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/iov.h"
  13 #include "hw/qdev.h"
  14 #include "hw/virtio/virtio.h"
  15 #include "hw/virtio/virtio-rng.h"
  16 #include "sysemu/rng.h"
  17 #include "qom/object_interfaces.h"
  18 #include "trace.h"
  19
  20 static bool is_guest_ready(VirtIORNG *vrng)
  21 {
  22     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  23     if (virtio_queue_ready(vrng->vq)
  24         && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  25         return true;
  26     }
  27     trace_virtio_rng_guest_not_ready(vrng);
  28     return false;
  29 }
  30
  31 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  32 {
  33     unsigned int in, out;
  34
  35     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  36     return in;
  37 }
  38
  39 static void virtio_rng_process(VirtIORNG *vrng);
  40
  41 /* Send data from a char device over to the guest */
  42 static void chr_read(void *opaque, const void *buf, size_t size)
  43 {
  44     VirtIORNG *vrng = opaque;
  45     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  46     VirtQueueElement elem;
  47     size_t len;
  48     int offset;
  49
  50     if (!is_guest_ready(vrng)) {
  51         return;
  52     }
  53
  54     vrng->quota_remaining -= size;
  55
  56     offset = 0;
  57     while (offset < size) {
  58         if (!virtqueue_pop(vrng->vq, &elem)) {
  59             break;
  60         }
  61         len = iov_from_buf(elem.in_sg, elem.in_num,
  62                            0, buf + offset, size - offset);
  63         offset += len;
  64
  65         virtqueue_push(vrng->vq, &elem, len);
  66         trace_virtio_rng_pushed(vrng, len);
  67     }
  68     virtio_notify(vdev, vrng->vq);
  69 }
  70
  71 static void virtio_rng_process(VirtIORNG *vrng)
  72 {
  73     size_t size;
  74     unsigned quota;
  75
  76     if (!is_guest_ready(vrng)) {
  77         return;
  78     }
  79
  80     if (vrng->quota_remaining < 0) {
  81         quota = 0;
  82     } else {
  83         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  84     }
  85     size = get_request_size(vrng->vq, quota);
  86
  87     trace_virtio_rng_request(vrng, size, quota);
  88
  89     size = MIN(vrng->quota_remaining, size);
  90     if (size) {
  91         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
  92     }
  93 }
  94
  95 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
  96 {
  97     VirtIORNG *vrng = VIRTIO_RNG(vdev);
  98     virtio_rng_process(vrng);
  99 }
 100
 101 static uint64_t get_features(VirtIODevice *vdev, uint64_t f)
 102 {
 103     return f;
 104 }
 105
 106 static void virtio_rng_save(QEMUFile *f, void *opaque)
 107 {
 108     VirtIODevice *vdev = opaque;
 109
 110     virtio_save(vdev, f);
 111 }
 112
 113 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 114 {
 115     VirtIORNG *vrng = opaque;
 116     int ret;
 117
 118     if (version_id != 1) {
 119         return -EINVAL;
 120     }
 121     ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id);
 122     if (ret != 0) {
 123         return ret;
 124     }
 125
 126     /* We may have an element ready but couldn't process it due to a quota
 127      * limit.  Make sure to try again after live migration when the quota may
 128      * have been reset.
 129      */
 130     virtio_rng_process(vrng);
 131
 132     return 0;
 133 }
 134
 135 static void check_rate_limit(void *opaque)
 136 {
 137     VirtIORNG *vrng = opaque;
 138
 139     vrng->quota_remaining = vrng->conf.max_bytes;
 140     virtio_rng_process(vrng);
 141     timer_mod(vrng->rate_limit_timer,
 142                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 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
 199     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 200                                                check_rate_limit, vrng);
 201
 202     timer_mod(vrng->rate_limit_timer,
 203                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 204
 205     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 206                     virtio_rng_load, vrng);
 207 }
 208
 209 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 210 {
 211     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 212     VirtIORNG *vrng = VIRTIO_RNG(dev);
 213
 214     timer_del(vrng->rate_limit_timer);
 215     timer_free(vrng->rate_limit_timer);
 216     unregister_savevm(dev, "virtio-rng", vrng);
 217     virtio_cleanup(vdev);
 218 }
 219
 220 static Property virtio_rng_properties[] = {
 221     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 222      * you have an entropy source capable of generating more entropy than this
 223      * and you can pass it through via virtio-rng, then hats off to you.  Until
 224      * then, this is unlimited for all practical purposes.
 225      */
 226     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 227     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 228     DEFINE_PROP_END_OF_LIST(),
 229 };
 230
 231 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 232 {
 233     DeviceClass *dc = DEVICE_CLASS(klass);
 234     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 235
 236     dc->props = virtio_rng_properties;
 237     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 238     vdc->realize = virtio_rng_device_realize;
 239     vdc->unrealize = virtio_rng_device_unrealize;
 240     vdc->get_features = get_features;
 241 }
 242
 243 static void virtio_rng_initfn(Object *obj)
 244 {
 245     VirtIORNG *vrng = VIRTIO_RNG(obj);
 246
 247     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 248                              (Object **)&vrng->conf.rng,
 249                              qdev_prop_allow_set_link_before_realize,
 250                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 251 }
 252
 253 static const TypeInfo virtio_rng_info = {
 254     .name = TYPE_VIRTIO_RNG,
 255     .parent = TYPE_VIRTIO_DEVICE,
 256     .instance_size = sizeof(VirtIORNG),
 257     .instance_init = virtio_rng_initfn,
 258     .class_init = virtio_rng_class_init,
 259 };
 260
 261 static void virtio_register_types(void)
 262 {
 263     type_register_static(&virtio_rng_info);
 264 }
 265
 266 type_init(virtio_register_types)