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/*
* 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, bool 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);
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);
if (!user_creatable_complete(USER_CREATABLE(default_backend),
errp)) {
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), "rng", default_backend,
&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_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)