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bd688fc9 EGE |
1 | /* |
2 | * Lock to inhibit accelerator ioctls | |
3 | * | |
4 | * Copyright (c) 2022 Red Hat Inc. | |
5 | * | |
6 | * Author: Emanuele Giuseppe Esposito <eesposit@redhat.com> | |
7 | * | |
8 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
9 | * of this software and associated documentation files (the "Software"), to deal | |
10 | * in the Software without restriction, including without limitation the rights | |
11 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
12 | * copies of the Software, and to permit persons to whom the Software is | |
13 | * furnished to do so, subject to the following conditions: | |
14 | * | |
15 | * The above copyright notice and this permission notice shall be included in | |
16 | * all copies or substantial portions of the Software. | |
17 | * | |
18 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
19 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
20 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | |
21 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
22 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
23 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
24 | * THE SOFTWARE. | |
25 | */ | |
26 | ||
27 | #include "qemu/osdep.h" | |
28 | #include "qemu/thread.h" | |
29 | #include "qemu/main-loop.h" | |
30 | #include "hw/core/cpu.h" | |
31 | #include "sysemu/accel-blocker.h" | |
32 | ||
33 | static QemuLockCnt accel_in_ioctl_lock; | |
34 | static QemuEvent accel_in_ioctl_event; | |
35 | ||
36 | void accel_blocker_init(void) | |
37 | { | |
38 | qemu_lockcnt_init(&accel_in_ioctl_lock); | |
39 | qemu_event_init(&accel_in_ioctl_event, false); | |
40 | } | |
41 | ||
42 | void accel_ioctl_begin(void) | |
43 | { | |
44 | if (likely(qemu_mutex_iothread_locked())) { | |
45 | return; | |
46 | } | |
47 | ||
48 | /* block if lock is taken in kvm_ioctl_inhibit_begin() */ | |
49 | qemu_lockcnt_inc(&accel_in_ioctl_lock); | |
50 | } | |
51 | ||
52 | void accel_ioctl_end(void) | |
53 | { | |
54 | if (likely(qemu_mutex_iothread_locked())) { | |
55 | return; | |
56 | } | |
57 | ||
58 | qemu_lockcnt_dec(&accel_in_ioctl_lock); | |
59 | /* change event to SET. If event was BUSY, wake up all waiters */ | |
60 | qemu_event_set(&accel_in_ioctl_event); | |
61 | } | |
62 | ||
63 | void accel_cpu_ioctl_begin(CPUState *cpu) | |
64 | { | |
65 | if (unlikely(qemu_mutex_iothread_locked())) { | |
66 | return; | |
67 | } | |
68 | ||
69 | /* block if lock is taken in kvm_ioctl_inhibit_begin() */ | |
70 | qemu_lockcnt_inc(&cpu->in_ioctl_lock); | |
71 | } | |
72 | ||
73 | void accel_cpu_ioctl_end(CPUState *cpu) | |
74 | { | |
75 | if (unlikely(qemu_mutex_iothread_locked())) { | |
76 | return; | |
77 | } | |
78 | ||
79 | qemu_lockcnt_dec(&cpu->in_ioctl_lock); | |
80 | /* change event to SET. If event was BUSY, wake up all waiters */ | |
81 | qemu_event_set(&accel_in_ioctl_event); | |
82 | } | |
83 | ||
84 | static bool accel_has_to_wait(void) | |
85 | { | |
86 | CPUState *cpu; | |
87 | bool needs_to_wait = false; | |
88 | ||
89 | CPU_FOREACH(cpu) { | |
90 | if (qemu_lockcnt_count(&cpu->in_ioctl_lock)) { | |
91 | /* exit the ioctl, if vcpu is running it */ | |
92 | qemu_cpu_kick(cpu); | |
93 | needs_to_wait = true; | |
94 | } | |
95 | } | |
96 | ||
97 | return needs_to_wait || qemu_lockcnt_count(&accel_in_ioctl_lock); | |
98 | } | |
99 | ||
100 | void accel_ioctl_inhibit_begin(void) | |
101 | { | |
102 | CPUState *cpu; | |
103 | ||
104 | /* | |
105 | * We allow to inhibit only when holding the BQL, so we can identify | |
106 | * when an inhibitor wants to issue an ioctl easily. | |
107 | */ | |
108 | g_assert(qemu_mutex_iothread_locked()); | |
109 | ||
110 | /* Block further invocations of the ioctls outside the BQL. */ | |
111 | CPU_FOREACH(cpu) { | |
112 | qemu_lockcnt_lock(&cpu->in_ioctl_lock); | |
113 | } | |
114 | qemu_lockcnt_lock(&accel_in_ioctl_lock); | |
115 | ||
116 | /* Keep waiting until there are running ioctls */ | |
117 | while (true) { | |
118 | ||
119 | /* Reset event to FREE. */ | |
120 | qemu_event_reset(&accel_in_ioctl_event); | |
121 | ||
122 | if (accel_has_to_wait()) { | |
123 | /* | |
124 | * If event is still FREE, and there are ioctls still in progress, | |
125 | * wait. | |
126 | * | |
127 | * If an ioctl finishes before qemu_event_wait(), it will change | |
128 | * the event state to SET. This will prevent qemu_event_wait() from | |
129 | * blocking, but it's not a problem because if other ioctls are | |
130 | * still running the loop will iterate once more and reset the event | |
131 | * status to FREE so that it can wait properly. | |
132 | * | |
133 | * If an ioctls finishes while qemu_event_wait() is blocking, then | |
134 | * it will be waken up, but also here the while loop makes sure | |
135 | * to re-enter the wait if there are other running ioctls. | |
136 | */ | |
137 | qemu_event_wait(&accel_in_ioctl_event); | |
138 | } else { | |
139 | /* No ioctl is running */ | |
140 | return; | |
141 | } | |
142 | } | |
143 | } | |
144 | ||
145 | void accel_ioctl_inhibit_end(void) | |
146 | { | |
147 | CPUState *cpu; | |
148 | ||
149 | qemu_lockcnt_unlock(&accel_in_ioctl_lock); | |
150 | CPU_FOREACH(cpu) { | |
151 | qemu_lockcnt_unlock(&cpu->in_ioctl_lock); | |
152 | } | |
153 | } | |
154 |