/* * Copyright (c) 2012-2013, 2015-2018 ARM Limited * All rights reserved. * * The license below extends only to copyright in the software and shall * not be construed as granting a license to any other intellectual * property including but not limited to intellectual property relating * to a hardware implementation of the functionality of the software * licensed hereunder. You may use the software subject to the license * terms below provided that you ensure that this notice is replicated * unmodified and in its entirety in all distributions of the software, * modified or unmodified, in source code or in binary form. * * Copyright (c) 2002-2005 The Regents of The University of Michigan * Copyright (c) 2010 Advanced Micro Devices, Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer; * redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution; * neither the name of the copyright holders nor the names of its * contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * Authors: Erik Hallnor * Dave Greene */ /** * @file * Miss Status and Handling Register (MSHR) definitions. */ #include "mem/cache/mshr.hh" #include #include #include #include #include "base/logging.hh" #include "base/types.hh" #include "debug/Cache.hh" #include "mem/cache/cache.hh" #include "sim/core.hh" MSHR::MSHR() : downstreamPending(false), pendingModified(false), postInvalidate(false), postDowngrade(false), isForward(false) { } MSHR::TargetList::TargetList() : needsWritable(false), hasUpgrade(false), allocOnFill(false), hasFromCache(false) {} void MSHR::TargetList::updateFlags(PacketPtr pkt, Target::Source source, bool alloc_on_fill) { if (source != Target::FromSnoop) { if (pkt->needsWritable()) { needsWritable = true; } // StoreCondReq is effectively an upgrade if it's in an MSHR // since it would have been failed already if we didn't have a // read-only copy if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) { hasUpgrade = true; } // potentially re-evaluate whether we should allocate on a fill or // not allocOnFill = allocOnFill || alloc_on_fill; if (source != Target::FromPrefetcher) { hasFromCache = hasFromCache || pkt->fromCache(); } } } void MSHR::TargetList::populateFlags() { resetFlags(); for (auto& t: *this) { updateFlags(t.pkt, t.source, t.allocOnFill); } } inline void MSHR::TargetList::add(PacketPtr pkt, Tick readyTime, Counter order, Target::Source source, bool markPending, bool alloc_on_fill) { updateFlags(pkt, source, alloc_on_fill); if (markPending) { // Iterate over the SenderState stack and see if we find // an MSHR entry. If we do, set the downstreamPending // flag. Otherwise, do nothing. MSHR *mshr = pkt->findNextSenderState(); if (mshr != nullptr) { assert(!mshr->downstreamPending); mshr->downstreamPending = true; } else { // No need to clear downstreamPending later markPending = false; } } emplace_back(pkt, readyTime, order, source, markPending, alloc_on_fill); } static void replaceUpgrade(PacketPtr pkt) { // remember if the current packet has data allocated bool has_data = pkt->hasData() || pkt->hasRespData(); if (pkt->cmd == MemCmd::UpgradeReq) { pkt->cmd = MemCmd::ReadExReq; DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n"); } else if (pkt->cmd == MemCmd::SCUpgradeReq) { pkt->cmd = MemCmd::SCUpgradeFailReq; DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n"); } else if (pkt->cmd == MemCmd::StoreCondReq) { pkt->cmd = MemCmd::StoreCondFailReq; DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n"); } if (!has_data) { // there is no sensible way of setting the data field if the // new command actually would carry data assert(!pkt->hasData()); if (pkt->hasRespData()) { // we went from a packet that had no data (neither request, // nor response), to one that does, and therefore we need to // actually allocate space for the data payload pkt->allocate(); } } } void MSHR::TargetList::replaceUpgrades() { if (!hasUpgrade) return; for (auto& t : *this) { replaceUpgrade(t.pkt); } hasUpgrade = false; } void MSHR::TargetList::clearDownstreamPending() { for (auto& t : *this) { if (t.markedPending) { // Iterate over the SenderState stack and see if we find // an MSHR entry. If we find one, clear the // downstreamPending flag by calling // clearDownstreamPending(). This recursively clears the // downstreamPending flag in all caches this packet has // passed through. MSHR *mshr = t.pkt->findNextSenderState(); if (mshr != nullptr) { mshr->clearDownstreamPending(); } t.markedPending = false; } } } bool MSHR::TargetList::checkFunctional(PacketPtr pkt) { for (auto& t : *this) { if (pkt->checkFunctional(t.pkt)) { return true; } } return false; } void MSHR::TargetList::print(std::ostream &os, int verbosity, const std::string &prefix) const { for (auto& t : *this) { const char *s; switch (t.source) { case Target::FromCPU: s = "FromCPU"; break; case Target::FromSnoop: s = "FromSnoop"; break; case Target::FromPrefetcher: s = "FromPrefetcher"; break; default: s = ""; break; } ccprintf(os, "%s%s: ", prefix, s); t.pkt->print(os, verbosity, ""); ccprintf(os, "\n"); } } void MSHR::allocate(Addr blk_addr, unsigned blk_size, PacketPtr target, Tick when_ready, Counter _order, bool alloc_on_fill) { blkAddr = blk_addr; blkSize = blk_size; isSecure = target->isSecure(); readyTime = when_ready; order = _order; assert(target); isForward = false; _isUncacheable = target->req->isUncacheable(); inService = false; downstreamPending = false; assert(targets.isReset()); // Don't know of a case where we would allocate a new MSHR for a // snoop (mem-side request), so set source according to request here Target::Source source = (target->cmd == MemCmd::HardPFReq) ? Target::FromPrefetcher : Target::FromCPU; targets.add(target, when_ready, _order, source, true, alloc_on_fill); assert(deferredTargets.isReset()); } void MSHR::clearDownstreamPending() { assert(downstreamPending); downstreamPending = false; // recursively clear flag on any MSHRs we will be forwarding // responses to targets.clearDownstreamPending(); } void MSHR::markInService(bool pending_modified_resp) { assert(!inService); inService = true; pendingModified = targets.needsWritable || pending_modified_resp; postInvalidate = postDowngrade = false; if (!downstreamPending) { // let upstream caches know that the request has made it to a // level where it's going to get a response targets.clearDownstreamPending(); } } void MSHR::deallocate() { assert(targets.empty()); targets.resetFlags(); assert(deferredTargets.isReset()); inService = false; } /* * Adds a target to an MSHR */ void MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order, bool alloc_on_fill) { // assume we'd never issue a prefetch when we've got an // outstanding miss assert(pkt->cmd != MemCmd::HardPFReq); // uncacheable accesses always allocate a new MSHR, and cacheable // accesses ignore any uncacheable MSHRs, thus we should never // have targets addded if originally allocated uncacheable assert(!_isUncacheable); // if there's a request already in service for this MSHR, we will // have to defer the new target until after the response if any of // the following are true: // - there are other targets already deferred // - there's a pending invalidate to be applied after the response // comes back (but before this target is processed) // - the MSHR's first (and only) non-deferred target is a cache // maintenance packet // - the new target is a cache maintenance packet (this is probably // overly conservative but certainly safe) // - this target requires a writable block and either we're not // getting a writable block back or we have already snooped // another read request that will downgrade our writable block // to non-writable (Shared or Owned) PacketPtr tgt_pkt = targets.front().pkt; if (pkt->req->isCacheMaintenance() || tgt_pkt->req->isCacheMaintenance() || !deferredTargets.empty() || (inService && (hasPostInvalidate() || (pkt->needsWritable() && (!isPendingModified() || hasPostDowngrade() || isForward))))) { // need to put on deferred list if (inService && hasPostInvalidate()) replaceUpgrade(pkt); deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true, alloc_on_fill); } else { // No request outstanding, or still OK to append to // outstanding request: append to regular target list. Only // mark pending if current request hasn't been issued yet // (isn't in service). targets.add(pkt, whenReady, _order, Target::FromCPU, !inService, alloc_on_fill); } } bool MSHR::handleSnoop(PacketPtr pkt, Counter _order) { DPRINTF(Cache, "%s for %s\n", __func__, pkt->print()); // when we snoop packets the needsWritable and isInvalidate flags // should always be the same, however, this assumes that we never // snoop writes as they are currently not marked as invalidations panic_if((pkt->needsWritable() != pkt->isInvalidate()) && !pkt->req->isCacheMaintenance(), "%s got snoop %s where needsWritable, " "does not match isInvalidate", name(), pkt->print()); if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { // Request has not been issued yet, or it's been issued // locally but is buffered unissued at some downstream cache // which is forwarding us this snoop. Either way, the packet // we're snooping logically precedes this MSHR's request, so // the snoop has no impact on the MSHR, but must be processed // in the standard way by the cache. The only exception is // that if we're an L2+ cache buffering an UpgradeReq from a // higher-level cache, and the snoop is invalidating, then our // buffered upgrades must be converted to read exclusives, // since the upper-level cache no longer has a valid copy. // That is, even though the upper-level cache got out on its // local bus first, some other invalidating transaction // reached the global bus before the upgrade did. if (pkt->needsWritable() || pkt->req->isCacheInvalidate()) { targets.replaceUpgrades(); deferredTargets.replaceUpgrades(); } return false; } // From here on down, the request issued by this MSHR logically // precedes the request we're snooping. if (pkt->needsWritable() || pkt->req->isCacheInvalidate()) { // snooped request still precedes the re-request we'll have to // issue for deferred targets, if any... deferredTargets.replaceUpgrades(); } PacketPtr tgt_pkt = targets.front().pkt; if (hasPostInvalidate() || tgt_pkt->req->isCacheInvalidate()) { // a prior snoop has already appended an invalidation or a // cache invalidation operation is in progress, so logically // we don't have the block anymore; no need for further // snooping. return true; } if (isPendingModified() || pkt->isInvalidate()) { // We need to save and replay the packet in two cases: // 1. We're awaiting a writable copy (Modified or Exclusive), // so this MSHR is the orgering point, and we need to respond // after we receive data. // 2. It's an invalidation (e.g., UpgradeReq), and we need // to forward the snoop up the hierarchy after the current // transaction completes. // Start by determining if we will eventually respond or not, // matching the conditions checked in Cache::handleSnoop bool will_respond = isPendingModified() && pkt->needsResponse() && !pkt->isClean(); // The packet we are snooping may be deleted by the time we // actually process the target, and we consequently need to // save a copy here. Clear flags and also allocate new data as // the original packet data storage may have been deleted by // the time we get to process this packet. In the cases where // we are not responding after handling the snoop we also need // to create a copy of the request to be on the safe side. In // the latter case the cache is responsible for deleting both // the packet and the request as part of handling the deferred // snoop. PacketPtr cp_pkt = will_respond ? new Packet(pkt, true, true) : new Packet(new Request(*pkt->req), pkt->cmd, blkSize, pkt->id); if (will_respond) { // we are the ordering point, and will consequently // respond, and depending on whether the packet // needsWritable or not we either pass a Shared line or a // Modified line pkt->setCacheResponding(); // inform the cache hierarchy that this cache had the line // in the Modified state, even if the response is passed // as Shared (and thus non-writable) pkt->setResponderHadWritable(); // in the case of an uncacheable request there is no need // to set the responderHadWritable flag, but since the // recipient does not care there is no harm in doing so } targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, downstreamPending && targets.needsWritable, false); if (pkt->needsWritable() || pkt->isInvalidate()) { // This transaction will take away our pending copy postInvalidate = true; } if (isPendingModified() && pkt->isClean()) { pkt->setSatisfied(); } } if (!pkt->needsWritable() && !pkt->req->isUncacheable()) { // This transaction will get a read-shared copy, downgrading // our copy if we had a writable one postDowngrade = true; // make sure that any downstream cache does not respond with a // writable (and dirty) copy even if it has one, unless it was // explicitly asked for one pkt->setHasSharers(); } return true; } MSHR::TargetList MSHR::extractServiceableTargets(PacketPtr pkt) { TargetList ready_targets; // If the downstream MSHR got an invalidation request then we only // service the first of the FromCPU targets and any other // non-FromCPU target. This way the remaining FromCPU targets // issue a new request and get a fresh copy of the block and we // avoid memory consistency violations. if (pkt->cmd == MemCmd::ReadRespWithInvalidate) { auto it = targets.begin(); assert((it->source == Target::FromCPU) || (it->source == Target::FromPrefetcher)); ready_targets.push_back(*it); it = targets.erase(it); while (it != targets.end()) { if (it->source == Target::FromCPU) { it++; } else { assert(it->source == Target::FromSnoop); ready_targets.push_back(*it); it = targets.erase(it); } } ready_targets.populateFlags(); } else { std::swap(ready_targets, targets); } targets.populateFlags(); return ready_targets; } bool MSHR::promoteDeferredTargets() { if (targets.empty() && deferredTargets.empty()) { // nothing to promote return false; } // the deferred targets can be generally promoted unless they // contain a cache maintenance request // find the first target that is a cache maintenance request auto it = std::find_if(deferredTargets.begin(), deferredTargets.end(), [](MSHR::Target &t) { return t.pkt->req->isCacheMaintenance(); }); if (it == deferredTargets.begin()) { // if the first deferred target is a cache maintenance packet // then we can promote provided the targets list is empty and // we can service it on its own if (targets.empty()) { targets.splice(targets.end(), deferredTargets, it); } } else { // if a cache maintenance operation exists, we promote all the // deferred targets that precede it, or all deferred targets // otherwise targets.splice(targets.end(), deferredTargets, deferredTargets.begin(), it); } deferredTargets.populateFlags(); targets.populateFlags(); order = targets.front().order; readyTime = std::max(curTick(), targets.front().readyTime); return true; } void MSHR::promoteWritable() { if (deferredTargets.needsWritable && !(hasPostInvalidate() || hasPostDowngrade())) { // We got a writable response, but we have deferred targets // which are waiting to request a writable copy (not because // of a pending invalidate). This can happen if the original // request was for a read-only block, but we got a writable // response anyway. Since we got the writable copy there's no // need to defer the targets, so move them up to the regular // target list. assert(!targets.needsWritable); targets.needsWritable = true; // if any of the deferred targets were upper-level cache // requests marked downstreamPending, need to clear that assert(!downstreamPending); // not pending here anymore deferredTargets.clearDownstreamPending(); // this clears out deferredTargets too targets.splice(targets.end(), deferredTargets); deferredTargets.resetFlags(); } } bool MSHR::checkFunctional(PacketPtr pkt) { // For printing, we treat the MSHR as a whole as single entity. // For other requests, we iterate over the individual targets // since that's where the actual data lies. if (pkt->isPrint()) { pkt->checkFunctional(this, blkAddr, isSecure, blkSize, nullptr); return false; } else { return (targets.checkFunctional(pkt) || deferredTargets.checkFunctional(pkt)); } } bool MSHR::sendPacket(BaseCache &cache) { return cache.sendMSHRQueuePacket(this); } void MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const { ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s %s\n", prefix, blkAddr, blkAddr + blkSize - 1, isSecure ? "s" : "ns", isForward ? "Forward" : "", allocOnFill() ? "AllocOnFill" : "", needsWritable() ? "Wrtbl" : "", _isUncacheable ? "Unc" : "", inService ? "InSvc" : "", downstreamPending ? "DwnPend" : "", postInvalidate ? "PostInv" : "", postDowngrade ? "PostDowngr" : "", hasFromCache() ? "HasFromCache" : ""); if (!targets.empty()) { ccprintf(os, "%s Targets:\n", prefix); targets.print(os, verbosity, prefix + " "); } if (!deferredTargets.empty()) { ccprintf(os, "%s Deferred Targets:\n", prefix); deferredTargets.print(os, verbosity, prefix + " "); } } std::string MSHR::print() const { std::ostringstream str; print(str); return str.str(); }