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