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

> 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.

Yes, something like that should be fine, although I think the intention is to 
have only one writer to each portion of the store.  How about the domU 
increments / toggles the value and the dom0 daemon could notice when it 
hasn't been updated 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?

There's a flag in the Xen startinfo that tells a domain if it's dom0 or not 
(and if it's a driver domain, etc.).

The most straightforward thing to do is probably to write a kernel driver 
using the Linux watchdog API and then have that talk to the xenstore.  
This'll allow you to use the standard daemon without any changes.

The kernel API for watchdogs is fairly simple so it should be straightforward 
once the XenStore / XenBus stuff is all up and running.


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