qemu/hw/virtio/virtio-rng.c
<<
>>
Prefs
   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
  25static 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
  36static 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
  44static void virtio_rng_process(VirtIORNG *vrng);
  45
  46/* Send data from a char device over to the guest */
  47static 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
  95static 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
 125static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 126{
 127    VirtIORNG *vrng = VIRTIO_RNG(vdev);
 128    virtio_rng_process(vrng);
 129}
 130
 131static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
 132{
 133    return f;
 134}
 135
 136static 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
 153static 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
 162static 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
 175static 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        user_creatable_complete(USER_CREATABLE(default_backend),
 198                                &local_err);
 199        if (local_err) {
 200            error_propagate(errp, local_err);
 201            object_unref(default_backend);
 202            return;
 203        }
 204
 205        object_property_add_child(OBJECT(dev), "default-backend",
 206                                  default_backend, &error_abort);
 207
 208        /* The child property took a reference, we can safely drop ours now */
 209        object_unref(default_backend);
 210
 211        object_property_set_link(OBJECT(dev), default_backend,
 212                                 "rng", &error_abort);
 213    }
 214
 215    vrng->rng = vrng->conf.rng;
 216    if (vrng->rng == NULL) {
 217        error_setg(errp, "'rng' parameter expects a valid object");
 218        return;
 219    }
 220
 221    virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
 222
 223    vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 224    vrng->quota_remaining = vrng->conf.max_bytes;
 225    vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
 226                                               check_rate_limit, vrng);
 227    vrng->activate_timer = true;
 228
 229    vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
 230                                                     vrng);
 231}
 232
 233static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
 234{
 235    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
 236    VirtIORNG *vrng = VIRTIO_RNG(dev);
 237
 238    qemu_del_vm_change_state_handler(vrng->vmstate);
 239    timer_del(vrng->rate_limit_timer);
 240    timer_free(vrng->rate_limit_timer);
 241    virtio_del_queue(vdev, 0);
 242    virtio_cleanup(vdev);
 243}
 244
 245static const VMStateDescription vmstate_virtio_rng = {
 246    .name = "virtio-rng",
 247    .minimum_version_id = 1,
 248    .version_id = 1,
 249    .fields = (VMStateField[]) {
 250        VMSTATE_VIRTIO_DEVICE,
 251        VMSTATE_END_OF_LIST()
 252    },
 253};
 254
 255static Property virtio_rng_properties[] = {
 256    /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
 257     * you have an entropy source capable of generating more entropy than this
 258     * and you can pass it through via virtio-rng, then hats off to you.  Until
 259     * then, this is unlimited for all practical purposes.
 260     */
 261    DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
 262    DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
 263    DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *),
 264    DEFINE_PROP_END_OF_LIST(),
 265};
 266
 267static void virtio_rng_class_init(ObjectClass *klass, void *data)
 268{
 269    DeviceClass *dc = DEVICE_CLASS(klass);
 270    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
 271
 272    device_class_set_props(dc, virtio_rng_properties);
 273    dc->vmsd = &vmstate_virtio_rng;
 274    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 275    vdc->realize = virtio_rng_device_realize;
 276    vdc->unrealize = virtio_rng_device_unrealize;
 277    vdc->get_features = get_features;
 278    vdc->set_status = virtio_rng_set_status;
 279}
 280
 281static const TypeInfo virtio_rng_info = {
 282    .name = TYPE_VIRTIO_RNG,
 283    .parent = TYPE_VIRTIO_DEVICE,
 284    .instance_size = sizeof(VirtIORNG),
 285    .class_init = virtio_rng_class_init,
 286};
 287
 288static void virtio_register_types(void)
 289{
 290    type_register_static(&virtio_rng_info);
 291}
 292
 293type_init(virtio_register_types)
 294