Re: [PATCH 1/4] xen-netfront: remove unused variable `extra'

From: Paul Durrant <Paul.Durrant@citrix.com>
To: annie li <annie.li@oracle.com>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Wei Liu <wei.liu2@citrix.com>,
	Ian Campbell <Ian.Campbell@citrix.com>,
	"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>
Subject: Re: [PATCH 1/4] xen-netfront: remove unused variable `extra'
Date: Tue, 19 Mar 2013 10:03:58 +0000	[thread overview]
Message-ID: <291EDFCB1E9E224A99088639C4762022013F7D2D3563__17465.3005124584$1363688047$gmane$org@LONPMAILBOX01.citrite.net> (raw)
In-Reply-To: <5148359C.8040906@oracle.com>

> -----Original Message-----
[snip] 
> For TCPv4 GSO, it seems one extra info request(NETTXF_extra_info) is
> enough in my winpv driver, and I did not process the
> XEN_NETIF_EXTRA_MORE.
> Do you create two extra info requests for bothTCPv4 and TCPv6 GSO like
> following?
> 
>   * [Request 2: netif_tx_extra]  (only if request 1 has NETTXF_extra_info)
>   * [Request 3: netif_tx_extra]  (only if request 2 has
> XEN_NETIF_EXTRA_MORE)
> 

No, I just use one. I don't use XEN_NETIF_EXTRA_FLAG_MORE. I thought you were questioning the existence of extra segments rather than this flag. I guess I got the wrong end of the stick.
I've not seen anything use XEN_NETIF_EXTRA_FLAG_MORE, but that's not to say nothing will use it in the future. Clearly something is needed to indicate subsequent extra segments should they ever be needed.

  Paul

> 
> > Extra segments are certainly not redundant; the Citrix Windows PV drivers
> send TSOs using them and handle LRO using them too.
> 
> About the LRO, upstream netback does not create any response with
> XEN_NETIF_EXTRA_MORE, so I assume your dom0 did such process?
> 
> Thanks
> Annie