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 "qemu-common.h"
28 #include "sysemu/tcg.h"
29 #include "sysemu/replay.h"
30 #include "sysemu/cpu-timers.h"
31 #include "qemu/main-loop.h"
32 #include "qemu/notify.h"
33 #include "qemu/guest-random.h"
34 #include "exec/exec-all.h"
35 #include "hw/boards.h"
36 
37 #include "tcg-accel-ops.h"
38 #include "tcg-accel-ops-mttcg.h"
39 
40 typedef struct MttcgForceRcuNotifier {
41     Notifier notifier;
42     CPUState *cpu;
43 } MttcgForceRcuNotifier;
44 
45 static void do_nothing(CPUState *cpu, run_on_cpu_data d)
46 {
47 }
48 
49 static void mttcg_force_rcu(Notifier *notify, void *data)
50 {
51     CPUState *cpu = container_of(notify, MttcgForceRcuNotifier, notifier)->cpu;
52 
53     /*
54      * Called with rcu_registry_lock held, using async_run_on_cpu() ensures
55      * that there are no deadlocks.
56      */
57     async_run_on_cpu(cpu, do_nothing, RUN_ON_CPU_NULL);
58 }
59 
60 /*
61  * In the multi-threaded case each vCPU has its own thread. The TLS
62  * variable current_cpu can be used deep in the code to find the
63  * current CPUState for a given thread.
64  */
65 
66 static void *mttcg_cpu_thread_fn(void *arg)
67 {
68     MttcgForceRcuNotifier force_rcu;
69     CPUState *cpu = arg;
70 
71     assert(tcg_enabled());
72     g_assert(!icount_enabled());
73 
74     rcu_register_thread();
75     force_rcu.notifier.notify = mttcg_force_rcu;
76     force_rcu.cpu = cpu;
77     rcu_add_force_rcu_notifier(&force_rcu.notifier);
78     tcg_register_thread();
79 
80     qemu_mutex_lock_iothread();
81     qemu_thread_get_self(cpu->thread);
82 
83     cpu->thread_id = qemu_get_thread_id();
84     cpu->can_do_io = 1;
85     current_cpu = cpu;
86     cpu_thread_signal_created(cpu);
87     qemu_guest_random_seed_thread_part2(cpu->random_seed);
88 
89     /* process any pending work */
90     cpu->exit_request = 1;
91 
92     do {
93         if (cpu_can_run(cpu)) {
94             int r;
95             qemu_mutex_unlock_iothread();
96             r = tcg_cpus_exec(cpu);
97             qemu_mutex_lock_iothread();
98             switch (r) {
99             case EXCP_DEBUG:
100                 cpu_handle_guest_debug(cpu);
101                 break;
102             case EXCP_HALTED:
103                 /*
104                  * during start-up the vCPU is reset and the thread is
105                  * kicked several times. If we don't ensure we go back
106                  * to sleep in the halted state we won't cleanly
107                  * start-up when the vCPU is enabled.
108                  *
109                  * cpu->halted should ensure we sleep in wait_io_event
110                  */
111                 g_assert(cpu->halted);
112                 break;
113             case EXCP_ATOMIC:
114                 qemu_mutex_unlock_iothread();
115                 cpu_exec_step_atomic(cpu);
116                 qemu_mutex_lock_iothread();
117             default:
118                 /* Ignore everything else? */
119                 break;
120             }
121         }
122 
123         qatomic_mb_set(&cpu->exit_request, 0);
124         qemu_wait_io_event(cpu);
125     } while (!cpu->unplug || cpu_can_run(cpu));
126 
127     tcg_cpus_destroy(cpu);
128     qemu_mutex_unlock_iothread();
129     rcu_remove_force_rcu_notifier(&force_rcu.notifier);
130     rcu_unregister_thread();
131     return NULL;
132 }
133 
134 void mttcg_kick_vcpu_thread(CPUState *cpu)
135 {
136     cpu_exit(cpu);
137 }
138 
139 void mttcg_start_vcpu_thread(CPUState *cpu)
140 {
141     char thread_name[VCPU_THREAD_NAME_SIZE];
142 
143     g_assert(tcg_enabled());
144     tcg_cpu_init_cflags(cpu, current_machine->smp.max_cpus > 1);
145 
146     cpu->thread = g_new0(QemuThread, 1);
147     cpu->halt_cond = g_malloc0(sizeof(QemuCond));
148     qemu_cond_init(cpu->halt_cond);
149 
150     /* create a thread per vCPU with TCG (MTTCG) */
151     snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
152              cpu->cpu_index);
153 
154     qemu_thread_create(cpu->thread, thread_name, mttcg_cpu_thread_fn,
155                        cpu, QEMU_THREAD_JOINABLE);
156 
157 #ifdef _WIN32
158     cpu->hThread = qemu_thread_get_handle(cpu->thread);
159 #endif
160 }
161