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/osdep.h"
  13 #include "qemu/iov.h"
  14 #include "hw/qdev.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 #include "trace.h"
  20
  21 static bool is_guest_ready(VirtIORNG *vrng)
  22 {
  23     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  24     if (virtio_queue_ready(vrng->vq)
  25         && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  26         return true;
  27     }
  28     trace_virtio_rng_guest_not_ready(vrng);
  29     return false;
  30 }
  31
  32 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  33 {
  34     unsigned int in, out;
  35
  36     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  37     return in;
  38 }
  39
  40 static void virtio_rng_process(VirtIORNG *vrng);
  41
  42 /* Send data from a char device over to the guest */
  43 static void chr_read(void *opaque, const void *buf, size_t size)
  44 {
  45     VirtIORNG *vrng = opaque;
  46     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  47     VirtQueueElement *elem;
  48     size_t len;
  49     int offset;
  50
  51     if (!is_guest_ready(vrng)) {
  52         return;
  53     }
  54
  55     vrng->quota_remaining -= size;
  56
  57     offset = 0;
  58     while (offset < size) {
  59         elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
  60         if (!elem) {
  61             break;
  62         }
  63         len = iov_from_buf(elem->in_sg, elem->in_num,
  64                            0, buf + offset, size - offset);
  65         offset += len;
  66
  67         virtqueue_push(vrng->vq, elem, len);
  68         trace_virtio_rng_pushed(vrng, len);
  69         g_free(elem);
  70     }
  71     virtio_notify(vdev, vrng->vq);
  72
  73     if (!virtio_queue_empty(vrng->vq)) {
  74         /* If we didn't drain the queue, call virtio_rng_process
  75          * to take care of asking for more data as appropriate.
  76          */
  77         virtio_rng_process(vrng);
  78     }
  79 }
  80
  81 static void virtio_rng_process(VirtIORNG *vrng)
  82 {
  83     size_t size;
  84     unsigned quota;
  85
  86     if (!is_guest_ready(vrng)) {
  87         return;
  88     }
  89
  90     if (vrng->activate_timer) {
  91         timer_mod(vrng->rate_limit_timer,
  92                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
  93         vrng->activate_timer = false;
  94     }
  95
  96     if (vrng->quota_remaining < 0) {
  97         quota = 0;
  98     } else {
  99         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
 100     }
 101     size = get_request_size(vrng->vq, quota);
 102
 103     trace_virtio_rng_request(vrng, size, quota);
 104
 105     size = MIN(vrng->quota_remaining, size);
 106     if (size) {
 107         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
 108     }
 109 }
 110
 111 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 112 {
 113     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 114     virtio_rng_process(vrng);
 115 }
 116
 117 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 118 {
 119     return f;
 120 }
 121
 122 static void virtio_rng_save(QEMUFile *f, void *opaque)
 123 {
 124     VirtIODevice *vdev = opaque;
 125
 126     virtio_save(vdev, f);
 127 }
 128
 129 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 130 {
 131     VirtIORNG *vrng = opaque;
 132     int ret;
 133
 134     if (version_id != 1) {
 135         return -EINVAL;
 136     }
 137     ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id);
 138     if (ret != 0) {
 139         return ret;
 140     }
 141
 142     /* We may have an element ready but couldn't process it due to a quota
 143      * limit.  Make sure to try again after live migration when the quota may
 144      * have been reset.
 145      */
 146     virtio_rng_process(vrng);
 147
 148     return 0;
 149 }
 150
 151 static void check_rate_limit(void *opaque)
 152 {
 153     VirtIORNG *vrng = opaque;
 154
 155     vrng->quota_remaining = vrng->conf.max_bytes;
 156     virtio_rng_process(vrng);
 157     vrng->activate_timer = true;
 158 }
 159
 160 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 161 {
 162     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 163     VirtIORNG *vrng = VIRTIO_RNG(dev);
 164     Error *local_err = NULL;
 165
 166     if (vrng->conf.period_ms <= 0) {
 167         error_setg(errp, "'period' parameter expects a positive integer");
 168         return;
 169     }
 170
 171     /* Workaround: Property parsing does not enforce unsigned integers,
 172      * So this is a hack to reject such numbers. */
 173     if (vrng->conf.max_bytes > INT64_MAX) {
 174         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 175                    "and less than 2^63");
 176         return;
 177     }
 178
 179     if (vrng->conf.rng == NULL) {
 180         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 181
 182         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 183                                 &local_err);
 184         if (local_err) {
 185             error_propagate(errp, local_err);
 186             object_unref(OBJECT(vrng->conf.default_backend));
 187             return;
 188         }
 189
 190         object_property_add_child(OBJECT(dev),
 191                                   "default-backend",
 192                                   OBJECT(vrng->conf.default_backend),
 193                                   NULL);
 194
 195         /* The child property took a reference, we can safely drop ours now */
 196         object_unref(OBJECT(vrng->conf.default_backend));
 197
 198         object_property_set_link(OBJECT(dev),
 199                                  OBJECT(vrng->conf.default_backend),
 200                                  "rng", NULL);
 201     }
 202
 203     vrng->rng = vrng->conf.rng;
 204     if (vrng->rng == NULL) {
 205         error_setg(errp, "'rng' parameter expects a valid object");
 206         return;
 207     }
 208
 209     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 210
 211     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 212     vrng->quota_remaining = vrng->conf.max_bytes;
 213     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 214                                                check_rate_limit, vrng);
 215     vrng->activate_timer = true;
 216     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 217                     virtio_rng_load, vrng);
 218 }
 219
 220 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 221 {
 222     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 223     VirtIORNG *vrng = VIRTIO_RNG(dev);
 224
 225     timer_del(vrng->rate_limit_timer);
 226     timer_free(vrng->rate_limit_timer);
 227     unregister_savevm(dev, "virtio-rng", vrng);
 228     virtio_cleanup(vdev);
 229 }
 230
 231 static Property virtio_rng_properties[] = {
 232     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 233      * you have an entropy source capable of generating more entropy than this
 234      * and you can pass it through via virtio-rng, then hats off to you.  Until
 235      * then, this is unlimited for all practical purposes.
 236      */
 237     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 238     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 239     DEFINE_PROP_END_OF_LIST(),
 240 };
 241
 242 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 243 {
 244     DeviceClass *dc = DEVICE_CLASS(klass);
 245     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 246
 247     dc->props = virtio_rng_properties;
 248     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 249     vdc->realize = virtio_rng_device_realize;
 250     vdc->unrealize = virtio_rng_device_unrealize;
 251     vdc->get_features = get_features;
 252 }
 253
 254 static void virtio_rng_initfn(Object *obj)
 255 {
 256     VirtIORNG *vrng = VIRTIO_RNG(obj);
 257
 258     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 259                              (Object **)&vrng->conf.rng,
 260                              qdev_prop_allow_set_link_before_realize,
 261                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 262 }
 263
 264 static const TypeInfo virtio_rng_info = {
 265     .name = TYPE_VIRTIO_RNG,
 266     .parent = TYPE_VIRTIO_DEVICE,
 267     .instance_size = sizeof(VirtIORNG),
 268     .instance_init = virtio_rng_initfn,
 269     .class_init = virtio_rng_class_init,
 270 };
 271
 272 static void virtio_register_types(void)
 273 {
 274     type_register_static(&virtio_rng_info);
 275 }
 276
 277 type_init(virtio_register_types)