virtio-rng.c (8135B)
1 /* 2 * A virtio device implementing a hardware random number generator. 3 * 4 * Copyright 2012 Red Hat, Inc. 5 * Copyright 2012 Amit Shah <amit.shah@redhat.com> 6 * 7 * This work is licensed under the terms of the GNU GPL, version 2 or 8 * (at your option) any later version. See the COPYING file in the 9 * top-level directory. 10 */ 11 12 #include "qemu/osdep.h" 13 #include "qapi/error.h" 14 #include "qemu/iov.h" 15 #include "qemu/module.h" 16 #include "qemu/timer.h" 17 #include "hw/virtio/virtio.h" 18 #include "hw/qdev-properties.h" 19 #include "hw/virtio/virtio-rng.h" 20 #include "sysemu/rng.h" 21 #include "sysemu/runstate.h" 22 #include "qom/object_interfaces.h" 23 #include "trace.h" 24 25 static bool is_guest_ready(VirtIORNG *vrng) 26 { 27 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 28 if (virtio_queue_ready(vrng->vq) 29 && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { 30 return true; 31 } 32 trace_virtio_rng_guest_not_ready(vrng); 33 return false; 34 } 35 36 static size_t get_request_size(VirtQueue *vq, unsigned quota) 37 { 38 unsigned int in, out; 39 40 virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); 41 return in; 42 } 43 44 static void virtio_rng_process(VirtIORNG *vrng); 45 46 /* Send data from a char device over to the guest */ 47 static void chr_read(void *opaque, const void *buf, size_t size) 48 { 49 VirtIORNG *vrng = opaque; 50 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 51 VirtQueueElement *elem; 52 size_t len; 53 int offset; 54 55 if (!is_guest_ready(vrng)) { 56 return; 57 } 58 59 /* we can't modify the virtqueue until 60 * our state is fully synced 61 */ 62 63 if (!runstate_check(RUN_STATE_RUNNING)) { 64 trace_virtio_rng_cpu_is_stopped(vrng, size); 65 return; 66 } 67 68 vrng->quota_remaining -= size; 69 70 offset = 0; 71 while (offset < size) { 72 elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement)); 73 if (!elem) { 74 break; 75 } 76 trace_virtio_rng_popped(vrng); 77 len = iov_from_buf(elem->in_sg, elem->in_num, 78 0, buf + offset, size - offset); 79 offset += len; 80 81 virtqueue_push(vrng->vq, elem, len); 82 trace_virtio_rng_pushed(vrng, len); 83 g_free(elem); 84 } 85 virtio_notify(vdev, vrng->vq); 86 87 if (!virtio_queue_empty(vrng->vq)) { 88 /* If we didn't drain the queue, call virtio_rng_process 89 * to take care of asking for more data as appropriate. 90 */ 91 virtio_rng_process(vrng); 92 } 93 } 94 95 static void virtio_rng_process(VirtIORNG *vrng) 96 { 97 size_t size; 98 unsigned quota; 99 100 if (!is_guest_ready(vrng)) { 101 return; 102 } 103 104 if (vrng->activate_timer) { 105 timer_mod(vrng->rate_limit_timer, 106 qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms); 107 vrng->activate_timer = false; 108 } 109 110 if (vrng->quota_remaining < 0) { 111 quota = 0; 112 } else { 113 quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); 114 } 115 size = get_request_size(vrng->vq, quota); 116 117 trace_virtio_rng_request(vrng, size, quota); 118 119 size = MIN(vrng->quota_remaining, size); 120 if (size) { 121 rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); 122 } 123 } 124 125 static void handle_input(VirtIODevice *vdev, VirtQueue *vq) 126 { 127 VirtIORNG *vrng = VIRTIO_RNG(vdev); 128 virtio_rng_process(vrng); 129 } 130 131 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp) 132 { 133 return f; 134 } 135 136 static void virtio_rng_vm_state_change(void *opaque, bool running, 137 RunState state) 138 { 139 VirtIORNG *vrng = opaque; 140 141 trace_virtio_rng_vm_state_change(vrng, running, state); 142 143 /* We may have an element ready but couldn't process it due to a quota 144 * limit or because CPU was stopped. Make sure to try again when the 145 * CPU restart. 146 */ 147 148 if (running && is_guest_ready(vrng)) { 149 virtio_rng_process(vrng); 150 } 151 } 152 153 static void check_rate_limit(void *opaque) 154 { 155 VirtIORNG *vrng = opaque; 156 157 vrng->quota_remaining = vrng->conf.max_bytes; 158 virtio_rng_process(vrng); 159 vrng->activate_timer = true; 160 } 161 162 static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status) 163 { 164 VirtIORNG *vrng = VIRTIO_RNG(vdev); 165 166 if (!vdev->vm_running) { 167 return; 168 } 169 vdev->status = status; 170 171 /* Something changed, try to process buffers */ 172 virtio_rng_process(vrng); 173 } 174 175 static void virtio_rng_device_realize(DeviceState *dev, Error **errp) 176 { 177 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 178 VirtIORNG *vrng = VIRTIO_RNG(dev); 179 180 if (vrng->conf.period_ms <= 0) { 181 error_setg(errp, "'period' parameter expects a positive integer"); 182 return; 183 } 184 185 /* Workaround: Property parsing does not enforce unsigned integers, 186 * So this is a hack to reject such numbers. */ 187 if (vrng->conf.max_bytes > INT64_MAX) { 188 error_setg(errp, "'max-bytes' parameter must be non-negative, " 189 "and less than 2^63"); 190 return; 191 } 192 193 if (vrng->conf.rng == NULL) { 194 Object *default_backend = object_new(TYPE_RNG_BUILTIN); 195 196 if (!user_creatable_complete(USER_CREATABLE(default_backend), 197 errp)) { 198 object_unref(default_backend); 199 return; 200 } 201 202 object_property_add_child(OBJECT(dev), "default-backend", 203 default_backend); 204 205 /* The child property took a reference, we can safely drop ours now */ 206 object_unref(default_backend); 207 208 object_property_set_link(OBJECT(dev), "rng", default_backend, 209 &error_abort); 210 } 211 212 vrng->rng = vrng->conf.rng; 213 if (vrng->rng == NULL) { 214 error_setg(errp, "'rng' parameter expects a valid object"); 215 return; 216 } 217 218 virtio_init(vdev, VIRTIO_ID_RNG, 0); 219 220 vrng->vq = virtio_add_queue(vdev, 8, handle_input); 221 vrng->quota_remaining = vrng->conf.max_bytes; 222 vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, 223 check_rate_limit, vrng); 224 vrng->activate_timer = true; 225 226 vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change, 227 vrng); 228 } 229 230 static void virtio_rng_device_unrealize(DeviceState *dev) 231 { 232 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 233 VirtIORNG *vrng = VIRTIO_RNG(dev); 234 235 qemu_del_vm_change_state_handler(vrng->vmstate); 236 timer_free(vrng->rate_limit_timer); 237 virtio_del_queue(vdev, 0); 238 virtio_cleanup(vdev); 239 } 240 241 static const VMStateDescription vmstate_virtio_rng = { 242 .name = "virtio-rng", 243 .minimum_version_id = 1, 244 .version_id = 1, 245 .fields = (VMStateField[]) { 246 VMSTATE_VIRTIO_DEVICE, 247 VMSTATE_END_OF_LIST() 248 }, 249 }; 250 251 static Property virtio_rng_properties[] = { 252 /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s. If 253 * you have an entropy source capable of generating more entropy than this 254 * and you can pass it through via virtio-rng, then hats off to you. Until 255 * then, this is unlimited for all practical purposes. 256 */ 257 DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX), 258 DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16), 259 DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *), 260 DEFINE_PROP_END_OF_LIST(), 261 }; 262 263 static void virtio_rng_class_init(ObjectClass *klass, void *data) 264 { 265 DeviceClass *dc = DEVICE_CLASS(klass); 266 VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass); 267 268 device_class_set_props(dc, virtio_rng_properties); 269 dc->vmsd = &vmstate_virtio_rng; 270 set_bit(DEVICE_CATEGORY_MISC, dc->categories); 271 vdc->realize = virtio_rng_device_realize; 272 vdc->unrealize = virtio_rng_device_unrealize; 273 vdc->get_features = get_features; 274 vdc->set_status = virtio_rng_set_status; 275 } 276 277 static const TypeInfo virtio_rng_info = { 278 .name = TYPE_VIRTIO_RNG, 279 .parent = TYPE_VIRTIO_DEVICE, 280 .instance_size = sizeof(VirtIORNG), 281 .class_init = virtio_rng_class_init, 282 }; 283 284 static void virtio_register_types(void) 285 { 286 type_register_static(&virtio_rng_info); 287 } 288 289 type_init(virtio_register_types)