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/memory-internal.h"
  24
  25 bool exit_request;
  26 CPUState *tcg_current_cpu;
  27
  28 /* exit the current TB from a signal handler. The host registers are
  29    restored in a state compatible with the CPU emulator
  30  */
  31 #if defined(CONFIG_SOFTMMU)
  32 void cpu_resume_from_signal(CPUState *cpu, void *puc)
  33 {
  34     /* XXX: restore cpu registers saved in host registers */
  35
  36     cpu->exception_index = -1;
  37     siglongjmp(cpu->jmp_env, 1);
  38 }
  39
  40 void cpu_reloading_memory_map(void)
  41 {
  42     if (qemu_in_vcpu_thread()) {
  43         /* The guest can in theory prolong the RCU critical section as long
  44          * as it feels like. The major problem with this is that because it
  45          * can do multiple reconfigurations of the memory map within the
  46          * critical section, we could potentially accumulate an unbounded
  47          * collection of memory data structures awaiting reclamation.
  48          *
  49          * Because the only thing we're currently protecting with RCU is the
  50          * memory data structures, it's sufficient to break the critical section
  51          * in this callback, which we know will get called every time the
  52          * memory map is rearranged.
  53          *
  54          * (If we add anything else in the system that uses RCU to protect
  55          * its data structures, we will need to implement some other mechanism
  56          * to force TCG CPUs to exit the critical section, at which point this
  57          * part of this callback might become unnecessary.)
  58          *
  59          * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which
  60          * only protects cpu->as->dispatch. Since we know our caller is about
  61          * to reload it, it's safe to split the critical section.
  62          */
  63         rcu_read_unlock();
  64         rcu_read_lock();
  65     }
  66 }
  67 #endif
  68
  69 void cpu_loop_exit(CPUState *cpu)
  70 {
  71     cpu->current_tb = NULL;
  72     siglongjmp(cpu->jmp_env, 1);
  73 }
  74
  75 void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
  76 {
  77     if (pc) {
  78         cpu_restore_state(cpu, pc);
  79     }
  80     cpu->current_tb = NULL;
  81     siglongjmp(cpu->jmp_env, 1);
  82 }