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 "hw/qdev.h" 17 #include "hw/virtio/virtio.h" 18 #include "hw/virtio/virtio-rng.h" 19 #include "sysemu/rng.h" 20 #include "qom/object_interfaces.h" 21 #include "trace.h" 22 23 static bool is_guest_ready(VirtIORNG *vrng) 24 { 25 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 26 if (virtio_queue_ready(vrng->vq) 27 && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { 28 return true; 29 } 30 trace_virtio_rng_guest_not_ready(vrng); 31 return false; 32 } 33 34 static size_t get_request_size(VirtQueue *vq, unsigned quota) 35 { 36 unsigned int in, out; 37 38 virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); 39 return in; 40 } 41 42 static void virtio_rng_process(VirtIORNG *vrng); 43 44 /* Send data from a char device over to the guest */ 45 static void chr_read(void *opaque, const void *buf, size_t size) 46 { 47 VirtIORNG *vrng = opaque; 48 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 49 VirtQueueElement *elem; 50 size_t len; 51 int offset; 52 53 if (!is_guest_ready(vrng)) { 54 return; 55 } 56 57 /* we can't modify the virtqueue until 58 * our state is fully synced 59 */ 60 61 if (!runstate_check(RUN_STATE_RUNNING)) { 62 trace_virtio_rng_cpu_is_stopped(vrng, size); 63 return; 64 } 65 66 vrng->quota_remaining -= size; 67 68 offset = 0; 69 while (offset < size) { 70 elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement)); 71 if (!elem) { 72 break; 73 } 74 trace_virtio_rng_popped(vrng); 75 len = iov_from_buf(elem->in_sg, elem->in_num, 76 0, buf + offset, size - offset); 77 offset += len; 78 79 virtqueue_push(vrng->vq, elem, len); 80 trace_virtio_rng_pushed(vrng, len); 81 g_free(elem); 82 } 83 virtio_notify(vdev, vrng->vq); 84 85 if (!virtio_queue_empty(vrng->vq)) { 86 /* If we didn't drain the queue, call virtio_rng_process 87 * to take care of asking for more data as appropriate. 88 */ 89 virtio_rng_process(vrng); 90 } 91 } 92 93 static void virtio_rng_process(VirtIORNG *vrng) 94 { 95 size_t size; 96 unsigned quota; 97 98 if (!is_guest_ready(vrng)) { 99 return; 100 } 101 102 if (vrng->activate_timer) { 103 timer_mod(vrng->rate_limit_timer, 104 qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms); 105 vrng->activate_timer = false; 106 } 107 108 if (vrng->quota_remaining < 0) { 109 quota = 0; 110 } else { 111 quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); 112 } 113 size = get_request_size(vrng->vq, quota); 114 115 trace_virtio_rng_request(vrng, size, quota); 116 117 size = MIN(vrng->quota_remaining, size); 118 if (size) { 119 rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); 120 } 121 } 122 123 static void handle_input(VirtIODevice *vdev, VirtQueue *vq) 124 { 125 VirtIORNG *vrng = VIRTIO_RNG(vdev); 126 virtio_rng_process(vrng); 127 } 128 129 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp) 130 { 131 return f; 132 } 133 134 static void virtio_rng_vm_state_change(void *opaque, int running, 135 RunState state) 136 { 137 VirtIORNG *vrng = opaque; 138 139 trace_virtio_rng_vm_state_change(vrng, running, state); 140 141 /* We may have an element ready but couldn't process it due to a quota 142 * limit or because CPU was stopped. Make sure to try again when the 143 * CPU restart. 144 */ 145 146 if (running && is_guest_ready(vrng)) { 147 virtio_rng_process(vrng); 148 } 149 } 150 151 static void check_rate_limit(void *opaque) 152 { 153 VirtIORNG *vrng = opaque; 154 155 vrng->quota_remaining = vrng->conf.max_bytes; 156 virtio_rng_process(vrng); 157 vrng->activate_timer = true; 158 } 159 160 static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status) 161 { 162 VirtIORNG *vrng = VIRTIO_RNG(vdev); 163 164 if (!vdev->vm_running) { 165 return; 166 } 167 vdev->status = status; 168 169 /* Something changed, try to process buffers */ 170 virtio_rng_process(vrng); 171 } 172 173 static void virtio_rng_device_realize(DeviceState *dev, Error **errp) 174 { 175 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 176 VirtIORNG *vrng = VIRTIO_RNG(dev); 177 Error *local_err = NULL; 178 179 if (vrng->conf.period_ms <= 0) { 180 error_setg(errp, "'period' parameter expects a positive integer"); 181 return; 182 } 183 184 /* Workaround: Property parsing does not enforce unsigned integers, 185 * So this is a hack to reject such numbers. */ 186 if (vrng->conf.max_bytes > INT64_MAX) { 187 error_setg(errp, "'max-bytes' parameter must be non-negative, " 188 "and less than 2^63"); 189 return; 190 } 191 192 if (vrng->conf.rng == NULL) { 193 vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM)); 194 195 user_creatable_complete(USER_CREATABLE(vrng->conf.default_backend), 196 &local_err); 197 if (local_err) { 198 error_propagate(errp, local_err); 199 object_unref(OBJECT(vrng->conf.default_backend)); 200 return; 201 } 202 203 object_property_add_child(OBJECT(dev), 204 "default-backend", 205 OBJECT(vrng->conf.default_backend), 206 NULL); 207 208 /* The child property took a reference, we can safely drop ours now */ 209 object_unref(OBJECT(vrng->conf.default_backend)); 210 211 object_property_set_link(OBJECT(dev), 212 OBJECT(vrng->conf.default_backend), 213 "rng", NULL); 214 } 215 216 vrng->rng = vrng->conf.rng; 217 if (vrng->rng == NULL) { 218 error_setg(errp, "'rng' parameter expects a valid object"); 219 return; 220 } 221 222 virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0); 223 224 vrng->vq = virtio_add_queue(vdev, 8, handle_input); 225 vrng->quota_remaining = vrng->conf.max_bytes; 226 vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, 227 check_rate_limit, vrng); 228 vrng->activate_timer = true; 229 230 vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change, 231 vrng); 232 } 233 234 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp) 235 { 236 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 237 VirtIORNG *vrng = VIRTIO_RNG(dev); 238 239 qemu_del_vm_change_state_handler(vrng->vmstate); 240 timer_del(vrng->rate_limit_timer); 241 timer_free(vrng->rate_limit_timer); 242 virtio_cleanup(vdev); 243 } 244 245 static const VMStateDescription vmstate_virtio_rng = { 246 .name = "virtio-rng", 247 .minimum_version_id = 1, 248 .version_id = 1, 249 .fields = (VMStateField[]) { 250 VMSTATE_VIRTIO_DEVICE, 251 VMSTATE_END_OF_LIST() 252 }, 253 }; 254 255 static Property virtio_rng_properties[] = { 256 /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s. If 257 * you have an entropy source capable of generating more entropy than this 258 * and you can pass it through via virtio-rng, then hats off to you. Until 259 * then, this is unlimited for all practical purposes. 260 */ 261 DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX), 262 DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16), 263 DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *), 264 DEFINE_PROP_END_OF_LIST(), 265 }; 266 267 static void virtio_rng_class_init(ObjectClass *klass, void *data) 268 { 269 DeviceClass *dc = DEVICE_CLASS(klass); 270 VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass); 271 272 dc->props = virtio_rng_properties; 273 dc->vmsd = &vmstate_virtio_rng; 274 set_bit(DEVICE_CATEGORY_MISC, dc->categories); 275 vdc->realize = virtio_rng_device_realize; 276 vdc->unrealize = virtio_rng_device_unrealize; 277 vdc->get_features = get_features; 278 vdc->set_status = virtio_rng_set_status; 279 } 280 281 static const TypeInfo virtio_rng_info = { 282 .name = TYPE_VIRTIO_RNG, 283 .parent = TYPE_VIRTIO_DEVICE, 284 .instance_size = sizeof(VirtIORNG), 285 .class_init = virtio_rng_class_init, 286 }; 287 288 static void virtio_register_types(void) 289 { 290 type_register_static(&virtio_rng_info); 291 } 292 293 type_init(virtio_register_types) 294