a3bf4aa6ec
Added stat to the cache to account for HardPF'ed blocks that are evicted before being referenced (over-prefetching).
2721 lines
103 KiB
C++
2721 lines
103 KiB
C++
/*
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* Copyright (c) 2010-2016 ARM Limited
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* All rights reserved.
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*
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* The license below extends only to copyright in the software and shall
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* not be construed as granting a license to any other intellectual
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* property including but not limited to intellectual property relating
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* to a hardware implementation of the functionality of the software
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* licensed hereunder. You may use the software subject to the license
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* terms below provided that you ensure that this notice is replicated
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* unmodified and in its entirety in all distributions of the software,
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* modified or unmodified, in source code or in binary form.
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*
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* Copyright (c) 2002-2005 The Regents of The University of Michigan
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* Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Erik Hallnor
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* Dave Greene
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* Nathan Binkert
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* Steve Reinhardt
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* Ron Dreslinski
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* Andreas Sandberg
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*/
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/**
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* @file
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* Cache definitions.
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*/
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#include "mem/cache/cache.hh"
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#include "base/misc.hh"
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#include "base/types.hh"
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#include "debug/Cache.hh"
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#include "debug/CachePort.hh"
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#include "debug/CacheTags.hh"
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#include "debug/CacheVerbose.hh"
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#include "mem/cache/blk.hh"
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#include "mem/cache/mshr.hh"
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#include "mem/cache/prefetch/base.hh"
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#include "sim/sim_exit.hh"
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Cache::Cache(const CacheParams *p)
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: BaseCache(p, p->system->cacheLineSize()),
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tags(p->tags),
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prefetcher(p->prefetcher),
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doFastWrites(true),
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prefetchOnAccess(p->prefetch_on_access),
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clusivity(p->clusivity),
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writebackClean(p->writeback_clean),
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tempBlockWriteback(nullptr),
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writebackTempBlockAtomicEvent(this, false,
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EventBase::Delayed_Writeback_Pri)
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{
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tempBlock = new CacheBlk();
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tempBlock->data = new uint8_t[blkSize];
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cpuSidePort = new CpuSidePort(p->name + ".cpu_side", this,
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"CpuSidePort");
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memSidePort = new MemSidePort(p->name + ".mem_side", this,
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"MemSidePort");
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tags->setCache(this);
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if (prefetcher)
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prefetcher->setCache(this);
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}
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Cache::~Cache()
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{
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delete [] tempBlock->data;
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delete tempBlock;
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delete cpuSidePort;
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delete memSidePort;
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}
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void
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Cache::regStats()
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{
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BaseCache::regStats();
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}
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void
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Cache::cmpAndSwap(CacheBlk *blk, PacketPtr pkt)
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{
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assert(pkt->isRequest());
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uint64_t overwrite_val;
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bool overwrite_mem;
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uint64_t condition_val64;
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uint32_t condition_val32;
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int offset = tags->extractBlkOffset(pkt->getAddr());
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uint8_t *blk_data = blk->data + offset;
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assert(sizeof(uint64_t) >= pkt->getSize());
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overwrite_mem = true;
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// keep a copy of our possible write value, and copy what is at the
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// memory address into the packet
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pkt->writeData((uint8_t *)&overwrite_val);
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pkt->setData(blk_data);
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if (pkt->req->isCondSwap()) {
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if (pkt->getSize() == sizeof(uint64_t)) {
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condition_val64 = pkt->req->getExtraData();
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overwrite_mem = !std::memcmp(&condition_val64, blk_data,
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sizeof(uint64_t));
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} else if (pkt->getSize() == sizeof(uint32_t)) {
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condition_val32 = (uint32_t)pkt->req->getExtraData();
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overwrite_mem = !std::memcmp(&condition_val32, blk_data,
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sizeof(uint32_t));
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} else
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panic("Invalid size for conditional read/write\n");
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}
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if (overwrite_mem) {
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std::memcpy(blk_data, &overwrite_val, pkt->getSize());
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blk->status |= BlkDirty;
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}
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}
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void
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Cache::satisfyCpuSideRequest(PacketPtr pkt, CacheBlk *blk,
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bool deferred_response, bool pending_downgrade)
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{
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assert(pkt->isRequest());
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assert(blk && blk->isValid());
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// Occasionally this is not true... if we are a lower-level cache
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// satisfying a string of Read and ReadEx requests from
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// upper-level caches, a Read will mark the block as shared but we
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// can satisfy a following ReadEx anyway since we can rely on the
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// Read requester(s) to have buffered the ReadEx snoop and to
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// invalidate their blocks after receiving them.
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// assert(!pkt->needsWritable() || blk->isWritable());
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assert(pkt->getOffset(blkSize) + pkt->getSize() <= blkSize);
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// Check RMW operations first since both isRead() and
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// isWrite() will be true for them
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if (pkt->cmd == MemCmd::SwapReq) {
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cmpAndSwap(blk, pkt);
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} else if (pkt->isWrite()) {
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// we have the block in a writable state and can go ahead,
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// note that the line may be also be considered writable in
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// downstream caches along the path to memory, but always
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// Exclusive, and never Modified
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assert(blk->isWritable());
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// Write or WriteLine at the first cache with block in writable state
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if (blk->checkWrite(pkt)) {
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pkt->writeDataToBlock(blk->data, blkSize);
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}
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// Always mark the line as dirty (and thus transition to the
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// Modified state) even if we are a failed StoreCond so we
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// supply data to any snoops that have appended themselves to
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// this cache before knowing the store will fail.
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blk->status |= BlkDirty;
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DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d (write)\n",
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__func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize());
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} else if (pkt->isRead()) {
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if (pkt->isLLSC()) {
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blk->trackLoadLocked(pkt);
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}
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// all read responses have a data payload
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assert(pkt->hasRespData());
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pkt->setDataFromBlock(blk->data, blkSize);
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// determine if this read is from a (coherent) cache, or not
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// by looking at the command type; we could potentially add a
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// packet attribute such as 'FromCache' to make this check a
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// bit cleaner
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if (pkt->cmd == MemCmd::ReadExReq ||
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pkt->cmd == MemCmd::ReadSharedReq ||
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pkt->cmd == MemCmd::ReadCleanReq ||
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pkt->cmd == MemCmd::SCUpgradeFailReq) {
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assert(pkt->getSize() == blkSize);
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// special handling for coherent block requests from
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// upper-level caches
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if (pkt->needsWritable()) {
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// sanity check
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assert(pkt->cmd == MemCmd::ReadExReq ||
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pkt->cmd == MemCmd::SCUpgradeFailReq);
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// if we have a dirty copy, make sure the recipient
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// keeps it marked dirty (in the modified state)
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if (blk->isDirty()) {
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pkt->setCacheResponding();
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}
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// on ReadExReq we give up our copy unconditionally,
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// even if this cache is mostly inclusive, we may want
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// to revisit this
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invalidateBlock(blk);
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} else if (blk->isWritable() && !pending_downgrade &&
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!pkt->hasSharers() &&
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pkt->cmd != MemCmd::ReadCleanReq) {
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// we can give the requester a writable copy on a read
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// request if:
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// - we have a writable copy at this level (& below)
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// - we don't have a pending snoop from below
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// signaling another read request
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// - no other cache above has a copy (otherwise it
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// would have set hasSharers flag when
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// snooping the packet)
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// - the read has explicitly asked for a clean
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// copy of the line
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if (blk->isDirty()) {
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// special considerations if we're owner:
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if (!deferred_response) {
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// respond with the line in Modified state
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// (cacheResponding set, hasSharers not set)
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pkt->setCacheResponding();
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if (clusivity == Enums::mostly_excl) {
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// if this cache is mostly exclusive with
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// respect to the cache above, drop the
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// block, no need to first unset the dirty
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// bit
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invalidateBlock(blk);
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} else {
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// if this cache is mostly inclusive, we
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// keep the block in the Exclusive state,
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// and pass it upwards as Modified
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// (writable and dirty), hence we have
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// multiple caches, all on the same path
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// towards memory, all considering the
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// same block writable, but only one
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// considering it Modified
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// we get away with multiple caches (on
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// the same path to memory) considering
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// the block writeable as we always enter
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// the cache hierarchy through a cache,
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// and first snoop upwards in all other
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// branches
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blk->status &= ~BlkDirty;
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}
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} else {
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// if we're responding after our own miss,
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// there's a window where the recipient didn't
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// know it was getting ownership and may not
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// have responded to snoops correctly, so we
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// have to respond with a shared line
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pkt->setHasSharers();
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}
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}
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} else {
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// otherwise only respond with a shared copy
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pkt->setHasSharers();
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}
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}
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} else {
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// Upgrade or Invalidate
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assert(pkt->isUpgrade() || pkt->isInvalidate());
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// for invalidations we could be looking at the temp block
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// (for upgrades we always allocate)
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invalidateBlock(blk);
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DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d (invalidation)\n",
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__func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize());
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}
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}
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/////////////////////////////////////////////////////
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//
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// Access path: requests coming in from the CPU side
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//
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/////////////////////////////////////////////////////
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bool
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Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
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PacketList &writebacks)
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{
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// sanity check
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assert(pkt->isRequest());
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chatty_assert(!(isReadOnly && pkt->isWrite()),
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"Should never see a write in a read-only cache %s\n",
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name());
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DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d\n", __func__,
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pkt->cmdString(), pkt->getAddr(), pkt->getSize());
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if (pkt->req->isUncacheable()) {
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DPRINTF(Cache, "%s%s addr %#llx uncacheable\n", pkt->cmdString(),
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pkt->req->isInstFetch() ? " (ifetch)" : "",
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pkt->getAddr());
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// flush and invalidate any existing block
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CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
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if (old_blk && old_blk->isValid()) {
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if (old_blk->isDirty() || writebackClean)
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writebacks.push_back(writebackBlk(old_blk));
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else
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writebacks.push_back(cleanEvictBlk(old_blk));
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tags->invalidate(old_blk);
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old_blk->invalidate();
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}
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blk = NULL;
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// lookupLatency is the latency in case the request is uncacheable.
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lat = lookupLatency;
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return false;
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}
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ContextID id = pkt->req->hasContextId() ?
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pkt->req->contextId() : InvalidContextID;
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// Here lat is the value passed as parameter to accessBlock() function
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// that can modify its value.
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blk = tags->accessBlock(pkt->getAddr(), pkt->isSecure(), lat, id);
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DPRINTF(Cache, "%s%s addr %#llx size %d (%s) %s\n", pkt->cmdString(),
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pkt->req->isInstFetch() ? " (ifetch)" : "",
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pkt->getAddr(), pkt->getSize(), pkt->isSecure() ? "s" : "ns",
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blk ? "hit " + blk->print() : "miss");
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if (pkt->isEviction()) {
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// We check for presence of block in above caches before issuing
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// Writeback or CleanEvict to write buffer. Therefore the only
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// possible cases can be of a CleanEvict packet coming from above
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// encountering a Writeback generated in this cache peer cache and
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// waiting in the write buffer. Cases of upper level peer caches
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// generating CleanEvict and Writeback or simply CleanEvict and
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// CleanEvict almost simultaneously will be caught by snoops sent out
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// by crossbar.
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WriteQueueEntry *wb_entry = writeBuffer.findMatch(pkt->getAddr(),
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pkt->isSecure());
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if (wb_entry) {
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assert(wb_entry->getNumTargets() == 1);
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PacketPtr wbPkt = wb_entry->getTarget()->pkt;
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assert(wbPkt->isWriteback());
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if (pkt->isCleanEviction()) {
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// The CleanEvict and WritebackClean snoops into other
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// peer caches of the same level while traversing the
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// crossbar. If a copy of the block is found, the
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// packet is deleted in the crossbar. Hence, none of
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// the other upper level caches connected to this
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// cache have the block, so we can clear the
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// BLOCK_CACHED flag in the Writeback if set and
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// discard the CleanEvict by returning true.
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wbPkt->clearBlockCached();
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return true;
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} else {
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assert(pkt->cmd == MemCmd::WritebackDirty);
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// Dirty writeback from above trumps our clean
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// writeback... discard here
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// Note: markInService will remove entry from writeback buffer.
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markInService(wb_entry);
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delete wbPkt;
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}
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}
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}
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// Writeback handling is special case. We can write the block into
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// the cache without having a writeable copy (or any copy at all).
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if (pkt->isWriteback()) {
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assert(blkSize == pkt->getSize());
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// we could get a clean writeback while we are having
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// outstanding accesses to a block, do the simple thing for
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// now and drop the clean writeback so that we do not upset
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// any ordering/decisions about ownership already taken
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if (pkt->cmd == MemCmd::WritebackClean &&
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mshrQueue.findMatch(pkt->getAddr(), pkt->isSecure())) {
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DPRINTF(Cache, "Clean writeback %#llx to block with MSHR, "
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"dropping\n", pkt->getAddr());
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return true;
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}
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if (blk == NULL) {
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// need to do a replacement
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blk = allocateBlock(pkt->getAddr(), pkt->isSecure(), writebacks);
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if (blk == NULL) {
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// no replaceable block available: give up, fwd to next level.
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incMissCount(pkt);
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return false;
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}
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tags->insertBlock(pkt, blk);
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blk->status = (BlkValid | BlkReadable);
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if (pkt->isSecure()) {
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blk->status |= BlkSecure;
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}
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}
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// only mark the block dirty if we got a writeback command,
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// and leave it as is for a clean writeback
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if (pkt->cmd == MemCmd::WritebackDirty) {
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blk->status |= BlkDirty;
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}
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// if the packet does not have sharers, it is passing
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// writable, and we got the writeback in Modified or Exclusive
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// state, if not we are in the Owned or Shared state
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if (!pkt->hasSharers()) {
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blk->status |= BlkWritable;
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}
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// nothing else to do; writeback doesn't expect response
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assert(!pkt->needsResponse());
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std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
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DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
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incHitCount(pkt);
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return true;
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} else if (pkt->cmd == MemCmd::CleanEvict) {
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if (blk != NULL) {
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// Found the block in the tags, need to stop CleanEvict from
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// propagating further down the hierarchy. Returning true will
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// treat the CleanEvict like a satisfied write request and delete
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// it.
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return true;
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}
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// We didn't find the block here, propagate the CleanEvict further
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// down the memory hierarchy. Returning false will treat the CleanEvict
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// like a Writeback which could not find a replaceable block so has to
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// go to next level.
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return false;
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} else if ((blk != NULL) &&
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(pkt->needsWritable() ? blk->isWritable() : blk->isReadable())) {
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// OK to satisfy access
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incHitCount(pkt);
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satisfyCpuSideRequest(pkt, blk);
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return true;
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}
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// Can't satisfy access normally... either no block (blk == NULL)
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// or have block but need writable
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incMissCount(pkt);
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if (blk == NULL && pkt->isLLSC() && pkt->isWrite()) {
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// complete miss on store conditional... just give up now
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pkt->req->setExtraData(0);
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return true;
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}
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return false;
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}
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|
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void
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Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
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{
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while (!writebacks.empty()) {
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PacketPtr wbPkt = writebacks.front();
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// We use forwardLatency here because we are copying writebacks to
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// write buffer. Call isCachedAbove for both Writebacks and
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// CleanEvicts. If isCachedAbove returns true we set BLOCK_CACHED flag
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// in Writebacks and discard CleanEvicts.
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if (isCachedAbove(wbPkt)) {
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if (wbPkt->cmd == MemCmd::CleanEvict) {
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// Delete CleanEvict because cached copies exist above. The
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// packet destructor will delete the request object because
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// this is a non-snoop request packet which does not require a
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// response.
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delete wbPkt;
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} else if (wbPkt->cmd == MemCmd::WritebackClean) {
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// clean writeback, do not send since the block is
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// still cached above
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assert(writebackClean);
|
|
delete wbPkt;
|
|
} else {
|
|
assert(wbPkt->cmd == MemCmd::WritebackDirty);
|
|
// Set BLOCK_CACHED flag in Writeback and send below, so that
|
|
// the Writeback does not reset the bit corresponding to this
|
|
// address in the snoop filter below.
|
|
wbPkt->setBlockCached();
|
|
allocateWriteBuffer(wbPkt, forward_time);
|
|
}
|
|
} else {
|
|
// If the block is not cached above, send packet below. Both
|
|
// CleanEvict and Writeback with BLOCK_CACHED flag cleared will
|
|
// reset the bit corresponding to this address in the snoop filter
|
|
// below.
|
|
allocateWriteBuffer(wbPkt, forward_time);
|
|
}
|
|
writebacks.pop_front();
|
|
}
|
|
}
|
|
|
|
void
|
|
Cache::doWritebacksAtomic(PacketList& writebacks)
|
|
{
|
|
while (!writebacks.empty()) {
|
|
PacketPtr wbPkt = writebacks.front();
|
|
// Call isCachedAbove for both Writebacks and CleanEvicts. If
|
|
// isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
|
|
// and discard CleanEvicts.
|
|
if (isCachedAbove(wbPkt, false)) {
|
|
if (wbPkt->cmd == MemCmd::WritebackDirty) {
|
|
// Set BLOCK_CACHED flag in Writeback and send below,
|
|
// so that the Writeback does not reset the bit
|
|
// corresponding to this address in the snoop filter
|
|
// below. We can discard CleanEvicts because cached
|
|
// copies exist above. Atomic mode isCachedAbove
|
|
// modifies packet to set BLOCK_CACHED flag
|
|
memSidePort->sendAtomic(wbPkt);
|
|
}
|
|
} else {
|
|
// If the block is not cached above, send packet below. Both
|
|
// CleanEvict and Writeback with BLOCK_CACHED flag cleared will
|
|
// reset the bit corresponding to this address in the snoop filter
|
|
// below.
|
|
memSidePort->sendAtomic(wbPkt);
|
|
}
|
|
writebacks.pop_front();
|
|
// In case of CleanEvicts, the packet destructor will delete the
|
|
// request object because this is a non-snoop request packet which
|
|
// does not require a response.
|
|
delete wbPkt;
|
|
}
|
|
}
|
|
|
|
|
|
void
|
|
Cache::recvTimingSnoopResp(PacketPtr pkt)
|
|
{
|
|
DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__,
|
|
pkt->cmdString(), pkt->getAddr(), pkt->getSize());
|
|
|
|
assert(pkt->isResponse());
|
|
assert(!system->bypassCaches());
|
|
|
|
// determine if the response is from a snoop request we created
|
|
// (in which case it should be in the outstandingSnoop), or if we
|
|
// merely forwarded someone else's snoop request
|
|
const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
|
|
outstandingSnoop.end();
|
|
|
|
if (!forwardAsSnoop) {
|
|
// the packet came from this cache, so sink it here and do not
|
|
// forward it
|
|
assert(pkt->cmd == MemCmd::HardPFResp);
|
|
|
|
outstandingSnoop.erase(pkt->req);
|
|
|
|
DPRINTF(Cache, "Got prefetch response from above for addr "
|
|
"%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
|
|
recvTimingResp(pkt);
|
|
return;
|
|
}
|
|
|
|
// forwardLatency is set here because there is a response from an
|
|
// upper level cache.
|
|
// To pay the delay that occurs if the packet comes from the bus,
|
|
// we charge also headerDelay.
|
|
Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
|
|
// Reset the timing of the packet.
|
|
pkt->headerDelay = pkt->payloadDelay = 0;
|
|
memSidePort->schedTimingSnoopResp(pkt, snoop_resp_time);
|
|
}
|
|
|
|
void
|
|
Cache::promoteWholeLineWrites(PacketPtr pkt)
|
|
{
|
|
// Cache line clearing instructions
|
|
if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
|
|
(pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
|
|
pkt->cmd = MemCmd::WriteLineReq;
|
|
DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
|
|
}
|
|
}
|
|
|
|
bool
|
|
Cache::recvTimingReq(PacketPtr pkt)
|
|
{
|
|
DPRINTF(CacheTags, "%s tags: %s\n", __func__, tags->print());
|
|
|
|
assert(pkt->isRequest());
|
|
|
|
// Just forward the packet if caches are disabled.
|
|
if (system->bypassCaches()) {
|
|
// @todo This should really enqueue the packet rather
|
|
bool M5_VAR_USED success = memSidePort->sendTimingReq(pkt);
|
|
assert(success);
|
|
return true;
|
|
}
|
|
|
|
promoteWholeLineWrites(pkt);
|
|
|
|
if (pkt->cacheResponding()) {
|
|
// a cache above us (but not where the packet came from) is
|
|
// responding to the request, in other words it has the line
|
|
// in Modified or Owned state
|
|
DPRINTF(Cache, "Cache above responding to %#llx (%s): "
|
|
"not responding\n",
|
|
pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
|
|
|
|
// if the packet needs the block to be writable, and the cache
|
|
// that has promised to respond (setting the cache responding
|
|
// flag) is not providing writable (it is in Owned rather than
|
|
// the Modified state), we know that there may be other Shared
|
|
// copies in the system; go out and invalidate them all
|
|
assert(pkt->needsWritable() && !pkt->responderHadWritable());
|
|
|
|
// an upstream cache that had the line in Owned state
|
|
// (dirty, but not writable), is responding and thus
|
|
// transferring the dirty line from one branch of the
|
|
// cache hierarchy to another
|
|
|
|
// send out an express snoop and invalidate all other
|
|
// copies (snooping a packet that needs writable is the
|
|
// same as an invalidation), thus turning the Owned line
|
|
// into a Modified line, note that we don't invalidate the
|
|
// block in the current cache or any other cache on the
|
|
// path to memory
|
|
|
|
// create a downstream express snoop with cleared packet
|
|
// flags, there is no need to allocate any data as the
|
|
// packet is merely used to co-ordinate state transitions
|
|
Packet *snoop_pkt = new Packet(pkt, true, false);
|
|
|
|
// also reset the bus time that the original packet has
|
|
// not yet paid for
|
|
snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
|
|
|
|
// make this an instantaneous express snoop, and let the
|
|
// other caches in the system know that the another cache
|
|
// is responding, because we have found the authorative
|
|
// copy (Modified or Owned) that will supply the right
|
|
// data
|
|
snoop_pkt->setExpressSnoop();
|
|
snoop_pkt->setCacheResponding();
|
|
|
|
// this express snoop travels towards the memory, and at
|
|
// every crossbar it is snooped upwards thus reaching
|
|
// every cache in the system
|
|
bool M5_VAR_USED success = memSidePort->sendTimingReq(snoop_pkt);
|
|
// express snoops always succeed
|
|
assert(success);
|
|
|
|
// main memory will delete the snoop packet
|
|
|
|
// queue for deletion, as opposed to immediate deletion, as
|
|
// the sending cache is still relying on the packet
|
|
pendingDelete.reset(pkt);
|
|
|
|
// no need to take any further action in this particular cache
|
|
// as an upstram cache has already committed to responding,
|
|
// and we have already sent out any express snoops in the
|
|
// section above to ensure all other copies in the system are
|
|
// invalidated
|
|
return true;
|
|
}
|
|
|
|
// anything that is merely forwarded pays for the forward latency and
|
|
// the delay provided by the crossbar
|
|
Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
|
|
|
|
// We use lookupLatency here because it is used to specify the latency
|
|
// to access.
|
|
Cycles lat = lookupLatency;
|
|
CacheBlk *blk = NULL;
|
|
bool satisfied = false;
|
|
{
|
|
PacketList writebacks;
|
|
// Note that lat is passed by reference here. The function
|
|
// access() calls accessBlock() which can modify lat value.
|
|
satisfied = access(pkt, blk, lat, writebacks);
|
|
|
|
// copy writebacks to write buffer here to ensure they logically
|
|
// proceed anything happening below
|
|
doWritebacks(writebacks, forward_time);
|
|
}
|
|
|
|
// Here we charge the headerDelay that takes into account the latencies
|
|
// of the bus, if the packet comes from it.
|
|
// The latency charged it is just lat that is the value of lookupLatency
|
|
// modified by access() function, or if not just lookupLatency.
|
|
// In case of a hit we are neglecting response latency.
|
|
// In case of a miss we are neglecting forward latency.
|
|
Tick request_time = clockEdge(lat) + pkt->headerDelay;
|
|
// Here we reset the timing of the packet.
|
|
pkt->headerDelay = pkt->payloadDelay = 0;
|
|
|
|
// track time of availability of next prefetch, if any
|
|
Tick next_pf_time = MaxTick;
|
|
|
|
bool needsResponse = pkt->needsResponse();
|
|
|
|
if (satisfied) {
|
|
// should never be satisfying an uncacheable access as we
|
|
// flush and invalidate any existing block as part of the
|
|
// lookup
|
|
assert(!pkt->req->isUncacheable());
|
|
|
|
// hit (for all other request types)
|
|
|
|
if (prefetcher && (prefetchOnAccess || (blk && blk->wasPrefetched()))) {
|
|
if (blk)
|
|
blk->status &= ~BlkHWPrefetched;
|
|
|
|
// Don't notify on SWPrefetch
|
|
if (!pkt->cmd.isSWPrefetch())
|
|
next_pf_time = prefetcher->notify(pkt);
|
|
}
|
|
|
|
if (needsResponse) {
|
|
pkt->makeTimingResponse();
|
|
// @todo: Make someone pay for this
|
|
pkt->headerDelay = pkt->payloadDelay = 0;
|
|
|
|
// In this case we are considering request_time that takes
|
|
// into account the delay of the xbar, if any, and just
|
|
// lat, neglecting responseLatency, modelling hit latency
|
|
// just as lookupLatency or or the value of lat overriden
|
|
// by access(), that calls accessBlock() function.
|
|
cpuSidePort->schedTimingResp(pkt, request_time, true);
|
|
} else {
|
|
DPRINTF(Cache, "%s satisfied %s addr %#llx, no response needed\n",
|
|
__func__, pkt->cmdString(), pkt->getAddr(),
|
|
pkt->getSize());
|
|
|
|
// queue the packet for deletion, as the sending cache is
|
|
// still relying on it; if the block is found in access(),
|
|
// CleanEvict and Writeback messages will be deleted
|
|
// here as well
|
|
pendingDelete.reset(pkt);
|
|
}
|
|
} else {
|
|
// miss
|
|
|
|
Addr blk_addr = blockAlign(pkt->getAddr());
|
|
|
|
// ignore any existing MSHR if we are dealing with an
|
|
// uncacheable request
|
|
MSHR *mshr = pkt->req->isUncacheable() ? nullptr :
|
|
mshrQueue.findMatch(blk_addr, pkt->isSecure());
|
|
|
|
// Software prefetch handling:
|
|
// To keep the core from waiting on data it won't look at
|
|
// anyway, send back a response with dummy data. Miss handling
|
|
// will continue asynchronously. Unfortunately, the core will
|
|
// insist upon freeing original Packet/Request, so we have to
|
|
// create a new pair with a different lifecycle. Note that this
|
|
// processing happens before any MSHR munging on the behalf of
|
|
// this request because this new Request will be the one stored
|
|
// into the MSHRs, not the original.
|
|
if (pkt->cmd.isSWPrefetch()) {
|
|
assert(needsResponse);
|
|
assert(pkt->req->hasPaddr());
|
|
assert(!pkt->req->isUncacheable());
|
|
|
|
// There's no reason to add a prefetch as an additional target
|
|
// to an existing MSHR. If an outstanding request is already
|
|
// in progress, there is nothing for the prefetch to do.
|
|
// If this is the case, we don't even create a request at all.
|
|
PacketPtr pf = nullptr;
|
|
|
|
if (!mshr) {
|
|
// copy the request and create a new SoftPFReq packet
|
|
RequestPtr req = new Request(pkt->req->getPaddr(),
|
|
pkt->req->getSize(),
|
|
pkt->req->getFlags(),
|
|
pkt->req->masterId());
|
|
pf = new Packet(req, pkt->cmd);
|
|
pf->allocate();
|
|
assert(pf->getAddr() == pkt->getAddr());
|
|
assert(pf->getSize() == pkt->getSize());
|
|
}
|
|
|
|
pkt->makeTimingResponse();
|
|
|
|
// request_time is used here, taking into account lat and the delay
|
|
// charged if the packet comes from the xbar.
|
|
cpuSidePort->schedTimingResp(pkt, request_time, true);
|
|
|
|
// If an outstanding request is in progress (we found an
|
|
// MSHR) this is set to null
|
|
pkt = pf;
|
|
}
|
|
|
|
if (mshr) {
|
|
/// MSHR hit
|
|
/// @note writebacks will be checked in getNextMSHR()
|
|
/// for any conflicting requests to the same block
|
|
|
|
//@todo remove hw_pf here
|
|
|
|
// Coalesce unless it was a software prefetch (see above).
|
|
if (pkt) {
|
|
assert(!pkt->isWriteback());
|
|
// CleanEvicts corresponding to blocks which have
|
|
// outstanding requests in MSHRs are simply sunk here
|
|
if (pkt->cmd == MemCmd::CleanEvict) {
|
|
pendingDelete.reset(pkt);
|
|
} else {
|
|
DPRINTF(Cache, "%s coalescing MSHR for %s addr %#llx size %d\n",
|
|
__func__, pkt->cmdString(), pkt->getAddr(),
|
|
pkt->getSize());
|
|
|
|
assert(pkt->req->masterId() < system->maxMasters());
|
|
mshr_hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
|
|
// We use forward_time here because it is the same
|
|
// considering new targets. We have multiple
|
|
// requests for the same address here. It
|
|
// specifies the latency to allocate an internal
|
|
// buffer and to schedule an event to the queued
|
|
// port and also takes into account the additional
|
|
// delay of the xbar.
|
|
mshr->allocateTarget(pkt, forward_time, order++,
|
|
allocOnFill(pkt->cmd));
|
|
if (mshr->getNumTargets() == numTarget) {
|
|
noTargetMSHR = mshr;
|
|
setBlocked(Blocked_NoTargets);
|
|
// need to be careful with this... if this mshr isn't
|
|
// ready yet (i.e. time > curTick()), we don't want to
|
|
// move it ahead of mshrs that are ready
|
|
// mshrQueue.moveToFront(mshr);
|
|
}
|
|
}
|
|
// We should call the prefetcher reguardless if the request is
|
|
// satisfied or not, reguardless if the request is in the MSHR or
|
|
// not. The request could be a ReadReq hit, but still not
|
|
// satisfied (potentially because of a prior write to the same
|
|
// cache line. So, even when not satisfied, tehre is an MSHR
|
|
// already allocated for this, we need to let the prefetcher know
|
|
// about the request
|
|
if (prefetcher) {
|
|
// Don't notify on SWPrefetch
|
|
if (!pkt->cmd.isSWPrefetch())
|
|
next_pf_time = prefetcher->notify(pkt);
|
|
}
|
|
}
|
|
} else {
|
|
// no MSHR
|
|
assert(pkt->req->masterId() < system->maxMasters());
|
|
if (pkt->req->isUncacheable()) {
|
|
mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
|
|
} else {
|
|
mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
|
|
}
|
|
|
|
if (pkt->isEviction() ||
|
|
(pkt->req->isUncacheable() && pkt->isWrite())) {
|
|
// We use forward_time here because there is an
|
|
// uncached memory write, forwarded to WriteBuffer.
|
|
allocateWriteBuffer(pkt, forward_time);
|
|
} else {
|
|
if (blk && blk->isValid()) {
|
|
// should have flushed and have no valid block
|
|
assert(!pkt->req->isUncacheable());
|
|
|
|
// If we have a write miss to a valid block, we
|
|
// need to mark the block non-readable. Otherwise
|
|
// if we allow reads while there's an outstanding
|
|
// write miss, the read could return stale data
|
|
// out of the cache block... a more aggressive
|
|
// system could detect the overlap (if any) and
|
|
// forward data out of the MSHRs, but we don't do
|
|
// that yet. Note that we do need to leave the
|
|
// block valid so that it stays in the cache, in
|
|
// case we get an upgrade response (and hence no
|
|
// new data) when the write miss completes.
|
|
// As long as CPUs do proper store/load forwarding
|
|
// internally, and have a sufficiently weak memory
|
|
// model, this is probably unnecessary, but at some
|
|
// point it must have seemed like we needed it...
|
|
assert(pkt->needsWritable());
|
|
assert(!blk->isWritable());
|
|
blk->status &= ~BlkReadable;
|
|
}
|
|
// Here we are using forward_time, modelling the latency of
|
|
// a miss (outbound) just as forwardLatency, neglecting the
|
|
// lookupLatency component.
|
|
allocateMissBuffer(pkt, forward_time);
|
|
}
|
|
|
|
if (prefetcher) {
|
|
// Don't notify on SWPrefetch
|
|
if (!pkt->cmd.isSWPrefetch())
|
|
next_pf_time = prefetcher->notify(pkt);
|
|
}
|
|
}
|
|
}
|
|
|
|
if (next_pf_time != MaxTick)
|
|
schedMemSideSendEvent(next_pf_time);
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
// See comment in cache.hh.
|
|
PacketPtr
|
|
Cache::getBusPacket(PacketPtr cpu_pkt, CacheBlk *blk,
|
|
bool needsWritable) const
|
|
{
|
|
bool blkValid = blk && blk->isValid();
|
|
|
|
if (cpu_pkt->req->isUncacheable()) {
|
|
// note that at the point we see the uncacheable request we
|
|
// flush any block, but there could be an outstanding MSHR,
|
|
// and the cache could have filled again before we actually
|
|
// send out the forwarded uncacheable request (blk could thus
|
|
// be non-null)
|
|
return NULL;
|
|
}
|
|
|
|
if (!blkValid &&
|
|
(cpu_pkt->isUpgrade() ||
|
|
cpu_pkt->isEviction())) {
|
|
// Writebacks that weren't allocated in access() and upgrades
|
|
// from upper-level caches that missed completely just go
|
|
// through.
|
|
return NULL;
|
|
}
|
|
|
|
assert(cpu_pkt->needsResponse());
|
|
|
|
MemCmd cmd;
|
|
// @TODO make useUpgrades a parameter.
|
|
// Note that ownership protocols require upgrade, otherwise a
|
|
// write miss on a shared owned block will generate a ReadExcl,
|
|
// which will clobber the owned copy.
|
|
const bool useUpgrades = true;
|
|
if (blkValid && useUpgrades) {
|
|
// only reason to be here is that blk is read only and we need
|
|
// it to be writable
|
|
assert(needsWritable);
|
|
assert(!blk->isWritable());
|
|
cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
|
|
} else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
|
|
cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
|
|
// Even though this SC will fail, we still need to send out the
|
|
// request and get the data to supply it to other snoopers in the case
|
|
// where the determination the StoreCond fails is delayed due to
|
|
// all caches not being on the same local bus.
|
|
cmd = MemCmd::SCUpgradeFailReq;
|
|
} else if (cpu_pkt->cmd == MemCmd::WriteLineReq ||
|
|
cpu_pkt->cmd == MemCmd::InvalidateReq) {
|
|
// forward as invalidate to all other caches, this gives us
|
|
// the line in Exclusive state, and invalidates all other
|
|
// copies
|
|
cmd = MemCmd::InvalidateReq;
|
|
} else {
|
|
// block is invalid
|
|
cmd = needsWritable ? MemCmd::ReadExReq :
|
|
(isReadOnly ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
|
|
}
|
|
PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
|
|
|
|
// if there are upstream caches that have already marked the
|
|
// packet as having sharers (not passing writable), pass that info
|
|
// downstream
|
|
if (cpu_pkt->hasSharers()) {
|
|
// note that cpu_pkt may have spent a considerable time in the
|
|
// MSHR queue and that the information could possibly be out
|
|
// of date, however, there is no harm in conservatively
|
|
// assuming the block has sharers
|
|
pkt->setHasSharers();
|
|
DPRINTF(Cache, "%s passing hasSharers from %s to %s addr %#llx "
|
|
"size %d\n",
|
|
__func__, cpu_pkt->cmdString(), pkt->cmdString(),
|
|
pkt->getAddr(), pkt->getSize());
|
|
}
|
|
|
|
// the packet should be block aligned
|
|
assert(pkt->getAddr() == blockAlign(pkt->getAddr()));
|
|
|
|
pkt->allocate();
|
|
DPRINTF(Cache, "%s created %s from %s for addr %#llx size %d\n",
|
|
__func__, pkt->cmdString(), cpu_pkt->cmdString(), pkt->getAddr(),
|
|
pkt->getSize());
|
|
return pkt;
|
|
}
|
|
|
|
|
|
Tick
|
|
Cache::recvAtomic(PacketPtr pkt)
|
|
{
|
|
// We are in atomic mode so we pay just for lookupLatency here.
|
|
Cycles lat = lookupLatency;
|
|
|
|
// Forward the request if the system is in cache bypass mode.
|
|
if (system->bypassCaches())
|
|
return ticksToCycles(memSidePort->sendAtomic(pkt));
|
|
|
|
promoteWholeLineWrites(pkt);
|
|
|
|
// follow the same flow as in recvTimingReq, and check if a cache
|
|
// above us is responding
|
|
if (pkt->cacheResponding()) {
|
|
DPRINTF(Cache, "Cache above responding to %#llx (%s): "
|
|
"not responding\n",
|
|
pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
|
|
|
|
// if a cache is responding, and it had the line in Owned
|
|
// rather than Modified state, we need to invalidate any
|
|
// copies that are not on the same path to memory
|
|
assert(pkt->needsWritable() && !pkt->responderHadWritable());
|
|
lat += ticksToCycles(memSidePort->sendAtomic(pkt));
|
|
|
|
return lat * clockPeriod();
|
|
}
|
|
|
|
// should assert here that there are no outstanding MSHRs or
|
|
// writebacks... that would mean that someone used an atomic
|
|
// access in timing mode
|
|
|
|
CacheBlk *blk = NULL;
|
|
PacketList writebacks;
|
|
bool satisfied = access(pkt, blk, lat, writebacks);
|
|
|
|
// handle writebacks resulting from the access here to ensure they
|
|
// logically proceed anything happening below
|
|
doWritebacksAtomic(writebacks);
|
|
|
|
if (!satisfied) {
|
|
// MISS
|
|
|
|
PacketPtr bus_pkt = getBusPacket(pkt, blk, pkt->needsWritable());
|
|
|
|
bool is_forward = (bus_pkt == NULL);
|
|
|
|
if (is_forward) {
|
|
// just forwarding the same request to the next level
|
|
// no local cache operation involved
|
|
bus_pkt = pkt;
|
|
}
|
|
|
|
DPRINTF(Cache, "Sending an atomic %s for %#llx (%s)\n",
|
|
bus_pkt->cmdString(), bus_pkt->getAddr(),
|
|
bus_pkt->isSecure() ? "s" : "ns");
|
|
|
|
#if TRACING_ON
|
|
CacheBlk::State old_state = blk ? blk->status : 0;
|
|
#endif
|
|
|
|
lat += ticksToCycles(memSidePort->sendAtomic(bus_pkt));
|
|
|
|
// We are now dealing with the response handling
|
|
DPRINTF(Cache, "Receive response: %s for addr %#llx (%s) in state %i\n",
|
|
bus_pkt->cmdString(), bus_pkt->getAddr(),
|
|
bus_pkt->isSecure() ? "s" : "ns",
|
|
old_state);
|
|
|
|
// If packet was a forward, the response (if any) is already
|
|
// in place in the bus_pkt == pkt structure, so we don't need
|
|
// to do anything. Otherwise, use the separate bus_pkt to
|
|
// generate response to pkt and then delete it.
|
|
if (!is_forward) {
|
|
if (pkt->needsResponse()) {
|
|
assert(bus_pkt->isResponse());
|
|
if (bus_pkt->isError()) {
|
|
pkt->makeAtomicResponse();
|
|
pkt->copyError(bus_pkt);
|
|
} else if (pkt->cmd == MemCmd::InvalidateReq) {
|
|
if (blk) {
|
|
// invalidate response to a cache that received
|
|
// an invalidate request
|
|
satisfyCpuSideRequest(pkt, blk);
|
|
}
|
|
} else if (pkt->cmd == MemCmd::WriteLineReq) {
|
|
// note the use of pkt, not bus_pkt here.
|
|
|
|
// write-line request to the cache that promoted
|
|
// the write to a whole line
|
|
blk = handleFill(pkt, blk, writebacks,
|
|
allocOnFill(pkt->cmd));
|
|
satisfyCpuSideRequest(pkt, blk);
|
|
} else if (bus_pkt->isRead() ||
|
|
bus_pkt->cmd == MemCmd::UpgradeResp) {
|
|
// we're updating cache state to allow us to
|
|
// satisfy the upstream request from the cache
|
|
blk = handleFill(bus_pkt, blk, writebacks,
|
|
allocOnFill(pkt->cmd));
|
|
satisfyCpuSideRequest(pkt, blk);
|
|
} else {
|
|
// we're satisfying the upstream request without
|
|
// modifying cache state, e.g., a write-through
|
|
pkt->makeAtomicResponse();
|
|
}
|
|
}
|
|
delete bus_pkt;
|
|
}
|
|
}
|
|
|
|
// Note that we don't invoke the prefetcher at all in atomic mode.
|
|
// It's not clear how to do it properly, particularly for
|
|
// prefetchers that aggressively generate prefetch candidates and
|
|
// rely on bandwidth contention to throttle them; these will tend
|
|
// to pollute the cache in atomic mode since there is no bandwidth
|
|
// contention. If we ever do want to enable prefetching in atomic
|
|
// mode, though, this is the place to do it... see timingAccess()
|
|
// for an example (though we'd want to issue the prefetch(es)
|
|
// immediately rather than calling requestMemSideBus() as we do
|
|
// there).
|
|
|
|
// do any writebacks resulting from the response handling
|
|
doWritebacksAtomic(writebacks);
|
|
|
|
// if we used temp block, check to see if its valid and if so
|
|
// clear it out, but only do so after the call to recvAtomic is
|
|
// finished so that any downstream observers (such as a snoop
|
|
// filter), first see the fill, and only then see the eviction
|
|
if (blk == tempBlock && tempBlock->isValid()) {
|
|
// the atomic CPU calls recvAtomic for fetch and load/store
|
|
// sequentuially, and we may already have a tempBlock
|
|
// writeback from the fetch that we have not yet sent
|
|
if (tempBlockWriteback) {
|
|
// if that is the case, write the prevoius one back, and
|
|
// do not schedule any new event
|
|
writebackTempBlockAtomic();
|
|
} else {
|
|
// the writeback/clean eviction happens after the call to
|
|
// recvAtomic has finished (but before any successive
|
|
// calls), so that the response handling from the fill is
|
|
// allowed to happen first
|
|
schedule(writebackTempBlockAtomicEvent, curTick());
|
|
}
|
|
|
|
tempBlockWriteback = (blk->isDirty() || writebackClean) ?
|
|
writebackBlk(blk) : cleanEvictBlk(blk);
|
|
blk->invalidate();
|
|
}
|
|
|
|
if (pkt->needsResponse()) {
|
|
pkt->makeAtomicResponse();
|
|
}
|
|
|
|
return lat * clockPeriod();
|
|
}
|
|
|
|
|
|
void
|
|
Cache::functionalAccess(PacketPtr pkt, bool fromCpuSide)
|
|
{
|
|
if (system->bypassCaches()) {
|
|
// Packets from the memory side are snoop request and
|
|
// shouldn't happen in bypass mode.
|
|
assert(fromCpuSide);
|
|
|
|
// The cache should be flushed if we are in cache bypass mode,
|
|
// so we don't need to check if we need to update anything.
|
|
memSidePort->sendFunctional(pkt);
|
|
return;
|
|
}
|
|
|
|
Addr blk_addr = blockAlign(pkt->getAddr());
|
|
bool is_secure = pkt->isSecure();
|
|
CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
|
|
MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
|
|
|
|
pkt->pushLabel(name());
|
|
|
|
CacheBlkPrintWrapper cbpw(blk);
|
|
|
|
// Note that just because an L2/L3 has valid data doesn't mean an
|
|
// L1 doesn't have a more up-to-date modified copy that still
|
|
// needs to be found. As a result we always update the request if
|
|
// we have it, but only declare it satisfied if we are the owner.
|
|
|
|
// see if we have data at all (owned or otherwise)
|
|
bool have_data = blk && blk->isValid()
|
|
&& pkt->checkFunctional(&cbpw, blk_addr, is_secure, blkSize,
|
|
blk->data);
|
|
|
|
// data we have is dirty if marked as such or if we have an
|
|
// in-service MSHR that is pending a modified line
|
|
bool have_dirty =
|
|
have_data && (blk->isDirty() ||
|
|
(mshr && mshr->inService && mshr->isPendingModified()));
|
|
|
|
bool done = have_dirty
|
|
|| cpuSidePort->checkFunctional(pkt)
|
|
|| mshrQueue.checkFunctional(pkt, blk_addr)
|
|
|| writeBuffer.checkFunctional(pkt, blk_addr)
|
|
|| memSidePort->checkFunctional(pkt);
|
|
|
|
DPRINTF(CacheVerbose, "functional %s %#llx (%s) %s%s%s\n",
|
|
pkt->cmdString(), pkt->getAddr(), is_secure ? "s" : "ns",
|
|
(blk && blk->isValid()) ? "valid " : "",
|
|
have_data ? "data " : "", done ? "done " : "");
|
|
|
|
// We're leaving the cache, so pop cache->name() label
|
|
pkt->popLabel();
|
|
|
|
if (done) {
|
|
pkt->makeResponse();
|
|
} else {
|
|
// if it came as a request from the CPU side then make sure it
|
|
// continues towards the memory side
|
|
if (fromCpuSide) {
|
|
memSidePort->sendFunctional(pkt);
|
|
} else if (forwardSnoops && cpuSidePort->isSnooping()) {
|
|
// if it came from the memory side, it must be a snoop request
|
|
// and we should only forward it if we are forwarding snoops
|
|
cpuSidePort->sendFunctionalSnoop(pkt);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/////////////////////////////////////////////////////
|
|
//
|
|
// Response handling: responses from the memory side
|
|
//
|
|
/////////////////////////////////////////////////////
|
|
|
|
|
|
void
|
|
Cache::handleUncacheableWriteResp(PacketPtr pkt)
|
|
{
|
|
WriteQueueEntry *wq_entry =
|
|
dynamic_cast<WriteQueueEntry*>(pkt->senderState);
|
|
assert(wq_entry);
|
|
|
|
WriteQueueEntry::Target *target = wq_entry->getTarget();
|
|
Packet *tgt_pkt = target->pkt;
|
|
|
|
// we send out invalidation reqs and get invalidation
|
|
// responses for write-line requests
|
|
assert(tgt_pkt->cmd != MemCmd::WriteLineReq);
|
|
|
|
int stats_cmd_idx = tgt_pkt->cmdToIndex();
|
|
Tick miss_latency = curTick() - target->recvTime;
|
|
assert(pkt->req->masterId() < system->maxMasters());
|
|
mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] +=
|
|
miss_latency;
|
|
|
|
tgt_pkt->makeTimingResponse();
|
|
// if this packet is an error copy that to the new packet
|
|
if (pkt->isError())
|
|
tgt_pkt->copyError(pkt);
|
|
// Reset the bus additional time as it is now accounted for
|
|
tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
|
|
Tick completion_time = clockEdge(responseLatency) +
|
|
pkt->headerDelay + pkt->payloadDelay;
|
|
|
|
cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true);
|
|
|
|
wq_entry->popTarget();
|
|
assert(!wq_entry->hasTargets());
|
|
|
|
bool wasFull = writeBuffer.isFull();
|
|
writeBuffer.deallocate(wq_entry);
|
|
|
|
if (wasFull && !writeBuffer.isFull()) {
|
|
clearBlocked(Blocked_NoWBBuffers);
|
|
}
|
|
|
|
delete pkt;
|
|
}
|
|
|
|
void
|
|
Cache::recvTimingResp(PacketPtr pkt)
|
|
{
|
|
assert(pkt->isResponse());
|
|
|
|
// all header delay should be paid for by the crossbar, unless
|
|
// this is a prefetch response from above
|
|
panic_if(pkt->headerDelay != 0 && pkt->cmd != MemCmd::HardPFResp,
|
|
"%s saw a non-zero packet delay\n", name());
|
|
|
|
bool is_error = pkt->isError();
|
|
|
|
if (is_error) {
|
|
DPRINTF(Cache, "Cache received packet with error for addr %#llx (%s), "
|
|
"cmd: %s\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns",
|
|
pkt->cmdString());
|
|
}
|
|
|
|
DPRINTF(Cache, "Handling response %s for addr %#llx size %d (%s)\n",
|
|
pkt->cmdString(), pkt->getAddr(), pkt->getSize(),
|
|
pkt->isSecure() ? "s" : "ns");
|
|
|
|
// if this is a write, we should be looking at an uncacheable
|
|
// write
|
|
if (pkt->isWrite()) {
|
|
assert(pkt->req->isUncacheable());
|
|
handleUncacheableWriteResp(pkt);
|
|
return;
|
|
}
|
|
|
|
// we have dealt with any (uncacheable) writes above, from here on
|
|
// we know we are dealing with an MSHR due to a miss or a prefetch
|
|
MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState);
|
|
assert(mshr);
|
|
|
|
if (mshr == noTargetMSHR) {
|
|
// we always clear at least one target
|
|
clearBlocked(Blocked_NoTargets);
|
|
noTargetMSHR = NULL;
|
|
}
|
|
|
|
// Initial target is used just for stats
|
|
MSHR::Target *initial_tgt = mshr->getTarget();
|
|
int stats_cmd_idx = initial_tgt->pkt->cmdToIndex();
|
|
Tick miss_latency = curTick() - initial_tgt->recvTime;
|
|
|
|
if (pkt->req->isUncacheable()) {
|
|
assert(pkt->req->masterId() < system->maxMasters());
|
|
mshr_uncacheable_lat[stats_cmd_idx][pkt->req->masterId()] +=
|
|
miss_latency;
|
|
} else {
|
|
assert(pkt->req->masterId() < system->maxMasters());
|
|
mshr_miss_latency[stats_cmd_idx][pkt->req->masterId()] +=
|
|
miss_latency;
|
|
}
|
|
|
|
bool wasFull = mshrQueue.isFull();
|
|
|
|
PacketList writebacks;
|
|
|
|
Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
|
|
|
|
// upgrade deferred targets if the response has no sharers, and is
|
|
// thus passing writable
|
|
if (!pkt->hasSharers()) {
|
|
mshr->promoteWritable();
|
|
}
|
|
|
|
bool is_fill = !mshr->isForward &&
|
|
(pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
|
|
|
|
CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
|
|
|
|
if (is_fill && !is_error) {
|
|
DPRINTF(Cache, "Block for addr %#llx being updated in Cache\n",
|
|
pkt->getAddr());
|
|
|
|
blk = handleFill(pkt, blk, writebacks, mshr->allocOnFill);
|
|
assert(blk != NULL);
|
|
}
|
|
|
|
// allow invalidation responses originating from write-line
|
|
// requests to be discarded
|
|
bool is_invalidate = pkt->isInvalidate();
|
|
|
|
// First offset for critical word first calculations
|
|
int initial_offset = initial_tgt->pkt->getOffset(blkSize);
|
|
|
|
while (mshr->hasTargets()) {
|
|
MSHR::Target *target = mshr->getTarget();
|
|
Packet *tgt_pkt = target->pkt;
|
|
|
|
switch (target->source) {
|
|
case MSHR::Target::FromCPU:
|
|
Tick completion_time;
|
|
// Here we charge on completion_time the delay of the xbar if the
|
|
// packet comes from it, charged on headerDelay.
|
|
completion_time = pkt->headerDelay;
|
|
|
|
// Software prefetch handling for cache closest to core
|
|
if (tgt_pkt->cmd.isSWPrefetch()) {
|
|
// a software prefetch would have already been ack'd immediately
|
|
// with dummy data so the core would be able to retire it.
|
|
// this request completes right here, so we deallocate it.
|
|
delete tgt_pkt->req;
|
|
delete tgt_pkt;
|
|
break; // skip response
|
|
}
|
|
|
|
// unlike the other packet flows, where data is found in other
|
|
// caches or memory and brought back, write-line requests always
|
|
// have the data right away, so the above check for "is fill?"
|
|
// cannot actually be determined until examining the stored MSHR
|
|
// state. We "catch up" with that logic here, which is duplicated
|
|
// from above.
|
|
if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
|
|
assert(!is_error);
|
|
// we got the block in a writable state, so promote
|
|
// any deferred targets if possible
|
|
mshr->promoteWritable();
|
|
// NB: we use the original packet here and not the response!
|
|
blk = handleFill(tgt_pkt, blk, writebacks, mshr->allocOnFill);
|
|
assert(blk != NULL);
|
|
|
|
// treat as a fill, and discard the invalidation
|
|
// response
|
|
is_fill = true;
|
|
is_invalidate = false;
|
|
}
|
|
|
|
if (is_fill) {
|
|
satisfyCpuSideRequest(tgt_pkt, blk,
|
|
true, mshr->hasPostDowngrade());
|
|
|
|
// How many bytes past the first request is this one
|
|
int transfer_offset =
|
|
tgt_pkt->getOffset(blkSize) - initial_offset;
|
|
if (transfer_offset < 0) {
|
|
transfer_offset += blkSize;
|
|
}
|
|
|
|
// If not critical word (offset) return payloadDelay.
|
|
// responseLatency is the latency of the return path
|
|
// from lower level caches/memory to an upper level cache or
|
|
// the core.
|
|
completion_time += clockEdge(responseLatency) +
|
|
(transfer_offset ? pkt->payloadDelay : 0);
|
|
|
|
assert(!tgt_pkt->req->isUncacheable());
|
|
|
|
assert(tgt_pkt->req->masterId() < system->maxMasters());
|
|
missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
|
|
completion_time - target->recvTime;
|
|
} else if (pkt->cmd == MemCmd::UpgradeFailResp) {
|
|
// failed StoreCond upgrade
|
|
assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
|
|
tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
|
|
tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
|
|
// responseLatency is the latency of the return path
|
|
// from lower level caches/memory to an upper level cache or
|
|
// the core.
|
|
completion_time += clockEdge(responseLatency) +
|
|
pkt->payloadDelay;
|
|
tgt_pkt->req->setExtraData(0);
|
|
} else {
|
|
// not a cache fill, just forwarding response
|
|
// responseLatency is the latency of the return path
|
|
// from lower level cahces/memory to the core.
|
|
completion_time += clockEdge(responseLatency) +
|
|
pkt->payloadDelay;
|
|
if (pkt->isRead() && !is_error) {
|
|
// sanity check
|
|
assert(pkt->getAddr() == tgt_pkt->getAddr());
|
|
assert(pkt->getSize() >= tgt_pkt->getSize());
|
|
|
|
tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
|
|
}
|
|
}
|
|
tgt_pkt->makeTimingResponse();
|
|
// if this packet is an error copy that to the new packet
|
|
if (is_error)
|
|
tgt_pkt->copyError(pkt);
|
|
if (tgt_pkt->cmd == MemCmd::ReadResp &&
|
|
(is_invalidate || mshr->hasPostInvalidate())) {
|
|
// If intermediate cache got ReadRespWithInvalidate,
|
|
// propagate that. Response should not have
|
|
// isInvalidate() set otherwise.
|
|
tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
|
|
DPRINTF(Cache, "%s updated cmd to %s for addr %#llx\n",
|
|
__func__, tgt_pkt->cmdString(), tgt_pkt->getAddr());
|
|
}
|
|
// Reset the bus additional time as it is now accounted for
|
|
tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
|
|
cpuSidePort->schedTimingResp(tgt_pkt, completion_time, true);
|
|
break;
|
|
|
|
case MSHR::Target::FromPrefetcher:
|
|
assert(tgt_pkt->cmd == MemCmd::HardPFReq);
|
|
if (blk)
|
|
blk->status |= BlkHWPrefetched;
|
|
delete tgt_pkt->req;
|
|
delete tgt_pkt;
|
|
break;
|
|
|
|
case MSHR::Target::FromSnoop:
|
|
// I don't believe that a snoop can be in an error state
|
|
assert(!is_error);
|
|
// response to snoop request
|
|
DPRINTF(Cache, "processing deferred snoop...\n");
|
|
assert(!(is_invalidate && !mshr->hasPostInvalidate()));
|
|
handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
|
|
break;
|
|
|
|
default:
|
|
panic("Illegal target->source enum %d\n", target->source);
|
|
}
|
|
|
|
mshr->popTarget();
|
|
}
|
|
|
|
if (blk && blk->isValid()) {
|
|
// an invalidate response stemming from a write line request
|
|
// should not invalidate the block, so check if the
|
|
// invalidation should be discarded
|
|
if (is_invalidate || mshr->hasPostInvalidate()) {
|
|
invalidateBlock(blk);
|
|
} else if (mshr->hasPostDowngrade()) {
|
|
blk->status &= ~BlkWritable;
|
|
}
|
|
}
|
|
|
|
if (mshr->promoteDeferredTargets()) {
|
|
// avoid later read getting stale data while write miss is
|
|
// outstanding.. see comment in timingAccess()
|
|
if (blk) {
|
|
blk->status &= ~BlkReadable;
|
|
}
|
|
mshrQueue.markPending(mshr);
|
|
schedMemSideSendEvent(clockEdge() + pkt->payloadDelay);
|
|
} else {
|
|
mshrQueue.deallocate(mshr);
|
|
if (wasFull && !mshrQueue.isFull()) {
|
|
clearBlocked(Blocked_NoMSHRs);
|
|
}
|
|
|
|
// Request the bus for a prefetch if this deallocation freed enough
|
|
// MSHRs for a prefetch to take place
|
|
if (prefetcher && mshrQueue.canPrefetch()) {
|
|
Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(),
|
|
clockEdge());
|
|
if (next_pf_time != MaxTick)
|
|
schedMemSideSendEvent(next_pf_time);
|
|
}
|
|
}
|
|
// reset the xbar additional timinig as it is now accounted for
|
|
pkt->headerDelay = pkt->payloadDelay = 0;
|
|
|
|
// copy writebacks to write buffer
|
|
doWritebacks(writebacks, forward_time);
|
|
|
|
// if we used temp block, check to see if its valid and then clear it out
|
|
if (blk == tempBlock && tempBlock->isValid()) {
|
|
// We use forwardLatency here because we are copying
|
|
// Writebacks/CleanEvicts to write buffer. It specifies the latency to
|
|
// allocate an internal buffer and to schedule an event to the
|
|
// queued port.
|
|
if (blk->isDirty() || writebackClean) {
|
|
PacketPtr wbPkt = writebackBlk(blk);
|
|
allocateWriteBuffer(wbPkt, forward_time);
|
|
// Set BLOCK_CACHED flag if cached above.
|
|
if (isCachedAbove(wbPkt))
|
|
wbPkt->setBlockCached();
|
|
} else {
|
|
PacketPtr wcPkt = cleanEvictBlk(blk);
|
|
// Check to see if block is cached above. If not allocate
|
|
// write buffer
|
|
if (isCachedAbove(wcPkt))
|
|
delete wcPkt;
|
|
else
|
|
allocateWriteBuffer(wcPkt, forward_time);
|
|
}
|
|
blk->invalidate();
|
|
}
|
|
|
|
DPRINTF(CacheVerbose, "Leaving %s with %s for addr %#llx\n", __func__,
|
|
pkt->cmdString(), pkt->getAddr());
|
|
delete pkt;
|
|
}
|
|
|
|
PacketPtr
|
|
Cache::writebackBlk(CacheBlk *blk)
|
|
{
|
|
chatty_assert(!isReadOnly || writebackClean,
|
|
"Writeback from read-only cache");
|
|
assert(blk && blk->isValid() && (blk->isDirty() || writebackClean));
|
|
|
|
writebacks[Request::wbMasterId]++;
|
|
|
|
Request *req = new Request(tags->regenerateBlkAddr(blk->tag, blk->set),
|
|
blkSize, 0, Request::wbMasterId);
|
|
if (blk->isSecure())
|
|
req->setFlags(Request::SECURE);
|
|
|
|
req->taskId(blk->task_id);
|
|
blk->task_id= ContextSwitchTaskId::Unknown;
|
|
blk->tickInserted = curTick();
|
|
|
|
PacketPtr pkt =
|
|
new Packet(req, blk->isDirty() ?
|
|
MemCmd::WritebackDirty : MemCmd::WritebackClean);
|
|
|
|
DPRINTF(Cache, "Create Writeback %#llx writable: %d, dirty: %d\n",
|
|
pkt->getAddr(), blk->isWritable(), blk->isDirty());
|
|
|
|
if (blk->isWritable()) {
|
|
// not asserting shared means we pass the block in modified
|
|
// state, mark our own block non-writeable
|
|
blk->status &= ~BlkWritable;
|
|
} else {
|
|
// we are in the Owned state, tell the receiver
|
|
pkt->setHasSharers();
|
|
}
|
|
|
|
// make sure the block is not marked dirty
|
|
blk->status &= ~BlkDirty;
|
|
|
|
pkt->allocate();
|
|
std::memcpy(pkt->getPtr<uint8_t>(), blk->data, blkSize);
|
|
|
|
return pkt;
|
|
}
|
|
|
|
PacketPtr
|
|
Cache::cleanEvictBlk(CacheBlk *blk)
|
|
{
|
|
assert(!writebackClean);
|
|
assert(blk && blk->isValid() && !blk->isDirty());
|
|
// Creating a zero sized write, a message to the snoop filter
|
|
Request *req =
|
|
new Request(tags->regenerateBlkAddr(blk->tag, blk->set), blkSize, 0,
|
|
Request::wbMasterId);
|
|
if (blk->isSecure())
|
|
req->setFlags(Request::SECURE);
|
|
|
|
req->taskId(blk->task_id);
|
|
blk->task_id = ContextSwitchTaskId::Unknown;
|
|
blk->tickInserted = curTick();
|
|
|
|
PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
|
|
pkt->allocate();
|
|
DPRINTF(Cache, "%s%s %x Create CleanEvict\n", pkt->cmdString(),
|
|
pkt->req->isInstFetch() ? " (ifetch)" : "",
|
|
pkt->getAddr());
|
|
|
|
return pkt;
|
|
}
|
|
|
|
void
|
|
Cache::memWriteback()
|
|
{
|
|
CacheBlkVisitorWrapper visitor(*this, &Cache::writebackVisitor);
|
|
tags->forEachBlk(visitor);
|
|
}
|
|
|
|
void
|
|
Cache::memInvalidate()
|
|
{
|
|
CacheBlkVisitorWrapper visitor(*this, &Cache::invalidateVisitor);
|
|
tags->forEachBlk(visitor);
|
|
}
|
|
|
|
bool
|
|
Cache::isDirty() const
|
|
{
|
|
CacheBlkIsDirtyVisitor visitor;
|
|
tags->forEachBlk(visitor);
|
|
|
|
return visitor.isDirty();
|
|
}
|
|
|
|
bool
|
|
Cache::writebackVisitor(CacheBlk &blk)
|
|
{
|
|
if (blk.isDirty()) {
|
|
assert(blk.isValid());
|
|
|
|
Request request(tags->regenerateBlkAddr(blk.tag, blk.set),
|
|
blkSize, 0, Request::funcMasterId);
|
|
request.taskId(blk.task_id);
|
|
|
|
Packet packet(&request, MemCmd::WriteReq);
|
|
packet.dataStatic(blk.data);
|
|
|
|
memSidePort->sendFunctional(&packet);
|
|
|
|
blk.status &= ~BlkDirty;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
bool
|
|
Cache::invalidateVisitor(CacheBlk &blk)
|
|
{
|
|
|
|
if (blk.isDirty())
|
|
warn_once("Invalidating dirty cache lines. Expect things to break.\n");
|
|
|
|
if (blk.isValid()) {
|
|
assert(!blk.isDirty());
|
|
tags->invalidate(&blk);
|
|
blk.invalidate();
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
CacheBlk*
|
|
Cache::allocateBlock(Addr addr, bool is_secure, PacketList &writebacks)
|
|
{
|
|
CacheBlk *blk = tags->findVictim(addr);
|
|
|
|
// It is valid to return NULL if there is no victim
|
|
if (!blk)
|
|
return nullptr;
|
|
|
|
if (blk->isValid()) {
|
|
Addr repl_addr = tags->regenerateBlkAddr(blk->tag, blk->set);
|
|
MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
|
|
if (repl_mshr) {
|
|
// must be an outstanding upgrade request
|
|
// on a block we're about to replace...
|
|
assert(!blk->isWritable() || blk->isDirty());
|
|
assert(repl_mshr->needsWritable());
|
|
// too hard to replace block with transient state
|
|
// allocation failed, block not inserted
|
|
return NULL;
|
|
} else {
|
|
DPRINTF(Cache, "replacement: replacing %#llx (%s) with %#llx (%s): %s\n",
|
|
repl_addr, blk->isSecure() ? "s" : "ns",
|
|
addr, is_secure ? "s" : "ns",
|
|
blk->isDirty() ? "writeback" : "clean");
|
|
|
|
if (blk->wasPrefetched()) {
|
|
unusedPrefetches++;
|
|
}
|
|
// Will send up Writeback/CleanEvict snoops via isCachedAbove
|
|
// when pushing this writeback list into the write buffer.
|
|
if (blk->isDirty() || writebackClean) {
|
|
// Save writeback packet for handling by caller
|
|
writebacks.push_back(writebackBlk(blk));
|
|
} else {
|
|
writebacks.push_back(cleanEvictBlk(blk));
|
|
}
|
|
}
|
|
}
|
|
|
|
return blk;
|
|
}
|
|
|
|
void
|
|
Cache::invalidateBlock(CacheBlk *blk)
|
|
{
|
|
if (blk != tempBlock)
|
|
tags->invalidate(blk);
|
|
blk->invalidate();
|
|
}
|
|
|
|
// Note that the reason we return a list of writebacks rather than
|
|
// inserting them directly in the write buffer is that this function
|
|
// is called by both atomic and timing-mode accesses, and in atomic
|
|
// mode we don't mess with the write buffer (we just perform the
|
|
// writebacks atomically once the original request is complete).
|
|
CacheBlk*
|
|
Cache::handleFill(PacketPtr pkt, CacheBlk *blk, PacketList &writebacks,
|
|
bool allocate)
|
|
{
|
|
assert(pkt->isResponse() || pkt->cmd == MemCmd::WriteLineReq);
|
|
Addr addr = pkt->getAddr();
|
|
bool is_secure = pkt->isSecure();
|
|
#if TRACING_ON
|
|
CacheBlk::State old_state = blk ? blk->status : 0;
|
|
#endif
|
|
|
|
// When handling a fill, we should have no writes to this line.
|
|
assert(addr == blockAlign(addr));
|
|
assert(!writeBuffer.findMatch(addr, is_secure));
|
|
|
|
if (blk == NULL) {
|
|
// better have read new data...
|
|
assert(pkt->hasData());
|
|
|
|
// only read responses and write-line requests have data;
|
|
// note that we don't write the data here for write-line - that
|
|
// happens in the subsequent satisfyCpuSideRequest.
|
|
assert(pkt->isRead() || pkt->cmd == MemCmd::WriteLineReq);
|
|
|
|
// need to do a replacement if allocating, otherwise we stick
|
|
// with the temporary storage
|
|
blk = allocate ? allocateBlock(addr, is_secure, writebacks) : NULL;
|
|
|
|
if (blk == NULL) {
|
|
// No replaceable block or a mostly exclusive
|
|
// cache... just use temporary storage to complete the
|
|
// current request and then get rid of it
|
|
assert(!tempBlock->isValid());
|
|
blk = tempBlock;
|
|
tempBlock->set = tags->extractSet(addr);
|
|
tempBlock->tag = tags->extractTag(addr);
|
|
// @todo: set security state as well...
|
|
DPRINTF(Cache, "using temp block for %#llx (%s)\n", addr,
|
|
is_secure ? "s" : "ns");
|
|
} else {
|
|
tags->insertBlock(pkt, blk);
|
|
}
|
|
|
|
// we should never be overwriting a valid block
|
|
assert(!blk->isValid());
|
|
} else {
|
|
// existing block... probably an upgrade
|
|
assert(blk->tag == tags->extractTag(addr));
|
|
// either we're getting new data or the block should already be valid
|
|
assert(pkt->hasData() || blk->isValid());
|
|
// don't clear block status... if block is already dirty we
|
|
// don't want to lose that
|
|
}
|
|
|
|
if (is_secure)
|
|
blk->status |= BlkSecure;
|
|
blk->status |= BlkValid | BlkReadable;
|
|
|
|
// sanity check for whole-line writes, which should always be
|
|
// marked as writable as part of the fill, and then later marked
|
|
// dirty as part of satisfyCpuSideRequest
|
|
if (pkt->cmd == MemCmd::WriteLineReq) {
|
|
assert(!pkt->hasSharers());
|
|
// at the moment other caches do not respond to the
|
|
// invalidation requests corresponding to a whole-line write
|
|
assert(!pkt->cacheResponding());
|
|
}
|
|
|
|
// here we deal with setting the appropriate state of the line,
|
|
// and we start by looking at the hasSharers flag, and ignore the
|
|
// cacheResponding flag (normally signalling dirty data) if the
|
|
// packet has sharers, thus the line is never allocated as Owned
|
|
// (dirty but not writable), and always ends up being either
|
|
// Shared, Exclusive or Modified, see Packet::setCacheResponding
|
|
// for more details
|
|
if (!pkt->hasSharers()) {
|
|
// we could get a writable line from memory (rather than a
|
|
// cache) even in a read-only cache, note that we set this bit
|
|
// even for a read-only cache, possibly revisit this decision
|
|
blk->status |= BlkWritable;
|
|
|
|
// check if we got this via cache-to-cache transfer (i.e., from a
|
|
// cache that had the block in Modified or Owned state)
|
|
if (pkt->cacheResponding()) {
|
|
// we got the block in Modified state, and invalidated the
|
|
// owners copy
|
|
blk->status |= BlkDirty;
|
|
|
|
chatty_assert(!isReadOnly, "Should never see dirty snoop response "
|
|
"in read-only cache %s\n", name());
|
|
}
|
|
}
|
|
|
|
DPRINTF(Cache, "Block addr %#llx (%s) moving from state %x to %s\n",
|
|
addr, is_secure ? "s" : "ns", old_state, blk->print());
|
|
|
|
// if we got new data, copy it in (checking for a read response
|
|
// and a response that has data is the same in the end)
|
|
if (pkt->isRead()) {
|
|
// sanity checks
|
|
assert(pkt->hasData());
|
|
assert(pkt->getSize() == blkSize);
|
|
|
|
std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
|
|
}
|
|
// We pay for fillLatency here.
|
|
blk->whenReady = clockEdge() + fillLatency * clockPeriod() +
|
|
pkt->payloadDelay;
|
|
|
|
return blk;
|
|
}
|
|
|
|
|
|
/////////////////////////////////////////////////////
|
|
//
|
|
// Snoop path: requests coming in from the memory side
|
|
//
|
|
/////////////////////////////////////////////////////
|
|
|
|
void
|
|
Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
|
|
bool already_copied, bool pending_inval)
|
|
{
|
|
// sanity check
|
|
assert(req_pkt->isRequest());
|
|
assert(req_pkt->needsResponse());
|
|
|
|
DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__,
|
|
req_pkt->cmdString(), req_pkt->getAddr(), req_pkt->getSize());
|
|
// timing-mode snoop responses require a new packet, unless we
|
|
// already made a copy...
|
|
PacketPtr pkt = req_pkt;
|
|
if (!already_copied)
|
|
// do not clear flags, and allocate space for data if the
|
|
// packet needs it (the only packets that carry data are read
|
|
// responses)
|
|
pkt = new Packet(req_pkt, false, req_pkt->isRead());
|
|
|
|
assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
|
|
pkt->hasSharers());
|
|
pkt->makeTimingResponse();
|
|
if (pkt->isRead()) {
|
|
pkt->setDataFromBlock(blk_data, blkSize);
|
|
}
|
|
if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
|
|
// Assume we defer a response to a read from a far-away cache
|
|
// A, then later defer a ReadExcl from a cache B on the same
|
|
// bus as us. We'll assert cacheResponding in both cases, but
|
|
// in the latter case cacheResponding will keep the
|
|
// invalidation from reaching cache A. This special response
|
|
// tells cache A that it gets the block to satisfy its read,
|
|
// but must immediately invalidate it.
|
|
pkt->cmd = MemCmd::ReadRespWithInvalidate;
|
|
}
|
|
// Here we consider forward_time, paying for just forward latency and
|
|
// also charging the delay provided by the xbar.
|
|
// forward_time is used as send_time in next allocateWriteBuffer().
|
|
Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
|
|
// Here we reset the timing of the packet.
|
|
pkt->headerDelay = pkt->payloadDelay = 0;
|
|
DPRINTF(CacheVerbose,
|
|
"%s created response: %s addr %#llx size %d tick: %lu\n",
|
|
__func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize(),
|
|
forward_time);
|
|
memSidePort->schedTimingSnoopResp(pkt, forward_time, true);
|
|
}
|
|
|
|
uint32_t
|
|
Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
|
|
bool is_deferred, bool pending_inval)
|
|
{
|
|
DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d\n", __func__,
|
|
pkt->cmdString(), pkt->getAddr(), pkt->getSize());
|
|
// deferred snoops can only happen in timing mode
|
|
assert(!(is_deferred && !is_timing));
|
|
// pending_inval only makes sense on deferred snoops
|
|
assert(!(pending_inval && !is_deferred));
|
|
assert(pkt->isRequest());
|
|
|
|
// the packet may get modified if we or a forwarded snooper
|
|
// responds in atomic mode, so remember a few things about the
|
|
// original packet up front
|
|
bool invalidate = pkt->isInvalidate();
|
|
bool M5_VAR_USED needs_writable = pkt->needsWritable();
|
|
|
|
// at the moment we could get an uncacheable write which does not
|
|
// have the invalidate flag, and we need a suitable way of dealing
|
|
// with this case
|
|
panic_if(invalidate && pkt->req->isUncacheable(),
|
|
"%s got an invalidating uncacheable snoop request %s to %#llx",
|
|
name(), pkt->cmdString(), pkt->getAddr());
|
|
|
|
uint32_t snoop_delay = 0;
|
|
|
|
if (forwardSnoops) {
|
|
// first propagate snoop upward to see if anyone above us wants to
|
|
// handle it. save & restore packet src since it will get
|
|
// rewritten to be relative to cpu-side bus (if any)
|
|
bool alreadyResponded = pkt->cacheResponding();
|
|
if (is_timing) {
|
|
// copy the packet so that we can clear any flags before
|
|
// forwarding it upwards, we also allocate data (passing
|
|
// the pointer along in case of static data), in case
|
|
// there is a snoop hit in upper levels
|
|
Packet snoopPkt(pkt, true, true);
|
|
snoopPkt.setExpressSnoop();
|
|
// the snoop packet does not need to wait any additional
|
|
// time
|
|
snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
|
|
cpuSidePort->sendTimingSnoopReq(&snoopPkt);
|
|
|
|
// add the header delay (including crossbar and snoop
|
|
// delays) of the upward snoop to the snoop delay for this
|
|
// cache
|
|
snoop_delay += snoopPkt.headerDelay;
|
|
|
|
if (snoopPkt.cacheResponding()) {
|
|
// cache-to-cache response from some upper cache
|
|
assert(!alreadyResponded);
|
|
pkt->setCacheResponding();
|
|
}
|
|
// upstream cache has the block, or has an outstanding
|
|
// MSHR, pass the flag on
|
|
if (snoopPkt.hasSharers()) {
|
|
pkt->setHasSharers();
|
|
}
|
|
// If this request is a prefetch or clean evict and an upper level
|
|
// signals block present, make sure to propagate the block
|
|
// presence to the requester.
|
|
if (snoopPkt.isBlockCached()) {
|
|
pkt->setBlockCached();
|
|
}
|
|
} else {
|
|
cpuSidePort->sendAtomicSnoop(pkt);
|
|
if (!alreadyResponded && pkt->cacheResponding()) {
|
|
// cache-to-cache response from some upper cache:
|
|
// forward response to original requester
|
|
assert(pkt->isResponse());
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!blk || !blk->isValid()) {
|
|
DPRINTF(CacheVerbose, "%s snoop miss for %s addr %#llx size %d\n",
|
|
__func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize());
|
|
return snoop_delay;
|
|
} else {
|
|
DPRINTF(Cache, "%s snoop hit for %s addr %#llx size %d, "
|
|
"old state is %s\n", __func__, pkt->cmdString(),
|
|
pkt->getAddr(), pkt->getSize(), blk->print());
|
|
}
|
|
|
|
chatty_assert(!(isReadOnly && blk->isDirty()),
|
|
"Should never have a dirty block in a read-only cache %s\n",
|
|
name());
|
|
|
|
// We may end up modifying both the block state and the packet (if
|
|
// we respond in atomic mode), so just figure out what to do now
|
|
// and then do it later. If we find dirty data while snooping for
|
|
// an invalidate, we don't need to send a response. The
|
|
// invalidation itself is taken care of below.
|
|
bool respond = blk->isDirty() && pkt->needsResponse() &&
|
|
pkt->cmd != MemCmd::InvalidateReq;
|
|
bool have_writable = blk->isWritable();
|
|
|
|
// Invalidate any prefetch's from below that would strip write permissions
|
|
// MemCmd::HardPFReq is only observed by upstream caches. After missing
|
|
// above and in it's own cache, a new MemCmd::ReadReq is created that
|
|
// downstream caches observe.
|
|
if (pkt->mustCheckAbove()) {
|
|
DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s from"
|
|
" lower cache\n", pkt->getAddr(), pkt->cmdString());
|
|
pkt->setBlockCached();
|
|
return snoop_delay;
|
|
}
|
|
|
|
if (pkt->isRead() && !invalidate) {
|
|
// reading without requiring the line in a writable state
|
|
assert(!needs_writable);
|
|
pkt->setHasSharers();
|
|
|
|
// if the requesting packet is uncacheable, retain the line in
|
|
// the current state, otherwhise unset the writable flag,
|
|
// which means we go from Modified to Owned (and will respond
|
|
// below), remain in Owned (and will respond below), from
|
|
// Exclusive to Shared, or remain in Shared
|
|
if (!pkt->req->isUncacheable())
|
|
blk->status &= ~BlkWritable;
|
|
}
|
|
|
|
if (respond) {
|
|
// prevent anyone else from responding, cache as well as
|
|
// memory, and also prevent any memory from even seeing the
|
|
// request
|
|
pkt->setCacheResponding();
|
|
if (have_writable) {
|
|
// inform the cache hierarchy that this cache had the line
|
|
// in the Modified state so that we avoid unnecessary
|
|
// invalidations (see Packet::setResponderHadWritable)
|
|
pkt->setResponderHadWritable();
|
|
|
|
// in the case of an uncacheable request there is no point
|
|
// in setting the responderHadWritable flag, but since the
|
|
// recipient does not care there is no harm in doing so
|
|
} else {
|
|
// if the packet has needsWritable set we invalidate our
|
|
// copy below and all other copies will be invalidates
|
|
// through express snoops, and if needsWritable is not set
|
|
// we already called setHasSharers above
|
|
}
|
|
|
|
// if we are returning a writable and dirty (Modified) line,
|
|
// we should be invalidating the line
|
|
panic_if(!invalidate && !pkt->hasSharers(),
|
|
"%s is passing a Modified line through %s to %#llx, "
|
|
"but keeping the block",
|
|
name(), pkt->cmdString(), pkt->getAddr());
|
|
|
|
if (is_timing) {
|
|
doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
|
|
} else {
|
|
pkt->makeAtomicResponse();
|
|
// packets such as upgrades do not actually have any data
|
|
// payload
|
|
if (pkt->hasData())
|
|
pkt->setDataFromBlock(blk->data, blkSize);
|
|
}
|
|
}
|
|
|
|
if (!respond && is_timing && is_deferred) {
|
|
// if it's a deferred timing snoop to which we are not
|
|
// responding, then we've made a copy of both the request and
|
|
// the packet, delete them here
|
|
assert(pkt->needsResponse());
|
|
delete pkt->req;
|
|
delete pkt;
|
|
}
|
|
|
|
// Do this last in case it deallocates block data or something
|
|
// like that
|
|
if (invalidate) {
|
|
invalidateBlock(blk);
|
|
}
|
|
|
|
DPRINTF(Cache, "new state is %s\n", blk->print());
|
|
|
|
return snoop_delay;
|
|
}
|
|
|
|
|
|
void
|
|
Cache::recvTimingSnoopReq(PacketPtr pkt)
|
|
{
|
|
DPRINTF(CacheVerbose, "%s for %s addr %#llx size %d\n", __func__,
|
|
pkt->cmdString(), pkt->getAddr(), pkt->getSize());
|
|
|
|
// Snoops shouldn't happen when bypassing caches
|
|
assert(!system->bypassCaches());
|
|
|
|
// no need to snoop requests that are not in range
|
|
if (!inRange(pkt->getAddr())) {
|
|
return;
|
|
}
|
|
|
|
bool is_secure = pkt->isSecure();
|
|
CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
|
|
|
|
Addr blk_addr = blockAlign(pkt->getAddr());
|
|
MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
|
|
|
|
// Update the latency cost of the snoop so that the crossbar can
|
|
// account for it. Do not overwrite what other neighbouring caches
|
|
// have already done, rather take the maximum. The update is
|
|
// tentative, for cases where we return before an upward snoop
|
|
// happens below.
|
|
pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
|
|
lookupLatency * clockPeriod());
|
|
|
|
// Inform request(Prefetch, CleanEvict or Writeback) from below of
|
|
// MSHR hit, set setBlockCached.
|
|
if (mshr && pkt->mustCheckAbove()) {
|
|
DPRINTF(Cache, "Setting block cached for %s from"
|
|
"lower cache on mshr hit %#x\n",
|
|
pkt->cmdString(), pkt->getAddr());
|
|
pkt->setBlockCached();
|
|
return;
|
|
}
|
|
|
|
// Let the MSHR itself track the snoop and decide whether we want
|
|
// to go ahead and do the regular cache snoop
|
|
if (mshr && mshr->handleSnoop(pkt, order++)) {
|
|
DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
|
|
"mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
|
|
mshr->print());
|
|
|
|
if (mshr->getNumTargets() > numTarget)
|
|
warn("allocating bonus target for snoop"); //handle later
|
|
return;
|
|
}
|
|
|
|
//We also need to check the writeback buffers and handle those
|
|
WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
|
|
if (wb_entry) {
|
|
DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
|
|
pkt->getAddr(), is_secure ? "s" : "ns");
|
|
// Expect to see only Writebacks and/or CleanEvicts here, both of
|
|
// which should not be generated for uncacheable data.
|
|
assert(!wb_entry->isUncacheable());
|
|
// There should only be a single request responsible for generating
|
|
// Writebacks/CleanEvicts.
|
|
assert(wb_entry->getNumTargets() == 1);
|
|
PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
|
|
assert(wb_pkt->isEviction());
|
|
|
|
if (pkt->isEviction()) {
|
|
// if the block is found in the write queue, set the BLOCK_CACHED
|
|
// flag for Writeback/CleanEvict snoop. On return the snoop will
|
|
// propagate the BLOCK_CACHED flag in Writeback packets and prevent
|
|
// any CleanEvicts from travelling down the memory hierarchy.
|
|
pkt->setBlockCached();
|
|
DPRINTF(Cache, "Squashing %s from lower cache on writequeue hit"
|
|
" %#x\n", pkt->cmdString(), pkt->getAddr());
|
|
return;
|
|
}
|
|
|
|
// conceptually writebacks are no different to other blocks in
|
|
// this cache, so the behaviour is modelled after handleSnoop,
|
|
// the difference being that instead of querying the block
|
|
// state to determine if it is dirty and writable, we use the
|
|
// command and fields of the writeback packet
|
|
bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
|
|
pkt->needsResponse() && pkt->cmd != MemCmd::InvalidateReq;
|
|
bool have_writable = !wb_pkt->hasSharers();
|
|
bool invalidate = pkt->isInvalidate();
|
|
|
|
if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
|
|
assert(!pkt->needsWritable());
|
|
pkt->setHasSharers();
|
|
wb_pkt->setHasSharers();
|
|
}
|
|
|
|
if (respond) {
|
|
pkt->setCacheResponding();
|
|
|
|
if (have_writable) {
|
|
pkt->setResponderHadWritable();
|
|
}
|
|
|
|
doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
|
|
false, false);
|
|
}
|
|
|
|
if (invalidate) {
|
|
// Invalidation trumps our writeback... discard here
|
|
// Note: markInService will remove entry from writeback buffer.
|
|
markInService(wb_entry);
|
|
delete wb_pkt;
|
|
}
|
|
}
|
|
|
|
// If this was a shared writeback, there may still be
|
|
// other shared copies above that require invalidation.
|
|
// We could be more selective and return here if the
|
|
// request is non-exclusive or if the writeback is
|
|
// exclusive.
|
|
uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
|
|
|
|
// Override what we did when we first saw the snoop, as we now
|
|
// also have the cost of the upwards snoops to account for
|
|
pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
|
|
lookupLatency * clockPeriod());
|
|
}
|
|
|
|
bool
|
|
Cache::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
|
|
{
|
|
// Express snoop responses from master to slave, e.g., from L1 to L2
|
|
cache->recvTimingSnoopResp(pkt);
|
|
return true;
|
|
}
|
|
|
|
Tick
|
|
Cache::recvAtomicSnoop(PacketPtr pkt)
|
|
{
|
|
// Snoops shouldn't happen when bypassing caches
|
|
assert(!system->bypassCaches());
|
|
|
|
// no need to snoop requests that are not in range.
|
|
if (!inRange(pkt->getAddr())) {
|
|
return 0;
|
|
}
|
|
|
|
CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
|
|
uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
|
|
return snoop_delay + lookupLatency * clockPeriod();
|
|
}
|
|
|
|
|
|
QueueEntry*
|
|
Cache::getNextQueueEntry()
|
|
{
|
|
// Check both MSHR queue and write buffer for potential requests,
|
|
// note that null does not mean there is no request, it could
|
|
// simply be that it is not ready
|
|
MSHR *miss_mshr = mshrQueue.getNext();
|
|
WriteQueueEntry *wq_entry = writeBuffer.getNext();
|
|
|
|
// If we got a write buffer request ready, first priority is a
|
|
// full write buffer (but only if we have no uncacheable write
|
|
// responses outstanding, possibly revisit this last part),
|
|
// otherwhise we favour the miss requests
|
|
if (wq_entry &&
|
|
((writeBuffer.isFull() && writeBuffer.numInService() == 0) ||
|
|
!miss_mshr)) {
|
|
// need to search MSHR queue for conflicting earlier miss.
|
|
MSHR *conflict_mshr =
|
|
mshrQueue.findPending(wq_entry->blkAddr,
|
|
wq_entry->isSecure);
|
|
|
|
if (conflict_mshr && conflict_mshr->order < wq_entry->order) {
|
|
// Service misses in order until conflict is cleared.
|
|
return conflict_mshr;
|
|
|
|
// @todo Note that we ignore the ready time of the conflict here
|
|
}
|
|
|
|
// No conflicts; issue write
|
|
return wq_entry;
|
|
} else if (miss_mshr) {
|
|
// need to check for conflicting earlier writeback
|
|
WriteQueueEntry *conflict_mshr =
|
|
writeBuffer.findPending(miss_mshr->blkAddr,
|
|
miss_mshr->isSecure);
|
|
if (conflict_mshr) {
|
|
// not sure why we don't check order here... it was in the
|
|
// original code but commented out.
|
|
|
|
// The only way this happens is if we are
|
|
// doing a write and we didn't have permissions
|
|
// then subsequently saw a writeback (owned got evicted)
|
|
// We need to make sure to perform the writeback first
|
|
// To preserve the dirty data, then we can issue the write
|
|
|
|
// should we return wq_entry here instead? I.e. do we
|
|
// have to flush writes in order? I don't think so... not
|
|
// for Alpha anyway. Maybe for x86?
|
|
return conflict_mshr;
|
|
|
|
// @todo Note that we ignore the ready time of the conflict here
|
|
}
|
|
|
|
// No conflicts; issue read
|
|
return miss_mshr;
|
|
}
|
|
|
|
// fall through... no pending requests. Try a prefetch.
|
|
assert(!miss_mshr && !wq_entry);
|
|
if (prefetcher && mshrQueue.canPrefetch()) {
|
|
// If we have a miss queue slot, we can try a prefetch
|
|
PacketPtr pkt = prefetcher->getPacket();
|
|
if (pkt) {
|
|
Addr pf_addr = blockAlign(pkt->getAddr());
|
|
if (!tags->findBlock(pf_addr, pkt->isSecure()) &&
|
|
!mshrQueue.findMatch(pf_addr, pkt->isSecure()) &&
|
|
!writeBuffer.findMatch(pf_addr, pkt->isSecure())) {
|
|
// Update statistic on number of prefetches issued
|
|
// (hwpf_mshr_misses)
|
|
assert(pkt->req->masterId() < system->maxMasters());
|
|
mshr_misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
|
|
|
|
// allocate an MSHR and return it, note
|
|
// that we send the packet straight away, so do not
|
|
// schedule the send
|
|
return allocateMissBuffer(pkt, curTick(), false);
|
|
} else {
|
|
// free the request and packet
|
|
delete pkt->req;
|
|
delete pkt;
|
|
}
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
bool
|
|
Cache::isCachedAbove(PacketPtr pkt, bool is_timing) const
|
|
{
|
|
if (!forwardSnoops)
|
|
return false;
|
|
// Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
|
|
// Writeback snoops into upper level caches to check for copies of the
|
|
// same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
|
|
// packet, the cache can inform the crossbar below of presence or absence
|
|
// of the block.
|
|
if (is_timing) {
|
|
Packet snoop_pkt(pkt, true, false);
|
|
snoop_pkt.setExpressSnoop();
|
|
// Assert that packet is either Writeback or CleanEvict and not a
|
|
// prefetch request because prefetch requests need an MSHR and may
|
|
// generate a snoop response.
|
|
assert(pkt->isEviction());
|
|
snoop_pkt.senderState = NULL;
|
|
cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
|
|
// Writeback/CleanEvict snoops do not generate a snoop response.
|
|
assert(!(snoop_pkt.cacheResponding()));
|
|
return snoop_pkt.isBlockCached();
|
|
} else {
|
|
cpuSidePort->sendAtomicSnoop(pkt);
|
|
return pkt->isBlockCached();
|
|
}
|
|
}
|
|
|
|
Tick
|
|
Cache::nextQueueReadyTime() const
|
|
{
|
|
Tick nextReady = std::min(mshrQueue.nextReadyTime(),
|
|
writeBuffer.nextReadyTime());
|
|
|
|
// Don't signal prefetch ready time if no MSHRs available
|
|
// Will signal once enoguh MSHRs are deallocated
|
|
if (prefetcher && mshrQueue.canPrefetch()) {
|
|
nextReady = std::min(nextReady,
|
|
prefetcher->nextPrefetchReadyTime());
|
|
}
|
|
|
|
return nextReady;
|
|
}
|
|
|
|
bool
|
|
Cache::sendMSHRQueuePacket(MSHR* mshr)
|
|
{
|
|
assert(mshr);
|
|
|
|
// use request from 1st target
|
|
PacketPtr tgt_pkt = mshr->getTarget()->pkt;
|
|
|
|
DPRINTF(Cache, "%s MSHR %s for addr %#llx size %d\n", __func__,
|
|
tgt_pkt->cmdString(), tgt_pkt->getAddr(),
|
|
tgt_pkt->getSize());
|
|
|
|
CacheBlk *blk = tags->findBlock(mshr->blkAddr, mshr->isSecure);
|
|
|
|
if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
|
|
// we should never have hardware prefetches to allocated
|
|
// blocks
|
|
assert(blk == NULL);
|
|
|
|
// We need to check the caches above us to verify that
|
|
// they don't have a copy of this block in the dirty state
|
|
// at the moment. Without this check we could get a stale
|
|
// copy from memory that might get used in place of the
|
|
// dirty one.
|
|
Packet snoop_pkt(tgt_pkt, true, false);
|
|
snoop_pkt.setExpressSnoop();
|
|
// We are sending this packet upwards, but if it hits we will
|
|
// get a snoop response that we end up treating just like a
|
|
// normal response, hence it needs the MSHR as its sender
|
|
// state
|
|
snoop_pkt.senderState = mshr;
|
|
cpuSidePort->sendTimingSnoopReq(&snoop_pkt);
|
|
|
|
// Check to see if the prefetch was squashed by an upper cache (to
|
|
// prevent us from grabbing the line) or if a Check to see if a
|
|
// writeback arrived between the time the prefetch was placed in
|
|
// the MSHRs and when it was selected to be sent or if the
|
|
// prefetch was squashed by an upper cache.
|
|
|
|
// It is important to check cacheResponding before
|
|
// prefetchSquashed. If another cache has committed to
|
|
// responding, it will be sending a dirty response which will
|
|
// arrive at the MSHR allocated for this request. Checking the
|
|
// prefetchSquash first may result in the MSHR being
|
|
// prematurely deallocated.
|
|
if (snoop_pkt.cacheResponding()) {
|
|
auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
|
|
assert(r.second);
|
|
|
|
// if we are getting a snoop response with no sharers it
|
|
// will be allocated as Modified
|
|
bool pending_modified_resp = !snoop_pkt.hasSharers();
|
|
markInService(mshr, pending_modified_resp);
|
|
|
|
DPRINTF(Cache, "Upward snoop of prefetch for addr"
|
|
" %#x (%s) hit\n",
|
|
tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
|
|
return false;
|
|
}
|
|
|
|
if (snoop_pkt.isBlockCached()) {
|
|
DPRINTF(Cache, "Block present, prefetch squashed by cache. "
|
|
"Deallocating mshr target %#x.\n",
|
|
mshr->blkAddr);
|
|
|
|
// Deallocate the mshr target
|
|
if (mshrQueue.forceDeallocateTarget(mshr)) {
|
|
// Clear block if this deallocation resulted freed an
|
|
// mshr when all had previously been utilized
|
|
clearBlocked(Blocked_NoMSHRs);
|
|
}
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// either a prefetch that is not present upstream, or a normal
|
|
// MSHR request, proceed to get the packet to send downstream
|
|
PacketPtr pkt = getBusPacket(tgt_pkt, blk, mshr->needsWritable());
|
|
|
|
mshr->isForward = (pkt == NULL);
|
|
|
|
if (mshr->isForward) {
|
|
// not a cache block request, but a response is expected
|
|
// make copy of current packet to forward, keep current
|
|
// copy for response handling
|
|
pkt = new Packet(tgt_pkt, false, true);
|
|
assert(!pkt->isWrite());
|
|
}
|
|
|
|
// play it safe and append (rather than set) the sender state,
|
|
// as forwarded packets may already have existing state
|
|
pkt->pushSenderState(mshr);
|
|
|
|
if (!memSidePort->sendTimingReq(pkt)) {
|
|
// we are awaiting a retry, but we
|
|
// delete the packet and will be creating a new packet
|
|
// when we get the opportunity
|
|
delete pkt;
|
|
|
|
// note that we have now masked any requestBus and
|
|
// schedSendEvent (we will wait for a retry before
|
|
// doing anything), and this is so even if we do not
|
|
// care about this packet and might override it before
|
|
// it gets retried
|
|
return true;
|
|
} else {
|
|
// As part of the call to sendTimingReq the packet is
|
|
// forwarded to all neighbouring caches (and any caches
|
|
// above them) as a snoop. Thus at this point we know if
|
|
// any of the neighbouring caches are responding, and if
|
|
// so, we know it is dirty, and we can determine if it is
|
|
// being passed as Modified, making our MSHR the ordering
|
|
// point
|
|
bool pending_modified_resp = !pkt->hasSharers() &&
|
|
pkt->cacheResponding();
|
|
markInService(mshr, pending_modified_resp);
|
|
return false;
|
|
}
|
|
}
|
|
|
|
bool
|
|
Cache::sendWriteQueuePacket(WriteQueueEntry* wq_entry)
|
|
{
|
|
assert(wq_entry);
|
|
|
|
// always a single target for write queue entries
|
|
PacketPtr tgt_pkt = wq_entry->getTarget()->pkt;
|
|
|
|
DPRINTF(Cache, "%s write %s for addr %#llx size %d\n", __func__,
|
|
tgt_pkt->cmdString(), tgt_pkt->getAddr(),
|
|
tgt_pkt->getSize());
|
|
|
|
PacketPtr pkt = nullptr;
|
|
bool delete_pkt = false;
|
|
|
|
if (tgt_pkt->isEviction()) {
|
|
assert(!wq_entry->isUncacheable());
|
|
// no response expected, just forward packet as it is
|
|
pkt = tgt_pkt;
|
|
} else {
|
|
// the only thing we deal with besides eviction commands
|
|
// are uncacheable writes
|
|
assert(tgt_pkt->req->isUncacheable() && tgt_pkt->isWrite());
|
|
// not a cache block request, but a response is expected
|
|
// make copy of current packet to forward, keep current
|
|
// copy for response handling
|
|
pkt = new Packet(tgt_pkt, false, true);
|
|
pkt->setData(tgt_pkt->getConstPtr<uint8_t>());
|
|
delete_pkt = true;
|
|
}
|
|
|
|
pkt->pushSenderState(wq_entry);
|
|
|
|
if (!memSidePort->sendTimingReq(pkt)) {
|
|
if (delete_pkt) {
|
|
// we are awaiting a retry, but we
|
|
// delete the packet and will be creating a new packet
|
|
// when we get the opportunity
|
|
delete pkt;
|
|
}
|
|
// note that we have now masked any requestBus and
|
|
// schedSendEvent (we will wait for a retry before
|
|
// doing anything), and this is so even if we do not
|
|
// care about this packet and might override it before
|
|
// it gets retried
|
|
return true;
|
|
} else {
|
|
markInService(wq_entry);
|
|
return false;
|
|
}
|
|
}
|
|
|
|
void
|
|
Cache::serialize(CheckpointOut &cp) const
|
|
{
|
|
bool dirty(isDirty());
|
|
|
|
if (dirty) {
|
|
warn("*** The cache still contains dirty data. ***\n");
|
|
warn(" Make sure to drain the system using the correct flags.\n");
|
|
warn(" This checkpoint will not restore correctly and dirty data in "
|
|
"the cache will be lost!\n");
|
|
}
|
|
|
|
// Since we don't checkpoint the data in the cache, any dirty data
|
|
// will be lost when restoring from a checkpoint of a system that
|
|
// wasn't drained properly. Flag the checkpoint as invalid if the
|
|
// cache contains dirty data.
|
|
bool bad_checkpoint(dirty);
|
|
SERIALIZE_SCALAR(bad_checkpoint);
|
|
}
|
|
|
|
void
|
|
Cache::unserialize(CheckpointIn &cp)
|
|
{
|
|
bool bad_checkpoint;
|
|
UNSERIALIZE_SCALAR(bad_checkpoint);
|
|
if (bad_checkpoint) {
|
|
fatal("Restoring from checkpoints with dirty caches is not supported "
|
|
"in the classic memory system. Please remove any caches or "
|
|
" drain them properly before taking checkpoints.\n");
|
|
}
|
|
}
|
|
|
|
///////////////
|
|
//
|
|
// CpuSidePort
|
|
//
|
|
///////////////
|
|
|
|
AddrRangeList
|
|
Cache::CpuSidePort::getAddrRanges() const
|
|
{
|
|
return cache->getAddrRanges();
|
|
}
|
|
|
|
bool
|
|
Cache::CpuSidePort::recvTimingReq(PacketPtr pkt)
|
|
{
|
|
assert(!cache->system->bypassCaches());
|
|
|
|
bool success = false;
|
|
|
|
// always let express snoop packets through if even if blocked
|
|
if (pkt->isExpressSnoop()) {
|
|
// do not change the current retry state
|
|
bool M5_VAR_USED bypass_success = cache->recvTimingReq(pkt);
|
|
assert(bypass_success);
|
|
return true;
|
|
} else if (blocked || mustSendRetry) {
|
|
// either already committed to send a retry, or blocked
|
|
success = false;
|
|
} else {
|
|
// pass it on to the cache, and let the cache decide if we
|
|
// have to retry or not
|
|
success = cache->recvTimingReq(pkt);
|
|
}
|
|
|
|
// remember if we have to retry
|
|
mustSendRetry = !success;
|
|
return success;
|
|
}
|
|
|
|
Tick
|
|
Cache::CpuSidePort::recvAtomic(PacketPtr pkt)
|
|
{
|
|
return cache->recvAtomic(pkt);
|
|
}
|
|
|
|
void
|
|
Cache::CpuSidePort::recvFunctional(PacketPtr pkt)
|
|
{
|
|
// functional request
|
|
cache->functionalAccess(pkt, true);
|
|
}
|
|
|
|
Cache::
|
|
CpuSidePort::CpuSidePort(const std::string &_name, Cache *_cache,
|
|
const std::string &_label)
|
|
: BaseCache::CacheSlavePort(_name, _cache, _label), cache(_cache)
|
|
{
|
|
}
|
|
|
|
Cache*
|
|
CacheParams::create()
|
|
{
|
|
assert(tags);
|
|
|
|
return new Cache(this);
|
|
}
|
|
///////////////
|
|
//
|
|
// MemSidePort
|
|
//
|
|
///////////////
|
|
|
|
bool
|
|
Cache::MemSidePort::recvTimingResp(PacketPtr pkt)
|
|
{
|
|
cache->recvTimingResp(pkt);
|
|
return true;
|
|
}
|
|
|
|
// Express snooping requests to memside port
|
|
void
|
|
Cache::MemSidePort::recvTimingSnoopReq(PacketPtr pkt)
|
|
{
|
|
// handle snooping requests
|
|
cache->recvTimingSnoopReq(pkt);
|
|
}
|
|
|
|
Tick
|
|
Cache::MemSidePort::recvAtomicSnoop(PacketPtr pkt)
|
|
{
|
|
return cache->recvAtomicSnoop(pkt);
|
|
}
|
|
|
|
void
|
|
Cache::MemSidePort::recvFunctionalSnoop(PacketPtr pkt)
|
|
{
|
|
// functional snoop (note that in contrast to atomic we don't have
|
|
// a specific functionalSnoop method, as they have the same
|
|
// behaviour regardless)
|
|
cache->functionalAccess(pkt, false);
|
|
}
|
|
|
|
void
|
|
Cache::CacheReqPacketQueue::sendDeferredPacket()
|
|
{
|
|
// sanity check
|
|
assert(!waitingOnRetry);
|
|
|
|
// there should never be any deferred request packets in the
|
|
// queue, instead we resly on the cache to provide the packets
|
|
// from the MSHR queue or write queue
|
|
assert(deferredPacketReadyTime() == MaxTick);
|
|
|
|
// check for request packets (requests & writebacks)
|
|
QueueEntry* entry = cache.getNextQueueEntry();
|
|
|
|
if (!entry) {
|
|
// can happen if e.g. we attempt a writeback and fail, but
|
|
// before the retry, the writeback is eliminated because
|
|
// we snoop another cache's ReadEx.
|
|
} else {
|
|
// let our snoop responses go first if there are responses to
|
|
// the same addresses
|
|
if (checkConflictingSnoop(entry->blkAddr)) {
|
|
return;
|
|
}
|
|
waitingOnRetry = entry->sendPacket(cache);
|
|
}
|
|
|
|
// if we succeeded and are not waiting for a retry, schedule the
|
|
// next send considering when the next queue is ready, note that
|
|
// snoop responses have their own packet queue and thus schedule
|
|
// their own events
|
|
if (!waitingOnRetry) {
|
|
schedSendEvent(cache.nextQueueReadyTime());
|
|
}
|
|
}
|
|
|
|
Cache::
|
|
MemSidePort::MemSidePort(const std::string &_name, Cache *_cache,
|
|
const std::string &_label)
|
|
: BaseCache::CacheMasterPort(_name, _cache, _reqQueue, _snoopRespQueue),
|
|
_reqQueue(*_cache, *this, _snoopRespQueue, _label),
|
|
_snoopRespQueue(*_cache, *this, _label), cache(_cache)
|
|
{
|
|
}
|