[Xen-devel] [ANNOUNCE] Heads-up, Xen watchdog driver in the works

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

Hi guys,

Thought I'd just mention I'm working on an in-Xen watchdog interface, just so 
we don't duplicate effort.  If anyone (e.g. distributors or other OS ports) 
wants to have any input on the design, I'd be happy to hear it.

Summary:
A software watchdog for guests implemented in Xen itself, a watchdog hypercall 
API, a Linux driver that supports this and (eventually) a bit of extra tools 
support.

The rationale is that a software watchdog within Xen itself will provide 
greater assurance than a software watchdog implemented in a domU kernel.  The 
guest simply initialises its Xen watchdog using an init hypercall, then must 
periodically call back into Xen to reset the watchdog timeout - if it fails 
to do this, Xen will reboot the domain.  Being implemented entirely outside 
the guest ensures that even in the event of catastrophic corruption, or 
interrupts being left disabled, the guest will still be rebooted on watchdog 
timeout.  Guests run a watchdog driver that presents this functionality to 
userspace daemons in the standard way for their particular OS.

This work does not preclude using a real hardware watchdog under the control 
of dom0, and would be suitably complimentary to such configurations.  It will 
mainly be of interest for high availability systems.

Possible future work includes an implementation for HVM guests, emulating a 
real hardware watchdog card (not so useful whilst the emulator is in dom0 but 
should work well with the stub domain support).

Development snapshots are available at: 
http://xenbits.xensource.com/maw/xen-watchdog.hg (nb. this is a replacement 
for my previous tree of the same name)

The code there is a rough first cut, but appears to work.  Migration and 
suspend are currently not supported.  I have an extensible hypercall API and 
broader feature set in the works, and migration / suspend will eventually be 
supported too.  Feel free to contact me for more information.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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