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);
21 struct completion have_data;
23 unsigned int data_avail;
26 bool hwrng_register_done;
30 static void random_recv_done(struct virtqueue *vq)
32 struct virtrng_info *vi = vq->vdev->priv;
34 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
35 if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
38 complete(&vi->have_data);
41 /* The host will fill any buffer we give it with sweet, sweet randomness. */
42 static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
44 struct scatterlist sg;
46 sg_init_one(&sg, buf, size);
48 /* There should always be room for one buffer. */
49 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
51 virtqueue_kick(vi->vq);
54 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
57 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
59 if (vi->hwrng_removed)
64 reinit_completion(&vi->have_data);
65 register_buffer(vi, buf, size);
71 ret = wait_for_completion_killable(&vi->have_data);
77 return vi->data_avail;
80 static void virtio_cleanup(struct hwrng *rng)
82 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
85 wait_for_completion(&vi->have_data);
88 static int probe_common(struct virtio_device *vdev)
91 struct virtrng_info *vi = NULL;
93 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
97 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
102 sprintf(vi->name, "virtio_rng.%d", index);
103 init_completion(&vi->have_data);
105 vi->hwrng = (struct hwrng) {
107 .cleanup = virtio_cleanup,
108 .priv = (unsigned long)vi,
114 /* We expect a single virtqueue. */
115 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
116 if (IS_ERR(vi->vq)) {
117 err = PTR_ERR(vi->vq);
124 ida_simple_remove(&rng_index_ida, index);
130 static void remove_common(struct virtio_device *vdev)
132 struct virtrng_info *vi = vdev->priv;
134 vi->hwrng_removed = true;
136 complete(&vi->have_data);
137 vdev->config->reset(vdev);
139 if (vi->hwrng_register_done)
140 hwrng_unregister(&vi->hwrng);
141 vdev->config->del_vqs(vdev);
142 ida_simple_remove(&rng_index_ida, vi->index);
146 static int virtrng_probe(struct virtio_device *vdev)
148 return probe_common(vdev);
151 static void virtrng_remove(struct virtio_device *vdev)
156 static void virtrng_scan(struct virtio_device *vdev)
158 struct virtrng_info *vi = vdev->priv;
161 err = hwrng_register(&vi->hwrng);
163 vi->hwrng_register_done = true;
166 #ifdef CONFIG_PM_SLEEP
167 static int virtrng_freeze(struct virtio_device *vdev)
173 static int virtrng_restore(struct virtio_device *vdev)
177 err = probe_common(vdev);
179 struct virtrng_info *vi = vdev->priv;
182 * Set hwrng_removed to ensure that virtio_read()
183 * does not block waiting for data before the
184 * registration is complete.
186 vi->hwrng_removed = true;
187 err = hwrng_register(&vi->hwrng);
189 vi->hwrng_register_done = true;
190 vi->hwrng_removed = false;
198 static const struct virtio_device_id id_table[] = {
199 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
203 static struct virtio_driver virtio_rng_driver = {
204 .driver.name = KBUILD_MODNAME,
205 .driver.owner = THIS_MODULE,
206 .id_table = id_table,
207 .probe = virtrng_probe,
208 .remove = virtrng_remove,
209 .scan = virtrng_scan,
210 #ifdef CONFIG_PM_SLEEP
211 .freeze = virtrng_freeze,
212 .restore = virtrng_restore,
216 module_virtio_driver(virtio_rng_driver);
217 MODULE_DEVICE_TABLE(virtio, id_table);
218 MODULE_DESCRIPTION("Virtio random number driver");
219 MODULE_LICENSE("GPL");