qemu

FORK: QEMU emulator
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cpu-exec-common.c (2861B)

      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 
     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);
     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 }