aboutsummaryrefslogtreecommitdiff
path: root/hw/virtio/virtio-rng.c
blob: a8df41b11b5de7ad433d791462494e86af72ae85 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
/*
 * A virtio device implementing a hardware random number generator.
 *
 * Copyright 2012 Red Hat, Inc.
 * Copyright 2012 Amit Shah <amit.shah@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or
 * (at your option) any later version.  See the COPYING file in the
 * top-level directory.
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/iov.h"
#include "qemu/module.h"
#include "qemu/timer.h"
#include "hw/virtio/virtio.h"
#include "hw/qdev-properties.h"
#include "hw/virtio/virtio-rng.h"
#include "sysemu/rng.h"
#include "sysemu/runstate.h"
#include "qom/object_interfaces.h"
#include "trace.h"

static bool is_guest_ready(VirtIORNG *vrng)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
    if (virtio_queue_ready(vrng->vq)
        && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
        return true;
    }
    trace_virtio_rng_guest_not_ready(vrng);
    return false;
}

static size_t get_request_size(VirtQueue *vq, unsigned quota)
{
    unsigned int in, out;

    virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
    return in;
}

static void virtio_rng_process(VirtIORNG *vrng);

/* Send data from a char device over to the guest */
static void chr_read(void *opaque, const void *buf, size_t size)
{
    VirtIORNG *vrng = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
    VirtQueueElement *elem;
    size_t len;
    int offset;

    if (!is_guest_ready(vrng)) {
        return;
    }

    /* we can't modify the virtqueue until
     * our state is fully synced
     */

    if (!runstate_check(RUN_STATE_RUNNING)) {
        trace_virtio_rng_cpu_is_stopped(vrng, size);
        return;
    }

    vrng->quota_remaining -= size;

    offset = 0;
    while (offset < size) {
        elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
        if (!elem) {
            break;
        }
        trace_virtio_rng_popped(vrng);
        len = iov_from_buf(elem->in_sg, elem->in_num,
                           0, buf + offset, size - offset);
        offset += len;

        virtqueue_push(vrng->vq, elem, len);
        trace_virtio_rng_pushed(vrng, len);
        g_free(elem);
    }
    virtio_notify(vdev, vrng->vq);

    if (!virtio_queue_empty(vrng->vq)) {
        /* If we didn't drain the queue, call virtio_rng_process
         * to take care of asking for more data as appropriate.
         */
        virtio_rng_process(vrng);
    }
}

static void virtio_rng_process(VirtIORNG *vrng)
{
    size_t size;
    unsigned quota;

    if (!is_guest_ready(vrng)) {
        return;
    }

    if (vrng->activate_timer) {
        timer_mod(vrng->rate_limit_timer,
                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
        vrng->activate_timer = false;
    }

    if (vrng->quota_remaining < 0) {
        quota = 0;
    } else {
        quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
    }
    size = get_request_size(vrng->vq, quota);

    trace_virtio_rng_request(vrng, size, quota);

    size = MIN(vrng->quota_remaining, size);
    if (size) {
        rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
    }
}

static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIORNG *vrng = VIRTIO_RNG(vdev);
    virtio_rng_process(vrng);
}

static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
{
    return f;
}

static void virtio_rng_vm_state_change(void *opaque, int running,
                                       RunState state)
{
    VirtIORNG *vrng = opaque;

    trace_virtio_rng_vm_state_change(vrng, running, state);

    /* We may have an element ready but couldn't process it due to a quota
     * limit or because CPU was stopped.  Make sure to try again when the
     * CPU restart.
     */

    if (running && is_guest_ready(vrng)) {
        virtio_rng_process(vrng);
    }
}

static void check_rate_limit(void *opaque)
{
    VirtIORNG *vrng = opaque;

    vrng->quota_remaining = vrng->conf.max_bytes;
    virtio_rng_process(vrng);
    vrng->activate_timer = true;
}

static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status)
{
    VirtIORNG *vrng = VIRTIO_RNG(vdev);

    if (!vdev->vm_running) {
        return;
    }
    vdev->status = status;

    /* Something changed, try to process buffers */
    virtio_rng_process(vrng);
}

static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtIORNG *vrng = VIRTIO_RNG(dev);
    Error *local_err = NULL;

    if (vrng->conf.period_ms <= 0) {
        error_setg(errp, "'period' parameter expects a positive integer");
        return;
    }

    /* Workaround: Property parsing does not enforce unsigned integers,
     * So this is a hack to reject such numbers. */
    if (vrng->conf.max_bytes > INT64_MAX) {
        error_setg(errp, "'max-bytes' parameter must be non-negative, "
                   "and less than 2^63");
        return;
    }

    if (vrng->conf.rng == NULL) {
        Object *default_backend = object_new(TYPE_RNG_BUILTIN);

        user_creatable_complete(USER_CREATABLE(default_backend),
                                &local_err);
        if (local_err) {
            error_propagate(errp, local_err);
            object_unref(default_backend);
            return;
        }

        object_property_add_child(OBJECT(dev), "default-backend",
                                  default_backend);

        /* The child property took a reference, we can safely drop ours now */
        object_unref(default_backend);

        object_property_set_link(OBJECT(dev), default_backend,
                                 "rng", &error_abort);
    }

    vrng->rng = vrng->conf.rng;
    if (vrng->rng == NULL) {
        error_setg(errp, "'rng' parameter expects a valid object");
        return;
    }

    virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);

    vrng->vq = virtio_add_queue(vdev, 8, handle_input);
    vrng->quota_remaining = vrng->conf.max_bytes;
    vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
                                               check_rate_limit, vrng);
    vrng->activate_timer = true;

    vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
                                                     vrng);
}

static void virtio_rng_device_unrealize(DeviceState *dev)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtIORNG *vrng = VIRTIO_RNG(dev);

    qemu_del_vm_change_state_handler(vrng->vmstate);
    timer_del(vrng->rate_limit_timer);
    timer_free(vrng->rate_limit_timer);
    virtio_del_queue(vdev, 0);
    virtio_cleanup(vdev);
}

static const VMStateDescription vmstate_virtio_rng = {
    .name = "virtio-rng",
    .minimum_version_id = 1,
    .version_id = 1,
    .fields = (VMStateField[]) {
        VMSTATE_VIRTIO_DEVICE,
        VMSTATE_END_OF_LIST()
    },
};

static Property virtio_rng_properties[] = {
    /* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s.  If
     * you have an entropy source capable of generating more entropy than this
     * and you can pass it through via virtio-rng, then hats off to you.  Until
     * then, this is unlimited for all practical purposes.
     */
    DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
    DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
    DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *),
    DEFINE_PROP_END_OF_LIST(),
};

static void virtio_rng_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);
    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);

    device_class_set_props(dc, virtio_rng_properties);
    dc->vmsd = &vmstate_virtio_rng;
    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
    vdc->realize = virtio_rng_device_realize;
    vdc->unrealize = virtio_rng_device_unrealize;
    vdc->get_features = get_features;
    vdc->set_status = virtio_rng_set_status;
}

static const TypeInfo virtio_rng_info = {
    .name = TYPE_VIRTIO_RNG,
    .parent = TYPE_VIRTIO_DEVICE,
    .instance_size = sizeof(VirtIORNG),
    .class_init = virtio_rng_class_init,
};

static void virtio_register_types(void)
{
    type_register_static(&virtio_rng_info);
}

type_init(virtio_register_types)