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 "exec/exec-all.h"
  24
  25 bool tcg_allowed;
  26
  27 /* exit the current TB, but without causing any exception to be raised */
  28 void cpu_loop_exit_noexc(CPUState *cpu)
  29 {
  30     cpu->exception_index = -1;
  31     cpu_loop_exit(cpu);
  32 }
  33
  34 #if defined(CONFIG_SOFTMMU)
  35 void 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
  64 void 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
  71 void 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
  79 void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
  80 {
  81     cpu->exception_index = EXCP_ATOMIC;
  82     cpu_loop_exit_restore(cpu, pc);
  83 }