[ClusterLabs] XenServer guest and host watchdog

Valentin Vidic Valentin.Vidic at CARNet.hr
Sat Sep 9 05:49:56 EDT 2017

On Fri, Sep 08, 2017 at 09:39:26PM +0100, Andrew Cooper wrote:
> Yes.  The internal mechanism of the host watchdog is to use one
> performance counter to count retired instructions and generate an NMI
> roughly once every half second (give or take C and P states).
> Separately, there is a one second timer (the same framework as all other
> timers in Xen, including the guest watchdog), which triggers a softirq
> (lower priority, runs on the return-to-guest path), which increments a
> local variable.  If the NMI handler doesn't observe this local variable
> incrementing in the timeout period, Xen crash the entire system.

Thanks for the explanation.  And in addition to the software guest
and host watchdogs, an external watchdog device like ipmi_watchdog
or iTCO_wdt can be used inside dom0.


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