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virtio-crypto: fix virtio_queue_set_notification() race 

We must check for new virtqueue buffers after re-enabling notifications.
This prevents the race condition where the guest added buffers just
after we stopped popping the virtqueue but before we re-enabled
notifications.

I think the virtio-crypto code was based on virtio-net but this crucial
detail was missed.  virtio-net does not have the race condition because
it processes the virtqueue one more time after re-enabling
notifications.

Cc: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Gonglei <arei.gonglei@huawei.com>
This commit is contained in:
Stefan Hajnoczi 2016-11-16 20:17:32 +00:00 committed by Michael S. Tsirkin
parent 453ac8835b
commit 600f5ce356
1 changed files with 11 additions and 2 deletions
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9
hw/virtio/virtio-crypto.c
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@ -692,8 +692,17 @@ static void virtio_crypto_dataq_bh(void *opaque)
return; return;
} }
for (;;) {
virtio_crypto_handle_dataq(vdev, q->dataq); virtio_crypto_handle_dataq(vdev, q->dataq);
virtio_queue_set_notification(q->dataq, 1); virtio_queue_set_notification(q->dataq, 1);
/* Are we done or did the guest add more buffers? */
if (virtio_queue_empty(q->dataq)) {
break;
}
virtio_queue_set_notification(q->dataq, 0);
}
} }
static void static void