cache.cc revision 13948
112853Sgabeblack@google.com/*
212853Sgabeblack@google.com * Copyright (c) 2010-2019 ARM Limited
312853Sgabeblack@google.com * All rights reserved.
412853Sgabeblack@google.com *
512853Sgabeblack@google.com * The license below extends only to copyright in the software and shall
612853Sgabeblack@google.com * not be construed as granting a license to any other intellectual
712853Sgabeblack@google.com * property including but not limited to intellectual property relating
812853Sgabeblack@google.com * to a hardware implementation of the functionality of the software
912853Sgabeblack@google.com * licensed hereunder.  You may use the software subject to the license
1012853Sgabeblack@google.com * terms below provided that you ensure that this notice is replicated
1112853Sgabeblack@google.com * unmodified and in its entirety in all distributions of the software,
1212853Sgabeblack@google.com * modified or unmodified, in source code or in binary form.
1312853Sgabeblack@google.com *
1412853Sgabeblack@google.com * Copyright (c) 2002-2005 The Regents of The University of Michigan
1512853Sgabeblack@google.com * Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
1612853Sgabeblack@google.com * All rights reserved.
1712853Sgabeblack@google.com *
1812853Sgabeblack@google.com * Redistribution and use in source and binary forms, with or without
1912853Sgabeblack@google.com * modification, are permitted provided that the following conditions are
2012853Sgabeblack@google.com * met: redistributions of source code must retain the above copyright
2112853Sgabeblack@google.com * notice, this list of conditions and the following disclaimer;
2212853Sgabeblack@google.com * redistributions in binary form must reproduce the above copyright
2312853Sgabeblack@google.com * notice, this list of conditions and the following disclaimer in the
2412853Sgabeblack@google.com * documentation and/or other materials provided with the distribution;
2512853Sgabeblack@google.com * neither the name of the copyright holders nor the names of its
2612853Sgabeblack@google.com * contributors may be used to endorse or promote products derived from
2712853Sgabeblack@google.com * this software without specific prior written permission.
2812853Sgabeblack@google.com *
2912853Sgabeblack@google.com * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
3012853Sgabeblack@google.com * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
3112853Sgabeblack@google.com * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
3212853Sgabeblack@google.com * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
3312853Sgabeblack@google.com * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
3412853Sgabeblack@google.com * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
3512853Sgabeblack@google.com * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
3612853Sgabeblack@google.com * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
3712853Sgabeblack@google.com * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
3812853Sgabeblack@google.com * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
3912853Sgabeblack@google.com * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
4012853Sgabeblack@google.com *
4112853Sgabeblack@google.com * Authors: Erik Hallnor
4212853Sgabeblack@google.com *          Dave Greene
4312853Sgabeblack@google.com *          Nathan Binkert
4412853Sgabeblack@google.com *          Steve Reinhardt
4512853Sgabeblack@google.com *          Ron Dreslinski
4612853Sgabeblack@google.com *          Andreas Sandberg
4712853Sgabeblack@google.com *          Nikos Nikoleris
4812853Sgabeblack@google.com */
4912853Sgabeblack@google.com
5012853Sgabeblack@google.com/**
5112853Sgabeblack@google.com * @file
5212853Sgabeblack@google.com * Cache definitions.
5312853Sgabeblack@google.com */
5412853Sgabeblack@google.com
5512853Sgabeblack@google.com#include "mem/cache/cache.hh"
5612853Sgabeblack@google.com
5712853Sgabeblack@google.com#include <cassert>
5812853Sgabeblack@google.com
5912853Sgabeblack@google.com#include "base/compiler.hh"
6012853Sgabeblack@google.com#include "base/logging.hh"
6112853Sgabeblack@google.com#include "base/trace.hh"
6212853Sgabeblack@google.com#include "base/types.hh"
6312853Sgabeblack@google.com#include "debug/Cache.hh"
6412853Sgabeblack@google.com#include "debug/CacheTags.hh"
6512853Sgabeblack@google.com#include "debug/CacheVerbose.hh"
6612853Sgabeblack@google.com#include "enums/Clusivity.hh"
6712853Sgabeblack@google.com#include "mem/cache/cache_blk.hh"
6812853Sgabeblack@google.com#include "mem/cache/mshr.hh"
6912853Sgabeblack@google.com#include "mem/cache/tags/base.hh"
7012853Sgabeblack@google.com#include "mem/cache/write_queue_entry.hh"
7112853Sgabeblack@google.com#include "mem/request.hh"
7212853Sgabeblack@google.com#include "params/Cache.hh"
7312853Sgabeblack@google.com
7412853Sgabeblack@google.comCache::Cache(const CacheParams *p)
7512853Sgabeblack@google.com    : BaseCache(p, p->system->cacheLineSize()),
7612853Sgabeblack@google.com      doFastWrites(true)
7712853Sgabeblack@google.com{
7812853Sgabeblack@google.com}
7912853Sgabeblack@google.com
8012853Sgabeblack@google.comvoid
8112853Sgabeblack@google.comCache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
8212853Sgabeblack@google.com                      bool deferred_response, bool pending_downgrade)
8312853Sgabeblack@google.com{
8412853Sgabeblack@google.com    BaseCache::satisfyRequest(pkt, blk);
8512853Sgabeblack@google.com
8612853Sgabeblack@google.com    if (pkt->isRead()) {
8712853Sgabeblack@google.com        // determine if this read is from a (coherent) cache or not
8812853Sgabeblack@google.com        if (pkt->fromCache()) {
8912853Sgabeblack@google.com            assert(pkt->getSize() == blkSize);
9012853Sgabeblack@google.com            // special handling for coherent block requests from
9112853Sgabeblack@google.com            // upper-level caches
9212853Sgabeblack@google.com            if (pkt->needsWritable()) {
9312853Sgabeblack@google.com                // sanity check
9412853Sgabeblack@google.com                assert(pkt->cmd == MemCmd::ReadExReq ||
9512853Sgabeblack@google.com                       pkt->cmd == MemCmd::SCUpgradeFailReq);
9612853Sgabeblack@google.com                assert(!pkt->hasSharers());
9712853Sgabeblack@google.com
9812853Sgabeblack@google.com                // if we have a dirty copy, make sure the recipient
9912853Sgabeblack@google.com                // keeps it marked dirty (in the modified state)
10012853Sgabeblack@google.com                if (blk->isDirty()) {
10112853Sgabeblack@google.com                    pkt->setCacheResponding();
10212853Sgabeblack@google.com                    blk->status &= ~BlkDirty;
10312853Sgabeblack@google.com                }
10412853Sgabeblack@google.com            } else if (blk->isWritable() && !pending_downgrade &&
10512853Sgabeblack@google.com                       !pkt->hasSharers() &&
10612853Sgabeblack@google.com                       pkt->cmd != MemCmd::ReadCleanReq) {
10712853Sgabeblack@google.com                // we can give the requester a writable copy on a read
10812853Sgabeblack@google.com                // request if:
10912853Sgabeblack@google.com                // - we have a writable copy at this level (& below)
11012853Sgabeblack@google.com                // - we don't have a pending snoop from below
11112853Sgabeblack@google.com                //   signaling another read request
11212853Sgabeblack@google.com                // - no other cache above has a copy (otherwise it
11312853Sgabeblack@google.com                //   would have set hasSharers flag when
11412853Sgabeblack@google.com                //   snooping the packet)
11512853Sgabeblack@google.com                // - the read has explicitly asked for a clean
11612853Sgabeblack@google.com                //   copy of the line
11712853Sgabeblack@google.com                if (blk->isDirty()) {
11812853Sgabeblack@google.com                    // special considerations if we're owner:
11912853Sgabeblack@google.com                    if (!deferred_response) {
12012853Sgabeblack@google.com                        // respond with the line in Modified state
12112853Sgabeblack@google.com                        // (cacheResponding set, hasSharers not set)
12212853Sgabeblack@google.com                        pkt->setCacheResponding();
12312853Sgabeblack@google.com
12412853Sgabeblack@google.com                        // if this cache is mostly inclusive, we
12512853Sgabeblack@google.com                        // keep the block in the Exclusive state,
12612853Sgabeblack@google.com                        // and pass it upwards as Modified
12712853Sgabeblack@google.com                        // (writable and dirty), hence we have
12812853Sgabeblack@google.com                        // multiple caches, all on the same path
12912853Sgabeblack@google.com                        // towards memory, all considering the
13012853Sgabeblack@google.com                        // same block writable, but only one
13112853Sgabeblack@google.com                        // considering it Modified
13212853Sgabeblack@google.com
13312853Sgabeblack@google.com                        // we get away with multiple caches (on
13412853Sgabeblack@google.com                        // the same path to memory) considering
13512853Sgabeblack@google.com                        // the block writeable as we always enter
13612853Sgabeblack@google.com                        // the cache hierarchy through a cache,
13712853Sgabeblack@google.com                        // and first snoop upwards in all other
13812853Sgabeblack@google.com                        // branches
13912853Sgabeblack@google.com                        blk->status &= ~BlkDirty;
14012853Sgabeblack@google.com                    } else {
14112853Sgabeblack@google.com                        // if we're responding after our own miss,
14212853Sgabeblack@google.com                        // there's a window where the recipient didn't
14312853Sgabeblack@google.com                        // know it was getting ownership and may not
14412853Sgabeblack@google.com                        // have responded to snoops correctly, so we
14512853Sgabeblack@google.com                        // have to respond with a shared line
14612853Sgabeblack@google.com                        pkt->setHasSharers();
14712853Sgabeblack@google.com                    }
14812853Sgabeblack@google.com                }
14912853Sgabeblack@google.com            } else {
15012853Sgabeblack@google.com                // otherwise only respond with a shared copy
15112853Sgabeblack@google.com                pkt->setHasSharers();
15212853Sgabeblack@google.com            }
15312853Sgabeblack@google.com        }
15412853Sgabeblack@google.com    }
15512853Sgabeblack@google.com}
15612853Sgabeblack@google.com
15712853Sgabeblack@google.com/////////////////////////////////////////////////////
15812853Sgabeblack@google.com//
15912853Sgabeblack@google.com// Access path: requests coming in from the CPU side
16012853Sgabeblack@google.com//
16112853Sgabeblack@google.com/////////////////////////////////////////////////////
16212853Sgabeblack@google.com
16312853Sgabeblack@google.combool
16412853Sgabeblack@google.comCache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat)
16512853Sgabeblack@google.com{
16612853Sgabeblack@google.com
16712853Sgabeblack@google.com    if (pkt->req->isUncacheable()) {
16812853Sgabeblack@google.com        assert(pkt->isRequest());
16912853Sgabeblack@google.com
17012853Sgabeblack@google.com        chatty_assert(!(isReadOnly && pkt->isWrite()),
17112853Sgabeblack@google.com                      "Should never see a write in a read-only cache %s\n",
17212853Sgabeblack@google.com                      name());
17312853Sgabeblack@google.com
17412853Sgabeblack@google.com        DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
17512853Sgabeblack@google.com
17612853Sgabeblack@google.com        // lookupLatency is the latency in case the request is uncacheable.
17712853Sgabeblack@google.com        lat = lookupLatency;
17812853Sgabeblack@google.com
17912853Sgabeblack@google.com        // flush and invalidate any existing block
18012853Sgabeblack@google.com        CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
18112853Sgabeblack@google.com        if (old_blk && old_blk->isValid()) {
18212853Sgabeblack@google.com            BaseCache::evictBlock(old_blk, clockEdge(lat + forwardLatency));
18312853Sgabeblack@google.com        }
18412853Sgabeblack@google.com
18512853Sgabeblack@google.com        blk = nullptr;
18612853Sgabeblack@google.com        return false;
18712853Sgabeblack@google.com    }
18812853Sgabeblack@google.com
18912853Sgabeblack@google.com    return BaseCache::access(pkt, blk, lat);
19012853Sgabeblack@google.com}
19112853Sgabeblack@google.com
19212853Sgabeblack@google.comvoid
19312853Sgabeblack@google.comCache::doWritebacks(PacketPtr pkt, Tick forward_time)
19412853Sgabeblack@google.com{
19512853Sgabeblack@google.com    // We use forwardLatency here because we are copying writebacks to
19612853Sgabeblack@google.com    // write buffer.
19712853Sgabeblack@google.com
19812853Sgabeblack@google.com    // Call isCachedAbove for Writebacks, CleanEvicts and
19912853Sgabeblack@google.com    // WriteCleans to discover if the block is cached above.
20012853Sgabeblack@google.com    if (isCachedAbove(pkt)) {
20112853Sgabeblack@google.com        if (pkt->cmd == MemCmd::CleanEvict) {
20212853Sgabeblack@google.com            // Delete CleanEvict because cached copies exist above. The
20312853Sgabeblack@google.com            // packet destructor will delete the request object because
20412853Sgabeblack@google.com            // this is a non-snoop request packet which does not require a
20512853Sgabeblack@google.com            // response.
20612853Sgabeblack@google.com            delete pkt;
20712853Sgabeblack@google.com        } else if (pkt->cmd == MemCmd::WritebackClean) {
20812853Sgabeblack@google.com            // clean writeback, do not send since the block is
20912853Sgabeblack@google.com            // still cached above
21012853Sgabeblack@google.com            assert(writebackClean);
21112853Sgabeblack@google.com            delete pkt;
21212853Sgabeblack@google.com        } else {
21312853Sgabeblack@google.com            assert(pkt->cmd == MemCmd::WritebackDirty ||
21412853Sgabeblack@google.com                   pkt->cmd == MemCmd::WriteClean);
21512853Sgabeblack@google.com            // Set BLOCK_CACHED flag in Writeback and send below, so that
21612853Sgabeblack@google.com            // the Writeback does not reset the bit corresponding to this
21712853Sgabeblack@google.com            // address in the snoop filter below.
21812853Sgabeblack@google.com            pkt->setBlockCached();
21912853Sgabeblack@google.com            allocateWriteBuffer(pkt, forward_time);
22012853Sgabeblack@google.com        }
22112853Sgabeblack@google.com    } else {
22212853Sgabeblack@google.com        // If the block is not cached above, send packet below. Both
22312853Sgabeblack@google.com        // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
22412853Sgabeblack@google.com        // reset the bit corresponding to this address in the snoop filter
22512853Sgabeblack@google.com        // below.
22612853Sgabeblack@google.com        allocateWriteBuffer(pkt, forward_time);
22712853Sgabeblack@google.com    }
22812853Sgabeblack@google.com}
22912853Sgabeblack@google.com
23012853Sgabeblack@google.comvoid
23112853Sgabeblack@google.comCache::doWritebacksAtomic(PacketPtr pkt)
23212853Sgabeblack@google.com{
23312853Sgabeblack@google.com    // Call isCachedAbove for both Writebacks and CleanEvicts. If
23412853Sgabeblack@google.com    // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
23512853Sgabeblack@google.com    // and discard CleanEvicts.
23612853Sgabeblack@google.com    if (isCachedAbove(pkt, false)) {
23712853Sgabeblack@google.com        if (pkt->cmd == MemCmd::WritebackDirty ||
23812853Sgabeblack@google.com            pkt->cmd == MemCmd::WriteClean) {
23912853Sgabeblack@google.com            // Set BLOCK_CACHED flag in Writeback and send below,
24012853Sgabeblack@google.com            // so that the Writeback does not reset the bit
24112853Sgabeblack@google.com            // corresponding to this address in the snoop filter
24212853Sgabeblack@google.com            // below. We can discard CleanEvicts because cached
24312853Sgabeblack@google.com            // copies exist above. Atomic mode isCachedAbove
24412853Sgabeblack@google.com            // modifies packet to set BLOCK_CACHED flag
24512853Sgabeblack@google.com            memSidePort.sendAtomic(pkt);
24612853Sgabeblack@google.com        }
24712853Sgabeblack@google.com    } else {
24812853Sgabeblack@google.com        // If the block is not cached above, send packet below. Both
24912853Sgabeblack@google.com        // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
25012853Sgabeblack@google.com        // reset the bit corresponding to this address in the snoop filter
25112853Sgabeblack@google.com        // below.
25212853Sgabeblack@google.com        memSidePort.sendAtomic(pkt);
25312853Sgabeblack@google.com    }
25412853Sgabeblack@google.com
25512853Sgabeblack@google.com    // In case of CleanEvicts, the packet destructor will delete the
25612853Sgabeblack@google.com    // request object because this is a non-snoop request packet which
25712853Sgabeblack@google.com    // does not require a response.
25812853Sgabeblack@google.com    delete pkt;
25912853Sgabeblack@google.com}
26012853Sgabeblack@google.com
26112853Sgabeblack@google.comvoid
26212853Sgabeblack@google.comCache::recvTimingSnoopResp(PacketPtr pkt)
26312853Sgabeblack@google.com{
26412853Sgabeblack@google.com    DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
26512853Sgabeblack@google.com
26612853Sgabeblack@google.com    // determine if the response is from a snoop request we created
26712853Sgabeblack@google.com    // (in which case it should be in the outstandingSnoop), or if we
26812853Sgabeblack@google.com    // merely forwarded someone else's snoop request
26912853Sgabeblack@google.com    const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
27012853Sgabeblack@google.com        outstandingSnoop.end();
27112853Sgabeblack@google.com
27212853Sgabeblack@google.com    if (!forwardAsSnoop) {
27312853Sgabeblack@google.com        // the packet came from this cache, so sink it here and do not
27412853Sgabeblack@google.com        // forward it
27512853Sgabeblack@google.com        assert(pkt->cmd == MemCmd::HardPFResp);
27612853Sgabeblack@google.com
27712853Sgabeblack@google.com        outstandingSnoop.erase(pkt->req);
27812853Sgabeblack@google.com
27912853Sgabeblack@google.com        DPRINTF(Cache, "Got prefetch response from above for addr "
28012853Sgabeblack@google.com                "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
28112853Sgabeblack@google.com        recvTimingResp(pkt);
28212853Sgabeblack@google.com        return;
28312853Sgabeblack@google.com    }
28412853Sgabeblack@google.com
28512853Sgabeblack@google.com    // forwardLatency is set here because there is a response from an
28612853Sgabeblack@google.com    // upper level cache.
28712853Sgabeblack@google.com    // To pay the delay that occurs if the packet comes from the bus,
28812853Sgabeblack@google.com    // we charge also headerDelay.
28912853Sgabeblack@google.com    Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
29012853Sgabeblack@google.com    // Reset the timing of the packet.
29112853Sgabeblack@google.com    pkt->headerDelay = pkt->payloadDelay = 0;
29212853Sgabeblack@google.com    memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time);
29312853Sgabeblack@google.com}
29412853Sgabeblack@google.com
29512853Sgabeblack@google.comvoid
29612853Sgabeblack@google.comCache::promoteWholeLineWrites(PacketPtr pkt)
29712853Sgabeblack@google.com{
29812853Sgabeblack@google.com    // Cache line clearing instructions
29912853Sgabeblack@google.com    if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
30012853Sgabeblack@google.com        (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
30112853Sgabeblack@google.com        pkt->cmd = MemCmd::WriteLineReq;
30212853Sgabeblack@google.com        DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
30312853Sgabeblack@google.com    }
30412853Sgabeblack@google.com}
30512853Sgabeblack@google.com
30612853Sgabeblack@google.comvoid
30712853Sgabeblack@google.comCache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
30812853Sgabeblack@google.com{
30912853Sgabeblack@google.com    // should never be satisfying an uncacheable access as we
31012853Sgabeblack@google.com    // flush and invalidate any existing block as part of the
31112853Sgabeblack@google.com    // lookup
31212853Sgabeblack@google.com    assert(!pkt->req->isUncacheable());
31312853Sgabeblack@google.com
31412853Sgabeblack@google.com    BaseCache::handleTimingReqHit(pkt, blk, request_time);
31512853Sgabeblack@google.com}
31612853Sgabeblack@google.com
31712853Sgabeblack@google.comvoid
31812853Sgabeblack@google.comCache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
31912853Sgabeblack@google.com                           Tick request_time)
32012853Sgabeblack@google.com{
32112853Sgabeblack@google.com    if (pkt->req->isUncacheable()) {
32212853Sgabeblack@google.com        // ignore any existing MSHR if we are dealing with an
32312853Sgabeblack@google.com        // uncacheable request
32412853Sgabeblack@google.com
32512853Sgabeblack@google.com        // should have flushed and have no valid block
32612853Sgabeblack@google.com        assert(!blk || !blk->isValid());
32712853Sgabeblack@google.com
32812853Sgabeblack@google.com        mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
32912853Sgabeblack@google.com
33012853Sgabeblack@google.com        if (pkt->isWrite()) {
33112853Sgabeblack@google.com            allocateWriteBuffer(pkt, forward_time);
33212853Sgabeblack@google.com        } else {
33312853Sgabeblack@google.com            assert(pkt->isRead());
33412853Sgabeblack@google.com
33512853Sgabeblack@google.com            // uncacheable accesses always allocate a new MSHR
33612853Sgabeblack@google.com
33712853Sgabeblack@google.com            // Here we are using forward_time, modelling the latency of
33812853Sgabeblack@google.com            // a miss (outbound) just as forwardLatency, neglecting the
33912853Sgabeblack@google.com            // lookupLatency component.
34012853Sgabeblack@google.com            allocateMissBuffer(pkt, forward_time);
34112853Sgabeblack@google.com        }
34212853Sgabeblack@google.com
34312853Sgabeblack@google.com        return;
34412853Sgabeblack@google.com    }
34512853Sgabeblack@google.com
34612853Sgabeblack@google.com    Addr blk_addr = pkt->getBlockAddr(blkSize);
34712853Sgabeblack@google.com
34812853Sgabeblack@google.com    MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
34912853Sgabeblack@google.com
35012853Sgabeblack@google.com    // Software prefetch handling:
35112853Sgabeblack@google.com    // To keep the core from waiting on data it won't look at
35212853Sgabeblack@google.com    // anyway, send back a response with dummy data. Miss handling
35312853Sgabeblack@google.com    // will continue asynchronously. Unfortunately, the core will
35412853Sgabeblack@google.com    // insist upon freeing original Packet/Request, so we have to
35512853Sgabeblack@google.com    // create a new pair with a different lifecycle. Note that this
35612853Sgabeblack@google.com    // processing happens before any MSHR munging on the behalf of
35712853Sgabeblack@google.com    // this request because this new Request will be the one stored
35812853Sgabeblack@google.com    // into the MSHRs, not the original.
35912853Sgabeblack@google.com    if (pkt->cmd.isSWPrefetch()) {
36012853Sgabeblack@google.com        assert(pkt->needsResponse());
36112853Sgabeblack@google.com        assert(pkt->req->hasPaddr());
36212853Sgabeblack@google.com        assert(!pkt->req->isUncacheable());
36312853Sgabeblack@google.com
36412853Sgabeblack@google.com        // There's no reason to add a prefetch as an additional target
36512853Sgabeblack@google.com        // to an existing MSHR. If an outstanding request is already
36612853Sgabeblack@google.com        // in progress, there is nothing for the prefetch to do.
36712853Sgabeblack@google.com        // If this is the case, we don't even create a request at all.
36812853Sgabeblack@google.com        PacketPtr pf = nullptr;
36912853Sgabeblack@google.com
37012853Sgabeblack@google.com        if (!mshr) {
37112853Sgabeblack@google.com            // copy the request and create a new SoftPFReq packet
37212853Sgabeblack@google.com            RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(),
37312853Sgabeblack@google.com                                                       pkt->req->getSize(),
37412853Sgabeblack@google.com                                                       pkt->req->getFlags(),
37512853Sgabeblack@google.com                                                       pkt->req->masterId());
37612853Sgabeblack@google.com            pf = new Packet(req, pkt->cmd);
37712853Sgabeblack@google.com            pf->allocate();
37812853Sgabeblack@google.com            assert(pf->matchAddr(pkt));
37912853Sgabeblack@google.com            assert(pf->getSize() == pkt->getSize());
38012853Sgabeblack@google.com        }
38112853Sgabeblack@google.com
38212853Sgabeblack@google.com        pkt->makeTimingResponse();
38312853Sgabeblack@google.com
38412853Sgabeblack@google.com        // request_time is used here, taking into account lat and the delay
38512853Sgabeblack@google.com        // charged if the packet comes from the xbar.
38612853Sgabeblack@google.com        cpuSidePort.schedTimingResp(pkt, request_time);
38712853Sgabeblack@google.com
38812853Sgabeblack@google.com        // If an outstanding request is in progress (we found an
38912853Sgabeblack@google.com        // MSHR) this is set to null
39012853Sgabeblack@google.com        pkt = pf;
39112853Sgabeblack@google.com    }
39212853Sgabeblack@google.com
39312853Sgabeblack@google.com    BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time);
39412853Sgabeblack@google.com}
39512853Sgabeblack@google.com
39612853Sgabeblack@google.comvoid
39712853Sgabeblack@google.comCache::recvTimingReq(PacketPtr pkt)
39812853Sgabeblack@google.com{
39912853Sgabeblack@google.com    DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
40012853Sgabeblack@google.com
40112853Sgabeblack@google.com    promoteWholeLineWrites(pkt);
40212853Sgabeblack@google.com
40312853Sgabeblack@google.com    if (pkt->cacheResponding()) {
40412853Sgabeblack@google.com        // a cache above us (but not where the packet came from) is
40512853Sgabeblack@google.com        // responding to the request, in other words it has the line
40612853Sgabeblack@google.com        // in Modified or Owned state
40712853Sgabeblack@google.com        DPRINTF(Cache, "Cache above responding to %s: not responding\n",
40812853Sgabeblack@google.com                pkt->print());
40912853Sgabeblack@google.com
41012853Sgabeblack@google.com        // if the packet needs the block to be writable, and the cache
41112853Sgabeblack@google.com        // that has promised to respond (setting the cache responding
41212853Sgabeblack@google.com        // flag) is not providing writable (it is in Owned rather than
41312853Sgabeblack@google.com        // the Modified state), we know that there may be other Shared
41412853Sgabeblack@google.com        // copies in the system; go out and invalidate them all
41512853Sgabeblack@google.com        assert(pkt->needsWritable() && !pkt->responderHadWritable());
41612853Sgabeblack@google.com
41712853Sgabeblack@google.com        // an upstream cache that had the line in Owned state
41812853Sgabeblack@google.com        // (dirty, but not writable), is responding and thus
41912853Sgabeblack@google.com        // transferring the dirty line from one branch of the
42012853Sgabeblack@google.com        // cache hierarchy to another
42112853Sgabeblack@google.com
42212853Sgabeblack@google.com        // send out an express snoop and invalidate all other
42312853Sgabeblack@google.com        // copies (snooping a packet that needs writable is the
42412853Sgabeblack@google.com        // same as an invalidation), thus turning the Owned line
42512853Sgabeblack@google.com        // into a Modified line, note that we don't invalidate the
42612853Sgabeblack@google.com        // block in the current cache or any other cache on the
42712853Sgabeblack@google.com        // path to memory
42812853Sgabeblack@google.com
42912853Sgabeblack@google.com        // create a downstream express snoop with cleared packet
43012853Sgabeblack@google.com        // flags, there is no need to allocate any data as the
43112853Sgabeblack@google.com        // packet is merely used to co-ordinate state transitions
43212853Sgabeblack@google.com        Packet *snoop_pkt = new Packet(pkt, true, false);
43312853Sgabeblack@google.com
43412853Sgabeblack@google.com        // also reset the bus time that the original packet has
43512853Sgabeblack@google.com        // not yet paid for
43612853Sgabeblack@google.com        snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
43712853Sgabeblack@google.com
43812853Sgabeblack@google.com        // make this an instantaneous express snoop, and let the
43912853Sgabeblack@google.com        // other caches in the system know that the another cache
44012853Sgabeblack@google.com        // is responding, because we have found the authorative
44112853Sgabeblack@google.com        // copy (Modified or Owned) that will supply the right
44212853Sgabeblack@google.com        // data
44312853Sgabeblack@google.com        snoop_pkt->setExpressSnoop();
44412853Sgabeblack@google.com        snoop_pkt->setCacheResponding();
44512853Sgabeblack@google.com
44612853Sgabeblack@google.com        // this express snoop travels towards the memory, and at
44712853Sgabeblack@google.com        // every crossbar it is snooped upwards thus reaching
44812853Sgabeblack@google.com        // every cache in the system
44912853Sgabeblack@google.com        bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt);
45012853Sgabeblack@google.com        // express snoops always succeed
45112853Sgabeblack@google.com        assert(success);
45212853Sgabeblack@google.com
45312853Sgabeblack@google.com        // main memory will delete the snoop packet
45412853Sgabeblack@google.com
45512853Sgabeblack@google.com        // queue for deletion, as opposed to immediate deletion, as
45612853Sgabeblack@google.com        // the sending cache is still relying on the packet
45712853Sgabeblack@google.com        pendingDelete.reset(pkt);
45812853Sgabeblack@google.com
45912853Sgabeblack@google.com        // no need to take any further action in this particular cache
46012853Sgabeblack@google.com        // as an upstram cache has already committed to responding,
46112853Sgabeblack@google.com        // and we have already sent out any express snoops in the
46212853Sgabeblack@google.com        // section above to ensure all other copies in the system are
46312853Sgabeblack@google.com        // invalidated
46412853Sgabeblack@google.com        return;
46512853Sgabeblack@google.com    }
46612853Sgabeblack@google.com
46712853Sgabeblack@google.com    BaseCache::recvTimingReq(pkt);
46812853Sgabeblack@google.com}
46912853Sgabeblack@google.com
47012853Sgabeblack@google.comPacketPtr
47112853Sgabeblack@google.comCache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
47212853Sgabeblack@google.com                        bool needsWritable,
47312853Sgabeblack@google.com                        bool is_whole_line_write) const
47412853Sgabeblack@google.com{
47512853Sgabeblack@google.com    // should never see evictions here
47612853Sgabeblack@google.com    assert(!cpu_pkt->isEviction());
47712853Sgabeblack@google.com
47812853Sgabeblack@google.com    bool blkValid = blk && blk->isValid();
47912853Sgabeblack@google.com
48012853Sgabeblack@google.com    if (cpu_pkt->req->isUncacheable() ||
48112853Sgabeblack@google.com        (!blkValid && cpu_pkt->isUpgrade()) ||
48212853Sgabeblack@google.com        cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
48312853Sgabeblack@google.com        // uncacheable requests and upgrades from upper-level caches
48412853Sgabeblack@google.com        // that missed completely just go through as is
48512853Sgabeblack@google.com        return nullptr;
48612853Sgabeblack@google.com    }
48712853Sgabeblack@google.com
48812853Sgabeblack@google.com    assert(cpu_pkt->needsResponse());
48912853Sgabeblack@google.com
49012853Sgabeblack@google.com    MemCmd cmd;
49112853Sgabeblack@google.com    // @TODO make useUpgrades a parameter.
49212853Sgabeblack@google.com    // Note that ownership protocols require upgrade, otherwise a
49312853Sgabeblack@google.com    // write miss on a shared owned block will generate a ReadExcl,
494    // which will clobber the owned copy.
495    const bool useUpgrades = true;
496    assert(cpu_pkt->cmd != MemCmd::WriteLineReq || is_whole_line_write);
497    if (is_whole_line_write) {
498        assert(!blkValid || !blk->isWritable());
499        // forward as invalidate to all other caches, this gives us
500        // the line in Exclusive state, and invalidates all other
501        // copies
502        cmd = MemCmd::InvalidateReq;
503    } else if (blkValid && useUpgrades) {
504        // only reason to be here is that blk is read only and we need
505        // it to be writable
506        assert(needsWritable);
507        assert(!blk->isWritable());
508        cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
509    } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
510               cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
511        // Even though this SC will fail, we still need to send out the
512        // request and get the data to supply it to other snoopers in the case
513        // where the determination the StoreCond fails is delayed due to
514        // all caches not being on the same local bus.
515        cmd = MemCmd::SCUpgradeFailReq;
516    } else {
517        // block is invalid
518
519        // If the request does not need a writable there are two cases
520        // where we need to ensure the response will not fetch the
521        // block in dirty state:
522        // * this cache is read only and it does not perform
523        //   writebacks,
524        // * this cache is mostly exclusive and will not fill (since
525        //   it does not fill it will have to writeback the dirty data
526        //   immediately which generates uneccesary writebacks).
527        bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
528        cmd = needsWritable ? MemCmd::ReadExReq :
529            (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
530    }
531    PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
532
533    // if there are upstream caches that have already marked the
534    // packet as having sharers (not passing writable), pass that info
535    // downstream
536    if (cpu_pkt->hasSharers() && !needsWritable) {
537        // note that cpu_pkt may have spent a considerable time in the
538        // MSHR queue and that the information could possibly be out
539        // of date, however, there is no harm in conservatively
540        // assuming the block has sharers
541        pkt->setHasSharers();
542        DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
543                __func__, cpu_pkt->print(), pkt->print());
544    }
545
546    // the packet should be block aligned
547    assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
548
549    pkt->allocate();
550    DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
551            cpu_pkt->print());
552    return pkt;
553}
554
555
556Cycles
557Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk)
558{
559    // deal with the packets that go through the write path of
560    // the cache, i.e. any evictions and writes
561    if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
562        (pkt->req->isUncacheable() && pkt->isWrite())) {
563        Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt));
564
565        // at this point, if the request was an uncacheable write
566        // request, it has been satisfied by a memory below and the
567        // packet carries the response back
568        assert(!(pkt->req->isUncacheable() && pkt->isWrite()) ||
569               pkt->isResponse());
570
571        return latency;
572    }
573
574    // only misses left
575
576    PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable(),
577                                         pkt->isWholeLineWrite(blkSize));
578
579    bool is_forward = (bus_pkt == nullptr);
580
581    if (is_forward) {
582        // just forwarding the same request to the next level
583        // no local cache operation involved
584        bus_pkt = pkt;
585    }
586
587    DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
588            bus_pkt->print());
589
590#if TRACING_ON
591    CacheBlk::State old_state = blk ? blk->status : 0;
592#endif
593
594    Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt));
595
596    bool is_invalidate = bus_pkt->isInvalidate();
597
598    // We are now dealing with the response handling
599    DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
600            bus_pkt->print(), old_state);
601
602    // If packet was a forward, the response (if any) is already
603    // in place in the bus_pkt == pkt structure, so we don't need
604    // to do anything.  Otherwise, use the separate bus_pkt to
605    // generate response to pkt and then delete it.
606    if (!is_forward) {
607        if (pkt->needsResponse()) {
608            assert(bus_pkt->isResponse());
609            if (bus_pkt->isError()) {
610                pkt->makeAtomicResponse();
611                pkt->copyError(bus_pkt);
612            } else if (pkt->isWholeLineWrite(blkSize)) {
613                // note the use of pkt, not bus_pkt here.
614
615                // write-line request to the cache that promoted
616                // the write to a whole line
617                const bool allocate = allocOnFill(pkt->cmd) &&
618                    (!writeAllocator || writeAllocator->allocate());
619                blk = handleFill(bus_pkt, blk, allocate);
620                assert(blk != NULL);
621                is_invalidate = false;
622                satisfyRequest(pkt, blk);
623            } else if (bus_pkt->isRead() ||
624                       bus_pkt->cmd == MemCmd::UpgradeResp) {
625                // we're updating cache state to allow us to
626                // satisfy the upstream request from the cache
627                blk = handleFill(bus_pkt, blk, allocOnFill(pkt->cmd));
628                satisfyRequest(pkt, blk);
629                maintainClusivity(pkt->fromCache(), blk);
630            } else {
631                // we're satisfying the upstream request without
632                // modifying cache state, e.g., a write-through
633                pkt->makeAtomicResponse();
634            }
635        }
636        delete bus_pkt;
637    }
638
639    if (is_invalidate && blk && blk->isValid()) {
640        invalidateBlock(blk);
641    }
642
643    return latency;
644}
645
646Tick
647Cache::recvAtomic(PacketPtr pkt)
648{
649    promoteWholeLineWrites(pkt);
650
651    // follow the same flow as in recvTimingReq, and check if a cache
652    // above us is responding
653    if (pkt->cacheResponding()) {
654        assert(!pkt->req->isCacheInvalidate());
655        DPRINTF(Cache, "Cache above responding to %s: not responding\n",
656                pkt->print());
657
658        // if a cache is responding, and it had the line in Owned
659        // rather than Modified state, we need to invalidate any
660        // copies that are not on the same path to memory
661        assert(pkt->needsWritable() && !pkt->responderHadWritable());
662
663        return memSidePort.sendAtomic(pkt);
664    }
665
666    return BaseCache::recvAtomic(pkt);
667}
668
669
670/////////////////////////////////////////////////////
671//
672// Response handling: responses from the memory side
673//
674/////////////////////////////////////////////////////
675
676
677void
678Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk)
679{
680    QueueEntry::Target *initial_tgt = mshr->getTarget();
681    // First offset for critical word first calculations
682    const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
683
684    const bool is_error = pkt->isError();
685    // allow invalidation responses originating from write-line
686    // requests to be discarded
687    bool is_invalidate = pkt->isInvalidate() &&
688        !mshr->wasWholeLineWrite;
689
690    MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
691    for (auto &target: targets) {
692        Packet *tgt_pkt = target.pkt;
693        switch (target.source) {
694          case MSHR::Target::FromCPU:
695            Tick completion_time;
696            // Here we charge on completion_time the delay of the xbar if the
697            // packet comes from it, charged on headerDelay.
698            completion_time = pkt->headerDelay;
699
700            // Software prefetch handling for cache closest to core
701            if (tgt_pkt->cmd.isSWPrefetch()) {
702                // a software prefetch would have already been ack'd
703                // immediately with dummy data so the core would be able to
704                // retire it. This request completes right here, so we
705                // deallocate it.
706                delete tgt_pkt;
707                break; // skip response
708            }
709
710            // unlike the other packet flows, where data is found in other
711            // caches or memory and brought back, write-line requests always
712            // have the data right away, so the above check for "is fill?"
713            // cannot actually be determined until examining the stored MSHR
714            // state. We "catch up" with that logic here, which is duplicated
715            // from above.
716            if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
717                assert(!is_error);
718                assert(blk);
719                assert(blk->isWritable());
720            }
721
722            if (blk && blk->isValid() && !mshr->isForward) {
723                satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
724
725                // How many bytes past the first request is this one
726                int transfer_offset =
727                    tgt_pkt->getOffset(blkSize) - initial_offset;
728                if (transfer_offset < 0) {
729                    transfer_offset += blkSize;
730                }
731
732                // If not critical word (offset) return payloadDelay.
733                // responseLatency is the latency of the return path
734                // from lower level caches/memory to an upper level cache or
735                // the core.
736                completion_time += clockEdge(responseLatency) +
737                    (transfer_offset ? pkt->payloadDelay : 0);
738
739                assert(!tgt_pkt->req->isUncacheable());
740
741                assert(tgt_pkt->req->masterId() < system->maxMasters());
742                missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
743                    completion_time - target.recvTime;
744            } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
745                // failed StoreCond upgrade
746                assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
747                       tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
748                       tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
749                // responseLatency is the latency of the return path
750                // from lower level caches/memory to an upper level cache or
751                // the core.
752                completion_time += clockEdge(responseLatency) +
753                    pkt->payloadDelay;
754                tgt_pkt->req->setExtraData(0);
755            } else {
756                // We are about to send a response to a cache above
757                // that asked for an invalidation; we need to
758                // invalidate our copy immediately as the most
759                // up-to-date copy of the block will now be in the
760                // cache above. It will also prevent this cache from
761                // responding (if the block was previously dirty) to
762                // snoops as they should snoop the caches above where
763                // they will get the response from.
764                if (is_invalidate && blk && blk->isValid()) {
765                    invalidateBlock(blk);
766                }
767                // not a cache fill, just forwarding response
768                // responseLatency is the latency of the return path
769                // from lower level cahces/memory to the core.
770                completion_time += clockEdge(responseLatency) +
771                    pkt->payloadDelay;
772                if (pkt->isRead() && !is_error) {
773                    // sanity check
774                    assert(pkt->matchAddr(tgt_pkt));
775                    assert(pkt->getSize() >= tgt_pkt->getSize());
776
777                    tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
778                }
779
780                // this response did not allocate here and therefore
781                // it was not consumed, make sure that any flags are
782                // carried over to cache above
783                tgt_pkt->copyResponderFlags(pkt);
784            }
785            tgt_pkt->makeTimingResponse();
786            // if this packet is an error copy that to the new packet
787            if (is_error)
788                tgt_pkt->copyError(pkt);
789            if (tgt_pkt->cmd == MemCmd::ReadResp &&
790                (is_invalidate || mshr->hasPostInvalidate())) {
791                // If intermediate cache got ReadRespWithInvalidate,
792                // propagate that.  Response should not have
793                // isInvalidate() set otherwise.
794                tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
795                DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
796                        tgt_pkt->print());
797            }
798            // Reset the bus additional time as it is now accounted for
799            tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
800            cpuSidePort.schedTimingResp(tgt_pkt, completion_time);
801            break;
802
803          case MSHR::Target::FromPrefetcher:
804            assert(tgt_pkt->cmd == MemCmd::HardPFReq);
805            if (blk)
806                blk->status |= BlkHWPrefetched;
807            delete tgt_pkt;
808            break;
809
810          case MSHR::Target::FromSnoop:
811            // I don't believe that a snoop can be in an error state
812            assert(!is_error);
813            // response to snoop request
814            DPRINTF(Cache, "processing deferred snoop...\n");
815            // If the response is invalidating, a snooping target can
816            // be satisfied if it is also invalidating. If the reponse is, not
817            // only invalidating, but more specifically an InvalidateResp and
818            // the MSHR was created due to an InvalidateReq then a cache above
819            // is waiting to satisfy a WriteLineReq. In this case even an
820            // non-invalidating snoop is added as a target here since this is
821            // the ordering point. When the InvalidateResp reaches this cache,
822            // the snooping target will snoop further the cache above with the
823            // WriteLineReq.
824            assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
825                   pkt->req->isCacheMaintenance() ||
826                   mshr->hasPostInvalidate());
827            handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
828            break;
829
830          default:
831            panic("Illegal target->source enum %d\n", target.source);
832        }
833    }
834
835    maintainClusivity(targets.hasFromCache, blk);
836
837    if (blk && blk->isValid()) {
838        // an invalidate response stemming from a write line request
839        // should not invalidate the block, so check if the
840        // invalidation should be discarded
841        if (is_invalidate || mshr->hasPostInvalidate()) {
842            invalidateBlock(blk);
843        } else if (mshr->hasPostDowngrade()) {
844            blk->status &= ~BlkWritable;
845        }
846    }
847}
848
849PacketPtr
850Cache::evictBlock(CacheBlk *blk)
851{
852    PacketPtr pkt = (blk->isDirty() || writebackClean) ?
853        writebackBlk(blk) : cleanEvictBlk(blk);
854
855    invalidateBlock(blk);
856
857    return pkt;
858}
859
860PacketPtr
861Cache::cleanEvictBlk(CacheBlk *blk)
862{
863    assert(!writebackClean);
864    assert(blk && blk->isValid() && !blk->isDirty());
865
866    // Creating a zero sized write, a message to the snoop filter
867    RequestPtr req = std::make_shared<Request>(
868        regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId);
869
870    if (blk->isSecure())
871        req->setFlags(Request::SECURE);
872
873    req->taskId(blk->task_id);
874
875    PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
876    pkt->allocate();
877    DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
878
879    return pkt;
880}
881
882/////////////////////////////////////////////////////
883//
884// Snoop path: requests coming in from the memory side
885//
886/////////////////////////////////////////////////////
887
888void
889Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
890                              bool already_copied, bool pending_inval)
891{
892    // sanity check
893    assert(req_pkt->isRequest());
894    assert(req_pkt->needsResponse());
895
896    DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
897    // timing-mode snoop responses require a new packet, unless we
898    // already made a copy...
899    PacketPtr pkt = req_pkt;
900    if (!already_copied)
901        // do not clear flags, and allocate space for data if the
902        // packet needs it (the only packets that carry data are read
903        // responses)
904        pkt = new Packet(req_pkt, false, req_pkt->isRead());
905
906    assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
907           pkt->hasSharers());
908    pkt->makeTimingResponse();
909    if (pkt->isRead()) {
910        pkt->setDataFromBlock(blk_data, blkSize);
911    }
912    if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
913        // Assume we defer a response to a read from a far-away cache
914        // A, then later defer a ReadExcl from a cache B on the same
915        // bus as us. We'll assert cacheResponding in both cases, but
916        // in the latter case cacheResponding will keep the
917        // invalidation from reaching cache A. This special response
918        // tells cache A that it gets the block to satisfy its read,
919        // but must immediately invalidate it.
920        pkt->cmd = MemCmd::ReadRespWithInvalidate;
921    }
922    // Here we consider forward_time, paying for just forward latency and
923    // also charging the delay provided by the xbar.
924    // forward_time is used as send_time in next allocateWriteBuffer().
925    Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
926    // Here we reset the timing of the packet.
927    pkt->headerDelay = pkt->payloadDelay = 0;
928    DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
929            pkt->print(), forward_time);
930    memSidePort.schedTimingSnoopResp(pkt, forward_time);
931}
932
933uint32_t
934Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
935                   bool is_deferred, bool pending_inval)
936{
937    DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
938    // deferred snoops can only happen in timing mode
939    assert(!(is_deferred && !is_timing));
940    // pending_inval only makes sense on deferred snoops
941    assert(!(pending_inval && !is_deferred));
942    assert(pkt->isRequest());
943
944    // the packet may get modified if we or a forwarded snooper
945    // responds in atomic mode, so remember a few things about the
946    // original packet up front
947    bool invalidate = pkt->isInvalidate();
948    bool M5_VAR_USED needs_writable = pkt->needsWritable();
949
950    // at the moment we could get an uncacheable write which does not
951    // have the invalidate flag, and we need a suitable way of dealing
952    // with this case
953    panic_if(invalidate && pkt->req->isUncacheable(),
954             "%s got an invalidating uncacheable snoop request %s",
955             name(), pkt->print());
956
957    uint32_t snoop_delay = 0;
958
959    if (forwardSnoops) {
960        // first propagate snoop upward to see if anyone above us wants to
961        // handle it.  save & restore packet src since it will get
962        // rewritten to be relative to cpu-side bus (if any)
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 this request is a prefetch or clean evict and an upper level
981            // signals block present, make sure to propagate the block
982            // presence to the requester.
983            if (snoopPkt.isBlockCached()) {
984                pkt->setBlockCached();
985            }
986            // If the request was satisfied by snooping the cache
987            // above, mark the original packet as satisfied too.
988            if (snoopPkt.satisfied()) {
989                pkt->setSatisfied();
990            }
991
992            // Copy over flags from the snoop response to make sure we
993            // inform the final destination
994            pkt->copyResponderFlags(&snoopPkt);
995        } else {
996            bool already_responded = pkt->cacheResponding();
997            cpuSidePort.sendAtomicSnoop(pkt);
998            if (!already_responded && pkt->cacheResponding()) {
999                // cache-to-cache response from some upper cache:
1000                // forward response to original requester
1001                assert(pkt->isResponse());
1002            }
1003        }
1004    }
1005
1006    bool respond = false;
1007    bool blk_valid = blk && blk->isValid();
1008    if (pkt->isClean()) {
1009        if (blk_valid && blk->isDirty()) {
1010            DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
1011                    __func__, pkt->print(), blk->print());
1012            PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
1013
1014            if (is_timing) {
1015                // anything that is merely forwarded pays for the forward
1016                // latency and the delay provided by the crossbar
1017                Tick forward_time = clockEdge(forwardLatency) +
1018                    pkt->headerDelay;
1019                doWritebacks(wb_pkt, forward_time);
1020            } else {
1021                doWritebacksAtomic(wb_pkt);
1022            }
1023            pkt->setSatisfied();
1024        }
1025    } else if (!blk_valid) {
1026        DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
1027                pkt->print());
1028        if (is_deferred) {
1029            // we no longer have the block, and will not respond, but a
1030            // packet was allocated in MSHR::handleSnoop and we have
1031            // to delete it
1032            assert(pkt->needsResponse());
1033
1034            // we have passed the block to a cache upstream, that
1035            // cache should be responding
1036            assert(pkt->cacheResponding());
1037
1038            delete pkt;
1039        }
1040        return snoop_delay;
1041    } else {
1042        DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
1043                pkt->print(), blk->print());
1044
1045        // We may end up modifying both the block state and the packet (if
1046        // we respond in atomic mode), so just figure out what to do now
1047        // and then do it later. We respond to all snoops that need
1048        // responses provided we have the block in dirty state. The
1049        // invalidation itself is taken care of below. We don't respond to
1050        // cache maintenance operations as this is done by the destination
1051        // xbar.
1052        respond = blk->isDirty() && pkt->needsResponse();
1053
1054        chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
1055                      "a dirty block in a read-only cache %s\n", name());
1056    }
1057
1058    // Invalidate any prefetch's from below that would strip write permissions
1059    // MemCmd::HardPFReq is only observed by upstream caches.  After missing
1060    // above and in it's own cache, a new MemCmd::ReadReq is created that
1061    // downstream caches observe.
1062    if (pkt->mustCheckAbove()) {
1063        DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
1064                "from lower cache\n", pkt->getAddr(), pkt->print());
1065        pkt->setBlockCached();
1066        return snoop_delay;
1067    }
1068
1069    if (pkt->isRead() && !invalidate) {
1070        // reading without requiring the line in a writable state
1071        assert(!needs_writable);
1072        pkt->setHasSharers();
1073
1074        // if the requesting packet is uncacheable, retain the line in
1075        // the current state, otherwhise unset the writable flag,
1076        // which means we go from Modified to Owned (and will respond
1077        // below), remain in Owned (and will respond below), from
1078        // Exclusive to Shared, or remain in Shared
1079        if (!pkt->req->isUncacheable())
1080            blk->status &= ~BlkWritable;
1081        DPRINTF(Cache, "new state is %s\n", blk->print());
1082    }
1083
1084    if (respond) {
1085        // prevent anyone else from responding, cache as well as
1086        // memory, and also prevent any memory from even seeing the
1087        // request
1088        pkt->setCacheResponding();
1089        if (!pkt->isClean() && blk->isWritable()) {
1090            // inform the cache hierarchy that this cache had the line
1091            // in the Modified state so that we avoid unnecessary
1092            // invalidations (see Packet::setResponderHadWritable)
1093            pkt->setResponderHadWritable();
1094
1095            // in the case of an uncacheable request there is no point
1096            // in setting the responderHadWritable flag, but since the
1097            // recipient does not care there is no harm in doing so
1098        } else {
1099            // if the packet has needsWritable set we invalidate our
1100            // copy below and all other copies will be invalidates
1101            // through express snoops, and if needsWritable is not set
1102            // we already called setHasSharers above
1103        }
1104
1105        // if we are returning a writable and dirty (Modified) line,
1106        // we should be invalidating the line
1107        panic_if(!invalidate && !pkt->hasSharers(),
1108                 "%s is passing a Modified line through %s, "
1109                 "but keeping the block", name(), pkt->print());
1110
1111        if (is_timing) {
1112            doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
1113        } else {
1114            pkt->makeAtomicResponse();
1115            // packets such as upgrades do not actually have any data
1116            // payload
1117            if (pkt->hasData())
1118                pkt->setDataFromBlock(blk->data, blkSize);
1119        }
1120
1121        // When a block is compressed, it must first be decompressed before
1122        // being read, and this increases the snoop delay.
1123        if (compressor && pkt->isRead()) {
1124            snoop_delay += compressor->getDecompressionLatency(blk);
1125        }
1126    }
1127
1128    if (!respond && is_deferred) {
1129        assert(pkt->needsResponse());
1130        delete pkt;
1131    }
1132
1133    // Do this last in case it deallocates block data or something
1134    // like that
1135    if (blk_valid && invalidate) {
1136        invalidateBlock(blk);
1137        DPRINTF(Cache, "new state is %s\n", blk->print());
1138    }
1139
1140    return snoop_delay;
1141}
1142
1143
1144void
1145Cache::recvTimingSnoopReq(PacketPtr pkt)
1146{
1147    DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
1148
1149    // no need to snoop requests that are not in range
1150    if (!inRange(pkt->getAddr())) {
1151        return;
1152    }
1153
1154    bool is_secure = pkt->isSecure();
1155    CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
1156
1157    Addr blk_addr = pkt->getBlockAddr(blkSize);
1158    MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
1159
1160    // Update the latency cost of the snoop so that the crossbar can
1161    // account for it. Do not overwrite what other neighbouring caches
1162    // have already done, rather take the maximum. The update is
1163    // tentative, for cases where we return before an upward snoop
1164    // happens below.
1165    pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
1166                                         lookupLatency * clockPeriod());
1167
1168    // Inform request(Prefetch, CleanEvict or Writeback) from below of
1169    // MSHR hit, set setBlockCached.
1170    if (mshr && pkt->mustCheckAbove()) {
1171        DPRINTF(Cache, "Setting block cached for %s from lower cache on "
1172                "mshr hit\n", pkt->print());
1173        pkt->setBlockCached();
1174        return;
1175    }
1176
1177    // Let the MSHR itself track the snoop and decide whether we want
1178    // to go ahead and do the regular cache snoop
1179    if (mshr && mshr->handleSnoop(pkt, order++)) {
1180        DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
1181                "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
1182                mshr->print());
1183
1184        if (mshr->getNumTargets() > numTarget)
1185            warn("allocating bonus target for snoop"); //handle later
1186        return;
1187    }
1188
1189    //We also need to check the writeback buffers and handle those
1190    WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
1191    if (wb_entry) {
1192        DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
1193                pkt->getAddr(), is_secure ? "s" : "ns");
1194        // Expect to see only Writebacks and/or CleanEvicts here, both of
1195        // which should not be generated for uncacheable data.
1196        assert(!wb_entry->isUncacheable());
1197        // There should only be a single request responsible for generating
1198        // Writebacks/CleanEvicts.
1199        assert(wb_entry->getNumTargets() == 1);
1200        PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
1201        assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
1202
1203        if (pkt->isEviction()) {
1204            // if the block is found in the write queue, set the BLOCK_CACHED
1205            // flag for Writeback/CleanEvict snoop. On return the snoop will
1206            // propagate the BLOCK_CACHED flag in Writeback packets and prevent
1207            // any CleanEvicts from travelling down the memory hierarchy.
1208            pkt->setBlockCached();
1209            DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
1210                    "hit\n", __func__, pkt->print());
1211            return;
1212        }
1213
1214        // conceptually writebacks are no different to other blocks in
1215        // this cache, so the behaviour is modelled after handleSnoop,
1216        // the difference being that instead of querying the block
1217        // state to determine if it is dirty and writable, we use the
1218        // command and fields of the writeback packet
1219        bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
1220            pkt->needsResponse();
1221        bool have_writable = !wb_pkt->hasSharers();
1222        bool invalidate = pkt->isInvalidate();
1223
1224        if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
1225            assert(!pkt->needsWritable());
1226            pkt->setHasSharers();
1227            wb_pkt->setHasSharers();
1228        }
1229
1230        if (respond) {
1231            pkt->setCacheResponding();
1232
1233            if (have_writable) {
1234                pkt->setResponderHadWritable();
1235            }
1236
1237            doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
1238                                   false, false);
1239        }
1240
1241        if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
1242            // Invalidation trumps our writeback... discard here
1243            // Note: markInService will remove entry from writeback buffer.
1244            markInService(wb_entry);
1245            delete wb_pkt;
1246        }
1247    }
1248
1249    // If this was a shared writeback, there may still be
1250    // other shared copies above that require invalidation.
1251    // We could be more selective and return here if the
1252    // request is non-exclusive or if the writeback is
1253    // exclusive.
1254    uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
1255
1256    // Override what we did when we first saw the snoop, as we now
1257    // also have the cost of the upwards snoops to account for
1258    pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
1259                                         lookupLatency * clockPeriod());
1260}
1261
1262Tick
1263Cache::recvAtomicSnoop(PacketPtr pkt)
1264{
1265    // no need to snoop requests that are not in range.
1266    if (!inRange(pkt->getAddr())) {
1267        return 0;
1268    }
1269
1270    CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
1271    uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
1272    return snoop_delay + lookupLatency * clockPeriod();
1273}
1274
1275bool
1276Cache::isCachedAbove(PacketPtr pkt, bool is_timing)
1277{
1278    if (!forwardSnoops)
1279        return false;
1280    // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
1281    // Writeback snoops into upper level caches to check for copies of the
1282    // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
1283    // packet, the cache can inform the crossbar below of presence or absence
1284    // of the block.
1285    if (is_timing) {
1286        Packet snoop_pkt(pkt, true, false);
1287        snoop_pkt.setExpressSnoop();
1288        // Assert that packet is either Writeback or CleanEvict and not a
1289        // prefetch request because prefetch requests need an MSHR and may
1290        // generate a snoop response.
1291        assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
1292        snoop_pkt.senderState = nullptr;
1293        cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1294        // Writeback/CleanEvict snoops do not generate a snoop response.
1295        assert(!(snoop_pkt.cacheResponding()));
1296        return snoop_pkt.isBlockCached();
1297    } else {
1298        cpuSidePort.sendAtomicSnoop(pkt);
1299        return pkt->isBlockCached();
1300    }
1301}
1302
1303bool
1304Cache::sendMSHRQueuePacket(MSHR* mshr)
1305{
1306    assert(mshr);
1307
1308    // use request from 1st target
1309    PacketPtr tgt_pkt = mshr->getTarget()->pkt;
1310
1311    if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
1312        DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
1313
1314        // we should never have hardware prefetches to allocated
1315        // blocks
1316        assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure));
1317
1318        // We need to check the caches above us to verify that
1319        // they don't have a copy of this block in the dirty state
1320        // at the moment. Without this check we could get a stale
1321        // copy from memory that might get used in place of the
1322        // dirty one.
1323        Packet snoop_pkt(tgt_pkt, true, false);
1324        snoop_pkt.setExpressSnoop();
1325        // We are sending this packet upwards, but if it hits we will
1326        // get a snoop response that we end up treating just like a
1327        // normal response, hence it needs the MSHR as its sender
1328        // state
1329        snoop_pkt.senderState = mshr;
1330        cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
1331
1332        // Check to see if the prefetch was squashed by an upper cache (to
1333        // prevent us from grabbing the line) or if a Check to see if a
1334        // writeback arrived between the time the prefetch was placed in
1335        // the MSHRs and when it was selected to be sent or if the
1336        // prefetch was squashed by an upper cache.
1337
1338        // It is important to check cacheResponding before
1339        // prefetchSquashed. If another cache has committed to
1340        // responding, it will be sending a dirty response which will
1341        // arrive at the MSHR allocated for this request. Checking the
1342        // prefetchSquash first may result in the MSHR being
1343        // prematurely deallocated.
1344        if (snoop_pkt.cacheResponding()) {
1345            auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
1346            assert(r.second);
1347
1348            // if we are getting a snoop response with no sharers it
1349            // will be allocated as Modified
1350            bool pending_modified_resp = !snoop_pkt.hasSharers();
1351            markInService(mshr, pending_modified_resp);
1352
1353            DPRINTF(Cache, "Upward snoop of prefetch for addr"
1354                    " %#x (%s) hit\n",
1355                    tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
1356            return false;
1357        }
1358
1359        if (snoop_pkt.isBlockCached()) {
1360            DPRINTF(Cache, "Block present, prefetch squashed by cache.  "
1361                    "Deallocating mshr target %#x.\n",
1362                    mshr->blkAddr);
1363
1364            // Deallocate the mshr target
1365            if (mshrQueue.forceDeallocateTarget(mshr)) {
1366                // Clear block if this deallocation resulted freed an
1367                // mshr when all had previously been utilized
1368                clearBlocked(Blocked_NoMSHRs);
1369            }
1370
1371            // given that no response is expected, delete Request and Packet
1372            delete tgt_pkt;
1373
1374            return false;
1375        }
1376    }
1377
1378    return BaseCache::sendMSHRQueuePacket(mshr);
1379}
1380
1381Cache*
1382CacheParams::create()
1383{
1384    assert(tags);
1385    assert(replacement_policy);
1386
1387    return new Cache(this);
1388}
1389