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Commit bb347d98 authored by Ian Molton's avatar Ian Molton Committed by Herbert Xu
Browse files

hwrng: virtio-rng - Convert to new API 



This patch converts virtio-rng to the new hw_rng API.

In the process it fixes a previously untriggered buffering bug where the
buffer is not drained correctly if it has a non-multiple-of-4 length.

Performance has improved under qemu-kvm testing also.

Signed-off-by: default avatarIan Molton <ian.molton@collabora.co.uk>
Acked-by: default avatarMatt Mackall <mpm@selenic.com>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 83863243

drivers/char/hw_random/virtio-rng.c

+27 −51
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
 *  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>
@@ -23,78 +24,64 @@ 
#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 unsigned int data_avail;

static DECLARE_COMPLETION(have_data);

static bool busy;



static void random_recv_done(struct virtqueue *vq)

{

	unsigned int len;



	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */

	if (!vq->vq_ops->get_buf(vq, &len))

	if (!vq->vq_ops->get_buf(vq, &data_avail))

		return;



	data_left += len;

	complete(&have_data);

}



static void register_buffer(void)

/* The host will fill any buffer we give it with sweet, sweet randomness. */

static void register_buffer(u8 *buf, size_t size)

{

	struct scatterlist sg;



	sg_init_one(&sg, random_data+data_left, RANDOM_DATA_SIZE-data_left);

	sg_init_one(&sg, buf, size);



	/* There should always be room for one buffer. */

	if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) < 0)

	if (vq->vq_ops->add_buf(vq, &sg, 0, 1, buf) < 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)

static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)

{

	if (data_left >= sizeof(u32))

		return 1;



again:

	if (!busy) {

		busy = true;

		init_completion(&have_data);

		register_buffer(buf, size);

	}



	if (!wait)

		return 0;



	wait_for_completion(&have_data);



	/* Not enough?  Re-register. */

	if (unlikely(data_left < sizeof(u32))) {

		register_buffer();

		goto again;

	}

	busy = false;



	return 1;

	return data_avail;

}



/* virtio_data_present() must have succeeded before this is called. */

static int virtio_data_read(struct hwrng *rng, u32 *data)

static void virtio_cleanup(struct hwrng *rng)

{

	BUG_ON(data_left < sizeof(u32));

	data_left -= sizeof(u32);

	*data = random_data[data_left / 4];



	if (data_left < sizeof(u32)) {

		init_completion(&have_data);

		register_buffer();

	}

	return sizeof(*data);

	if (busy)

		wait_for_completion(&have_data);

}





static struct hwrng virtio_hwrng = {

	.name		= "virtio",

	.data_present = virtio_data_present,

	.data_read = virtio_data_read,

	.cleanup	= virtio_cleanup,

	.read		= virtio_read,

};



static int virtrng_probe(struct virtio_device *vdev)
@@ -112,7 +99,6 @@ static int virtrng_probe(struct virtio_device *vdev) 
		return err;

	}



	register_buffer();

	return 0;

}
@@ -138,21 +124,11 @@ static struct virtio_driver virtio_rng = { 


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;

	return register_virtio_driver(&virtio_rng);

}



static void __exit fini(void)

{

	kfree(random_data);

	unregister_virtio_driver(&virtio_rng);

}

module_init(init);