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 "qapi/qmp/qerror.h" 15 #include "hw/virtio/virtio.h" 16 #include "hw/virtio/virtio-rng.h" 17 #include "sysemu/rng.h" 18 #include "qom/object_interfaces.h" 19 #include "trace.h" 20 21 static bool is_guest_ready(VirtIORNG *vrng) 22 { 23 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 24 if (virtio_queue_ready(vrng->vq) 25 && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { 26 return true; 27 } 28 trace_virtio_rng_guest_not_ready(vrng); 29 return false; 30 } 31 32 static size_t get_request_size(VirtQueue *vq, unsigned quota) 33 { 34 unsigned int in, out; 35 36 virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); 37 return in; 38 } 39 40 static void virtio_rng_process(VirtIORNG *vrng); 41 42 /* Send data from a char device over to the guest */ 43 static void chr_read(void *opaque, const void *buf, size_t size) 44 { 45 VirtIORNG *vrng = opaque; 46 VirtIODevice *vdev = VIRTIO_DEVICE(vrng); 47 VirtQueueElement elem; 48 size_t len; 49 int offset; 50 51 if (!is_guest_ready(vrng)) { 52 return; 53 } 54 55 vrng->quota_remaining -= size; 56 57 offset = 0; 58 while (offset < size) { 59 if (!virtqueue_pop(vrng->vq, &elem)) { 60 break; 61 } 62 len = iov_from_buf(elem.in_sg, elem.in_num, 63 0, buf + offset, size - offset); 64 offset += len; 65 66 virtqueue_push(vrng->vq, &elem, len); 67 trace_virtio_rng_pushed(vrng, len); 68 } 69 virtio_notify(vdev, vrng->vq); 70 } 71 72 static void virtio_rng_process(VirtIORNG *vrng) 73 { 74 size_t size; 75 unsigned quota; 76 77 if (!is_guest_ready(vrng)) { 78 return; 79 } 80 81 if (vrng->quota_remaining < 0) { 82 quota = 0; 83 } else { 84 quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); 85 } 86 size = get_request_size(vrng->vq, quota); 87 88 trace_virtio_rng_request(vrng, size, quota); 89 90 size = MIN(vrng->quota_remaining, size); 91 if (size) { 92 rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); 93 } 94 } 95 96 static void handle_input(VirtIODevice *vdev, VirtQueue *vq) 97 { 98 VirtIORNG *vrng = VIRTIO_RNG(vdev); 99 virtio_rng_process(vrng); 100 } 101 102 static uint64_t get_features(VirtIODevice *vdev, uint64_t f) 103 { 104 return f; 105 } 106 107 static void virtio_rng_save(QEMUFile *f, void *opaque) 108 { 109 VirtIODevice *vdev = opaque; 110 111 virtio_save(vdev, f); 112 } 113 114 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id) 115 { 116 VirtIORNG *vrng = opaque; 117 int ret; 118 119 if (version_id != 1) { 120 return -EINVAL; 121 } 122 ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id); 123 if (ret != 0) { 124 return ret; 125 } 126 127 /* We may have an element ready but couldn't process it due to a quota 128 * limit. Make sure to try again after live migration when the quota may 129 * have been reset. 130 */ 131 virtio_rng_process(vrng); 132 133 return 0; 134 } 135 136 static void check_rate_limit(void *opaque) 137 { 138 VirtIORNG *vrng = opaque; 139 140 vrng->quota_remaining = vrng->conf.max_bytes; 141 virtio_rng_process(vrng); 142 timer_mod(vrng->rate_limit_timer, 143 qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms); 144 } 145 146 static void virtio_rng_device_realize(DeviceState *dev, Error **errp) 147 { 148 VirtIODevice *vdev = VIRTIO_DEVICE(dev); 149 VirtIORNG *vrng = VIRTIO_RNG(dev); 150 Error *local_err = NULL; 151 152 if (vrng->conf.period_ms <= 0) { 153 error_setg(errp, "'period' parameter expects a positive integer"); 154 return; 155 } 156 157 /* Workaround: Property parsing does not enforce unsigned integers, 158 * So this is a hack to reject such numbers. */ 159 if (vrng->conf.max_bytes > INT64_MAX) { 160 error_setg(errp, "'max-bytes' parameter must be non-negative, " 161 "and less than 2^63"); 162 return; 163 } 164 165 if (vrng->conf.rng == NULL) { 166 vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM)); 167 168 user_creatable_complete(OBJECT(vrng->conf.default_backend), 169 &local_err); 170 if (local_err) { 171 error_propagate(errp, local_err); 172 object_unref(OBJECT(vrng->conf.default_backend)); 173 return; 174 } 175 176 object_property_add_child(OBJECT(dev), 177 "default-backend", 178 OBJECT(vrng->conf.default_backend), 179 NULL); 180 181 /* The child property took a reference, we can safely drop ours now */ 182 object_unref(OBJECT(vrng->conf.default_backend)); 183 184 object_property_set_link(OBJECT(dev), 185 OBJECT(vrng->conf.default_backend), 186 "rng", NULL); 187 } 188 189 vrng->rng = vrng->conf.rng; 190 if (vrng->rng == NULL) { 191 error_setg(errp, "'rng' parameter expects a valid object"); 192 return; 193 } 194 195 virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0); 196 197 vrng->vq = virtio_add_queue(vdev, 8, handle_input); 198 vrng->quota_remaining = vrng->conf.max_bytes; 199 200 vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, 201 check_rate_limit, vrng); 202 203 timer_mod(vrng->rate_limit_timer, 204 qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms); 205 206 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