From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH] kvm: qemu: Handle tap fds with IFF_VNET_HDR Date: Wed, 20 Aug 2008 13:01:33 -0500 Message-ID: <48AC5BFD.6020607@codemonkey.ws> 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> <48AC59BD.9080407@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Mark McLoughlin , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from py-out-1112.google.com ([64.233.166.183]:55741 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750923AbYHTSCS (ORCPT ); Wed, 20 Aug 2008 14:02:18 -0400 Received: by py-out-1112.google.com with SMTP id p76so381333pyb.10 for ; Wed, 20 Aug 2008 11:02:17 -0700 (PDT) In-Reply-To: <48AC59BD.9080407@qumranet.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > 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. >> >> > > You need to know this before you create a virtual machine. I suggested > a 'qemu -capabilities' thing to describe what this qemu can do. > $ echo -e 'info version\nquit' | qemu-system-x86_64 -S -hda /dev/null -monitor stdio -vnc none Okay, a little hacky, but so are a lot of things that libvirt is doing :-) A proper -version flag that also has a bitmap of 'features' may be reasonable too. Regards, Anthony Liguori