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SubjectRe: [PATCH net-next 1/2] virtio_net: allow hypervisor to indicate linkspeed and duplex setting
On Thu, Dec 14, 2017 at 02:33:53PM -0500, Jason Baron wrote:
> If the hypervisor exports the link and duplex speed, let's use that instead
> of the default unknown speed. The user can still overwrite it later if
> desired via: 'ethtool -s'. This allows the hypervisor to set the default
> link speed and duplex setting without requiring guest changes and is
> consistent with how other network drivers operate. We ran into some cases
> where the guest software was failing due to a lack of linkspeed and had to
> fall back to a fully emulated network device that does export a linkspeed
> and duplex setting.
>
> Implement by adding a new VIRTIO_NET_F_SPEED_DUPLEX feature flag, to
> indicate that a linkspeed and duplex setting are present.
>
> Signed-off-by: Jason Baron <jbaron@akamai.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>

Sounds fine, but please register the new feature bit
with the virtio TC by sending en email to the virtio
mailing list (subscriber only, wish I could fix that).

We do not want conflicts there.

> ---
> drivers/net/virtio_net.c | 11 ++++++++++-
> include/uapi/linux/virtio_net.h | 4 ++++
> 2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 6fb7b65..e7a2ad6 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2671,6 +2671,14 @@ static int virtnet_probe(struct virtio_device *vdev)
> netif_set_real_num_rx_queues(dev, vi->curr_queue_pairs);
>
> virtnet_init_settings(dev);
> + if (virtio_has_feature(vdev, VIRTIO_NET_F_SPEED_DUPLEX)) {
> + vi->speed = virtio_cread32(vdev,
> + offsetof(struct virtio_net_config,
> + speed));
> + vi->duplex = virtio_cread8(vdev,
> + offsetof(struct virtio_net_config,
> + duplex));
> + }
>
> err = register_netdev(dev);
> if (err) {
> @@ -2796,7 +2804,8 @@ static struct virtio_device_id id_table[] = {
> VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
> VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
> VIRTIO_NET_F_CTRL_MAC_ADDR, \
> - VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
> + VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> + VIRTIO_NET_F_SPEED_DUPLEX
>
> static unsigned int features[] = {
> VIRTNET_FEATURES,
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index fc353b5..acfcf68 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -36,6 +36,7 @@
> #define VIRTIO_NET_F_GUEST_CSUM 1 /* Guest handles pkts w/ partial csum */
> #define VIRTIO_NET_F_CTRL_GUEST_OFFLOADS 2 /* Dynamic offload configuration. */
> #define VIRTIO_NET_F_MTU 3 /* Initial MTU advice */
> +#define VIRTIO_NET_F_SPEED_DUPLEX 4 /* Host set linkspeed and duplex */
> #define VIRTIO_NET_F_MAC 5 /* Host has given MAC address. */
> #define VIRTIO_NET_F_GUEST_TSO4 7 /* Guest can handle TSOv4 in. */
> #define VIRTIO_NET_F_GUEST_TSO6 8 /* Guest can handle TSOv6 in. */
> @@ -76,6 +77,9 @@ struct virtio_net_config {
> __u16 max_virtqueue_pairs;
> /* Default maximum transmit unit advice */
> __u16 mtu;
> + /* Host exported linkspeed and duplex */
> + __u32 speed;
> + __u8 duplex;
> } __attribute__((packed));
>
> /*
> --
> 2.6.1

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