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 "sysemu/tcg.h" 24 #include "exec/exec-all.h" 25 26 bool tcg_allowed; 27 28 /* exit the current TB, but without causing any exception to be raised */ 29 void cpu_loop_exit_noexc(CPUState *cpu) 30 { 31 cpu->exception_index = -1; 32 cpu_loop_exit(cpu); 33 } 34 35 #if defined(CONFIG_SOFTMMU) 36 void cpu_reloading_memory_map(void) 37 { 38 if (qemu_in_vcpu_thread() && current_cpu->running) { 39 /* The guest can in theory prolong the RCU critical section as long 40 * as it feels like. The major problem with this is that because it 41 * can do multiple reconfigurations of the memory map within the 42 * critical section, we could potentially accumulate an unbounded 43 * collection of memory data structures awaiting reclamation. 44 * 45 * Because the only thing we're currently protecting with RCU is the 46 * memory data structures, it's sufficient to break the critical section 47 * in this callback, which we know will get called every time the 48 * memory map is rearranged. 49 * 50 * (If we add anything else in the system that uses RCU to protect 51 * its data structures, we will need to implement some other mechanism 52 * to force TCG CPUs to exit the critical section, at which point this 53 * part of this callback might become unnecessary.) 54 * 55 * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which 56 * only protects cpu->as->dispatch. Since we know our caller is about 57 * to reload it, it's safe to split the critical section. 58 */ 59 rcu_read_unlock(); 60 rcu_read_lock(); 61 } 62 } 63 #endif 64 65 void cpu_loop_exit(CPUState *cpu) 66 { 67 /* Undo the setting in cpu_tb_exec. */ 68 cpu->can_do_io = 1; 69 siglongjmp(cpu->jmp_env, 1); 70 } 71 72 void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc) 73 { 74 if (pc) { 75 cpu_restore_state(cpu, pc, true); 76 } 77 cpu_loop_exit(cpu); 78 } 79 80 void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc) 81 { 82 cpu->exception_index = EXCP_ATOMIC; 83 cpu_loop_exit_restore(cpu, pc); 84 } 85