1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Randomness driver for virtio
4 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
8 #include <linux/hw_random.h>
9 #include <linux/scatterlist.h>
10 #include <linux/spinlock.h>
11 #include <linux/virtio.h>
12 #include <linux/virtio_rng.h>
13 #include <linux/module.h>
14 #include <linux/slab.h>
16 static DEFINE_IDA(rng_index_ida);
23 bool hwrng_register_done;
26 struct completion have_data;
27 unsigned int data_avail;
28 unsigned int data_idx;
29 /* minimal size returned by rng_buffer_size() */
30 #if SMP_CACHE_BYTES < 32
33 u8 data[SMP_CACHE_BYTES];
37 static void random_recv_done(struct virtqueue *vq)
39 struct virtrng_info *vi = vq->vdev->priv;
41 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
42 if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
47 complete(&vi->have_data);
50 static void request_entropy(struct virtrng_info *vi)
52 struct scatterlist sg;
54 reinit_completion(&vi->have_data);
58 sg_init_one(&sg, vi->data, sizeof(vi->data));
60 /* There should always be room for one buffer. */
61 virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
63 virtqueue_kick(vi->vq);
66 static unsigned int copy_data(struct virtrng_info *vi, void *buf,
69 size = min_t(unsigned int, size, vi->data_avail);
70 memcpy(buf, vi->data + vi->data_idx, size);
72 vi->data_avail -= size;
73 if (vi->data_avail == 0)
78 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
81 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
85 if (vi->hwrng_removed)
90 /* copy available data */
92 chunk = copy_data(vi, buf, size);
100 /* We have already copied available entropy,
101 * so either size is 0 or data_avail is 0
104 /* data_avail is 0 but a request is pending */
105 ret = wait_for_completion_killable(&vi->have_data);
108 /* if vi->data_avail is 0, we have been interrupted
109 * by a cleanup, but buffer stays in the queue
111 if (vi->data_avail == 0)
114 chunk = copy_data(vi, buf + read, size);
122 static void virtio_cleanup(struct hwrng *rng)
124 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
126 complete(&vi->have_data);
129 static int probe_common(struct virtio_device *vdev)
132 struct virtrng_info *vi = NULL;
134 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
138 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
143 sprintf(vi->name, "virtio_rng.%d", index);
144 init_completion(&vi->have_data);
146 vi->hwrng = (struct hwrng) {
148 .cleanup = virtio_cleanup,
149 .priv = (unsigned long)vi,
155 /* We expect a single virtqueue. */
156 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
157 if (IS_ERR(vi->vq)) {
158 err = PTR_ERR(vi->vq);
162 virtio_device_ready(vdev);
164 /* we always have a pending entropy request */
170 ida_simple_remove(&rng_index_ida, index);
176 static void remove_common(struct virtio_device *vdev)
178 struct virtrng_info *vi = vdev->priv;
180 vi->hwrng_removed = true;
183 complete(&vi->have_data);
184 if (vi->hwrng_register_done)
185 hwrng_unregister(&vi->hwrng);
186 virtio_reset_device(vdev);
187 vdev->config->del_vqs(vdev);
188 ida_simple_remove(&rng_index_ida, vi->index);
192 static int virtrng_probe(struct virtio_device *vdev)
194 return probe_common(vdev);
197 static void virtrng_remove(struct virtio_device *vdev)
202 static void virtrng_scan(struct virtio_device *vdev)
204 struct virtrng_info *vi = vdev->priv;
207 err = hwrng_register(&vi->hwrng);
209 vi->hwrng_register_done = true;
212 #ifdef CONFIG_PM_SLEEP
213 static int virtrng_freeze(struct virtio_device *vdev)
219 static int virtrng_restore(struct virtio_device *vdev)
223 err = probe_common(vdev);
225 struct virtrng_info *vi = vdev->priv;
228 * Set hwrng_removed to ensure that virtio_read()
229 * does not block waiting for data before the
230 * registration is complete.
232 vi->hwrng_removed = true;
233 err = hwrng_register(&vi->hwrng);
235 vi->hwrng_register_done = true;
236 vi->hwrng_removed = false;
244 static const struct virtio_device_id id_table[] = {
245 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
249 static struct virtio_driver virtio_rng_driver = {
250 .driver.name = KBUILD_MODNAME,
251 .driver.owner = THIS_MODULE,
252 .id_table = id_table,
253 .probe = virtrng_probe,
254 .remove = virtrng_remove,
255 .scan = virtrng_scan,
256 #ifdef CONFIG_PM_SLEEP
257 .freeze = virtrng_freeze,
258 .restore = virtrng_restore,
262 module_virtio_driver(virtio_rng_driver);
263 MODULE_DEVICE_TABLE(virtio, id_table);
264 MODULE_DESCRIPTION("Virtio random number driver");
265 MODULE_LICENSE("GPL");