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");