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>
15 static DEFINE_IDA(rng_index_ida);
20 struct completion have_data;
22 unsigned int data_avail;
25 bool hwrng_register_done;
29 static void random_recv_done(struct virtqueue *vq)
31 struct virtrng_info *vi = vq->vdev->priv;
33 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
34 if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
37 complete(&vi->have_data);
40 /* The host will fill any buffer we give it with sweet, sweet randomness. */
41 static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
43 struct scatterlist sg;
45 sg_init_one(&sg, buf, size);
47 /* There should always be room for one buffer. */
48 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
50 virtqueue_kick(vi->vq);
53 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
56 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
58 if (vi->hwrng_removed)
63 reinit_completion(&vi->have_data);
64 register_buffer(vi, buf, size);
70 ret = wait_for_completion_killable(&vi->have_data);
76 return vi->data_avail;
79 static void virtio_cleanup(struct hwrng *rng)
81 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
84 wait_for_completion(&vi->have_data);
87 static int probe_common(struct virtio_device *vdev)
90 struct virtrng_info *vi = NULL;
92 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
96 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
101 sprintf(vi->name, "virtio_rng.%d", index);
102 init_completion(&vi->have_data);
104 vi->hwrng = (struct hwrng) {
106 .cleanup = virtio_cleanup,
107 .priv = (unsigned long)vi,
113 /* We expect a single virtqueue. */
114 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
115 if (IS_ERR(vi->vq)) {
116 err = PTR_ERR(vi->vq);
123 ida_simple_remove(&rng_index_ida, index);
129 static void remove_common(struct virtio_device *vdev)
131 struct virtrng_info *vi = vdev->priv;
133 vi->hwrng_removed = true;
135 complete(&vi->have_data);
136 vdev->config->reset(vdev);
138 if (vi->hwrng_register_done)
139 hwrng_unregister(&vi->hwrng);
140 vdev->config->del_vqs(vdev);
141 ida_simple_remove(&rng_index_ida, vi->index);
145 static int virtrng_probe(struct virtio_device *vdev)
147 return probe_common(vdev);
150 static void virtrng_remove(struct virtio_device *vdev)
155 static void virtrng_scan(struct virtio_device *vdev)
157 struct virtrng_info *vi = vdev->priv;
160 err = hwrng_register(&vi->hwrng);
162 vi->hwrng_register_done = true;
165 #ifdef CONFIG_PM_SLEEP
166 static int virtrng_freeze(struct virtio_device *vdev)
172 static int virtrng_restore(struct virtio_device *vdev)
176 err = probe_common(vdev);
178 struct virtrng_info *vi = vdev->priv;
181 * Set hwrng_removed to ensure that virtio_read()
182 * does not block waiting for data before the
183 * registration is complete.
185 vi->hwrng_removed = true;
186 err = hwrng_register(&vi->hwrng);
188 vi->hwrng_register_done = true;
189 vi->hwrng_removed = false;
197 static struct virtio_device_id id_table[] = {
198 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
202 static struct virtio_driver virtio_rng_driver = {
203 .driver.name = KBUILD_MODNAME,
204 .driver.owner = THIS_MODULE,
205 .id_table = id_table,
206 .probe = virtrng_probe,
207 .remove = virtrng_remove,
208 .scan = virtrng_scan,
209 #ifdef CONFIG_PM_SLEEP
210 .freeze = virtrng_freeze,
211 .restore = virtrng_restore,
215 module_virtio_driver(virtio_rng_driver);
216 MODULE_DEVICE_TABLE(virtio, id_table);
217 MODULE_DESCRIPTION("Virtio random number driver");
218 MODULE_LICENSE("GPL");