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