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/guest-random.h" 32 #include "exec/exec-all.h" 33 #include "hw/boards.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 #define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10) 65 66 static inline int64_t rr_next_kick_time(void) 67 { 68 return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD; 69 } 70 71 /* Kick the currently round-robin scheduled vCPU to next */ 72 static void rr_kick_next_cpu(void) 73 { 74 CPUState *cpu; 75 do { 76 cpu = qatomic_mb_read(&rr_current_cpu); 77 if (cpu) { 78 cpu_exit(cpu); 79 } 80 } while (cpu != qatomic_mb_read(&rr_current_cpu)); 81 } 82 83 static void rr_kick_thread(void *opaque) 84 { 85 timer_mod(rr_kick_vcpu_timer, rr_next_kick_time()); 86 rr_kick_next_cpu(); 87 } 88 89 static void rr_start_kick_timer(void) 90 { 91 if (!rr_kick_vcpu_timer && CPU_NEXT(first_cpu)) { 92 rr_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, 93 rr_kick_thread, NULL); 94 } 95 if (rr_kick_vcpu_timer && !timer_pending(rr_kick_vcpu_timer)) { 96 timer_mod(rr_kick_vcpu_timer, rr_next_kick_time()); 97 } 98 } 99 100 static void rr_stop_kick_timer(void) 101 { 102 if (rr_kick_vcpu_timer && timer_pending(rr_kick_vcpu_timer)) { 103 timer_del(rr_kick_vcpu_timer); 104 } 105 } 106 107 static void rr_wait_io_event(void) 108 { 109 CPUState *cpu; 110 111 while (all_cpu_threads_idle()) { 112 rr_stop_kick_timer(); 113 qemu_cond_wait_iothread(first_cpu->halt_cond); 114 } 115 116 rr_start_kick_timer(); 117 118 CPU_FOREACH(cpu) { 119 qemu_wait_io_event_common(cpu); 120 } 121 } 122 123 /* 124 * Destroy any remaining vCPUs which have been unplugged and have 125 * finished running 126 */ 127 static void rr_deal_with_unplugged_cpus(void) 128 { 129 CPUState *cpu; 130 131 CPU_FOREACH(cpu) { 132 if (cpu->unplug && !cpu_can_run(cpu)) { 133 tcg_cpus_destroy(cpu); 134 break; 135 } 136 } 137 } 138 139 /* 140 * In the single-threaded case each vCPU is simulated in turn. If 141 * there is more than a single vCPU we create a simple timer to kick 142 * the vCPU and ensure we don't get stuck in a tight loop in one vCPU. 143 * This is done explicitly rather than relying on side-effects 144 * elsewhere. 145 */ 146 147 static void *rr_cpu_thread_fn(void *arg) 148 { 149 CPUState *cpu = arg; 150 151 assert(tcg_enabled()); 152 rcu_register_thread(); 153 tcg_register_thread(); 154 155 qemu_mutex_lock_iothread(); 156 qemu_thread_get_self(cpu->thread); 157 158 cpu->thread_id = qemu_get_thread_id(); 159 cpu->can_do_io = 1; 160 cpu_thread_signal_created(cpu); 161 qemu_guest_random_seed_thread_part2(cpu->random_seed); 162 163 /* wait for initial kick-off after machine start */ 164 while (first_cpu->stopped) { 165 qemu_cond_wait_iothread(first_cpu->halt_cond); 166 167 /* process any pending work */ 168 CPU_FOREACH(cpu) { 169 current_cpu = cpu; 170 qemu_wait_io_event_common(cpu); 171 } 172 } 173 174 rr_start_kick_timer(); 175 176 cpu = first_cpu; 177 178 /* process any pending work */ 179 cpu->exit_request = 1; 180 181 while (1) { 182 qemu_mutex_unlock_iothread(); 183 replay_mutex_lock(); 184 qemu_mutex_lock_iothread(); 185 186 if (icount_enabled()) { 187 /* Account partial waits to QEMU_CLOCK_VIRTUAL. */ 188 icount_account_warp_timer(); 189 /* 190 * Run the timers here. This is much more efficient than 191 * waking up the I/O thread and waiting for completion. 192 */ 193 icount_handle_deadline(); 194 } 195 196 replay_mutex_unlock(); 197 198 if (!cpu) { 199 cpu = first_cpu; 200 } 201 202 while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) { 203 204 qatomic_mb_set(&rr_current_cpu, cpu); 205 current_cpu = cpu; 206 207 qemu_clock_enable(QEMU_CLOCK_VIRTUAL, 208 (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0); 209 210 if (cpu_can_run(cpu)) { 211 int r; 212 213 qemu_mutex_unlock_iothread(); 214 if (icount_enabled()) { 215 icount_prepare_for_run(cpu); 216 } 217 r = tcg_cpus_exec(cpu); 218 if (icount_enabled()) { 219 icount_process_data(cpu); 220 } 221 qemu_mutex_lock_iothread(); 222 223 if (r == EXCP_DEBUG) { 224 cpu_handle_guest_debug(cpu); 225 break; 226 } else if (r == EXCP_ATOMIC) { 227 qemu_mutex_unlock_iothread(); 228 cpu_exec_step_atomic(cpu); 229 qemu_mutex_lock_iothread(); 230 break; 231 } 232 } else if (cpu->stop) { 233 if (cpu->unplug) { 234 cpu = CPU_NEXT(cpu); 235 } 236 break; 237 } 238 239 cpu = CPU_NEXT(cpu); 240 } /* while (cpu && !cpu->exit_request).. */ 241 242 /* Does not need qatomic_mb_set because a spurious wakeup is okay. */ 243 qatomic_set(&rr_current_cpu, NULL); 244 245 if (cpu && cpu->exit_request) { 246 qatomic_mb_set(&cpu->exit_request, 0); 247 } 248 249 if (icount_enabled() && all_cpu_threads_idle()) { 250 /* 251 * When all cpus are sleeping (e.g in WFI), to avoid a deadlock 252 * in the main_loop, wake it up in order to start the warp timer. 253 */ 254 qemu_notify_event(); 255 } 256 257 rr_wait_io_event(); 258 rr_deal_with_unplugged_cpus(); 259 } 260 261 rcu_unregister_thread(); 262 return NULL; 263 } 264 265 void rr_start_vcpu_thread(CPUState *cpu) 266 { 267 char thread_name[VCPU_THREAD_NAME_SIZE]; 268 static QemuCond *single_tcg_halt_cond; 269 static QemuThread *single_tcg_cpu_thread; 270 271 g_assert(tcg_enabled()); 272 parallel_cpus = false; 273 274 if (!single_tcg_cpu_thread) { 275 cpu->thread = g_malloc0(sizeof(QemuThread)); 276 cpu->halt_cond = g_malloc0(sizeof(QemuCond)); 277 qemu_cond_init(cpu->halt_cond); 278 279 /* share a single thread for all cpus with TCG */ 280 snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG"); 281 qemu_thread_create(cpu->thread, thread_name, 282 rr_cpu_thread_fn, 283 cpu, QEMU_THREAD_JOINABLE); 284 285 single_tcg_halt_cond = cpu->halt_cond; 286 single_tcg_cpu_thread = cpu->thread; 287 #ifdef _WIN32 288 cpu->hThread = qemu_thread_get_handle(cpu->thread); 289 #endif 290 } else { 291 /* we share the thread */ 292 cpu->thread = single_tcg_cpu_thread; 293 cpu->halt_cond = single_tcg_halt_cond; 294 cpu->thread_id = first_cpu->thread_id; 295 cpu->can_do_io = 1; 296 cpu->created = true; 297 } 298 } 299