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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 "exec/exec-all.h"
24 #include "tcg.h"
25 #include "qemu/atomic.h"
26 #include "sysemu/qtest.h"
27 #include "qemu/timer.h"
28 #include "qemu/rcu.h"
29 #include "exec/tb-hash.h"
30 #include "exec/tb-lookup.h"
31 #include "exec/log.h"
32 #include "qemu/main-loop.h"
33 #if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
34 #include "hw/i386/apic.h"
35 #endif
36 #include "sysemu/cpus.h"
37 #include "sysemu/replay.h"
38
39 /* -icount align implementation. */
40
41 typedef struct SyncClocks {
42 int64_t diff_clk;
43 int64_t last_cpu_icount;
44 int64_t realtime_clock;
45 } SyncClocks;
46
47 #if !defined(CONFIG_USER_ONLY)
48 /* Allow the guest to have a max 3ms advance.
49 * The difference between the 2 clocks could therefore
50 * oscillate around 0.
51 */
52 #define VM_CLOCK_ADVANCE 3000000
53 #define THRESHOLD_REDUCE 1.5
54 #define MAX_DELAY_PRINT_RATE 2000000000LL
55 #define MAX_NB_PRINTS 100
56
57 static void align_clocks(SyncClocks *sc, const CPUState *cpu)
58 {
59 int64_t cpu_icount;
60
61 if (!icount_align_option) {
62 return;
63 }
64
65 cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
66 sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount);
67 sc->last_cpu_icount = cpu_icount;
68
69 if (sc->diff_clk > VM_CLOCK_ADVANCE) {
70 #ifndef _WIN32
71 struct timespec sleep_delay, rem_delay;
72 sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
73 sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
74 if (nanosleep(&sleep_delay, &rem_delay) < 0) {
75 sc->diff_clk = rem_delay.tv_sec * 1000000000LL + rem_delay.tv_nsec;
76 } else {
77 sc->diff_clk = 0;
78 }
79 #else
80 Sleep(sc->diff_clk / SCALE_MS);
81 sc->diff_clk = 0;
82 #endif
83 }
84 }
85
86 static void print_delay(const SyncClocks *sc)
87 {
88 static float threshold_delay;
89 static int64_t last_realtime_clock;
90 static int nb_prints;
91
92 if (icount_align_option &&
93 sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
94 nb_prints < MAX_NB_PRINTS) {
95 if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
96 (-sc->diff_clk / (float)1000000000LL <
97 (threshold_delay - THRESHOLD_REDUCE))) {
98 threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
99 printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
100 threshold_delay - 1,
101 threshold_delay);
102 nb_prints++;
103 last_realtime_clock = sc->realtime_clock;
104 }
105 }
106 }
107
108 static void init_delay_params(SyncClocks *sc,
109 const CPUState *cpu)
110 {
111 if (!icount_align_option) {
112 return;
113 }
114 sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
115 sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock;
116 sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
117 if (sc->diff_clk < max_delay) {
118 max_delay = sc->diff_clk;
119 }
120 if (sc->diff_clk > max_advance) {
121 max_advance = sc->diff_clk;
122 }
123
124 /* Print every 2s max if the guest is late. We limit the number
125 of printed messages to NB_PRINT_MAX(currently 100) */
126 print_delay(sc);
127 }
128 #else
129 static void align_clocks(SyncClocks *sc, const CPUState *cpu)
130 {
131 }
132
133 static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
134 {
135 }
136 #endif /* CONFIG USER ONLY */
137
138 /* Execute a TB, and fix up the CPU state afterwards if necessary */
139 static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb)
140 {
141 CPUArchState *env = cpu->env_ptr;
142 uintptr_t ret;
143 TranslationBlock *last_tb;
144 int tb_exit;
145 uint8_t *tb_ptr = itb->tc.ptr;
146
147 qemu_log_mask_and_addr(CPU_LOG_EXEC, itb->pc,
148 "Trace %d: %p ["
149 TARGET_FMT_lx "/" TARGET_FMT_lx "/%#x] %s\n",
150 cpu->cpu_index, itb->tc.ptr,
151 itb->cs_base, itb->pc, itb->flags,
152 lookup_symbol(itb->pc));
153
154 #if defined(DEBUG_DISAS)
155 if (qemu_loglevel_mask(CPU_LOG_TB_CPU)
156 && qemu_log_in_addr_range(itb->pc)) {
157 qemu_log_lock();
158 int flags = 0;
159 if (qemu_loglevel_mask(CPU_LOG_TB_FPU)) {
160 flags |= CPU_DUMP_FPU;
161 }
162 #if defined(TARGET_I386)
163 flags |= CPU_DUMP_CCOP;
164 #endif
165 log_cpu_state(cpu, flags);
166 qemu_log_unlock();
167 }
168 #endif /* DEBUG_DISAS */
169
170 cpu->can_do_io = !use_icount;
171 ret = tcg_qemu_tb_exec(env, tb_ptr);
172 cpu->can_do_io = 1;
173 last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
174 tb_exit = ret & TB_EXIT_MASK;
175 trace_exec_tb_exit(last_tb, tb_exit);
176
177 if (tb_exit > TB_EXIT_IDX1) {
178 /* We didn't start executing this TB (eg because the instruction
179 * counter hit zero); we must restore the guest PC to the address
180 * of the start of the TB.
181 */
182 CPUClass *cc = CPU_GET_CLASS(cpu);
183 qemu_log_mask_and_addr(CPU_LOG_EXEC, last_tb->pc,
184 "Stopped execution of TB chain before %p ["
185 TARGET_FMT_lx "] %s\n",
186 last_tb->tc.ptr, last_tb->pc,
187 lookup_symbol(last_tb->pc));
188 if (cc->synchronize_from_tb) {
189 cc->synchronize_from_tb(cpu, last_tb);
190 } else {
191 assert(cc->set_pc);
192 cc->set_pc(cpu, last_tb->pc);
193 }
194 }
195 return ret;
196 }
197
198 #ifndef CONFIG_USER_ONLY
199 /* Execute the code without caching the generated code. An interpreter
200 could be used if available. */
201 static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
202 TranslationBlock *orig_tb, bool ignore_icount)
203 {
204 TranslationBlock *tb;
205 uint32_t cflags = curr_cflags() | CF_NOCACHE;
206
207 if (ignore_icount) {
208 cflags &= ~CF_USE_ICOUNT;
209 }
210
211 /* Should never happen.
212 We only end up here when an existing TB is too long. */
213 cflags |= MIN(max_cycles, CF_COUNT_MASK);
214
215 mmap_lock();
216 tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base,
217 orig_tb->flags, cflags);
218 tb->orig_tb = orig_tb;
219 mmap_unlock();
220
221 /* execute the generated code */
222 trace_exec_tb_nocache(tb, tb->pc);
223 cpu_tb_exec(cpu, tb);
224
225 mmap_lock();
226 tb_phys_invalidate(tb, -1);
227 mmap_unlock();
228 tcg_tb_remove(tb);
229 }
230 #endif
231
232 void cpu_exec_step_atomic(CPUState *cpu)
233 {
234 CPUClass *cc = CPU_GET_CLASS(cpu);
235 TranslationBlock *tb;
236 target_ulong cs_base, pc;
237 uint32_t flags;
238 uint32_t cflags = 1;
239 uint32_t cf_mask = cflags & CF_HASH_MASK;
240 /* volatile because we modify it between setjmp and longjmp */
241 volatile bool in_exclusive_region = false;
242
243 if (sigsetjmp(cpu->jmp_env, 0) == 0) {
244 tb = tb_lookup__cpu_state(cpu, &pc, &cs_base, &flags, cf_mask);
245 if (tb == NULL) {
246 mmap_lock();
247 tb = tb_gen_code(cpu, pc, cs_base, flags, cflags);
248 mmap_unlock();
249 }
250
251 start_exclusive();
252
253 /* Since we got here, we know that parallel_cpus must be true. */
254 parallel_cpus = false;
255 in_exclusive_region = true;
256 cc->cpu_exec_enter(cpu);
257 /* execute the generated code */
258 trace_exec_tb(tb, pc);
259 cpu_tb_exec(cpu, tb);
260 cc->cpu_exec_exit(cpu);
261 } else {
262 /*
263 * The mmap_lock is dropped by tb_gen_code if it runs out of
264 * memory.
265 */
266 #ifndef CONFIG_SOFTMMU
267 tcg_debug_assert(!have_mmap_lock());
268 #endif
269 assert_no_pages_locked();
270 }
271
272 if (in_exclusive_region) {
273 /* We might longjump out of either the codegen or the
274 * execution, so must make sure we only end the exclusive
275 * region if we started it.
276 */
277 parallel_cpus = true;
278 end_exclusive();
279 }
280 }
281
282 struct tb_desc {
283 target_ulong pc;
284 target_ulong cs_base;
285 CPUArchState *env;
286 tb_page_addr_t phys_page1;
287 uint32_t flags;
288 uint32_t cf_mask;
289 uint32_t trace_vcpu_dstate;
290 };
291
292 static bool tb_lookup_cmp(const void *p, const void *d)
293 {
294 const TranslationBlock *tb = p;
295 const struct tb_desc *desc = d;
296
297 if (tb->pc == desc->pc &&
298 tb->page_addr[0] == desc->phys_page1 &&
299 tb->cs_base == desc->cs_base &&
300 tb->flags == desc->flags &&
301 tb->trace_vcpu_dstate == desc->trace_vcpu_dstate &&
302 (tb_cflags(tb) & (CF_HASH_MASK | CF_INVALID)) == desc->cf_mask) {
303 /* check next page if needed */
304 if (tb->page_addr[1] == -1) {
305 return true;
306 } else {
307 tb_page_addr_t phys_page2;
308 target_ulong virt_page2;
309
310 virt_page2 = (desc->pc & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
311 phys_page2 = get_page_addr_code(desc->env, virt_page2);
312 if (tb->page_addr[1] == phys_page2) {
313 return true;
314 }
315 }
316 }
317 return false;
318 }
319
320 TranslationBlock *tb_htable_lookup(CPUState *cpu, target_ulong pc,
321 target_ulong cs_base, uint32_t flags,
322 uint32_t cf_mask)
323 {
324 tb_page_addr_t phys_pc;
325 struct tb_desc desc;
326 uint32_t h;
327
328 cf_mask &= ~CF_CLUSTER_MASK;
329 cf_mask |= cpu->cluster_index << CF_CLUSTER_SHIFT;
330
331 desc.env = (CPUArchState *)cpu->env_ptr;
332 desc.cs_base = cs_base;
333 desc.flags = flags;
334 desc.cf_mask = cf_mask;
335 desc.trace_vcpu_dstate = *cpu->trace_dstate;
336 desc.pc = pc;
337 phys_pc = get_page_addr_code(desc.env, pc);
338 if (phys_pc == -1) {
339 return NULL;
340 }
341 desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
342 h = tb_hash_func(phys_pc, pc, flags, cf_mask, *cpu->trace_dstate);
343 return qht_lookup_custom(&tb_ctx.htable, &desc, h, tb_lookup_cmp);
344 }
345
346 void tb_set_jmp_target(TranslationBlock *tb, int n, uintptr_t addr)
347 {
348 if (TCG_TARGET_HAS_direct_jump) {
349 uintptr_t offset = tb->jmp_target_arg[n];
350 uintptr_t tc_ptr = (uintptr_t)tb->tc.ptr;
351 tb_target_set_jmp_target(tc_ptr, tc_ptr + offset, addr);
352 } else {
353 tb->jmp_target_arg[n] = addr;
354 }
355 }
356
357 static inline void tb_add_jump(TranslationBlock *tb, int n,
358 TranslationBlock *tb_next)
359 {
360 uintptr_t old;
361
362 assert(n < ARRAY_SIZE(tb->jmp_list_next));
363 qemu_spin_lock(&tb_next->jmp_lock);
364
365 /* make sure the destination TB is valid */
366 if (tb_next->cflags & CF_INVALID) {
367 goto out_unlock_next;
368 }
369 /* Atomically claim the jump destination slot only if it was NULL */
370 old = atomic_cmpxchg(&tb->jmp_dest[n], (uintptr_t)NULL, (uintptr_t)tb_next);
371 if (old) {
372 goto out_unlock_next;
373 }
374
375 /* patch the native jump address */
376 tb_set_jmp_target(tb, n, (uintptr_t)tb_next->tc.ptr);
377
378 /* add in TB jmp list */
379 tb->jmp_list_next[n] = tb_next->jmp_list_head;
380 tb_next->jmp_list_head = (uintptr_t)tb | n;
381
382 qemu_spin_unlock(&tb_next->jmp_lock);
383
384 qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
385 "Linking TBs %p [" TARGET_FMT_lx
386 "] index %d -> %p [" TARGET_FMT_lx "]\n",
387 tb->tc.ptr, tb->pc, n,
388 tb_next->tc.ptr, tb_next->pc);
389 return;
390
391 out_unlock_next:
392 qemu_spin_unlock(&tb_next->jmp_lock);
393 return;
394 }
395
396 static inline TranslationBlock *tb_find(CPUState *cpu,
397 TranslationBlock *last_tb,
398 int tb_exit, uint32_t cf_mask)
399 {
400 TranslationBlock *tb;
401 target_ulong cs_base, pc;
402 uint32_t flags;
403
404 tb = tb_lookup__cpu_state(cpu, &pc, &cs_base, &flags, cf_mask);
405 if (tb == NULL) {
406 mmap_lock();
407 tb = tb_gen_code(cpu, pc, cs_base, flags, cf_mask);
408 mmap_unlock();
409 /* We add the TB in the virtual pc hash table for the fast lookup */
410 atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb);
411 }
412 #ifndef CONFIG_USER_ONLY
413 /* We don't take care of direct jumps when address mapping changes in
414 * system emulation. So it's not safe to make a direct jump to a TB
415 * spanning two pages because the mapping for the second page can change.
416 */
417 if (tb->page_addr[1] != -1) {
418 last_tb = NULL;
419 }
420 #endif
421 /* See if we can patch the calling TB. */
422 if (last_tb) {
423 tb_add_jump(last_tb, tb_exit, tb);
424 }
425 return tb;
426 }
427
428 static inline bool cpu_handle_halt(CPUState *cpu)
429 {
430 if (cpu->halted) {
431 #if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
432 if ((cpu->interrupt_request & CPU_INTERRUPT_POLL)
433 && replay_interrupt()) {
434 X86CPU *x86_cpu = X86_CPU(cpu);
435 qemu_mutex_lock_iothread();
436 apic_poll_irq(x86_cpu->apic_state);
437 cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
438 qemu_mutex_unlock_iothread();
439 }
440 #endif
441 if (!cpu_has_work(cpu)) {
442 return true;
443 }
444
445 cpu->halted = 0;
446 }
447
448 return false;
449 }
450
451 static inline void cpu_handle_debug_exception(CPUState *cpu)
452 {
453 CPUClass *cc = CPU_GET_CLASS(cpu);
454 CPUWatchpoint *wp;
455
456 if (!cpu->watchpoint_hit) {
457 QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
458 wp->flags &= ~BP_WATCHPOINT_HIT;
459 }
460 }
461
462 cc->debug_excp_handler(cpu);
463 }
464
465 static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
466 {
467 if (cpu->exception_index < 0) {
468 #ifndef CONFIG_USER_ONLY
469 if (replay_has_exception()
470 && cpu->icount_decr.u16.low + cpu->icount_extra == 0) {
471 /* try to cause an exception pending in the log */
472 cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0, curr_cflags()), true);
473 }
474 #endif
475 if (cpu->exception_index < 0) {
476 return false;
477 }
478 }
479
480 if (cpu->exception_index >= EXCP_INTERRUPT) {
481 /* exit request from the cpu execution loop */
482 *ret = cpu->exception_index;
483 if (*ret == EXCP_DEBUG) {
484 cpu_handle_debug_exception(cpu);
485 }
486 cpu->exception_index = -1;
487 return true;
488 } else {
489 #if defined(CONFIG_USER_ONLY)
490 /* if user mode only, we simulate a fake exception
491 which will be handled outside the cpu execution
492 loop */
493 #if defined(TARGET_I386)
494 CPUClass *cc = CPU_GET_CLASS(cpu);
495 cc->do_interrupt(cpu);
496 #endif
497 *ret = cpu->exception_index;
498 cpu->exception_index = -1;
499 return true;
500 #else
501 if (replay_exception()) {
502 CPUClass *cc = CPU_GET_CLASS(cpu);
503 qemu_mutex_lock_iothread();
504 cc->do_interrupt(cpu);
505 qemu_mutex_unlock_iothread();
506 cpu->exception_index = -1;
507 } else if (!replay_has_interrupt()) {
508 /* give a chance to iothread in replay mode */
509 *ret = EXCP_INTERRUPT;
510 return true;
511 }
512 #endif
513 }
514
515 return false;
516 }
517
518 static inline bool cpu_handle_interrupt(CPUState *cpu,
519 TranslationBlock **last_tb)
520 {
521 CPUClass *cc = CPU_GET_CLASS(cpu);
522
523 /* Clear the interrupt flag now since we're processing
524 * cpu->interrupt_request and cpu->exit_request.
525 * Ensure zeroing happens before reading cpu->exit_request or
526 * cpu->interrupt_request (see also smp_wmb in cpu_exit())
527 */
528 atomic_mb_set(&cpu->icount_decr.u16.high, 0);
529
530 if (unlikely(atomic_read(&cpu->interrupt_request))) {
531 int interrupt_request;
532 qemu_mutex_lock_iothread();
533 interrupt_request = cpu->interrupt_request;
534 if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
535 /* Mask out external interrupts for this step. */
536 interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
537 }
538 if (interrupt_request & CPU_INTERRUPT_DEBUG) {
539 cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
540 cpu->exception_index = EXCP_DEBUG;
541 qemu_mutex_unlock_iothread();
542 return true;
543 }
544 if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
545 /* Do nothing */
546 } else if (interrupt_request & CPU_INTERRUPT_HALT) {
547 replay_interrupt();
548 cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
549 cpu->halted = 1;
550 cpu->exception_index = EXCP_HLT;
551 qemu_mutex_unlock_iothread();
552 return true;
553 }
554 #if defined(TARGET_I386)
555 else if (interrupt_request & CPU_INTERRUPT_INIT) {
556 X86CPU *x86_cpu = X86_CPU(cpu);
557 CPUArchState *env = &x86_cpu->env;
558 replay_interrupt();
559 cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
560 do_cpu_init(x86_cpu);
561 cpu->exception_index = EXCP_HALTED;
562 qemu_mutex_unlock_iothread();
563 return true;
564 }
565 #else
566 else if (interrupt_request & CPU_INTERRUPT_RESET) {
567 replay_interrupt();
568 cpu_reset(cpu);
569 qemu_mutex_unlock_iothread();
570 return true;
571 }
572 #endif
573 /* The target hook has 3 exit conditions:
574 False when the interrupt isn't processed,
575 True when it is, and we should restart on a new TB,
576 and via longjmp via cpu_loop_exit. */
577 else {
578 if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
579 replay_interrupt();
580 cpu->exception_index = -1;
581 *last_tb = NULL;
582 }
583 /* The target hook may have updated the 'cpu->interrupt_request';
584 * reload the 'interrupt_request' value */
585 interrupt_request = cpu->interrupt_request;
586 }
587 if (interrupt_request & CPU_INTERRUPT_EXITTB) {
588 cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB;
589 /* ensure that no TB jump will be modified as
590 the program flow was changed */
591 *last_tb = NULL;
592 }
593
594 /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
595 qemu_mutex_unlock_iothread();
596 }
597
598 /* Finally, check if we need to exit to the main loop. */
599 if (unlikely(atomic_read(&cpu->exit_request)
600 || (use_icount && cpu->icount_decr.u16.low + cpu->icount_extra == 0))) {
601 atomic_set(&cpu->exit_request, 0);
602 if (cpu->exception_index == -1) {
603 cpu->exception_index = EXCP_INTERRUPT;
604 }
605 return true;
606 }
607
608 return false;
609 }
610
611 static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
612 TranslationBlock **last_tb, int *tb_exit)
613 {
614 uintptr_t ret;
615 int32_t insns_left;
616
617 trace_exec_tb(tb, tb->pc);
618 ret = cpu_tb_exec(cpu, tb);
619 tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
620 *tb_exit = ret & TB_EXIT_MASK;
621 if (*tb_exit != TB_EXIT_REQUESTED) {
622 *last_tb = tb;
623 return;
624 }
625
626 *last_tb = NULL;
627 insns_left = atomic_read(&cpu->icount_decr.u32);
628 if (insns_left < 0) {
629 /* Something asked us to stop executing chained TBs; just
630 * continue round the main loop. Whatever requested the exit
631 * will also have set something else (eg exit_request or
632 * interrupt_request) which will be handled by
633 * cpu_handle_interrupt. cpu_handle_interrupt will also
634 * clear cpu->icount_decr.u16.high.
635 */
636 return;
637 }
638
639 /* Instruction counter expired. */
640 assert(use_icount);
641 #ifndef CONFIG_USER_ONLY
642 /* Ensure global icount has gone forward */
643 cpu_update_icount(cpu);
644 /* Refill decrementer and continue execution. */
645 insns_left = MIN(0xffff, cpu->icount_budget);
646 cpu->icount_decr.u16.low = insns_left;
647 cpu->icount_extra = cpu->icount_budget - insns_left;
648 if (!cpu->icount_extra) {
649 /* Execute any remaining instructions, then let the main loop
650 * handle the next event.
651 */
652 if (insns_left > 0) {
653 cpu_exec_nocache(cpu, insns_left, tb, false);
654 }
655 }
656 #endif
657 }
658
659 /* main execution loop */
660
661 int cpu_exec(CPUState *cpu)
662 {
663 CPUClass *cc = CPU_GET_CLASS(cpu);
664 int ret;
665 SyncClocks sc = { 0 };
666
667 /* replay_interrupt may need current_cpu */
668 current_cpu = cpu;
669
670 if (cpu_handle_halt(cpu)) {
671 return EXCP_HALTED;
672 }
673
674 rcu_read_lock();
675
676 cc->cpu_exec_enter(cpu);
677
678 /* Calculate difference between guest clock and host clock.
679 * This delay includes the delay of the last cycle, so
680 * what we have to do is sleep until it is 0. As for the
681 * advance/delay we gain here, we try to fix it next time.
682 */
683 init_delay_params(&sc, cpu);
684
685 /* prepare setjmp context for exception handling */
686 if (sigsetjmp(cpu->jmp_env, 0) != 0) {
687 #if defined(__clang__) || !QEMU_GNUC_PREREQ(4, 6)
688 /* Some compilers wrongly smash all local variables after
689 * siglongjmp. There were bug reports for gcc 4.5.0 and clang.
690 * Reload essential local variables here for those compilers.
691 * Newer versions of gcc would complain about this code (-Wclobbered). */
692 cpu = current_cpu;
693 cc = CPU_GET_CLASS(cpu);
694 #else /* buggy compiler */
695 /* Assert that the compiler does not smash local variables. */
696 g_assert(cpu == current_cpu);
697 g_assert(cc == CPU_GET_CLASS(cpu));
698 #endif /* buggy compiler */
699 #ifndef CONFIG_SOFTMMU
700 tcg_debug_assert(!have_mmap_lock());
701 #endif
702 if (qemu_mutex_iothread_locked()) {
703 qemu_mutex_unlock_iothread();
704 }
705 }
706
707 /* if an exception is pending, we execute it here */
708 while (!cpu_handle_exception(cpu, &ret)) {
709 TranslationBlock *last_tb = NULL;
710 int tb_exit = 0;
711
712 while (!cpu_handle_interrupt(cpu, &last_tb)) {
713 uint32_t cflags = cpu->cflags_next_tb;
714 TranslationBlock *tb;
715
716 /* When requested, use an exact setting for cflags for the next
717 execution. This is used for icount, precise smc, and stop-
718 after-access watchpoints. Since this request should never
719 have CF_INVALID set, -1 is a convenient invalid value that
720 does not require tcg headers for cpu_common_reset. */
721 if (cflags == -1) {
722 cflags = curr_cflags();
723 } else {
724 cpu->cflags_next_tb = -1;
725 }
726
727 tb = tb_find(cpu, last_tb, tb_exit, cflags);
728 cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit);
729 /* Try to align the host and virtual clocks
730 if the guest is in advance */
731 align_clocks(&sc, cpu);
732 }
733 }
734
735 cc->cpu_exec_exit(cpu);
736 rcu_read_unlock();
737
738 return ret;
739 }