hw/virtio-rng.c

   1 /*
   2  * A virtio device implementing a hardware random number generator.
   3  *
   4  * Copyright 2012 Red Hat, Inc.
   5  * Copyright 2012 Amit Shah <amit.shah@redhat.com>
   6  *
   7  * This work is licensed under the terms of the GNU GPL, version 2 or
   8  * (at your option) any later version.  See the COPYING file in the
   9  * top-level directory.
  10  */
  11
  12 #include "qemu/iov.h"
  13 #include "hw/qdev.h"
  14 #include "qapi/qmp/qerror.h"
  15 #include "hw/virtio.h"
  16 #include "hw/virtio-rng.h"
  17 #include "qemu/rng.h"
  18
  19 static bool is_guest_ready(VirtIORNG *vrng)
  20 {
  21     if (virtio_queue_ready(vrng->vq)
  22         && (vrng->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) {
  23         return true;
  24     }
  25     return false;
  26 }
  27
  28 static size_t get_request_size(VirtQueue *vq, unsigned quota)
  29 {
  30     unsigned int in, out;
  31
  32     virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
  33     return in;
  34 }
  35
  36 static void virtio_rng_process(VirtIORNG *vrng);
  37
  38 /* Send data from a char device over to the guest */
  39 static void chr_read(void *opaque, const void *buf, size_t size)
  40 {
  41     VirtIORNG *vrng = opaque;
  42     VirtQueueElement elem;
  43     size_t len;
  44     int offset;
  45
  46     if (!is_guest_ready(vrng)) {
  47         return;
  48     }
  49
  50     vrng->quota_remaining -= size;
  51
  52     offset = 0;
  53     while (offset < size) {
  54         if (!virtqueue_pop(vrng->vq, &elem)) {
  55             break;
  56         }
  57         len = iov_from_buf(elem.in_sg, elem.in_num,
  58                            0, buf + offset, size - offset);
  59         offset += len;
  60
  61         virtqueue_push(vrng->vq, &elem, len);
  62     }
  63     virtio_notify(&vrng->vdev, vrng->vq);
  64 }
  65
  66 static void virtio_rng_process(VirtIORNG *vrng)
  67 {
  68     size_t size;
  69     unsigned quota;
  70
  71     if (!is_guest_ready(vrng)) {
  72         return;
  73     }
  74
  75     if (vrng->quota_remaining < 0) {
  76         quota = 0;
  77     } else {
  78         quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
  79     }
  80     size = get_request_size(vrng->vq, quota);
  81     size = MIN(vrng->quota_remaining, size);
  82     if (size) {
  83         rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
  84     }
  85 }
  86
  87 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
  88 {
  89     VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
  90     virtio_rng_process(vrng);
  91 }
  92
  93 static uint32_t get_features(VirtIODevice *vdev, uint32_t f)
  94 {
  95     return f;
  96 }
  97
  98 static void virtio_rng_save(QEMUFile *f, void *opaque)
  99 {
 100     VirtIORNG *vrng = opaque;
 101
 102     virtio_save(&vrng->vdev, f);
 103 }
 104
 105 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 106 {
 107     VirtIORNG *vrng = opaque;
 108
 109     if (version_id != 1) {
 110         return -EINVAL;
 111     }
 112     virtio_load(&vrng->vdev, f);
 113
 114     /* We may have an element ready but couldn't process it due to a quota
 115      * limit.  Make sure to try again after live migration when the quota may
 116      * have been reset.
 117      */
 118     virtio_rng_process(vrng);
 119
 120     return 0;
 121 }
 122
 123 static void check_rate_limit(void *opaque)
 124 {
 125     VirtIORNG *s = opaque;
 126
 127     s->quota_remaining = s->conf->max_bytes;
 128     virtio_rng_process(s);
 129     qemu_mod_timer(s->rate_limit_timer,
 130                    qemu_get_clock_ms(vm_clock) + s->conf->period_ms);
 131 }
 132
 133
 134 VirtIODevice *virtio_rng_init(DeviceState *dev, VirtIORNGConf *conf)
 135 {
 136     VirtIORNG *vrng;
 137     VirtIODevice *vdev;
 138     Error *local_err = NULL;
 139
 140     vdev = virtio_common_init("virtio-rng", VIRTIO_ID_RNG, 0,
 141                               sizeof(VirtIORNG));
 142
 143     vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
 144
 145     vrng->rng = conf->rng;
 146     if (vrng->rng == NULL) {
 147         qerror_report(QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object");
 148         return NULL;
 149     }
 150
 151     rng_backend_open(vrng->rng, &local_err);
 152     if (local_err) {
 153         qerror_report_err(local_err);
 154         error_free(local_err);
 155         return NULL;
 156     }
 157
 158     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 159     vrng->vdev.get_features = get_features;
 160
 161     vrng->qdev = dev;
 162     vrng->conf = conf;
 163
 164     assert(vrng->conf->max_bytes <= INT64_MAX);
 165     vrng->quota_remaining = vrng->conf->max_bytes;
 166
 167     vrng->rate_limit_timer = qemu_new_timer_ms(vm_clock,
 168                                                check_rate_limit, vrng);
 169
 170     qemu_mod_timer(vrng->rate_limit_timer,
 171                    qemu_get_clock_ms(vm_clock) + vrng->conf->period_ms);
 172
 173     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
 174                     virtio_rng_load, vrng);
 175
 176     return vdev;
 177 }
 178
 179 void virtio_rng_exit(VirtIODevice *vdev)
 180 {
 181     VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
 182
 183     qemu_del_timer(vrng->rate_limit_timer);
 184     qemu_free_timer(vrng->rate_limit_timer);
 185     unregister_savevm(vrng->qdev, "virtio-rng", vrng);
 186     virtio_cleanup(vdev);
 187 }