/*
* Copyright (c) 2012-2016 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
* 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
* Steve Reinhardt
* Ron Dreslinski
* Andreas Hansson
*/
/**
* @file
* Describes a cache based on template policies.
*/
#ifndef __MEM_CACHE_CACHE_HH__
#define __MEM_CACHE_CACHE_HH__
#include <unordered_set>
#include "base/misc.hh" // fatal, panic, and warn
#include "enums/Clusivity.hh"
#include "mem/cache/base.hh"
#include "mem/cache/blk.hh"
#include "mem/cache/mshr.hh"
#include "mem/cache/tags/base.hh"
#include "params/Cache.hh"
#include "sim/eventq.hh"
//Forward decleration
class BasePrefetcher;
/**
* A template-policy based cache. The behavior of the cache can be altered by
* supplying different template policies. TagStore handles all tag and data
* storage @sa TagStore, \ref gem5MemorySystem "gem5 Memory System"
*/
class Cache : public BaseCache
{
protected:
/**
* The CPU-side port extends the base cache slave port with access
* functions for functional, atomic and timing requests.
*/
class CpuSidePort : public CacheSlavePort
{
private:
// a pointer to our specific cache implementation
Cache *cache;
protected:
virtual bool recvTimingSnoopResp(PacketPtr pkt);
virtual bool recvTimingReq(PacketPtr pkt);
virtual Tick recvAtomic(PacketPtr pkt);
virtual void recvFunctional(PacketPtr pkt);
virtual AddrRangeList getAddrRanges() const;
public:
CpuSidePort(const std::string &_name, Cache *_cache,
const std::string &_label);
};
/**
* Override the default behaviour of sendDeferredPacket to enable
* the memory-side cache port to also send requests based on the
* current MSHR status. This queue has a pointer to our specific
* cache implementation and is used by the MemSidePort.
*/
class CacheReqPacketQueue : public ReqPacketQueue
{
protected:
Cache &cache;
SnoopRespPacketQueue &snoopRespQueue;
public:
CacheReqPacketQueue(Cache &cache, MasterPort &port,
SnoopRespPacketQueue &snoop_resp_queue,
const std::string &label) :
ReqPacketQueue(cache, port, label), cache(cache),
snoopRespQueue(snoop_resp_queue) { }
/**
* Override the normal sendDeferredPacket and do not only
* consider the transmit list (used for responses), but also
* requests.
*/
virtual void sendDeferredPacket();
/**
* Check if there is a conflicting snoop response about to be
* send out, and if so simply stall any requests, and schedule
* a send event at the same time as the next snoop response is
* being sent out.
*/
bool checkConflictingSnoop(Addr addr)
{
if (snoopRespQueue.hasAddr(addr)) {
DPRINTF(CachePort, "Waiting for snoop response to be "
"sent\n");
Tick when = snoopRespQueue.deferredPacketReadyTime();
schedSendEvent(when);
return true;
}
return false;
}
};
/**
* The memory-side port extends the base cache master port with
* access functions for functional, atomic and timing snoops.
*/
class MemSidePort : public CacheMasterPort
{
private:
/** The cache-specific queue. */
CacheReqPacketQueue _reqQueue;
SnoopRespPacketQueue _snoopRespQueue;
// a pointer to our specific cache implementation
Cache *cache;
protected:
virtual void recvTimingSnoopReq(PacketPtr pkt);
virtual bool recvTimingResp(PacketPtr pkt);
virtual Tick recvAtomicSnoop(PacketPtr pkt);
virtual void recvFunctionalSnoop(PacketPtr pkt);
public:
MemSidePort(const std::string &_name, Cache *_cache,
const std::string &_label);
};
/** Tag and data Storage */
BaseTags *tags;
/** Prefetcher */
BasePrefetcher *prefetcher;
/** Temporary cache block for occasional transitory use */
CacheBlk *tempBlock;
/**
* This cache should allocate a block on a line-sized write miss.
*/
const bool doFastWrites;
/**
* Turn line-sized writes into WriteInvalidate transactions.
*/
void promoteWholeLineWrites(PacketPtr pkt);
/**
* Notify the prefetcher on every access, not just misses.
*/
const bool prefetchOnAccess;
/**
* Clusivity with respect to the upstream cache, determining if we
* fill into both this cache and the cache above on a miss. Note
* that we currently do not support strict clusivity policies.
*/
const Enums::Clusivity clusivity;
/**
* Determine if clean lines should be written back or not. In
* cases where a downstream cache is mostly inclusive we likely
* want it to act as a victim cache also for lines that have not
* been modified. Hence, we cannot simply drop the line (or send a
* clean evict), but rather need to send the actual data.
*/
const bool writebackClean;
/**
* Upstream caches need this packet until true is returned, so
* hold it for deletion until a subsequent call
*/
std::unique_ptr<Packet> pendingDelete;
/**
* Writebacks from the tempBlock, resulting on the response path
* in atomic mode, must happen after the call to recvAtomic has
* finished (for the right ordering of the packets). We therefore
* need to hold on to the packets, and have a method and an event
* to send them.
*/
PacketPtr tempBlockWriteback;
/**
* Send the outstanding tempBlock writeback. To be called after
* recvAtomic finishes in cases where the block we filled is in
* fact the tempBlock, and now needs to be written back.
*/
void writebackTempBlockAtomic() {
assert(tempBlockWriteback != nullptr);
PacketList writebacks{tempBlockWriteback};
doWritebacksAtomic(writebacks);
tempBlockWriteback = nullptr;
}
/**
* An event to writeback the tempBlock after recvAtomic
* finishes. To avoid other calls to recvAtomic getting in
* between, we create this event with a higher priority.
*/
EventWrapper<Cache, &Cache::writebackTempBlockAtomic> \
writebackTempBlockAtomicEvent;
/**
* Store the outstanding requests that we are expecting snoop
* responses from so we can determine which snoop responses we
* generated and which ones were merely forwarded.
*/
std::unordered_set<RequestPtr> outstandingSnoop;
/**
* Does all the processing necessary to perform the provided request.
* @param pkt The memory request to perform.
* @param blk The cache block to be updated.
* @param lat The latency of the access.
* @param writebacks List for any writebacks that need to be performed.
* @return Boolean indicating whether the request was satisfied.
*/
bool access(PacketPtr pkt, CacheBlk *&blk,
Cycles &lat, PacketList &writebacks);
/**
*Handle doing the Compare and Swap function for SPARC.
*/
void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
/**
* Find a block frame for new block at address addr targeting the
* given security space, assuming that the block is not currently
* in the cache. Append writebacks if any to provided packet
* list. Return free block frame. May return nullptr if there are
* no replaceable blocks at the moment.
*/
CacheBlk *allocateBlock(Addr addr, bool is_secure, PacketList &writebacks);
/**
* Invalidate a cache block.
*
* @param blk Block to invalidate
*/
void invalidateBlock(CacheBlk *blk);
/**
* Maintain the clusivity of this cache by potentially
* invalidating a block. This method works in conjunction with
* satisfyRequest, but is separate to allow us to handle all MSHR
* targets before potentially dropping a block.
*
* @param from_cache Whether we have dealt with a packet from a cache
* @param blk The block that should potentially be dropped
*/
void maintainClusivity(bool from_cache, CacheBlk *blk);
/**
* Populates a cache block and handles all outstanding requests for the
* satisfied fill request. This version takes two memory requests. One
* contains the fill data, the other is an optional target to satisfy.
* @param pkt The memory request with the fill data.
* @param blk The cache block if it already exists.
* @param writebacks List for any writebacks that need to be performed.
* @param allocate Whether to allocate a block or use the temp block
* @return Pointer to the new cache block.
*/
CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
PacketList &writebacks, bool allocate);
/**
* Determine whether we should allocate on a fill or not. If this
* cache is mostly inclusive with regards to the upstream cache(s)
* we always allocate (for any non-forwarded and cacheable
* requests). In the case of a mostly exclusive cache, we allocate
* on fill if the packet did not come from a cache, thus if we:
* are dealing with a whole-line write (the latter behaves much
* like a writeback), the original target packet came from a
* non-caching source, or if we are performing a prefetch or LLSC.
*
* @param cmd Command of the incoming requesting packet
* @return Whether we should allocate on the fill
*/
inline bool allocOnFill(MemCmd cmd) const override
{
return clusivity == Enums::mostly_incl ||
cmd == MemCmd::WriteLineReq ||
cmd == MemCmd::ReadReq ||
cmd == MemCmd::WriteReq ||
cmd.isPrefetch() ||
cmd.isLLSC();
}
/**
* Performs the access specified by the request.
* @param pkt The request to perform.
* @return The result of the access.
*/
bool recvTimingReq(PacketPtr pkt);
/**
* Insert writebacks into the write buffer
*/
void doWritebacks(PacketList& writebacks, Tick forward_time);
/**
* Send writebacks down the memory hierarchy in atomic mode
*/
void doWritebacksAtomic(PacketList& writebacks);
/**
* Handling the special case of uncacheable write responses to
* make recvTimingResp less cluttered.
*/
void handleUncacheableWriteResp(PacketPtr pkt);
/**
* Handles a response (cache line fill/write ack) from the bus.
* @param pkt The response packet
*/
void recvTimingResp(PacketPtr pkt);
/**
* Snoops bus transactions to maintain coherence.
* @param pkt The current bus transaction.
*/
void recvTimingSnoopReq(PacketPtr pkt);
/**
* Handle a snoop response.
* @param pkt Snoop response packet
*/
void recvTimingSnoopResp(PacketPtr pkt);
/**
* Performs the access specified by the request.
* @param pkt The request to perform.
* @return The number of ticks required for the access.
*/
Tick recvAtomic(PacketPtr pkt);
/**
* Snoop for the provided request in the cache and return the estimated
* time taken.
* @param pkt The memory request to snoop
* @return The number of ticks required for the snoop.
*/
Tick recvAtomicSnoop(PacketPtr pkt);
/**
* Performs the access specified by the request.
* @param pkt The request to perform.
* @param fromCpuSide from the CPU side port or the memory side port
*/
void functionalAccess(PacketPtr pkt, bool fromCpuSide);
/**
* Perform any necessary updates to the block and perform any data
* exchange between the packet and the block. The flags of the
* packet are also set accordingly.
*
* @param pkt Request packet from upstream that hit a block
* @param blk Cache block that the packet hit
* @param deferred_response Whether this hit is to block that
* originally missed
* @param pending_downgrade Whether the writable flag is to be removed
*
* @return True if the block is to be invalidated
*/
void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
bool deferred_response = false,
bool pending_downgrade = false);
void doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
bool already_copied, bool pending_inval);
/**
* Perform an upward snoop if needed, and update the block state
* (possibly invalidating the block). Also create a response if required.
*
* @param pkt Snoop packet
* @param blk Cache block being snooped
* @param is_timing Timing or atomic for the response
* @param is_deferred Is this a deferred snoop or not?
* @param pending_inval Do we have a pending invalidation?
*
* @return The snoop delay incurred by the upwards snoop
*/
uint32_t handleSnoop(PacketPtr pkt, CacheBlk *blk,
bool is_timing, bool is_deferred, bool pending_inval);
/**
* Create a writeback request for the given block.
* @param blk The block to writeback.
* @return The writeback request for the block.
*/
PacketPtr writebackBlk(CacheBlk *blk);
/**
* Create a CleanEvict request for the given block.
* @param blk The block to evict.
* @return The CleanEvict request for the block.
*/
PacketPtr cleanEvictBlk(CacheBlk *blk);
void memWriteback() override;
void memInvalidate() override;
bool isDirty() const override;
/**
* Cache block visitor that writes back dirty cache blocks using
* functional writes.
*
* \return Always returns true.
*/
bool writebackVisitor(CacheBlk &blk);
/**
* Cache block visitor that invalidates all blocks in the cache.
*
* @warn Dirty cache lines will not be written back to memory.
*
* \return Always returns true.
*/
bool invalidateVisitor(CacheBlk &blk);
/**
* Create an appropriate downstream bus request packet for the
* given parameters.
* @param cpu_pkt The miss that needs to be satisfied.
* @param blk The block currently in the cache corresponding to
* cpu_pkt (nullptr if none).
* @param needsWritable Indicates that the block must be writable
* even if the request in cpu_pkt doesn't indicate that.
* @return A new Packet containing the request, or nullptr if the
* current request in cpu_pkt should just be forwarded on.
*/
PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
bool needsWritable) const;
/**
* Return the next queue entry to service, either a pending miss
* from the MSHR queue, a buffered write from the write buffer, or
* something from the prefetcher. This function is responsible
* for prioritizing among those sources on the fly.
*/
QueueEntry* getNextQueueEntry();
/**
* Send up a snoop request and find cached copies. If cached copies are
* found, set the BLOCK_CACHED flag in pkt.
*/
bool isCachedAbove(PacketPtr pkt, bool is_timing = true) const;
/**
* Return whether there are any outstanding misses.
*/
bool outstandingMisses() const
{
return !mshrQueue.isEmpty();
}
CacheBlk *findBlock(Addr addr, bool is_secure) const {
return tags->findBlock(addr, is_secure);
}
bool inCache(Addr addr, bool is_secure) const override {
return (tags->findBlock(addr, is_secure) != 0);
}
bool inMissQueue(Addr addr, bool is_secure) const override {
return (mshrQueue.findMatch(addr, is_secure) != 0);
}
/**
* Find next request ready time from among possible sources.
*/
Tick nextQueueReadyTime() const;
public:
/** Instantiates a basic cache object. */
Cache(const CacheParams *p);
/** Non-default destructor is needed to deallocate memory. */
virtual ~Cache();
void regStats() override;
/**
* Take an MSHR, turn it into a suitable downstream packet, and
* send it out. This construct allows a queue entry to choose a suitable
* approach based on its type.
*
* @param mshr The MSHR to turn into a packet and send
* @return True if the port is waiting for a retry
*/
bool sendMSHRQueuePacket(MSHR* mshr);
/**
* Similar to sendMSHR, but for a write-queue entry
* instead. Create the packet, and send it, and if successful also
* mark the entry in service.
*
* @param wq_entry The write-queue entry to turn into a packet and send
* @return True if the port is waiting for a retry
*/
bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
/** serialize the state of the caches
* We currently don't support checkpointing cache state, so this panics.
*/
void serialize(CheckpointOut &cp) const override;
void unserialize(CheckpointIn &cp) override;
};
/**
* Wrap a method and present it as a cache block visitor.
*
* For example the forEachBlk method in the tag arrays expects a
* callable object/function as their parameter. This class wraps a
* method in an object and presents callable object that adheres to
* the cache block visitor protocol.
*/
class CacheBlkVisitorWrapper : public CacheBlkVisitor
{
public:
typedef bool (Cache::*VisitorPtr)(CacheBlk &blk);
CacheBlkVisitorWrapper(Cache &_cache, VisitorPtr _visitor)
: cache(_cache), visitor(_visitor) {}
bool operator()(CacheBlk &blk) override {
return (cache.*visitor)(blk);
}
private:
Cache &cache;
VisitorPtr visitor;
};
/**
* Cache block visitor that determines if there are dirty blocks in a
* cache.
*
* Use with the forEachBlk method in the tag array to determine if the
* array contains dirty blocks.
*/
class CacheBlkIsDirtyVisitor : public CacheBlkVisitor
{
public:
CacheBlkIsDirtyVisitor()
: _isDirty(false) {}
bool operator()(CacheBlk &blk) override {
if (blk.isDirty()) {
_isDirty = true;
return false;
} else {
return true;
}
}
/**
* Does the array contain a dirty line?
*
* \return true if yes, false otherwise.
*/
bool isDirty() const { return _isDirty; };
private:
bool _isDirty;
};
#endif // __MEM_CACHE_CACHE_HH__