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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/iov.h"
#include "hw/qdev.h"
#include "qapi/qmp/qerror.h"
#include "hw/virtio.h"
#include "hw/virtio-rng.h"
#include "qemu/rng.h"
typedef struct VirtIORNG {
VirtIODevice vdev;
DeviceState *qdev;
/* Only one vq - guest puts buffer(s) on it when it needs entropy */
VirtQueue *vq;
VirtIORNGConf *conf;
RngBackend *rng;
/* We purposefully don't migrate this state. The quota will reset on the
* destination as a result. Rate limiting is host state, not guest state.
*/
QEMUTimer *rate_limit_timer;
int64_t quota_remaining;
} VirtIORNG;
static bool is_guest_ready(VirtIORNG *vrng)
{
if (virtio_queue_ready(vrng->vq)
&& (vrng->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) {
return true;
}
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;
VirtQueueElement elem;
size_t len;
int offset;
if (!is_guest_ready(vrng)) {
return;
}
vrng->quota_remaining -= size;
offset = 0;
while (offset < size) {
if (!virtqueue_pop(vrng->vq, &elem)) {
break;
}
len = iov_from_buf(elem.in_sg, elem.in_num,
0, buf + offset, size - offset);
offset += len;
virtqueue_push(vrng->vq, &elem, len);
}
virtio_notify(&vrng->vdev, vrng->vq);
}
static void virtio_rng_process(VirtIORNG *vrng)
{
size_t size;
unsigned quota;
if (!is_guest_ready(vrng)) {
return;
}
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);
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 = DO_UPCAST(VirtIORNG, vdev, vdev);
virtio_rng_process(vrng);
}
static uint32_t get_features(VirtIODevice *vdev, uint32_t f)
{
return f;
}
static void virtio_rng_save(QEMUFile *f, void *opaque)
{
VirtIORNG *vrng = opaque;
virtio_save(&vrng->vdev, f);
}
static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
{
VirtIORNG *vrng = opaque;
if (version_id != 1) {
return -EINVAL;
}
virtio_load(&vrng->vdev, f);
/* We may have an element ready but couldn't process it due to a quota
* limit. Make sure to try again after live migration when the quota may
* have been reset.
*/
virtio_rng_process(vrng);
return 0;
}
static void check_rate_limit(void *opaque)
{
VirtIORNG *s = opaque;
s->quota_remaining = s->conf->max_bytes;
virtio_rng_process(s);
qemu_mod_timer(s->rate_limit_timer,
qemu_get_clock_ms(vm_clock) + s->conf->period_ms);
}
VirtIODevice *virtio_rng_init(DeviceState *dev, VirtIORNGConf *conf)
{
VirtIORNG *vrng;
VirtIODevice *vdev;
Error *local_err = NULL;
vdev = virtio_common_init("virtio-rng", VIRTIO_ID_RNG, 0,
sizeof(VirtIORNG));
vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
vrng->rng = conf->rng;
if (vrng->rng == NULL) {
qerror_report(QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object");
return NULL;
}
rng_backend_open(vrng->rng, &local_err);
if (local_err) {
qerror_report_err(local_err);
error_free(local_err);
return NULL;
}
vrng->vq = virtio_add_queue(vdev, 8, handle_input);
vrng->vdev.get_features = get_features;
vrng->qdev = dev;
vrng->conf = conf;
assert(vrng->conf->max_bytes <= INT64_MAX);
vrng->quota_remaining = vrng->conf->max_bytes;
vrng->rate_limit_timer = qemu_new_timer_ms(vm_clock,
check_rate_limit, vrng);
qemu_mod_timer(vrng->rate_limit_timer,
qemu_get_clock_ms(vm_clock) + vrng->conf->period_ms);
register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
virtio_rng_load, vrng);
return vdev;
}
void virtio_rng_exit(VirtIODevice *vdev)
{
VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
qemu_del_timer(vrng->rate_limit_timer);
qemu_free_timer(vrng->rate_limit_timer);
unregister_savevm(vrng->qdev, "virtio-rng", vrng);
virtio_cleanup(vdev);
}
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