[PATCH net-next v6 3/6] virtio_net: Add a lock for the command VQ.

[Daniel Jurgens]

The command VQ will no longer be protected by the RTNL lock. Use a
mutex to protect the control buffer header and the VQ.

Signed-off-by: Daniel Jurgens <dani...@nvidia.com>
Reviewed-by: Jiri Pirko <j...@nvidia.com>
---
 drivers/net/virtio_net.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 451879d570a8..d7bad74a395f 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -411,6 +411,9 @@ struct virtnet_info {
        /* Has control virtqueue */
        bool has_cvq;
 
+       /* Lock to protect the control VQ */
+       struct mutex cvq_lock;
+
        /* Host can handle any s/g split between our header and packet data */
        bool any_header_sg;
 
@@ -2675,6 +2678,7 @@ static bool virtnet_send_command_reply(struct 
virtnet_info *vi, u8 class, u8 cmd
        /* Caller should know better */
        BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
 
+       mutex_lock(&vi->cvq_lock);
        vi->ctrl->status = ~0;
        vi->ctrl->hdr.class = class;
        vi->ctrl->hdr.cmd = cmd;
@@ -2697,11 +2701,12 @@ static bool virtnet_send_command_reply(struct 
virtnet_info *vi, u8 class, u8 cmd
        if (ret < 0) {
                dev_warn(&vi->vdev->dev,
                         "Failed to add sgs for command vq: %d\n.", ret);
+               mutex_unlock(&vi->cvq_lock);
                return false;
        }
 
        if (unlikely(!virtqueue_kick(vi->cvq)))
-               return vi->ctrl->status == VIRTIO_NET_OK;
+               goto unlock;
 
        /* Spin for a response, the kick causes an ioport write, trapping
         * into the hypervisor, so the request should be handled immediately.
@@ -2712,6 +2717,8 @@ static bool virtnet_send_command_reply(struct 
virtnet_info *vi, u8 class, u8 cmd
                cpu_relax();
        }
 
+unlock:
+       mutex_unlock(&vi->cvq_lock);
        return vi->ctrl->status == VIRTIO_NET_OK;
 }
 
@@ -5736,6 +5743,8 @@ static int virtnet_probe(struct virtio_device *vdev)
        if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
                vi->has_cvq = true;
 
+       mutex_init(&vi->cvq_lock);
+
        if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) {
                mtu = virtio_cread16(vdev,
                                     offsetof(struct virtio_net_config,
-- 
2.44.0