Re: [Xen-devel] PROBLEM: xen-netfront: ethtool settings changed in 4.4.134 causing packet loss

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 06/05/2018 04:43 PM, Liam Shepherd wrote:
> When upgrading from 4.4.132 to 4.4.135 I started observing about 3%
> packet loss on PV on HVM domU interfaces. Specifically TX dropped
> packets (As reported by ifconfig).
>
> It seems that the default ethtool settings have changed.
>
> Previously (4.4.132):
> tx-checksumming: on
>      tx-checksum-ipv4: on [fixed]
>      tx-checksum-ip-generic: off [fixed]
>      tx-checksum-ipv6: on
>      tx-checksum-fcoe-crc: off [fixed]
>      tx-checksum-sctp: off [fixed]
> scatter-gather: on
>      tx-scatter-gather: on
>      tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: on
>      tx-tcp-segmentation: on
>      tx-tcp-ecn-segmentation: off [fixed]
>      tx-tcp6-segmentation: on
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: on
>
> Now (4.4.135):
> tx-checksumming: on
>      tx-checksum-ipv4: on [fixed]
>      tx-checksum-ip-generic: off [fixed]
>      tx-checksum-ipv6: off
>      tx-checksum-fcoe-crc: off [fixed]
>      tx-checksum-sctp: off [fixed]
> scatter-gather: off
>      tx-scatter-gather: off
>      tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: off
>      tx-tcp-segmentation: off
>      tx-tcp-ecn-segmentation: off [fixed]
>      tx-tcp6-segmentation: off
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: off [requested on]
>
> Manually running 'ethtool -K INT tso on sg on' on all interfaces stops
> the packet loss again. They're then set like this:
> tx-checksumming: on
>      tx-checksum-ipv4: on [fixed]
>      tx-checksum-ip-generic: off [fixed]
>      tx-checksum-ipv6: off
>      tx-checksum-fcoe-crc: off [fixed]
>      tx-checksum-sctp: off [fixed]
> scatter-gather: on
>      tx-scatter-gather: on
>      tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: on
>      tx-tcp-segmentation: on
>      tx-tcp-ecn-segmentation: off [fixed]
>      tx-tcp6-segmentation: off [requested on]
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: on
>
> I've traced it to a commit in 4.4.134:
> 6be4fe832954db3b359b72107a6c60e34d939b26
> xen-netfront: Fix race between device setup and open
> [ Upstream commit f599c64fdf7d9c108e8717fb04bc41c680120da4 ]
> https://patchwork.kernel.org/patch/10328969/
>
> Once that is reverted on 4.4.135, the ethtool settings are as 4.4.132
> and there is no packet loss.
Thanks for the bug report. Changing the ethtool settings was certainly 
not intended with that change. I'll take a look to see what has gone wrong.
--
Ross Lagerwall

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