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 "qemu/module.h"
  16 #include "qemu/timer.h"
  17 #include "hw/virtio/virtio.h"
  18 #include "hw/qdev-properties.h"
  19 #include "hw/virtio/virtio-rng.h"
  20 #include "sysemu/rng.h"
  21 #include "sysemu/runstate.h"
  22 #include "qom/object_interfaces.h"
  23 #include "trace.h"
  24
  25 static bool is_guest_ready(VirtIORNG *vrng)
  26 {
  27     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  28     if (virtio_queue_ready(vrng->vq)
  29         && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  30         return true;
  31     }
  32     trace_virtio_rng_guest_not_ready(vrng);
  33     return false;
  34 }
  35
  36 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  37 {
  38     unsigned int in, out;
  39
  40     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  41     return in;
  42 }
  43
  44 static void virtio_rng_process(VirtIORNG *vrng);
  45
  46 /* Send data from a char device over to the guest */
  47 static void chr_read(void *opaque, const void *buf, size_t size)
  48 {
  49     VirtIORNG *vrng = opaque;
  50     VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
  51     VirtQueueElement *elem;
  52     size_t len;
  53     int offset;
  54
  55     if (!is_guest_ready(vrng)) {
  56         return;
  57     }
  58
  59     /* we can't modify the virtqueue until
  60      * our state is fully synced
  61      */
  62
  63     if (!runstate_check(RUN_STATE_RUNNING)) {
  64         trace_virtio_rng_cpu_is_stopped(vrng, size);
  65         return;
  66     }
  67
  68     vrng->quota_remaining -= size;
  69
  70     offset = 0;
  71     while (offset < size) {
  72         elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
  73         if (!elem) {
  74             break;
  75         }
  76         trace_virtio_rng_popped(vrng);
  77         len = iov_from_buf(elem->in_sg, elem->in_num,
  78                            0, buf + offset, size - offset);
  79         offset += len;
  80
  81         virtqueue_push(vrng->vq, elem, len);
  82         trace_virtio_rng_pushed(vrng, len);
  83         g_free(elem);
  84     }
  85     virtio_notify(vdev, vrng->vq);
  86
  87     if (!virtio_queue_empty(vrng->vq)) {
  88         /* If we didn't drain the queue, call virtio_rng_process
  89          * to take care of asking for more data as appropriate.
  90          */
  91         virtio_rng_process(vrng);
  92     }
  93 }
  94
  95 static void virtio_rng_process(VirtIORNG *vrng)
  96 {
  97     size_t size;
  98     unsigned quota;
  99
 100     if (!is_guest_ready(vrng)) {
 101         return;
 102     }
 103
 104     if (vrng->activate_timer) {
 105         timer_mod(vrng->rate_limit_timer,
 106                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
 107         vrng->activate_timer = false;
 108     }
 109
 110     if (vrng->quota_remaining < 0) {
 111         quota = 0;
 112     } else {
 113         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
 114     }
 115     size = get_request_size(vrng->vq, quota);
 116
 117     trace_virtio_rng_request(vrng, size, quota);
 118
 119     size = MIN(vrng->quota_remaining, size);
 120     if (size) {
 121         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
 122     }
 123 }
 124
 125 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 126 {
 127     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 128     virtio_rng_process(vrng);
 129 }
 130
 131 static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 132 {
 133     return f;
 134 }
 135
 136 static void virtio_rng_vm_state_change(void *opaque, int running,
 137                                        RunState state)
 138 {
 139     VirtIORNG *vrng = opaque;
 140
 141     trace_virtio_rng_vm_state_change(vrng, running, state);
 142
 143     /* We may have an element ready but couldn't process it due to a quota
 144      * limit or because CPU was stopped.  Make sure to try again when the
 145      * CPU restart.
 146      */
 147
 148     if (running && is_guest_ready(vrng)) {
 149         virtio_rng_process(vrng);
 150     }
 151 }
 152
 153 static void check_rate_limit(void *opaque)
 154 {
 155     VirtIORNG *vrng = opaque;
 156
 157     vrng->quota_remaining = vrng->conf.max_bytes;
 158     virtio_rng_process(vrng);
 159     vrng->activate_timer = true;
 160 }
 161
 162 static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status)
 163 {
 164     VirtIORNG *vrng = VIRTIO_RNG(vdev);
 165
 166     if (!vdev->vm_running) {
 167         return;
 168     }
 169     vdev->status = status;
 170
 171     /* Something changed, try to process buffers */
 172     virtio_rng_process(vrng);
 173 }
 174
 175 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 176 {
 177     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 178     VirtIORNG *vrng = VIRTIO_RNG(dev);
 179     Error *local_err = NULL;
 180
 181     if (vrng->conf.period_ms <= 0) {
 182         error_setg(errp, "'period' parameter expects a positive integer");
 183         return;
 184     }
 185
 186     /* Workaround: Property parsing does not enforce unsigned integers,
 187      * So this is a hack to reject such numbers. */
 188     if (vrng->conf.max_bytes > INT64_MAX) {
 189         error_setg(errp, "'max-bytes' parameter must be non-negative, "
 190                    "and less than 2^63");
 191         return;
 192     }
 193
 194     if (vrng->conf.rng == NULL) {
 195         Object *default_backend = object_new(TYPE_RNG_BUILTIN);
 196
 197         if (!user_creatable_complete(USER_CREATABLE(default_backend),
 198                                      &local_err)) {
 199             error_propagate(errp, local_err);
 200             object_unref(default_backend);
 201             return;
 202         }
 203
 204         object_property_add_child(OBJECT(dev), "default-backend",
 205                                   default_backend);
 206
 207         /* The child property took a reference, we can safely drop ours now */
 208         object_unref(default_backend);
 209
 210         object_property_set_link(OBJECT(dev), "rng", default_backend,
 211                                  &error_abort);
 212     }
 213
 214     vrng->rng = vrng->conf.rng;
 215     if (vrng->rng == NULL) {
 216         error_setg(errp, "'rng' parameter expects a valid object");
 217         return;
 218     }
 219
 220     virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 221
 222     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 223     vrng->quota_remaining = vrng->conf.max_bytes;
 224     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 225                                                check_rate_limit, vrng);
 226     vrng->activate_timer = true;
 227
 228     vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
 229                                                      vrng);
 230 }
 231
 232 static void virtio_rng_device_unrealize(DeviceState *dev)
 233 {
 234     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 235     VirtIORNG *vrng = VIRTIO_RNG(dev);
 236
 237     qemu_del_vm_change_state_handler(vrng->vmstate);
 238     timer_del(vrng->rate_limit_timer);
 239     timer_free(vrng->rate_limit_timer);
 240     virtio_del_queue(vdev, 0);
 241     virtio_cleanup(vdev);
 242 }
 243
 244 static const VMStateDescription vmstate_virtio_rng = {
 245     .name = "virtio-rng",
 246     .minimum_version_id = 1,
 247     .version_id = 1,
 248     .fields = (VMStateField[]) {
 249         VMSTATE_VIRTIO_DEVICE,
 250         VMSTATE_END_OF_LIST()
 251     },
 252 };
 253
 254 static Property virtio_rng_properties[] = {
 255     /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 256      * you have an entropy source capable of generating more entropy than this
 257      * and you can pass it through via virtio-rng, then hats off to you.  Until
 258      * then, this is unlimited for all practical purposes.
 259      */
 260     DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 261     DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 262     DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *),
 263     DEFINE_PROP_END_OF_LIST(),
 264 };
 265
 266 static void virtio_rng_class_init(ObjectClass *klass, void *data)
 267 {
 268     DeviceClass *dc = DEVICE_CLASS(klass);
 269     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 270
 271     device_class_set_props(dc, virtio_rng_properties);
 272     dc->vmsd = &vmstate_virtio_rng;
 273     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 274     vdc->realize = virtio_rng_device_realize;
 275     vdc->unrealize = virtio_rng_device_unrealize;
 276     vdc->get_features = get_features;
 277     vdc->set_status = virtio_rng_set_status;
 278 }
 279
 280 static const TypeInfo virtio_rng_info = {
 281     .name = TYPE_VIRTIO_RNG,
 282     .parent = TYPE_VIRTIO_DEVICE,
 283     .instance_size = sizeof(VirtIORNG),
 284     .class_init = virtio_rng_class_init,
 285 };
 286
 287 static void virtio_register_types(void)
 288 {
 289     type_register_static(&virtio_rng_info);
 290 }
 291
 292 type_init(virtio_register_types)