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hwrng: virtio - always add a pending request

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[ Upstream commit 9a4b612d67 ]

If we ensure we have already some data available by enqueuing
again the buffer once data are exhausted, we can return what we
have without waiting for the device answer.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Link: https://lore.kernel.org/r/20211028101111.128049-5-lvivier@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Stable-dep-of: ac52578d6e ("hwrng: virtio - Fix race on data_avail and actual data")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Laurent Vivier 2021-10-28 12:11:11 +02:00 committed by Greg Kroah-Hartman
parent 9a9ef96529
commit 64410e7b03
1 changed files with 12 additions and 14 deletions
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26
drivers/char/hw_random/virtio-rng.c
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@ -20,7 +20,6 @@ struct virtrng_info {
struct virtqueue *vq;
char name[25];
int index;
bool busy;
bool hwrng_register_done;
bool hwrng_removed;
/* data transfer */
@ -44,16 +43,18 @@ static void random_recv_done(struct virtqueue *vq)
return;
vi->data_idx = 0;
vi->busy = false;
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)
static void request_entropy(struct virtrng_info *vi)
{
struct scatterlist sg;
reinit_completion(&vi->have_data);
vi->data_avail = 0;
vi->data_idx = 0;
sg_init_one(&sg, vi->data, sizeof(vi->data));
/* There should always be room for one buffer. */
@ -69,6 +70,8 @@ static unsigned int copy_data(struct virtrng_info *vi, void *buf,
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;
}
@ -98,13 +101,7 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
* so either size is 0 or data_avail is 0
*/
while (size != 0) {
/* data_avail is 0 */
if (!vi->busy) {
/* no pending request, ask for more */
vi->busy = true;
reinit_completion(&vi->have_data);
register_buffer(vi);
}
/* data_avail is 0 but a request is pending */
ret = wait_for_completion_killable(&vi->have_data);
if (ret < 0)
return ret;
@ -126,8 +123,7 @@ static void virtio_cleanup(struct hwrng *rng)
{
struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
if (vi->busy)
complete(&vi->have_data);
complete(&vi->have_data);
}
static int probe_common(struct virtio_device *vdev)
@ -163,6 +159,9 @@ static int probe_common(struct virtio_device *vdev)
goto err_find;
}
/* we always have a pending entropy request */
request_entropy(vi);
return 0;
err_find:
@ -181,7 +180,6 @@ static void remove_common(struct virtio_device *vdev)
vi->data_idx = 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);