src/mem/cache/blk.hh - arm/gem5 - Git at Google

 /*
  * 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) 2003-2005 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
  *          Andreas Sandberg
  */

 /** @file
  * Definitions of a simple cache block class.
  */

 #ifndef __MEM_CACHE_BLK_HH__
 #define __MEM_CACHE_BLK_HH__

 #include <list>

 #include "base/printable.hh"
 #include "mem/packet.hh"
 #include "mem/request.hh"

 /**
  * Cache block status bit assignments
  */
 enum CacheBlkStatusBits : unsigned {
     /** valid, readable */
     BlkValid =          0x01,
     /** write permission */
     BlkWritable =       0x02,
     /** read permission (yes, block can be valid but not readable) */
     BlkReadable =       0x04,
     /** dirty (modified) */
     BlkDirty =          0x08,
     /** block was a hardware prefetch yet unaccessed*/
     BlkHWPrefetched =   0x20,
     /** block holds data from the secure memory space */
     BlkSecure =         0x40,
 };

 /**
  * A Basic Cache block.
  * Contains the tag, status, and a pointer to data.
  */
 class CacheBlk
 {
   public:
     /** Task Id associated with this block */
     uint32_t task_id;

     /** Data block tag value. */
     Addr tag;
     /**
      * Contains a copy of the data in this block for easy access. This is used
      * for efficient execution when the data could be actually stored in
      * another format (COW, compressed, sub-blocked, etc). In all cases the
      * data stored here should be kept consistant with the actual data
      * referenced by this block.
      */
     uint8_t *data;

     /** block state: OR of CacheBlkStatusBit */
     typedef unsigned State;

     /** The current status of this block. @sa CacheBlockStatusBits */
     State status;

     /** Which curTick() will this block be accessable */
     Tick whenReady;

     /**
      * The set and way this block belongs to.
      * @todo Move this into subclasses when we fix CacheTags to use them.
      */
     int set, way;

     /** whether this block has been touched */
     bool isTouched;

     /** Number of references to this block since it was brought in. */
     unsigned refCount;

     /** holds the source requestor ID for this block. */
     int srcMasterId;

     Tick tickInserted;

   protected:
     /**
      * Represents that the indicated thread context has a "lock" on
      * the block, in the LL/SC sense.
      */
     class Lock {
       public:
         ContextID contextId;     // locking context
         Addr lowAddr;      // low address of lock range
         Addr highAddr;     // high address of lock range

         // check for matching execution context, and an address that
         // is within the lock
         bool matches(const RequestPtr req) const
         {
             Addr req_low = req->getPaddr();
             Addr req_high = req_low + req->getSize() -1;
             return (contextId == req->contextId()) &&
                    (req_low >= lowAddr) && (req_high <= highAddr);
         }

         // check if a request is intersecting and thus invalidating the lock
         bool intersects(const RequestPtr req) const
         {
             Addr req_low = req->getPaddr();
             Addr req_high = req_low + req->getSize() - 1;

             return (req_low <= highAddr) && (req_high >= lowAddr);
         }

         Lock(const RequestPtr req)
             : contextId(req->contextId()),
               lowAddr(req->getPaddr()),
               highAddr(lowAddr + req->getSize() - 1)
         {
         }
     };

     /** List of thread contexts that have performed a load-locked (LL)
      * on the block since the last store. */
     std::list<Lock> lockList;

   public:

     CacheBlk()
         : task_id(ContextSwitchTaskId::Unknown),
           tag(0), data(0), status(0), whenReady(0),
           set(-1), way(-1), isTouched(false), refCount(0),
           srcMasterId(Request::invldMasterId),
           tickInserted(0)
     {}

     CacheBlk(const CacheBlk&) = delete;
     CacheBlk& operator=(const CacheBlk&) = delete;

     /**
      * Checks the write permissions of this block.
      * @return True if the block is writable.
      */
     bool isWritable() const
     {
         const State needed_bits = BlkWritable | BlkValid;
         return (status & needed_bits) == needed_bits;
     }

     /**
      * Checks the read permissions of this block.  Note that a block
      * can be valid but not readable if there is an outstanding write
      * upgrade miss.
      * @return True if the block is readable.
      */
     bool isReadable() const
     {
         const State needed_bits = BlkReadable | BlkValid;
         return (status & needed_bits) == needed_bits;
     }

     /**
      * Checks that a block is valid.
      * @return True if the block is valid.
      */
     bool isValid() const
     {
         return (status & BlkValid) != 0;
     }

     /**
      * Invalidate the block and clear all state.
      */
     void invalidate()
     {
         status = 0;
         isTouched = false;
         lockList.clear();
     }

     /**
      * Check to see if a block has been written.
      * @return True if the block is dirty.
      */
     bool isDirty() const
     {
         return (status & BlkDirty) != 0;
     }

     /**
      * Check if this block was the result of a hardware prefetch, yet to
      * be touched.
      * @return True if the block was a hardware prefetch, unaccesed.
      */
     bool wasPrefetched() const
     {
         return (status & BlkHWPrefetched) != 0;
     }

     /**
      * Check if this block holds data from the secure memory space.
      * @return True if the block holds data from the secure memory space.
      */
     bool isSecure() const
     {
         return (status & BlkSecure) != 0;
     }

     /**
      * Track the fact that a local locked was issued to the
      * block. Invalidate any previous LL to the same address.
      */
     void trackLoadLocked(PacketPtr pkt)
     {
         assert(pkt->isLLSC());
         auto l = lockList.begin();
         while (l != lockList.end()) {
             if (l->intersects(pkt->req))
                 l = lockList.erase(l);
             else
                 ++l;
         }

         lockList.emplace_front(pkt->req);
     }

     /**
      * Clear the any load lock that intersect the request, and is from
      * a different context.
      */
     void clearLoadLocks(RequestPtr req)
     {
         auto l = lockList.begin();
         while (l != lockList.end()) {
             if (l->intersects(req) && l->contextId != req->contextId()) {
                 l = lockList.erase(l);
             } else {
                 ++l;
             }
         }
     }

     /**
      * Pretty-print a tag, and interpret state bits to readable form
      * including mapping to a MOESI state.
      *
      * @return string with basic state information
      */
     std::string print() const
     {
         /**
          *  state       M   O   E   S   I
          *  writable    1   0   1   0   0
          *  dirty       1   1   0   0   0
          *  valid       1   1   1   1   0
          *
          *  state   writable    dirty   valid
          *  M       1           1       1
          *  O       0           1       1
          *  E       1           0       1
          *  S       0           0       1
          *  I       0           0       0
          *
          * Note that only one cache ever has a block in Modified or
          * Owned state, i.e., only one cache owns the block, or
          * equivalently has the BlkDirty bit set. However, multiple
          * caches on the same path to memory can have a block in the
          * Exclusive state (despite the name). Exclusive means this
          * cache has the only copy at this level of the hierarchy,
          * i.e., there may be copies in caches above this cache (in
          * various states), but there are no peers that have copies on
          * this branch of the hierarchy, and no caches at or above
          * this level on any other branch have copies either.
          **/
         unsigned state = isWritable() << 2 | isDirty() << 1 | isValid();
         char s = '?';
         switch (state) {
           case 0b111: s = 'M'; break;
           case 0b011: s = 'O'; break;
           case 0b101: s = 'E'; break;
           case 0b001: s = 'S'; break;
           case 0b000: s = 'I'; break;
           default:    s = 'T'; break; // @TODO add other types
         }
         return csprintf("state: %x (%c) valid: %d writable: %d readable: %d "
                         "dirty: %d tag: %x", status, s, isValid(),
                         isWritable(), isReadable(), isDirty(), tag);
     }

     /**
      * Handle interaction of load-locked operations and stores.
      * @return True if write should proceed, false otherwise.  Returns
      * false only in the case of a failed store conditional.
      */
     bool checkWrite(PacketPtr pkt)
     {
         assert(pkt->isWrite());

         // common case
         if (!pkt->isLLSC() && lockList.empty())
             return true;

         RequestPtr req = pkt->req;

         if (pkt->isLLSC()) {
             // it's a store conditional... have to check for matching
             // load locked.
             bool success = false;

             auto l = lockList.begin();
             while (!success && l != lockList.end()) {
                 if (l->matches(pkt->req)) {
                     // it's a store conditional, and as far as the
                     // memory system can tell, the requesting
                     // context's lock is still valid.
                     success = true;
                     lockList.erase(l);
                 } else {
                     ++l;
                 }
             }

             req->setExtraData(success ? 1 : 0);
             // clear any intersected locks from other contexts (our LL
             // should already have cleared them)
             clearLoadLocks(req);
             return success;
         } else {
             // a normal write, if there is any lock not from this
             // context we clear the list, thus for a private cache we
             // never clear locks on normal writes
             clearLoadLocks(req);
             return true;
         }
     }
 };

 /**
  * Simple class to provide virtual print() method on cache blocks
  * without allocating a vtable pointer for every single cache block.
  * Just wrap the CacheBlk object in an instance of this before passing
  * to a function that requires a Printable object.
  */
 class CacheBlkPrintWrapper : public Printable
 {
     CacheBlk *blk;
   public:
     CacheBlkPrintWrapper(CacheBlk *_blk) : blk(_blk) {}
     virtual ~CacheBlkPrintWrapper() {}
     void print(std::ostream &o, int verbosity = 0,
                const std::string &prefix = "") const;
 };

 /**
  * Base class for cache block visitor, operating on the cache block
  * base class (later subclassed for the various tag classes). This
  * visitor class is used as part of the forEachBlk interface in the
  * tag classes.
  */
 class CacheBlkVisitor
 {
   public:

     CacheBlkVisitor() {}
     virtual ~CacheBlkVisitor() {}

     virtual bool operator()(CacheBlk &blk) = 0;
 };

 #endif //__MEM_CACHE_BLK_HH__
	/*
	* 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) 2003-2005 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
	* Andreas Sandberg
	*/

	/** @file
	* Definitions of a simple cache block class.
	*/

	#ifndef __MEM_CACHE_BLK_HH__
	#define __MEM_CACHE_BLK_HH__

	#include <list>

	#include "base/printable.hh"
	#include "mem/packet.hh"
	#include "mem/request.hh"

	/**
	* Cache block status bit assignments
	*/
	enum CacheBlkStatusBits : unsigned {
	/** valid, readable */
	BlkValid = 0x01,
	/** write permission */
	BlkWritable = 0x02,
	/** read permission (yes, block can be valid but not readable) */
	BlkReadable = 0x04,
	/** dirty (modified) */
	BlkDirty = 0x08,
	/** block was a hardware prefetch yet unaccessed*/
	BlkHWPrefetched = 0x20,
	/** block holds data from the secure memory space */
	BlkSecure = 0x40,
	};

	/**
	* A Basic Cache block.
	* Contains the tag, status, and a pointer to data.
	*/
	class CacheBlk
	{
	public:
	/** Task Id associated with this block */
	uint32_t task_id;

	/** Data block tag value. */
	Addr tag;
	/**
	* Contains a copy of the data in this block for easy access. This is used
	* for efficient execution when the data could be actually stored in
	* another format (COW, compressed, sub-blocked, etc). In all cases the
	* data stored here should be kept consistant with the actual data
	* referenced by this block.
	*/
	uint8_t *data;

	/** block state: OR of CacheBlkStatusBit */
	typedef unsigned State;

	/** The current status of this block. @sa CacheBlockStatusBits */
	State status;

	/** Which curTick() will this block be accessable */
	Tick whenReady;

	/**
	* The set and way this block belongs to.
	* @todo Move this into subclasses when we fix CacheTags to use them.
	*/
	int set, way;

	/** whether this block has been touched */
	bool isTouched;

	/** Number of references to this block since it was brought in. */
	unsigned refCount;

	/** holds the source requestor ID for this block. */
	int srcMasterId;

	Tick tickInserted;

	protected:
	/**
	* Represents that the indicated thread context has a "lock" on
	* the block, in the LL/SC sense.
	*/
	class Lock {
	public:
	ContextID contextId; // locking context
	Addr lowAddr; // low address of lock range
	Addr highAddr; // high address of lock range

	// check for matching execution context, and an address that
	// is within the lock
	bool matches(const RequestPtr req) const
	{
	Addr req_low = req->getPaddr();
	Addr req_high = req_low + req->getSize() -1;
	return (contextId == req->contextId()) &&
	(req_low >= lowAddr) && (req_high <= highAddr);
	}

	// check if a request is intersecting and thus invalidating the lock
	bool intersects(const RequestPtr req) const
	{
	Addr req_low = req->getPaddr();
	Addr req_high = req_low + req->getSize() - 1;

	return (req_low <= highAddr) && (req_high >= lowAddr);
	}

	Lock(const RequestPtr req)
	: contextId(req->contextId()),
	lowAddr(req->getPaddr()),
	highAddr(lowAddr + req->getSize() - 1)
	{
	}
	};

	/** List of thread contexts that have performed a load-locked (LL)
	* on the block since the last store. */
	std::list<Lock> lockList;

	public:

	CacheBlk()
	: task_id(ContextSwitchTaskId::Unknown),
	tag(0), data(0), status(0), whenReady(0),
	set(-1), way(-1), isTouched(false), refCount(0),
	srcMasterId(Request::invldMasterId),
	tickInserted(0)
	{}

	CacheBlk(const CacheBlk&) = delete;
	CacheBlk& operator=(const CacheBlk&) = delete;

	/**
	* Checks the write permissions of this block.
	* @return True if the block is writable.
	*/
	bool isWritable() const
	{
	const State needed_bits = BlkWritable \| BlkValid;
	return (status & needed_bits) == needed_bits;
	}

	/**
	* Checks the read permissions of this block. Note that a block
	* can be valid but not readable if there is an outstanding write
	* upgrade miss.
	* @return True if the block is readable.
	*/
	bool isReadable() const
	{
	const State needed_bits = BlkReadable \| BlkValid;
	return (status & needed_bits) == needed_bits;
	}

	/**
	* Checks that a block is valid.
	* @return True if the block is valid.
	*/
	bool isValid() const
	{
	return (status & BlkValid) != 0;
	}

	/**
	* Invalidate the block and clear all state.
	*/
	void invalidate()
	{
	status = 0;
	isTouched = false;
	lockList.clear();
	}

	/**
	* Check to see if a block has been written.
	* @return True if the block is dirty.
	*/
	bool isDirty() const
	{
	return (status & BlkDirty) != 0;
	}

	/**
	* Check if this block was the result of a hardware prefetch, yet to
	* be touched.
	* @return True if the block was a hardware prefetch, unaccesed.
	*/
	bool wasPrefetched() const
	{
	return (status & BlkHWPrefetched) != 0;
	}

	/**
	* Check if this block holds data from the secure memory space.
	* @return True if the block holds data from the secure memory space.
	*/
	bool isSecure() const
	{
	return (status & BlkSecure) != 0;
	}

	/**
	* Track the fact that a local locked was issued to the
	* block. Invalidate any previous LL to the same address.
	*/
	void trackLoadLocked(PacketPtr pkt)
	{
	assert(pkt->isLLSC());
	auto l = lockList.begin();
	while (l != lockList.end()) {
	if (l->intersects(pkt->req))
	l = lockList.erase(l);
	else
	++l;
	}

	lockList.emplace_front(pkt->req);
	}

	/**
	* Clear the any load lock that intersect the request, and is from
	* a different context.
	*/
	void clearLoadLocks(RequestPtr req)
	{
	auto l = lockList.begin();
	while (l != lockList.end()) {
	if (l->intersects(req) && l->contextId != req->contextId()) {
	l = lockList.erase(l);
	} else {
	++l;
	}
	}
	}

	/**
	* Pretty-print a tag, and interpret state bits to readable form
	* including mapping to a MOESI state.
	*
	* @return string with basic state information
	*/
	std::string print() const
	{
	/**
	* state M O E S I
	* writable 1 0 1 0 0
	* dirty 1 1 0 0 0
	* valid 1 1 1 1 0
	*
	* state writable dirty valid
	* M 1 1 1
	* O 0 1 1
	* E 1 0 1
	* S 0 0 1
	* I 0 0 0
	*
	* Note that only one cache ever has a block in Modified or
	* Owned state, i.e., only one cache owns the block, or
	* equivalently has the BlkDirty bit set. However, multiple
	* caches on the same path to memory can have a block in the
	* Exclusive state (despite the name). Exclusive means this
	* cache has the only copy at this level of the hierarchy,
	* i.e., there may be copies in caches above this cache (in
	* various states), but there are no peers that have copies on
	* this branch of the hierarchy, and no caches at or above
	* this level on any other branch have copies either.
	**/
	unsigned state = isWritable() << 2 \| isDirty() << 1 \| isValid();
	char s = '?';
	switch (state) {
	case 0b111: s = 'M'; break;
	case 0b011: s = 'O'; break;
	case 0b101: s = 'E'; break;
	case 0b001: s = 'S'; break;
	case 0b000: s = 'I'; break;
	default: s = 'T'; break; // @TODO add other types
	}
	return csprintf("state: %x (%c) valid: %d writable: %d readable: %d "
	"dirty: %d tag: %x", status, s, isValid(),
	isWritable(), isReadable(), isDirty(), tag);
	}

	/**
	* Handle interaction of load-locked operations and stores.
	* @return True if write should proceed, false otherwise. Returns
	* false only in the case of a failed store conditional.
	*/
	bool checkWrite(PacketPtr pkt)
	{
	assert(pkt->isWrite());

	// common case
	if (!pkt->isLLSC() && lockList.empty())
	return true;

	RequestPtr req = pkt->req;

	if (pkt->isLLSC()) {
	// it's a store conditional... have to check for matching
	// load locked.
	bool success = false;

	auto l = lockList.begin();
	while (!success && l != lockList.end()) {
	if (l->matches(pkt->req)) {
	// it's a store conditional, and as far as the
	// memory system can tell, the requesting
	// context's lock is still valid.
	success = true;
	lockList.erase(l);
	} else {
	++l;
	}
	}

	req->setExtraData(success ? 1 : 0);
	// clear any intersected locks from other contexts (our LL
	// should already have cleared them)
	clearLoadLocks(req);
	return success;
	} else {
	// a normal write, if there is any lock not from this
	// context we clear the list, thus for a private cache we
	// never clear locks on normal writes
	clearLoadLocks(req);
	return true;
	}
	}
	};

	/**
	* Simple class to provide virtual print() method on cache blocks
	* without allocating a vtable pointer for every single cache block.
	* Just wrap the CacheBlk object in an instance of this before passing
	* to a function that requires a Printable object.
	*/
	class CacheBlkPrintWrapper : public Printable
	{
	CacheBlk *blk;
	public:
	CacheBlkPrintWrapper(CacheBlk *_blk) : blk(_blk) {}
	virtual ~CacheBlkPrintWrapper() {}
	void print(std::ostream &o, int verbosity = 0,
	const std::string &prefix = "") const;
	};

	/**
	* Base class for cache block visitor, operating on the cache block
	* base class (later subclassed for the various tag classes). This
	* visitor class is used as part of the forEachBlk interface in the
	* tag classes.
	*/
	class CacheBlkVisitor
	{
	public:

	CacheBlkVisitor() {}
	virtual ~CacheBlkVisitor() {}

	virtual bool operator()(CacheBlk &blk) = 0;
	};

	#endif //__MEM_CACHE_BLK_HH__