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 "qapi/qmp/qerror.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
  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     return false;
  28 }
  29
  30 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  31 {
  32     unsigned int in, out;
  33
  34     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  35     return in;
  36 }
  37
  38 static void virtio_rng_process(VirtIORNG *vrng);
  39
  40 /* Send data from a char device over to the guest */
  41 static void chr_read(void *opaque, const void *buf, size_t size)
  42 {
  43     VirtIORNG *vrng = opaque;
  44     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  45     VirtQueueElement elem;
  46     size_t len;
  47     int offset;
  48
  49     if (!is_guest_ready(vrng)) {
  50         return;
  51     }
  52
  53     vrng->quota_remaining -= size;
  54
  55     offset = 0;
  56     while (offset < size) {
  57         if (!virtqueue_pop(vrng->vq, &elem)) {
  58             break;
  59         }
  60         len = iov_from_buf(elem.in_sg, elem.in_num,
  61                            0, buf + offset, size - offset);
  62         offset += len;
  63
  64         virtqueue_push(vrng->vq, &elem, len);
  65     }
  66     virtio_notify(vdev, vrng->vq);
  67 }
  68
  69 static void virtio_rng_process(VirtIORNG *vrng)
  70 {
  71     size_t size;
  72     unsigned quota;
  73
  74     if (!is_guest_ready(vrng)) {
  75         return;
  76     }
  77
  78     if (vrng->quota_remaining < 0) {
  79         quota = 0;
  80     } else {
  81         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  82     }
  83     size = get_request_size(vrng->vq, quota);
  84     size = MIN(vrng->quota_remaining, size);
  85     if (size) {
  86         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
  87     }
  88 }
  89
  90 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
  91 {
  92     VirtIORNG *vrng = VIRTIO_RNG(vdev);
  93     virtio_rng_process(vrng);
  94 }
  95
  96 static uint32_t get_features(VirtIODevice *vdev, uint32_t f)
  97 {
  98     return f;
  99 }
 100
 101 static void virtio_rng_save(QEMUFile *f, void *opaque)
 102 {
 103     VirtIODevice *vdev = opaque;
 104
 105     virtio_save(vdev, f);
 106 }
 107
 108 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 109 {
 110     if (version_id != 1) {
 111         return -EINVAL;
 112     }
 113     return virtio_load(VIRTIO_DEVICE(opaque), f, version_id);
 114 }
 115
 116 static int virtio_rng_load_device(VirtIODevice *vdev, QEMUFile *f,
 117                                   int version_id)
 118 {
 119     /* We may have an element ready but couldn't process it due to a quota
 120      * limit.  Make sure to try again after live migration when the quota may
 121      * have been reset.
 122      */
 123     virtio_rng_process(VIRTIO_RNG(vdev));
 124
 125     return 0;
 126 }
 127
 128 static void check_rate_limit(void *opaque)
 129 {
 130     VirtIORNG *vrng = opaque;
 131
 132     vrng->quota_remaining = vrng->conf.max_bytes;
 133     virtio_rng_process(vrng);
 134     timer_mod(vrng->rate_limit_timer,
 135                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 136 }
 137
 138 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 139 {
 140     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 141     VirtIORNG *vrng = VIRTIO_RNG(dev);
 142     Error *local_err = NULL;
 143
 144     if (!vrng->conf.period_ms > 0) {
 145         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "period",
 146                   "a positive number");
 147         return;
 148     }
 149
 150     if (vrng->conf.rng == NULL) {
 151         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 152
 153         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 154                                 &local_err);
 155         if (local_err) {
 156             error_propagate(errp, local_err);
 157             object_unref(OBJECT(vrng->conf.default_backend));
 158             return;
 159         }
 160
 161         object_property_add_child(OBJECT(dev),
 162                                   "default-backend",
 163                                   OBJECT(vrng->conf.default_backend),
 164                                   NULL);
 165
 166         /* The child property took a reference, we can safely drop ours now */
 167         object_unref(OBJECT(vrng->conf.default_backend));
 168
 169         object_property_set_link(OBJECT(dev),
 170                                  OBJECT(vrng->conf.default_backend),
 171                                  "rng", NULL);
 172     }
 173
 174     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 175
 176     vrng->rng = vrng->conf.rng;
 177     if (vrng->rng == NULL) {
 178         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object");
 179         return;
 180     }
 181
 182     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 183
 184     assert(vrng->conf.max_bytes <= INT64_MAX);
 185     vrng->quota_remaining = vrng->conf.max_bytes;
 186
 187     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 188                                                check_rate_limit, vrng);
 189
 190     timer_mod(vrng->rate_limit_timer,
 191                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 192
 193     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 194                     virtio_rng_load, vrng);
 195 }
 196
 197 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 198 {
 199     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 200     VirtIORNG *vrng = VIRTIO_RNG(dev);
 201
 202     timer_del(vrng->rate_limit_timer);
 203     timer_free(vrng->rate_limit_timer);
 204     unregister_savevm(dev, "virtio-rng", vrng);
 205     virtio_cleanup(vdev);
 206 }
 207
 208 static Property virtio_rng_properties[] = {
 209     DEFINE_VIRTIO_RNG_PROPERTIES(VirtIORNG, conf),
 210     DEFINE_PROP_END_OF_LIST(),
 211 };
 212
 213 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 214 {
 215     DeviceClass *dc = DEVICE_CLASS(klass);
 216     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 217
 218     dc->props = virtio_rng_properties;
 219     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 220     vdc->realize = virtio_rng_device_realize;
 221     vdc->unrealize = virtio_rng_device_unrealize;
 222     vdc->get_features = get_features;
 223     vdc->load = virtio_rng_load_device;
 224 }
 225
 226 static void virtio_rng_initfn(Object *obj)
 227 {
 228     VirtIORNG *vrng = VIRTIO_RNG(obj);
 229
 230     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 231                              (Object **)&vrng->conf.rng,
 232                              qdev_prop_allow_set_link_before_realize,
 233                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 234 }
 235
 236 static const TypeInfo virtio_rng_info = {
 237     .name = TYPE_VIRTIO_RNG,
 238     .parent = TYPE_VIRTIO_DEVICE,
 239     .instance_size = sizeof(VirtIORNG),
 240     .instance_init = virtio_rng_initfn,
 241     .class_init = virtio_rng_class_init,
 242 };
 243
 244 static void virtio_register_types(void)
 245 {
 246     type_register_static(&virtio_rng_info);
 247 }
 248
 249 type_init(virtio_register_types)