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virtio: console makes incorrect assumption about virtio API

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The get_buf() API sets the second arg to the number of bytes *written*
by the other side; in this case it should be zero as these are output buffers.

lguest gets this right (obviously kvm's console doesn't), resulting in
continual buildup of console writes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Amit Shah <amit.shah@redhat.com>
This commit is contained in:
Rusty Russell
2010-04-08 09:46:16 -06:00
parent 162a689a13
commit 9ff4cfab82
1 changed files with 3 additions and 7 deletions
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10
drivers/char/virtio_console.c
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@@ -416,20 +416,16 @@ static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count)
out_vq->vq_ops->kick(out_vq); out_vq->vq_ops->kick(out_vq);
if (ret < 0) { if (ret < 0) {
len = 0; in_count = 0;
goto fail; goto fail;
} }
/* /* Wait till the host acknowledges it pushed out the data we sent. */
* Wait till the host acknowledges it pushed out the data we
* sent. Also ensure we return to userspace the number of
* bytes that were successfully consumed by the host.
*/
while (!out_vq->vq_ops->get_buf(out_vq, &len)) while (!out_vq->vq_ops->get_buf(out_vq, &len))
cpu_relax(); cpu_relax();
fail: fail:
/* We're expected to return the amount of data we wrote */ /* We're expected to return the amount of data we wrote */
return len; return in_count;
} }
/* /*