LXR qemu/accel/tcg/cpu-exec-common.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 2.1 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
  20#include "qemu/osdep.h"
  21#include "cpu.h"
  22#include "sysemu/cpus.h"
  23#include "sysemu/tcg.h"
  24#include "exec/exec-all.h"
  25
  26bool tcg_allowed;
  27
  28/* exit the current TB, but without causing any exception to be raised */
  29void cpu_loop_exit_noexc(CPUState *cpu)
  30{
  31    cpu->exception_index = -1;
  32    cpu_loop_exit(cpu);
  33}
  34
  35#if defined(CONFIG_SOFTMMU)
  36void cpu_reloading_memory_map(void)
  37{
  38    if (qemu_in_vcpu_thread() && current_cpu->running) {
  39        /* The guest can in theory prolong the RCU critical section as long
  40         * as it feels like. The major problem with this is that because it
  41         * can do multiple reconfigurations of the memory map within the
  42         * critical section, we could potentially accumulate an unbounded
  43         * collection of memory data structures awaiting reclamation.
  44         *
  45         * Because the only thing we're currently protecting with RCU is the
  46         * memory data structures, it's sufficient to break the critical section
  47         * in this callback, which we know will get called every time the
  48         * memory map is rearranged.
  49         *
  50         * (If we add anything else in the system that uses RCU to protect
  51         * its data structures, we will need to implement some other mechanism
  52         * to force TCG CPUs to exit the critical section, at which point this
  53         * part of this callback might become unnecessary.)
  54         *
  55         * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which
  56         * only protects cpu->as->dispatch. Since we know our caller is about
  57         * to reload it, it's safe to split the critical section.
  58         */
  59        rcu_read_unlock();
  60        rcu_read_lock();
  61    }
  62}
  63#endif
  64
  65void cpu_loop_exit(CPUState *cpu)
  66{
  67    /* Undo the setting in cpu_tb_exec.  */
  68    cpu->can_do_io = 1;
  69    siglongjmp(cpu->jmp_env, 1);
  70}
  71
  72void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
  73{
  74    if (pc) {
  75        cpu_restore_state(cpu, pc, true);
  76    }
  77    cpu_loop_exit(cpu);
  78}
  79
  80void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
  81{
  82    cpu->exception_index = EXCP_ATOMIC;
  83    cpu_loop_exit_restore(cpu, pc);
  84}
  85