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/iov.h" 13 #include "hw/qdev.h" 14 #include "hw/virtio/virtio.h" 15 #include "hw/virtio/virtio-rng.h" 16 #include "sysemu/rng.h" 17 #include "qom/object_interfaces.h" 18 #include "trace.h" 19 20 static bool is_guest_ready(VirtIORNG *vrng) 21 { 22 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 23 if (virtio_queue_ready(vrng->vq) 24 && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { 25 return true; 26 } 27 trace_virtio_rng_guest_not_ready(vrng); 28 return false; 29 } 30 31 static size_t get_request_size(VirtQueue *vq, unsigned quota) 32 { 33 unsigned int in, out; 34 35 virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); 36 return in; 37 } 38 39 static void virtio_rng_process(VirtIORNG *vrng); 40 41 /* Send data from a char device over to the guest */ 42 static void chr_read(void *opaque, const void *buf, size_t size) 43 { 44 VirtIORNG *vrng = opaque; 45 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 46 VirtQueueElement elem; 47 size_t len; 48 int offset; 49 50 if (!is_guest_ready(vrng)) { 51 return; 52 } 53 54 vrng->quota_remaining -= size; 55 56 offset = 0; 57 while (offset < size) { 58 if (!virtqueue_pop(vrng->vq, &elem)) { 59 break; 60 } 61 len = iov_from_buf(elem.in_sg, elem.in_num, 62 0, buf + offset, size - offset); 63 offset += len; 64 65 virtqueue_push(vrng->vq, &elem, len); 66 trace_virtio_rng_pushed(vrng, len); 67 } 68 virtio_notify(vdev, vrng->vq); 69 } 70 71 static void virtio_rng_process(VirtIORNG *vrng) 72 { 73 size_t size; 74 unsigned quota; 75 76 if (!is_guest_ready(vrng)) { 77 return; 78 } 79 80 if (vrng->activate_timer) { 81 timer_mod(vrng->rate_limit_timer, 82 qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms); 83 vrng->activate_timer = false; 84 } 85 86 if (vrng->quota_remaining < 0) { 87 quota = 0; 88 } else { 89 quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); 90 } 91 size = get_request_size(vrng->vq, quota); 92 93 trace_virtio_rng_request(vrng, size, quota); 94 95 size = MIN(vrng->quota_remaining, size); 96 if (size) { 97 rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); 98 } 99 } 100 101 static void handle_input(VirtIODevice *vdev, VirtQueue *vq) 102 { 103 VirtIORNG *vrng = VIRTIO_RNG(vdev); 104 virtio_rng_process(vrng); 105 } 106 107 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp) 108 { 109 return f; 110 } 111 112 static void virtio_rng_save(QEMUFile *f, void *opaque) 113 { 114 VirtIODevice *vdev = opaque; 115 116 virtio_save(vdev, f); 117 } 118 119 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id) 120 { 121 VirtIORNG *vrng = opaque; 122 int ret; 123 124 if (version_id != 1) { 125 return -EINVAL; 126 } 127 ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id); 128 if (ret != 0) { 129 return ret; 130 } 131 132 /* We may have an element ready but couldn't process it due to a quota 133 * limit. Make sure to try again after live migration when the quota may 134 * have been reset. 135 */ 136 virtio_rng_process(vrng); 137 138 return 0; 139 } 140 141 static void check_rate_limit(void *opaque) 142 { 143 VirtIORNG *vrng = opaque; 144 145 vrng->quota_remaining = vrng->conf.max_bytes; 146 virtio_rng_process(vrng); 147 vrng->activate_timer = true; 148 } 149 150 static void virtio_rng_device_realize(DeviceState *dev, Error **errp) 151 { 152 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 153 VirtIORNG *vrng = VIRTIO_RNG(dev); 154 Error *local_err = NULL; 155 156 if (vrng->conf.period_ms <= 0) { 157 error_setg(errp, "'period' parameter expects a positive integer"); 158 return; 159 } 160 161 /* Workaround: Property parsing does not enforce unsigned integers, 162 * So this is a hack to reject such numbers. */ 163 if (vrng->conf.max_bytes > INT64_MAX) { 164 error_setg(errp, "'max-bytes' parameter must be non-negative, " 165 "and less than 2^63"); 166 return; 167 } 168 169 if (vrng->conf.rng == NULL) { 170 vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM)); 171 172 user_creatable_complete(OBJECT(vrng->conf.default_backend), 173 &local_err); 174 if (local_err) { 175 error_propagate(errp, local_err); 176 object_unref(OBJECT(vrng->conf.default_backend)); 177 return; 178 } 179 180 object_property_add_child(OBJECT(dev), 181 "default-backend", 182 OBJECT(vrng->conf.default_backend), 183 NULL); 184 185 /* The child property took a reference, we can safely drop ours now */ 186 object_unref(OBJECT(vrng->conf.default_backend)); 187 188 object_property_set_link(OBJECT(dev), 189 OBJECT(vrng->conf.default_backend), 190 "rng", NULL); 191 } 192 193 vrng->rng = vrng->conf.rng; 194 if (vrng->rng == NULL) { 195 error_setg(errp, "'rng' parameter expects a valid object"); 196 return; 197 } 198 199 virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0); 200 201 vrng->vq = virtio_add_queue(vdev, 8, handle_input); 202 vrng->quota_remaining = vrng->conf.max_bytes; 203 vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, 204 check_rate_limit, vrng); 205 vrng->activate_timer = true; 206 register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save, 207 virtio_rng_load, vrng); 208 } 209 210 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp) 211 { 212 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 213 VirtIORNG *vrng = VIRTIO_RNG(dev); 214 215 timer_del(vrng->rate_limit_timer); 216 timer_free(vrng->rate_limit_timer); 217 unregister_savevm(dev, "virtio-rng", vrng); 218 virtio_cleanup(vdev); 219 } 220 221 static Property virtio_rng_properties[] = { 222 /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s. If 223 * you have an entropy source capable of generating more entropy than this 224 * and you can pass it through via virtio-rng, then hats off to you. Until 225 * then, this is unlimited for all practical purposes. 226 */ 227 DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX), 228 DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16), 229 DEFINE_PROP_END_OF_LIST(), 230 }; 231 232 static void virtio_rng_class_init(ObjectClass *klass, void *data) 233 { 234 DeviceClass *dc = DEVICE_CLASS(klass); 235 VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass); 236 237 dc->props = virtio_rng_properties; 238 set_bit(DEVICE_CATEGORY_MISC, dc->categories); 239 vdc->realize = virtio_rng_device_realize; 240 vdc->unrealize = virtio_rng_device_unrealize; 241 vdc->get_features = get_features; 242 } 243 244 static void virtio_rng_initfn(Object *obj) 245 { 246 VirtIORNG *vrng = VIRTIO_RNG(obj); 247 248 object_property_add_link(obj, "rng", TYPE_RNG_BACKEND, 249 (Object **)&vrng->conf.rng, 250 qdev_prop_allow_set_link_before_realize, 251 OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL); 252 } 253 254 static const TypeInfo virtio_rng_info = { 255 .name = TYPE_VIRTIO_RNG, 256 .parent = TYPE_VIRTIO_DEVICE, 257 .instance_size = sizeof(VirtIORNG), 258 .instance_init = virtio_rng_initfn, 259 .class_init = virtio_rng_class_init, 260 }; 261 262 static void virtio_register_types(void) 263 { 264 type_register_static(&virtio_rng_info); 265 } 266 267 type_init(virtio_register_types) 268