Re: [libvirt] question about guest status

On Wed, 15 Feb 2012 11:00:25 +0000 "Daniel P. Berrange" <berrange(a)redhat.com&gt; wrote: > On Wed, Feb 15, 2012 at 02:44:18PM +0800, Wen Congyang wrote: >> Hi all: >> >> If the guest runs on xen, we can know the guest OS paniced, and the guest status >> is paniced. But if the guest runs on qemu/kvm, we need the same feature. And the >> feature to know guest-is-panic is a very very good feature for enterprise. >> >> We have some ways to know that guest has paniced: >> 1. watchdog timeouts >> It is not a good way, because we can not say "the guest is paniced" in 100% accuracy >> 2. use a PV driver(like the XEN) >> The old RHELs do not have such driver... >> It can not work for the second kernel... >> 3. Adding a function for console-logging (in ring buffer or some) and check messages >> given by guests. If we allow some filtering script or some, we can catch Linux's >> panic messages. We can say the guest paniced if we catch such messages. We may be >> able to catch other events by other script >> >> I prefer to 3 now. Does anyone have a better idea? > > I have discussed this with Anthony before and the thought was that QEMU/KVM > should provide some kind of paravirtualized crash notification service to > the guest. ie option 2. such a device would likely be quite simple and > thus possible to backport to older kernels as needed > AFAIK, linux kernel has notifier at panic but it doesn't work if kdump is enabled. And IIRC, There was a discussion in lkml that any modules should not be called when

crash_kexec() is called. So, no chance to notify it from the module in the 1st kernel, now. Calling it from 2nd kernel will work but the bahavior will be different from non-kdump guest. Can't we do notify by hypercall ? But this will require guest modification..

Thanks, -Kame