From: Haiyang Zhang <haiyangz@microsoft.com>
To: Jarod Wilson <jarod@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        KY Srinivasan <kys@microsoft.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Shrikrishna Khare <skhare@vmware.com>,
        "VMware, Inc." <pv-drivers@vmware.com>
Subject: RE: [PATCH net-next 5/6] net: use core MTU range checking in virt
 drivers
Thread-Topic: [PATCH net-next 5/6] net: use core MTU range checking in virt
 drivers
Thread-Index: AQHSKbE9IJuQJBXoHUetb5rQekcRzqCvz3lg
Date: Wed, 19 Oct 2016 14:07:47 +0000
Message-ID: <BLUPR03MB141289B9E24503DF35D5AAC3CAD20@BLUPR03MB1412.namprd03.prod.outlook.com>
References: <20161019023333.15760-1-jarod@redhat.com>
 <20161019023333.15760-6-jarod@redhat.com>
In-Reply-To: <20161019023333.15760-6-jarod@redhat.com>
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> -----Original Message-----
> From: Jarod Wilson [mailto:jarod@redhat.com]
> Sent: Tuesday, October 18, 2016 10:34 PM
> To: linux-kernel@vger.kernel.org
> Cc: Jarod Wilson <jarod@redhat.com>; netdev@vger.kernel.org;
> virtualization@lists.linux-foundation.org; KY Srinivasan
> <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>; Michael S.
> Tsirkin <mst@redhat.com>; Shrikrishna Khare <skhare@vmware.com>; VMware,
> Inc. <pv-drivers@vmware.com>
> 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@vger.kernel.org
> CC: virtualization@lists.linux-foundation.org
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: "Michael S. Tsirkin" <mst@redhat.com>
> CC: Shrikrishna Khare <skhare@vmware.com>
> CC: "VMware, Inc." <pv-drivers@vmware.com>
> Signed-off-by: Jarod Wilson <jarod@redhat.com>
> ---
>  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