From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43321) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZHk1g-0008Qq-M5 for qemu-devel@nongnu.org; Tue, 21 Jul 2015 22:44:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZHk1d-0002QL-En for qemu-devel@nongnu.org; Tue, 21 Jul 2015 22:44:56 -0400 Received: from mail-pd0-f182.google.com ([209.85.192.182]:35989) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZHk1d-0002EV-9A for qemu-devel@nongnu.org; Tue, 21 Jul 2015 22:44:53 -0400 Received: by pdjr16 with SMTP id r16so132832009pdj.3 for ; Tue, 21 Jul 2015 19:44:30 -0700 (PDT) Message-ID: <55AF038C.2050300@igel.co.jp> Date: Wed, 22 Jul 2015 11:44:28 +0900 From: Tetsuya Mukawa MIME-Version: 1.0 References: <1434945048-27958-1-git-send-email-mukawa@igel.co.jp> <20150622095617-mutt-send-email-mst@redhat.com> <5589194A.9050102@igel.co.jp> <20150623111301-mutt-send-email-mst@redhat.com> <558A4436.5050903@igel.co.jp> <20150624074815-mutt-send-email-mst@redhat.com> <20150719154650-mutt-send-email-mst@redhat.com> In-Reply-To: <20150719154650-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 0/5] Add feature to start QEMU without vhost-user backend List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Marcel Apfelbaum , jasowang@redhat.com, qemu-devel@nongnu.org, n.nikolaev@virtualopensystems.com, stefanha@redhat.com On 2015/07/19 21:48, Michael S. Tsirkin wrote: > On Wed, Jun 24, 2015 at 07:57:45AM +0200, Michael S. Tsirkin wrote: >> On Wed, Jun 24, 2015 at 02:46:30PM +0900, Tetsuya Mukawa wrote: >>> On 2015/06/23 18:41, Michael S. Tsirkin wrote: >>>> On Tue, Jun 23, 2015 at 05:31:06PM +0900, Tetsuya Mukawa wrote: >>>>> On 2015/06/22 17:14, Michael S. Tsirkin wrote: >>>>>> On Mon, Jun 22, 2015 at 12:50:43PM +0900, Tetsuya Mukawa wrote: >>>>>>> Hi guys, >>>>>>> >>>>>>> Here are patches to add feature to start QEMU without vhost-user backend. >>>>>>> Currently, if we want to use vhost-user backend, the backend must start before >>>>>>> QEMU. >>>>>> Aren't you looking for something like xinetd? >>>>> It will help for restricting starting order, but not help for >>>>> reconnection of vhost-user backend. >>>> At this point, I suggest that we always connect at vm start. >>>> With that, you can add an option to reset the VM >>>> on backend disconnect. >>>> So >>>> - detect backend disconnect >>>> - reset and stop (notifying management) >>>> - reconnect or detect backend reconnect >>>> - proceed with boot >>>> >>>> As I tried to explain below, getting the full functionality >>>> will require guest driver changes. They aren't hard to get >>>> done, patches welcome. >>>> >>> Could you please let me know your thinking about using >>> DEVICE_NEEDS_RESET for vhost-user reconnection? >>> If it's works, I will try to submit it. >> DEVICE_NEEDS_RESET is hard to handle correctly in guest: >> you need to reconfigure a bunch of state, >> so far no one wrote the necessary support. > But yes, if you write the guest code, I think > it can work. > > We probably want a feature bit so host can know guest can > handle reconnections, but that's a minor detail, it > would be easy to add afterwards. > Hi Michael, I appreciate for your suggestion. I will check the virtio-net driver of linux and the virtio-net device of QEMU to know how difficult to implement DEVICE_NEEDS_RESET. Regards, Tetsuya