From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760627Ab2CNKHZ (ORCPT ); Wed, 14 Mar 2012 06:07:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45853 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760331Ab2CNKHY (ORCPT ); Wed, 14 Mar 2012 06:07:24 -0400 Message-ID: <4F606DCC.3020908@redhat.com> Date: Wed, 14 Mar 2012 12:07:08 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1 MIME-Version: 1.0 To: Wen Congyang CC: "Daniel P. Berrange" , kvm list , qemu-devel , "linux-kernel@vger.kernel.org" , KAMEZAWA Hiroyuki , Jan Kiszka , Gleb Natapov , Amit Shah Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked References: <4F58664D.1070800@cn.fujitsu.com> <4F58943E.1050402@redhat.com> <4F595B31.9090301@cn.fujitsu.com> <4F5DBC26.7060204@cn.fujitsu.com> <4F5DD0FD.9070904@redhat.com> <20120313091843.GB3800@redhat.com> <4F5F25BF.7060100@redhat.com> <4F6056FE.3020202@cn.fujitsu.com> <4F6063C8.8010005@redhat.com> <4F606A7C.9090900@cn.fujitsu.com> In-Reply-To: <4F606A7C.9090900@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/14/2012 11:53 AM, Wen Congyang wrote: > At 03/14/2012 05:24 PM, Avi Kivity Wrote: > > On 03/14/2012 10:29 AM, Wen Congyang wrote: > >> At 03/13/2012 06:47 PM, Avi Kivity Wrote: > >>> On 03/13/2012 11:18 AM, Daniel P. Berrange wrote: > >>>> On Mon, Mar 12, 2012 at 12:33:33PM +0200, Avi Kivity wrote: > >>>>> On 03/12/2012 11:04 AM, Wen Congyang wrote: > >>>>>> Do you have any other comments about this patch? > >>>>>> > >>>>> > >>>>> Not really, but I'm not 100% convinced the patch is worthwhile. It's > >>>>> likely to only be used by Linux, which has kexec facilities, and you can > >>>>> put talk to management via virtio-serial and describe the crash in more > >>>>> details than a simple hypercall. > >>>> > >>>> As mentioned before, I don't think virtio-serial is a good fit for this. > >>>> We want something that is simple & guaranteed always available. Using > >>>> virtio-serial requires significant setup work on both the host and guest. > >>> > >>> So what? It needs to be done anyway for the guest agent. > >>> > >>>> Many management application won't know to make a vioserial device available > >>>> to all guests they create. > >>> > >>> Then they won't know to deal with the panic event either. > >>> > >>>> Most administrators won't even configure kexec, > >>>> let alone virtio serial on top of it. > >>> > >>> It should be done by the OS vendor, not the individual admin. > >>> > >>>> The hypercall requires zero host > >>>> side config, and zero guest side config, which IMHO is what we need for > >>>> this feature. > >>> > >>> If it was this one feature, yes. But we keep getting more and more > >>> features like that and we bloat the hypervisor. There's a reason we > >>> have a host-to-guest channel, we should use it. > >>> > >> > >> I donot know how to use virtio-serial. > > > > I don't either, copying Amit. > > > >> I start vm like this: > >> qemu ...\ > >> -device virtio-serial \ > >> -chardev socket,path=/tmp/foo,server,nowait,id=foo \ > >> -device virtserialport,chardev=foo,name=port1 ... > >> > >> You said that there are too many channels. Does it mean /tmp/foo is a channel? > > > > Probably. > > Hmm, if we use virtio-serial, the guest kernel writes something into the channel when > the os is panicked. Is it right? Right. > If so, is this channel visible to guest userspace? If the channle is visible to guest > userspace, the program running in userspace may write the same message to the channel. > Surely there's some kind of access control on channels. -- error compiling committee.c: too many arguments to function