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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 ffc5ce9c27
commit e8f51401d6
1 changed files with 12 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/char/hw_random/virtio-rng.c
+12 -14
View File
@@ -20,7 +20,6 @@ struct virtrng_info {
struct virtqueue *vq; struct virtqueue *vq;
char name[25]; char name[25];
int index; int index;
bool busy;
bool hwrng_register_done; bool hwrng_register_done;
bool hwrng_removed; bool hwrng_removed;
/* data transfer */ /* data transfer */
@@ -44,16 +43,18 @@ static void random_recv_done(struct virtqueue *vq)
return; return;
vi->data_idx = 0; vi->data_idx = 0;
vi->busy = false;
complete(&vi->have_data); complete(&vi->have_data);
} }
/* The host will fill any buffer we give it with sweet, sweet randomness. */ static void request_entropy(struct virtrng_info *vi)
static void register_buffer(struct virtrng_info *vi)
{ {
struct scatterlist sg; 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)); sg_init_one(&sg, vi->data, sizeof(vi->data));
/* There should always be room for one buffer. */ /* 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); memcpy(buf, vi->data + vi->data_idx, size);
vi->data_idx += size; vi->data_idx += size;
vi->data_avail -= size; vi->data_avail -= size;
if (vi->data_avail == 0)
request_entropy(vi);
return size; 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 * so either size is 0 or data_avail is 0
*/ */
while (size != 0) { while (size != 0) {
/* data_avail is 0 */ /* data_avail is 0 but a request is pending */
if (!vi->busy) {
/* no pending request, ask for more */
vi->busy = true;
reinit_completion(&vi->have_data);
register_buffer(vi);
}
ret = wait_for_completion_killable(&vi->have_data); ret = wait_for_completion_killable(&vi->have_data);
if (ret < 0) if (ret < 0)
return ret; return ret;
@@ -126,8 +123,7 @@ static void virtio_cleanup(struct hwrng *rng)
{ {
struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 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) static int probe_common(struct virtio_device *vdev)
@@ -163,6 +159,9 @@ static int probe_common(struct virtio_device *vdev)
goto err_find; goto err_find;
} }
/* we always have a pending entropy request */
request_entropy(vi);
return 0; return 0;
err_find: err_find:
@@ -181,7 +180,6 @@ static void remove_common(struct virtio_device *vdev)
vi->data_idx = 0; vi->data_idx = 0;
complete(&vi->have_data); complete(&vi->have_data);
vdev->config->reset(vdev); vdev->config->reset(vdev);
vi->busy = false;
if (vi->hwrng_register_done) if (vi->hwrng_register_done)
hwrng_unregister(&vi->hwrng); hwrng_unregister(&vi->hwrng);
vdev->config->del_vqs(vdev); vdev->config->del_vqs(vdev);