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 #define VMSTATE_VIRTIO_DEVICE_USE_NEW
  13
  14 #include "qemu/osdep.h"
  15 #include "qapi/error.h"
  16 #include "qemu/iov.h"
  17 #include "hw/qdev.h"
  18 #include "hw/virtio/virtio.h"
  19 #include "hw/virtio/virtio-rng.h"
  20 #include "sysemu/rng.h"
  21 #include "qom/object_interfaces.h"
  22 #include "trace.h"
  23
  24 static bool is_guest_ready(VirtIORNG *vrng)
  25 {
  26     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  27     if (virtio_queue_ready(vrng->vq)
  28         && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  29         return true;
  30     }
  31     trace_virtio_rng_guest_not_ready(vrng);
  32     return false;
  33 }
  34
  35 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  36 {
  37     unsigned int in, out;
  38
  39     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  40     return in;
  41 }
  42
  43 static void virtio_rng_process(VirtIORNG *vrng);
  44
  45 /* Send data from a char device over to the guest */
  46 static void chr_read(void *opaque, const void *buf, size_t size)
  47 {
  48     VirtIORNG *vrng = opaque;
  49     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  50     VirtQueueElement *elem;
  51     size_t len;
  52     int offset;
  53
  54     if (!is_guest_ready(vrng)) {
  55         return;
  56     }
  57
  58     vrng->quota_remaining -= size;
  59
  60     offset = 0;
  61     while (offset < size) {
  62         elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
  63         if (!elem) {
  64             break;
  65         }
  66         len = iov_from_buf(elem->in_sg, elem->in_num,
  67                            0, buf + offset, size - offset);
  68         offset += len;
  69
  70         virtqueue_push(vrng->vq, elem, len);
  71         trace_virtio_rng_pushed(vrng, len);
  72         g_free(elem);
  73     }
  74     virtio_notify(vdev, vrng->vq);
  75
  76     if (!virtio_queue_empty(vrng->vq)) {
  77         /* If we didn't drain the queue, call virtio_rng_process
  78          * to take care of asking for more data as appropriate.
  79          */
  80         virtio_rng_process(vrng);
  81     }
  82 }
  83
  84 static void virtio_rng_process(VirtIORNG *vrng)
  85 {
  86     size_t size;
  87     unsigned quota;
  88
  89     if (!is_guest_ready(vrng)) {
  90         return;
  91     }
  92
  93     if (vrng->activate_timer) {
  94         timer_mod(vrng->rate_limit_timer,
  95                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
  96         vrng->activate_timer = false;
  97     }
  98
  99     if (vrng->quota_remaining < 0) {
 100         quota = 0;
 101     } else {
 102         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
 103     }
 104     size = get_request_size(vrng->vq, quota);
 105
 106     trace_virtio_rng_request(vrng, size, quota);
 107
 108     size = MIN(vrng->quota_remaining, size);
 109     if (size) {
 110         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
 111     }
 112 }
 113
 114 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 115 {
 116     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 117     virtio_rng_process(vrng);
 118 }
 119
 120 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 121 {
 122     return f;
 123 }
 124
 125 static int virtio_rng_post_load(void *opaque, int version_id)
 126 {
 127     VirtIORNG *vrng = opaque;
 128
 129     /* We may have an element ready but couldn't process it due to a quota
 130      * limit.  Make sure to try again after live migration when the quota may
 131      * have been reset.
 132      */
 133     virtio_rng_process(vrng);
 134
 135     return 0;
 136 }
 137
 138 static void check_rate_limit(void *opaque)
 139 {
 140     VirtIORNG *vrng = opaque;
 141
 142     vrng->quota_remaining = vrng->conf.max_bytes;
 143     virtio_rng_process(vrng);
 144     vrng->activate_timer = true;
 145 }
 146
 147 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 148 {
 149     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 150     VirtIORNG *vrng = VIRTIO_RNG(dev);
 151     Error *local_err = NULL;
 152
 153     if (vrng->conf.period_ms <= 0) {
 154         error_setg(errp, "'period' parameter expects a positive integer");
 155         return;
 156     }
 157
 158     /* Workaround: Property parsing does not enforce unsigned integers,
 159      * So this is a hack to reject such numbers. */
 160     if (vrng->conf.max_bytes > INT64_MAX) {
 161         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 162                    "and less than 2^63");
 163         return;
 164     }
 165
 166     if (vrng->conf.rng == NULL) {
 167         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 168
 169         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 170                                 &local_err);
 171         if (local_err) {
 172             error_propagate(errp, local_err);
 173             object_unref(OBJECT(vrng->conf.default_backend));
 174             return;
 175         }
 176
 177         object_property_add_child(OBJECT(dev),
 178                                   "default-backend",
 179                                   OBJECT(vrng->conf.default_backend),
 180                                   NULL);
 181
 182         /* The child property took a reference, we can safely drop ours now */
 183         object_unref(OBJECT(vrng->conf.default_backend));
 184
 185         object_property_set_link(OBJECT(dev),
 186                                  OBJECT(vrng->conf.default_backend),
 187                                  "rng", NULL);
 188     }
 189
 190     vrng->rng = vrng->conf.rng;
 191     if (vrng->rng == NULL) {
 192         error_setg(errp, "'rng' parameter expects a valid object");
 193         return;
 194     }
 195
 196     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 197
 198     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 199     vrng->quota_remaining = vrng->conf.max_bytes;
 200     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 201                                                check_rate_limit, vrng);
 202     vrng->activate_timer = true;
 203 }
 204
 205 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 206 {
 207     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 208     VirtIORNG *vrng = VIRTIO_RNG(dev);
 209
 210     timer_del(vrng->rate_limit_timer);
 211     timer_free(vrng->rate_limit_timer);
 212     virtio_cleanup(vdev);
 213 }
 214
 215 static const VMStateDescription vmstate_virtio_rng = {
 216     .name = "virtio-rng",
 217     .minimum_version_id = 1,
 218     .version_id = 1,
 219     .fields = (VMStateField[]) {
 220         VMSTATE_VIRTIO_DEVICE,
 221         VMSTATE_END_OF_LIST()
 222     },
 223     .post_load =  virtio_rng_post_load,
 224 };
 225
 226 static Property virtio_rng_properties[] = {
 227     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 228      * you have an entropy source capable of generating more entropy than this
 229      * and you can pass it through via virtio-rng, then hats off to you.  Until
 230      * then, this is unlimited for all practical purposes.
 231      */
 232     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 233     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 234     DEFINE_PROP_END_OF_LIST(),
 235 };
 236
 237 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 238 {
 239     DeviceClass *dc = DEVICE_CLASS(klass);
 240     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 241
 242     dc->props = virtio_rng_properties;
 243     dc->vmsd = &vmstate_virtio_rng;
 244     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 245     vdc->realize = virtio_rng_device_realize;
 246     vdc->unrealize = virtio_rng_device_unrealize;
 247     vdc->get_features = get_features;
 248 }
 249
 250 static void virtio_rng_initfn(Object *obj)
 251 {
 252     VirtIORNG *vrng = VIRTIO_RNG(obj);
 253
 254     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 255                              (Object **)&vrng->conf.rng,
 256                              qdev_prop_allow_set_link_before_realize,
 257                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 258 }
 259
 260 static const TypeInfo virtio_rng_info = {
 261     .name = TYPE_VIRTIO_RNG,
 262     .parent = TYPE_VIRTIO_DEVICE,
 263     .instance_size = sizeof(VirtIORNG),
 264     .instance_init = virtio_rng_initfn,
 265     .class_init = virtio_rng_class_init,
 266 };
 267
 268 static void virtio_register_types(void)
 269 {
 270     type_register_static(&virtio_rng_info);
 271 }
 272
 273 type_init(virtio_register_types)