| 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/lockcnt.h" |
| 29 | #include "qemu/thread.h" |
| 30 | #include "qemu/main-loop.h" |
| 31 | #include "hw/core/cpu.h" |
| 32 | #include "system/accel-blocker.h" |
| 33 | |
| 34 | static QemuLockCnt accel_in_ioctl_lock; |
| 35 | static QemuEvent accel_in_ioctl_event; |
| 36 | |
| 37 | void accel_blocker_init(void) |
| 38 | { |
| 39 | qemu_lockcnt_init(&accel_in_ioctl_lock); |
| 40 | qemu_event_init(&accel_in_ioctl_event, false); |
| 41 | } |
| 42 | |
| 43 | void accel_ioctl_begin(void) |
| 44 | { |
| 45 | if (likely(bql_locked())) { |
| 46 | return; |
| 47 | } |
| 48 | |
| 49 | /* block if lock is taken in kvm_ioctl_inhibit_begin() */ |
| 50 | qemu_lockcnt_inc(&accel_in_ioctl_lock); |
| 51 | } |
| 52 | |
| 53 | void accel_ioctl_end(void) |
| 54 | { |
| 55 | if (likely(bql_locked())) { |
| 56 | return; |
| 57 | } |
| 58 | |
| 59 | qemu_lockcnt_dec(&accel_in_ioctl_lock); |
| 60 | /* change event to SET. If event was BUSY, wake up all waiters */ |
| 61 | qemu_event_set(&accel_in_ioctl_event); |
| 62 | } |
| 63 | |
| 64 | void accel_cpu_ioctl_begin(CPUState *cpu) |
| 65 | { |
| 66 | if (unlikely(bql_locked())) { |
| 67 | return; |
| 68 | } |
| 69 | |
| 70 | /* block if lock is taken in kvm_ioctl_inhibit_begin() */ |
| 71 | qemu_lockcnt_inc(&cpu->in_ioctl_lock); |
| 72 | } |
| 73 | |
| 74 | void accel_cpu_ioctl_end(CPUState *cpu) |
| 75 | { |
| 76 | if (unlikely(bql_locked())) { |
| 77 | return; |
| 78 | } |
| 79 | |
| 80 | qemu_lockcnt_dec(&cpu->in_ioctl_lock); |
| 81 | /* change event to SET. If event was BUSY, wake up all waiters */ |
| 82 | qemu_event_set(&accel_in_ioctl_event); |
| 83 | } |
| 84 | |
| 85 | static bool accel_has_to_wait(void) |
| 86 | { |
| 87 | CPUState *cpu; |
| 88 | bool needs_to_wait = false; |
| 89 | |
| 90 | CPU_FOREACH(cpu) { |
| 91 | if (qemu_lockcnt_count(&cpu->in_ioctl_lock)) { |
| 92 | /* exit the ioctl, if vcpu is running it */ |
| 93 | qemu_cpu_kick(cpu); |
| 94 | needs_to_wait = true; |
| 95 | } |
| 96 | } |
| 97 | |
| 98 | return needs_to_wait || qemu_lockcnt_count(&accel_in_ioctl_lock); |
| 99 | } |
| 100 | |
| 101 | void accel_ioctl_inhibit_begin(void) |
| 102 | { |
| 103 | CPUState *cpu; |
| 104 | |
| 105 | /* |
| 106 | * We allow to inhibit only when holding the BQL, so we can identify |
| 107 | * when an inhibitor wants to issue an ioctl easily. |
| 108 | */ |
| 109 | g_assert(bql_locked()); |
| 110 | |
| 111 | /* Block further invocations of the ioctls outside the BQL. */ |
| 112 | CPU_FOREACH(cpu) { |
| 113 | qemu_lockcnt_lock(&cpu->in_ioctl_lock); |
| 114 | } |
| 115 | qemu_lockcnt_lock(&accel_in_ioctl_lock); |
| 116 | |
| 117 | /* Keep waiting until there are running ioctls */ |
| 118 | while (true) { |
| 119 | |
| 120 | /* Reset event to FREE. */ |
| 121 | qemu_event_reset(&accel_in_ioctl_event); |
| 122 | |
| 123 | if (accel_has_to_wait()) { |
| 124 | /* |
| 125 | * If event is still FREE, and there are ioctls still in progress, |
| 126 | * wait. |
| 127 | * |
| 128 | * If an ioctl finishes before qemu_event_wait(), it will change |
| 129 | * the event state to SET. This will prevent qemu_event_wait() from |
| 130 | * blocking, but it's not a problem because if other ioctls are |
| 131 | * still running the loop will iterate once more and reset the event |
| 132 | * status to FREE so that it can wait properly. |
| 133 | * |
| 134 | * If an ioctls finishes while qemu_event_wait() is blocking, then |
| 135 | * it will be waken up, but also here the while loop makes sure |
| 136 | * to re-enter the wait if there are other running ioctls. |
| 137 | */ |
| 138 | qemu_event_wait(&accel_in_ioctl_event); |
| 139 | } else { |
| 140 | /* No ioctl is running */ |
| 141 | return; |
| 142 | } |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | void accel_ioctl_inhibit_end(void) |
| 147 | { |
| 148 | CPUState *cpu; |
| 149 | |
| 150 | qemu_lockcnt_unlock(&accel_in_ioctl_lock); |
| 151 | CPU_FOREACH(cpu) { |
| 152 | qemu_lockcnt_unlock(&cpu->in_ioctl_lock); |
| 153 | } |
| 154 | } |
| 155 |