src/arch/alpha/tlb.cc - amd/gem5 - Git at Google

 /*
  * Copyright (c) 2001-2005 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: Nathan Binkert
  *          Steve Reinhardt
  *          Andrew Schultz
  */

 #include "arch/alpha/tlb.hh"

 #include <algorithm>
 #include <memory>
 #include <string>
 #include <vector>

 #include "arch/alpha/faults.hh"
 #include "arch/alpha/pagetable.hh"
 #include "arch/generic/debugfaults.hh"
 #include "base/inifile.hh"
 #include "base/str.hh"
 #include "base/trace.hh"
 #include "cpu/thread_context.hh"
 #include "debug/TLB.hh"
 #include "sim/full_system.hh"

 using namespace std;

 namespace AlphaISA {

 ///////////////////////////////////////////////////////////////////////
 //
 //  Alpha TLB
 //

 #ifdef DEBUG
 bool uncacheBit39 = false;
 bool uncacheBit40 = false;
 #endif

 #define MODE2MASK(X) (1 << (X))

 TLB::TLB(const Params *p)
     : BaseTLB(p), table(p->size), nlu(0)
 {
     flushCache();
 }

 TLB::~TLB()
 {
 }

 void
 TLB::regStats()
 {
     BaseTLB::regStats();

     fetch_hits
         .name(name() + ".fetch_hits")
         .desc("ITB hits");
     fetch_misses
         .name(name() + ".fetch_misses")
         .desc("ITB misses");
     fetch_acv
         .name(name() + ".fetch_acv")
         .desc("ITB acv");
     fetch_accesses
         .name(name() + ".fetch_accesses")
         .desc("ITB accesses");

     fetch_accesses = fetch_hits + fetch_misses;

     read_hits
         .name(name() + ".read_hits")
         .desc("DTB read hits")
         ;

     read_misses
         .name(name() + ".read_misses")
         .desc("DTB read misses")
         ;

     read_acv
         .name(name() + ".read_acv")
         .desc("DTB read access violations")
         ;

     read_accesses
         .name(name() + ".read_accesses")
         .desc("DTB read accesses")
         ;

     write_hits
         .name(name() + ".write_hits")
         .desc("DTB write hits")
         ;

     write_misses
         .name(name() + ".write_misses")
         .desc("DTB write misses")
         ;

     write_acv
         .name(name() + ".write_acv")
         .desc("DTB write access violations")
         ;

     write_accesses
         .name(name() + ".write_accesses")
         .desc("DTB write accesses")
         ;

     data_hits
         .name(name() + ".data_hits")
         .desc("DTB hits")
         ;

     data_misses
         .name(name() + ".data_misses")
         .desc("DTB misses")
         ;

     data_acv
         .name(name() + ".data_acv")
         .desc("DTB access violations")
         ;

     data_accesses
         .name(name() + ".data_accesses")
         .desc("DTB accesses")
         ;

     data_hits = read_hits + write_hits;
     data_misses = read_misses + write_misses;
     data_acv = read_acv + write_acv;
     data_accesses = read_accesses + write_accesses;
 }

 // look up an entry in the TLB
 TlbEntry *
 TLB::lookup(Addr vpn, uint8_t asn)
 {
     // assume not found...
     TlbEntry *retval = NULL;

     if (EntryCache[0]) {
         if (vpn == EntryCache[0]->tag &&
             (EntryCache[0]->asma || EntryCache[0]->asn == asn))
             retval = EntryCache[0];
         else if (EntryCache[1]) {
             if (vpn == EntryCache[1]->tag &&
                 (EntryCache[1]->asma || EntryCache[1]->asn == asn))
                 retval = EntryCache[1];
             else if (EntryCache[2] && vpn == EntryCache[2]->tag &&
                      (EntryCache[2]->asma || EntryCache[2]->asn == asn))
                 retval = EntryCache[2];
         }
     }

     if (retval == NULL) {
         PageTable::const_iterator i = lookupTable.find(vpn);
         if (i != lookupTable.end()) {
             while (i->first == vpn) {
                 int index = i->second;
                 TlbEntry *entry = &table[index];
                 assert(entry->valid);
                 if (vpn == entry->tag && (entry->asma || entry->asn == asn)) {
                     retval = updateCache(entry);
                     break;
                 }

                 ++i;
             }
         }
     }

     DPRINTF(TLB, "lookup %#x, asn %#x -> %s ppn %#x\n", vpn, (int)asn,
             retval ? "hit" : "miss", retval ? retval->ppn : 0);
     return retval;
 }

 Fault
 TLB::checkCacheability(RequestPtr &req, bool itb)
 {
     // in Alpha, cacheability is controlled by upper-level bits of the
     // physical address

     /*
      * We support having the uncacheable bit in either bit 39 or bit
      * 40.  The Turbolaser platform (and EV5) support having the bit
      * in 39, but Tsunami (which Linux assumes uses an EV6) generates
      * accesses with the bit in 40.  So we must check for both, but we
      * have debug flags to catch a weird case where both are used,
      * which shouldn't happen.
      */


     if (req->getPaddr() & PAddrUncachedBit43) {
         // IPR memory space not implemented
         if (PAddrIprSpace(req->getPaddr())) {
             return std::make_shared<UnimpFault>(
                 "IPR memory space not implemented!");
         } else {
             // mark request as uncacheable
             req->setFlags(Request::UNCACHEABLE | Request::STRICT_ORDER);

             // Clear bits 42:35 of the physical address (10-2 in
             // Tsunami manual)
             req->setPaddr(req->getPaddr() & PAddrUncachedMask);
         }
         // We shouldn't be able to read from an uncachable address in Alpha as
         // we don't have a ROM and we don't want to try to fetch from a device
         // register as we destroy any data that is clear-on-read.
         if (req->isUncacheable() && itb)
             return std::make_shared<UnimpFault>(
                 "CPU trying to fetch from uncached I/O");

     }
     return NoFault;
 }


 // insert a new TLB entry
 void
 TLB::insert(Addr addr, TlbEntry &entry)
 {
     flushCache();
     VAddr vaddr = addr;
     if (table[nlu].valid) {
         Addr oldvpn = table[nlu].tag;
         PageTable::iterator i = lookupTable.find(oldvpn);

         if (i == lookupTable.end())
             panic("TLB entry not found in lookupTable");

         int index;
         while ((index = i->second) != nlu) {
             if (table[index].tag != oldvpn)
                 panic("TLB entry not found in lookupTable");

             ++i;
         }

         DPRINTF(TLB, "remove @%d: %#x -> %#x\n", nlu, oldvpn, table[nlu].ppn);

         lookupTable.erase(i);
     }

     DPRINTF(TLB, "insert @%d: %#x -> %#x\n", nlu, vaddr.vpn(), entry.ppn);

     table[nlu] = entry;
     table[nlu].tag = vaddr.vpn();
     table[nlu].valid = true;

     lookupTable.insert(make_pair(vaddr.vpn(), nlu));
     nextnlu();
 }

 void
 TLB::flushAll()
 {
     DPRINTF(TLB, "flushAll\n");
     std::fill(table.begin(), table.end(), TlbEntry());
     flushCache();
     lookupTable.clear();
     nlu = 0;
 }

 void
 TLB::flushProcesses()
 {
     flushCache();
     PageTable::iterator i = lookupTable.begin();
     PageTable::iterator end = lookupTable.end();
     while (i != end) {
         int index = i->second;
         TlbEntry *entry = &table[index];
         assert(entry->valid);

         // we can't increment i after we erase it, so save a copy and
         // increment it to get the next entry now
         PageTable::iterator cur = i;
         ++i;

         if (!entry->asma) {
             DPRINTF(TLB, "flush @%d: %#x -> %#x\n", index,
                     entry->tag, entry->ppn);
             entry->valid = false;
             lookupTable.erase(cur);
         }
     }
 }

 void
 TLB::flushAddr(Addr addr, uint8_t asn)
 {
     flushCache();
     VAddr vaddr = addr;

     PageTable::iterator i = lookupTable.find(vaddr.vpn());
     if (i == lookupTable.end())
         return;

     while (i != lookupTable.end() && i->first == vaddr.vpn()) {
         int index = i->second;
         TlbEntry *entry = &table[index];
         assert(entry->valid);

         if (vaddr.vpn() == entry->tag && (entry->asma || entry->asn == asn)) {
             DPRINTF(TLB, "flushaddr @%d: %#x -> %#x\n", index, vaddr.vpn(),
                     entry->ppn);

             // invalidate this entry
             entry->valid = false;

             lookupTable.erase(i++);
         } else {
             ++i;
         }
     }
 }


 void
 TLB::serialize(CheckpointOut &cp) const
 {
     const unsigned size(table.size());
     SERIALIZE_SCALAR(size);
     SERIALIZE_SCALAR(nlu);

     for (int i = 0; i < size; i++)
         table[i].serializeSection(cp, csprintf("Entry%d", i));
 }

 void
 TLB::unserialize(CheckpointIn &cp)
 {
     unsigned size(0);
     UNSERIALIZE_SCALAR(size);
     UNSERIALIZE_SCALAR(nlu);

     table.resize(size);
     for (int i = 0; i < size; i++) {
         table[i].unserializeSection(cp, csprintf("Entry%d", i));
         if (table[i].valid) {
             lookupTable.insert(make_pair(table[i].tag, i));
         }
     }
 }

 Fault
 TLB::translateInst(RequestPtr req, ThreadContext *tc)
 {
     //If this is a pal pc, then set PHYSICAL
     if (FullSystem && PcPAL(req->getPC()))
         req->setFlags(Request::PHYSICAL);

     if (PcPAL(req->getPC())) {
         // strip off PAL PC marker (lsb is 1)
         req->setPaddr((req->getVaddr() & ~3) & PAddrImplMask);
         fetch_hits++;
         return NoFault;
     }

     if (req->getFlags() & Request::PHYSICAL) {
         req->setPaddr(req->getVaddr());
     } else {
         // verify that this is a good virtual address
         if (!validVirtualAddress(req->getVaddr())) {
             fetch_acv++;
             return std::make_shared<ItbAcvFault>(req->getVaddr());
         }


         // VA<42:41> == 2, VA<39:13> maps directly to PA<39:13> for EV5
         // VA<47:41> == 0x7e, VA<40:13> maps directly to PA<40:13> for EV6
         if (VAddrSpaceEV6(req->getVaddr()) == 0x7e) {
             // only valid in kernel mode
             if (ICM_CM(tc->readMiscRegNoEffect(IPR_ICM)) !=
                 mode_kernel) {
                 fetch_acv++;
                 return std::make_shared<ItbAcvFault>(req->getVaddr());
             }

             req->setPaddr(req->getVaddr() & PAddrImplMask);

             // sign extend the physical address properly
             if (req->getPaddr() & PAddrUncachedBit40)
                 req->setPaddr(req->getPaddr() | ULL(0xf0000000000));
             else
                 req->setPaddr(req->getPaddr() & ULL(0xffffffffff));
         } else {
             // not a physical address: need to look up pte
             int asn = DTB_ASN_ASN(tc->readMiscRegNoEffect(IPR_DTB_ASN));
             TlbEntry *entry = lookup(VAddr(req->getVaddr()).vpn(),
                               asn);

             if (!entry) {
                 fetch_misses++;
                 return std::make_shared<ItbPageFault>(req->getVaddr());
             }

             req->setPaddr((entry->ppn << PageShift) +
                           (VAddr(req->getVaddr()).offset()
                            & ~3));

             // check permissions for this access
             if (!(entry->xre &
                   (1 << ICM_CM(tc->readMiscRegNoEffect(IPR_ICM))))) {
                 // instruction access fault
                 fetch_acv++;
                 return std::make_shared<ItbAcvFault>(req->getVaddr());
             }

             fetch_hits++;
         }
     }

     // check that the physical address is ok (catch bad physical addresses)
     if (req->getPaddr() & ~PAddrImplMask) {
         return std::make_shared<MachineCheckFault>();
     }

     return checkCacheability(req, true);

 }

 Fault
 TLB::translateData(RequestPtr req, ThreadContext *tc, bool write)
 {
     mode_type mode =
         (mode_type)DTB_CM_CM(tc->readMiscRegNoEffect(IPR_DTB_CM));

     /**
      * Check for alignment faults
      */
     if (req->getVaddr() & (req->getSize() - 1)) {
         DPRINTF(TLB, "Alignment Fault on %#x, size = %d\n", req->getVaddr(),
                 req->getSize());
         uint64_t flags = write ? MM_STAT_WR_MASK : 0;
         return std::make_shared<DtbAlignmentFault>(req->getVaddr(),
                                                    req->getFlags(),
                                                    flags);
     }

     if (PcPAL(req->getPC())) {
         mode = (req->getFlags() & AlphaRequestFlags::ALTMODE) ?
             (mode_type)ALT_MODE_AM(
                 tc->readMiscRegNoEffect(IPR_ALT_MODE))
             : mode_kernel;
     }

     if (req->getFlags() & Request::PHYSICAL) {
         req->setPaddr(req->getVaddr());
     } else {
         // verify that this is a good virtual address
         if (!validVirtualAddress(req->getVaddr())) {
             if (write) { write_acv++; } else { read_acv++; }
             uint64_t flags = (write ? MM_STAT_WR_MASK : 0) |
                 MM_STAT_BAD_VA_MASK |
                 MM_STAT_ACV_MASK;
             return std::make_shared<DtbPageFault>(req->getVaddr(),
                                                   req->getFlags(),
                                                   flags);
         }

         // Check for "superpage" mapping
         if (VAddrSpaceEV6(req->getVaddr()) == 0x7e) {
             // only valid in kernel mode
             if (DTB_CM_CM(tc->readMiscRegNoEffect(IPR_DTB_CM)) !=
                 mode_kernel) {
                 if (write) { write_acv++; } else { read_acv++; }
                 uint64_t flags = ((write ? MM_STAT_WR_MASK : 0) |
                                   MM_STAT_ACV_MASK);

                 return std::make_shared<DtbAcvFault>(req->getVaddr(),
                                                      req->getFlags(),
                                                      flags);
             }

             req->setPaddr(req->getVaddr() & PAddrImplMask);

             // sign extend the physical address properly
             if (req->getPaddr() & PAddrUncachedBit40)
                 req->setPaddr(req->getPaddr() | ULL(0xf0000000000));
             else
                 req->setPaddr(req->getPaddr() & ULL(0xffffffffff));
         } else {
             if (write)
                 write_accesses++;
             else
                 read_accesses++;

             int asn = DTB_ASN_ASN(tc->readMiscRegNoEffect(IPR_DTB_ASN));

             // not a physical address: need to look up pte
             TlbEntry *entry = lookup(VAddr(req->getVaddr()).vpn(), asn);

             if (!entry) {
                 // page fault
                 if (write) { write_misses++; } else { read_misses++; }
                 uint64_t flags = (write ? MM_STAT_WR_MASK : 0) |
                     MM_STAT_DTB_MISS_MASK;
                 return (req->getFlags() & AlphaRequestFlags::VPTE) ?
                     (Fault)(std::make_shared<PDtbMissFault>(req->getVaddr(),
                                                             req->getFlags(),
                                                             flags)) :
                     (Fault)(std::make_shared<NDtbMissFault>(req->getVaddr(),
                                                             req->getFlags(),
                                                             flags));
             }

             req->setPaddr((entry->ppn << PageShift) +
                           VAddr(req->getVaddr()).offset());

             if (write) {
                 if (!(entry->xwe & MODE2MASK(mode))) {
                     // declare the instruction access fault
                     write_acv++;
                     uint64_t flags = MM_STAT_WR_MASK |
                         MM_STAT_ACV_MASK |
                         (entry->fonw ? MM_STAT_FONW_MASK : 0);
                     return std::make_shared<DtbPageFault>(req->getVaddr(),
                                                           req->getFlags(),
                                                           flags);
                 }
                 if (entry->fonw) {
                     write_acv++;
                     uint64_t flags = MM_STAT_WR_MASK | MM_STAT_FONW_MASK;
                     return std::make_shared<DtbPageFault>(req->getVaddr(),
                                                           req->getFlags(),
                                                           flags);
                 }
             } else {
                 if (!(entry->xre & MODE2MASK(mode))) {
                     read_acv++;
                     uint64_t flags = MM_STAT_ACV_MASK |
                         (entry->fonr ? MM_STAT_FONR_MASK : 0);
                     return std::make_shared<DtbAcvFault>(req->getVaddr(),
                                                          req->getFlags(),
                                                          flags);
                 }
                 if (entry->fonr) {
                     read_acv++;
                     uint64_t flags = MM_STAT_FONR_MASK;
                     return std::make_shared<DtbPageFault>(req->getVaddr(),
                                                           req->getFlags(),
                                                           flags);
                 }
             }
         }

         if (write)
             write_hits++;
         else
             read_hits++;
     }

     // check that the physical address is ok (catch bad physical addresses)
     if (req->getPaddr() & ~PAddrImplMask) {
         return std::make_shared<MachineCheckFault>();
     }

     return checkCacheability(req);
 }

 TlbEntry &
 TLB::index(bool advance)
 {
     TlbEntry *entry = &table[nlu];

     if (advance)
         nextnlu();

     return *entry;
 }

 Fault
 TLB::translateAtomic(RequestPtr req, ThreadContext *tc, Mode mode)
 {
     if (mode == Execute)
         return translateInst(req, tc);
     else
         return translateData(req, tc, mode == Write);
 }

 void
 TLB::translateTiming(RequestPtr req, ThreadContext *tc,
         Translation *translation, Mode mode)
 {
     assert(translation);
     translation->finish(translateAtomic(req, tc, mode), req, tc, mode);
 }

 Fault
 TLB::finalizePhysical(RequestPtr req, ThreadContext *tc, Mode mode) const
 {
     return NoFault;
 }

 } // namespace AlphaISA

 AlphaISA::TLB *
 AlphaTLBParams::create()
 {
     return new AlphaISA::TLB(this);
 }
	/*
	* Copyright (c) 2001-2005 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: Nathan Binkert
	* Steve Reinhardt
	* Andrew Schultz
	*/

	#include "arch/alpha/tlb.hh"

	#include <algorithm>
	#include <memory>
	#include <string>
	#include <vector>

	#include "arch/alpha/faults.hh"
	#include "arch/alpha/pagetable.hh"
	#include "arch/generic/debugfaults.hh"
	#include "base/inifile.hh"
	#include "base/str.hh"
	#include "base/trace.hh"
	#include "cpu/thread_context.hh"
	#include "debug/TLB.hh"
	#include "sim/full_system.hh"

	using namespace std;

	namespace AlphaISA {

	///////////////////////////////////////////////////////////////////////
	//
	// Alpha TLB
	//

	#ifdef DEBUG
	bool uncacheBit39 = false;
	bool uncacheBit40 = false;
	#endif

	#define MODE2MASK(X) (1 << (X))

	TLB::TLB(const Params *p)
	: BaseTLB(p), table(p->size), nlu(0)
	{
	flushCache();
	}

	TLB::~TLB()
	{
	}

	void
	TLB::regStats()
	{
	BaseTLB::regStats();

	fetch_hits
	.name(name() + ".fetch_hits")
	.desc("ITB hits");
	fetch_misses
	.name(name() + ".fetch_misses")
	.desc("ITB misses");
	fetch_acv
	.name(name() + ".fetch_acv")
	.desc("ITB acv");
	fetch_accesses
	.name(name() + ".fetch_accesses")
	.desc("ITB accesses");

	fetch_accesses = fetch_hits + fetch_misses;

	read_hits
	.name(name() + ".read_hits")
	.desc("DTB read hits")
	;

	read_misses
	.name(name() + ".read_misses")
	.desc("DTB read misses")
	;

	read_acv
	.name(name() + ".read_acv")
	.desc("DTB read access violations")
	;

	read_accesses
	.name(name() + ".read_accesses")
	.desc("DTB read accesses")
	;

	write_hits
	.name(name() + ".write_hits")
	.desc("DTB write hits")
	;

	write_misses
	.name(name() + ".write_misses")
	.desc("DTB write misses")
	;

	write_acv
	.name(name() + ".write_acv")
	.desc("DTB write access violations")
	;

	write_accesses
	.name(name() + ".write_accesses")
	.desc("DTB write accesses")
	;

	data_hits
	.name(name() + ".data_hits")
	.desc("DTB hits")
	;

	data_misses
	.name(name() + ".data_misses")
	.desc("DTB misses")
	;

	data_acv
	.name(name() + ".data_acv")
	.desc("DTB access violations")
	;

	data_accesses
	.name(name() + ".data_accesses")
	.desc("DTB accesses")
	;

	data_hits = read_hits + write_hits;
	data_misses = read_misses + write_misses;
	data_acv = read_acv + write_acv;
	data_accesses = read_accesses + write_accesses;
	}

	// look up an entry in the TLB
	TlbEntry *
	TLB::lookup(Addr vpn, uint8_t asn)
	{
	// assume not found...
	TlbEntry *retval = NULL;

	if (EntryCache[0]) {
	if (vpn == EntryCache[0]->tag &&
	(EntryCache[0]->asma \|\| EntryCache[0]->asn == asn))
	retval = EntryCache[0];
	else if (EntryCache[1]) {
	if (vpn == EntryCache[1]->tag &&
	(EntryCache[1]->asma \|\| EntryCache[1]->asn == asn))
	retval = EntryCache[1];
	else if (EntryCache[2] && vpn == EntryCache[2]->tag &&
	(EntryCache[2]->asma \|\| EntryCache[2]->asn == asn))
	retval = EntryCache[2];
	}
	}

	if (retval == NULL) {
	PageTable::const_iterator i = lookupTable.find(vpn);
	if (i != lookupTable.end()) {
	while (i->first == vpn) {
	int index = i->second;
	TlbEntry *entry = &table[index];
	assert(entry->valid);
	if (vpn == entry->tag && (entry->asma \|\| entry->asn == asn)) {
	retval = updateCache(entry);
	break;
	}

	++i;
	}
	}
	}

	DPRINTF(TLB, "lookup %#x, asn %#x -> %s ppn %#x\n", vpn, (int)asn,
	retval ? "hit" : "miss", retval ? retval->ppn : 0);
	return retval;
	}

	Fault
	TLB::checkCacheability(RequestPtr &req, bool itb)
	{
	// in Alpha, cacheability is controlled by upper-level bits of the
	// physical address

	/*
	* We support having the uncacheable bit in either bit 39 or bit
	* 40. The Turbolaser platform (and EV5) support having the bit
	* in 39, but Tsunami (which Linux assumes uses an EV6) generates
	* accesses with the bit in 40. So we must check for both, but we
	* have debug flags to catch a weird case where both are used,
	* which shouldn't happen.
	*/


	if (req->getPaddr() & PAddrUncachedBit43) {
	// IPR memory space not implemented
	if (PAddrIprSpace(req->getPaddr())) {
	return std::make_shared<UnimpFault>(
	"IPR memory space not implemented!");
	} else {
	// mark request as uncacheable
	req->setFlags(Request::UNCACHEABLE \| Request::STRICT_ORDER);

	// Clear bits 42:35 of the physical address (10-2 in
	// Tsunami manual)
	req->setPaddr(req->getPaddr() & PAddrUncachedMask);
	}
	// We shouldn't be able to read from an uncachable address in Alpha as
	// we don't have a ROM and we don't want to try to fetch from a device
	// register as we destroy any data that is clear-on-read.
	if (req->isUncacheable() && itb)
	return std::make_shared<UnimpFault>(
	"CPU trying to fetch from uncached I/O");

	}
	return NoFault;
	}


	// insert a new TLB entry
	void
	TLB::insert(Addr addr, TlbEntry &entry)
	{
	flushCache();
	VAddr vaddr = addr;
	if (table[nlu].valid) {
	Addr oldvpn = table[nlu].tag;
	PageTable::iterator i = lookupTable.find(oldvpn);

	if (i == lookupTable.end())
	panic("TLB entry not found in lookupTable");

	int index;
	while ((index = i->second) != nlu) {
	if (table[index].tag != oldvpn)
	panic("TLB entry not found in lookupTable");

	++i;
	}

	DPRINTF(TLB, "remove @%d: %#x -> %#x\n", nlu, oldvpn, table[nlu].ppn);

	lookupTable.erase(i);
	}

	DPRINTF(TLB, "insert @%d: %#x -> %#x\n", nlu, vaddr.vpn(), entry.ppn);

	table[nlu] = entry;
	table[nlu].tag = vaddr.vpn();
	table[nlu].valid = true;

	lookupTable.insert(make_pair(vaddr.vpn(), nlu));
	nextnlu();
	}

	void
	TLB::flushAll()
	{
	DPRINTF(TLB, "flushAll\n");
	std::fill(table.begin(), table.end(), TlbEntry());
	flushCache();
	lookupTable.clear();
	nlu = 0;
	}

	void
	TLB::flushProcesses()
	{
	flushCache();
	PageTable::iterator i = lookupTable.begin();
	PageTable::iterator end = lookupTable.end();
	while (i != end) {
	int index = i->second;
	TlbEntry *entry = &table[index];
	assert(entry->valid);

	// we can't increment i after we erase it, so save a copy and
	// increment it to get the next entry now
	PageTable::iterator cur = i;
	++i;

	if (!entry->asma) {
	DPRINTF(TLB, "flush @%d: %#x -> %#x\n", index,
	entry->tag, entry->ppn);
	entry->valid = false;
	lookupTable.erase(cur);
	}
	}
	}

	void
	TLB::flushAddr(Addr addr, uint8_t asn)
	{
	flushCache();
	VAddr vaddr = addr;

	PageTable::iterator i = lookupTable.find(vaddr.vpn());
	if (i == lookupTable.end())
	return;

	while (i != lookupTable.end() && i->first == vaddr.vpn()) {
	int index = i->second;
	TlbEntry *entry = &table[index];
	assert(entry->valid);

	if (vaddr.vpn() == entry->tag && (entry->asma \|\| entry->asn == asn)) {
	DPRINTF(TLB, "flushaddr @%d: %#x -> %#x\n", index, vaddr.vpn(),
	entry->ppn);

	// invalidate this entry
	entry->valid = false;

	lookupTable.erase(i++);
	} else {
	++i;
	}
	}
	}


	void
	TLB::serialize(CheckpointOut &cp) const
	{
	const unsigned size(table.size());
	SERIALIZE_SCALAR(size);
	SERIALIZE_SCALAR(nlu);

	for (int i = 0; i < size; i++)
	table[i].serializeSection(cp, csprintf("Entry%d", i));
	}

	void
	TLB::unserialize(CheckpointIn &cp)
	{
	unsigned size(0);
	UNSERIALIZE_SCALAR(size);
	UNSERIALIZE_SCALAR(nlu);

	table.resize(size);
	for (int i = 0; i < size; i++) {
	table[i].unserializeSection(cp, csprintf("Entry%d", i));
	if (table[i].valid) {
	lookupTable.insert(make_pair(table[i].tag, i));
	}
	}
	}

	Fault
	TLB::translateInst(RequestPtr req, ThreadContext *tc)
	{
	//If this is a pal pc, then set PHYSICAL
	if (FullSystem && PcPAL(req->getPC()))
	req->setFlags(Request::PHYSICAL);

	if (PcPAL(req->getPC())) {
	// strip off PAL PC marker (lsb is 1)
	req->setPaddr((req->getVaddr() & ~3) & PAddrImplMask);
	fetch_hits++;
	return NoFault;
	}

	if (req->getFlags() & Request::PHYSICAL) {
	req->setPaddr(req->getVaddr());
	} else {
	// verify that this is a good virtual address
	if (!validVirtualAddress(req->getVaddr())) {
	fetch_acv++;
	return std::make_shared<ItbAcvFault>(req->getVaddr());
	}


	// VA<42:41> == 2, VA<39:13> maps directly to PA<39:13> for EV5
	// VA<47:41> == 0x7e, VA<40:13> maps directly to PA<40:13> for EV6
	if (VAddrSpaceEV6(req->getVaddr()) == 0x7e) {
	// only valid in kernel mode
	if (ICM_CM(tc->readMiscRegNoEffect(IPR_ICM)) !=
	mode_kernel) {
	fetch_acv++;
	return std::make_shared<ItbAcvFault>(req->getVaddr());
	}

	req->setPaddr(req->getVaddr() & PAddrImplMask);

	// sign extend the physical address properly
	if (req->getPaddr() & PAddrUncachedBit40)
	req->setPaddr(req->getPaddr() \| ULL(0xf0000000000));
	else
	req->setPaddr(req->getPaddr() & ULL(0xffffffffff));
	} else {
	// not a physical address: need to look up pte
	int asn = DTB_ASN_ASN(tc->readMiscRegNoEffect(IPR_DTB_ASN));
	TlbEntry *entry = lookup(VAddr(req->getVaddr()).vpn(),
	asn);

	if (!entry) {
	fetch_misses++;
	return std::make_shared<ItbPageFault>(req->getVaddr());
	}

	req->setPaddr((entry->ppn << PageShift) +
	(VAddr(req->getVaddr()).offset()
	& ~3));

	// check permissions for this access
	if (!(entry->xre &
	(1 << ICM_CM(tc->readMiscRegNoEffect(IPR_ICM))))) {
	// instruction access fault
	fetch_acv++;
	return std::make_shared<ItbAcvFault>(req->getVaddr());
	}

	fetch_hits++;
	}
	}

	// check that the physical address is ok (catch bad physical addresses)
	if (req->getPaddr() & ~PAddrImplMask) {
	return std::make_shared<MachineCheckFault>();
	}

	return checkCacheability(req, true);

	}

	Fault
	TLB::translateData(RequestPtr req, ThreadContext *tc, bool write)
	{
	mode_type mode =
	(mode_type)DTB_CM_CM(tc->readMiscRegNoEffect(IPR_DTB_CM));

	/**
	* Check for alignment faults
	*/
	if (req->getVaddr() & (req->getSize() - 1)) {
	DPRINTF(TLB, "Alignment Fault on %#x, size = %d\n", req->getVaddr(),
	req->getSize());
	uint64_t flags = write ? MM_STAT_WR_MASK : 0;
	return std::make_shared<DtbAlignmentFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}

	if (PcPAL(req->getPC())) {
	mode = (req->getFlags() & AlphaRequestFlags::ALTMODE) ?
	(mode_type)ALT_MODE_AM(
	tc->readMiscRegNoEffect(IPR_ALT_MODE))
	: mode_kernel;
	}

	if (req->getFlags() & Request::PHYSICAL) {
	req->setPaddr(req->getVaddr());
	} else {
	// verify that this is a good virtual address
	if (!validVirtualAddress(req->getVaddr())) {
	if (write) { write_acv++; } else { read_acv++; }
	uint64_t flags = (write ? MM_STAT_WR_MASK : 0) \|
	MM_STAT_BAD_VA_MASK \|
	MM_STAT_ACV_MASK;
	return std::make_shared<DtbPageFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}

	// Check for "superpage" mapping
	if (VAddrSpaceEV6(req->getVaddr()) == 0x7e) {
	// only valid in kernel mode
	if (DTB_CM_CM(tc->readMiscRegNoEffect(IPR_DTB_CM)) !=
	mode_kernel) {
	if (write) { write_acv++; } else { read_acv++; }
	uint64_t flags = ((write ? MM_STAT_WR_MASK : 0) \|
	MM_STAT_ACV_MASK);

	return std::make_shared<DtbAcvFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}

	req->setPaddr(req->getVaddr() & PAddrImplMask);

	// sign extend the physical address properly
	if (req->getPaddr() & PAddrUncachedBit40)
	req->setPaddr(req->getPaddr() \| ULL(0xf0000000000));
	else
	req->setPaddr(req->getPaddr() & ULL(0xffffffffff));
	} else {
	if (write)
	write_accesses++;
	else
	read_accesses++;

	int asn = DTB_ASN_ASN(tc->readMiscRegNoEffect(IPR_DTB_ASN));

	// not a physical address: need to look up pte
	TlbEntry *entry = lookup(VAddr(req->getVaddr()).vpn(), asn);

	if (!entry) {
	// page fault
	if (write) { write_misses++; } else { read_misses++; }
	uint64_t flags = (write ? MM_STAT_WR_MASK : 0) \|
	MM_STAT_DTB_MISS_MASK;
	return (req->getFlags() & AlphaRequestFlags::VPTE) ?
	(Fault)(std::make_shared<PDtbMissFault>(req->getVaddr(),
	req->getFlags(),
	flags)) :
	(Fault)(std::make_shared<NDtbMissFault>(req->getVaddr(),
	req->getFlags(),
	flags));
	}

	req->setPaddr((entry->ppn << PageShift) +
	VAddr(req->getVaddr()).offset());

	if (write) {
	if (!(entry->xwe & MODE2MASK(mode))) {
	// declare the instruction access fault
	write_acv++;
	uint64_t flags = MM_STAT_WR_MASK \|
	MM_STAT_ACV_MASK \|
	(entry->fonw ? MM_STAT_FONW_MASK : 0);
	return std::make_shared<DtbPageFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}
	if (entry->fonw) {
	write_acv++;
	uint64_t flags = MM_STAT_WR_MASK \| MM_STAT_FONW_MASK;
	return std::make_shared<DtbPageFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}
	} else {
	if (!(entry->xre & MODE2MASK(mode))) {
	read_acv++;
	uint64_t flags = MM_STAT_ACV_MASK \|
	(entry->fonr ? MM_STAT_FONR_MASK : 0);
	return std::make_shared<DtbAcvFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}
	if (entry->fonr) {
	read_acv++;
	uint64_t flags = MM_STAT_FONR_MASK;
	return std::make_shared<DtbPageFault>(req->getVaddr(),
	req->getFlags(),
	flags);
	}
	}
	}

	if (write)
	write_hits++;
	else
	read_hits++;
	}

	// check that the physical address is ok (catch bad physical addresses)
	if (req->getPaddr() & ~PAddrImplMask) {
	return std::make_shared<MachineCheckFault>();
	}

	return checkCacheability(req);
	}

	TlbEntry &
	TLB::index(bool advance)
	{
	TlbEntry *entry = &table[nlu];

	if (advance)
	nextnlu();

	return *entry;
	}

	Fault
	TLB::translateAtomic(RequestPtr req, ThreadContext *tc, Mode mode)
	{
	if (mode == Execute)
	return translateInst(req, tc);
	else
	return translateData(req, tc, mode == Write);
	}

	void
	TLB::translateTiming(RequestPtr req, ThreadContext *tc,
	Translation *translation, Mode mode)
	{
	assert(translation);
	translation->finish(translateAtomic(req, tc, mode), req, tc, mode);
	}

	Fault
	TLB::finalizePhysical(RequestPtr req, ThreadContext *tc, Mode mode) const
	{
	return NoFault;
	}

	} // namespace AlphaISA

	AlphaISA::TLB *
	AlphaTLBParams::create()
	{
	return new AlphaISA::TLB(this);
	}