diff options
Diffstat (limited to 'hw/virtio-rng.c')
| -rw-r--r-- | hw/virtio-rng.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/hw/virtio-rng.c b/hw/virtio-rng.c new file mode 100644 index 0000000000..e063127df6 --- /dev/null +++ b/hw/virtio-rng.c @@ -0,0 +1,205 @@ +/* + * 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 "qdev.h" +#include "virtio.h" +#include "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); +} |