Merge remote-tracking branch 'remotes/mcayland/tags/qemu-openbios-20220115' into...
[qemu.git] / accel / tcg / 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 2.1 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, true);
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 }