From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: [PATCH] kvm: qemu: Handle tap fds with IFF_VNET_HDR Date: Wed, 20 Aug 2008 19:11:55 +0100 Message-ID: <20080820181155.GI6521@redhat.com> References: <1218485535-877-1-git-send-email-markmc@redhat.com> <48A1957C.4070007@qumranet.com> <1218638393.29159.38.camel@muff> <48A30ABE.3040903@qumranet.com> <1219251898.5068.33.camel@muff> <48AC5923.3040901@codemonkey.ws> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mark McLoughlin , Avi Kivity , kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from mx1.redhat.com ([66.187.233.31]:56939 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752168AbYHTSMA (ORCPT ); Wed, 20 Aug 2008 14:12:00 -0400 Content-Disposition: inline In-Reply-To: <48AC5923.3040901@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Aug 20, 2008 at 12:49:23PM -0500, Anthony Liguori wrote: > Mark McLoughlin wrote: > >Allow users to pass an IFF_VNET_HDR tap fd via "-net tap,fd=X" > >by querying the fd with the recently added TUNGETIFF ioctl() to > >see if IFF_VNET_HDR has been enabled. > > > >Note: users wishing to pass an IFF_VNET_HDR tap fd to qemu > >should check both that a) this version of qemu can handle > >such an fd and b) that the TUNGETIFF ioctl() is available in > >the running kernel. > > > >We add a comment to the "qemu -help" output to indicate to > >users that this version of qemu supports IFF_VNET_HDR. > > > > The -help output is not a supported interface. An info command in the > monitor would be a better way to detect this. The reason mark suggested -help is that libvirt already looks at -help output to determine what command line args are supported. Whether its stable or not, its the only way to determine supported args. Hopefully in the future we can just look for presence of -config, and then just use a config file to launch QEMU, so we'll have minimal dependance on this data 'format' for -help :-) The IFF_VNET_HDR stuff is a little different - its more a capability of the virtualization engine that a startup option. I'd welcome some kind of way to query capabilities in general, such as the -capabilites arg suggested. This would include stuff like the list of supported NIC models, supported disk backends, supported disk formats, sound hardware, etc. Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|