From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38431) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7l7A-0000GM-7m for qemu-devel@nongnu.org; Wed, 14 Mar 2012 06:07:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S7l73-0007xq-Sf for qemu-devel@nongnu.org; Wed, 14 Mar 2012 06:07:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41114) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7l73-0007xh-KC for qemu-devel@nongnu.org; Wed, 14 Mar 2012 06:07:21 -0400 Message-ID: <4F606DCC.3020908@redhat.com> Date: Wed, 14 Mar 2012 12:07:08 +0200 From: Avi Kivity MIME-Version: 1.0 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 Subject: Re: [Qemu-devel] [PATCH 0/2 v3] kvm: notify host when guest panicked List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wen Congyang Cc: Gleb Natapov , kvm list , Jan Kiszka , qemu-devel , "linux-kernel@vger.kernel.org" , Amit Shah , KAMEZAWA Hiroyuki 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