tcg: move tcg related files into accel/tcg/ subdirectory

move cputlb.c, cpu-exec-common.c and cpu-exec.c related tcg exec
file into accel/tcg/ subdirectory.

Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <1496383606-18060-3-git-send-email-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 683 insertions, 0 deletions

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
new file mode 100644
index 0000000..3581618
--- /dev/null
+++ b/accel/tcg/cpu-exec.c
@@ -0,0 +1,683 @@
+/*
+ *  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 "qemu/osdep.h"
+#include "cpu.h"
+#include "trace.h"
+#include "disas/disas.h"
+#include "exec/exec-all.h"
+#include "tcg.h"
+#include "qemu/atomic.h"
+#include "sysemu/qtest.h"
+#include "qemu/timer.h"
+#include "exec/address-spaces.h"
+#include "qemu/rcu.h"
+#include "exec/tb-hash.h"
+#include "exec/log.h"
+#include "qemu/main-loop.h"
+#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
+#include "hw/i386/apic.h"
+#endif
+#include "sysemu/cpus.h"
+#include "sysemu/replay.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 */
+
+/* Execute a TB, and fix up the CPU state afterwards if necessary */
+static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb)
+{
+    CPUArchState *env = cpu->env_ptr;
+    uintptr_t ret;
+    TranslationBlock *last_tb;
+    int tb_exit;
+    uint8_t *tb_ptr = itb->tc_ptr;
+
+    qemu_log_mask_and_addr(CPU_LOG_EXEC, itb->pc,
+                           "Trace %p [%d: " TARGET_FMT_lx "] %s\n",
+                           itb->tc_ptr, cpu->cpu_index, itb->pc,
+                           lookup_symbol(itb->pc));
+
+#if defined(DEBUG_DISAS)
+    if (qemu_loglevel_mask(CPU_LOG_TB_CPU)
+        && qemu_log_in_addr_range(itb->pc)) {
+        qemu_log_lock();
+#if defined(TARGET_I386)
+        log_cpu_state(cpu, CPU_DUMP_CCOP);
+#else
+        log_cpu_state(cpu, 0);
+#endif
+        qemu_log_unlock();
+    }
+#endif /* DEBUG_DISAS */
+
+    cpu->can_do_io = !use_icount;
+    ret = tcg_qemu_tb_exec(env, tb_ptr);
+    cpu->can_do_io = 1;
+    last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
+    tb_exit = ret & TB_EXIT_MASK;
+    trace_exec_tb_exit(last_tb, tb_exit);
+
+    if (tb_exit > 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);
+        qemu_log_mask_and_addr(CPU_LOG_EXEC, last_tb->pc,
+                               "Stopped execution of TB chain before %p ["
+                               TARGET_FMT_lx "] %s\n",
+                               last_tb->tc_ptr, last_tb->pc,
+                               lookup_symbol(last_tb->pc));
+        if (cc->synchronize_from_tb) {
+            cc->synchronize_from_tb(cpu, last_tb);
+        } else {
+            assert(cc->set_pc);
+            cc->set_pc(cpu, last_tb->pc);
+        }
+    }
+    return ret;
+}
+
+#ifndef CONFIG_USER_ONLY
+/* 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, bool ignore_icount)
+{
+    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_lock();
+    tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
+                     max_cycles | CF_NOCACHE
+                         | (ignore_icount ? CF_IGNORE_ICOUNT : 0));
+    tb->orig_tb = orig_tb;
+    tb_unlock();
+
+    /* execute the generated code */
+    trace_exec_tb_nocache(tb, tb->pc);
+    cpu_tb_exec(cpu, tb);
+
+    tb_lock();
+    tb_phys_invalidate(tb, -1);
+    tb_free(tb);
+    tb_unlock();
+}
+#endif
+
+static void cpu_exec_step(CPUState *cpu)
+{
+    CPUClass *cc = CPU_GET_CLASS(cpu);
+    CPUArchState *env = (CPUArchState *)cpu->env_ptr;
+    TranslationBlock *tb;
+    target_ulong cs_base, pc;
+    uint32_t flags;
+
+    cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
+    if (sigsetjmp(cpu->jmp_env, 0) == 0) {
+        mmap_lock();
+        tb_lock();
+        tb = tb_gen_code(cpu, pc, cs_base, flags,
+                         1 | CF_NOCACHE | CF_IGNORE_ICOUNT);
+        tb->orig_tb = NULL;
+        tb_unlock();
+        mmap_unlock();
+
+        cc->cpu_exec_enter(cpu);
+        /* execute the generated code */
+        trace_exec_tb_nocache(tb, pc);
+        cpu_tb_exec(cpu, tb);
+        cc->cpu_exec_exit(cpu);
+
+        tb_lock();
+        tb_phys_invalidate(tb, -1);
+        tb_free(tb);
+        tb_unlock();
+    } else {
+        /* We may have exited due to another problem here, so we need
+         * to reset any tb_locks we may have taken but didn't release.
+         * The mmap_lock is dropped by tb_gen_code if it runs out of
+         * memory.
+         */
+#ifndef CONFIG_SOFTMMU
+        tcg_debug_assert(!have_mmap_lock());
+#endif
+        tb_lock_reset();
+    }
+}
+
+void cpu_exec_step_atomic(CPUState *cpu)
+{
+    start_exclusive();
+
+    /* Since we got here, we know that parallel_cpus must be true.  */
+    parallel_cpus = false;
+    cpu_exec_step(cpu);
+    parallel_cpus = true;
+
+    end_exclusive();
+}
+
+struct tb_desc {
+    target_ulong pc;
+    target_ulong cs_base;
+    CPUArchState *env;
+    tb_page_addr_t phys_page1;
+    uint32_t flags;
+};
+
+static bool tb_cmp(const void *p, const void *d)
+{
+    const TranslationBlock *tb = p;
+    const struct tb_desc *desc = d;
+
+    if (tb->pc == desc->pc &&
+        tb->page_addr[0] == desc->phys_page1 &&
+        tb->cs_base == desc->cs_base &&
+        tb->flags == desc->flags &&
+        !atomic_read(&tb->invalid)) {
+        /* check next page if needed */
+        if (tb->page_addr[1] == -1) {
+            return true;
+        } else {
+            tb_page_addr_t phys_page2;
+            target_ulong virt_page2;
+
+            virt_page2 = (desc->pc & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
+            phys_page2 = get_page_addr_code(desc->env, virt_page2);
+            if (tb->page_addr[1] == phys_page2) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+TranslationBlock *tb_htable_lookup(CPUState *cpu, target_ulong pc,
+                                   target_ulong cs_base, uint32_t flags)
+{
+    tb_page_addr_t phys_pc;
+    struct tb_desc desc;
+    uint32_t h;
+
+    desc.env = (CPUArchState *)cpu->env_ptr;
+    desc.cs_base = cs_base;
+    desc.flags = flags;
+    desc.pc = pc;
+    phys_pc = get_page_addr_code(desc.env, pc);
+    desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
+    h = tb_hash_func(phys_pc, pc, flags);
+    return qht_lookup(&tcg_ctx.tb_ctx.htable, tb_cmp, &desc, h);
+}
+
+static inline TranslationBlock *tb_find(CPUState *cpu,
+                                        TranslationBlock *last_tb,
+                                        int tb_exit)
+{
+    CPUArchState *env = (CPUArchState *)cpu->env_ptr;
+    TranslationBlock *tb;
+    target_ulong cs_base, pc;
+    uint32_t flags;
+    bool have_tb_lock = false;
+
+    /* 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 = atomic_rcu_read(&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_htable_lookup(cpu, pc, cs_base, flags);
+        if (!tb) {
+
+            /* mmap_lock is needed by tb_gen_code, and mmap_lock must be
+             * taken outside tb_lock. As system emulation is currently
+             * single threaded the locks are NOPs.
+             */
+            mmap_lock();
+            tb_lock();
+            have_tb_lock = true;
+
+            /* There's a chance that our desired tb has been translated while
+             * taking the locks so we check again inside the lock.
+             */
+            tb = tb_htable_lookup(cpu, pc, cs_base, flags);
+            if (!tb) {
+                /* if no translated code available, then translate it now */
+                tb = tb_gen_code(cpu, pc, cs_base, flags, 0);
+            }
+
+            mmap_unlock();
+        }
+
+        /* We add the TB in the virtual pc hash table for the fast lookup */
+        atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb);
+    }
+#ifndef CONFIG_USER_ONLY
+    /* We don't take care of direct jumps when address mapping changes in
+     * system emulation. So it's not safe to make a direct jump to a TB
+     * spanning two pages because the mapping for the second page can change.
+     */
+    if (tb->page_addr[1] != -1) {
+        last_tb = NULL;
+    }
+#endif
+    /* See if we can patch the calling TB. */
+    if (last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
+        if (!have_tb_lock) {
+            tb_lock();
+            have_tb_lock = true;
+        }
+        if (!tb->invalid) {
+            tb_add_jump(last_tb, tb_exit, tb);
+        }
+    }
+    if (have_tb_lock) {
+        tb_unlock();
+    }
+    return tb;
+}
+
+static inline bool cpu_handle_halt(CPUState *cpu)
+{
+    if (cpu->halted) {
+#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
+        if ((cpu->interrupt_request & CPU_INTERRUPT_POLL)
+            && replay_interrupt()) {
+            X86CPU *x86_cpu = X86_CPU(cpu);
+            qemu_mutex_lock_iothread();
+            apic_poll_irq(x86_cpu->apic_state);
+            cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
+            qemu_mutex_unlock_iothread();
+        }
+#endif
+        if (!cpu_has_work(cpu)) {
+            return true;
+        }
+
+        cpu->halted = 0;
+    }
+
+    return false;
+}
+
+static inline 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);
+}
+
+static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
+{
+    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;
+            return true;
+        } 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)
+            CPUClass *cc = CPU_GET_CLASS(cpu);
+            cc->do_interrupt(cpu);
+#endif
+            *ret = cpu->exception_index;
+            cpu->exception_index = -1;
+            return true;
+#else
+            if (replay_exception()) {
+                CPUClass *cc = CPU_GET_CLASS(cpu);
+                qemu_mutex_lock_iothread();
+                cc->do_interrupt(cpu);
+                qemu_mutex_unlock_iothread();
+                cpu->exception_index = -1;
+            } else if (!replay_has_interrupt()) {
+                /* give a chance to iothread in replay mode */
+                *ret = EXCP_INTERRUPT;
+                return true;
+            }
+#endif
+        }
+#ifndef CONFIG_USER_ONLY
+    } else if (replay_has_exception()
+               && cpu->icount_decr.u16.low + cpu->icount_extra == 0) {
+        /* try to cause an exception pending in the log */
+        cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0), true);
+        *ret = -1;
+        return true;
+#endif
+    }
+
+    return false;
+}
+
+static inline bool cpu_handle_interrupt(CPUState *cpu,
+                                        TranslationBlock **last_tb)
+{
+    CPUClass *cc = CPU_GET_CLASS(cpu);
+
+    if (unlikely(atomic_read(&cpu->interrupt_request))) {
+        int interrupt_request;
+        qemu_mutex_lock_iothread();
+        interrupt_request = cpu->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;
+            qemu_mutex_unlock_iothread();
+            return true;
+        }
+        if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
+            /* Do nothing */
+        } else if (interrupt_request & CPU_INTERRUPT_HALT) {
+            replay_interrupt();
+            cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
+            cpu->halted = 1;
+            cpu->exception_index = EXCP_HLT;
+            qemu_mutex_unlock_iothread();
+            return true;
+        }
+#if defined(TARGET_I386)
+        else if (interrupt_request & CPU_INTERRUPT_INIT) {
+            X86CPU *x86_cpu = X86_CPU(cpu);
+            CPUArchState *env = &x86_cpu->env;
+            replay_interrupt();
+            cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
+            do_cpu_init(x86_cpu);
+            cpu->exception_index = EXCP_HALTED;
+            qemu_mutex_unlock_iothread();
+            return true;
+        }
+#else
+        else if (interrupt_request & CPU_INTERRUPT_RESET) {
+            replay_interrupt();
+            cpu_reset(cpu);
+            qemu_mutex_unlock_iothread();
+            return true;
+        }
+#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.  */
+        else {
+            if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
+                replay_interrupt();
+                *last_tb = NULL;
+            }
+            /* The target hook may have updated the 'cpu->interrupt_request';
+             * reload the 'interrupt_request' value */
+            interrupt_request = cpu->interrupt_request;
+        }
+        if (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 */
+            *last_tb = NULL;
+        }
+
+        /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
+        qemu_mutex_unlock_iothread();
+    }
+
+    /* Finally, check if we need to exit to the main loop.  */
+    if (unlikely(atomic_read(&cpu->exit_request)
+        || (use_icount && cpu->icount_decr.u16.low + cpu->icount_extra == 0))) {
+        atomic_set(&cpu->exit_request, 0);
+        cpu->exception_index = EXCP_INTERRUPT;
+        return true;
+    }
+
+    return false;
+}
+
+static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
+                                    TranslationBlock **last_tb, int *tb_exit)
+{
+    uintptr_t ret;
+    int32_t insns_left;
+
+    trace_exec_tb(tb, tb->pc);
+    ret = cpu_tb_exec(cpu, tb);
+    tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
+    *tb_exit = ret & TB_EXIT_MASK;
+    if (*tb_exit != TB_EXIT_REQUESTED) {
+        *last_tb = tb;
+        return;
+    }
+
+    *last_tb = NULL;
+    insns_left = atomic_read(&cpu->icount_decr.u32);
+    atomic_set(&cpu->icount_decr.u16.high, 0);
+    if (insns_left < 0) {
+        /* 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.  But we need to ensure the zeroing of icount_decr
+         * comes before the next read of cpu->exit_request
+         * or cpu->interrupt_request.
+         */
+        smp_mb();
+        return;
+    }
+
+    /* Instruction counter expired.  */
+    assert(use_icount);
+#ifndef CONFIG_USER_ONLY
+    /* Ensure global icount has gone forward */
+    cpu_update_icount(cpu);
+    /* Refill decrementer and continue execution.  */
+    insns_left = MIN(0xffff, cpu->icount_budget);
+    cpu->icount_decr.u16.low = insns_left;
+    cpu->icount_extra = cpu->icount_budget - insns_left;
+    if (!cpu->icount_extra) {
+        /* Execute any remaining instructions, then let the main loop
+         * handle the next event.
+         */
+        if (insns_left > 0) {
+            cpu_exec_nocache(cpu, insns_left, tb, false);
+        }
+    }
+#endif
+}
+
+/* main execution loop */
+
+int cpu_exec(CPUState *cpu)
+{
+    CPUClass *cc = CPU_GET_CLASS(cpu);
+    int ret;
+    SyncClocks sc = { 0 };
+
+    /* replay_interrupt may need current_cpu */
+    current_cpu = cpu;
+
+    if (cpu_handle_halt(cpu)) {
+        return EXCP_HALTED;
+    }
+
+    rcu_read_lock();
+
+    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 */
+    if (sigsetjmp(cpu->jmp_env, 0) != 0) {
+#if defined(__clang__) || !QEMU_GNUC_PREREQ(4, 6)
+        /* Some compilers wrongly smash all local variables after
+         * siglongjmp. There were bug reports for gcc 4.5.0 and clang.
+         * Reload essential local variables here for those compilers.
+         * Newer versions of gcc would complain about this code (-Wclobbered). */
+        cpu = current_cpu;
+        cc = CPU_GET_CLASS(cpu);
+#else /* buggy compiler */
+        /* Assert that the compiler does not smash local variables. */
+        g_assert(cpu == current_cpu);
+        g_assert(cc == CPU_GET_CLASS(cpu));
+#endif /* buggy compiler */
+        cpu->can_do_io = 1;
+        tb_lock_reset();
+        if (qemu_mutex_iothread_locked()) {
+            qemu_mutex_unlock_iothread();
+        }
+    }
+
+    /* if an exception is pending, we execute it here */
+    while (!cpu_handle_exception(cpu, &ret)) {
+        TranslationBlock *last_tb = NULL;
+        int tb_exit = 0;
+
+        while (!cpu_handle_interrupt(cpu, &last_tb)) {
+            TranslationBlock *tb = tb_find(cpu, last_tb, tb_exit);
+            cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit);
+            /* Try to align the host and virtual clocks
+               if the guest is in advance */
+            align_clocks(&sc, cpu);
+        }
+    }
+
+    cc->cpu_exec_exit(cpu);
+    rcu_read_unlock();
+
+    return ret;
+}