290 lines
7.9 KiB
C
290 lines
7.9 KiB
C
/*
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* A virtio device implementing a hardware random number generator.
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*
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* Copyright 2012 Red Hat, Inc.
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* Copyright 2012 Amit Shah <amit.shah@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* (at your option) any later version. See the COPYING file in the
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* top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "qemu/iov.h"
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#include "qemu/module.h"
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#include "qemu/timer.h"
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#include "hw/virtio/virtio.h"
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#include "hw/qdev-properties.h"
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#include "hw/virtio/virtio-rng.h"
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#include "sysemu/rng.h"
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#include "sysemu/runstate.h"
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#include "qom/object_interfaces.h"
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#include "trace.h"
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static bool is_guest_ready(VirtIORNG *vrng)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
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if (virtio_queue_ready(vrng->vq)
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&& (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
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return true;
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}
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trace_virtio_rng_guest_not_ready(vrng);
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return false;
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}
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static size_t get_request_size(VirtQueue *vq, unsigned quota)
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{
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unsigned int in, out;
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virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
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return in;
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}
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static void virtio_rng_process(VirtIORNG *vrng);
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/* Send data from a char device over to the guest */
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static void chr_read(void *opaque, const void *buf, size_t size)
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{
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VirtIORNG *vrng = opaque;
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VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
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VirtQueueElement *elem;
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size_t len;
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int offset;
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if (!is_guest_ready(vrng)) {
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return;
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}
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/* we can't modify the virtqueue until
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* our state is fully synced
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*/
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if (!runstate_check(RUN_STATE_RUNNING)) {
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trace_virtio_rng_cpu_is_stopped(vrng, size);
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return;
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}
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vrng->quota_remaining -= size;
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offset = 0;
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while (offset < size) {
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elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
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if (!elem) {
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break;
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}
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trace_virtio_rng_popped(vrng);
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len = iov_from_buf(elem->in_sg, elem->in_num,
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0, buf + offset, size - offset);
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offset += len;
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virtqueue_push(vrng->vq, elem, len);
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trace_virtio_rng_pushed(vrng, len);
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g_free(elem);
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}
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virtio_notify(vdev, vrng->vq);
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if (!virtio_queue_empty(vrng->vq)) {
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/* If we didn't drain the queue, call virtio_rng_process
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* to take care of asking for more data as appropriate.
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*/
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virtio_rng_process(vrng);
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}
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}
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static void virtio_rng_process(VirtIORNG *vrng)
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{
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size_t size;
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unsigned quota;
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if (!is_guest_ready(vrng)) {
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return;
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}
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if (vrng->activate_timer) {
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timer_mod(vrng->rate_limit_timer,
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qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
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vrng->activate_timer = false;
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}
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if (vrng->quota_remaining < 0) {
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quota = 0;
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} else {
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quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
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}
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size = get_request_size(vrng->vq, quota);
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trace_virtio_rng_request(vrng, size, quota);
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size = MIN(vrng->quota_remaining, size);
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if (size) {
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rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
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}
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}
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static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
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{
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VirtIORNG *vrng = VIRTIO_RNG(vdev);
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virtio_rng_process(vrng);
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}
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static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
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{
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return f;
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}
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static void virtio_rng_vm_state_change(void *opaque, bool running,
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RunState state)
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{
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VirtIORNG *vrng = opaque;
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trace_virtio_rng_vm_state_change(vrng, running, state);
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/* We may have an element ready but couldn't process it due to a quota
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* limit or because CPU was stopped. Make sure to try again when the
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* CPU restart.
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*/
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if (running && is_guest_ready(vrng)) {
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virtio_rng_process(vrng);
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}
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}
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static void check_rate_limit(void *opaque)
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{
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VirtIORNG *vrng = opaque;
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vrng->quota_remaining = vrng->conf.max_bytes;
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virtio_rng_process(vrng);
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vrng->activate_timer = true;
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}
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static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status)
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{
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VirtIORNG *vrng = VIRTIO_RNG(vdev);
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if (!vdev->vm_running) {
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return;
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}
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vdev->status = status;
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/* Something changed, try to process buffers */
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virtio_rng_process(vrng);
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}
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static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(dev);
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VirtIORNG *vrng = VIRTIO_RNG(dev);
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if (vrng->conf.period_ms <= 0) {
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error_setg(errp, "'period' parameter expects a positive integer");
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return;
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}
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/* Workaround: Property parsing does not enforce unsigned integers,
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* So this is a hack to reject such numbers. */
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if (vrng->conf.max_bytes > INT64_MAX) {
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error_setg(errp, "'max-bytes' parameter must be non-negative, "
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"and less than 2^63");
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return;
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}
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if (vrng->conf.rng == NULL) {
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Object *default_backend = object_new(TYPE_RNG_BUILTIN);
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if (!user_creatable_complete(USER_CREATABLE(default_backend),
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errp)) {
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object_unref(default_backend);
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return;
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}
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object_property_add_child(OBJECT(dev), "default-backend",
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default_backend);
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/* The child property took a reference, we can safely drop ours now */
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object_unref(default_backend);
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object_property_set_link(OBJECT(dev), "rng", default_backend,
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&error_abort);
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}
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vrng->rng = vrng->conf.rng;
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if (vrng->rng == NULL) {
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error_setg(errp, "'rng' parameter expects a valid object");
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return;
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}
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virtio_init(vdev, VIRTIO_ID_RNG, 0);
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vrng->vq = virtio_add_queue(vdev, 8, handle_input);
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vrng->quota_remaining = vrng->conf.max_bytes;
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vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
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check_rate_limit, vrng);
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vrng->activate_timer = true;
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vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
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vrng);
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}
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static void virtio_rng_device_unrealize(DeviceState *dev)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(dev);
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VirtIORNG *vrng = VIRTIO_RNG(dev);
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qemu_del_vm_change_state_handler(vrng->vmstate);
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timer_free(vrng->rate_limit_timer);
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virtio_del_queue(vdev, 0);
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virtio_cleanup(vdev);
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}
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static const VMStateDescription vmstate_virtio_rng = {
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.name = "virtio-rng",
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.minimum_version_id = 1,
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.version_id = 1,
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.fields = (VMStateField[]) {
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VMSTATE_VIRTIO_DEVICE,
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VMSTATE_END_OF_LIST()
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},
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};
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static Property virtio_rng_properties[] = {
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/* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s. If
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* you have an entropy source capable of generating more entropy than this
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* and you can pass it through via virtio-rng, then hats off to you. Until
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* then, this is unlimited for all practical purposes.
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*/
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DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
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DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
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DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *),
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DEFINE_PROP_END_OF_LIST(),
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};
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static void virtio_rng_class_init(ObjectClass *klass, void *data)
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{
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DeviceClass *dc = DEVICE_CLASS(klass);
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VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
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device_class_set_props(dc, virtio_rng_properties);
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dc->vmsd = &vmstate_virtio_rng;
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set_bit(DEVICE_CATEGORY_MISC, dc->categories);
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vdc->realize = virtio_rng_device_realize;
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vdc->unrealize = virtio_rng_device_unrealize;
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vdc->get_features = get_features;
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vdc->set_status = virtio_rng_set_status;
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}
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static const TypeInfo virtio_rng_info = {
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.name = TYPE_VIRTIO_RNG,
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.parent = TYPE_VIRTIO_DEVICE,
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.instance_size = sizeof(VirtIORNG),
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.class_init = virtio_rng_class_init,
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};
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static void virtio_register_types(void)
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{
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type_register_static(&virtio_rng_info);
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}
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type_init(virtio_register_types)
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