hw/virtio/virtio-rng.c - qemu - Git at Google

 /*
  * 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 "system/rng.h"
 #include "system/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 == 0 ||
         vrng->conf.max_bytes > INT64_MAX) {
         error_setg(errp, "'max-bytes' parameter must be positive, "
                    "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 = (const VMStateField[]) {
         VMSTATE_VIRTIO_DEVICE,
         VMSTATE_END_OF_LIST()
     },
 };

 static const 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 *),
 };

 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)
	/*
	* 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 "system/rng.h"
	#include "system/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 == 0 \|\|
	vrng->conf.max_bytes > INT64_MAX) {
	error_setg(errp, "'max-bytes' parameter must be positive, "
	"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 = (const VMStateField[]) {
	VMSTATE_VIRTIO_DEVICE,
	VMSTATE_END_OF_LIST()
	},
	};

	static const 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 *),
	};

	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)