/* * 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 "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 int in, out; virtqueue_get_avail_bytes(vq, &in, &out); 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; if (!is_guest_ready(vrng)) { return; } size = get_request_size(vrng->vq); 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); }