[PATCH net v3 1/2] virtio-net: check feature before configuring the vq coalescing command

[Heng Qi]

Virtio spec says:

        The driver MUST have negotiated the VIRTIO_NET_F_VQ_NOTF_COAL
        feature when issuing commands VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET
        and VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET.

So we add the feature negotiation check to
virtnet_send_{r,t}x_ctrl_coal_vq_cmd as a basis for the next bugfix patch.

Suggested-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Heng Qi <hen...@linux.alibaba.com>
---
v2->v3:
  - Break out the feature check and the fix into separate patches.

 drivers/net/virtio_net.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0383a3e136d6..b1176be8fcfd 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3658,6 +3658,9 @@ static int virtnet_send_rx_ctrl_coal_vq_cmd(struct 
virtnet_info *vi,
 {
        int err;
 
+       if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
+               return -EOPNOTSUPP;
+
        err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(queue),
                                            max_usecs, max_packets);
        if (err)
@@ -3675,6 +3678,9 @@ static int virtnet_send_tx_ctrl_coal_vq_cmd(struct 
virtnet_info *vi,
 {
        int err;
 
+       if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
+               return -EOPNOTSUPP;
+
        err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(queue),
                                            max_usecs, max_packets);
        if (err)
-- 
2.32.0.3.g01195cf9f