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Re: [Xen-users] Watchdog support in XEN?

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Watchdog support in XEN?
From: "Andreas Bach Aaen (AH/TED)" <andreas.bach.aaen@xxxxxxxxxxxx>
Date: Tue, 26 Jul 2005 22:21:42 +0200
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On Tirsdag 26 juli 2005 22:13, Mark Williamson wrote:
> > So my question does XEN provide a "hardware" watchdog that the user
> > domains can use?
> > It might be safer that the counter and trigger resides in the XEN domain
> > than in the user domains.
>
> A sensible and straightforward way to do this would be to wait for the
> XenStore code to be fully merged, then set up an attribute in the XenStore
> which is written to periodically by the domU to say that it's live.  A
> daemon in dom0 can watch this and restart the domain if the attribute isn't
> updated for a while.  The hypervisor won't need to know about this.

This seems like a good idea. I expect that you have atomic writes in the 
XenStore, so the dom0 deamon simply increments a timer that the domU needs to 
reset once in a while. This could be written into the watchdog userspace 
deamon that automatically detect that it's inside a virtual machine and not 
directly on real hardware. What is the cleanest way to detect id you are 
running in domU or not?

Regards,
-- 
Andreas Bach Aaen              System Developer, M. Sc. 
Ericsson Danmark A/S           tel: +45 89 38 51 00
Skanderborgvej 232             fax: +45 89 38 51 01
8260 Viby J      Denmark       andreas.bach.aaen@xxxxxxxxxxxx

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