.com delete wbPkt; 21412855Sgabeblack@google.com } else { 21512855Sgabeblack@google.com assert(wbPkt->cmd == MemCmd::WritebackDirty || 21612855Sgabeblack@google.com wbPkt->cmd == MemCmd::WriteClean); 21712855Sgabeblack@google.com // Set BLOCK_CACHED flag in Writeback and send below, so that 21812855Sgabeblack@google.com // the Writeback does not reset the bit corresponding to this 21912855Sgabeblack@google.com // address in the snoop filter below. 22012855Sgabeblack@google.com wbPkt->setBlockCached(); 22112855Sgabeblack@google.com allocateWriteBuffer(wbPkt, forward_time); 22212855Sgabeblack@google.com } 22312855Sgabeblack@google.com } else { 22412855Sgabeblack@google.com // If the block is not cached above, send packet below. Both 22512855Sgabeblack@google.com // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 22612855Sgabeblack@google.com // reset the bit corresponding to this address in the snoop filter 22712855Sgabeblack@google.com // below. 22812855Sgabeblack@google.com allocateWriteBuffer(wbPkt, forward_time); 22912855Sgabeblack@google.com } 23012855Sgabeblack@google.com writebacks.pop_front(); 23112855Sgabeblack@google.com } 23212855Sgabeblack@google.com} 23312855Sgabeblack@google.com 23412855Sgabeblack@google.comvoid 23512855Sgabeblack@google.comCache::doWritebacksAtomic(PacketList& writebacks) 23612855Sgabeblack@google.com{ 23712855Sgabeblack@google.com while (!writebacks.empty()) { 23812855Sgabeblack@google.com PacketPtr wbPkt = writebacks.front(); 23912855Sgabeblack@google.com // Call isCachedAbove for both Writebacks and CleanEvicts. If 24012855Sgabeblack@google.com // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks 24112855Sgabeblack@google.com // and discard CleanEvicts. 24212855Sgabeblack@google.com if (isCachedAbove(wbPkt, false)) { 24312855Sgabeblack@google.com if (wbPkt->cmd == MemCmd::WritebackDirty || 24412855Sgabeblack@google.com wbPkt->cmd == MemCmd::WriteClean) { 24512855Sgabeblack@google.com // Set BLOCK_CACHED flag in Writeback and send below, 24612855Sgabeblack@google.com // so that the Writeback does not reset the bit 24712855Sgabeblack@google.com // corresponding to this address in the snoop filter 24812855Sgabeblack@google.com // below. We can discard CleanEvicts because cached 24912855Sgabeblack@google.com // copies exist above. Atomic mode isCachedAbove 25012855Sgabeblack@google.com // modifies packet to set BLOCK_CACHED flag 25112855Sgabeblack@google.com memSidePort.sendAtomic(wbPkt); 25212855Sgabeblack@google.com } 25312855Sgabeblack@google.com } else { 25412855Sgabeblack@google.com // If the block is not cached above, send packet below. Both 25512855Sgabeblack@google.com // CleanEvict and Writeback with BLOCK_CACHED flag cleared will 25612855Sgabeblack@google.com // reset the bit corresponding to this address in the snoop filter 25712855Sgabeblack@google.com // below. 25812855Sgabeblack@google.com memSidePort.sendAtomic(wbPkt); 25912855Sgabeblack@google.com } 26012855Sgabeblack@google.com writebacks.pop_front(); 26112855Sgabeblack@google.com // In case of CleanEvicts, the packet destructor will delete the 26212855Sgabeblack@google.com // request object because this is a non-snoop request packet which 26312855Sgabeblack@google.com // does not require a response. 26412855Sgabeblack@google.com delete wbPkt; 26512855Sgabeblack@google.com } 26612855Sgabeblack@google.com} 26712855Sgabeblack@google.com 26812855Sgabeblack@google.com 26912855Sgabeblack@google.comvoid 27012855Sgabeblack@google.comCache::recvTimingSnoopResp(PacketPtr pkt) 27112855Sgabeblack@google.com{ 27212855Sgabeblack@google.com DPRINTF(Cache, "%s for %s\n", __func__, pkt->print()); 27312855Sgabeblack@google.com 27412855Sgabeblack@google.com // determine if the response is from a snoop request we created 27512855Sgabeblack@google.com // (in which case it should be in the outstandingSnoop), or if we 27612855Sgabeblack@google.com // merely forwarded someone else's snoop request 27712855Sgabeblack@google.com const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) == 27812855Sgabeblack@google.com outstandingSnoop.end(); 27912855Sgabeblack@google.com 28012855Sgabeblack@google.com if (!forwardAsSnoop) { 28112855Sgabeblack@google.com // the packet came from this cache, so sink it here and do not 28212855Sgabeblack@google.com // forward it 28312855Sgabeblack@google.com assert(pkt->cmd == MemCmd::HardPFResp); 28412855Sgabeblack@google.com 28512855Sgabeblack@google.com outstandingSnoop.erase(pkt->req); 28612855Sgabeblack@google.com 28712855Sgabeblack@google.com DPRINTF(Cache, "Got prefetch response from above for addr " 28812855Sgabeblack@google.com "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns"); 28912855Sgabeblack@google.com recvTimingResp(pkt); 29012855Sgabeblack@google.com return; 29112855Sgabeblack@google.com } 29212855Sgabeblack@google.com 29312855Sgabeblack@google.com // forwardLatency is set here because there is a response from an 29412855Sgabeblack@google.com // upper level cache. 29512855Sgabeblack@google.com // To pay the delay that occurs if the packet comes from the bus, 29612855Sgabeblack@google.com // we charge also headerDelay. 29712855Sgabeblack@google.com Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay; 29812855Sgabeblack@google.com // Reset the timing of the packet. 29912855Sgabeblack@google.com pkt->headerDelay = pkt->payloadDelay = 0; 30012855Sgabeblack@google.com memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time); 30112855Sgabeblack@google.com} 30212855Sgabeblack@google.com 30312855Sgabeblack@google.comvoid 30412855Sgabeblack@google.comCache::promoteWholeLineWrites(PacketPtr pkt) 30512855Sgabeblack@google.com{ 30612855Sgabeblack@google.com // Cache line clearing instructions 30712855Sgabeblack@google.com if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) && 30812855Sgabeblack@google.com (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) { 30912855Sgabeblack@google.com pkt->cmd = MemCmd::WriteLineReq; 31012855Sgabeblack@google.com DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n"); 31112855Sgabeblack@google.com } 31212855Sgabeblack@google.com} 31312855Sgabeblack@google.com 31412855Sgabeblack@google.comvoid 31512855Sgabeblack@google.comCache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time) 31612855Sgabeblack@google.com{ 31712855Sgabeblack@google.com // should never be satisfying an uncacheable access as we 31812855Sgabeblack@google.com // flush and invalidate any existing block as part of the 31912855Sgabeblack@google.com // lookup 32012855Sgabeblack@google.com assert(!pkt->req->isUncacheable()); 32112855Sgabeblack@google.com 32212855Sgabeblack@google.com BaseCache::handleTimingReqHit(pkt, blk, request_time); 32312855Sgabeblack@google.com} 32412855Sgabeblack@google.com 32512855Sgabeblack@google.comvoid 32612855Sgabeblack@google.comCache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time, 32712855Sgabeblack@google.com Tick request_time) 32812855Sgabeblack@google.com{ 32912855Sgabeblack@google.com if (pkt->req->isUncacheable()) { 33012855Sgabeblack@google.com // ignore any existing MSHR if we are dealing with an 33112855Sgabeblack@google.com // uncacheable request 33212855Sgabeblack@google.com 33312855Sgabeblack@google.com // should have flushed and have no valid block 33412855Sgabeblack@google.com assert(!blk || !blk->isValid()); 33512855Sgabeblack@google.com 33612855Sgabeblack@google.com mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++; 33712855Sgabeblack@google.com 33812855Sgabeblack@google.com if (pkt->isWrite()) { 33912855Sgabeblack@google.com allocateWriteBuffer(pkt, forward_time); 34012855Sgabeblack@google.com } else { 34112855Sgabeblack@google.com assert(pkt->isRead()); 34212855Sgabeblack@google.com 34312855Sgabeblack@google.com // uncacheable accesses always allocate a new MSHR 34412855Sgabeblack@google.com 34512855Sgabeblack@google.com // Here we are using forward_time, modelling the latency of 34612855Sgabeblack@google.com // a miss (outbound) just as forwardLatency, neglecting the 34712855Sgabeblack@google.com // lookupLatency component. 34812855Sgabeblack@google.com allocateMissBuffer(pkt, forward_time); 34912855Sgabeblack@google.com } 35012855Sgabeblack@google.com 35112855Sgabeblack@google.com return; 35212855Sgabeblack@google.com } 35312855Sgabeblack@google.com 35412855Sgabeblack@google.com Addr blk_addr = pkt->getBlockAddr(blkSize); 35512855Sgabeblack@google.com 35612855Sgabeblack@google.com MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure()); 35712855Sgabeblack@google.com 35812855Sgabeblack@google.com // Software prefetch handling: 35912855Sgabeblack@google.com // To keep the core from waiting on data it won't look at 36012855Sgabeblack@google.com // anyway, send back a response with dummy data. Miss handling 36112855Sgabeblack@google.com // will continue asynchronously. Unfortunately, the core will 36212855Sgabeblack@google.com // insist upon freeing original Packet/Request, so we have to 36312855Sgabeblack@google.com // create a new pair with a different lifecycle. Note that this 36412855Sgabeblack@google.com // processing happens before any MSHR munging on the behalf of 36512855Sgabeblack@google.com // this request because this new Request will be the one stored 36612855Sgabeblack@google.com // into the MSHRs, not the original. 36712855Sgabeblack@google.com if (pkt->cmd.isSWPrefetch()) { 36812855Sgabeblack@google.com assert(pkt->needsResponse()); 36912855Sgabeblack@google.com assert(pkt->req->hasPaddr()); 37012855Sgabeblack@google.com assert(!pkt->req->isUncacheable()); 37112855Sgabeblack@google.com 37212855Sgabeblack@google.com // There's no reason to add a prefetch as an additional target 37312855Sgabeblack@google.com // to an existing MSHR. If an outstanding request is already 37412855Sgabeblack@google.com // in progress, there is nothing for the prefetch to do. 37512855Sgabeblack@google.com // If this is the case, we don't even create a request at all. 37612855Sgabeblack@google.com PacketPtr pf = nullptr; 37712855Sgabeblack@google.com 37812855Sgabeblack@google.com if (!mshr) { 37912855Sgabeblack@google.com // copy the request and create a new SoftPFReq packet 38012855Sgabeblack@google.com RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(), 38112855Sgabeblack@google.com pkt->req->getSize(), 38212855Sgabeblack@google.com pkt->req->getFlags(), 38312855Sgabeblack@google.com pkt->req->masterId()); 38412855Sgabeblack@google.com pf = new Packet(req, pkt->cmd); 38512855Sgabeblack@google.com pf->allocate(); 38612855Sgabeblack@google.com assert(pf->getAddr() == pkt->getAddr()); 38712855Sgabeblack@google.com assert(pf->getSize() == pkt->getSize()); 38812855Sgabeblack@google.com } 38912855Sgabeblack@google.com 39012855Sgabeblack@google.com pkt->makeTimingResponse(); 39112855Sgabeblack@google.com 39212855Sgabeblack@google.com // request_time is used here, taking into account lat and the delay 39312855Sgabeblack@google.com // charged if the packet comes from the xbar. 39412855Sgabeblack@google.com cpuSidePort.schedTimingResp(pkt, request_time); 39512855Sgabeblack@google.com 39612855Sgabeblack@google.com // If an outstanding request is in progress (we found an 39712855Sgabeblack@google.com // MSHR) this is set to null 39812855Sgabeblack@google.com pkt = pf; 39912855Sgabeblack@google.com } 40012855Sgabeblack@google.com 40112855Sgabeblack@google.com BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time); 40212855Sgabeblack@google.com} 40312855Sgabeblack@google.com 40412855Sgabeblack@google.comvoid 40512855Sgabeblack@google.comCache::recvTimingReq(PacketPtr pkt) 40612855Sgabeblack@google.com{ 40712855Sgabeblack@google.com DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print()); 40812855Sgabeblack@google.com 40912855Sgabeblack@google.com promoteWholeLineWrites(pkt); 41012855Sgabeblack@google.com 41112855Sgabeblack@google.com if (pkt->cacheResponding()) { 41212855Sgabeblack@google.com // a cache above us (but not where the packet came from) is 41312855Sgabeblack@google.com // responding to the request, in other words it has the line 41412855Sgabeblack@google.com // in Modified or Owned state 41512855Sgabeblack@google.com DPRINTF(Cache, "Cache above responding to %s: not responding\n", 41612855Sgabeblack@google.com pkt->print()); 41712855Sgabeblack@google.com 41812855Sgabeblack@google.com // if the packet needs the block to be writable, and the cache 41912855Sgabeblack@google.com // that has promised to respond (setting the cache responding 42012855Sgabeblack@google.com // flag) is not providing writable (it is in Owned rather than 42112855Sgabeblack@google.com // the Modified state), we know that there may be other Shared 42212855Sgabeblack@google.com // copies in the system; go out and invalidate them all 42312855Sgabeblack@google.com assert(pkt->needsWritable() && !pkt->responderHadWritable()); 42412855Sgabeblack@google.com 42512855Sgabeblack@google.com // an upstream cache that had the line in Owned state 42612855Sgabeblack@google.com // (dirty, but not writable), is responding and thus 42712855Sgabeblack@google.com // transferring the dirty line from one branch of the 42812855Sgabeblack@google.com // cache hierarchy to another 42912855Sgabeblack@google.com 43012855Sgabeblack@google.com // send out an express snoop and invalidate all other 43112855Sgabeblack@google.com // copies (snooping a packet that needs writable is the 43212855Sgabeblack@google.com // same as an invalidation), thus turning the Owned line 43312855Sgabeblack@google.com // into a Modified line, note that we don't invalidate the 43412855Sgabeblack@google.com // block in the current cache or any other cache on the 43512855Sgabeblack@google.com // path to memory 43612855Sgabeblack@google.com 43712855Sgabeblack@google.com // create a downstream express snoop with cleared packet 43812855Sgabeblack@google.com // flags, there is no need to allocate any data as the 43912855Sgabeblack@google.com // packet is merely used to co-ordinate state transitions 44012855Sgabeblack@google.com Packet *snoop_pkt = new Packet(pkt, true, false); 44112855Sgabeblack@google.com 44212855Sgabeblack@google.com // also reset the bus time that the original packet has 44312855Sgabeblack@google.com // not yet paid for 44412855Sgabeblack@google.com snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0; 44512855Sgabeblack@google.com 44612855Sgabeblack@google.com // make this an instantaneous express snoop, and let the 44712855Sgabeblack@google.com // other caches in the system know that the another cache 44812855Sgabeblack@google.com // is responding, because we have found the authorative 44912855Sgabeblack@google.com // copy (Modified or Owned) that will supply the right 45012855Sgabeblack@google.com // data 45112855Sgabeblack@google.com snoop_pkt->setExpressSnoop(); 45212855Sgabeblack@google.com snoop_pkt->setCacheResponding(); 45312855Sgabeblack@google.com 45412855Sgabeblack@google.com // this express snoop travels towards the memory, and at 45512855Sgabeblack@google.com // every crossbar it is snooped upwards thus reaching 45612855Sgabeblack@google.com // every cache in the system 45712855Sgabeblack@google.com bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt); 45812855Sgabeblack@google.com // express snoops always succeed 45912855Sgabeblack@google.com assert(success); 46012855Sgabeblack@google.com 46112855Sgabeblack@google.com // main memory will delete the snoop packet 46212855Sgabeblack@google.com 46312855Sgabeblack@google.com // queue for deletion, as opposed to immediate deletion, as 46412855Sgabeblack@google.com // the sending cache is still relying on the packet 46512855Sgabeblack@google.com pendingDelete.reset(pkt); 46612855Sgabeblack@google.com 46712855Sgabeblack@google.com // no need to take any further action in this particular cache 46812855Sgabeblack@google.com // as an upstram cache has already committed to responding, 46912855Sgabeblack@google.com // and we have already sent out any express snoops in the 47012855Sgabeblack@google.com // section above to ensure all other copies in the system are 47112855Sgabeblack@google.com // invalidated 47212855Sgabeblack@google.com return; 47312855Sgabeblack@google.com } 47412855Sgabeblack@google.com 47512855Sgabeblack@google.com BaseCache::recvTimingReq(pkt); 47612855Sgabeblack@google.com} 47712855Sgabeblack@google.com 47812855Sgabeblack@google.comPacketPtr 47912855Sgabeblack@google.comCache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk, 48012855Sgabeblack@google.com bool needsWritable, 48112855Sgabeblack@google.com bool is_whole_line_write) const 48212855Sgabeblack@google.com{ 48312855Sgabeblack@google.com // should never see evictions here 48412855Sgabeblack@google.com assert(!cpu_pkt->isEviction()); 48512855Sgabeblack@google.com 48612855Sgabeblack@google.com bool blkValid = blk && blk->isValid(); 48712855Sgabeblack@google.com 48812855Sgabeblack@google.com if (cpu_pkt->req->isUncacheable() || 48912855Sgabeblack@google.com (!blkValid && cpu_pkt->isUpgrade()) || 49012855Sgabeblack@google.com cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) { 49112855Sgabeblack@google.com // uncacheable requests and upgrades from upper-level caches 49212855Sgabeblack@google.com // that missed completely just go through as is 49312855Sgabeblack@google.com return nullptr; 49412855Sgabeblack@google.com } 49512855Sgabeblack@google.com 49612855Sgabeblack@google.com assert(cpu_pkt->needsResponse()); 49712855Sgabeblack@google.com 49812855Sgabeblack@google.com MemCmd cmd; 49912855Sgabeblack@google.com // @TODO make useUpgrades a parameter. 50012855Sgabeblack@google.com // Note that ownership protocols require upgrade, otherwise a 50112855Sgabeblack@google.com // write miss on a shared owned block will generate a ReadExcl, 50212855Sgabeblack@google.com // which will clobber the owned copy. 50312855Sgabeblack@google.com const bool useUpgrades = true; 50412855Sgabeblack@google.com assert(cpu_pkt->cmd != MemCmd::WriteLineReq || is_whole_line_write); 50512855Sgabeblack@google.com if (is_whole_line_write) { 50612855Sgabeblack@google.com assert(!blkValid || !blk->isWritable()); 50712855Sgabeblack@google.com // forward as invalidate to all other caches, this gives us 50812855Sgabeblack@google.com // the line in Exclusive state, and invalidates all other 50912855Sgabeblack@google.com // copies 51012855Sgabeblack@google.com cmd = MemCmd::InvalidateReq; 51112855Sgabeblack@google.com } else if (blkValid && useUpgrades) { 51212855Sgabeblack@google.com // only reason to be here is that blk is read only and we need 51312855Sgabeblack@google.com // it to be writable 51412855Sgabeblack@google.com assert(needsWritable); 51512855Sgabeblack@google.com assert(!blk->isWritable()); 51612855Sgabeblack@google.com cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq; 51712855Sgabeblack@google.com } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq || 51812855Sgabeblack@google.com cpu_pkt->cmd == MemCmd::StoreCondFailReq) { 51912855Sgabeblack@google.com // Even though this SC will fail, we still need to send out the 52012855Sgabeblack@google.com // request and get the data to supply it to other snoopers in the case 52112855Sgabeblack@google.com // where the determination the StoreCond fails is delayed due to 52212855Sgabeblack@google.com // all caches not being on the same local bus. 52312855Sgabeblack@google.com cmd = MemCmd::SCUpgradeFailReq; 52412855Sgabeblack@google.com } else { 52512855Sgabeblack@google.com // block is invalid 52612855Sgabeblack@google.com 52712855Sgabeblack@google.com // If the request does not need a writable there are two cases 52812855Sgabeblack@google.com // where we need to ensure the response will not fetch the 52912855Sgabeblack@google.com // block in dirty state: 53012855Sgabeblack@google.com // * this cache is read only and it does not perform 53112855Sgabeblack@google.com // writebacks, 53212855Sgabeblack@google.com // * this cache is mostly exclusive and will not fill (since 53312855Sgabeblack@google.com // it does not fill it will have to writeback the dirty data 53412855Sgabeblack@google.com // immediately which generates uneccesary writebacks). 53512855Sgabeblack@google.com bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl; 53612855Sgabeblack@google.com cmd = needsWritable ? MemCmd::ReadExReq : 53712855Sgabeblack@google.com (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq); 53812855Sgabeblack@google.com } 53912855Sgabeblack@google.com PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize); 54012855Sgabeblack@google.com 54112855Sgabeblack@google.com // if there are upstream caches that have already marked the 54212855Sgabeblack@google.com // packet as having sharers (not passing writable), pass that info 54312855Sgabeblack@google.com // downstream 54412855Sgabeblack@google.com if (cpu_pkt->hasSharers() && !needsWritable) { 54512855Sgabeblack@google.com // note that cpu_pkt may have spent a considerable time in the 54612855Sgabeblack@google.com // MSHR queue and that the information could possibly be out 54712855Sgabeblack@google.com // of date, however, there is no harm in conservatively 54812855Sgabeblack@google.com // assuming the block has sharers 54912855Sgabeblack@google.com pkt->setHasSharers(); 55012855Sgabeblack@google.com DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n", 55112855Sgabeblack@google.com __func__, cpu_pkt->print(), pkt->print()); 55212855Sgabeblack@google.com } 55312855Sgabeblack@google.com 55412855Sgabeblack@google.com // the packet should be block aligned 55512855Sgabeblack@google.com assert(pkt->getAddr() == pkt->getBlockAddr(blkSize)); 55612855Sgabeblack@google.com 55712855Sgabeblack@google.com pkt->allocate(); 55812855Sgabeblack@google.com DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(), 55912855Sgabeblack@google.com cpu_pkt->print()); 56012855Sgabeblack@google.com return pkt; 56112855Sgabeblack@google.com} 56212855Sgabeblack@google.com 56312855Sgabeblack@google.com 56412855Sgabeblack@google.comCycles 56512855Sgabeblack@google.comCache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk, 56612855Sgabeblack@google.com PacketList &writebacks) 56712855Sgabeblack@google.com{ 56812855Sgabeblack@google.com // deal with the packets that go through the write path of 56912855Sgabeblack@google.com // the cache, i.e. any evictions and writes 57012855Sgabeblack@google.com if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean || 57112855Sgabeblack@google.com (pkt->req->isUncacheable() && pkt->isWrite())) { 57212855Sgabeblack@google.com Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt)); 57312855Sgabeblack@google.com 57412855Sgabeblack@google.com // at this point, if the request was an uncacheable write 57512855Sgabeblack@google.com // request, it has been satisfied by a memory below and the 57612855Sgabeblack@google.com // packet carries the response back 57712855Sgabeblack@google.com assert(!(pkt->req->isUncacheable() && pkt->isWrite()) || 57812855Sgabeblack@google.com pkt->isResponse()); 57912855Sgabeblack@google.com 58012855Sgabeblack@google.com return latency; 58112855Sgabeblack@google.com } 58212855Sgabeblack@google.com 58312855Sgabeblack@google.com // only misses left 58412855Sgabeblack@google.com 58512855Sgabeblack@google.com PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable(), 58612855Sgabeblack@google.com pkt->isWholeLineWrite(blkSize)); 58712855Sgabeblack@google.com 58812855Sgabeblack@google.com bool is_forward = (bus_pkt == nullptr); 58912855Sgabeblack@google.com 59012855Sgabeblack@google.com if (is_forward) { 59112855Sgabeblack@google.com // just forwarding the same request to the next level 59212855Sgabeblack@google.com // no local cache operation involved 59312855Sgabeblack@google.com bus_pkt = pkt; 59412855Sgabeblack@google.com } 59512855Sgabeblack@google.com 59612855Sgabeblack@google.com DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__, 59712855Sgabeblack@google.com bus_pkt->print()); 59812855Sgabeblack@google.com 59912855Sgabeblack@google.com#if TRACING_ON 60012855Sgabeblack@google.com CacheBlk::State old_state = blk ? blk->status : 0; 60112855Sgabeblack@google.com#endif 60212855Sgabeblack@google.com 60312855Sgabeblack@google.com Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt)); 60412855Sgabeblack@google.com 60512855Sgabeblack@google.com bool is_invalidate = bus_pkt->isInvalidate(); 60612855Sgabeblack@google.com 60712855Sgabeblack@google.com // We are now dealing with the response handling 60812855Sgabeblack@google.com DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__, 60912855Sgabeblack@google.com bus_pkt->print(), old_state); 61012855Sgabeblack@google.com 61112855Sgabeblack@google.com // If packet was a forward, the response (if any) is already 61212855Sgabeblack@google.com // in place in the bus_pkt == pkt structure, so we don't need 61312855Sgabeblack@google.com // to do anything. Otherwise, use the separate bus_pkt to 61412855Sgabeblack@google.com // generate response to pkt and then delete it. 61512855Sgabeblack@google.com if (!is_forward) { 61612855Sgabeblack@google.com if (pkt->needsResponse()) { 61712855Sgabeblack@google.com assert(bus_pkt->isResponse()); 61812855Sgabeblack@google.com if (bus_pkt->isError()) { 61912855Sgabeblack@google.com pkt->makeAtomicResponse(); 62012855Sgabeblack@google.com pkt->copyError(bus_pkt); 62112855Sgabeblack@google.com } else if (pkt->isWholeLineWrite(blkSize)) { 62212855Sgabeblack@google.com // note the use of pkt, not bus_pkt here. 62312855Sgabeblack@google.com 62412855Sgabeblack@google.com // write-line request to the cache that promoted 62512855Sgabeblack@google.com // the write to a whole line 62612855Sgabeblack@google.com const bool allocate = allocOnFill(pkt->cmd) && 62712855Sgabeblack@google.com (!writeAllocator || writeAllocator->allocate()); 62812855Sgabeblack@google.com blk = handleFill(bus_pkt, blk, writebacks, allocate); 62912855Sgabeblack@google.com assert(blk != NULL); 63012855Sgabeblack@google.com is_invalidate = false; 63112855Sgabeblack@google.com satisfyRequest(pkt, blk); 63212855Sgabeblack@google.com } else if (bus_pkt->isRead() || 63312855Sgabeblack@google.com bus_pkt->cmd == MemCmd::UpgradeResp) { 63412855Sgabeblack@google.com // we're updating cache state to allow us to 63512855Sgabeblack@google.com // satisfy the upstream request from the cache 63612855Sgabeblack@google.com blk = handleFill(bus_pkt, blk, writebacks, 63712855Sgabeblack@google.com allocOnFill(pkt->cmd)); 63812855Sgabeblack@google.com satisfyRequest(pkt, blk); 63912855Sgabeblack@google.com maintainClusivity(pkt->fromCache(), blk); 64012855Sgabeblack@google.com } else { 64112855Sgabeblack@google.com // we're satisfying the upstream request without 64212855Sgabeblack@google.com // modifying cache state, e.g., a write-through 64312855Sgabeblack@google.com pkt->makeAtomicResponse(); 64412855Sgabeblack@google.com } 64512855Sgabeblack@google.com } 64612855Sgabeblack@google.com delete bus_pkt; 64712855Sgabeblack@google.com } 64812855Sgabeblack@google.com 64912855Sgabeblack@google.com if (is_invalidate && blk && blk->isValid()) { 65012855Sgabeblack@google.com invalidateBlock(blk); 65112855Sgabeblack@google.com } 65212855Sgabeblack@google.com 65312855Sgabeblack@google.com return latency; 65412855Sgabeblack@google.com} 65512855Sgabeblack@google.com 65612855Sgabeblack@google.comTick 65712855Sgabeblack@google.comCache::recvAtomic(PacketPtr pkt) 65812855Sgabeblack@google.com{ 65912855Sgabeblack@google.com promoteWholeLineWrites(pkt); 66012855Sgabeblack@google.com 66112855Sgabeblack@google.com // follow the same flow as in recvTimingReq, and check if a cache 66212855Sgabeblack@google.com // above us is responding 66312855Sgabeblack@google.com if (pkt->cacheResponding()) { 66412855Sgabeblack@google.com assert(!pkt->req->isCacheInvalidate()); 66512855Sgabeblack@google.com DPRINTF(Cache, "Cache above responding to %s: not responding\n", 66612855Sgabeblack@google.com pkt->print()); 66712855Sgabeblack@google.com 66812855Sgabeblack@google.com // if a cache is responding, and it had the line in Owned 66912855Sgabeblack@google.com // rather than Modified state, we need to invalidate any 67012855Sgabeblack@google.com // copies that are not on the same path to memory 67112855Sgabeblack@google.com assert(pkt->needsWritable() && !pkt->responderHadWritable()); 67212855Sgabeblack@google.com 67312855Sgabeblack@google.com return memSidePort.sendAtomic(pkt); 67412855Sgabeblack@google.com } 67512855Sgabeblack@google.com 67612855Sgabeblack@google.com return BaseCache::recvAtomic(pkt); 67712855Sgabeblack@google.com} 67812855Sgabeblack@google.com 67912855Sgabeblack@google.com 68012855Sgabeblack@google.com///////////////////////////////////////////////////// 68112855Sgabeblack@google.com// 68212855Sgabeblack@google.com// Response handling: responses from the memory side 68312855Sgabeblack@google.com// 68412855Sgabeblack@google.com///////////////////////////////////////////////////// 68512855Sgabeblack@google.com 68612855Sgabeblack@google.com 68712855Sgabeblack@google.comvoid 68812855Sgabeblack@google.comCache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk) 68912855Sgabeblack@google.com{ 69012855Sgabeblack@google.com MSHR::Target *initial_tgt = mshr->getTarget(); 69112855Sgabeblack@google.com // First offset for critical word first calculations 69212855Sgabeblack@google.com const int initial_offset = initial_tgt->pkt->getOffset(blkSize); 69312855Sgabeblack@google.com 69412855Sgabeblack@google.com const bool is_error = pkt->isError(); 69512855Sgabeblack@google.com // allow invalidation responses originating from write-line 69612855Sgabeblack@google.com // requests to be discarded 69712855Sgabeblack@google.com bool is_invalidate = pkt->isInvalidate() && 69812855Sgabeblack@google.com !mshr->wasWholeLineWrite; 69912855Sgabeblack@google.com 70012855Sgabeblack@google.com MSHR::TargetList targets = mshr->extractServiceableTargets(pkt); 70112855Sgabeblack@google.com for (auto &target: targets) { 70212855Sgabeblack@google.com Packet *tgt_pkt = target.pkt; 70312855Sgabeblack@google.com switch (target.source) { 70412855Sgabeblack@google.com case MSHR::Target::FromCPU: 70512855Sgabeblack@google.com Tick completion_time; 70612855Sgabeblack@google.com // Here we charge on completion_time the delay of the xbar if the 70712855Sgabeblack@google.com // packet comes from it, charged on headerDelay. 70812855Sgabeblack@google.com completion_time = pkt->headerDelay; 70912855Sgabeblack@google.com 71012855Sgabeblack@google.com // Software prefetch handling for cache closest to core 71112855Sgabeblack@google.com if (tgt_pkt->cmd.isSWPrefetch()) { 71212855Sgabeblack@google.com // a software prefetch would have already been ack'd 71312855Sgabeblack@google.com // immediately with dummy data so the core would be able to 71412855Sgabeblack@google.com // retire it. This request completes right here, so we 71512855Sgabeblack@google.com // deallocate it. 71612855Sgabeblack@google.com delete tgt_pkt; 71712855Sgabeblack@google.com break; // skip response 71812855Sgabeblack@google.com } 71912855Sgabeblack@google.com 72012855Sgabeblack@google.com // unlike the other packet flows, where data is found in other 72112855Sgabeblack@google.com // caches or memory and brought back, write-line requests always 72212855Sgabeblack@google.com // have the data right away, so the above check for "is fill?" 72312855Sgabeblack@google.com // cannot actually be determined until examining the stored MSHR 72412855Sgabeblack@google.com // state. We "catch up" with that logic here, which is duplicated 72512855Sgabeblack@google.com // from above. 72612855Sgabeblack@google.com if (tgt_pkt->cmd == MemCmd::WriteLineReq) { 72712855Sgabeblack@google.com assert(!is_error); 72812855Sgabeblack@google.com assert(blk); 72912855Sgabeblack@google.com assert(blk->isWritable()); 73012855Sgabeblack@google.com } 731 732 if (blk && blk->isValid() && !mshr->isForward) { 733 satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade()); 734 735 // How many bytes past the first request is this one 736 int transfer_offset = 737 tgt_pkt->getOffset(blkSize) - initial_offset; 738 if (transfer_offset < 0) { 739 transfer_offset += blkSize; 740 } 741 742 // If not critical word (offset) return payloadDelay. 743 // responseLatency is the latency of the return path 744 // from lower level caches/memory to an upper level cache or 745 // the core. 746 completion_time += clockEdge(responseLatency) + 747 (transfer_offset ? pkt->payloadDelay : 0); 748 749 assert(!tgt_pkt->req->isUncacheable()); 750 751 assert(tgt_pkt->req->masterId() < system->maxMasters()); 752 missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] += 753 completion_time - target.recvTime; 754 } else if (pkt->cmd == MemCmd::UpgradeFailResp) { 755 // failed StoreCond upgrade 756 assert(tgt_pkt->cmd == MemCmd::StoreCondReq || 757 tgt_pkt->cmd == MemCmd::StoreCondFailReq || 758 tgt_pkt->cmd == MemCmd::SCUpgradeFailReq); 759 // responseLatency is the latency of the return path 760 // from lower level caches/memory to an upper level cache or 761 // the core. 762 completion_time += clockEdge(responseLatency) + 763 pkt->payloadDelay; 764 tgt_pkt->req->setExtraData(0); 765 } else { 766 // We are about to send a response to a cache above 767 // that asked for an invalidation; we need to 768 // invalidate our copy immediately as the most 769 // up-to-date copy of the block will now be in the 770 // cache above. It will also prevent this cache from 771 // responding (if the block was previously dirty) to 772 // snoops as they should snoop the caches above where 773 // they will get the response from. 774 if (is_invalidate && blk && blk->isValid()) { 775 invalidateBlock(blk); 776 } 777 // not a cache fill, just forwarding response 778 // responseLatency is the latency of the return path 779 // from lower level cahces/memory to the core. 780 completion_time += clockEdge(responseLatency) + 781 pkt->payloadDelay; 782 if (pkt->isRead() && !is_error) { 783 // sanity check 784 assert(pkt->getAddr() == tgt_pkt->getAddr()); 785 assert(pkt->getSize() >= tgt_pkt->getSize()); 786 787 tgt_pkt->setData(pkt->getConstPtr<uint8_t>()); 788 } 789 } 790 tgt_pkt->makeTimingResponse(); 791 // if this packet is an error copy that to the new packet 792 if (is_error) 793 tgt_pkt->copyError(pkt); 794 if (tgt_pkt->cmd == MemCmd::ReadResp && 795 (is_invalidate || mshr->hasPostInvalidate())) { 796 // If intermediate cache got ReadRespWithInvalidate, 797 // propagate that. Response should not have 798 // isInvalidate() set otherwise. 799 tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate; 800 DPRINTF(Cache, "%s: updated cmd to %s\n", __func__, 801 tgt_pkt->print()); 802 } 803 // Reset the bus additional time as it is now accounted for 804 tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0; 805 cpuSidePort.schedTimingResp(tgt_pkt, completion_time); 806 break; 807 808 case MSHR::Target::FromPrefetcher: 809 assert(tgt_pkt->cmd == MemCmd::HardPFReq); 810 if (blk) 811 blk->status |= BlkHWPrefetched; 812 delete tgt_pkt; 813 break; 814 815 case MSHR::Target::FromSnoop: 816 // I don't believe that a snoop can be in an error state 817 assert(!is_error); 818 // response to snoop request 819 DPRINTF(Cache, "processing deferred snoop...\n"); 820 // If the response is invalidating, a snooping target can 821 // be satisfied if it is also invalidating. If the reponse is, not 822 // only invalidating, but more specifically an InvalidateResp and 823 // the MSHR was created due to an InvalidateReq then a cache above 824 // is waiting to satisfy a WriteLineReq. In this case even an 825 // non-invalidating snoop is added as a target here since this is 826 // the ordering point. When the InvalidateResp reaches this cache, 827 // the snooping target will snoop further the cache above with the 828 // WriteLineReq. 829 assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp || 830 pkt->req->isCacheMaintenance() || 831 mshr->hasPostInvalidate()); 832 handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate()); 833 break; 834 835 default: 836 panic("Illegal target->source enum %d\n", target.source); 837 } 838 } 839 840 maintainClusivity(targets.hasFromCache, blk); 841 842 if (blk && blk->isValid()) { 843 // an invalidate response stemming from a write line request 844 // should not invalidate the block, so check if the 845 // invalidation should be discarded 846 if (is_invalidate || mshr->hasPostInvalidate()) { 847 invalidateBlock(blk); 848 } else if (mshr->hasPostDowngrade()) { 849 blk->status &= ~BlkWritable; 850 } 851 } 852} 853 854PacketPtr 855Cache::evictBlock(CacheBlk *blk) 856{ 857 PacketPtr pkt = (blk->isDirty() || writebackClean) ? 858 writebackBlk(blk) : cleanEvictBlk(blk); 859 860 invalidateBlock(blk); 861 862 return pkt; 863} 864 865PacketPtr 866Cache::cleanEvictBlk(CacheBlk *blk) 867{ 868 assert(!writebackClean); 869 assert(blk && blk->isValid() && !blk->isDirty()); 870 871 // Creating a zero sized write, a message to the snoop filter 872 RequestPtr req = std::make_shared<Request>( 873 regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId); 874 875 if (blk->isSecure()) 876 req->setFlags(Request::SECURE); 877 878 req->taskId(blk->task_id); 879 880 PacketPtr pkt = new Packet(req, MemCmd::CleanEvict); 881 pkt->allocate(); 882 DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print()); 883 884 return pkt; 885} 886 887///////////////////////////////////////////////////// 888// 889// Snoop path: requests coming in from the memory side 890// 891///////////////////////////////////////////////////// 892 893void 894Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data, 895 bool already_copied, bool pending_inval) 896{ 897 // sanity check 898 assert(req_pkt->isRequest()); 899 assert(req_pkt->needsResponse()); 900 901 DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print()); 902 // timing-mode snoop responses require a new packet, unless we 903 // already made a copy... 904 PacketPtr pkt = req_pkt; 905 if (!already_copied) 906 // do not clear flags, and allocate space for data if the 907 // packet needs it (the only packets that carry data are read 908 // responses) 909 pkt = new Packet(req_pkt, false, req_pkt->isRead()); 910 911 assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() || 912 pkt->hasSharers()); 913 pkt->makeTimingResponse(); 914 if (pkt->isRead()) { 915 pkt->setDataFromBlock(blk_data, blkSize); 916 } 917 if (pkt->cmd == MemCmd::ReadResp && pending_inval) { 918 // Assume we defer a response to a read from a far-away cache 919 // A, then later defer a ReadExcl from a cache B on the same 920 // bus as us. We'll assert cacheResponding in both cases, but 921 // in the latter case cacheResponding will keep the 922 // invalidation from reaching cache A. This special response 923 // tells cache A that it gets the block to satisfy its read, 924 // but must immediately invalidate it. 925 pkt->cmd = MemCmd::ReadRespWithInvalidate; 926 } 927 // Here we consider forward_time, paying for just forward latency and 928 // also charging the delay provided by the xbar. 929 // forward_time is used as send_time in next allocateWriteBuffer(). 930 Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay; 931 // Here we reset the timing of the packet. 932 pkt->headerDelay = pkt->payloadDelay = 0; 933 DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__, 934 pkt->print(), forward_time); 935 memSidePort.schedTimingSnoopResp(pkt, forward_time); 936} 937 938uint32_t 939Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing, 940 bool is_deferred, bool pending_inval) 941{ 942 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print()); 943 // deferred snoops can only happen in timing mode 944 assert(!(is_deferred && !is_timing)); 945 // pending_inval only makes sense on deferred snoops 946 assert(!(pending_inval && !is_deferred)); 947 assert(pkt->isRequest()); 948 949 // the packet may get modified if we or a forwarded snooper 950 // responds in atomic mode, so remember a few things about the 951 // original packet up front 952 bool invalidate = pkt->isInvalidate(); 953 bool M5_VAR_USED needs_writable = pkt->needsWritable(); 954 955 // at the moment we could get an uncacheable write which does not 956 // have the invalidate flag, and we need a suitable way of dealing 957 // with this case 958 panic_if(invalidate && pkt->req->isUncacheable(), 959 "%s got an invalidating uncacheable snoop request %s", 960 name(), pkt->print()); 961 962 uint32_t snoop_delay = 0; 963 964 if (forwardSnoops) { 965 // first propagate snoop upward to see if anyone above us wants to 966 // handle it. save & restore packet src since it will get 967 // rewritten to be relative to cpu-side bus (if any) 968 bool alreadyResponded = pkt->cacheResponding(); 969 if (is_timing) { 970 // copy the packet so that we can clear any flags before 971 // forwarding it upwards, we also allocate data (passing 972 // the pointer along in case of static data), in case 973 // there is a snoop hit in upper levels 974 Packet snoopPkt(pkt, true, true); 975 snoopPkt.setExpressSnoop(); 976 // the snoop packet does not need to wait any additional 977 // time 978 snoopPkt.headerDelay = snoopPkt.payloadDelay = 0; 979 cpuSidePort.sendTimingSnoopReq(&snoopPkt); 980 981 // add the header delay (including crossbar and snoop 982 // delays) of the upward snoop to the snoop delay for this 983 // cache 984 snoop_delay += snoopPkt.headerDelay; 985 986 if (snoopPkt.cacheResponding()) { 987 // cache-to-cache response from some upper cache 988 assert(!alreadyResponded); 989 pkt->setCacheResponding(); 990 } 991 // upstream cache has the block, or has an outstanding 992 // MSHR, pass the flag on 993 if (snoopPkt.hasSharers()) { 994 pkt->setHasSharers(); 995 } 996 // If this request is a prefetch or clean evict and an upper level 997 // signals block present, make sure to propagate the block 998 // presence to the requester. 999 if (snoopPkt.isBlockCached()) { 1000 pkt->setBlockCached(); 1001 } 1002 // If the request was satisfied by snooping the cache 1003 // above, mark the original packet as satisfied too. 1004 if (snoopPkt.satisfied()) { 1005 pkt->setSatisfied(); 1006 } 1007 } else { 1008 cpuSidePort.sendAtomicSnoop(pkt); 1009 if (!alreadyResponded && pkt->cacheResponding()) { 1010 // cache-to-cache response from some upper cache: 1011 // forward response to original requester 1012 assert(pkt->isResponse()); 1013 } 1014 } 1015 } 1016 1017 bool respond = false; 1018 bool blk_valid = blk && blk->isValid(); 1019 if (pkt->isClean()) { 1020 if (blk_valid && blk->isDirty()) { 1021 DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n", 1022 __func__, pkt->print(), blk->print()); 1023 PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id); 1024 PacketList writebacks; 1025 writebacks.push_back(wb_pkt); 1026 1027 if (is_timing) { 1028 // anything that is merely forwarded pays for the forward 1029 // latency and the delay provided by the crossbar 1030 Tick forward_time = clockEdge(forwardLatency) + 1031 pkt->headerDelay; 1032 doWritebacks(writebacks, forward_time); 1033 } else { 1034 doWritebacksAtomic(writebacks); 1035 } 1036 pkt->setSatisfied(); 1037 } 1038 } else if (!blk_valid) { 1039 DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__, 1040 pkt->print()); 1041 if (is_deferred) { 1042 // we no longer have the block, and will not respond, but a 1043 // packet was allocated in MSHR::handleSnoop and we have 1044 // to delete it 1045 assert(pkt->needsResponse()); 1046 1047 // we have passed the block to a cache upstream, that 1048 // cache should be responding 1049 assert(pkt->cacheResponding()); 1050 1051 delete pkt; 1052 } 1053 return snoop_delay; 1054 } else { 1055 DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__, 1056 pkt->print(), blk->print()); 1057 1058 // We may end up modifying both the block state and the packet (if 1059 // we respond in atomic mode), so just figure out what to do now 1060 // and then do it later. We respond to all snoops that need 1061 // responses provided we have the block in dirty state. The 1062 // invalidation itself is taken care of below. We don't respond to 1063 // cache maintenance operations as this is done by the destination 1064 // xbar. 1065 respond = blk->isDirty() && pkt->needsResponse(); 1066 1067 chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have " 1068 "a dirty block in a read-only cache %s\n", name()); 1069 } 1070 1071 // Invalidate any prefetch's from below that would strip write permissions 1072 // MemCmd::HardPFReq is only observed by upstream caches. After missing 1073 // above and in it's own cache, a new MemCmd::ReadReq is created that 1074 // downstream caches observe. 1075 if (pkt->mustCheckAbove()) { 1076 DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s " 1077 "from lower cache\n", pkt->getAddr(), pkt->print()); 1078 pkt->setBlockCached(); 1079 return snoop_delay; 1080 } 1081 1082 if (pkt->isRead() && !invalidate) { 1083 // reading without requiring the line in a writable state 1084 assert(!needs_writable); 1085 pkt->setHasSharers(); 1086 1087 // if the requesting packet is uncacheable, retain the line in 1088 // the current state, otherwhise unset the writable flag, 1089 // which means we go from Modified to Owned (and will respond 1090 // below), remain in Owned (and will respond below), from 1091 // Exclusive to Shared, or remain in Shared 1092 if (!pkt->req->isUncacheable()) 1093 blk->status &= ~BlkWritable; 1094 DPRINTF(Cache, "new state is %s\n", blk->print()); 1095 } 1096 1097 if (respond) { 1098 // prevent anyone else from responding, cache as well as 1099 // memory, and also prevent any memory from even seeing the 1100 // request 1101 pkt->setCacheResponding(); 1102 if (!pkt->isClean() && blk->isWritable()) { 1103 // inform the cache hierarchy that this cache had the line 1104 // in the Modified state so that we avoid unnecessary 1105 // invalidations (see Packet::setResponderHadWritable) 1106 pkt->setResponderHadWritable(); 1107 1108 // in the case of an uncacheable request there is no point 1109 // in setting the responderHadWritable flag, but since the 1110 // recipient does not care there is no harm in doing so 1111 } else { 1112 // if the packet has needsWritable set we invalidate our 1113 // copy below and all other copies will be invalidates 1114 // through express snoops, and if needsWritable is not set 1115 // we already called setHasSharers above 1116 } 1117 1118 // if we are returning a writable and dirty (Modified) line, 1119 // we should be invalidating the line 1120 panic_if(!invalidate && !pkt->hasSharers(), 1121 "%s is passing a Modified line through %s, " 1122 "but keeping the block", name(), pkt->print()); 1123 1124 if (is_timing) { 1125 doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval); 1126 } else { 1127 pkt->makeAtomicResponse(); 1128 // packets such as upgrades do not actually have any data 1129 // payload 1130 if (pkt->hasData()) 1131 pkt->setDataFromBlock(blk->data, blkSize); 1132 } 1133 } 1134 1135 if (!respond && is_deferred) { 1136 assert(pkt->needsResponse()); 1137 delete pkt; 1138 } 1139 1140 // Do this last in case it deallocates block data or something 1141 // like that 1142 if (blk_valid && invalidate) { 1143 invalidateBlock(blk); 1144 DPRINTF(Cache, "new state is %s\n", blk->print()); 1145 } 1146 1147 return snoop_delay; 1148} 1149 1150 1151void 1152Cache::recvTimingSnoopReq(PacketPtr pkt) 1153{ 1154 DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print()); 1155 1156 // no need to snoop requests that are not in range 1157 if (!inRange(pkt->getAddr())) { 1158 return; 1159 } 1160 1161 bool is_secure = pkt->isSecure(); 1162 CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure); 1163 1164 Addr blk_addr = pkt->getBlockAddr(blkSize); 1165 MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure); 1166 1167 // Update the latency cost of the snoop so that the crossbar can 1168 // account for it. Do not overwrite what other neighbouring caches 1169 // have already done, rather take the maximum. The update is 1170 // tentative, for cases where we return before an upward snoop 1171 // happens below. 1172 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, 1173 lookupLatency * clockPeriod()); 1174 1175 // Inform request(Prefetch, CleanEvict or Writeback) from below of 1176 // MSHR hit, set setBlockCached. 1177 if (mshr && pkt->mustCheckAbove()) { 1178 DPRINTF(Cache, "Setting block cached for %s from lower cache on " 1179 "mshr hit\n", pkt->print()); 1180 pkt->setBlockCached(); 1181 return; 1182 } 1183 1184 // Bypass any existing cache maintenance requests if the request 1185 // has been satisfied already (i.e., the dirty block has been 1186 // found). 1187 if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) { 1188 return; 1189 } 1190 1191 // Let the MSHR itself track the snoop and decide whether we want 1192 // to go ahead and do the regular cache snoop 1193 if (mshr && mshr->handleSnoop(pkt, order++)) { 1194 DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)." 1195 "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns", 1196 mshr->print()); 1197 1198 if (mshr->getNumTargets() > numTarget) 1199 warn("allocating bonus target for snoop"); //handle later 1200 return; 1201 } 1202 1203 //We also need to check the writeback buffers and handle those 1204 WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure); 1205 if (wb_entry) { 1206 DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n", 1207 pkt->getAddr(), is_secure ? "s" : "ns"); 1208 // Expect to see only Writebacks and/or CleanEvicts here, both of 1209 // which should not be generated for uncacheable data. 1210 assert(!wb_entry->isUncacheable()); 1211 // There should only be a single request responsible for generating 1212 // Writebacks/CleanEvicts. 1213 assert(wb_entry->getNumTargets() == 1); 1214 PacketPtr wb_pkt = wb_entry->getTarget()->pkt; 1215 assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean); 1216 1217 if (pkt->isEviction()) { 1218 // if the block is found in the write queue, set the BLOCK_CACHED 1219 // flag for Writeback/CleanEvict snoop. On return the snoop will 1220 // propagate the BLOCK_CACHED flag in Writeback packets and prevent 1221 // any CleanEvicts from travelling down the memory hierarchy. 1222 pkt->setBlockCached(); 1223 DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue " 1224 "hit\n", __func__, pkt->print()); 1225 return; 1226 } 1227 1228 // conceptually writebacks are no different to other blocks in 1229 // this cache, so the behaviour is modelled after handleSnoop, 1230 // the difference being that instead of querying the block 1231 // state to determine if it is dirty and writable, we use the 1232 // command and fields of the writeback packet 1233 bool respond = wb_pkt->cmd == MemCmd::WritebackDirty && 1234 pkt->needsResponse(); 1235 bool have_writable = !wb_pkt->hasSharers(); 1236 bool invalidate = pkt->isInvalidate(); 1237 1238 if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) { 1239 assert(!pkt->needsWritable()); 1240 pkt->setHasSharers(); 1241 wb_pkt->setHasSharers(); 1242 } 1243 1244 if (respond) { 1245 pkt->setCacheResponding(); 1246 1247 if (have_writable) { 1248 pkt->setResponderHadWritable(); 1249 } 1250 1251 doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(), 1252 false, false); 1253 } 1254 1255 if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) { 1256 // Invalidation trumps our writeback... discard here 1257 // Note: markInService will remove entry from writeback buffer. 1258 markInService(wb_entry); 1259 delete wb_pkt; 1260 } 1261 } 1262 1263 // If this was a shared writeback, there may still be 1264 // other shared copies above that require invalidation. 1265 // We could be more selective and return here if the 1266 // request is non-exclusive or if the writeback is 1267 // exclusive. 1268 uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false); 1269 1270 // Override what we did when we first saw the snoop, as we now 1271 // also have the cost of the upwards snoops to account for 1272 pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay + 1273 lookupLatency * clockPeriod()); 1274} 1275 1276Tick 1277Cache::recvAtomicSnoop(PacketPtr pkt) 1278{ 1279 // no need to snoop requests that are not in range. 1280 if (!inRange(pkt->getAddr())) { 1281 return 0; 1282 } 1283 1284 CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure()); 1285 uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false); 1286 return snoop_delay + lookupLatency * clockPeriod(); 1287} 1288 1289bool 1290Cache::isCachedAbove(PacketPtr pkt, bool is_timing) 1291{ 1292 if (!forwardSnoops) 1293 return false; 1294 // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and 1295 // Writeback snoops into upper level caches to check for copies of the 1296 // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict 1297 // packet, the cache can inform the crossbar below of presence or absence 1298 // of the block. 1299 if (is_timing) { 1300 Packet snoop_pkt(pkt, true, false); 1301 snoop_pkt.setExpressSnoop(); 1302 // Assert that packet is either Writeback or CleanEvict and not a 1303 // prefetch request because prefetch requests need an MSHR and may 1304 // generate a snoop response. 1305 assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean); 1306 snoop_pkt.senderState = nullptr; 1307 cpuSidePort.sendTimingSnoopReq(&snoop_pkt); 1308 // Writeback/CleanEvict snoops do not generate a snoop response. 1309 assert(!(snoop_pkt.cacheResponding())); 1310 return snoop_pkt.isBlockCached(); 1311 } else { 1312 cpuSidePort.sendAtomicSnoop(pkt); 1313 return pkt->isBlockCached(); 1314 } 1315} 1316 1317bool 1318Cache::sendMSHRQueuePacket(MSHR* mshr) 1319{ 1320 assert(mshr); 1321 1322 // use request from 1st target 1323 PacketPtr tgt_pkt = mshr->getTarget()->pkt; 1324 1325 if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) { 1326 DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print()); 1327 1328 // we should never have hardware prefetches to allocated 1329 // blocks 1330 assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure)); 1331 1332 // We need to check the caches above us to verify that 1333 // they don't have a copy of this block in the dirty state 1334 // at the moment. Without this check we could get a stale 1335 // copy from memory that might get used in place of the 1336 // dirty one. 1337 Packet snoop_pkt(tgt_pkt, true, false); 1338 snoop_pkt.setExpressSnoop(); 1339 // We are sending this packet upwards, but if it hits we will 1340 // get a snoop response that we end up treating just like a 1341 // normal response, hence it needs the MSHR as its sender 1342 // state 1343 snoop_pkt.senderState = mshr; 1344 cpuSidePort.sendTimingSnoopReq(&snoop_pkt); 1345 1346 // Check to see if the prefetch was squashed by an upper cache (to 1347 // prevent us from grabbing the line) or if a Check to see if a 1348 // writeback arrived between the time the prefetch was placed in 1349 // the MSHRs and when it was selected to be sent or if the 1350 // prefetch was squashed by an upper cache. 1351 1352 // It is important to check cacheResponding before 1353 // prefetchSquashed. If another cache has committed to 1354 // responding, it will be sending a dirty response which will 1355 // arrive at the MSHR allocated for this request. Checking the 1356 // prefetchSquash first may result in the MSHR being 1357 // prematurely deallocated. 1358 if (snoop_pkt.cacheResponding()) { 1359 auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req); 1360 assert(r.second); 1361 1362 // if we are getting a snoop response with no sharers it 1363 // will be allocated as Modified 1364 bool pending_modified_resp = !snoop_pkt.hasSharers(); 1365 markInService(mshr, pending_modified_resp); 1366 1367 DPRINTF(Cache, "Upward snoop of prefetch for addr" 1368 " %#x (%s) hit\n", 1369 tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns"); 1370 return false; 1371 } 1372 1373 if (snoop_pkt.isBlockCached()) { 1374 DPRINTF(Cache, "Block present, prefetch squashed by cache. " 1375 "Deallocating mshr target %#x.\n", 1376 mshr->blkAddr); 1377 1378 // Deallocate the mshr target 1379 if (mshrQueue.forceDeallocateTarget(mshr)) { 1380 // Clear block if this deallocation resulted freed an 1381 // mshr when all had previously been utilized 1382 clearBlocked(Blocked_NoMSHRs); 1383 } 1384 1385 // given that no response is expected, delete Request and Packet 1386 delete tgt_pkt; 1387 1388 return false; 1389 } 1390 } 1391 1392 return BaseCache::sendMSHRQueuePacket(mshr); 1393} 1394 1395Cache* 1396CacheParams::create() 1397{ 1398 assert(tags); 1399 assert(replacement_policy); 1400 1401 return new Cache(this); 1402} 1403