1 files changed, 163 insertions, 73 deletions

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index ef46a9cfd832..dd998f4fe4f2 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -1,22 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * 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 <asm/barrier.h>
 #include <linux/err.h>
 #include <linux/hw_random.h>
 #include <linux/scatterlist.h>
@@ -24,103 +12,180 @@
 #include <linux/virtio.h>
 #include <linux/virtio_rng.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 
-static struct virtqueue *vq;
-static unsigned int data_avail;
-static DECLARE_COMPLETION(have_data);
-static bool busy;
+static DEFINE_IDA(rng_index_ida);
+
+struct virtrng_info {
+	struct hwrng hwrng;
+	struct virtqueue *vq;
+	char name[25];
+	int index;
+	bool hwrng_register_done;
+	bool hwrng_removed;
+	/* data transfer */
+	struct completion have_data;
+	unsigned int data_avail;
+	unsigned int data_idx;
+	/* minimal size returned by rng_buffer_size() */
+#if SMP_CACHE_BYTES < 32
+	u8 data[32];
+#else
+	u8 data[SMP_CACHE_BYTES];
+#endif
+};
 
 static void random_recv_done(struct virtqueue *vq)
 {
+	struct virtrng_info *vi = vq->vdev->priv;
+	unsigned int len;
+
 	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
-	if (!virtqueue_get_buf(vq, &data_avail))
+	if (!virtqueue_get_buf(vi->vq, &len))
 		return;
 
-	complete(&have_data);
+	smp_store_release(&vi->data_avail, len);
+	complete(&vi->have_data);
 }
 
-/* The host will fill any buffer we give it with sweet, sweet randomness. */
-static void register_buffer(u8 *buf, size_t size)
+static void request_entropy(struct virtrng_info *vi)
 {
 	struct scatterlist sg;
 
-	sg_init_one(&sg, buf, size);
+	reinit_completion(&vi->have_data);
+	vi->data_idx = 0;
+
+	sg_init_one(&sg, vi->data, sizeof(vi->data));
 
 	/* There should always be room for one buffer. */
-	if (virtqueue_add_inbuf(vq, &sg, 1, buf, GFP_KERNEL) < 0)
-		BUG();
+	virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
 
-	virtqueue_kick(vq);
+	virtqueue_kick(vi->vq);
+}
+
+static unsigned int copy_data(struct virtrng_info *vi, void *buf,
+			      unsigned int size)
+{
+	size = min_t(unsigned int, size, vi->data_avail);
+	memcpy(buf, vi->data + vi->data_idx, size);
+	vi->data_idx += size;
+	vi->data_avail -= size;
+	if (vi->data_avail == 0)
+		request_entropy(vi);
+	return size;
 }
 
 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;
+	unsigned int chunk;
+	size_t read;
+
+	if (vi->hwrng_removed)
+		return -ENODEV;
 
-	if (!busy) {
-		busy = true;
-		init_completion(&have_data);
-		register_buffer(buf, size);
+	read = 0;
+
+	/* copy available data */
+	if (smp_load_acquire(&vi->data_avail)) {
+		chunk = copy_data(vi, buf, size);
+		size -= chunk;
+		read += chunk;
 	}
 
 	if (!wait)
-		return 0;
+		return read;
 
-	ret = wait_for_completion_killable(&have_data);
-	if (ret < 0)
-		return ret;
+	/* We have already copied available entropy,
+	 * so either size is 0 or data_avail is 0
+	 */
+	while (size != 0) {
+		/* data_avail is 0 but a request is pending */
+		ret = wait_for_completion_killable(&vi->have_data);
+		if (ret < 0)
+			return ret;
+		/* if vi->data_avail is 0, we have been interrupted
+		 * by a cleanup, but buffer stays in the queue
+		 */
+		if (vi->data_avail == 0)
+			return read;
 
-	busy = false;
+		chunk = copy_data(vi, buf + read, size);
+		size -= chunk;
+		read += chunk;
+	}
 
-	return data_avail;
+	return read;
 }
 
 static void virtio_cleanup(struct hwrng *rng)
 {
-	if (busy)
-		wait_for_completion(&have_data);
-}
+	struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
 
-
-static struct hwrng virtio_hwrng = {
-	.name		= "virtio",
-	.cleanup	= virtio_cleanup,
-	.read		= virtio_read,
-};
+	complete(&vi->have_data);
+}
 
 static int probe_common(struct virtio_device *vdev)
 {
-	int err;
+	int err, index;
+	struct virtrng_info *vi = NULL;
 
-	if (vq) {
-		/* We only support one device for now */
-		return -EBUSY;
+	vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
+	if (!vi)
+		return -ENOMEM;
+
+	vi->index = index = ida_alloc(&rng_index_ida, 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,
+	};
+	vdev->priv = vi;
+
 	/* We expect a single virtqueue. */
-	vq = virtio_find_single_vq(vdev, random_recv_done, "input");
-	if (IS_ERR(vq)) {
-		err = PTR_ERR(vq);
-		vq = NULL;
-		return err;
+	vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
+	if (IS_ERR(vi->vq)) {
+		err = PTR_ERR(vi->vq);
+		goto err_find;
 	}
 
-	err = hwrng_register(&virtio_hwrng);
-	if (err) {
-		vdev->config->del_vqs(vdev);
-		vq = NULL;
-		return err;
-	}
+	virtio_device_ready(vdev);
+
+	/* we always have a pending entropy request */
+	request_entropy(vi);
 
 	return 0;
+
+err_find:
+	ida_free(&rng_index_ida, index);
+err_ida:
+	kfree(vi);
+	return err;
 }
 
 static void remove_common(struct virtio_device *vdev)
 {
-	vdev->config->reset(vdev);
-	busy = false;
-	hwrng_unregister(&virtio_hwrng);
+	struct virtrng_info *vi = vdev->priv;
+
+	vi->hwrng_removed = true;
+	vi->data_avail = 0;
+	vi->data_idx = 0;
+	complete(&vi->have_data);
+	if (vi->hwrng_register_done)
+		hwrng_unregister(&vi->hwrng);
+	virtio_reset_device(vdev);
 	vdev->config->del_vqs(vdev);
-	vq = NULL;
+	ida_free(&rng_index_ida, vi->index);
+	kfree(vi);
 }
 
 static int virtrng_probe(struct virtio_device *vdev)
@@ -133,7 +198,16 @@ static void virtrng_remove(struct virtio_device *vdev)
 	remove_common(vdev);
 }
 
-#ifdef CONFIG_PM
+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;
+}
+
 static int virtrng_freeze(struct virtio_device *vdev)
 {
 	remove_common(vdev);
@@ -142,25 +216,41 @@ static int virtrng_freeze(struct virtio_device *vdev)
 
 static int virtrng_restore(struct virtio_device *vdev)
 {
-	return probe_common(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[] = {
+static const 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,
-#ifdef CONFIG_PM
-	.freeze =	virtrng_freeze,
-	.restore =	virtrng_restore,
-#endif
+	.scan =		virtrng_scan,
+	.freeze =	pm_sleep_ptr(virtrng_freeze),
+	.restore =	pm_sleep_ptr(virtrng_restore),
 };
 
 module_virtio_driver(virtio_rng_driver);