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 "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     vrng->quota_remaining -= size;
  57
  58     offset = 0;
  59     while (offset < size) {
  60         elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
  61         if (!elem) {
  62             break;
  63         }
  64         len = iov_from_buf(elem->in_sg, elem->in_num,
  65                            0, buf + offset, size - offset);
  66         offset += len;
  67
  68         virtqueue_push(vrng->vq, elem, len);
  69         trace_virtio_rng_pushed(vrng, len);
  70         g_free(elem);
  71     }
  72     virtio_notify(vdev, vrng->vq);
  73
  74     if (!virtio_queue_empty(vrng->vq)) {
  75         /* If we didn't drain the queue, call virtio_rng_process
  76          * to take care of asking for more data as appropriate.
  77          */
  78         virtio_rng_process(vrng);
  79     }
  80 }
  81
  82 static void virtio_rng_process(VirtIORNG *vrng)
  83 {
  84     size_t size;
  85     unsigned quota;
  86
  87     if (!is_guest_ready(vrng)) {
  88         return;
  89     }
  90
  91     if (vrng->activate_timer) {
  92         timer_mod(vrng->rate_limit_timer,
  93                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
  94         vrng->activate_timer = false;
  95     }
  96
  97     if (vrng->quota_remaining < 0) {
  98         quota = 0;
  99     } else {
 100         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
 101     }
 102     size = get_request_size(vrng->vq, quota);
 103
 104     trace_virtio_rng_request(vrng, size, quota);
 105
 106     size = MIN(vrng->quota_remaining, size);
 107     if (size) {
 108         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
 109     }
 110 }
 111
 112 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 113 {
 114     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 115     virtio_rng_process(vrng);
 116 }
 117
 118 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 119 {
 120     return f;
 121 }
 122
 123 static int virtio_rng_post_load(void *opaque, int version_id)
 124 {
 125     VirtIORNG *vrng = opaque;
 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     vrng->activate_timer = true;
 143 }
 144
 145 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 146 {
 147     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 148     VirtIORNG *vrng = VIRTIO_RNG(dev);
 149     Error *local_err = NULL;
 150
 151     if (vrng->conf.period_ms <= 0) {
 152         error_setg(errp, "'period' parameter expects a positive integer");
 153         return;
 154     }
 155
 156     /* Workaround: Property parsing does not enforce unsigned integers,
 157      * So this is a hack to reject such numbers. */
 158     if (vrng->conf.max_bytes > INT64_MAX) {
 159         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 160                    "and less than 2^63");
 161         return;
 162     }
 163
 164     if (vrng->conf.rng == NULL) {
 165         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 166
 167         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 168                                 &local_err);
 169         if (local_err) {
 170             error_propagate(errp, local_err);
 171             object_unref(OBJECT(vrng->conf.default_backend));
 172             return;
 173         }
 174
 175         object_property_add_child(OBJECT(dev),
 176                                   "default-backend",
 177                                   OBJECT(vrng->conf.default_backend),
 178                                   NULL);
 179
 180         /* The child property took a reference, we can safely drop ours now */
 181         object_unref(OBJECT(vrng->conf.default_backend));
 182
 183         object_property_set_link(OBJECT(dev),
 184                                  OBJECT(vrng->conf.default_backend),
 185                                  "rng", NULL);
 186     }
 187
 188     vrng->rng = vrng->conf.rng;
 189     if (vrng->rng == NULL) {
 190         error_setg(errp, "'rng' parameter expects a valid object");
 191         return;
 192     }
 193
 194     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 195
 196     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 197     vrng->quota_remaining = vrng->conf.max_bytes;
 198     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 199                                                check_rate_limit, vrng);
 200     vrng->activate_timer = true;
 201 }
 202
 203 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 204 {
 205     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 206     VirtIORNG *vrng = VIRTIO_RNG(dev);
 207
 208     timer_del(vrng->rate_limit_timer);
 209     timer_free(vrng->rate_limit_timer);
 210     virtio_cleanup(vdev);
 211 }
 212
 213 static const VMStateDescription vmstate_virtio_rng = {
 214     .name = "virtio-rng",
 215     .minimum_version_id = 1,
 216     .version_id = 1,
 217     .fields = (VMStateField[]) {
 218         VMSTATE_VIRTIO_DEVICE,
 219         VMSTATE_END_OF_LIST()
 220     },
 221     .post_load =  virtio_rng_post_load,
 222 };
 223
 224 static Property virtio_rng_properties[] = {
 225     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 226      * you have an entropy source capable of generating more entropy than this
 227      * and you can pass it through via virtio-rng, then hats off to you.  Until
 228      * then, this is unlimited for all practical purposes.
 229      */
 230     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 231     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 232     DEFINE_PROP_END_OF_LIST(),
 233 };
 234
 235 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 236 {
 237     DeviceClass *dc = DEVICE_CLASS(klass);
 238     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 239
 240     dc->props = virtio_rng_properties;
 241     dc->vmsd = &vmstate_virtio_rng;
 242     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 243     vdc->realize = virtio_rng_device_realize;
 244     vdc->unrealize = virtio_rng_device_unrealize;
 245     vdc->get_features = get_features;
 246 }
 247
 248 static void virtio_rng_initfn(Object *obj)
 249 {
 250     VirtIORNG *vrng = VIRTIO_RNG(obj);
 251
 252     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 253                              (Object **)&vrng->conf.rng,
 254                              qdev_prop_allow_set_link_before_realize,
 255                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 256 }
 257
 258 static const TypeInfo virtio_rng_info = {
 259     .name = TYPE_VIRTIO_RNG,
 260     .parent = TYPE_VIRTIO_DEVICE,
 261     .instance_size = sizeof(VirtIORNG),
 262     .instance_init = virtio_rng_initfn,
 263     .class_init = virtio_rng_class_init,
 264 };
 265
 266 static void virtio_register_types(void)
 267 {
 268     type_register_static(&virtio_rng_info);
 269 }
 270
 271 type_init(virtio_register_types)