Re: [libvirt] question about guest status

["Daniel P. Berrange" <berrange redhat com>]

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

Option 3 is too much of a unreliable hack IMHO.

Daniel
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