2 * QEMU TCG Single Threaded vCPUs implementation
4 * Copyright (c) 2003-2008 Fabrice Bellard
5 * Copyright (c) 2014 Red Hat Inc.
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
26 #include "qemu/osdep.h"
27 #include "sysemu/tcg.h"
28 #include "sysemu/replay.h"
29 #include "sysemu/cpu-timers.h"
30 #include "qemu/main-loop.h"
31 #include "qemu/notify.h"
32 #include "qemu/guest-random.h"
33 #include "exec/exec-all.h"
35 #include "tcg-accel-ops.h"
36 #include "tcg-accel-ops-rr.h"
37 #include "tcg-accel-ops-icount.h"
39 /* Kick all RR vCPUs */
40 void rr_kick_vcpu_thread(CPUState
*unused
)
52 * The kick timer is responsible for moving single threaded vCPU
53 * emulation on to the next vCPU. If more than one vCPU is running a
54 * timer event with force a cpu->exit so the next vCPU can get
57 * The timer is removed if all vCPUs are idle and restarted again once
58 * idleness is complete.
61 static QEMUTimer
*rr_kick_vcpu_timer
;
62 static CPUState
*rr_current_cpu
;
64 static inline int64_t rr_next_kick_time(void)
66 return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL
) + TCG_KICK_PERIOD
;
69 /* Kick the currently round-robin scheduled vCPU to next */
70 static void rr_kick_next_cpu(void)
74 cpu
= qatomic_mb_read(&rr_current_cpu
);
78 } while (cpu
!= qatomic_mb_read(&rr_current_cpu
));
81 static void rr_kick_thread(void *opaque
)
83 timer_mod(rr_kick_vcpu_timer
, rr_next_kick_time());
87 static void rr_start_kick_timer(void)
89 if (!rr_kick_vcpu_timer
&& CPU_NEXT(first_cpu
)) {
90 rr_kick_vcpu_timer
= timer_new_ns(QEMU_CLOCK_VIRTUAL
,
91 rr_kick_thread
, NULL
);
93 if (rr_kick_vcpu_timer
&& !timer_pending(rr_kick_vcpu_timer
)) {
94 timer_mod(rr_kick_vcpu_timer
, rr_next_kick_time());
98 static void rr_stop_kick_timer(void)
100 if (rr_kick_vcpu_timer
&& timer_pending(rr_kick_vcpu_timer
)) {
101 timer_del(rr_kick_vcpu_timer
);
105 static void rr_wait_io_event(void)
109 while (all_cpu_threads_idle()) {
110 rr_stop_kick_timer();
111 qemu_cond_wait_iothread(first_cpu
->halt_cond
);
114 rr_start_kick_timer();
117 qemu_wait_io_event_common(cpu
);
122 * Destroy any remaining vCPUs which have been unplugged and have
125 static void rr_deal_with_unplugged_cpus(void)
130 if (cpu
->unplug
&& !cpu_can_run(cpu
)) {
131 tcg_cpus_destroy(cpu
);
137 static void rr_force_rcu(Notifier
*notify
, void *data
)
143 * In the single-threaded case each vCPU is simulated in turn. If
144 * there is more than a single vCPU we create a simple timer to kick
145 * the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
146 * This is done explicitly rather than relying on side-effects
150 static void *rr_cpu_thread_fn(void *arg
)
155 g_assert(tcg_enabled());
156 tcg_cpu_init_cflags(cpu
, false);
158 rcu_register_thread();
159 force_rcu
.notify
= rr_force_rcu
;
160 rcu_add_force_rcu_notifier(&force_rcu
);
161 tcg_register_thread();
163 qemu_mutex_lock_iothread();
164 qemu_thread_get_self(cpu
->thread
);
166 cpu
->thread_id
= qemu_get_thread_id();
168 cpu_thread_signal_created(cpu
);
169 qemu_guest_random_seed_thread_part2(cpu
->random_seed
);
171 /* wait for initial kick-off after machine start */
172 while (first_cpu
->stopped
) {
173 qemu_cond_wait_iothread(first_cpu
->halt_cond
);
175 /* process any pending work */
178 qemu_wait_io_event_common(cpu
);
182 rr_start_kick_timer();
186 /* process any pending work */
187 cpu
->exit_request
= 1;
190 qemu_mutex_unlock_iothread();
192 qemu_mutex_lock_iothread();
194 if (icount_enabled()) {
195 /* Account partial waits to QEMU_CLOCK_VIRTUAL. */
196 icount_account_warp_timer();
198 * Run the timers here. This is much more efficient than
199 * waking up the I/O thread and waiting for completion.
201 icount_handle_deadline();
204 replay_mutex_unlock();
210 while (cpu
&& cpu_work_list_empty(cpu
) && !cpu
->exit_request
) {
212 qatomic_mb_set(&rr_current_cpu
, cpu
);
215 qemu_clock_enable(QEMU_CLOCK_VIRTUAL
,
216 (cpu
->singlestep_enabled
& SSTEP_NOTIMER
) == 0);
218 if (cpu_can_run(cpu
)) {
221 qemu_mutex_unlock_iothread();
222 if (icount_enabled()) {
223 icount_prepare_for_run(cpu
);
225 r
= tcg_cpus_exec(cpu
);
226 if (icount_enabled()) {
227 icount_process_data(cpu
);
229 qemu_mutex_lock_iothread();
231 if (r
== EXCP_DEBUG
) {
232 cpu_handle_guest_debug(cpu
);
234 } else if (r
== EXCP_ATOMIC
) {
235 qemu_mutex_unlock_iothread();
236 cpu_exec_step_atomic(cpu
);
237 qemu_mutex_lock_iothread();
240 } else if (cpu
->stop
) {
248 } /* while (cpu && !cpu->exit_request).. */
250 /* Does not need qatomic_mb_set because a spurious wakeup is okay. */
251 qatomic_set(&rr_current_cpu
, NULL
);
253 if (cpu
&& cpu
->exit_request
) {
254 qatomic_mb_set(&cpu
->exit_request
, 0);
257 if (icount_enabled() && all_cpu_threads_idle()) {
259 * When all cpus are sleeping (e.g in WFI), to avoid a deadlock
260 * in the main_loop, wake it up in order to start the warp timer.
266 rr_deal_with_unplugged_cpus();
269 rcu_remove_force_rcu_notifier(&force_rcu
);
270 rcu_unregister_thread();
274 void rr_start_vcpu_thread(CPUState
*cpu
)
276 char thread_name
[VCPU_THREAD_NAME_SIZE
];
277 static QemuCond
*single_tcg_halt_cond
;
278 static QemuThread
*single_tcg_cpu_thread
;
280 if (!single_tcg_cpu_thread
) {
281 cpu
->thread
= g_new0(QemuThread
, 1);
282 cpu
->halt_cond
= g_new0(QemuCond
, 1);
283 qemu_cond_init(cpu
->halt_cond
);
285 /* share a single thread for all cpus with TCG */
286 snprintf(thread_name
, VCPU_THREAD_NAME_SIZE
, "ALL CPUs/TCG");
287 qemu_thread_create(cpu
->thread
, thread_name
,
289 cpu
, QEMU_THREAD_JOINABLE
);
291 single_tcg_halt_cond
= cpu
->halt_cond
;
292 single_tcg_cpu_thread
= cpu
->thread
;
294 cpu
->hThread
= qemu_thread_get_handle(cpu
->thread
);
297 /* we share the thread */
298 cpu
->thread
= single_tcg_cpu_thread
;
299 cpu
->halt_cond
= single_tcg_halt_cond
;
300 cpu
->thread_id
= first_cpu
->thread_id
;