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 "config.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
  28 /* -icount align implementation. */
  29
  30 typedef struct SyncClocks {
  31     int64_t diff_clk;
  32     int64_t last_cpu_icount;
  33     int64_t realtime_clock;
  34 } SyncClocks;
  35
  36 #if !defined(CONFIG_USER_ONLY)
  37 /* Allow the guest to have a max 3ms advance.
  38  * The difference between the 2 clocks could therefore
  39  * oscillate around 0.
  40  */
  41 #define VM_CLOCK_ADVANCE 3000000
  42 #define THRESHOLD_REDUCE 1.5
  43 #define MAX_DELAY_PRINT_RATE 2000000000LL
  44 #define MAX_NB_PRINTS 100
  45
  46 static void align_clocks(SyncClocks *sc, const CPUState *cpu)
  47 {
  48     int64_t cpu_icount;
  49
  50     if (!icount_align_option) {
  51         return;
  52     }
  53
  54     cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
  55     sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount);
  56     sc->last_cpu_icount = cpu_icount;
  57
  58     if (sc->diff_clk > VM_CLOCK_ADVANCE) {
  59 #ifndef _WIN32
  60         struct timespec sleep_delay, rem_delay;
  61         sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
  62         sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
  63         if (nanosleep(&sleep_delay, &rem_delay) < 0) {
  64             sc->diff_clk -= (sleep_delay.tv_sec - rem_delay.tv_sec) * 1000000000LL;
  65             sc->diff_clk -= sleep_delay.tv_nsec - rem_delay.tv_nsec;
  66         } else {
  67             sc->diff_clk = 0;
  68         }
  69 #else
  70         Sleep(sc->diff_clk / SCALE_MS);
  71         sc->diff_clk = 0;
  72 #endif
  73     }
  74 }
  75
  76 static void print_delay(const SyncClocks *sc)
  77 {
  78     static float threshold_delay;
  79     static int64_t last_realtime_clock;
  80     static int nb_prints;
  81
  82     if (icount_align_option &&
  83         sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
  84         nb_prints < MAX_NB_PRINTS) {
  85         if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
  86             (-sc->diff_clk / (float)1000000000LL <
  87              (threshold_delay - THRESHOLD_REDUCE))) {
  88             threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
  89             printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
  90                    threshold_delay - 1,
  91                    threshold_delay);
  92             nb_prints++;
  93             last_realtime_clock = sc->realtime_clock;
  94         }
  95     }
  96 }
  97
  98 static void init_delay_params(SyncClocks *sc,
  99                               const CPUState *cpu)
 100 {
 101     if (!icount_align_option) {
 102         return;
 103     }
 104     sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 105     sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
 106                    sc->realtime_clock +
 107                    cpu_get_clock_offset();
 108     sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
 109     if (sc->diff_clk < max_delay) {
 110         max_delay = sc->diff_clk;
 111     }
 112     if (sc->diff_clk > max_advance) {
 113         max_advance = sc->diff_clk;
 114     }
 115
 116     /* Print every 2s max if the guest is late. We limit the number
 117        of printed messages to NB_PRINT_MAX(currently 100) */
 118     print_delay(sc);
 119 }
 120 #else
 121 static void align_clocks(SyncClocks *sc, const CPUState *cpu)
 122 {
 123 }
 124
 125 static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
 126 {
 127 }
 128 #endif /* CONFIG USER ONLY */
 129
 130 void cpu_loop_exit(CPUState *cpu)
 131 {
 132     cpu->current_tb = NULL;
 133     siglongjmp(cpu->jmp_env, 1);
 134 }
 135
 136 /* exit the current TB from a signal handler. The host registers are
 137    restored in a state compatible with the CPU emulator
 138  */
 139 #if defined(CONFIG_SOFTMMU)
 140 void cpu_resume_from_signal(CPUState *cpu, void *puc)
 141 {
 142     /* XXX: restore cpu registers saved in host registers */
 143
 144     cpu->exception_index = -1;
 145     siglongjmp(cpu->jmp_env, 1);
 146 }
 147 #endif
 148
 149 /* Execute a TB, and fix up the CPU state afterwards if necessary */
 150 static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, uint8_t *tb_ptr)
 151 {
 152     CPUArchState *env = cpu->env_ptr;
 153     uintptr_t next_tb;
 154
 155 #if defined(DEBUG_DISAS)
 156     if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
 157 #if defined(TARGET_I386)
 158         log_cpu_state(cpu, CPU_DUMP_CCOP);
 159 #elif defined(TARGET_M68K)
 160         /* ??? Should not modify env state for dumping.  */
 161         cpu_m68k_flush_flags(env, env->cc_op);
 162         env->cc_op = CC_OP_FLAGS;
 163         env->sr = (env->sr & 0xffe0) | env->cc_dest | (env->cc_x << 4);
 164         log_cpu_state(cpu, 0);
 165 #else
 166         log_cpu_state(cpu, 0);
 167 #endif
 168     }
 169 #endif /* DEBUG_DISAS */
 170
 171     next_tb = tcg_qemu_tb_exec(env, tb_ptr);
 172     trace_exec_tb_exit((void *) (next_tb & ~TB_EXIT_MASK),
 173                        next_tb & TB_EXIT_MASK);
 174
 175     if ((next_tb & TB_EXIT_MASK) > TB_EXIT_IDX1) {
 176         /* We didn't start executing this TB (eg because the instruction
 177          * counter hit zero); we must restore the guest PC to the address
 178          * of the start of the TB.
 179          */
 180         CPUClass *cc = CPU_GET_CLASS(cpu);
 181         TranslationBlock *tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
 182         if (cc->synchronize_from_tb) {
 183             cc->synchronize_from_tb(cpu, tb);
 184         } else {
 185             assert(cc->set_pc);
 186             cc->set_pc(cpu, tb->pc);
 187         }
 188     }
 189     if ((next_tb & TB_EXIT_MASK) == TB_EXIT_REQUESTED) {
 190         /* We were asked to stop executing TBs (probably a pending
 191          * interrupt. We've now stopped, so clear the flag.
 192          */
 193         cpu->tcg_exit_req = 0;
 194     }
 195     return next_tb;
 196 }
 197
 198 /* Execute the code without caching the generated code. An interpreter
 199    could be used if available. */
 200 static void cpu_exec_nocache(CPUArchState *env, int max_cycles,
 201                              TranslationBlock *orig_tb)
 202 {
 203     CPUState *cpu = ENV_GET_CPU(env);
 204     TranslationBlock *tb;
 205
 206     /* Should never happen.
 207        We only end up here when an existing TB is too long.  */
 208     if (max_cycles > CF_COUNT_MASK)
 209         max_cycles = CF_COUNT_MASK;
 210
 211     tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
 212                      max_cycles);
 213     cpu->current_tb = tb;
 214     /* execute the generated code */
 215     trace_exec_tb_nocache(tb, tb->pc);
 216     cpu_tb_exec(cpu, tb->tc_ptr);
 217     cpu->current_tb = NULL;
 218     tb_phys_invalidate(tb, -1);
 219     tb_free(tb);
 220 }
 221
 222 static TranslationBlock *tb_find_slow(CPUArchState *env,
 223                                       target_ulong pc,
 224                                       target_ulong cs_base,
 225                                       uint64_t flags)
 226 {
 227     CPUState *cpu = ENV_GET_CPU(env);
 228     TranslationBlock *tb, **ptb1;
 229     unsigned int h;
 230     tb_page_addr_t phys_pc, phys_page1;
 231     target_ulong virt_page2;
 232
 233     tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
 234
 235     /* find translated block using physical mappings */
 236     phys_pc = get_page_addr_code(env, pc);
 237     phys_page1 = phys_pc & TARGET_PAGE_MASK;
 238     h = tb_phys_hash_func(phys_pc);
 239     ptb1 = &tcg_ctx.tb_ctx.tb_phys_hash[h];
 240     for(;;) {
 241         tb = *ptb1;
 242         if (!tb)
 243             goto not_found;
 244         if (tb->pc == pc &&
 245             tb->page_addr[0] == phys_page1 &&
 246             tb->cs_base == cs_base &&
 247             tb->flags == flags) {
 248             /* check next page if needed */
 249             if (tb->page_addr[1] != -1) {
 250                 tb_page_addr_t phys_page2;
 251
 252                 virt_page2 = (pc & TARGET_PAGE_MASK) +
 253                     TARGET_PAGE_SIZE;
 254                 phys_page2 = get_page_addr_code(env, virt_page2);
 255                 if (tb->page_addr[1] == phys_page2)
 256                     goto found;
 257             } else {
 258                 goto found;
 259             }
 260         }
 261         ptb1 = &tb->phys_hash_next;
 262     }
 263  not_found:
 264    /* if no translated code available, then translate it now */
 265     tb = tb_gen_code(cpu, pc, cs_base, flags, 0);
 266
 267  found:
 268     /* Move the last found TB to the head of the list */
 269     if (likely(*ptb1)) {
 270         *ptb1 = tb->phys_hash_next;
 271         tb->phys_hash_next = tcg_ctx.tb_ctx.tb_phys_hash[h];
 272         tcg_ctx.tb_ctx.tb_phys_hash[h] = tb;
 273     }
 274     /* we add the TB in the virtual pc hash table */
 275     cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
 276     return tb;
 277 }
 278
 279 static inline TranslationBlock *tb_find_fast(CPUArchState *env)
 280 {
 281     CPUState *cpu = ENV_GET_CPU(env);
 282     TranslationBlock *tb;
 283     target_ulong cs_base, pc;
 284     int flags;
 285
 286     /* we record a subset of the CPU state. It will
 287        always be the same before a given translated block
 288        is executed. */
 289     cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
 290     tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];
 291     if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||
 292                  tb->flags != flags)) {
 293         tb = tb_find_slow(env, pc, cs_base, flags);
 294     }
 295     return tb;
 296 }
 297
 298 static void cpu_handle_debug_exception(CPUArchState *env)
 299 {
 300     CPUState *cpu = ENV_GET_CPU(env);
 301     CPUClass *cc = CPU_GET_CLASS(cpu);
 302     CPUWatchpoint *wp;
 303
 304     if (!cpu->watchpoint_hit) {
 305         QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
 306             wp->flags &= ~BP_WATCHPOINT_HIT;
 307         }
 308     }
 309
 310     cc->debug_excp_handler(cpu);
 311 }
 312
 313 /* main execution loop */
 314
 315 volatile sig_atomic_t exit_request;
 316
 317 int cpu_exec(CPUArchState *env)
 318 {
 319     CPUState *cpu = ENV_GET_CPU(env);
 320     CPUClass *cc = CPU_GET_CLASS(cpu);
 321 #ifdef TARGET_I386
 322     X86CPU *x86_cpu = X86_CPU(cpu);
 323 #endif
 324     int ret, interrupt_request;
 325     TranslationBlock *tb;
 326     uint8_t *tc_ptr;
 327     uintptr_t next_tb;
 328     SyncClocks sc;
 329
 330     /* This must be volatile so it is not trashed by longjmp() */
 331     volatile bool have_tb_lock = false;
 332
 333     if (cpu->halted) {
 334         if (!cpu_has_work(cpu)) {
 335             return EXCP_HALTED;
 336         }
 337
 338         cpu->halted = 0;
 339     }
 340
 341     current_cpu = cpu;
 342
 343     /* As long as current_cpu is null, up to the assignment just above,
 344      * requests by other threads to exit the execution loop are expected to
 345      * be issued using the exit_request global. We must make sure that our
 346      * evaluation of the global value is performed past the current_cpu
 347      * value transition point, which requires a memory barrier as well as
 348      * an instruction scheduling constraint on modern architectures.  */
 349     smp_mb();
 350
 351     if (unlikely(exit_request)) {
 352         cpu->exit_request = 1;
 353     }
 354
 355     cc->cpu_exec_enter(cpu);
 356     cpu->exception_index = -1;
 357
 358     /* Calculate difference between guest clock and host clock.
 359      * This delay includes the delay of the last cycle, so
 360      * what we have to do is sleep until it is 0. As for the
 361      * advance/delay we gain here, we try to fix it next time.
 362      */
 363     init_delay_params(&sc, cpu);
 364
 365     /* prepare setjmp context for exception handling */
 366     for(;;) {
 367         if (sigsetjmp(cpu->jmp_env, 0) == 0) {
 368             /* if an exception is pending, we execute it here */
 369             if (cpu->exception_index >= 0) {
 370                 if (cpu->exception_index >= EXCP_INTERRUPT) {
 371                     /* exit request from the cpu execution loop */
 372                     ret = cpu->exception_index;
 373                     if (ret == EXCP_DEBUG) {
 374                         cpu_handle_debug_exception(env);
 375                     }
 376                     break;
 377                 } else {
 378 #if defined(CONFIG_USER_ONLY)
 379                     /* if user mode only, we simulate a fake exception
 380                        which will be handled outside the cpu execution
 381                        loop */
 382 #if defined(TARGET_I386)
 383                     cc->do_interrupt(cpu);
 384 #endif
 385                     ret = cpu->exception_index;
 386                     break;
 387 #else
 388                     cc->do_interrupt(cpu);
 389                     cpu->exception_index = -1;
 390 #endif
 391                 }
 392             }
 393
 394             next_tb = 0; /* force lookup of first TB */
 395             for(;;) {
 396                 interrupt_request = cpu->interrupt_request;
 397                 if (unlikely(interrupt_request)) {
 398                     if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
 399                         /* Mask out external interrupts for this step. */
 400                         interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
 401                     }
 402                     if (interrupt_request & CPU_INTERRUPT_DEBUG) {
 403                         cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
 404                         cpu->exception_index = EXCP_DEBUG;
 405                         cpu_loop_exit(cpu);
 406                     }
 407 #if defined(TARGET_ARM) || defined(TARGET_SPARC) || defined(TARGET_MIPS) || \
 408     defined(TARGET_PPC) || defined(TARGET_ALPHA) || defined(TARGET_CRIS) || \
 409     defined(TARGET_MICROBLAZE) || defined(TARGET_LM32) ||                   \
 410     defined(TARGET_UNICORE32) || defined(TARGET_TRICORE)
 411                     if (interrupt_request & CPU_INTERRUPT_HALT) {
 412                         cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
 413                         cpu->halted = 1;
 414                         cpu->exception_index = EXCP_HLT;
 415                         cpu_loop_exit(cpu);
 416                     }
 417 #endif
 418 #if defined(TARGET_I386)
 419                     if (interrupt_request & CPU_INTERRUPT_INIT) {
 420                         cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0);
 421                         do_cpu_init(x86_cpu);
 422                         cpu->exception_index = EXCP_HALTED;
 423                         cpu_loop_exit(cpu);
 424                     }
 425 #else
 426                     if (interrupt_request & CPU_INTERRUPT_RESET) {
 427                         cpu_reset(cpu);
 428                     }
 429 #endif
 430 #if defined(TARGET_I386)
 431 #if !defined(CONFIG_USER_ONLY)
 432                     if (interrupt_request & CPU_INTERRUPT_POLL) {
 433                         cpu->interrupt_request &= ~CPU_INTERRUPT_POLL;
 434                         apic_poll_irq(x86_cpu->apic_state);
 435                     }
 436 #endif
 437                     if (interrupt_request & CPU_INTERRUPT_SIPI) {
 438                             do_cpu_sipi(x86_cpu);
 439                     } else if (env->hflags2 & HF2_GIF_MASK) {
 440                         if ((interrupt_request & CPU_INTERRUPT_SMI) &&
 441                             !(env->hflags & HF_SMM_MASK)) {
 442                             cpu_svm_check_intercept_param(env, SVM_EXIT_SMI,
 443                                                           0);
 444                             cpu->interrupt_request &= ~CPU_INTERRUPT_SMI;
 445                             do_smm_enter(x86_cpu);
 446                             next_tb = 0;
 447                         } else if ((interrupt_request & CPU_INTERRUPT_NMI) &&
 448                                    !(env->hflags2 & HF2_NMI_MASK)) {
 449                             cpu->interrupt_request &= ~CPU_INTERRUPT_NMI;
 450                             env->hflags2 |= HF2_NMI_MASK;
 451                             do_interrupt_x86_hardirq(env, EXCP02_NMI, 1);
 452                             next_tb = 0;
 453                         } else if (interrupt_request & CPU_INTERRUPT_MCE) {
 454                             cpu->interrupt_request &= ~CPU_INTERRUPT_MCE;
 455                             do_interrupt_x86_hardirq(env, EXCP12_MCHK, 0);
 456                             next_tb = 0;
 457                         } else if ((interrupt_request & CPU_INTERRUPT_HARD) &&
 458                                    (((env->hflags2 & HF2_VINTR_MASK) &&
 459                                      (env->hflags2 & HF2_HIF_MASK)) ||
 460                                     (!(env->hflags2 & HF2_VINTR_MASK) &&
 461                                      (env->eflags & IF_MASK &&
 462                                       !(env->hflags & HF_INHIBIT_IRQ_MASK))))) {
 463                             int intno;
 464                             cpu_svm_check_intercept_param(env, SVM_EXIT_INTR,
 465                                                           0);
 466                             cpu->interrupt_request &= ~(CPU_INTERRUPT_HARD |
 467                                                         CPU_INTERRUPT_VIRQ);
 468                             intno = cpu_get_pic_interrupt(env);
 469                             qemu_log_mask(CPU_LOG_TB_IN_ASM, "Servicing hardware INT=0x%02x\n", intno);
 470                             do_interrupt_x86_hardirq(env, intno, 1);
 471                             /* ensure that no TB jump will be modified as
 472                                the program flow was changed */
 473                             next_tb = 0;
 474 #if !defined(CONFIG_USER_ONLY)
 475                         } else if ((interrupt_request & CPU_INTERRUPT_VIRQ) &&
 476                                    (env->eflags & IF_MASK) &&
 477                                    !(env->hflags & HF_INHIBIT_IRQ_MASK)) {
 478                             int intno;
 479                             /* FIXME: this should respect TPR */
 480                             cpu_svm_check_intercept_param(env, SVM_EXIT_VINTR,
 481                                                           0);
 482                             intno = ldl_phys(cpu->as,
 483                                              env->vm_vmcb
 484                                              + offsetof(struct vmcb,
 485                                                         control.int_vector));
 486                             qemu_log_mask(CPU_LOG_TB_IN_ASM, "Servicing virtual hardware INT=0x%02x\n", intno);
 487                             do_interrupt_x86_hardirq(env, intno, 1);
 488                             cpu->interrupt_request &= ~CPU_INTERRUPT_VIRQ;
 489                             next_tb = 0;
 490 #endif
 491                         }
 492                     }
 493 #elif defined(TARGET_PPC)
 494                     if (interrupt_request & CPU_INTERRUPT_HARD) {
 495                         ppc_hw_interrupt(env);
 496                         if (env->pending_interrupts == 0) {
 497                             cpu->interrupt_request &= ~CPU_INTERRUPT_HARD;
 498                         }
 499                         next_tb = 0;
 500                     }
 501 #elif defined(TARGET_LM32)
 502                     if ((interrupt_request & CPU_INTERRUPT_HARD)
 503                         && (env->ie & IE_IE)) {
 504                         cpu->exception_index = EXCP_IRQ;
 505                         cc->do_interrupt(cpu);
 506                         next_tb = 0;
 507                     }
 508 #elif defined(TARGET_MICROBLAZE)
 509                     if ((interrupt_request & CPU_INTERRUPT_HARD)
 510                         && (env->sregs[SR_MSR] & MSR_IE)
 511                         && !(env->sregs[SR_MSR] & (MSR_EIP | MSR_BIP))
 512                         && !(env->iflags & (D_FLAG | IMM_FLAG))) {
 513                         cpu->exception_index = EXCP_IRQ;
 514                         cc->do_interrupt(cpu);
 515                         next_tb = 0;
 516                     }
 517 #elif defined(TARGET_MIPS)
 518                     if ((interrupt_request & CPU_INTERRUPT_HARD) &&
 519                         cpu_mips_hw_interrupts_pending(env)) {
 520                         /* Raise it */
 521                         cpu->exception_index = EXCP_EXT_INTERRUPT;
 522                         env->error_code = 0;
 523                         cc->do_interrupt(cpu);
 524                         next_tb = 0;
 525                     }
 526 #elif defined(TARGET_TRICORE)
 527                     if ((interrupt_request & CPU_INTERRUPT_HARD)) {
 528                         cc->do_interrupt(cpu);
 529                         next_tb = 0;
 530                     }
 531
 532 #elif defined(TARGET_OPENRISC)
 533                     {
 534                         int idx = -1;
 535                         if ((interrupt_request & CPU_INTERRUPT_HARD)
 536                             && (env->sr & SR_IEE)) {
 537                             idx = EXCP_INT;
 538                         }
 539                         if ((interrupt_request & CPU_INTERRUPT_TIMER)
 540                             && (env->sr & SR_TEE)) {
 541                             idx = EXCP_TICK;
 542                         }
 543                         if (idx >= 0) {
 544                             cpu->exception_index = idx;
 545                             cc->do_interrupt(cpu);
 546                             next_tb = 0;
 547                         }
 548                     }
 549 #elif defined(TARGET_SPARC)
 550                     if (interrupt_request & CPU_INTERRUPT_HARD) {
 551                         if (cpu_interrupts_enabled(env) &&
 552                             env->interrupt_index > 0) {
 553                             int pil = env->interrupt_index & 0xf;
 554                             int type = env->interrupt_index & 0xf0;
 555
 556                             if (((type == TT_EXTINT) &&
 557                                   cpu_pil_allowed(env, pil)) ||
 558                                   type != TT_EXTINT) {
 559                                 cpu->exception_index = env->interrupt_index;
 560                                 cc->do_interrupt(cpu);
 561                                 next_tb = 0;
 562                             }
 563                         }
 564                     }
 565 #elif defined(TARGET_ARM)
 566                     if (interrupt_request & CPU_INTERRUPT_FIQ
 567                         && !(env->daif & PSTATE_F)) {
 568                         cpu->exception_index = EXCP_FIQ;
 569                         cc->do_interrupt(cpu);
 570                         next_tb = 0;
 571                     }
 572                     /* ARMv7-M interrupt return works by loading a magic value
 573                        into the PC.  On real hardware the load causes the
 574                        return to occur.  The qemu implementation performs the
 575                        jump normally, then does the exception return when the
 576                        CPU tries to execute code at the magic address.
 577                        This will cause the magic PC value to be pushed to
 578                        the stack if an interrupt occurred at the wrong time.
 579                        We avoid this by disabling interrupts when
 580                        pc contains a magic address.  */
 581                     if (interrupt_request & CPU_INTERRUPT_HARD
 582                         && !(env->daif & PSTATE_I)
 583                         && (!IS_M(env) || env->regs[15] < 0xfffffff0)) {
 584                         cpu->exception_index = EXCP_IRQ;
 585                         cc->do_interrupt(cpu);
 586                         next_tb = 0;
 587                     }
 588 #elif defined(TARGET_UNICORE32)
 589                     if (interrupt_request & CPU_INTERRUPT_HARD
 590                         && !(env->uncached_asr & ASR_I)) {
 591                         cpu->exception_index = UC32_EXCP_INTR;
 592                         cc->do_interrupt(cpu);
 593                         next_tb = 0;
 594                     }
 595 #endif
 596                     /* The target hook has 3 exit conditions:
 597                        False when the interrupt isn't processed,
 598                        True when it is, and we should restart on a new TB,
 599                        and via longjmp via cpu_loop_exit.  */
 600                     if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
 601                         next_tb = 0;
 602                     }
 603                     /* Don't use the cached interrupt_request value,
 604                        do_interrupt may have updated the EXITTB flag. */
 605                     if (cpu->interrupt_request & CPU_INTERRUPT_EXITTB) {
 606                         cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB;
 607                         /* ensure that no TB jump will be modified as
 608                            the program flow was changed */
 609                         next_tb = 0;
 610                     }
 611                 }
 612                 if (unlikely(cpu->exit_request)) {
 613                     cpu->exit_request = 0;
 614                     cpu->exception_index = EXCP_INTERRUPT;
 615                     cpu_loop_exit(cpu);
 616                 }
 617                 spin_lock(&tcg_ctx.tb_ctx.tb_lock);
 618                 have_tb_lock = true;
 619                 tb = tb_find_fast(env);
 620                 /* Note: we do it here to avoid a gcc bug on Mac OS X when
 621                    doing it in tb_find_slow */
 622                 if (tcg_ctx.tb_ctx.tb_invalidated_flag) {
 623                     /* as some TB could have been invalidated because
 624                        of memory exceptions while generating the code, we
 625                        must recompute the hash index here */
 626                     next_tb = 0;
 627                     tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
 628                 }
 629                 if (qemu_loglevel_mask(CPU_LOG_EXEC)) {
 630                     qemu_log("Trace %p [" TARGET_FMT_lx "] %s\n",
 631                              tb->tc_ptr, tb->pc, lookup_symbol(tb->pc));
 632                 }
 633                 /* see if we can patch the calling TB. When the TB
 634                    spans two pages, we cannot safely do a direct
 635                    jump. */
 636                 if (next_tb != 0 && tb->page_addr[1] == -1) {
 637                     tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK),
 638                                 next_tb & TB_EXIT_MASK, tb);
 639                 }
 640                 have_tb_lock = false;
 641                 spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
 642
 643                 /* cpu_interrupt might be called while translating the
 644                    TB, but before it is linked into a potentially
 645                    infinite loop and becomes env->current_tb. Avoid
 646                    starting execution if there is a pending interrupt. */
 647                 cpu->current_tb = tb;
 648                 barrier();
 649                 if (likely(!cpu->exit_request)) {
 650                     trace_exec_tb(tb, tb->pc);
 651                     tc_ptr = tb->tc_ptr;
 652                     /* execute the generated code */
 653                     next_tb = cpu_tb_exec(cpu, tc_ptr);
 654                     switch (next_tb & TB_EXIT_MASK) {
 655                     case TB_EXIT_REQUESTED:
 656                         /* Something asked us to stop executing
 657                          * chained TBs; just continue round the main
 658                          * loop. Whatever requested the exit will also
 659                          * have set something else (eg exit_request or
 660                          * interrupt_request) which we will handle
 661                          * next time around the loop.
 662                          */
 663                         tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
 664                         next_tb = 0;
 665                         break;
 666                     case TB_EXIT_ICOUNT_EXPIRED:
 667                     {
 668                         /* Instruction counter expired.  */
 669                         int insns_left;
 670                         tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
 671                         insns_left = cpu->icount_decr.u32;
 672                         if (cpu->icount_extra && insns_left >= 0) {
 673                             /* Refill decrementer and continue execution.  */
 674                             cpu->icount_extra += insns_left;
 675                             if (cpu->icount_extra > 0xffff) {
 676                                 insns_left = 0xffff;
 677                             } else {
 678                                 insns_left = cpu->icount_extra;
 679                             }
 680                             cpu->icount_extra -= insns_left;
 681                             cpu->icount_decr.u16.low = insns_left;
 682                         } else {
 683                             if (insns_left > 0) {
 684                                 /* Execute remaining instructions.  */
 685                                 cpu_exec_nocache(env, insns_left, tb);
 686                                 align_clocks(&sc, cpu);
 687                             }
 688                             cpu->exception_index = EXCP_INTERRUPT;
 689                             next_tb = 0;
 690                             cpu_loop_exit(cpu);
 691                         }
 692                         break;
 693                     }
 694                     default:
 695                         break;
 696                     }
 697                 }
 698                 cpu->current_tb = NULL;
 699                 /* Try to align the host and virtual clocks
 700                    if the guest is in advance */
 701                 align_clocks(&sc, cpu);
 702                 /* reset soft MMU for next block (it can currently
 703                    only be set by a memory fault) */
 704             } /* for(;;) */
 705         } else {
 706             /* Reload env after longjmp - the compiler may have smashed all
 707              * local variables as longjmp is marked 'noreturn'. */
 708             cpu = current_cpu;
 709             env = cpu->env_ptr;
 710             cc = CPU_GET_CLASS(cpu);
 711 #ifdef TARGET_I386
 712             x86_cpu = X86_CPU(cpu);
 713 #endif
 714             if (have_tb_lock) {
 715                 spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
 716                 have_tb_lock = false;
 717             }
 718         }
 719     } /* for(;;) */
 720
 721     cc->cpu_exec_exit(cpu);
 722
 723     /* fail safe : never use current_cpu outside cpu_exec() */
 724     current_cpu = NULL;
 725     return ret;
 726 }