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