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 "qemu/iov.h"
  14 #include "hw/qdev.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         elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
  60         if (!elem) {
  61             break;
  62         }
  63         len = iov_from_buf(elem->in_sg, elem->in_num,
  64                            0, buf + offset, size - offset);
  65         offset += len;
  66
  67         virtqueue_push(vrng->vq, elem, len);
  68         trace_virtio_rng_pushed(vrng, len);
  69         g_free(elem);
  70     }
  71     virtio_notify(vdev, vrng->vq);
  72 }
  73
  74 static void virtio_rng_process(VirtIORNG *vrng)
  75 {
  76     size_t size;
  77     unsigned quota;
  78
  79     if (!is_guest_ready(vrng)) {
  80         return;
  81     }
  82
  83     if (vrng->activate_timer) {
  84         timer_mod(vrng->rate_limit_timer,
  85                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
  86         vrng->activate_timer = false;
  87     }
  88
  89     if (vrng->quota_remaining < 0) {
  90         quota = 0;
  91     } else {
  92         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  93     }
  94     size = get_request_size(vrng->vq, quota);
  95
  96     trace_virtio_rng_request(vrng, size, quota);
  97
  98     size = MIN(vrng->quota_remaining, size);
  99     if (size) {
 100         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
 101     }
 102 }
 103
 104 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 105 {
 106     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 107     virtio_rng_process(vrng);
 108 }
 109
 110 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 111 {
 112     return f;
 113 }
 114
 115 static void virtio_rng_save(QEMUFile *f, void *opaque)
 116 {
 117     VirtIODevice *vdev = opaque;
 118
 119     virtio_save(vdev, f);
 120 }
 121
 122 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 123 {
 124     VirtIORNG *vrng = opaque;
 125     int ret;
 126
 127     if (version_id != 1) {
 128         return -EINVAL;
 129     }
 130     ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id);
 131     if (ret != 0) {
 132         return ret;
 133     }
 134
 135     /* We may have an element ready but couldn't process it due to a quota
 136      * limit.  Make sure to try again after live migration when the quota may
 137      * have been reset.
 138      */
 139     virtio_rng_process(vrng);
 140
 141     return 0;
 142 }
 143
 144 static void check_rate_limit(void *opaque)
 145 {
 146     VirtIORNG *vrng = opaque;
 147
 148     vrng->quota_remaining = vrng->conf.max_bytes;
 149     virtio_rng_process(vrng);
 150     vrng->activate_timer = true;
 151 }
 152
 153 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 154 {
 155     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 156     VirtIORNG *vrng = VIRTIO_RNG(dev);
 157     Error *local_err = NULL;
 158
 159     if (vrng->conf.period_ms <= 0) {
 160         error_setg(errp, "'period' parameter expects a positive integer");
 161         return;
 162     }
 163
 164     /* Workaround: Property parsing does not enforce unsigned integers,
 165      * So this is a hack to reject such numbers. */
 166     if (vrng->conf.max_bytes > INT64_MAX) {
 167         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 168                    "and less than 2^63");
 169         return;
 170     }
 171
 172     if (vrng->conf.rng == NULL) {
 173         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 174
 175         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 176                                 &local_err);
 177         if (local_err) {
 178             error_propagate(errp, local_err);
 179             object_unref(OBJECT(vrng->conf.default_backend));
 180             return;
 181         }
 182
 183         object_property_add_child(OBJECT(dev),
 184                                   "default-backend",
 185                                   OBJECT(vrng->conf.default_backend),
 186                                   NULL);
 187
 188         /* The child property took a reference, we can safely drop ours now */
 189         object_unref(OBJECT(vrng->conf.default_backend));
 190
 191         object_property_set_link(OBJECT(dev),
 192                                  OBJECT(vrng->conf.default_backend),
 193                                  "rng", NULL);
 194     }
 195
 196     vrng->rng = vrng->conf.rng;
 197     if (vrng->rng == NULL) {
 198         error_setg(errp, "'rng' parameter expects a valid object");
 199         return;
 200     }
 201
 202     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 203
 204     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 205     vrng->quota_remaining = vrng->conf.max_bytes;
 206     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 207                                                check_rate_limit, vrng);
 208     vrng->activate_timer = true;
 209     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 210                     virtio_rng_load, vrng);
 211 }
 212
 213 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 214 {
 215     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 216     VirtIORNG *vrng = VIRTIO_RNG(dev);
 217
 218     timer_del(vrng->rate_limit_timer);
 219     timer_free(vrng->rate_limit_timer);
 220     unregister_savevm(dev, "virtio-rng", vrng);
 221     virtio_cleanup(vdev);
 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     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 242     vdc->realize = virtio_rng_device_realize;
 243     vdc->unrealize = virtio_rng_device_unrealize;
 244     vdc->get_features = get_features;
 245 }
 246
 247 static void virtio_rng_initfn(Object *obj)
 248 {
 249     VirtIORNG *vrng = VIRTIO_RNG(obj);
 250
 251     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 252                              (Object **)&vrng->conf.rng,
 253                              qdev_prop_allow_set_link_before_realize,
 254                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 255 }
 256
 257 static const TypeInfo virtio_rng_info = {
 258     .name = TYPE_VIRTIO_RNG,
 259     .parent = TYPE_VIRTIO_DEVICE,
 260     .instance_size = sizeof(VirtIORNG),
 261     .instance_init = virtio_rng_initfn,
 262     .class_init = virtio_rng_class_init,
 263 };
 264
 265 static void virtio_register_types(void)
 266 {
 267     type_register_static(&virtio_rng_info);
 268 }
 269
 270 type_init(virtio_register_types)