On Wed, Apr 17, 2024 at 3:31 AM Daniel Jurgens <danielj@xxxxxxxxxx> wrote:
>
> The command VQ will no longer be protected by the RTNL lock. Use a
> spinlock to protect the control buffer header and the VQ.
>
> Signed-off-by: Daniel Jurgens <danielj@xxxxxxxxxx>
> Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 0ee192b45e1e..d02f83a919a7 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -282,6 +282,7 @@ struct virtnet_info {
>
> /* Has control virtqueue */
> bool has_cvq;
> + spinlock_t cvq_lock;
Spinlock is instead of mutex which is problematic as there's no
guarantee on when the driver will get a reply. And it became even more
serious after 0d197a147164 ("virtio-net: add cond_resched() to the
command waiting loop").
Any reason we can't use mutex?
Thanks
>
> /* Host can handle any s/g split between our header and packet data */
> bool any_header_sg;
> @@ -2529,6 +2530,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
> /* Caller should know better */
> BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
>
> + guard(spinlock)(&vi->cvq_lock);
> vi->ctrl->status = ~0;
> vi->ctrl->hdr.class = class;
> vi->ctrl->hdr.cmd = cmd;
> @@ -4818,8 +4820,10 @@ static int virtnet_probe(struct virtio_device *vdev)
> virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
> vi->any_header_sg = true;
>
> - if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
> + if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> vi->has_cvq = true;
> + spin_lock_init(&vi->cvq_lock);
> + }
>
> if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) {
> mtu = virtio_cread16(vdev,
> --
> 2.34.1
>
