From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760783Ab2CNKs5 (ORCPT ); Wed, 14 Mar 2012 06:48:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53684 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753992Ab2CNKs4 (ORCPT ); Wed, 14 Mar 2012 06:48:56 -0400 Message-ID: <4F607789.4010109@redhat.com> Date: Wed, 14 Mar 2012 12:48:41 +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: Gleb Natapov CC: Wen Congyang , "Daniel P. Berrange" , kvm list , qemu-devel , "linux-kernel@vger.kernel.org" , KAMEZAWA Hiroyuki , Jan Kiszka , Amit Shah Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked References: <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> <4F606DCC.3020908@redhat.com> <4F60726E.3090807@cn.fujitsu.com> <4F607325.6050607@redhat.com> <20120314104608.GU2304@redhat.com> In-Reply-To: <20120314104608.GU2304@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 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 12:46 PM, Gleb Natapov wrote: > On Wed, Mar 14, 2012 at 12:29:57PM +0200, Avi Kivity wrote: > > On 03/14/2012 12:26 PM, Wen Congyang wrote: > > > >> 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. > > > > > > The virtio-serial depends on more things than touching the hypervisor. So I think touching > > > the hypervisor is more reliable than using virtio-serial device, and it is very simple and > > > easy to use. > > > > > > If we pass something from guest userspace to host, we can use virtio-serial. But If we pass > > > something from guest kernelspace to host, I still prefer to touch the hypervisor. > > > > There's no argument that it's easier. My concern is different, we're > > adding more and more stuff to the hypervisor because it's easier, which > > bloats it. Every time we do it we add to compatibility and security > > problems. > > > > The panic notification is *really* simple, so I don't expect it to cause > > a lot of problems. But still, if it's possible not to change the > > hypervisor, we must make an effort in that direction. > > > One more point against using virtio-serial is that it will be likely > compiled as a module which means panic during early boot will not be > reported. I don't think we want to use the driver. Instead, have a small piece of code that resets the device and pushes out a string (the panic message?) without any interrupts etc. It's still going to be less reliable than a hypercall, I agree. -- error compiling committee.c: too many arguments to function