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 34 #include "tcg-accel-ops.h" 35 #include "tcg-accel-ops-rr.h" 36 #include "tcg-accel-ops-icount.h" 37 38 /* Kick all RR vCPUs */ 39 void rr_kick_vcpu_thread(CPUState *unused) 40 { 41 CPUState *cpu; 42 43 CPU_FOREACH(cpu) { 44 cpu_exit(cpu); 45 }; 46 } 47 48 /* 49 * TCG vCPU kick timer 50 * 51 * The kick timer is responsible for moving single threaded vCPU 52 * emulation on to the next vCPU. If more than one vCPU is running a 53 * timer event with force a cpu->exit so the next vCPU can get 54 * scheduled. 55 * 56 * The timer is removed if all vCPUs are idle and restarted again once 57 * idleness is complete. 58 */ 59 60 static QEMUTimer *rr_kick_vcpu_timer; 61 static CPUState *rr_current_cpu; 62 63 #define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10) 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 /* 139 * In the single-threaded case each vCPU is simulated in turn. If 140 * there is more than a single vCPU we create a simple timer to kick 141 * the vCPU and ensure we don't get stuck in a tight loop in one vCPU. 142 * This is done explicitly rather than relying on side-effects 143 * elsewhere. 144 */ 145 146 static void *rr_cpu_thread_fn(void *arg) 147 { 148 CPUState *cpu = arg; 149 150 assert(tcg_enabled()); 151 rcu_register_thread(); 152 tcg_register_thread(); 153 154 qemu_mutex_lock_iothread(); 155 qemu_thread_get_self(cpu->thread); 156 157 cpu->thread_id = qemu_get_thread_id(); 158 cpu->can_do_io = 1; 159 cpu_thread_signal_created(cpu); 160 qemu_guest_random_seed_thread_part2(cpu->random_seed); 161 162 /* wait for initial kick-off after machine start */ 163 while (first_cpu->stopped) { 164 qemu_cond_wait_iothread(first_cpu->halt_cond); 165 166 /* process any pending work */ 167 CPU_FOREACH(cpu) { 168 current_cpu = cpu; 169 qemu_wait_io_event_common(cpu); 170 } 171 } 172 173 rr_start_kick_timer(); 174 175 cpu = first_cpu; 176 177 /* process any pending work */ 178 cpu->exit_request = 1; 179 180 while (1) { 181 qemu_mutex_unlock_iothread(); 182 replay_mutex_lock(); 183 qemu_mutex_lock_iothread(); 184 185 if (icount_enabled()) { 186 /* Account partial waits to QEMU_CLOCK_VIRTUAL. */ 187 icount_account_warp_timer(); 188 /* 189 * Run the timers here. This is much more efficient than 190 * waking up the I/O thread and waiting for completion. 191 */ 192 icount_handle_deadline(); 193 } 194 195 replay_mutex_unlock(); 196 197 if (!cpu) { 198 cpu = first_cpu; 199 } 200 201 while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) { 202 203 qatomic_mb_set(&rr_current_cpu, cpu); 204 current_cpu = cpu; 205 206 qemu_clock_enable(QEMU_CLOCK_VIRTUAL, 207 (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0); 208 209 if (cpu_can_run(cpu)) { 210 int r; 211 212 qemu_mutex_unlock_iothread(); 213 if (icount_enabled()) { 214 icount_prepare_for_run(cpu); 215 } 216 r = tcg_cpus_exec(cpu); 217 if (icount_enabled()) { 218 icount_process_data(cpu); 219 } 220 qemu_mutex_lock_iothread(); 221 222 if (r == EXCP_DEBUG) { 223 cpu_handle_guest_debug(cpu); 224 break; 225 } else if (r == EXCP_ATOMIC) { 226 qemu_mutex_unlock_iothread(); 227 cpu_exec_step_atomic(cpu); 228 qemu_mutex_lock_iothread(); 229 break; 230 } 231 } else if (cpu->stop) { 232 if (cpu->unplug) { 233 cpu = CPU_NEXT(cpu); 234 } 235 break; 236 } 237 238 cpu = CPU_NEXT(cpu); 239 } /* while (cpu && !cpu->exit_request).. */ 240 241 /* Does not need qatomic_mb_set because a spurious wakeup is okay. */ 242 qatomic_set(&rr_current_cpu, NULL); 243 244 if (cpu && cpu->exit_request) { 245 qatomic_mb_set(&cpu->exit_request, 0); 246 } 247 248 if (icount_enabled() && all_cpu_threads_idle()) { 249 /* 250 * When all cpus are sleeping (e.g in WFI), to avoid a deadlock 251 * in the main_loop, wake it up in order to start the warp timer. 252 */ 253 qemu_notify_event(); 254 } 255 256 rr_wait_io_event(); 257 rr_deal_with_unplugged_cpus(); 258 } 259 260 rcu_unregister_thread(); 261 return NULL; 262 } 263 264 void rr_start_vcpu_thread(CPUState *cpu) 265 { 266 char thread_name[VCPU_THREAD_NAME_SIZE]; 267 static QemuCond *single_tcg_halt_cond; 268 static QemuThread *single_tcg_cpu_thread; 269 270 g_assert(tcg_enabled()); 271 tcg_cpu_init_cflags(cpu, false); 272 273 if (!single_tcg_cpu_thread) { 274 cpu->thread = g_malloc0(sizeof(QemuThread)); 275 cpu->halt_cond = g_malloc0(sizeof(QemuCond)); 276 qemu_cond_init(cpu->halt_cond); 277 278 /* share a single thread for all cpus with TCG */ 279 snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG"); 280 qemu_thread_create(cpu->thread, thread_name, 281 rr_cpu_thread_fn, 282 cpu, QEMU_THREAD_JOINABLE); 283 284 single_tcg_halt_cond = cpu->halt_cond; 285 single_tcg_cpu_thread = cpu->thread; 286 #ifdef _WIN32 287 cpu->hThread = qemu_thread_get_handle(cpu->thread); 288 #endif 289 } else { 290 /* we share the thread */ 291 cpu->thread = single_tcg_cpu_thread; 292 cpu->halt_cond = single_tcg_halt_cond; 293 cpu->thread_id = first_cpu->thread_id; 294 cpu->can_do_io = 1; 295 cpu->created = true; 296 } 297 } 298