From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wen Congyang Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked Date: Wed, 14 Mar 2012 19:11:32 +0800 Message-ID: <4F607CE4.2060809@cn.fujitsu.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , kvm list , Jan Kiszka , "linux-kernel@vger.kernel.org" , qemu-devel , Amit Shah , KAMEZAWA Hiroyuki To: Avi Kivity Return-path: In-Reply-To: <4F607789.4010109@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.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