1 /* 2 * QEMU TCG Single 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 36 #include "tcg-accel-ops.h" 37 #include "tcg-accel-ops-rr.h" 38 #include "tcg-accel-ops-icount.h" 39 40 /* Kick all RR vCPUs */ 41 void rr_kick_vcpu_thread(CPUState *unused) 42 { 43 CPUState *cpu; 44 45 CPU_FOREACH(cpu) { 46 cpu_exit(cpu); 47 }; 48 } 49 50 /* 51 * TCG vCPU kick timer 52 * 53 * The kick timer is responsible for moving single threaded vCPU 54 * emulation on to the next vCPU. If more than one vCPU is running a 55 * timer event with force a cpu->exit so the next vCPU can get 56 * scheduled. 57 * 58 * The timer is removed if all vCPUs are idle and restarted again once 59 * idleness is complete. 60 */ 61 62 static QEMUTimer *rr_kick_vcpu_timer; 63 static CPUState *rr_current_cpu; 64 65 static inline int64_t rr_next_kick_time(void) 66 { 67 return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD; 68 } 69 70 /* Kick the currently round-robin scheduled vCPU to next */ 71 static void rr_kick_next_cpu(void) 72 { 73 CPUState *cpu; 74 do { 75 cpu = qatomic_mb_read(&rr_current_cpu); 76 if (cpu) { 77 cpu_exit(cpu); 78 } 79 } while (cpu != qatomic_mb_read(&rr_current_cpu)); 80 } 81 82 static void rr_kick_thread(void *opaque) 83 { 84 timer_mod(rr_kick_vcpu_timer, rr_next_kick_time()); 85 rr_kick_next_cpu(); 86 } 87 88 static void rr_start_kick_timer(void) 89 { 90 if (!rr_kick_vcpu_timer && CPU_NEXT(first_cpu)) { 91 rr_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, 92 rr_kick_thread, NULL); 93 } 94 if (rr_kick_vcpu_timer && !timer_pending(rr_kick_vcpu_timer)) { 95 timer_mod(rr_kick_vcpu_timer, rr_next_kick_time()); 96 } 97 } 98 99 static void rr_stop_kick_timer(void) 100 { 101 if (rr_kick_vcpu_timer && timer_pending(rr_kick_vcpu_timer)) { 102 timer_del(rr_kick_vcpu_timer); 103 } 104 } 105 106 static void rr_wait_io_event(void) 107 { 108 CPUState *cpu; 109 110 while (all_cpu_threads_idle()) { 111 rr_stop_kick_timer(); 112 qemu_cond_wait_iothread(first_cpu->halt_cond); 113 } 114 115 rr_start_kick_timer(); 116 117 CPU_FOREACH(cpu) { 118 qemu_wait_io_event_common(cpu); 119 } 120 } 121 122 /* 123 * Destroy any remaining vCPUs which have been unplugged and have 124 * finished running 125 */ 126 static void rr_deal_with_unplugged_cpus(void) 127 { 128 CPUState *cpu; 129 130 CPU_FOREACH(cpu) { 131 if (cpu->unplug && !cpu_can_run(cpu)) { 132 tcg_cpus_destroy(cpu); 133 break; 134 } 135 } 136 } 137 138 static void rr_force_rcu(Notifier *notify, void *data) 139 { 140 rr_kick_next_cpu(); 141 } 142 143 /* 144 * In the single-threaded case each vCPU is simulated in turn. If 145 * there is more than a single vCPU we create a simple timer to kick 146 * the vCPU and ensure we don't get stuck in a tight loop in one vCPU. 147 * This is done explicitly rather than relying on side-effects 148 * elsewhere. 149 */ 150 151 static void *rr_cpu_thread_fn(void *arg) 152 { 153 Notifier force_rcu; 154 CPUState *cpu = arg; 155 156 assert(tcg_enabled()); 157 rcu_register_thread(); 158 force_rcu.notify = rr_force_rcu; 159 rcu_add_force_rcu_notifier(&force_rcu); 160 tcg_register_thread(); 161 162 qemu_mutex_lock_iothread(); 163 qemu_thread_get_self(cpu->thread); 164 165 cpu->thread_id = qemu_get_thread_id(); 166 cpu->can_do_io = 1; 167 cpu_thread_signal_created(cpu); 168 qemu_guest_random_seed_thread_part2(cpu->random_seed); 169 170 /* wait for initial kick-off after machine start */ 171 while (first_cpu->stopped) { 172 qemu_cond_wait_iothread(first_cpu->halt_cond); 173 174 /* process any pending work */ 175 CPU_FOREACH(cpu) { 176 current_cpu = cpu; 177 qemu_wait_io_event_common(cpu); 178 } 179 } 180 181 rr_start_kick_timer(); 182 183 cpu = first_cpu; 184 185 /* process any pending work */ 186 cpu->exit_request = 1; 187 188 while (1) { 189 qemu_mutex_unlock_iothread(); 190 replay_mutex_lock(); 191 qemu_mutex_lock_iothread(); 192 193 if (icount_enabled()) { 194 /* Account partial waits to QEMU_CLOCK_VIRTUAL. */ 195 icount_account_warp_timer(); 196 /* 197 * Run the timers here. This is much more efficient than 198 * waking up the I/O thread and waiting for completion. 199 */ 200 icount_handle_deadline(); 201 } 202 203 replay_mutex_unlock(); 204 205 if (!cpu) { 206 cpu = first_cpu; 207 } 208 209 while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) { 210 211 qatomic_mb_set(&rr_current_cpu, cpu); 212 current_cpu = cpu; 213 214 qemu_clock_enable(QEMU_CLOCK_VIRTUAL, 215 (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0); 216 217 if (cpu_can_run(cpu)) { 218 int r; 219 220 qemu_mutex_unlock_iothread(); 221 if (icount_enabled()) { 222 icount_prepare_for_run(cpu); 223 } 224 r = tcg_cpus_exec(cpu); 225 if (icount_enabled()) { 226 icount_process_data(cpu); 227 } 228 qemu_mutex_lock_iothread(); 229 230 if (r == EXCP_DEBUG) { 231 cpu_handle_guest_debug(cpu); 232 break; 233 } else if (r == EXCP_ATOMIC) { 234 qemu_mutex_unlock_iothread(); 235 cpu_exec_step_atomic(cpu); 236 qemu_mutex_lock_iothread(); 237 break; 238 } 239 } else if (cpu->stop) { 240 if (cpu->unplug) { 241 cpu = CPU_NEXT(cpu); 242 } 243 break; 244 } 245 246 cpu = CPU_NEXT(cpu); 247 } /* while (cpu && !cpu->exit_request).. */ 248 249 /* Does not need qatomic_mb_set because a spurious wakeup is okay. */ 250 qatomic_set(&rr_current_cpu, NULL); 251 252 if (cpu && cpu->exit_request) { 253 qatomic_mb_set(&cpu->exit_request, 0); 254 } 255 256 if (icount_enabled() && all_cpu_threads_idle()) { 257 /* 258 * When all cpus are sleeping (e.g in WFI), to avoid a deadlock 259 * in the main_loop, wake it up in order to start the warp timer. 260 */ 261 qemu_notify_event(); 262 } 263 264 rr_wait_io_event(); 265 rr_deal_with_unplugged_cpus(); 266 } 267 268 rcu_remove_force_rcu_notifier(&force_rcu); 269 rcu_unregister_thread(); 270 return NULL; 271 } 272 273 void rr_start_vcpu_thread(CPUState *cpu) 274 { 275 char thread_name[VCPU_THREAD_NAME_SIZE]; 276 static QemuCond *single_tcg_halt_cond; 277 static QemuThread *single_tcg_cpu_thread; 278 279 g_assert(tcg_enabled()); 280 tcg_cpu_init_cflags(cpu, false); 281 282 if (!single_tcg_cpu_thread) { 283 cpu->thread = g_new0(QemuThread, 1); 284 cpu->halt_cond = g_new0(QemuCond, 1); 285 qemu_cond_init(cpu->halt_cond); 286 287 /* share a single thread for all cpus with TCG */ 288 snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG"); 289 qemu_thread_create(cpu->thread, thread_name, 290 rr_cpu_thread_fn, 291 cpu, QEMU_THREAD_JOINABLE); 292 293 single_tcg_halt_cond = cpu->halt_cond; 294 single_tcg_cpu_thread = cpu->thread; 295 #ifdef _WIN32 296 cpu->hThread = qemu_thread_get_handle(cpu->thread); 297 #endif 298 } else { 299 /* we share the thread */ 300 cpu->thread = single_tcg_cpu_thread; 301 cpu->halt_cond = single_tcg_halt_cond; 302 cpu->thread_id = first_cpu->thread_id; 303 cpu->can_do_io = 1; 304 cpu->created = true; 305 } 306 } 307