qemu/accel/tcg/cpu-exec-common.c

/*
 *  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 2.1 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 "sysemu/cpus.h"
#include "sysemu/tcg.h"
#include "exec/exec-all.h"

bool tcg_allowed;

/* exit the current TB, but without causing any exception to be raised */
void cpu_loop_exit_noexc(CPUState *cpu)
{
    cpu->exception_index = -1;
    cpu_loop_exit(cpu);
}

#if defined(CONFIG_SOFTMMU)
void cpu_reloading_memory_map(void)
{
    if (qemu_in_vcpu_thread() && current_cpu->running) {
        /* The guest can in theory prolong the RCU critical section as long
         * as it feels like. The major problem with this is that because it
         * can do multiple reconfigurations of the memory map within the
         * critical section, we could potentially accumulate an unbounded
         * collection of memory data structures awaiting reclamation.
         *
         * Because the only thing we're currently protecting with RCU is the
         * memory data structures, it's sufficient to break the critical section
         * in this callback, which we know will get called every time the
         * memory map is rearranged.
         *
         * (If we add anything else in the system that uses RCU to protect
         * its data structures, we will need to implement some other mechanism
         * to force TCG CPUs to exit the critical section, at which point this
         * part of this callback might become unnecessary.)
         *
         * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which
         * only protects cpu->as->dispatch. Since we know our caller is about
         * to reload it, it's safe to split the critical section.
         */
        rcu_read_unlock();
        rcu_read_lock();
    }
}
#endif

void cpu_loop_exit(CPUState *cpu)
{
    /* Undo the setting in cpu_tb_exec.  */
    cpu->can_do_io = 1;
    siglongjmp(cpu->jmp_env, 1);
}

void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
{
    if (pc) {
        cpu_restore_state(cpu, pc, true);
    }
    cpu_loop_exit(cpu);
}

void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
{
    cpu->exception_index = EXCP_ATOMIC;
    cpu_loop_exit_restore(cpu, pc);
}