From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:56998) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7llN-00058o-8W for qemu-devel@nongnu.org; Wed, 14 Mar 2012 06:49:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S7llG-0001iS-Qo for qemu-devel@nongnu.org; Wed, 14 Mar 2012 06:49:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41856) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7llG-0001fI-JI for qemu-devel@nongnu.org; Wed, 14 Mar 2012 06:48:54 -0400 Message-ID: <4F607789.4010109@redhat.com> Date: Wed, 14 Mar 2012 12:48:41 +0200 From: Avi Kivity MIME-Version: 1.0 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 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: Gleb Natapov Cc: kvm list , Jan Kiszka , "linux-kernel@vger.kernel.org" , qemu-devel , Amit Shah , KAMEZAWA Hiroyuki 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