cpu-exec.c

   1 /*
   2  *  emulator main execution loop
   3  *
   4  *  Copyright (c) 2003-2005 Fabrice Bellard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19 #include "qemu/osdep.h"
  20 #include "cpu.h"
  21 #include "trace.h"
  22 #include "disas/disas.h"
  23 #include "tcg.h"
  24 #include "qemu/atomic.h"
  25 #include "sysemu/qtest.h"
  26 #include "qemu/timer.h"
  27 #include "exec/address-spaces.h"
  28 #include "qemu/rcu.h"
  29 #include "exec/tb-hash.h"
  30 #include "exec/log.h"
  31 #if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
  32 #include "hw/i386/apic.h"
  33 #endif
  34 #include "sysemu/replay.h"
  35
  36 /* -icount align implementation. */
  37
  38 typedef struct SyncClocks {
  39     int64_t diff_clk;
  40     int64_t last_cpu_icount;
  41     int64_t realtime_clock;
  42 } SyncClocks;
  43
  44 #if !defined(CONFIG_USER_ONLY)
  45 /* Allow the guest to have a max 3ms advance.
  46  * The difference between the 2 clocks could therefore
  47  * oscillate around 0.
  48  */
  49 #define VM_CLOCK_ADVANCE 3000000
  50 #define THRESHOLD_REDUCE 1.5
  51 #define MAX_DELAY_PRINT_RATE 2000000000LL
  52 #define MAX_NB_PRINTS 100
  53
  54 static void align_clocks(SyncClocks *sc, const CPUState *cpu)
  55 {
  56     int64_t cpu_icount;
  57
  58     if (!icount_align_option) {
  59         return;
  60     }
  61
  62     cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
  63     sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount);
  64     sc->last_cpu_icount = cpu_icount;
  65
  66     if (sc->diff_clk > VM_CLOCK_ADVANCE) {
  67 #ifndef _WIN32
  68         struct timespec sleep_delay, rem_delay;
  69         sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
  70         sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
  71         if (nanosleep(&sleep_delay, &rem_delay) < 0) {
  72             sc->diff_clk = rem_delay.tv_sec * 1000000000LL + rem_delay.tv_nsec;
  73         } else {
  74             sc->diff_clk = 0;
  75         }
  76 #else
  77         Sleep(sc->diff_clk / SCALE_MS);
  78         sc->diff_clk = 0;
  79 #endif
  80     }
  81 }
  82
  83 static void print_delay(const SyncClocks *sc)
  84 {
  85     static float threshold_delay;
  86     static int64_t last_realtime_clock;
  87     static int nb_prints;
  88
  89     if (icount_align_option &&
  90         sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
  91         nb_prints < MAX_NB_PRINTS) {
  92         if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
  93             (-sc->diff_clk / (float)1000000000LL <
  94              (threshold_delay - THRESHOLD_REDUCE))) {
  95             threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
  96             printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
  97                    threshold_delay - 1,
  98                    threshold_delay);
  99             nb_prints++;
 100             last_realtime_clock = sc->realtime_clock;
 101         }
 102     }
 103 }
 104
 105 static void init_delay_params(SyncClocks *sc,
 106                               const CPUState *cpu)
 107 {
 108     if (!icount_align_option) {
 109         return;
 110     }
 111     sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
 112     sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock;
 113     sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
 114     if (sc->diff_clk < max_delay) {
 115         max_delay = sc->diff_clk;
 116     }
 117     if (sc->diff_clk > max_advance) {
 118         max_advance = sc->diff_clk;
 119     }
 120
 121     /* Print every 2s max if the guest is late. We limit the number
 122        of printed messages to NB_PRINT_MAX(currently 100) */
 123     print_delay(sc);
 124 }
 125 #else
 126 static void align_clocks(SyncClocks *sc, const CPUState *cpu)
 127 {
 128 }
 129
 130 static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
 131 {
 132 }
 133 #endif /* CONFIG USER ONLY */
 134
 135 /* Execute a TB, and fix up the CPU state afterwards if necessary */
 136 static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb)
 137 {
 138     CPUArchState *env = cpu->env_ptr;
 139     uintptr_t next_tb;
 140     uint8_t *tb_ptr = itb->tc_ptr;
 141
 142     qemu_log_mask(CPU_LOG_EXEC, "Trace %p [" TARGET_FMT_lx "] %s\n",
 143                   itb->tc_ptr, itb->pc, lookup_symbol(itb->pc));
 144
 145 #if defined(DEBUG_DISAS)
 146     if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
 147 #if defined(TARGET_I386)
 148         log_cpu_state(cpu, CPU_DUMP_CCOP);
 149 #elif defined(TARGET_M68K)
 150         /* ??? Should not modify env state for dumping.  */
 151         cpu_m68k_flush_flags(env, env->cc_op);
 152         env->cc_op = CC_OP_FLAGS;
 153         env->sr = (env->sr & 0xffe0) | env->cc_dest | (env->cc_x << 4);
 154         log_cpu_state(cpu, 0);
 155 #else
 156         log_cpu_state(cpu, 0);
 157 #endif
 158     }
 159 #endif /* DEBUG_DISAS */
 160
 161     cpu->can_do_io = !use_icount;
 162     next_tb = tcg_qemu_tb_exec(env, tb_ptr);
 163     cpu->can_do_io = 1;
 164     trace_exec_tb_exit((void *) (next_tb & ~TB_EXIT_MASK),
 165                        next_tb & TB_EXIT_MASK);
 166
 167     if ((next_tb & TB_EXIT_MASK) > TB_EXIT_IDX1) {
 168         /* We didn't start executing this TB (eg because the instruction
 169          * counter hit zero); we must restore the guest PC to the address
 170          * of the start of the TB.
 171          */
 172         CPUClass *cc = CPU_GET_CLASS(cpu);
 173         TranslationBlock *tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
 174         qemu_log_mask(CPU_LOG_EXEC,
 175                       "Stopped execution of TB chain before %p ["
 176                       TARGET_FMT_lx "] %s\n",
 177                       itb->tc_ptr, itb->pc, lookup_symbol(itb->pc));
 178         if (cc->synchronize_from_tb) {
 179             cc->synchronize_from_tb(cpu, tb);
 180         } else {
 181             assert(cc->set_pc);
 182             cc->set_pc(cpu, tb->pc);
 183         }
 184     }
 185     if ((next_tb & TB_EXIT_MASK) == TB_EXIT_REQUESTED) {
 186         /* We were asked to stop executing TBs (probably a pending
 187          * interrupt. We've now stopped, so clear the flag.
 188          */
 189         cpu->tcg_exit_req = 0;
 190     }
 191     return next_tb;
 192 }
 193
 194 /* Execute the code without caching the generated code. An interpreter
 195    could be used if available. */
 196 static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
 197                              TranslationBlock *orig_tb, bool ignore_icount)
 198 {
 199     TranslationBlock *tb;
 200
 201     /* Should never happen.
 202        We only end up here when an existing TB is too long.  */
 203     if (max_cycles > CF_COUNT_MASK)
 204         max_cycles = CF_COUNT_MASK;
 205
 206     tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
 207                      max_cycles | CF_NOCACHE
 208                          | (ignore_icount ? CF_IGNORE_ICOUNT : 0));
 209     tb->orig_tb = tcg_ctx.tb_ctx.tb_invalidated_flag ? NULL : orig_tb;
 210     cpu->current_tb = tb;
 211     /* execute the generated code */
 212     trace_exec_tb_nocache(tb, tb->pc);
 213     cpu_tb_exec(cpu, tb);
 214     cpu->current_tb = NULL;
 215     tb_phys_invalidate(tb, -1);
 216     tb_free(tb);
 217 }
 218
 219 static TranslationBlock *tb_find_physical(CPUState *cpu,
 220                                           target_ulong pc,
 221                                           target_ulong cs_base,
 222                                           uint64_t flags)
 223 {
 224     CPUArchState *env = (CPUArchState *)cpu->env_ptr;
 225     TranslationBlock *tb, **ptb1;
 226     unsigned int h;
 227     tb_page_addr_t phys_pc, phys_page1;
 228     target_ulong virt_page2;
 229
 230     tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
 231
 232     /* find translated block using physical mappings */
 233     phys_pc = get_page_addr_code(env, pc);
 234     phys_page1 = phys_pc & TARGET_PAGE_MASK;
 235     h = tb_phys_hash_func(phys_pc);
 236     ptb1 = &tcg_ctx.tb_ctx.tb_phys_hash[h];
 237     for(;;) {
 238         tb = *ptb1;
 239         if (!tb) {
 240             return NULL;
 241         }
 242         if (tb->pc == pc &&
 243             tb->page_addr[0] == phys_page1 &&
 244             tb->cs_base == cs_base &&
 245             tb->flags == flags) {
 246             /* check next page if needed */
 247             if (tb->page_addr[1] != -1) {
 248                 tb_page_addr_t phys_page2;
 249
 250                 virt_page2 = (pc & TARGET_PAGE_MASK) +
 251                     TARGET_PAGE_SIZE;
 252                 phys_page2 = get_page_addr_code(env, virt_page2);
 253                 if (tb->page_addr[1] == phys_page2) {
 254                     break;
 255                 }
 256             } else {
 257                 break;
 258             }
 259         }
 260         ptb1 = &tb->phys_hash_next;
 261     }
 262
 263     /* Move the TB to the head of the list */
 264     *ptb1 = tb->phys_hash_next;
 265     tb->phys_hash_next = tcg_ctx.tb_ctx.tb_phys_hash[h];
 266     tcg_ctx.tb_ctx.tb_phys_hash[h] = tb;
 267     return tb;
 268 }
 269
 270 static TranslationBlock *tb_find_slow(CPUState *cpu,
 271                                       target_ulong pc,
 272                                       target_ulong cs_base,
 273                                       uint64_t flags)
 274 {
 275     TranslationBlock *tb;
 276
 277     tb = tb_find_physical(cpu, pc, cs_base, flags);
 278     if (tb) {
 279         goto found;
 280     }
 281
 282 #ifdef CONFIG_USER_ONLY
 283     /* mmap_lock is needed by tb_gen_code, and mmap_lock must be
 284      * taken outside tb_lock.  Since we're momentarily dropping
 285      * tb_lock, there's a chance that our desired tb has been
 286      * translated.
 287      */
 288     tb_unlock();
 289     mmap_lock();
 290     tb_lock();
 291     tb = tb_find_physical(cpu, pc, cs_base, flags);
 292     if (tb) {
 293         mmap_unlock();
 294         goto found;
 295     }
 296 #endif
 297
 298     /* if no translated code available, then translate it now */
 299     tb = tb_gen_code(cpu, pc, cs_base, flags, 0);
 300
 301 #ifdef CONFIG_USER_ONLY
 302     mmap_unlock();
 303 #endif
 304
 305 found:
 306     /* we add the TB in the virtual pc hash table */
 307     cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
 308     return tb;
 309 }
 310
 311 static inline TranslationBlock *tb_find_fast(CPUState *cpu)
 312 {
 313     CPUArchState *env = (CPUArchState *)cpu->env_ptr;
 314     TranslationBlock *tb;
 315     target_ulong cs_base, pc;
 316     int flags;
 317
 318     /* we record a subset of the CPU state. It will
 319        always be the same before a given translated block
 320        is executed. */
 321     cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
 322     tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];
 323     if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||
 324                  tb->flags != flags)) {
 325         tb = tb_find_slow(cpu, pc, cs_base, flags);
 326     }
 327     return tb;
 328 }
 329
 330 static void cpu_handle_debug_exception(CPUState *cpu)
 331 {
 332     CPUClass *cc = CPU_GET_CLASS(cpu);
 333     CPUWatchpoint *wp;
 334
 335     if (!cpu->watchpoint_hit) {
 336         QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
 337             wp->flags &= ~BP_WATCHPOINT_HIT;
 338         }
 339     }
 340
 341     cc->debug_excp_handler(cpu);
 342 }
 343
 344 /* main execution loop */
 345
 346 int cpu_exec(CPUState *cpu)
 347 {
 348     CPUClass *cc = CPU_GET_CLASS(cpu);
 349 #ifdef TARGET_I386
 350     X86CPU *x86_cpu = X86_CPU(cpu);
 351     CPUArchState *env = &x86_cpu->env;
 352 #endif
 353     int ret, interrupt_request;
 354     TranslationBlock *tb;
 355     uintptr_t next_tb;
 356     SyncClocks sc;
 357
 358     /* replay_interrupt may need current_cpu */
 359     current_cpu = cpu;
 360
 361     if (cpu->halted) {
 362 #if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
 363         if ((cpu->interrupt_request & CPU_INTERRUPT_POLL)
 364             && replay_interrupt()) {
 365             apic_poll_irq(x86_cpu->apic_state);
 366             cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
 367         }
 368 #endif
 369         if (!cpu_has_work(cpu)) {
 370             current_cpu = NULL;
 371             return EXCP_HALTED;
 372         }
 373
 374         cpu->halted = 0;
 375     }
 376
 377     atomic_mb_set(&tcg_current_cpu, cpu);
 378     rcu_read_lock();
 379
 380     if (unlikely(atomic_mb_read(&exit_request))) {
 381         cpu->exit_request = 1;
 382     }
 383
 384     cc->cpu_exec_enter(cpu);
 385
 386     /* Calculate difference between guest clock and host clock.
 387      * This delay includes the delay of the last cycle, so
 388      * what we have to do is sleep until it is 0. As for the
 389      * advance/delay we gain here, we try to fix it next time.
 390      */
 391     init_delay_params(&sc, cpu);
 392
 393     /* prepare setjmp context for exception handling */
 394     for(;;) {
 395         if (sigsetjmp(cpu->jmp_env, 0) == 0) {
 396             /* if an exception is pending, we execute it here */
 397             if (cpu->exception_index >= 0) {
 398                 if (cpu->exception_index >= EXCP_INTERRUPT) {
 399                     /* exit request from the cpu execution loop */
 400                     ret = cpu->exception_index;
 401                     if (ret == EXCP_DEBUG) {
 402                         cpu_handle_debug_exception(cpu);
 403                     }
 404                     cpu->exception_index = -1;
 405                     break;
 406                 } else {
 407 #if defined(CONFIG_USER_ONLY)
 408                     /* if user mode only, we simulate a fake exception
 409                        which will be handled outside the cpu execution
 410                        loop */
 411 #if defined(TARGET_I386)
 412                     cc->do_interrupt(cpu);
 413 #endif
 414                     ret = cpu->exception_index;
 415                     cpu->exception_index = -1;
 416                     break;
 417 #else
 418                     if (replay_exception()) {
 419                         cc->do_interrupt(cpu);
 420                         cpu->exception_index = -1;
 421                     } else if (!replay_has_interrupt()) {
 422                         /* give a chance to iothread in replay mode */
 423                         ret = EXCP_INTERRUPT;
 424                         break;
 425                     }
 426 #endif
 427                 }
 428             } else if (replay_has_exception()
 429                        && cpu->icount_decr.u16.low + cpu->icount_extra == 0) {
 430                 /* try to cause an exception pending in the log */
 431                 cpu_exec_nocache(cpu, 1, tb_find_fast(cpu), true);
 432                 ret = -1;
 433                 break;
 434             }
 435
 436             next_tb = 0; /* force lookup of first TB */
 437             for(;;) {
 438                 interrupt_request = cpu->interrupt_request;
 439                 if (unlikely(interrupt_request)) {
 440                     if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
 441                         /* Mask out external interrupts for this step. */
 442                         interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
 443                     }
 444                     if (interrupt_request & CPU_INTERRUPT_DEBUG) {
 445                         cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
 446                         cpu->exception_index = EXCP_DEBUG;
 447                         cpu_loop_exit(cpu);
 448                     }
 449                     if (replay_mode == REPLAY_MODE_PLAY
 450                         && !replay_has_interrupt()) {
 451                         /* Do nothing */
 452                     } else if (interrupt_request & CPU_INTERRUPT_HALT) {
 453                         replay_interrupt();
 454                         cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
 455                         cpu->halted = 1;
 456                         cpu->exception_index = EXCP_HLT;
 457                         cpu_loop_exit(cpu);
 458                     }
 459 #if defined(TARGET_I386)
 460                     else if (interrupt_request & CPU_INTERRUPT_INIT) {
 461                         replay_interrupt();
 462                         cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0);
 463                         do_cpu_init(x86_cpu);
 464                         cpu->exception_index = EXCP_HALTED;
 465                         cpu_loop_exit(cpu);
 466                     }
 467 #else
 468                     else if (interrupt_request & CPU_INTERRUPT_RESET) {
 469                         replay_interrupt();
 470                         cpu_reset(cpu);
 471                         cpu_loop_exit(cpu);
 472                     }
 473 #endif
 474                     /* The target hook has 3 exit conditions:
 475                        False when the interrupt isn't processed,
 476                        True when it is, and we should restart on a new TB,
 477                        and via longjmp via cpu_loop_exit.  */
 478                     else {
 479                         replay_interrupt();
 480                         if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
 481                             next_tb = 0;
 482                         }
 483                     }
 484                     /* Don't use the cached interrupt_request value,
 485                        do_interrupt may have updated the EXITTB flag. */
 486                     if (cpu->interrupt_request & CPU_INTERRUPT_EXITTB) {
 487                         cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB;
 488                         /* ensure that no TB jump will be modified as
 489                            the program flow was changed */
 490                         next_tb = 0;
 491                     }
 492                 }
 493                 if (unlikely(cpu->exit_request
 494                              || replay_has_interrupt())) {
 495                     cpu->exit_request = 0;
 496                     cpu->exception_index = EXCP_INTERRUPT;
 497                     cpu_loop_exit(cpu);
 498                 }
 499                 tb_lock();
 500                 tb = tb_find_fast(cpu);
 501                 /* Note: we do it here to avoid a gcc bug on Mac OS X when
 502                    doing it in tb_find_slow */
 503                 if (tcg_ctx.tb_ctx.tb_invalidated_flag) {
 504                     /* as some TB could have been invalidated because
 505                        of memory exceptions while generating the code, we
 506                        must recompute the hash index here */
 507                     next_tb = 0;
 508                     tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
 509                 }
 510                 /* see if we can patch the calling TB. When the TB
 511                    spans two pages, we cannot safely do a direct
 512                    jump. */
 513                 if (next_tb != 0 && tb->page_addr[1] == -1
 514                     && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
 515                     tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK),
 516                                 next_tb & TB_EXIT_MASK, tb);
 517                 }
 518                 tb_unlock();
 519                 if (likely(!cpu->exit_request)) {
 520                     trace_exec_tb(tb, tb->pc);
 521                     /* execute the generated code */
 522                     cpu->current_tb = tb;
 523                     next_tb = cpu_tb_exec(cpu, tb);
 524                     cpu->current_tb = NULL;
 525                     switch (next_tb & TB_EXIT_MASK) {
 526                     case TB_EXIT_REQUESTED:
 527                         /* Something asked us to stop executing
 528                          * chained TBs; just continue round the main
 529                          * loop. Whatever requested the exit will also
 530                          * have set something else (eg exit_request or
 531                          * interrupt_request) which we will handle
 532                          * next time around the loop.  But we need to
 533                          * ensure the tcg_exit_req read in generated code
 534                          * comes before the next read of cpu->exit_request
 535                          * or cpu->interrupt_request.
 536                          */
 537                         smp_rmb();
 538                         next_tb = 0;
 539                         break;
 540                     case TB_EXIT_ICOUNT_EXPIRED:
 541                     {
 542                         /* Instruction counter expired.  */
 543                         int insns_left = cpu->icount_decr.u32;
 544                         if (cpu->icount_extra && insns_left >= 0) {
 545                             /* Refill decrementer and continue execution.  */
 546                             cpu->icount_extra += insns_left;
 547                             insns_left = MIN(0xffff, cpu->icount_extra);
 548                             cpu->icount_extra -= insns_left;
 549                             cpu->icount_decr.u16.low = insns_left;
 550                         } else {
 551                             if (insns_left > 0) {
 552                                 /* Execute remaining instructions.  */
 553                                 tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
 554                                 cpu_exec_nocache(cpu, insns_left, tb, false);
 555                                 align_clocks(&sc, cpu);
 556                             }
 557                             cpu->exception_index = EXCP_INTERRUPT;
 558                             next_tb = 0;
 559                             cpu_loop_exit(cpu);
 560                         }
 561                         break;
 562                     }
 563                     default:
 564                         break;
 565                     }
 566                 }
 567                 /* Try to align the host and virtual clocks
 568                    if the guest is in advance */
 569                 align_clocks(&sc, cpu);
 570                 /* reset soft MMU for next block (it can currently
 571                    only be set by a memory fault) */
 572             } /* for(;;) */
 573         } else {
 574 #if defined(__clang__) || !QEMU_GNUC_PREREQ(4, 6)
 575             /* Some compilers wrongly smash all local variables after
 576              * siglongjmp. There were bug reports for gcc 4.5.0 and clang.
 577              * Reload essential local variables here for those compilers.
 578              * Newer versions of gcc would complain about this code (-Wclobbered). */
 579             cpu = current_cpu;
 580             cc = CPU_GET_CLASS(cpu);
 581 #ifdef TARGET_I386
 582             x86_cpu = X86_CPU(cpu);
 583             env = &x86_cpu->env;
 584 #endif
 585 #else /* buggy compiler */
 586             /* Assert that the compiler does not smash local variables. */
 587             g_assert(cpu == current_cpu);
 588             g_assert(cc == CPU_GET_CLASS(cpu));
 589 #ifdef TARGET_I386
 590             g_assert(x86_cpu == X86_CPU(cpu));
 591             g_assert(env == &x86_cpu->env);
 592 #endif
 593 #endif /* buggy compiler */
 594             cpu->can_do_io = 1;
 595             tb_lock_reset();
 596         }
 597     } /* for(;;) */
 598
 599     cc->cpu_exec_exit(cpu);
 600     rcu_read_unlock();
 601
 602     /* fail safe : never use current_cpu outside cpu_exec() */
 603     current_cpu = NULL;
 604
 605     /* Does not need atomic_mb_set because a spurious wakeup is okay.  */
 606     atomic_set(&tcg_current_cpu, NULL);
 607     return ret;
 608 }