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hwrng: virtio-rng - Convert to new API

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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: Ian Molton <ian.molton@collabora.co.uk>
Acked-by: Matt Mackall <mpm@selenic.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ian Molton 2009-12-01 15:26:33 +08:00 committed by Herbert Xu
parent 8386324381
commit bb347d9807
1 changed files with 27 additions and 51 deletions
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78
drivers/char/hw_random/virtio-rng.c
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@ -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,
.name = "virtio",
.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);