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?

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