1 /*
2  * QEMU TCG Multi Threaded vCPUs implementation
3  *
4  * Copyright (c) 2003-2008 Fabrice Bellard
5  * Copyright (c) 2014 Red Hat Inc.
6  *
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:
13  *
14  * The above copyright notice and this permission notice shall be included in
15  * all copies or substantial portions of the Software.
16  *
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
23  * THE SOFTWARE.
24  */
25 
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"
34 #include "hw/boards.h"
35 
36 #include "tcg-accel-ops.h"
37 #include "tcg-accel-ops-mttcg.h"
38 
39 typedef struct MttcgForceRcuNotifier {
40     Notifier notifier;
41     CPUState *cpu;
42 } MttcgForceRcuNotifier;
43 
44 static void do_nothing(CPUState *cpu, run_on_cpu_data d)
45 {
46 }
47 
48 static void mttcg_force_rcu(Notifier *notify, void *data)
49 {
50     CPUState *cpu = container_of(notify, MttcgForceRcuNotifier, notifier)->cpu;
51 
52     /*
53      * Called with rcu_registry_lock held, using async_run_on_cpu() ensures
54      * that there are no deadlocks.
55      */
56     async_run_on_cpu(cpu, do_nothing, RUN_ON_CPU_NULL);
57 }
58 
59 /*
60  * In the multi-threaded case each vCPU has its own thread. The TLS
61  * variable current_cpu can be used deep in the code to find the
62  * current CPUState for a given thread.
63  */
64 
65 static void *mttcg_cpu_thread_fn(void *arg)
66 {
67     MttcgForceRcuNotifier force_rcu;
68     CPUState *cpu = arg;
69 
70     assert(tcg_enabled());
71     g_assert(!icount_enabled());
72 
73     tcg_cpu_init_cflags(cpu, current_machine->smp.max_cpus > 1);
74 
75     rcu_register_thread();
76     force_rcu.notifier.notify = mttcg_force_rcu;
77     force_rcu.cpu = cpu;
78     rcu_add_force_rcu_notifier(&force_rcu.notifier);
79     tcg_register_thread();
80 
81     qemu_mutex_lock_iothread();
82     qemu_thread_get_self(cpu->thread);
83 
84     cpu->thread_id = qemu_get_thread_id();
85     cpu->can_do_io = 1;
86     current_cpu = cpu;
87     cpu_thread_signal_created(cpu);
88     qemu_guest_random_seed_thread_part2(cpu->random_seed);
89 
90     /* process any pending work */
91     cpu->exit_request = 1;
92 
93     do {
94         if (cpu_can_run(cpu)) {
95             int r;
96             qemu_mutex_unlock_iothread();
97             r = tcg_cpus_exec(cpu);
98             qemu_mutex_lock_iothread();
99             switch (r) {
100             case EXCP_DEBUG:
101                 cpu_handle_guest_debug(cpu);
102                 break;
103             case EXCP_HALTED:
104                 /*
105                  * during start-up the vCPU is reset and the thread is
106                  * kicked several times. If we don't ensure we go back
107                  * to sleep in the halted state we won't cleanly
108                  * start-up when the vCPU is enabled.
109                  *
110                  * cpu->halted should ensure we sleep in wait_io_event
111                  */
112                 g_assert(cpu->halted);
113                 break;
114             case EXCP_ATOMIC:
115                 qemu_mutex_unlock_iothread();
116                 cpu_exec_step_atomic(cpu);
117                 qemu_mutex_lock_iothread();
118             default:
119                 /* Ignore everything else? */
120                 break;
121             }
122         }
123 
124         qatomic_mb_set(&cpu->exit_request, 0);
125         qemu_wait_io_event(cpu);
126     } while (!cpu->unplug || cpu_can_run(cpu));
127 
128     tcg_cpus_destroy(cpu);
129     qemu_mutex_unlock_iothread();
130     rcu_remove_force_rcu_notifier(&force_rcu.notifier);
131     rcu_unregister_thread();
132     return NULL;
133 }
134 
135 void mttcg_kick_vcpu_thread(CPUState *cpu)
136 {
137     cpu_exit(cpu);
138 }
139 
140 void mttcg_start_vcpu_thread(CPUState *cpu)
141 {
142     char thread_name[VCPU_THREAD_NAME_SIZE];
143 
144     cpu->thread = g_new0(QemuThread, 1);
145     cpu->halt_cond = g_malloc0(sizeof(QemuCond));
146     qemu_cond_init(cpu->halt_cond);
147 
148     /* create a thread per vCPU with TCG (MTTCG) */
149     snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
150              cpu->cpu_index);
151 
152     qemu_thread_create(cpu->thread, thread_name, mttcg_cpu_thread_fn,
153                        cpu, QEMU_THREAD_JOINABLE);
154 
155 #ifdef _WIN32
156     cpu->hThread = qemu_thread_get_handle(cpu->thread);
157 #endif
158 }
159