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 } 154 155