/* * emulator main execution loop * * Copyright (c) 2003-2005 Fabrice Bellard * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, see <http://www.gnu.org/licenses/>. */ #include "config.h" #include "cpu.h" #include "trace.h" #include "disas/disas.h" #include "tcg.h" #include "qemu/atomic.h" #include "sysemu/qtest.h" #include "qemu/timer.h" #include "exec/address-spaces.h" #include "exec/memory-internal.h" #include "qemu/rcu.h" #include "exec/tb-hash.h" /* -icount align implementation. */ typedef struct SyncClocks { int64_t diff_clk; int64_t last_cpu_icount; int64_t realtime_clock; } SyncClocks; #if !defined(CONFIG_USER_ONLY) /* Allow the guest to have a max 3ms advance. * The difference between the 2 clocks could therefore * oscillate around 0. */ #define VM_CLOCK_ADVANCE 3000000 #define THRESHOLD_REDUCE 1.5 #define MAX_DELAY_PRINT_RATE 2000000000LL #define MAX_NB_PRINTS 100 static void align_clocks(SyncClocks *sc, const CPUState *cpu) { int64_t cpu_icount; if (!icount_align_option) { return; } cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low; sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount); sc->last_cpu_icount = cpu_icount; if (sc->diff_clk > VM_CLOCK_ADVANCE) { #ifndef _WIN32 struct timespec sleep_delay, rem_delay; sleep_delay.tv_sec = sc->diff_clk / 1000000000LL; sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL; if (nanosleep(&sleep_delay, &rem_delay) < 0) { sc->diff_clk = rem_delay.tv_sec * 1000000000LL + rem_delay.tv_nsec; } else { sc->diff_clk = 0; } #else Sleep(sc->diff_clk / SCALE_MS); sc->diff_clk = 0; #endif } } static void print_delay(const SyncClocks *sc) { static float threshold_delay; static int64_t last_realtime_clock; static int nb_prints; if (icount_align_option && sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE && nb_prints < MAX_NB_PRINTS) { if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) || (-sc->diff_clk / (float)1000000000LL < (threshold_delay - THRESHOLD_REDUCE))) { threshold_delay = (-sc->diff_clk / 1000000000LL) + 1; printf("Warning: The guest is now late by %.1f to %.1f seconds\n", threshold_delay - 1, threshold_delay); nb_prints++; last_realtime_clock = sc->realtime_clock; } } } static void init_delay_params(SyncClocks *sc, const CPUState *cpu) { if (!icount_align_option) { return; } sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT); sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock; sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low; if (sc->diff_clk < max_delay) { max_delay = sc->diff_clk; } if (sc->diff_clk > max_advance) { max_advance = sc->diff_clk; } /* Print every 2s max if the guest is late. We limit the number of printed messages to NB_PRINT_MAX(currently 100) */ print_delay(sc); } #else static void align_clocks(SyncClocks *sc, const CPUState *cpu) { } static void init_delay_params(SyncClocks *sc, const CPUState *cpu) { } #endif /* CONFIG USER ONLY */ void cpu_loop_exit(CPUState *cpu) { cpu->current_tb = NULL; siglongjmp(cpu->jmp_env, 1); } /* exit the current TB from a signal handler. The host registers are restored in a state compatible with the CPU emulator */ #if defined(CONFIG_SOFTMMU) void cpu_resume_from_signal(CPUState *cpu, void *puc) { /* XXX: restore cpu registers saved in host registers */ cpu->exception_index = -1; siglongjmp(cpu->jmp_env, 1); } void cpu_reload_memory_map(CPUState *cpu) { AddressSpaceDispatch *d; if (qemu_in_vcpu_thread()) { /* Do not let the guest prolong the critical section as much as it * as it desires. * * Currently, this is prevented by the I/O thread's periodinc kicking * of the VCPU thread (iothread_requesting_mutex, qemu_cpu_kick_thread) * but this will go away once TCG's execution moves out of the global * mutex. * * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which * only protects cpu->as->dispatch. Since we reload it below, we can * split the critical section. */ rcu_read_unlock(); rcu_read_lock(); } /* The CPU and TLB are protected by the iothread lock. */ d = atomic_rcu_read(&cpu->as->dispatch); cpu->memory_dispatch = d; tlb_flush(cpu, 1); } #endif /* Execute a TB, and fix up the CPU state afterwards if necessary */ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, uint8_t *tb_ptr) { CPUArchState *env = cpu->env_ptr; uintptr_t next_tb; #if defined(DEBUG_DISAS) if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) { #if defined(TARGET_I386) log_cpu_state(cpu, CPU_DUMP_CCOP); #elif defined(TARGET_M68K) /* ??? Should not modify env state for dumping. */ cpu_m68k_flush_flags(env, env->cc_op); env->cc_op = CC_OP_FLAGS; env->sr = (env->sr & 0xffe0) | env->cc_dest | (env->cc_x << 4); log_cpu_state(cpu, 0); #else log_cpu_state(cpu, 0); #endif } #endif /* DEBUG_DISAS */ cpu->can_do_io = !use_icount; next_tb = tcg_qemu_tb_exec(env, tb_ptr); cpu->can_do_io = 1; trace_exec_tb_exit((void *) (next_tb & ~TB_EXIT_MASK), next_tb & TB_EXIT_MASK); if ((next_tb & TB_EXIT_MASK) > TB_EXIT_IDX1) { /* We didn't start executing this TB (eg because the instruction * counter hit zero); we must restore the guest PC to the address * of the start of the TB. */ CPUClass *cc = CPU_GET_CLASS(cpu); TranslationBlock *tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK); if (cc->synchronize_from_tb) { cc->synchronize_from_tb(cpu, tb); } else { assert(cc->set_pc); cc->set_pc(cpu, tb->pc); } } if ((next_tb & TB_EXIT_MASK) == TB_EXIT_REQUESTED) { /* We were asked to stop executing TBs (probably a pending * interrupt. We've now stopped, so clear the flag. */ cpu->tcg_exit_req = 0; } return next_tb; } /* Execute the code without caching the generated code. An interpreter could be used if available. */ static void cpu_exec_nocache(CPUState *cpu, int max_cycles, TranslationBlock *orig_tb) { TranslationBlock *tb; /* Should never happen. We only end up here when an existing TB is too long. */ if (max_cycles > CF_COUNT_MASK) max_cycles = CF_COUNT_MASK; tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags, max_cycles | CF_NOCACHE); tb->orig_tb = tcg_ctx.tb_ctx.tb_invalidated_flag ? NULL : orig_tb; cpu->current_tb = tb; /* execute the generated code */ trace_exec_tb_nocache(tb, tb->pc); cpu_tb_exec(cpu, tb->tc_ptr); cpu->current_tb = NULL; tb_phys_invalidate(tb, -1); tb_free(tb); } static TranslationBlock *tb_find_slow(CPUState *cpu, target_ulong pc, target_ulong cs_base, uint64_t flags) { CPUArchState *env = (CPUArchState *)cpu->env_ptr; TranslationBlock *tb, **ptb1; unsigned int h; tb_page_addr_t phys_pc, phys_page1; target_ulong virt_page2; tcg_ctx.tb_ctx.tb_invalidated_flag = 0; /* find translated block using physical mappings */ phys_pc = get_page_addr_code(env, pc); phys_page1 = phys_pc & TARGET_PAGE_MASK; h = tb_phys_hash_func(phys_pc); ptb1 = &tcg_ctx.tb_ctx.tb_phys_hash[h]; for(;;) { tb = *ptb1; if (!tb) goto not_found; if (tb->pc == pc && tb->page_addr[0] == phys_page1 && tb->cs_base == cs_base && tb->flags == flags) { /* check next page if needed */ if (tb->page_addr[1] != -1) { tb_page_addr_t phys_page2; virt_page2 = (pc & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE; phys_page2 = get_page_addr_code(env, virt_page2); if (tb->page_addr[1] == phys_page2) goto found; } else { goto found; } } ptb1 = &tb->phys_hash_next; } not_found: /* if no translated code available, then translate it now */ tb = tb_gen_code(cpu, pc, cs_base, flags, 0); found: /* Move the last found TB to the head of the list */ if (likely(*ptb1)) { *ptb1 = tb->phys_hash_next; tb->phys_hash_next = tcg_ctx.tb_ctx.tb_phys_hash[h]; tcg_ctx.tb_ctx.tb_phys_hash[h] = tb; } /* we add the TB in the virtual pc hash table */ cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb; return tb; } static inline TranslationBlock *tb_find_fast(CPUState *cpu) { CPUArchState *env = (CPUArchState *)cpu->env_ptr; TranslationBlock *tb; target_ulong cs_base, pc; int flags; /* we record a subset of the CPU state. It will always be the same before a given translated block is executed. */ cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]; if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base || tb->flags != flags)) { tb = tb_find_slow(cpu, pc, cs_base, flags); } return tb; } static void cpu_handle_debug_exception(CPUState *cpu) { CPUClass *cc = CPU_GET_CLASS(cpu); CPUWatchpoint *wp; if (!cpu->watchpoint_hit) { QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) { wp->flags &= ~BP_WATCHPOINT_HIT; } } cc->debug_excp_handler(cpu); } /* main execution loop */ volatile sig_atomic_t exit_request; int cpu_exec(CPUState *cpu) { CPUClass *cc = CPU_GET_CLASS(cpu); #ifdef TARGET_I386 X86CPU *x86_cpu = X86_CPU(cpu); CPUArchState *env = &x86_cpu->env; #endif int ret, interrupt_request; TranslationBlock *tb; uint8_t *tc_ptr; uintptr_t next_tb; SyncClocks sc; /* This must be volatile so it is not trashed by longjmp() */ volatile bool have_tb_lock = false; if (cpu->halted) { if (!cpu_has_work(cpu)) { return EXCP_HALTED; } cpu->halted = 0; } current_cpu = cpu; /* As long as current_cpu is null, up to the assignment just above, * requests by other threads to exit the execution loop are expected to * be issued using the exit_request global. We must make sure that our * evaluation of the global value is performed past the current_cpu * value transition point, which requires a memory barrier as well as * an instruction scheduling constraint on modern architectures. */ smp_mb(); rcu_read_lock(); if (unlikely(exit_request)) { cpu->exit_request = 1; } cc->cpu_exec_enter(cpu); /* Calculate difference between guest clock and host clock. * This delay includes the delay of the last cycle, so * what we have to do is sleep until it is 0. As for the * advance/delay we gain here, we try to fix it next time. */ init_delay_params(&sc, cpu); /* prepare setjmp context for exception handling */ for(;;) { if (sigsetjmp(cpu->jmp_env, 0) == 0) { /* if an exception is pending, we execute it here */ if (cpu->exception_index >= 0) { if (cpu->exception_index >= EXCP_INTERRUPT) { /* exit request from the cpu execution loop */ ret = cpu->exception_index; if (ret == EXCP_DEBUG) { cpu_handle_debug_exception(cpu); } cpu->exception_index = -1; break; } else { #if defined(CONFIG_USER_ONLY) /* if user mode only, we simulate a fake exception which will be handled outside the cpu execution loop */ #if defined(TARGET_I386) cc->do_interrupt(cpu); #endif ret = cpu->exception_index; cpu->exception_index = -1; break; #else cc->do_interrupt(cpu); cpu->exception_index = -1; #endif } } next_tb = 0; /* force lookup of first TB */ for(;;) { interrupt_request = cpu->interrupt_request; if (unlikely(interrupt_request)) { if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) { /* Mask out external interrupts for this step. */ interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK; } if (interrupt_request & CPU_INTERRUPT_DEBUG) { cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG; cpu->exception_index = EXCP_DEBUG; cpu_loop_exit(cpu); } if (interrupt_request & CPU_INTERRUPT_HALT) { cpu->interrupt_request &= ~CPU_INTERRUPT_HALT; cpu->halted = 1; cpu->exception_index = EXCP_HLT; cpu_loop_exit(cpu); } #if defined(TARGET_I386) if (interrupt_request & CPU_INTERRUPT_INIT) { cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0); do_cpu_init(x86_cpu); cpu->exception_index = EXCP_HALTED; cpu_loop_exit(cpu); } #else if (interrupt_request & CPU_INTERRUPT_RESET) { cpu_reset(cpu); } #endif /* The target hook has 3 exit conditions: False when the interrupt isn't processed, True when it is, and we should restart on a new TB, and via longjmp via cpu_loop_exit. */ if (cc->cpu_exec_interrupt(cpu, interrupt_request)) { next_tb = 0; } /* Don't use the cached interrupt_request value, do_interrupt may have updated the EXITTB flag. */ if (cpu->interrupt_request & CPU_INTERRUPT_EXITTB) { cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB; /* ensure that no TB jump will be modified as the program flow was changed */ next_tb = 0; } } if (unlikely(cpu->exit_request)) { cpu->exit_request = 0; cpu->exception_index = EXCP_INTERRUPT; cpu_loop_exit(cpu); } spin_lock(&tcg_ctx.tb_ctx.tb_lock); have_tb_lock = true; tb = tb_find_fast(cpu); /* Note: we do it here to avoid a gcc bug on Mac OS X when doing it in tb_find_slow */ if (tcg_ctx.tb_ctx.tb_invalidated_flag) { /* as some TB could have been invalidated because of memory exceptions while generating the code, we must recompute the hash index here */ next_tb = 0; tcg_ctx.tb_ctx.tb_invalidated_flag = 0; } if (qemu_loglevel_mask(CPU_LOG_EXEC)) { qemu_log("Trace %p [" TARGET_FMT_lx "] %s\n", tb->tc_ptr, tb->pc, lookup_symbol(tb->pc)); } /* see if we can patch the calling TB. When the TB spans two pages, we cannot safely do a direct jump. */ if (next_tb != 0 && tb->page_addr[1] == -1) { tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK), next_tb & TB_EXIT_MASK, tb); } have_tb_lock = false; spin_unlock(&tcg_ctx.tb_ctx.tb_lock); /* cpu_interrupt might be called while translating the TB, but before it is linked into a potentially infinite loop and becomes env->current_tb. Avoid starting execution if there is a pending interrupt. */ cpu->current_tb = tb; barrier(); if (likely(!cpu->exit_request)) { trace_exec_tb(tb, tb->pc); tc_ptr = tb->tc_ptr; /* execute the generated code */ next_tb = cpu_tb_exec(cpu, tc_ptr); switch (next_tb & TB_EXIT_MASK) { case TB_EXIT_REQUESTED: /* Something asked us to stop executing * chained TBs; just continue round the main * loop. Whatever requested the exit will also * have set something else (eg exit_request or * interrupt_request) which we will handle * next time around the loop. */ next_tb = 0; break; case TB_EXIT_ICOUNT_EXPIRED: { /* Instruction counter expired. */ int insns_left = cpu->icount_decr.u32; if (cpu->icount_extra && insns_left >= 0) { /* Refill decrementer and continue execution. */ cpu->icount_extra += insns_left; insns_left = MIN(0xffff, cpu->icount_extra); cpu->icount_extra -= insns_left; cpu->icount_decr.u16.low = insns_left; } else { if (insns_left > 0) { /* Execute remaining instructions. */ tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK); cpu_exec_nocache(cpu, insns_left, tb); align_clocks(&sc, cpu); } cpu->exception_index = EXCP_INTERRUPT; next_tb = 0; cpu_loop_exit(cpu); } break; } default: break; } } cpu->current_tb = NULL; /* Try to align the host and virtual clocks if the guest is in advance */ align_clocks(&sc, cpu); /* reset soft MMU for next block (it can currently only be set by a memory fault) */ } /* for(;;) */ } else { /* Reload env after longjmp - the compiler may have smashed all * local variables as longjmp is marked 'noreturn'. */ cpu = current_cpu; cc = CPU_GET_CLASS(cpu); cpu->can_do_io = 1; #ifdef TARGET_I386 x86_cpu = X86_CPU(cpu); env = &x86_cpu->env; #endif if (have_tb_lock) { spin_unlock(&tcg_ctx.tb_ctx.tb_lock); have_tb_lock = false; } } } /* for(;;) */ cc->cpu_exec_exit(cpu); rcu_read_unlock(); /* fail safe : never use current_cpu outside cpu_exec() */ current_cpu = NULL; return ret; }