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
  19 static bool is_guest_ready(VirtIORNG *vrng)
  20 {
  21     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  22     if (virtio_queue_ready(vrng->vq)
  23         && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  24         return true;
  25     }
  26     return false;
  27 }
  28
  29 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  30 {
  31     unsigned int in, out;
  32
  33     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  34     return in;
  35 }
  36
  37 static void virtio_rng_process(VirtIORNG *vrng);
  38
  39 /* Send data from a char device over to the guest */
  40 static void chr_read(void *opaque, const void *buf, size_t size)
  41 {
  42     VirtIORNG *vrng = opaque;
  43     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  44     VirtQueueElement elem;
  45     size_t len;
  46     int offset;
  47
  48     if (!is_guest_ready(vrng)) {
  49         return;
  50     }
  51
  52     vrng->quota_remaining -= size;
  53
  54     offset = 0;
  55     while (offset < size) {
  56         if (!virtqueue_pop(vrng->vq, &elem)) {
  57             break;
  58         }
  59         len = iov_from_buf(elem.in_sg, elem.in_num,
  60                            0, buf + offset, size - offset);
  61         offset += len;
  62
  63         virtqueue_push(vrng->vq, &elem, len);
  64     }
  65     virtio_notify(vdev, vrng->vq);
  66 }
  67
  68 static void virtio_rng_process(VirtIORNG *vrng)
  69 {
  70     size_t size;
  71     unsigned quota;
  72
  73     if (!is_guest_ready(vrng)) {
  74         return;
  75     }
  76
  77     if (vrng->quota_remaining < 0) {
  78         quota = 0;
  79     } else {
  80         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  81     }
  82     size = get_request_size(vrng->vq, quota);
  83     size = MIN(vrng->quota_remaining, size);
  84     if (size) {
  85         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
  86     }
  87 }
  88
  89 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
  90 {
  91     VirtIORNG *vrng = VIRTIO_RNG(vdev);
  92     virtio_rng_process(vrng);
  93 }
  94
  95 static uint32_t get_features(VirtIODevice *vdev, uint32_t f)
  96 {
  97     return f;
  98 }
  99
 100 static void virtio_rng_save(QEMUFile *f, void *opaque)
 101 {
 102     VirtIODevice *vdev = opaque;
 103
 104     virtio_save(vdev, f);
 105 }
 106
 107 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 108 {
 109     VirtIORNG *vrng = opaque;
 110     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
 111
 112     if (version_id != 1) {
 113         return -EINVAL;
 114     }
 115     virtio_load(vdev, f);
 116
 117     /* We may have an element ready but couldn't process it due to a quota
 118      * limit.  Make sure to try again after live migration when the quota may
 119      * have been reset.
 120      */
 121     virtio_rng_process(vrng);
 122
 123     return 0;
 124 }
 125
 126 static void check_rate_limit(void *opaque)
 127 {
 128     VirtIORNG *vrng = opaque;
 129
 130     vrng->quota_remaining = vrng->conf.max_bytes;
 131     virtio_rng_process(vrng);
 132     timer_mod(vrng->rate_limit_timer,
 133                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 134 }
 135
 136 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 137 {
 138     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 139     VirtIORNG *vrng = VIRTIO_RNG(dev);
 140     Error *local_err = NULL;
 141
 142     if (!vrng->conf.period_ms > 0) {
 143         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "period",
 144                   "a positive number");
 145         return;
 146     }
 147
 148     if (vrng->conf.rng == NULL) {
 149         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 150
 151         object_property_add_child(OBJECT(dev),
 152                                   "default-backend",
 153                                   OBJECT(vrng->conf.default_backend),
 154                                   NULL);
 155
 156         object_property_set_link(OBJECT(dev),
 157                                  OBJECT(vrng->conf.default_backend),
 158                                  "rng", NULL);
 159     }
 160
 161     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 162
 163     vrng->rng = vrng->conf.rng;
 164     if (vrng->rng == NULL) {
 165         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object");
 166         return;
 167     }
 168
 169     rng_backend_open(vrng->rng, &local_err);
 170     if (local_err) {
 171         error_propagate(errp, local_err);
 172         return;
 173     }
 174
 175     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 176
 177     assert(vrng->conf.max_bytes <= INT64_MAX);
 178     vrng->quota_remaining = vrng->conf.max_bytes;
 179
 180     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 181                                                check_rate_limit, vrng);
 182
 183     timer_mod(vrng->rate_limit_timer,
 184                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 185
 186     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 187                     virtio_rng_load, vrng);
 188 }
 189
 190 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 191 {
 192     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 193     VirtIORNG *vrng = VIRTIO_RNG(dev);
 194
 195     timer_del(vrng->rate_limit_timer);
 196     timer_free(vrng->rate_limit_timer);
 197     unregister_savevm(dev, "virtio-rng", vrng);
 198     virtio_cleanup(vdev);
 199 }
 200
 201 static Property virtio_rng_properties[] = {
 202     DEFINE_VIRTIO_RNG_PROPERTIES(VirtIORNG, conf),
 203     DEFINE_PROP_END_OF_LIST(),
 204 };
 205
 206 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 207 {
 208     DeviceClass *dc = DEVICE_CLASS(klass);
 209     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 210
 211     dc->props = virtio_rng_properties;
 212     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 213     vdc->realize = virtio_rng_device_realize;
 214     vdc->unrealize = virtio_rng_device_unrealize;
 215     vdc->get_features = get_features;
 216 }
 217
 218 static void virtio_rng_initfn(Object *obj)
 219 {
 220     VirtIORNG *vrng = VIRTIO_RNG(obj);
 221
 222     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 223                              (Object **)&vrng->conf.rng, NULL);
 224 }
 225
 226 static const TypeInfo virtio_rng_info = {
 227     .name = TYPE_VIRTIO_RNG,
 228     .parent = TYPE_VIRTIO_DEVICE,
 229     .instance_size = sizeof(VirtIORNG),
 230     .instance_init = virtio_rng_initfn,
 231     .class_init = virtio_rng_class_init,
 232 };
 233
 234 static void virtio_register_types(void)
 235 {
 236     type_register_static(&virtio_rng_info);
 237 }
 238
 239 type_init(virtio_register_types)