hw/virtio/virtio-rng.c

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