From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760858Ab2CNLJr (ORCPT ); Wed, 14 Mar 2012 07:09:47 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:12173 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754456Ab2CNLJl (ORCPT ); Wed, 14 Mar 2012 07:09:41 -0400 X-IronPort-AV: E=Sophos;i="4.73,583,1325433600"; d="scan'208";a="4533868" Message-ID: <4F607CE4.2060809@cn.fujitsu.com> Date: Wed, 14 Mar 2012 19:11:32 +0800 From: Wen Congyang User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100413 Fedora/3.0.4-2.fc13 Thunderbird/3.0.4 MIME-Version: 1.0 To: Avi Kivity CC: Gleb Natapov , "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> <4F607789.4010109@redhat.com> In-Reply-To: <4F607789.4010109@redhat.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2012-03-14 19:07:36, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2012-03-14 19:07:36, Serialize complete at 2012-03-14 19:07:36 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At 03/14/2012 06:48 PM, Avi Kivity Wrote: > 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. Do you still want to use complicated and less reliable way? I think the other ones prefer to touch the hypervisor. Thanks Wen Congyang