virtio: An entropy device, as suggested by hpa.

Note that by itself, having a "hardware" random generator does very
little: you should probably run "rngd" in your guest to feed this into
the kernel entropy pool.

Included:
	virtio_rng: dont use vmalloced addresses for virtio

	If virtio_rng is build as a module, random_data is an address
	in vmalloc space. As virtio expects guest real addresses, this
	can cause any kind of funny behaviour, so lets allocate
	random_data dynamically with kmalloc.

	Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 8d6c2089d2a8480bf1829d0b3d24bca959b22a31..efd0b4db7c8ed6c5d6c6bbc5a473466f898fdf1d 100644 (file)
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -112,3 +112,12 @@ config HW_RANDOM_PASEMI
 
          If unsure, say Y.
 
+config HW_RANDOM_VIRTIO
+       tristate "VirtIO Random Number Generator support"
+       depends on HW_RANDOM && VIRTIO
+       ---help---
+         This driver provides kernel-side support for the virtual Random Number
+         Generator hardware.
+
+         To compile this driver as a module, choose M here: the
+         module will be called virtio-rng.  If unsure, say N.

diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index c8b7300e2fb183f6ed6c6d1eb4f6ccfa358fb6bc..b4940ddbb35f5993c80c164dbea1a2046915d1dd 100644 (file)
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o
 obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o
 obj-$(CONFIG_HW_RANDOM_PASEMI) += pasemi-rng.o
+obj-$(CONFIG_HW_RANDOM_VIRTIO) += virtio-rng.o

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
new file mode 100644 (file)
index 0000000..d0e563e
--- /dev/null
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -0,0 +1,155 @@
+/*
+ * 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>
+
+/* The host will fill any buffer we give it with sweet, sweet randomness.  We
+ * give it 64 bytes at a time, and the hwrng framework takes it 4 bytes at a
+ * time. */
+#define RANDOM_DATA_SIZE 64
+
+static struct virtqueue *vq;
+static u32 *random_data;
+static unsigned int data_left;
+static DECLARE_COMPLETION(have_data);
+
+static void random_recv_done(struct virtqueue *vq)
+{
+       int len;
+
+       /* We never get spurious callbacks. */
+       if (!vq->vq_ops->get_buf(vq, &len))
+               BUG();
+
+       data_left = len / sizeof(random_data[0]);
+       complete(&have_data);
+}
+
+static void register_buffer(void)
+{
+       struct scatterlist sg;
+
+       sg_init_one(&sg, random_data, RANDOM_DATA_SIZE);
+       /* There should always be room for one buffer. */
+       if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0)
+               BUG();
+       vq->vq_ops->kick(vq);
+}
+
+/* At least we don't udelay() in a loop like some other drivers. */
+static int virtio_data_present(struct hwrng *rng, int wait)
+{
+       if (data_left)
+               return 1;
+
+       if (!wait)
+               return 0;
+
+       wait_for_completion(&have_data);
+       return 1;
+}
+
+/* virtio_data_present() must have succeeded before this is called. */
+static int virtio_data_read(struct hwrng *rng, u32 *data)
+{
+       BUG_ON(!data_left);
+
+       *data = random_data[--data_left];
+
+       if (!data_left) {
+               init_completion(&have_data);
+               register_buffer();
+       }
+       return sizeof(*data);
+}
+
+static struct hwrng virtio_hwrng = {
+       .name = "virtio",
+       .data_present = virtio_data_present,
+       .data_read = virtio_data_read,
+};
+
+static int virtrng_probe(struct virtio_device *vdev)
+{
+       int err;
+
+       /* We expect a single virtqueue. */
+       vq = vdev->config->find_vq(vdev, 0, random_recv_done);
+       if (IS_ERR(vq))
+               return PTR_ERR(vq);
+
+       err = hwrng_register(&virtio_hwrng);
+       if (err) {
+               vdev->config->del_vq(vq);
+               return err;
+       }
+
+       register_buffer();
+       return 0;
+}
+
+static void virtrng_remove(struct virtio_device *vdev)
+{
+       vdev->config->reset(vdev);
+       hwrng_unregister(&virtio_hwrng);
+       vdev->config->del_vq(vq);
+}
+
+static struct virtio_device_id id_table[] = {
+       { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
+       { 0 },
+};
+
+static struct virtio_driver virtio_rng = {
+       .driver.name =  KBUILD_MODNAME,
+       .driver.owner = THIS_MODULE,
+       .id_table =     id_table,
+       .probe =        virtrng_probe,
+       .remove =       __devexit_p(virtrng_remove),
+};
+
+static int __init init(void)
+{
+       int err;
+
+       random_data = kmalloc(RANDOM_DATA_SIZE, GFP_KERNEL);
+       if (!random_data)
+               return -ENOMEM;
+
+       err = register_virtio_driver(&virtio_rng);
+       if (err)
+               kfree(random_data);
+       return err;
+}
+
+static void __exit fini(void)
+{
+       kfree(random_data);
+       unregister_virtio_driver(&virtio_rng);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio random number driver");
+MODULE_LICENSE("GPL");

diff --git a/include/linux/virtio_rng.h b/include/linux/virtio_rng.h
new file mode 100644 (file)
index 0000000..331afb6
--- /dev/null
+++ b/include/linux/virtio_rng.h
@@ -0,0 +1,8 @@
+#ifndef _LINUX_VIRTIO_RNG_H
+#define _LINUX_VIRTIO_RNG_H
+#include <linux/virtio_config.h>
+
+/* The ID for virtio_rng */
+#define VIRTIO_ID_RNG  4
+
+#endif /* _LINUX_VIRTIO_RNG_H */