aboutsummaryrefslogtreecommitdiff
path: root/accel/tcg/tcg-cpus-rr.c
blob: 0181d2e4ebcafb91e4f03899a7a61e74d99cf3e8 (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
/*
 * QEMU TCG Single Threaded vCPUs implementation
 *
 * Copyright (c) 2003-2008 Fabrice Bellard
 * Copyright (c) 2014 Red Hat Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "qemu-common.h"
#include "sysemu/tcg.h"
#include "sysemu/replay.h"
#include "qemu/main-loop.h"
#include "qemu/guest-random.h"
#include "exec/exec-all.h"
#include "hw/boards.h"

#include "tcg-cpus.h"
#include "tcg-cpus-rr.h"
#include "tcg-cpus-icount.h"

/* Kick all RR vCPUs */
void rr_kick_vcpu_thread(CPUState *unused)
{
    CPUState *cpu;

    CPU_FOREACH(cpu) {
        cpu_exit(cpu);
    };
}

/*
 * TCG vCPU kick timer
 *
 * The kick timer is responsible for moving single threaded vCPU
 * emulation on to the next vCPU. If more than one vCPU is running a
 * timer event with force a cpu->exit so the next vCPU can get
 * scheduled.
 *
 * The timer is removed if all vCPUs are idle and restarted again once
 * idleness is complete.
 */

static QEMUTimer *rr_kick_vcpu_timer;
static CPUState *rr_current_cpu;

#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)

static inline int64_t rr_next_kick_time(void)
{
    return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
}

/* Kick the currently round-robin scheduled vCPU to next */
static void rr_kick_next_cpu(void)
{
    CPUState *cpu;
    do {
        cpu = qatomic_mb_read(&rr_current_cpu);
        if (cpu) {
            cpu_exit(cpu);
        }
    } while (cpu != qatomic_mb_read(&rr_current_cpu));
}

static void rr_kick_thread(void *opaque)
{
    timer_mod(rr_kick_vcpu_timer, rr_next_kick_time());
    rr_kick_next_cpu();
}

static void rr_start_kick_timer(void)
{
    if (!rr_kick_vcpu_timer && CPU_NEXT(first_cpu)) {
        rr_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
                                           rr_kick_thread, NULL);
    }
    if (rr_kick_vcpu_timer && !timer_pending(rr_kick_vcpu_timer)) {
        timer_mod(rr_kick_vcpu_timer, rr_next_kick_time());
    }
}

static void rr_stop_kick_timer(void)
{
    if (rr_kick_vcpu_timer && timer_pending(rr_kick_vcpu_timer)) {
        timer_del(rr_kick_vcpu_timer);
    }
}

static void rr_wait_io_event(void)
{
    CPUState *cpu;

    while (all_cpu_threads_idle()) {
        rr_stop_kick_timer();
        qemu_cond_wait_iothread(first_cpu->halt_cond);
    }

    rr_start_kick_timer();

    CPU_FOREACH(cpu) {
        qemu_wait_io_event_common(cpu);
    }
}

/*
 * Destroy any remaining vCPUs which have been unplugged and have
 * finished running
 */
static void rr_deal_with_unplugged_cpus(void)
{
    CPUState *cpu;

    CPU_FOREACH(cpu) {
        if (cpu->unplug && !cpu_can_run(cpu)) {
            tcg_cpus_destroy(cpu);
            break;
        }
    }
}

/*
 * In the single-threaded case each vCPU is simulated in turn. If
 * there is more than a single vCPU we create a simple timer to kick
 * the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
 * This is done explicitly rather than relying on side-effects
 * elsewhere.
 */

static void *rr_cpu_thread_fn(void *arg)
{
    CPUState *cpu = arg;

    assert(tcg_enabled());
    rcu_register_thread();
    tcg_register_thread();

    qemu_mutex_lock_iothread();
    qemu_thread_get_self(cpu->thread);

    cpu->thread_id = qemu_get_thread_id();
    cpu->can_do_io = 1;
    cpu_thread_signal_created(cpu);
    qemu_guest_random_seed_thread_part2(cpu->random_seed);

    /* wait for initial kick-off after machine start */
    while (first_cpu->stopped) {
        qemu_cond_wait_iothread(first_cpu->halt_cond);

        /* process any pending work */
        CPU_FOREACH(cpu) {
            current_cpu = cpu;
            qemu_wait_io_event_common(cpu);
        }
    }

    rr_start_kick_timer();

    cpu = first_cpu;

    /* process any pending work */
    cpu->exit_request = 1;

    while (1) {
        qemu_mutex_unlock_iothread();
        replay_mutex_lock();
        qemu_mutex_lock_iothread();

        if (icount_enabled()) {
            /* Account partial waits to QEMU_CLOCK_VIRTUAL.  */
            icount_account_warp_timer();
            /*
             * Run the timers here.  This is much more efficient than
             * waking up the I/O thread and waiting for completion.
             */
            icount_handle_deadline();
        }

        replay_mutex_unlock();

        if (!cpu) {
            cpu = first_cpu;
        }

        while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) {

            qatomic_mb_set(&rr_current_cpu, cpu);
            current_cpu = cpu;

            qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
                              (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);

            if (cpu_can_run(cpu)) {
                int r;

                qemu_mutex_unlock_iothread();
                if (icount_enabled()) {
                    icount_prepare_for_run(cpu);
                }
                r = tcg_cpus_exec(cpu);
                if (icount_enabled()) {
                    icount_process_data(cpu);
                }
                qemu_mutex_lock_iothread();

                if (r == EXCP_DEBUG) {
                    cpu_handle_guest_debug(cpu);
                    break;
                } else if (r == EXCP_ATOMIC) {
                    qemu_mutex_unlock_iothread();
                    cpu_exec_step_atomic(cpu);
                    qemu_mutex_lock_iothread();
                    break;
                }
            } else if (cpu->stop) {
                if (cpu->unplug) {
                    cpu = CPU_NEXT(cpu);
                }
                break;
            }

            cpu = CPU_NEXT(cpu);
        } /* while (cpu && !cpu->exit_request).. */

        /* Does not need qatomic_mb_set because a spurious wakeup is okay.  */
        qatomic_set(&rr_current_cpu, NULL);

        if (cpu && cpu->exit_request) {
            qatomic_mb_set(&cpu->exit_request, 0);
        }

        if (icount_enabled() && all_cpu_threads_idle()) {
            /*
             * When all cpus are sleeping (e.g in WFI), to avoid a deadlock
             * in the main_loop, wake it up in order to start the warp timer.
             */
            qemu_notify_event();
        }

        rr_wait_io_event();
        rr_deal_with_unplugged_cpus();
    }

    rcu_unregister_thread();
    return NULL;
}

void rr_start_vcpu_thread(CPUState *cpu)
{
    char thread_name[VCPU_THREAD_NAME_SIZE];
    static QemuCond *single_tcg_halt_cond;
    static QemuThread *single_tcg_cpu_thread;

    g_assert(tcg_enabled());
    parallel_cpus = false;

    if (!single_tcg_cpu_thread) {
        cpu->thread = g_malloc0(sizeof(QemuThread));
        cpu->halt_cond = g_malloc0(sizeof(QemuCond));
        qemu_cond_init(cpu->halt_cond);

        /* share a single thread for all cpus with TCG */
        snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG");
        qemu_thread_create(cpu->thread, thread_name,
                           rr_cpu_thread_fn,
                           cpu, QEMU_THREAD_JOINABLE);

        single_tcg_halt_cond = cpu->halt_cond;
        single_tcg_cpu_thread = cpu->thread;
#ifdef _WIN32
        cpu->hThread = qemu_thread_get_handle(cpu->thread);
#endif
    } else {
        /* we share the thread */
        cpu->thread = single_tcg_cpu_thread;
        cpu->halt_cond = single_tcg_halt_cond;
        cpu->thread_id = first_cpu->thread_id;
        cpu->can_do_io = 1;
        cpu->created = true;
    }
}

const CpusAccel tcg_cpus_rr = {
    .create_vcpu_thread = rr_start_vcpu_thread,
    .kick_vcpu_thread = rr_kick_vcpu_thread,

    .handle_interrupt = tcg_cpus_handle_interrupt,
};