9pfs: fix crash when fsdev is missing
[qemu.git] / 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 }
80
81 void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
82 {
83 cpu->exception_index = EXCP_ATOMIC;
84 cpu_loop_exit_restore(cpu, pc);
85 }