Re: [PATCH 2/4] vhost: complete TSO settings

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Fri, Mar 25, 2016 at 02:01:32PM +0800, Yuanhan Liu wrote:
> Commit d0cf91303d73 ("vhost: add Tx offload capabilities") has only
> done partial settings for enabling TSO, and left the following part
> to the application, say vhost-switch example, by commit 9fd72e3cbd29
> ("examples/vhost: add virtio offload").
> 
> - Setting PKT_TX_IP_CKSUM and ipv4_hdr->hdr_checksum = 0 for IPv4.
> 
> - calculate the pseudo header checksum without taking ip_len in
>   account, and set it in the TCP header
> 
> Here we complete the left part in vhost side, so that an user (such
> as OVS) can do minimal (or even no) changes to get TSO enabled.
> 
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
...
> +			ipv4_hdr->hdr_checksum = 0;

Nah.. we can't do that here. This hurts VM2VM case badly.

Thanks Qian for letting me be aware of it.

	--yliu