Files
gem5/src/cpu/simple/base.hh
Tuan Ta 25dc765889 cpu: support atomic memory request type with AtomicOpFunctor
This patch enables all 4 CPU models (AtomicSimpleCPU, TimingSimpleCPU,
MinorCPU and DerivO3CPU) to issue atomic memory (AMO) requests to memory
system.

Atomic memory instruction is treated as a special store instruction in
all CPU models.

In simple CPUs, an AMO request with an associated AtomicOpFunctor is
simply sent to L1 dcache.

In MinorCPU, an AMO request bypasses store buffer and waits for any
conflicting store request(s) currently in the store buffer to retire
before the AMO request is sent to the cache. AMO requests are not buffered
in the store buffer, so their effects appear immediately in the cache.

In DerivO3CPU, an AMO request is inserted in the store buffer so that it
is delivered to the cache only after all previous stores are issued to
the cache. Data forwarding between between an outstanding AMO in the
store buffer and a subsequent load is not allowed since the AMO request
does not hold valid data until it's executed in the cache.

This implementation assumes that a target ISA implementation must insert
enough memory fences as micro-ops around an atomic instruction to
enforce a correct order of memory instructions with respect to its
memory consistency model. Without extra memory fences, this implementation
can allow AMOs and other memory instructions that do not conflict
(i.e., not target the same address) to reorder.

This implementation also assumes that atomic instructions execute within
a cache line boundary since the cache for now is not able to execute an
operation on two different cache lines in one single step. Therefore,
ISAs like x86 that require multi-cache-line atomic instructions need to
either use a pair of locking load and unlocking store or change the
cache implementation to guarantee the atomicity of an atomic
instruction.

Change-Id: Ib8a7c81868ac05b98d73afc7d16eb88486f8cf9a
Reviewed-on: https://gem5-review.googlesource.com/c/8188
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
2019-02-08 15:27:04 +00:00

177 lines
5.5 KiB
C++

/*
* Copyright (c) 2011-2012,2015 ARM Limited
* Copyright (c) 2013 Advanced Micro Devices, Inc.
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* licensed hereunder. You may use the software subject to the license
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* 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
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* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
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* 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
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* 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
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Steve Reinhardt
* Dave Greene
* Nathan Binkert
*/
#ifndef __CPU_SIMPLE_BASE_HH__
#define __CPU_SIMPLE_BASE_HH__
#include "base/statistics.hh"
#include "config/the_isa.hh"
#include "cpu/base.hh"
#include "cpu/checker/cpu.hh"
#include "cpu/exec_context.hh"
#include "cpu/pc_event.hh"
#include "cpu/simple_thread.hh"
#include "cpu/static_inst.hh"
#include "mem/packet.hh"
#include "mem/port.hh"
#include "mem/request.hh"
#include "sim/eventq.hh"
#include "sim/full_system.hh"
#include "sim/system.hh"
// forward declarations
class Checkpoint;
class Process;
class Processor;
class ThreadContext;
namespace TheISA
{
class DTB;
class ITB;
}
namespace Trace {
class InstRecord;
}
struct BaseSimpleCPUParams;
class BPredUnit;
class SimpleExecContext;
class BaseSimpleCPU : public BaseCPU
{
protected:
ThreadID curThread;
BPredUnit *branchPred;
void checkPcEventQueue();
void swapActiveThread();
public:
BaseSimpleCPU(BaseSimpleCPUParams *params);
virtual ~BaseSimpleCPU();
void wakeup(ThreadID tid) override;
void init() override;
public:
Trace::InstRecord *traceData;
CheckerCPU *checker;
std::vector<SimpleExecContext*> threadInfo;
std::list<ThreadID> activeThreads;
/** Current instruction */
TheISA::MachInst inst;
StaticInstPtr curStaticInst;
StaticInstPtr curMacroStaticInst;
protected:
enum Status {
Idle,
Running,
Faulting,
ITBWaitResponse,
IcacheRetry,
IcacheWaitResponse,
IcacheWaitSwitch,
DTBWaitResponse,
DcacheRetry,
DcacheWaitResponse,
DcacheWaitSwitch,
};
Status _status;
public:
Addr dbg_vtophys(Addr addr);
void checkForInterrupts();
void setupFetchRequest(const RequestPtr &req);
void preExecute();
void postExecute();
void advancePC(const Fault &fault);
void haltContext(ThreadID thread_num) override;
// statistics
void regStats() override;
void resetStats() override;
void startup() override;
virtual Fault readMem(Addr addr, uint8_t* data, unsigned size,
Request::Flags flags)
{ panic("readMem() is not implemented\n"); }
virtual Fault initiateMemRead(Addr addr, unsigned size,
Request::Flags flags)
{ panic("initiateMemRead() is not implemented\n"); }
virtual Fault writeMem(uint8_t* data, unsigned size, Addr addr,
Request::Flags flags, uint64_t* res)
{ panic("writeMem() is not implemented\n"); }
virtual Fault amoMem(Addr addr, uint8_t* data, unsigned size,
Request::Flags flags,
AtomicOpFunctor *amo_op)
{ panic("amoMem() is not implemented\n"); }
virtual Fault initiateMemAMO(Addr addr, unsigned size,
Request::Flags flags,
AtomicOpFunctor *amo_op)
{ panic("initiateMemAMO() is not implemented\n"); }
void countInst();
Counter totalInsts() const override;
Counter totalOps() const override;
void serializeThread(CheckpointOut &cp, ThreadID tid) const override;
void unserializeThread(CheckpointIn &cp, ThreadID tid) override;
};
#endif // __CPU_SIMPLE_BASE_HH__