RE: [PATCH net-next 5/6] net: use core MTU range checking in virt drivers

[Haiyang Zhang]

> -----Original Message-----
> From: Jarod Wilson [mailto:jarod@xxxxxxxxxx]
> Sent: Tuesday, October 18, 2016 10:34 PM
> To: linux-kernel@xxxxxxxxxxxxxxx
> Cc: Jarod Wilson <jarod@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; KY Srinivasan
> <kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Michael S.
> Tsirkin <mst@xxxxxxxxxx>; Shrikrishna Khare <skhare@xxxxxxxxxx>; VMware,
> Inc. <pv-drivers@xxxxxxxxxx>
> Subject: [PATCH net-next 5/6] net: use core MTU range checking in virt
> drivers
> 
> hyperv_net:
> - set min/max_mtu
> 
> virtio_net:
> - set min/max_mtu
> - remove virtnet_change_mtu
> 
> vmxnet3:
> - set min/max_mtu
> 
> CC: netdev@xxxxxxxxxxxxxxx
> CC: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> CC: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> CC: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> CC: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> CC: Shrikrishna Khare <skhare@xxxxxxxxxx>
> CC: "VMware, Inc." <pv-drivers@xxxxxxxxxx>
> Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
> ---
>  drivers/net/hyperv/hyperv_net.h   |  4 ++--
>  drivers/net/hyperv/netvsc_drv.c   | 14 +++++++-------
>  drivers/net/virtio_net.c          | 23 ++++++++++-------------
>  drivers/net/vmxnet3/vmxnet3_drv.c |  7 ++++---
>  4 files changed, 23 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h
> b/drivers/net/hyperv/hyperv_net.h
> index f4fbcb5..3958ada 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -606,8 +606,8 @@ struct nvsp_message {
>  } __packed;
> 
> 
> -#define NETVSC_MTU 65536
> -#define NETVSC_MTU_MIN 68
> +#define NETVSC_MTU 65535

Why change it to 65535? For Hyperv host, this should be 65536.


> @@ -1343,6 +1336,13 @@ static int netvsc_probe(struct hv_device *dev,
> 
>  	netif_carrier_off(net);
> 
> +	/* MTU range: 68 - 1500 or 65521 */
> +	net->min_mtu = NETVSC_MTU_MIN;
> +	if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
> +		net->max_mtu = NETVSC_MTU - ETH_HLEN;
> +	else
> +		net->max_mtu = ETH_DATA_LEN;
> +
>  	netvsc_init_settings(net);
> 
>  	net_device_ctx = netdev_priv(net);

nvdev->nvsp_version is not set until after rndis_filter_device_add()
is successfully completed.
You need to move this part to the place just before this line:
 ret = register_netdev(net);

Thanks,
- Haiyang