From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wen Congyang Subject: Re: [PATCH] kvm: notify host when guest paniced Date: Thu, 01 Mar 2012 13:21:29 +0800 Message-ID: <4F4F0759.6040106@cn.fujitsu.com> References: <4F4AF1FB.6000903@cn.fujitsu.com> <4F4CB926.6050600@redhat.com> <4F4D7F5E.5040202@cn.fujitsu.com> <4F4DF4C6.90609@redhat.com> <20120229095557.GE24600@redhat.com> <4F4DF749.7060507@redhat.com> <20120229100550.GF24600@redhat.com> <4F4DF913.5030809@redhat.com> <4F4DFB37.8060208@cn.fujitsu.com> <4F4E0061.1050508@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , kvm list , KAMEZAWA Hiroyuki , "Daniel P. Berrange" , linux-kernel@vger.kernel.org, qemu-devel To: Avi Kivity Return-path: In-Reply-To: <4F4E0061.1050508@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org At 02/29/2012 06:39 PM, Avi Kivity Wrote: > On 02/29/2012 12:17 PM, Wen Congyang wrote: >>>>> >>>> Yes, crash can be so severe that it is not even detected by a kernel >>>> itself, so not OOPS message even printed. But in most cases if kernel is >>>> functional enough to print OOPS it is functional enough to call single >>>> hypercall instruction. >>> >>> Why not print the oops to virtio-serial? Or even just a regular serial >>> port? That's what bare metal does. >> >> If virtio-serial's driver has bug or the guest doesn't have such device... > > We have the same issue with the hypercall; and virtio-serial is > available on many deployed versions. virtio-serial is available, but it is an optional device. If the guest does not have this device, the guest cannot tell the host that is is paniced. So I still prefer to touch the hypervisor. Thanks Wen Congyang > >>> >>>>>> Having special kdump >>>>>> kernel that transfers dump to a host via virtio-serial channel though >>>>>> sounds interesting. May be that's what you mean. >>>>> >>>>> Yes. The "panic, starting dump" signal should be initiated by the >>>>> panicking kernel though, in case the dump fails. >>>>> >>>> Then panic hypercall sounds like a reasonable solution. >>> >>> It is, but I'm trying to see if we can get away with doing nothing. >>> >> >> If we have a reliable way with doing nothing, it is better. But I donot >> find such way. > > We won't have a 100% reliable way. But I think a variant of the driver > that doesn't use interrupts, or just using the ordinary serial driver, > should be reliable enough. > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38670) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S2yR9-0001ep-MG for qemu-devel@nongnu.org; Thu, 01 Mar 2012 00:20:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S2yR7-0005f8-PL for qemu-devel@nongnu.org; Thu, 01 Mar 2012 00:20:19 -0500 Received: from [222.73.24.84] (port=61482 helo=song.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S2yR7-0005eX-Dc for qemu-devel@nongnu.org; Thu, 01 Mar 2012 00:20:17 -0500 Message-ID: <4F4F0759.6040106@cn.fujitsu.com> Date: Thu, 01 Mar 2012 13:21:29 +0800 From: Wen Congyang MIME-Version: 1.0 References: <4F4AF1FB.6000903@cn.fujitsu.com> <4F4CB926.6050600@redhat.com> <4F4D7F5E.5040202@cn.fujitsu.com> <4F4DF4C6.90609@redhat.com> <20120229095557.GE24600@redhat.com> <4F4DF749.7060507@redhat.com> <20120229100550.GF24600@redhat.com> <4F4DF913.5030809@redhat.com> <4F4DFB37.8060208@cn.fujitsu.com> <4F4E0061.1050508@redhat.com> In-Reply-To: <4F4E0061.1050508@redhat.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [Qemu-devel] [PATCH] kvm: notify host when guest paniced List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Gleb Natapov , kvm list , qemu-devel , linux-kernel@vger.kernel.org, KAMEZAWA Hiroyuki At 02/29/2012 06:39 PM, Avi Kivity Wrote: > On 02/29/2012 12:17 PM, Wen Congyang wrote: >>>>> >>>> Yes, crash can be so severe that it is not even detected by a kernel >>>> itself, so not OOPS message even printed. But in most cases if kernel is >>>> functional enough to print OOPS it is functional enough to call single >>>> hypercall instruction. >>> >>> Why not print the oops to virtio-serial? Or even just a regular serial >>> port? That's what bare metal does. >> >> If virtio-serial's driver has bug or the guest doesn't have such device... > > We have the same issue with the hypercall; and virtio-serial is > available on many deployed versions. virtio-serial is available, but it is an optional device. If the guest does not have this device, the guest cannot tell the host that is is paniced. So I still prefer to touch the hypervisor. Thanks Wen Congyang > >>> >>>>>> Having special kdump >>>>>> kernel that transfers dump to a host via virtio-serial channel though >>>>>> sounds interesting. May be that's what you mean. >>>>> >>>>> Yes. The "panic, starting dump" signal should be initiated by the >>>>> panicking kernel though, in case the dump fails. >>>>> >>>> Then panic hypercall sounds like a reasonable solution. >>> >>> It is, but I'm trying to see if we can get away with doing nothing. >>> >> >> If we have a reliable way with doing nothing, it is better. But I donot >> find such way. > > We won't have a 100% reliable way. But I think a variant of the driver > that doesn't use interrupts, or just using the ordinary serial driver, > should be reliable enough. >