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 "qemu/main-loop.h" 31 #include "qemu/notify.h" 32 #include "qemu/guest-random.h" 33 #include "exec/exec-all.h" 34 35 #include "tcg-accel-ops.h" 36 #include "tcg-accel-ops-rr.h" 37 #include "tcg-accel-ops-icount.h" 38 39 /* Kick all RR vCPUs */ 40 void rr_kick_vcpu_thread(CPUState *unused) 41 { 42 CPUState *cpu; 43 44 CPU_FOREACH(cpu) { 45 cpu_exit(cpu); 46 }; 47 } 48 49 /* 50 * TCG vCPU kick timer 51 * 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 55 * scheduled. 56 * 57 * The timer is removed if all vCPUs are idle and restarted again once 58 * idleness is complete. 59 */ 60 61 static QEMUTimer *rr_kick_vcpu_timer; 62 static CPUState *rr_current_cpu; 63 64 static inline int64_t rr_next_kick_time(void) 65 { 66 return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD; 67 } 68 69 /* Kick the currently round-robin scheduled vCPU to next */ 70 static void rr_kick_next_cpu(void) 71 { 72 CPUState *cpu; 73 do { 74 cpu = qatomic_mb_read(&rr_current_cpu); 75 if (cpu) { 76 cpu_exit(cpu); 77 } 78 } while (cpu != qatomic_mb_read(&rr_current_cpu)); 79 } 80 81 static void rr_kick_thread(void *opaque) 82 { 83 timer_mod(rr_kick_vcpu_timer, rr_next_kick_time()); 84 rr_kick_next_cpu(); 85 } 86 87 static void rr_start_kick_timer(void) 88 { 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); 92 } 93 if (rr_kick_vcpu_timer && !timer_pending(rr_kick_vcpu_timer)) { 94 timer_mod(rr_kick_vcpu_timer, rr_next_kick_time()); 95 } 96 } 97 98 static void rr_stop_kick_timer(void) 99 { 100 if (rr_kick_vcpu_timer && timer_pending(rr_kick_vcpu_timer)) { 101 timer_del(rr_kick_vcpu_timer); 102 } 103 } 104 105 static void rr_wait_io_event(void) 106 { 107 CPUState *cpu; 108 109 while (all_cpu_threads_idle()) { 110 rr_stop_kick_timer(); 111 qemu_cond_wait_iothread(first_cpu->halt_cond); 112 } 113 114 rr_start_kick_timer(); 115 116 CPU_FOREACH(cpu) { 117 qemu_wait_io_event_common(cpu); 118 } 119 } 120 121 /* 122 * Destroy any remaining vCPUs which have been unplugged and have 123 * finished running 124 */ 125 static void rr_deal_with_unplugged_cpus(void) 126 { 127 CPUState *cpu; 128 129 CPU_FOREACH(cpu) { 130 if (cpu->unplug && !cpu_can_run(cpu)) { 131 tcg_cpus_destroy(cpu); 132 break; 133 } 134 } 135 } 136 137 static void rr_force_rcu(Notifier *notify, void *data) 138 { 139 rr_kick_next_cpu(); 140 } 141 142 /* 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 147 * elsewhere. 148 */ 149 150 static void *rr_cpu_thread_fn(void *arg) 151 { 152 Notifier force_rcu; 153 CPUState *cpu = arg; 154 155 assert(tcg_enabled()); 156 rcu_register_thread(); 157 force_rcu.notify = rr_force_rcu; 158 rcu_add_force_rcu_notifier(&force_rcu); 159 tcg_register_thread(); 160 161 qemu_mutex_lock_iothread(); 162 qemu_thread_get_self(cpu->thread); 163 164 cpu->thread_id = qemu_get_thread_id(); 165 cpu->can_do_io = 1; 166 cpu_thread_signal_created(cpu); 167 qemu_guest_random_seed_thread_part2(cpu->random_seed); 168 169 /* wait for initial kick-off after machine start */ 170 while (first_cpu->stopped) { 171 qemu_cond_wait_iothread(first_cpu->halt_cond); 172 173 /* process any pending work */ 174 CPU_FOREACH(cpu) { 175 current_cpu = cpu; 176 qemu_wait_io_event_common(cpu); 177 } 178 } 179 180 rr_start_kick_timer(); 181 182 cpu = first_cpu; 183 184 /* process any pending work */ 185 cpu->exit_request = 1; 186 187 while (1) { 188 qemu_mutex_unlock_iothread(); 189 replay_mutex_lock(); 190 qemu_mutex_lock_iothread(); 191 192 if (icount_enabled()) { 193 /* Account partial waits to QEMU_CLOCK_VIRTUAL. */ 194 icount_account_warp_timer(); 195 /* 196 * Run the timers here. This is much more efficient than 197 * waking up the I/O thread and waiting for completion. 198 */ 199 icount_handle_deadline(); 200 } 201 202 replay_mutex_unlock(); 203 204 if (!cpu) { 205 cpu = first_cpu; 206 } 207 208 while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) { 209 210 qatomic_mb_set(&rr_current_cpu, cpu); 211 current_cpu = cpu; 212 213 qemu_clock_enable(QEMU_CLOCK_VIRTUAL, 214 (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0); 215 216 if (cpu_can_run(cpu)) { 217 int r; 218 219 qemu_mutex_unlock_iothread(); 220 if (icount_enabled()) { 221 icount_prepare_for_run(cpu); 222 } 223 r = tcg_cpus_exec(cpu); 224 if (icount_enabled()) { 225 icount_process_data(cpu); 226 } 227 qemu_mutex_lock_iothread(); 228 229 if (r == EXCP_DEBUG) { 230 cpu_handle_guest_debug(cpu); 231 break; 232 } else if (r == EXCP_ATOMIC) { 233 qemu_mutex_unlock_iothread(); 234 cpu_exec_step_atomic(cpu); 235 qemu_mutex_lock_iothread(); 236 break; 237 } 238 } else if (cpu->stop) { 239 if (cpu->unplug) { 240 cpu = CPU_NEXT(cpu); 241 } 242 break; 243 } 244 245 cpu = CPU_NEXT(cpu); 246 } /* while (cpu && !cpu->exit_request).. */ 247 248 /* Does not need qatomic_mb_set because a spurious wakeup is okay. */ 249 qatomic_set(&rr_current_cpu, NULL); 250 251 if (cpu && cpu->exit_request) { 252 qatomic_mb_set(&cpu->exit_request, 0); 253 } 254 255 if (icount_enabled() && all_cpu_threads_idle()) { 256 /* 257 * When all cpus are sleeping (e.g in WFI), to avoid a deadlock 258 * in the main_loop, wake it up in order to start the warp timer. 259 */ 260 qemu_notify_event(); 261 } 262 263 rr_wait_io_event(); 264 rr_deal_with_unplugged_cpus(); 265 } 266 267 rcu_remove_force_rcu_notifier(&force_rcu); 268 rcu_unregister_thread(); 269 return NULL; 270 } 271 272 void rr_start_vcpu_thread(CPUState *cpu) 273 { 274 char thread_name[VCPU_THREAD_NAME_SIZE]; 275 static QemuCond *single_tcg_halt_cond; 276 static QemuThread *single_tcg_cpu_thread; 277 278 g_assert(tcg_enabled()); 279 tcg_cpu_init_cflags(cpu, false); 280 281 if (!single_tcg_cpu_thread) { 282 cpu->thread = g_malloc0(sizeof(QemuThread)); 283 cpu->halt_cond = g_malloc0(sizeof(QemuCond)); 284 qemu_cond_init(cpu->halt_cond); 285 286 /* share a single thread for all cpus with TCG */ 287 snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG"); 288 qemu_thread_create(cpu->thread, thread_name, 289 rr_cpu_thread_fn, 290 cpu, QEMU_THREAD_JOINABLE); 291 292 single_tcg_halt_cond = cpu->halt_cond; 293 single_tcg_cpu_thread = cpu->thread; 294 #ifdef _WIN32 295 cpu->hThread = qemu_thread_get_handle(cpu->thread); 296 #endif 297 } else { 298 /* we share the thread */ 299 cpu->thread = single_tcg_cpu_thread; 300 cpu->halt_cond = single_tcg_halt_cond; 301 cpu->thread_id = first_cpu->thread_id; 302 cpu->can_do_io = 1; 303 cpu->created = true; 304 } 305 } 306