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     VirtIORNG *vrng = opaque;
 111     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
 112
 113     if (version_id != 1) {
 114         return -EINVAL;
 115     }
 116     virtio_load(vdev, f);
 117
 118     /* We may have an element ready but couldn't process it due to a quota
 119      * limit.  Make sure to try again after live migration when the quota may
 120      * have been reset.
 121      */
 122     virtio_rng_process(vrng);
 123
 124     return 0;
 125 }
 126
 127 static void check_rate_limit(void *opaque)
 128 {
 129     VirtIORNG *vrng = opaque;
 130
 131     vrng->quota_remaining = vrng->conf.max_bytes;
 132     virtio_rng_process(vrng);
 133     timer_mod(vrng->rate_limit_timer,
 134                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 135 }
 136
 137 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 138 {
 139     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 140     VirtIORNG *vrng = VIRTIO_RNG(dev);
 141     Error *local_err = NULL;
 142
 143     if (!vrng->conf.period_ms > 0) {
 144         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "period",
 145                   "a positive number");
 146         return;
 147     }
 148
 149     if (vrng->conf.rng == NULL) {
 150         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 151
 152         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 153                                 &local_err);
 154         if (local_err) {
 155             error_propagate(errp, local_err);
 156             object_unref(OBJECT(vrng->conf.default_backend));
 157             return;
 158         }
 159
 160         object_property_add_child(OBJECT(dev),
 161                                   "default-backend",
 162                                   OBJECT(vrng->conf.default_backend),
 163                                   NULL);
 164
 165         /* The child property took a reference, we can safely drop ours now */
 166         object_unref(OBJECT(vrng->conf.default_backend));
 167
 168         object_property_set_link(OBJECT(dev),
 169                                  OBJECT(vrng->conf.default_backend),
 170                                  "rng", NULL);
 171     }
 172
 173     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 174
 175     vrng->rng = vrng->conf.rng;
 176     if (vrng->rng == NULL) {
 177         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object");
 178         return;
 179     }
 180
 181     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 182
 183     assert(vrng->conf.max_bytes <= INT64_MAX);
 184     vrng->quota_remaining = vrng->conf.max_bytes;
 185
 186     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 187                                                check_rate_limit, vrng);
 188
 189     timer_mod(vrng->rate_limit_timer,
 190                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 191
 192     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 193                     virtio_rng_load, vrng);
 194 }
 195
 196 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 197 {
 198     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 199     VirtIORNG *vrng = VIRTIO_RNG(dev);
 200
 201     timer_del(vrng->rate_limit_timer);
 202     timer_free(vrng->rate_limit_timer);
 203     unregister_savevm(dev, "virtio-rng", vrng);
 204     virtio_cleanup(vdev);
 205 }
 206
 207 static Property virtio_rng_properties[] = {
 208     DEFINE_VIRTIO_RNG_PROPERTIES(VirtIORNG, conf),
 209     DEFINE_PROP_END_OF_LIST(),
 210 };
 211
 212 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 213 {
 214     DeviceClass *dc = DEVICE_CLASS(klass);
 215     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 216
 217     dc->props = virtio_rng_properties;
 218     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 219     vdc->realize = virtio_rng_device_realize;
 220     vdc->unrealize = virtio_rng_device_unrealize;
 221     vdc->get_features = get_features;
 222 }
 223
 224 static void virtio_rng_initfn(Object *obj)
 225 {
 226     VirtIORNG *vrng = VIRTIO_RNG(obj);
 227
 228     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 229                              (Object **)&vrng->conf.rng,
 230                              qdev_prop_allow_set_link_before_realize,
 231                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 232 }
 233
 234 static const TypeInfo virtio_rng_info = {
 235     .name = TYPE_VIRTIO_RNG,
 236     .parent = TYPE_VIRTIO_DEVICE,
 237     .instance_size = sizeof(VirtIORNG),
 238     .instance_init = virtio_rng_initfn,
 239     .class_init = virtio_rng_class_init,
 240 };
 241
 242 static void virtio_register_types(void)
 243 {
 244     type_register_static(&virtio_rng_info);
 245 }
 246
 247 type_init(virtio_register_types)