/*
* Copyright (c) 2012 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 <algorithm>
#include <cassert>
#include <string>
#include <vector>
#include "base/misc.hh"
#include "base/types.hh"
#include "debug/Cache.hh"
#include "mem/cache/cache.hh"
#include "mem/cache/mshr.hh"
#include "sim/core.hh"
using namespace std;
MSHR::MSHR() : readyTime(0), _isUncacheable(false), downstreamPending(false),
pendingDirty(false), postInvalidate(false),
postDowngrade(false), queue(NULL), order(0), addr(0), size(0),
inService(false), isForward(false), threadNum(InvalidThreadID),
data(NULL)
{
}
MSHR::TargetList::TargetList()
: needsExclusive(false), hasUpgrade(false)
{}
inline void
MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
Counter order, Target::Source source, bool markPending)
{
if (source != Target::FromSnoop) {
if (pkt->needsExclusive()) {
needsExclusive = 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;
}
}
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<MSHR>();
if (mshr != NULL) {
assert(!mshr->downstreamPending);
mshr->downstreamPending = true;
}
}
push_back(Target(pkt, readyTime, order, source, markPending));
}
static void
replaceUpgrade(PacketPtr pkt)
{
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");
}
}
void
MSHR::TargetList::replaceUpgrades()
{
if (!hasUpgrade)
return;
Iterator end_i = end();
for (Iterator i = begin(); i != end_i; ++i) {
replaceUpgrade(i->pkt);
}
hasUpgrade = false;
}
void
MSHR::TargetList::clearDownstreamPending()
{
Iterator end_i = end();
for (Iterator i = begin(); i != end_i; ++i) {
if (i->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 = i->pkt->findNextSenderState<MSHR>();
if (mshr != NULL) {
mshr->clearDownstreamPending();
}
}
}
}
bool
MSHR::TargetList::checkFunctional(PacketPtr pkt)
{
Iterator end_i = end();
for (Iterator i = begin(); i != end_i; ++i) {
if (pkt->checkFunctional(i->pkt)) {
return true;
}
}
return false;
}
void
MSHR::TargetList::
print(std::ostream &os, int verbosity, const std::string &prefix) const
{
ConstIterator end_i = end();
for (ConstIterator i = begin(); i != end_i; ++i) {
const char *s;
switch (i->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);
i->pkt->print(os, verbosity, "");
}
}
void
MSHR::allocate(Addr _addr, int _size, PacketPtr target,
Tick whenReady, Counter _order)
{
addr = _addr;
size = _size;
readyTime = whenReady;
order = _order;
assert(target);
isForward = false;
_isUncacheable = target->req->isUncacheable();
inService = false;
downstreamPending = false;
threadNum = 0;
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, whenReady, _order, source, true);
assert(deferredTargets.isReset());
data = NULL;
}
void
MSHR::clearDownstreamPending()
{
assert(downstreamPending);
downstreamPending = false;
// recursively clear flag on any MSHRs we will be forwarding
// responses to
targets.clearDownstreamPending();
}
bool
MSHR::markInService(PacketPtr pkt)
{
assert(!inService);
if (isForwardNoResponse()) {
// we just forwarded the request packet & don't expect a
// response, so get rid of it
assert(getNumTargets() == 1);
popTarget();
return true;
}
inService = true;
pendingDirty = (targets.needsExclusive ||
(!pkt->sharedAsserted() && pkt->memInhibitAsserted()));
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();
}
return false;
}
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)
{
// 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)
// - this target requires an exclusive block and either we're not
// getting an exclusive block back or we have already snooped
// another read request that will downgrade our exclusive block
// to shared
// assume we'd never issue a prefetch when we've got an
// outstanding miss
assert(pkt->cmd != MemCmd::HardPFReq);
if (inService &&
(!deferredTargets.empty() || hasPostInvalidate() ||
(pkt->needsExclusive() &&
(!isPendingDirty() || hasPostDowngrade() || isForward)))) {
// need to put on deferred list
if (hasPostInvalidate())
replaceUpgrade(pkt);
deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true);
} 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);
}
}
bool
MSHR::handleSnoop(PacketPtr pkt, Counter _order)
{
DPRINTF(Cache, "%s for %s address %x size %d\n", __func__,
pkt->cmdString(), pkt->getAddr(), pkt->getSize());
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->needsExclusive()) {
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->needsExclusive()) {
// snooped request still precedes the re-request we'll have to
// issue for deferred targets, if any...
deferredTargets.replaceUpgrades();
}
if (hasPostInvalidate()) {
// a prior snoop has already appended an invalidation, so
// logically we don't have the block anymore; no need for
// further snooping.
return true;
}
if (isPendingDirty() || pkt->isInvalidate()) {
// We need to save and replay the packet in two cases:
// 1. We're awaiting an exclusive copy, so ownership is pending,
// 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.
// Actual target device (typ. a memory) will delete the
// packet on reception, so we need to save a copy here.
PacketPtr cp_pkt = new Packet(pkt, true);
targets.add(cp_pkt, curTick(), _order, Target::FromSnoop,
downstreamPending && targets.needsExclusive);
if (isPendingDirty()) {
pkt->assertMemInhibit();
pkt->setSupplyExclusive();
}
if (pkt->needsExclusive()) {
// This transaction will take away our pending copy
postInvalidate = true;
}
}
if (!pkt->needsExclusive()) {
// This transaction will get a read-shared copy, downgrading
// our copy if we had an exclusive one
postDowngrade = true;
pkt->assertShared();
}
return true;
}
bool
MSHR::promoteDeferredTargets()
{
assert(targets.empty());
if (deferredTargets.empty()) {
return false;
}
// swap targets & deferredTargets lists
std::swap(targets, deferredTargets);
// clear deferredTargets flags
deferredTargets.resetFlags();
order = targets.front().order;
readyTime = std::max(curTick(), targets.front().readyTime);
return true;
}
void
MSHR::handleFill(Packet *pkt, CacheBlk *blk)
{
if (!pkt->sharedAsserted()
&& !(hasPostInvalidate() || hasPostDowngrade())
&& deferredTargets.needsExclusive) {
// We got an exclusive response, but we have deferred targets
// which are waiting to request an exclusive copy (not because
// of a pending invalidate). This can happen if the original
// request was for a read-only (non-exclusive) block, but we
// got an exclusive copy anyway because of the E part of the
// MOESI/MESI protocol. Since we got the exclusive copy
// there's no need to defer the targets, so move them up to
// the regular target list.
assert(!targets.needsExclusive);
targets.needsExclusive = 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, addr, size, NULL);
return false;
} else {
return (targets.checkFunctional(pkt) ||
deferredTargets.checkFunctional(pkt));
}
}
void
MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const
{
ccprintf(os, "%s[%x:%x] %s %s %s state: %s %s %s %s %s\n",
prefix, addr, addr+size-1,
isForward ? "Forward" : "",
isForwardNoResponse() ? "ForwNoResp" : "",
needsExclusive() ? "Excl" : "",
_isUncacheable ? "Unc" : "",
inService ? "InSvc" : "",
downstreamPending ? "DwnPend" : "",
hasPostInvalidate() ? "PostInv" : "",
hasPostDowngrade() ? "PostDowngr" : "");
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
{
ostringstream str;
print(str);
return str.str();
}