From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57578) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xr92i-0004TA-N7 for qemu-devel@nongnu.org; Wed, 19 Nov 2014 12:27:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xr92e-0006xv-Pv for qemu-devel@nongnu.org; Wed, 19 Nov 2014 12:27:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38729) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xr92e-0006xr-Fw for qemu-devel@nongnu.org; Wed, 19 Nov 2014 12:27:44 -0500 Date: Wed, 19 Nov 2014 17:27:30 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20141119172729.GL2355@work-vm> References: <1412358473-31398-1-git-send-email-dgilbert@redhat.com> <1412358473-31398-13-git-send-email-dgilbert@redhat.com> <20141103031244.GH8949@voom.redhat.com> <8617F122-9356-492C-B663-62C101F5EE6B@cs.umu.se> <20141118035317.GB2867@voom.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141118035317.GB2867@voom.redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 12/47] Handle bi-directional communication for fd migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: Andrea Arcangeli , yamahata@private.email.ne.jp, quintela@redhat.com, Cristian Klein , qemu-devel@nongnu.org, amit.shah@redhat.com, yanghy@cn.fujitsu.com * David Gibson (david@gibson.dropbear.id.au) wrote: > On Mon, Nov 03, 2014 at 03:53:03PM +0200, Cristian Klein wrote: > > On 03 Nov 2014, at 5:12 , David Gibson wrote: > > > > > On Fri, Oct 03, 2014 at 06:47:18PM +0100, Dr. David Alan Gilbert (git) wrote: > > >> From: Cristian Klein > > > > > > This patch really, really requires a rationale in the commit message. > > > The reason it's necessary is certainly not obvious. > > > > ??????" > > libvirt prefers opening the TCP connection itself, for two reasons. First, connection failed errors can be detected easier, without having to parse qemu???s error output. Second, libvirt might be asked to secure the transfer by tunnelling the communication through an TLS layer. Therefore, libvirt opens the TCP connection itself and passes an FD to qemu using QMP and a POSIX-specific mechanism. Hence, in order to make the reverse-path work in such cases, qemu needs to distinguish if the transmitted FD is a socket (reverse-path available) or not (reverse-path might not be available) and use the corresponding abstraction. > > ??????" > > > > If the above message is clarifies the purpose of this commit, feel > > free to add it in the next version of the patch. > > That would help, yes. I've added that text into the commit message. Dave > > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK