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 #include "tcg/tcg.h"
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     rcu_register_thread();
74     force_rcu.notifier.notify = mttcg_force_rcu;
75     force_rcu.cpu = cpu;
76     rcu_add_force_rcu_notifier(&force_rcu.notifier);
77     tcg_register_thread();
78 
79     qemu_mutex_lock_iothread();
80     qemu_thread_get_self(cpu->thread);
81 
82     cpu->thread_id = qemu_get_thread_id();
83     cpu->can_do_io = 1;
84     current_cpu = cpu;
85     cpu_thread_signal_created(cpu);
86     qemu_guest_random_seed_thread_part2(cpu->random_seed);
87 
88     /* process any pending work */
89     cpu->exit_request = 1;
90 
91     do {
92         if (cpu_can_run(cpu)) {
93             int r;
94             qemu_mutex_unlock_iothread();
95             r = tcg_cpus_exec(cpu);
96             qemu_mutex_lock_iothread();
97             switch (r) {
98             case EXCP_DEBUG:
99                 cpu_handle_guest_debug(cpu);
100                 break;
101             case EXCP_HALTED:
102                 /*
103                  * during start-up the vCPU is reset and the thread is
104                  * kicked several times. If we don't ensure we go back
105                  * to sleep in the halted state we won't cleanly
106                  * start-up when the vCPU is enabled.
107                  *
108                  * cpu->halted should ensure we sleep in wait_io_event
109                  */
110                 g_assert(cpu->halted);
111                 break;
112             case EXCP_ATOMIC:
113                 qemu_mutex_unlock_iothread();
114                 cpu_exec_step_atomic(cpu);
115                 qemu_mutex_lock_iothread();
116             default:
117                 /* Ignore everything else? */
118                 break;
119             }
120         }
121 
122         qatomic_set_mb(&cpu->exit_request, 0);
123         qemu_wait_io_event(cpu);
124     } while (!cpu->unplug || cpu_can_run(cpu));
125 
126     tcg_cpus_destroy(cpu);
127     qemu_mutex_unlock_iothread();
128     rcu_remove_force_rcu_notifier(&force_rcu.notifier);
129     rcu_unregister_thread();
130     return NULL;
131 }
132 
133 void mttcg_kick_vcpu_thread(CPUState *cpu)
134 {
135     cpu_exit(cpu);
136 }
137 
138 void mttcg_start_vcpu_thread(CPUState *cpu)
139 {
140     char thread_name[VCPU_THREAD_NAME_SIZE];
141 
142     g_assert(tcg_enabled());
143     tcg_cpu_init_cflags(cpu, current_machine->smp.max_cpus > 1);
144 
145     cpu->thread = g_new0(QemuThread, 1);
146     cpu->halt_cond = g_malloc0(sizeof(QemuCond));
147     qemu_cond_init(cpu->halt_cond);
148 
149     /* create a thread per vCPU with TCG (MTTCG) */
150     snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
151              cpu->cpu_index);
152 
153     qemu_thread_create(cpu->thread, thread_name, mttcg_cpu_thread_fn,
154                        cpu, QEMU_THREAD_JOINABLE);
155 
156 #ifdef _WIN32
157     cpu->hThread = qemu_thread_get_handle(cpu->thread);
158 #endif
159 }
160