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/virtio/virtio.h" 17 #include "hw/qdev-properties.h" 18 #include "hw/virtio/virtio-rng.h" 19 #include "sysemu/rng.h" 20 #include "sysemu/sysemu.h" 21 #include "qom/object_interfaces.h" 22 #include "trace.h" 23 24 static bool is_guest_ready(VirtIORNG *vrng) 25 { 26 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 27 if (virtio_queue_ready(vrng->vq) 28 && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { 29 return true; 30 } 31 trace_virtio_rng_guest_not_ready(vrng); 32 return false; 33 } 34 35 static size_t get_request_size(VirtQueue *vq, unsigned quota) 36 { 37 unsigned int in, out; 38 39 virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); 40 return in; 41 } 42 43 static void virtio_rng_process(VirtIORNG *vrng); 44 45 /* Send data from a char device over to the guest */ 46 static void chr_read(void *opaque, const void *buf, size_t size) 47 { 48 VirtIORNG *vrng = opaque; 49 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 50 VirtQueueElement *elem; 51 size_t len; 52 int offset; 53 54 if (!is_guest_ready(vrng)) { 55 return; 56 } 57 58 /* we can't modify the virtqueue until 59 * our state is fully synced 60 */ 61 62 if (!runstate_check(RUN_STATE_RUNNING)) { 63 trace_virtio_rng_cpu_is_stopped(vrng, size); 64 return; 65 } 66 67 vrng->quota_remaining -= size; 68 69 offset = 0; 70 while (offset < size) { 71 elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement)); 72 if (!elem) { 73 break; 74 } 75 trace_virtio_rng_popped(vrng); 76 len = iov_from_buf(elem->in_sg, elem->in_num, 77 0, buf + offset, size - offset); 78 offset += len; 79 80 virtqueue_push(vrng->vq, elem, len); 81 trace_virtio_rng_pushed(vrng, len); 82 g_free(elem); 83 } 84 virtio_notify(vdev, vrng->vq); 85 86 if (!virtio_queue_empty(vrng->vq)) { 87 /* If we didn't drain the queue, call virtio_rng_process 88 * to take care of asking for more data as appropriate. 89 */ 90 virtio_rng_process(vrng); 91 } 92 } 93 94 static void virtio_rng_process(VirtIORNG *vrng) 95 { 96 size_t size; 97 unsigned quota; 98 99 if (!is_guest_ready(vrng)) { 100 return; 101 } 102 103 if (vrng->activate_timer) { 104 timer_mod(vrng->rate_limit_timer, 105 qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms); 106 vrng->activate_timer = false; 107 } 108 109 if (vrng->quota_remaining < 0) { 110 quota = 0; 111 } else { 112 quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); 113 } 114 size = get_request_size(vrng->vq, quota); 115 116 trace_virtio_rng_request(vrng, size, quota); 117 118 size = MIN(vrng->quota_remaining, size); 119 if (size) { 120 rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); 121 } 122 } 123 124 static void handle_input(VirtIODevice *vdev, VirtQueue *vq) 125 { 126 VirtIORNG *vrng = VIRTIO_RNG(vdev); 127 virtio_rng_process(vrng); 128 } 129 130 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp) 131 { 132 return f; 133 } 134 135 static void virtio_rng_vm_state_change(void *opaque, int running, 136 RunState state) 137 { 138 VirtIORNG *vrng = opaque; 139 140 trace_virtio_rng_vm_state_change(vrng, running, state); 141 142 /* We may have an element ready but couldn't process it due to a quota 143 * limit or because CPU was stopped. Make sure to try again when the 144 * CPU restart. 145 */ 146 147 if (running && is_guest_ready(vrng)) { 148 virtio_rng_process(vrng); 149 } 150 } 151 152 static void check_rate_limit(void *opaque) 153 { 154 VirtIORNG *vrng = opaque; 155 156 vrng->quota_remaining = vrng->conf.max_bytes; 157 virtio_rng_process(vrng); 158 vrng->activate_timer = true; 159 } 160 161 static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status) 162 { 163 VirtIORNG *vrng = VIRTIO_RNG(vdev); 164 165 if (!vdev->vm_running) { 166 return; 167 } 168 vdev->status = status; 169 170 /* Something changed, try to process buffers */ 171 virtio_rng_process(vrng); 172 } 173 174 static void virtio_rng_device_realize(DeviceState *dev, Error **errp) 175 { 176 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 177 VirtIORNG *vrng = VIRTIO_RNG(dev); 178 Error *local_err = NULL; 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 vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM)); 195 196 user_creatable_complete(USER_CREATABLE(vrng->conf.default_backend), 197 &local_err); 198 if (local_err) { 199 error_propagate(errp, local_err); 200 object_unref(OBJECT(vrng->conf.default_backend)); 201 return; 202 } 203 204 object_property_add_child(OBJECT(dev), 205 "default-backend", 206 OBJECT(vrng->conf.default_backend), 207 NULL); 208 209 /* The child property took a reference, we can safely drop ours now */ 210 object_unref(OBJECT(vrng->conf.default_backend)); 211 212 object_property_set_link(OBJECT(dev), 213 OBJECT(vrng->conf.default_backend), 214 "rng", NULL); 215 } 216 217 vrng->rng = vrng->conf.rng; 218 if (vrng->rng == NULL) { 219 error_setg(errp, "'rng' parameter expects a valid object"); 220 return; 221 } 222 223 virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0); 224 225 vrng->vq = virtio_add_queue(vdev, 8, handle_input); 226 vrng->quota_remaining = vrng->conf.max_bytes; 227 vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, 228 check_rate_limit, vrng); 229 vrng->activate_timer = true; 230 231 vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change, 232 vrng); 233 } 234 235 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp) 236 { 237 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 238 VirtIORNG *vrng = VIRTIO_RNG(dev); 239 240 qemu_del_vm_change_state_handler(vrng->vmstate); 241 timer_del(vrng->rate_limit_timer); 242 timer_free(vrng->rate_limit_timer); 243 virtio_cleanup(vdev); 244 } 245 246 static const VMStateDescription vmstate_virtio_rng = { 247 .name = "virtio-rng", 248 .minimum_version_id = 1, 249 .version_id = 1, 250 .fields = (VMStateField[]) { 251 VMSTATE_VIRTIO_DEVICE, 252 VMSTATE_END_OF_LIST() 253 }, 254 }; 255 256 static Property virtio_rng_properties[] = { 257 /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s. If 258 * you have an entropy source capable of generating more entropy than this 259 * and you can pass it through via virtio-rng, then hats off to you. Until 260 * then, this is unlimited for all practical purposes. 261 */ 262 DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX), 263 DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16), 264 DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *), 265 DEFINE_PROP_END_OF_LIST(), 266 }; 267 268 static void virtio_rng_class_init(ObjectClass *klass, void *data) 269 { 270 DeviceClass *dc = DEVICE_CLASS(klass); 271 VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass); 272 273 dc->props = virtio_rng_properties; 274 dc->vmsd = &vmstate_virtio_rng; 275 set_bit(DEVICE_CATEGORY_MISC, dc->categories); 276 vdc->realize = virtio_rng_device_realize; 277 vdc->unrealize = virtio_rng_device_unrealize; 278 vdc->get_features = get_features; 279 vdc->set_status = virtio_rng_set_status; 280 } 281 282 static const TypeInfo virtio_rng_info = { 283 .name = TYPE_VIRTIO_RNG, 284 .parent = TYPE_VIRTIO_DEVICE, 285 .instance_size = sizeof(VirtIORNG), 286 .class_init = virtio_rng_class_init, 287 }; 288 289 static void virtio_register_types(void) 290 { 291 type_register_static(&virtio_rng_info); 292 } 293 294 type_init(virtio_register_types) 295