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