From mboxrd@z Thu Jan 1 00:00:00 1970 From: annie li Subject: Re: [PATCH 1/4] xen-netfront: remove unused variable `extra' Date: Tue, 19 Mar 2013 10:39:14 +0800 Message-ID: <5147CFD2.8040803__10983.0459849492$1363660855$gmane$org@oracle.com> References: <1363602955-24790-1-git-send-email-wei.liu2@citrix.com> <1363602955-24790-2-git-send-email-wei.liu2@citrix.com> <1363606922.30193.21.camel@zakaz.uk.xensource.com> <1363608271.29093.196.camel@zion.uk.xensource.com> <1363608860.30193.39.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1363608860.30193.39.camel@zakaz.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: "netdev@vger.kernel.org" , "konrad.wilk@oracle.com" , Wei Liu , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 2013-3-18 20:14, Ian Campbell wrote: > On Mon, 2013-03-18 at 12:04 +0000, Wei Liu wrote: >> On Mon, 2013-03-18 at 11:42 +0000, Ian Campbell wrote: >>> On Mon, 2013-03-18 at 10:35 +0000, Wei Liu wrote: >>> >>> I think a few more words are needed here since from the code you are >>> removing it seems very much like gso is used for something. If you have >>> a proof that the "extra = gso" case is never hit then please explain it. >>> Perhaps a reference to the removal of the last user? >>> >>> Or maybe it is the case that it should be used and the bug is that it >>> isn't? >>> >> Looks like the latter one. 'extra' field should be used to get hold of >> the last extra info in the ring. ;-) >> >> But, the only extra info in upstream kernel is XEN_NETIF_EXTRA_TYPE_GSO, >> so there's really no other extra info in the ring at that point. Could >> it be possible that it is something from classic Xen kernel? > The classic kernel netfront has exactly the same code it seems and > netif_extra_type_gso is the only one I've ever heard of. > > Maybe this extra thing is just redundant unless/until a second extra > comes along. In our windows pv driver, we do not process this for GSO in tx path either. Maybe we ignored processing for some special GSO? BTW, what is XEN_NETIF_EXTRA_FLAG_MORE actually for? Backend only processes it in xen_netback_tx_build_gops, but netfront xmit path does not really set this flag. I did process it in rx path of my windows pv driver(linux netfront did that too), but it seems unnecessary since netback does not set this flag at all. Thanks Annie