summaryrefslogtreecommitdiff
path: root/src/cpu/kvm/base.hh
blob: df6a67808b886c105e0b66d2de171800d715a084 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
/*
 * 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.
 *
 * 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: Andreas Sandberg
 */

#ifndef __CPU_KVM_BASE_HH__
#define __CPU_KVM_BASE_HH__

#include <pthread.h>

#include <csignal>
#include <memory>

#include "base/statistics.hh"
#include "cpu/kvm/perfevent.hh"
#include "cpu/kvm/timer.hh"
#include "cpu/kvm/vm.hh"
#include "cpu/base.hh"
#include "cpu/simple_thread.hh"

/** Signal to use to trigger exits from KVM */
#define KVM_KICK_SIGNAL SIGRTMIN

// forward declarations
class ThreadContext;
struct BaseKvmCPUParams;

/**
 * Base class for KVM based CPU models
 *
 * All architecture specific KVM implementation should inherit from
 * this class. The most basic CPU models only need to override the
 * updateKvmState() and updateThreadContext() methods to implement
 * state synchronization between gem5 and KVM.
 *
 * The architecture specific implementation is also responsible for
 * delivering interrupts into the VM. This is typically done by
 * overriding tick() and checking the thread context before entering
 * into the VM. In order to deliver an interrupt, the implementation
 * then calls KvmVM::setIRQLine() or BaseKvmCPU::kvmInterrupt()
 * depending on the specifics of the underlying hardware/drivers.
 */
class BaseKvmCPU : public BaseCPU
{
  public:
    BaseKvmCPU(BaseKvmCPUParams *params);
    virtual ~BaseKvmCPU();

    void init();
    void startup();
    void regStats();

    void serializeThread(CheckpointOut &cp,
                         ThreadID tid) const M5_ATTR_OVERRIDE;
    void unserializeThread(CheckpointIn &cp,
                           ThreadID tid) M5_ATTR_OVERRIDE;

    DrainState drain() M5_ATTR_OVERRIDE;
    void drainResume() M5_ATTR_OVERRIDE;

    void switchOut();
    void takeOverFrom(BaseCPU *cpu);

    void verifyMemoryMode() const;

    MasterPort &getDataPort() { return dataPort; }
    MasterPort &getInstPort() { return instPort; }

    void wakeup();
    void activateContext(ThreadID thread_num);
    void suspendContext(ThreadID thread_num);
    void deallocateContext(ThreadID thread_num);
    void haltContext(ThreadID thread_num);

    ThreadContext *getContext(int tn);

    Counter totalInsts() const;
    Counter totalOps() const;

    /** Dump the internal state to the terminal. */
    virtual void dump() const;

    /**
     * Force an exit from KVM.
     *
     * Send a signal to the thread owning this vCPU to get it to exit
     * from KVM. Ignored if the vCPU is not executing.
     */
    void kick() const { pthread_kill(vcpuThread, KVM_KICK_SIGNAL); }

    /**
     * A cached copy of a thread's state in the form of a SimpleThread
     * object.
     *
     * Normally the actual thread state is stored in the KVM vCPU. If KVM has
     * been running this copy is will be out of date. If we recently handled
     * some events within gem5 that required state to be updated this could be
     * the most up-to-date copy. When getContext() or updateThreadContext() is
     * called this copy gets updated.  The method syncThreadContext can
     * be used within a KVM CPU to update the thread context if the
     * KVM state is dirty (i.e., the vCPU has been run since the last
     * update).
     */
    SimpleThread *thread;

    /** ThreadContext object, provides an interface for external
     * objects to modify this thread's state.
     */
    ThreadContext *tc;

    KvmVM &vm;

  protected:
    /**
     *
     * @dot
     *   digraph {
     *     Idle;
     *     Running;
     *     RunningService;
     *     RunningServiceCompletion;
     *
     *     Idle -> Idle;
     *     Idle -> Running [label="activateContext()", URL="\ref activateContext"];
     *     Running -> Running [label="tick()", URL="\ref tick"];
     *     Running -> RunningService [label="tick()", URL="\ref tick"];
     *     Running -> Idle [label="suspendContext()", URL="\ref suspendContext"];
     *     Running -> Idle [label="drain()", URL="\ref drain"];
     *     Idle -> Running [label="drainResume()", URL="\ref drainResume"];
     *     RunningService -> RunningServiceCompletion [label="handleKvmExit()", URL="\ref handleKvmExit"];
     *     RunningServiceCompletion -> Running [label="tick()", URL="\ref tick"];
     *     RunningServiceCompletion -> RunningService [label="tick()", URL="\ref tick"];
     *   }
     * @enddot
     */
    enum Status {
        /** Context not scheduled in KVM.
         *
         * The CPU generally enters this state when the guest execute
         * an instruction that halts the CPU (e.g., WFI on ARM or HLT
         * on X86) if KVM traps this instruction. Ticks are not
         * scheduled in this state.
         *
         * @see suspendContext()
         */
        Idle,
        /** Running normally.
         *
         * This is the normal run state of the CPU. KVM will be
         * entered next time tick() is called.
         */
        Running,
        /** Requiring service at the beginning of the next cycle.
         *
         * The virtual machine has exited and requires service, tick()
         * will call handleKvmExit() on the next cycle. The next state
         * after running service is determined in handleKvmExit() and
         * depends on what kind of service the guest requested:
         * <ul>
         *   <li>IO/MMIO: RunningServiceCompletion
         *   <li>Halt: Idle
         *   <li>Others: Running
         * </ul>
         */
        RunningService,
        /** Service completion in progress.
         *
         * The VM has requested service that requires KVM to be
         * entered once in order to get to a consistent state. This
         * happens in handleKvmExit() or one of its friends after IO
         * exits. After executing tick(), the CPU will transition into
         * the Running or RunningService state.
         */
        RunningServiceCompletion,
    };

    /** CPU run state */
    Status _status;

    /**
     * Execute the CPU until the next event in the main event queue or
     * until the guest needs service from gem5.
     */
    void tick();

    /**
     * Get the value of the hardware cycle counter in the guest.
     *
     * This method is supposed to return the total number of cycles
     * executed in hardware mode relative to some arbitrary point in
     * the past. It's mainly used when estimating the number of cycles
     * actually executed by the CPU in kvmRun(). The default behavior
     * of this method is to use the cycles performance counter, but
     * some architectures may want to use internal registers instead.
     *
     * @return Number of host cycles executed relative to an undefined
     * point in the past.
     */
    virtual uint64_t getHostCycles() const;

    /**
     * Request KVM to run the guest for a given number of ticks. The
     * method returns the approximate number of ticks executed.
     *
     * @note The returned number of ticks can be both larger or
     * smaller than the requested number of ticks. A smaller number
     * can, for example, occur when the guest executes MMIO. A larger
     * number is typically due to performance counter inaccuracies.
     *
     * @note This method is virtual in order to allow implementations
     * to check for architecture specific events (e.g., interrupts)
     * before entering the VM.
     *
     * @note It is the response of the caller (normally tick()) to
     * make sure that the KVM state is synchronized and that the TC is
     * invalidated after entering KVM.
     *
     * @note This method does not normally cause any state
     * transitions. However, if it may suspend the CPU by suspending
     * the thread, which leads to a transition to the Idle state. In
     * such a case, kvm <i>must not</i> be entered.
     *
     * @param ticks Number of ticks to execute, set to 0 to exit
     * immediately after finishing pending operations.
     * @return Number of ticks executed (see note)
     */
    virtual Tick kvmRun(Tick ticks);

    /**
     * Request the CPU to run until draining completes.
     *
     * This function normally calls kvmRun(0) to make KVM finish
     * pending MMIO operations. Architecures implementing
     * archIsDrained() must override this method.
     *
     * @see BaseKvmCPU::archIsDrained()
     *
     * @return Number of ticks executed
     */
    virtual Tick kvmRunDrain();

    /**
     * Get a pointer to the kvm_run structure containing all the input
     * and output parameters from kvmRun().
     */
    struct kvm_run *getKvmRunState() { return _kvmRun; };

    /**
     * Retrieve a pointer to guest data stored at the end of the
     * kvm_run structure. This is mainly used for PIO operations
     * (KVM_EXIT_IO).
     *
     * @param offset Offset as specified by the kvm_run structure
     * @return Pointer to guest data
     */
    uint8_t *getGuestData(uint64_t offset) const {
        return (uint8_t *)_kvmRun + offset;
    };

    /**
     * @addtogroup KvmInterrupts
     * @{
     */
    /**
     * Send a non-maskable interrupt to the guest
     *
     * @note The presence of this call depends on Kvm::capUserNMI().
     */
    void kvmNonMaskableInterrupt();

    /**
     * Send a normal interrupt to the guest
     *
     * @note Make sure that ready_for_interrupt_injection in kvm_run
     * is set prior to calling this function. If not, an interrupt
     * window must be requested by setting request_interrupt_window in
     * kvm_run to 1 and restarting the guest.
     *
     * @param interrupt Structure describing the interrupt to send
     */
    void kvmInterrupt(const struct kvm_interrupt &interrupt);

    /** @} */

    /** @{ */
    /**
     * Get/Set the register state of the guest vCPU
     *
     * KVM has two different interfaces for accessing the state of the
     * guest CPU. One interface updates 'normal' registers and one
     * updates 'special' registers. The distinction between special
     * and normal registers isn't very clear and is architecture
     * dependent.
     */
    void getRegisters(struct kvm_regs &regs) const;
    void setRegisters(const struct kvm_regs &regs);
    void getSpecialRegisters(struct kvm_sregs &regs) const;
    void setSpecialRegisters(const struct kvm_sregs &regs);
    /** @} */

    /** @{ */
    /**
     * Get/Set the guest FPU/vector state
     */
    void getFPUState(struct kvm_fpu &state) const;
    void setFPUState(const struct kvm_fpu &state);
    /** @} */

    /** @{ */
    /**
     * Get/Set single register using the KVM_(SET|GET)_ONE_REG API.
     *
     * @note The presence of this call depends on Kvm::capOneReg().
     */
    void setOneReg(uint64_t id, const void *addr);
    void setOneReg(uint64_t id, uint64_t value) { setOneReg(id, &value); }
    void setOneReg(uint64_t id, uint32_t value) { setOneReg(id, &value); }
    void getOneReg(uint64_t id, void *addr) const;
    uint64_t getOneRegU64(uint64_t id) const {
        uint64_t value;
        getOneReg(id, &value);
        return value;
    }
    uint32_t getOneRegU32(uint64_t id) const {
        uint32_t value;
        getOneReg(id, &value);
        return value;
    }
    /** @} */

    /**
     * Get and format one register for printout.
     *
     * This function call getOneReg() to retrieve the contents of one
     * register and automatically formats it for printing.
     *
     * @note The presence of this call depends on Kvm::capOneReg().
     */
    std::string getAndFormatOneReg(uint64_t id) const;

    /** @{ */
    /**
     * Update the KVM state from the current thread context
     *
     * The base CPU calls this method before starting the guest CPU
     * when the contextDirty flag is set. The architecture dependent
     * CPU implementation is expected to update all guest state
     * (registers, special registers, and FPU state).
     */
    virtual void updateKvmState() = 0;

    /**
     * Update the current thread context with the KVM state
     *
     * The base CPU after the guest updates any of the KVM state. In
     * practice, this happens after kvmRun is called. The architecture
     * dependent code is expected to read the state of the guest CPU
     * and update gem5's thread state.
     */
    virtual void updateThreadContext() = 0;

    /**
     * Update a thread context if the KVM state is dirty with respect
     * to the cached thread context.
     */
    void syncThreadContext();

    /**
     * Update the KVM if the thread context is dirty.
     */
    void syncKvmState();
    /** @} */

    /** @{ */
    /**
     * Main kvmRun exit handler, calls the relevant handleKvmExit*
     * depending on exit type.
     *
     * @return Number of ticks spent servicing the exit request
     */
    virtual Tick handleKvmExit();

    /**
     * The guest performed a legacy IO request (out/inp on x86)
     *
     * @return Number of ticks spent servicing the IO request
     */
    virtual Tick handleKvmExitIO();

    /**
     * The guest requested a monitor service using a hypercall
     *
     * @return Number of ticks spent servicing the hypercall
     */
    virtual Tick handleKvmExitHypercall();

    /**
     * The guest exited because an interrupt window was requested
     *
     * The guest exited because an interrupt window was requested
     * (request_interrupt_window in the kvm_run structure was set to 1
     * before calling kvmRun) and it is now ready to receive
     *
     * @return Number of ticks spent servicing the IRQ
     */
    virtual Tick handleKvmExitIRQWindowOpen();

    /**
     * An unknown architecture dependent error occurred when starting
     * the vCPU
     *
     * The kvm_run data structure contains the hardware error
     * code. The defaults behavior of this method just prints the HW
     * error code and panics. Architecture dependent implementations
     * may want to override this method to provide better,
     * hardware-aware, error messages.
     *
     * @return Number of ticks delay the next CPU tick
     */
    virtual Tick handleKvmExitUnknown();

    /**
     * An unhandled virtualization exception occured
     *
     * Some KVM virtualization drivers return unhandled exceptions to
     * the user-space monitor. This interface is currently only used
     * by the Intel VMX KVM driver.
     *
     * @return Number of ticks delay the next CPU tick
     */
    virtual Tick handleKvmExitException();

    /**
     * KVM failed to start the virtualized CPU
     *
     * The kvm_run data structure contains the hardware-specific error
     * code.
     *
     * @return Number of ticks delay the next CPU tick
     */
    virtual Tick handleKvmExitFailEntry();
    /** @} */

    /**
     * Is the architecture specific code in a state that prevents
     * draining?
     *
     * This method should return false if there are any pending events
     * in the guest vCPU that won't be carried over to the gem5 state
     * and thus will prevent correct checkpointing or CPU handover. It
     * might, for example, check for pending interrupts that have been
     * passed to the vCPU but not acknowledged by the OS. Architecures
     * implementing this method <i>must</i> override
     * kvmRunDrain().
     *
     * @see BaseKvmCPU::kvmRunDrain()
     *
     * @return true if the vCPU is drained, false otherwise.
     */
    virtual bool archIsDrained() const { return true; }

    /**
     * Inject a memory mapped IO request into gem5
     *
     * @param paddr Physical address
     * @param data Pointer to the source/destination buffer
     * @param size Memory access size
     * @param write True if write, False if read
     * @return Number of ticks spent servicing the memory access
     */
    Tick doMMIOAccess(Addr paddr, void *data, int size, bool write);

    /** @{ */
    /**
     * Set the signal mask used in kvmRun()
     *
     * This method allows the signal mask of the thread executing
     * kvmRun() to be overridden inside the actual system call. This
     * allows us to mask timer signals used to force KVM exits while
     * in gem5.
     *
     * The signal mask can be disabled by setting it to NULL.
     *
     * @param mask Signals to mask
     */
    void setSignalMask(const sigset_t *mask);
    /** @} */

    /**
     * @addtogroup KvmIoctl
     * @{
     */
    /**
     * vCPU ioctl interface.
     *
     * @param request KVM vCPU request
     * @param p1 Optional request parameter
     *
     * @return -1 on error (error number in errno), ioctl dependent
     * value otherwise.
     */
    int ioctl(int request, long p1) const;
    int ioctl(int request, void *p1) const {
        return ioctl(request, (long)p1);
    }
    int ioctl(int request) const {
        return ioctl(request, 0L);
    }
    /** @} */


    /**
     * KVM memory port. Uses the default MasterPort behavior, but
     * panics on timing accesses.
     */
    class KVMCpuPort : public MasterPort
    {

      public:
        KVMCpuPort(const std::string &_name, BaseKvmCPU *_cpu)
            : MasterPort(_name, _cpu)
        { }

      protected:
        bool recvTimingResp(PacketPtr pkt)
        {
            panic("The KVM CPU doesn't expect recvTimingResp!\n");
            return true;
        }

        void recvReqRetry()
        {
            panic("The KVM CPU doesn't expect recvReqRetry!\n");
        }

    };

    /** Port for data requests */
    KVMCpuPort dataPort;

    /** Unused dummy port for the instruction interface */
    KVMCpuPort instPort;

    /**
     * Is the gem5 context dirty? Set to true to force an update of
     * the KVM vCPU state upon the next call to kvmRun().
     */
    bool threadContextDirty;

    /**
     * Is the KVM state dirty? Set to true to force an update of
     * the KVM vCPU state upon the next call to kvmRun().
     */
    bool kvmStateDirty;

    /** KVM internal ID of the vCPU */
    const long vcpuID;

    /** ID of the vCPU thread */
    pthread_t vcpuThread;

  private:
    struct TickEvent : public Event
    {
        BaseKvmCPU &cpu;

        TickEvent(BaseKvmCPU &c)
            : Event(CPU_Tick_Pri), cpu(c) {}

        void process() { cpu.tick(); }

        const char *description() const {
            return "BaseKvmCPU tick";
        }
    };

    /**
     * Service MMIO requests in the mmioRing.
     *
     *
     * @return Number of ticks spent servicing the MMIO requests in
     * the MMIO ring buffer
     */
    Tick flushCoalescedMMIO();

    /**
     * Setup a signal handler to catch the timer signal used to
     * switch back to the monitor.
     */
    void setupSignalHandler();

    /**
     * Discard a (potentially) pending signal.
     *
     * @param signum Signal to discard
     * @return true if the signal was pending, false otherwise.
     */
    bool discardPendingSignal(int signum) const;

    /**
     * Thread-specific initialization.
     *
     * Some KVM-related initialization requires us to know the TID of
     * the thread that is going to execute our event queue. For
     * example, when setting up timers, we need to know the TID of the
     * thread executing in KVM in order to deliver the timer signal to
     * that thread. This method is called as the first event in this
     * SimObject's event queue.
     *
     * @see startup
     */
    void startupThread();

    /** Try to drain the CPU if a drain is pending */
    bool tryDrain();

    /** Execute the KVM_RUN ioctl */
    void ioctlRun();

    /** KVM vCPU file descriptor */
    int vcpuFD;
    /** Size of MMAPed kvm_run area */
    int vcpuMMapSize;
    /**
     * Pointer to the kvm_run structure used to communicate parameters
     * with KVM.
     *
     * @note This is the base pointer of the MMAPed KVM region. The
     * first page contains the kvm_run structure. Subsequent pages may
     * contain other data such as the MMIO ring buffer.
     */
    struct kvm_run *_kvmRun;
    /**
     * Coalesced MMIO ring buffer. NULL if coalesced MMIO is not
     * supported.
     */
    struct kvm_coalesced_mmio_ring *mmioRing;
    /** Cached page size of the host */
    const long pageSize;

    TickEvent tickEvent;

    /**
     * Setup an instruction break if there is one pending.
     *
     * Check if there are pending instruction breaks in the CPU's
     * instruction event queue and schedule an instruction break using
     * PerfEvent.
     *
     * @note This method doesn't currently handle the main system
     * instruction event queue.
     */
    void setupInstStop();

    /** @{ */
    /** Setup hardware performance counters */
    void setupCounters();

    /**
     * Setup the guest instruction counter.
     *
     * Setup the guest instruction counter and optionally request a
     * signal every N instructions executed by the guest. This method
     * will re-attach the counter if the counter has already been
     * attached and its sampling settings have changed.
     *
     * @param period Signal period, set to 0 to disable signaling.
     */
    void setupInstCounter(uint64_t period = 0);

    /** Currently active instruction count breakpoint */
    uint64_t activeInstPeriod;

    /**
     * Guest cycle counter.
     *
     * This is the group leader of all performance counters measuring
     * the guest system. It can be used in conjunction with the
     * PerfKvmTimer (see perfControlledByTimer) to trigger exits from
     * KVM.
     */
    PerfKvmCounter hwCycles;

    /**
     * Guest instruction counter.
     *
     * This counter is typically only used to measure the number of
     * instructions executed by the guest. However, it can also be
     * used to trigger exits from KVM if the configuration script
     * requests an exit after a certain number of instructions.
     *
     * @see setupInstBreak
     * @see scheduleInstStop
     */
    PerfKvmCounter hwInstructions;

    /**
     * Does the runTimer control the performance counters?
     *
     * The run timer will automatically enable and disable performance
     * counters if a PerfEvent-based timer is used to control KVM
     * exits.
     */
    bool perfControlledByTimer;
    /** @} */

    /**
     * Timer used to force execution into the monitor after a
     * specified number of simulation tick equivalents have executed
     * in the guest. This counter generates the signal specified by
     * KVM_TIMER_SIGNAL.
     */
    std::unique_ptr<BaseKvmTimer> runTimer;

    /** Host factor as specified in the configuration */
    float hostFactor;

  public:
    /* @{ */
    Stats::Scalar numInsts;
    Stats::Scalar numVMExits;
    Stats::Scalar numVMHalfEntries;
    Stats::Scalar numExitSignal;
    Stats::Scalar numMMIO;
    Stats::Scalar numCoalescedMMIO;
    Stats::Scalar numIO;
    Stats::Scalar numHalt;
    Stats::Scalar numInterrupts;
    Stats::Scalar numHypercalls;
    /* @} */

    /** Number of instructions executed by the CPU */
    Counter ctrInsts;
};

#endif