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->activate_timer) {
  81         timer_mod(vrng->rate_limit_timer,
  82                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
  83         vrng->activate_timer = false;
  84     }
  85
  86     if (vrng->quota_remaining < 0) {
  87         quota = 0;
  88     } else {
  89         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  90     }
  91     size = get_request_size(vrng->vq, quota);
  92
  93     trace_virtio_rng_request(vrng, size, quota);
  94
  95     size = MIN(vrng->quota_remaining, size);
  96     if (size) {
  97         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
  98     }
  99 }
 100
 101 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 102 {
 103     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 104     virtio_rng_process(vrng);
 105 }
 106
 107 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 108 {
 109     return f;
 110 }
 111
 112 static void virtio_rng_save(QEMUFile *f, void *opaque)
 113 {
 114     VirtIODevice *vdev = opaque;
 115
 116     virtio_save(vdev, f);
 117 }
 118
 119 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 120 {
 121     VirtIORNG *vrng = opaque;
 122     int ret;
 123
 124     if (version_id != 1) {
 125         return -EINVAL;
 126     }
 127     ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id);
 128     if (ret != 0) {
 129         return ret;
 130     }
 131
 132     /* We may have an element ready but couldn't process it due to a quota
 133      * limit.  Make sure to try again after live migration when the quota may
 134      * have been reset.
 135      */
 136     virtio_rng_process(vrng);
 137
 138     return 0;
 139 }
 140
 141 static void check_rate_limit(void *opaque)
 142 {
 143     VirtIORNG *vrng = opaque;
 144
 145     vrng->quota_remaining = vrng->conf.max_bytes;
 146     virtio_rng_process(vrng);
 147     vrng->activate_timer = true;
 148 }
 149
 150 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 151 {
 152     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 153     VirtIORNG *vrng = VIRTIO_RNG(dev);
 154     Error *local_err = NULL;
 155
 156     if (vrng->conf.period_ms <= 0) {
 157         error_setg(errp, "'period' parameter expects a positive integer");
 158         return;
 159     }
 160
 161     /* Workaround: Property parsing does not enforce unsigned integers,
 162      * So this is a hack to reject such numbers. */
 163     if (vrng->conf.max_bytes > INT64_MAX) {
 164         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 165                    "and less than 2^63");
 166         return;
 167     }
 168
 169     if (vrng->conf.rng == NULL) {
 170         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 171
 172         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 173                                 &local_err);
 174         if (local_err) {
 175             error_propagate(errp, local_err);
 176             object_unref(OBJECT(vrng->conf.default_backend));
 177             return;
 178         }
 179
 180         object_property_add_child(OBJECT(dev),
 181                                   "default-backend",
 182                                   OBJECT(vrng->conf.default_backend),
 183                                   NULL);
 184
 185         /* The child property took a reference, we can safely drop ours now */
 186         object_unref(OBJECT(vrng->conf.default_backend));
 187
 188         object_property_set_link(OBJECT(dev),
 189                                  OBJECT(vrng->conf.default_backend),
 190                                  "rng", NULL);
 191     }
 192
 193     vrng->rng = vrng->conf.rng;
 194     if (vrng->rng == NULL) {
 195         error_setg(errp, "'rng' parameter expects a valid object");
 196         return;
 197     }
 198
 199     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 200
 201     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 202     vrng->quota_remaining = vrng->conf.max_bytes;
 203     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 204                                                check_rate_limit, vrng);
 205     vrng->activate_timer = true;
 206     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 207                     virtio_rng_load, vrng);
 208 }
 209
 210 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 211 {
 212     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 213     VirtIORNG *vrng = VIRTIO_RNG(dev);
 214
 215     timer_del(vrng->rate_limit_timer);
 216     timer_free(vrng->rate_limit_timer);
 217     unregister_savevm(dev, "virtio-rng", vrng);
 218     virtio_cleanup(vdev);
 219 }
 220
 221 static Property virtio_rng_properties[] = {
 222     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 223      * you have an entropy source capable of generating more entropy than this
 224      * and you can pass it through via virtio-rng, then hats off to you.  Until
 225      * then, this is unlimited for all practical purposes.
 226      */
 227     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 228     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 229     DEFINE_PROP_END_OF_LIST(),
 230 };
 231
 232 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 233 {
 234     DeviceClass *dc = DEVICE_CLASS(klass);
 235     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 236
 237     dc->props = virtio_rng_properties;
 238     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 239     vdc->realize = virtio_rng_device_realize;
 240     vdc->unrealize = virtio_rng_device_unrealize;
 241     vdc->get_features = get_features;
 242 }
 243
 244 static void virtio_rng_initfn(Object *obj)
 245 {
 246     VirtIORNG *vrng = VIRTIO_RNG(obj);
 247
 248     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 249                              (Object **)&vrng->conf.rng,
 250                              qdev_prop_allow_set_link_before_realize,
 251                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 252 }
 253
 254 static const TypeInfo virtio_rng_info = {
 255     .name = TYPE_VIRTIO_RNG,
 256     .parent = TYPE_VIRTIO_DEVICE,
 257     .instance_size = sizeof(VirtIORNG),
 258     .instance_init = virtio_rng_initfn,
 259     .class_init = virtio_rng_class_init,
 260 };
 261
 262 static void virtio_register_types(void)
 263 {
 264     type_register_static(&virtio_rng_info);
 265 }
 266
 267 type_init(virtio_register_types)