virtio-net: fix ring handling in receive

A bug crept in while doing the virtio 1.0 enablement in
commit 6e4d62c2 (virtio-net: enable virtio 1.0)

+       idx = virtio_modern16_to_cpu(&virtiodev, vq_rx.used->idx);

[...]

-       vq_rx.avail->ring[vq_rx.avail->idx % vq_rx.size] = id - 1;
+       vq_rx.avail->ring[idx % vq_rx.size] = virtio_cpu_to_modern16(&virtiodev, id - 1);
        sync();
-       vq_rx.avail->idx += 1;
+       vq_rx.avail->idx = virtio_cpu_to_modern16(&virtiodev, idx + 1);

Should be using avail->idx in place of used->idx.

Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/libvirtio/virtio-net.c b/lib/libvirtio/virtio-net.c
index fc620a2..2573031 100644
--- a/lib/libvirtio/virtio-net.c
+++ b/lib/libvirtio/virtio-net.c
@@ -266,6 +266,7 @@ static int virtionet_receive(char *buf, int maxlen)
 {
 	uint32_t len = 0;
 	uint32_t id, idx;
+	uint16_t avail_idx;
 
 	idx = virtio_modern16_to_cpu(&virtiodev, vq_rx.used->idx);
 
@@ -304,9 +305,10 @@ static int virtionet_receive(char *buf, int maxlen)
 	/* Move indices to next entries */
 	last_rx_idx = last_rx_idx + 1;
 
-	vq_rx.avail->ring[idx % vq_rx.size] = virtio_cpu_to_modern16(&virtiodev, id - 1);
+	avail_idx = virtio_modern16_to_cpu(&virtiodev, vq_rx.avail->idx);
+	vq_rx.avail->ring[avail_idx % vq_rx.size] = virtio_cpu_to_modern16(&virtiodev, id - 1);
 	sync();
-	vq_rx.avail->idx = virtio_cpu_to_modern16(&virtiodev, idx + 1);
+	vq_rx.avail->idx = virtio_cpu_to_modern16(&virtiodev, avail_idx + 1);
 
 	/* Tell HV that RX queue entry is ready */
 	virtio_queue_notify(&virtiodev, VQ_RX);