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-rw-r--r--hw/virtio/virtio-rng.c289
1 files changed, 289 insertions, 0 deletions
diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
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+++ b/hw/virtio/virtio-rng.c
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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_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)
generated by cgit v1.2.3 (git 2.39.1) at 2025-07-28 07:42:44 +0000