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 "qapi/error.h"
  14 #include "qemu/iov.h"
  15 #include "hw/qdev.h"
  16 #include "hw/virtio/virtio.h"
  17 #include "hw/virtio/virtio-rng.h"
  18 #include "sysemu/rng.h"
  19 #include "qom/object_interfaces.h"
  20 #include "trace.h"
  21
  22 static bool is_guest_ready(VirtIORNG *vrng)
  23 {
  24     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  25     if (virtio_queue_ready(vrng->vq)
  26         && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  27         return true;
  28     }
  29     trace_virtio_rng_guest_not_ready(vrng);
  30     return false;
  31 }
  32
  33 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  34 {
  35     unsigned int in, out;
  36
  37     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  38     return in;
  39 }
  40
  41 static void virtio_rng_process(VirtIORNG *vrng);
  42
  43 /* Send data from a char device over to the guest */
  44 static void chr_read(void *opaque, const void *buf, size_t size)
  45 {
  46     VirtIORNG *vrng = opaque;
  47     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  48     VirtQueueElement *elem;
  49     size_t len;
  50     int offset;
  51
  52     if (!is_guest_ready(vrng)) {
  53         return;
  54     }
  55
  56     /* we can't modify the virtqueue until
  57      * our state is fully synced
  58      */
  59
  60     if (!runstate_check(RUN_STATE_RUNNING)) {
  61         trace_virtio_rng_cpu_is_stopped(vrng, size);
  62         return;
  63     }
  64
  65     vrng->quota_remaining -= size;
  66
  67     offset = 0;
  68     while (offset < size) {
  69         elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
  70         if (!elem) {
  71             break;
  72         }
  73         trace_virtio_rng_popped(vrng);
  74         len = iov_from_buf(elem->in_sg, elem->in_num,
  75                            0, buf + offset, size - offset);
  76         offset += len;
  77
  78         virtqueue_push(vrng->vq, elem, len);
  79         trace_virtio_rng_pushed(vrng, len);
  80         g_free(elem);
  81     }
  82     virtio_notify(vdev, vrng->vq);
  83
  84     if (!virtio_queue_empty(vrng->vq)) {
  85         /* If we didn't drain the queue, call virtio_rng_process
  86          * to take care of asking for more data as appropriate.
  87          */
  88         virtio_rng_process(vrng);
  89     }
  90 }
  91
  92 static void virtio_rng_process(VirtIORNG *vrng)
  93 {
  94     size_t size;
  95     unsigned quota;
  96
  97     if (!is_guest_ready(vrng)) {
  98         return;
  99     }
 100
 101     if (vrng->activate_timer) {
 102         timer_mod(vrng->rate_limit_timer,
 103                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 104         vrng->activate_timer = false;
 105     }
 106
 107     if (vrng->quota_remaining < 0) {
 108         quota = 0;
 109     } else {
 110         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
 111     }
 112     size = get_request_size(vrng->vq, quota);
 113
 114     trace_virtio_rng_request(vrng, size, quota);
 115
 116     size = MIN(vrng->quota_remaining, size);
 117     if (size) {
 118         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
 119     }
 120 }
 121
 122 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 123 {
 124     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 125     virtio_rng_process(vrng);
 126 }
 127
 128 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 129 {
 130     return f;
 131 }
 132
 133 static void virtio_rng_vm_state_change(void *opaque, int running,
 134                                        RunState state)
 135 {
 136     VirtIORNG *vrng = opaque;
 137
 138     trace_virtio_rng_vm_state_change(vrng, running, state);
 139
 140     /* We may have an element ready but couldn't process it due to a quota
 141      * limit or because CPU was stopped.  Make sure to try again when the
 142      * CPU restart.
 143      */
 144
 145     if (running && is_guest_ready(vrng)) {
 146         virtio_rng_process(vrng);
 147     }
 148 }
 149
 150 static void check_rate_limit(void *opaque)
 151 {
 152     VirtIORNG *vrng = opaque;
 153
 154     vrng->quota_remaining = vrng->conf.max_bytes;
 155     virtio_rng_process(vrng);
 156     vrng->activate_timer = true;
 157 }
 158
 159 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 160 {
 161     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 162     VirtIORNG *vrng = VIRTIO_RNG(dev);
 163     Error *local_err = NULL;
 164
 165     if (vrng->conf.period_ms <= 0) {
 166         error_setg(errp, "'period' parameter expects a positive integer");
 167         return;
 168     }
 169
 170     /* Workaround: Property parsing does not enforce unsigned integers,
 171      * So this is a hack to reject such numbers. */
 172     if (vrng->conf.max_bytes > INT64_MAX) {
 173         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 174                    "and less than 2^63");
 175         return;
 176     }
 177
 178     if (vrng->conf.rng == NULL) {
 179         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 180
 181         user_creatable_complete(OBJECT(vrng->conf.default_backend),
 182                                 &local_err);
 183         if (local_err) {
 184             error_propagate(errp, local_err);
 185             object_unref(OBJECT(vrng->conf.default_backend));
 186             return;
 187         }
 188
 189         object_property_add_child(OBJECT(dev),
 190                                   "default-backend",
 191                                   OBJECT(vrng->conf.default_backend),
 192                                   NULL);
 193
 194         /* The child property took a reference, we can safely drop ours now */
 195         object_unref(OBJECT(vrng->conf.default_backend));
 196
 197         object_property_set_link(OBJECT(dev),
 198                                  OBJECT(vrng->conf.default_backend),
 199                                  "rng", NULL);
 200     }
 201
 202     vrng->rng = vrng->conf.rng;
 203     if (vrng->rng == NULL) {
 204         error_setg(errp, "'rng' parameter expects a valid object");
 205         return;
 206     }
 207
 208     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 209
 210     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 211     vrng->quota_remaining = vrng->conf.max_bytes;
 212     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 213                                                check_rate_limit, vrng);
 214     vrng->activate_timer = true;
 215
 216     vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
 217                                                      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     qemu_del_vm_change_state_handler(vrng->vmstate);
 226     timer_del(vrng->rate_limit_timer);
 227     timer_free(vrng->rate_limit_timer);
 228     virtio_cleanup(vdev);
 229 }
 230
 231 static const VMStateDescription vmstate_virtio_rng = {
 232     .name = "virtio-rng",
 233     .minimum_version_id = 1,
 234     .version_id = 1,
 235     .fields = (VMStateField[]) {
 236         VMSTATE_VIRTIO_DEVICE,
 237         VMSTATE_END_OF_LIST()
 238     },
 239 };
 240
 241 static Property virtio_rng_properties[] = {
 242     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 243      * you have an entropy source capable of generating more entropy than this
 244      * and you can pass it through via virtio-rng, then hats off to you.  Until
 245      * then, this is unlimited for all practical purposes.
 246      */
 247     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 248     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 249     DEFINE_PROP_END_OF_LIST(),
 250 };
 251
 252 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 253 {
 254     DeviceClass *dc = DEVICE_CLASS(klass);
 255     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 256
 257     dc->props = virtio_rng_properties;
 258     dc->vmsd = &vmstate_virtio_rng;
 259     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 260     vdc->realize = virtio_rng_device_realize;
 261     vdc->unrealize = virtio_rng_device_unrealize;
 262     vdc->get_features = get_features;
 263 }
 264
 265 static void virtio_rng_initfn(Object *obj)
 266 {
 267     VirtIORNG *vrng = VIRTIO_RNG(obj);
 268
 269     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
 270                              (Object **)&vrng->conf.rng,
 271                              qdev_prop_allow_set_link_before_realize,
 272                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 273 }
 274
 275 static const TypeInfo virtio_rng_info = {
 276     .name = TYPE_VIRTIO_RNG,
 277     .parent = TYPE_VIRTIO_DEVICE,
 278     .instance_size = sizeof(VirtIORNG),
 279     .instance_init = virtio_rng_initfn,
 280     .class_init = virtio_rng_class_init,
 281 };
 282
 283 static void virtio_register_types(void)
 284 {
 285     type_register_static(&virtio_rng_info);
 286 }
 287
 288 type_init(virtio_register_types)