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 "qdev.h" 14 #include "qapi/qmp/qerror.h" 15 #include "virtio.h" 16 #include "virtio-rng.h" 17 #include "qemu/rng.h" 18 19 typedef struct VirtIORNG { 20 VirtIODevice vdev; 21 22 DeviceState *qdev; 23 24 /* Only one vq - guest puts buffer(s) on it when it needs entropy */ 25 VirtQueue *vq; 26 27 VirtIORNGConf *conf; 28 29 RngBackend *rng; 30 31 /* We purposefully don't migrate this state. The quota will reset on the 32 * destination as a result. Rate limiting is host state, not guest state. 33 */ 34 QEMUTimer *rate_limit_timer; 35 int64_t quota_remaining; 36 } VirtIORNG; 37 38 static bool is_guest_ready(VirtIORNG *vrng) 39 { 40 if (virtio_queue_ready(vrng->vq) 41 && (vrng->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) { 42 return true; 43 } 44 return false; 45 } 46 47 static size_t get_request_size(VirtQueue *vq, unsigned quota) 48 { 49 unsigned int in, out; 50 51 virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); 52 return in; 53 } 54 55 static void virtio_rng_process(VirtIORNG *vrng); 56 57 /* Send data from a char device over to the guest */ 58 static void chr_read(void *opaque, const void *buf, size_t size) 59 { 60 VirtIORNG *vrng = opaque; 61 VirtQueueElement elem; 62 size_t len; 63 int offset; 64 65 if (!is_guest_ready(vrng)) { 66 return; 67 } 68 69 vrng->quota_remaining -= size; 70 71 offset = 0; 72 while (offset < size) { 73 if (!virtqueue_pop(vrng->vq, &elem)) { 74 break; 75 } 76 len = iov_from_buf(elem.in_sg, elem.in_num, 77 0, buf + offset, size - offset); 78 offset += len; 79 80 virtqueue_push(vrng->vq, &elem, len); 81 } 82 virtio_notify(&vrng->vdev, vrng->vq); 83 } 84 85 static void virtio_rng_process(VirtIORNG *vrng) 86 { 87 size_t size; 88 unsigned quota; 89 90 if (!is_guest_ready(vrng)) { 91 return; 92 } 93 94 if (vrng->quota_remaining < 0) { 95 quota = 0; 96 } else { 97 quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); 98 } 99 size = get_request_size(vrng->vq, quota); 100 size = MIN(vrng->quota_remaining, size); 101 if (size) { 102 rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); 103 } 104 } 105 106 static void handle_input(VirtIODevice *vdev, VirtQueue *vq) 107 { 108 VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev); 109 virtio_rng_process(vrng); 110 } 111 112 static uint32_t get_features(VirtIODevice *vdev, uint32_t f) 113 { 114 return f; 115 } 116 117 static void virtio_rng_save(QEMUFile *f, void *opaque) 118 { 119 VirtIORNG *vrng = opaque; 120 121 virtio_save(&vrng->vdev, f); 122 } 123 124 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id) 125 { 126 VirtIORNG *vrng = opaque; 127 128 if (version_id != 1) { 129 return -EINVAL; 130 } 131 virtio_load(&vrng->vdev, f); 132 133 /* We may have an element ready but couldn't process it due to a quota 134 * limit. Make sure to try again after live migration when the quota may 135 * have been reset. 136 */ 137 virtio_rng_process(vrng); 138 139 return 0; 140 } 141 142 static void check_rate_limit(void *opaque) 143 { 144 VirtIORNG *s = opaque; 145 146 s->quota_remaining = s->conf->max_bytes; 147 virtio_rng_process(s); 148 qemu_mod_timer(s->rate_limit_timer, 149 qemu_get_clock_ms(vm_clock) + s->conf->period_ms); 150 } 151 152 153 VirtIODevice *virtio_rng_init(DeviceState *dev, VirtIORNGConf *conf) 154 { 155 VirtIORNG *vrng; 156 VirtIODevice *vdev; 157 Error *local_err = NULL; 158 159 vdev = virtio_common_init("virtio-rng", VIRTIO_ID_RNG, 0, 160 sizeof(VirtIORNG)); 161 162 vrng = DO_UPCAST(VirtIORNG, vdev, vdev); 163 164 vrng->rng = conf->rng; 165 if (vrng->rng == NULL) { 166 qerror_report(QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object"); 167 return NULL; 168 } 169 170 rng_backend_open(vrng->rng, &local_err); 171 if (local_err) { 172 qerror_report_err(local_err); 173 error_free(local_err); 174 return NULL; 175 } 176 177 vrng->vq = virtio_add_queue(vdev, 8, handle_input); 178 vrng->vdev.get_features = get_features; 179 180 vrng->qdev = dev; 181 vrng->conf = conf; 182 183 assert(vrng->conf->max_bytes <= INT64_MAX); 184 vrng->quota_remaining = vrng->conf->max_bytes; 185 186 vrng->rate_limit_timer = qemu_new_timer_ms(vm_clock, 187 check_rate_limit, vrng); 188 189 qemu_mod_timer(vrng->rate_limit_timer, 190 qemu_get_clock_ms(vm_clock) + vrng->conf->period_ms); 191 192 register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save, 193 virtio_rng_load, vrng); 194 195 return vdev; 196 } 197 198 void virtio_rng_exit(VirtIODevice *vdev) 199 { 200 VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev); 201 202 qemu_del_timer(vrng->rate_limit_timer); 203 qemu_free_timer(vrng->rate_limit_timer); 204 unregister_savevm(vrng->qdev, "virtio-rng", vrng); 205 virtio_cleanup(vdev); 206 } 207