v4.19.13 snapshot.
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
new file mode 100644
index 0000000..b89df66
--- /dev/null
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -0,0 +1,231 @@
+/*
+ * Randomness driver for virtio
+ * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/err.h>
+#include <linux/hw_random.h>
+#include <linux/scatterlist.h>
+#include <linux/spinlock.h>
+#include <linux/virtio.h>
+#include <linux/virtio_rng.h>
+#include <linux/module.h>
+
+static DEFINE_IDA(rng_index_ida);
+
+struct virtrng_info {
+ struct hwrng hwrng;
+ struct virtqueue *vq;
+ struct completion have_data;
+ char name[25];
+ unsigned int data_avail;
+ int index;
+ bool busy;
+ bool hwrng_register_done;
+ bool hwrng_removed;
+};
+
+static void random_recv_done(struct virtqueue *vq)
+{
+ struct virtrng_info *vi = vq->vdev->priv;
+
+ /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
+ if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
+ return;
+
+ complete(&vi->have_data);
+}
+
+/* The host will fill any buffer we give it with sweet, sweet randomness. */
+static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
+{
+ struct scatterlist sg;
+
+ sg_init_one(&sg, buf, size);
+
+ /* There should always be room for one buffer. */
+ virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
+
+ virtqueue_kick(vi->vq);
+}
+
+static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
+{
+ int ret;
+ struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
+
+ if (vi->hwrng_removed)
+ return -ENODEV;
+
+ if (!vi->busy) {
+ vi->busy = true;
+ init_completion(&vi->have_data);
+ register_buffer(vi, buf, size);
+ }
+
+ if (!wait)
+ return 0;
+
+ ret = wait_for_completion_killable(&vi->have_data);
+ if (ret < 0)
+ return ret;
+
+ vi->busy = false;
+
+ return vi->data_avail;
+}
+
+static void virtio_cleanup(struct hwrng *rng)
+{
+ struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
+
+ if (vi->busy)
+ wait_for_completion(&vi->have_data);
+}
+
+static int probe_common(struct virtio_device *vdev)
+{
+ int err, index;
+ struct virtrng_info *vi = NULL;
+
+ vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
+ if (!vi)
+ return -ENOMEM;
+
+ vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
+ if (index < 0) {
+ err = index;
+ goto err_ida;
+ }
+ sprintf(vi->name, "virtio_rng.%d", index);
+ init_completion(&vi->have_data);
+
+ vi->hwrng = (struct hwrng) {
+ .read = virtio_read,
+ .cleanup = virtio_cleanup,
+ .priv = (unsigned long)vi,
+ .name = vi->name,
+ .quality = 1000,
+ };
+ vdev->priv = vi;
+
+ /* We expect a single virtqueue. */
+ vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
+ if (IS_ERR(vi->vq)) {
+ err = PTR_ERR(vi->vq);
+ goto err_find;
+ }
+
+ return 0;
+
+err_find:
+ ida_simple_remove(&rng_index_ida, index);
+err_ida:
+ kfree(vi);
+ return err;
+}
+
+static void remove_common(struct virtio_device *vdev)
+{
+ struct virtrng_info *vi = vdev->priv;
+
+ vi->hwrng_removed = true;
+ vi->data_avail = 0;
+ complete(&vi->have_data);
+ vdev->config->reset(vdev);
+ vi->busy = false;
+ if (vi->hwrng_register_done)
+ hwrng_unregister(&vi->hwrng);
+ vdev->config->del_vqs(vdev);
+ ida_simple_remove(&rng_index_ida, vi->index);
+ kfree(vi);
+}
+
+static int virtrng_probe(struct virtio_device *vdev)
+{
+ return probe_common(vdev);
+}
+
+static void virtrng_remove(struct virtio_device *vdev)
+{
+ remove_common(vdev);
+}
+
+static void virtrng_scan(struct virtio_device *vdev)
+{
+ struct virtrng_info *vi = vdev->priv;
+ int err;
+
+ err = hwrng_register(&vi->hwrng);
+ if (!err)
+ vi->hwrng_register_done = true;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int virtrng_freeze(struct virtio_device *vdev)
+{
+ remove_common(vdev);
+ return 0;
+}
+
+static int virtrng_restore(struct virtio_device *vdev)
+{
+ int err;
+
+ err = probe_common(vdev);
+ if (!err) {
+ struct virtrng_info *vi = vdev->priv;
+
+ /*
+ * Set hwrng_removed to ensure that virtio_read()
+ * does not block waiting for data before the
+ * registration is complete.
+ */
+ vi->hwrng_removed = true;
+ err = hwrng_register(&vi->hwrng);
+ if (!err) {
+ vi->hwrng_register_done = true;
+ vi->hwrng_removed = false;
+ }
+ }
+
+ return err;
+}
+#endif
+
+static struct virtio_device_id id_table[] = {
+ { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
+ { 0 },
+};
+
+static struct virtio_driver virtio_rng_driver = {
+ .driver.name = KBUILD_MODNAME,
+ .driver.owner = THIS_MODULE,
+ .id_table = id_table,
+ .probe = virtrng_probe,
+ .remove = virtrng_remove,
+ .scan = virtrng_scan,
+#ifdef CONFIG_PM_SLEEP
+ .freeze = virtrng_freeze,
+ .restore = virtrng_restore,
+#endif
+};
+
+module_virtio_driver(virtio_rng_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio random number driver");
+MODULE_LICENSE("GPL");