From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] kvm: notify host when guest paniced Date: Wed, 29 Feb 2012 12:52:35 +0200 Message-ID: <20120229105235.GH24600@redhat.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> <20120229104449.GG24600@redhat.com> <4F4E0299.9080800@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Wen Congyang , kvm list , KAMEZAWA Hiroyuki , "Daniel P. Berrange" , linux-kernel@vger.kernel.org, qemu-devel To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <4F4E0299.9080800@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, Feb 29, 2012 at 12:48:57PM +0200, Avi Kivity wrote: > On 02/29/2012 12:44 PM, Gleb Natapov 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. > > > > > The more interface is complex the more chances it will fail during > > panic. Regular serial is likely more reliable than virtio-serial. > > Hypercall is likely more reliable than uart. On serial user can > > fake panic notification. > > The serial device is under control of the kernel, so the user can only > access it if the kernel so allows. > Yes, but if we will hijack UART for panic notification VM user will not be able to use it for anything else. virtio-serial have many channels, but AFAIK it does not work at early stages of boot process. -- Gleb.