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 #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         if (!virtqueue_pop(vrng->vq, &elem)) {
  60             break;
  61         }
  62         len = iov_from_buf(elem.in_sg, elem.in_num,
  63                            0, buf + offset, size - offset);
  64         offset += len;
  65
  66         virtqueue_push(vrng->vq, &elem, len);
  67         trace_virtio_rng_pushed(vrng, len);
  68     }
  69     virtio_notify(vdev, vrng->vq);
  70 }
  71
  72 static void virtio_rng_process(VirtIORNG *vrng)
  73 {
  74     size_t size;
  75     unsigned quota;
  76
  77     if (!is_guest_ready(vrng)) {
  78         return;
  79     }
  80
  81     if (vrng->quota_remaining < 0) {
  82         quota = 0;
  83     } else {
  84         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  85     }
  86     size = get_request_size(vrng->vq, quota);
  87
  88     trace_virtio_rng_request(vrng, size, quota);
  89
  90     size = MIN(vrng->quota_remaining, size);
  91     if (size) {
  92         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
  93     }
  94 }
  95
  96 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
  97 {
  98     VirtIORNG *vrng = VIRTIO_RNG(vdev);
  99     virtio_rng_process(vrng);
 100 }
 101
 102 static uint32_t get_features(VirtIODevice *vdev, uint32_t f)
 103 {
 104     return f;
 105 }
 106
 107 static void virtio_rng_save(QEMUFile *f, void *opaque)
 108 {
 109     VirtIODevice *vdev = opaque;
 110
 111     virtio_save(vdev, f);
 112 }
 113
 114 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 115 {
 116     VirtIORNG *vrng = opaque;
 117     int ret;
 118
 119     if (version_id != 1) {
 120         return -EINVAL;
 121     }
 122     ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id);
 123     if (ret != 0) {
 124         return ret;
 125     }
 126
 127     /* We may have an element ready but couldn't process it due to a quota
 128      * limit.  Make sure to try again after live migration when the quota may
 129      * have been reset.
 130      */
 131     virtio_rng_process(vrng);
 132
 133     return 0;
 134 }
 135
 136 static void check_rate_limit(void *opaque)
 137 {
 138     VirtIORNG *vrng = opaque;
 139
 140     vrng->quota_remaining = vrng->conf.max_bytes;
 141     virtio_rng_process(vrng);
 142     timer_mod(vrng->rate_limit_timer,
 143                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 144 }
 145
 146 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 147 {
 148     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 149     VirtIORNG *vrng = VIRTIO_RNG(dev);
 150     Error *local_err = NULL;
 151
 152     if (vrng->conf.period_ms <= 0) {
 153         error_setg(errp, "'period' parameter expects a positive integer");
 154         return;
 155     }
 156
 157     /* Workaround: Property parsing does not enforce unsigned integers,
 158      * So this is a hack to reject such numbers. */
 159     if (vrng->conf.max_bytes > INT64_MAX) {
 160         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 161                    "and less than 2^63");
 162         return;
 163     }
 164
 165     if (vrng->conf.rng == NULL) {
 166         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 167
 168         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 169                                 &local_err);
 170         if (local_err) {
 171             error_propagate(errp, local_err);
 172             object_unref(OBJECT(vrng->conf.default_backend));
 173             return;
 174         }
 175
 176         object_property_add_child(OBJECT(dev),
 177                                   "default-backend",
 178                                   OBJECT(vrng->conf.default_backend),
 179                                   NULL);
 180
 181         /* The child property took a reference, we can safely drop ours now */
 182         object_unref(OBJECT(vrng->conf.default_backend));
 183
 184         object_property_set_link(OBJECT(dev),
 185                                  OBJECT(vrng->conf.default_backend),
 186                                  "rng", NULL);
 187     }
 188
 189     vrng->rng = vrng->conf.rng;
 190     if (vrng->rng == NULL) {
 191         error_setg(errp, "'rng' parameter expects a valid object");
 192         return;
 193     }
 194
 195     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 196
 197     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 198     vrng->quota_remaining = vrng->conf.max_bytes;
 199
 200     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 201                                                check_rate_limit, vrng);
 202
 203     timer_mod(vrng->rate_limit_timer,
 204                    qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 205
 206     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 207                     virtio_rng_load, vrng);
 208 }
 209
 210 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 211 {
 212     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 213     VirtIORNG *vrng = VIRTIO_RNG(dev);
 214
 215     timer_del(vrng->rate_limit_timer);
 216     timer_free(vrng->rate_limit_timer);
 217     unregister_savevm(dev, "virtio-rng", vrng);
 218     virtio_cleanup(vdev);
 219 }
 220
 221 static Property virtio_rng_properties[] = {
 222     DEFINE_VIRTIO_RNG_PROPERTIES(VirtIORNG, conf),
 223     DEFINE_PROP_END_OF_LIST(),
 224 };
 225
 226 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 227 {
 228     DeviceClass *dc = DEVICE_CLASS(klass);
 229     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 230
 231     dc->props = virtio_rng_properties;
 232     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 233     vdc->realize = virtio_rng_device_realize;
 234     vdc->unrealize = virtio_rng_device_unrealize;
 235     vdc->get_features = get_features;
 236 }
 237
 238 static void virtio_rng_initfn(Object *obj)
 239 {
 240     VirtIORNG *vrng = VIRTIO_RNG(obj);
 241
 242     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 243                              (Object **)&vrng->conf.rng,
 244                              qdev_prop_allow_set_link_before_realize,
 245                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 246 }
 247
 248 static const TypeInfo virtio_rng_info = {
 249     .name = TYPE_VIRTIO_RNG,
 250     .parent = TYPE_VIRTIO_DEVICE,
 251     .instance_size = sizeof(VirtIORNG),
 252     .instance_init = virtio_rng_initfn,
 253     .class_init = virtio_rng_class_init,
 254 };
 255
 256 static void virtio_register_types(void)
 257 {
 258     type_register_static(&virtio_rng_info);
 259 }
 260
 261 type_init(virtio_register_types)